Photocatalytic activity of low temperature oxidized Ti-6Al-4V.

PubMed

Unosson, Erik; Persson, Cecilia; Welch, Ken; Engqvist, Håkan

2012-05-01

Numerous advanced surface modification techniques exist to improve bone integration and antibacterial properties of titanium based implants and prostheses. A simple and straightforward method of obtaining uniform and controlled TiO(2) coatings of devices with complex shapes is H(2)O(2)-oxidation and hot water aging. Based on the photoactivated bactericidal properties of TiO(2), this study was aimed at optimizing the treatment to achieve high photocatalytic activity. Ti-6Al-4V samples were H(2)O(2)-oxidized and hot water aged for up to 24 and 72 h, respectively. Degradation measurements of rhodamine B during UV-A illumination of samples showed a near linear relationship between photocatalytic activity and total treatment time, and a nanoporous coating was observed by scanning electron microscopy. Grazing incidence X-ray diffraction showed a gradual decrease in crystallinity of the surface layer, suggesting that the increase in surface area rather than anatase formation was responsible for the increase in photocatalytic activity.

Visible light driven multifunctional photocatalysis in TeO2-based semiconductor glass ceramics

NASA Astrophysics Data System (ADS)

Kushwaha, Himmat Singh; Thomas, Paramanandam; Vaish, Rahul

2017-01-01

Photocatalytic xCaCu3Ti4O12-(100-x)TeO2 (x=0.25 mol% to 3 mol%), glass nanocomposites were fabricated and investigated for wastewater treatment, self-cleaning surfaces, and photocatalytic hydrogen evolution. Visible light active crystals of Cu-doped TiO2 and TiTe3O8 were grown by optimized crystallization of as-quenched glasses. The visible light photocatalytic activity of glass samples was investigated for estrogenic pharmaceutical pollutants, and the degradation rate was obtained as 168.56 min-1 m-2. A higher photocatalytic H2 production rate was observed (135 μmole h-1 g-1) for the crystallized CaCu3Ti4O12-TeO2 (x=3. 0) glass plate under visible light. The self-cleaning performance was observed using contact angle measurements for water under dark and light conditions. These visible light active glass ceramics are a cost effective sustainable solution for water treatment and self-cleaning applications.

Self-Biased Hybrid Piezoelectric-Photoelectrochemical Cell with Photocatalytic Functionalities.

PubMed

Tan, Chuan Fu; Ong, Wei Li; Ho, Ghim Wei

2015-07-28

Utilizing solar energy for environmental and energy remediations based on photocatalytic hydrogen (H2) generation and water cleaning poses great challenges due to inadequate visible-light power conversion, high recombination rate, and intermittent availability of solar energy. Here, we report an energy-harvesting technology that utilizes multiple energy sources for development of sustainable operation of dual photocatalytic reactions. The fabricated hybrid cell combines energy harvesting from light and vibration to run a power-free photocatalytic process that exploits novel metal-semiconductor branched heterostructure (BHS) of its visible light absorption, high charge-separation efficiency, and piezoelectric properties to overcome the aforementioned challenges. The desirable characteristics of conductive flexible piezoelectrode in conjunction with pronounced light scattering of hierarchical structure originate intrinsically from the elaborate design yet facile synthesis of BHS. This self-powered photocatalysis system could potentially be used as H2 generator and water treatment system to produce clean energy and water resources.

UV/TiO₂ photocatalytic oxidation of recalcitrant organic matter: effect of salinity and pH.

PubMed

Muthukumaran, Shobha; Song, Lili; Zhu, Bo; Myat, Darli; Chen, Jin-Yuan; Gray, Stephen; Duke, Mikel

2014-01-01

Photocatalytic oxidation processes have interest for water treatment since these processes can remove recalcitrant organic compounds and operate at mild conditions of temperature and pressure. However, performance under saline conditions present in many water resources is not well known. This study aims to explore the basic effects of photocatalysis on the removal of organic matter in the presence of salt. A laboratory-scale photocatalytic reactor system, employing ultraviolet (UV)/titanium dioxide (TiO₂) photocatalysis was evaluated for its ability to remove the humic acid (HA) from saline water. The particle size and zeta potential of TiO₂ under different conditions including solution pH and sodium chloride (NaCl) concentrations were characterized. The overall degradation of organics over the NaCl concentration range of 500-2,000 mg/L was found to be 80% of the non-saline equivalent after 180 min of the treatment. The results demonstrated that the adsorption of HA onto the TiO₂ particles was dependent on both the pH and salinity due to electrostatic interaction and highly unstable agglomerated dispersion. This result supports UV/TiO₂ as a viable means to remove organic compounds, but the presence of salt in waters to be treated will influence the performance of the photocatalytic oxidation process.

JSC ECLSS R/T Program Overview

NASA Technical Reports Server (NTRS)

Behrend, A. F.

1990-01-01

Viewgraphs on Johnson Space Center Environmental Control and Life Support System (ECLSS) research and technology program overview are presented. Topics covered include: advancements in electrochemical CO2 removal; supercritical water waste oxidation; electrooxidation for post-treatment of reclaimed water; and photocatalytic post-treatment of reclaimed water.

PHOTOCATALYTIC OXIDATION OF METHYL-TERT-BUTYL ETHER FOR DRINKING WATER TREATMENT

EPA Science Inventory

The photo-oxidation of methyl tert-butyl ether (MTBE) in water was investigated to determine the feasibility of using photocatalysis for the treatment of MTBE-contaminated drinking water. The feasibility assessment was conducted using slurries of titanium dioxide in both a photo-...

Photocatalytic ozonation of urban wastewater and surface water using immobilized TiO2 with LEDs: Micropollutants, antibiotic resistance genes and estrogenic activity.

PubMed

Moreira, Nuno F F; Sousa, José M; Macedo, Gonçalo; Ribeiro, Ana R; Barreiros, Luisa; Pedrosa, Marta; Faria, Joaquim L; Pereira, M Fernando R; Castro-Silva, Sérgio; Segundo, Marcela A; Manaia, Célia M; Nunes, Olga C; Silva, Adrián M T

2016-05-01

Photocatalytic ozonation was employed for the first time in continuous mode with TiO2-coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO2 catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01-0.20 ng L(-1)). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes (intI1, blaTEM, qnrS, sul1). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1, increased to values close to the pre-treatment levels, the ARGs (blaTEM, qnrS and sul1) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Using Nanomaterials to Solve Environmental Problems: Advancing the Science and Engineering of Photocatalysis

NASA Astrophysics Data System (ADS)

Brame, Jonathon Andrew

Photocatalysis is a process by which materials can transfer light energy into chemical energy in the form of reactive oxygen species (ROS), which can then oxidize chemical and biological contaminants in water. Whereas photocatalysis offers the potential to treat many recalcitrant priority pollutants in a cost-effective manner, it has yet to become a viable, wide-spread treatment option due to implementation barriers that include limitations in treatment efficiency and relatively high costs of some photocatalytic material. This thesis seeks to increase the applicability and understanding of nanomaterial-enhanced photocatalytic oxidation processes to help overcome these barriers. Increased photocatalytic efficiency can be accomplished through informed choice of ROS-producing materials. For example, hydroxyl radicals are shown to be much more susceptible to hindrance by natural organic matter (NOM), phosphate and wastewater treatment plant effluent than 1O 2, which is only slightly inhibited by NOM and not by phosphate or wastewater effluent. Additionally, a novel crystallization mechanism for photocatalytic TiO2 nanotubes enabled photo-production of multiple ROS types. This "cocktail" of reactive oxygen species contributed to increased efficiency. Novel applications for nanotechnology-enhanced photocatalysis were demonstrated at the lab scale. These include (1) photocatalytic pre-treatment of weathered oil from the 2010 Gulf oil spill, which increased soluble organic carbon content (indicative of increased bioavailability) by 60% and enhanced subsequent biodegradation by 37%; and (2) a water disinfection case study in rural Swaziland, which produced a prototype fluidized bed photoreactor capable of removing 99.9% of bacteria and viruses in <60 seconds. These projects show both a variety of applications for photocatalysis, and ways to increase its efficiency and effectiveness. To achieve wide-spread implementation, however, the price of photocatalysis must be reduced. Extensive reuse of treatment materials (>60 cycles), and utilization of less-purified starting materials (>90% cost reduction) highlight possible ways to reduce the cost of nanomaterial photocatalysis. By reducing financial implementation barriers, defining niches where photocatalysis can be superiorly effective, engineering reactor systems that enable real-world testing of this technology, and increasing understanding of photocatalytic inhibition mechanisms, photocatalysis can become a tool to help solve global water challenges.

Graphene wrapped Copper Phthalocyanine nanotube: Enhanced photocatalytic activity for industrial waste water treatment

NASA Astrophysics Data System (ADS)

Mukherjee, Moumita; Ghorai, Uttam Kumar; Samanta, Madhupriya; Santra, Angshuman; Das, Gour P.; Chattopadhyay, Kalyan K.

2017-10-01

To improve the photocatalytic performance of metal phthalocyanine based catalyst, Copper Phthalocyanine (CuPc) functionalized reduced graphene oxide (RGO) nanocomposite has been synthesized through a simple chemical approach. The obtained product was characterized by X-ray diffraction technique (XRD), Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible spectroscopy (UV-vis) and High resolution transmission electron microscopy (HRTEM). The photocatalytic activity of the RGO/CuPc nanocomposite was performed by the degradation of Rhodamine B (RhB) under visible light irradiation. The photocatalytic studies revealed that the RGO/CuPc nanocomposite exhibits much stronger catalytic behavior than the pristine CuPc nanotube. A plausible mechanism for the photodegradation of Rhodamine B (RhB) was suggested. The RGO wrapped CuPc nanotube composite materials offer great potential as active photocatalysts for degradation of organic pollutions in industrial waste water.

Chemically Assisted Photocatalytic Oxidation System

NASA Technical Reports Server (NTRS)

Andino, Jean; Wu, Chang-Yu; Mazyck, David; Teixeira, Arthur A.

2009-01-01

The chemically assisted photocatalytic oxidation system (CAPOS) has been proposed for destroying microorganisms and organic chemicals that may be suspended in the air or present on surfaces of an air-handling system that ventilates an indoor environment. The CAPOS would comprise an upstream and a downstream stage that would implement a tandem combination of two partly redundant treatments. In the upstream stage, the air stream and, optionally, surfaces of the air-handling system would be treated with ozone, which would be generated from oxygen in the air by means of an electrical discharge or ultraviolet light. In the second stage, the air laden with ozone and oxidation products from the first stage would be made to flow in contact with a silica-titania photocatalyst exposed to ultraviolet light in the presence of water vapor. Hydroxyl radicals generated by the photocatalytic action would react with both carbon containing chemicals and microorganisms to eventually produce water and carbon dioxide, and ozone from the first stage would be photocatalytically degraded to O2. The net products of the two-stage treatment would be H2O, CO2, and O2.

PHOTOCATALYTIC TREATMENT OF AIR EMISSIONS RESULTING FROM GROUND-WATER TREATMENT, "GROUND WATER CURRENTS" EPA/542-N-01-008, ISSUE 42

EPA Science Inventory

A new system for treating off-gas from ground water remediation systems containing chlorinated organic compounds has been demosntrated under USEPA's Superfund Innovative Technical Evaluation (SITE) Program. Results indicate that this technology, known as the adsorption-integrated...

Treatment of secondary effluent by sequential combination of photocatalytic oxidation with ceramic membrane filtration.

PubMed

Song, Lili; Zhu, Bo; Jegatheesan, Veeriah; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

2018-02-01

The aim of the present work was to experimentally evaluate an alternative advanced wastewater treatment system, which combines the action of photocatalytic oxidation with ceramic membrane filtration. Experiments were carried out using laboratory scale TiO 2 /UV photocatalytic reactor and tubular ceramic microfiltration (CMF) system to treat the secondary effluent (SE). A 100-nm pore size CMF membrane was investigated in cross flow mode under constant transmembrane pressure of 20 kPa. The results show that specific flux decline of CMF membrane with and without TiO 2 /UV photocatalytic treatment was 30 and 50%, respectively, after 60 min of filtration. Data evaluation revealed that the adsorption of organic compounds onto the TiO 2 particles was dependent on the pH of the suspension and was considerably higher at low pH. The liquid chromatography-organic carbon detector (LC-OCD) technique was used to characterise the dissolved organic matter (DOM) present in the SE and was monitored following photocatalysis and CMF. The results showed that there was no removal of biopolymers and slight removal of humics, building blocks and the other oxidation by-products after TiO 2 /UV photocatalytic treatment. This result suggested that the various ions present in the SE act as scavengers, which considerably decrease the efficiency of the photocatalytic oxidation reactions. On the other hand, the CMF was effective for removing 50% of biopolymers with no further removal of other organic components after photocatalytic treatment. Thus, the quantity of biopolymers in SE has an apparent correlation with the filterability of water samples in CMF.

Novel synthesis of ZnO/PMMA nanocomposites for photocatalytic applications

PubMed Central

Di Mauro, Alessandro; Cantarella, Maria; Nicotra, Giuseppe; Pellegrino, Giovanna; Gulino, Antonino; Brundo, Maria Violetta; Privitera, Vittorio; Impellizzeri, Giuliana

2017-01-01

The incorporation of nanostructured photocatalysts in polymers is a strategic way to obtain novel water purification systems. This approach takes the advantages of: (1) the presence of nanostructured photocatalyst; (2) the flexibility of polymer; (3) the immobilization of photocatalyst, that avoids the recovery of the nanoparticles after the water treatment. Here we present ZnO-polymer nanocomposites with high photocatalytic performance and stability. Poly (methyl methacrylate) (PMMA) powders were coated with a thin layer of ZnO (80 nm thick) by atomic layer deposition at low temperature (80 °C). Then the method of sonication and solution casting was performed so to obtain the ZnO/PMMA nanocomposites. A complete morphological, structural, and chemical characterization was made by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The remarkable photocatalytic efficiency of the nanocomposites was demonstrated by the degradation of methylene blue (MB) dye and phenol in aqueous solution under UV light irradiation. The composites also resulted reusable and stable, since they maintained an unmodified photo-activity after several MB discoloration runs. Thus, these results demonstrate that the proposed ZnO/PMMA nanocomposite is a promising candidate for photocatalytic applications and, in particular, for novel water treatment. PMID:28098229

Bibliography of work on the heterogeneous photocatalytic removal of hazardous compounds from water and air: Update Number 1 to June, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blake, D.M.

1995-11-01

This report is an update of a bibliography, published in May, 1994, of research performed on the photocatalytic oxidation of organic or inorganic compounds in air or water and on the photocatalytic reduction of metal-containing ions in water. The general focus of the research is on removing hazardous contaminants from air water to meet environmental or health regulations. The processes covered are based on the application of heterogeneous photocatalysts. The current state-of-the-art in catalysts are forms of titanium dioxide or modifications of titanium dioxide, but work on other heterogeneous catalysts is also included in this compilation. This update contains 574more » references, most published between January, 1993 and June, 1995, but some references are from earlier work that were not included in the previous report. A new section has been added which gives information about companies that are active in providing products based on photocatalytic processes or that can provide pilot, demonstration, or commercial-scale water- or air-treatment systems. Key words, assigned by the author of this report, have been included with the citations in the listing of the bibliography.« less

Comparison of photo-Fenton, O3/H2O2/UV and photocatalytic processes for the treatment of gray water.

PubMed

Hassanshahi, Nahid; Karimi-Jashni, Ayoub

2018-06-21

This research was carried out to compare and optimize the gray water treatment performance by the photo-Fenton, photocatalysis and ozone/H 2 O 2 /UV processes. Experimental design and optimization were carried out using Central Composite Design of Response Surface Methodology. The results of experiments showed that the most effective and influencing factors in photo-Fenton process were H 2 O 2 /Fe 2+ ratio, in ozone/H 2 O 2 /UV experiment were O 3 concentration, H 2 O 2 concentration, reaction time and pH and in photocatalytic process were TiO 2 concentration, pH and reaction time. The highest COD removal in photo-Fenton, ozone/H 2 O 2 /UV and photocatalytic process were 90%, 92% and 55%, respectively. The results were analyzed by design expert software and for all three processes second-order models were proposed to simulate the COD removal efficiency. In conclusion the ozone/H 2 O 2 /UV process is recommended for the treatment of gray water, since it was able to remove both COD and turbidity by 92% and 93%, respectively. Copyright © 2018 Elsevier Inc. All rights reserved.

Comparative analysis of the photocatalytic reduction of drinking water oxoanions using titanium dioxide.

PubMed

Marks, Randal; Yang, Ting; Westerhoff, Paul; Doudrick, Kyle

2016-11-01

Regulated oxidized pollutants in drinking water can have significant health effects, resulting in the need for ancillary treatment processes. Oxoanions (e.g., nitrate) are one important class of oxidized inorganic ions. Ion exchange and reverse osmosis are often used treatment processes for oxoanions, but these separation processes leave behind a concentrated waste product that still requires treatment or disposal. Photocatalysis has emerged as a sustainable treatment technology capable of catalytically reducing oxoanions directly to innocuous byproducts. Compared with the large volume of knowledge available for photocatalytic oxidation, very little knowledge exists regarding photocatalytic reduction of oxoanion pollutants. This study investigates the reduction of various oxoanions of concern in drinking water (nitrate, nitrite, bromate, perchlorate, chlorate, chlorite, chromate) using a commercial titanium dioxide photocatalyst and a polychromatic light source. Results showed that oxoanions were readily reduced under acidic conditions in the presence of formate, which served as a hole scavenger, with the first-order rate decreasing as follows: bromate > nitrite > chlorate > nitrate > dichromate > perchlorate, corresponding to rate constants of 0.33, 0.080, 0.052, 0.0074, 0.0041, and 0 cm 2 /photons × 10 18 , respectively. Only bromate and nitrite were reduced at neutral pH, with substantially lower rate constants of 0.034 and 0.0021 cm 2 /photons × 10 18 , respectively. No direct relationship between oxoanion physicochemical properties, including electronegativity of central atom, internal bond strength, and polarizability was discovered. However, observations presented herein suggest the presence of kinetic barriers unique to each oxoanion and provides a framework for investigating photocatalytic reduction mechanisms of oxoanions in order to design better photocatalysts and optimize treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ozone and photocatalytic processes to remove the antibiotic sulfamethoxazole from water.

PubMed

Beltrán, Fernando J; Aguinaco, Almudena; García-Araya, Juan F; Oropesa, Ana

2008-08-01

In this study, water containing the pharmaceutical compound sulfamethoxazole (SMT) was subjected to the various treatments of different oxidation processes involving ozonation, and photolysis and catalysis under different experimental conditions. Removal rates of SMT and total organic carbon (TOC), from experiments of simple UVA radiation, ozonation (O(3)), catalytic ozonation (O(3)/TiO(2)), ozone photolysis (O(3)/UVA), photocatalytic oxidation (O(2)/TiO(2)/UVA) and photocatalytic ozonation (O(3)/UVA/TiO(2)), have been compared. Photocatalytic ozonation leads to the highest SMT removal rate (pH 7 in buffered systems, complete removal is achieved in less than 5min) and total organic carbon (in unbuffered systems, with initial pH=4, 93% TOC removal is reached). Also, lowest ozone consumption per TOC removed and toxicity was achieved with the O(3)/UVA/TiO(2) process. Direct ozone and free radical reactions were found to be the principal mechanisms for SMT and TOC removal, respectively. In photocatalytic ozonation, with buffered (pH 7) aqueous solutions phosphates (buffering salts) and accumulation of bicarbonate scavengers inhibit the reactions completely on the TiO(2) surface. As a consequence, TOC removal diminishes. In all cases, hydrogen peroxide plays a key role in TOC mineralization. According to the results obtained in this work the use of photocatalytic ozonation is recommended to achieve a high mineralization degree of water containing SMT type compounds.

Urban wastewater treatment by using Ag/ZnO and Pt/TiO2 photocatalysts.

PubMed

Murcia Mesa, Julie J; Arias Bolivar, Lizeth G; Sarmiento, Hugo Alfonso Rojas; Martínez, Elsa Giovanna Ávila; Páez, César Jaramillo; Lara, Mayra Anabel; Santos, José Antonio Navío; Del Carmen Hidalgo López, María

2018-03-02

In this study, the treatment of wastewater coming from a river highly polluted with domestic and industrial effluents was evaluated. For this purpose, series of photocatalysts obtained by ZnO and TiO 2 modification were evaluated. The effect of metal addition and Ti precursor (in the case of the titania series) over the physicochemical and photocatalytic properties of the materials obtained was also analyzed. The evaluation of the photocatalytic activity showed that semiconductor modification and precursor used in the materials synthesis are important factors influencing the physicochemical and therefore the photocatalytic properties of the materials obtained. The water samples analyzed in the present work were taken from a highly polluted river, and it was found that the effectiveness of the photocatalytic treatment increases when the reaction time increases and for both, wastewater samples and isolated Escherichia coli strain follow the next order Pt/TiO 2 < ZnO. It was also observed that biochemical and chemical demand oxygen and turbidity significantly decrease after treatment, thus indicating that photocatalysis is a non-selective technology, which can lead to recover wastewater containing different pollutants.

Solar photocatalytic ozonation of a mixture of pharmaceutical compounds in water.

PubMed

Márquez, Gracia; Rodríguez, Eva M; Beltrán, Fernando J; Álvarez, Pedro M

2014-10-01

Aqueous solutions of mixtures of four pharmaceutical compounds (atenolol, hydrochlorothiazide, ofloxacin and trimethoprim) both in Milli-Q ultrapure water and in a secondary effluent from a municipal wastewater treatment plant have been treated at pH 7 by different oxidation methods, such as conventional ozonation, photolytic ozonation, TiO2 catalytic ozonation, TiO2 photocatalytic oxidation and TiO2 photocatalytic ozonation. Experiments were carried out using a solar compound parabolic concentrator. The performance results have been compared in terms of removal of emerging contaminants (ECs), generation rate of phenolic intermediates, organic matter mineralization, ecotoxicity removal and enhancement of biodegradability. Also, the consumption of ozone to achieve certain treatment goals (95% removal of ECs and 40% mineralization) is discussed. Results reveal that solar photocatalytic ozonation is a promising oxidation method as it led to the best results in terms of EC mineralization (∼85%), toxicity removal (∼90%) and efficient use of ozone (∼2mgO3mgEC(-1) to achieve complete EC removal and ∼18mgO3mgTOC(-1) to achieve 40% EC mineralization, respectively). Copyright © 2014 Elsevier Ltd. All rights reserved.

Solar photocatalytic treatment of quinolones: intermediates and toxicity evaluation.

PubMed

Sirtori, Carla; Zapata, Ana; Malato, Sixto; Gernjak, Wolfgang; Fernández-Alba, Amadeo R; Agüera, Ana

2009-05-01

In this study, degradation of Flumequine (FLU) and nalidixic acid (NXA) in distilled water by two solar photocatalytic processes, TiO(2) and photo-Fenton, was evaluated. Intermediates and acute toxicity of the photoproducts generated were also studied. Degradation efficiency by heterogeneous photocatalysis with TiO(2) was similar for NXA and FLU, which were completely degraded after 25 min of illumination. Less NXA mineralisation was reached after 80 min of illumination. Photo-Fenton degradation of both substances was very quick (<25 min of illumination time), and the same mineralisation was reached in both cases. The kinetic parameters of the two substances were calculated for comparison of their photocatalytic degradation. In all cases, photocatalytic processes were associated with a reduction in toxicity, as evaluated by Vibrio fischeri bioassay. Furthermore, a sharp decrease in inhibition was observed from the beginning of the treatment, even when FLU and NXA were still present in the reaction solution (first samples). These results demonstrate that in both photocatalytic processes studied, toxicity decreases significantly, producing a phototreated sample within safe toxicity limits. The intermediates formed during photocatalytic degradation were studied by liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS).

Graphene nanoplatelets induced tailoring in photocatalytic activity and antibacterial characteristics of MgO/graphene nanoplatelets nanocomposites

NASA Astrophysics Data System (ADS)

Arshad, Aqsa; Iqbal, Javed; Siddiq, M.; Mansoor, Qaisar; Ismail, M.; Mehmood, Faisal; Ajmal, M.; Abid, Zubia

2017-01-01

The synthesis, physical, photocatalytic, and antibacterial properties of MgO and graphene nanoplatelets (GNPs) nanocomposites are reported. The crystallinity, phase, morphology, chemical bonding, and vibrational modes of prepared nanomaterials are studied. The conductive nature of GNPs is tailored via photocatalysis and enhanced antibacterial activity. It is interestingly observed that the MgO/GNPs nanocomposites with optimized GNPs content show a significant photocatalytic activity (97.23% degradation) as compared to bare MgO (43%) which makes it the potential photocatalyst for purification of industrial waste water. In addition, the effect of increased amount of GNPs on antibacterial performance of nanocomposites against pathogenic micro-organisms is researched, suggesting them toxic. MgO/GNPs 25% nanocomposite may have potential applications in waste water treatment and nanomedicine due its multifunctionality.

Water-splitting using photocatalytic porphyrin-nanotube composite devices

DOEpatents

Shelnutt, John A [Tijeras, NM; Miller, James E [Albuquerque, NM; Wang, Zhongchun [Albuquerque, NM; Medforth, Craig J [Winters, CA

2008-03-04

A method for generating hydrogen by photocatalytic decomposition of water using porphyrin nanotube composites. In some embodiments, both hydrogen and oxygen are generated by photocatalytic decomposition of water.

New large solar photocatalytic plant: set-up and preliminary results.

PubMed

Malato, S; Blanco, J; Vidal, A; Fernández, P; Cáceres, J; Trincado, P; Oliveira, J C; Vincent, M

2002-04-01

A European industrial consortium called SOLARDETOX has been created as the result of an EC-DGXII BRITE-EURAM-III-financed project on solar photocatalytic detoxification of water. The project objective was to develop a simple, efficient and commercially competitive water-treatment technology, based on compound parabolic collectors (CPCs) solar collectors and TiO2 photocatalysis, to make possible easy design and installation. The design, set-up and preliminary results of the main project deliverable, the first European industrial solar detoxification treatment plant, is presented. This plant has been designed for the batch treatment of 2 m3 of water with a 100 m2 collector-aperture area and aqueous aerated suspensions of polycrystalline TiO2 irradiated by sunlight. Fully automatic control reduces operation and maintenance manpower. Plant behaviour has been compared (using dichloroacetic acid and cyanide at 50 mg l(-1) initial concentration as model compounds) with the small CPC pilot plants installed at the Plataforma Solar de Almería several years ago. The first results with high-content cyanide (1 g l(-1)) waste water are presented and plant treatment capacity is calculated.

Porous Electrospun Fibers Embedding TiO2 for Adsorption and Photocatalytic Degradation of Water Pollutants.

PubMed

Lee, Chang-Gu; Javed, Hassan; Zhang, Danning; Kim, Jae-Hong; Westerhoff, Paul; Li, Qilin; Alvarez, Pedro J J

2018-04-03

Using a bipolymer system consisting of polyvinylpyrrolidone (PVP) and poly(vinylidene fluoride) (PVDF), P25-TiO 2 was immobilized into thin film mats of porous electrospun fibers. Pores were introduced by dissolving sacrificial PVP to increase surface area and enhance access to TiO 2 . The highest photocatalytic activity was achieved using a PVDF:PVP weight ratio of 2:1. Methylene blue (MB) was used to visualize contaminant removal, assess the sorption capacity (5.93 ± 0.23 mg/g) and demonstrate stable removal kinetics ( k MB > 0.045 min -1 ) under UVA irradiation (3.64 × 10 -9 einstein/cm 2 /s) over 10 cycles. Treatment was also accomplished via sequential MB sorption in the dark and subsequent photocatalytic degradation under UVA irradiation, to illustrate that these processes could be uncoupled to overcome limited light penetration. The photocatalytic mat degraded bisphenol A and 17α-ethynylestradiol in secondary wastewater effluent (17 mg TOC/L), and (relative to TiO 2 slurry) immobilization of TiO 2 in the mat mitigated performance inhibition by co-occurring organics that scavenge oxidation capacity. This significantly lowered the electrical energy-per-order of reaction (EEO) needed to remove such endocrine disruptors in the presence of oxidant scavenging/inhibitory organics. Thus, effective TiO 2 immobilization into polymers with affinity toward specific priority pollutants could both increase the efficiency and reduce energy requirements of photocatalytic water treatment.

The Equipment of Using AZOLLA for O2-Supplimentation and its Test

NASA Astrophysics Data System (ADS)

Liu, Xia-Shi; Chen, Min; Bian, Zu-Liang; Liu, Chung-Chu

The water-consuming amount in a long-term astro-navigation is large. In order to reduce the burden of water supply from Earth ground, the space station needs to resolve the problems of water supply. For this reason, the recovery and regeneration of urine solution of spacemen, and its utilization possess a key importance. Many investigations on this aspect have been reported. Our research based on "biological absorption-purification-UV photocatalytic oxidation" techniques with a relevant treating equipment that for a comprehensive treatment to fresh urine of spacemen has been created. In this equipment, the urine solution was used as the nutrient solution for the biological parts in ecological life ensurant system, after absorbing the nutrient, it was decomposed, metabolized and purified in some distance, and created a favorable condition for the follow-up oxidation treatment by UV-Photocatalytic Oxidation. After these two processes, the treated urine solution reached the GB5749-85 standard of water quality. Some main indexes are as table one. Chroma<5-15 Feculent degree-NTU-1.20-3 --5 Total rigidity-according to CaCO3-mg/L-3.60-450 N-NO3--mg/L-0.60-20 Soluble total solid-mg/L-543-1000 Bacterial gross-cfu/ml-13-100 Coliform group-No./L-<3-3 Key words-Photocatalytic Oxidation , Ultraviolet

Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate.

PubMed

Akerdi, Abdollah Gholami; Bahrami, S Hajir; Arami, Mokhtar; Pajootan, Elmira

2016-09-01

Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recent advances based on the synergetic effect of adsorption for removal of dyes from waste water using photocatalytic process.

PubMed

Natarajan, Subramanian; Bajaj, Hari C; Tayade, Rajesh J

2018-03-01

The problem of textile dye pollution has been addressed by various methods, mainly physical, chemical, biological, and acoustical. These methods mainly separate and/or remove the dye present in water. Recently, advanced oxidation processes (AOP) have been focused for removal of dye from waste water due to their advantages such as ecofriendly, economic and capable to degrade many dyes or organic pollutant present in water. Photocatalysis is one of the advance oxidation processes, mainly carried out under irradiation of light and suitable photocatalytic materials. The photocatalytic activity of the photocatalytic materials mainly depends on the band gap, surface area, and generation of electron-hole pair for degradation dyes present in water. It has been observed that the surface area plays a major role in photocatalytic degradation of dyes, by providing higher surface area, which leads to the higher adsorption of dye molecule on the surface of photocatalyst and enhances the photocatalytic activity. This present review discusses the synergic effect of adsorption of dyes on the photocatalytic efficiency of various nanostructured high surface area photocatalysts. In addition, it also provides the properties of the water polluting dyes, their mechanism and various photocatalytic materials; and their morphology used for the dye degradation under irradiation of light along with the future prospects of highly adsorptive photocatalytic material and their application in photocatalytic removal of dye from waste water. Copyright © 2017. Published by Elsevier B.V.

Palladium-doped-ZrO2-multiwalled carbon nanotubes nanocomposite: an advanced photocatalyst for water treatment

NASA Astrophysics Data System (ADS)

Anku, William Wilson; Oppong, Samuel Osei-Bonsu; Shukla, Sudheesh Kumar; Agorku, Eric Selorm; Govender, Poomani Penny

2016-06-01

The photocatalytic degradation of organic pollutants from water using palladium-doped-zirconium oxide-multiwalled carbon nanotubes (Pd-ZrO2-MWCNTs) nanocomposites is presented. A series of Pd doped-ZrO2-MWCNTs nanocomposites with varying percentage compositions of Pd were prepared by the homogenous co-precipitation method. The photocatalytic applicability of the materials was investigated by the degradation of acid blue 40 dye in water under simulated solar light. The optical, morphological and structural properties of the nanocomposites were evaluated using X-ray powder diffraction, Fourier transformer infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, BET surface area analysis and (UV-Vis) spectroscopy. The Pd-ZrO2-MWCNTs nanocomposites showed enhanced photocatalytic activity toward the degradation of the acid blue 40 dye under visible light compared with bare ZrO2 and ZrO2-MWCNTs alone. The remarkable photocatalytic activity of Pd-ZrO2-MWCNTs nanocomposites in the visible light makes it an ideal photocatalyst for the removal of organic pollutants in water. The 0.5 % Pd-ZrO2-MWCNT was the most efficient photocatalyst with 98 % degradation after 3 h with corresponding K a and band gap values of 16.8 × 10-3 m-1 and 2.79 eV, respectively.

Photocatalytic degradation of humic acids using substrate-supported Fe³⁺-doped TiO₂ nanotubes under UV/O₃ for water purification.

PubMed

Yuan, Rongfang; Zhou, Beihai; Zhang, Xuemin; Guan, Huanhuan

2015-11-01

In this paper, Fe(3+)-doped TiO2 nanotubes (Fe-TNTs) were successfully synthesized using hydrothermal method. Four different types of substrates, more specifically, ceramsite, zeolite, activated alumina, and activated carbon (AC), have been investigated in the study. The substrate-supported Fe-TNTs were used to effectively decompose humic acids (HAs) in water under O3/UV conditions. The experiment results show that the highest photocatalytic activity was obtained in the presence of AC-supported 1.0 atomic percent (at.%) Fe-TNTs calcined at 500 °C, as HAs was removed by 97.4%, with a pseudo-first-order rate constant of 0.126/min. The removal efficiencies of HAs reduced when the catalysts was repeatedly used, since the amount of adsorption sites of the supporting substrates decreased. However, even after the catalyst was repeatedly used for five times, the removal efficiency of HAs in the presence of AC-supported catalyst, which was 78.5%, was still sufficient in water treatment. The enhanced photocatalytic activity of AC-supported Fe-TNTs was related to a synergistic effect of AC adsorption and Fe-TNT photocatalytic ozonation.

Titania nano-coated quartz wool for the photocatalytic mineralisation of emerging organic contaminants.

PubMed

Saracino, M; Pretali, L; Capobianco, M L; Emmi, S S; Navacchia, M L; Bezzi, F; Mingazzini, C; Burresi, E; Zanelli, A

2018-01-01

Many emerging contaminants pass through conventional wastewater treatment plants, contaminating surface and drinking water. The implementation of advanced oxidation processes in existing plants for emerging contaminant remediation is one of the challenges for the enhancement of water quality in the industrialised countries. This paper reports on the production of a TiO 2 nano-layer on quartz wool in a relevant amount, its characterisation by X-ray diffraction and scanning electron microscopy, and its use as a photocatalyst under ultraviolet radiation for the simultaneous mineralisation of five emerging organic contaminants (benzophenone-3, benzophenone-4, carbamazepine, diclofenac, and triton X-100) dissolved in deionised water and tap water. This treatment was compared with direct ultraviolet photolysis and with photocatalytic degradation on commercial TiO 2 micropearls. The disappearance of every pollutant was measured by high performance liquid chromatography and mineralisation was assessed by the determination of total organic carbon. After 4 hours of treatment with the TiO 2 nano-coated quartz wool, the mineralisation exceeds 90% in deionised water and is about 70% in tap water. This catalyst was reused for seven cycles without significant efficiency loss.

Pilot scale thin film plate reactors for the photocatalytic treatment of sugar refinery wastewater.

PubMed

Saran, S; Kamalraj, G; Arunkumar, P; Devipriya, S P

2016-09-01

Pilot scale thin film plate reactors (TFPR) were fabricated to study the solar photocatalytic treatment of wastewater obtained from the secondary treatment plant of a sugar refinery. Silver-impregnated titanium dioxide (TiO2) was prepared by a facile chemical reduction method, characterized, and immobilized onto the surface of ceramic tiles used in the pilot scale reactors. On 8 h of solar irradiation, percentage reduction of chemical oxygen demand (COD) of the wastewater by Ag/TiO2, pure TiO2, and control (without catalyst) TFPR was about 95, 86, and 22 % respectively. The effects of operational parameters such as, flow rate, pH, and addition of hydrogen peroxide (H2O2) were optimized as they influence the rate of COD reduction. Under 3 h of solar irradiation, 99 % COD reduction was observed at an optimum flow rate of 15 L h(-1), initial pH of 2, and addition of 5 mM of H2O2. The results show that Ag/TiO2 TFPR could be effectively used for the tertiary treatment of sugar refinery effluent using sunlight as the energy source. The treated water could be reused for industrial purposes, thus reducing the water footprint of the industry. Graphical Abstract Sugar refinery effluent treatment by solar photocatalytic TFPR.

Design and evaluation of a compact photocatalytic reactor for water treatment.

PubMed

Kete, Marko; Pliekhova, Olena; Matoh, Lev; Štangar, Urška Lavrenčič

2017-08-15

A compact reactor for photocatalytic oxidation and photocatalytic ozonation water treatment was developed and evaluated by using four model pollutants. Additionally, combinations of pollutants were evaluated. Specially produced Al 2 O 3 porous reticulated monolith foams served as TiO 2 carriers, offering a high surface area support. UV lamps were placed in the interior to achieve reduced dimensions of the reactor (12 cm in diameter × 20 cm in height). Despite its small size, the overall photocatalytic cleaning capacity was substantial. It was evaluated by measuring the degradation of LAS + PBIS and RB19 as representatives of surfactants and textile dyes, respectively. These contaminants are commonly found in household grey wastewater with phenol as a trace contaminant. Three different commercial photocatalysts and one mixture of photocatalysts (P25, P90, PC500 and P25 + PC500) were introduced in the sol-gel processing and immobilized on foamed Al 2 O 3 monoliths. RB19 and phenol were easily degradable, while LAS and PBIS were more resistant. The experiments were conducted at neutral-acidic pH because alkaline pH negatively influences both photocatalyic ozonation (PCOZ) and photocatalysis. The synergistic effect of PCOZ was generally much more expressed in mineralization reactions. Total organic carbon TOC half lives were in the range of between 13 and 43 min in the case of individual pollutants in double-deionized water. However, for the mixed pollutants in tap water, the TOC half-life only increased to 53 min with the most efficient catalyst (P90). In comparison to photocatalysis, the PCOZ process is more suitable for treating wastewater with a high loading of organic pollutants due to its higher cleaning capacity. Therefore, PCOZ may prove more effective in industrial applications.

Photocatalytic degradation of acid blue 74 in water using Ag-Ag2O-Zno nanostuctures anchored on graphene oxide

NASA Astrophysics Data System (ADS)

Umukoro, Eseoghene H.; Peleyeju, Moses G.; Ngila, Jane C.; Arotiba, Omotayo A.

2016-01-01

Water pollution due to industrial effluents from industries which utilize dyes in the manufacturing of their products has serious implications on aquatic lives and the general environment. Thus, there is need for the removal of dyes from wastewater before being discharged into the environment. In this study, a nanocomposite consisting of silver, silver oxide (Ag2O), zinc oxide (ZnO) and graphene oxide (GO) was synthesized, characterized and photocatalytically applied in the degradation (and possibly mineralization) of organic pollutants in water treatment process. The Ag-Ag2O-ZnO nanostructure was synthesized by a co-precipitation method and calcined at 400 °C. It was functionalized using 3-aminopropyl triethoxysilane and further anchored on carboxylated graphene oxide via the formation of an amide bond to give the Ag-Ag2O-ZnO/GO nanocomposite. The prepared nanocomposite was characterized by UV-Vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The applicability of Ag-Ag2O-ZnO/GO nanocomposite as a photocatalyst was investigated in the photocatalytic degradation of acid blue 74 dye under visible light irradiation in synthetic wastewater containing the dye. The results indicated that Ag-Ag2O-ZnO/GO nanocomposite has a higher photocatalytic activity (90% removal) compared to Ag-Ag2O-ZnO (85% removal) and ZnO (75% removal) respectively and thus lends itself to application in water treatment, where the removal of organics is very important.

Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.

PubMed

Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

2010-02-01

A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. (c) 2009 Elsevier Ltd. All rights reserved.

Photocatalytic quartz fiber felts with carbon-connected TiO2 nanoparticles for capillarity-driven continuous-flow water treatment

NASA Astrophysics Data System (ADS)

Zhang, Xiaofei; Su, Xiaowen; Gao, Wenqiang; Wang, Fulei; Liu, Zhihe; Zhan, Jie; Liu, Baishan; Wang, Ruosong; Liu, Hong; Sang, Yuanhua

2018-06-01

Immobility of photocatalysts on substrates is a vital factor for the practical application of photocatalysis in polluted water/air treatment. In this study, TiO2 homogenously loaded quartz fiber felt was prepared by assembling of carboxyl-contained organic molecules functionalized TiO2 nanoparticles on the surface of amino group-modified quartz fiber by electrostatic adsorption between them and followed by an anneal process. The immobilization of TiO2 nanoparticles overcomes one main obstacle of the photocatalysts recycling in photocatalysis application. In addition, a plasma treatment endowed the hybrid photocatalyst a high hydrophilic property. Due to the homogeneous distribution of TiO2, charge carriers' separation by carbon, and full contact between water and the photocatalyst derived from the high hydrophilia, the TiO2/quartz fiber felt shows excellent photocatalytic performance. Based on the stable loading and the capillarity effect of the contacted fibers photocatalyst, a demo capillarity-driven continuous-flow water treatment photocatalysis reactor was designed and built up. The TiO2 nanoparticle/quartz fiber hybrid photocatalyst can disposal organic contaminants in actual industrial waste water from a dyeing factory in the continuous-flow reactor. The chemical oxygen demand (COD) of the industrial waste water was decreased from 104 to 45 mg/L, overcoming the problem of deep water treatment which is difficult to solve by other methods. This study provides a new photocatalyst and reaction mode for the continuous-flow photocatalysis application.

New Photocatalysis for Effective Degradation of Organic Pollutants in Water

NASA Astrophysics Data System (ADS)

Zarei Chaleshtori, M.; Saupe, G. B.; Masoud, S.

2009-12-01

The presence of harmful compounds in water supplies and in the discharge of wastewater from chemical industries, power plants, and agricultural sources is a topic of global concern. The processes and technologies available at the present time for the treatment of polluted water are varied that include traditional water treatment processes such as biological, thermal and chemical treatment. All these water treatment processes, have limitations of their own and none is cost effective. Advanced oxidation processes have been proposed as an alternative for the treatment of this kind of wastewater. Heterogeneous photocatalysis has recently emerged as an efficient method for purifying water. TiO2 has generally been demonstrated to be the most active semiconductor material for decontamination water. One significant factor is the cost of separation TiO2, which is generally a powder having a very small particle size from the water after treatment by either sedimentation or ultrafiltration. The new photocatalyst, HTiNbO5, has been tested to determine whether its photocatalytic efficiency is good enough for use in photocatalytic water purification since it has high surface area and relatively large particle size. The larger particle sizes of the porous materials facilitate catalyst removal from a solution, after purification has taken place. It can be separated from water easily than TiO2, a significant technical improvement that might eliminate the tedious final filtration necessary with a slurry. These materials are characterized and tested as water decontamination photocatalysts. The new catalyst exhibited excellent catalytic activity, but with a strong pH dependence on the photo efficiency. These results suggest that elimination of the ion exchange character of the catalyst may greatly improve its performance at various pHs. This new research proposes to study the effects of a topotactic dehydration reaction on these new porous material catalysts.

Study of the generated genetic polymorphisms during the photocatalytic elimination of Klebsiella pneumoniae in water.

PubMed

Venieri, Danae; Fraggedaki, Antonia; Binas, Vassilios; Zachopoulos, Apostolos; Kiriakidis, George; Mantzavinos, Dionissios

2015-03-01

Klebsiella pneumoniae is considered to be an emerging pathogen persisting under extreme environmentally stressed conditions. The aim of the present study is the investigation of inactivation rates of this pathogen in water by means of heterogeneous photocatalytic treatment under solar irradiation and the induced genetic variance applying RAPD-PCR as a molecular typing tool. Novel Mn- and Co-doped TiO2 catalysts were assessed in terms of their disinfection efficiency. The reference strain of K. pneumoniae proved to be readily inactivated, since disinfection occurred rapidly (i.e. after only 10 min of treatment) and low levels of bacterial regrowth were recorded in the dark and under natural sunlight. Binary doped titania exhibited the best photocatalytic activity, verifying the synergistic effect induced by composite dopants. Applying RAPD analysis to viable cells after treatment we concluded that increasing the treatment time led to considerable alteration of RAPD profiles and the homology coefficient ranged almost between 35 and 60%. RAPD-PCR proved to be a useful typing molecular tool that under standardized conditions exhibits highly reproducible results. Genetic variation among isolates increased in relation to the period of treatment and prolonged irradiation in each case affected the overall alteration in band patterns. RAPD patterns were highly diverse between treated and untreated isolates when disinfection was performed with the Co-doped titania. The broad spectrum of genetic variance and generated polymorphisms has the potential to increase the already significant virulence of the species.

Structure-reactivity relationship of naphthenic acids in the photocatalytic degradation process.

PubMed

de Oliveira Livera, Diogo; Leshuk, Tim; Peru, Kerry M; Headley, John V; Gu, Frank

2018-06-01

Bitumen extraction in Canada's oil sands generates oil sands process-affected water (OSPW) as a toxic by-product. Naphthenic acids (NAs) contribute to the water's toxicity, and treatment methods may need to be implemented to enable safe discharge. Heterogeneous photocatalysis is a promising advanced oxidation process (AOP) for OSPW remediation, however, its successful implementation requires understanding of the complicated relationship between structure and reactivity of NAs. This work aimed to study the effect of various structural properties of model compounds on the photocatalytic degradation kinetics via high resolution mass spectrometry (HRMS), including diamondoid structures, heteroatomic species, and degree of unsaturation. The rate of photocatalytic treatment increased significantly with greater structural complexity, namely with carbon number, aromaticity and degree of cyclicity, properties that render particular NAs recalcitrant to biodegradation. It is hypothesized that a superoxide radical-mediated pathway explains these observations and offers additional benefits over traditional hydroxyl radical-based AOPs. Detailed structure-reactivity investigations of NAs in photocatalysis have not previously been undertaken, and the results described herein illustrate the potential benefit of combining photocatalysis and biodegradation as a complete OSPW remediation technology. Copyright © 2018 Elsevier Ltd. All rights reserved.

Temperature dependence and P/Ti ratio in phosphoric acid treatment of titanium dioxide and powder properties.

PubMed

Onoda, H; Matsukura, A

2015-02-01

Titanium dioxide has photocatalytic activity and is used as a white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, titanium dioxide was shaken with phosphoric acid to synthesize a white pigment for cosmetics. Titanium dioxide was treated with 0.1 mol/L of phosphoric acid at various P/Ti molar ratios, and then shaken in hot water for 1 h. The chemical composition, powder properties, photocatalytic activity, colour phase, and smoothness of the obtained powder were studied. The obtained materials indicated XRD peaks of titanium dioxide, however the peaks diminished subsequent to phosphoric acid treatment. The samples included small particles with sub-micrometer size. The photocatalytic activity of the obtained powders decreased, decomposing less sebum on the skin. Samples prepared at high P/Ti ratio with high shaking temperature indicated low whiteness in in L*a*b* colour space. The shaking and heating temperature and P/Ti ratio had influence on the smoothness of the obtained materials. Phosphoric acid treatment of titanium dioxide is an effective method to inhibit photocatalytic activity for a white pigment. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Nanosized TiO[subscript 2] for Photocatalytic Water Splitting Studied by Oxygen Sensor and Data Logger

ERIC Educational Resources Information Center

Zhang, Ruinan; Liu, Song; Yuan, Hongyan; Xiao, Dan; Choi, Martin M. F.

2012-01-01

Photocatalytic water splitting by semiconductor photocatalysts has attracted considerable attention in the past few decades. In this experiment, nanosized titanium dioxide (nano-TiO[subscript 2]) particles are used to photocatalytically split water, which is then monitored by an oxygen sensor. Sacrificial reagents such as organics (EDTA) and metal…

Preparation and photocatalytic activity of nonmetal Co-doped titanium dioxide photocatalyst

NASA Astrophysics Data System (ADS)

Sun, Xiaogang; Xing, Jun; Qiu, Jingping

2016-06-01

A series of boron and sulfur co-doped titanium dioxide (TiO2) photocatalysts were prepared by a sol-gel method using boric acid, thiourea and tetrabutyl titanate [Ti(OC4H9)4] as precursors. The photoabsorbance of as-prepared photocatalysts was measured by UV-Vis diffuse reflectance spectroscopy (DRS), and its microstructure was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and N2 adsorption-desorption measurements. The prepared photocatalysts consisted of the anatase phase mainly in the form of spherical particles. The photocatalytic performance was studied by photodegradation of methyl blue (MB) in water under UV and visible light irradiation. The calcination temperature and the codoping content influenced the photoactivity. The synergistic effect of boron and sulfur co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of codoped TiO2 was also confirmed, the photocatalytic activity of TiO2 remained above 91% of that of the fresh sample after being used four times. It was shown that the co-doped TiO2 could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants.

On-line monitoring of the photocatalytic degradation of 2,4-D and dicamba using a solid-phase extraction-multisyringe flow injection system.

PubMed

Chávez-Moreno, Carmín; Ferrer, Laura; Hinojosa-Reyes, Laura; Hernández-Ramírez, Aracely; Cerdà, Víctor; Guzmán-Mar, Jorge

2013-11-15

A fully automated on-line system for monitoring the photocatalytic degradation of herbicides was developed using multisyringe flow injection analysis (MSFIA) coupled to a solid phase extraction (SPE) unit with UV detection. The calibration curves were linear in the concentration range of 100-1000 μg L(-1) for 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 500-3000 μg L(-1) for 2,4-dichlorophenoxyacetic acid (2,4-D), while the detection limits were 30 and 135 μg L(-1) for dicamba and 2,4-D, respectively. The monitoring of the photocatalytic degradation (TiO2 anatase/UV 254 nm) of these two herbicides was performed by MSFIA-SPE system using a small sample volume (2 mL) in a fully automated approach. The degradation was assessed in ultrapure and drinking water with initial concentrations of 1000 and 2000 μg L(-1) for dicamba and 2,4-D, respectively. Degradation percentages of approximately 85% were obtained for both herbicides in ultrapure water after 45 min of photocatalytic treatment. A similar degradation efficiency in drinking water was observed for 2,4-D, whereas dicamba exhibited a lower degradation percentage (75%), which could be attributed to the presence of inorganic species in this kind of water. Copyright © 2013 Elsevier Ltd. All rights reserved.

One-pot template-free synthesis of porous CdMoO4 microspheres and their enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Madhusudan, Puttaswamy; Zhang, Jinfeng; Yu, Jiaguo; Cheng, Bei; Xu, Difa; Zhang, Jun

2016-11-01

The optical and catalytic performances of materials strongly depend on their size, morphology, dimensionality and structure. Herein, we demonstrate a facile one-pot template free synthesis of hierarchical CdMoO4 porous microspheres via a simple low temperature oil bath method. The photoactivity of the as-prepared samples was evaluated by photocatalytic decolorization of Methyl Orange (MO) and Methylene Blue (MB) mixed dye aqueous solutions at ambient temperature under full solar spectrum. The results indicated that the concentration of ammonium molybdate and reaction time greatly influence the diameter, average crystallite size, specific surface area, pore structure and photocatalytic activity of the prepared samples. Especially, under the suitable conditions the prepared hierarchical CdMoO porous microspheres exhibited enhanced photocatalytic activity and high stability. Furthermore, it is found that the photocatalytic activity and formation rate of hydroxyl radicals greatly depend on the particle sizes and morphology of as-prepared samples. This work not only demonstrates a simple way to fabricate the hierarchical CdMoO4 porous microspheres but also shows a possibility for utilization of CdMoO4 porous microspheres for the photocatalytic treatment of waste water pollutants.

Photocatalytic Nanocomposites for the Protection of European Architectural Heritage.

PubMed

Gherardi, Francesca; Roveri, Marco; Goidanich, Sara; Toniolo, Lucia

2018-01-03

In the field of stone protection, the introduction of inorganic nanoparticles, such as TiO₂, ZnO, and Ag in polymeric blends can enhance the protective action of pristine treatments, as well as confer additional properties (photocatalytic, antifouling, and antibacterial). In the framework of the "Nano-Cathedral" European project, nanostructured photocatalytic protective treatments were formulated by using different TiO₂ nanoparticles, solvents, and silane/siloxane systems in the blends. The results about the characterization and application of two promising nano-TiO₂ based products applied on Apuan marble and Ajarte limestone are here reported, aiming at investigating the complex system "treatment/stone-substrate". The nanocomposites show better performances when compared to a commercial reference siloxane based protective treatment, resulting in different performances once applied on different carbonatic substrates, with very low and high open porosity, confirming the necessity of correlating precisely the characteristics of the stone material to those of the protective formulations. In particular, the TiO₂ photocatalytic behavior is strictly linked to the amount of available nanoparticles and to the active surface area. The alkyl silane oligomers of the water-based formulation have a good penetration into the microstructure of Ajarte limestone, whereas the solvent-based and small size monomeric formulation shows better results for Apuan marble, granting a good coverage of the pores. The encouraging results obtained so far in lab will be confirmed by monitoring tests aiming at assessing the effectiveness of the treatments applied in pilot sites of historical Gothic Cathedrals.

Photocatalytic Nanocomposites for the Protection of European Architectural Heritage

PubMed Central

Roveri, Marco; Goidanich, Sara; Toniolo, Lucia

2018-01-01

In the field of stone protection, the introduction of inorganic nanoparticles, such as TiO2, ZnO, and Ag in polymeric blends can enhance the protective action of pristine treatments, as well as confer additional properties (photocatalytic, antifouling, and antibacterial). In the framework of the “Nano-Cathedral” European project, nanostructured photocatalytic protective treatments were formulated by using different TiO2 nanoparticles, solvents, and silane/siloxane systems in the blends. The results about the characterization and application of two promising nano-TiO2 based products applied on Apuan marble and Ajarte limestone are here reported, aiming at investigating the complex system “treatment/stone-substrate”. The nanocomposites show better performances when compared to a commercial reference siloxane based protective treatment, resulting in different performances once applied on different carbonatic substrates, with very low and high open porosity, confirming the necessity of correlating precisely the characteristics of the stone material to those of the protective formulations. In particular, the TiO2 photocatalytic behavior is strictly linked to the amount of available nanoparticles and to the active surface area. The alkyl silane oligomers of the water-based formulation have a good penetration into the microstructure of Ajarte limestone, whereas the solvent-based and small size monomeric formulation shows better results for Apuan marble, granting a good coverage of the pores. The encouraging results obtained so far in lab will be confirmed by monitoring tests aiming at assessing the effectiveness of the treatments applied in pilot sites of historical Gothic Cathedrals. PMID:29301338

Solar energy harvesting by magnetic-semiconductor nanoheterostructure in water treatment technology.

PubMed

Mahmoodi, Vahid; Bastami, Tahereh Rohani; Ahmadpour, Ali

2018-03-01

Photocatalytic degradation of toxic organic pollutants in the wastewater using dispersed semiconductor nanophotocatalysts has a number of advantages such as high activity, cost effectiveness, and utilization of free solar energy. However, it is difficult to recover and recycle nanophotocatalysts since the fine dispersed nanoparticles are easily suspended in waters. Furthermore, a large amount of photocatalysts will lead to color contamination. Thus, it is necessary to prepare photocatalysts with easy separation for the reusable application. To take advantage of high photocatalysis activity and reusability, magnetic photocatalysts with separation function were utilized. In this review, the photocatalytic principle, structure, and application of the magnetic-semiconductor nanoheterostructure photocatalysts under solar light are evaluated. Graphical abstract ᅟ.

Disinfection of iceberg lettuce by titanium dioxide-UV photocatalytic reaction.

PubMed

Kim, Youngbong; Choi, Yoonjung; Kim, Soohyun; Park, Jonghyun; Chung, Myongsoo; Song, Kyung Bin; Hwang, Ingyun; Kwon, Kisung; Park, Jiyong

2009-09-01

Securing the physical quality and microbial safety of fresh foods has been a major focus in the food industry. To improve quality and increase the shelf life of fresh produce, disinfection methods have been developed. Titanium dioxide (TiO2) photocatalytic reactions under UV radiation produce hydroxyl radicals that can be used for disinfection of foodborne pathogenic bacteria. We investigated the effects of TiO2-UV photocatalytic disinfection on the shelf life of iceberg lettuce. Counts of natural microflora (total aerobic bacteria, coliforms, psychrotrophic bacteria, and yeasts and molds) and inoculated pathogenic bacteria (Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Salmonella Typhimurium) on iceberg lettuce were determined after 20-min treatments with TiO2-UV, UV radiation, a sodium hypochlorite (NaOCl) solution, and tap water. TiO2-UV treatment reduced the number of microorganisms by 1.8 to 2.8 log CFU/g compared with reductions of 0.9 to 1.4 and 0.7 to 1.1 log CFU/g obtained with UV radiation and NaOCl treatments, respectively. Treatment with tap water was used as a control and resulted in no reductions. Counts of microflora for iceberg lettuce at 4 and 25 degrees C were determined during a 9-day period. TiO2-UV treatment resulted in 1.2- and 4.3-log increases in the counts of total aerobic bacteria at 4 and 25 degrees C, respectively, compared with 1.3- to 1.6-log and 4.4- to 4.8-log increases due to UV radiation and NaOCl treatments.

Photocatalytic Active Bismuth Fluoride/Oxyfluoride Surface Crystallized 2Bi2O3-B2O3 Glass-Ceramics

NASA Astrophysics Data System (ADS)

Sharma, Sumeet Kumar; Singh, V. P.; Chauhan, Vishal S.; Kushwaha, H. S.; Vaish, Rahul

2018-03-01

The present article deals with 2Bi2O3-B2O3 (BBO) glass whose photocatalytic activity has been enhanced by the method of wet etching using an aqueous solution of hydrofluoric acid (HF). X-ray diffraction of the samples reveals that etching with an aqueous solution of HF leads to the formation of BiF3 and BiO0.1F2.8 phases. Surface morphology obtained from scanning electron microscopy show granular and plate-like morphology on the etched glass samples. Rhodamine 6G (Rh 6G) has been used to investigate the photocatalytic activity of the as-quenched and etched glasses. Enhanced visible light-driven photocatalytic activity was observed in HF etched glass-ceramics compared to the as-quenched BBO glass. Contact angle of the as-quenched glass was 90.2°, which decreases up to 20.02° with an increase in concentration of HF in the etching solution. Enhanced photocatalytic activity and increase in the hydrophilic nature suggests the efficient treatment of water pollutants by using the prepared surface crystallized glass-ceramics.

Ozone-UV-catalysis based advanced oxidation process for wastewater treatment.

PubMed

Tichonovas, Martynas; Krugly, Edvinas; Jankunaite, Dalia; Racys, Viktoras; Martuzevicius, Dainius

2017-07-01

A bench-scale advanced oxidation (AO) reactor was investigated for the degradation of six pollutants (2-naphthol, phenol, oxalic acid, phthalate, methylene blue, and D-glucose) in a model wastewater at with the aim to test opportunities for the further upscale to industrial applications. Six experimental conditions were designed to completely examine the experimental reactor, including photolysis, photocatalysis, ozonation, photolytic ozonation, catalytic ozonation, and photocatalytic ozonation. The stationary catalyst construction was made from commercially available TiO 2 nanopowder by mounting it on a glass support and subsequently characterized for morphology (X-ray diffraction analysis and scanning electron microscopy) as well as durability. The ozone was generated in a dielectrical barrier discharge reactor using air as a source of oxygen. The degradation efficiency was estimated by the decrease in total organic carbon (TOC) concentration as well as toxicity using Daphnia magna, and degradation by-products by ultra-performance liquid chromatography-mass spectrometry. The photocatalytic ozonation was the most effective for the treatment of all model wastewater. The photocatalytic ozonation was most effective against ozonation and photolytic ozonation at tested pH values. A complete toxicity loss was obtained after the treatment using photocatalytic ozonation. The possible degradation pathway of the phthalate by oxidation was suggested based on aromatic ring opening reactions. The catalyst used at this experiment confirmed as a durable for continuous use with almost no loss of activity over time. The design of the reactor was found to be very effective for water treatment using photocatalytic ozonation. Such design has a high potential and can be further upscaled to industrial applications due to the simplicity and versatility of manufacturing and maintenance.

Assessment of the roles of reactive oxygen species in the UV and visible light photocatalytic degradation of cyanotoxins and water taste and odor compounds using C-TiO2.

PubMed

Fotiou, Theodora; Triantis, Theodoros M; Kaloudis, Triantafyllos; O'Shea, Kevin E; Dionysiou, Dionysios D; Hiskia, Anastasia

2016-03-01

Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO2, limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO2 (C-TiO2) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen (1)O2, superoxide radical anion [Formula: see text] ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is [Formula: see text] , with OH and (1)O2 playing minor roles in the degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic Cellulosic Electrospun Fibers for the Degradation of Potent Cyanobacteria Toxin Microcystin-LR

DTIC Science & Technology

2012-01-01

treatment applications using solar light as a renewable source of energy. Introduction The need for low cost and efficient water treatment strategies... photocatalysis with nanoparticles (such as titania, TiO2) show tremendous promise as a simple and energy efficient tech- nology for water purification and...which limits the amount of available sunlight that can be used for photocatalysis . To circumvent this issue, methods have been developed to extend

Removal of humic acid using TiO2 photocatalytic process--fractionation and molecular weight characterisation studies.

PubMed

Liu, Sanly; Lim, May; Fabris, Rolando; Chow, Christopher; Chiang, Ken; Drikas, Mary; Amal, Rose

2008-05-01

The photocatalytic removal of humic acid (HA) using TiO2 under UVA irradiation was examined by monitoring changes in the UV(254) absorbance, dissolved organic carbon (DOC) concentration, apparent molecular weight distribution, and trihalomethane formation potentials (THMFPs) over treatment time. A resin fractionation technique in which the samples were fractionated into four components: very hydrophobic acids (VHA), slightly hydrophobic acids, hydrophilic charged (CHA) and hydrophilic neutral (NEU) was also employed to elucidate the changes in the chemical nature of the HA components during treatment. The UVA/TiO2 process was found to be effective in removing more than 80% DOC and 90% UV(254) absorbance. The THMFPs of samples were decreased to below 20 microg l(-1) after treatments, which demonstrate the potential to meet increasingly stringent regulatory level of trihalomethanes in water. Resin fractionation analysis showed that the VHA fraction was decreased considerably as a result of photocatalytic treatments, forming CHA intermediates which were further degraded with increased irradiation time. The NEU fraction, which comprised of non-UV-absorbing low molecular weight compounds, was found to be the most persistent component.

Bibliography of Work on the Heterogeneous Photocatalytic Removal of Hazardous Compounds from Water and Air--Update Number 4 to October 2001

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blake, D.

2001-11-19

This report is the fifth in a series of bibliographies of work on the photocatalytic oxidation of organic or inorganic compounds in air or water and on the photocatalytic reduction of inorganic compounds in water. This search contains information extracted from 1149 new references to papers, books, and reports from searches conducted between October 1996 and April 2001.

Removal of toluene from water by photocatalytic oxidation with activated carbon supported Fe(3+)-doped TiO2 nanotubes.

PubMed

Yuan, Rongfang; Zhou, Beihai; Ma, Li

2014-01-01

In this work, activated carbon (AC)-supported TiO2 containing 1.0% (mass percent) of 1.0 at.% (atomic percent) Fe(3+)-doped TiO2 nanotubes (Fe-TNTs) were successfully synthesized. The catalyst was used to effectively decompose toluene in water under O3/UV conditions, and some properties including the morphology, X-ray photoelectron spectroscopy, X-ray diffraction patterns, specific surface area and UV-visible diffuse reflectance spectroscopy were analyzed. A removal efficiency of 90.7% was achieved in the presence of fresh AC-supported Fe-TNTs calcined at 550 °C, with a pseudo-first-order rate constant of 0.038/min. The removal efficiency of toluene was reduced when the catalysts were repeatedly used, since the amount of adsorption sites of the supporting substrates decreased. However, even after AC-supported catalyst was used four times, the removal efficiency of toluene was still sufficient in water treatment. The enhanced photocatalytic activity of AC-supported Fe-TNTs was related to the synergistic effect of AC adsorption and Fe-TNTs photocatalytic ozonation. The water from a petrochemical company in China was used to obtain the removal efficiency of the pollutants, and the toluene and total organic carbon removal efficiencies were 69.9% and 58.3%, respectively.

Application of concrete surfaces as novel substrate for immobilization of TiO2 nano powder in photocatalytic treatment of phenolic water.

PubMed

Delnavaz, Mohammad; Ayati, Bita; Ganjidoust, Hossein; Sanjabi, Sohrab

2015-01-01

In this study, concrete application as a substrate for TiO2 nano powder immobilization in heterogeneous photocatalytic process was evaluated. TiO2 immobilization on the pervious concrete surface was done by different procedures containing slurry method (SM), cement mixed method (CMM) and different concrete sealer formulations. Irradiation of TiO2 was prepared by UV-A and UV-C lamps. Phenolic wastewater was selected as a pollutant and efficiency of the process was determined in various operation conditions including influent phenol concentration, pH, TiO2 concentration, immobilization method and UV lamp intensity. The removal efficiency of photocatalytic process in 4 h irradiation time and phenol concentration ranges of 25-500 mg/L was more than 80 %. Intermediates were identified by GC/Mass and spectrophotometric analysis. According to the results, photocatalytic reactions followed the pseudo-first-order kinetics and can effectively treate phenol under optimal conditions.

Fabrication of visible light-triggered photocatalytic materials from the coupling of n-type zinc oxide and p-type copper oxide

NASA Astrophysics Data System (ADS)

Gorospe, A. B.; Herrera, M. U.

2017-04-01

Coupling of copper oxide (CuO) and zinc oxide (ZnO) was done by chemical precipitation method. In this method, copper sulfate pentahydrate and zinc sulfate heptahydrate salt precursors were separately dissolved in distilled water; then were mixed together. The copper sulfate-zinc sulfate solution was then combined with a sodium hydroxide solution. The precipitates were collected and washed in distilled water and ethanol several times, then filtered and dried. The dried sample was grounded, and then undergone heat treatment. After heating, the sample was grounded again. Zinc oxide powder and copper oxide powder were also fabricated using chemical precipitation method. X-Ray Diffraction measurements of the coupled CuO/ZnO powder showed the presence of CuO and ZnO in the fabricated sample. Furthermore, other peaks shown by XRD were also identified corresponding to copper, copper (II) oxide, copper sulfate and zinc sulfate. Results of the photocatalytic activity investigation show that the sample exhibited superior photocatalytic degradation of methyl orange under visible light illumination compared to copper oxide powder and zinc oxide powder. This may be attributed to the lower energy gap at the copper oxide-zinc oxide interface, compared to zinc oxide, allowing visible light to trigger its photocatalytic activity.

Nitrogen doped nanocrystalline semiconductor metal oxide: An efficient UV active photocatalyst for the oxidation of an organic dye using slurry Photoreactor.

PubMed

Ramachandran, Saranya; Sivasamy, A; Kumar, B Dinesh

2016-12-01

Water pollution is a cause for serious concern in today's world. A major contributor to water pollution is industrial effluents containing dyes and other organic molecules. Waste water treatment has become a priority area in today's applied scientific research as it seeks to minimize the toxicity of the effluents being discharged and increase the possibility of water recycling. An efficient and eco-friendly way of degrading toxic molecules is to use nano metal-oxide photocatalysts. The present study aims at enhancing the photocatalytic activity of a semiconductor metal oxide by doping it with nitrogen. A sol-gel cum combustion method was employed to synthesize the catalyst. The prepared catalyst was characterized by FT-IR, XRD, UV-DRS, FESEM and AFM techniques. UV-DRS result showed the catalyst to possess band gap energy of 2.97eV, thus making it active in the UV region of the spectrum. Its photocatalytic activity was evaluated by the degradation of a model pollutant-Orange G dye, under UV light irradiation. Preliminary experiments were carried out to study the effects of pH, catalyst dosage and initial dye concentration on the extent of dye degradation. Kinetic studies revealed that the reaction followed pseudo first order kinetics. The effect of electrolytes on catalyst efficiency was also studied. The progress of the reaction was monitored by absorption studies and measuring the reduction in COD. The catalyst thus prepared was seen to have a high photocatalytic efficiency. The use of this catalyst is a promising means of waste water treatment. Copyright © 2016 Elsevier Inc. All rights reserved.

Direct Z-scheme TiO2/CdS hierarchical photocatalyst for enhanced photocatalytic H2-production activity

NASA Astrophysics Data System (ADS)

Meng, Aiyun; Zhu, Bicheng; Zhong, Bo; Zhang, Liuyang; Cheng, Bei

2017-11-01

Photocatalytic H2 evolution, which utilizes solar energy via water splitting, is a promising route to deal with concerns about energy and environment. Herein, a direct Z-scheme TiO2/CdS binary hierarchical photocatalyst was fabricated via a successive ionic layer adsorption and reaction (SILAR) technique, and photocatalytic H2 production was measured afterwards. The as-prepared TiO2/CdS hybrid photocatalyst exhibited noticeably promoted photocatalytic H2-production activity of 51.4 μmol h-1. The enhancement of photocatalytic activity was ascribed to the hierarchical structure, as well as the efficient charge separation and migration from TiO2 nanosheets to CdS nanoparticles (NPs) at their tight contact interfaces. Moreover, the direct Z-scheme photocatalytic reaction mechanism was demonstrated to elucidate the improved photocatalytic performance of TiO2/CdS composite photocatalyst. The photoluminescence (PL) analysis of hydroxyl radicals were conducted to provide clues for the direct Z-scheme mechanism. This work provides a facile route for the construction of redox mediator-free Z-scheme photocatalytic system for photocatalytic water splitting.

Competitive removal of pharmaceuticals from environmental waters by adsorption and photocatalytic degradation.

PubMed

Rioja, N; Benguria, P; Peñas, F J; Zorita, S

2014-10-01

This work explores the competitive removal of pharmaceuticals from synthetic and environmental waters by combined adsorption-photolysis treatment. Five drugs usually present in waterways have been used as target compounds, some are pseudo-persistent pollutants (carbamazepine, clofibric acid, and sulfamethoxazole) and others are largely consumed (diclofenac and ibuprofen). The effect of the light source on adsorption of drugs onto activated carbons followed by photolysis with TiO2 was assessed, being UV-C light the most effective for drug removal in both deionized water and river water. Different composites prepared from titania nanoparticles and powdered activated carbons were tested in several combined adsorption-photocatalysis assays. The composites prepared by calcination at 400 °C exhibited much better performance than those synthesized at 500 °C, being the C400 composite the most effective one. Furthermore, some synthetic waters containing dissolved species and environmental waters were used to investigate the effect of the aqueous matrix on each drug removal. In general, photocatalyst deactivation was found in synthetic and environmental waters. This was particularly evident in the experiments performed with bicarbonate ions as well as with wastewater effluent. In contrast, tests conducted in seawater showed adsorption and photocatalytic degradation yields comparable to those obtained in deionized water. Considering the peculiarities of substrate competition in each aqueous matrix, the combined adsorption-photolysis treatment generally increased the overall elimination of drugs in water.

Solar-Enhanced Advanced Oxidation Processes for Water Treatment: Simultaneous Removal of Pathogens and Chemical Pollutants.

PubMed

Tsydenova, Oyuna; Batoev, Valeriy; Batoeva, Agniya

2015-08-14

The review explores the feasibility of simultaneous removal of pathogens and chemical pollutants by solar-enhanced advanced oxidation processes (AOPs). The AOPs are based on in-situ generation of reactive oxygen species (ROS), most notably hydroxyl radicals •OH, that are capable of destroying both pollutant molecules and pathogen cells. The review presents evidence of simultaneous removal of pathogens and chemical pollutants by photocatalytic processes, namely TiO2 photocatalysis and photo-Fenton. Complex water matrices with high loads of pathogens and chemical pollutants negatively affect the efficiency of disinfection and pollutant removal. This is due to competition between chemical substances and pathogens for generated ROS. Other possible negative effects include light screening, competitive photon absorption, adsorption on the catalyst surface (thereby inhibiting its photocatalytic activity), etc. Besides, some matrix components may serve as nutrients for pathogens, thus hindering the disinfection process. Each type of water/wastewater would require a tailor-made approach and the variables that were shown to influence the processes-catalyst/oxidant concentrations, incident radiation flux, and pH-need to be adjusted in order to achieve the required degree of pollutant and pathogen removal. Overall, the solar-enhanced AOPs hold promise as an environmentally-friendly way to substitute or supplement conventional water/wastewater treatment, particularly in areas without access to centralized drinking water or sewage/wastewater treatment facilities.

