42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 1 2012-10-01 2012-10-01 false Non-powered air-purifying particulate filter...-purifying particulate filter efficiency level determination. (a) Twenty filters of each non-powered air-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid sodium...

42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 1 2014-10-01 2014-10-01 false Non-powered air-purifying particulate filter...-purifying particulate filter efficiency level determination. (a) Twenty filters of each non-powered air-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid sodium...

42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 1 2013-10-01 2013-10-01 false Non-powered air-purifying particulate filter...-purifying particulate filter efficiency level determination. (a) Twenty filters of each non-powered air-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid sodium...

Evaluation of ionic air purifiers for reducing aerosol exposure in confined indoor spaces.

PubMed

Grinshpun, S A; Mainelis, G; Trunov, M; Adhikari, A; Reponen, T; Willeke, K

2005-08-01

Numerous techniques have been developed over the years for reducing aerosol exposure in indoor air environments. Among indoor air purifiers of different types, ionic emitters have gained increasing attention and are presently used for removing dust particles, aeroallergens and airborne microorganisms from indoor air. In this study, five ionic air purifiers (two wearable and three stationary) that produce unipolar air ions were evaluated with respect to their ability to reduce aerosol exposure in confined indoor spaces. The concentration decay of respirable particles of different properties was monitored in real time inside the breathing zone of a human manikin, which was placed in a relatively small (2.6 m3) walk-in chamber during the operation of an ionic air purifier in calm air and under mixing air condition. The particle removal efficiency as a function of particle size was determined using the data collected with a size-selective optical particle counter. The removal efficiency of the more powerful of the two wearable ionic purifiers reached about 50% after 15 min and almost 100% after 1.5 h of continuous operation in the chamber under calm air conditions. In the absence of external ventilation, air mixing, especially vigorous one (900 CFM), enhanced the air cleaning effect. Similar results were obtained when the manikin was placed inside a partial enclosure that simulated an aircraft seating configuration. All three stationary ionic air purifiers tested in this study were found capable of reducing the aerosol concentration in a confined indoor space. The most powerful stationary unit demonstrated an extremely high particle removal efficiency that increased sharply to almost 90% within 5-6 min, reaching about 100% within 10-12 min for all particle sizes (0.3-3 microm) tested in the chamber. For the units of the same emission rate, the data suggest that the ion polarity per se (negative vs. positive) does not affect the performance but the ion emission rate

Home Air Purifiers Eradicate Harmful Pathogens

NASA Technical Reports Server (NTRS)

2014-01-01

Marshall Space Flight Center funded the University of Madison-Wisconsin to develop ethylene scrubbers to keep produce fresh in space. Akida Holdings of Jacksonville, Florida, licensed the technology and developed Airocide, an air purifier that can kill airborne pathogens. Previously designed for industrial spaces, there is now a specially designed unit for home use.

Kinetic analysis of competition between aerosol particle removal and generation by ionization air purifiers.

PubMed

Alshawa, Ahmad; Russell, Ashley R; Nizkorodov, Sergey A

2007-04-01

Ionization air purifiers are increasingly used to remove aerosol particles from indoor air. However, certain ionization air purifiers also emit ozone. Reactions between the emitted ozone and unsaturated volatile organic compounds (VOC) commonly found in indoor air produce additional respirable aerosol particles in the ultrafine (<0.1 microm) and fine (<2.5 microm) size domains. A simple kinetic model is used to analyze the competition between the removal and generation of particulate matter by ionization air purifiers under conditions of a typical residential building. This model predicts that certain widely used ionization air purifiers may actually increase the mass concentration of fine and ultrafine particulates in the presence of common unsaturated VOC, such as limonene contained in many household cleaning products. This prediction is supported by an explicit observation of ultrafine particle nucleation events caused by the addition of D-limonene to a ventilated office room equipped with a common ionization air purifier.

Performance of ultraviolet photocatalytic oxidation for indoor air cleaning applications.

PubMed

Hodgson, A T; Destaillats, H; Sullivan, D P; Fisk, W J

2007-08-01

Ultraviolet photocatalytic oxidation (UVPCO) systems for removal of volatile organic compounds (VOCs) from air are being considered for use in office buildings. Here, we report an experimental evaluation of a UVPCO device with tungsten oxide modified titanium dioxide (TiO2) as the photocatalyst. The device was challenged with complex VOC mixtures. One mixture contained 27 VOCs characteristic of office buildings and another comprised 10 VOCs emitted by cleaning products, in both cases at realistic concentrations (low ppb range). VOC conversion efficiencies varied widely, usually exceeded 20%, and were as high as approximately 80% at about 0.03 s residence time. Conversion efficiency generally diminished with increased airflow rate, and followed the order: alcohols and glycol ethers > aldehydes, ketones, and terpene hydrocarbons > aromatic and alkane hydrocarbons > halogenated aliphatic hydrocarbons. Conversion efficiencies correlated with the Henry's law constant more closely than with other physicochemical parameters. An empirical model based on the Henry's law constant and the gas-phase reaction rate with hydroxyl radical provided reasonable estimates of pseudo-first order photocatalytic reaction rates. Formaldehyde, acetaldehyde, acetone, formic acid and acetic acid were produced by the device due to incomplete mineralization of common VOCs. Formaldehyde outlet/inlet concentration ratios were in the range 1.9-7.2. Implementation of air cleaning technologies for both VOCs and particles in office buildings may improve indoor air quality, or enable indoor air quality levels to be maintained with reduced outdoor air supply and concomitant energy savings. One promising air cleaning technology is ultraviolet photocatalytic oxidation (UVPCO) air cleaning. For the prototype device evaluated here with realistic mixtures of VOCs, conversion efficiencies typically exceeded the minimum required to counteract predicted VOC concentration increases from a 50% reduction in

Effectiveness of photocatalytic filter for removing volatile organic compounds in the heating, ventilation, and air conditioning system.