Solar-Enhanced Advanced Oxidation Processes for Water Treatment: Simultaneous Removal of Pathogens and Chemical Pollutants

PubMed Central

Tsydenova, Oyuna; Batoev, Valeriy; Batoeva, Agniya

2015-01-01

The review explores the feasibility of simultaneous removal of pathogens and chemical pollutants by solar-enhanced advanced oxidation processes (AOPs). The AOPs are based on in-situ generation of reactive oxygen species (ROS), most notably hydroxyl radicals •OH, that are capable of destroying both pollutant molecules and pathogen cells. The review presents evidence of simultaneous removal of pathogens and chemical pollutants by photocatalytic processes, namely TiO2 photocatalysis and photo-Fenton. Complex water matrices with high loads of pathogens and chemical pollutants negatively affect the efficiency of disinfection and pollutant removal. This is due to competition between chemical substances and pathogens for generated ROS. Other possible negative effects include light screening, competitive photon absorption, adsorption on the catalyst surface (thereby inhibiting its photocatalytic activity), etc. Besides, some matrix components may serve as nutrients for pathogens, thus hindering the disinfection process. Each type of water/wastewater would require a tailor-made approach and the variables that were shown to influence the processes—catalyst/oxidant concentrations, incident radiation flux, and pH—need to be adjusted in order to achieve the required degree of pollutant and pathogen removal. Overall, the solar-enhanced AOPs hold promise as an environmentally-friendly way to substitute or supplement conventional water/wastewater treatment, particularly in areas without access to centralized drinking water or sewage/wastewater treatment facilities. PMID:26287222

Photocatalytic self-cleaning transparent 2Bi2O3-B2O3 glass ceramics

NASA Astrophysics Data System (ADS)

Sharma, Sumeet Kumar; Singh, V. P.; Chauhan, Vishal S.; Kushwaha, H. S.; Vaish, Rahul

2017-09-01

Photocatalytic response of as-quenched and heat-treated 2Bi2O3-B2O3 glasses was studied. X ray diffraction reveals that the controlled heat treatment of glasses at 380 °C for 1 h, 2 h, and 3 h shows the formation of Bi4B2O9 crystals embedded in 2Bi2O3-B2O3 the host glass matrix. Scanning electron microscopic images reveal the presence of nanocrystallization in as-quenched glass. Significant photocatalytic activities were observed in as-quenched transparent glass. Photocatalytic activities were studied using the degradation of Resazurin as well as pharmaceutical 17 β-Estradiol under UV irradiation. Measurement of contact angle shows enhanced hydrophilicity with the increase in crystallization of the samples. Further, for as quenched 2Bi2O3-B2O3 glass ceramic, under UV irradiation, the water contact angle decreased from 92.7° to 39.5° and the sample surface transformed from hydrophobic to hydrophilic. Effective photocatalytic performance along with photoinduced hydrophilicity promotes 2Bi2O3-B2O3 glass ceramics in self-cleaning applications.

In situ one-step hydrothermal synthesis of oxygen-containing groups-modified g-C3N4 for the improved photocatalytic H2-evolution performance

NASA Astrophysics Data System (ADS)

Wu, Xinhe; Chen, Fengyun; Wang, Xuefei; Yu, Huogen

2018-01-01

Surface modification of g-C3N4 is one of the most effective strategies to boost its photocatalytic H2-evolution performance via promoting the interfacial catalytic reactions. In this study, an in situ one-step hydrothermal method was developed to prepare the oxygen-containing groups-modified g-C3N4 (OG/g-C3N4) by a facile and green hydrothermal treatment of bulk g-C3N4 in pure water without any additives. It was found that the hydrothermal treatment (180 °C) not only could greatly increase the specific surface area (from 2.3 to 69.8 m2 g-1), but also caused the formation of oxygen-containing groups (sbnd OH and Cdbnd O) on the OG/g-C3N4 surface, via the interlayer delamination and intralayer depolymerization of bulk g-C3N4. Photocatalytic experimental results indicated that after hydrothermal treatment, the resultant OG/g-C3N4 samples showed an obviously improved H2-evolution performance. Especially, when the hydrothermal time was 6 h, the resultant OG/g-C3N4(6 h) exhibited the highest photocatalytic activity, which was clearly higher than that of the bulk g-C3N4 by a factor of ca. 7. In addition to the higher specific surface area, the enhanced H2-evolution rate of OG/g-C3N4 photocatalysts can be mainly attributed to the formation of oxygen-containing groups, which possibly works as the effective H2-evolution active sites. Considering the facie and green synthesis method, the present work may provide a new insight for the development of highly efficient photocatalytic materials.

Minimization of methabenzthiazuron residues in leaching water using amended soils and photocatalytic treatment with TiO2 and ZnO.

PubMed

Fenoll, José; Flores, Pilar; Hellín, Pilar; Hernández, Joaquín; Navarro, Simon

2014-04-01

In the present work, potential groundwater pollution by methabenzthiazuron (MTBU) and the effect of three different amendments (composted sheep manure, composted pine bark and spent coffee grounds) on its mobility were investigated under laboratory conditions. The efficiency of ZnO and TiO2 suspensions in the photocatalytic degradation of MTBU in leaching water was also investigated. The relative and cumulative breakthrough curves were obtained from disturbed soil columns. The presence and/or addition of organic matter drastically reduced the movement of the herbicide. On other hand, photocatalytic experiments showed that the addition of ZnO and TiO2 strongly enhances the degradation rate of this herbicide compared with the results of photolytic experiments under artificial light. ZnO appeared to be more effective in MTBU oxidation than TiO2. The results obtained point to the interest of using organic wastes and heterogeneous photocatalysis for reducing the pollution of groundwater by pesticide drainage. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Preparation of graphene-ZrO2 nanocomposites by heat treatment and photocatalytic degradation of organic dyes.

PubMed

Cho, Bum Hwi; Ko, Weon Bae

2013-11-01

ZrO2 nanoparticles were synthesized by combining a solution containing zinconyl chloride in distilled water with a NH4OH solution under microwave irradiation. Graphene and ZrO2 nanocomposites were synthesized in an electric furnace at 700 degrees C for 2 hours. The heated graphene-ZrO2 nanocomposites were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In addition, UV-vis spectrophotometry was used to evaluate the heated graphene-ZrO2 nanocomposites as a catalyst in the photocatalytic degradation of organic dyes. The photocatalytic effect of the heated graphene-ZrO2 nanocomposites was compared with that of unheated graphene nanoparticles, heated graphene nanoparticles, and unheated graphene-ZrO2 nanocomposites in organic dyes (methylene blue, methyl orange, and rhodamine B) under ultraviolet light at 254 nm.

Disinfection of Spacecraft Potable Water Systems by Photocatalytic Oxidation Using UV-A Light Emitting Diodes

NASA Technical Reports Server (NTRS)

Birmele, Michele N.; O'Neal, Jeremy A.; Roberts, Michael S.

2011-01-01

Ultraviolet (UV) light has long been used in terrestrial water treatment systems for photodisinfection and the removal of organic compounds by several processes including photoadsorption, photolysis, and photocatalytic oxidation/reduction. Despite its effectiveness for water treatment, UV has not been explored for spacecraft applications because of concerns about the safety and reliability of mercury-containing UV lamps. However, recent advances in ultraviolet light emitting diodes (UV LEDs) have enabled the utilization of nanomaterials that possess the appropriate optical properties for the manufacture of LEDs capable of producing monochromatic light at germicidal wavelengths. This report describes the testing of a commercial-off-the-shelf, high power Nichia UV-A LED (250mW A365nnJ for the excitation of titanium dioxide as a point-of-use (POD) disinfection device in a potable water system. The combination of an immobilized, high surface area photocatalyst with a UV-A LED is promising for potable water system disinfection since toxic chemicals and resupply requirements are reduced. No additional consumables like chemical biocides, absorption columns, or filters are required to disinfect and/or remove potentially toxic disinfectants from the potable water prior to use. Experiments were conducted in a static test stand consisting of a polypropylene microtiter plate containing 3mm glass balls coated with titanium dioxide. Wells filled with water were exposed to ultraviolet light from an actively-cooled UV-A LED positioned above each well and inoculated with six individual challenge microorganisms recovered from the International Space Station (ISS): Burkholderia cepacia, Cupriavidus metallidurans, Methylobacterium fujisawaense, Pseudomonas aeruginosa, Sphingomonas paucimobilis and Wautersia basilensis. Exposure to the Nichia UV-A LED with photocatalytic oxidation resulted in a complete (>7-log) reduction of each challenge bacteria population in <180 minutes of contact time. With continued advances in the design and manufacture of UV-A LEDs and semi-conducting photocatalysts, LED activated photochemical process technology promises to extend its application to spacecraft environmental systems.

Coaxial nanofibers containing TiO2 in the shell for water treatment applications

NASA Astrophysics Data System (ADS)

Kizildag, N.; Geltmeyer, J.; Ucar, N.; De Buysser, K.; De Clerck, K.

2017-10-01

In recent years, the basic electrospinning setup has undergone many modifications carried out to enhance the quality and improve the functionality of the resulting nanofibers. Being one of these modifications, coaxial electrospinning has attracted great attention. It enables to use different materials in nanofiber production and produce multi-layered and functional nanofibers in one step. In this study, TiO2 has been added to the shell layer of coaxial nanofibers to develop functional nanofibers which may be used in water treatment applications. The coaxial nanofibers containing TiO2 in the shell layer are compared to uniaxial nanofibers containing TiO2 in bulk fiber structure, regarding their morphology and photocatalytic activity. Uniform uniaxial and coaxial nanofibers with TiO2 were obtained. The average nanofiber diameter of coaxial nanofibers were higher. Coaxial nanofibers, which contained lower amount of TiO2, displayed similar performance to uniaxial nanofibers with TiO2 in terms of photocatalytic degradation ability against isoproturon.

Charge transfer between biogenic jarosite derived Fe3+and TiO2 enhances visible light photocatalytic activity of TiO2.

PubMed

Chowdhury, Mahabubur; Shoko, Sipiwe; Cummings, Fransciuos; Fester, Veruscha; Ojumu, Tunde Victor

2017-04-01

In this work, we have shown that mining waste derived Fe 3+ can be used to enhance the photocatalytic activity of TiO 2 . This will allow us to harness a waste product from the mines, and utilize it to enhance TiO 2 photocatalytic waste water treatment efficiency. An organic linker mediated route was utilized to create a composite of TiO 2 and biogenic jarosite. Evidence of FeOTi bonding in the TiO 2 /jarosite composite was apparent from the FTIR, EFTEM, EELS and ELNEFS analysis. The as prepared material showed enhanced photocatalytic activity compared to pristine TiO 2 , biogenic jarosite and mechanically mixed sample of jarosite and TiO 2 under both simulated and natural solar irradiation. The prepared material can reduce the electrical energy consumption by 4 times compared to pristine P25 for degradation of organic pollutant in water. The material also showed good recyclability. Results obtained from sedimentation experiments showed that the larger sized jarosite material provided the surface to TiO 2 nanoparticles, which increases the settling rate of the materials. This allowed simple and efficient recovery of the catalyst from the reaction system after completion of photocatalysis. Enhanced photocatalytic activity of the composite material was due to effective charge transfer between TiO 2 and jarosite derived Fe 3+ as was shown from the EELS and ELNEFS. Generation of OH was supported by photoluminesence (PL) experiments. Copyright © 2016. Published by Elsevier B.V.

Facile One-Step Sonochemical Synthesis and Photocatalytic Properties of Graphene/Ag3PO4 Quantum Dots Composites

NASA Astrophysics Data System (ADS)

Reheman, Abulajiang; Tursun, Yalkunjan; Dilinuer, Talifu; Halidan, Maimaiti; Kadeer, Kuerbangnisha; Abulizi, Abulikemu

2018-03-01

In this study, a novel graphene/Ag3PO4 quantum dot (rGO/Ag3PO4 QD) composite was successfully synthesized via a facile one-step photo-ultrasonic-assisted reduction method for the first time. The composites were analyzed by various techniques. According to the obtained results, Ag3PO4 QDs with a size of 1-4 nm were uniformly dispersed on rGO nanosheets to form rGO/Ag3PO4 QD composites. The photocatalytic activity of rGO/Ag3PO4 QD composites was evaluated by the decomposition of methylene blue (MB). Meanwhile, effects of the surfactant dosage and the amount of rGO on the photocatalytic activity were also investigated. It was found that rGO/Ag3PO4 QDs (WrGO:Wcomposite = 2.3%) composite exhibited better photocatalytic activity and stability with degrading 97.5% of MB within 5 min. The improved photocatalytic activities and stabilities were majorly related to the synergistic effect between Ag3PO4 QDs and rGO with high specific surface area, which gave rise to efficient interfacial transfer of photogenerated electrons and holes on both materials. Moreover, possible formation and photocatalytic mechanisms of rGO/Ag3PO4 QDs were proposed. The obtained rGO/Ag3PO4 QDs photocatalysts would have great potentials in sewage treatment and water splitting.

Facile synthesis of flake-like TiO2/C nano-composites for photocatalytic H2 evolution under visible-light irradiation

NASA Astrophysics Data System (ADS)

Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai

2017-01-01

The production of H2 by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H2 by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO2/C nano-flakes, which was used as an efficient visible-light photocatalyst for H2 evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO2 nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m2 g-1 and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H2 production rate of 57.2 μmol h-1 under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO2 and carbon in this hybrid catalyst. This work highlights the potential of TiO2/C nano-flakes in the field of photocatalytic H2 evolution under visible-light irradiation.

Chemically stable and reusable nano zero-valent iron/graphite-like carbon nitride nanohybrid for efficient photocatalytic treatment of Cr(VI) and rhodamine B under visible light

NASA Astrophysics Data System (ADS)

Liang, Zhiyu; Wen, Qingjuan; Wang, Xiu; Zhang, Fuwei; Yu, Yan

2016-11-01

Graphite-like carbon nitride (g-C3N4) displays strong potential applications in visible-light photocatalytic for water treatment, but its applications are greatly restricted by high recombination probability of photo-generated electron-hole pairs, as well as a weak reduction ability toward the heavy metals. In this work, we reported the synthesis of nZVI-g-C3N4 nano-hybrid with highly efficiency toward the photodegradation of RhB and Cr(VI) under the visible light irradiation. The nZVI nanoparticles can well be immobilized and dispersed on the surface of g-C3N4 nanosheets by a facile borohydride-reduction method. As-synthesized nZVI-g-C3N4 has an improved photocatalytic activity much better than that of the pure g-C3N4, wherein over 92.9% of Cr(VI) and 99.9% of RhB can be removed by using nZVI-g-C3N4. The nZVI particles not only contributes to the reduction and immobilization of Cr(VI), but also accelerates the photocatalytic degradation efficiency of RhB due to a lower recombination rate of photoexcited holes and electrons. Moreover, nZVI-g-C3N4 preserves superior photodegradation efficiency after five experimental cycles. It can be attributed that nZVI-g-C3N4 photocatalyst is chemically stable, and part of nZVI can be recovered by g-C3N4. We believe that, the composite of nZVI-g-C3N4 reported here could provide guidance for the design of efficient and reusable materials to remove both the organic compounds and heavy metal ions from waste waters.

Surface engineering of graphitic carbon nitride polymers with cocatalysts for photocatalytic overall water splitting

PubMed Central

Zhang, Guigang; Lan, Zhi-An

2017-01-01

Graphitic carbon nitride based polymers, being metal-free, accessible, environmentally benign and sustainable, have been widely investigated for artificial photosynthesis in recent years for the photocatalytic splitting of water to produce hydrogen fuel. However, the photocatalytic stoichiometric splitting of pure water into H2 and O2 with a molecular ratio of 2 : 1 is far from easy, and is usually hindered by the huge activation energy barrier and sluggish surface redox reaction kinetics. Herein, we provide a concise overview of cocatalyst modified graphitic carbon nitride based photocatalysts, with our main focus on the modulation of the water splitting redox reaction kinetics. We believe that a timely and concise review on this promising but challenging research topic will certainly be beneficial for general readers and researchers in order to better understand the property–activity relationship towards overall water splitting, which could also trigger the development of new organic architectures for photocatalytic overall water splitting through the rational control of surface chemistry. PMID:28959425

One-step construction of heterostructured metal-organics@Bi2O3 with improved photoinduced charge transfer and enhanced activity in photocatalytic degradation of sulfamethoxazole under solar light irradiation.

PubMed

Bao, Yueping; Lim, Teik-Thye; Goei, Ronn; Zhong, Ziyi; Wang, Rong; Hu, Xiao

2018-08-01

A facile one-step assembly method was developed for the preparation of metal-organics @Bi 2 O 3 composites for photocatalysis. Two kinds of metal-organics (Ti-bdc and Cu-btc)@Bi 2 O 3 composites were synthesized via the coordination of btc 3- /bdc 2- and metal ions (Ti 4+ /Cu 2+ ) as well as OH on the surface of Bi 2 O 3 . Compared with pure Bi 2 O 3, Ti-bdc@Bi 2 O 3 shows a 1.7 times higher photocatalytic activity in the degradation of sulfamethoxazole (SMX) under a simulated solar irradiation with a cumulative removal of 62% within 60 min. The high photocatalytic activity could be attributed to the high charge separation, enhanced electron transfer as well as the low recombination rate of photo-generated electrons and holes due to the construction of hetero-structures. The stability test showed that Ti-bdc@Bi 2 O 3 is more stable in water than Cu-btc@Bi 2 O 3 . Furthermore, through the radical-trapping experiments and main intermediates detection, it is demonstrated that the photo-generated holes as well as the OH and O 2 - formed dominate the photocatalytic decomposition of SMX. These findings demonstrate the potential usage of a facile method to synthesize metal-organics and metal oxides composites, some of which possess high water stability and thus could be employed for water treatment. Copyright © 2018. Published by Elsevier Ltd.

Effect of γ-irradiation on the growth of ZnO nanorod films for photocatalytic disinfection of contaminated water.

PubMed

Alarcón, Julio; Ponce, Silvia; Paraguay-Delgado, Francisco; Rodríguez, Juan

2011-12-01

The growth of ZnO nanorods on a flat substrate containing γ-irradiated seeds and their ability to photocatalytically eliminate bacteria in water were studied. The seed layer was obtained, by the spray pyrolysis technique, from zinc acetate solutions γ-irradiated within the range from 0 to 100 kGy. Subsequently, to grow the rods, the seeds were immersed in a basic solution of zinc nitrate maintained at 90 °C. The rate of crystal growth on the seed layer during the thermal bath treatment was kept constant. The resulting materials were characterized morphologically by scanning electron and atomic force microscopies; X-ray diffraction was used to study their morphology and structure and ultraviolet-visible spectroscopy to determine their absorbance. The obtained seed films were morphologically dependent on the radiation dose and this was correlated with the ZnO nanorod films which presented a texture in the (002) direction perpendicular to the substrate. The rods have a hexagonal mean cross section between 20 and 140 nm. Using these rods, the photocatalytic degradation of Escherichia coli bacteria in water was studied; a positive influence of the crystalline texture on the degradation rate was observed. Copyright © 2011 Elsevier Inc. All rights reserved.

Flexible graphene composites for removal of methylene blue dye-contaminant from water

NASA Astrophysics Data System (ADS)

Oliva, J.; Martinez, A. I.; Oliva, A. I.; Garcia, C. R.; Martinez-Luevanos, A.; Garcia-Lobato, M.; Ochoa-Valiente, R.; Berlanga, A.

2018-04-01

This work presents the use of flexible graphene composites (FGCs) fabricated by a casting method for the removal of Methylene blue (MB) dye from water. Those FGCs with elastic modulus of 15 MPa had enough mechanical resistance to support the Al2O3:Eu3+ and SrAl2O4:Bi3+ photocatalytic powders. After the incorporation of those powders in the FGCs, their photocatalytic activity was evaluated by monitoring the degradation of MB dye under solar irradiation. Scanning electron microscopy (SEM) images demonstrate that the surface of FGCs with catalysts powders presents pores with sizes in the range of 15-40 μm, which favored the sunlight absorption by scattering effects. Moreover, X-Ray diffraction measurements confirmed the formation of the composites by displacements of their diffraction peaks. The MB dye was completely removed (by photocatalysis and by physical adsorption) from the water after 180 min and 270 min by using the FGCs with Al2O3:Eu3+ and SrAl2O4:Bi3+ catalysts respectively. Hence, the results of photocatalytic activity suggest that our FGCs could be used as an effective support of catalyst powders for the easy removal of dye contaminants in wastewater treatment plants.

Comparative study of Gram-negative bacteria response to solar photocatalytic inactivation.

PubMed

Achouri, Faouzi; BenSaid, Myriam; Bousselmi, Latifa; Corbel, Serge; Schneider, Raphaël; Ghrabi, Ahmed

2018-06-03

Solar photocatalytic inactivation of Gram-negative bacteria with immobilized TiO 2 -P25 in a fixed-bed reactor was modeled with simplified kinetic equations. The kinetic parameters are the following: the photocatalytic inactivation coefficient (k d,QUV ), the initial bacterial reduction rate (A) in the contact with the disinfecting agent, and the threshold level of damage (n) were determined to report the effect of Q UV /TiO 2 -P25 on bacterial cultivability and viability and to compare the response of bacterial strains to photocatalytic treatment. In addition, the integration of the reactivation coefficient (C r ) in the photocatalytic inactivation equation allowed evaluating the ability of bacterial reactivation after photocatalytic stress. Results showed different responses of the bacteria strains to photocatalytic stress and the ability of certain bacterial strains such as Escherichia coli ATCC25922 and Pseudomonas aeruginosa ATCC4114 to resuscitate after photocatalytic treatment.

Assessment of solar photocatalysis to purify on-site rinse waters from tractor cisterns used in grapevine pest control: field experimentation.

PubMed

Pichat, P; Vannier, S; Dussaud, J; Rubis, J P

2005-01-01

The aim of this study was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (currently most often rejected) in terms of efficacy and on-site practicality for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate of area S = 1 m2 onto which a TiO2-coated thin material had been slightly pressed, a tank, and an aquarium-type pump powered by a photovoltaic panel (appropriate for isolated locations). For a vineyard of area A = 0.15 km2, the rinse water (about 90 L) corresponding to each of four typical vine treatments in summer was analysed (major pesticides for each treatment, TOC, Microtox test and, in one case, BOD5) by independent laboratories, before and after purification for 8 days. The S/A ratio tested was found insufficient even if the photocatalytic treatment markedly improved the quality of the rinse waters. From the relatively low final organic content reached in one case, it is calculated that a three-time higher S/A ratio might suffice, but new trials are necessary to determine whether it is valid for other typical cases. Inferred contribution of inorganic ions to the post-photocatalytic treatment toxicity points to the need for an additional detoxification. These field experiments have also demonstrated that the purifying prototype is robust, and easy to install and use on site by the wine grower.

Capillary photoelectrode structures for photoelectrochemical and photocatalytic cells

DOEpatents

Wang, Xudong; Li, Zhaodong; Cai, Zhiyong; Yao, Chunhua

2017-05-02

Photocatalytic structures having a capillary-force based electrolyte delivery system are provided. Also provided are photoelectrochemical and photocatalytic cells incorporating the structures and methods for using the cells to generate hydrogen and/or oxygen from water. The photocatalytic structures use an electrolyte-transporting strip comprising a porous network of cellulose nanofibers to transport electrolyte from a body of the electrolyte to a porous photoelectrode or a porous photocatalytic substrate via capillary force.

A review of heterogeneous photocatalysis for water and surface disinfection.

PubMed

Byrne, John Anthony; Dunlop, Patrick Stuart Morris; Hamilton, Jeremy William John; Fernández-Ibáñez, Pilar; Polo-López, Inmaculada; Sharma, Preetam Kumar; Vennard, Ashlene Sarah Margaret

2015-03-30

Photo-excitation of certain semiconductors can lead to the production of reactive oxygen species that can inactivate microorganisms. The mechanisms involved are reviewed, along with two important applications. The first is the use of photocatalysis to enhance the solar disinfection of water. It is estimated that 750 million people do not have accessed to an improved source for drinking and many more rely on sources that are not safe. If one can utilize photocatalysis to enhance the solar disinfection of water and provide an inexpensive, simple method of water disinfection, then it could help reduce the risk of waterborne disease. The second application is the use of photocatalytic coatings to combat healthcare associated infections. Two challenges are considered, i.e., the use of photocatalytic coatings to give "self-disinfecting" surfaces to reduce the risk of transmission of infection via environmental surfaces, and the use of photocatalytic coatings for the decontamination and disinfection of medical devices. In the final section, the development of novel photocatalytic materials for use in disinfection applications is reviewed, taking account of materials, developed for other photocatalytic applications, but which may be transferable for disinfection purposes.

Solar photocatalytic water oxidation over Ag3PO4/g-C3N4 composite materials mediated by metallic Ag and graphene

NASA Astrophysics Data System (ADS)

Cui, Xingkai; Tian, Lin; Xian, Xiaozhai; Tang, Hua; Yang, Xiaofei

2018-02-01

Solar-driven water splitting over semiconductor-based photocatalysts provides direct conversion of solar energy to chemical energy, in which electron-hole separation and charge transport are critical for enhancing the photocatalytic activity of semiconducting materials. Moreover, the search for active photocatalysts that efficiently oxidize water remains a challenging task. Here, we demonstrate that a series of Ag3PO4/Ag/graphene/graphitic carbon nitride (g-C3N4) heterostructured materials can drive photocatalytic water oxidation efficiently under LED illumination. The water oxidation behavior of as-prepared composite photocatalysts in relation to the added amount of g-C3N4 and the roles of electron mediators was investigated in detail. Based on the illuminated Z-scheme photocatalytic mechanism, the photogenerated electrons and holes can be separated effectively and the electron-hole recombination of bulk material is suppressed. The reduced metallic Ag nanoparticles were found to function as the center for the accumulation of electrons from Ag3PO4 and holes from g-C3N4. By exploiting the proper addition of g-C3N4 into the composite, photocatalytic oxygen evolution performance over the heterostructured materials could be suitably tuned, which resulted in highly efficient water oxidation.

Flower-like N-doped MoS2 for photocatalytic degradation of RhB by visible light irradiation

NASA Astrophysics Data System (ADS)

Liu, Peitao; Liu, Yonggang; Ye, Weichun; Ma, Ji; Gao, Daqiang

2016-06-01

In this paper, the photocatalytic performance and reusability of N-doped MoS2 nanoflowers with the specific surface area of 114.2 m2 g-1 was evaluated by discoloring of RhB under visible light irradiation. Results indicated that the 20 mg fabricated catalyst could completely degrade 50 ml of 30 mg l-1 RhB in 70 min with excellent recycling and structural stability. The optimized N-doped MoS2 nanoflowers showed a reaction rate constant (k) as high as 0.06928 min-1 which was 26.4 times that of bare MoS2 nanosheets (k = 0.00262). In addition, it was about seven times that of P25 (k = 0.01) (Hou et al 2015 Sci. Rep. 5 15228). The obtained outstanding photocatalytic performance of N-doped MoS2 nanoflowers provides potential applications in water pollution treatment, as well as other related fields.

Microbial disinfection of water with endotoxin degradation by photocatalysis using Ag@TiO2 core shell nanoparticles.

PubMed

S, Sreeja; K, Vidya Shetty

2016-09-01

The studies on photocatalytic disinfection of water contaminated with Escherichia coli using Ag core and TiO2 shell (Ag@TiO2) nanoparticles under UV irradiation showed that these nanoparticles are very efficient in water disinfection both in their free and immobilised form. Complete disinfection of 40 × 10(8) CFU/mL could be achieved in 60 min with 0.4 g/L catalyst loading and in 35 min with 1 g/L catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in photocatalytic disinfection of water. Kinetics of disinfection followed Chick's law, and the pseudo-first-order rate constant was 0.0168 min(-1) for a catalyst loading of 0.1 g/L. Disinfection of water and degradation of endotoxins (harmful disinfection residual) occurred simultaneously during photocatalysis thereby making the treated water safe for use. Endotoxin degradation showed a shifting order of kinetics. The rate of photocatalysis with nanoparticles immobilised in cellulose acetate film was marginally lower as compared to that of free nanoparticles. Negligible Ag ion leakage and re-growth of cells post-photo-catalytic treatment of water confirmed that complete disintegration of E. coli occurred during photocatalysis making the treated water safe for use. Therefore, Ag@TiO2 nanoparticles have a potential for large-scale application in drinking water treatment plants and household purification units.

Enhanced photocatalytic CO₂-reduction activity of electrospun mesoporous TiO₂ nanofibers by solvothermal treatment.

PubMed

Fu, Junwei; Cao, Shaowen; Yu, Jiaguo; Low, Jingxiang; Lei, Yongpeng

2014-06-28

Photocatalytic reduction of CO2 into renewable hydrocarbon fuels using semiconductor photocatalysts is considered as a potential solution to the energy deficiency and greenhouse effect. In this work, mesoporous TiO2 nanofibers with high specific surface areas and abundant surface hydroxyl groups are prepared using an electrospinning strategy combined with a subsequent calcination process, followed by a solvothermal treatment. The solvothermally treated mesoporous TiO2 nanofibers exhibit excellent photocatalytic performance on CO2 reduction into hydrocarbon fuels. The significantly improved photocatalytic activity can be attributed to the enhanced CO2 adsorption capacity and the improved charge separation after solvothermal treatment. The highest activity is achieved for the sample with a 2-h solvothermal treatment, showing 6- and 25-fold higher CH4 production rate than those of TiO2 nanofibers without solvothermal treatment and P25, respectively. This work may also provide a prototype for studying the effect of solvothermal treatment on the structure and photocatalytic activity of semiconductor photocatalysts.

Slurry photocatalytic membrane reactor technology for removal of pharmaceutical compounds from wastewater: Towards cytostatic drug elimination.

PubMed

Janssens, Raphael; Mandal, Mrinal Kanti; Dubey, Kashyap Kumar; Luis, Patricia

2017-12-01

The potential of photocatalytic membrane reactors (PMR) to degrade cytostatic drugs is presented in this work as an emerging technology for wastewater treatment. Cytostatic drugs are pharmaceutical compounds (PhCs) commonly used in cancer treatment. Such compounds and their metabolites, as well as their degraded by-products have genotoxic and mutagenic effects. A major challenge of cytostatic removal stands in the fact that most drugs are delivered to ambulant patients leading to diluted concentration in the municipal waste. Therefore safe strategies should be developed in order to collect and degrade the micro-pollutants using appropriate treatment technologies. Degradation of cytostatic compounds can be achieved with different conventional processes such as chemical oxidation, photolysis or photocatalysis but the treatment performances obtained are lower than the ones observed with slurry PMRs. Therefore the reasons why slurry PMRs may be considered as the next generation technology will be discussed in this work together with the limitations related to the mechanical abrasion of polymeric and ceramic membranes, catalyst suspension and interferences with the water matrix. Furthermore key recommendations are presented in order to develop a renewable energy powered water treatment based on long lifetime materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Factorial design application in photocatalytic wastewater degradation from TNT industry-red water.

PubMed

Guz, Ricardo; de Moura, Cristiane; da Cunha, Mário Antônio Alves; Rodrigues, Marcio Barreto

2017-03-01

In trinitrotoluene (TNT) purification process, realized in industries, there are two washes carried out at the end of the procedure. The first is performed with vaporized water, from which the first effluent, called yellow water, is originated. Then, a second wash is performed using sodium sulfite, generating the red water effluent. The objective of this work was to get the best conditions for photocatalytic degradation of the second effluent, red water, in order to reduce toxicity and adjust legal parameters according to regulatory agencies for dumping these effluents into waterways. It has used a statistical evaluation for factor interaction (pH, concentration) that affects heterogeneous photocatalysis with titanium dioxide (TiO 2 ). Thus, the treatment applied in the factorial experimental design consisted of using a volume equal to 500 mL of the effluent to 0.1 % by batch treatment, which has changed TiO 2  pH and concentration, according to the design, with 20 min time for evaluation, where it was used as response to the reduction of UV-Vis absorption. According to the design responses, it has obtained optimum values for the parameters evaluated: pH = 6.5 and concentration of 100 mg/L of TiO 2 were shown to be efficient when applied to red water effluent, obtaining approximately 91 % of discoloration.

Preparation of novel poly(vinylidene fluoride)/TiO2 photocatalysis membranes for use in direct contact membrane distillation

NASA Astrophysics Data System (ADS)

Li, Yukun; Dong, Shuying; Zhu, Liang

2018-03-01

Immobilization of TiO2 is a potential approach to obtain photocatalytic membranes that could eliminate concentration polarization in sewage disposal for direct contact membrane distillation (DCMD) process. A simple non-solvent-induced phase separation (NIPS) method was proposed to prepare poly(vinylidene fluoride) (PVDF) membrane, and the double-coating technology was further used to prepare the self-cleaning membranes with different TiO2 content. The effects of TiO2 nano-particles on membrane crystal form, morphology, porosity, pore size, pore size distribution, hydrophobicity, permeation, and photocatalytic efficiency were investigated, respectively. The flux of the prepared membranes is higher than the membrane (MS) provided by Membrane Solutions, LLC, in DCMD process. The contact angle between water and membrane could be increased 22° by introducing photocatalytic layer containing TiO2. During the photocatalytic test, 65.78-96.31% degrading rate of 15 mg/L Rhodamine B (RhB) was achieved. The relative flux of the membrane T-3 can be recovered to 0.96 in photocatalysis-membrane reactor for 8 h UV radiation. The fabricated membrane has great potential in high-salty dyeing wastewater treatment due to its high hydrophobicity and photocatalytic capability. [Figure not available: see fulltext.

Advances in photocatalytic disinfection of bacteria: Development of photocatalysts and mechanisms.

PubMed

Wang, Wanjun; Huang, Guocheng; Yu, Jimmy C; Wong, Po Keung

2015-08-01

Photocatalysis has attracted worldwide attention due to its potential in solar energy conversion. As a "green" advanced oxidation technology, it has been extensively used for water disinfection and wastewater treatment. This article provides a review of the recent progress in solar energy-induced photocatalytic disinfection of bacteria, focusing on the development of highly efficient photocatalysts and their underlying mechanisms in bacterial inactivation. The photocatalysts are classified into TiO2-based and non-TiO2-based systems, as TiO2 is the most investigated photocatalyst. The synthesis methods, modification strategies, bacterial disinfection activities and mechanisms of different types of photocatalysts are reviewed in detail. Emphasis is given to the modified TiO2, including noble metal deposition, non-metal doping, dye sensitization and composite TiO2, along with typical non-TiO2-based photocatalysts for bacterial disinfection, including metal oxides, sulfides, bismuth metallates, graphene-based photocatalysts, carbon nitride-based photocatalysts and natural photocatalysts. A simple and versatile methodology by using a partition system combined with scavenging study is introduced to study the photocatalytic disinfection mechanisms in different photocatalytic systems. This review summarizes the current state of the work on photocatalytic disinfection of bacteria, and is expected to offer useful insights for the future development in the field. Copyright © 2015. Published by Elsevier B.V.

Biofiltration using C. fluminea for E.coli removal from water: Comparison with ozonation and photocatalytic oxidation.

PubMed

Gomes, João F; Lopes, Ana; Gonçalves, Daniel; Luxo, Cristina; Gmurek, Marta; Costa, Raquel; Quinta-Ferreira, Rosa M; Martins, Rui C; Matos, Ana

2018-06-06

Corbicula fluminea, an Asian clam, is one of the worst invasive species in Europe that can survive in very adverse environmental conditions. Despite its negative impacts, the species also has the capacity to bioaccumulate heavy metals, contaminants and can be exploited for wastewater treatment purposes. The capacity of the Asian clam to remove Escherichia coli, used as fecal contamination indicator, was analyzed. Conventional wastewater treatment plants are not suitable to remove bacteria, thus resulting in treated municipal wastewater with high bacterial loads. E. coli clearance rate was analyzed as function of the number of clams. The bivalves can remove bacteria until concentrations below the detection limit in about 6 h. The adsorption on the clam shells' and bioaccumulation on the soft tissues were also analyzed. The depuration of clams along 48 h were analyzed revealing that no bacteria was detected in the water. Thus, these results suggest that Asian clam can bioprocess E. coli. On the other hand, results obtained by this methodology were compared with ozonation and photocatalytic oxidation using TiO 2 , Ag, Au, Pd-TiO 2 . In all treatments it was possible to achieve concentrations of E. coli below the detection limit. However, photocatalytic oxidation demands about 4700 folds more energy than ozonation, besides the costs associated with catalysts. Comparing complexity of ozonation with biofiltration, this study suggests that application of biofiltration using C. fluminea can be a suitable solution to minimize the presence of bacteria in wastewater, reducing environmental and economic impacts. Copyright © 2018 Elsevier Ltd. All rights reserved.

Membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment.

PubMed

Rivero, M J; Parsons, S A; Jeffrey, P; Pidou, M; Jefferson, B

2006-01-01

Urban water recycling is now becoming an important issue where water resources are becoming scarce. This paper looks at reusing grey water; the preference is treatment processes based on biological systems to remove the dissolved organic content. Here, an alternative process, photocatalysis is discussed as it is an attractive technology that could be well-suited for treating the recalcitrant organic compounds found in grey water. The photocatalytic process oxidises organic reactants at a catalyst surface in the presence of ultraviolet light. Given enough exposure time, organic compounds will be oxidized into CO2 and water. The best contact is achieved in a slurry reactor but a second step to separate and recover the catalyst is need. This paper discusses a new membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment.

Recent Progress in Metal‐Organic Frameworks for Applications in Electrocatalytic and Photocatalytic Water Splitting

PubMed Central

Wang, Wei; Xu, Xiaomin; Zhou, Wei

2017-01-01

The development of clean and renewable energy materials as alternatives to fossil fuels is foreseen as a potential solution to the crucial problems of environmental pollution and energy shortages. Hydrogen is an ideal energy material for the future, and water splitting using solar/electrical energy is one way to generate hydrogen. Metal‐organic frameworks (MOFs) are a class of porous materials with unique properties that have received rapidly growing attention in recent years for applications in water splitting due to their remarkable design flexibility, ultra‐large surface‐to‐volume ratios and tunable pore channels. This review focuses on recent progress in the application of MOFs in electrocatalytic and photocatalytic water splitting for hydrogen generation, including both oxygen and hydrogen evolution. It starts with the fundamentals of electrocatalytic and photocatalytic water splitting and the related factors to determine the catalytic activity. The recent progress in the exploitation of MOFs for water splitting is then summarized, and strategies for designing MOF‐based catalysts for electrocatalytic and photocatalytic water splitting are presented. Finally, major challenges in the field of water splitting are highlighted, and some perspectives of MOF‐based catalysts for water splitting are proposed. PMID:28435777

Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments.

PubMed

Brosillon, Stephan; Bancon-Montigny, Chrystelle; Mendret, Julie

2014-08-01

This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (μgL(-1)). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2-UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrochemically assisted photocatalysis: Highly efficient treatment using thermal titanium oxides doped and non-doped electrodes for water disinfection.

PubMed

Dos Santos, Andreia Betina Kreuser; Claro, Elis Marina Turini; Montagnolli, Renato Nallin; Cruz, Jaqueline Matos; Lopes, Paulo Renato Matos; Bidoia, Ederio Dino

2017-12-15

Electrochemically assisted photocatalysis (by electronic drainage) is a highly promising method for disinfection of water. In this research, the efficiency of photolytic oxidation using UV-A radiation and electrochemically assisted photocatalysis (with electric potential of 1.5 V) was studied by using electrodes prepared by thermal treatment and doped with silver, for inactivation of Escherichia coli and Staphylococcus aureus. The Chick-Watson microorganism inactivation model was applied and the electrical energy consumption of the process was calculated. It was observed no significant inactivation of microorganisms when UV-A light or electric potential were applied separately. However, the electrochemically assisted photocatalytic process, with Ag-doped electrode completely inactivated the microbial population after 10 (E. coli) and 60 min (S. aureus). The best performing non-doped electrodes achieved 52.74% (E. coli) and 44.09% (S. aureus) inactivation rates after 60 min. Thus, electrochemically assisted photocatalytic activity was not only effective for the inactivation of microorganisms, but also notably low on electrical energy consumption during the treatment due to small current and low electric potential applied. Copyright © 2017 Elsevier Ltd. All rights reserved.

High Efficient Visible-Light Photocatalytic Performance of Cu/ZnO/rGO Nanocomposite for Decomposing of Aqueous Ammonia and Treatment of Domestic Wastewater.

PubMed

He, Shiying; Hou, Pengfu; Petropoulos, Evangelos; Feng, Yanfang; Yu, Yingliang; Xue, Lihong; Yang, Linzhang

2018-01-01

Photocatalytic removal of ammonium-nitrogen ( NH 4 + -N) from water using solar energy is an approach of high interest and applicability due to the convenience in application. ZnO has a great potential in photocatalytic decomposition of NH 4 + -N and conversion of this nutrient to under visible light irradiations. However the applicability of pristine ZnO though is limited due to its reduced capacity to utilize light from natural light. Herein, we report a two-step ZnO-modified strategy (Cu-doped ZnO nanoparticles, immobilized on reduced graphene oxide (rGO) sheets) for the promotion of photocatalytic degradation of NH 4 + -N under visible light. UV-Vis spectra showed that the Cu/ZnO/rGO can be highly efficient in the utilization of photons from the visible region. Hence, Cu/ZnO/rGO managed to demonstrate adequate photocatalytic activity and effective NH 4 + -N removal from water under visible light compared to single ZnO. Specifically, up to 83.1% of NH 4 + -N (initial concentration 50 mg·L -1 , catalyst dosage 2 g·L -1 , pH 10) was removed within 2 h retention time under Xe lamp irradiation. From the catalysis, the major by-product was N 2 . The high ammonia degradation efficiency from the ZnO/Cu/rGO is attributed to the improvement of the reactive oxygen species (ROSs) production efficiency and the further activation of the interfacial catalytic sites. This study also demonstrated that such nanocomposite is a recyclable agent. Its NH 4 + -N removal capacity remained effective even after five batch cycles. In addition, Cu/ZnO/rGO was applied to treat real domestic wastewater, and it was found that chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies can reach 84.3, 80.7, and 90.3%, respectively. Thus, Cu/ZnO/rGO in the presence of solar light can be a promising photocatalyst in the field of wastewater treatment.

Solar photocatalytic degradation of naphthenic acids in oil sands process-affected water.

PubMed

Leshuk, Tim; Wong, Timothy; Linley, Stuart; Peru, Kerry M; Headley, John V; Gu, Frank

2016-02-01

Bitumen mining in the Canadian oil sands creates large volumes of oil sands process-affected water (OSPW), the toxicity of which is due in part to naphthenic acids (NAs) and other acid extractable organics (AEO). The objective of this work was to evaluate the potential of solar photocatalysis over TiO2 to remove AEO from OSPW. One day of photocatalytic treatment under natural sunlight (25 MJ/m(2) over ∼14 h daylight) eradicated AEO from raw OSPW, and acute toxicity of the OSPW toward Vibrio fischeri was eliminated. Nearly complete mineralization of organic carbon was achieved within 1-7 day equivalents of sunlight exposure, and degradation was shown to proceed through a superoxide-mediated oxidation pathway. High resolution mass spectrometry (HRMS) analysis of oxidized intermediate compounds indicated preferential degradation of the heavier and more cyclic NAs (higher number of double bond equivalents), which are the most environmentally persistent fractions. The photocatalyst was shown to be recyclable for multiple uses, and thus solar photocatalysis may be a promising "green" advanced oxidation process (AOP) for OSPW treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic overall water splitting promoted by an α-β phase junction on Ga2O3.

PubMed

Wang, Xiang; Xu, Qian; Li, Mingrun; Shen, Shuai; Wang, Xiuli; Wang, Yaochuan; Feng, Zhaochi; Shi, Jingying; Han, Hongxian; Li, Can

2012-12-21

When Alpha met Beta: a tuneable α-β surface phase junction on Ga(2)O(3) can significantly improve photocatalytic overall water splitting into H(2) and O(2) over individual α-Ga(2)O(3) or β-Ga(2)O(3) surface phases. This enhanced photocatalytic performance is mainly attributed to the efficient charge separation and transfer across the α-β phase junction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimized photodegradation of Bisphenol A in water using ZnO, TiO2 and SnO2 photocatalysts under UV radiation as a decontamination procedure

NASA Astrophysics Data System (ADS)

Abo, Rudy; Kummer, Nicolai-Alexeji; Merkel, Broder J.

2016-09-01

Experiments on photodegradation of Bisphenol A (BPA) were carried out in water samples by means photocatalytic and photo-oxidation methods in the presence of ZnO, TiO2 and SnO2 catalysts. The objective of this study was to develop an improved technique that can be used as a remediation procedure for a BPA-contaminated surface water and groundwater based on the UV solar radiation. The photodegradation of BPA in water performed under a low-intensity UV source mimics the UVC and UVA spectrum of solar radiation between 254 and 365 nm. The archived results reveal higher degradation rates observed in the presence of ZnO than with TiO2 and SnO2 catalysts during 20 h of irradiation. The intervention of the advanced photocatalytic oxidation (PCO) reduces the time of degradation to less than 1 h to reach a degradation rate of 90 % for BPA in water. The study proposes the use of ZnO as a competitor catalyst to the traditional TiO2, providing the most effective treatment of contaminated water with phenolic products.

One-pot synthesis of ternary Ag₂CO₃/Ag/AgCl photocatalyst in natural geothermal water with enhanced photocatalytic activity under visible light irradiation.

PubMed

Yao, Xiaxi; Liu, Xiaoheng

2014-09-15

Geothermal water is a clean, cheap and renewable resource and it is widely distributed all over the world. In this work, ternary Ag2CO3/Ag/AgCl photocatalyst has been successfully synthesized via a one-pot precipitation method in natural geothermal water at room temperature, wherein the geothermal water serves as the source of chlorine and carbonate. The results suggest that the Ag/AgCl nanoparticles are anchored on the surface of Ag2CO3 and Ag2CO3/Ag/AgCl composite shows strong absorption ability in the visible light region. The evaluation of the photocatalytic activity indicates that the as-synthesized Ag2CO3/Ag/AgCl photocatalyst exhibits higher photocatalytic performance for the degradation of methylene blue (MB) aqueous solution under visible light irradiation than one-component (Ag2CO3), two-component (Ag/AgCl, Ag2CO3/AgCl) and the mechanical mixture of Ag2CO3 and Ag/AgCl. The trapping experiments confirmed that holes (h(+)) and (•)O2(-) were the two main active species in the photocatalytic process. Finally, a possible Z-scheme photocatalytic mechanism of the charge transfer was proposed for the enhanced photocatalytic performance. This work may open up new insights into the application of cheap geothermal water resources in the word and provide new opportunities for facile fabrication of Ag/AgCl-based photocatalysts. Copyright © 2014 Elsevier B.V. All rights reserved.

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

DOE PAGES

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres; ...

2017-02-13

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

Solar CPC pilot plant photocatalytic degradation of bisphenol A in waters and wastewaters using suspended and supported-TiO2. Influence of photogenerated species.

PubMed

Saggioro, Enrico Mendes; Oliveira, Anabela Sousa; Pavesi, Thelma; Tototzintle, Margarita Jiménez; Maldonado, Manuel Ignacio; Correia, Fábio Verissimo; Moreira, Josino Costa

2014-11-01

Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO2) was performed under different conditions. Suspensions of the TiO2 were used to compare the degradation efficiency of BPA (20 mg L(-1)) in batch and compound parabolic collector (CPC) reactors. A TiO2 catalyst supported on glass spheres was prepared (sol-gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L(-1)). The influence of OH·, O2 (·-), and h (+) on the BPA degradation were evaluated. The radicals OH· and O2 (·-) were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO2 to degrade BPA in batch or CPC reactors was 0.1 g L(-1). According to biological tests, the BPA LC50 in 24 h for E. andrei was of 1.7 × 10(-2) mg cm(-2). The photocatalytic degradation of BPA mediated by TiO2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment.

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

NASA Astrophysics Data System (ADS)

Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

2014-12-01

Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

New insight into the disinfection mechanism of Fusarium monoliforme and Aspergillus niger by TiO2 photocatalyst under low intensity UVA light.

PubMed

Pokhum, Chonlada; Viboonratanasri, Duangamon; Chawengkijwanich, Chamorn

2017-11-01

Titanium dioxide (TiO 2) photocatalytic reaction has great potential for the disinfection of harmful pathogens. However, the disinfection mechanisms of TiO 2 photocatalysis are not yet well-known for fungi and protozoa. In this work, the photocatalytic disinfection mechanism of Fusarium monoliforme and Aspergillus niger under low intensity UVA light (365nm, <10W/m 2 ) was studied at the ultrastructural level. Photocatalytic treatments showed that the photocatalytic oxidation of 10% TiO 2 based paint was efficacious in the complete disinfection of F. monoliforme under low intensity UVA light. No growth of F. monoliforme was observed on agar plate in the subsequent dark. Transmission electron microscopy (TEM) of F. monoliforme exposed to TiO 2 photocatalysis treatment showed a distinct damage to electron-dense outer cell wall, but not to an underlying electron-transparent layer cell wall. The TEM image revealed that the UVA-light only did not damage cell wall, cell membrane and cellular organelles. Unlike, A. niger was more sensitive to UVA-light. Serious destructions of cell membrane and cellular organelles were shown in A. niger exposed to UVA-light only and photocatalytic treatments. However, morphological change in A. niger cell wall was only observed in photocatalytic treatment. Changes to the outermost melanin like layer and cell wall of A. niger spore due to photocatalytic treatment were greatly apparent while the intracellular organelles of A. niger spore were not affected. Therefore, regrowth of A. niger on agar plate was expected from the germination of A. niger spore in the subsequent dark. These observations give a better understanding of the photocatalytic disinfection mechanism toward fungi. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation and photocatalytic activities of 3D flower-like CuO nanostructures

NASA Astrophysics Data System (ADS)

Qingfei, Fan; Qi, Lan; Meili, Zhang; Ximei, Fan; Zuowan, Zhou; Chaoliang, Zhang

2016-08-01

Hierarchical 3D flower-like CuO nanostructures on the Cu substrates were synthesized by a wet chemical method and subsequent heat treatment. The synthesis, structure and morphologies of obtained samples under different concentrations of Na2S2O3 were investigated in detail and the possible growth mechanisms of the 3D flower-like CuO nanostructures were discussed. Na2S2O3 plays a key role in the generation of the 3D flower-like CuO nanostructures. When the concentration of Na2S2O3 is more than 0.4 mol/L, the 3D flower-like CuO nanostructures can be prepared on the Cu foils. The photocatalytic performances were studied by analyzing the degradation of methyl orange (MO) in aqueous solution in the presence of hydroxide water (H2O2). The 3D flower-like CuO nanostructures exhibit higher photocatalytic activity (96.2% degradation rate) than commercial CuO particles (36.3% degradation rate). The origin of the higher photocatalytic activity of the 3D flower-like CuO nanostructures was also discussed. Project supported by the High-Tech Research and Development Program of China (No. 2009AA03Z427).

Visible-light active conducting polymer nanostructures with superior photocatalytic activity

NASA Astrophysics Data System (ADS)

Ghosh, Srabanti; Kouame, Natalie Amoin; Remita, Samy; Ramos, Laurence; Goubard, Fabrice; Aubert, Pierre-Henri; Dazzi, Alexandre; Deniset-Besseau, Ariane; Remita, Hynd

2015-12-01

The development of visible-light responsive photocatalysts would permit more efficient use of solar energy, and thus would bring sustainable solutions to many environmental issues. Conductive polymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a wide range of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidative polymerization demonstrate unprecedented photocatalytic activities for water treatment without the assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2 as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and are characterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOT-based photocatalysts are very stable with cycling and can be reused without appreciable loss of activity. Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts as compared to nanometric spindles suggesting size and shape dependent photocatalytic properties. The visible-light active photocatalytic properties of the polymer nanostructures present promising applications in solar light harvesting and broader fields.

Photocatalytic activity and reusability of ZnO layer synthesised by electrolysis, hydrogen peroxide and heat treatment.

PubMed

Akhmal Saadon, Syaiful; Sathishkumar, Palanivel; Mohd Yusoff, Abdull Rahim; Hakim Wirzal, Mohd Dzul; Rahmalan, Muhammad Taufiq; Nur, Hadi

2016-08-01

In this study, the zinc oxide (ZnO) layer was synthesised on the surface of Zn plates by three different techniques, i.e. electrolysis, hydrogen peroxide and heat treatment. The synthesised ZnO layers were characterised using scanning electron microscopy, X-ray diffraction, UV-visible diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of the ZnO layer was further assessed against methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB was achieved up to 84%, 79% and 65% within 1 h for ZnO layers synthesised by electrolysis, heat and hydrogen peroxide treatment, respectively. The reusability results show that electrolysis and heat-treated ZnO layers have considerable photocatalytic stability. Furthermore, the results confirmed that the photocatalytic efficiency of ZnO was directly associated with the thickness and enlarged surface area of the layer. Finally, this study proved that the ZnO layers synthesised by electrolysis and heat treatment had shown better operational stability and reusability.

Photoelectrical, photophysical and photocatalytic properties of Al based MOFs: MIL-53(Al) and MIL-53-NH{sub 2}(Al)

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Yang; Li, Huiliang; Liu, Yuanyuan, E-mail: yyliu@sdu.edu.cn

Two Al based MOFs (MIL-53(Al) and MIL-53-NH{sub 2} (Al)) were synthesized, and their photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water were investigated. Different from the ligand to metal charge transfer process previously reported, we proposes a new photocatalytic mechanism based on electron tunneling according to the results of theoretical calculation, steady state and time resolved fluorescence spectra. The organic linkers absorb photons, giving rise to electrons and holes. Then, the photogenerated electrons tunnel through the AlO{sub 6}-octahedra, which not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activitymore » of Al based MOFs. - Graphical abstract: The photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water of two Al based MOFs were investigated. A new photocatalytic mechanism was proposed based on electron tunneling according to the results of both theoretical calculation and steady state, time resolved fluorescence spectra. The electron tunneling process not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activity of Al based MOFs.« less

Research Update: Photoelectrochemical water splitting and photocatalytic hydrogen production using ferrites (MFe2O4) under visible light irradiation

NASA Astrophysics Data System (ADS)

Dillert, Ralf; Taffa, Dereje H.; Wark, Michael; Bredow, Thomas; Bahnemann, Detlef W.

2015-10-01

The utilization of solar light for the photoelectrochemical and photocatalytic production of molecular hydrogen from water is a scientific and technical challenge. Semiconductors with suitable properties to promote solar-driven water splitting are a desideratum. A hitherto rarely investigated group of semiconductors are ferrites with the empirical formula MFe2O4 and related compounds. This contribution summarizes the published results of the experimental investigations on the photoelectrochemical and photocatalytic properties of these compounds. It will be shown that the potential of this group of compounds in regard to the production of solar hydrogen has not been fully explored yet.

Direct Coupling of Thermo- and Photocatalysis for Conversion of CO2 -H2 O into Fuels.

PubMed

Zhang, Li; Kong, Guoguo; Meng, Yaping; Tian, Jinshu; Zhang, Lijie; Wan, Shaolong; Lin, Jingdong; Wang, Yong

2017-12-08

Photocatalytic CO 2 reduction into renewable hydrocarbon solar fuels is considered as a promising strategy to simultaneously address global energy and environmental issues. This study focused on the direct coupling of photocatalytic water splitting and thermocatalytic hydrogenation of CO 2 in the conversion of CO 2 -H 2 O into fuels. Specifically, it was found that direct coupling of thermo- and photocatalysis over Au-Ru/TiO 2 leads to activity 15 times higher (T=358 K; ca. 99 % CH 4 selectivity) in the conversion of CO 2 -H 2 O into fuels than that of photocatalytic water splitting. This is ascribed to the promoting effect of thermocatalytic hydrogenation of CO 2 by hydrogen atoms generated in situ by photocatalytic water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photocatalytic degradation of recalcitrant organic pollutants in water using a novel cylindrical multi-column photoreactor packed with TiO2-coated silica gel beads.

PubMed

Li, Dawei; Zhu, Qi; Han, Chengjie; Yang, Yingnan; Jiang, Weizhong; Zhang, Zhenya

2015-03-21

A novel cylindrical multi-column photocatalytic reactor (CMCPR) has been developed and successfully applied for the degradation of methyl orange (MO), amoxicillin (AMX) and 3-chlorophenol (3-CP) in water. Due to its higher adsorption capacity and simpler molecular structure, 3-CP compared with MO and AMX obtained the highest photodegradation (100%) and mineralization (78.1%) after 300-min photocatalytic reaction. Electrical energy consumption for photocatalytic degradation of MO, AMX and 3-CP using CMCPR was 5.79×10(4), 7.31×10(4) and 2.52×10(4) kW h m(-3) order(-1), respectively, which were less than one-thousand of those by reported photoreactors. The higher flow rate (15 mL min(-1)), lower initial concentration (5 mg L(-1)) and acidic condition (pH 3) were more favorable for the photocatalytic degradation of MO using CMCPR. Five repetitive operations of CMCPR achieved more than 97.0% photodegradation of MO in each cycle and gave a relative standard deviation of 0.72%. In comparison with reported slurry and thin-film photoreactors, CMCPR exhibited higher photocatalytic efficiency, lower energy consumption and better repetitive operation performance for the degradation of MO, AMX and 3-CP in water. The results demonstrated the feasibility of utilizing CMCPR for the degradation of recalcitrant organic pollutants in water. Copyright © 2014 Elsevier B.V. All rights reserved.

N-Doped TiO₂-Coated Ceramic Membrane for Carbamazepine Degradation in Different Water Qualities.

PubMed

Luster, Enbal; Avisar, Dror; Horovitz, Inna; Lozzi, Luca; Baker, Mark A; Grilli, Rossana; Mamane, Hadas

2017-07-31

The photocatalytic degradation of the model pollutant carbamazepine (CBZ) was investigated under simulated solar irradiation with an N-doped TiO₂-coated Al₂O₃ photocatalytic membrane, using different water types. The photocatalytic membrane combines photocatalysis and membrane filtration in a single step. The impact of each individual constituent such as acidity, alkalinity, dissolved organic matter (DOM), divalent cations (Mg 2+ and Ca 2+ ), and Cl - on the degradation of CBZ was examined. CBZ in water was efficiently degraded by an N-doped TiO₂-coated Al₂O₃ membrane. However, elements added to the water, which simulate the constituents of natural water, had an impact on the CBZ degradation. Water alkalinity inhibited CBZ degradation mostly due to increase in pH while radical scavenging by carbonate was more dominant at higher values (>200 mg/L as CaCO₃). A negative effect of Ca 2+ addition on photocatalytic degradation was found only in combination with phosphate buffer, probably caused by deposition of CaHPO₄ or CaHPO₄·2H₂O on the catalyst surface. The presence of Cl - and Mg 2+ ions had no effect on CBZ degradation. DOM significantly inhibited CBZ degradation for all tested background organic compounds. The photocatalytic activity of N-doped TiO₂-coated Al₂O₃ membranes gradually decreased after continuous use; however, it was successfully regenerated by 0.1% HCl chemical cleaning. Nevertheless, dissolution of metals like Al and Ti should be monitored following acid cleaning.

Bioinspired hierarchical nanotubular titania immobilized with platinum nanoparticles for photocatalytic hydrogen production.

PubMed

Liu, Xiaoyan; Li, Jiao; Zhang, Yiming; Huang, Jianguo

2015-05-11

A bioinspired nanocomposite composed of platinum nanoparticles and nanotubular titania was fabricated in which the titania matter was templated by natural cellulose substance. The composite possesses three- dimensional hierarchical structures, and ultrafine metallic platinum particles with sizes of ca. 2 nm were immobilized uniformly on the surfaces of the titania nanotubes. Such a nanocomposite with 1.06 wt % of platinum content shows the optimal photocatalytic hydrogen production activity from water splitting of 16.44 mmol h(-1)  g(-1) , and excessive loading of platinum results in poorer photocatalytic performance. The structural integrity of the nanocomposite upon cyclic water-splitting processes results in its sufficient photocatalytic stability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanostructures, systems, and methods for photocatalysis

DOEpatents

Reece, Steven Y.; Jarvi, Thomas D.

2015-12-08

The present invention generally relates to nanostructures and compositions comprising nanostructures, methods of making and using the nanostructures, and related systems. In some embodiments, a nanostructure comprises a first region and a second region, wherein a first photocatalytic reaction (e.g., an oxidation reaction) can be carried out at the first region and a second photocatalytic reaction (e.g., a reduction reaction) can be carried out at the second region. In some cases, the first photocatalytic reaction is the formation of oxygen gas from water and the second photocatalytic reaction is the formation of hydrogen gas from water. In some embodiments, a nanostructure comprises at least one semiconductor material, and, in some cases, at least one catalytic material and/or at least one photosensitizing agent.

In situ photodeposition of cobalt on CdS nanorod for promoting photocatalytic hydrogen production under visible light irradiation

NASA Astrophysics Data System (ADS)

Chen, Wei; Wang, Yanhong; Liu, Mei; Gao, Li; Mao, Liqun; Fan, Zeyun; Shangguan, Wenfeng

2018-06-01

Non-noble metal Co were loaded on CdS for enhancing photocatalytic activity of water splitting by a simple and efficient in situ photodeposition method. The Co particles with diameter ca. 5 nm were photoreduced and then loaded on the surface of CdS. The loading of Co can not only effectively promote the separation of electrons and holes photoexcited by CdS, but reduce the overpotential of hydrogen evolution as well, thus enhancing photocatalytic activity of water splitting. The highest photocatalytic H2 evolution rate of Co/CdS reaches up to 1299 μmol h-1 under visible light irradiation(λ > 420 nm) when the amount of loading is 1.0 wt%, which is 17 times of that of pure CdS and achieves 80% of that of 0.5 wt%Pt/CdS. This work not only exhibits a pathway to obtain photocatalysts with high photocatalytic activity for hydrogen production, but provides a possibility for the utilization of low cost Co as a substitute for noble metals in photocatalytic hydrogen production.

Photocatalytic degradation of oilfield produced water using graphitic carbon nitride embedded in electrospun polyacrylonitrile nanofibers.

PubMed

Alias, Nur Hashimah; Jaafar, Juhana; Samitsu, Sadaki; Yusof, Norhaniza; Othman, Mohd Hafiz Dzarfan; Rahman, Mukhlis A; Ismail, Ahmad Fauzi; Aziz, Farhana; Salleh, Wan Norharyati Wan; Othman, Nur Hidayati

2018-08-01

Separation and purification of oilfield produced water (OPW) is a major environmental challenge due to the co-production of the OPW during petroleum exploration and production operations. Effective capture of oil contaminant and its in-situ photodegradation is one of the promising methods to purify the OPW. Based on the photocatalytic capability of graphitic carbon nitride (GCN) which was recently rediscovered, photodegradation capability of GCN for OPW was investigated in this study. GCN was synthesized by calcination of urea and further exfoliated into nanosheets. The GCNs were incorporated into polyacrylonitrile nanofibers using electrospinning, which gave a liquid-permeable self-supporting photocatalytic nanofiber mat that can be handled by hand. The photocatalytic nanofiber demonstrated 85.4% degradation of OPW under visible light irradiation, and improved the degradation to 96.6% under UV light. Effective photodegradation of the photocatalytic nanofiber for OPW originates from synergetic effects of oil adsorption by PAN nanofibers and oil photodegradation by GCNs. This study provides an insight for industrial application on purification of OPW through photocatalytic degradation under solar irradiation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis and photocatalytic activity of sepiolite supportednano-TiO2 composites prepared by a mild solid-state sintering process

NASA Astrophysics Data System (ADS)

Liao, L. M.; Wang, Z. Q.; Liang, H.; Feng, J.; Zhang, D.

2016-08-01

Supported nano-TiO2photocatalysts play an important role in water environment restoration because of their potential application to photocatalytic degradation of organic contaminants in waste water. With sepiolite as the support, the nano-TiO2/sepiolite composite photocatalysts were synthesized by an easily operated and mild solid-state sintering process.The microstructureand photocatalytic property of the sepiolite supportednano-TiO2 composites were characterized and analyzed by X-ray diffraction spectroscopy, UV-Visible spectroscopy and fluorescence spectroscopy. In addition, the influences of calcination temperature and load ratios on the photocatalytic activity of sepiolite supported nano-TiO2 composites were studied.The results indicated that appropriate ratios of sepiolite supports to nano-TiO2contributed to uniform dispersion of nanoparticles, and enhanced the absorption ability within the UV-Vis range, and consequently increased the photocatalytic activity of the composites.Under the preparation conditions of 90 wt. % TiO2 loading and calcinated at 400 °C, a maximum in photocatalytic activity ofnano-TiO2 sepiolite composite was obtained.

Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO2 suspensions.

PubMed

Sharma, Virender K; Graham, Nigel J D; Li, Xiang-Zhong; Yuan, Bao-Ling

2010-02-01

Photocatalytic oxidation using UV irradiation of TiO(2) has been studied extensively and has many potential industrial applications, including the degradation of recalcitrant contaminants in water and wastewater treatment. A limiting factor in the oxidation process is the recombination of conduction band electrons (e(-)(cb)) with electron holes (h(vb)(+)) on the irradiated TiO(2) surface; thus, in aqueous conditions, the presence of an effective electron scavenger will be beneficial to the efficiency of the oxidation process. Ferrate (FeO(4)(2-)) has received much recent attention as a water treatment chemical since it behaves simultaneously as an oxidant and coagulant. The combination of ferrate [Fe(VI)] with UV/TiO(2) photocatalysis offers an oxidation synergism arising from the Fe(VI) scavenging of e(-)(cb) and the corresponding beneficial formation of Fe(V) from the Fe(VI) reduction. This paper reviews recent studies concerning the photocatalytic oxidation of problematic pollutants with and without ferrate. The paper reviews the published results of laboratory experiments designed to follow the photocatalytic degradation of selected contaminants of environmental significance and the influence of the experimental conditions (e.g. pH, reactant concentrations and dissolved oxygen). The specific compounds are as follows: ammonia, cyanate, formic acid, bisphenol-A, dibutyl- and dimethyl-phthalate and microcystin-LR. The principal focus in these studies has been on the rates of reaction rather than on reaction pathways and products. The presence of UV/TiO(2) accelerates the chemical reduction of ferrate, and the reduction rate decreases with pH owing to deprotonation of ferrate ion. For all the selected contaminant substances, the photocatalytic oxidation rate was greater in the presence of ferrate, and this was believed to be synergistic rather than additive. The presence of dissolved oxygen in solution reduced the degradation rate of dimethyl phthalate in the ferrate/photocatalysis system. In the study of microcystin-LR, it was evident that an optimal ferrate concentration exists, whereby higher Fe(VI) concentrations above the optimum leads to a reduction in microcystin-LR degradation. In addition, the rate of microcystin-LR degradation was found to be strongly dependent on pH and was greatest at pH 6. The initial rate of photocatalytic reduction under different conditions was analysed using a Langmuirian form. Decrease in rates in the presence of dissolved oxygen may be due to competition between oxygen and ferrate as electron scavengers and to non-productive radical species interactions. The reaction between ferrate(VI) and microcystins-LR in the pH range of 6.0-10.0 is most likely controlled by the protonated Fe(VI) species, HFeO(4)(-). The photocatalytic oxidation of selected, recalcitrant contaminants was found to be significantly greater in the presence of ferrate, arising from the role of ferrate in inhibiting the h(vb)(+)-e(-)(cb) pair recombination on TiO(2) surfaces and the corresponding generation of highly oxidative Fe(V) species. The performance of the ferrate/photocatalysis system is strongly influenced by the reaction conditions, particularly the pH and dissolved oxygen concentration, arising from the complex nature of the interactions between the catalyst and the solution. Overall, the treatment performance of the Fe(VI)-TiO(2)-UV system is generally superior to alternative chemical oxidation methods. The formation of intermediate Fe(V) species in the photocatalytic reduction of ferrate(VI) requires confirmation, and a method involving electron paramagnetic resonance spectroscopy could be applied for this. The reactivity of Fe(V) with the selected contaminants is required in order to better understand the role of ferrate in the Fe(VI)-TiO(2)-UV oxidation system. To increase the practical utility of the system, it is recommended that future studies involving the photocatalytic oxidation of pollutants in the presence of ferrate(VI) should focus on developing modified TiO(2) surfaces that are photocatalytic under visible light conditions.

Bare TiO2 and graphene oxide TiO2 photocatalysts on the degradation of selected pesticides and influence of the water matrix

NASA Astrophysics Data System (ADS)

Cruz, Marta; Gomez, Cristina; Duran-Valle, Carlos J.; Pastrana-Martínez, Luisa M.; Faria, Joaquim L.; Silva, Adrián M. T.; Faraldos, Marisol; Bahamonde, Ana

2017-09-01

The photocatalytic activity of a home-made titanium dioxide (TiO2) and its corresponding composite based on graphene oxide (GO), the GO-TiO2 catalyst, has been investigated under UV-vis in the photodegradation of a mixture of four pesticides classified by the European Union as priority pollutants: diuron, alachlor, isoproturon and atrazine. The influence of two water matrices (ultrapure or natural water) was also studied. Natural water led to a decrease on the degradation of the studied pollutants when the bare TiO2 photocatalyst was employed, since this water contains both inorganic and organic species that are dissolved and commonly restrain the photocatalytic process. On the contrary, the photo-efficiency of the GO-TiO2 composite seems to be less affected by water matrix variation, with very good initial pesticide photodegradation rates under both natural and ultrapure water matrices. A comparative study between GO-TiO2 and the commercial Evonik TiO2 P25 catalyst was also carried out to analyze the photocatalytic degradation of these pesticides under visible light illumination conditions. Once again, a higher photocatalytic activity was found for the GO-TiO2 composite.

Assessing Photocatalytic Oxidation Using Modified TiO 2 Nanomaterials for Virus Inactivation in Drinking Water: Mechanisms and Application

NASA Astrophysics Data System (ADS)

Liga, Michael Vincent

Photocatalytic oxidation is an alternative water treatment method under consideration for disinfecting water. Chlorine disinfection can form harmful byproducts, and some viruses (e.g. adenoviruses) are resistant to other alternative disinfection methods. Photocatalytic oxidation using nano-sized photocatalytic particles (e.g. TiO2, fullerene) holds promise; however, it is limited by its low efficiency and long required treatment times. This research focuses on improving virus inactivation by photocatalytic oxidation by modifying catalysts for improved activity, by analyzing virus inactivation kinetics, and by elucidating the inactivation mechanisms of adenovirus serotype 2 (AdV2) and bacteriophage MS2. Modifying TiO2 with silver (nAg/TiO2) or silica (SiO2-TiO2) improves the inactivation kinetics of bacteriophage MS2 by a factor of 3-10. nAg/ TiO2 increases hydroxyl radical (HO·) production while SiO2 increases the adsorption of MS2 to TiO 2. These results suggest that modifying the photocatalyst surface to increase contaminant adsorption is an important improvement strategy along with increasing HO· production. The inactivation kinetics of AdV2 by P25 TiO2 is much slower than the MS2 inactivation kinetics and displays a strong shoulder, which is not present in the MS2 kinetics. nAg/TiO2 initially improves the inactivation rate of AdV2. SiO2-TiO2 reduces the AdV2 inactivation kinetics since adsorption is not significantly enhanced, as it is with MS2. Amino-C60 is highly effective for AdV2 inactivation under visible light irradiation, making it a good material for use in solar disinfection systems. The efficacy of amino-fullerene also demonstrates that singlet oxygen is effective for AdV2 inactivation. When exposed to irradiated TiO2, AdV2 hexon proteins are heavily damaged resulting in the release of DNA. DNA damage is also present but may occur after capsids break. With MS2, the host interaction protein is rapidly damaged, but not the coat protein. The kinetics of MS2 inactivation are rapid since it may quickly lose its ability to attach to host cells, while AdV2 kinetics are slower since the entire capsid must undergo heavy oxidation before inactivation occurs. Adenovirus inactivation likely occurs through breaching the capsid followed by radical attack of DNA and core proteins.

Research Update: Photoelectrochemical water splitting and photocatalytic hydrogen production using ferrites (MFe{sub 2}O{sub 4}) under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dillert, Ralf; Laboratorium für Nano- und Quantenengineering, Gottfried Wilhelm Leibniz Universität Hannover, Schneiderberg 39, 30167 Hannover; Taffa, Dereje H.

2015-10-01

The utilization of solar light for the photoelectrochemical and photocatalytic production of molecular hydrogen from water is a scientific and technical challenge. Semiconductors with suitable properties to promote solar-driven water splitting are a desideratum. A hitherto rarely investigated group of semiconductors are ferrites with the empirical formula MFe{sub 2}O{sub 4} and related compounds. This contribution summarizes the published results of the experimental investigations on the photoelectrochemical and photocatalytic properties of these compounds. It will be shown that the potential of this group of compounds in regard to the production of solar hydrogen has not been fully explored yet.