PubMed

Yu, Kuo-Pin; Lee, Grace Whei-May; Huang, Wei-Ming; Wu, Chih-Cheng; Lou, Chia-ling; Yang, Shinhao

2006-05-01

Nowadays, the heating, ventilation, and air conditioning (HVAC) system has been an important facility for maintaining indoor air quality. However, the primary function of typical HVAC systems is to control the temperature and humidity of the supply air. Most indoor air pollutants, such as volatile organic compounds (VOCs), cannot be removed by typical HVAC systems. Thus, some air handling units for removing VOCs should be added in typical HVAC systems. Among all of the air cleaning techniques used to remove indoor VOCs, photocatalytic oxidation is an attractive alternative technique for indoor air purification and deodorization. The objective of this research is to investigate the VOC removal efficiency of the photocatalytic filter in a HVAC system. Toluene and formaldehyde were chosen as the target pollutants. The experiments were conducted in a stainless steel chamber equipped with a simplified HVAC system. A mechanical filter coated with Degussa P25 titania photocatalyst and two commercial photocatalytic filters were used as the photocatalytic filters in this simplified HVAC system. The total air change rates were controlled at 0.5, 0.75, 1, 1.25, and 1.5 hr(-1), and the relative humidity (RH) was controlled at 30%, 50%, and 70%. The ultraviolet lamp used was a 4-W, ultraviolet-C (central wavelength at 254 nm) strip light bulb. The first-order decay constant of toluene and formaldehyde found in this study ranged from 0.381 to 1.01 hr(-1) under different total air change rates, from 0.34 to 0.433 hr(-1) under different RH, and from 0.381 to 0.433 hr(-1) for different photocatalytic filters.

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...

Recirculating Thermocatalytic Air Purifier for Collective Protection

DTIC Science & Technology

2006-01-01

stearothermophilus (Bs) spores, which are generally accepted to be more heat resistant than anthrax spores. The results for the Bg and Bs spore...7 who performed thermal deactivation tests using Bg spores in a different reactor geometry. Shankle’s data imply complete sterilization of Bg...400 CFM Catalytic Air Purifier Model, Book 2: Effects of Heat Transfer and Flow on Thermal Sterilization . CB-67-2738-12.2, Physical Protection

Studying the fate of non-volatile organic compounds in a commercial plasma air purifier.

PubMed

Schmid, Stefan; Seiler, Cornelia; Gerecke, Andreas C; Hächler, Herbert; Hilbi, Hubert; Frey, Joachim; Weidmann, Simon; Meier, Lukas; Berchtold, Christian; Zenobi, Renato

2013-07-15

Degradation of non-volatile organic compounds-environmental toxins (methyltriclosane and phenanthrene), bovine serum albumin, as well as bioparticles (Legionella pneumophila, Bacillus subtilis, and Bacillus anthracis)-in a commercially available plasma air purifier based on a cold plasma was studied in detail, focusing on its efficiency and on the resulting degradation products. This system is capable of handling air flow velocities of up to 3.0m s(-1) (3200Lmin(-1)), much higher than other plasma-based reactors described in the literature, which generally are limited to air flow rates below 10Lmin(-1). Mass balance studies consistently indicated a reduction in concentration of the compounds/particles after passage through the plasma air purifier, 31% for phenanthrene, 17% for methyltriclosane, and 80% for bovine serum albumin. L. pneumophila did not survive passage through the plasma air purifier, and cell counts of aerosolized spores of B. subtilis and B. anthracis were reduced by 26- and 15-fold, depending on whether it was run at 10Hz or 50Hz, respectively. However rather than chemical degradation, deposition on the inner surfaces of the plasma air purifier occured. Our interpretation is that putative "degradation" efficiencies were largely due to electrostatic precipitation rather than to decomposition into smaller molecules. Copyright © 2013 Elsevier B.V. All rights reserved.

Photocatalytic/Magnetic Composite Particles

NASA Technical Reports Server (NTRS)

Wu, Chang-Yu; Goswami, Yogi; Garretson, Charles; Andino, Jean; Mazyck, David

2007-01-01

Photocatalytic/magnetic composite particles have been invented as improved means of exploiting established methods of photocatalysis for removal of chemical and biological pollutants from air and water. The photocatalytic components of the composite particles are formulated for high levels of photocatalytic activity, while the magnetic components make it possible to control the movements of the particles through the application of magnetic fields. The combination of photocatalytic and magnetic properties can be exploited in designing improved air- and water treatment reactors.