Origin of the improved photocatalytic activity of Cu incorporated TiO2 for hydrogen generation from water

NASA Astrophysics Data System (ADS)

Hu, Qianqian; Huang, Jiquan; Li, Guojing; Jiang, Yabin; Lan, Hai; Guo, Wang; Cao, Yongge

2016-09-01

Cu incorporated TiO2 has been regarded as a low-cost photocatalyst with excellent photocatalytic performance for water splitting. Here we try to exploit the origin of its high reactivity by fabricating a series of Cu incorporated TiO2 films with the same Cu content under different atmosphere. Based on the comprehensive structure and surface characterizations, it is found that CuO is unstable and will be reduced to Cu2O or even to metallic Cu under light irradiation during the photocatalytic reaction, and Cu2O is an efficient co-catalyst that promotes the separation of photogenerated carriers while metallic Cu can further boost the photocatalytic activity. Besides, it is also noticed that the chemisorbed oxygen on the particle surface blocks the water splitting. By depositing TiO2 films under oxygen rich condition, oxygen vacancy is decreased greatly, which facilitates the removal of chemisorbed oxygen and the formation of metallic Cu during photocatalytic reaction, resulting in an ultra-high H2 evolution rate of 2.80 μmol cm-2 h-1, which is about 55 times higher than that of pure TiO2.

Solar Spectrum Photocatalytic Conversion of CO2 and Water Vapor Into Hydrocarbons Using TiO2 Nanoparticle Membranes

NASA Astrophysics Data System (ADS)

Rani, Sanju; Bao, Ningzhong; Roy, Somnath C.

2014-01-01

A viable option for recycling carbon dioxide is through the sunlight-powered photocatalytic conversion of CO2 and water vapor into hydrocarbon fuels over highly active nanocatalysts. With photocatalytic CO2 reduction sunlight, a renewable energy source as durable as the sun, is used to drive the catalytic reaction with the resultant fuel products compatible with the current hydrocarbon-based energy infrastructure. The use of co-catalyst (Cu, Pt)-sensitized TiO2 nanoparticle wafers in the photocatalytic conversion of CO2 and water vapor to hydrocarbon fuels, with optimal humidity levels and exposure times established. We also attempted to increase product formation by sputtering both co-catalysts on the nanoparticle wafer's surface, with the resulting product rates significantly higher than that of either the Cu or Pt coated samples. When the TiO2 nanoparticle wafers are used in a flow-through membrane implementation we find a significant increase in product rates of formation, including methane, hydrogen, and carbon monoxide. We believe that nanocatalyst-based flow-through membranes are a viable route for achieving large-scale and low cost photocatalytic solar fuel production.

CONTINUOUS-MODE PHOTOCATALYTIC DEGRADATION OF CHLORINATED PHENOLS AND PESTICIDES IN WATER USING A BENCH-SCALE TIO2 ROTATING DISK REACTOR

EPA Science Inventory

Photocatalytic degradation of phenol, chlorinated phenols, and lindane was evaluated in a continuous flow TiOz rotating disk photocatalytic reactor (RDPR). The RDPR operated at a hydraulic residence time of 0.25 day and at a disk angular velocity of 12 rpm. At low molar feed conc...

A new photocatalytic reactor for trace contaminant control: a water polishing system.

PubMed

Gonzalez-Martin, A; Kim, J; Van Hyfte, J; Rutherford, L A; Andrews, C

2001-01-01

In spacecraft water recovery systems there is a need to develop a postprocessor water polishing system to remove organic impurities to levels below 250 micrograms/L (ppb) with a minimum use of expendables. This article addresses the development of a photocatalytic process as a postprocessor water polishing system that is microgravity compatible, operates at room temperature, and requires only a minimal use of both oxygen gas (or air) and electrical power for low energy UV-A (315-400 nm) lamps. In the photocatalytic process, organic contaminants are degraded to benign end products on semiconductor surfaces, usually TiO2. Some challenging issues related to the use of TiO2 for the degradation of organic contaminants have been addressed. These include: i) efficient and stable catalytic material; ii) immobilization of the catalyst to produce a high surface area material that can be used in packed-bed reactors, iii) effective light penetration, iv) effective, microgravity-compatible, oxidant delivery; v) reduced pressure drop, and vi) minimum retention time. The research and development performed on this photocatalytic process is presented in detail. Grant numbers: NAS9-97182.

Direct synthesis of mesostructured carbon nanofibers decorated with silver-nanoparticles as a multifunctional membrane for water treatment

NASA Astrophysics Data System (ADS)

Aboueloyoun Taha, Ahmed

2015-12-01

One-dimensional (1D) porous carbon nanofibers (CNFs) decorated by silver (Ag) nanoparticles (NPs) were prepared using a one-pot/self-template synthesis strategy by combining electrospinning and carbonization methods. The characterization results revealed that AgNPs were homogenously distributed along the CNFs and possessed a relatively uniform nano-size of about 12 nm. The novel membrane distinctively displayed enhanced photocatalytic activity under visible-light irradiation. The membrane exhibited excellent dye degradation and bacteria disinfection in batch experiments. The high photocatalytic activity can be attributed to the highly accessible surface areas, good light absorption capability, and high separation efficiency of photogenerated electron-hole pairs. The as-prepared membranes can be easily recycled because of their 1D property.

N-Doped TiO2-Coated Ceramic Membrane for Carbamazepine Degradation in Different Water Qualities

PubMed Central

Luster, Enbal; Avisar, Dror; Horovitz, Inna; Lozzi, Luca; Baker, Mark A.; Grilli, Rossana; Mamane, Hadas

2017-01-01

The photocatalytic degradation of the model pollutant carbamazepine (CBZ) was investigated under simulated solar irradiation with an N-doped TiO2-coated Al2O3 photocatalytic membrane, using different water types. The photocatalytic membrane combines photocatalysis and membrane filtration in a single step. The impact of each individual constituent such as acidity, alkalinity, dissolved organic matter (DOM), divalent cations (Mg2+ and Ca2+), and Cl− on the degradation of CBZ was examined. CBZ in water was efficiently degraded by an N-doped TiO2-coated Al2O3 membrane. However, elements added to the water, which simulate the constituents of natural water, had an impact on the CBZ degradation. Water alkalinity inhibited CBZ degradation mostly due to increase in pH while radical scavenging by carbonate was more dominant at higher values (>200 mg/L as CaCO3). A negative effect of Ca2+ addition on photocatalytic degradation was found only in combination with phosphate buffer, probably caused by deposition of CaHPO4 or CaHPO4·2H2O on the catalyst surface. The presence of Cl− and Mg2+ ions had no effect on CBZ degradation. DOM significantly inhibited CBZ degradation for all tested background organic compounds. The photocatalytic activity of N-doped TiO2-coated Al2O3 membranes gradually decreased after continuous use; however, it was successfully regenerated by 0.1% HCl chemical cleaning. Nevertheless, dissolution of metals like Al and Ti should be monitored following acid cleaning. PMID:28758982

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

PubMed Central

Agócs, Tamás Zoltán; Puskás, István; Varga, Erzsébet; Molnár, Mónika

2016-01-01

Advanced oxidation processes (AOPs) are considered highly competitive water treatment technologies for the removal of organic pollutants. Among AOP techniques, photocatalysis has recently been the most widely studied. Our aims were to investigate how the dispersion of nanosized titanium dioxide (nanoTiO2) applied in photodegradation-based procedures can be stabilized with cyclodextrins in order to obtain a new, more efficient photocatalyst for the purification of waters polluted by xenobiotics applying UV irradiation. During our work, on the one hand, we studied the behavior and stability of nanoTiO2 in cyclodextrin solutions. On the other hand, we used various monomer and polymer cyclodextrin derivatives, and assessed the options for nanoTiO2 stabilization in the presence of various salts and tap water on the basis of turbidity tests. The physical stability of nanoTiO2 dispersions is diminished in the presence of the salts found in tap water (and occurring also in surface waters and ground water) and they are precipitated immediately. This colloidal instability can be improved by cyclodextrin derivatives. Based on the results of our studies we have selected carboxymethyl β-cyclodextrin polymer (CMBCD-P) for stabilization of nanoTiO2 dispersions. The photocatalytic degradation of methylene blue and ibuprofen as model organic pollutants in various media (distilled water, NaCl solution and tap water) has been studied using nanoTiO2 as catalyst stabilized by CMBCD-P. CMBCD-P itself showed a catalytic effect on the UV degradation of methylene blue. In addition to enhancing the colloid stability of nanoTiO2 CMBCD-P showed also synergistic effects in catalyzing the photodecomposition process of the dye. On the other hand, ibuprofen as a model pharmaceutical, a pollutant of emerging concern (EP), was protected by CMBCD-P against the photocatalytic degradation showing that inclusion complex formation can result in opposite effects depending on the structure of the host–guest complex. PMID:28144360

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants.

PubMed

Agócs, Tamás Zoltán; Puskás, István; Varga, Erzsébet; Molnár, Mónika; Fenyvesi, Éva

2016-01-01

Advanced oxidation processes (AOPs) are considered highly competitive water treatment technologies for the removal of organic pollutants. Among AOP techniques, photocatalysis has recently been the most widely studied. Our aims were to investigate how the dispersion of nanosized titanium dioxide (nanoTiO 2 ) applied in photodegradation-based procedures can be stabilized with cyclodextrins in order to obtain a new, more efficient photocatalyst for the purification of waters polluted by xenobiotics applying UV irradiation. During our work, on the one hand, we studied the behavior and stability of nanoTiO 2 in cyclodextrin solutions. On the other hand, we used various monomer and polymer cyclodextrin derivatives, and assessed the options for nanoTiO 2 stabilization in the presence of various salts and tap water on the basis of turbidity tests. The physical stability of nanoTiO 2 dispersions is diminished in the presence of the salts found in tap water (and occurring also in surface waters and ground water) and they are precipitated immediately. This colloidal instability can be improved by cyclodextrin derivatives. Based on the results of our studies we have selected carboxymethyl β-cyclodextrin polymer (CMBCD-P) for stabilization of nanoTiO 2 dispersions. The photocatalytic degradation of methylene blue and ibuprofen as model organic pollutants in various media (distilled water, NaCl solution and tap water) has been studied using nanoTiO 2 as catalyst stabilized by CMBCD-P. CMBCD-P itself showed a catalytic effect on the UV degradation of methylene blue. In addition to enhancing the colloid stability of nanoTiO 2 CMBCD-P showed also synergistic effects in catalyzing the photodecomposition process of the dye. On the other hand, ibuprofen as a model pharmaceutical, a pollutant of emerging concern (EP), was protected by CMBCD-P against the photocatalytic degradation showing that inclusion complex formation can result in opposite effects depending on the structure of the host-guest complex.

Emission spectroscopy of divalent-cation-doped GaN photocatalysts

NASA Astrophysics Data System (ADS)

Hirai, Takeshi; Harada, Takashi; Ikeda, Shigeru; Matsumura, Michio; Saito, Nobuo; Nishiyama, Hiroshi; Inoue, Yasunobu; Harada, Yoshiyuki; Ohno, Nobuhito; Maeda, Kazuhiko; Kubota, Jun; Domen, Kazunari

2011-12-01

Photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra of GaN particles doped with divalent cations (Mg2+, Zn2+, and Be2+), which promote photocatalytic overall water splitting, were investigated. The PL and TRPL spectra were mainly attributed to donor-acceptor pair recombination between the divalent cation dopants and divalent anion impurities (O2- and S2-) unintentionally introduced from raw materials, which form acceptor and donor levels, respectively. These levels are likely to provide holes and electrons required for photocatalytic reactions, contributing to the photocatalytic activity of the GaN-based photocatalysts for overall water splitting.

Efficient adsorption and photocatalytic degradation of organic pollutants diluted in water using fluoride-modified hydrophobic mesoporous silica

NASA Astrophysics Data System (ADS)

Yamashita, Hiromi; Maekawa, Kazuhiro; Nakao, Hidetoshi; Anpo, Masakazu

2004-10-01

Using a mixture of tetraethylammonium fluoride and dodecylamine as templates, hydrophobic mesoporous silica supports were prepared. The fine anatase TiO 2 photocatalysts were prepared on the fluoride-modified hydrophobic mesoporous silica and the adsorption properties and the photocatalytic degradation of an aqueous 2-propanol or 2-hexanol solution into CO 2 and H 2O have been studied. The amount of adsorption and the photocatalytic reactivities increased with increasing the content of fluoride ions on these photocatalysts. 2-Hexanol diluted in water was adsorbed on the hydrophobic catalysts more efficiently than 2-propanol.

Wastewater treatment by sonophotocatalysis using PEG modified TiO2 film in a circular Photocatalytic-Ultrasonic system.

PubMed

Hu, Xiaohong; Zhu, Qi; Gu, Zhibin; Zhang, Nan; Liu, Na; Stanislaus, Mishma S; Li, Dawei; Yang, Yingnan

2017-05-01

TiO 2 photocatalyst film recently has been utilized as the potential candidate for the wastewater treatment, due to its high stability and low toxicity. In order to further increase the photocatalytic ability and stability, different molecular weight of polyethylene glycol (PEG) were used to modify TiO 2 structure to synthesize porous thin film used in the developed Photocatalytic-Ultrasonic system in this work. The results showed that PEG2000 modified TiO 2 calcinated under 450°C for 2h exhibited the highest photocatalytic activity, attributed to the smallest crystallite size and optimal particle size. Over 95.0% of rhodamine B (Rh B) was photocatalytically degraded by optimized PEG 2000 -TiO 2 film after 60min of UV irradiation, while only about 50.8% of Rh B was decolored over pure TiO 2 film. Furthermore, optimized PEG 2000 -TiO 2 film was used in a circular Photocatalytic-Ultrasonic system, and the obtained synergy (0.6519) of sonophotocatalysis indicated its extremely high efficiency for Rh B degradation. In this Photocatalytic-Ultrasonic system, larger amount of PEG 2000 -TiO 2 coated glass beads, stronger ultrasonic power and longer experimental time could result to higher degradation efficiency of Rh B. In addition, repetitive experiments showed that about 97.2% of Rh B were still degraded in the fifth experiment by sonophotocatalysis using PEG 2000 -TiO 2 film. Therefore, PEG 2000 -TiO 2 film used in Photocatalytic-Ultrasonic system has promising potential for wastewater treatment, due to its excellent photocatalytic activity and high stability. Copyright © 2016 Elsevier B.V. All rights reserved.

High UV light performance for the degradation of Rhodamine B dye by synthesized Bi2S3ZnO nanocomposite

NASA Astrophysics Data System (ADS)

Sangareswari, M.; Meenakshi Sundaram, M.

2017-05-01

Heterogeneous photocatalytic degradation of organics in water and wastewater by large band gap semiconductors has offered an attractive alternative for environmental remediation. Zinc oxide is a very fast and efficient catalyst because of its wide band gap and large exciton binding energy. In this study, an efficient Bi2S3ZnO was synthesized by sonochemical method. The obtained product was further characterized by TEM, SEM, XRD, FT-IR and UV-DRS analysis. Scanning electron microscopy images revealed that Bi2S3ZnO has flower-like structure. The synthesized flower-like Bi2S3ZnO nanocomposites were more efficient than commercial ZnO for the degradation of organic contaminants under UV light irradiation. The prepared material shows enhanced photocatalytic activity on Rhodamine B dye solution under UV light irradiation. The percentage removal of dye was calculated by UV-Vis spectrophotometer. In addition, Bi2S3ZnO showed tremendous photocatalytic stability after seven cycles under UV light irradiation. A possible mechanism for the photocatalytic oxidative degradation was also discussed. It is concluded that the Bi2S3ZnO nanocomposite acts as an excellent photocatalyst for the decomposition of RhB and it could be a potential material for essential wastewater treatment.

Photocatalytic polyoxometalate compositions of tungstovanadates and uses as water oxidation catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Craig L.; Gueletii, Iourii V.; Song, Jie

This disclosure relates to photocatalytic polyoxometalate compositions of tungstovanadates and uses as water oxidation catalysts. In certain embodiments, the disclosure relates to compositions comprising water, a complex of a tetra-metal oxide cluster and VW.sub.9O.sub.34 ligands, and a photosensitizer. Typically, the metal oxide cluster is Co. In certain embodiments, the disclosure relates to electrodes and other devices comprising water oxidation catalysts disclosed herein and uses in generating fuels and electrical power from solar energy.

Sprayed nanostructured TiO2 films for efficient photocatalytic degradation of textile azo dye.

PubMed

Stambolova, Irina; Shipochka, Capital Em Cyrillicaria; Blaskov, Vladimir; Loukanov, Alexandrе; Vassilev, Sasho

2012-12-05

Spray pyrolysis procedure for preparation of nanostructured TiO(2) films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO(2) were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO(2) is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80 ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO(2), which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films. Copyright © 2012 Elsevier B.V. All rights reserved.

Influence of pH-control in phosphoric acid treatment of titanium oxide and their powder properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onoda, Hiroaki, E-mail: onoda@kpu.ac.jp; Matsukura, Aki

Highlights: • The photocatalytic activity was suppressed by phosphoric acid treatment. • The obtained pigment had small particles with sub-micrometer size. • By phosphoric acid treatment, the smoothness of samples improved. - Abstract: Titanium oxide that has the photocatalytic activity is used as a white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, titanium oxide was shaken with phosphoric acid at various pH to synthesize a novel white pigment for cosmetics. Their chemical composition, powder properties, photocatalytic activity, color phase, and smoothness were studied. The obtainedmore » materials indicated XRD peaks of titanium oxide, however, these peak intensity became weak by phosphoric acid treatment. These samples without heating and heated at 100 °C included the small particles with sub-micrometer size. The photocatalytic activity of the obtained powders became weak by phosphoric acid treatment at pH 4 and 5 to protect the sebum on the skin.« less

Efficient photocatalytic oxidation of arsenite from contaminated water by Fe2O3-Mn2O3 nanocomposite under UVA radiation and process optimization with experimental design.

PubMed

Eslami, Hadi; Ehrampoush, Mohammad Hassan; Esmaeili, Abbas; Ebrahimi, Ali Asghar; Salmani, Mohammad Hossein; Ghaneian, Mohammad Taghi; Falahzadeh, Hossein

2018-09-01

The efficiency of photocatalytic oxidation process in arsenite (As(III)) removal from contaminated water by a new Fe 2 O 3 -Mn 2 O 3 nanocomposite under UV A radiation was investigated. The effect of nanocomposite dosage, pH and initial As(III) concentration on the photocatalytic oxidation of As(III) were studied by experimental design. The synthesized nanocomposite had a uniform and spherical morphological structure and contained 49.83% of Fe 2 O 3 and 29.36% of Mn 2 O 3 . Based on the experimental design model, in photocatalytic oxidation process, the effect of pH was higher than other parameters. At nanocomposite concentrations of more than 12 mg L -1 , pH 4 to 6 and oxidation time of 30 min, photocatalytic oxidation efficiency was more than 95% for initial As(III) concentration of less than 500 μg L -1 . By decreasing pH and increasing the nanocomposite concentration, the photocatalytic oxidation efficiency was increased. Furthermore, by increasing the oxidation time from 10 to 240 min, in addition to oxidation of As(III) to arsenate (As(V)), the residual As(V) was adsorbed on the Fe 2 O 3 -Mn 2 O 3 nanocomposite and total As concentration was decreased. Therefore, Fe 2 O 3 -Mn 2 O 3 nanocomposite as a bimetal oxide, at low doses and short time, can enhance and improve the efficiency of the photocatalytic oxidation and adsorption of As(III) from contaminated water resources. Furthermore, the energy and material costs of the UV A /Fe 2 O 3 -Mn 2 O 3 system for photocatalytic oxidation of 1  mg L -1 As(III) in the 1 L laboratory scale reactor was 0.0051 €. Copyright © 2018 Elsevier Ltd. All rights reserved.

Physicochemical and photocatalytic studies of Ln3+- ZnO for water disinfection and wastewater treatment applications

NASA Astrophysics Data System (ADS)

Ibrahim, Marwa M.; Asal, Saad

2017-12-01

In the present work, x mol Ln3+ modified ZnO Nano-particles (Ln = Sm3+, Eu3+ and Gd3+ ions; x = 0.008, 0.015, 0.025, 0.03 and 0.05) were synthesized by precipitation method. These Nano-particles are characterized by different advanced techniques; such as X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopic (EDX), UV-Visible diffuse reflectance, and fluorescence (FL) spectroscopy. Doping by lanthanides improves the crystal, surface area, porosity, morphology, as well as the optical adsorption and emission of UV light properties of the prepared photo-catalysts. Photo-catalytic activity for the prepared Nano-materials was determined using both, fluorescent probe and dye methods. Results showed that the highly active Nano-particle is 0.025 Gd3+-ZnO. The highly active sample (0.025 mol Gd3+- ZnO) successfully mineralized textile dye and real refractory wastewater samples under sunlight illumination using CPC photo-reactor. Prepared photo-catalysts were also applied for water disinfection.

Optimization of Malachite Green Removal from Water by TiO₂ Nanoparticles under UV Irradiation.

PubMed

Ma, Yongmei; Ni, Maofei; Li, Siyue

2018-06-13

TiO₂ nanoparticles with surface porosity were prepared by a simple and efficient method and presented for the removal of malachite green (MG), a representative organic pollutant, from aqueous solution. Photocatalytic degradation experiments were systematically conducted to investigate the influence of TiO₂ dosage, pH value, and initial concentrations of MG. The kinetics of the reaction were monitored via UV spectroscopy and the kinetic process can be well predicted by the pseudo first-order model. The rate constants of the reaction kinetics were found to decrease as the initial MG concentration increased; increased via elevated pH value at a certain amount of TiO₂ dosage. The maximum efficiency of photocatalytic degradation was obtained when the TiO₂ dosage, pH value and initial concentrations of MG were 0.6 g/L, 8 and 10 −5 mol/L (M), respectively. Results from this study provide a novel optimization and an efficient strategy for water pollutant treatment.

Investigation into adsorption and photocatalytic degradation of gaseous benzene in an annular fluidized bed photocatalytic reactor.

PubMed

Geng, Qijin; Tang, Shankang; Wang, Lintong; Zhang, Yunchen

2015-01-01

The adsorption and photocatalytic degradation of gaseous benzene were investigated considering the operating variables and kinetic mechanism using nano-titania agglomerates in an annular fluidized bed photocatalytic reactor (AFBPR) designed. The special adsorption equilibrium constant, adsorption active sites, and apparent reaction rate coefficient of benzene were determined by linear regression analysis at various gas velocities and relative humidities (RH). Based on a series of photocatalytic degradation kinetic equations, the influences of operating variables on degradation efficiency, apparent reaction rate coefficient and half-life were explored. The findings indicated that the operating variables have obviously influenced the adsorption/photocatalytic degradation and corresponding kinetic parameters. In the photocatalytic degradation process, the relationship between photocatalytic degradation efficiency and RH indicated that water molecules have a dual-function which was related to the structure characteristics of benzene. The optimal operating conditions for photocatalytic degradation of gaseous benzene in AFBPR were determined as the fluidization number at 1.9 and RH required related to benzene concentration. This investigation highlights the importance of controlling RH and benzene concentration in order to obtain the desired synergy effect in photocatalytic degradation processes.

Enhanced photocatalytic H2-production activity of graphene-modified titania nanosheets

NASA Astrophysics Data System (ADS)

Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

2011-09-01

Graphene-modified TiO2 nanosheets with exposed (001) facets (graphene/TiO2) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO2 nanosheets with exposed (001) facets in an ethanol-water solvent. These nanocomposite samples showed high photocatalytic H2-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ~1.0 wt%, giving a H2-production rate of 736 μmol h-1 g-1 with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO2 nanosheets by more than 41 times. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene z.rad- (-0.08 V vs. SHE, pH = 0) in comparison to the conduction band (-0.24 V) of anatase TiO2, meanwhile the aforementioned absolute value is higher than the reduction potential of H+ (0 V), which favors the electron transfer from the conduction band (CB) of TiO2 to graphene sheets and the reduction of H+, thus enhancing photocatalytic H2-production activity. The proposed mechanism for the observed photocatalytic performance of TiO2 nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon material as an effective co-catalyst.

Photochemically deposited nano-Ag/sol-gel TiO2-In2O3 mixed oxide mesoporous-assembled nanocrystals for photocatalytic dye degradation.

PubMed

Sreethawong, Thammanoon; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

2014-05-01

This work focused on the improvement of the photocatalytic activity for Congo Red (CR) azo dye degradation of mesoporous-assembled 0.95 TiO2-0.05 In2O3 mixed oxide photocatalyst (with a TiO2-to-In2O3 molar ratio of 0.95:0.05) by loading with Ag nanoparticles. The mesoporous-assembled 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was synthesized by a hydrolytic sol-gel method with the aid of a structure-directing surfactant, prior to loading with various Ag contents (0.5-2 wt.%) by a photochemical deposition method. The optimum Ag loading content was found to be 1.5 wt.%, exhibiting a great increase in photocatalytic CR dye degradation activity. The 1.5 wt.% Ag-loaded 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was further applied for the CR dye degradation in the presence of water hardness. Different types (Ca2+ and Ca2+ -Mg2+ mixture) and concentrations (200 and 500 mg/l) of water hardness were investigated. The results showed that the water hardness reduced the photocatalytic CR dye degradation activity, particularly for the extremely hard water with 500 mg/l of Ca2+ -Mg2+ mixture. The adjustment of initial solution pH of the CR dye-containing hard water to an appropriate value was found to improve the photocatalytic CR dye degradation activity under the identical reaction conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

TiO2 Processed by pressurized hot solvents as a novel photocatalyst for photocatalytic reduction of carbon dioxide

NASA Astrophysics Data System (ADS)

Reli, Martin; Kobielusz, Marcin; Matějová, Lenka; Daniš, Stanislav; Macyk, Wojciech; Obalová, Lucie; Kuśtrowski, Piotr; Rokicińska, Anna; Kočí, Kamila

2017-01-01

Anatase-brookite TiO2 photocatalysts were prepared by the sol-gel process controlled within reverse micelles and processing by pressurized hot solvents-water/methanol/water (TiO2(M)) and water/ethanol/water (TiO2(E)), as an unconventional alternative to common calcination. The main goal of this work was to prepare anatase-brookite mixtures by processing by two different alcohols (methanol and ethanol) and evaluate the influence of the alcohol on the photocatalytic activity. Prepared photocatalysts were characterized by organic elemental analysis, nitrogen physisorption, XRD, UV-vis, photoelectrochemical and spectroelectrochemical measurements and XPS. The prepared photocatalysts efficiency was tested on the photocatalytic reduction of carbon dioxide and compared with commercial TiO2 Evonik P25. Both prepared nanocomposites were more efficient towards methane production but Evonik P25 was the most efficient towards hydrogen generated through water splitting. The higher performance of anatase-brookite mixture towards methane production can be explained by (i) a higher photocatalytic activity of brookite than rutile; (ii) a large surface area of anatase-brookite composites enabling better carbon dioxide adsorption; (iii) the photoinduced electron transfer from the brookite conduction band to the anatase conduction band. On the other hand, a higher production of hydrogen in the presence of Evonik P25 is caused by a better charge separation in anatase-rutile than anatase-brookite phase compositions. TiO2(M) appeared more active than TiO2(E) in the photocatalytic reduction of carbon dioxide due to a lower density of defects created in the crystal lattice.

4-chlorophenol removal from water using graphite and graphene oxides as photocatalysts.

PubMed

Bustos-Ramírez, Karina; Barrera-Díaz, Carlos Eduardo; De Icaza-Herrera, Miguel; Martínez-Hernández, Ana Laura; Natividad-Rangel, Reyna; Velasco-Santos, Carlos

2015-01-01

Graphite and graphene oxides have been studied amply in the last decade, due to their diverse properties and possible applications. Recently, their functionality as photocatalytic materials in water splitting was reported. Research in these materials is increasing due to their band gap values around 1.8-4 eV, and therefore, these are comparable with other photocatalysts currently used in heterogeneous photocatalytic processes. Thus, this research reports the photocatalytic effectiveness of graphite oxide (GO) and graphene oxide (GEO) in the degradation of 4-chlorophenol (4-CP) in water. Under the conditions defined for this research, 92 and 97% of 4-CP were degraded with GO and GEO respectively, also 97% of total organic carbon was removed. In addition, by-products of 4-CP that produce a yellow solution obtained only using photolysis are eliminated by photocatalyst process with GO and GEO. The degradation of 4-CP was monitored by UV-Vis spectroscopy, High Performance Liquid Chromatography (HPLC) and Chemical Oxygen Demand (COD). Thus, photocatalytic activity to remove 4-CP from water employing GO and GEO without doping is successfully showed, and therefore, a new gate in research for these materials is opened.

Improved waste water treatment by bio-synthesized Graphene Sand Composite.

PubMed

Poornima Parvathi, V; Umadevi, M; Bhaviya Raj, R

2015-10-01

The photocatalytic and antibacterial properties of graphene biosynthesized from sugar and anchored on sand particles has been focused here. The morphology and composition of the synthesized Graphene Sand Composite (GSC) was investigated by means of X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDAX), Fourier Transform Infra-red Spectroscopy (FTIR) and UV-Visible spectroscopy. SEM images show wrinkly edges. This is characteristic of graphenic morphology. Three types of waste water samples namely, textile waste (TW), sugarcane industrial waste water (SW) and domestic waste water from a local purification center at Kodaikanal (KWW) were collected and treated. Adsorption experiments showed effective removal of impurities at 0.2 g of GSC. Photocatalytic activity was analyzed under visible and ultraviolet irradiation. The rate constant for TW increased to 0.0032/min for visible light irradiation from 0.0029/min under UV irradiation. SW showed similar improved activity with rate constant as 0.0023/min in visible irradiation compared to 0.0016/min under UV irradiation. For KWW enhanced activity was seen only in visible light irradiation with rate constant 0.0025/min. GSC showed an inhibition zone of 20 mm against the bacterium Escherichia coli. Results suggest development of economic and effective waste water management systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic treatment of pharmaceutical wastewater using new multiwall-carbon nanotubes/TiO{sub 2}/SiO{sub 2} nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czech, Bożena, E-mail: bczech@hektor.umcs.lublin.pl; Buda, Waldemar

For the photocatalytic removal of bisphenol A (BPA) and carbamazepine (CBZ) from water solution a new multiwall-carbon nanotubes and TiO{sub 2}/SiO{sub 2} nanocomposites (MWCNT–TiO{sub 2}–SiO{sub 2}) were applied. Nanocomposites with the addition of 0.15–17.8 wt% MWCNT show high potential for the removal of both pollutants. The starting concentration of each contaminant was halved during 20 min of UVA irradiation. The decomposition process of CBZ over investigated nanocomposites proceeded differently than it was observed for the classical photocatalyst P25. The kinetics of the removal followed as a pseudo-first order regime with the k{sub 1} in range 0.0827–0.1751 min{sup −1} for BPA andmore » 0.0131–0.0743 min{sup −1} for CBZ. Toxicity to Vibrio fischeri and Daphnia magna was significantly reduced indicating formation of non-toxic products of photooxidation of tested contaminants. - Highlights: • MWCNT enhanced TiO{sub 2} activity in UVA and the removal of BPA and CBZ. • At least 50% PPCPs removal during 30 min of photocatalytic treatment was observed. • MWCNT changed the mechanism of CBZ decomposition but not BPA. • Decomposition products of both BPA and CBZ possessed low toxicity. • Photocatalysis may be recommended for the initial treatment of pharmaceutical wastewater.« less

Solution-combustion synthesis of doped TiO2 compounds and its potential antileishmanial activity mediated by photodynamic therapy.

PubMed

Lopera, A A; Velásquez, A M A; Clementino, L C; Robledo, S; Montoya, A; de Freitas, L M; Bezzon, V D N; Fontana, C R; Garcia, C; Graminha, M A S

2018-06-01

Photodynamic therapy has emerged as an alternative treatment for cutaneous leishmaniasis, and compounds with photocatalytic behavior are promising candidates to develop new therapeutic strategies for the treatment of this parasitic disease. Titanium dioxide TiO 2 is a semiconductor ceramic material that shows excellent photocatalytic and antimicrobial activity under Ultraviolet irradiation. Due to the harmful effects of UV radiation, many efforts have been made in order to enhance both photocatalytic and antimicrobial properties of TiO 2 in the visible region of the spectrum by doping or through modifications in the route of synthesis. Herein, Fe-, Zn-, or Pt- doped TiO 2 nanostructures were synthesized by solution-combustion route. The obtained compounds presented aggregates of 100 nm, formed by particles smaller than 20 nm. Doping compounds shift the absorption spectrum towards the visible region, allowing production of reactive oxygen species in the presence of oxygen and molecular water when the system is irradiated in the visible spectrum. The Pt (EC 50  = 18.2 ± 0.8 μg/mL) and Zn (EC 50  = 16.4 ± 0.3 μg/mL) -doped TiO 2 presented the higher antileishmanial activities under visible irradiation and their application as photosensitizers in photodynamic therapy (PDT) strategies for the treatment of cutaneous leishmaniasis should be considered. Copyright © 2018 Elsevier B.V. All rights reserved.

Simultaneous biological-photocatalytic treatment with strain CDS-8 and TiO2 for chlorothalonil removal from liquid and soil.

PubMed

Wu, Minghui; Deng, Jing; Li, Junjie; Li, Ying; Li, Jinze; Xu, Heng

2016-12-15

In this study, a novel chlorothalonil (CTN) degrading bacterial strain CDS-8, identified as Pseudomonas sp., was combined with photocatalyst titanium dioxide (TiO 2 ) for the CTN degradation in liquid and soil. After 7day incubation, 90.73% of CTN was removed from mineral salt medium (MSM) by CDS-8 with the optimal condition at pH 7.0 and 30°C. Single biodegradation or photocatalytic degradation could not degrade CTN completely, and many toxic and persistent intermediate metabolites remained. However, simultaneous biological-photocatalytic treatments could markedly remove CTN and reduce the chemical oxygen demand (COD) which could not be removed by single biodegradation or photocatalytic degradation. In MSM, treatment with CDS-8/40mgL -1 TiO 2 showed the highest COD removal rate (84.10%). Furthermore, combined CDS-8/TiO 2 treatments could effectively degrade CTN in soil. In treatments with CDS-8/20mgkg -1 TiO 2 of soil, the maximum CTN removal rate reached 97.55% in turned soils. However, with CDS-8/40mgkg -1 TiO 2 of soil, the maximum CTN removal rate (94.94%) was found in static soil. In general, the combined biological-photocatalytic treatments provided a promising alternative candidate for the remediation of CTN-contaminated sites. Copyright © 2016 Elsevier B.V. All rights reserved.

Fast mineralization and detoxification of amoxicillin and diclofenac by photocatalytic ozonation and application to an urban wastewater.

PubMed

Moreira, Nuno F F; Orge, Carla A; Ribeiro, Ana R; Faria, Joaquim L; Nunes, Olga C; Pereira, M Fernando R; Silva, Adrián M T

2015-12-15

The degradation of two organic pollutants (amoxicillin and diclofenac) in 0.1 mM aqueous solutions was studied by using advanced oxidation processes, namely ozonation, photolysis, photolytic ozonation, photocatalysis and photocatalytic ozonation. Diclofenac was degraded quickly under direct photolysis by artificial light (medium-pressure vapor arc, λ(exc) > 300 nm), while amoxicillin remained very stable. In the presence of ozone, regardless of the type of process, complete degradation of both organic pollutants was observed in less than 20 min. Photolysis or ozonation on their own led to modest values of total organic carbon (TOC) removal (<6% or 41%, respectively in 180 min), while for photocatalysis (no ozone present) a significant fraction of nonoxidizable compounds remained in the treated water (∼15% after 180 min). In the case of photolytic ozonation, the kinetics of TOC removal was slow. In contrast, a relatively fast and complete mineralization of amoxicillin and diclofenac (30 and 120 min, respectively) was achieved when applying the photocatalytic ozonation process. The absence of toxicity of the treated waters was confirmed by growth inhibition assays using two different microorganisms, Escherichia coli and Staphylococcus aureus. Photocatalytic ozonation was also applied to an urban wastewater spiked with both amoxicillin and diclofenac. The parent pollutants were easily oxidized, but the TOC removal was only as much as 68%, mainly due to the persistent presence of oxamic acid in the treated sample. The same treatment allowed the effective degradation of a wide group of micropollutants (pesticides, pharmaceuticals, hormones and an industrial compound) detected in non-spiked urban wastewater. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic oxide films in the built environment

NASA Astrophysics Data System (ADS)

Österlund, Lars; Topalian, Zareh

2014-11-01

The possibility to increase human comfort in buildings is a powerful driving force for the introduction of new technology. Among other things our sense of comfort depends on air quality, temperature, lighting level, and the possibility of having visual contact between indoors and outdoors. Indeed there is an intimate connection between energy, comfort, and health issues in the built environment, leading to a need for intelligent building materials and green architecture. Photocatalytic materials can be applied as coatings, filters, and be embedded in building materials to provide self-cleaning, antibacterial, air cleaning, deodorizing, and water cleaning functions utilizing either solar light or artificial illumination sources - either already present in buildings, or by purposefully designed luminaries. Huge improvements in indoor comfort can thus be made, and also alleviate negative health effects associated with buildings, such as the sick-house syndrome. At the same time huge cost savings can be made by reducing maintenance costs. Photocatalytic oxides can be chemically modified by changing their acid-base surface properties, which can be used to overcome deactivation problems commonly encountered for TiO2 in air cleaning applications. In addition, the wetting properties of oxides can be tailored by surface chemical modifications and thus be made e.g. oleophobic and water repellent. Here we show results of surface acid modified TiO2 coatings on various substrates by means of photo-fixation of surface sulfate species by a method invented in our group. In particular, we show that such surface treatments of photocatalytic concrete made by mixing TiO2 nanoparticles in reactive concrete powders result in concrete surfaces with beneficial self-cleaning properties. We propose that such approaches are feasible for a number of applications in the built environment, including glass, tiles, sheet metals, plastics, etc.

Titanium Dioxide Coatings Sprayed by a Water-Stabilized Plasma Gun (WSP) with Argon and Nitrogen as the Powder Feeding Gas: Differences in Structural, Mechanical and Photocatalytic Behavior

NASA Astrophysics Data System (ADS)

Ctibor, P.; Pala, Z.; Sedláček, J.; Štengl, V.; Píš, I.; Zahoranová, T.; Nehasil, V.

2012-06-01

Titanium dioxide coatings were sprayed by a water-stabilized plasma gun to form robust self-supporting bodies with a photocatalytically active surface. Agglomerated nanometric powder was used as a feedstock. In one case argon was used as a powder-feeding as well as coating-cooling gas whereas in the other case nitrogen was used. Stainless steel was used as a substrate and the coatings were released after the cooling. Over one millimeter thick self-supporting bodies were studied by XRD, HR-TEM, XPS, Raman spectroscopy, UV-VIS spectrophotometry and photocatalytic tests. Selected tests were done at the surface as well as at the bottom side representing the contact surface with the substrate during the spray process. Porosity was studied by image analysis on polished cross sections where also microhardness was measured. The dominant phase present in the sprayed samples was rutile, whereas anatase was only a minor component. The hydrogen content in the nitrogen-assisted coating was higher, but the character of the optical absorption edge remained the same for both samples. Photoelectron spectroscopy revealed differences in the character of the O1s peak between both samples. The photocatalytic activity was tested by decomposition of acetone at UV illumination, whereas also the end products—CO and CO2—were monitored. The nitrogen-assisted coating was revealed as a more efficient photocatalyst. Certain aspects of a thermal post-treatment on the coatings are discussed as well. Color and electrical conductivity are markedly changed at annealing at 760 °C, whereas only very small changes of the as-sprayed coating character correspond to annealing at 500 °C.

Synthesis, characterization and photocatalytic performance of PbS/Ni2P flowers

NASA Astrophysics Data System (ADS)

Liu, Shuling; Han, Lefang; Liu, Hui

2016-11-01

Flower-like PbS/Ni2P composites were synthesized by a facile two-step chemical route. The morphology and structure of the resulting composites were investigated by SEM and TEM images and XRD spectra, respectively. The results showed that the as-obtained composites were composed of the cubic PbS flowers and hexagonal Ni2P nanoparticles, and Ni2P nanoparticles coated on the surfaces of flower-like PbS microstructure. It was found that changing the molar ratio to 3:1, flower-like PbS/Ni2P composites have been successfully synthesized by using cationic cetyltrimethylammonium bromide(CTAB) and anionic sodium dodecyl sulfate (SDS) as template. Furthermore, using methylene blue(MB) as a model organic pollutant, the photocatalytic degradation experiments indicated that the as-prepared composites showed enhanced photocatalytic degradation activity for methylene blue(75%) which is as higher as that of the only flower-like PbS (16.6%) and only Ni2P nanoparticles (44.8%) at the same time. This work may be expected to find its potential application in water pollution treatment.

Synthesis of three-dimensional AgI@TiO2 nanoparticles with improved photocatalytic performance.

PubMed

An, Changhua; Jiang, Wen; Wang, Jizhuang; Wang, Shutao; Ma, Zhanhua; Li, Yanpeng

2013-06-28

Three-dimensional (3D) TiO2 with an acanthosphere-like morphology composed of nanothorns has been used as a suitable support to fabricate a visible-light-induced 3D AgI@TiO2 nanophotocatalyst. The structural characterization revealed that the size of the obtained AgI@TiO2 nanocomposite was close to that of pristine TiO2 particles, where AgI nanoparticles were evenly dispersed on the surfaces of "thorns" of TiO2. The as-achieved 3D AgI@TiO2 nanophotocatalyst exhibited enhanced photocatalytic performance towards photodegradation of organic pollutants, e.g., rhodamine B (RhB), in comparison with TiO2, P25, AgI and AgI@P25 with the same quantity. The enhanced photocatalytic performance is attributed to the strong visible light absorption and the defined interfaces between AgI nanoparticles and TiO2 nanothorns with efficient separation of photogenerated carriers. The excellent performance of the 3D AgI@TiO2 nanophotocatalyst suggests its promising applications in water treatment and environmental remediation.

Enhanced photocatalytic performance of CeO2-TiO2 nanocomposite for degradation of crystal violet dye and industrial waste effluent

NASA Astrophysics Data System (ADS)

Zahoor, Mehvish; Arshad, Amara; Khan, Yaqoob; Iqbal, Mazhar; Bajwa, Sadia Zafar; Soomro, Razium Ali; Ahmad, Ishaq; Butt, Faheem K.; Iqbal, M. Zubair; Wu, Aiguo; Khan, Waheed S.

2018-03-01

This study presents the synthesis of CeO2-TiO2 nanocomposite and its potential application for the visible light-driven photocatalytic degradation of model crystal violet dye as well as real industrial waste water. The ceria-titania (CeO2-TiO2) nanocomposite material was synthesised using facile hydrothermal route without the assistance of any template molecule. As-prepared composite was characterised by SEM, TEM, HRTEM, XRD, XPS for surface features, morphological and crystalline characters. The formed nanostructures were determined to possess crystal-like geometrical shape and average size less than 100 nm. The as-synthesised nanocomposite was further investigated for their heterogeneous photocatalytic potential against the oxidative degradation of CV dye taken as model pollutant. The photo-catalytic performance of the as-synthesised material was evaluated both under ultra-violet as well as visible light. Best photocatalytic performance was achieved under visible light with complete degradation (100%) exhibited within 60 min of irradiation time. The kinetics of the photocatalytic process were also considered and the reaction rate constant for CeO2-TiO2 nanocomposite was determined to be 0.0125 and 0.0662 min-1 for ultra-violet and visible region, respectively. In addition, the as-synthesised nanocomposite demonstrated promising results when considered for the photo-catalytic degradation of coloured industrial waste water collected from local textile industry situated in Faisalabad region of Pakistan. Enhanced photo-catalytic performance of CeO2-TiO2 nanocomposite was proposed owing to heterostructure formation leading to reduced electron-hole recombination.

Solar-based detoxification of phenol and p-nitrophenol by sequential TiO2 photocatalysis and photosynthetically aerated biological treatment.

PubMed

Essam, Tamer; Aly Amin, Magdy; El Tayeb, Ossama; Mattiasson, Bo; Guieysse, Benoit

2007-04-01

Simulated solar UV/TiO(2) photocatalysis was efficient to detoxify a mixture of 100 mgphenoll(-1) and 50 mgp-nitrophenol (PNP) l(-1) and allow the subsequent biodegradation of the remaining pollutants and their photocatalytic products under photosynthetic aeration with Chlorella vulgaris. Photocatalytic degradation of phenol and PNP was well described by pseudo-first order kinetics (r(2)>0.98) with removal rate constants of 1.9x10(-4) and 2.8x10(-4)min(-1), respectively, when the pollutants were provided together and 5.7x10(-4) and 9.7x10(-4)min(-1), respectively, when they were provided individually. Photocatalytic pre-treatment of the mixture during 60 h removed 50+/-1% and 62+/-2% of the phenol and PNP initially present but only 11+/-3% of the initial COD. Hydroquinone, nitrate and catechol were identified as PNP photocatalytic products and catechol and hydroquinone as phenol photocatalytic products. Subsequent biological treatment of the pre-treated samples removed the remaining contaminants and their photocatalytic products as well as 81-83% of the initial COD, allowing complete detoxification of the mixture to C. vulgaris. Similar detoxification efficiencies were recorded after biological treatment of the irradiated mixture with activated sludge microflora or with an acclimated consortia composed of a phenol-degrading Alcaligenes sp. and a PNP-degrading Arthrobacter sp., although the acclimated strains biodegraded the remaining pollutants faster. Biological treatment of the non-irradiated mixture was inefficient due to C. vulgaris inhibition.

Effects of donor doping and acceptor doping on rutile TiO2 particles for photocatalytic O2 evolution by water oxidation

NASA Astrophysics Data System (ADS)

Amano, Fumiaki; Tosaki, Ryosuke; Sato, Kyosuke; Higuchi, Yamato

2018-02-01

Crystalline defects of photocatalyst particles may be considered to be the recombination center of photoexcited electrons and holes. In this study, we investigated the photocatalytic activity of cation-doped rutile TiO2 photocatalysts for O2 evolution from an aqueous silver nitrate solution under ultraviolet light irradiation. The photocatalytic activity of rutile TiO2 was enhanced by donor doping of Ta5+ and Nb5+ with a valence higher than that of Ti4+, regardless of increased density of electrons and Ti3+ species (an electron trapped in Ti4+ sites). Conversely, acceptor doping of lower valence cations such as In3+ and Ga3+ decreased photocatalytic activity for O2 evolution by water oxidation. The doping of equal valence cations such as Sn4+ and Ge4+ hardly changed the activity of non-doped TiO2. This study demonstrates that Ti3+ species, which is a crystalline defect, enhanced the photocatalytic activity of semiconductor oxides, for example rutile TiO2 with large crystalline size.

Enhanced synergetic effect of Cr(VI) ion removal and anionic dye degradation with superparamagnetic cobalt ferrite meso-macroporous nanospheres

NASA Astrophysics Data System (ADS)

Thomas, Bintu; Alexander, L. K.

2018-02-01

The overall effectiveness of a photocatalytic water treatment method strongly depends on various physicochemical factors. Superparamagnetic photocatalysts have incomparable advantage of easy separation using external magnetic fields. So, the synthesis of efficient superparamagnetic photocatalysts and the development of a deep understanding of the factors influencing their catalytic performances are important. Co x Zn1- x Fe2O4 ( x = 0, 0.5, 1) ferrite nanospheres were synthesized by the solvothermal route. The reduction of Cr(VI) and degradation of methyl orange (MO) impurities were carried out in single- and binary-component system under visible light irradiation. The adsorption experiments were done by the catalyst in the water solution containing the impurities. The magnetic and optical properties were studied by VSM and UV-Vis analysis. The nature of porosity was investigated using the BET method. 3D nanospheres of diameter about 5-10 nm were fabricated. The binary-contaminant system exhibited synergetic photocatalytic effect (80% improvement in activity rate) against the nanoparticles. The corresponding mechanism is discussed. CoFe2O4 exhibited better adsorption, photocatalytic and magnetic separation efficiency due to its higher surface area (50% higher), narrower band gap (25% lesser), smaller crystallite size, a strong magnetic strength (51.35 emu/g) and meso-macro hierarchical porous structure. The adsorption of Cr(VI) and MO can be approximated to the Langmuir and Freundlich model, respectively.

Novel Solar Photocatalytic Reactor for Wastewater Treatment

NASA Astrophysics Data System (ADS)

Sutisna; Rokhmat, M.; Wibowo, E.; Murniati, R.; Khairurrijal; Abdullah, M.

2017-07-01

A new solar photocatalytic reactor (photoreactor) using TiO2 nanoparticles coated onto plastic granules has been designed. Catalyst granules are placed into the cavity of a reactor panel made of glass. A pump is used to circulate wastewater in the photoreactor. Methylene blue (MB) dissolved in water was chosen as the wastewater model. The performance of the photoreactor was evaluated based on changes in MB concentration with respect to time. The photoreactor showed a good performance by degrading 10 L of MB solution up to 96.54% after 48 h of solar irradiation. The photoreactor was scaled up by enlarging the panel area to twice its original size. The increase in the surface area of the reactor panel and therefore of the mass of catalyst granules and reactor volume led to a three-fold increase of the photodegradation rate. In addition, the MB degradation kinetics were also studied. Data analysis confirmed the applicability of the pseudo-first-order Langmuir-Hinshelwood model. The proposed photoreactor has great potential for use in large-scale wastewater treatment.

Remediation of the effect of adding cyanides on an algal/bacterial treatment of a mixture of organic pollutants in a continuous photobioreactor.

PubMed

Essam, Tamer; ElRakaiby, Marwa; Agha, Azza

2014-09-01

The effect of inorganic pollutants on the treatment of organic pollutants using algal/bacterial microcosm was investigated in a continuous photobioreactor. The microcosm was composed of Chlorella vulgaris MM1 and Pseudomonas MT1 and was able to efficiently treat artificial waste-water contaminated with 6.4 salicylate and 2.2 mM phenol at a hydraulic retention time of 4 days. No negative effect was recorded when the waste-water was supplemented with 1.6 mM thiocyanate; however, the treatment efficiency severely deteriorated when the system was challenged with 0.74 mM cyanide. Addition of 2 g NaHCO3 l(-1) did not improve the efficiency of the treatment. Toxicity of the pollutants to the alga was cyanide > thiocyanate > phenol > salicylate. The high toxicity of the waste-water was eliminated either by a 25-fold dilution or by photocatalytic pre-treatment which allowed the subsequent efficient biological treatment.

Terbuthylazine and desethylterbuthylazine: Recent occurrence, mobility and removal techniques.

PubMed

Tasca, Andrea Luca; Puccini, Monica; Fletcher, Ashleigh

2018-07-01

The herbicide terbuthylazine (TBA) has displaced atrazine in most of EU countries, becoming one of the most regularly used pesticides and, therefore, frequently detected in natural waters. The affinity of TBA for soil organic matter suggests prolonged contamination; degradation leads to the release of the metabolite desethylterbuthylazine (DET), which has higher water solubility and binds more weakly to organic matter compared to the parent compound, resulting in higher associated risk for contamination of groundwater resources. Additionally, TBA and DET are chemicals of emerging concern because of their persistence and toxicity towards aquatic organisms; moreover, they are known to have significant endocrine disruption capacity to wildlife and humans. Conventional treatments applied during drinking water production do not lead to the complete removal of these chemicals; activated carbon provides the greatest efficiency, whereas ozonation can generate by-products with comparable oestrogenic activity to atrazine. Hydrogen peroxide alone is ineffective to degrade TBA, while UV/H 2 O 2 advanced oxidation and photocatalysis are the most effective processes for oxidation of TBA. It has been determined that direct photolysis gives the highest degradation efficiency of all UV/H 2 O 2 treatments, while most of the photocatalytic degradation is attributed to OH radicals, and TiO 2 solar-photocatalytic ozonation can lead to almost complete TBA removal in ∼30 min. Constructed wetlands provide a valuable buffer capacity, protecting downstream surface waters from contaminated runoff. TBA and DET occurrence are summarized and removal techniques are critically evaluated and compared, to provide the reader with a comprehensive guide to state-of-the-art TBA removal and potential future treatments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

NASA Astrophysics Data System (ADS)

Wang, Xiaodong; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun

2013-09-01

Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO2 particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO2/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

New porous titanium–niobium oxide for photocatalytic degradation of bromocresol green dye in aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaleshtori, Maryam Zarei, E-mail: mzarei@utep.edu; Hosseini, Mahsa; Edalatpour, Roya

2013-10-15

Graphical abstract: The photocatalytic activity of different porous titanium–niobium oxides was evaluated toward degradation of bromocresol green (BG) under UV light. A better catalytic activity was observed for all samples at lower pH. Catalysts have a stronger ability for degradation of BG in acid media than in alkaline media. - Highlights: • Different highly structured titanium–niobium oxides have been prepared using improved methods of synthesis. • Photo-degradation of bromocresol green dye (BG) with nanostructure titanium–niobium oxide catalysts was carried out under UV light. • The photo-catalytic activity of all catalysts was higher in lower pH. • Titanium–niobium oxide catalysts aremore » considerably stable and reusable. - Abstract: In this study, high surface area semiconductors, non porous and porous titanium–niobium oxides derived from KTiNbO{sub 5} were synthesized, characterized and developed for their utility as photocatalysts for decontamination with sunlight. These materials were then used in the photocatalytic degradation of bromocresol green dye (BG) in aqueous solution using UV light and their catalytic activities were evaluated at various pHs. For all catalysts, the photocatalytic degradation of BG was most efficient in acidic solutions. Results show that the new porous oxides have large porous and high surface areas and high catalytic activity. A topotactic dehydration treatment greatly improves catalyst performance at various pHs. Stability and long term activity of porous materials (topo and non-topo) in photocatalysis reactions was also tested. These results suggest that the new materials can be used to efficiently purify contaminated water.« less

Photocatalytic processes assisted by artificial solar light for soil washing effluent treatment.

PubMed

Satyro, Suéllen; Race, Marco; Marotta, Raffaele; Dezotti, Márcia; Guida, Marco; Clarizia, Laura

2017-03-01

Contaminated soil has become a growing issue in recent years. The most common technique used to remove contaminants (such as metals) from the soil is the soil washing process. However, this process produces a final effluent containing chelating agents (i.e., ethylenediaminedisuccinic acid, also known as EDDS) and extracted metals (i.e., Cu, Fe, and Zn) at concentrations higher than discharge limits allowed by the Italian and Brazilian environmental law. Therefore, it is necessary to develop further treatments before its proper disposal or reuse. In the present study, soil washing tests were carried out through two sequential paths. Moreover, different artificial sunlight-driven photocatalytic treatments were used to remove Cu, Zn, Fe, and EDDS from soil washing effluents. Metal concentrations after the additional treatment were within the Brazilian and Italian regulatory limits for discharging in public sewers. The combined TiO 2 -photocatalytic processes applied were enough to decontaminate the effluents, allowing their reuse in soil washing treatment. Ecotoxicological assessment using different living organisms was carried out to assess the impact of the proposed two-step photocatalytic process on the effluent ecotoxicity. Graphical Abstract ᅟ.

Metal-Organic Framework-Stabilized CO2/Water Interfacial Route for Photocatalytic CO2 Conversion.

PubMed

Luo, Tian; Zhang, Jianling; Li, Wei; He, Zhenhong; Sun, Xiaofu; Shi, Jinbiao; Shao, Dan; Zhang, Bingxing; Tan, Xiuniang; Han, Buxing

2017-11-29

Here, we propose a CO 2 /water interfacial route for photocatalytic CO 2 conversion by utilizing a metal-organic framework (MOF) as both an emulsifier and a catalyst. The CO 2 reduction occurring at the CO 2 /water interface produces formate with remarkably enhanced efficiency as compared with that in conventional solvent. The route is efficient, facile, adjustable, and environmentally benign, which is applicable for the CO 2 transformation photocatalyzed by different kinds of MOFs.

An intermolecular heterobimetallic system for photocatalytic water reduction.

PubMed

Hansen, Sven; Klahn, Marcus; Beweries, Torsten; Rosenthal, Uwe

2012-04-01

Teamwork: A new intermolecular heterobimetallic system for photocatalytic water reduction, consisting of a photosensitizer of the type [Ru(bpy)(2)(L)](PF(6))(2) (L=bidentate ligand), a dichloro palladium complex PdCl(2)(L) serving as the water reduction catalyst, and triethyl amine as electron donor, is presented. Variations of the ligand as well as of the palladium source results in a significant improvement of the performance of the catalyst system. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous graphitic carbon nitride synthesized via direct polymerization of urea for efficient sunlight-driven photocatalytic hydrogen production

NASA Astrophysics Data System (ADS)

Zhang, Yuewei; Liu, Jinghai; Wu, Guan; Chen, Wei

2012-08-01

Energy captured directly from sunlight provides an attractive approach towards fulfilling the need for green energy resources on the terawatt scale with minimal environmental impact. Collecting and storing solar energy into fuel through photocatalyzed water splitting to generate hydrogen in a cost-effective way is desirable. To achieve this goal, low cost and environmentally benign urea was used to synthesize the metal-free photocatalyst graphitic carbon nitride (g-C3N4). A porous structure is achieved via one-step polymerization of the single precursor. The porous structure with increased BET surface area and pore volume shows a much higher hydrogen production rate under simulated sunlight irradiation than thiourea-derived and dicyanamide-derived g-C3N4. The presence of an oxygen atom is presumed to play a key role in adjusting the textural properties. Further improvement of the photocatalytic function can be expected with after-treatment due to its rich chemistry in functionalization.Energy captured directly from sunlight provides an attractive approach towards fulfilling the need for green energy resources on the terawatt scale with minimal environmental impact. Collecting and storing solar energy into fuel through photocatalyzed water splitting to generate hydrogen in a cost-effective way is desirable. To achieve this goal, low cost and environmentally benign urea was used to synthesize the metal-free photocatalyst graphitic carbon nitride (g-C3N4). A porous structure is achieved via one-step polymerization of the single precursor. The porous structure with increased BET surface area and pore volume shows a much higher hydrogen production rate under simulated sunlight irradiation than thiourea-derived and dicyanamide-derived g-C3N4. The presence of an oxygen atom is presumed to play a key role in adjusting the textural properties. Further improvement of the photocatalytic function can be expected with after-treatment due to its rich chemistry in functionalization. Electronic supplementary information (ESI) available: Methods for preparing and characterizing UCN, TCN and DCN samples. Methods for examining the photocatalytic hydrogen production. FTIR, XPS, and digital photos of three products are shown in Fig. S1-6. See DOI: 10.1039/c2nr30948c

Efficient Photocatalytic Degradation of Norfloxacin in Aqueous Media by Hydrothermally Synthesized Immobilized TiO2/Ti Films with Exposed {001} Facets.

PubMed

Sayed, Murtaza; Shah, Luqman Ali; Khan, Javed Ali; Shah, Noor S; Nisar, Jan; Khan, Hasan M; Zhang, Pengyi; Khan, Abdur Rahman

2016-12-22

In this study, a novel immobilized TiO 2 /Ti film with exposed {001} facets was prepared via a facile one-pot hydrothermal route for the degradation of norfloxacin from aqueous media. The effects of various hydrothermal conditions (i.e., solution pH, hydrothermal time (H T ) and HF concentration) on the growth of {001} faceted TiO 2 /Ti film were investigated. The maximum photocatalytic performance of {001} faceted TiO 2 /Ti film was observed when prepared at pH 2.62, H T of 3 h and at HF concentration of 0.02 M. The as-prepared {001} faceted TiO 2 /Ti films were fully characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS). More importantly, the as-prepared {001} faceted TiO 2 /Ti film exhibited excellent photocatalytic performance toward degradation of norfloxacin in various water matrices (Milli-Q water, tap water, river water and synthetic wastewater). The individual influence of various anions (SO 4 2- , HCO 3 - , NO 3 - , Cl - ) and cations (K + , Ca 2+ , Mg 2+ , Cu 2+ , Na + , Fe 3+ ) usually present in the real water samples on the photocatalytic performance of as-prepared TiO 2 /Ti film with exposed {001} facet was investigated. The mechanistic studies revealed that • OH is mainly involved in the photocatalytic degradation of norfloxacin by {001} faceted TiO 2 /Ti film. In addition, norfloxacin degradation byproducts were investigated, on the basis of which degradation schemes were proposed.

Degradation of imidacloprid in water by photo-Fenton and TiO2 photocatalysis at a solar pilot plant: a comparative study.

PubMed

Malato, S; Caceres, J; Agüera, A; Mezcua, M; Hernando, D; Vial, J; Fernández-Alba, A R

2001-11-01

The technical feasibility, mechanisms, and performance of degradation of aqueous imidacloprid have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (<2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with photo-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal anytoxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detected which were always the same. At the end of both processes low concentration (<0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around 1 mg/L of formate in the case of photo-Fenton.

Adsorption and photocatalytic degradation of pharmaceuticals by BiOClxIy nanospheres in aqueous solution

NASA Astrophysics Data System (ADS)

Wang, Xiaoning; Bi, Wenlong; Zhai, Pingping; Wang, Xiaobing; Li, Hongjing; Mailhot, Gilles; Dong, Wenbo

2016-01-01

BiOClxIy nanospheres have been synthesised via precipitation method in ethylene glycol (EG)-water (H2O) mixed solvent at 80 °C and ambient pressure. Results of BiOClxIy characterisation showed that these composite materials well combined BiOCl with BiOI crystals, which displayed flower-like hierarchical nanospheres consisted of numerous nanosheets and possessed smaller particle size, higher surface area than those in previous papers. The great surface area resulted in its high adsorption abilities of hydroxyphenylacetic acid (p-HPA) in the dark, the adsorption process could be suitably described by a pseudo-second-order kinetics model and the adsorption isotherms could be well fitted with Freundlich and Langmuir equations. The photocatalytic degradation of p-HPA and acetaminophen (ACTP) were investigated under simulated solar and visible irradiation using BiOClxIy catalyst for the first time. The combination of BiOCl and BiOI to a certain extent has largely improved the remove efficiency, and BiOCl0.75I0.25 was the optimal catalyst with almost 100% removal of p-HPA and 80% removal of ACTP under solar light for 3 h. Experimental results demonstrated that the photocatalytic degradation of p-HPA and ACTP followed pseudo-first-order kinetics and O2rad - and dissolved oxygen play predominant roles in photocatalytic process efficiency. This research will supply an environment-friendly photocatalyst for pharmaceutical wastewater treatment under sunlight.

A facile fabrication of nitrogen-doped electrospun In2O3 nanofibers with improved visible-light photocatalytic activity

NASA Astrophysics Data System (ADS)

Lu, Na; Shao, Changlu; Li, Xinghua; Miao, Fujun; Wang, Kexin; Liu, Yichun

2017-01-01

Semiconductor photocatalysis demonstrates to be an effective approach for eliminating most types of environment contaminants and for producing hydrogen. Herein, a facile synthesis route combining electrospinning technique and thermal treatment method under NH3 atmosphere has been presented as a straightforward protocol for the fabrication of nitrogen-doped In2O3 (N-In2O3) nanofibers, the nitrogen content of which can be well controlled by adjusting the annealing temperature. Photocatalytic tests show that the N-In2O3 nanofibers demonstrate an improved degradation rate of Rhodamine B (RB) compared with pure In2O3 nanofibers under visible-light irradiation. This can be attributed to the nitrogen atom introducing at interstitial sites as well as the generation of oxygen vacancy on the surface of In2O3 nanofibers, resulting in the enhanced utilization of visible light for the N-In2O3 nanofibers. Furthermore, the obtained N-In2O3 nanofibers with the advantage of ultra-long one-dimensional nanostructures can be recycled several times by facile sedimentation and hence present almost no decrease in photocatalytic activity indicative of a well regeneration capability. Therefore, the as-fabricated nitrogen-doped In2O3 nanofibers as a promising photocatalyst present good photocatalytic degradation of organic pollutant in waste water for practical application.

Fluorine- and iron-modified hierarchical anatase microsphere photocatalyst for water cleaning: facile wet chemical synthesis and wavelength-sensitive photocatalytic reactivity.

PubMed

Liu, Shaohong; Sun, Xudong; Li, Ji-Guang; Li, Xiaodong; Xiu, Zhimeng; Yang, He; Xue, Xiangxin

2010-03-16

High photocatalytic efficiency, easy recovery, and no biological toxicity are three key properties related to the practical application of anatase photocatalyst in water cleaning, but seem to be incompatible. Nanoparticles-constructed hierarchical anatase microspheres with high crystallinity and good dispersion prepared in this study via one-step solution processing at 90 degrees C under atmospheric pressure by using ammonium fluotitanate as the titanium source and urea as the precipitant can reconcile these three requirements. The hierarchical microspheres were found to grow via an aggregative mechanism, and contact recrystallization occurred at high additions of the FeCl(3) electrolyte into the reaction system. Simultaneous incorporation of fluorine and iron into the TiO(2) matrix was confirmed by combined analysis of X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis absorption spectroscopy. Surface structure and morphology changes of the microspheres induced by high-temperature annealing were clearly observed by field-emission scanning electron microscopy, especially for the phase-transformed particles. The original nanoparticles-constructed rough surfaces partially became smooth, resulting in a sharp drop in photocatalytic efficiency. Interestingly, iron loading has detrimental effects on the visible-light photocatalytic activity of both the as-prepared and the postannealed anatase microspheres but greatly enhances the photocatalytic activity of the as-prepared anatase microspheres under UV irradiation. No matter under UV or visible-light irradiation, the fluorine-loaded anatase microspheres and especially the postannealed ones show excellent photocatalytic performance. The underlying mechanism of fluorine and iron loading on the photocatalytic efficacy of the anatase microspheres was discussed in detail. Beyond photocatalytic applications, this kind of material is of great importance to the assembling of photoactive photonic crystal that can control light motion.

Solar photocatalytic treatment of trimethoprim in four environmental matrices at a pilot scale: transformation products and ecotoxicity evaluation.

PubMed

Michael, I; Hapeshi, E; Osorio, V; Perez, S; Petrovic, M; Zapata, A; Malato, S; Barceló, D; Fatta-Kassinos, D

2012-07-15

The pilot-scale solar degradation of trimethoprim (TMP) in different water matrices (demineralized water: DW, simulated natural freshwater: SW; simulated wastewater: SWW; and real effluent: RE) was investigated in this study. DOC removal was lower in the case of SW compared to DW, which can be attributed to the presence of inorganic anions which may act as scavengers of the HO·. Furthermore, the presence of organic carbon and higher salt content in SWW and RE led to lower mineralization per dose of hydrogen peroxide compared to DW and SW. Toxicity assays in SWW and RE were also performed indicating that toxicity is attributed to the compounds present in RE and their by-products formed during solar Fenton treatment and not to the intermediates formed by the oxidation of TMP. A large number of compounds generated by the photocatalytic transformation of TMP were identified by UPLC-QToF/MS. The degradation pathway revealed differences among the four matrices; however hydroxylation, demethylation and cleavage reactions were observed in all matrices. To the best of our knowledge this is the first time that TMP degradation products have been identified by adopting a solar Fenton process at a pilot-scale set-up, using four different aqueous matrices. Copyright © 2012 Elsevier B.V. All rights reserved.

Hierarchical FeTiO3-TiO2 hollow spheres for efficient simulated sunlight-driven water oxidation.

PubMed

Han, Taoran; Chen, Yajie; Tian, Guohui; Wang, Jian-Qiang; Ren, Zhiyu; Zhou, Wei; Fu, Honggang

2015-10-14

Oxygen generation is the key step for the photocatalytic overall water splitting and considered to be kinetically more challenging than hydrogen generation. Here, an effective water oxidation catalyst of hierarchical FeTiO3-TiO2 hollow spheres are prepared via a two-step sequential solvothermal processes and followed by thermal treatment. The existence of an effective heterointerface and built-in electric field in the surface space charge region in FeTiO3-TiO2 hollow spheres plays a positive role in promoting the separation of photoinduced electron-hole pairs. Surface photovoltage, transient-state photovoltage, fluorescence and electrochemical characterization are used to investigate the transfer process of photoinduced charge carriers. The photogenerated charge carriers in the hierarchical FeTiO3-TiO2 hollow spheres with a proper molar ratio display much higher separation efficiency and longer lifetime than those in the FeTiO3 alone. Moreover, it is suggested that the hierarchical porous hollow structure can contribute to the enhancement of light utilization, surface active sites and material transportation through the framework walls. This specific synergy significantly contributes to the remarkable improvement of the photocatalytic water oxidation activity of the hierarchical FeTiO3-TiO2 hollow spheres under simulated sunlight (AM1.5).

Solar photocatalytic oxidation of recalcitrant natural metabolic by-products of amoxicillin biodegradation.

PubMed

Pereira, João H O S; Reis, Ana C; Homem, Vera; Silva, José A; Alves, Arminda; Borges, Maria T; Boaventura, Rui A R; Vilar, Vítor J P; Nunes, Olga C

2014-11-15

The contamination of the aquatic environment by non-metabolized and metabolized antibiotic residues has brought the necessity of alternative treatment steps to current water decontamination technologies. This work assessed the feasibility of using a multistage treatment system for amoxicillin (AMX) spiked solutions combining: i) a biological treatment process using an enriched culture to metabolize AMX, with ii) a solar photocatalytic system to achieve the removal of the metabolized transformation products (TPs) identified via LC-MS, recalcitrant to further biological degradation. Firstly, a mixed culture (MC) was obtained through the enrichment of an activated sludge sample collected in an urban wastewater treatment plant (WWTP). Secondly, different aqueous matrices spiked with AMX were treated with the MC and the metabolic transformation products were identified. Thirdly, the efficiency of two solar assisted photocatalytic processes (TiO2/UV or Fe(3+)/Oxalate/H2O2/UV-Vis) was assessed in the degradation of the obtained TPs using a lab-scale prototype photoreactor equipped with a compound parabolic collector (CPC). Highest AMX specific biodegradation rates were obtained in buffer and urban wastewater (WW) media (0.10 ± 0.01 and 0.13 ± 0.07 g(AMX) g(biomass)(-1) h(-1), respectively). The resulting TPs, which no longer presented antibacterial activity, were identified as amoxicilloic acid (m/z = 384). The performance of the Fe(3+)/Oxalate/H2O2/UV-Vis system in the removal of the TPs from WW medium was superior to the TiO2/UV process (TPs no longer detected after 40 min (QUV = 2.6 kJ L(-1)), against incomplete TPs removal after 240 min (QUV = 14.9 kJ L(-1)), respectively). Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect of water presence on the photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene in the gas-phase

NASA Astrophysics Data System (ADS)

Korologos, Christos A.; Philippopoulos, Constantine J.; Poulopoulos, Stavros G.

2011-12-01

In the present work, the gas-solid heterogeneous photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) over UV-irradiated titanium dioxide was studied in an annular reactor operated in the CSTR (continuous stirred-tank reactor) mode. GC-FID and GC-MS were used for analysing reactor inlet and outlet streams. Initial BTEX concentrations were in the low parts per million (ppmv) range, whereas the water concentration was in the range of 0-35,230 ppmv and the residence time varied from 50 to 210 s. The effect of water addition on the photocatalytic process showed strong dependence on the type of the BTEX and the water vapour concentration. The increase in residence time resulted in a considerable increase in the conversion achieved for all compounds and experimental conditions. There was a clear interaction between residence time and water presence regarding the effect on conversions achieved. It was established that conversions over 95% could be achieved by adjusting appropriately the experimental conditions and especially the water concentration in the reactor. In all cases, no by-products were detected above the detection limit and carbon dioxide was the only compound detected. Finally, various Langmuir-Hinshelwood kinetic models have been tested in the analysis of the experimental data obtained. The kinetic data obtained confirmed that water had an active participation in the photocatalytic reactions of benzene, toluene, ethylbenzene and m-xylene since the model involving reaction of BTEX and water adsorbed on different active sites yielded the most successful fitting to the experimental results for the first three compounds, whereas the kinetic model based on the assumption that reaction between VOC and water dissociatively adsorbed on the photocatalyst takes place was the most appropriate in the case of m-xylene.

Surface modification of oxygen-deficient ZnO nanotubes by interstitially incorporated carbon: a superior photocatalytic platform for sustainable water and surface treatments

NASA Astrophysics Data System (ADS)

Ninnora Meethal, Bhabhina; Ramanarayanan, Rajita; Swaminathan, Sindhu

2018-05-01

An interesting architecture of robust, highly reproducible, template-free synthesis of phase pure carbon-incorporated short ZnO nanotubes through polymer assisted sol-gel method is presented here. These nanotubes exhibit enormous surface oxygen vacancies and mid bandgap levels confirmed by X-ray photoelectron spectroscopy. These carbon-modified nanotubes exhibit encouraging results in photocatalytic studies, as there is a 16% greater degradation of contaminant dye than in the pristine ZnO nanotube. The reactive oxygen species generated from the photocatalysts were experimentally confirmed and quantified. Super hydrophilic nature renders these nanotubes suitable for antifogging application as observed from contact angle measurements. Characterisation and mechanism of a competent material with improved photoresponse, promising greater energy efficiency and anti-fog have been described in this investigation.