Fabrication of Simple Indoor Air Haze Purifier using Domestic Discarded Substances and Its Haze Removal Performance

NASA Astrophysics Data System (ADS)

Wang, Zhou; Cao, Haoshu; Zhao, Shuang

2018-01-01

Based on the concept of circular economy, discarded plastic bottles stuffed with discarded cotton, clothing and sofa cushion were used as pre-filter to remove big particles (dust and coal dust) in air and 4 L tap water in discarded plastic bottle was worked as an absorbing medium to dissolve the water soluble ions in air (SO4 2-, NO3-, NH4+, Cl- and Ca2+). Moreover, the internet control design was used in this homemade indoor air haze purifier to achieve the performance of remote control and intelligent management. The experimental results showed that this indoor air haze purifier can effectively reduce the level of indoor air haze and the air quality after 20 minutes treatment is higher than that of two commercial well-known air haze purifier

Air Purifiers Eliminate Pathogens, Preserve Food

NASA Technical Reports Server (NTRS)

2009-01-01

NASA-funded researchers produced an ethylene reduction device for a plant growth unit. KES Science & Technology Inc., a Kennesaw, Georgia-based company specializing in sustaining perishable foods, licensed the ethylene scrubbing technology. KES partnered with Akida Holdings, of Jacksonville, Florida, which now markets the NASA-developed technology as AiroCide. According to the company, it is the only air purifier that completely destroys airborne bacteria, mold, fungi, mycotoxins, viruses, volatile organic compounds (like ethylene), and odors. What?s more, the devices have no filters that need changing and produce no harmful byproducts, such as the ozone created by some filtration systems.

Investigating the influence of photocatalytic cool wall adoption on meteorology and air quality in the Los Angeles basin

NASA Astrophysics Data System (ADS)

Zhang, J.; Tang, X.; Levinson, R.; Destaillats, H.; Mohegh, A.; Li, Y.; Tao, W.; Liu, J.; Ban-Weiss, G. A.

2017-12-01

Solar reflective "cool materials" can be used to lower urban temperatures, useful for mitigating the urban heat island effect and adapting to the local impacts of climate change. While numerous past studies have investigated the climate impacts of cool surfaces, few studies have investigated their effects on air pollution. Meteorological changes from increases in surface albedo can lead to temperature and transport induced modifications in air pollutant concentrations. In an effort to maintain high albedos in polluted environments, cool surfaces can also be made using photocatalytic "self-cleaning" materials. These photocatalytic materials can also remove NOx from ambient air, with possible consequences on ambient gas and particle phase pollutant concentrations. In this research, we investigate the impact of widespread deployment of cool walls on urban meteorology and air pollutant concentrations in the Los Angeles basin. Both photocatalytic and standard (not photocatalytic) high albedo wall materials are investigated. Simulations using a coupled meteorology-chemistry model (WRF-Chem) show that cool walls could effectively decrease urban temperatures in the Los Angeles basin. Preliminary results indicate that meteorology-induced changes from adopting standard cool walls could lead to ozone concentration reductions of up to 0.5 ppb. NOx removal induced by photocatalytic materials was modeled by modifying the WRF-Chem dry deposition scheme, with deposition rates informed by laboratory measurements of various commercially available materials. Simulation results indicate that increased deposition of NOx by photocatalytic materials could increase ozone concentrations, analogous to the ozone "weekend effect" in which reduced weekend NOx emissions can lead to increases in ozone. The impacts of cool walls on particulate matter concentrations are also discussed. Changes in particulate matter concentrations are found to be driven by albedo-induced changes in air pollutant

42 CFR 84.170 - Non-powered air-purifying particulate respirators; description.

Code of Federal Regulations, 2013 CFR

2013-10-01

... inhalation pressure to draw the ambient air through the air-purifying filter elements (filters) to remove... classified into three series, N-, R-, and P-series. The N-series filters are restricted to use in those workplaces free of oil aerosols. The R- and P-series filters are intended for removal of any particulate that...

42 CFR 84.170 - Non-powered air-purifying particulate respirators; description.

Code of Federal Regulations, 2011 CFR

2011-10-01

... inhalation pressure to draw the ambient air through the air-purifying filter elements (filters) to remove... classified into three series, N-, R-, and P-series. The N-series filters are restricted to use in those workplaces free of oil aerosols. The R- and P-series filters are intended for removal of any particulate that...

42 CFR 84.170 - Non-powered air-purifying particulate respirators; description.

Code of Federal Regulations, 2014 CFR

2014-10-01

... inhalation pressure to draw the ambient air through the air-purifying filter elements (filters) to remove... classified into three series, N-, R-, and P-series. The N-series filters are restricted to use in those workplaces free of oil aerosols. The R- and P-series filters are intended for removal of any particulate that...

42 CFR 84.170 - Non-powered air-purifying particulate respirators; description.

Code of Federal Regulations, 2012 CFR

2012-10-01

... inhalation pressure to draw the ambient air through the air-purifying filter elements (filters) to remove... classified into three series, N-, R-, and P-series. The N-series filters are restricted to use in those workplaces free of oil aerosols. The R- and P-series filters are intended for removal of any particulate that...

42 CFR 84.170 - Non-powered air-purifying particulate respirators; description.

Code of Federal Regulations, 2010 CFR

2010-10-01

... inhalation pressure to draw the ambient air through the air-purifying filter elements (filters) to remove... classified into three series, N-, R-, and P-series. The N-series filters are restricted to use in those workplaces free of oil aerosols. The R- and P-series filters are intended for removal of any particulate that...

Development of a new photocatalytic oxidation air filter for aircraft cabin.

PubMed

Ginestet, A; Pugnet, D; Rowley, J; Bull, K; Yeomans, H

2005-10-01

A new photocatalytic oxidation air filter (PCO unit) has been designed for aircraft cabin applications. The PCO unit is designed as a regenerable VOC removal system in order to improve the quality of the recirculated air entering the aircraft cabin. The PCO was designed to be a modular unit, with four UV lamps sandwiched between two interchangeable titanium dioxide coated panels. Performances of the PCO unit has been measured in a single pass mode test rig in order to show the ability of the unit to decrease the amount of VOCs (toluene, ethanol, and acetone) entering it (VOCs are fed separately), and in a multipass mode test rig in order to measure the ability of the unit to clean the air of an experimental room polluted with the same VOCs (fed separately). Triangular cell panels have been chosen instead of the wire mesh panels because they have higher efficiency. The efficiency of the PCO unit depends on the type of VOCs that challenges it, toluene being the most difficult one to oxidise. The efficiency of the PCO unit decreases when the air flow rate increases. The multipass mode test results show that the VOCs are oxidized but additional testing time would be necessary in order to show if they can be fully oxidized. The intermediate reaction products are mainly acetaldehyde and formaldehyde whose amount depends on the challenge VOC. The intermediate reaction products are also oxidized and additional testing time would be necessary in order to show if they can be fully oxidized. The development of this new photocatalytic air filter is still going on. The VOC/odor removing adsorbers are available for only a small proportion of aircraft currently in service. The photocatalytic oxidation (PCO) technique has appeared to be a promising solution to odors problems met in aircraft. This article reports the test results of a new photocatalytic oxidation air filter (PCO unit) designed for aircraft cabin applications. The overall efficiency of the PCO unit is function of

Photocatalytic Active Radiation Measurements and Use

NASA Technical Reports Server (NTRS)

Davis, Bruce A.; Underwood, Lauren W.

2011-01-01

Photocatalytic materials are being used to purify air, to kill microbes, and to keep surfaces clean. A wide variety of materials are being developed, many of which have different abilities to absorb various wavelengths of light. Material variability, combined with both spectral illumination intensity and spectral distribution variability, will produce a wide range of performance results. The proposed technology estimates photocatalytic active radiation (PcAR), a unit of radiation that normalizes the amount of light based on its spectral distribution and on the ability of the material to absorb that radiation. Photocatalytic reactions depend upon the number of electron-hole pairs generated at the photocatalytic surface. The number of electron-hole pairs produced depends on the number of photons per unit area per second striking the surface that can be absorbed and whose energy exceeds the bandgap of the photocatalytic material. A convenient parameter to describe the number of useful photons is the number of moles of photons striking the surface per unit area per second. The unit of micro-einsteins (or micromoles) of photons per m2 per sec is commonly used for photochemical and photoelectric-like phenomena. This type of parameter is used in photochemistry, such as in the conversion of light energy for photosynthesis. Photosynthetic response correlates with the number of photons rather than by energy because, in this photochemical process, each molecule is activated by the absorption of one photon. In photosynthesis, the number of photons absorbed in the 400 700 nm spectral range is estimated and is referred to as photosynthetic active radiation (PAR). PAR is defined in terms of the photosynthetic photon flux density measured in micro-einsteins of photons per m2 per sec. PcAR is an equivalent, similarly modeled parameter that has been defined for the photocatalytic processes. Two methods to measure the PcAR level are being proposed. In the first method, a calibrated

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.

Can TiO2-based photocatalytic textiles be used to improve the urban air quality?

NASA Astrophysics Data System (ADS)

Ródenas, Mila; Fages, Eduardo; Fatarella, Enrico; Herrero, David; Castagnoli, Lidia; Borràs, Esther; Vera, Teresa; Gómez, Tatiana; Catota, Marlon; Carreño, Javier; Hernández, Daniel; Gimeno, Cristina; López, Ramón; Muñoz, Amalia

2017-04-01

Despite current legislation and efforts made to improve urban air quality, significant negative effects still persist. That is the case of traffic, which impact on air pollution is a growing problem. For this reason, depollution measures are necessary to reach safer air quality levels. Recently, the use of titanium dioxide (TiO2) based photocatalytic self-cleaning and de-polluting materials has been considered to remove air pollutants, especially NOx. TiO2 can be found in the market under different formats for environmental purposes, and its effectiveness depends not only on the support (concrete, paints, etc) but also on the impregnation method (layer, embedded, etc). By combining laboratory and field campaigns, the LIFE PHOTOCITYTEX project was conceived to demonstrate the effectiveness of using TiO2-based photocatalytic nanomaterials in textiles as a way of alleviating the air pollution in urban areas. Within the project, which is already within its last year, two one-year extensive passive dosimetric campaigns have already been completed to assess their impact on the selected urban sites, measuring before and after the installation of the photocatalytic textile prototypes, respectively. Also, intensive active measurement campaigns (using active dosimetry, monitors and instrumentation for physical parameters) have been conducted to account for winter and summer conditions. Besides, lab-tests have been concluded to determine optimal photocatalytic formulations on textiles, and these have been tested at the EUPHORE simulation chambers under typical environmental conditions of various European cities. Besides the effect on NOx, which has been the main focus of the study, VOCs formation and abatement has been assessed, yielding in a better overall understanding of the whole process and its implications. Very promising results on the deep reduction of NOx have been observed at EUPHORE. From the calculation of the uptake coefficient, a mathematical model tool foresees