Structural and photocatalytic studies on pure and Sn ion doped ZnO-graphene nanocomposites

NASA Astrophysics Data System (ADS)

Beura, Rosalin; Thangadurai, P.

2016-05-01

Graphene based metal oxide nanocomposites have been widely used as a photocatalyst for the treatment of water pollutants. This work demonstrates the synthesis of graphene composite with pure and Sn ion doped-ZnO and their photocatalytic properties are reported. Structural studies were carried out by X-ray diffraction and Raman spectroscopy to confirm the formation of the nanocomposites. Microstructure was characterized by scanning electron microscopy showing rod shaped ZnO and the layer structured graphene in the ZnO-graphene composite. In comparison with the undoped ZnO-graphene composite, the Sn ion doped ZnO-graphene composite have shown better degradation of methyl orange dye that is about 99% of degradation. Band gap of the composite materials was calculated to be 3.36 eV from the UV-Vis result.

A potential photocatalytic, antimicrobial and anticancer activity of chitosan-copper nanocomposite.

PubMed

Arjunan, Nithya; Singaravelu, Chandra Mohan; Kulanthaivel, Jeganathan; Kandasamy, Jothivenkatachalam

2017-11-01

In this study, chitosan-copper (CS-Cu) nanocomposite was synthesized without the aid of any external chemical reducing agents. The optical, structural, spectral, thermal and morphological analyses were carried out by several techniques. The prepared nanocomposite acts as a photocatalyst for the removal of Rhodamine B (RhB) and Conge red (CR) dyes under visible light irradiation. The pseudo first order kinetics was derived according to Langmuir-Hinshelwood (L-H) model. The nanocomposite also proved to be an excellent antimicrobial agent against Gram-positive and Gram-negative bacteria; and also show activity against fungus. The advanced material was used for the major research areas which include photocatalytic materials for waste water treatment; biological applications in the development of drug resistant antimicrobials and anticancer agents. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural and photocatalytic studies on pure and Sn ion doped ZnO-graphene nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beura, Rosalin; Thangadurai, P., E-mail: thangaduraip.nst@pondiuni.edu.in

2016-05-23

Graphene based metal oxide nanocomposites have been widely used as a photocatalyst for the treatment of water pollutants. This work demonstrates the synthesis of graphene composite with pure and Sn ion doped-ZnO and their photocatalytic properties are reported. Structural studies were carried out by X-ray diffraction and Raman spectroscopy to confirm the formation of the nanocomposites. Microstructure was characterized by scanning electron microscopy showing rod shaped ZnO and the layer structured graphene in the ZnO-graphene composite. In comparison with the undoped ZnO-graphene composite, the Sn ion doped ZnO-graphene composite have shown better degradation of methyl orange dye that is aboutmore » 99% of degradation. Band gap of the composite materials was calculated to be 3.36 eV from the UV-Vis result.« less

Photocatalytic Removal of Microcystin-LR by Advanced WO3-Based Nanoparticles under Simulated Solar Light

PubMed Central

Zhao, Chao; Li, Dawei; Feng, Chuanping; Zhang, Zhenya; Sugiura, Norio; Yang, Yingnan

2015-01-01

A series of advanced WO3-based photocatalysts including CuO/WO3, Pd/WO3, and Pt/WO3 were synthesized for the photocatalytic removal of microcystin-LR (MC-LR) under simulated solar light. In the present study, Pt/WO3 exhibited the best performance for the photocatalytic degradation of MC-LR. The MC-LR degradation can be described by pseudo-first-order kinetic model. Chloride ion (Cl−) with proper concentration could enhance the MC-LR degradation. The presence of metal cations (Cu2+ and Fe3+) improved the photocatalytic degradation of MC-LR. This study suggests that Pt/WO3 photocatalytic oxidation under solar light is a promising option for the purification of water containing MC-LR. PMID:25884038

Quantification of photocatalytic oxygenation of human blood.

PubMed

Subrahmanyam, Aryasomayajula; Thangaraj, Paul R; Kanuru, Chandrasekhar; Jayakumar, Albert; Gopal, Jayashree

2014-04-01

Photocatalytic oxygenation of human blood is an emerging concept based on the principle of photocatalytic splitting of water into oxygen and hydrogen. This communication reports: (i) a design of a photocatalytic cell (PC) that separates the blood from UV (incident) radiation source, (ii) a pH, temperature and flow controlled circuit designed for quantifying the oxygenation of human blood by photocatalysis and (iii) measuring the current efficacy of ITO/TiO2 nano thin films in oxygenating human blood in a dynamic circuit in real time. The average increase in oxygen saturation was around 5% above baseline compared to control (p<0.0005). We believe this is one of the first attempts to quantify photocatalytic oxygenation of human blood under controlled conditions. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Photocatalytic treatment of bioaerosols: impact of the reactor design.

PubMed

Josset, Sébastien; Taranto, Jérôme; Keller, Nicolas; Keller, Valérie; Lett, Marie-Claire

2010-04-01

Comparing the UV-A photocatalytic treatment of bioaerosols contaminated with different airborne microorganisms such as L. pneumophila bacteria, T2 bacteriophage viruses and B. atrophaeus bacterial spores, pointed out a decontamination sensitivity following the bacteria > virus > bacterial spore ranking order, differing from that obtained for liquid-phase or surface UV-A photocatalytic disinfection. First-principles CFD investigation applied to a model annular photoreactor evidenced that larger the microorganism size, higher the hit probability with the photocatalytic surfaces. Applied to a commercial photocatalytic purifier case-study, the CFD calculations showed that the performances of the studied purifier could strongly benefit from rational reactor design engineering. The results obtained highlighted the required necessity to specifically investigate the removal of airborne microorganisms in terms of reactor design, and not to simply transpose the results obtained from studies performed toward chemical pollutants, especially for a successful commercial implementation of air decontamination photoreactors. This illustrated the importance of the aerodynamics in air decontamination, directly resulting from the microorganism morphology.

New insights into the photocatalytic activity of 3-D core-shell P25@silica nanocomposites: impact of mesoporous coating.

PubMed

Gong, Yichao; Wang, Dan Ping; Wu, Renbing; Gazi, Sarifuddin; Soo, Han Sen; Sritharan, Thirumany; Chen, Zhong

2017-04-11

In this report, a three-dimensional (3-D) network of core-shell TiO 2 (P25)-mesoporous SiO 2 (P25@mSiO 2 ) nanocomposites was prepared via a controllable surfactant-assisted sol-gel method. The nanocomposites were investigated for photocatalytic reactions of organic dye degradation, water splitting, and CO 2 reduction to understand the roles of the mSiO 2 shell in these photocatalytic reactions. It was found that the mSiO 2 shell accelerates the photodegradation of the organic dye, but dramatically reduces the photocatalytic activity of P25 in water splitting and CO 2 reduction. The roles played by the mSiO 2 shell in the photocatalytic reactions are summarized as: (1) effective prevention of agglomeration of P25 nanoparticles, (2) facilitating the transfer of uncharged photo-generated ˙OH radicals via the abundant -OH groups on the mesoporous surface, (3) provision of increased reaction sites between ˙OH radicals and dye molecules by its mesoporous nanostructure and large surface area, and (4) prevention of diffusion of the photo-generated charge carriers (photoelectrons and photoholes) because of its insulating nature.

Removal of dissolved humic acid from water by photocatalytic oxidation using a silver orthophosphate semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatakeyama, Keisuke, E-mail: hatakeyamak@pref.tottori.jp; Okuda, Masukazu; Kuki, Takahiro

2012-12-15

Graphical abstract: Display Omitted Highlights: ► The photocatalytic property of a silver orthophosphate (Ag{sub 3}PO{sub 4}) was investigated for humic acid degradation. ► The Ag{sub 3}PO{sub 4} shows high photocatalytic activity under visible light. ► The photocatalytic activity was greatly improved by employing the precipitation method. -- Abstract: In order to remove dissolved organic matter such as humic acid from water, a silver orthophosphate (Ag{sub 3}PO{sub 4}) was newly employed as a heterogeneous photocatalyst. Here, Ag{sub 3}PO{sub 4} was prepared by simple ion-exchange and precipitation methods, and the physico-chemical properties were characterized by X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, scanningmore » electron microscopy, particle distribution measurements and Brunauer–Emmett–Teller (BET) analysis. The degradation of humic acid was faster over Ag{sub 3}PO{sub 4} catalyst than over conventional TiO{sub 2} (P-25). The total photocatalytic properties were improved by employing not an ion-exchange method but a precipitation method; humic acid degradation was performed with a removal ratio of dissolved organic carbon of 75% under visible light (λ = 451 nm) for 2-h irradiation.« less

Fabrication and Wettability Study of WO3 Coated Photocatalytic Membrane for Oil-Water Separation: A Comparative Study with ZnO Coated Membrane.

PubMed

Gondal, Mohammed A; Sadullah, Muhammad S; Qahtan, Talal F; Dastageer, Mohamed A; Baig, Umair; McKinley, Gareth H

2017-05-10

Superhydrophilic and underwater superoleophobic surfaces were fabricated by facile spray coating of nanostructured WO 3 on stainless steel meshes and compared its performance in oil-water separation with ZnO coated meshes. The gravity driven oil-water separation system was designed using these surfaces as the separation media and it was noticed that WO 3 coated stainless steel mesh showed high separation efficiency (99%), with pore size as high as 150 µm, whereas ZnO coated surfaces failed in the process of oil-water separation when the pore exceeded 50 µm size. Since, nanostructured WO 3 is a well known catalyst, the simultaneous photocatalytic degradation of organic pollutants present in the separated water from the oil water separation process were tested using WO 3 coated surfaces under UV radiation and the efficiency of this degradation was found to be quite significant. These results assure that with little improvisation on the oil water separation system, these surfaces can be made multifunctional to work simultaneously for oil-water separation and demineralization of organic pollutants from the separated water. Fabrication of the separating surface, their morphological characteristics, wettability, oil water separation efficiency and photo-catalytic degradation efficiency are enunciated.

The role of hydrothermally prepared supported photocatalytic composite in organic micro-pollutants removal from the water.

PubMed

Shivaraju, H P; Byrappa, K

2012-07-01

This work deals with the non-biodegradable micro-pollutants degradation by supported photocatalyst based heterogeneous photocatalytic reaction. TiO2 based supported photocatalyst was prepared by the hydrothermal technique to improve the photocatalytic performance along with easy recovery of suspended photocatalyst from aqueous medium after photoreaction. TO2 deposited calcium alumino-silicate beads (CASB) supports were prepared under mild hydrothermal conditions (Temparature-200 degrees C, Duration-24 h). In the present study, industrial dyes such as Amaranth and Brilliant Yellow were used as model micro-pollutants in aqueous solution. A real time pesticide industrial effluent was tested for its photocatalytic removal of organic pollutants using TO2 deposited CASB supported photocatalytic composite as an effective photocatalyst. Photocatalytic degradation of micro-pollutants present in aqueous medium was carried out in a batch photoreactor, at atmospheric pressure and temperature (28 degrees C). The influence of different light sources, irradiation time, catalyst load and catalytic performance is discussed. The photocatalytic degradation of micro-pollutants in aqueous medium was evaluated by determination of COD and %T. Easy separation and recovery of suspended photocatalysts from aqueous solution is the major advantage of hydrothermally prepared supported photocatalytic composite.

Rational Design of Porous Conjugated Polymers and Roles of Residual Palladium for Photocatalytic Hydrogen Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Lianwei; Cai, Zhengxu; Wu, Qinghe

Developing high efficient photocatalyts for splitting water into oxygen and hydrogen is one of the biggest chemical challenges in solar energy utilization. In this paper, we report our effort in rationally designing conjugated porous polymer (CPP) photocatalysts for photocatalytic hydrogen production (PHP) from water. A series of CPP photocatalysts with different chromophore components and bipyridyl (bpy) contents were synthesized and found to evolve hydrogen photocatalytically from water. The PHP activity of bpy-containing CPPs can be greatly enhanced due to the improved light absorption, better wettability, higher crystallinity and the improved charge separation process. Moreover, the CPP photocatalyst made of strongmore » and fully conjugated donor chromo-phore DBD shows the highest hydrogen production rate ~ 33 μmol/h. The results indicate that copolymerization between a strong donor and weak acceptor is a useful strategy for the devel-opment of efficient photocatalysts. This study clarifies that the residual palladium in the CPP networks plays a key role for the catalytic performance. The PHP activity of CPP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt% of extra platinum cocat-alyst.« less

Bibliography of work on the photocatalytic removal of hazardous compounds from water and air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blake, D.M.

1994-05-01

This is a bibliography of information in the open literature on work that has been done to date on the photocatalytic oxidation of compounds, principally organic compounds. The goal of the listing is removing hazardous oompounds from water or air. It contains lists of substances and literature citations. The bibliography includes information obtained through the middle of 1993 and some selected references for the balance of that year.

Photocatalytic Oxidation of Oil Contaminated Water Using TiO2/UV

NASA Astrophysics Data System (ADS)

Vargas Solla, Monica; Romero Rojas, Jairo

2017-04-01

Currently, oil is one of the most used energy sources all around the world, for example to make motor engines work. That prevailing usage of oil is the reason why water sources are under serious pollution risks with compounds that are hard to remove, such as hydrocarbons. There are a few water treatment processes known as Advanced Oxidation Processes, which search for a way to treat polluted water with toxic refractory compounds, to make its reuse more feasible and to avoid or at least appease the injurious effects of pollution over ecosystems. A heterogeneous photocatalysis water treatment technology, sorted as an Advanced Oxidation Process, which is intended to treat refractory compound polluted water by the use of TiO2 and UV light, is presented in this investigation. The evidence about its efficiency in hydrocarbon removal from used motor oil polluted water, since it is an extremely important pollutant due to its complexity, toxicity and recalcitrant characteristics, is also presented through COD, Oil and Grease and Hydrocarbons analysis.

Photocatalysts Based on Cobalt-Chelating Conjugated Polymers for Hydrogen Evolution from Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Lianwei; Hadt, Ryan G.; Yao, Shiyu

Developing photocatalytic systems for water splitting to generate oxygen and hydrogen is one of the biggest chemical challenges in solar energy utilization. In this work, we report the first example of heterogeneous photocatalysts for hydrogen evolution based on in-chain cobalt-chelating conjugated polymers. Four conjugated polymers chelated with earth abundant cobalt ions were synthesized and found to evolve hydrogen photocatalytically from water. These polymers are designed to combine functions of the conjugated backbone as light-harvesting antenna and electron transfer conduit with the in-chain bipyridyl chelated transition metal centers as catalytic active sites. In addition, these polymers are soluble in organic solvents,more » enabling effective interactions with the substrates as well as detailed characterization. We also found a polymer-dependent optimal cobalt chelating concentration at which the highest photocatalytic hydrogen production (PHP) activity can be achieved.« less

INTEGRATION OF PHOTOCATALYTIC OXIDATION WITH AIR STRIPPING OF CONTAMINATED AQUIFERS

EPA Science Inventory

Bench scale laboratory studies and pilot scale studies in a simulated field-test situation were performed to evaluate the integration of gas-solid ultaviolet (UV) photocatalytic oxidation (PCO) downstream if an air stripper unit as a technology for cost-effectively treating water...

Ternary and coupled binary zinc tin oxide nanopowders: Synthesis, characterization, and potential application in photocatalytic processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivetić, T.B., E-mail: tamara.ivetic@df.uns.ac.rs; Finčur, N.L.; Đačanin, Lj. R.

2015-02-15

Highlights: • Mechanochemically synthesized nanocrystalline zinc tin oxide (ZTO) powders. • Photocatalytic degradation of alprazolam in the presence of ZTO water suspensions. • Coupled binary ZTO exhibits enhanced photocatalytic activity compared to ternary ZTO. - Abstract: In this paper, ternary and coupled binary zinc tin oxide nanocrystalline powders were prepared via simple solid-state mechanochemical method. X-ray diffraction, scanning electron microscopy, Raman and reflectance spectroscopy were used to study the structure and optical properties of the obtained powder samples. The thermal behavior of zinc tin oxide system was examined through simultaneous thermogravimetric-differential scanning calorimetric analysis. The efficiencies of ternary (Zn{sub 2}SnO{submore » 4} and ZnSnO{sub 3}) and coupled binary (ZnO/SnO{sub 2}) zinc tin oxide water suspensions in the photocatalytic degradation of alprazolam, short-acting anxiolytic of the benzodiazepine class of psychoactive drugs, under UV irradiation were determined and compared with the efficiency of pure ZnO and SnO{sub 2}.« less

Z-scheme Ag3PO4/POM/GO heterojunction with enhanced photocatalytic performance for degradation and water splitting.

PubMed

Liu, Guodong; Zhao, Xinfu; Zhang, Jian; Liu, Shaojie; Sha, Jingquan

2018-05-01

To develop solar light-driven photocatalysts with high activity and structural stability, Ag3PO4/POM/GO heterojunction has been successfully prepared by a facile method at room temperature. Ag3PO4/POM/GO shows remarkably enhanced activity and stability for photocatalytic degradation and H2 production from water-splitting under simulated solar light. The degradation rate of Ag3PO4/POM/GO is 1.8 times and 1.2 times those of Ag3PO4 and Ag3PO4/POMs, respectively. H2 production using Ag3PO4/POM/GO is 2.0 times that of Ag3PO4/GO. The enhanced photocatalytic performance of Ag3PO4/POM/GO is attributed to the increased surface area, electronegativity and structure stability. The Z-scheme system of Ag3PO4/POM/GO effectively promotes charge separation, resulting in enhanced photocatalytic performance under simulated solar light.

Solar photocatalytic degradation of some hazardous water-soluble pesticides at pilot-plant scale.

PubMed

Oller, I; Gernjak, W; Maldonado, M I; Pérez-Estrada, L A; Sánchez-Pérez, J A; Malato, S

2006-12-01

The technical feasibility and performance of photocatalytic degradation of six water-soluble pesticides (cymoxanil, methomyl, oxamyl, dimethoate, pyrimethanil and telone) have been studied at pilot-plant scale in two well-defined systems which are of special interest because natural solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. TiO(2) photocatalysis tests were performed in a 35L solar pilot plant with three Compound Parabolic Collectors (CPCs) under natural illumination and a 75L solar pilot plant with four CPC units was used for homogeneous photocatalysis tests. The initial pesticide concentration studied was 50 mg L(-1) and the catalyst concentrations employed were 200 mg L(-1) of TiO(2) and 20 mg L(-1) of iron. Both toxicity (Vibrio fischeri, Biofix) and biodegradability (Zahn-Wellens test) of the initial pesticide solutions were also measured. Total disappearance of the parent compounds and nearly complete mineralization were attained with all pesticides tested. Treatment time, hydrogen peroxide consumption and release of heteroatoms are discussed.

Novel tiO2 nanocatalysts for wastewater purification: tapping energy from the sun.

PubMed

Liu, Y; Li, J; Qiu, X; Burda, C

2006-01-01

Water treatment using TiO2 semiconductor as a durable heterogeneous photocatalyst has been the focus of environmentalists in recent years. Currently, we developed an inexpensive and highly efficient approach for synthesizing nitrogen-doped TiO2 with lower band-gap energy that can respond to visible light. Doping on the molecular scale led to an enhanced nitrogen concentration of up to 21.8%. Reflectance measurements showed the synthesized N-doped TiO2 nanoparticles are catalytically active with the absorbance that extends into the visible region up to 600 nm. The water purification potential of this new class of compound was evaluated by studying the photodegradation of Acid Orange 7 (AO7) and E. coli. Experiments were conducted to compare the photocatalytic activities of N-doped TiO2 nanocatalysts and commercially available Degussa P25 power under identical solar light exposure. N-doped TiO2 demonstrated superior photocatalytic activities in both chemical compound degradation and bactericidal reactions. The result of this study shows the potential of applying new generations of catalyst for wastewater purification and disinfection.

Photocatalytic Nanofiltration Membranes with Self-Cleaning Property for Wastewater Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Yan; Zhang, Chao; He, Ai

Membrane fouling is one of the most severe problems restricting membrane separation technology for wastewater treatment. This work reports a photocatalytic nanofiltration membrane (NFM) with self-cleaning property fabricated using a facile biomimetic mineralization process. In this strategy, a polydopamine (PDA)/polyethyleneimine (PEI) intermediate layer is fabricated on an ultrafiltration membrane via a co-deposition method followed by mineralization of a photocatalytic layer consisting of beta-FeOOH nanorods. The PDA-PEI layer acts both as a nanofiltration selective layer and an intermediate layer for anchoring the beta-FeOOH nanorods via strong coordination complexes between Fe3+ and catechol groups. In visible light, the beta-(F)eOOH layer exhibits efficientmore » photocatalytic activity for degrading dyes through the photo-Fenton reaction in the presence of hydrogen peroxide, endowing the NFM concurrently with effective nanofiltration performance and self-cleaning capability. Moreover, the mineralized NFMs exhibit satisfactory stability under simultaneous filtration and photocatalysis processing, showing great potential in advanced wastewater treatment.« less

Solar photocatalytic disinfection with immobilised TiO(2) at pilot-plant scale.

PubMed

Sordo, Carlos; Van Grieken, Rafael; Marugán, Javier; Fernández-Ibáñez, Pilar

2010-01-01

The photocatalytic disinfection efficiency has been investigated for two immobilized TiO(2) catalytic systems (wall reactor and fixed-bed reactor) in a solar pilot plant. Their performances have been compared with the use of a slurry reactor and the solar disinfection without catalyst. The use of photocatalytic TiO(2) wall reactors does no show clear benefits over the solar disinfection process in the absence of catalyst. The reason is that the efficiency of the solar disinfection is so high that the presence of titania in the reactor wall reduces the global efficiency due to the competition for the absorption of photons. As expected, the maximum efficiency was shown by the slurry TiO(2) reactor, due to the optimum contact between bacteria and catalyst. However, it is noticeable that the use of the fixed-bed reactor leads to inactivation rate quite close to that of the slurry, requiring comparable accumulated solar energy of about 6 kJ L(-1) to achieve a 6-log decrease in the concentration of viable bacteria and allowing a total disinfection of the water (below the detection limit of 1 CFU mL(-1)). Not only the high titania surface area of this configuration is responsible for the bacteria inactivation but the important contribution of the mechanical stress has to be considered. The main advantage of the fixed-bed TiO(2) catalyst is the outstanding stability, without deactivation effects after ten reaction cycles, being readily applicable for continuous water treatment systems.

Influence of parameters on the heterogeneous photocatalytic degradation of pesticides and phenolic contaminants in wastewater: a short review.

PubMed

Ahmed, Saber; Rasul, M G; Brown, R; Hashib, M A

2011-03-01

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. This paper aims to review and summarize the recent works on the titanium dioxide (TiO(2)) photocatalytic oxidation of pesticides and phenolic compounds, predominant in storm and wastewater effluents. The effects of various operating parameters on the photocatalytic degradation of pesticides and phenols are discussed. Results reported here suggest that the photocatalytic degradation of organic compounds depends on the type and composition of the photocatalyst and, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, catalyst application mode, and calcination temperature in the water environment. A substantial amount of research has focused on the enhancement of TiO(2) photocatalysis by modification with metal, non-metal and ion doping. Recent developments in TiO(2) photocatalysis for the degradation of various pesticides and phenols are also highlighted in this review. It is evident from the literature survey that photocatalysis has good potential to remove a variety of organic pollutants. However, there is still a need to determine the practical utility of this technique on a commercial scale. Copyright © 2010 Elsevier Ltd. All rights reserved.

Photocatalytic oxidation of ammonia by cadmium sulfide/titanate nanotubes synthesised by microwave hydrothermal method.

PubMed

Chen, Y-C; Lo, S-L; Ou, H-H; Chen, C-H

2011-01-01

CdS/Titanate nanotubes (TNTs) were successfully synthesised by a simple, rapid, and reliable microwave hydrothermal method. The CdS nanoparticles synthesised using a 140-W microwave irradiation power at 423 K photodegraded 26% ammonia in water, while the photocatalytic efficiency increased to 52.3% using the synthesised CdS/TNTs composites. The results indicated that the CdS/TNTs photocatalysts possess improved photocatalytic activity than that of CdS or TNTs materials alone.

Photocatalytic performance of Cu-doped TiO2 nanofibers treated by the hydrothermal synthesis and air-thermal treatment

NASA Astrophysics Data System (ADS)

Wu, Ming-Chung; Wu, Po-Yeh; Lin, Ting-Han; Lin, Tz-Feng

2018-02-01

Series of transition metal-doped TiO2 (metal/TiO2) is prepared by combining the hydrothermal synthesis and air-thermal treatment without any reduction process. The selected transition metal precursors, including Ag, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, Y, and Zn, were individually doped into TiO2 nanofibers to evaluate the photocatalytic degradation activity and photocatalytic hydrogen generation. Consider the photocatalytic performance of these synthesized metal/TiO2 under UV-A irradiation, copper doped TiO2 nanofibers (Cu/TiO2 NFs) was chosen for further study due to its extraordinary reactivity. Systematical studies were spread to optimize the doping concentration and the calcination condition for much higher photocatalytic activity Cu/TiO2 NFs. In the photocatalytic degradation test, 0.5 mol%-Cu/TiO2 NFs calcined at 650 °C exhibits the highest activity, which is even higher than commercial TiO2-AEROXIDE® TiO2 P25 under UV-A irradiation. The synthesized 0.5 mol%-Cu/TiO2-650 NFs also have the capability in the photocatalytic hydrogen production. The hydrogen evolution rates are 200 μmol/g·h under UV-A irradiation and 280 μmol/g·h under UV-B irradiation. The density of state calculated by CASTEP for Cu/TiO2 indicates that Cu doping contributes to the states near valence band edge and narrows the band gap. The disclosed process in this study is industrial safe, convenient and cost-effective. We further produce a significant amount of TiO2-based catalysts without any hydrogen reduction treatment.

Black TiO2 synthesized via magnesiothermic reduction for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Xiangdong; Fu, Rong; Yin, Qianqian; Wu, Han; Guo, Xiaoling; Xu, Ruohan; Zhong, Qianyun

2018-04-01

Utilizing solar energy for hydrogen evolution is a great challenge for its insufficient visible-light power conversion. In this paper, we report a facile magnesiothermic reduction of commercial TiO2 nanoparticles under Ar atmosphere and at 550 °C followed by acid treatment to synthesize reduced black TiO2 powders, which possesses a unique crystalline core-amorphous shell structure composed of disordered surface and oxygen vacancies and shows significantly improved optical absorption in the visible region. The unique core-shell structure and high absorption enable the reduced black TiO2 powders to exhibit enhanced photocatalytic activity, including splitting of water in the presence of Pt as a cocatalyst and degradation of methyl blue (MB) under visible light irradiation. Photocatalytic evaluations indicate that the oxygen vacancies play key roles in the catalytic process. The maximum hydrogen production rates are 16.1 and 163 μmol h-1 g-1 under the full solar wavelength range of light and visible light, respectively. This facile and versatile method could be potentially used for large scale production of colored TiO2 with remarkable enhancement in the visible light absorption and solar-driven hydrogen production.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Feng; College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025; Zhang, Siwen

Highlights: • Walnut-like ZnO nanostructures are synthesized through a facile hydrothermal method. • Morphologies and microstructures of the as-obtained ZnO products were investigated. • The photocatalytic results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. - Abstract: Walnut-like ZnO nanostructures are successfully synthesized through a facile hydrothermal method. The structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The photocatalytic properties of ZnO nanowalnuts are investigated by photodegradating several organic dyes, such as Congo red (CR), methyl orange (MO) andmore » eosin red aqueous solutions under UV irradiation, respectively. The results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. In addition, eosin red and Congo red (CR) aqueous solution degradation experiments are also conducted in the same condition, respectively. It showed that ZnO nanowalnuts represent high photocatalytic activities with a degradation efficiency of 87% for CR with 115 min of irradiation and 97% for eosin red with 55 min of irradiation. The reported ZnO products may be promising candidates as the photocatalysts in waste water treatment.« less

Photocatalytic performance of crystalline titania polymorphs in the degradation of hazardous pharmaceuticals and dyes

NASA Astrophysics Data System (ADS)

Thuong Huyen Tran, Thi; Kosslick, Hendrik; Schulz, Axel; Liem Nguyen, Quang

2017-03-01

In the present work, nano-sized TiO2 polymorphs (anatase, brookite, and rutile) were synthesized via hydrothermal treatment of an amorphous titania. Three polymorphs were characterized by XRD, Raman spectroscopy, SEM, UV-Vis DRS, and N2-sorption measurements. The photocatalytic degradation experiments were performed with low catalyst concentration, high organic loading under a 60 W UV-Vis solarium lamp irradiation. The photocatalytic degradation was monitored by UV-Vis spectroscopy and TOC measurements. Cinnamic acid, ibuprofen, phenol, diatrizoic acid and the dyes rhodamine B and rose bengal were used as model pollutants. The formation of intermediates was studied by ESI-TOF-MS measurements. The presence of active species was checked by quenching the activity by addition of scavengers. The photocatalytic activity decreased in the order: anatase  ⩾  brookite  >  rutile, with growing recalcitrance of organic compounds. The differences in the activity are more pronounced in the degree of mineralization. The valence band holes and superoxide radicals were the major active species in the photocatalytic treatment with anatase and brookite, whereas hydroxyl radicals and superoxide radicals contributed mainly in the treatment with rutile explaining the lower activity of rutile. The complementary use of UV-Vis spectroscopy and TOC measurements was required to obtain a comprehensive realistic assessment on the photocatalytic performance of catalyst. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8-12 November 2016, Ha Long City, Vietnam.

Biologically Inspired Materials for Electro-Responsive Coatings and the Photo-Oxidation of Water

DTIC Science & Technology

2010-02-01

believed to be the first non-sacrificial electron acceptor capable of driving the metalloporphyrin- sensitized photocatalytic oxidation of water. Thesis ...passionate about, Angie encouraged and empowered me to keep trying new ideas. With her help, I was able to develop my thesis studies of photocatalytic...year and was a part of nearly every piece of this thesis . Throughout the thesis I try to acknowledge data that was acquired or analyzed by someone

Photocatalytic degradation of sulfamethoxazole in aqueous solution using a floating TiO2-expanded perlite photocatalyst.

PubMed

Długosz, Maciej; Żmudzki, Paweł; Kwiecień, Anna; Szczubiałka, Krzysztof; Krzek, Jan; Nowakowska, Maria

2015-11-15

Photocatalytic degradation of an antibiotic, sulfamethoxazole (SMX), in aqueous solution using a novel floating TiO2-expanded perlite photocatalyst (EP-TiO2-773) and radiation from the near UV spectral range was studied. The process is important considering that SMX is known to be a widespread and highly persistent pollutant of water resources. SMX degradation was described using a pseudo-first-order kinetic equation according to the Langmuir-Hinshelwood model. The products of the SMX photocatalytic degradation were identified. The effect of pH on the kinetics and mechanism of SMX photocatalytic degradation was explained. Copyright © 2015 Elsevier B.V. All rights reserved.

Oxidative stress responses of Daphnia magna exposed to effluents spiked with emerging contaminants under ozonation and advanced oxidation processes.

PubMed

Oropesa, Ana Lourdes; Novais, Sara C; Lemos, Marco F L; Espejo, Azahara; Gravato, Carlos; Beltrán, Fernando

2017-01-01

Integration of conventional wastewater treatments with advanced oxidation processes (AOPs) has become of great interest to remove pharmaceuticals and their metabolites from wastewater. However, application of these technologies generates reactive oxygen species (ROS) that may reach superficial waters through effluents from sewage treatment plants. The main objective of the present study was to elucidate if ROS present in real effluents after biological and then chemical (single ozonation, solar photolytic ozonation, solar photocatalytic ozonation (TiO 2 , Fe 3 O 4 ) and solar photocatalytic oxidation (TiO 2 )) treatments induce oxidative stress in Daphnia magna. For this, the activity of two antioxidant enzymes (superoxide dismutase and catalase) and the level of lipid peroxidation were determined in Daphnia. The results of oxidative stress biomarkers studied suggest that D. magna is able to cope with the superoxide ion radical (O 2 · - ) present in the treated effluent due to single ozonation by mainly inducing the antioxidant activity superoxide dismutase, thus preventing lipid peroxidation. Lethal effects (measured in terms of immobility) were not observed in these organisms after exposure to any solution. Therefore, in order to probe the ecological efficiency of urban wastewater treatments, studies on lethal and sublethal effects in D. magna would be advisable.

High photocatalytic activity of Fe2O3/TiO2 nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid.

PubMed

Lee, Shu Chin; Lintang, Hendrik O; Yuliati, Leny

2017-01-01

Two series of Fe 2 O 3 /TiO 2 samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe 2 O 3 /TiO 2 for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe 2 O 3 /TiO 2 nanocomposites prepared by impregnation showed lower activity than the unmodified TiO 2 , mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe 2 O 3 /TiO 2 nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO 2 . Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe 2 O 3 (0.5)/TiO 2 . The improved activity of TiO 2 after photodeposition of Fe 2 O 3 was contributed to the formation of a heterojunction between the Fe 2 O 3 and TiO 2 nanoparticles that improved charge transfer and suppressed electron-hole recombination. A further investigation on the role of the active species on Fe 2 O 3 /TiO 2 confirmed that the crucial active species were both holes and superoxide radicals. The Fe 2 O 3 (0.5)/TiO 2 sample also showed good stability and reusability, suggesting its potential for water purification applications.

Two-dimensional molybdenum disulphide nanoflakes synthesized by liquid-solid phase reaction method: regenerative photocatalytic performance under UV-visible light irradiation by advance oxidation process

NASA Astrophysics Data System (ADS)

Afsar, M. F.; Rafiq, M. A.; Siddique, Fizza; Saira, F.; Chaudhary, M. M.; Hasan, M. M.; Tok, A. I. Y.

2018-05-01

Molybdenum disulphide (MoS2) nanoflakes were prepared through liquid-solid phase reaction technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) analysis revealed the formation of pure, polycrystalline, hexagonal phase of MoS2 nanoflakes. The texture coefficient (T{c}hkl) analysis showed that (100) plane was preferentially oriented. The specific surface area of the nanoflakes was 21 m2 g‑1 as determined using Brunaure-Emmett-Teller (BET) technique. A band gap of ∼2.05 eV for MoS2 nanoflakes was estimated from UV-visible spectrum. Regenerative photocatalytic activity of MoS2 nanoflakes was assessed by degrading methylene blue (MB) and safranin-o (SO) dyes under UV-visible light irradiation. Under light irradiation, degradation efficiency for MB was ∼99.58% in 100 min while for SO it was ∼99.89% in 70 min. The MoS2 nanoflakes exhibited excellent photocatalytic performance and good stability in a wide pH range (3–11). MoS2 nanoflakes showed a high reaction rate constant (k app ) for SO ∼ 0.104 49 min‑1 and MB ∼ 0.092 18 min‑1 as compared to other MoS2 nanostructures. The obtained exceptional photocatalytic performance of MoS2 nanoflakes offers potential applications for the treatment of polluted water as well as in other correlated fields.

Photocatalytic degradation of isoproturon herbicide over TiO2/Al-MCM-41 composite systems using solar light.

PubMed

Phanikrishna Sharma, M V; Durga Kumari, V; Subrahmanyam, M

2008-06-01

The present investigation covers immobilization of TiO2 using a simple solid state dispersion technique over mesoporous Al-MCM-41 support for the treatment of isoproturon herbicide. Catalysts are characterized by XRD, X-ray photo electron spectroscopy (XPS), surface area, UV-Vis diffused reflectance spectra (DRS), SEM and TEM. A detailed photocatalytic degradation study of isoproturon under solar light in aqueous suspensions is reported. The 10 wt% TiO2/Al-MCM-41 composite system found to be optimum with high degradation activity. The reaction follows pseudo-first order kinetics. The parameters like TiO2 loading over Al-MCM-41, amount of catalyst, concentration of substrate, pH effect, durability of the catalyst, activity comparison of TiO2 and Al-MCM-41 supported system are studied. The mineralization of isoproturon is monitored by TOC. Based on the degradation products detected through LC-MS, a plausible degradation mechanism is proposed. The data indicates that TiO2/Al-MCM-41 composite system is an effective photocatalyst for treatment of isoproturon in contaminated water.

Hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanocomposites: Enhanced and stable photocatalytic performance for water purification under visible light irradiation

NASA Astrophysics Data System (ADS)

Guo, Na; Li, Haiyan; Xu, Xingjian; Yu, Hongwen

2016-12-01

Novel hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanophotocatalyst with remarkable photocatalytic capability were prepared by simply depositing the Ag3PO4 onto the surface of crumpled Fe3O4@MoS2 nanosphere. The nanocomposites were characterized by XRD, TEM, HRTEM, XPS, BET, and UV-vis DRS. The outcome of the photocatalytic experiments demonstrated that Fe3O4@MoS2/Ag3PO4 with 6 wt% content of Ag3PO4 (FM/A-6%) showed the highest photocatalytic activity upon the degradation Congo red (CR) and Rhodamine B (RhB) under both visible light and simulated sunlight irradiation. In addition, FM/A-6% possessed larger specific surface area (76.56 m2/g) and excellent optical property. The possible Z-scheme charge carriers transfer mechanism for the enhanced photocatalytic properties of the FM/A-6% was also discussed. The Z-scheme charge carriers transfer mechanism established between MoS2 and Ag3PO4 facilitate the charge separation efficiency. Moreover, FM/A-6% can be separated and collected easily by external magnetic field and maintain high activity after five times photoreaction cycles. Given the remarkable photocatalytic performance and high stability of FM/A-6% nanocomposite, it is looking forward to exhibit great potential for applications in water purification.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability.

PubMed

Pawar, Rajendra C; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S

2016-08-08

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g(-1)) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g(-1)). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

NASA Astrophysics Data System (ADS)

Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S.

2016-08-01

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g-1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g-1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

PubMed Central

Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-ho; Ahn, Sunghoon; Lee, Caroline S.

2016-01-01

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g−1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g−1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective. PMID:27498979

Reusability Performance of Zinc Oxide Nanoparticles for Photocatalytic Degradation of POME

NASA Astrophysics Data System (ADS)

Zarifah Zainuri, Nur; Hanis Hayati Hairom, Nur; Abu Bakar Sidik, Dilaelyana; Misdan, Nurasyikin; Yusof, Norhaniza; Wahab Mohammad, Abdul

2018-03-01

Performance and reusability of different zinc oxide nanoparticles (ZnO-PVP and ZnO-PEG) for photocatalytic degradation of palm-mill oil effluent (POME) has been studied. The nanoparticles properties were characterised with fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM results show that ZnO-PEG nanoparticles exhibit the smaller size than ZnO-PVP with less agglomeration. It was found that ZnO-PEG shows better effectiveness than ZnO-PVP in reducing turbidity, colour and increasing the dissolved oxygen (DO). By using two types of reusability methods: (a) oven drying (b) hot water rinsing, the oven drying method portrayed the most efficient route for POME treatment. This research would be a solution to the palm oil industry for photocatalyst recovering as well as reduction of the chemical usage in order to meet the development of advanced and greener technologies.

Virus inactivation by silver doped titanium dioxide nanoparticles for drinking water treatment.

PubMed

Liga, Michael V; Bryant, Erika L; Colvin, Vicki L; Li, Qilin

2011-01-01

Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO(2)) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO(2) nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO(2) was compared to the base TiO(2) material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO(2) material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation. Copyright © 2010 Elsevier Ltd. All rights reserved.

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation

PubMed Central

Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

2016-01-01

Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge. PMID:26755070

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation.

PubMed

Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

2016-01-12

Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge.

TiO2/porous adsorbents: Recent advances and novel applications.

PubMed

MiarAlipour, Shayan; Friedmann, Donia; Scott, Jason; Amal, Rose

2018-01-05

This article reviews two interrelated areas of research: the first is the use of TiO 2 -supported adsorbent materials as enhanced heterogeneous photocatalysts and their application to various reactions for organic pollutant removal from air and water; the second is the combination of adsorbent materials with TiO 2 photocatalysts which aims to efficiently regenerate adsorbent materials using illumination. By reviewing both areas of research, the following topics are covered; (i) photocatalytic activation of TiO 2; (ii) related properties of photocatalytic TiO 2; (iii) shortcomings of photocatalytic processes; (iv) preparation methods of composite TiO 2 /adsorbent materials and their photocatalytic performance; (v) properties of common adsorbents and their applications for pollutant removal from air and water; (vi) adsorbent regeneration methods and their economic and operational issues; (vii) conclusions and future outlooks. This topic has not been previously reviewed to such an extent, and considerable knowledge can be gained from assembling the large number of studies on adsorption-photocatalysis combinations. As such, this review provides guidance for researchers working in the fields of environmental and chemical engineering focussing on organic pollutant removal and the engineering of new high performance photocatalytic TiO 2 -supported porous adsorbent materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation

NASA Astrophysics Data System (ADS)

Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

2016-01-01

Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge.

The influence of photocatalytic interior paints on indoor air quality

NASA Astrophysics Data System (ADS)

Auvinen, Joonas; Wirtanen, Leif

2008-06-01

A clean indoor air is important for the well-being and health of people. Lately, new photocatalytic paints have been launched on the market, which are claimed to have air-purifying effects. Photocatalysis initiates radical reactions. Radicals are formed when a photocatalyst (e.g. TiO2) is subjected to radiation. Typical radicals are the hydroxyl radical (radOH) and the superoxide radical (radO2-). Radicals cause chain reactions, which degrade and decompose organic compounds. The end products of these chain reactions are water and carbon dioxide, if the reactions are fully completed (mineralization). If mineralization does not take place, then a great number of side products can be formed, whose properties are not well understood. The side products of photocatalytic reactions can be permanent and stabile. The decomposition of indoor air impurities on the surface of photocatalytic paints is not obvious. The ability of photocatalytic indoor paints to reduce chemical indoor air impurities is the key issue of this study. Six different paints with different binder systems, such as lime, polyorganic siloxane, silica sol-gel and organic binders, were examined. The experiments were divided into three topics: degradation of an organic binder, photocatalytic decomposition of formaldehyde, and a volatile organic compound (VOC) mixture consisting of five different indoor air VOCs. All tests were carried out in an environmental test chamber under dynamic conditions. The test results indicate that many indoor pollutants are generated under normal- and UVA-light. Typical compounds formed include formaldehyde, acetone, acetaldehyde, etc. A clear decrease of formaldehyde or the VOC mixture concentration was not observed. All possibly generated compounds could not be collected or analyzed in this research project, but the measurements show that photocatalytic reactions do not generate only carbon dioxide and water. Photocatalytic decomposition of indoor air impurities can, however, produce many side products, which may be stabile and harmful.

Effects of indium contents on photocatalytic performance of ZnIn{sub 2}S{sub 4} for hydrogen evolution under visible light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Kelin; Zhu, Rongshu, E-mail: rszhu@hitsz.edu.cn; Public Platform for Technological Service in Urban Waste Reuse and Energy Regeneration, Shenzhen 518055

2015-12-15

A series of ZnIn{sub x}S{sub 4+y} (x=1.6, 2.0, 2.3, 2.6, 2.9, 3.1) photocatalysts were synthesized via a facile hydrothermal method and characterized by various analytical techniques, such as XRD, EDS, UV–vis DRS, SEM, TEM, BET and PL. The ZnIn{sub x}S{sub 4+y} photocatalysts had a similar crystal structure. With the increase of indium content, the absorption edges of ZnIn{sub x}S{sub 4+y} photocatalysts shifted to longer wavelength, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite. Especially, when x=2.3, ZnIn{sub 2.3}S{sub 4+y} catalyst had smallest crystal size, largestmore » specific surface area and total pore volume. Additionally, the morphology of ZnIn{sub x}S{sub 4+y} greatly depended on the contents of indium. The photocatalytic activity of ZnIn{sub x}S{sub 4+y} was evaluated by photocatalytic hydrogen production from water under visible light. The ZnIn{sub 2.3}S{sub 4+y} sample had the highest photocatalytic activity among these ZnIn{sub x}S{sub 4+y} photocatalysts and its hydrogen production rate was 363 μmol/g h. - Graphical abstract: First, a series of catalysts were synthesized. And then those were characterized by various analytical techniques (such as SEM). finally, The photocatalytic activity of catalyst was evaluated by photocatalytic hydrogen production from water under visible light. - Highlights: • The photocatalytic property was studied upon visible-light irradiation. • ZnIn{sub x}S{sub 4+y} photocatalysts show superior photocatalytic activity. • The catalyst of grain size, morphology and BET are related to indium content. • ZnIn{sub x}S{sub 4+y} photocatalysts were synthesized via a facile hydrothermal method.« less

Phosphate Changes Effect of Humic Acids on TiO2 Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

PubMed

Long, Mingce; Brame, Jonathon; Qin, Fan; Bao, Jiming; Li, Qilin; Alvarez, Pedro J J

2017-01-03

A major challenge for photocatalytic water purification with TiO 2 is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO 2 photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups in HA and the TiO 2 surface in the presence of phosphate. This configuration can reduce hole consumption and facilitate electron transfer to O 2 by the adsorbed HA (indicated by linear sweep voltammetry), which mitigates electron-hole recombination and enhances contaminant degradation. A decrease in HA surface adsorption and hole scavenging (the predominant inhibitory mechanisms of HA) by phosphate (2 mM) was indicated by a 50% decrease in the photocatalytic degradation rate of HA and 80% decrease in the decay rate coefficient of interfacial-related photooxidation in photocurrent transients. These results, which were validated with other compounds (FFA and cimetidine), indicate that anchoring phosphate - or anions that exert similar effects on the TiO 2 surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.

H2 spillover enhanced hydrogenation capability of TiO2 used for photocatalytic splitting of water: a traditional phenomenon for new applications.

PubMed

Zhu, Yingming; Liu, Dongsheng; Meng, Ming

2014-06-07

Black TiO2 was usually obtained via hydrogenation at high pressure and high temperature. Herein, we reported a facile hydrogenation of TiO2 in the presence of a small amount of Pt at relatively low temperature and atmospheric pressure. The hydrogen spillover from Pt to TiO2 accounts well for the greatly enhanced hydrogenation capability. The as-synthesized Pt/TiO2 exhibits remarkably improved photocatalytic activity for water splitting.

Synergistic Effect of a Molecular Cocatalyst and a Heterojunction in a 1 D Semiconductor Photocatalyst for Robust and Highly Efficient Solar Hydrogen Production.

PubMed

Jiang, Daochuan; Irfan, Rana Muhammad; Sun, Zijun; Lu, Dapeng; Du, Pingwu

2016-11-09

Photocatalytic production of hydrogen by water splitting is a promising pathway for the conversion of solar energy into chemical energy. However, the photocatalytic conversion efficiency is often limited by the sluggish transfer of the photogenerated charge carriers, charge recombination, and subsequent slow catalytic reactions. Herein, we report a highly active noble-metal-free photocatalytic system for hydrogen production in water. The system contains a water-soluble nickel complex as a molecular cocatalyst and zinc sulfide on 1D cadmium sulfide as the heterojunction photocatalyst. The complex can efficiently transport photogenerated electrons and holes over a heterojunction photocatalyst to hamper charge recombination, leading to highly improved catalytic efficiency and durability of a heterojunction photocatalyst- molecular cocatalyst system. The results show that under optimal conditions, the average apparent quantum yield was approximately 58.3 % after 7 h of irradiation with monochromatic 420 nm light. In contrast, the value is only 16.8 % if the molecular cocatalyst is absent. Such a remarkable performance in a molecular cocatalyst-based photocatalytic system without any noble metal loading has, to the best of our knowledge, not been reported to date. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water-driven micromotors for rapid photocatalytic degradation of biological and chemical warfare agents.

PubMed

Li, Jinxing; Singh, Virendra V; Sattayasamitsathit, Sirilak; Orozco, Jahir; Kaufmann, Kevin; Dong, Renfeng; Gao, Wei; Jurado-Sanchez, Beatriz; Fedorak, Yuri; Wang, Joseph

2014-11-25

Threats of chemical and biological warfare agents (CBWA) represent a serious global concern and require rapid and efficient neutralization methods. We present a highly effective micromotor strategy for photocatalytic degradation of CBWA based on light-activated TiO2/Au/Mg microspheres that propel autonomously in natural water and obviate the need for external fuel, decontaminating reagent, or mechanical agitation. The activated TiO2/Au/Mg micromotors generate highly reactive oxygen species responsible for the efficient destruction of the cell membranes of the anthrax simulant Bacillus globigii spore, as well as rapid and complete in situ mineralization of the highly persistent organophosphate nerve agents into nonharmful products. The water-driven propulsion of the TiO2/Au/Mg micromotors facilitates efficient fluid transport and dispersion of the photogenerated reactive oxidative species and their interaction with the CBWA. Coupling of the photocatalytic surface of the micromotors and their autonomous water-driven propulsion thus leads to a reagent-free operation which holds a considerable promise for diverse "green" defense and environmental applications.

Immobilized TiO2 on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process.

PubMed

Cunha, Deivisson Lopes; Kuznetsov, Alexei; Achete, Carlos Alberto; Machado, Antonio Eduardo da Hora; Marques, Marcia

2018-01-01

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO 2 -P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO 2 leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO 2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO 2 -400 °C). The TiO 2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO 2 -400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment.

Immobilized TiO2 on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process

PubMed Central

Kuznetsov, Alexei; Achete, Carlos Alberto; Machado, Antonio Eduardo da Hora; Marques, Marcia

2018-01-01

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO2-P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO2 leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO2-400 °C). The TiO2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO2-400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment. PMID:29527416

Treatment of chlorinated solvents by TiO2 photocatalysis and photo-Fenton: influence of operating conditions in a solar pilot plant.

PubMed

Rodríguez, S Malato; Gálvez, J Blanco; Rubio, Manuel I Maldonado; Ibáñez, P Fernández; Gernjak, W; Alberola, I Oller

2005-01-01

Titanium dioxide photocatalysis (using 20 0mg l(-1) of TiO2), under aerobic and anaerobic conditions, and photo-Fenton (2 and 56 mg l(-1) iron) were applied to the treatment of different NBCS (non-biodegradable chlorinated solvents), such as dichloroethane, dichloromethane and trichloromethane dissolved in water at 50 mg l(-1). All the tests were performed in a 35-l solar pilot plant with compound parabolic collectors (CPCs) under natural illumination. The two solar treatments were compared with attention to chloride release and TOC mineralisation, as the main parameters. Photo-Fenton was found to be the more appropriate treatment for these compounds, assuming volatilisation as a drawback of photocatalytic degradation of NBCS dissolved in water. In this context, several operating parameters related to NBCS degradation, e.g., treatment time, temperature, hydrogen peroxide consumption and volatility of parent compounds are discussed. The correct choice of operating conditions can very often diminish the problem of volatilisation during treatment.

Product selectivity of visible-light photocatalytic reduction of carbon dioxide using titanium dioxide doped by different nitrogen-sources

NASA Astrophysics Data System (ADS)

Zhang, Zhaoguo; Huang, Zhengfeng; Cheng, Xudong; Wang, Qingli; Chen, Yi; Dong, Peimei; Zhang, Xiwen

2015-11-01

The influence of nitrogen-source on the photocatalytic properties of nitrogen-doped titanium dioxide is herein first investigated from the perspective of the chemical bond form of the nitrogen element in the nitrogen-source. The definitive role of groups such as Nsbnd N from the nitrogen-source on the surface of as-prepared samples in the selectivity of the dominant product of photocatalytic reduction is demonstrated. Well-crystallized one-dimensional Nsbnd TiO2 nanorod arrays with a preferred orientation of the rutile (3 1 0) facet are manufactured via a hydrothermal treatment using hydrazine and ammonia variously as the source of nitrogen. Significant selectivity of the dominant reduced products has been exhibited for Nsbnd TiO2 prepared from different nitrogen-sources in carbon dioxide photocatalytic reduction under visible light illumination. CH4 is the main product with N2H4-doped Nsbnd TiO2, while CO is the main product with NH3-doped Nsbnd TiO2, which can be attributed to the existence of the reducing Nsbnd N groups in the N2H4-doped Nsbnd TiO2 surfaces after the hydrothermal treatment. Compared with the approaches previously reported, the facile one-step route utilized here accomplishes the fabrication of Nsbnd TiO2 possessing visible-light activity and attainment of selectivity of dominant photocatalytic reduction product simultaneously by choosing a nitrogen-source with appropriate chemical bond form, which provides a completely new approach to understanding the effects of doping treatment on photocatalytic properties.

LCA of greywater management within a water circular economy restorative thinking framework.

PubMed

Dominguez, Sara; Laso, Jara; Margallo, María; Aldaco, Rubén; Rivero, Maria J; Irabien, Ángel; Ortiz, Inmaculada

2018-04-15

Greywater reuse is an attractive option for the sustainable management of water under water scarcity circumstances, within a water circular economy restorative thinking framework. Its successful deployment relies on the availability of low cost and environmentally friendly technologies. The life cycle assessment (LCA) approach provides the appropriate methodological tool for the evaluation of alternative treatments based on environmental decision criteria and, therefore, it is highly useful during the process conceptual design. This methodology should be employed in the early design phase to select those technologies with lower environmental impact. This work reports the comparative LCA of three scenarios for greywater reuse: photocatalysis, photovoltaic solar-driven photocatalysis and membrane biological reactor, in order to help the selection of the most environmentally friendly technology. The study has been focused on the removal of the surfactant sodium dodecylbenzenesulfonate, which is used in the formulation of detergents and personal care products and, thus, widely present in greywater. LCA was applied using the Environmental Sustainability Assessment methodology to obtain two main environmental indicators in order to simplify the decision making process: natural resources and environmental burdens. Energy consumption is the main contributor to both indicators owing to the high energy consumption of the light source for the photocatalytic greywater treatment. In order to reduce its environmental burdens, the most desirable scenario would be the use of solar light for the photocatalytic transformation. However, while the technological challenge of direct use of solar light is approached, the environmental suitability of the photovoltaic solar energy driven photocatalysis technology to greywater reuse has been demonstrated, as it involves the smallest environmental impact among the three studied alternatives. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancement of visible-light photoactivity by polypropylene coated plasmonic Au/TiO2 for dye degradation in water solution

NASA Astrophysics Data System (ADS)

D'Amato, C. A.; Giovannetti, R.; Zannotti, M.; Rommozzi, E.; Ferraro, S.; Seghetti, C.; Minicucci, M.; Gunnella, R.; Di Cicco, A.

2018-05-01

A new approach to obtain a heterogeneous photocatalytic material with gold nanoparticles and TiO2 semiconductor was performed exploiting the reducing ability of acetylacetone, a chemical present in the TiO2 paste formulation. Gold/TiO2 heterogeneous catalyst supported on polypropylene [PP@Au-TiO2]A was prepared; composition, structure and morphology of this new material were defined by using UV-Vis spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD), X-ray Fluorescence (XRF), Raman Spectroscopy, Photoluminescence and Diffuse Reflectance Spectroscopy. The new material was tested in the photocatalytic degradation of Alizarin Red S in water solution, as target pollutant, under visible light and correlated with structural and spectroscopic characterizations. [PP@Au-TiO2]A showed higher photocatalytic activity respect to pure [PP@TiO2]A with an improvement of photodegradation kinetic. The best performance was obtained using [PP@Au-TiO2]A sample with 0.006 wt.% of Au and the photocatalytic improvement was correlated with the band gap energy decrease of photocatalyst.

Photocatalytic degradation using design of experiments: a review and example of the Congo red degradation.

PubMed

Sakkas, Vasilios A; Islam, Md Azharul; Stalikas, Constantine; Albanis, Triantafyllos A

2010-03-15

The use of chemometric methods such as response surface methodology (RSM) based on statistical design of experiments (DOEs) is becoming increasingly widespread in several sciences such as analytical chemistry, engineering and environmental chemistry. Applied catalysis, is certainly not the exception. It is clear that photocatalytic processes mated with chemometric experimental design play a crucial role in the ability of reaching the optimum of the catalytic reactions. The present article reviews the major applications of RSM in modern experimental design combined with photocatalytic degradation processes. Moreover, the theoretical principles and designs that enable to obtain a polynomial regression equation, which expresses the influence of process parameters on the response are thoroughly discussed. An original experimental work, the photocatalytic degradation of the dye Congo red (CR) using TiO(2) suspensions and H(2)O(2), in natural surface water (river water) is comprehensively described as a case study, in order to provide sufficient guidelines to deal with this subject, in a rational and integrated way. (c) 2009 Elsevier B.V. All rights reserved.

Photocatalytic Water Splitting for O2 Production under Visible Light Irradiation Using NdVO4-V2O5 Hybrid Powders

PubMed Central

Chiang, Tzu Hsuan; Chen, Tso-Ming

2017-01-01

The study investigated photocatalytic water splitting for O2 production under visible light irradiation using neodymium vanadium oxide (NdVO4) and vanadium oxide (V2O5) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO3 solution were obtained, and the highest photocatalytic O2 evolution was 2.63 μmol/h, when the hybrid powders were prepared by mixing Nd and V at a volume ratio of 1:3 at a calcination temperature of 350 °C for 1 h. The hybrid powders were synthesized by neodymium nitrate and ammonium metavanadate using the glycothermal method in ethylene glycol at 120 °C for 1 h. The hybrid powders consisted of two shapes, NdVO4 nanoparticles and the cylindrical V2O5 particles, and they possessed the ability for photocatalytic oxygen (O2) evolution during irradiation with visible light. The band gaps and structures of the hybrid powders were analyzed using UV-visible spectroscopy and transmission electron microscopy. PMID:28772692

Antibiotic removal from water: A highly efficient silver phosphate-based Z-scheme photocatalytic system under natural solar light.

PubMed

Wang, Jiajia; Chen, Hui; Tang, Lin; Zeng, Guangming; Liu, Yutang; Yan, Ming; Deng, Yaocheng; Feng, Haopeng; Yu, Jiangfang; Wang, Longlu

2018-10-15

Photocatalytic degradation is an alternative method to remove pharmaceutical compounds from water, however it is hard to achieve efficient rate because of the low efficiency of photocatalysts. In this study, an efficient Z-Scheme photocatalyst was constructed by integrating graphitic carbon nitride (CN) and reduced graphene oxide (rGO) with AP via a simple facile precipitation method. Excitedly, ternary AP/rGO/CN composite showed superior photocatalytic and anti-photocorrosion performances under both intense sunlight and weak indoor light irradiation. NOF can be completely degraded in only 30 min and about 85% of NOF can be mineralized after 2 h irradiation under intensive sunlight irradiation. rGO could work not only as a sheltering layer to protect AP from photocorrosion but also as a mediator for Z-Scheme electron transport, which can protect AP from the photoreduction. This strategy could be a promising method to construct photocatalytic system with high efficiency for the removal of antibiotics under natural light irradiation. Copyright © 2018 Elsevier B.V. All rights reserved.

Novel Bi₁₂O₁₅Cl₆ Photocatalyst for the Degradation of Bisphenol A under Visible-Light Irradiation.

PubMed

Wang, Chu-Ya; Zhang, Xing; Song, Xiang-Ning; Wang, Wei-Kang; Yu, Han-Qing

2016-03-02

Bisphenol A (BPA), a typical endocrine-disrupting chemical, is widely present in water environments, and its efficient and cost-effective removal is greatly needed. Among various physicochemical methods for BPA degradation, visible-light-driven catalytic degradation of BPA is a promising approach because of its utilization of solar energy. Bismuth oxychloride (BiOCl) is recognized as an efficient photocatalyst, but its band gap, >3.0 eV, makes it inefficient for solar energy utilization, especially for degrading nondye pollutants like BPA. Thus, preparation and application of bismuth oxychloride photocatalysts with an increased visible-light activity are essential. In this work, inspired by density functional theory calculations, a novel bismuth oxychloride photocatalyst, Bi12O15Cl6, was designed. The nanosheets were successfully synthesized using a facile solvothermal method followed by a thermal treatment route. The prepared Bi12O15Cl6 nanosheets had a favorable energy band structure and thus exhibited a superior visible-light photocatalytic activity for degrading BPA. The BPA degradation rate by the Bi12O15Cl6 was determined to be 13.6 and 8.7 times faster than those for BiOCl and TiO2 (P25), respectively. The photogenerated reactive species and degradation intermediates were identified, and the photocatalytic mechanism was elucidated. Furthermore, the as-synthesized Bi12O15Cl6 nanosheets remained stable in the photocatalytic process and could be used repeatedly, demonstrating their promising application in the degradation of diverse pollutants in water and wastewater.

Sunlight-promoted photocatalytic hydrogen gas evolution from water-suspended cellulose: a systematic study.

PubMed

Speltini, Andrea; Sturini, Michela; Dondi, Daniele; Annovazzi, Enrico; Maraschi, Federica; Caratto, Valentina; Profumo, Antonella; Buttafava, Armando

2014-10-01

This work presents a systematic study of cellulose (CLS) as a sacrificial biomass for photocatalytic H2 evolution from water. The idea is indeed to couple a largely available and not expensive biomass, and water, with a renewable energy like solar radiation. An aqueous CLS suspension irradiated either at 366 nm (UV-A) or under sunlight in the presence of Pt/TiO2 behaves as a H2 evolving system. The effects of irradiation time, catalyst and CLS concentrations, pH and water salinity are studied. Addition of CLS to the sample significantly improved H2 evolution from water splitting, with yields up to ten fold higher than those observed in neat water. The mechanism of the photocatalytic process relies on the TiO2-mediated CLS hydrolysis, under irradiation. The polysaccharide depolymerisation generates water-soluble species and intermediates, among them 5-hydroxymethylfurfural (HMF) was identified. These intermediates are readily oxidized following the glucose photoreforming, thus enhancing water hydrogen ion reduction to give gas-phase H2. The formation of "colored" by-products from HMF self-polymerization involves a sort of "in situ dye sensitization" that allows an effective photoreaction even under solar light. The procedure is evaluated and successfully extended on cellulosic biomasses, i.e. rice husk and alfalfa (Medicago sativa) stems, not previously investigated for this application.

NASA's Potential Contributions for Remediation of Retention Ponds Using Solar Ultraviolet Radiation and Photocatalysis

NASA Technical Reports Server (NTRS)

Underwood, Lauren W.; Ryan, Robert E.

2007-01-01

This Candidate Solution uses NASA Earth science research on atmospheric ozone and aerosols data (1) to help improve the prediction capabilities of water runoff models that are used to estimate runoff pollution from retention ponds, and (2) to understand the pollutant removal contribution and potential of photocatalytically coated materials that could be used in these ponds. Models (the EPA's SWMM and the USGS SLAMM) exist that estimate the release of pollutants into the environment from storm-water-related retention pond runoff. UV irradiance data acquired from the satellite mission Aura and from the OMI Surface UV algorithm will be incorporated into these models to enhance their capabilities, not only by increasing the general understanding of retention pond function (both the efficacy and efficiency) but additionally by adding photocatalytic materials to these retention ponds, augmenting their performance. State and local officials who run pollution protection programs could then develop and implement photocatalytic technologies for water pollution control in retention ponds and use them in conjunction with existing runoff models. More effective decisions about water pollution protection programs could be made, the persistence and toxicity of waste generated could be minimized, and subsequently our natural water resources would be improved. This Candidate Solution is in alignment with the Water Management and Public Health National Applications.

Photochemical removal of aniline in aqueous solutions: switching from photocatalytic degradation to photo-enhanced polymerization recovery.

PubMed

Tang, Heqing; Li, Jing; Bie, Yeqiang; Zhu, Lihua; Zou, Jing

2010-03-15

Organic pollutants may be treated by either a degradation process or a recovery process in the view point of sustainable chemistry. Photocatalytic removal of aniline was investigated in aqueous solutions. It was found that the photocatalytic oxidation of aniline resulted in its degradation or polymerization, depending on its concentration. Hence a new treatment strategy was proposed in combination of photocatalytic degradation and polymerization, where the polymerization was in fact a recovery process. When aniline concentration was as low as 0.1 mmol L(-1), it was possible to photocatalytically degrade aniline, which could be further enhanced by increasing solution pH, modifying TiO(2) surface with the addition of anions, or coupling with the photoreduction of added oxidants. When aniline concentration was increased to about 1 mmol L(-1), the photocatalytic oxidation was observed to yield the polymerization of aniline, leading to nanocomposites of polyaniline (PAN) and TiO(2). Alternatively, the photo-enhanced chemical polymerization of aniline at higher concentrations (>or=50 mmol L(-1)) in the presence of chemical oxidants produced PAN nanostructures. The conversion of pollutant aniline to valuable PAN nanostructures or nano-PAN/TiO(2) composites is suggestive for possible applications in the treatment of aniline wastewaters as a sustainable environmental protection measure. (c) 2009 Elsevier B.V. All rights reserved.

THE PHOTOCATALYTIC OXIDATION OF LOW CONCENTRATION MTBE ON TITANIUM DIOXIDE FROM GROUNDWATER IN A FALLING FILM REACTOR

EPA Science Inventory

This study focuses on three objectives: 1) to determine the feasibility of using a falling-film slurry photocatalytic reactor for the degradation of MTBE in water, 2) to assess the feasibility of MTBE photo-oxidation on TiO2 at low initial MTBE concentrations (<10 mg/L), and 3) t...

Facile synthesis of BiOI in hierarchical nanostructure preparation and its photocatalytic application to organic dye removal and biocidal effect of bacteria.

PubMed

Long, Yang; Wang, Yi; Zhang, Dun; Ju, Peng; Sun, Yan

2016-11-01

Novel BiOI hierarchical nanostructures with porous architecture was prepared at room temperature by an economical, facile and rapid route. The coupling adsorption and degradation efficiency of rhodamine B (RhB), methylene blue (MB), and methyl orange (MO) could achieve 98.7%, 43.2%, 76.9% within 180min in the presence of BiOI, respectively. BiOI hierarchical nanostructures also exhibit excellent effective biocidal performances, and the disinfection rate of the typical biofouling bacteria Bacillus sp. and Pseudoalteromonas sp. could reach 99.9% and 99.8% in 60min, respectively. The circulate photocatalytic degradation of RhB experiment verified the good stability and reusability of BiOI hierarchical nanostructures. Based on active specie trapping experiments, the superoxide radicals (O2(-)) and holes (h(+)) were proved to be the main reactive species in the BiOI-based system. The obviously enhanced coupling adsorption and photocatalytic degradation performance of BiOI hierarchical nanostructures could be mainly attributed to the large surface area (64.5m(2)/g), negatively charged surface and the intrinsic electron structure. This study provides a new strategy to develop novel photocatalysts for water treatment and marine antifouling. Copyright © 2016 Elsevier Inc. All rights reserved.

Efficient visible-light photocatalytic and enhanced photocorrosion inhibition of Ag2WO4 decorated MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Thangavel, Sakthivel; Thangavel, Srinivas; Raghavan, Nivea; Alagu, Raja; Venugopal, Gunasekaran

2017-11-01

The use of two-dimensional nanomaterials as co-catalysts in the photodegradation of toxic compounds using light irradiation is an attractive ecofriendly process. In this study, we prepared a novel MoS2/Ag2WO4 nanohybrid via a one-step hydrothermal approach and the photocatalytic properties were investigated by the degradation of methyl-orange under stimulated irradiation. The nanohybrid exhibits enhanced efficiency in dye degradation compared to the bare Ag2WO4 nanorods; the same has been evidently confirmed with UV-visible spectra and total organic carbon removal analysis. The pseudo-first order rate constant of the nanohybrid is nearly 1.8 fold higher than that of the bare Ag2WO4 nanorods. With the aid of classical radical quenching and photoluminescence spectral analysis, a reasonable mechanism has been derived for the addition of MoS2 to nanohybrids to enhance the photocatalytic efficiency. MoS2 prevents photocorrosion of Ag2WO4 and also diminishes the number of photogenerated electron-hole recombination. Our findings could provide new insights in understanding the mechanism of the MoS2/Ag2WO4 nanohybrid as an efficient photocatalyst suitable for waste-water treatment and remedial applications.

Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles with highly enhanced photocatalytic activity and stability under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiu, Zhiliang; Shandong Provincial Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics, Key Laboratory of Amorphous and Polycrystalline Materials, Qilu University of Technology, Jinan 250353; Wu, Yongzhong, E-mail: wuyz@sdu.edu.cn

2014-11-15

Highlights: • Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared. • The photocatalytic activity of Ag{sub 3}PO{sub 4} is increased by 6 times by GO wrapping. • The hybrid photocatalysts exhibited excellent stability. - Abstract: Graphene oxide (GO) wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared by in situ deposition–precipitation method. By hybridization of Ag{sub 3}PO{sub 4} with GO nanosheets, a 6-fold enhancement in the photodegradation rate toward orange methyl (MO) under visible light irradiation (λ ≥ 420 nm) was observed compared with the pure Ag{sub 3}PO{sub 4} sub-microsparticles. The hybrid photocatalysts also exhibited excellent stability in the successive MOmore » degradation experiments. The highly enhanced photocatalytic activity and stability were mainly attributed to the quick transfer of the photogenerated electrons from Ag{sub 3}PO{sub 4} to GO nanosheets, which could effectively suppress the electron–hole pairs recombination and thus inhibit the photocorrosion of Ag{sub 3}PO{sub 4}. These high-efficient and stable hybrid photocatalysts were expected to show considerable potential applications in wastewater treatment and water splitting.« less

Photocatalytic activity enhancement of anatase-graphene nanocomposite for methylene removal: Degradation and kinetics

NASA Astrophysics Data System (ADS)

Rezaei, Mostafa; Salem, Shiva

2016-10-01

In the present research, the TiO2-graphene nanocomposite was synthesized by an eco-friendly method. The blackberry juice was introduced to graphene oxide (GO) as a reducing agent to produce the graphene nano-sheets. The nanocomposite of anatase-graphene was developed as a photocatalyst for the degradation of methylene blue, owing to the larger specific surface area and synergistic effect of reduced graphene oxide (RGO). The UV spectroscopy measurements showed that the prepared nanocomposite exhibited an excellent photocatalytic activity toward the methylene blue degradation. The rate of electron transfer of redox sheets is much higher than that observed on GO, indicating the applicability of proposed method for the production of anatase-RGO nanocomposite for treatment of water contaminated by cationic dye. The prepared materials were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy and transmission electron microscopy. A facile and rapid route was applied for the uniform deposition of anatase nanoparticles on the sheets. The resulting nanocomposite contained nanoparticles with a mean diameter of 10 nm. A mechanism for the photocatalytic activity of nanocomposite was suggested and the degradation reaction obeyed the second-order kinetics. It was concluded that the degradation kinetics is changed due to the reduction of GO in the presence of blackberry juice.

Technologies for deposition of transition metal oxide thin films: application as functional layers in “Smart windows” and photocatalytic systems

NASA Astrophysics Data System (ADS)

Gesheva, K.; Ivanova, T.; Bodurov, G.; Szilágyi, I. M.; Justh, N.; Kéri, O.; Boyadjiev, S.; Nagy, D.; Aleksandrova, M.

2016-02-01

“Smart windows” are envisaged for future low-energy, high-efficient architectural buildings, as well as for the car industry. By switching from coloured to fully bleached state, these windows regulate the energy of solar flux entering the interior. Functional layers in these devices are the transition metals oxides. The materials (transitional metal oxides) used in smart windows can be also applied as photoelectrodes in water splitting photocells for hydrogen production or as photocatalytic materials for self-cleaning surfaces, waste water treatment and pollution removal. Solar energy utilization is recently in the main scope of numerous world research laboratories and energy organizations, working on protection against conventional fuel exhaustion. The paper presents results from research on transition metal oxide thin films, fabricated by different methods - atomic layer deposition, atmospheric pressure chemical vapour deposition, physical vapour deposition, and wet chemical methods, suitable for flowthrough production process. The lower price of the chemical deposition processes is especially important when the method is related to large-scale glazing applications. Conclusions are derived about which processes are recently considered as most prospective, related to electrochromic materials and devices manufacturing.

Photocatalytic degradation of methyl orange dye in water solutions in the presence of MWCNT/TiO{sub 2} composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Da Dalt, S., E-mail: silvana.da.dalt@ufrgs.br; Alves, A.K.; Bergmann, C.P.

2013-05-15

Highlights: ► MWCNTs/TiO{sub 2} composites were obtained to degrade organic dyes in water. ► MWCNT/TiO{sub 2} composites were analyzed by photocatalysis and structural characterization. ► The photocatalytic shows efficient method for the degradation of dyes from aqueous effluents. - Abstract: The textile and dyestuff industries are the primary sources of the release of synthetic dyes into the environment and usually there are major pollutants in dye wastewaters. Because of their toxicity and slow degradation, these dyes are categorized as environmentally hazardous materials. In this context, carbon nanotubes/TiO{sub 2} (CNTs/TiO{sub 2}) composites were prepared using multi-walled CNTs (MWCNTs), titanium (IV) propoxidemore » and commercial TiO{sub 2} (P25{sup ®}) as titanium oxide sources, to degrade the methyl orange dye in solution through photocatalyst activity using UV irradiation. The composites were prepared by solution processing followed by thermal treatment at 400, 500 and 600 °C. The heterojunction between nanotubes and TiO{sub 2} was confirmed by XRD, specific surface area. The coating morphology was observed with SEM and TEM.« less

Temperature-assisted photochemical construction of CdS-based ordered porous films with photocatalytic activities on solution surfaces.

PubMed

Huang, Zhenxun; Sun, Fengqiang; Zhang, Yu; Gu, Kaiyuan; Zou, Xueqiong; Huang, Yuying; Wu, Qingsong; Zhang, Zihe

2011-04-15

Taking a colloidal monolayer floating on the surface of a precursor solution as template, free-standing CdS/Cd composites and pure CdS (CdS-based) ordered porous films had been prepared by a temperature-assisted photochemical strategy. After irradiation with UV-light and heat treatment, the films formed hemi-spherical pores due to the preferable deposition of CdS and Cd onto the PS spheres during the photochemical and interfacial reactions. When the temperature increased from 15 to 60°C, the air/water interface gradually changed into a vapor/water interface on the surface of the solution, resulting in variations of the final compositions. The optical properties of the films were hence changed. Because of the free-standing characteristic, the ordered porous films were first transferred on surface of polluted solutions as photocatalysts, which was a new mode in application of photocatalysts. The photocatalytic activities of films showed regular variations with the compositions in photodegradation of Rhodamine B. This method provides a simple route for tuning the properties of porous films through control of its composition and a flexible application of films on any surface. Copyright © 2011 Elsevier Inc. All rights reserved.

Phytoremediation of 1,4-dioxane-containing recovered groundwater.

PubMed

Ferro, Ari M; Kennedy, Jean; LaRue, James C

2013-01-01

The results of a pilot-scale phytoremediation study are reported in this paper. Small plots of trees established on a closed municipal waste landfill site were irrigated with recovered groundwater containing 1,4-dioxane (dioxane) and other volatile organic compounds (VOCs). The plots were managed to minimize the leaching of irrigation water, and leaching was quantified by the use of bromide tracer. Results indicated that the dioxane (2.5 microg/L) was effectively removed, probably via phytovolatilization, and that a full-scale phytoremediation system could be used. A system is now in place at the site in which the recovered groundwater can be treated using two different approaches. A physical treatment system (PTS) will be used during the winter months, and a 12 ha phytoremediation system (stands of coniferous trees) will be used during the growing season. The PTS removes VOCs using an air-stripper, and destroys dioxane using a photo-catalytic oxidation process. Treated water will be routed to the local sewer system. The phytoremediation system, located on the landfill, will be irrigated with effluent from the PTS air-stripper containing dioxane. Seasonal use of the phytoremediation system will reduce reliance on the photo-catalytic oxidation process that is extremely energy consumptive and expensive to operate.

A controlled wet-spinning and dip-coating process for preparation of high-permeable TiO2 hollow fiber membranes.

PubMed

Zhang, Qi; Wang, Hua; Fan, Xinfei; Chen, Shuo; Yu, Hongtao; Quan, Xie

2016-01-01

In order to improve the permeate flux of photocatalytic membranes, we present an approach for coupling TiO2 with ceramic hollow fiber membranes. The ceramic hollow fiber membranes with high permeate flux were fabricated by a controlled wet-spinning process using polyethersulfone (PESf) and ceramic powder as precursors and 1-methyl-2-pyrrolidinone as solvent, and the subsequent TiO2 coating was performed by a dip-coating process using tetra-n-butyl titanate as precursor. It has been found that the PESf/ceramic powder ratio could influence the structure of the membranes. Here the as-prepared TiO2 hollow fiber membranes had a pure water flux of 4,450 L/(m(2)·h). The performance of the TiO2 hollow fiber membrane was evaluated using humic acid (HA) as a test substance. The results demonstrated that this membrane exhibited a higher permeate flux under UV irradiation than in the dark and the HA removal efficiency was enhanced. The approach described here provides an operable route to the development of high-permeable photocatalytic membranes for water treatment.

Mesoporous TiO2/graphene composite films for the photocatalytic degradation of eco-persistent pollutants

NASA Astrophysics Data System (ADS)

Kusumawati, Yuly; Pauporté, Thierry; Viana, Bruno; Zouzelka, Radek; Remzova, Monika; Rathousky, Jiri

2017-03-01

Graphene/oxide composite structures are attracting increasing attention for many advanced applications. In the present work, mesoporous layers composed of TiO2 nanoparticles and graphene at various concentrations have been coated on conductive glass substrates. They have been tested for the photocatalytic degradation of 4-chlorophenol used as a model compound of an eco-persistent pollutant dilute in water. The formation of intermediate degradation products, namely, hydroquinone and benzoquinone, has been followed. The results show the high photocatalytic activity of the layers and a beneficial effect of graphene for an optimum concentration of 1.2 wt. %. The decrease in the activity observed at higher graphene content is assigned to the light absorption by this component. The key parameters for the enhancement of the photocatalytic performance are discussed.

Converting Carbohydrates to Carbon-Based Photocatalysts for Environmental Treatment.

PubMed

Hu, Zhuofeng; Shen, Zhurui; Yu, Jimmy C

2017-06-20

Carbohydrates in biomass can be converted to semiconductive hydrothermal carbonation carbon (HTCC), a material that contains plenty of sp 2 -hybridization structures. Under solar light illumination, HTCC generates photoexcited electrons, holes, and hydroxyl radicals. These species can be used for photocatalytic treatment such as water disinfection and degradation of organic pollutants. The photocatalytic activity of HTCC can be significantly enhanced by iodine doping. The enhancement mechanism is investigated by density functional theoretical calculations and electrochemical measurements. The iodine dopants twist and optimize the structures of the sp 2 -hybridization in HTCC, thereby favoring photon-induced excitation. Moreover, the iodine dopants facilitate the charge transfer between different sp 2 -hybridization structures, thus increasing the conductivity and activity of the HTCC. An added benefit is that the I-doped HTCC exhibits lower cytotoxic effect than the pure HTCC. In addition to monosaccharides (glucose), disaccharides (sucrose), and polysaccharides (starch), we have also transformed crops (e.g., rice), plants (e.g., grass), and even agricultural waste (e.g., straw) and animal waste (e.g., cow dung). The conversion of carbohydrates to HTCC may be considered as a "Trash to Treasure" approach. We believe this discovery will attract a lot of attention from researchers involved in environmental catalysis, waste recycling, and pollution treatment.

Efficient electricity production and simultaneously wastewater treatment via a high-performance photocatalytic fuel cell.

PubMed

Liu, Yanbiao; Li, Jinhua; Zhou, Baoxue; Li, Xuejin; Chen, Hongchong; Chen, Quanpeng; Wang, Zhongsheng; Li, Lei; Wang, Jiulin; Cai, Weimin

2011-07-01

A great quantity of wastewater were discharged into water body, causing serious environmental pollution. Meanwhile, the organic compounds in wastewater are important sources of energy. In this work, a high-performance short TiO(2) nanotube array (STNA) electrode was applied as photoanode material in a novel photocatalytic fuel cell (PFC) system for electricity production and simultaneously wastewater treatment. The results of current work demonstrate that various model compounds as well as real wastewater samples can be used as substrates for the PFC system. As a representative of model compounds, the acetic acid solution produces the highest cell performance with short-circuit current density 1.42 mA cm(-2), open-circuit voltage 1.48 V and maximum power density output 0.67 mW cm(-2). The STNA photoanode reveals obviously enhanced cell performance compared with TiO(2) nanoparticulate film electrode or other long nanotubes electrode. Moreover, the photoanode material, electrolyte concentration, pH of the initial solution, and cathode material were found to be important factors influencing the system performance of PFC. Therefore, the proposed fuel cell system provides a novel way of energy conversion and effective disposal mode of organics and serves well as a promising technology for wastewater treatment. Copyright © 2011 Elsevier Ltd. All rights reserved.

New rare earth hafnium oxynitride perovskites with photocatalytic activity in water oxidation and reduction.

PubMed

Black, Ashley P; Suzuki, Hajime; Higashi, Masanobu; Frontera, Carlos; Ritter, Clemens; De, Chandan; Sundaresan, A; Abe, Ryu; Fuertes, Amparo

2018-02-06

RHfO 2 N perovskites with R = La, Nd and Sm show a GdFeO 3 -type structure and are semiconductors with band gaps of 3.35, 3.40 and 2.85 eV and relative dielectric constants of 30, 16 and 28 respectively. These compounds have adequate reduction and oxidation potentials to conduct the overall water splitting reaction, and the analogous perovskite LaZrO 2 N with a band gap of 2.8 eV shows photocatalytic activity under visible light irradiation for O 2 evolution.

Effect of different processes and Ti/Zn molar ratios on the structure, morphology, and enhanced photoelectrochemical and photocatalytic performance of Ti3+ self-doped titanium-zinc hybrid oxides

NASA Astrophysics Data System (ADS)

Fu, Rongrong; Wang, Qingyao; Gao, Shanmin; Wang, Zeyan; Huang, Baibiao; Dai, Ying; Lu, Jun

2015-07-01

Ti3+ self-doped titanium-zinc hybrid oxides with different phase compositions and morphologies were successfully synthesized using Zn powder as the reductant and Zn source by a chemical-reduction precipitation method with subsequent thermal treatment. The fabricated Ti3+ self-doped TiO2(A)/TiO2(R), TiO2(A)/TiO2(R)/ZnTiO3, and TiO2(A)/ZnO heterojunctions were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The effects of various Ti/Zn molar ratios and preparation processes on the structural, morphological, optical, photocurrent and photocatalytic properties of the resultant samples were investigated systematically. Results reveal that Ti3+ self-doping enhances the photoabsorption capability of titanium-zinc hybrid oxides in the visible-light region. Moreover, different processes and Ti/Zn molar ratios play great influences on the structure, morphology, optical, photocurrent and photocatalytic properties of the final products. Ti3+ self-doped titanium-zinc hybrid oxides exhibit excellent photocurrent and photocatalytic activity than pure TiO2 and ZnTiO3 under visible-light irradiation (λ ≥ 400 nm). The most active Ti3+ self-doped titanium-zinc hybrid oxides photoanode presents significantly improved water splitting performance. The synergistic effect between the Ti3+ self-doped and heterojunctions is responsible for the enhanced performance of these materials.

Hierarchical heterostructures of p-type bismuth oxychloride nanosheets on n-type zinc ferrite electrospun nanofibers with enhanced visible-light photocatalytic activities and magnetic separation properties.

PubMed

Sun, Yucong; Shao, Changlu; Li, Xinghua; Guo, Xiaohui; Zhou, Xuejiao; Li, Xiaowei; Liu, Yichun

2018-04-15

P-type bismuth oxychloride (p-BiOCl) nanosheets were uniformly grown on n-type zinc ferrite (n-ZnFe 2 O 4 ) electrospun nanofibers via a solvothermal technique to form hierarchical heterostructures of p-BiOCl/n-ZnFe 2 O 4 (p-BiOCl/n-ZnFe 2 O 4 H-Hs). The density and loading amounts of the BiOCl nanosheets with exposed {0 0 1} facets were easily controlled by adjusting the reactant concentration in the solvothermal process. The p-BiOCl/n-ZnFe 2 O 4 H-Hs exhibited enhanced visible-light photocatalytic activities for the degradation of Rhodamine B (RhB). The apparent first-order rate of the p-BiOCl/n-ZnFe 2 O 4 H-Hs and its normalized constant were about 12.6- and 8-fold higher than pure ZnFe 2 O 4 nanofibers. This suggests that both the improved charge separation efficiency from the uniform p-n heterojunctions and the enlarged active surface sites from the hierarchical structures increase the photocatalytic performances. Furthermore, the p-BiOCl/n-ZnFe 2 O 4 H-Hs could be efficiently separated from the solution with an external magnetic field via the ferromagnetic behavior of ZnFe 2 O 4 nanofibers. The magnetic p-BiOCl/n-ZnFe 2 O 4 H-Hs with enhanced visible-light photocatalytic performances might have potential applications in water treatment. Copyright © 2018. Published by Elsevier Inc.

Effect of different processes and Ti/Zn molar ratios on the structure, morphology, and enhanced photoelectrochemical and photocatalytic performance of Ti3+ self-doped titanium–zinc hybrid oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Rongrong; Wang, Qingyao; Gao, shanmin

2015-07-01

Ti3+ self-doped titanium–zinc hybrid oxides with different phase compositions and morphologies were successfully synthesized using Zn powder as the reductant and Zn source by a chemical-reduction precipitation method with subsequent thermal treatment. The fabricated Ti3+ self-doped TiO2(A)/TiO2(R), TiO2(A)/TiO2(R)/ZnTiO3, and TiO2(A)/ZnO heterojunctions were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectroscopy. The effects of various Ti/Zn molar ratios and preparation processes on the structural, morphological, optical, photocurrent and photocatalytic properties of the resultant samples were investigated systematically. Results reveal that Ti3+ self-doping enhances the photoabsorption capability of titanium–zinc hybrid oxidesmore » in the visible-light region. Moreover, different processes and Ti/Zn molar ratios play great influences on the structure, morphology, optical, photocurrent and photocatalytic properties of the final products. Ti3+ self-doped titanium–zinc hybrid oxides exhibit excellent photocurrent and photocatalytic activity than pure TiO2 and ZnTiO3 under visible-light irradiation (λ ≥ 400 nm). The most active Ti3+ self-doped titanium–zinc hybrid oxides photoanode presents significantly improved water splitting performance. The synergistic effect between the Ti3+ self-doped and heterojunctions is responsible for the enhanced performance of these materials.« less

Semiconductor Heterojunctions for Enhanced Visible Light Photocatalytic H 2 Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikari, Shiba P.; Hood, Zachary D.; Lachgar, Abdou

Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron-hole recombination and narrow photo-response range. In this study, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C 3N 4), and UV light active, strontium pyroniobate, Sr 2Nb 2O 7. Heterojunctions made from a combination of g-C 3N 4 and nitrogen-doped Sr 2Nb 2O 7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogenmore » evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C 3N 4 and N-doped Sr 2Nb 2O 7 at 700 °C (CN/SNON-700) showed better performance than heterojunction made from g-C 3N 4 and Sr 2Nb 2O 7 (CN/SNO). Finally, a plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.« less

Semiconductor Heterojunctions for Enhanced Visible Light Photocatalytic H 2 Production

DOE PAGES

Adhikari, Shiba P.; Hood, Zachary D.; Lachgar, Abdou

2018-04-17

Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron-hole recombination and narrow photo-response range. In this study, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C 3N 4), and UV light active, strontium pyroniobate, Sr 2Nb 2O 7. Heterojunctions made from a combination of g-C 3N 4 and nitrogen-doped Sr 2Nb 2O 7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogenmore » evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C 3N 4 and N-doped Sr 2Nb 2O 7 at 700 °C (CN/SNON-700) showed better performance than heterojunction made from g-C 3N 4 and Sr 2Nb 2O 7 (CN/SNO). Finally, a plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.« less

Ag-doped TiO2 hollow microspheres with visible light response by template-free route for removal of tetracycline hydrochloride from aqueous solution

NASA Astrophysics Data System (ADS)

Zhang, Jian; Li, Xuanhua; Peng, Meiling; Tang, Yuanyuan; Ke, Anqi; Gan, Wei; Fu, Xucheng; Hao, Hequn

2018-06-01

In this study, Ag-doped TiO2 hollow microspheres were synthesized by a template-free route, and their photocatalytic performance and catalytic mechanism were investigated. The hollow microspheres were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and UV–vis spectroscopy. Ag-doped hollow TiO2 microspheres exhibited excellent photocatalytic performance for tetracycline hydrochloride (TC) in water. TC degradation follows pseudo first-order kinetics, and hydroxyl radical (OH·) and holes (h+) were active substances in the photocatalytic reaction.

Surface spintronics enhanced photo-catalytic hydrogen evolution: Mechanisms, strategies, challenges and future

NASA Astrophysics Data System (ADS)

Zhang, Wenyan; Gao, Wei; Zhang, Xuqiang; Li, Zhen; Lu, Gongxuan

2018-03-01

Hydrogen is a green energy carrier with high enthalpy and zero environmental pollution emission characteristics. Photocatalytic hydrogen evolution (HER) is a sustainable and promising way to generate hydrogen. Despite of great achievements in photocatalytic HER research, its efficiency is still limited due to undesirable electron transfer loss, high HER over-potential and low stability of some photocatalysts, which lead to their unsatisfied performance in HER and anti-photocorrosion properties. In recent years, many spintronics works have shown their enhancing effects on photo-catalytic HER. For example, it was reported that spin polarized photo-electrons could result in higher photocurrents and HER turn-over frequency (up to 200%) in photocatalytic system. Two strategies have been developed for electron spin polarizing, which resort to heavy atom effect and magnetic induction respectively. Both theoretical and experimental studies show that controlling spin state of OHrad radicals in photocatalytic reaction can not only decrease OER over-potential (even to 0 eV) of water splitting, but improve stability and charge lifetime of photocatalysts. A convenient strategy have been developed for aligning spin state of OHrad by utilizing chiral molecules to spin filter photo-electrons. By chiral-induced spin filtering, electron polarization can approach to 74%, which is significantly larger than some traditional transition metal devices. Those achievements demonstrate bright future of spintronics in enhancing photocatalytic HER, nevertheless, there is little work systematically reviewing and analysis this topic. This review focuses on recent achievements of spintronics in photocatalytic HER study, and systematically summarizes the related mechanisms and important strategies proposed. Besides, the challenges and developing trends of spintronics enhanced photo-catalytic HER research are discussed, expecting to comprehend and explore such interdisciplinary research in photocatalytic HER.

Environmental application of nanotechnology: air, soil, and water.

PubMed

Ibrahim, Rusul Khaleel; Hayyan, Maan; AlSaadi, Mohammed Abdulhakim; Hayyan, Adeeb; Ibrahim, Shaliza

2016-07-01

Global deterioration of water, soil, and atmosphere by the release of toxic chemicals from the ongoing anthropogenic activities is becoming a serious problem throughout the world. This poses numerous issues relevant to ecosystem and human health that intensify the application challenges of conventional treatment technologies. Therefore, this review sheds the light on the recent progresses in nanotechnology and its vital role to encompass the imperative demand to monitor and treat the emerging hazardous wastes with lower cost, less energy, as well as higher efficiency. Essentially, the key aspects of this account are to briefly outline the advantages of nanotechnology over conventional treatment technologies and to relevantly highlight the treatment applications of some nanomaterials (e.g., carbon-based nanoparticles, antibacterial nanoparticles, and metal oxide nanoparticles) in the following environments: (1) air (treatment of greenhouse gases, volatile organic compounds, and bioaerosols via adsorption, photocatalytic degradation, thermal decomposition, and air filtration processes), (2) soil (application of nanomaterials as amendment agents for phytoremediation processes and utilization of stabilizers to enhance their performance), and (3) water (removal of organic pollutants, heavy metals, pathogens through adsorption, membrane processes, photocatalysis, and disinfection processes).

Bibliography of work on the heterogeneous photocatalytic removal of hazardous compounds from water and air, Update Number 2 to October 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blake, D.M.

1997-01-01

The Solar Industrial Program has developed processes that destroy hazardous substances in or remove them from water and air. The processes of interest in this report are based on the application of heterogeneous photocatalysts, principally titanium dioxide or modifications thereof, but work on other heterogeneous catalysts is included in this compilation. This report continues bibliographies that were published in May, 1994, and October, 1995. The previous reports included 663 and 574 citations, respectively. This update contains an additional 518 references. These were published during the period from June 1995 to October 1996, or are references from prior years that weremore » not included in the previous reports. The work generally focuses on removing hazardous contaminants from air or water to meet environmental or health regulations. This report also references work on properties of semiconductor photocatalysts and applications of photocatalytic chemistry in organic synthesis. This report follows the same organization as the previous publications. The first part provides citations for work done in a few broad categories that are generic to the process. Three tables provide references to work on specific substances. The first table lists organic compounds that are included in various lists of hazardous substances identified by the US Environmental Protection Agency (EPA). The second table lists compounds not included in those categories, but which have been treated in a photocatalytic process. The third table covers inorganic compounds that are on EPA lists of hazardous materials or that have been treated by a photocatalytic process. A short update on companies that are active in providing products or services based on photocatalytic processes is provided.« less

Photocatalytic water splitting—The untamed dream: A review of recent advances

DOE PAGES

Jafari, Tahereh; Moharreri, Ehsan; Amin, Alireza Shirazi; ...

2016-07-09

Here, photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO 2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed tomore » overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability« less

Solution processable RGO-CdZnS composite for solar light responsive photocatalytic degradation of 4-Nitrophenol

NASA Astrophysics Data System (ADS)

Ibrahim, Sk; Chakraborty, Koushik; Pal, Tanusri; Ghosh, Surajit

2017-05-01

We report the one pot single step synthesis and characterization of solution processable reduced graphene oxide (RGO) - cadmium zinc sulfide (CdZnS) nanocomposite materials. The composite was characterized structurally and morphologically by XRD and TEM studies. The reduction of GO in RGO-CdZnS composite, was confirmed by XPS and Raman spectroscopy. The photocatalytic activity of the RGO-CdZnS composite was investigated towards the degradation of 4-Nitrophenol. A notable increase of photocatalytic efficiency of RGO-CdZnS compare to controlled CdZnS was observed. Here RGO plays a crucial role to efficient photo induced charge separation from the CdZnS, and decreases the electron-hole recombination probability and subsequently enhanced the photocatalytic activity of the RGO-CdZnS composite material under simulated solar light irradiation. This work highlights the potential application of RGO-based materials in the field of photocatalytic degradation of organic water pollutant.

Photo-illuminated diamond as a solid-state source of solvated electrons in water for nitrogen reduction.

PubMed

Zhu, Di; Zhang, Linghong; Ruther, Rose E; Hamers, Robert J

2013-09-01

The photocatalytic reduction of N₂ to NH₃ is typically hampered by poor binding of N₂ to catalytic materials and by the very high energy of the intermediates involved in this reaction. Solvated electrons directly introduced into the reactant solution can provide an alternative pathway to overcome such limitations. Here we demonstrate that illuminated hydrogen-terminated diamond yields facile electron emission into water, thus inducing reduction of N₂ to NH₃ at ambient temperature and pressure. Transient absorption measurements at 632 nm reveal the presence of solvated electrons adjacent to the diamond after photoexcitation. Experiments using inexpensive synthetic diamond samples and diamond powder show that photocatalytic activity is strongly dependent on the surface termination and correlates with the production of solvated electrons. The use of diamond to eject electrons into a reactant liquid represents a new paradigm for photocatalytic reduction, bringing electrons directly to reactants without requiring molecular adsorption to the surface.

A tunable azine covalent organic framework platform for visible light-induced hydrogen generation

PubMed Central

Vyas, Vijay S.; Haase, Frederik; Stegbauer, Linus; Savasci, Gökcen; Podjaski, Filip; Ochsenfeld, Christian; Lotsch, Bettina V.

2015-01-01

Hydrogen evolution from photocatalytic reduction of water holds promise as a sustainable source of carbon-free energy. Covalent organic frameworks (COFs) present an interesting new class of photoactive materials, which combine three key features relevant to the photocatalytic process, namely crystallinity, porosity and tunability. Here we synthesize a series of water- and photostable 2D azine-linked COFs from hydrazine and triphenylarene aldehydes with varying number of nitrogen atoms. The electronic and steric variations in the precursors are transferred to the resulting frameworks, thus leading to a progressively enhanced light-induced hydrogen evolution with increasing nitrogen content in the frameworks. Our results demonstrate that by the rational design of COFs on a molecular level, it is possible to precisely adjust their structural and optoelectronic properties, thus resulting in enhanced photocatalytic activities. This is expected to spur further interest in these photofunctional frameworks where rational supramolecular engineering may lead to new material applications. PMID:26419805

Combined process of electrocoagulation and photocatalytic degradation for the treatment of olive washing wastewater.

PubMed

Ates, Hasan; Dizge, Nadir; Yatmaz, H Cengiz

2017-01-01

In this study, an electrocoagulation reactor (ECR) and photocatalytic reactor (PCR) were tested to understand the performance of combined electrocoagulation and photocatalytic-degradation of olive washing wastewater (OWW). The effects of initial pH (6.0, 6.9, 8.0, 9.0), applied voltage (10.0, 12.5, 15.0 V), and operating time (30, 60, 90, 120 min) were investigated in the electrocoagulation reactor when aluminum electrodes were used as both anode and cathode. The pH, conductivity, color, chemical oxygen demand (COD), and phenol were measured versus time to determine the efficiency of the ECR and PCR process. It was observed that electrocoagulation as a single treatment process supplied the COD removal of 62.5%, color removal of 98.1%, and total phenol removal of 87% at optimum conditions as pH 6.9, applied voltage of 12.5 V, and operating time of 120 min. Moreover, final pH and conductivity were 7.7 and 980 μS/cm, respectively. On the other hand, the effect of semiconductor catalyst type (TiO 2 and ZnO) and loading (1, 2, 3 g/L) were tested using PCR as a stand-alone technique. It was found that photocatalytic degradation as a single treatment process when using 1 g/L ZnO achieved the COD removal of 46%, color removal of 99% with a total phenol removal of 41% at optimum conditions. Final pH and conductivity were 6.2 and 915 μS/cm, respectively. Among semiconductor catalysts, TiO 2 and ZnO performed identical efficiencies for both COD and total phenol removal. Moreover, combination in which electrochemical degradation was employed as a pre-treatment to the photocatalytic degradation process obtained high COD removal of 88% and total phenol, as well as color removal of 100% for the OWW. The electrochemical treatment alone was not effective, but in combination with the photocatalytic process, led to a high-quality effluent. Finally, sludge collected from the electrocoagulation process was characterized by attenuated total reflection Fourier transform infrared and X-ray powder diffraction analyses.

Highly hydrophilic poly(vinylidene fluoride)/meso-titania hybrid mesoporous membrane for photocatalytic membrane reactor in water

NASA Astrophysics Data System (ADS)

Wang, Meng; Yang, Guang; Jin, Peng; Tang, Hao; Wang, Huanhuan; Chen, Yong

2016-01-01

The high hydrophobicity of poly(vinylidene fluoride) (PVDF) membrane remains an obstacle to be applied in some purification processes of water or wastewater. Herein, a highly hydrophilic hybrid mesoporous titania membrane composed of mesoporous anatase titania (meso-TiO2) materials inside the three-dimensional (3D) macropores of PVDF membrane was successfully prepared by using the dual-templated synthesis method combined with solvent extraction and applied as the photocatalytic membrane reactor for the photodegredation of organic dye in water. The structure and the properties of as-prepared hybrid membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption-desorption and contact angle measurements. It was found that the hydrophilicity of PVDF membrane can be significantly improved by filling mesoporous TiO2 inside the 3D macropores of PVDF membrane. Moreover, such a PVDF/meso-TiO2 hybrid membrane exhibits promising photocatalytic degradation of dye in water due to the existence of mesoporous anatase TiO2 materials inside PVDF membrane. This study provides a new strategy to simultaneously introduce hydrophilicity and some desirable properties into PVDF and other hydrophobic membranes.

Heptanuclear CoII5CoIII2 Cluster as Efficient Water Oxidation Catalyst.

PubMed

Xu, Jia-Heng; Guo, Ling-Yu; Su, Hai-Feng; Gao, Xiang; Wu, Xiao-Fan; Wang, Wen-Guang; Tung, Chen-Ho; Sun, Di

2017-02-06

Inspired by the transition-metal-oxo cubical Mn 4 CaO 5 in photosystem II, we herein report a disc-like heptanuclear mixed-valent cobalt cluster, [Co II 5 Co III 2 (mdea) 4 (N 3 ) 2 (CH 3 CN) 6 (OH) 2 (H 2 O) 2 ·4ClO 4 ] (1, H 2 mdea = N-methyldiethanolamine), for photocatalytic oxygen evolution. The topology of the Co 7 core resembles a small piece of cobaltate protected by terminal H 2 O, N 3 - , CH 3 CN, and multidentate N-methyldiethanolamine at the periphery. Under the optimal photocatalytic conditions, 1 exhibits water oxidation activity with a turnover number (TON) of 210 and a turnover frequency (TOF initial ) of 0.23 s -1 . Importantly, electrospray mass spectrometry (ESI-MS) was used to not only identify the possible main active species in the water oxidation reaction but also monitor the evolutions of oxidation states of cobalt during the photocatalytic reactions. These results shed light on the design concept of new water oxidation catalysts and mechanism-related issues such as the key active intermediate and oxidation state evolution in the oxygen evolution process. The magnetic properties of 1 were also discussed in detail.

Thin-film fixed-bed reactor for solar photocatalytic inactivation of Aeromonas hydrophila: influence of water quality

PubMed Central

2012-01-01

Background Controlling fish disease is one of the major concerns in contemporary aquaculture. The use of antibiotics or chemical disinfection cannot provide a healthy aquaculture system without residual effects. Water quality is also important in determining the success or failure of fish production. Several solar photocatalytic reactors have been used to treat drinking water or waste water without leaving chemical residues. This study has investigated the impact of several key aspects of water quality on the inactivation of the pathogenic bacterium Aeromonas hydrophila using a pilot-scale thin-film fixed-bed reactor (TFFBR) system. Results The level of inactivation of Aeromonas hydrophila ATCC 35654 was determined using a TFFBR with a photocatalytic area of 0.47 m2 under the influence of various water quality variables (pH, conductivity, turbidity and colour) under high solar irradiance conditions (980–1100 W m-2), at a flow rate of 4.8 L h-1 through the reactor. Bacterial enumeration were obtained through conventional plate count using trypticase soy agar media, cultured in conventional aerobic conditions to detect healthy cells and under ROS-neutralised conditions to detect both healthy and sub-lethally injured (oxygen-sensitive) cells. The results showed that turbidity has a major influence on solar photocatalytic inactivation of A. hydrophila. Humic acids appear to decrease TiO2 effectiveness under full sunlight and reduce microbial inactivation. pH in the range 7–9 and salinity both have no major effect on the extent of photoinactivation or sub-lethal injury. Conclusions This study demonstrates the effectiveness of the TFFBR in the inactivation of Aeromonas hydrophila under the influence of several water quality variables at high solar irradiance, providing an opportunity for the application of solar photocatalysis in aquaculture systems, as long as turbidity remains low. PMID:23194331

Conformal Nitrogen-Doped TiO 2 Photocatalytic Coatings for Sunlight-Activated Membranes

DOE PAGES

Lee, Anna; Libera, Joseph A.; Waldman, Ruben Z.; ...

2017-01-24

Photocatalytic degradation of organic contaminants is enticing for addressing challenging, nontraditional water sources. A novel nitrogen-doping method is utilized to grow conformal titania coatings with visible-light activity on porous membranes. Here, the resulting membranes exhibit effective degradation of model organic species in simulated sunlight while at the same time requiring substantially lower transmembrane pressure than undoped membranes.

Synthesis of gadolinium doped titanium(IV) oxide and their photocatalytic activity to decrease chemical oxygen demand (COD) value of water pollutants

NASA Astrophysics Data System (ADS)

Eddy, Diana Rakhmawaty; Dwiyanti, Dina; Rahayu, Iman; Hastiawan, Iwan; Bahti, Husein H.

2017-05-01

Pesticides are widely used for the control of plant disease. Unfortunately they are highly toxic to terraneous and aquatic life; this is a particular problem in agricultural areas. TiO2 is widely used for pesticide control because of its photocatalytic activity, but it still has inadequacy in its wide band gap. Alternatively, the wide band gap of TiO2 could be narrowed by modification with rare earth element such as gadolinium, so the photocatalytic activity of TiO2could be significantly enhanced. The purpose of this experiment is to synthesize Gd/TiO2 and its application to reduce COD of water pollutants such as carbosulfan pesticide. This experiment is done by doping gadolinium oxide into titanium tetra isopropoxide by sol-gel method. The crystal structure is characterized by using XRD, shown anatase successfully obtained with the smallest crystallite size is 37.655 nm, indicated optimum calcination time is 4 hours. SEM-EDX result shown morphology of crystal is big aggregates. Photocatalytic activity is tested to carbosulfan pesticide, obtained the COD percent decreases up to 87.88%.

Studies on the efficient dual performance of Mn1-xNixFe2O4 spinel nanoparticles in photodegradation and antibacterial activity.

PubMed

Jesudoss, S K; Vijaya, J Judith; Kennedy, L John; Rajan, P Iyyappa; Al-Lohedan, Hamad A; Ramalingam, R Jothi; Kaviyarasu, K; Bououdina, M

2016-12-01

The present work describes the successful synthesize of spinel magnetic ferrite Mn 1-x Ni x Fe 2 O 4 (x=0.0, 0.1, 0.2, 0.3, 0.4 & 0.5) nanoparticles via a simple microwave combustion method which was then evaluated for its photocatalytic activity in the degradation of indigo carmine (IC) synthetic dye, a major water pollutant. Our results reveal that the synthesized of Ni 2+ doped MnFe 2 O 4 nanoparticles possess well-crystalline pure cubic spinel phase, exhibit excellent optical and magnetic properties. Further, the photocatalytic performance of the synthesized nanoparticles at different concentration ratios of Ni 2+ ions was monitored by photocatalytic degradation of indigo carmine synthetic dye under UV (λ=365nm) light irradiation. In order to get maximum photocatalytic degradation (PCD) efficiency, we have optimized various parameters, which include catalyst dosage, initial dye concentration, pH and Ni 2+ dopant content. It was found that the reaction was facilitated with optimum catalyst dose of 50mg/100mL, high dye concentrations of 150mg/L and acidic pH and among all the synthesized samples, Mn 0·5 Ni 0.5 Fe 2 O 4 exhibit superior performance of photocatalytic activity on the degradation of indigo carmine synthetic dye. These results highlighted the potential use of effective, low-cost and easily available photocatalysts for the promotion of wastewater treatment and environmental remediation. In addition, the antibacterial activity of spinel magnetic Mn 1-x Ni x Fe 2 O 4 nanoparticles against two Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram negative bacteria (Pseudomonas aeruginosa and Escherichia coli) was also examined. Our antibacterial activity results are comparable with the results obtained using the antibiotic, streptomycin. Copyright © 2016 Elsevier B.V. All rights reserved.

The facile synthesis of a single atom-dispersed silver-modified ultrathin g-C3N4 hybrid for the enhanced visible-light photocatalytic degradation of sulfamethazine with peroxymonosulfate.

PubMed

Wang, Fengliang; Wang, Yingfei; Li, Yanyan; Cui, Xuhui; Zhang, Qianxin; Xie, Zhijie; Liu, Haijin; Feng, Yiping; Lv, Wenying; Liu, Guoguang

2018-05-22

Enabling the optimal usage of solar energy is considered to be one of the most pressing challenges in the photocatalytic remediation of water resident contaminants. Herein, a single-atom dispersed Ag loaded ultrathin g-C3N4 hybrid (AgTCM/UCN) was prepared through a facile co-polymerization of dicyandiamide with silver tricyanomethanide (AgTCM) and NH4Cl, and used as a visible light driven photocatalyst for the degradation of sulfamethazine (SMT) in the presence of peroxymonosulfate (PMS). Under UV light, visible light and simulated sunlight irradiation, the AgTCM/UCN/PMS process showed higher efficiency for SMT degradation than AgTCM/UCN, UCN/PMS, and g-C3N4/PMS systems. This enhanced photocatalytic activity may be attributed to the synergistic effects encompassing the surface plasmon resonance (SPR) of Ag, high surface area of UCN, and efficient charge separation of PMS. Electron-spin resonance (ESR) and reactive species (RSs) scavenger-quenching experiments revealed that SO4˙- was generated following the addition of PMS, whereas O2˙- and h+ were predominantly responsible for the degradation of SMT. Three degradation pathways of SMT were deduced, including the cleavage of sulfonamide bonds, SO2 extrusion, and the oxidation of the aniline moiety, based on mass spectrometry and theoretical calculations. The degradation of SMT in ambient water revealed that the AgTCM/UCN/PMS photocatalytic process can be efficaciously applied for the remediation of SMT contaminated natural waters, particularly sea water.

Two-dimensional carbon-based nanocomposites for photocatalytic energy generation and environmental remediation applications

PubMed Central

Kumar, Suneel; Kumar, Ashish; Bahuguna, Ashish; Sharma, Vipul

2017-01-01

In the pursuit towards the use of sunlight as a sustainable source for energy generation and environmental remediation, photocatalytic water splitting and photocatalytic pollutant degradation have recently gained significant importance. Research in this field is aimed at solving the global energy crisis and environmental issues in an ecologically-friendly way by using two of the most abundant natural resources, namely sunlight and water. Over the past few years, carbon-based nanocomposites, particularly graphene and graphitic carbon nitride, have attracted much attention as interesting materials in this field. Due to their unique chemical and physical properties, carbon-based nanocomposites have made a substantial contribution towards the generation of clean, renewable and viable forms of energy from light-based water splitting and pollutant removal. This review article provides a comprehensive overview of the recent research progress in the field of energy generation and environmental remediation using two-dimensional carbon-based nanocomposites. It begins with a brief introduction to the field, basic principles of photocatalytic water splitting for energy generation and environmental remediation, followed by the properties of carbon-based nanocomposites. Then, the development of various graphene-based nanocomposites for the above-mentioned applications is presented, wherein graphene plays different roles, including electron acceptor/transporter, cocatalyst, photocatalyst and photosensitizer. Subsequently, the development of different graphitic carbon nitride-based nanocomposites as photocatalysts for energy and environmental applications is discussed in detail. This review concludes by highlighting the advantages and challenges involved in the use of two-dimensional carbon-based nanocomposites for photocatalysis. Finally, the future perspectives of research in this field are also briefly mentioned. PMID:28884063

Two-dimensional carbon-based nanocomposites for photocatalytic energy generation and environmental remediation applications.

PubMed

Kumar, Suneel; Kumar, Ashish; Bahuguna, Ashish; Sharma, Vipul; Krishnan, Venkata

2017-01-01

In the pursuit towards the use of sunlight as a sustainable source for energy generation and environmental remediation, photocatalytic water splitting and photocatalytic pollutant degradation have recently gained significant importance. Research in this field is aimed at solving the global energy crisis and environmental issues in an ecologically-friendly way by using two of the most abundant natural resources, namely sunlight and water. Over the past few years, carbon-based nanocomposites, particularly graphene and graphitic carbon nitride, have attracted much attention as interesting materials in this field. Due to their unique chemical and physical properties, carbon-based nanocomposites have made a substantial contribution towards the generation of clean, renewable and viable forms of energy from light-based water splitting and pollutant removal. This review article provides a comprehensive overview of the recent research progress in the field of energy generation and environmental remediation using two-dimensional carbon-based nanocomposites. It begins with a brief introduction to the field, basic principles of photocatalytic water splitting for energy generation and environmental remediation, followed by the properties of carbon-based nanocomposites. Then, the development of various graphene-based nanocomposites for the above-mentioned applications is presented, wherein graphene plays different roles, including electron acceptor/transporter, cocatalyst, photocatalyst and photosensitizer. Subsequently, the development of different graphitic carbon nitride-based nanocomposites as photocatalysts for energy and environmental applications is discussed in detail. This review concludes by highlighting the advantages and challenges involved in the use of two-dimensional carbon-based nanocomposites for photocatalysis. Finally, the future perspectives of research in this field are also briefly mentioned.

Temperature dependent optical characterization of Ni-TiO2 thin films as potential photocatalytic material

NASA Astrophysics Data System (ADS)

De, Rajnarayan; Haque, S. Maidul; Tripathi, S.; Rao, K. Divakar; Singh, Ranveer; Som, T.; Sahoo, N. K.

2017-09-01

Along with other transition metal doped titanium dioxide materials, Ni-TiO2 is considered to be one of the most efficient materials for catalytic applications due to its suitable energy band positions in the electronic structure. The present manuscript explores the possibility of improving the photocatalytic activity of RF magnetron sputtered Ni-TiO2 films upon heat treatment. Optical, structural and morphological and photocatalytic properties of the films have been investigated in detail for as deposited and heat treated samples. Evolution of refractive index (RI) and total film thickness as estimated from spectroscopic ellipsometry characterization are found to be in agreement with the trend in density and total film thickness estimated from grazing incidence X-ray reflectivity measurement. Interestingly, the evolution of these macroscopic properties were found to be correlated with the corresponding microstructural modifications realized in terms of anatase to rutile phase transformation and appearance of a secondary phase namely NiTiO3 at high temperature. Corresponding morphological properties of the films were also found to be temperature dependent which leads to modifications in the grain structure. An appreciable reduction of optical band gap from 2.9 to 2.5 eV of Ni-TiO2 thin films was also observed as a result of post deposition heat treatment. Testing of photocatalytic activity of the films performed under UV illumination demonstrates heat treatment under atmospheric ambience to be an effective means to enhance the photocatalytic efficiency of transition metal doped titania samples.

Adsorption and photodegradation of methylene blue by iron oxide impregnated on granular activated carbons in an oxalate solution

NASA Astrophysics Data System (ADS)

Kadirova, Zukhra C.; Katsumata, Ken-ichi; Isobe, Toshihiro; Matsushita, Nobuhiro; Nakajima, Akira; Okada, Kiyoshi

2013-11-01

The photocatalytic adsorbents BAU-OA, BAU-CL and BAU-HA with varying iron oxide content (9-10 mass%) were prepared by heat treatment at 250 °C from commercial activated carbon (BAU) impregnated with iron oxalate, chloride, tris-benzohydroxamate, respectively. The XRD patterns showed amorphous structure in the BAU-CL sample (SBET 50 m2/g) and low crystallinity (as FeOOH and Fe2O3 phases) in the BAU-HA and BAU-OA samples (SBET 4 and 111 m2/g, respectively). The methylene blue adsorption capacities was decreased in order of BAU-OA < BAU-CL < BAU-HA sample and the adsorption followed Langmuir model. The apparent MB photodegradation rate constant (kapp) was increased in same order BAU-HA < BAU-CL < BAU-OA under the standard experimental conditions (initial MB concentrations 0.015-0.025 mM; sample content - 10 mg/l; initial oxalic acid concentration - 0.43 mM; pH 3-4; UV illumination). The process included high efficiency combination of adsorption, heterogeneous and homogeneous catalysis under UV and solar lights illumination without addition of hydrogen peroxide. The detoxification of water sample containing organic dyes was confirmed after combined sorption-photocatalytic treatment.

Dopant controlled photoinduced hydrophilicity and photocatalytic activity of SnO2 thin films

NASA Astrophysics Data System (ADS)

Talinungsang; Dhar Purkayastha, Debarun; Krishna, M. Ghanashyam

2018-07-01

The influence of Fe and Ni (1 wt.%) doping on the wettability and photocatalytic activity of sol-gel derived SnO2 films is reported. X-ray diffraction studies revealed the presence of tetragonal phase for both pure and doped SnO2 thin films. The crystallite size was of the order of 8 nm indicating the nanocrystalline nature of the films. The pure SnO2 films which were hydrophilic with a contact angle of 11.8° showed increase in contact angle with doping (38.7° for Fe and 48.6° for Ni). This is accompanied by decrease in surface energy and root mean square roughness, with doping of SnO2 film. In order to further increase the water contact angle, the film surfaces were modified using a layer of stearic acid. As a consequence, the water contact angles increased to 108°, 110° and 111° for the pure, Fe and Ni doped SnO2 films respectively, rendering them hydrophobic. Significantly, the unmodified surfaces that did not exhibit any change under UV irradiation showed photoinduced hydrophilicity on modification with stearic acid. There was a red-shift in the optical band gap of SnO2 films from 3.8 to 3.5 eV with doping, indicating the possibility of dopant controlled photocatalytic activity. This was confirmed by observing the photocatalytic degradation of an aqueous solution of methylene blue under UV irradiation. There was, indeed, significant improvement in the photocatalytic efficiency of the metal doped SnO2 thin film in comparison to undoped film. The current work, thus, demonstrates a simple method to chemically engineer the wettability and photocatalytic activity of SnO2 thin film surfaces.

Constructing a MoS₂ QDs/CdS Core/Shell Flowerlike Nanosphere Hierarchical Heterostructure for the Enhanced Stability and Photocatalytic Activity.

PubMed

Liang, Shijing; Zhou, Zhouming; Wu, Xiuqin; Zhu, Shuying; Bi, Jinhong; Zhou, Limin; Liu, Minghua; Wu, Ling

2016-02-15

MoS₂ quantum dots (QDs)/CdS core/shell nanospheres with a hierarchical heterostructure have been prepared by a simple microwave hydrothermal method. The as-prepared samples are characterized by XRD, TEM, SEM, UV-VIS diffuse reflectance spectra (DRS) and N₂-sorption in detail. The photocatalytic activities of the samples are evaluated by water splitting into hydrogen. Results show that the as-prepared MoS₂ QDs/CdS core/shell nanospheres with a diameter of about 300 nm are composed of the shell of CdS nanorods and the core of MoS₂ QDs. For the photocatalytic reaction, the samples exhibit a high stability of the photocatalytic activity and a much higher hydrogen evolution rate than the pure CdS, the composite prepared by a physical mixture, and the Pt-loaded CdS sample. In addition, the stability of CdS has also been greatly enhanced. The effect of the reaction time on the formations of nanospheres, the photoelectric properties and the photocatalytic activities of the samples has been investigated. Finally, a possible photocatalytic reaction process has also been proposed.

The role of visible light active TiO2 specimens on the solar photocatalytic disinfection of E. coli.

PubMed

Birben, Nazmiye Cemre; Tomruk, Ayse; Bekbolet, Miray

2017-05-01

Solar photocatalytic disinfection efficiency of novel visible light activated (VLA) photocatalysts was evaluated with the aim of assessing inactivation of Escherichia coli as the pathogen indicator organism present in drinking water. Influence of humic acid (HA) on the photocatalytic disinfection efficiency of the specified VLA TiO 2 specimens i.e., N-doped, Se-doped, and Se-N co-doped TiO 2 was also investigated. Photocatalytic disinfection efficiency was assessed by the enumeration of bacteria following selected irradiation periods. Degradation and compositional changes in organic matter (OM) was also tracked by means of UV-vis and advanced fluorescence spectroscopic (EEM features) parameters. Photocatalytic mineralization of the organic matter was followed by dissolved organic carbon contents. Presence of HA as a model organic compound of natural organic matter (NOM) displayed a retardation effect on solar photocatalytic abatement of E. coli. However, no distinctly different effect was observed under solar photolytic conditions due to the presence of HA. Regrowth of E. coli could not be assessed under the specified experimental conditions. A comparison was introduced with respect to the use of undoped TiO 2 P-25 as the photocatalyst.

Synthesis of BiVO4-GO-PVDF nanocomposite: An excellent, newly designed material for high photocatalytic activity towards organic dye degradation by tuning band gap energies

NASA Astrophysics Data System (ADS)

Biswas, Md Rokon Ud Dowla; Oh, Won-Chun

2018-06-01

BiVO4-GO-PVDF (PVDF = Polyvinylidene Difluoride) photocatalyst is successfully synthesized by ultrasonication method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques. Morphology of BiVO4-GO-PVDF looks like a human embryo embedded inside an amniotic sac. Photocatalytic performance of BiVO4-GO-PVDF for decolorization of methylene blue is investigated. BiVO4-GO-PVDF system reveals enhanced photocatalytic activity degradation of methylene blue (MB), Rhodamine B (RhB) & Safranin-O (SO) in water under visible light irradiation as compared to the pure BiVO4 catalyst, BiVO4 & PTFE decorated on the graphene sheet. The experimental result reveals that the covering of graphene sheets in this composite catalyst enhances photocatalytic performance under visible light. This enhanced activity is mainly attributed to effective quenching of the photogenerated electron-hole pairs confirmed by photoluminescence spectra. Trapping experiments of radicals and holes were conducted to detect reactive species generated in the photocatalytic system, experimental results revealed that direct hole oxidation reaction is obviously dominant during photocatalytic reactions on the BiVO4-GO-PVDF system.

Microwave modification of surface hydroxyl density for g-C3N4 with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

An, Na; Zhao, Yang; Mao, Zhiyong; Agrawal, Dinesh Kumar; Wang, Dajian

2018-03-01

Microwave modification was performed on graphitic carbon nitride (g-C3N4) photocatalysts to tail the surface hydroxyl content for enhanced photocatalytic activity in this work. The influence of microwave heating on the surface hydroxyl density was investigated by a suite of characterization methods. The microwave treated g-C3N4 (MT-g-C3N4) delivered a higher photocatalytic activity in degradation of Rhodamine B (RhB) under visible light irradiation than pristine g-C3N4 due to its improved separation efficiency of photogenerated charge carries and promoted absorption capacity of RhB reactants on surface, which resulted from the increased surface hydroxyl density induced by microwave treatment. This study provides a simple and convenient method to modify g-C3N4 materials with enhanced photocatalytic activity for the potential application in photocatalytic elimination of environmental pollutants.

Revealing the relationship between the photocatalytic property and structure characteristic of reduced TiO2 by hydrogen and carbon monoxide treatment.

PubMed

Liu, Yunpeng; Li, Yuhang; Yang, Siyuan; Lin, Yuan; Zuo, Jianliang; Liang, Hong; Peng, Feng

2018-06-04

The hydrogenation (reduction) has been considered as an effective method to improve the photocatalytic activity of TiO2, however, the underlying relationship between structure and photocatalytic performance has still not been adequately unveiled so far. Herein, to obtain insight into the effect of structure on photocatalytic activity, two types of reduced TiO2 were prepared by CO (CO-TiO2) and H2 (H-TiO2), respectively. For H-TiO2, Ti-H bonds and oxygen vacancies are formed on the surface of H-TiO2, resulting in a more disorder surface lattice. However, for CO-TiO2, the more Ti-OH bonds are formed on the surface and the more bulk oxygen vacancies are introduced, the disorder layer of CO-TiO2 is relatively thin owing to the most of surface vacancies repaired by Ti-OH bonds. Under the simulated solar irradiation, the photocatalytic H2 evolution rate of CO-TiO2 reaches 7.17 mmol g-1 h-1, which is 4.14 and 1.50 times those of TiO2 and H-TiO2, respectively. The photocatalytic degradation rate constant of methyl orange on CO-TiO2 is 2.45 and 6.39 times those on H-TiO2 and TiO2. The superior photocatalytic activity of CO-TiO2 is attributed to the effective separation and transfer of the photo-generated electron-hole pairs, due to the synergistic effects of oxygen vacancies and surface Ti-OH bonds. This study reveals the relation between the photocatalytic property and structure, and provides a new method to prepare highly active TiO2 for H2 production and environmental treatment. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Starch mediated CdS nanoparticles and their photocatalytic performance under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firdaus, Farha, E-mail: Farha-firdaus@yahoo.co.in; Faraz, Mohd

Green synthesis of Cadmium Sulphide (CdS-S) nanoparticles is of considerable interest due to its biocompatible and nontoxicity. Here, we present a biomolecule stimulated chemical method was adopted for the successful synthesis of CdS-S nanoparticles using starch as a capping agent. The CdS-S nanoparticles were characterized by various analytical techniques. The CdS-S nanoparicles exhibit photocatalytic activity against methyl orange (MO) at pH 9 in Visible light and the reaction follows pseudo first-order kinetics. The comparative photocatalytic activity revealed that CdS-S nanoparticles remarkably enhanced activities as compared to the commercial TiO{sub 2} nanoparticles. The outcome of these studies offers valuable for planningmore » CdS-S nanoparticles having photocatalytic activities helpful for the formulation of waste water remediation.« less

Photocatalytic Degradation Effect of μ-Dielectric Barrier Discharge Plasma Treated Titanium Dioxide Nanoparticles on Environmental Contaminant.

PubMed

Seo, Hyeon Jin; Hwang, Ki-Hwan; Na, Young Hoon; Boo, Jin-Hyo

2018-09-01

This study focused on the photocatalytic degradation effect of the μ-dielectric barrier discharge (μ-DBD) plasma treated titanium dioxide (TiO2) nanoparticles on environmental contaminant such as formaldehyde. TiO2 nanoparticles were treated by a μ-DBD plasma source with nitrogen gas. We analyzed the degradation of formaldehyde with the plasma treated TiO2 nanoparticles by UV-visible spectrophotometer (UV-VIS), and demonstrated that the photocatalytic activity of the μ-DBD plasma-treated TiO2 nanoparticles showed significantly high catalytic efficiency rather than without plasma treated TiO2 nanoparticles. Field emission scanning electron microscopes (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and water contact angle analyzer were used to measure the effects of photocatalytic degradation for the plasma treated TiO2 nanoparticles.

Photocatalytic degradation of humic acid in saline waters. Part 1. Artificial seawater: influence of TiO2, temperature, pH, and air-flow.

PubMed

Al-Rasheed, Radwan; Cardin, David J

2003-06-01

We report the first systematic study on the photocatalytic oxidation of humic acid (HA) in artificial seawater (ASW). TiO(2) (Degussa P25) dispersions were used as the catalyst with irradiation from a medium-pressure mercury lamp. The optimum quantity of catalyst was found to be between 2 and 2.5 gl(-1); while the decomposition was fastest at low pH values (pH 4.5 in the range examined), and the optimum air-flow, using an immersion well reactor with a capacity of 400 ml, was 850 ml min(-1). Reactivity increased with air-flow up to this figure, above which foaming prevented operation of the reactor. Using pure oxygen, an optimal flow rate was observed at 300 ml min(-1), above which reactivity remains essentially constant. Following treatment for 1 h, low-salinity water (2700 mg l(-1)) was completely mineralised, whereas ASW (46000 mg l(-1)) had traces of HA remaining. These effects are interpreted and kinetic data presented. To avoid problems of precipitation due to change of ionic strength humic substances were prepared directly in ASW, and the effects of ASW on catalyst suspension and precipitation have been taken into account. The Langmuir-Hinshelwood kinetic model has been shown to be followed only approximately for the catalytic oxidation of HA in ASW. The activation energy for the reaction derived from an Arrhenius treatment was 17 (+/-0.6) kJ mol(-1).

Preparation of Heat Treated Titanium Dioxide (TiO2) Nanoparticles for Water Purification

NASA Astrophysics Data System (ADS)

Araoyinbo, A. O.; Abdullah, M. M. A. B.; Rahmat, A.; Azmi, A. I.; Vizureanu, P.; Rahim, W. M. F. Wan Abd

2018-06-01

Photocatalysis using the semiconductor titanium dioxide (TiO2) has proven to be a successful technology for waste water purification. The photocatalytic treatment is an alternative method for the removal of soluble organic compounds in waste water. In this research, titanium dioxide nanoparticles were synthesized by sol-gel method using titanium tetraisopropoxide (TTIP) as a precursor. The sol was dried in the oven at 120°C after aging for 24 hours. The dried powder was then calcined at 400°C and 700°C with a heating rate of 10°C/min. The phase transformation of the heat treated titanium dioxide nanoparticles were characterized by X-Ray Diffraction (XRD, and the surface morphology by Scanning Electron Microscopy (SEM). The photocatalytic activity of the heat treated titanium dioxide nanoparticles in the degradation of methyl orange (MO) dye under ultraviolet (UV) light irradiation has been studied. At calcination temperature of 400°C, only anatase phase was observed, as the calcination temperature increases to 700°C, the rutile phase was present. The SEM images show the irregular shape of titanium dioxide particles and the agglomeration which tends to be more significant at calcined temperature of 700°C. Degradation of methyl orange by 5 mg heat treated titanium dioxide nanoparticles gives the highest percentage of degradation after irradiation by UV lamp for 4 hours.

MATRIX PHOTOCATALYTIC, INC. PHOTOCATALYTIC OXIDATION TECHNOLOGY - INNOVATIVE TECHNOLOGY EVALUATION REPORT

EPA Science Inventory

The Matrix Technology involves the exposure of titanium dioxide (Ti02) particles to ultraviolet light (UV). The Ti02 is activated by UV light to produce high oxidizing hydroxyl radicals. Maxtrix also uses hydrogen peroxide (H202) and ozone (03) to enhance the treatment systems p...

Parameters affecting the photocatalytic degradation of dyes using TiO2: a review

NASA Astrophysics Data System (ADS)

Reza, Khan Mamun; Kurny, ASW; Gulshan, Fahmida

2017-07-01

Traditional chemical, physical and biological processes for treating wastewater containing textile dye have such disadvantages as high cost, high energy requirement and generation of secondary pollution during treatment process. The advanced oxidation processes technology has been attracting growing attention for the decomposition of organic dyes. Such processes are based on the light-enhanced generation of highly reactive hydroxyl radicals, which oxidize the organic matter in solution and convert it completely into water, CO2 and inorganic compounds. In this presentation, the photocatalytic degradation of dyes in aqueous solution using TiO2 as photocatalyst under solar and UV irradiation has been reviewed. It is observed that the degradation of dyes depends on several parameters such as pH, catalyst concentration, substrate concentration and the presence of oxidants. Reaction temperature and the intensity of light also affect the degradation of dyes. Particle size, BET-surface area and different mineral forms of TiO2 also have influence on the degradation rate.

Facile formation of Ag{sub 2}WO{sub 4}/AgX (X = Cl, Br, I) hybrid nanorods with enhanced visible-light-driven photoelectrochemical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jingjing; Yu, Caiyun; Zheng, Changcheng

2015-01-15

Highlights: • Ag{sub 2}WO{sub 4}/AgX hybrid nanorods were prepared by a facile in-situ anion exchange reaction. • Ag{sub 2}WO{sub 4} nanorods and different X{sup −} ions were reacted in water at room temperature. • The hybrids possess significantly enhanced photoelectrochemical properties. • Ag{sub 2}WO{sub 4}/AgBr hybrids exhibit the highest photocatalytic activity among three samples. • The active species tests were also investigated to confirm photocatalytic mechanism. - Abstract: In this work, we demonstrated a general strategy for the preparation of a series of uniform Ag{sub 2}WO{sub 4}/AgX (X = Cl, Br, I) hybrid nanorods by a facile in-situ anion exchangemore » reaction occurring at room temperature between pregrown Ag{sub 2}WO{sub 4} nanorods and different X{sup −} ions in water. Compared with Ag{sub 2}WO{sub 4} nanorods, further investigation has revealed that the as-prepared hybrid nanorods possess significantly enhanced photocurrent response and photocatalytic activity in degrading methyl orange (MO) under visible-light irradiation. In particular, the Ag{sub 2}WO{sub 4}/AgBr hybrid nanorods exhibit the highest photocatalytic activity among the three kinds of samples. The active species tests indicate that superoxide anion radicals and photogenerated holes are responsible for the enhanced photocatalytic performance.« less

Removal of MCs by Bi2O2CO3: adsorption and the potential of photocatalytic degradation.

PubMed

Wang, Yujiao; Cao, Yanqiu; Li, Hongmei; Gong, Aijun; Han, Jintao; Qian, Zhen; Chao, Wenran

2018-04-01

Microcystins (MCs) is a kind of hepatotoxin, which is the secondary metabolite of cyanobacteria. Bi 2 O 2 CO 3 (BOC) is a kind of cheap and nontoxic semiconductor material. BOC was synthetized by solvothermal method and then microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were removed by BOC, through adsorption and photocatalytic degradation. When the dosage of BOC is 6 g/L, the MC-LR and MC-RR in the natural water sample can be completely adsorbed in 30 min and then after 12 h irradiation, MC-LR and MC-RR were photocatalytically degraded by BOC.

Advanced nanoporous TiO2 photocatalysts by hydrogen plasma for efficient solar-light photocatalytic application

NASA Astrophysics Data System (ADS)

An, Ha-Rim; Park, So Young; Kim, Hyeran; Lee, Che Yoon; Choi, Saehae; Lee, Soon Chang; Seo, Soonjoo; Park, Edmond Changkyun; Oh, You-Kwan; Song, Chan-Geun; Won, Jonghan; Kim, Youn Jung; Lee, Jouhahn; Lee, Hyun Uk; Lee, Young-Chul

2016-07-01

We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) — approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) — resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications.

Advanced nanoporous TiO2 photocatalysts by hydrogen plasma for efficient solar-light photocatalytic application

PubMed Central

An, Ha-Rim; Park, So Young; Kim, Hyeran; Lee, Che Yoon; Choi, Saehae; Lee, Soon Chang; Seo, Soonjoo; Park, Edmond Changkyun; Oh, You-Kwan; Song, Chan-Geun; Won, Jonghan; Kim, Youn Jung; Lee, Jouhahn; Lee, Hyun Uk; Lee, Young-Chul

2016-01-01

We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) — approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) — resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications. PMID:27406992

Heterogeneous photocatalytic oxidation of atmospheric trace contaminants

NASA Technical Reports Server (NTRS)

Ollis, David F.; Peral, Jose

1991-01-01

The following subject areas are covered: (1) design and construction of continuous flow photoreactor for study of oxidation of trace atmospheric contaminants; (2) establishment of kinetics of acetone oxidation including adsorption equilibration, variation of oxidation rate with acetone concentration and water (inhibitor), and variation of rate and apparent quantum yield with light intensity; (3) exploration of kinetics of butanol oxidation, including rate variation with concentration of butanol, and lack of inhibition by water; and (4) exploration of kinetics of catalyst deactivation during oxidation of butanol, including deactivation rate, influence of dark conditions, and establishment of photocatalytic regeneration of activity in alcohol-free air.

Photocatalytic destruction of chlorinated solvents in water with solar energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacheco, J.E.; Prairie, M.R.; Yellowhorse, L.

1993-08-01

Sandia National Laboratories and the National Renewable Energy Laboratory are developing a photocatalytic process to destroy organic contaminants in water. Tests with common water pollutants have been conducted at Sandia's Solar Thermal Facility using a near commercial scale, single-axis tracking parabolic trough system with a glass pipe reactor mounted at its focus. Experiments at this scale provide verification of laboratory studies and allow examination of design and operation issues at a real-lifescale. The catalyst, titanium dioxide (TiO[sub 2]), is a harmless material found in paint, cosmetics, and toothpaste. Experiments were conducted to determine the effects of key process parameters onmore » destruction rates of chlorinated organic compounds that are common water pollutants. This paper summarizes the engineering-scale results of these experiments and analyses.« less

Beads-on-String Structured Nanofibers for Smart and Reversible Oil/Water Separation with Outstanding Antifouling Property.

PubMed

Wang, Yuanfeng; Lai, Chuilin; Wang, Xiaowen; Liu, Yang; Hu, Huawen; Guo, Yujuan; Ma, Kaikai; Fei, Bin; Xin, John H

2016-09-28

It is challenging to explore a unified solution for the treatment of oily wastewater from complex sources. Thus, membrane materials with flexible separation schemes are highly desired. Herein, we fabricated a smart membrane by electrospinning TiO2 doped polyvinylidene fluoride (PVDF) nanofibers. The as-formed beads-on-string structure and hierarchical roughness of the nanofibers contribute to its superwetting/resisting property to liquids, which is desirable in oil/water separation. Switched simply by UV (or sunlight) irradiation and heating treatment, the smart membrane can realize reversible separation of oil/water mixtures by selectively allowing water or oil to pass through alone. Most importantly, the as-prepared nanofiber membrane possesses outstanding antifouling and self-cleaning performance resulting from the photocatalytic property of TiO2, which has practical significance in saving solvents and recycling materials. This work provides a route for fabricating cost-effective, easily scaled up, and recyclable membranes for on-demand oil/water separation in versatile situations, which can be of great usage in the new green separation technology.

Template-free fabrication of hierarchically flower-like tungsten trioxide assemblies with enhanced visible-light-driven photocatalytic activity.

PubMed

Yu, Jiaguo; Qi, Lifang

2009-09-30

Hierarchically flower-like tungsten trioxide assemblies were fabricated on a large scale by a simple hydrothermal treatment of sodium tungstate in aqueous solution of nitric acid. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and N(2) adsorption-desorption measurements. The photocatalytic activity was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that the three-dimensional tungsten trioxide assemblies were constructed from two-dimensional layers, which were further composed of a large number of interconnected lathy nanoplates with different sizes. Such flower-like assemblies exhibited hierarchically porous structure and higher visible-light photocatalytic activity than the samples without such hierarchical structures due to their specific hierarchical pores that served as the transport paths for light and reactants. After five recycles for the photodegradation of RhB, the catalyst did not exhibit any great loss in activity, confirming hierarchically flower-like tungsten trioxide was stability and not photocorroded. This study may provide new insight into environmentally benign preparation and design of novel photocatalytic materials and enhancement of photocatalytic activity.

Fe2O3/ZnO/ZnFe2O4 composites for the efficient photocatalytic degradation of organic dyes under visible light

NASA Astrophysics Data System (ADS)

Li, Xiaojuan; Jin, Bo; Huang, Jingwen; Zhang, Qingchun; Peng, Rufang; Chu, Shijin

2018-06-01

In this study, novel ternary Fe2O3/ZnO/ZnFe2O4 (ZFO) composites were successfully prepared through a simple hydrothermal reaction with subsequent thermal treatment. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) measurement, and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic degradation of rhodamine B (Rh B) under visible light irradiation indicated that the ZFO composites calcined at 500 °C has the best photocatalytic activity (the photocatalytic degradation efficiency can reach up to 95.7% within 60 min) and can maintain a stable photocatalytic degradation efficiency for at least three cycles. In addition, the photocatalytic activity of ZFO composites toward dye decomposition follows the order cationic Rh B > anionic methyl orange. Finally, using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species during the degradation reaction of Rh B.

Roles of Bi, M and VO{sub 4} tetrahedron in photocatalytic properties of novel Bi{sub 0.5}M{sub 0.5}VO{sub 4} (M=La, Eu, Sm and Y) solid solutions for overall water splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Hui; Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University, shanghai 200240; Faculty of Engineering Sciences, Kyushu University, Fukuoka 816-8580

2012-02-15

Novel Bi{sub 0.5}M{sub 0.5}VO{sub 4} (BMV; M=La, Eu, Sm and Y) solid solutions were prepared and studied in this paper. All the samples were proved to produce H{sub 2} and O{sub 2} simultaneously from pure water under the irradiation of UV light. M-O bond lengths were proved to increase with M cations by refining cell parameters and atomic positions. Besides, band gaps, energy gaps and photocatalytic activities of BMV also changed with M cations. Both of M-O and V-O bond lengths were suggested to account for this phenomenon. Inactive A{sub 0.5}Y{sub 0.5}VO{sub 4} (A=La, Ce) for water splitting proved incorporationmore » of Bi rather than distortion of VO{sub 4} tetrahedron was a critical factor for improving efficiency of overall water splitting by facilitating the generation of electron and hole with lighter effective masses. Replacement of Bi by M cations not only gave indirect effect on band structure but also raised position of conduction band minimum to meet requirement of H{sub 2} production. - Graphical abstract: Novel Bi{sub 0.5}M{sub 0.5}VO{sub 4} (M=La, Eu, Sm and Y) solid solutions showed the high and stable photocatalytic activities for overall water splitting with their crystal radii of M elements. Highlights: Black-Right-Pointing-Pointer BMV solid solutions were novel highly efficient V-based photocatalysts for overall water splitting. Black-Right-Pointing-Pointer Photocatalytic activity of BMV solid solution related to the effective ionic radii of M cations. Black-Right-Pointing-Pointer Incorporation of Bi is one of key factors for the highly efficient activity of BMV solid solution. Black-Right-Pointing-Pointer Incorporation of Y is dispensable for H{sub 2} production.« less

Photodegradation of perfluorooctanoic acid by graphene oxide-deposited TiO2 nanotube arrays in aqueous phase.

PubMed

Park, Kyungmin; Ali, Imran; Kim, Jong-Oh

2018-07-15

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant in the environment with serious health risks including endocrine-disrupting characteristics, immunotoxicity, and causing developmental defects. The photocatalytic deposition has proven to be an inexpensive, effective, and sustainable technology for the removal of PFOA in the aqueous phase. Most investigations are conducted in ultrapure water at concentrations higher than those detected in actual water systems. A few studies deal with the toxicity of treated water. In this research, the photocatalytic degradation of PFOA, including photo-oxidative and photo-reductive degradation, is reviewed comprehensively. Compared to photo-oxidation, photo-reduction is more suitable for PFOA removal since it favors defluorination of PFOA and complete mineralization. We used graphene oxide/TiO 2 nanotubes array for photocatalytic degradation of PFOA. The effects of key parameters on the photocatalytic degradation and defluorination processes of PFOA, such as initial PFOA concentration, initial pH of the solution, an initial temperature of the solution, and external bias constant potential, are addressed. We observed that at pH 3 the PFOA degradation was around 83% in 4 h, and at 75 °C almost complete PFOA degradation was observed in 2.5 h. In photoelectrocatalytic process at 2.0 V external bias 97% of PFOA was degraded in 4 h. The mechanisms of the PFOA photodegradation process are also discussed in detail. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evaluation of solar photocatalysis using TiO2 slurry in the inactivation of Cryptosporidium parvum oocysts in water.

PubMed

Abeledo-Lameiro, María Jesús; Ares-Mazás, Elvira; Gómez-Couso, Hipólito

2016-10-01

Cryptosporidium is a genus of enteric protozoan parasites of medical and veterinary importance, whose oocysts have been reported to occur in different types of water worldwide, offering a great resistant to the water treatment processes. Heterogeneous solar photocatalysis using titanium dioxide (TiO2) slurry was evaluated on inactivation of Cryptosporidium parvum oocysts in water. Suspensions of TiO2 (0, 63, 100 and 200mg/L) in distilled water (DW) or simulated municipal wastewater treatment plant (MWTP) effluent spiked with C. parvum oocysts were exposed to simulated solar radiation. The use of TiO2 slurry at concentrations of 100 and 200mg/L in DW yielded a high level of oocyst inactivation after 5h of exposure (4.16±2.35% and 15.03±4.54%, respectively, vs 99.33±0.58%, initial value), representing a good improvement relative to the results obtained in the samples exposed without TiO2 (51.06±9.35%). However, in the assays carried out using simulated MWTP effluent, addition of the photocatalyst did not offer better results. Examination of the samples under bright field and epifluorescence microscopy revealed the existence of aggregates comprising TiO2 particles and parasitic forms, which size increased as the concentration of catalyst and the exposure time increased, while the intensity of fluorescence of the oocyst walls decreased. After photocatalytic disinfection process, the recovery of TiO2 slurry by sedimentation provided a substantial reduction in the parasitic load in treated water samples (57.81±1.10% and 82.10±2.64% for 200mg/L of TiO2 in DW and in simulated MWTP effluent, respectively). Although further studies are need to optimize TiO2 photocatalytic disinfection against Cryptosporidium, the results obtained in the present study show the effectiveness of solar photocatalysis using TiO2 slurry in the inactivation of C. parvum oocysts in distilled water. Copyright © 2016 Elsevier B.V. All rights reserved.

Solar photocatalysis for treatment of Acid Yellow-17 (AY-17) dye contaminated water using Ag@TiO2 core-shell structured nanoparticles.

PubMed

Khanna, Ankita; Shetty K, Vidya

2013-08-01

Wastewater released from textile industries causes water pollution, and it needs to be treated before discharge to the environment by cost effective technologies. Solar photocatalysis is a promising technology for the treatment of dye wastewater. The Ag@TiO2 nanoparticles comprising of Ag core and TiO2 shell (Ag@TiO2) have unique photocatalytic property of inhibition of electron-hole recombination and visible light absorption, which makes it a promising photocatalyst for use in solar photocatalysis and with higher photocatalytic rate. Therefore, in the present work, the Ag@TiO2 nanoparticles synthesized by one pot method with postcalcination step has been used for the degradation of Acid Yellow-17 (AY-17) dye under solar light irradiation. The Ag@TiO2 nanoparticles were characterized using thermogravimetric-differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. The catalyst has been found to be very effective in solar photocatalysis of AY-17, as compared to other catalysts. The effects of pH, catalyst loading, initial dye concentration, and oxidants on photocatalysis were also studied. The optimized parameters for degradation of AY-17 using Ag@TiO2 were found to be pH 3, dye/catalyst ratio of 1:10 (g/g), and 2 g/L of (NH4)2S2O8 as oxidant. Efficient decolorization and mineralization of AY-17 was achieved. The kinetics of color, total organic carbon, and chemical oxygen demand removal followed the Langmuir-Hinshelwood model. Ag@TiO2 catalyst can be reused thrice without much decline in efficiency. The catalyst exhibited its potential as economic photocatalyst for treatment of dye wastewater.

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

PubMed

Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

2014-08-01

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1

Hollow mesoporous TiO2 microspheres for enhanced photocatalytic degradation of acetaminophen in water.