PHOTOCITYTEX - A LIFE project on the air pollution treatment in European urban environments by means of photocatalytic textiles

NASA Astrophysics Data System (ADS)

Ródenas, Milagros; Fages, Eduardo; Fatarella, Enrico; Herrero, David; Castagnoli, Lidia; Borrás, Esther; Vera, Teresa; Gómez, Tatiana; Carreño, Javier; López, Ramón; Gimeno, Cristina; Catota, Marlon; Muñoz, Amalia

2016-04-01

In urban areas, air pollution from traffic is becoming a growing problem. In recent years the use of titanium dioxide (TiO2) based photocatalytic self-cleaning and de-polluting materials has been considered to remove these pollutants. TiO2 is now commercially available and used in construction material or paints for environmental purposes. Further work, however, is still required to clarify the potential impacts from wider TiO2 use. Specific test conditions are required to provide objective and accurate knowledge. Under the LIFE PHOTOCITYTEX project, the effectiveness of using TiO2-based photocatalytic nanomaterials in building textiles as a way of improving the air quality in urban areas will be assessed. Moreover, information on secondary products formed during the tests will be obtained, yielding a better overall understanding of the whole process and its implications. For this purpose, a series of demonstrations are foreseen, comprising 1. lab-test and development of textile prototypes at lab scale, 2. larger scale demonstration of the use of photocatalytic textiles in the depollution of urban environments employing the EUPHORE chambers to simulate a number of environmental conditions of various European cities and 3. field demonstrations installing the photocatalytic textiles in two urban locations in Quart de Poblet, a tunnel and a school. A one-year extensive passive dosimetric campaign has already being carried out to characterize the selected urban sites before the installation of the photocatalytic textile prototypes, and a similar campaign after their installation is ongoing. Also, more comprehensive intensive active measurement campaigns have been conducted to account for winter and summer conditions. In parallel, lab-tests have already been completed to determine optimal photocatalytic formulations on textiles, followed by experiments at EUPHORE. Information on the deployment of the campaigns is given together with laboratory conclusions and first

Chemical mechanisms of photocatalytic de-soiling and de-polluting processes in indoor environments and urban surfaces

NASA Astrophysics Data System (ADS)

Sleiman, M.; Rosseler, O.; Montesinos, N.; Litter, M.; Bikiel, D.; Kirchstetter, T.; Bluhm, H.; Ahmed, M.; Salmeron, M.; Destaillats, H.

2013-12-01

Photocatalysis has been postulated as a promising approach for the de-pollution of indoor air and urban atmospheres, and for self-cleaning surfaces. Building materials and coatings containing nano-sized TiO2 photocatalytic functionalities are gaining market share, including self-cleaning building envelope materials (coatings, mortar, plaster, architectural fabrics and tiles) and indoor air purifiers. While many studies have reported good performance of photocatalysis in the removal of organic pollutants from indoor air, more information is needed to understand secondary emissions of potentially harmful byproducts from photocatalytic air cleaners. This presentation will describe analytical methods and experimental results from room-sized chamber experiments using a realistic challenge VOC mixture at low ppb levels. We will also present results from separate studies that used synchrotron-based surface spectroscopic and mass spectrometric methods to better understand the photocatalytic mechanisms that regulate the de-soiling and de-polluting activity. Two photocatalytic processes were studied: de-noxification (NOx removal) and de-soiling (removal of deposited black carbon or soot). Ambient pressure XPS was used to study surface and gas-phase species formed during adsorption of NO2 on TiO2 and subsequent UV irradiation at λ = 365 nm. The results illustrate how NOx chemistry on TiO2 surfaces can be affected by the presence of water vapor, heteroatoms present as impurities, and carbonaceous soiling. The reactivity of NOx and NO3- on surfaces leads to reduced adsorbed and gas-phase nitrogenated species. These processes need to be considered in the engineering of depolluting materials and incorporated into atmospheric models. De-soiling properties were investigated by analyzing soot oxidation on TiO2 surfaces. Model soot samples were used as surrogates of urban grime. Using laser desorption coupled with time-of-flight (TOF) mass spectrometry synchrotron ionization, we

Photocatalytic degradation properties of V-doped TiO2 to automobile exhaust.