PubMed

Lin, Chin Jung; Yang, Wen-Ta; Chou, Chen-Yi; Liou, Sofia Ya Hsuan

2016-06-01

Hollow core-shell mesoporous TiO2 microspheres were synthesized by a template-free solvothermal route for efficient photocatalytic degradation of acetaminophen. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Barrett-Joyner-Halenda data revealed a micrometer-sized mesoporous anatase TiO2 hollow sphere with large surface area and efficient light harvesting. For the photocatalytic degradation of acetaminophen in 60 min, the conversion fraction of the drug increased from 88% over commercial Degussa P25 TiO2 to 94% over hollow spheres with about 25% increase in the initial reaction rate. Even after 10 repeated runs, the recycled hollow spheres showed good photodegradation activity. The intermediates generated in the photocatalytic reactions were eventually converted into molecules that are easier to handle. The simple fabrication route would facilitate the development of photocatalysts for the decomposition of environmental contaminants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solar Light Responsive Photocatalytic Activity of Reduced Graphene Oxide-Zinc Selenide Nanocomposite

NASA Astrophysics Data System (ADS)

Chakraborty, Koushik; Ibrahim, Sk; Das, Poulomi; Ghosh, Surajit; Pal, Tanusri

2017-10-01

Solution processable reduced graphene oxide-zinc selenide (RGO-ZnSe) nanocomposite has been successfully synthesized by an easy one-pot single-step solvothermal reaction. The RGO-ZnSe composite was characterized structurally and morphologically by the study of XRD analysis, SEM and TEM imaging. Reduction in graphene oxide was confirmed by FTIR spectroscopy analysis. Photocatalytic efficiency of RGO-ZnSe composite was investigated toward the degradation of Rhodamine B under solar light irradiation. Our study indicates that the RGO-ZnSe composite is catalytically more active compared to the controlled-ZnSe under the solar light illumination. Here, RGO plays an important role for photoinduced charge separation and subsequently hinders the electron-hole recombination probability that consequently enhances photocatalytic degradation efficiency. We expect that this type of RGO-based optoelectronics materials opens up a new avenue in the field of photocatalytic degradation of different organic water pollutants.

Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination.

PubMed

Saravanan, R; Karthikeyan, S; Gupta, V K; Sekaran, G; Narayanan, V; Stephen, A

2013-01-01

The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnO nanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by different techniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV-visible absorption spectroscopy. Further, the most photocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygen demand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail. Copyright © 2012 Elsevier B.V. All rights reserved.

Design of Single-Site Photocatalyst using Metal-Organic Framework as Matrix.

PubMed

Wen, Meicheng; Mori, Kohsuke; Kuwahara, Yasutaka; An, Taicheng; Yamashita, Hiromi

2018-05-14

Single-site photocatalyst generally displays excellent photocatalytic activtiy and considerable high stability as compared to homogeneous catalytic system. A rational structural design of single-site photocatalyst with isolated, uniform and spatially separated active sites in a given solid is of prime importance to achieve high photocatalytic activity. Intense attentions have been focused on the engineering and fabrication of single-site photocatalys by using porous materials as platform. Metal-organic frameworks (MOFs) hold great potential for the design and fabrication of single-site photocatalysts due to their remarkable porosity, ultrahigh surface area, extraordinary tailorability and significant diversity. MOFs can provide abundant number of binding sites for anchoring active sites, result in significant enhancement of photocatalytic performance. In this focus review, the development of single-site MOF photocatalysts that perform in important and challenging chemical redox reaction such as photocatalytic water splitting, photocatalytic CO₂ conversion and organic transformations is summarized thoroughly. The successful strategies applied for the construction of single-site MOF photocatalysts and major challenge toward practical application was summarized and pointed out, respectively. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noble-metal-free carbon nanotube-Cd0.1Zn0.9S composites for high visible-light photocatalytic H2-production performance

NASA Astrophysics Data System (ADS)

Yu, Jiaguo; Yang, Bin; Cheng, Bei

2012-03-01

Visible light photocatalytic H2 production from water splitting using solar light is of great importance from the viewpoint of solar energy conversion and storage. In this study, a novel visible-light-driven photocatalyst multiwalled carbon nanotube modified Cd0.1Zn0.9S solid solution (CNT/Cd0.1Zn0.9S) was prepared by a simple hydrothermal method. The prepared samples exhibited enhanced photocatalytic H2-production activity under visible light. CNT content had a great influence on photocatalytic activity and an optimum amount of CNT was determined to be ca. 0.25 wt%, at which the CNT/Cd0.1Zn0.9S displayed the highest photocatalytic activity under visible light, giving an H2-production rate of 78.2 μmol h-1 with an apparent quantum efficiency (QE) of 7.9% at 420 nm, even without any noble metal cocatalysts, exceeding that of pure Cd0.1Zn0.9S by more than 3.3 times. The enhanced photocatalytic activity was due to CNT as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. Furthermore, the prepared sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our findings demonstrated that CNT/Cd0.1Zn0.9S composites were a promising candidate for the development of high-performance photocatalysts in photocatalytic H2 production. This work not only shows a possibility for the utilization of low cost CNT as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon materials as effective co-catalysts.

Hierarchically 3D assembled strontium titanate nanomaterials for water splitting application

NASA Astrophysics Data System (ADS)

Moniruddin, Md; Afroz, Khurshida; Shabdan, Yerkin; Bizri, Baraa; Nuraje, Nurxat

2017-10-01

Water splitting is an important technique to store solar energy in the simple form of chemical energy, such as hydrogen. Strontium titanate (SrTiO3) is one of the most promising photocatalysts to produce hydrogen gas from water splitting. In this research, an electrospinning technique in combination with sol-gel method was developed to synthesize 3D porous SrTiO3 nanostructures. Different crystallite sizes of SrTiO3-nanofibers (STO-NFs) were produced by varying the synthesis parameters including precursor concentration and calcination temperature. The synthesized nanofibers were characterized using DSC, TGA, XRD, SEM, and TEM. The crystallite size of STO-NFs decreases with increasing precursor concentration (3.03-15.78 vol.%) and gradually increases as the calcination temperature increases within the range of 600-800 °C. The photocatalytic activity of different STO-NFs (based on crystallite size) was also evaluated by the amount of H2 production from water splitting under UV irradiation. The H2 evolution study demonstrated that the photocatalytic activity of the STO-NFs strongly depends on the crystallite size of the nanofibers, precursor concentration, and calcination temperature. The H2 production rate increases with increasing crystallite size and temperature, whereas it decreases with increasing precursor concentration. The photocatalytic performance of the STO-NFs was also compared with the commercial SrTiO3 nanoparticles (STO-NPs) after Pt addition as a cocatalyst, where the synthesized nanofibers showed 2 times higher H2 production rate (1.14 mmol/g-h) than that of the nanoparticles. This synthesis technique provides a good example to produce other inorganic photocatalytic 3D porous structure materials.

Photocatalytic activity enhancement of anatase-graphene nanocomposite for methylene removal: Degradation and kinetics.

PubMed

Rezaei, Mostafa; Salem, Shiva

2016-10-05

In the present research, the TiO2-graphene nanocomposite was synthesized by an eco-friendly method. The blackberry juice was introduced to graphene oxide (GO) as a reducing agent to produce the graphene nano-sheets. The nanocomposite of anatase-graphene was developed as a photocatalyst for the degradation of methylene blue, owing to the larger specific surface area and synergistic effect of reduced graphene oxide (RGO). The UV spectroscopy measurements showed that the prepared nanocomposite exhibited an excellent photocatalytic activity toward the methylene blue degradation. The rate of electron transfer of redox sheets is much higher than that observed on GO, indicating the applicability of proposed method for the production of anatase-RGO nanocomposite for treatment of water contaminated by cationic dye. The prepared materials were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy and transmission electron microscopy. A facile and rapid route was applied for the uniform deposition of anatase nanoparticles on the sheets. The resulting nanocomposite contained nanoparticles with a mean diameter of 10nm. A mechanism for the photocatalytic activity of nanocomposite was suggested and the degradation reaction obeyed the second-order kinetics. It was concluded that the degradation kinetics is changed due to the reduction of GO in the presence of blackberry juice. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanism of photocatalytic water oxidation on small TiO 2 nanoparticles

DOE PAGES

Muuronen, Mikko; Parker, Shane M.; Berardo, Enrico; ...

2016-12-07

Here, we present the first unconstrained nonadiabatic molecular dynamics (NAMD) simulations of photocatalytic water oxidation by small hydrated TiO 2 nanoparticles using Tully surface hopping and time-dependent density functional theory. The results indicate that ultrafast electron–proton transfer from physisorbed water to the photohole initiates the photo-oxidation on the S 1 potential energy surface. The new mechanism readily explains the observation of mobile hydroxyl radicals in recent experiments. Two key driving forces for the photo-oxidation reaction are identified: localization of the electron–hole pair and stabilization of the photohole by hydrogen bonding interaction. Our findings illustrate the scope of recent advances inmore » NAMD methods and emphasize the importance of explicit simulation of electronic excitations.« less

Facet-dependent photocatalytic properties of TiO(2) -based composites for energy conversion and environmental remediation.

PubMed

Ong, Wee-Jun; Tan, Lling-Lling; Chai, Siang-Piao; Yong, Siek-Ting; Mohamed, Abdul Rahman

2014-03-01

Titanium dioxide (TiO2 ) is one of the most widely investigated metal oxides because of its extraordinary surface, electronic, and photocatalytic properties. However, the large band gap of TiO2 and the considerable recombination of photogenerated electron-hole pairs limit its photocatalytic efficiency. Therefore, research attention is being increasingly directed towards engineering the surface structure of TiO2 on the atomic level (namely morphological control of {001} facets on the micro- and nanoscale) to fine-tune its physicochemical properties; this could ultimately lead to the optimization of selectivity and reactivity. This Review encompasses the fundamental principles to enhance the photocatalytic activity by using highly reactive {001}-faceted TiO2 -based composites. The current progress of such composites, with particular emphasis on the photodegradation of pollutants and photocatalytic water splitting for hydrogen generation, is also discussed. The progresses made are thoroughly examined for achieving remarkable photocatalytic performances, with additional insights with regard to charge transfer. Finally, a summary and some perspectives on the challenges and new research directions for future exploitation in this emerging frontier are provided, which hopefully would allow for harnessing the outstanding structural and electronic properties of {001} facets for various energy- and environmental-related applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Visible Light Photocatalytic Degradation of Organic Pollutants over Flower-Like Bi₂O₂CO₃ Dotted with Ag@AgBr.

PubMed

Lin, Shuanglong; Wang, Miao; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng; Yun, Nan

2016-10-31

A facile and feasible oil-in-water self-assembly approach was developed to synthesize flower-like Ag@AgBr/Bi₂O₂CO₃ micro-composites. The photocatalytic activities of the samples were evaluated through methylene blue degradation under visible light irradiation. Compared to Bi₂O₂CO₃, flower-like Ag@AgBr/Bi₂O₂CO₃ micro-composites show enhanced photocatalytic activities. In addition, results indicate that both the physicochemical properties and associated photocatalytic activities of Ag@AgBr/Bi₂O₂CO₃ composites are shown to be dependent on the loading quantity of Ag@AgBr. The highest photocatalytic performance was achieved at 7 wt % Ag@AgBr, degrading 95.18% methylene blue (MB) after 20 min of irradiation, which is over 1.52 and 3.56 times more efficient than that of pure Ag@AgBr and pure Bi₂O₂CO₃, respectively. Bisphenol A (BPA) was also degraded to further demonstrate the degradation ability of Ag@AgBr/Bi₂O₂CO₃. A photocatalytic mechanism for the degradation of organic compounds over Ag@AgBr/Bi₂O₂CO₃ was proposed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing Ag@AgX/bismuth (X = a halogen).

Boosting photocatalytic overall water splitting by Co doping into Mn3O4 nanoparticles as oxygen evolution cocatalysts.

PubMed

Yoshinaga, Taizo; Saruyama, Masaki; Xiong, Anke; Ham, Yeilin; Kuang, Yongbo; Niishiro, Ryo; Akiyama, Seiji; Sakamoto, Masanori; Hisatomi, Takashi; Domen, Kazunari; Teranishi, Toshiharu

2018-06-14

The effect of cobalt doping into a manganese oxide (tetragonal spinel Mn 3 O 4 ) nanoparticle cocatalyst up to Co/(Co + Mn) = 0.4 (mol/mol) on the activity of photocatalytic water oxidation was studied. Monodisperse ∼10 nm Co y Mn 1-y O (0 ≤y≤ 0.4) nanoparticles were uniformly loaded onto photocatalysts and converted to Co x Mn 3-x O 4 nanoparticles through calcination. 40 mol% cobalt-doped Mn 3 O 4 nanoparticle-loaded Rh@Cr 2 O 3 /SrTiO 3 photocatalyst exhibited 1.8 times-higher overall water splitting activity than that with pure Mn 3 O 4 nanoparticles. Investigation on the band structure and electrocatalytic water oxidation activity of Co x Mn 3-x O 4 nanoparticles revealed that the Co doping mainly contributes to the improvement of water oxidation kinetics on the surface of the cocatalyst nanoparticles.

Photocatalytic activity and antimicrobial properties of paper sheets modified with TiO2/Sodium alginate nanocomposites.

PubMed

Abdel Rehim, Mona H; El-Samahy, Magda A; Badawy, Abdelrahman A; Mohram, Maysa E

2016-09-05

Photocatalytic paper sheets were prepared by addition of different ratios of TiO2/Sodium alginate (TSA) nanocomposite. The modified paper sheets were characterized by XRD, TGA. Their morphology was studied by scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Photocatalytic activity of modified paper has been studied by analysis of chemical oxygen demand (COD) of waste-water. The results confirmed the mineralization of the waste-water and enhanced removal of chemical oxygen demand (COD) by increasing the amount of photocatalyst in the paper. Moreover, the results also confirmed that presence of sodium alginate as biopolymer increased adhesion of nanoparticles to paper fibers and reduced the harmful effect of the photocatalyst on them. The paper sheets containing 7% as well as 15% TSA showed high photocatalytic activity and anti-bacterial effect against Salmonella typhimurium higher than standard antibiotic beside other microorganisms such as Candida albicans. The maximum antimicrobial effect was found in case of specimen loaded with 15% TSA. Moreover, it was found that by adding 20% TSA to the paper matrix, the properties of the paper composite collapse. The obtained results confirm the possible utilization of the modified paper in both hygienic and food packaging applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rational Design of Porous Conjugated Polymers and Roles of Residual Palladium for Photocatalytic Hydrogen Production.

PubMed

Li, Lianwei; Cai, Zhengxu; Wu, Qinghe; Lo, Wai-Yip; Zhang, Na; Chen, Lin X; Yu, Luping

2016-06-22

Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst.

Photocatalytic hydrogen generation enhanced by band gap narrowing and improved charge carrier mobility in AgTaO3 by compensated co-doping.

PubMed

Li, Min; Zhang, Junying; Dang, Wenqiang; Cushing, Scott K; Guo, Dong; Wu, Nianqiang; Yin, Penggang

2013-10-14

The correlation of the electronic band structure with the photocatalytic activity of AgTaO3 has been studied by simulation and experiments. Doping wide band gap oxide semiconductors usually introduces discrete mid-gap states, which extends the light absorption but has limited benefit for photocatalytic activity. Density functional theory (DFT) calculations show that compensated co-doping in AgTaO3 can overcome this problem by increasing the light absorption and simultaneously improving the charge carrier mobility. N/H and N/F co-doping can delocalize the discrete mid-gap states created by sole N doping in AgTaO3, which increases the band curvature and the electron-to-hole effective mass ratio. In particular, N/F co-doping creates a continuum of states that extend the valence band of AgTaO3. N/F co-doping thus improves the light absorption without creating the mid-gap states, maintaining the necessary redox potentials for water splitting and preventing from charge carrier trapping. The experimental results have confirmed that the N/F-codoped AgTaO3 exhibits a red-shift of the absorption edge in comparison with the undoped AgTaO3, leading to remarkable enhancement of photocatalytic activity toward hydrogen generation from water.

Tuning Cu dopant of Zn 0.5 Cd 0.5 S nanocrystals enables high-performance photocatalytic H 2 evolution from water splitting under visible-light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Zongwei; Zhang, Bingkai; Zheng, Jiaxin

2016-08-01

Cu-doping into Zn1-xCdxS can greatly enhance the photocatalytic H2 evolution from water splitting under visible-light irradiation. However, it is still controversial for how the Cu-dopant improves this performance. Here, we report that appropriate Cu-doped Zn0.5Cd0.5S nanocrystals reach 21.4 mmol/h/g of H2 evolution rate without cocatalyst in the visible-light region, which is also 2.8 times as high as that of the undoped counterpart, and the corresponding apparent quantum efficiency is 18.8% at 428 nm. It is firstly confirmed that the Cu2+ changes into Cu+ after being doped by soft X-ray absorption spectroscopy (sXAS). We theoretically propose that the transformation of 2Cu2+more » to 2Cu+ results in one adjacent S2- vacancy (VS) in host during the doping process, while the Cu+-dopant and VS attract the photoexcited holes and electrons, respectively. Accordingly, the photocatalytic activity is improved due to the enhanced separation of photoexcited carriers accompanied with the enhanced light absorption resulting from the Cu+-dopant and 2Cu+/VS complex as possible active site for photocatalytic H2 evolution.« less

Advanced oxidation processes for the removal of natural organic matter from drinking water sources: A comprehensive review.

PubMed

Sillanpää, Mika; Ncibi, Mohamed Chaker; Matilainen, Anu

2018-02-15

Natural organic matter (NOM), a key component in aquatic environments, is a complex matrix of organic substances characterized by its fluctuating amounts in water and variable molecular and chemical properties, leading to various interaction schemes with the biogeosphere and hydrologic cycle. These factors, along with the increasing amounts of NOM in surface and ground waters, make the effort of removing naturally-occurring organics from drinking water supplies, and also from municipal wastewater effluents, a challenging task requiring the development of highly efficient and versatile water treatment technologies. Advanced oxidation processes (AOPs) received an increasing amount of attention from researchers around the world, especially during the last decade. The related processes were frequently reported to be among the most suitable water treatment technologies to remove NOM from drinking water supplies and mitigate the formation of disinfection by products (DBPs). Thus, the present work overviews recent research and development studies conducted on the application of AOPs to degrade NOM including UV and/or ozone-based applications, different Fenton processes and various heterogeneous catalytic and photocatalytic oxidative processes. Other non-conventional AOPs such as ultrasonication, ionizing radiation and plasma technologies were also reported. Furthermore, since AOPs are unlikely to achieve complete oxidation of NOM, integration schemes with other water treatment technologies were presented including membrane filtration, adsorption and others processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multi-Layered TiO2 Films towards Enhancement of Escherichia coli Inactivation

PubMed Central

Yoriya, Sorachon; Chumphu, Angkana; Pookmanee, Pusit; Laithong, Wreerat; Thepa, Sirichai; Songprakorp, Roongrojana

2016-01-01

Crystalline TiO2 has shown its great photocatalytic properties in bacterial inactivation. This work presents a design fabrication of low-cost, layered TiO2 films assembled reactors and a study of their performance for a better understanding to elucidate the photocatalytic effect on inactivation of E. coli in water. The ability to reduce the number of bacteria in water samples for the layered TiO2 composing reactors has been investigated as a function of time, while varying the parameters of light sources, initial concentration of bacteria, and ratios of TiO2 film area and volume of water. Herein, the layered TiO2 films have been fabricated on the glass plates by thermal spray coating prior to screen printing, allowing a good adhesion of the films. Surface topology and crystallographic phase of TiO2 for the screen-printed active layer have been characterized, resulting in the ratio of anatase:rutile being 80:20. Under exposure to sunlight and a given condition employed in this study, the optimized film area:water volume of 1:2.62 has shown a significant ability to reduce the E. coli cells in water samples. The ratio of surface area of photocatalytic active base to volume of water medium is believed to play a predominant role facilitating the cells inactivation. The kinetic rate of inactivation and its behavior are also described in terms of adsorption of reaction species at different contact times. PMID:28773930

Photocatalytic performance of electrospun CNT/TiO2 nanofibers in a simulated air purifier under visible light irradiation.

PubMed

Wongaree, Mathana; Chiarakorn, Siriluk; Chuangchote, Surawut; Sagawa, Takashi

2016-11-01

The photocatalytic treatment of gaseous benzene under visible light irradiation was developed using electrospun carbon nanotube/titanium dioxide (CNT/TiO 2 ) nanofibers as visible light active photocatalysts. The CNT/TiO 2 nanofibers were fabricated by electrospinning CNT/poly(vinyl pyrrolidone) (PVP) solution followed by the removal of PVP by calcination at 450 °C. The molar ratio of CNT/TiO 2 was fixed at 0.05:1 by weight, and the quantity of CNT/TiO 2 loaded in PVP solution varied between 30 and 60 % wt. CNT/TiO 2 nanofibers have high specific surface area (116 m 2 /g), significantly higher than that of TiO 2 nanofibers (44 m 2 /g). The photocatalytic performance of the CNT/TiO 2 nanofibers was investigated by decolorization of 1 × 10 -5  M methylene blue (MB) dye (in water solution) and degradation of 100 ppm gaseous benzene under visible light irradiation. The 50-CNT/TiO 2 nanofibers (calcined CNT/TiO 2 nanofibers fabricated from a spinning solution of 50 % wt CNT/TiO 2 based on PVP) had higher MB degradation efficiency (58 %) than did other CNT/TiO 2 nanofibers and pristine TiO 2 nanofibers (15 %) under visible light irradiation. The photocatalytic degradation of gaseous benzene under visible light irradiation on filters made of 50-CNT/TiO 2 nanofibers was carried out in a simulated air purifier system. Similar to MB results, the degradation efficiency of gaseous benzene by 50-CNT/TiO 2 nanofibers (52 %) was higher than by other CNT/TiO 2 nanofibers and pristine TiO 2 nanofibers (18 %). The synergistic effects of the larger surface area and lower band gap energy of CNT/TiO 2 nanofibers were presented as strong adsorption ability and greater visible light adsorption. The CNT/TiO 2 nanofiber prepared in this study has potential for use in air purifiers to improve air treatment efficiency with less energy.

Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods.

PubMed

Balcha, Abebe; Yadav, Om Prakash; Dey, Tania

2016-12-01

Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28 nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100 mg/L, an optimum photocatalyst load of 250 mg/L was needed to achieve dye degradation as high as 81 and 92.5 % for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4 × 10 -3 and 12.4 × 10 -3  min -1 , respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).

Facile synthesis of magnetic Fe3O4@BiOI@AgI for water decontamination with visible light irradiation: Different mechanisms for different organic pollutants degradation and bacterial disinfection.

PubMed

Liang, Jialiang; Liu, Fuyang; Li, Mian; Liu, Wen; Tong, Meiping

2018-06-15

Magnetic Fe 3 O 4 @BiOI@AgI (FBA) spheres were synthesized through a multi-step process. The fabricated photocatalysts were characterized by different techniques. To testify the visible light driven photocatalytic activity of FBA, Rhodamine B and Bisphenol A were chosen as model common and emerging organic contaminants, respectively. While, gram-negative strain Escherichia coli was selected as model waterborne bacteria. The results showed that under visible light irradiation, FBA contained strong photocatalytic degradation capacity towards both RhB and BPA. Moreover, FBA was also found to exhibit excellent disinfection activity towards E. coli. The photocatalytic mechanisms for different pollutants by FBA were determined and found to vary for different pollutants. Specifically, scavenger experiments, degradation intermediates determination, as well as theoretical density functional theory (DFT) analysis showed that RhB and BPA were degraded via photosensitization (dominated by e - and ·O 2 - ) and direct photocatalytic oxidation (contributed by h + , e - and ·O 2 - ), respectively. Whereas, E. coli cells yet were found to be inactivated by the generation of e - and ·O 2 - rather than by the released Ag + . Since it contained superparamagnetic property, FBA could be easily separated from the reaction suspension after use. Due to the excellent photo stability, FBA exhibited strong photocatalytic activity in the fourth reused recycle. Therefore, FBA could serve as a promising alternative for water purification. Copyright © 2018 Elsevier Ltd. All rights reserved.

Photocatalytic Pre-Oxidation of Arsenic (III) in Groundwater by a Visible-Light-Driven System with Magnetic Separating Characteristic

NASA Astrophysics Data System (ADS)

Cui, Y.; Liu, Y.; Peng, L.; Qin, Y.

2017-12-01

Arsenic was a typical toxic metalloid element and its contamination in groundwater was widely recognized as a global health problem, especially in north China, where people depended on groundwater as water resource. Arsenic was existed as As(III) in underground water, and has low affinity to the surface of various minerals and more toxic and more difficultly to be removed compared with As(V), so a pre-oxidation technology by transforming As (III) to As (V) is highly desirable. Electrochemical and oxidizing agents were traditional technology, which usually causes secondary pollution. A novel methodology is presented here, using prepared magnetic visible-light-driven nanomaterials as recyclable media to investigate As(III) pre-oxidation processing. Ag@AgCl core-shell nanowires were first synthesized by oxidation of Ag nanowires with moderate FeCl3, and exhibited excellent photocatalytic activity to As(III) with visible-light. The ratio of chloridization was proved to act as key effect on photocatalytic oxidation efficiency. Testing with simulated groundwater condition proved that pH, ionic strength and concentration of humic acid have obvious effects on Ag@AgCl photocatalytic ability. h+ and ·O2- were confirmed to be the main active species during the visible-light driven photocatalytic oxidation process for As(III) by trapping experiments with radical scavengers. Then Fe0 was introduced to prepare Fe-Ag nanowire and chloridized into Fe-Ag@AgCl to provide magnetic characteristic. The magnetic recycling and re-chloride experiments validated this visible-light-driven material has excellent stable and high reused ability as photocatalyst under visible light irradiation.

Evaluation of SnO2 for sunlight photocatalytic decontamination of water.

PubMed

Aslam, M; Qamar, M Tariq; Ali, Shahid; Rehman, Ateeq Ur; Soomro, M T; Ahmed, Ikram; Ismail, I M I; Hameed, A

2018-07-01

The broad bandgap tin (IV) oxide (SnO 2 ) is the least investigated semiconductor material for photocatalytic water decontamination in sunlight exposure. A detailed study covering the synthesis, characterization and the evaluation of photocatalytic activity of SnO 2 , in the natural sunlight exposure, is presented. The structural characterization by XRD revealed the formation of phase pure tetragonal SnO 2 with the average crystallite size of ∼41.5 nm whereas minor Sn 2+ states in the material were identified by XPS analysis. As explored by diffuse reflectance (DR) and photoluminescence (PL) spectroscopy, the material exhibited a distinct absorption edge at ∼3.4 eV. The morphological and microstructure analysis of the synthesized SnO 2 was carried out by FESEM and HRTEM. The electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP) predicted the better charge transport and retention ability of the material under illumination whereas the Mott-Schottky extrapolation prophesied the n-type behavior with the flat-band potential of -0.60 V. The photocatalytic activity of SnO 2 was assessed in the exposure of complete spectrum natural sunlight for the removal of 2,4,6-trichlorophenol. The HPLC and TOC analysis monitored the progress of degradation and mineralization whereas the released chloride ions were evaluated by ion chromatography. The effect of the transition metal ions (Fe 3+ , Cu 2+ , Ni 2+, and Zn 2+ ) as electron capture agents and H 2 O 2 as ROS generator was explored during the degradation process. The utility of the material for the simultaneous removal of chlorophenols in the mixture was also investigated. The SnO 2 exhibited sustained activity in the repeated use. Based on experimental evidence congregated, the mechanism of the removal process and the efficacy of SnO 2 for sunlight photocatalytic decontamination of water was established. Copyright © 2018 Elsevier Ltd. All rights reserved.

Oil-in-Water Self-Assembled Synthesis of Ag@AgCl Nano-Particles on Flower-like Bi2O2CO3 with Enhanced Visible-Light-Driven Photocatalytic Activity

PubMed Central

Lin, Shuanglong; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng

2016-01-01

In this work, a series of novel flower-like Ag@AgCl/Bi2O2CO3 were prepared by simple and feasible oil-in-water self-assembly processes. The phase structures of as-prepared samples were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray fluorescence spectrometer (XRF), etc. The characterization results indicated that the presence of Ag@AgCl did not affect the crystal structure, but exerted a great influence on the photocatalytic activity of Bi2O2CO3 and enhanced the absorption band of pure Bi2O2CO3. The photocatalytic activities of the Ag@AgCl/Bi2O2CO3 samples were determined by photocatalytic degradation of methylene blue (MB) under visible light irradiation. The Ag@AgCl (10 wt %)/Bi2O2CO3 composite showed the highest photocatalytic activity, degrading 97.9% MB after irradiation for 20 min, which is over 1.64 and 3.66 times faster than that of pure Ag@AgCl (calculated based on the equivalent Ag@AgCl content in Ag@AgCl (10 wt %)/Bi2O2CO3) and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further prove the degradation ability of Ag@AgCl/Bi2O2CO3. Photocurrent studies indicated that the recombination of photo-generated electron–hole pairs was decreased effectively due to the formation of heterojunctions between flower-like Bi2O2CO3 and Ag@AgCl nanoparticles. Trapping experiments indicated that O2−, h+ and Cl° acted as the main reactive species for MB degradation in the present photocatalytic system. Furthermore, the cycling experiments revealed the good stability of Ag@AgCl/Bi2O2CO3 composites. Based on the above, a photocatalytic mechanism for the degradation of organic compounds over Ag@AgCl/Bi2O2CO3 was proposed. PMID:28773607

Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

PubMed

Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

2014-01-01

Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and increased the utilization of solar energy, greatly boosting the photocatalytic activity for hydrogen production under UV-vis light.

CeO2 /Bi2 WO6 Heterostructured Microsphere with Excellent Visible-light-driven Photocatalytic Performance for Degradation of Tetracycline Hydrochloride.

PubMed

Zhang, Fengjun; Zou, Shuang; Wang, Tianye; Shi, Yuxi; Liu, Peng

2017-10-01

CeO 2 /Bi 2 WO 6 heterostructured microsphere with excellent and stable photocatalytic activity for degradation tetracyclines was successfully synthesized via a facile solvothermal route. The photocatalytic experiments indicated that CeO 2 /Bi 2 WO 6 heterostructured microspheres exhibited enhanced photocatalytic activity compared to pure Bi 2 WO 6 in both the degradation of tetracycline hydrochloride (TCH) and rhodamine B (RhB) under visible-light irradiation. The 1CeO 2 /2Bi 2 WO 6 exhibited the best photocatalytic activity for degradation of TCH, reaching 91% after 60 min reaction. The results suggested that the particular morphological conformation of the microspheres resulted in smaller size and more uniform morphology so as to increase the specific surface area. Meanwhile, the heterojunction was formed by coupling CeO 2 and Bi 2 WO 6 in the as-prepared microspheres, so that the separation efficiency of photogenerated electrons and holes was dramatically improved and the lifetimes of charge carriers were prolonged. Hence, introduction of CeO 2 could significantly enhance the photocatalytic activity of CeO 2 /Bi 2 WO 6 heterostructured microspheres and facilitate the degradation of TCH. This work provided not only a principle method to synthesize CeO 2 /Bi 2 WO 6 with the excellent photocatalytic performance for actual produce, but also a excellent property of the photocatalyst for potential application in photocatalytic treatment of tetracyclines wastewater from pharmaceutical factory. © 2017 The American Society of Photobiology.

Immobilization of CdS nanoparticles formed in reverse micelles onto aluminosilicate supports and their photocatalytic properties.

PubMed

Hirai, Takayuki; Bando, Yoko

2005-08-15

CdS nanoparticles, prepared in reverse micellar system, were immobilized onto thiol-modified aluminosilicate particles (ASSH) by a simple operation: addition of ASSH in the micellar solution and mild stirring. The resulting CdS nanoparticles-aluminosilicate composites (ASCdS) were used as photocatalysts for H2 generation from 2-propanol aqueous solution. The chemical properties of the aluminosilicate, such as affinity for water and other reactants, were found to affect the photocatalytic property of the CdS nanoparticles immobilized. Zeolite particles, having affinity for water and 2-propanol, gave a good ASCdS photocatalyst with respect to H2 generation.

Visible-Light-Driven BiOI-Based Janus Micromotor in Pure Water.

PubMed

Dong, Renfeng; Hu, Yan; Wu, Yefei; Gao, Wei; Ren, Biye; Wang, Qinglong; Cai, Yuepeng

2017-02-08

Light-driven synthetic micro-/nanomotors have attracted considerable attention due to their potential applications and unique performances such as remote motion control and adjustable velocity. Utilizing harmless and renewable visible light to supply energy for micro-/nanomotors in water represents a great challenge. In view of the outstanding photocatalytic performance of bismuth oxyiodide (BiOI), visible-light-driven BiOI-based Janus micromotors have been developed, which can be activated by a broad spectrum of light, including blue and green light. Such BiOI-based Janus micromotors can be propelled by photocatalytic reactions in pure water under environmentally friendly visible light without the addition of any other chemical fuels. The remote control of photocatalytic propulsion by modulating the power of visible light is characterized by velocity and mean-square displacement analysis of optical video recordings. In addition, the self-electrophoresis mechanism has been confirmed for such visible-light-driven BiOI-based Janus micromotors by demonstrating the effects of various coated layers (e.g., Al 2 O 3 , Pt, and Au) on the velocity of motors. The successful demonstration of visible-light-driven Janus micromotors holds a great promise for future biomedical and environmental applications.

Evaluation of copper slag to catalyze advanced oxidation processes for the removal of phenol in water.

PubMed

Huanosta-Gutiérrez, T; Dantas, Renato F; Ramírez-Zamora, R M; Esplugas, S

2012-04-30

The aim of this work was to evaluate the use of copper slag to catalyze phenol degradation in water by advanced oxidation processes (AOPs). Copper slag was tested in combination with H(2)O(2) (slag/H(2)O(2)) and H(2)O(2)/UV (slag/H(2)O(2)/UV). The studied methods promoted the complete photocatalytic degradation of phenol. Besides, they were able to reduce about 50% the TOC content in the samples. Slag/H(2)O(2)/UV and slag/H(2)O(2) treatments have favored biodegradability increment along the reaction time. Nevertheless, the irradiated method achieved higher values of the biodegradability indicator (BOD(5)/TOC). The toxicity assessment indicated the formation of more toxic compounds in both treatments. However, the control of the reaction time would minimize the environmental impact of the effluents. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorption of natural organic matter and disinfection byproduct precursors from surface water onto TiO2 nanoparticles: pH effects, isotherm modelling and implications for using TiO2 for drinking water treatment.

PubMed

Gora, Stephanie L; Andrews, Susan A

2017-05-01

Titanium dioxide is a photocatalyst that can remove organic contaminants of interest to the drinking water treatment industry, including natural organic matter (NOM) and disinfection byproduct (DBP) precursors. The photocatalytic reaction occurs in two steps: adsorption of the contaminant followed by degradation of the adsorbed contaminant upon irradiation with UV light. The second part of this process can lead to the formation of reactive intermediates and negative impacts on treated water quality, such as increased DBP formation potential (DBPfp). Adsorption alone does not result in the formation of reactive intermediates and thus may prove to be a safe way to incorporate TiO 2 into drinking water treatment processes. The goal of this study was to expand on the current understanding of NOM adsorption on TiO 2 and examine it in a drinking water context by observing NOM adsorption from real water sources and evaluating the effects of the resulting reductions on the DBPfp of the treated water. Bottle point isotherm tests were conducted with raw water from two Canadian water treatment plants adjusted to pH 4, pH 6 and pH 8 and dosed with TiO 2 nanoparticles. The DOC results were a good fit to a modified Freundlich isotherm. DBP precursors and liquid chromatography with organic carbon detection NOM fractions associated with DBP formation were removed to some extent at all pHs, but most effectively at pH 4. Copyright © 2017 Elsevier Ltd. All rights reserved.

An overview of advanced reduction processes for bromate removal from drinking water: Reducing agents, activation methods, applications and mechanisms.

PubMed

Xiao, Qian; Yu, Shuili; Li, Lei; Wang, Ting; Liao, Xinlei; Ye, Yubing

2017-02-15

Bromate (BrO 3 - ) is a possible human carcinogen regulated at a strict standard of 10μg/L in drinking water. Various techniques to eliminate BrO 3 - usually fall into three main categories: reducing bromide (Br - ) prior to formation of BrO 3 - , minimizing BrO 3 - formation during the ozonation process, and removing BrO 3 - from post-ozonation waters. However, the first two approaches exhibit low degradation efficiency and high treatment cost. The third workaround has obvious advantages, such as high reduction efficiency, more stable performance and easier combination with UV disinfection, and has therefore been widely implemented in water treatment. Recently, advanced reduction processes (ARPs), the photocatalysis of BrO 3 - , have attracted much attention due to improved performance. To increase the feasibility of photocatalytic systems, the focus of this work concerns new technological developments, followed by a summary of reducing agents, activation methods, operational parameters, and applications. The reaction mechanisms of two typical processes involving UV/sulfite homogeneous photocatalysis and UV/titanium dioxide heterogeneous photocatalysis are further summarized. The future research needs for ARPs to reach full-scale potential in drinking water treatment are suggested accordingly. Copyright © 2016. Published by Elsevier B.V.

DFT investigation on two-dimensional GeS/WS2 van der Waals heterostructure for direct Z-scheme photocatalytic overall water splitting

NASA Astrophysics Data System (ADS)

Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Huang, Baibiao

2018-03-01

Recently, extensive attention has been paid to the direct Z-scheme systems for photocatalytic water splitting where carriers migrate directly between the two semiconductors without a redox mediator. In the present work, the electronic structure and related properties of two-dimensional (2D) van de Waals (vdW) GeS/WX2 (X = O, S, Se, Te) heterojunction are systematically investigated by first-principles calculations. Our results demonstrate that, the GeS/WS2 heterojunction could form a direct Z-scheme system for photocatalytic water splitting, whereas the GeS/WX2 (X = O, Se, Te) can't, because of their respective unsuitable electronic structures. For the GeS/WS2 heterojunction, the GeS and WS2 monolayers serve as photocatalysts for the hydrogen evolution reactionand oxygen evolution reaction, respectively. The internal electric field induced by the electron transfer at the interface can promote the separation of photo-generated charge carriers and formation of the interface Z-scheme electron transfer. Remarkably, the designed GeS/WS2 heterojunction not only enhances the hydrogen production activity of GeS and the oxygen production ability of WS2 but also improves the light absorption of the two monolayers by reducing the band gaps. Moreover, it is found that narrowing the interlayer distance could enhance the internal electric field, improving the photocatalytic ability of the vdW heterojunction. This work provides fundamental insights for further design and preparation of emergent metal dichalcogenide catalysts, beneficial for the development in clean energy.

Modeling the photocatalytic mineralization in water of commercial formulation of estrogens 17-β estradiol (E2) and nomegestrol acetate in contraceptive pills in a solar powered compound parabolic collector.

PubMed

Colina-Márquez, José; Machuca-Martínez, Fiderman; Li Puma, Gianluca

2015-07-22

Endocrine disruptors in water are contaminants of emerging concern due to the potential risks they pose to the environment and to the aquatic ecosystems. In this study, a solar photocatalytic treatment process in a pilot-scale compound parabolic collector (CPC) was used to remove commercial estradiol formulations (17-β estradiol and nomegestrol acetate) from water. Photolysis alone degraded up to 50% of estradiol and removed 11% of the total organic carbon (TOC). In contrast, solar photocatalysis degraded up to 57% of estrogens and the TOC removal was 31%, with 0.6 g/L of catalyst load (TiO2 Aeroxide P-25) and 213.6 ppm of TOC as initial concentration of the commercial estradiols formulation. The adsorption of estrogens over the catalyst was insignificant and was modeled by the Langmuir isotherm. The TOC removal via photocatalysis in the photoreactor was modeled considering the reactor fluid-dynamics, the radiation field, the estrogens mass balance, and a modified Langmuir-Hinshelwood rate law, that was expressed in terms of the rate of photon adsorption. The optimum removal of the estrogens and TOC was achieved at a catalyst concentration of 0.4 g/L in 29 mm diameter tubular CPC reactors which approached the optimum catalyst concentration and optical thickness determined from the modeling of the absorption of solar radiation in the CPC, by the six-flux absorption-scattering model (SFM).

Nano-photocatalysts for the destruction of chloro-organic compounds and bacteria in water.

PubMed

Khaydarov, Rashid A; Khaydarov, Renat R; Gapurova, Olga

2013-09-15

The article deals with a novel electrochemical method of preparing nano-photocatalysts suspended in aqueous solution and their application for water treatment from chloro-organic compounds and bacteria. The nano-photocatalysts have been electrolytically synthesized in the cell with titanium and graphite electrodes. The synthesized nano-photocatalysts based on nanocarbon-titanium composition have the active functional groups including carbonyl (>C=O), hydroxyl (-OH), carboxyl (-COOH), and photocatalytic -Ti(OH)-O-Ti(OH)- formed on the surface of carbon nanoparticles. Here, we report that the synthesized nano-photocatalysts can destroy chloro-organic compounds including dichloro-diphenyl-trichloroethane (DDT), aldrin (C12H8Cl6), lindane (C6H6Cl6), and polychlorinated biphenyls (PCBs) and bacteria Escherichia coli in water under UV and sunlight. In addition, the method of nano-photocatalysts detection in water has been described. Copyright © 2013 Elsevier Inc. All rights reserved.

Inactivation of Escherichia coli by titanium dioxide photocatalytic oxidation.

EPA Science Inventory

Titanium dioxide in the anatase crystalline form was used as a photocatalyst to generate hydroxyl radicals in a flowthrough water reactor. Experiments were performed on pure cultures of Escherichia coli in dechlorinated tap water and a surface water sample to evaluate the disinfe...

Water Splitting via Decoupled Photocatalytic Water Oxidation and Electrochemical Proton Reduction Mediated by Electron-Coupled-Proton Buffer.

PubMed

Li, Fei; Yu, Fengshou; Du, Jian; Wang, Yong; Zhu, Yong; Li, Xiaona; Sun, Licheng

2017-10-18

Water splitting mediated by electron-coupled-proton buffer (ECPB) provides an efficient way to avoid gas mixing by separating oxygen evolution from hydrogen evolution in space and time. Though electrochemical and photoelectrochemcial water oxidation have been incorporated in such a two-step water splitting system, alternative ways to reduce the cost and energy input for decoupling two half-reactions are desired. Herein, we show the feasibility of photocatalytic oxygen evolution in a powder system with BiVO 4 as a photocatalyst and polyoxometalate H 3 PMo 12 O 40 as an electron and proton acceptor. The resulting reaction mixture was allowed to be directly used for the subsequent hydrogen evolution with the reduced H 3 PMo 12 O 40 as electron and proton donors. Our system exhibits excellent stability in repeated oxygen and hydrogen evolution, which brings considerable convenience to decoupled water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalysis of nickel ferrite for photocatalytic water oxidation using [Ru(bpy)3]2+ and S2O8(2-).

PubMed

Hong, Dachao; Yamada, Yusuke; Nagatomi, Takaharu; Takai, Yoshizo; Fukuzumi, Shunichi

2012-12-05

Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S(2)O(8)(2-) as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe(2)O(4)) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O(2) yield and O(2) evolution rate under ambient reaction conditions. NiFe(2)O(4) also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.

New semi-pilot-scale reactor to study the photocatalytic inactivation of phages contained in aerosol.

PubMed

Briggiler Marcó, Mariángeles; Negro, Antonio Carlos; Alfano, Orlando Mario; Quiberoni, Andrea Del Luján

2017-04-12

The aims of this work were to design and build a photocatalytic reactor (UV-A/TiO 2 ) to study the inactivation of phages contained in bioaerosols, which constitute the main dissemination via phages in industrial environments. The reactor is a close system with recirculation that consists of a stainless steel camera (cubic form, side of 60 cm) in which air containing the phage particles circulates and an acrylic compartment with six borosilicate plates covered with TiO 2 . The reactor is externally illuminated by 20 UV-A lamps. Both compartments are connected by a fan to facilitate the sample circulation. Samples are injected into the camera using two piston nebulizers working in series whereas several methodologies for sampling (impinger/syringe, sampling on photocatalytic plates, and impact of air on slide) were assayed. The reactor setup was carried out using phage B1 (Lactobacillus plantarum), and assays demonstrated a decrease of phage counts of 2.7 log orders after 1 h of photocatalytic treatment. Photonic efficiencies of inactivation were assessed by phage sampling on the photocatalytic plates or by impact of air on a glass slide at the photocatalytic reactor exit. Efficiencies of the same order of magnitude were observed using both sampling methods. This study demonstrated that the designed photocatalytic reactor is effective to inactivate phage B1 (Lb. plantarum) contained in bioaerosols.

Synthesis of zinc ferrite/silver iodide composite with enhanced photocatalytic antibacterial and pollutant degradation ability.

PubMed

Xu, Yuanguo; Liu, Qingqing; Xie, Meng; Huang, Shuquan; He, Minqiang; Huang, Liying; Xu, Hui; Li, Huaming

2018-05-22

ZnFe 2 O 4 /AgI composites were first prepared successfully with a hydrothermal method, and ZnFe 2 O 4 nanoparticles were uniformly decorated on the surface of AgI particles. The photocatalytic activities of the obtained ZnFe 2 O 4 /AgI composites were investigated by the degradation of organic pollutants and the inactivation of bacteria under visible light irradiation. The results showed that the introduction of ZnFe 2 O 4 greatly enhanced the light harvesting ability and improved the separation efficiency of the photogenerated charge carriers, which contributed to the enhanced generation of reactive species and thus promoted the photocatalytic performance. The 5% ZnFe 2 O 4 /AgI composite exhibited the optimal photocatalytic disinfection of E. coli (100% removal efficiency in 80 min) as well as the photocatalytic degradation of rhodamine B (RhB) (98.5% removal rate in 40 min). Furthermore, four consecutive cycles also demonstrated the stable photocatalytic activity of the as-prepared ZnFe 2 O 4 /AgI composites. In addition, H 2 O 2 was identified as the predominant active species in the photocatalytic inactivation of bacteria. This study indicated that ZnFe 2 O 4 /AgI composites are a promising candidate for the treatment of wastewater. Copyright © 2018 Elsevier Inc. All rights reserved.

Non-noble metal Cu-loaded TiO2 for enhanced photocatalytic H2 production.

PubMed

Foo, Wei Jian; Zhang, Chun; Ho, Ghim Wei

2013-01-21

Here we have demonstrated the preparation of high-quality, monodispersed and tunable phases of Cu nanoparticles. Structural and chemical composition studies depict the evolution of Cu-Cu(2)O-CuO nanoparticles at various process stages. The loading of Cu and Cu oxide nanoparticles on TiO(2) catalyst has enhanced the photocatalytic H(2) production. Comparatively, H(2) treatment produces well-dispersed Cu nanoparticles with thin oxide shells that show the highest H(2) production amongst the samples. The relatively higher photocatalytic performance is deemed to result from reduced structural defects, higher surface area and dispersivity as well as favorable charge transfer, which inhibits recombination. The Cu nanoparticles are shown to be a promising alternative to noble metal-loaded TiO(2) catalyst systems due to their low cost and high performance in photocatalytic applications.

Sodium citrate functionalized reusable Fe3O4@TiO2 photocatalyst for water purification

NASA Astrophysics Data System (ADS)

Li, Wenyu; Wu, Haoyi

2017-10-01

Easy-recycle photocatalysts are new materials for water treatment technologies. In order to improve the recyclable ability, we employed Fe3O4 particles, which were functionalized by sodium citrate, to serve as a substrate core to attract the deposition of a shell of TiO2 particles. When compared to the calcining process for preparing the composite, the TiO2 distributed homogeneously on the sodium citrate treated Fe3O4, forming a mesoporous shell layer. Due to the mesoporous structure, this Fe3O4@TiO2 exhibited high photocatalytic degradation activity to Rhodamine B, and it was easily recycled using a magnetic field to recover the catalyst from solution.

Recent progress in the development of carbonate-intercalated Zn/Cr LDH as a novel photocatalyst for hydrogen evolution aimed at the utilization of solar light.

PubMed

Parida, Kulamani; Mohapatra, Lagnamayee

2012-01-28

A series of novel photocatalysts Zn/Cr LDH with different Zn/Cr molar ratios (2 : 1, 3 : 1, 4 : 1 and 2 : 1-CO(3)) were fabricated by a co-precipitation method and evaluated for photodecomposition of water using visible light irradiation. Various characterization methods were employed to investigate the structures, morphologies and photocatalytic properties. In comparison to Zn/Cr (2 : 1) LDH, Zn/Cr-CO(3) (2 : 1) LDH extends the absorption edges to the visible region and exhibits good photocatalytic activity, even without the assistance of co-catalysts. The visible light photocatalytic activity is ascribed to the charge transfer spectra of octahedral Cr ions in LDH. Zn/Cr-CO(3) LDH shows enhanced photocatalytic activities compared to Zn/Cr LDH as carbonate ions oxidise by holes to form carbonate radicals, inhibit the rapid recombination of e(-) and h(+) charge carriers and thereby suppress the backward reaction to some extent. This work provides a detailed understanding of the semiconductor properties of LDHs for photocatalytical hydrogen evolution.

Degradation of selected industrial dyes using Mg-doped TiO2 polyscales under natural sun light as an alternative driving energy

NASA Astrophysics Data System (ADS)

Shivaraju, H. P.; Midhun, G.; Anil Kumar, K. M.; Pallavi, S.; Pallavi, N.; Behzad, Shahmoradi

2017-11-01

Designing photocatalytic materials with modified functionalities for the utilization of renewable energy sources as an alternative driving energy has attracted much attention in the area of sustainable wastewater treatment applications. Catalyst-assisted advanced oxidation process is an emerging treatment technology for organic pollutants and toxicants in industrial wastewater. Preparation of visible-light-responsive photocatalyst such as Mg-doped TiO2 polyscales was carried out under mild sol-gel technique. Mg-doped TiO2 polyscales were characterized by powder XRD, SEM, FTIR, and optical and photocatalytic activity techniques. The Mg-doped TiO2 showed a mixed phase of anatase and rutile with an excellent crystallinity, structural elucidations, polyscales morphology, consequent shifting of bandgap energy and adequate photocatalytic activities under visible range of light. Mg-doped TiO2 polyscales were investigated for their efficiencies in the degradation of most commonly used industrial dyes in the real-time textile wastewater. Mg-doped TiO2 polyscales showed excellent photocatalytic degradation efficiency in both model industrial dyes (65-95%) and textile wastewater (92%) under natural sunlight as an alternative and renewable driving energy.

Structural characteristics of mixed oxides MOx/SiO2 affecting photocatalytic decomposition of methylene blue

NASA Astrophysics Data System (ADS)

Gun'ko, V. M.; Blitz, J. P.; Bandaranayake, B.; Pakhlov, E. M.; Zarko, V. I.; Sulym, I. Ya.; Kulyk, K. S.; Galaburda, M. V.; Bogatyrev, V. M.; Oranska, O. I.; Borysenko, M. V.; Leboda, R.; Skubiszewska-Zięba, J.; Janush, W.

2012-06-01

A series of photocatalysts based on silica (nanoparticulate) supported titania, ceria, and ceria/zirconia were synthesized and characterized by a variety of techniques including surface area measurements, X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential, surface charge density, and photocatalytic behavior toward methylene blue decomposition. Thermal treatment at 600 °C increases the anatase content of the titania based catalysts detected by XRD. Changes in the infrared spectra before and after thermal treatment indicate that at low temperature there are more tbnd Sisbnd Osbnd Titbnd bonds than at high temperature. As these bonds break upon heating the SiO2 and TiO2 separate, allowing the TiO2 anatase phase to form. This results in an increased catalytic activity for the thermally treated samples. Nearly all titania based samples exhibit a negative surface charge density at pH 7 (initial pH of photocatalytic studies) which aids adsorption of methylene blue. The crystallinity of ceria and ceria/zirconia based catalysts are in some cases limited, and in others non-existent. Even though the energy band gap (Eg) can be lower for these catalysts than for the titania based catalysts, their photocatalytic properties are inferior.

Preparation of Ti species coating hydrotalcite by chemical vapor deposition for photodegradation of azo dye.

PubMed

Xiao, Gaofei; Zeng, HongYan; Xu, Sheng; Chen, ChaoRong; Zhao, Quan; Liu, XiaoJun

2017-10-01

TiO 2 in anatase crystal phase is a very effective catalyst in the photocatalytic oxidation of organic compounds in water. To improve its photocatalytic activity, the Ti-coating MgAl hydrotalcite (Ti-MgAl-LDH) was prepared by chemical vapor deposition (CVD) method. Response surface method (RSM) was employed to evaluate the effect of Ti species coating parameters on the photocatalytic activity, which was found to be affected by the furnace temperature, N 2 flow rate and influx time of precursor gas. Application of RSM successfully increased the photocatalytic efficiency of the Ti-MgAl-LDH in methylene blue photodegradation under UV irradiation, leading to improved economy of the process. According to the results from X-ray diffraction, scanning electron microscopy, Brunner-Emmet-Teller and Barrett-Joyner-Hallender, thermogravimetric and differential thermal analysis, UV-vis diffuse reflectance spectra analyses, the Ti species (TiO 2 or/and Ti 4+ ) were successfully coated on the MgAl-LDH matrix. The Ti species on the surface of the Ti-MgAl-LDH lead to a higher photocatalytic performance than commercial TiO 2 -P25. The results suggested that CVD method provided a new approach for the industrial preparation of Ti-coating MgAl-LDH material with good photocatalytic performances. Copyright © 2017. Published by Elsevier B.V.

Visible light photocatalytic H2-production activity of wide band gap ZnS nanoparticles based on the photosensitization of graphene

NASA Astrophysics Data System (ADS)

Wang, Faze; Zheng, Maojun; Zhu, Changqing; Zhang, Bin; Chen, Wen; Ma, Li; Shen, Wenzhong

2015-08-01

Visible light photocatalytic H2 production from water splitting is considered an attractive way to solve the increasing global energy crisis in modern life. In this study, a series of zinc sulfide nanoparticles and graphene (GR) sheet composites were synthesized by a two-step hydrothermal method, which used zinc chloride, sodium sulfide, and graphite oxide (GO) as the starting materials. The as-prepared ZnS-GR showed highly efficient visible light photocatalytic activity in hydrogen generation. The morphology and structure of the composites obtained by transmission electron microscope and x-ray diffraction exhibited a small crystallite size and a good interfacial contact between the ZnS nanoparticles and the two-dimensional (2D) GR sheet, which were beneficial for the photocatalysis. When the content of the GR in the catalyst was 0.1%, the ZG0.1 sample exhibited the highest H2-production rate of 7.42 μmol h-1 g-1, eight times more than the pure ZnS sample. This high visible-light photocatalytic H2 production activity is attributed to the photosensitization of GR. Irradiated by visible light, the electrons photogenerated from GR transfer to the conduction band of ZnS to participate in the photocatalytic process. This study presents the visible-light photocatalytic activity of wide bandgap ZnS and its application in H2 evolution.

Enhanced Visible Light Photocatalytic Degradation of Organic Pollutants over Flower-Like Bi2O2CO3 Dotted with Ag@AgBr

PubMed Central

Lin, Shuanglong; Wang, Miao; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng; Yun, Nan

2016-01-01

A facile and feasible oil-in-water self-assembly approach was developed to synthesize flower-like Ag@AgBr/Bi2O2CO3 micro-composites. The photocatalytic activities of the samples were evaluated through methylene blue degradation under visible light irradiation. Compared to Bi2O2CO3, flower-like Ag@AgBr/Bi2O2CO3 micro-composites show enhanced photocatalytic activities. In addition, results indicate that both the physicochemical properties and associated photocatalytic activities of Ag@AgBr/Bi2O2CO3 composites are shown to be dependent on the loading quantity of Ag@AgBr. The highest photocatalytic performance was achieved at 7 wt % Ag@AgBr, degrading 95.18% methylene blue (MB) after 20 min of irradiation, which is over 1.52 and 3.56 times more efficient than that of pure Ag@AgBr and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further demonstrate the degradation ability of Ag@AgBr/Bi2O2CO3. A photocatalytic mechanism for the degradation of organic compounds over Ag@AgBr/Bi2O2CO3 was proposed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing Ag@AgX/bismuth (X = a halogen). PMID:28774002

Visible light photocatalytic H2-production activity of wide band gap ZnS nanoparticles based on the photosensitization of grapheme.

PubMed

Wang, Faze; Zheng, Maojun; Zhu, Changqing; Zhang, Bin; Chen, Wen; Ma, Li; Shen, Wenzhong

2015-08-28

Visible light photocatalytic H(2) production from water splitting is considered an attractive way to solve the increasing global energy crisis in modern life. In this study, a series of zinc sulfide nanoparticles and graphene (GR) sheet composites were synthesized by a two-step hydrothermal method, which used zinc chloride, sodium sulfide, and graphite oxide (GO) as the starting materials. The as-prepared ZnS-GR showed highly efficient visible light photocatalytic activity in hydrogen generation. The morphology and structure of the composites obtained by transmission electron microscope and x-ray diffraction exhibited a small crystallite size and a good interfacial contact between the ZnS nanoparticles and the two-dimensional (2D) GR sheet,which were beneficial for the photocatalysis. When the content of the GR in the catalyst was 0.1%, the ZG0.1 sample exhibited the highest H(2)-production rate of 7.42 μmol h(−1) g(−1), eight times more than the pure ZnS sample. This high visible-light photocatalytic H(2) production activity is attributed to the photosensitization of GR. Irradiated by visible light, the electrons photogenerated from GR transfer to the conduction band of ZnS to participate in the photocatalytic process. This study presents the visible-light photocatalytic activity of wide bandgap ZnS and its application in H(2) evolution.

New understanding of photocatalytic properties of zigzag and armchair g-C3N4 nanotubes from electronic structures and carrier effective mass

NASA Astrophysics Data System (ADS)

Liu, Jianjun; Cheng, Bei

2018-02-01

Low-dimensional g-C3N4 nanostructures own distinct electronic structure and remarkable photocatalytic properties, hence their wide application in the photocatalysis field. However, the correlations of structures and photoinduced carrier migrations with the photocatalytic properties of g-C3N4 nanostructures remain unclear. In this study, the geometrical and electronic structures and the photocatalytic properties of zigzag (n, 0) and armchair (n, n) g-C3N4 nanotubes (n = 6, 9, 12) were systematically investigated using hybrid DFT. Results indicated that the differences in geometrical structures of g-C3N4 nanotubes changed the band gaps and effective mass of carriers. Accordingly, the photocatalytic properties of g-C3N4 nanotubes also changed. Notably, the change trends of band gaps and the effective mass of the electrons and holes were the opposite for zigzag (n, 0) and armchair (n, n) g-C3N4 nanotubes. The absolute band edge potential of (n, 0) and (n, n) g-C3N4 nanotubes can split water for hydrogen production. These theoretical results revealed the correlations of structures and carrier effective mass with the photocatalytic properties of g-C3N4 nanotubes, and provided significant guidance for designing low-dimensional g-C3N4 nanostructures.

Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NOx abatement

NASA Astrophysics Data System (ADS)

Tobaldi, D. M.; Pullar, R. C.; Gualtieri, A. F.; Otero-Irurueta, G.; Singh, M. K.; Seabra, M. P.; Labrincha, J. A.

2015-11-01

Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol-gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice.

Optimizing the deposition of hydrogen evolution sites on suspended semiconductor particles using on-line photocatalytic reforming of aqueous methanol solutions.

PubMed

Busser, G Wilma; Mei, Bastian; Muhler, Martin

2012-11-01

The deposition of hydrogen evolution sites on photocatalysts is a crucial step in the multistep process of synthesizing a catalyst that is active for overall photocatalytic water splitting. An alternative approach to conventional photodeposition was developed, applying the photocatalytic reforming of aqueous methanol solutions to deposit metal particles on semiconductor materials such as Ga₂O₃ and (Ga₀.₆ Zn₀.₄)(N₀.₆O₀.₄). The method allows optimizing the loading of the co-catalysts based on the stepwise addition of their precursors and the continuous online monitoring of the evolved hydrogen. Moreover, a synergetic effect between different co-catalysts can be directly established. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biosensor-based real-time monitoring of paracetamol photocatalytic degradation.

PubMed

Calas-Blanchard, Carole; Istamboulié, Georges; Bontoux, Margot; Plantard, Gaël; Goetz, Vincent; Noguer, Thierry

2015-07-01

This paper presents for the first time the integration of a biosensor for the on-line, real-time monitoring of a photocatalytic degradation process. Paracetamol was used as a model molecule due to its wide use and occurrence in environmental waters. The biosensor was developed based on tyrosinase immobilization in a polyvinylalcohol photocrosslinkable polymer. It was inserted in a computer-controlled flow system installed besides a photocatalytic reactor including titanium dioxide (TiO2) as photocatalyst. It was shown that the biosensor was able to accurately monitor the paracetamol degradation with time. Compared with conventional HPLC analysis, the described device provides a real-time information on the reaction advancement, allowing a better control of the photodegradation process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic Coats in Glass Drinking-Water Bottles

NASA Technical Reports Server (NTRS)

Andren, Anders W.; Armstrong, David E.; Anderson, Marc A.

2005-01-01

According to a proposal, the insides of glass bottles used to store drinking water would be coated with films consisting of or containing TiO2. In the presence of ultraviolet light, these films would help to remove bacteria, viruses, and trace organic contaminants from the water.

Property Characterization and Photocatalytic Activity Evaluation of BiGdO₃ Nanoparticles under Visible Light Irradiation.

PubMed

Luan, Jingfei; Shen, Yue; Zhang, Lingyan; Guo, Ningbin

2016-09-08

BiGdO₃ nanoparticles were prepared by a solid-state reaction method and applied in photocatalytic degradation of dyes in this study. BiGdO₃ was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, UV-Vis diffuse reflectance spectroscopy and transmission electron microscopy. The results showed that BiGdO₃ crystallized well with the fluorite-type structure, a face-centered cubic crystal system and a space group Fm3m 225. The lattice parameter of BiGdO₃ was 5.465 angstrom. The band gap of BiGdO₃ was estimated to be 2.25 eV. BiGdO₃ showed a strong optical absorption during the visible light region. Moreover, the photocatalytic activity of BiGdO₃ was evaluated by photocatalytic degradation of direct dyes in aqueous solution under visible light irradiation. BiGdO₃ demonstrated excellent photocatalytic activity in degrading Direct Orange 26 (DO-26) or Direct Red 23 (DR-23) under visible light irradiation. The photocatalytic degradation of DO-26 or DR-23 followed the first-order reaction kinetics, and the first-order rate constant was 0.0046 or 0.0023 min(-1) with BiGdO₃ as catalyst. The degradation intermediates of DO-26 were observed and the possible photocatalytic degradation pathway of DO-26 under visible light irradiation was provided. The effect of various operational parameters on the photocatalytic activity and the stability of BiGdO₃ particles were also discussed in detail. BiGdO₃/(visible light) photocatalysis system was confirmed to be suitable for textile industry wastewater treatment.

2D Transition-Metal-Dichalcogenide-Nanosheet-Based Composites for Photocatalytic and Electrocatalytic Hydrogen Evolution Reactions.

PubMed

Lu, Qipeng; Yu, Yifu; Ma, Qinglang; Chen, Bo; Zhang, Hua

2016-03-09

Hydrogen (H2) is one of the most important clean and renewable energy sources for future energy sustainability. Nowadays, photocatalytic and electrocatalytic hydrogen evolution reactions (HERs) from water splitting are considered as two of the most efficient methods to convert sustainable energy to the clean energy carrier, H2. Catalysts based on transition metal dichalcogenides (TMDs) are recognized as greatly promising substitutes for noble-metal-based catalysts for HER. The photocatalytic and electrocatalytic activities of TMD nanosheets for the HER can be further improved after hybridization with many kinds of nanomaterials, such as metals, oxides, sulfides, and carbon materials, through different methods including the in situ reduction method, the hot-injection method, the heating-up method, the hydro(solvo)thermal method, chemical vapor deposition (CVD), and thermal annealing. Here, recent progress in photocatalytic and electrocatalytic HERs using 2D TMD-based composites as catalysts is discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancing the photoresponse and photocatalytic properties of TiO 2 by controllably tuning defects across {101} facets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Piaopiao; Hood, Zachary D.; Oak Ridge National Lab.

Introducing defects into semiconductors with well-controlled exposed facets offers an effective route for the development of photocatalytic materials with greatly improved properties. Here, we report a facile ethylene glycol reduction procedure to make anatase titanium dioxide (TiO 2) with different concentrations of exposed {001} and {101} facets, leading to different surficial defects. TiO 2 with increased concentrations of {101} facets shows a 5-fold improvement in photocurrent generation as well as improved photocatalytic activity towards water splitting under visible light irradiation. Thus, the improved activity is ascribed to the oxygen vacancies as well as the variable surface chemical states, which collectivelymore » induce a slower recombination rate of photo-induced electron-hole pairs. This work also highlights a feasible strategy to obtain the defective TiO 2 and explore the synergistic effect of surface defects and different concentrations of exposed {001} and {101} facets for photocurrent and photocatalytic properties under visible light irradiation.« less

Catalytic photodegradation of pharmaceuticals - homogeneous and heterogeneous photocatalysis.

PubMed

Klementova, S; Kahoun, D; Doubkova, L; Frejlachova, K; Dusakova, M; Zlamal, M

2017-01-18

Photocatalytic degradation of pharmaceuticals (hydrocortisone, estradiol, and verapamil) and personal care product additives (parabens-methyl, ethyl, and propyl derivatives) was investigated in the homogeneous phase (with ferric ions as the catalyst) and on TiO 2 . Ferric ions in concentrations corresponding to concentrations in natural water bodies were shown to be a significant accelerator of the degradation in homogeneous reaction mixtures. In heterogeneous photocatalytic reactions on TiO 2 , lower reaction rates, but mineralisation to higher extents, were observed.

Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor.

PubMed

Zhou, Xu; Li, Fei; Li, Xiaona; Li, Hua; Wang, Yong; Sun, Licheng

2015-01-14

Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)5Cl](2+) as a sacrificial electron acceptor and water as an oxygen source. The photogenerated holes in the semiconductor are used to oxidize molecular catalysts into the high-valent Ru(IV)=O intermediates for 2e(-) oxidation.

Heterogeneous photocatalytic oxidation of atmospheric trace contaminants

NASA Technical Reports Server (NTRS)

Ollis, David F.

1994-01-01

Research was conducted on: (1) design and construction of a continuous flow photoreactor to study oxidation of trace atmospheric contaminants; (2) kinetics of acetone oxidation including adsorption equilibrium, variation of oxidatiin rate with acetone concentration and water, and variation of rate and apparent quantum yield with light intensity, and (3) kinetics of butanol oxidation, including rate variations; and (4) kinetics of catalyst deactivation including deactivation rate, influence of dark conditions, and photocatalytic regeneration in alcohol-free air.

Synergetic effect of MoS2 and graphene as cocatalysts for enhanced photocatalytic activity of BiPO4 nanoparticles

NASA Astrophysics Data System (ADS)

Lv, Hua; Liu, Yumin; Tang, Haibo; Zhang, Peng; Wang, Jianji

2017-12-01

The photodegradation of organic pollutants is an attractive green chemistry technology for water pollution control. Here we prepared a new composite material consisting of BiPO4 nanocrystals grown on layered graphene and MoS2 as a high-performance photocatalyst for the photodegradation of organic pollutants. This composite material was synthesized by a facile one-pot microwave-assisted hydrothermal technique in the presence of layered graphene and MoS2. Through optimizing the loading content of each component, the BiPO4-MoS2/graphene nanocomposite exhibited the highest photocatalytic activity for the degradation of Rhodamine (RhB) when the content of MoS2 and graphene was 2 wt% and 7 wt%, respectively. The enhanced photocatalytic activity of the new composite photocatalyst was attributed to the positive synergetic effect of the layered graphene and MoS2 as cocatalyst, which acted as electron collector and transporter for the interfacial electron transfer from BiPO4 to electron acceptor in the aqueous solution and thus suppressed the charge recombination and made the photogenerated holes more available to participated in the oxidation process. Moreover, the presence of layered MoS2/graphene hybrid could offer more reactive sites and activated the O2 molecular in water to form superoxide radical, thereby resulting in the enhanced photocatalytic activity.

Preparation of ErMnO3 by Sol-gel Method and its Photocatalytic Activity for Removal of Methyl Orange from Water

NASA Astrophysics Data System (ADS)

Xie, X. Y.; Yang, J. N.; Yu, L. L.; Min, J. Y.; Sun, D. D.; Tang, P. S.; Chen, H. F.

2018-05-01

The single phase perovskite ErMnO3 was synthesized using Er(NO3)3, manganese acetate, citric acid and urea by a facile sol-gel method. The gel of ErMnO3 precursor was kept for 36 hours in 100 °C oven to get the xerogel. Then, the xerogel was calcined at 800 °C for 12 hours in muffle furnace to prepare single phase ErMnO3. The prepared sample was characterized by thermogravimetry differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Under ultraviolet light, the photocatalytic activity of ErMnO3 was studied with methyl orange of 20 mg/L as the simulated sewage. The results show that the ErMnO3 sample particle size distribution is relatively uniform, the average grain size is mainly around 100 nm. The photocatalytic experiment demonstrates that ErMnO3 is highly photocatalytic activity for removal of methyl orange from water. When methyl orange of 20 mg/L is degraded for 120 min in the presence of ErMnO3, the degradation rate of methyl orange can reach about 95%. The degradation of methyl orange accords with first order kinetic model in presence ErMnO3 sample, and the apparent rate constant is 0.022 min-1.

Band-gap tailoring and visible-light-driven photocatalytic performance of porous (GaN)1-x(ZnO)x solid solution.

PubMed

Wu, Aimin; Li, Jing; Liu, Baodan; Yang, Wenjin; Jiang, Yanan; Liu, Lusheng; Zhang, Xinglai; Xiong, Changmin; Jiang, Xin

2017-02-21

(GaN) 1-x (ZnO) x solid solution has attracted extensive attention due to its feasible band-gap tunability and excellent photocatalytic performance in overall water splitting. However, its potential application in the photodegradation of organic pollutants and environmental processing has rarely been reported. In this study, we developed a rapid synthesis process to fabricate porous (GaN) 1-x (ZnO) x solid solution with a tunable band gap in the range of 2.38-2.76 eV for phenol photodegradation. Under visible-light irradiation, (GaN) 0.75 (ZnO) 0.25 solid solution achieved the highest photocatalytic performance compared to other (GaN) 1-x (ZnO) x solid solutions with x = 0.45, 0.65 and 0.85 due to its higher redox capability and lower lattice deformation. Slight Ag decoration with a content of 1 wt% on the surface of the (GaN) 0.75 (ZnO) 0.25 solid solution leads to a significant enhancement in phenol degradation, with a reaction rate eight times faster than that of pristine (GaN) 0.75 (ZnO) 0.25 . Interestingly, phenol in aqueous solution (10 mg L -1 ) can also be completely degraded within 60 min, even under the direct exposure of sunlight irradiation. The photocurrent response indicates that the enhanced photocatalytic activity of (GaN) 0.75 (ZnO) 0.25 /Ag is directly induced by the improved transfer efficiency of the photogenerated electrons at the interface. The excellent phenol degradation performance of (GaN) 1-x (ZnO) x /Ag further broadens their promising photocatalytic utilization in environmental processing, besides in overall water splitting for hydrogen production.

Facile in situ synthesis of wurtzite ZnS/ZnO core/shell heterostructure with highly efficient visible-light photocatalytic activity and photostability

NASA Astrophysics Data System (ADS)

Xiao, Jian-Hua; Huang, Wei-Qing; Hu, Yong-sheng; Zeng, Fan; Huang, Qin-Yi; Zhou, Bing-Xin; Pan, Anlian; Li, Kai; Huang, Gui-Fang

2018-02-01

High photocatalytic activity and photostability are the pursuit of the goal for designing promising photocatalysts. Herein, using ZnO to encapsulate ZnS nanoparticles is proposed as an effective strategy to enhance photocatalytic activity and anti-photocorrosion. The ZnS/ZnO core/shell heterostructures are obtained via an annealing treatment of ZnS nanoparticles produced by a facile wet chemical approach. Due to its small size, the nascent cubic sphalerite ZnS (s-ZnS) converts into a hexagonal wurtzite ZnS (w-ZnS)/ZnO core/shell structure after annealing treatment. In situ oxidation leads to increasing ZnO, simultaneously decreasing the w-ZnS content in the resultant w-ZnS/ZnO with thermal annealing time. The w-ZnS/ZnO core/shell heterostructures show high photocatalytic activity, demonstrated by the photodegradation rate of methylene blue being up to ten-fold and seven-fold higher than that of s-ZnS under UV and visible light irradiation, respectively, and the high capability of degrading rhodamine B. The enhanced photocatalytic activity may be attributed to the large specific surface and improved charge carrier separation at the core/shell interface. Moreover, it displays high photostability owing to the protection of the ZnO shell, greatly inhibiting the photocorrosion of ZnS. This facile in situ oxidation is effective and easily scalable, providing opportunities for developing novel core/shell structure photocatalysts with high activity and photostability.

Preparation of porous nitrogen-doped titanium dioxide microspheres and a study of their photocatalytic, antibacterial and electrochemical activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, S.; Chu, W., E-mail: chuwei65@yahoo.com.cn; Huang, Y.Y.