PubMed

Wang, Tong; Shen, Dongya; Xu, Tao; Jiang, Ruiling

2017-05-15

To improve the photocatalytic degradation properties of titanium dioxide (TiO 2 ) used as raw materials for purifying automobile exhaust (AE), the vanadium (V)-doped TiO 2 samples were prepared. The photocatalytic degradation efficiencies of V-doped TiO 2 to each component in AE were evaluated under ultraviolet (UV) and visible light irradiation, respectively. Results indicated that the photocatalytic activity of V-doped TiO 2 to AE was higher than that of pure TiO 2 , and the optimal V dopant content of TiO 2 was 1.0% under UV light irradiation. The degradation efficiencies of V-doped TiO 2 to NOx and HC were higher than those to CO 2 and CO in AE because of the reversible reaction between CO 2 and CO. In addition, it was found that the photocatalytic degradation efficiencies of V-doped TiO 2 to each component in AE were also increased under visible light irradiation. The V-doped TiO 2 also showed higher degradation efficiencies to NOx and HC than those to CO 2 and CO under visible light irradiation. The V doped TiO 2 presented higher photocatalytic activity to CO 2 than that to CO, but the reversible reaction between CO and CO 2 was not found under visible light irradiation. The photocatalytic reactions of pure and V-doped TiO 2 samples to each component in AE followed the first order kinetic pathway under the two light irradiations. It is concluded that the V doping is a feasible method to improve the photocatalytic degradation properties of TiO 2 to AE for air purification, developing a sustainable environmental purification technology based on TiO 2 materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Coated mesh photocatalytic reactor for air treatment applications: comparative study of support materials.

PubMed

Passalía, Claudio; Nocetti, Emanuel; Alfano, Orlando; Brandi, Rodolfo

2017-03-01

An experimental comparative study of different meshes as support materials for photocatalytic applications in gas phase is presented. The photocatalytic oxidation of dichloromethane in air was addressed employing different coated meshes in a laboratory-scale, continuous reactor. Two fiberglass meshes and a stainless steel mesh were studied regarding the catalyst load, adherence, and catalytic activity. Titanium dioxide photocatalyst was immobilized on the meshes by dip-coating cycles. Results indicate the feasibility of the dichloromethane elimination in the three cases. When the number of coating cycles was doubled, the achieved conversion levels were increased twofold for stainless steel and threefold for the fiberglass meshes. One of the fiberglass meshes (FG2) showed the highest reactivity per mass of catalyst and per catalytic surface area.

Photocatalytic Destruction of Nitrate Esters in Air

DTIC Science & Technology

2000-07-01

four technologies are thermal treatment (direct flame or incineration), absorption (scrubbing), biofiltration , and adsorption (activated carbon). The...recycling the water through an aqueous phase photocatalytic system. Both approaches eliminate the carbon and reduce the water consumption. The use...of an aqueous phase photocatalytic oxidation system increases the capital equipment cost but eliminates the chemical handling and wastewater issues

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.

Integration of a photocatalytic multi-tube reactor for indoor air purification in HVAC systems: a feasibility study.

PubMed

van Walsem, Jeroen; Roegiers, Jelle; Modde, Bart; Lenaerts, Silvia; Denys, Siegfried

2018-04-24

This work is focused on an in-depth experimental characterization of multi-tube reactors for indoor air purification integrated in ventilation systems. Glass tubes were selected as an excellent photocatalyst substrate to meet the challenging requirements of the operating conditions in a ventilation system in which high flow rates are typical. Glass tubes show a low-pressure drop which reduces the energy demand of the ventilator, and additionally, they provide a large exposed surface area to allow interaction between indoor air contaminants and the photocatalyst. Furthermore, the performance of a range of P25-loaded sol-gel coatings was investigated, based on their adhesion properties and photocatalytic activities. Moreover, the UV light transmission and photocatalytic reactor performance under various operating conditions were studied. These results provide vital insights for the further development and scaling up of multi-tube reactors in ventilation systems which can provide a better comfort, improved air quality in indoor environments, and reduced human exposure to harmful pollutants.

Integrated photocatalytic filtration array for indoor air quality control.

PubMed

Denny, Frans; Permana, Eric; Scott, Jason; Wang, Jing; Pui, David Y H; Amal, Rose

2010-07-15

Photocatalytic and filtration technologies were integrated to develop a hybrid system capable of removing and oxidizing organic pollutants from an air stream. A fluidized bed aerosol generator (FBAG) was adapted to prepare TiO(2)-loaded ventilation filters for the photodegradation of gas phase ethanol. Compared to a manually loaded filter, the ethanol photodegradation rate constant for the FBAG coated filter increased by 361%. Additionally, the presence of the photogenerated intermediate product, acetaldehyde, was reduced and the time for mineralization to CO(2) was accelerated. These improvements were attributed to the FBAG system providing a more uniform distribution of TiO(2) particles across the filter surface leading to greater accessibility by the UV light. A dual-UV-lamp system, as opposed to a single-lamp system, enhanced photocatalytic filter performance demonstrating the importance of high light irradiance and light distribution across the filter surface. Substituting the blacklight blue lamps with a UV-light-emitting-diode (UV-LED) array led to further improvement as well as suppressed the electrical energy per order (EE/O) by a factor of 6. These improvements derived from the more uniform distribution of light irradiance as well as the higher efficiency of UV-LEDs in converting electrical energy to photons.

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.