Graphical abstract: Porous N-doped TiO{sub 2} microspheres were prepared for the first time via plasma technique. The sample exhibited better photocatalytic activity, photoinduced inactivation activity and better electrochemical activity than those of TiO{sub 2} microspheres and P25. Display Omitted Highlights: ► Porous N-doped TiO{sub 2} microspheres were prepared via nitrogen plasma technique. ► Plasma treatment did not affect the porous structure of the TiO{sub 2} microspheres. ► With the plasma treatment, the N contents in the samples increased. ► Their photocatalytic, antibacterial and electrochemical activities were studied. -- Abstract: Nitrogen-doped titanium dioxide (N-doped TiO{sub 2}) microspheres with porous structure weremore » prepared via the nitrogen-assisted glow discharge plasma technique at room temperature for the first time. The samples were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption measurement, UV–Vis diffuse reflectance spectra, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The results indicated that the plasma treatment did not affect the porous structure of the TiO{sub 2} microspheres. With the plasma treatment, the N contents in the samples increased. During the photocatalytic degradation of methylene blue under simulative sunlight irradiation, the sample after plasma treatment for 60 min (N-TiO{sub 2}-60) exhibited higher photocatalytic activity than those of the TiO{sub 2} microspheres, P25 and other N-doped TiO{sub 2} microspheres. Furthermore, the N-TiO{sub 2}-60 showed excellent antibacterial activities towards Escherichia coli under visible irradiation. These should be attributed to the enhancement of the visible light region absorption for TiO{sub 2} after N-doping. Electrochemical data demonstrated that the N-doping not only enhanced the electrochemical activity of TiO{sub 2}, but also improved the reversibility of Li insertion/extraction reactions and the rate behavior of TiO{sub 2} during charge–discharge cycles.« less

Evaluation of water matrix effects, experimental parameters, and the degradation pathway during the TiO2 photocatalytical treatment of the antibiotic dicloxacillin.

PubMed

Villegas-Guzman, Paola; Silva-Agredo, Javier; González-Gómez, Duván; Giraldo-Aguirre, Ana L; Flórez-Acosta, Oscar; Torres-Palma, Ricardo A

2015-01-01

The photocalytic degradation of dicloxacillin (DXC) using TiO2 was studied in synthetic and natural waters. The degradation route and the effect of different experimental variables such as pH, applied power, and the initial concentrations of DXC and the catalyst were investigated. The best performances were achieved at a natural pH 5.8 and using 2.0 g L(-1) of TiO2 with 150 W of applied power. The photodegradation process followed Langmuir-Hinshelwood kinetics. The water matrix effect was evaluated in terms of degradation efficiency in the presence of organic compounds (oxalic acid, glucose), Fe(2+) ion and natural water. An increase in degradation was observed when ferrous ion was part of the solution, but the process was inhibited with all evaluated organic compounds. Similarly, inhibition was observed when natural water was used instead of distilled water. The extent of degradation of the process was evaluated following the evolution of chemical oxygen demand (COD), antimicrobial activity (AA), total organic carbon (TOC) and biochemical oxygen demand (BOD5). Total removal of DXC was achieved after 120 min of treatment and 95% mineralization was observed after 480 min of treatment. Additionally, the total removal of antimicrobial activity and a high level of biodegradability were observed after the photocalytical system had been operating for 240 min.

Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

PubMed

Liu, Wen; Sun, Weiling; Borthwick, Alistair G L; Wang, Ting; Li, Fan; Guan, Yidong

2016-11-05

Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

γ-Fe{sub 2}O{sub 3} nanoparticles: An easily recoverable effective photo-catalyst for the degradation of rose bengal and methylene blue dyes in the waste-water treatment plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Amit Kumar; Maji, Swarup Kumar; Adhikary, Bibhutosh, E-mail: bibhutoshadhikary@yahoo.in

2014-01-01

Graphical abstract: - Highlights: • γ-Fe{sub 2}O{sub 3} NPs from a single-source precursor and characterized by XRD, TEM, UV–vis spectra. • The NPs were tested as effective photocatalyst toward degradation of RB and MB dyes. • The possible pathway of the photocatalytic decomposition process has been discussed. • The active species, OH·, was detected by TA photoluminescence probing techniques. - Abstract: γ-Fe{sub 2}O{sub 3} nanoparticles (NPs) were synthesized from a single-source precursor complex [Fe{sub 3}O(C{sub 6}H{sub 5}COO){sub 6}(H{sub 2}O){sub 3}]NO{sub 3} by a simple thermal decomposition process and have been characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM)more » and UV–vis spectroscopic techniques. The NPs were highly pure and well crystallized having hexagonal morphology with an average particle size of 35 nm. The prepared γ-Fe{sub 2}O{sub 3} (maghemite) NPs show effective photo-catalytic activity toward the degradation of rose bengal (RB) and methylene blue (MB) dyes under visible light irradiation and can easily be recoverable in the presence of magnetic field for successive re-uses. The possible photo-catalytic decomposition mechanism is discussed through the detection of hydroxyl radical (OH·) by terephthalic acid photo-luminescence probing technique.« less

Preparation and photocatalytic activity of magnetic samarium-doped mesoporous titanium dioxide at the decomposition of methylene blue under visible light

NASA Astrophysics Data System (ADS)

Shi, Zhongliang; Lai, Hong; Yao, Shuhua

2012-08-01

Preparation of samarium-doped mesoporous titanium dioxide (Sm/MTiO2) coated magnetite (Fe3O4) photocatalysts (Sm/MTiO2/Fe3O4) and their activities under visible light were reported. The catalysts with Sm/MTiO2 shell and a Fe3O4 core were prepared by coating photoactive Sm/MTiO2 onto a magnetic Fe3O4 core through the hydrolysis of tetrabutyltitanate (Ti(OBu)4, TBT) with precursors of Sm(NO3)3 and TBT in the presence of Fe3O4 nanoparticles. The morphological, structural and optical properties of the prepared samples were characterized by BET surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of Sm ion content on the photocatalytic activity was studied. The photocatalytic activities of obtained photocatalysts under visible light were estimated by measuring the decomposition rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Sm/MTiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by a simple magnetic process. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.

Efficient removal of arsenite through photocatalytic oxidation and adsorption by ZrO2-Fe3O4 magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Sun, Tianyi; Zhao, Zhiwei; Liang, Zhijie; Liu, Jie; Shi, Wenxin; Cui, Fuyi

2017-09-01

Bifunctional ZrO2-Fe3O4 magnetic nanoparticles were synthesized and characterized, to remove As(III) through photocatalyic oxidation and adsorption. With a saturation magnetization of 27.39 emu/g, ZrO2-Fe3O4 nanoparticles with size of 10-30 nm could be easily separated from solutions with a simple magnetic process. Under UV light, As(III) could be completely oxidized to less toxic As(V) by ZrO2-Fe3O4 nanoparticles within 40 min in the photocatalytic reaction. Simultaneously, As(V) could be adsorbed onto the surface of nanoparticles with high efficiency. The adsorption of As(V) was well fitted by the pseudo-second-order model and the Freundlich isotherm model, respectively, and the maximum adsorption capacities of the nanoparticles was 133.48 mg/g at pH 7.0. As(III) could be effectively removed by ZrO2-Fe3O4 nanoparticles at initial pH range from 4 to 8. Among all the common coexisting ions investigated, except for chloride and sulfate, carbonate, silicate and phosphate decreased the As(III) removal by competing with arsenic species for adsorption sites. The synthesized magnetic ZrO2-Fe3O4 combined the photocatalytic oxidation property of ZrO2 and the high adsorption capacity of both ZrO2 and Fe3O4, which make it have significant potential applications in the As(III)-contaminated water treatment.

Synthesis of ammonium and sulfate ion-functionalized titanium dioxide for photocatalytic applications

NASA Astrophysics Data System (ADS)

Cheng, J. L.; Mi, J. Y.; Miao, H.; Sharifah Fatanah, B. S. A.; Wong, S. F.; Tay, B. K.

2017-04-01

Due to high band gap energy the optimum photocatalytic activities can only be achieved under UV light, thus limiting the practical application of TiO2. In this study, a method combining NH4 +/SO4 2--functionalization technique and post-treatment was developed and successfully applied to synthesize photoactive TiO2 samples which showed higher photocatalytic activity than the commercial P25 TiO2 under visible light radiation. The results also showed that the addition of (NH4)2SO4 surface functionalization on TiO2 increased the photocatalytic activity, which could be due to the combined effect of crystallinity and band gap energies. Moreover, the results showed that calcination temperature was inversely proportional to photocatalytic activity. The degradation efficiency for methylene blue under visible light was improved by 2 times from 10.7% for P25 nano Degussa TiO2 to 20.2% for the synthesized sample. The band gap energies were also reduced from 3.7 to 3.4 eV (under UV-Vis direct transition mode) indicating a red shift towards higher wavelength.

Intermittent photocatalytic activity of single CdS nanoparticles

PubMed Central

Li, Zhimin; Jiang, Yingyan; Wang, Xian; Chen, Hong-Yuan; Tao, Nongjian; Wang, Wei

2017-01-01

Semiconductor photocatalysis holds promising keys to address various energy and environmental challenges. Most studies to date are based on ensemble analysis, which may mask critical photocatalytic kinetics in single nanocatalysts. Here we report a study of imaging photocatalytic hydrogen production of single CdS nanoparticles with a plasmonic microscopy in an in operando manner. Surprisingly, we find that the photocatalytic reaction switches on and off stochastically despite the fact that the illumination is kept constant. The on and off states follow truncated and full-scale power-law distributions in broad time scales spanning 3–4 orders of magnitude, respectively, which can be described with a statistical model involving stochastic reactions rates at multiple active sites. This phenomenon is analogous to fluorescence photoblinking, but the underlying mechanism is different. As individual nanocatalyst represents the elementary photocatalytic platform, the discovery of the intermittent nature of the photocatalysis provides insights into the fundamental photochemistry and photophysics of semiconductor nanomaterials, which is anticipated to substantially benefit broad application fields such as clean energy, pollution treatment, and chemical synthesis. PMID:28923941

In vitro assessment of photocatalytic titanium oxide surface modified stainless steel orthodontic brackets for antiadherent and antibacterial properties against Lactobacillus acidophilus.

PubMed

Shah, Alok Girish; Shetty, Pradeep Chandra; Ramachandra, C S; Bhat, N Sham; Laxmikanth, S M

2011-11-01

To assess the antiadherent and antibacterial properties of surface modified stainless steel orthodontic brackets with photocatalytic titanium oxide (TiO(2)) against Lactobacillus acidophilus. This study was done on 120 specimens of stainless steel preadjusted edgewise appliance (PEA) orthodontic brackets. The specimens were divided into four test groups. Each group consisted of 30 specimens. Groups containing uncoated brackets acted as a control group for their respective experimental group containing coated brackets. Surface modification of brackets was carried out by the radiofrequency (RF) magnetron sputtering method with photocatalytic TiO(2). Brackets then were subjected to microbiological tests for assessment of the antiadherent and antibacterial properties of photocatalytic TiO(2) coating against L acidophilus. Orthodontic brackets coated with photocatalytic TiO(2) showed an antiadherent effect against L acidophilus compared with uncoated brackets. The bacterial mass that was bound to the TiO(2)-coated brackets was less when compared with the uncoated brackets. Furthermore, TiO(2)-coated brackets had a bactericidal effect on L acidophilus, which causes dental caries. Surface modification of orthodontic brackets with photocatalytic TiO(2) can be used to prevent the accumulation of dental plaque and the development of dental caries during orthodontic treatment.

Hydrothermal growth of TiO2 nanowire membranes sensitized with CdS quantum dots for the enhancement of photocatalytic performance

PubMed Central

2014-01-01

In this paper, TiO2 nanowires (NWs) on Ti foils were prepared using a simple hydrothermal approach and annealing treatment. CdS quantum dots (QDs) were assembled onto the crystallized TiO2 NWs by sequential chemical bath deposition. Ultraviolet-visible absorption spectra showed that CdS adds bands in the visible to the TiO2 absorption and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and helped improve the photocatalytic degradation efficiency. The results of photocatalytic experiment revealed that CdS-TiO2 NWs possessed higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation efficiency of 96.32% after ten cycles indicated that the as-prepared CdS-TiO2 composite exhibited excellent long-time recyclable ability and can be reused for the degradation of contaminants. PMID:24936164

Reducing the pollutant load of olive mill wastewater by photocatalytic membranes and monitoring the process using both tyrosinase biosensor and COD test

NASA Astrophysics Data System (ADS)

Martini, Elisabetta; Tomassetti, Mauro; Campanella, Luigi; Fortuna, Antonio

2013-12-01

Photocatalytic technique had already been employed in the treatment of olive mill wastewater (OMW) using the photocatalysis in suspension. The coupling of photocatalytic and membrane techniques should result in a very powerful process bringing great innovation to OMW depollution. Despite the potential advantages using these hybrid photoreactors, research on the combined use of photocatalysis and membranes has so far not been sufficiently developed. The present paper describes a study to assess the photocatalytic efficacy of a new ceramic membrane containing titanium dioxide, irradiated by UV light, used to abate the pollutant load of olive mill wastewater. Good results were obtained (more than 90% of the phenol content was removed and the COD decrease was of the order of 46-51 % in 24 h) particularly using the ceramic membrane compared with those offered by analogous catalytic membranes made of metallic or polymeric materials.

Reducing the pollutant load of olive mill wastewater by photocatalytic membranes and monitoring the process using both tyrosinase biosensor and COD test

PubMed Central

Martini, Elisabetta; Tomassetti, Mauro; Campanella, Luigi; Fortuna, Antonio

2013-01-01

Photocatalytic technique had already been employed in the treatment of olive mill wastewater (OMW) using the photocatalysis in suspension. The coupling of photocatalytic and membrane techniques should result in a very powerful process bringing great innovation to OMW depollution. Despite the potential advantages using these hybrid photoreactors, research on the combined use of photocatalysis and membranes has so far not been sufficiently developed. The present paper describes a study to assess the photocatalytic efficacy of a new ceramic membrane containing titanium dioxide, irradiated by UV light, used to abate the pollutant load of OMW. Good results were obtained (more than 90% of the phenol content was removed and the COD decrease was of the order of 46–51% in 24 h) particularly using the ceramic membrane compared with those offered by analogous catalytic membranes made of metallic or polymeric materials. PMID:24790964

Evaluation of an alternative method for wastewater treatment containing pesticides using solar photocatalytic oxidation and constructed wetlands.

PubMed

Berberidou, Chrysanthi; Kitsiou, Vasiliki; Lambropoulou, Dimitra A; Antoniadis, Αpostolos; Ntonou, Eleftheria; Zalidis, George C; Poulios, Ioannis

2017-06-15

The present study proposes an integrated system based on the synergetic action of solar photocatalytic oxidation with surface flow constructed wetlands for the purification of wastewater contaminated with pesticides. Experiments were conducted at pilot scale using simulated wastewater containing the herbicide clopyralid. Three photocatalytic methods under solar light were investigated: the photo-Fenton and the ferrioxalate reagent as well as the combination of photo-Fenton with TiO 2 P25, which all led to similar mineralization rates. The subsequent treatment in constructed wetlands resulted in further decrease of DOC and inorganic ions concentrations, especially of NO 3 - . Clopyralid was absent in the outlet of the wetlands, while the concentration of the detected intermediates was remarkably low. These findings are in good agreement with the results of phytotoxicity of the wastewater, after treatment with the ferrioxalate/wetlands process, which was significantly reduced. Thus, this integrated system based on solar photocatalysis and constructed wetlands has the potential to effectively detoxify wastewater containing pesticides, producing a purified effluent which could be exploited for reuse applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of the photocatalytic activity of Ln3+-TiO2 nanomaterial using fluorescence technique for real wastewater treatment.

PubMed

Saif, M; Aboul-Fotouh, S M K; El-Molla, S A; Ibrahim, M M; Ismail, L F M

2014-07-15

Evaluation the photocatalytic activity of different Ln(3+) modified TiO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, xmol Ln(3+) modified TiO2 nanomaterials (Ln = Nd(3+), Sm(3+), Eu(3+), Gd(3+), Dy(3+) and Er(3+) ions; x = 0.005, 0.008, 0.01, 0.02 and 0.03) were synthesized by sol-gel method and characterized using different advanced techniques. The photocatalytic efficiency of the modified TiO2 expressed in the charge carrier separation and OH radicals formation were assigned using TiO2 fluorescence quenching and fluorescence probe methods, respectively. The obtained fluorescence measurements confirm that doping treatment significantly decreases the electron-hole recombination probability in the obtained Ln(3+)/TiO2. Moreover, the rate of OH radicals formation is increased by doping. The highly active nanoparticles (0.02Gd(3+)/TiO2 and 0.01Eu(3+)/TiO2) were applied for industrial wastewater treatment using solar radiation as a renewable energy source. Copyright © 2014 Elsevier B.V. All rights reserved.

TiO₂ (rutile) embedded inulin--A versatile bio-nanocomposite for photocatalytic degradation of methylene blue.

PubMed

Jayanthi Kalaivani, G; Suja, S K

2016-06-05

Inulin, a water soluble carbohydrate polymer, was extracted from Allium sativum L. by hot water diffusion method. A novel bio-nanocomposite was prepared by embedding TiO2 (rutile) onto the inulin matrix. The extracted inulin and the prepared bio-nanocomposite were characterized using UV-vis, FT-IR, XRD, SEM, TEM and TGA techniques. The photocatalytic activity of the bio-nanocomposite for the degradation of methylene blue was studied under UV illumination in batch mode experiment and was found to be twice as high as that of pristine TiO2. The kapp for inulin-TiO2 (0.0449 min(-1)) was higher than that for TiO2 (0.0325 min(-1)) which may be due to the synergistic action of inulin and TiO2. The stabilization of photo excited electron suppressed the electron-hole pair recombination thereby inducing the electrons and the holes to participate in the photo reduction and oxidation processes, respectively and enhancing the photocatalytic activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

MnFe2 O4 Nanocrystals Wrapped in a Porous Organic Polymer: A Designed Architecture for Water-Splitting Photocatalysis.

PubMed

Dhanalaxmi, Karnekanti; Yadav, Rajkumar; Kundu, Sudipta K; Reddy, Benjaram Mahipal; Amoli, Vipin; Sinha, Anil Kumar; Mondal, John

2016-10-24

A novel MnFe 2 O 4 -porous organic polymer (POP) nanocomposite was synthesized by a facile hydrothermal method and using the highly cross-linked N-rich benzene-benzylamine POP. The nanocomposite presented highly efficient photocatalytic performance in the hydrogen evolution reaction (HER) from pure water without addition of any sacrificial agent under one AM 1.5 G sunlight illumination. A photocatalytic activity of 6.12 mmol h -1  g -1 was achieved in the absence of any noble metal cocatalyst, which is the highest H 2 production rate reported for nonprecious metal catalysts. The photocatalytic performance of MnFe 2 O 4 -POP could be attributed to the intrinsic synergistic effects of manganese ferrite (MnFe 2 O 4 ) nanoclusters interacting with the nitrogen dopant POP with a unique mesoporous nanoarchitecture and spatially confined growth of MnFe 2 O 4 in the interconnected POP network, leading to high visible-light absorption with fast electron transport. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

From Extended Nanofluidics to an Autonomous Solar-Light-Driven Micro Fuel-Cell Device.

PubMed

Pihosh, Yuriy; Uemura, Jin; Turkevych, Ivan; Mawatari, Kazuma; Kazoe, Yutaka; Smirnova, Adelina; Kitamori, Takehiko

2017-07-03

Autonomous micro/nano mechanical, chemical, and biomedical sensors require persistent power sources scaled to their size. Realization of autonomous micro-power sources is a challenging task, as it requires combination of wireless energy supply, conversion, storage, and delivery to the sensor. Herein, we realized a solar-light-driven power source that consists of a micro fuel cell (μFC) and a photocatalytic micro fuel generator (μFG) integrated on a single microfluidic chip. The μFG produces hydrogen by photocatalytic water splitting under solar light. The hydrogen fuel is then consumed by the μFC to generate electricity. Importantly, the by-product water returns back to the photocatalytic μFG via recirculation loop without losses. Both devices rely on novel phenomena in extended-nano-fluidic channels that ensure ultra-fast proton transport. As a proof of concept, we demonstrate that μFG/μFC source achieves remarkable energy density of ca. 17.2 mWh cm -2 at room temperature. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light-driven water oxidation for solar fuels

PubMed Central

Young, Karin J.; Martini, Lauren A.; Milot, Rebecca L.; III, Robert C. Snoeberger; Batista, Victor S.; Schmuttenmaer, Charles A.; Crabtree, Robert H.; Brudvig, Gary W.

2014-01-01

Light-driven water oxidation is an essential step for conversion of sunlight into storable chemical fuels. Fujishima and Honda reported the first example of photoelectrochemical water oxidation in 1972. In their system, TiO2 was irradiated with ultraviolet light, producing oxygen at the anode and hydrogen at a platinum cathode. Inspired by this system, more recent work has focused on functionalizing nanoporous TiO2 or other semiconductor surfaces with molecular adsorbates, including chromophores and catalysts that absorb visible light and generate electricity (i.e., dye-sensitized solar cells) or trigger water oxidation at low overpotentials (i.e., photocatalytic cells). The physics involved in harnessing multiple photochemical events for multielectron reactions, as required in the four-electron water oxidation process, has been the subject of much experimental and computational study. In spite of significant advances with regard to individual components, the development of highly efficient photocatalytic cells for solar water splitting remains an outstanding challenge. This article reviews recent progress in the field with emphasis on water-oxidation photoanodes inspired by the design of functionalized thin film semiconductors of typical dye-sensitized solar cells. PMID:25364029

Photodegradation of neonicotinoid insecticides in water by semiconductor oxides.

PubMed

Fenoll, José; Garrido, Isabel; Hellín, Pilar; Flores, Pilar; Navarro, Simón

2015-10-01

The photocatalytic degradation of three neonicotinoid insecticides (NIs), thiamethoxam (TH), imidacloprid (IM) and acetamiprid (AC), in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalysts under natural sunlight and artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the electron acceptor (Na2S2O8) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO2 alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such insecticides in optimal conditions and at constant volumetric rate of photon absorption. Thus, the complete disappearance of all the studied compounds was achieved after 10 and 30 min of artificial light irradiation, in the ZnO/Na2S2O8 and TiO2/Na2S2O8 systems, respectively. The highest degradation rate was noticed for IM, while the lowest rate constant was obtained for AC under artificial light irradiation. In addition, solar irradiation was more efficient compared to artificial light for the removal of these insecticides from water. The main photocatalytic intermediates detected during the degradation of NIs were identified.

Photocatalytic destruction of chlorinated solvents with solar energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacheco, J.; Prairie, M.; Yellowhorse, L.

1990-01-01

Sandia National Laboratories and the Solar Energy Research Institute are developing a photocatalytic process to destroy organic contaminants in water. Tests with common water pollutants are being conducted at Sandia's Solar Thermal Test Facility using a near commercial-scale single-axis tracking parabolic trough system with glass pipe mounted at its focus. Experiments at this scale provide verification of laboratory studies and allow examination of design and operation issues at a real-life scale. The catalyst, titanium dioxide (TiO{sub 2}), is a harmless material found in paint, cosmetics and toothpaste. Experiments were conducted to determine the effect of key process parameters on destructionmore » rates of two chlorinated organic compounds which are common water pollutants: trichloroethylene and trichloroethane. In this paper, we summarize the engineering-scale results of these experiments and analyses. 21 refs., 8 figs.« less

Role of water and carbonates in photocatalytic transformation of CO{sub 2} to CH{sub 4} on titania.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrijevic, N. M.; Vijayan, B. K.; Poluektov, O. G.

Using the electron paramagnetic resonance technique, we have elucidated the multiple roles of water and carbonates in the overall photocatalytic reduction of carbon dioxide to methane over titania nanoparticles. The formation of H atoms (reduction product) and {center_dot}OH radicals (oxidation product) from water, and CO{sub 3}{sup -} radical anions (oxidation product) from carbonates, was detected in CO{sub 2}-saturated titania aqueous dispersion under UV illumination. Additionally, methoxyl, {center_dot}OCH{sub 3}, and methyl, {center_dot}CH{sub 3}, radicals were identified as reaction intermediates. The two-electron, one-proton reaction proposed as an initial step in the reduction of CO{sub 2} on the surface of TiO{sub 2} ismore » supported by the results of first-principles calculations.« less

Role of Water and Carbonates in Photocatalytic Transformation of CO2 to CH4 on Titania

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrijevic, Nada; Vijayan, Baiju K.; Poluektov, Oleg G.

Using the electron paramagnetic resonance technique, we have elucidated the multiple roles of water and carbonates in the overall photocatalytic reduction of carbon dioxide to methane over titania nanoparticles. The formation of H atoms (reduction product) and {sm_bullet}OH radicals (oxidation product) from water, and CO{sub 3}{sup -} radical anions (oxidation product) from carbonates, was detected in CO{sub 2}-saturated titania aqueous dispersion under UV illumination. Additionally, methoxyl, {sm_bullet}OCH{sub 3}, and methyl, {sm_bullet}CH{sub 3}, radicals were identified as reaction intermediates. The two-electron, one-proton reaction proposed as an initial step in the reduction of CO{sub 2}, on the surface of TiO{sub 2}, ismore » supported by the results of first-principles calculations.« less

Insights into highly improved solar-driven photocatalytic oxygen evolution over integrated Ag3PO4/MoS2 heterostructures

NASA Astrophysics Data System (ADS)

Cui, Xingkai; Yang, Xiaofei; Xian, Xiaozhai; Tian, Lin; Tang, Hua; Liu, Qinqin

2018-04-01

Oxygen evolution has been considered as the rate-determining step in photocatalytic water splitting due to its sluggish four-electron half-reaction rate, the development of oxygen-evolving photocatalysts with well-defined morphologies and superior interfacial contact is highly important for achieving high-performance solar water splitting. Herein, we report the fabrication of Ag3PO4/MoS2 nanocomposites and, for the first time, their use in photocatalytic water splitting into oxygen under LED light illumination. Ag3PO4 nanoparticles were found to be anchored evenly on the surface of MoS2 nanosheets, confirming an efficient hybridization of two semiconductor materials. A maximum oxygen-generating rate of 201.6 mol L-1 g-1 h-1 was determined when 200 mg MoS2 nanosheets were incorporated into Ag3PO4 nanoparticles, which is around 5 times higher than that of bulk Ag3PO4. Obvious enhancements in light-harvesting property, as well as electron-hole separation and charge transportation are revealed by the combination of different characterizations. ESR analysis verified that more active oxygen-containing radicals generate over illuminated Ag3PO4/MoS2 composite photocatalysts rather than irradiated Ag3PO4. The improvement in oxygen evolution performance of Ag3PO4/MoS2 composite photocatalysts is ascribed to wide spectra response in the visible-light region, more efficient charge separation and enhanced oxidation capacity in the valence band (VB). This study provides new insights into the design and development of novel composite photocatalytic materials for solar-to-fuel conversion.

Reactivation and reuse of TiO2-SnS2 composite catalyst for solar-driven water treatment.

PubMed

Kovacic, Marin; Kopcic, Nina; Kusic, Hrvoje; Stangar, Urska Lavrencic; Dionysiou, Dionysios D; Bozic, Ana Loncaric

2018-01-01

One of the most important features of photocatalytic materials intended to be used for water treatment is their long-term stability. The study is focused on the application of thermal and chemical treatments for the reactivation of TiO 2 -SnS 2 composite photocatalyst, prepared by hydrothermal synthesis and immobilized on the glass support using titania/silica binder. Such a catalytic system was applied in solar-driven treatment, solar/TiO 2 -SnS 2 /H 2 O 2 , for the purification of water contaminated with diclofenac (DCF). The effectiveness of studied reactivation methods for retaining TiO 2 -SnS 2 activity in consecutive cycles was evaluated on basis of DCF removal and conversion, and TOC removal and mineralization of organic content. Besides these water quality parameters, biodegradability changes in DCF aqueous solution treated by solar/TiO 2 -SnS 2 /H 2 O 2 process using simply reused (air-dried) and thermally and chemically reactivated composite photocatalyst through six consecutive cycles were monitored. It was established that both thermal and chemical reactivation retain TiO 2 -SnS 2 activity in the second cycle of its reuse. However, both treatments caused the alteration in the TiO 2 -SnS 2 morphology due to the partial transformation of visible-active SnS 2 into non-active SnO 2 . Such alteration, repeated through consecutive reactivation and reuse, was reflected through gradual activity loss of TiO 2 -SnS 2 composite in applied solar-driven water treatment.

Self-doped Ti(3+)-TiO2 as a photocatalyst for the reduction of CO2 into a hydrocarbon fuel under visible light irradiation.

PubMed

Sasan, Koroush; Zuo, Fan; Wang, Yuan; Feng, Pingyun

2015-08-28

Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti(3+) into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation.

Lab-on-a-chip based total-phosphorus analysis device utilizing a photocatalytic reaction

NASA Astrophysics Data System (ADS)

Jung, Dong Geon; Jung, Daewoong; Kong, Seong Ho

2018-02-01

A lab-on-a-chip (LOC) device for total phosphorus (TP) analysis was fabricated for water quality monitoring. Many commercially available TP analysis systems used to estimate water quality have good sensitivity and accuracy. However, these systems also have many disadvantages such as bulky size, complex pretreatment processes, and high cost, which limit their application. In particular, conventional TP analysis systems require an indispensable pretreatment step, in which the fluidic analyte is heated to 120 °C for 30 min to release the dissolved phosphate, because many phosphates are soluble in water at a standard temperature and pressure. In addition, this pretreatment process requires elevated pressures of up to 1.1 kg cm-2 in order to prevent the evaporation of the heated analyte. Because of these limiting conditions required by the pretreatment processes used in conventional systems, it is difficult to miniaturize TP analysis systems. In this study, we employed a photocatalytic reaction in the pretreatment process. The reaction was carried out by illuminating a photocatalytic titanium dioxide (TiO2) surface formed in a microfluidic channel with ultraviolet (UV) light. This pretreatment process does not require elevated temperatures and pressures. By applying this simplified, photocatalytic-reaction-based pretreatment process to a TP analysis system, greater degrees of freedom are conferred to the design and fabrication of LOC devices for TP monitoring. The fabricated LOC device presented in this paper was characterized by measuring the TP concentration of an unknown sample, and comparing the results with those measured by a conventional TP analysis system. The TP concentrations of the unknown sample measured by the proposed LOC device and the conventional TP analysis system were 0.018 mgP/25 mL and 0.019 mgP/25 mL, respectively. The experimental results revealed that the proposed LOC device had a performance comparable to the conventional bulky TP analysis system. Therefore, our device could be directly employed in water quality monitoring as an alternative to conventional TP analysis systems.

Enhancement of photocatalytic degradation of furfural and acetophenone in water media using nano-TiO2-SiO2 deposited on cementitious materials.

PubMed

Soltan, Sahar; Jafari, Hoda; Afshar, Shahrara; Zabihi, Omid

2016-10-01

In the present study, silicon dioxide (SiO 2 ) nanoparticles were loaded to titanium dioxide (TiO 2 ) nano-particles by sol-gel method to make a high porosity photocatalyst nano-hybrid. These photocatalysts were synthesized using titanium tetrachloride and tetraethyl orthosilicate as titanium and silicon sources, respectively, and characterized by X-ray powder diffraction (XRD) and scanning electron microscope methods. Subsequently, the optimizations of the component and operation conditions were investigated. Then, nano-sized TiO 2 and TiO 2 -SiO 2 were supported on concrete bricks by the dip coating process. The photocatalytic activity of nano photocatalysts under UV irradiation was examined by studying the decomposition of aqueous solutions of furfural and acetophenone (10 mg/L) as model of organic pollutants to CO 2 and H 2 O at room temperature. A decrease in the concentration of these pollutants was assayed by using UV-visible absorption, gas chromatography technique, and chemical oxygen demand. The removal of these pollutants from water using the concrete-supported photocatalysts under UV irradiation was performed with a greater efficiency, which does not require an additional separation stage to recover the catalyst. Therefore, it would be applicable to use in industrial wastewater treatment at room temperature and atmospheric pressure within the optimized pH range.

Striving toward noble-metal-free photocatalytic water splitting: The hydrogenated-graphene-TiO 2 prototype

DOE PAGES

Nguyen-Phan, Thuy -Duong; Luo, Si; Liu, Zongyuan; ...

2015-08-20

Graphane, graphone and hydrogenated graphene (HG) have been extensively studied in recent years due to their interesting properties and potential use in commercial and industrial applications. The present study reports investigation of hydrogenated graphene/TiO 2-x (HGT) nanocomposites as photocatalysts for H 2 and O 2 production from water without the assistance of a noble metal co-catalyst. By combination of several techniques, the morphologies, bulk/atomic structure and electronic properties of all the powders were exhaustively interrogated. Hydrogenation treatment efficiently reduces TiO 2 nanoparticles, while the graphene oxide sheets undergo the topotactic transformation from a graphene-like structure to a mixture of graphiticmore » and turbostratic carbon (amorphous/disordered) upon altering the calcination atmosphere from a mildly reducing to a H 2-abundant environment. Remarkably, the hydrogenated graphene-TiO 2-x composite that results upon H 2-rich reduction exhibits the highest photocatalytic H 2 evolution performance equivalent to low loading of Pt (~0.12 wt%), whereas the addition of HG suppresses the O 2 production. As a result, we propose that such an enhancement can be attributed to a combination of factors including the introduction of oxygen vacancies and Ti 3+ states, retarding the recombination of charge carriers and thus, facilitating the charge transfer from TiO 2-x to the carbonaceous sheet.« less

Effects of doping on photocatalytic activity for water splitting of metal oxides and nitride

NASA Astrophysics Data System (ADS)

Arai, Naoki; Saito, Nobuo; Nishiyama, Hiroshi; Kadowaki, Haruhiko; Kobayashi, Hisayoshi; Sato, Kazunori; Inoue, Yasunobu

2007-09-01

The effects of metal-ion doping or replacement on the photocatalytic performance for water splitting of d 10 and d 0 metal oxides and d 10 metal nitride were studied. The photocatalysts examined were (1) α-Ga 2-2xIn 2xO 3 and ZnGa 2-2xIn 2xO 4 in which In 3+ was added to Ga IIO 3 and ZnGa IIO 4, respectively, (2) Y xIn 2-xO 3 being a solid solution of In IIO 3 and Y IIO 3, (3) metal ion doped CeO II, and (4) metal ion doped GaN. The photocatalytic activity of 1 wt % RuO II-loaded α-Ga 2-2xIn 2xO 3 increased sharply with increasing x, reached a maximum at around x=0.02, and considerably decreased with further increase in x. The DFT calculation showed that the band structures of α-Ga 2-2xIn 2xO 3 had the contribution of In 4d orbital to the valence band and of In5s orbital to the conduction band. Similar effects were observed for ZnGa 2-2xIn 2xO 4. RuO II-dispersed Y xIn 2-xO 3 had a capability of producing H II and O II in the range x=1.0-1.5 in which the highest activity was obtained at x=1.3. The structures of both InO 6 and YO 6 octahedra were deformed in the solid solution,, and the hybridization of In5s5p and Y4d orbitals in the conduction band was enhanced. Undoped CeO II was photocatalytically inactive, but metal ion-doped CeO II showed a considerable photocatalytic activity. The activation occurred in the case that metal ions doped had larger ion sizes than that of Ce 4+. The small amount doping of divalent metal ions (Zn 2+ and Mg 2+) converted photocatalytically inactive GaN to an efficient photocatalyst. The doping was shown to produce p-type GaN which had the large concentration and high mobility of holes. The roles of metal ion doping and replacement in the photocatalytic properties are discussed.

Property Characterization and Photocatalytic Activity Evaluation of BiGdO3 Nanoparticles under Visible Light Irradiation

PubMed Central

Luan, Jingfei; Shen, Yue; Zhang, Lingyan; Guo, Ningbin

2016-01-01

BiGdO3 nanoparticles were prepared by a solid-state reaction method and applied in photocatalytic degradation of dyes in this study. BiGdO3 was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, UV-Vis diffuse reflectance spectroscopy and transmission electron microscopy. The results showed that BiGdO3 crystallized well with the fluorite-type structure, a face-centered cubic crystal system and a space group Fm3m 225. The lattice parameter of BiGdO3 was 5.465 angstrom. The band gap of BiGdO3 was estimated to be 2.25 eV. BiGdO3 showed a strong optical absorption during the visible light region. Moreover, the photocatalytic activity of BiGdO3 was evaluated by photocatalytic degradation of direct dyes in aqueous solution under visible light irradiation. BiGdO3 demonstrated excellent photocatalytic activity in degrading Direct Orange 26 (DO-26) or Direct Red 23 (DR-23) under visible light irradiation. The photocatalytic degradation of DO-26 or DR-23 followed the first-order reaction kinetics, and the first-order rate constant was 0.0046 or 0.0023 min−1 with BiGdO3 as catalyst. The degradation intermediates of DO-26 were observed and the possible photocatalytic degradation pathway of DO-26 under visible light irradiation was provided. The effect of various operational parameters on the photocatalytic activity and the stability of BiGdO3 particles were also discussed in detail. BiGdO3/(visible light) photocatalysis system was confirmed to be suitable for textile industry wastewater treatment. PMID:27618018

Enhanced photocatalytic hydrogen evolution from in situ formation of few-layered MoS2/CdS nanosheet-based van der Waals heterostructures.

PubMed

Iqbal, Shahid; Pan, Ziwei; Zhou, Kebin

2017-05-25

Here we report for the first time that the H 2 bubbles generated by photocatalytic water splitting are effective in the layer-by-layer exfoliation of MoS 2 nanocrystals (NCs) into few layers. The as-obtained few layers can be in situ assembled with CdS nanosheets (NSs) into van der Waals heterostructures (vdWHs) of few-layered MoS 2 /CdS NSs which, in turn, are effective in charge separation and transfer, leading to enhanced photocatalytic H 2 production activity. The few-layered MoS 2 /CdS vdWHs exhibited a H 2 evolution rate of 140 mmol g (CdS) -1 h -1 and achieved an apparent quantum yield of 66% at 420 nm.

Preparation of Ag-loaded octahedral Bi2WO6 photocatalyst and its photocatalytic activity

NASA Astrophysics Data System (ADS)

An, Liang; Wang, Guanghui; Zhou, Xuan; Wang, Yi; Gao, Fang; Cheng, Yang

2014-12-01

In this work, an Ag-loaded octahedral Bi2WO6 photocatalyst has been successfully prepared by the hydrothermal method and photo deposition method. X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDX), field-emission scanning electron microscopy (FE-SEM) and ultra-violet adsorption spectrum (UV-Vis) were employed for characterization of the composite photocatalyst. Furthermore, two different photocatalysts including the obtained Ag-loaded octahedral Bi2WO6 were employed here for photodegradation of model contaminated water of Orange II (OII). Results show that Ag-loaded Bi2WO6 photocatalyst exhibits superior photocatalytic properties compared to the undoped Bi2WO6. The reasons for improvement in photocatalytic activity of the Ag-loaded octahedral Bi2WO6 were also discussed.

Titania carbon nanotube composites for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Pyrgiotakis, Georgios

Photocatalytic composites have been used for the past few decades in a wide range of applications. The most common application is the purification of air and water by removing toxic compounds. There is limited use however towards biocidal applications. Despite their high efficiency, photocatalytic materials are not comparable to the effectiveness of conventional biocidal compounds such as chlorine and alcoholic disinfectants. On the other hand, nearly a decade ago with the discovery of the carbon nanotubes a new vibrant scientific field emerged. Nanotubes are unique structures of carbon that posse amazing electrical, mechanical and thermal properties. In this research carbon nanotubes are used as photocatalytic enhancers. They were coated with anatase titania to form a composite material. Two different types of nanotubes (metallic versus non-metallic) were used and the photocatalytic activity was measured. The metallic tubes demonstrated exceptional photocatalytic properties, while non-metallic tubes had low photocatalytic efficiency. The reason for that difference was investigated and was the major focus of this research. The research concluded that the reasons for the high efficiency of the carbon nanotubes were (i) the metallic nature of the tubes and (ii) the possible bond between the titania coating and the underlying graphite layers (C-O-Ti). Since both composites had the same indications regarding the C-O-Ti bond, the metallic nature of the carbon nanotubes is believed to be the most dominant factor contributing to the enhancement of the photocatalysis. The composite material may have other potential applications such as for sensing and photovoltaic uses.

Novel β-C3N4/CuO nanoflakes: facile synthesis and unique photocatalytic performance

NASA Astrophysics Data System (ADS)

Zou, Lan-Rong; Huang, Gui-Fang; Li, Dong-Feng; Tian, Qing-Nan; Yang, Ke; Si, Yuan; Chang, Shengli; Zhang, Xue-Ao; Huang, Wei-Qing

2017-09-01

For the first time, novel β-C3N4/CuO composites with superior photocatalytic activity are successfully fabricated via a facile reflux method followed by a thermal process. The morphologies, particle size and microstructure of the synthesized β-C3N4/CuO composites largely depended upon copper chloride and the volume ratio of V water:V ethanol in the mixed precursors. The fabricated β-C3N4/CuO nanoflakes exhibited obviously enhanced visible light photocatalytic activity for the degradation of methylene blue (MB) with an  ˜3.4 and 1.9 fold increase in efficiency over that of pure g-C3N4 and commercial P25, respectively. The β-C3N4/CuO composite photocatalyst also showed photocatalytic activity for the degradation of methyl orange (MO). Moreover, the β-C3N4/CuO nanoflakes showed almost no loss of photocatalytic activity after three recycles of the degradation of the MB. A multiple synergetic mechanism in β-C3N4/CuO nanoflakes, which is featured by the highly reactive {0 0 2} facets, exposed many active sites of nanoflakes and the efficient charge separation are proposed to account for the distinguished photocatalytic activity. This work provides a facile and cost-effective strategy for designing novel β-C3N4/CuO photocatalysts for application in environmental purification.

Fabrication of Photocatalytic Paper Using TiO2 Nanoparticles Confined in Hollow Silica Capsules.

PubMed

Fujiwara, Kensei; Kuwahara, Yasutaka; Sumida, Yuki; Yamashita, Hiromi

2017-01-10

TiO 2 nanoparticles (NPs) encapsulated in hollow silica spheres (TiO 2 @HSSs) show a shielding-effect that can insulate photocatalytically active TiO 2 NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO 2 @HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO 2 @HSS, which has an ample void space between inner TiO 2 NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO 2 @HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO 2 @HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO 2 @HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO 2 NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO 2 and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

Effect of Pt Nanoparticles on the Photocatalytic Activity of ZnO Nanofibers

NASA Astrophysics Data System (ADS)

Di Mauro, Alessandro; Zimbone, Massimo; Scuderi, Mario; Nicotra, Giuseppe; Fragalà, Maria Elena; Impellizzeri, Giuliana

2015-12-01

For this study, we originally realized ZnO nanofibers (˜50 nm in mean radius) mixed with Pt nanoparticles (˜30 nm in mean radius), prepared by pulsed laser ablation in liquid, and investigated their photocatalytic performance. The material was synthesized by the simple electrospinning method coupled with subsequent thermal treatments. Methylene blue was employed as a representative dye pollutant to evaluate the photocatalytic activity of the nanofibers. It was found that the Pt-ZnO fibers exhibit a photodegradation reaction rate that is ˜40 % higher than the one obtained for reference ZnO fibers. These encouraging results demonstrate that Pt-ZnO nanofibers can be fruitfully applied for environmental applications.

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation

NASA Astrophysics Data System (ADS)

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-01

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H2 evolution has been studied extensively. TiO2 is a well-established semiconductor in the field of photocatalytic H2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C3N4-modified TiO2 nanobelts (TCN–Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K–g-C3N4 and the TiO2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C3N4, suggesting increased charge transfer efficiency. The H2 production efficiency of the TCN–Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H2 production activity was due to the superior charge separation and electron transfer efficiency of TCN–Kx composite materials.

Polyacrylamide hydrogel as a template in situ synthesis of CdS nanoparticles with high photocatalytic activity and photostability

NASA Astrophysics Data System (ADS)

Yang, Jiangbing; Gao, Jianping; Wang, Xiaoxue; Mei, Shunkang; Zhao, Ruiru; Hao, Chaoyue; Wu, Yongli; Zhai, Xiangang; Liu, Yu

2017-10-01

Porous polyacrylamide hydrogel (PAM) was prepared by polymerization at room temperature. Cadmium sulfide/polyacrylamide hydrogels (CdS/PAM) was synthesized by in situ loading CdS nanoparticles and used for photocatalytic decomposition of water for the first time. The size distribution of the loaded CdS nanoparticles is 3-12 nm. We studied the enhanced photocatalytic activity and photo-corrosion inhibition of CdS/PAM the compared with pure CdS and probed the mechanism of the improvement. In particular, the CdS/PAM prepared in 0.003 M CdCl2 solution exhibited the highest hydrogen production efficiency of 2.929 mmol g-1 h-1, about 79 times that of pure CdS. The results demonstrate that the formation of new N-Cd bond and high transmittance of CdS/PAM dramatically enhance photocatalytic activity. The electron cloud of nitrogen atom can attract holes and repel photogenerated electrons, which lowers the carrier recombination probability. The results also reveal that the excellent hydrophilicity of hydrogel plays an important role in the inhibition of photocorrosion. In addition, CdS/PAM is easily recycled and processed. The present work will pave a good way for the application of smart hydrogels in the field of photocatalytic hydrogen production. [Figure not available: see fulltext.

Enhanced visible light photocatalytic H2-production of g-C3N4/WS2 composite heterostructures

NASA Astrophysics Data System (ADS)

Akple, Maxwell Selase; Low, Jingxiang; Wageh, S.; Al-Ghamdi, Ahmed. A.; Yu, Jiaguo; Zhang, Jun

2015-12-01

As a clean and renewable solar H2-production system to address the increasing global environmental crisis and energy demand, photocatalytic hydrogen production from water splitting using earth abundant materials has received a lot of attention. In this study, WS2-graphitic carbon nitride (g-C3N4) composites were prepared using WO3 and thiourea as precursors through a gas-solid reaction. Different amount of WS2 were loaded on g-C3N4 to form the heterostructures and the composite samples exhibited enhanced photocatalytic activity for H2 production under visible light. The composite sample with 0.01 wt% WS2 exhibited the highest H2-production rate of 101 μmol g-1 h-1, which was even better than that of the Pt-C3N4 sample with the same loading content. The high photocatalytic activity was attributed to the formation of heterojunction between g-C3N4 and WS2 cocatalyst which allowed for effective separation of photogenerated charge carriers. This work showed the possibility for the utilization of low cost WS2 as an efficient cocatalyst to promote the photocatalytic H2 production of g-C3N4.

Enhanced visible light photocatalytic activity of copper-doped titanium oxide-zinc oxide heterojunction for methyl orange degradation

NASA Astrophysics Data System (ADS)

Dorraj, Masoumeh; Alizadeh, Mahdi; Sairi, Nor Asrina; Basirun, Wan Jefrey; Goh, Boon Tong; Woi, Pei Meng; Alias, Yatimah

2017-08-01

A novel Cu-doped TiO2 coupled with ZnO nanoparticles (Cu-TiO2/ZnO) was prepared by sol-gel method and subsequent precipitation for methyl orange (MO) photodegradation under visible light irradiation. The compositions and shapes of the as-prepared Cu-TiO2/ZnO nanocomposites were characterized by photoluminescence spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectra and Brunauer-Emmett-Teller adsorption isotherm techniques. The Cu-TiO2/ZnO nanocomposites showed considerably higher photocatalytic activity for MO removal from water under visible light irradiation than that of single-doped semiconductors. The effects of Cu-TiO2 and ZnO mass ratios on the photocatalytic reaction were also studied. A coupling percentage of 30% ZnO exhibited the highest photocatalytic activity. The enhanced photocatalytic activity of the Cu-TiO2/ZnO nanocomposites was mainly attributed to heterojunction formation, which allowed the efficient separation of photoinduced electron-hole pairs at the interface. Moreover, these novel nanocomposites could be recycled during MO degradation in a three-cycle experiment without evident deactivation, which is particularly important in environmental applications.

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts

NASA Astrophysics Data System (ADS)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu

2017-02-01

Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H2) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H2 evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu2MoS4 nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu2MoS4nanosheets. These layered Cu2MoS4 nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H2 production by water splitting. We have obtained superior H2 production rates by using Cu2MoS4 loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Apparatus for the investigation of high-temperature, high-pressure gas-phase heterogeneous catalytic and photo-catalytic materials.

PubMed

Alvino, Jason F; Bennett, Trystan; Kler, Rantej; Hudson, Rohan J; Aupoil, Julien; Nann, Thomas; Golovko, Vladimir B; Andersson, Gunther G; Metha, Gregory F

2017-05-01

A high-temperature, high-pressure, pulsed-gas sampling and detection system has been developed for testing new catalytic and photocatalytic materials for the production of solar fuels. The reactor is fitted with a sapphire window to allow the irradiation of photocatalytic samples from a lamp or solar simulator light source. The reactor has a volume of only 3.80 ml allowing for the investigation of very small quantities of a catalytic material, down to 1 mg. The stainless steel construction allows the cell to be heated to 350 °C and can withstand pressures up to 27 bar, limited only by the sapphire window. High-pressure sampling is made possible by a computer controlled pulsed valve that delivers precise gas flow, enabling catalytic reactions to be monitored across a wide range of pressures. A residual gas analyser mass spectrometer forms a part of the detection system, which is able to provide a rapid, real-time analysis of the gas composition within the photocatalytic reaction chamber. This apparatus is ideal for investigating a number of industrially relevant reactions including photocatalytic water splitting and CO 2 reduction. Initial catalytic results using Pt-doped and Ru nanoparticle-doped TiO 2 as benchmark experiments are presented.

Synthesis and photocatalytic performance of reduced graphene oxide-TiO2 nanocomposites for orange II degradation under UV light irradiation.

PubMed

Li, Tengfei; Wang, Tiecheng; Qu, Guangzhou; Liang, Dongli; Hu, Shibin

2017-05-01

To enhance the photocatalytic activity of TiO 2 , reduced graphene oxide-TiO 2 (RGO-TiO 2 ) composites with sandwich-like structure were synthesized using a simple solvothermal method. The morphology, crystalline information, and structural property of the photocatalyst were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transmission infrared spectroscopy. The photocatalytic performances of the RGO-TiO 2 composites were evaluated by the degradation of orange II (AO7) in water under UV light irradiation. The results showed that the RGO-TiO 2 composites exhibited much higher photocatalytic activity than TiO 2 and that the removal efficiency of AO7 could reach above 95% only after 20 min of UV light irradiation under the optimum condition. The improved photocatalytic activity might be attributed to the improved charge transfer and significant separation of the photoinduced electrons and holes in the presence of a two-dimensional graphene network. The results of recycling experiments show that RGO-TiO 2 composites have a high photostability, which is expected in the practical application. Radical trapping experiments indicated that ·OH plays a crucial role in the process of AO7 degradation.

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation.

PubMed

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-25

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H 2 evolution has been studied extensively. TiO 2 is a well-established semiconductor in the field of photocatalytic H 2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C 3 N 4 -modified TiO 2 nanobelts (TCN-Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K-g-C 3 N 4 and the TiO 2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C 3 N 4 , suggesting increased charge transfer efficiency. The H 2 production efficiency of the TCN-Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H 2 production activity was due to the superior charge separation and electron transfer efficiency of TCN-Kx composite materials.

Controllable one-pot synthesis of a nest-like Bi2WO6/BiVO4 composite with enhanced photocatalytic antifouling performance under visible light irradiation.

PubMed

Ju, Peng; Wang, Yi; Sun, Yan; Zhang, Dun

2016-03-21

In this study, a novel visible-light-sensitive Bi2WO6/BiVO4 composite photocatalyst was controllably synthesized through a facile one-pot hydrothermal method. The Bi2WO6/BiVO4 composite exhibited a perfect nest-like hierarchical microsphere structure, which was constructed by the self-assembly of nanoplates with the assistance of polyvinylpyrrolidone (PVP). The growth mechanism of the Bi2WO6/BiVO4 composite and the effect of its structure on its photocatalytic performance was investigated and proposed. Experimental results showed that the Bi2WO6/BiVO4 composites displayed enhanced photocatalytic antifouling activities under visible light irradiation compared to pure Bi2WO6 and BiVO4. Bi2WO6/BiVO4-1 exhibited the best photocatalytic antifouling performance, and almost all (99.99%) Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were killed within 30 min. Moreover, the Bi2WO6/BiVO4-1 composite exhibited excellent stability and reusability in the cycled experiments. The photocatalytic antifouling mechanism was proposed based on the active species trapping experiments, revealing that the photo-induced holes (h(+)) and hydroxyl radicals (˙OH) could attack the cell wall and cytoplasmic membrane directly and lead to the death of bacteria. The obviously enhanced photocatalytic activity of the Bi2WO6/BiVO4-1 composite could be mainly attributed to the formation of heterojunctions, accelerating the separation of photo-induced electrons and holes. Furthermore, the large BET surface area combined with the wide photoabsorption region further improved the photocatalytic performance of the Bi2WO6/BiVO4-1 composite. This study provides a new strategy to develop novel composite photocatalysts with enhanced photocatalytic performance for marine antifouling and water purification.

Proteobacteria become predominant during regrowth after water disinfection.

PubMed

Becerra-Castro, Cristina; Macedo, Gonçalo; Silva, Adrian M T; Manaia, Célia M; Nunes, Olga C

2016-12-15

Disinfection processes aim at reducing the number of viable cells through the generation of damages in different cellular structures and molecules. Since disinfection involves unspecific mechanisms, some microbial populations may be selected due to resilience to treatment and/or to high post-treatment fitness. In this study, the bacterial community composition of secondarily treated urban wastewater and of surface water collected in the intake area of a drinking water treatment plant was compared before and 3-days after disinfection with ultraviolet radiation, ozonation or photocatalytic ozonation. The aim was to assess the dynamics of the bacterial communities during regrowth after disinfection. In all the freshly collected samples, Proteobacteria and Bacteroidetes were the predominant phyla (40-50% and 20-30% of the reads, respectively). Surface water differed from wastewater mainly in the relative abundance of Actinobacteria (17% and <5% of the reads, respectively). After 3-days storage at light and room temperature, disinfected samples presented a shift of Gammaproteobacteria (from 8 to 10% to 33-65% of the reads) and Betaproteobacteria (from 14 to 20% to 31-37% of the reads), irrespective of the type of water and disinfection process used. Genera such as Pseudomonas, Acinetobacter or Rheinheimera presented a selective advantage after water disinfection. These variations were not observed in the non-disinfected controls. Given the ubiquity and genome plasticity of these bacteria, the results obtained suggest that disinfection processes may have implications on the microbiological quality of the disinfected water. Copyright © 2016 Elsevier B.V. All rights reserved.

Design improvement and performance evaluation of solar photocatalytic reactor for industrial effluent treatment.

PubMed

Nair, Ranjith G; Bharadwaj, P J; Samdarshi, S K

2016-12-01

This work reports the details of the design components and materials used in a linear compound parabolic trough reactor constructed with an aim to use the photocatalyst for solar photocatalytic applications. A compound parabolic trough reactor has been designed and engineered to exploit both UV and visible part of the solar irradiation. The developed compound parabolic trough reactor could receive almost 88% of UV radiation along with a major part of visible radiation. The performance of the reactor has been evaluated in terms of degradation of a probe pollutant using the parameters such as rate constant, residence time and photonic efficiency. An attempt has been made to assess the performance in different ranges of solar spectrum. Finally the developed reactor has been employed for the photocatalytic treatment of a paper mill effluent using Degussa P25 as the photocatalyst. The paper mill effluent collected from Nagaon paper mill, Assam, India has been treated under both batch mode and continuous mode using Degussa P25 photocatalyst under artificial and natural solar radiation, respectively. The photocatalytic degradation kinetics of the paper mill effluent has been determined using the reduction in total organic carbon (TOC) values of the effluent. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of pH on the microstructure of β-Ga2O3 and its enhanced photocatalytic activity for antibiotic degradation.

PubMed

Liu, Jin; Lu, Wei; Zhong, Qian; Wu, Hongzhang; Li, Yunlin; Li, Lili; Wang, Zhenling

2018-06-01

Semiconductor photocatalysis has become the focus of recent research on antibiotic treatment because it is a green and efficient technology. In this study, α-GaOOH with several novel microstructures has been synthesized at a low temperature and its subsequent thermal transformation. The influence of pH on the synthesis of α-GaOOH is studied, and the results indicate that pH played an important role in the microstructures of α-GaOOH and β-Ga 2 O 3 . All Ga 2 O 3 samples possess macro-mesoporous network structures and exhibits a remarkable photocatalytic activity for antibiotic degradation. The photoelectron chemical tests show that the separation efficiency of photogenerated charge carriers of Ga 2 O 3 -7.0 is higher than that of other Ga 2 O 3 . The enhanced photocatalytic activity of Ga 2 O 3 -7.0 is mainly ascribed to its morphology and oxygen vacancy. The active species trapping and photoluminescence measurement experiments indicate that OH and O 2 - are the major active species contributing to the photocatalytic process. This study will bring about the potential application in treatment of the antibiotic pollutants. Copyright © 2018 Elsevier Inc. All rights reserved.

Visible-light-driven photocatalytic activation of peroxymonosulfate by Cu2(OH)PO4 for effective decontamination.

PubMed

Liu, Guoshuai; Zhou, Yanan; Teng, Jie; Zhang, Jinna; You, Shijie

2018-06-01

The advanced oxidation process (AOP) based on SO 4 - radicals draws an increasing interest in water and wastewater treatment. Producing SO 4 - radicals from the activation of peroxymonosulfate (PMS) by transition metal ions or oxides may be problematic due to high operational cost and potential secondary pollution caused by metal leaching. To address this challenge, the present study reports the efficient production of SO 4 - radicals through visible-light-driven photocatalytic activation (VL-PCA) of PMS by using Cu 2 (OH)PO 4 single crystal for enhanced degradation of a typical recalcitrant organic pollutant, i.e., 2,4-dichlorophenol (2,4-DCP). It took only 7 min to achieve almost 100% removal of 2,4-DCP in the Cu 2 (OH)PO 4 /PMS system under visible-light irradiation and pH-neutral condition. The 2,4-DCP degradation was positively correlated to the amount of Cu 2 (OH)PO 4 and PMS. Both OH and SO 4 - radicals were responsible for enhanced degradation performance, indicated by radical scavenger experiments and electron spin resonance (ESR) measurements. The Cu 2 (OH)PO 4 single crystal exhibited good cyclic stability and negligible metal leaching. According to density functional theory (DFT) calculations, the visible-light-driven transformation of two copper states between trigonal bipyramidal sites and octahedral sites in the crystal structure of Cu 2 (OH)PO 4 facilitates the generation of OH and SO 4 - radicals from the activation of PMS and cleavage of O-O bonds. This study provides the proof-in-concept demonstration of activation of PMS driven by visible light, making the SO 4 - radicals-based AOPs much easier, more economical and more sustainable in engineering applications for water and wastewater treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Hierarchically nanostructured materials for sustainable environmental applications

PubMed Central

Ren, Zheng; Guo, Yanbing; Liu, Cai-Hong; Gao, Pu-Xian

2013-01-01

This review presents a comprehensive overview of the hierarchical nanostructured materials with either geometry or composition complexity in environmental applications. The hierarchical nanostructures offer advantages of high surface area, synergistic interactions, and multiple functionalities toward water remediation, biosensing, environmental gas sensing and monitoring as well as catalytic gas treatment. Recent advances in synthetic strategies for various hierarchical morphologies such as hollow spheres and urchin-shaped architectures have been reviewed. In addition to the chemical synthesis, the physical mechanisms associated with the materials design and device fabrication have been discussed for each specific application. The development and application of hierarchical complex perovskite oxide nanostructures have also been introduced in photocatalytic water remediation, gas sensing, and catalytic converter. Hierarchical nanostructures will open up many possibilities for materials design and device fabrication in environmental chemistry and technology. PMID:24790946

Hierarchically Nanostructured Materials for Sustainable Environmental Applications

NASA Astrophysics Data System (ADS)

Ren, Zheng; Guo, Yanbing; Liu, Cai-Hong; Gao, Pu-Xian

2013-11-01

This article presents a comprehensive overview of the hierarchical nanostructured materials with either geometry or composition complexity in environmental applications. The hierarchical nanostructures offer advantages of high surface area, synergistic interactions and multiple functionalities towards water remediation, environmental gas sensing and monitoring as well as catalytic gas treatment. Recent advances in synthetic strategies for various hierarchical morphologies such as hollow spheres and urchin-shaped architectures have been reviewed. In addition to the chemical synthesis, the physical mechanisms associated with the materials design and device fabrication have been discussed for each specific application. The development and application of hierarchical complex perovskite oxide nanostructures have also been introduced in photocatalytic water remediation, gas sensing and catalytic converter. Hierarchical nanostructures will open up many possibilities for materials design and device fabrication in environmental chemistry and technology.

Sonochemical synthesis of porous NiTiO3 nanorods for photocatalytic degradation of ceftiofur sodium.

PubMed

Pugazhenthiran, N; Kaviyarasan, K; Sivasankar, T; Emeline, A; Bahnemann, D; Mangalaraja, R V; Anandan, S

2017-03-01

Porous NiTiO 3 nanorods were synthesized through the sonochemical route followed by calcination at various temperature conditions. Surface morphology of the samples was tuned by varying the heat treatment temperature from 100 to 600°C. The synthesized NiTiO 3 nanorods were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, diffused reflectance spectroscopy, photoluminescence spectroscopy and Brunauer-Emmett-Teller (BET) analyses. The characterization studies revealed that the NiTiO 3 nanomaterial was tuned to porous and perfectly rod shaped structure during the heat treatment at 600°C. The porous NiTiO 3 nanorods showed visible optical response and thus can be utilized in the photocatalytic degradation of ceftiofur sodium (CFS) under direct sunlight. The photoluminescence intensity of the porous NiTiO 3 nanorods formed while heating at 600°C was lower than that of the as-synthesized NiTiO 3 sample owing to the photogenerated electrons delocalization along the one dimensional nanorods and this delocalization resulted in the reduction of the electron-hole recombination rate. The photocatalytic degradation of ceftiofur sodium (CFS) was carried out using NiTiO 3 nanorods under the direct sunlight irradiation and their intermediate products were analysed through HPLC to deduce the possible degradation mechanism. The porous NiTiO 3 nanorods exhibited an excellent photocatalytic activity towards the CFS degradation and further, the photocatalytic activity was increased by the addition of peroxomonosulfate owing to the simultaneous generation of both OH and SO 4 - . Copyright © 2016 Elsevier B.V. All rights reserved.

Insight into synergistically enhanced adsorption and visible light photocatalytic performance of Z-scheme heterojunction of SrTiO3(La,Cr)-decorated WO3 nanosheets

NASA Astrophysics Data System (ADS)

Liu, Xin; Jiang, Junzhe; Jia, Yushuai; Qiu, Jinmin; Xia, Tonglin; Zhang, Yuhong; Li, Yuqin; Chen, Xiangshu

2017-08-01

The efficient treatment of dye wastewater has been a hot topic of environment field. The integration of adsorption and photocatalytic degradation via fabrication of bi-component heterojunction photocatalyst is considered as a facile and effective strategy to enhance the dye elimination efficiency. In this report, a Z-scheme heterojunction material, SrTiO3(La,Cr)/WO3 with bifunction of adsorption and photocatalysis was successfully synthesized for efficient removal of methylene blue (MB) under visible light irradiation. The morphology and microstructure characterization demonstrates that the SrTiO3(La,Cr) nanoparticles are uniformly decorated on the WO3 nanosheets, forming an intimate heterojunction interface. MB degradation results indicate that the removal efficiency by the synergistic adsorption-photocatalysis process is greatly improved compared to pure WO3 and SrTiO3(La,Cr) with the adsorption and photocatalytic activity closely related to the composition of the material. The possible mechanism for the enhanced photocatalytic activity could be ascribed to the formation of a Z-scheme heterojunction system based on active species trapping experiments. Furthermore, the investigations of adsorption kinetics and isotherm show that the adsorption process follows pseudo-second-order kinetic model and Langmuir isotherm, respectively. Due to the synergistic advantages of negative zeta potential, large surface area and accelerated separation of photogenerated carriers driven by Z-scheme heterojunction, SrTiO3(La,Cr)/WO3 exhibits excellent adsorption-photocatalytic performance and stability on MB removal, which could be potentially used for practical wastewater treatment.

Polyethylene imine-grafted ACF@BiOI0.5Cl0.5 as a recyclable photocatalyst for high-efficient dye removal by adsorption-combined degradation

NASA Astrophysics Data System (ADS)

Li, Hongyan; Li, Najun; Chen, Dongyun; Xu, Qingfeng; Lu, Jianmei

2017-05-01

A recyclable photocatalyst with adsorption property was prepared for high-efficient complete removal of anionic dyes from water by synergetic adsorption and photocatalytic degradation. Firstly, binary bismuth oxyhalide composed as BiOI0.5Cl0.5 was immobilized on activated carbon fibers (ACF) to get a recyclable photocatalyst (ACF@BiOI0.5Cl0.5) via one-step solvothermal method. Then it was modified with branched polyethylene imine (PEI) whose abundant amino groups can adsorb contaminants from water by electrostatic interaction. SEM images showed that the nanosheets-based flower-like photocatalytic microspheres uniformly distributed on the ACF surface after grafting of small amount of PEI. But from TGA results we can deduce that the percentage of PEI grafted onto ACF@BiOI0.5Cl0.5 is about 18 wt%. During the synergistic process, the grafted PEI and immobilized BiOI0.5Cl0.5 are worked as the adsorbent and the photocatalyst, respectively. In addition, ACF, as flexible, conductive and corrosion-resistant supports, are beneficial to the photocatalytic degradation process. So the obtained composite PEI-g-ACF@BiOI0.5Cl0.5 has a high removal efficiency of contaminants under visible light irradiation with the synergistic effect of adsorption and photocatalytic degradation. And after facial separation without centrifuge, it can be reused without regeneration because of the real-time complete degradation of the adsorbed contaminants on the surface of the composite photocatalyst.

Structure of a model TiO2 photocatalytic interface

NASA Astrophysics Data System (ADS)

Hussain, H.; Tocci, G.; Woolcot, T.; Torrelles, X.; Pang, C. L.; Humphrey, D. S.; Yim, C. M.; Grinter, D. C.; Cabailh, G.; Bikondoa, O.; Lindsay, R.; Zegenhagen, J.; Michaelides, A.; Thornton, G.

2017-04-01

The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis.

Structure of a model TiO2 photocatalytic interface.

PubMed

Hussain, H; Tocci, G; Woolcot, T; Torrelles, X; Pang, C L; Humphrey, D S; Yim, C M; Grinter, D C; Cabailh, G; Bikondoa, O; Lindsay, R; Zegenhagen, J; Michaelides, A; Thornton, G

2017-04-01

The interaction of water with TiO 2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO 2 (110) interface with water. This has provided an atomic-level understanding of the water-TiO 2 interaction. However, nearly all of the previous studies of water/TiO 2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO 2 (110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O 2 and H 2 O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO 2 photocatalysis.

Graphene-Based Photocatalysts for Solar-Fuel Generation.

PubMed

Xiang, Quanjun; Cheng, Bei; Yu, Jiaguo

2015-09-21

The production of solar fuel through photocatalytic water splitting and CO2 reduction using photocatalysts has attracted considerable attention owing to the global energy shortage and growing environmental problems. During the past few years, many studies have demonstrated that graphene can markedly enhance the efficiency of photocatalysts for solar-fuel generation because of its unique 2D conjugated structure and electronic properties. Herein we summarize the recent advances in the application of graphene-based photocatalysts for solar-fuel production, including CO2 reduction to hydrocarbon fuel and water splitting to H2. A brief overview of the fundamental principles for splitting of water and reduction of CO2 is given. The different roles of graphene in these graphene-based photocatalysts for improving photocatalytic performance are discussed. Finally, the perspectives on the challenges and opportunities for future research in this promising area are also presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imidazolium-Based Ionic Liquids in Water: Assessment of Photocatalytic and Photochemical Transformation.

PubMed

Calza, Paola; Vione, Davide; Fabbri, Debora; Aigotti, Riccardo; Medana, Claudio

2015-09-15

The photoinduced transformation of two ionic liquids, 1-methylimidazolium hydrogensulfate (HMIM) and 1-ethyl-3-methylimidazolium hydrogensulfate (EMIM), was investigated under photocatalytic conditions in the presence of irradiated TiO2. We monitored substrate disappearance, transformation products (TPs), degree of mineralization, and toxicity of the irradiated systems. Acute toxicity measures suggested in both cases the occurrence of more toxic TPs than the parent molecules. A total of five TPs were detected by HPLC-HRMS from HMIM and nine from EMIM. Complete mineralization and stoichiometric release of nitrogen was achieved for both compounds within 4 h of irradiation. The photochemical transformation kinetics and pathways in surface waters (direct photolysis and indirect photoreactions) were studied for EMIM, to assess its persistence in sunlit water bodies such as rivers or lakes. Environmental phototransformation would be dominated by direct photolysis, with half-life times of up to one month under fine-weather conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

García, Abraham; Cotto, María; Duconge, José

The use of hydrogen as replacement for fossil fuels, on which we depend today, is a matter of great relevance. The sustainable generation of hydrogen as fuel is relevant from an environmental and economic point of view. In this study we have explored new synthetic routes for developing new photocatalysts to be used in water splitting, for hydrogen production. Different techniques have been used to produce hydrogen, such as electrolysis, even though these processes have been found to be energetically non suitable. In this research various photocatalytic materials were presented as possible alternatives for using in water splitting processes. Characterizationmore » of the new synthesized materials has been done by using different experimental techniques including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), surface area BET, and X-ray Diffraction (XRD). The efficiency of the synthesized photocatalysts was determined by evaluating the hydrogen evolution by the photocatalytic water splitting reaction.« less

Effect of the chloride ion as a hole scavenger on the photocatalytic conversion of CO2 in an aqueous solution over Ni-Al layered double hydroxides.

PubMed

Iguchi, Shoji; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

2015-07-21

The photocatalytic conversion of CO2 into useful chemical compounds in water without using organic sacrificial reagents is a promising method to overcome environmental and energy problems. Various synthesized layered double hydroxides (LDHs) are capable of reducing CO2 to CO in an aqueous solution under UV light irradiation. However, it is difficult to oxidize H2O to O2 in a photocatalytic system using LDHs as photocatalysts. In this study, we investigated the photocatalytic conversion of CO2 using a Ni-Al LDH in an aqueous solution of NaCl. Hypochlorous acid (HClO) was produced as an oxidation product of Cl(-) with the formation of reduction products such as CO and H2 under photoirradiation. We propose the inclusion of Cl(-) in the reaction solution to be one of the most promising ways for obtaining a hole scavenger, an approach that would enable the construction of an artificial photosynthesis system for the conversion of CO2.

Simple hydrothermal synthesis of metal oxides coupled nanocomposites: Structural, optical, magnetic and photocatalytic studies

NASA Astrophysics Data System (ADS)

Ganeshraja, Ayyakannu Sundaram; Clara, Antoni Samy; Rajkumar, Kanniah; Wang, Yanjie; Wang, Yu; Wang, Junhu; Anbalagan, Krishnamoorthy

2015-10-01

The present article is focused on recent developments toward the preparation of room temperature ferromagnetic nanocomposites using better photocatalytic performance. These nanocomposites were successfully prepared by a simple hydrothermal method and their molecular formulas were confirmed as Ti0.90Sn0.10O2 (S1), 0.2CuO-Ti0.73Sn0.06Cu0.21O2-δ (S2), and Ti0.82Sn0.09Fe0.09O2-δ (S3). The ICP, XRD, DRS, FTIR, Raman, XAFS, XPS, EPR, SEM-EDX, HRSEM, HRTEM, photoluminescence and vibrating sample magnetometric measurements were employed to characterize the phase structures, morphologies, optical and magnetic properties of the photocatalysts. The local structures of Sn4+ and Fe3+ were confirmed by 119Sn and 57Fe Mössbauer analysis. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in water under visible light irradiation. Among the samples, tin doped TiO2 (S1) showed the best photocatalytic performance and stability.

Enhanced photocatalytic degradation of methylene blue by metal-modified silicon nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brahiti, N., E-mail: dihiabrahiti@yahoo.fr; Université Mouloud MAMMERI de TiziOuzou, Département de Physique, Bastos; Hadjersi, T., E-mail: hadjersi@gmx.com

2015-02-15

Highlights: • SiNWs modified with Pd, Au and Pt were used as photocatalysts to degrade MB. • Yield of photodegardation increases with UV irradiation time. • SiNWs modified with Pd nanoparticles show the best photocatalytic activity. • A degradation of 97% was obtained after 200 min of UV irradiation. - Abstract: Silicon nanowires (SiNWs) modified with Au, Pt and Pd nanoparticles were used as heterogeneous photocatalysts for the photodegradation of methylene blue in water under UV light irradiation. The modification of SiNWs was carried out by deposition of metal nanoparticles using the electroless metal deposition (EMD) technique. The effect ofmore » metal nanoparticles deposition time on the photocatalytic activity was studied. It was found that the photocatalytic activity of modified SiNWs was enhanced when the deposition time of metal nanoparticles was increased. In addition of modified SiNWs with Pt, Au and Pd nanoparticles, oxidized silicon substrate (Ox-Si), oxidized silicon nanowires (Ox-SiNWs) and hydrogen-terminated silicon nanowires (H-SiNWs) were also evaluated for the photodegradation of methylene blue.« less

Kinetic study of photocatalytic degradation of carbamazepine, clofibric acid, iomeprol and iopromide assisted by different TiO2 materials--determination of intermediates and reaction pathways.

PubMed

Doll, Tusnelda E; Frimmel, Fritz H

2004-02-01

The light-induced degradation of clofibric acid, carbamazepine, iomeprol and iopromide under simulated solar irradiation has been investigated in aqueous solutions suspended with different TiO2 materials (P25 and Hombikat UV100). Kinetic studies showed that P25 had a better photocatalytic activity for clofibric acid and carbamazepine than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. The results can be explained by the higher adsorption capacity of Hombikat UV100 for iomeprol. The study also focuses on the identification and quantification of possible degradation products. The degradation process was monitored by determination of sum parameters and inorganic ions. In case of clofibric acid various aromatic and aliphatic degradation products have been identified and quantified. A possible multi-step degradation scheme for clofibric acid is proposed. This study proves the high potential of the photocatalytic oxidation process to transform and mineralize environmentally relevant pharmaceuticals and contrast media in water.

Highly Efficient Light-Driven TiO2-Au Janus Micromotors.

PubMed

Dong, Renfeng; Zhang, Qilu; Gao, Wei; Pei, Allen; Ren, Biye

2016-01-26

A highly efficient light-driven photocatalytic TiO2-Au Janus micromotor with wireless steering and velocity control is described. Unlike chemically propelled micromotors which commonly require the addition of surfactants or toxic chemical fuels, the fuel-free Janus micromotor (diameter ∼1.0 μm) can be powered in pure water under an extremely low ultraviolet light intensity (2.5 × 10(-3) W/cm(2)), and with 40 × 10(-3) W/cm(2), they can reach a high speed of 25 body length/s, which is comparable to common Pt-based chemically induced self-electrophoretic Janus micromotors. The photocatalytic propulsion can be switched on and off by incident light modulation. In addition, the speed of the photocatalytic TiO2-Au Janus micromotor can be accelerated by increasing the light intensity or by adding low concentrations of chemical fuel H2O2 (i.e., 0.1%). The attractive fuel-free propulsion performance, fast movement triggering response, low light energy requirement, and precise motion control of the TiO2-Au Janus photocatalytic micromotor hold considerable promise for diverse practical applications.

Facile approach to synthesis the curly leaf-like Nano-sheets of g-C3N4 with enhanced photocatalytic ability

NASA Astrophysics Data System (ADS)

Zhao, Zhiren; Li, Kebin; Muhmood, Tahir; Xia, Mingzhu; Wang, Fengyun

2018-03-01

Exfoliation of porous g-C3N4 has been proved a very effective way to prepare g-C3N4 nanosheets (2D layered materials). Here, we present an environment-friendly, high-efficiency and easy scale-up preparation method of curly leaf-like g-C3N4 nanosheets (CL-CN) by liquid-phase exfoliation of honeycomb-like porous g-C3N4 (HP-CN). Two-dimensional curly nanosheets have induced excellent physicochemical properties, i.e. large surface area, high fluorescence quantum efficiency, wide band gap and good water-dispersibility. The photocatalytic performance of CL-CN in degradation of RhB under visible light is much better than that of honeycomb-like porous g-C3N4 and bulk g-C3N4. The improved photocatalytic performance of CL-CN is well explained by the improved physicochemical properties and photocatalytic mechanism. In addition, CL-CN being a 2D layered material with excellent photoluminescence characteristic and non-toxic behavior can be widely applied in bio-medicine, bio-imaging and biosensors field.

Reduced graphene oxide-CdS nanocomposite with enhanced photocatalytic 4-Nitrophenol degradation

NASA Astrophysics Data System (ADS)

Chakraborty, Koushik; Ibrahim, Sk; Das, Poulomi; Ghosh, Surajit; Pal, Tanusri

2017-05-01

We report the photocatalytic activity of reduced graphene oxide cadmium sulfide (RGO-CdS) composite towards the degradation of 4-Nitrophenol (4-NP) under simulated solar light illumination. The solution processable RGO-CdS composite was synthesized by one pot single step low cost solvothermal process, where the reduction of graphene oxide (GO), synthesis and attachment of CdS onto RGO sheets were done simultaneously. The structural and morphological characterization of the RGO-CdS composite and the reduction of GO was confirmed by X-ray diffractometry, TEM imaging and Fourier transform infrared spectroscopy respectively. The photocatalytic efficiency of RGO-CdS composite is 2.6 times higher in compare to controlled CdS. In RGO-CdS composite the photo induced electrons transfer from CdS nanorod to RGO sheets, which reduces the recombination probability of photo generated electron-hole in the CdS. These well separated photoinduced charges enhanced the photocatalytic activity of the RGO-CdS composite. Our study establishes the RGO-CdS composite as a potential photocatalyst for the degradation of organic water pollutant.

New ZnO@Cardanol Porphyrin Composite Nanomaterials with Enhanced Photocatalytic Capability under Solar Light Irradiation

PubMed Central

Ribeiro, Viviane Gomes Pereira; Marcelo, Ana Maria Pereira; da Silva, Kássia Teixeira; da Silva, Fernando Luiz Firmino; Mota, João Paulo Ferreira; do Nascimento, João Paulo Costa; Sombra, Antonio Sérgio Bezerra; Clemente, Claudenilson da Silva; Mazzetto, Selma Elaine

2017-01-01

This work describes the synthesis, characterization, and photocatalytic activity of new composite nanomaterials based on ZnO nanostructures impregnated by lipophlilic porphyrins derived from cashew nut shell liquid (CNSL). The obtained nanomaterials were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and steady-state photoluminescence spectra (PL). The results confirm nanostructures showing average diameter of 55 nm and an improved absorption in the visible region. Further, the FTIR analysis proved the existence of non-covalent interactions between the porphyrin molecules and ZnO. The photocatalytic activity of prepared photocatalysts was investigated by degradation of rhodamine B (RhB) in aqueous solution under visible light irradiation and natural sunlight. It was demonstrated that the photocatalytic activity increases in the presence of the porphyrins and, also, depends on the irradiation source. The development of composite photocatalysts based on porphyrins derived from CNSL provides an alternative approach to eliminate efficiently toxic wastes from water under ambient conditions. PMID:28934117

Bi2O3 cocatalyst improving photocatalytic hydrogen evolution performance of TiO2

NASA Astrophysics Data System (ADS)

Xu, Difa; Hai, Yang; Zhang, Xiangchao; Zhang, Shiying; He, Rongan

2017-04-01

Photocatalytic hydrogen production using water splitting is of potential importance from the viewpoint of renewable energy development. Herein, Bi2O3-TiO2 composite photocatalysts presented as Bi-Bi2O3-anatase-rutile TiO2 multijunction were first fabricated by a simple impregnation-calcination method using Bi2O3 as H2-production cocatalysts. The obtained multijunction samples exhibit an obvious enhancement in photocatalytic H2 evolution activity in the presence of glycerol. The effect of Bi2O3 amount on H2-evolution activity of TiO2 was investigated and the optimal Bi2O3 content was found to be 0.89 mol%, achieving a H2-production rate of 920 μmol h-1, exceeding that of pure TiO2 by more than 73 times. The enhanced mechanism of photocatalytic H2-evolution activity is proposed. This study will provide new insight into the design and fabrication of TiO2-based hydrogen-production photocatalysts using low-cost Bi2O3 as cocatalyst.

Copper(II) imidazolate frameworks as highly efficient photocatalysts for reduction of CO{sub 2} into methanol under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jingtian; Luo, Deliang; Yang, Chengju

2013-07-15

Three copper(II) imidazolate frameworks were synthesized by a hydrothermal (or precipitation) reaction. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectra (FTIR), thermogravimetry (TG). Meanwhile, the photocatalytic activities of the samples for reduction of CO{sub 2} into methanol and degradation of methylene blue (MB) under visible light irradiation were also investigated. The results show that the as-prepared samples exhibit better photocatalytic activities for the reduction of carbon dioxide into methanol with water and degradation of MB under visible light irradiation. The orthorhombic copper(II) imidazolate frameworks with a bandmore » gap of 2.49 eV and green (G) color has the best photocatalytic activity for reduction of CO{sub 2} into methanol, 1712.7 μmol/g over 5 h, which is about three times as large as that of monoclinic copper(II) imidazolate frameworks with a band gap 2.70 eV and blue (J) color. The degradation kinetics of MB over three photocatalysts fitted well to the apparent first-order rate equation and the apparent rate constants for the degradation of MB over G, J and P (with pink color) are 0.0038, 0.0013 and 0.0016 min{sup −1}, respectively. The synergistic effects of smallest band gap and orthorhombic crystal phase structure are the critical factors for the better photocatalytic activities of G. Moreover, three frameworks can also be stable up to 250 °C. The investigation of Cu-based zeolitic imidazolate frameworks maybe provide a design strategy for a new class of photocatalysts applied in degradation of contaminations, reduction of CO{sub 2}, and even water splitting into hydrogen and oxygen under visible light. - Graphical abstract: Carbon dioxide was reduced into methanol with water over copper(II) imidazolate frameworks under visible light irradiation. - Highlights: • Three copper(II) imidazolate frameworks were first applied in the photo-reduction of CO{sub 2}. • The photocatalytic activities of the frameworks depend on their band gap and phase structures. • The photocatalytic activity of orthorhombic frameworks is 3 times that of monoclinic frameworks. • The degradation kinetics of MB over three photocatalysts followed the first-order rate equation. • The largest yield for reduction of CO{sub 2} into methanol on green framworks was 1712.7 μmol/g over 5 h.« less

Titanium dioxide/UV photocatalytic disinfection in fresh carrots.

PubMed

Cho, Mihee; Choi, Yoonjung; Park, Hyojin; Kim, Kwansik; Woo, Gun-Jo; Park, Jiyong

2007-01-01

Increased occurrences of fresh produce-related outbreaks of foodborne illness have focused attention on effective washing processes for fruits and vegetables. A titanium dioxide (TiO2) photocatalytic reaction under UV radiation provides a high rate of disinfection. The photo-killing effects of TiO2 on bacteria in liquid cultures under experimental conditions have been widely studied. However, the disinfection effects of the TiO2 photocatalytic reaction on fresh vegetables during a washing process have not been evaluated. Our objectives were to design a pilot-scale TiO2/UV photocatalytic reactor for fresh carrots and to compare the bactericidal effects of the TiO2/UV reaction against bacteria in liquid media and on carrots. TiO2/UV photocatalytic reactions for 40, 60, and 30 s were required for the complete killing of Escherichia coli, Salmonella Typhimurium, and Bacillus cereus (initial counts of approximately 6.7 log CFU/ml), respectively. The counts of total aerobic bacteria in fresh carrots and foodborne pathogenic bacteria in inoculated carrots were also measured. Counts of total aerobic bacteria were reduced by 1.8 log CFU/g after TiO2/UV photocatalytic disinfection for 20 min compared with a 1.1-log CFU/g reduction by UV alone. E. coli, Salmonella Typhimurium, and B. cereus (8 log CFU/ml) were inoculated onto carrots, and the number of surviving bacteria in carrots was determined after treatment. The TiO2/UV treatment exhibited 2.1-, 2.3-, and 1.8-log CFU/g reductions in the counts of E. coli, Salmonella Typhimurium, and B. cereus, respectively, compared with 1.3-, 1.2-, and 1.2-log CFU/g reductions by UV alone. The TiO2/UV photocatalyst reaction showed significant bactericidal effects, indicating that this process is applicable to nonthermal disinfection of fresh vegetables.

A hybrid regenerative water recovery system for lunar/Mars life support applications

NASA Technical Reports Server (NTRS)

Verostko, Charles E.; Edeen, Marybeth A.; Packham, Nigel J. C.

1992-01-01

Long-duration manned space missions will require integrated biological and physicochemical processes for recovery of resources from wastes. This paper discusses a hybrid regenerative biological and physicochemical water recovery system designed and built at NASA's Crew and Thermal Systems Division at Johnson Space Center. The system is sized for a four-person crew and consists of a two-stage, aerobic, trickling filter bioreactor; a reverse osmosis system; and a photocatalytic oxidation system. The system was designed to accommodate high organic and inorganic loadings and a low hydraulic loading. The bioreactor was designed to oxidize organics to carbon dioxide and water; the reverse osmosis system reduces inorganic content to potable quality; and the photocatalytic oxidation unit removes residual organic impurities (part per million range) and provides in situ disinfection. The design and performance of the hybrid system for producing potable/hygiene water is described. Aspects of the system such as closure, automation and integration are discussed and preliminary results presented.

Degradation and removal of Ceftriaxone sodium in aquatic environment with Bi2WO6/g-C3N4 photocatalyst.

PubMed

Zhao, Yanyan; Liang, Xuhua; Wang, Yongbo; Shi, Huanxian; Liu, Enzhou; Fan, Jun; Hu, Xiaoyun

2018-08-01

Modern chemistry aims to identify outstanding photocatalytic materials for antibiotic degradation given the overuse and misuse of antibiotics. Herein, highly efficient heterojunction photocatalysts composed of Bi 2 WO 6 nanoflowers (BW) and g-C 3 N 4 nanosheets (CNNs) were successfully synthesized. The Bi 2 WO 6 /g-C 3 N 4 (BW/CNNs) were presented for Ceftriaxone sodium degradation in the aquatic environment at low concentrations under visible light irradiation. The 40%-BW/CNNs showed excellent photocatalytic activity, and approximately 94.50% Ceftriaxone sodium was degraded under visible lightirradiation for 120 min. h + and O 2 - played major roles compared with ·OH in the photocatalytic process. The degradation mechanism and the intermediate products were proposed to better understand the reaction process. Moreover, the as-prepared photocatalysts were highly stable in recycling photocatalytic experiments. Therefore, the photocatalysts prepared in the study showed outstanding photocatalytic activity and potential applications in inhibiting environmental pollution. In addition, this work provides a new insight for constructing other high-performance, low-cost photocatalysts for wastewater treatment. Copyright © 2018 Elsevier Inc. All rights reserved.

Solvothermal fabrication and enhanced visible light photocatalytic activity of Cu2O-reduced graphene oxide composite microspheres for photodegradation of Rhodamine B

NASA Astrophysics Data System (ADS)

Sun, Lingling; Wang, Guohong; Hao, Ruirui; Han, Deyan; Cao, Sheng

2015-12-01

The addition of graphene oxide (GO) in the semiconductors has been regarded as one of the effective methods to enhance their photocatalytic activity. In this study, Cu2O-reduced graphene oxide (Cu2O-rGO) composites with low loading (0-0.5 wt.%) of graphene oxide (GO) were produced by a one-step green solvothermal method in ethanol system by using Cu(NO3)2·3H2O and glutamic acid as copper precursor and reducing agent, respectively. During the solvothermal treatment, GO was reduced to rGO. The as-prepared Cu2O-reduced graphene oxide composite microspheres exhibited enhanced photocatalytic activity toward the degradation of RhB aqueous solution under visible light irradiation. At the optimal loading of graphene oxide (0.05 wt.%), Cu2O-rGO composites showed the highest photocatalytic activity, exceeding that of pure Cu2O and commercial Degussa P25 by a factor of 2.9 and 7.9, respectively. The enhanced photocatalytic activity may be ascribed to the strong coupling interaction between Cu2O particles and rGO nanosheets, which reduces the recombination of charge carriers.

A mini-review on rare earth metal-doped TiO2 for photocatalytic remediation of wastewater.

PubMed

Saqib, Najm Us; Adnan, Rohana; Shah, Irfan

2016-08-01

Titanium dioxide (TiO2) has been considered a useful material for the treatment of wastewater due to its non-toxic character, chemical stability and excellent electrical and optical properties which contribute in its wide range of applications, particularly in environmental remediation technology. However, the wide band gap of TiO2 photocatalyst (anatase phase, 3.20 eV) limits its photocatalytic activity to the ultraviolet region of light. Besides that, the electron-hole pair recombination has been found to reduce the efficiency of the photocatalyst. To overcome these problems, tailoring of TiO2 surface with rare earth metals to improve its surface, optical and photocatalytic properties has been investigated by many researchers. The surface modifications with rare earth metals proved to enhance the efficiency of TiO2 photocatalyts by way of reducing the band gap by shifting the working wavelength to the visible region and inhibiting the anatase-to-rutile phase transformations. This review paper summarises the attempts on modification of TiO2 using rare earth metals describing their effect on the photocatalytic activities of the modified TiO2 photocatalyst.

Apparatus for photocatalytic treatment of liquids

NASA Technical Reports Server (NTRS)

Cooper, Gerald (Inventor); Ratcliff, Matthew A. (Inventor)

1992-01-01

Apparatus for decontaminating a contaminated fluid by using photocatalytic particles. The apparatus includes a reactor tank for holding a slurry of the contaminated fluid and the photocatalytic particles ultraviolet light irradiates the surface of the slurry, thereby activating the photocatalytic properties of the particles. Stirring blades for continuously agitate the irradiated fluid surface maintaining the particles in a suspended state within the fluid. A cross flow filter is used for separating the fluid from the semiconductor powder after the decomposition reaction is ended. The cross flow filter is occasionally back flushed to remove any caked semiconductor powder. The semiconductor powder may be recirculated back to the tank for reuse, or may be stored for future use. A series of reactor tanks may be used to gradually decompose a chemical in the fluid. The fluid may be pretreated to remove certain metal ions which interfere with the photocatalytic process. Such pretreatment may be accomplished by dispersing semiconductor particles within the fluid, which particles adsorb ions or photodeposit the metal as the free metal or its insoluble oxide or hydroxide, and then removing the semiconductor particles together with the adsorbed metal ions/oxides/hydroxide/free metal from the fluid.

Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

PubMed

Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

2013-07-01

Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

Environmentally Responsible Use of Nanomaterials for the Photocatalytic Reduction of Nitrate in Water

NASA Astrophysics Data System (ADS)

Doudrick, Kyle

Nitrate is the most prevalent water pollutant limiting the use of groundwater as a potable water source. The overarching goal of this dissertation was to leverage advances in nanotechnology to improve nitrate photocatalysis and transition treatment to the full-scale. The research objectives were to (1) examine commercial and synthesized photocatalysts, (2) determine the effect of water quality parameters (e.g., pH), (3) conduct responsible engineering by ensuring detection methods were in place for novel materials, and (4) develop a conceptual framework for designing nitrate-specific photocatalysts. The key issues for implementing photocatalysis for nitrate drinking water treatment were efficient nitrate removal at neutral pH and by-product selectivity toward nitrogen gases, rather than by-products that pose a human health concern (e.g., nitrite). Photocatalytic nitrate reduction was found to follow a series of proton-coupled electron transfers. The nitrate reduction rate was limited by the electron-hole recombination rate, and the addition of an electron donor (e.g., formate) was necessary to reduce the recombination rate and achieve efficient nitrate removal. Nano-sized photocatalysts with high surface areas mitigated the negative effects of competing aqueous anions. The key water quality parameter impacting by-product selectivity was pH. For pH < 4, the by-product selectivity was mostly N-gas with some NH4 +, but this shifted to NO2- above pH = 4, which suggests the need for proton localization to move beyond NO2 -. Co-catalysts that form a Schottky barrier, allowing for localization of electrons, were best for nitrate reduction. Silver was optimal in heterogeneous systems because of its ability to improve nitrate reduction activity and N-gas by-product selectivity, and graphene was optimal in two-electrode systems because of its ability to shuttle electrons to the working electrode. "Environmentally responsible use of nanomaterials" is to ensure that detection methods are in place for the nanomaterials tested. While methods exist for the metals and metal oxides examined, there are currently none for carbon nanotubes (CNTs) and graphene. Acknowledging that risk assessment encompasses dose-response and exposure, new analytical methods were developed for extracting and detecting CNTs and graphene in complex organic environmental (e.g., urban air) and biological matrices (e.g. rat lungs).

Evaluating the photo-catalytic application of Fenton's reagent augmented with TiO(2) and ZnO for the mineralization of an oil-water emulsion.

PubMed

Tony, Maha A; Zhao, Y Q; Purcell, P J; El-Sherbiny, M F

2009-04-01

In the present study, homogenous (photo-Fenton) and heterogeneous photo-assisted systems (Fenton/TiO(2)/UV, Fenton/ZnO/UV and Fenton/TiO(2)/UV/Air) were investigated for the treatment of a diesel-oil wastewater emulsion. The augmentation of the photo-Fenton process by heterogeneous TiO(2) increased the reaction rate, in terms of COD reduction efficiency from 61% to 71%. Furthermore, the COD removal efficiency was increased to 84% when air was bubbled through the reactants. However, if the Fenton/TiO(2) /UV/Air process is to be utilized as a treatment for this wastewater, the separation of the TiO(2) from the treated effluent would need further consideration.

Photocatalytic hydrogen production of the CdS/TiO2-WO3 ternary hybrid under visible light irradiation.

PubMed

Chen, Yi-Lin; Lo, Shang-Lien; Chang, Hsiang-Ling; Yeh, Hsiao-Mei; Sun, Liping; Oiu, Chunsheng

2016-01-01

An attractive and effective method for converting solar energy into clean and renewable hydrogen energy is photocatalytic water splitting over semiconductors. The study aimed at utilizing organic sacrificial agents in water, modeled by formic acid, in combination with visible light driven photocatalysts to produce hydrogen with high efficiencies. The photocatalytic hydrogen production of cadmium sulfide (CdS)/titanate nanotubes (TNTs) binary hybrid with specific CdS content was investigated. After visible light irradiation for 3 h, the hydrogen production rate of 25 wt% CdS/TNT achieved 179.35 μmol·h(-1). Thanks to the two-step process, CdS/TNTs-WO3 ternary hybrid can better promote the efficiency of water splitting compared with CdS/TNTs binary hybrid. The hydrogen production of 25 wt% CdS/TNTs-WO3 achieved 212.68 μmol·h(-1), under the same condition. Coating of platinum metal onto the WO3 could further promote the reaction. Results showed that 0.2 g 0.1 wt% Pt/WO3 + 0.2 g 25 wt% CdS/TNTs had the best hydrogen production rate of 428.43 μmol·h(-1). The resultant materials were well characterized by high-resolution transmission electron microscope, X-ray diffraction, scanning electron microscopy, and UV-Vis spectra.

Rapid disinfection of E-Coliform contaminated water using WO3 semiconductor catalyst by laser-induced photo-catalytic process.

PubMed

Gondal, Mohammed A; Khalil, Amjad

2008-04-01

Laser-induced photo-catalysis process using WO(3) semiconductor catalyst was applied for the study of disinfection effectiveness of E-coliform-contaminated water. For this purpose, wastewater polluted with E-coliform bacteria was exposed to 355 nm UV radiations generated by third harmonic of Nd: YAG laser in special glass cell with and without WO(3) catalyst. E-Coliform quantification was performed by direct plating method to obtain the efficiency of each disinfection treatment. The dependence of disinfection process on laser irradiation energy, amount of catalyst and duration of laser irradiation was also investigated. The disinfection with WO(3) was quite efficient inactivating E-coliforms. For inactivation of E-coliforms, less than 8 minutes' laser irradiation was required, so that, the treated water complies with the microbial standards for drinking water. This study opens the possibility of application of this simple method in rural areas of developing countries using solar radiation.

Solar photocatalytic treatment of synthetic municipal wastewater.

PubMed

Kositzi, M; Poulios, I; Malato, S; Caceres, J; Campos, A

2004-03-01

The photocatalytic organic content reduction of a selected synthetic municipal wastewater by the use of heterogeneous and homogeneous photocatalytic methods under solar irradiation has been studied at a pilot-plant scale at the Plataforma Solar de Almeria. In the case of heterogeneous photocatalysis the effect of catalysts and oxidants concentration on the decomposition degree of the wastewater was examined. By an accumulation energy of 50 kJL(-1) the synergetic effect of 0.2 gL(-1)TiO(2) P-25 with hydrogen peroxide (H(2)O(2)) and Na(2)S(2)O(8) leads to a 55% and 73% reduction of the initial organic carbon content, respectively. The photo-fenton process appears to be more efficient for this type of wastewater in comparison to the TiO(2)/oxidant system. An accumulation energy of 20 kJL(-1) leads to 80% reduction of the organic content. The presence of oxalate in the Fe(3+)/H(2)O(2) system leads to an additional improvement of the photocatalytic efficiency.

Synthesis and properties of Ag/ZnO/g-C3N4 ternary micro/nano composites by microwave-assisted method

NASA Astrophysics Data System (ADS)

Zhang, Zijie; Li, Xuexue; Chen, Haitao; Shao, Gang; Zhang, Rui; Lu, Hongxia

2018-01-01

Ag/ZnO/g-C3N4 ternary micro/nanocomposites, as novel visible-light-driven photocatalysts, were prepared by a simple and convenient microwave-assisted method. The resulting ternary structure micro/nano composites were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy and infrared radiation techniques to examine its phase structure, valence state, morphological, thermal and optical properties. Well crystallized Ag/ZnO/g-C3N4 ternary micro/nano composites were synthesized under microwave-radiation for 15 min with the output of 240 W. Further experiments indicated Ag(5.0mol%)/ZnO/g-C3N4 photocatalyst in degradation of methylene blue exhibited an outstanding photocatalytic activity and its reaction rate constant (k, 0.0084 min-1) is 7.5, 2.4 2.9 and 3.5 times higher than that of monolithic ZnO (k, 0.0011 min-1), ZnO/g-C3N4(k, 0.0035 min-1), Ag(5 mol%)/ZnO(k, 0.0029 min-1) and Ag(5mol%)/g-C3N4 (k, 0.0024 min-1) respectively. Finally, a possible photocatalytic mechanism of Ag/ZnO/g-C3N4 photocatalyst in degradation process was proposed. This work provides a feasible strategy to synthesize an efficient ZnO-based photocatalyst which combines structure and properties of different dimensional components and made this ternary system an exciting candidate for sunlight-driven photocatalytic water treatment.

MoS2 embedded TiO2 nanoparticles for concurrent role of adsorption and photocatalysis

NASA Astrophysics Data System (ADS)

Pal, Arnab; Jana, Tushar K.; Chatterjee, Kuntal

2018-04-01

In this work, MoS2 embedded TiO2 nanoparticles, synthesized through hydrothermal process, was successfully employed to remove organic pollutant dye like methylene blue(MB) through adsorption and as well as through photocatalysis under visible light irradiation. The system was characterized by structural and morphological study. The adsorption and photocatalytic study of MB were evaluated with different concentrations of dye in aqueous solution. This work brings the MoS2-TiO2 nanostructure as excellent adsorbent as well as efficient photocatalyst materials which can be used for organic dye removal towards waste-water treatment.

Status of research and development on photoelectrochemical hydrogen production in Korea

NASA Astrophysics Data System (ADS)

Kim, Jong Won; Lee, Jae S.; Baeg, Jin-Ook

2010-08-01

Conversion of solar energy into hydrogen is one of the most promising renewable energy technologies. Photocatalytic production of hydrogen from water, H2S and organic wastes using semiconductors is one of the potential strategies for converting the sunlight energy into chemical energy. Korea government paid great attention to the hydrogen economy and launched the HERC (Hydrogen Energy R&D Center) for supporting the R&D topics on hydrogen related technologies. The key issue for realizing the commercial application of solar water splitting hydrogen production technique is to find an efficient, stable and low-cost photocatalyst. Our research groups have continuously investigated to find oxide and composite photocatalysts for photoelectrochemical cell with high efficiency using computational design and synthesis method. But, fundamental research on semiconductor doping for band gap shifting and surface chemistry modification is still required. Various reaction media containing sacrificial agents should be developed to match with high activity photocatalysts to further improve the system efficiency. Water containing organic/inorganic waste and sea water are particularly suggested in the consideration that all these water sources are the most available water on the earth to the final commercial application of photocatalytic water splitting technique.

Construction of High Activity Titanium Dioxide Crystal Surface Heterostructures and Characterization of Its Basic Properties

NASA Astrophysics Data System (ADS)

Wang, Chunxiao; Li, DanQi; Shen, Tingting; Lu, Cheng; Sun, Jing; Wang, Xikui

2018-01-01

Heterogeneous photocatalytic materials, which combine the advantages of photocatalytic materials and heterojunction, have been developed rapidly in the field of environmental pollution control. In this paper, TiO2 surface heterojunction catalysts with different catalytic activity were prepared by controlling the amount of HF, and their XRD characterization was also carried out. In addition, the optimum amount of HF was determined by photocatalytic degradation of simulated dye wastewater by methylene blue solution. And the optimal amount of catalyst and the optimal pH reaction conditions for degradation experiments were used to screen the highly reactive titania surface heterojunction system and its optimum application conditions. It provides the possibility of application in the degradation of industrial wastewater and environmental treatment.

Pyrrole-regulated precipitation of titania nanorods on polymer fabrics for photocatalytic degradation of trace toluene in air

NASA Astrophysics Data System (ADS)

Gu, Yi-Jie; Wen, Wei; Xu, Yang; Wu, Jin-Ming

2018-03-01

When compared with nanoparticulate counterparts, TiO2 thin films with vertically aligned one-dimensional (1D) nanostructures exhibit enhanced photocatalytic activity because of the highly accessible surface area. The perpendicular of the 1D nanostructure reduces the charge migration path and hence the carrier recombination rate, which also contributes to the photocatalytic activity. Furthermore, TiO2 thin films on flexible substrates are more suitable to degrade pollutants in either water or air because of its easy recovery and free-bending shape. In this study, flexible polyethylene fabrics were firstly coated with a sol-gel nanoparticulate TiO2 seed layer. Quasi-aligned TiO2 nanorods were then precipitated homogeneously under an atmospheric pressure and a low temperature not exceeding 80 °C, using a peroxy-titanium complex precursor with the additive of pyrrole. It is found that the density of TiO2 nanorods increased with the increasing amount of pyrrole monomers. The resultant TiO2 film on polyethylene fabrics exhibited a much reduced band gap of ca. 2.86 eV, which can be attributed to the surface oxygen deficiencies. When utilized to assist photocatalytic degradation of trace toluene in air under the UV light illumination, the TiO2 film exhibited a gradually increased photocatalytic activity upon the increasing cycles for up to six, because of the gradual removal of trace organics on the TiO2 surface. The highest photocatalytic efficiency is recorded to be 5 times that of TiO2 nanotube arrays, which are regarded as an excellent photocatalyst for air cleaning.

Enhancing the surface properties of the immobilized Degussa P-25 TiO2 for the efficient photocatalytic removal of methylene blue from aqueous solution

NASA Astrophysics Data System (ADS)

Nawi, M. A.; Zain, Salmiah Md.

2012-06-01

A method has been developed for enhancing the surface properties of immobilized Degussa P-25 TiO2 nanoparticles on glass plate supports with excellent photocatalytic activity. The immobilization technique utilized a dip-coating method involving a coating solution containing Degussa P-25 TiO2 particles, epoxidized natural rubber (ENR-50) and poly vinyl chloride (PVC) in a mixture of toluene and dichloromethane. The optimum ratio of ENR/PVC blend was found to be 1:2. Immobilization process of the composite appeared to reduce the specific surface area by at least half of the pristine P-25 TiO2 particles. However, a systematic removal of ENR-50 additive via a 5 h photocatalytic process enabled the immobilized photocatalyst (P-25TiO2/ENR/PVC/5 h) to regenerate the surface area to within 86% of the pristine P-25 TiO2 particles, produce bigger pore volume and smaller particle size. The enhanced surface properties of the immobilized P-25/ENR/PVC/5 h photocatalyst system generated a photocatalytic performance as good as the slurry method of the P-25 TiO2 nanoparticles for the photocatalytic degradation of MB dye in aqueous solution. The immobilized P-25TiO2/ENR/PVC/5 h catalyst plate was also found to be highly reusable up to at least 10 runs without losing its photocatalytic efficiency. Above all, the system could avoid tedious filtration step of the treated water as normally observed with the aqueous slurry system.

Zr doped anatase supported reticulated ceramic foams for photocatalytic water purification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plesch, G., E-mail: plesch@fns.uniba.sk; Vargová, M.; Vogt, U.F.

2012-07-15

Highlights: ► Thick photocatalytic anatase films on macroporous reticulated ceramic foams. ► Alumina and alumina–mullite macroporous reticulated foams as photocatalyst support. ► Zr doping significantly improves the TiO{sub 2} film activity in phenol photomineralization. ► Comparison of photocatalytic activity of thick films and powder suspensions. -- Abstract: Titanium dioxide films were deposited on macroporous reticulated Al{sub 2}O{sub 3} and alumina–mullite foams with pore sizes of 15 ppi (pores per inch). Coatings were prepared from suspensions of precursor powders of Aeroxide{sup ®} P25 nanopowder and precipitated TiO{sub 2} by using a dip coating process. The TiO{sub 2} forms films with amore » thickness of ∼2–20 μm. The photocatalytic activity was characterized as the mineralization rate of an aqueous phenol solution under UVA irradiation by the TOC technique. Precipitated TiO{sub 2} films have nearly the same photocatalytic activity as a titania suspension, in which powder aggregates have a size comparable with the thickness of the films. Samples made of Aeroxide{sup ®} P25 nanopowder, in which the size of aggregates is ∼0.1 μm show higher efficiency of photodecomposition in suspensions with films. The doping of precipitated anatase with Zr(IV) in the atomic ratio Zr/Ti = 0.008 significantly improves the photocatalytic activity of the foam supported titania. Zr doped anatase films show better performance as the films prepared only from Aeroxide{sup ®} P25 nanopowder.« less

Photocatalytic enhancement of cesium removal by Prussian blue-deposited TiO2.

PubMed

Kim, Hyuncheol; Kim, Minsun; Kim, Wooyul; Lee, Wanno; Kim, Soonhyun

2018-06-19

After the Fukushima nuclear accident, tremendous efforts were made to treat radiocesium, radiostrontium, and other radioactive materials. For the first time, we demonstrate that a TiO 2 photocatalyst can significantly enhance Cs adsorption by Prussian blue-deposited TiO 2 (PB/TiO 2 ) under UV irradiation. In this study, we synthesized PB/TiO 2 using the photodeposition method. After the Cs ions were adsorbed on the PB/TiO 2 in darkness, we then exposed the PB/TiO 2 to UV light irradiation. This resulted in a further increase in Cs ion adsorption of more than 10 times the amount adsorbed in darkness. This photocatalytic-enhanced adsorption of Cs ions was not observed on PB mixed with SiO 2 , nor under visible light irradiation. We investigated the effects of PB concentration, PB/TiO 2 concentration, and gas purging on both dark and photocatalytic-enhanced adsorption of Cs ions by PB/TiO 2 . Based on the results, we suggest that the photocatalytic-enhanced adsorption of Cs ions on PB/TiO 2 is due to photocatalytic reduction of PB, which leads to additional adsorption of Cs ions. The change in solution color before and after the reaction, and the change in solution pH in the dark and during UV irradiation strongly support this suggestion. The photocatalytic-enhanced adsorption of Cs ions was equivalent during radioactive 137 Cs removal, indicating important applications for pollutant removal from contaminated water. Copyright © 2018 Elsevier B.V. All rights reserved.

Photocatalytic water splitting over titania supported copper and nickel oxide in photoelectrochemical cell; optimization of photoconversion efficiency

NASA Astrophysics Data System (ADS)

Muti Mohamed, Norani; Bashiri, Robabeh; Kait, Chong Fai; Sufian, Suriati

2018-04-01

we investigated the influence of fluctuating the preparation variables of TiO2 on the efficiency of photocatalytic water splitting in photoelectrochemical (PEC) cell. Hydrothermal associated sol-gel technique was applied to synthesis modified TiO2 with nickel and copper oxide. The variation of water (mL), acid (mL) and total metal loading (%) were mathematically modelled using central composite design (CCD) from the response surface method (RSM) to explore the single and combined effects of parameters on the system performance. The experimental data were fitted using quadratic polynomial regression model from analysis of variance (ANOVA). The coefficient of determination value of 98% confirms the linear relationship between the experimental and predicted values. The amount of water had maximum effect on the photoconversion efficiency due to a direct effect on the crystalline and the number of defects on the surface of photocatalyst. The optimal parameter ratios with maximum photoconversion efficiency were 16 mL, 3 mL and 5 % for water, acid and total metal loading, respectively.

Development and assessment of photo-catalytic membranes for water purification using solar radiation

NASA Astrophysics Data System (ADS)

Coto, M.; Troughton, S. C.; Duan, J.; Kumar, R. V.; Clyne, T. W.

2018-03-01

This paper describes a novel set-up for characterization of the performance of membranes designed for purification of water. It involves a recirculatory system, with continuous monitoring of the concentration in the water of a representative pollutant (Methylene Blue). Pressures, flow rates and temperatures are also measured. Results, in the form of rate constants for reduction in pollutant concentration, are presented for three different types of membrane, all of which incorporate relatively high surface areas of titania and have permeability values in a range making them suitable for this type of processing (∼10-11 m2). These results are rationalized in terms of the surface areas of the membranes, and the likely water flow characteristics within them. It is concluded that all of the titania surfaces within them have similar efficiencies for photo-catalytic oxidation of pollutants, but there are significant differences in the ways that the water is exposed to these surfaces, and hence in the pollutant oxidation rates. These points are relevant to the optimization of membrane design for this purpose.

Study on Control of NH4 +-N in Surface Water by Photocatalytic

NASA Astrophysics Data System (ADS)

Zuo, Xiaoran; He, Honghua; Yang, Yue; Yan, Chao; Zhou, Ying

2018-01-01

NH4 +-N has become the main pollution factor affecting the surface water quality in China. Based on the theory of photolysis, the feasibility of photolysis removing NH4 +-N in surface water is studied. The effects of pH, CaO2 content and photolysis time on removal rate of NH4 +-N are studied. The actual study is based on Laboratory studies results. Experimental results show: When the pH<7, photolysis can increase the NH4 +-N content. And when pH>8, the photolysis can greatly reduce the NH4 +-N content in water. CaO2 can greatly remove NH4 +-N. The removal rate of NH4 +-N increased with the increase of photocatalytic time. When irradiated with UV light for 108 hours or the sun is irradiated for about 40 days, NH4 +-N content can be reduced from 4mg/L to 0.5mg/L under the optimum experimental conditions. Adjusting the pH of surface water is the most important condition for controlling NH4 +-N content.

UV/TiO2 photocatalytic disinfection of carbon-bacteria complexes in activated carbon-filtered water: Laboratory and pilot-scale investigation.

PubMed

Zhao, Jin Hui; Chen, Wei; Zhao, Yaqian; Liu, Cuiyun; Liu, Ranbin

2015-01-01

The occurrence of carbon-bacteria complexes in activated carbon filtered water has posed a public health problem regarding the biological safety of drinking water. The application of combined process of ultraviolet radiation and nanostructure titanium dioxide (UV/TiO2) photocatalysis for the disinfection of carbon-bacteria complexes were assessed in this study. Results showed that a 1.07 Lg disinfection rate can be achieved using a UV dose of 20 mJ cm(-2), while the optimal UV intensity was 0.01 mW cm(-2). Particle sizes ≥8 μm decreased the disinfection efficiency, whereas variation in particle number in activated carbon-filtered water did not significantly affect the disinfection efficiency. Photoreactivation ratio was reduced from 12.07% to 1.69% when the UV dose was increased from 5 mJ cm(-2) to 20 mJ cm(-2). Laboratory and on-site pilot-scale experiments have demonstrated that UV/TiO2 photocatalytic disinfection technology is capable of controlling the risk posed by carbon-bacteria complexes and securing drinking water safety.

Synergistic properties of graphitic carbon nitride/cerium molybdate nanocomposites for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Bhargava, V. S.; Singh, Gajendar; Sharma, Manu

2018-05-01

A polymeric semiconductor (g-C3N4), based nanocomposites have been achieved much attention due to its excellent thermal, chemical stability and suitable band positions for water splitting. g-C3N4 based nanocomposites show good performance in the field of photocatalysis, sensors, Li-ion batteries, supercapacitors and water purification technology. In this work, a series of novel g-C3N4/CeM nano composites were synthesized using a facile one-step ultra-sonication method. X-ray diffraction (XRD) pattern confirms the formation of g-C3N4 and cerium molybdate. The photocatalytic activity of nanocomposites indicated the substantial degradation of Methylene Blue (MB) dye up to 97% over the surface of g-C3N4/CeM under visible light illumination. All the g-C3N4/CeM composites possess higher photocatalytic activity than pure cerium molybdate. The proposed mechanism demonstrated that the different weight ratios of photocatalyst were most likely attributed to a synergistic effect between g-C3N4 and CeM. This approach is very simple, cost effective, and free from any surfactant that makes it valuable catalyst for various future applications.

The effects of starting materials in the synthesis of (Ga(1-x)Znx)(N(1-x)O(x)) solid solution on its photocatalytic activity for overall water splitting under visible light.

PubMed

Hisatomi, Takashi; Maeda, Kazuhiko; Lu, Daling; Domen, Kazunari

2009-01-01

The influence of starting materials on the physicochemical and photocatalytic properties of (Ga(1-x)Zn(x))(N(1-x)O(x)) were investigated in an attempt to optimize the preparation conditions. The catalyst was successfully prepared by nitriding a starting mixture of ZnO and Ga2O3. A mixture of metallic zinc and GaN, however, did not afford the desired compound. The crystallinity, surface area, composition, and absorption characteristics of the resultant (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution are found to be dependent on the morphology of ZnO but largely insensitive to the choice of Ga2O3 polymorph. The use of coarser-grained ZnO results in a coarser-grained catalyst with elevated zinc and oxygen content and reduced uniformity in composition and crystallinity. The results demonstrate the importance of selecting appropriate ZnO and Ga2O3 starting materials for maximizing the photocatalytic activity of (Ga(1-x)Zn(x))(N(1-x)O(x)) for overall water splitting under visible light.

Enhanced photocatalytic hydrogen production from water-ethanol solution by Ruthenium doped La-NaTaO3

NASA Astrophysics Data System (ADS)

Husin, H.; Alam, P. N.; Zaki, M.; Sofyana; Jakfar; Husaini; Hasfita, F.

2018-04-01

The photocatalytic hydrogen production from ethanol aqueous solution, with the use ruthenium doped La-NaTaO3 has been investigated. Ruthenium doped La-NaTaO3 catalysts are prepared by impregnation method. The catalysts are by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Ru co-catalyst demonstrated from the TEM image shows a good dispersion on the surface of La-C-NaTaO3 with an average particle size between 4-5 nm. The photocatalytic reaction is carried out in a closed reactor with a gas circulation system. The catalytic activity of La-NaTaO3 improved markedly (6.6 times from pure water) when Ru is loaded onto its surface. The hydrogen production is notably enhanced in the presence of ethanol as electron donors. This result is much higher when compared with the rate of hydrogen production in the sample without co- catalysts about 9.4 times higher after Ru deposition from ethanol aqueous solution. Increasing the production of hydrogen on the Ru/La-NaTaO3 closely related to the decrease in recombination between electron-hole pairs.

Removal of 4-Nitrophenol from Water Using Ag–N–P-Tridoped TiO2 by Photocatalytic Oxidation Technique

PubMed Central

Achamo, Temesgen; Yadav, O. P.

2016-01-01

Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag–N–P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol–gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)–visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39–46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron–hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag–N–P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively. PMID:27081309

Investigation of titanium dioxide/ tungstic acid -based photocatalyst for human excrement wastewater treatment

NASA Astrophysics Data System (ADS)

Xu, Fei; Wang, Can; Xiao, Kemeng; Gao, Yufeng; Zhou, Tong; Xu, Heng

2018-05-01

An activated carbon (AC) coated with tungstic acid (WO3)/titanium dioxide (TiO2) nanocomposites photocatalytic material (ACWT) combined with Three-phase Fluidized Bed (TFB) was investigated for human excrement wastewater treatment. Under the ultraviolet (UV) and fluorescent lamp illumination, the ACWT had shown a good performance on chemical oxygen demand (COD) and total nitrogen (TN) removal but inefficient on ammonia nitrogen (NH3-N) removal. Optimized by Taguchi method, COD and TN removal efficiency was up to 88.39% and 55.07%, respectively. Among all the parameters, the dosage of ACWT had the largest contribution on the process. Bacterial community changes after treatment demonstrated that this photocatalytic system had a great sterilization effect on wastewater. These results confirmed that ACWT could be applied for the human excrement wastewater treatment.

Correlation of Photocatalytic Activity with Band Structure of Low-dimensional Semiconductor Nanostructures

NASA Astrophysics Data System (ADS)

Meng, Fanke

Photocatalytic hydrogen generation by water splitting is a promising technique to produce clean and renewable solar fuel. The development of effective semiconductor photocatalysts to obtain efficient photocatalytic activity is the key objective. However, two critical reasons prevent wide applications of semiconductor photocatalysts: low light usage efficiency and high rates of charge recombination. In this dissertation, several low-dimensional semiconductors were synthesized with hydrothermal, hydrolysis, and chemical impregnation methods. The band structures of the low-dimensional semiconductor materials were engineered to overcome the above mentioned two shortcomings. In addition, the correlation between the photocatalytic activity of the low-dimensional semiconductor materials and their band structures were studied. First, we studied the effect of oxygen vacancies on the photocatalytic activity of one-dimensional anatase TiO2 nanobelts. Given that the oxygen vacancy plays a significant role in band structure and photocatalytic performance of semiconductors, oxygen vacancies were introduced into the anatase TiO2 nanobelts during reduction in H2 at high temperature. The oxygen vacancies of the TiO2 nanobelts boosted visible-light-responsive photocatalytic activity but weakened ultraviolet-light-responsive photocatalytic activity. As oxygen vacancies are commonly introduced by dopants, these results give insight into why doping is not always beneficial to the overall photocatalytic performance despite increases in absorption. Second, we improved the photocatalytic performance of two-dimensional lanthanum titanate (La2Ti2 O7) nanosheets, which are widely studied as an efficient photocatalyst due to the unique layered crystal structure. Nitrogen was doped into the La2Ti2O7 nanosheets and then Pt nanoparticles were loaded onto the La2Ti2O7 nanosheets. Doping nitrogen narrowed the band gap of the La2Ti 2O7 nanosheets by introducing a continuum of states by the valence band edge, unlike the mid-gap states introduced by oxygen vacancies, leading to an improvement in visible and UV photocatalysis. The Pt nanoparticles both enhanced separation of charge carriers and acted as reaction sites for hydrogen evolution. The photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets was increased to ˜21 muM g-1 hr-1 from zero in visible light by nitrogen doping and Pt loading, showing the importance of the positioning of dopant energy levels within the band gap. Third, a hematite/reduced graphene oxide (alpha-Fe2 2O3/rGO) nanocomposite was synthesized by a hydrolysis method. The photocatalytic oxygen evolution rate of the hematite was increased from 387 to 752 muM g-1 hr-1 by incorporating rGO. Photoelectrochemical measurements showed that coupling the hematite nanoparticles with the rGO can greatly increase the photocurrent and reduce the charge recombination rate, overcoming the poor charge recombination characteristics of hematite and allowing its small band gap to be taken advantage of. Fourth, a Au/La 2Ti2O7/rGO heterostructure was synthesized to further enhance the photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets. The enhanced performance of photocatalytic water splitting was due to plasmonic energy transfer, which resulted from the plasmonic Au nanoparticles on the La2Ti 2O7 nanosheets. This heterostructure showed doping, charge extraction, and plasmonics work synergistically. Fifth, nanoscale p-n junctions on the rGO were formed by depositing the p-type MoS 2 nanoplatelets onto the n-type nitrogen-doped rGO. The p-MoS2/n-rGO heterostructure had significant photocatalytic hydrogen generation activity under solar light irradiation. The enhanced charge generation and suppressed charge recombination due to the p-n junctions led to enhance solar hydrogen generation reaction while allowing replacement of the expensive Pt nanoparticles with an eco-friendly alternative. The research results in this dissertation are contributed to a better understanding of the relationship between the band structure tuning and photocatalytic activity of low-dimensional semiconductor nanostructures. The results lay out guidelines for the enhancement of large band gap semiconductors with poor solar utilization and small band gap semiconductors with poor charge recombination characteristics alike. Additionally, it is shown that the rare earth co-catalyst can be replaced with an earth friendly alternative, leading to a further increase in performance. The findings of this thesis can be used to guide photocatalyst selection and optimization for solar to hydrogen conversion.

Graphene oxide based ultrafiltration membranes for photocatalytic degradation of organic pollutants in salty water.

PubMed

Pastrana-Martínez, Luisa M; Morales-Torres, Sergio; Figueiredo, José L; Faria, Joaquim L; Silva, Adrián M T

2015-06-15

Flat sheet ultrafiltration (UF) membranes with photocatalytic properties were prepared with lab-made TiO2 and graphene oxide-TiO2 (GOT), and also with a reference TiO2 photocatalyst from Evonik (P25). These membranes were tested in continuous operation mode for the degradation and mineralization of a pharmaceutical compound, diphenhydramine (DP), and an organic dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation. The effect of NaCl was investigated considering simulated brackish water (NaCl 0.5 g L(-1)) and simulated seawater (NaCl 35 g L(-1)). The results indicated that the membranes prepared with the GOT composite (M-GOT) exhibited the highest photocatalytic activity, outperforming those prepared with bare TiO2 (M-TiO2) and P25 (M-P25), both inactive under visible light illumination. The best performance of M-GOT may be due to the lower band-gap energy (2.9 eV) of GOT. In general, the permeate flux was also higher for M-GOT probably due to a combined effect of its highest photocatalytic activity, highest hydrophilicity (contact angles of 11°, 17° and 18° for M-GOT, M-TiO2 and M-P25, respectively) and higher porosity (71%). The presence of NaCl had a detrimental effect on the efficiency of the membranes, since chloride anions can act as hole and hydroxyl radical scavengers, but it did not affect the catalytic stability of these membranes. A hierarchically ordered membrane was also prepared by intercalating a freestanding GO membrane in the structure of the M-GOT membrane (M-GO/GOT). The results showed considerably higher pollutant removal in darkness and good photocatalytic activity under near-UV/Vis and visible light irradiation in continuous mode experiments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fabrication of TiO2/MoS2@zeolite photocatalyst and its photocatalytic activity for degradation of methyl orange under visible light

NASA Astrophysics Data System (ADS)

Zhang, Weiping; Xiao, Xinyan; Zheng, Lili; Wan, Caixia

2015-12-01

TiO2/MoS2@zeolite composite photocatalysts with visible-light activity were fabricated via a simple ultrasonic-hydrothermal synthesis method, using TiCl4 as Ti source, MoS2 as a direct sensitizer, glycerol water solution with certain dispersion agent as hydrolytic agent, and zeolite as carrier. The structure, morphology, composition, optical properties, and specific surface area of the as-prepared photocatalysts were characterized by using XRD, FTIR, SEM-EDS, TEM, XPS, UV-vis, PL and BET analyzer, respectively. And the photocatalytic degradation of methyl orange (MO) in aqueous suspension has been employed to evaluate the photocatalytic activity and degradation kinetics of as-prepared photocatalysts with xenon lamp as irradiation source. The results indicate that: (1) TiO2/MoS2@zeolite composite photocatalysts exhibit enhanced photocatalytic activities for methyl orange (MO) degradation compared to Degussa P25; (2) photocatalytic degradation of MO obeys Langmuir-Hinshelwood kinetic model (pseudo-first order reaction), and its degradation rate constant (kapp) (2.304 h-1) is higher than that of Degussa P25 (0.768 h-1); (3) the heterostructure consisted of zeolite, MoS2 and TiO2 nanostructure could provide synergistic effect for degradation of MO due to the efficient electron transfer process and better absorption property of TiO2/MoS2@zeolite composite photocatalyst.

Fabrication of NiS modified CdS nanorod p-n junction photocatalysts with enhanced visible-light photocatalytic H2-production activity.

PubMed

Zhang, Jun; Qiao, Shi Zhang; Qi, Lifang; Yu, Jiaguo

2013-08-07

Production of hydrogen from photocatalytic water splitting has become an attractive research area due to the possibility of converting solar energy into green chemical energy. In this study, novel NiS nanoparticle (NP) modified CdS nanorod (NR) p-n junction photocatalysts were prepared by a simple two-step hydrothermal method. Even without the Pt co-catalyst, the as-prepared NiS NP-CdS NR samples exhibited enhanced visible-light photocatalytic activity and good stability for H2-production. The optimal NiS loading content was determined to be 5 mol%, and the corresponding H2-production rate reached 1131 μmol h(-1) g(-1), which is even higher than that of the optimized Pt-CdS NRs. It is believed that the assembly of p-type NiS NPs on the surface of n-type CdS NRs could form a large number of p-n junctions, which could effectively reduce the recombination rates of electrons and holes, thus greatly enhancing the photocatalytic activity. This work not only shows a possibility for the utilization of low cost NiS nanoparticles as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also provides a new insight into the design and fabrication of other new p-n junction photocatalysts for enhancing H2-production activity.

High turnover in a photocatalytic system for water reduction to produce hydrogen using a Ru,  Rh,  Ru photoinitiated electron collector.

PubMed

Arachchige, Shamindri M; Shaw, Ryan; White, Travis A; Shenoy, Vimal; Tsui, Hei-Man; Brewer, Karen J

2011-04-18

Covalent coupling of Ru(II) light absorbers to a Rh(III) electron collecting site through polyazine bridging ligands affords photocatalytic production of H(2) in the presence of visible light and a sacrificial electron donor. A robust photocatalytic system displaying a high turnover of the photocatalyst has been developed using the photoinitiated electron collector [{(bpy)(2)Ru(dpp)}(2)RhBr(2)](5+) (bpy=2,2'-bipyridine; dpp=2,3-bis(2-pyridyl)pyrazine) and N,N-dimethylaniline in DMF/H(2)O. Studies have shown that increased [DMA], the headspace volume, and the use of DMF solvent improves the systems performance and stability providing mechanistic insight into the deactivation routes of the photocatalytic system. Photolysis of the system at 460 nm generates 20 mL of H(2) in 19.5 h with a maximum Φ=0.023 based on H(2) produced and an overall Φ=0.014 and 280 turnovers of the photocatalyst. The photocatalytic system also displays long-term photostability with 30 mL of H(2) generated and 420 turnovers in 50 h under the same conditions. Prolonged photolysis provides 820 mol H(2) per mole of catalyst. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monoclinic Tungsten Oxide with {100} Facet Orientation and Tuned Electronic Band Structure for Enhanced Photocatalytic Oxidations.

PubMed

Zhang, Ning; Chen, Chen; Mei, Zongwei; Liu, Xiaohe; Qu, Xiaolei; Li, Yunxiang; Li, Siqi; Qi, Weihong; Zhang, Yuanjian; Ye, Jinhua; Roy, Vellaisamy A L; Ma, Renzhi

2016-04-27

Exploring surface-exposed highly active crystal facets for photocatalytic oxidations is promising in utilizing monoclinic WO3 semiconductor. However, the previously reported highly active facets for monoclinic WO3 were mainly toward enhancing photocatalytic reductions. Here we report that the WO3 with {100} facet orientation and tuned surface electronic band structure can effectively enhance photocatalytic oxidation properties. The {100} faceted WO3 single crystals are synthesized via a facile hydrothermal method. The UV-visible diffuse reflectance, X-ray photoelectron spectroscopy valence band spectra, and photoelectrochemical measurements suggest that the {100} faceted WO3 has a much higher energy level of valence band maximum compared with the normal WO3 crystals without preferred orientation of the crystal face. The density functional theory calculations reveal that the shift of O 2p and W 5d states in {100} face induce a unique band structure. In comparison with the normal WO3, the {100} faceted WO3 exhibits an O2 evolution rate about 5.1 times in water splitting, and also shows an acetone evolution rate of 4.2 times as well as CO2 evolution rate of 3.8 times in gaseous degradation of 2-propanol. This study demonstrates an efficient crystal face engineering route to tune the surface electronic band structure for enhanced photocatalytic oxidations.

Effect of sacrificial agents on the dispersion of metal cocatalysts for photocatalytic hydrogen evolution

NASA Astrophysics Data System (ADS)

Cao, Shaowen; Shen, Baojia; Huang, Qian; Chen, Zhe

2018-06-01

Surface photodeposition of noble metal cocatalyst has been regarded as an effective approach to facilitate the separation of charge carriers and reduce the over-potential of water reduction, thus to enhance the photocatalytic H2-production activities of semiconductor photocatalyst. Herein, the influences of sacrificial agents used in the photodeposition process on the dispersion of noble metal nanoparticles are investigated, via a series of technique of photocatalytic hydrogen evolution test, microstructure analysis and photoelectrochemical measurement. As a result, the sacrificial agents are found to show large impact on the loading amount, particle size and distribution of different metals on the surface of g-C3N4. The real loading amount of Pt and Au is higher in methanol solution than that in triethanolamine solution. Better distribution and smaller size of Pt nanoparticles are achieved in the presence of methanol; while better distribution and smaller size of Au nanoparticles are achieved in the presence of triethanolamine. As a result, quite different charge transfer ability is achieved for the synthesized Pt and Au decorated g-C3N4, which subsequently leads to disparate photocatalytic activities of the same g-C3N4 photocatalyst under various conditions. The finding in this work indicates that the valid deposition content, particle size and distribution of metal cocatalysts should be carefully taken into account when comparing the photocatalytic activities among various samples.

Unraveling the enhanced photocatalytic activity and phototoxicity of ZnO/metal hybrid nanostructures from generation of reactive oxygen species and charge carriers.

PubMed

He, Weiwei; Wu, Haohao; Wamer, Wayne G; Kim, Hyun-Kyung; Zheng, Jiwen; Jia, Huimin; Zheng, Zhi; Yin, Jun-Jie

2014-09-10

An effective way for promoting photocatalytic activity of a semiconductor is deposition of noble metal nanoparticles (NPs) onto it. In this paper, we deposited Ag and Pd onto ZnO NPs to form ZnO/Ag and ZnO/Pd hybrid nanostructures. It was found that both Ag and Pd nanocomponents can greatly enhance the photocatalytic activity and phototoxicity of ZnO toward human skin cells. Using electron spin resonance spectroscopy with spin trapping and spin labeling techniques, we observed that either deposition of Ag or Pd resulted in a significant increase in photogenerated electrons and holes and production of reactive oxygen species including hydroxyl radicals, superoxide, and singlet oxygen. We compared the enhancing effects of Ag and Pd and found that Pd is more effective than Ag in promoting the generation of hydroxyl radicals and holes and the photocatalytic activity of ZnO. Conversely, Ag is more effective than Pd in enhancing electron transfer and the generation of superoxide and singlet oxygen. The mechanism underlying the differences in the effects of Ag and Pd may be related to differences in Fermi levels for Ag and Pd and band bending accompanied by effects on Schottky barriers. The results of these studies provide information valuable for designing hybrid nanomaterials having photocatalytic and photobiological activities useful for applications such as water purification and formulation of antibacterial products.

Synthesis and comparative photocatalytic activity of Pt/WO 3 and Au/WO 3 nanocomposites under sunlight-type excitation

NASA Astrophysics Data System (ADS)

Qamar, M.; Yamani, Z. H.; Gondal, M. A.; Alhooshani, K.

2011-09-01

The article deals with the synthesis of highly active visible-light-driven nanocomposite for the decontamination of water hazards under sunlight-type excitation. The surface of visible-light-active nanostructured photocatalyst tungsten oxide (WO 3) was modified with noble metals, such as platinum (Pt) and gold (Au) nanoparticles, and the resulting photocatalytic activity of the nanocomposites was investigated by studying the removal of Methyl Orange and 2,4-Dichlorophenoxyacetic acid (2,4-D) under sunlight-type excitation. The study revealed that the deposited noble metals are not always favorable for the enhancement of photocatalytic response of catalysts; the activity of WO 3 was enhanced manyfold (˜8 times) by depositing an optimum amount of Pt nanoparticles after certain photodeposition time whereas the presence of Au nanoparticles onto the WO 3 surface, under identical experimental conditions, affected the removal process negatively. The variation in the photocatalytic activity of nanocomposites was attributed to the size of the deposited metals; Pt nanoparticles were uniformly dispersed with narrow size distribution (2-4 nm) while the size distribution of Au nanoparticles was found to be 10-15 nm for similar preparation conditions. The effects of critical parameters, such as metal deposition time and metal contents, on the photocatalytic activity of WO 3 were investigated. Furthermore, Pt/WO 3 nanocomposites showed good stability and recyclability under the conditions studied.

Visible-light responsive photocatalytic fuel cell based on WO(3)/W photoanode and Cu(2)O/Cu photocathode for simultaneous wastewater treatment and electricity generation.

PubMed

Chen, Quanpeng; Li, Jinhua; Li, Xuejin; Huang, Ke; Zhou, Baoxue; Cai, Weimin; Shangguan, Wenfeng

2012-10-16

A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO(3)/W photoanode and Cu(2)O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO(3)/W photoanode is higher than that of Cu(2)O/Cu photocathode. An interior bias can be produced based on which the electrons of WO(3)/W photoanode can transfer from the external circuit to combine with the holes of Cu(2)O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO(3)/W photoanode and electrons of Cu(2)O/Cu photocathode. Organic compounds can be decomposed by the holes of WO(3)/W photoanode due to its high oxidation power (+3.1-3.2 V(NHE)). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.

A facile route to the synthesis of magnetically separable BiOBr/NiFe2O4 composites with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Li, Xiaowei; Wang, Li; Zhang, Lei; Zhuo, Shuping

2017-10-01

Novel magnetically separable BiOBr/NiFe2O4 composite photocatalysts with different mass ratios were fabricated through a facile hydrothermal treatment. The phases, morphologies and photophysical properties of the as-obtained samples were characterized by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microcopy (TEM) and diffuse reflection spectroscopy (DRS). Their visible light photocatalytic performances were examined by degradation of methylene blue (MB) and phenol. Compared with bare BiOBr and NiFe2O4, all heterostructured BiOBr/NiFe2O4 nanocomposites exhibited significantly enhanced photocatalytic efficiency. The BiOBr/NiFe2O4-20% composite showed the highest photodegradation capacity, which was about 3.2 and 22.4 times greater than that of individual BiOBr and NiFe2O4, respectively. The degradation efficiency of BiOBr/NiFe2O4-20% in the degradation of MB dye hardly changed after five cycles, signifying that the BiOBr/NiFe2O4-20% photocatalyst had excellent recyclability. In addition, BiOBr/NiFe2O4 composite photocatalysts could be easily separated from contaminant solution by using a magnet and recycled, exhibiting great potential for application in the fields of environmental purification of organic pollutants and wastewater treatment. In the light of experimental results, we proposed a photocatalytic mechanism which confirmed that the enhancement of photocatalytic performance for BiOBr/NiFe2O4 composites was mainly ascribed to the efficient separation of photo-induced charges resulting from the well-known "heterostructure effect" between NiFe2O4 nanorods and BiOBr nanosheets.

High performance sulfur, nitrogen and carbon doped mesoporous anatase-brookite TiO₂ photocatalyst for the removal of microcystin-LR under visible light irradiation.

PubMed

El-Sheikh, Said M; Zhang, Geshan; El-Hosainy, Hamza M; Ismail, Adel A; O'Shea, Kevin E; Falaras, Polycarpos; Kontos, Athanassios G; Dionysiou, Dionysios D

2014-09-15

Carbon, nitrogen and sulfur (C, N and S) doped mesoporous anatase-brookite nano-heterojunction titania photocatalysts have been synthesized through a simple sol-gel method in the presence of triblock copolymer Pluronic P123. XRD and Raman spectra revealed the formation of anatase and brookite mixed phases. XPS spectra indicated the presence of C, N and S dopants. The TEM images demonstrated the formation of almost monodisperse titania nanoparticles with particle sizes of approximately 10nm. N2 isotherm measurements confirmed that both doped and undoped titania anatase-brookite materials have mesoporous structure. The photocatalytic degradation of the cyanotoxin microcystin-LR (MC-LR) has been investigated using these novel nanomaterials under visible light illumination. The photocatalytic efficiency of the mesoporous titania anatase-brookite photocatalyst dramatically increased with the addition of the C, N and S non-metal, achieving complete degradation (∼ 100 %) of MC-LR. The results demonstrate the advantages of the synthetic approach and the great potential of the visible light activated C, N, and S doped titania photocatalysts for the treatment of organic micropollutants in contaminated waters under visible light. Copyright © 2014 Elsevier B.V. All rights reserved.

Post-activation of in situ Bsbnd F codoped g-C3N4 for enhanced photocatalytic H2 evolution

NASA Astrophysics Data System (ADS)

Cui, Yanjuan; Wang, Hao; Yang, Chuanfeng; Li, Ming; Zhao, Yimeng; Chen, Fangyan

2018-05-01

Porous graphitic carbon nitride polymer (p-CN-BF) with enhanced photoproduction of H2 from water was prepared by a two-step treatment process including in-situ Boron and fluorine codoping using [Emim]BF4 as dopants followed by post-calcination in air. Several techniques were employed to characterize the modified structure and elucidate the doping state of B and F. It was shown that in-situ doping method is necessary for efficient doping of heteroatoms into the molecular composition of CN. The difference of doping state of B and F was that B doping primary existing in the inside skeleton of CN, but F doping merely presents in the surface layer. The inside doped B made for the enhanced visible light absorption and the production of uniform porous structure during post-sintering process. By the synergistic effect of Bsbnd F codoping and post-activation, p-CN-BF showed much enhanced photoelectron generation, transmission and separation, therefore, it performs high photocatalytic activity for H2 evolution (351 μmol h-1), which was 13 and 5 times higher than samples only modified by Bsbnd F codoping (CN-BF) or post-annealing (P-CN).

Nano-ferrites for Water Splitting: Unprecedented High Photocatalytic Hydrogen Production under Visible Light

EPA Science Inventory

In the present investigation, hydrogen production via water splitting by nano ferrites has been studied using ethanol as the sacrificial donor. The nano ferrite has shown great potential in hydrogen generation with hydrogen yield of 8275 9moles/h/ g of photocatalyst under visible...

Different heat treatment of CeO2 nanoparticle composited with ZnO to enhance photocatalytic performance

NASA Astrophysics Data System (ADS)

Taufik, A.; Shabrany, H.; Saleh, R.

2017-04-01

In this study, ZnO/CeO2 nanocomposites were prepared with four variations of the molar ratio of ZnO to CeO2 nanoparticles. Both ZnO and CeO2 nanoparticles were synthesized using the sol-gel method at low temperature, followed by different heat treatments for CeO2 nanoparticles. Thermal phase transformation studies of the CeO2 nanoparticles were observed at annealing temperatures of 400-800°C. The complete crystalline structure of CeO2 nanoparticles was obtained at an annealing temperature of 800°C. The structural and optical properties of all samples were observed using several characterization techniques, such as X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller (BET) surface area analysis. The structural characterization results revealed that the prepared CeO2 nanoparticles were quite crystalline, with a cubic structure. The photocatalytic activities of all samples were tested under visible irradiation. The obtained results showed that ZnO/CeO2 nanocomposites with a molar ratio 1:0.3 exhibited the highest photocatalytic activity. Further understanding of the role of primary active species underlying the reaction mechanism involved in photocatalytic activity were carried out in controlled experiments by adding several scavengers. The detailed mechanism and its correlation with the properties of ZnO/CeO2 nanocomposites were discuss.

Dispersed-nanoparticle loading synthesis for monodisperse Au-titania composite particles and their crystallization for highly active UV and visible photocatalysts.

PubMed

Sakamoto, Takeshi; Nagao, Daisuke; Noba, Masahiro; Ishii, Haruyuki; Konno, Mikio

2014-06-24

Submicrometer-sized amorphous titania spheres incorporating Au nanoparticles (NPs) were prepared in a one-pot synthesis consisting of a sol-gel reaction of titanium(IV) isopropoxide in the presence of chloroauric acid and a successive reduction with sodium borohydride in a mixed solvent of ethanol/acetonitrile. The synthesis was allowed to prepare monodisperse titania spheres that homogeneously incorporated Au NPs with sizes of ca. 7 nm. The Au NP-loaded titania spheres underwent different crystallization processes, including 500 °C calcination in air, high-temperature hydrothermal treatment (HHT), and/or low-temperature hydrothermal treatment (LHT). Photocatalytic experiments were conducted with the Au NP-loaded crystalline titania spheres under irradiation of UV and visible light. A combined process of LHT at 80 °C followed by calcination at 500 °C could effectively crystallize titania spheres maintaining the dispersion state of Au NPs, which led to photocatalytic activity higher than that of commercial P25 under UV irradiation. Under visible light irradiation, the Au NP-titania spheres prepared with a crystallization process of LHT at 80 °C for 6 h showed photocatalytic activity much higher than a commercial product of visible light photocatalyst. Structure analysis of the visible light photocatalysts indicates the importance of prevention of the Au NPs aggregation in the crystallization processes for enhancement of photocatalytic activity.

Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NO{sub x} abatement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tobaldi, D.M., E-mail: david.tobaldi@ua.pt; Pullar, R.C.; Gualtieri, A.F.

2015-11-15

Titanium dioxide (TiO{sub 2}) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO{sub 2} has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO{sub 2} to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO{sub 2} lattice using our green sol–gel nanosynthesis method, used to create 10 nm TiO{sub 2} NPs. Two parallel routesmore » were studied to produce nitrogen-modified TiO{sub 2} nanoparticles (NPs), using HNO{sub 3}+NH{sub 3} (acid-precipitated base-peptised) and NH{sub 4}OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NO{sub x}) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NO{sub x} abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO{sub 2} NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice. - Graphical abstract: Nitrogen modified TiO{sub 2} synthesised via a green aqueous sol–gel method showed to degrade nitrogen oxides (NO{sub x}) under visible white-light (indoor artificial lighting), with a photocatalytic activity double than that of the standard P25 TiO{sub 2} NPs. - Highlights: • N–TiO{sub 2} synthesised via a green aqueous sol–gel method. • Advanced X-ray methods used to detect both crystalline and amorphous contents. • Microstructure fully addressed via XRPD and whole powder pattern modelling. • Photocatalytic NO{sub x} removal assessed using both solar and visible-light lamps.« less

Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

NASA Astrophysics Data System (ADS)

Chen, Yang; Lu, Chunxiao; Tang, Liang; Song, Yahui; Wei, Shengnan; Rong, Yang; Zhang, Zhaohong; Wang, Jun

2016-12-01

In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

Preparation and enhanced visible-light photocatalytic H2-production activity of CdS-sensitized Pt/TiO2 nanosheets with exposed (001) facets.

PubMed

Qi, Lifang; Yu, Jiaguo; Jaroniec, Mietek

2011-05-21

CdS-sensitized Pt/TiO(2) nanosheets with exposed (001) facets were prepared by hydrothermal treatment of a Ti(OC(4)H(9))(4)-HF-H(2)O mixed solution followed by photochemical reduction deposition of Pt nanoparticles (NPs) on TiO(2) nanosheets (TiO(2) NSs) and chemical bath deposition of CdS NPs on Pt/TiO(2) NSs, successively. The UV and visible-light driven photocatalytic activity of the as-prepared samples was evaluated by photocatalytic H(2) production from lactic acid aqueous solution under UV and visible-light (λ ≥ 420 nm) irradiation. It was shown that no photocatalytic H(2)-production activity was observed on the pure TiO(2) NSs under UV and/or visible-light irradiation. Deposition of CdS NPs on Pt/TiO(2) NSs caused significant enhancement of the UV and visible-light photocatalytic H(2)-production rates. The morphology of TiO(2) particles had also significant influence on the visible-light H(2)-production activity. Among TiO(2) NSs, P25 and the NPs studied, the CdS-sensitized Pt/TiO(2) NSs show the highest photocatalytic activity (13.9% apparent quantum efficiency obtained at 420 nm), exceeding that of CdS-sensitized Pt/P25 by 10.3% and that of Pt/NPs by 1.21%, which can be attributed to the combined effect of several factors including the presence of exposed (001) facets, surface fluorination and high specific surface area. After many replication experiments of the photocatalytic hydrogen production in the presence of lactic acid, the CdS-sensitized Pt/TiO(2) NSs did not show great loss in the photocatalytic activity, confirming that the CdS/Pt/TiO(2) NSs system is stable and not photocorroded. © The Owner Societies 2011