COST ANALYSIS OF ACTIVATED CARBON VERSUS PHOTOCATALYTIC OXIDATION FOR REMOVING ORGANIC COMPOUNDS FROM INDOOR AIR

EPA Science Inventory

A cost comparison has been conducted of 1 m3/s indoor air cleaners using granular activated carbon (GAC) vs. photocatalytic oxidation (PCO) for treating a steady-state inlet volatile organic compound (VOC) concentration of 0.3 mg/m3. The commercial GAC unit was costed assuming t...

Conversion and Estrogenicity of 17β-estradiol During Photolytic/Photocatalytic Oxidation and Catalytic Wet-air Oxidation.

PubMed

Bistan, Mirjana; Tišler, Tatjana; Pintar, Albin

2012-06-01

Estrogen 17β-estradiol (E2), produced by human body and excreted into municipal wastewaters, belongs to the group of endocrine disrupting compounds that are resistant to biological degradation. The aim of this study was to assess the efficiency of E2 removal from aqueous solutions by means of catalytic wet-air oxidation (CWAO) and photolytic/photocatalytic oxidation. CWAO experiments were conducted in a trickle-bed reactor at temperatures up to 230 °C and oxygen partial pressure of 10 bar over TiO2 and Ru/TiO2 solids. Photolytic/photocatalytic oxidation was carried out in a batch slurry reactor employing a TiO2 P-25 (Degussa) catalyst under visible or UV light. HPLC analysis and yeast estrogen screen assay were used to evaluate the removal of E2 and estrogenicity of treated samples. The latter was completely removed during photolytic/photocatalytic oxidation under UV (365 nm) light and photocatalytic oxidation under visible light. In CWAO experiments, complete removal of both E2 and estrogenicity from the feed solution were noticed in the presence of TiO2 and Ru/TiO2 catalysts.

The surface activity of purified ocular mucin at the air-liquid interface and interactions with meibomian lipids.

PubMed

Millar, Thomas J; Tragoulias, Sophia T; Anderton, Philip J; Ball, Malcolm S; Miano, Fausto; Dennis, Gary R; Mudgil, Poonam

2006-01-01

Ocular mucins are thought to contribute to the stability of the tear film by reducing surface tension. The purpose of this study was to compare the effect of different mucins and hyaluronic acid (HA) alone and mixed with meibomian lipids on the surface pressure at an air-liquid interface. A Langmuir trough and Wilhelmy balance were used to measure and compare the surface activity of bovine submaxillary gland mucin (BSM), purified BSM, purified bovine ocular mucin and HA, and mixtures of these with meibomian lipids, phosphatidylcholine, and phosphatidylglycerol. Their appearance at the surface of an air-buffer interface was examined using epifluorescence microscopy. Purified ocular mucin had no surface activity even at concentrations that were 100 times more than normally occur in tears. By contrast, commercial BSM caused changes to surface pressure that were concentration dependent. The surface pressure-area profiles showed surface activity with maximum surface pressures of 12.3-22.5 mN/m depending on the concentration. Purified BSM showed no surface activity at low concentrations, whereas higher concentrations reached a maximum surface pressure of 25 mN/m. HA showed no surface activity, at low or high concentrations. Epifluorescence showed that the mucins were located at the air-buffer interface and changed the appearance of lipid films. Purified bovine ocular mucin and HA have no surface activity. However, despite having no surface activity in their own right, ocular mucins are likely to be present at the surface of the tear film, where they cause an increase in surface pressure by causing a compression of the lipids (a reorganization of the lipids) and alter the viscoelastic properties at the surface.

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

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.

42 CFR 84.1143 - Dust, fume, and mist air-purifying filter tests; performance requirements; general.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 1 2013-10-01 2013-10-01 false Dust, fume, and mist air-purifying filter tests; performance requirements; general. 84.1143 Section 84.1143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF...

42 CFR 84.1143 - Dust, fume, and mist air-purifying filter tests; performance requirements; general.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 1 2014-10-01 2014-10-01 false Dust, fume, and mist air-purifying filter tests; performance requirements; general. 84.1143 Section 84.1143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF...

42 CFR 84.1143 - Dust, fume, and mist air-purifying filter tests; performance requirements; general.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 1 2010-10-01 2010-10-01 false Dust, fume, and mist air-purifying filter tests; performance requirements; general. 84.1143 Section 84.1143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF...

42 CFR 84.1143 - Dust, fume, and mist air-purifying filter tests; performance requirements; general.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 1 2011-10-01 2011-10-01 false Dust, fume, and mist air-purifying filter tests; performance requirements; general. 84.1143 Section 84.1143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF...

42 CFR 84.1143 - Dust, fume, and mist air-purifying filter tests; performance requirements; general.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 1 2012-10-01 2012-10-01 false Dust, fume, and mist air-purifying filter tests; performance requirements; general. 84.1143 Section 84.1143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF...

The feasibility of an air purifier and secondhand smoke education intervention in homes of inner city pregnant women and infants living with a smoker.

PubMed

Rice, Jessica L; Brigham, Emily; Dineen, Rebecca; Muqueeth, Sadiya; O'Keefe, Gena; Regenold, Stephanie; Koehler, Kirsten; Rule, Ana; McCormack, Meredith; Hansel, Nadia N; Diette, Gregory B

2018-01-01

Secondhand smoke (SHS) and other air pollutants adversely affect the health of pregnant women and infants. A feasibility study aimed at reducing air pollution in homes of pregnant women or infants living with a smoker was completed. In collaboration with the Baltimore City Health Department, women ≥ 18 years of age and either pregnant nonsmokers, or post-partum (any smoking status) with an infant age 0-12 months were recruited. Homes had at least one smoker. Intervention included two air purifiers and secondhand smoke education. Outcomes included feasibility, change in fine particulate matter (PM 2.5 ), air nicotine, and salivary cotinine pre- and post-intervention. Fifty women were enrolled (mean age 27 years, 92% African American, 71% single, 94% Medicaid eligible, 34% reported smoking) and 86% completed the study. Of the 50 women, 32 had infants and 18 were pregnant at time of enrollment. Post- intervention, 70% of participants reported smokers were less likely to smoke indoors, and 77% had at least one air purifier turned on at the final visit. Participant satisfaction was high (91%) and 98% would recommend air purifiers. Indoor PM 2.5 was significantly decreased (P < 0.001). Salivary cotinine was significantly decreased for non-smoking women (P < 0.01) but not infants, and no significant change in air nicotine occurred (P = 0.6). Air purifiers with SHS education is a feasible intervention in homes of women and infants. These data demonstrate reduction in indoor PM 2.5 and salivary cotinine in non-smoking adults. Air purifiers are not an alternative for smoking cessation and a home/ car smoking ban. Smoking cessation should be strongly encouraged for all pregnant women, and nonsmoking mothers with infants should be counseled to completely avoid SHS exposure. This study provides support for a future intervention evaluating clinical endpoints. Copyright © 2017. Published by Elsevier Inc.

Efficacy of photocatalytic HEPA filter on microorganism removal.

PubMed

Chuaybamroong, P; Chotigawin, R; Supothina, S; Sribenjalux, P; Larpkiattaworn, S; Wu, C-Y

2010-06-01

This study assessed the application of photocatalytic oxidation (PCO) to the high efficiency particulate air (HEPA) filter for disinfection of airborne microorganisms. Experiments were conducted at two TiO2 loadings (1870 +/- 169 and 3140 +/- 67 mg/m(2)) on the HEPA filter irradiated with UV-A at the intensity of 0.85 +/- 0.18 or 4.85 +/- 0.09 mW/cm(2) under two relative humidity conditions (45 +/- 5% and 75 +/- 5%). Inactivation and penetration of four microorganisms were tested, including Aspergillus niger, Penicillium citrinum, Staphylococcus epidermidis, and Bacillus subtilis. It was found that microorganisms retained on a photocatalytic filter were inactivated around 60-80% and even 100% for S. epidermidis when the PCO reactions occurred. Lower penetration was also found from the photocatalytic filter for all airborne microorganisms. High humidity decreased photocatalysis efficacy. Increasing TiO2 loading or irradiance intensity did not substantially affect its disinfection capability. The high efficiency particulate air filter is used widely to remove particulates and microorganisms from the air stream. However, the filter may become a source of microbes if those retained microorganisms proliferate and re-entrain back into the filtered air. This study demonstrates that such a problem can be handled effectively by using photocatalytic reactions to inactivate those confined microorganisms. A 60-100% microbe reduction can be achieved for a wide variety of microorganisms to provide better indoor air quality for hospitals, offices, and domestic applications.

Determination of ethane, pentane and isoprene in exhaled air--effects of breath-holding, flow rate and purified air.

PubMed

Lärstad, M A E; Torén, K; Bake, B; Olin, A-C

2007-01-01

Exhaled ethane, pentane and isoprene have been proposed as biomarkers of oxidative stress. The objectives were to explore whether ethane, pentane and isoprene are produced within the airways and to explore the effect of different sampling parameters on analyte concentrations. The flow dependency of the analyte concentrations, the concentrations in dead-space and alveolar air after breath-holding and the influence of inhaling purified air on analyte concentrations were investigated. The analytical method involved thermal desorption from sorbent tubes and gas chromatography. The studied group comprised 13 subjects with clinically stable asthma and 14 healthy controls. Ethane concentrations decreased slightly, but significantly, at higher flow rates in subjects with asthma (P = 0.0063) but not in healthy controls. Pentane levels were increased at higher flow rates both in healthy and asthmatic subjects (P = 0.022 and 0.0063 respectively). Isoprene levels were increased at higher flow rates, but only significantly in healthy subjects (P = 0.0034). After breath-holding, no significant changes in ethane levels were observed. Pentane and isoprene levels increased significantly after 20 s of breath-holding. Inhalation of purified air before exhalation resulted in a substantial decrease in ethane levels, a moderate decrease in pentane levels and an increase in isoprene levels. The major fractions of exhaled ethane, pentane and isoprene seem to be of systemic origin. There was, however, a tendency for ethane to be flow rate dependent in asthmatic subjects, although to a very limited extent, suggesting that small amounts of ethane may be formed in the airways.

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.

Effects of an ozone-generating air purifier on indoor secondary particles in three residential dwellings.

PubMed

Hubbard, H F; Coleman, B K; Sarwar, G; Corsi, R L

2005-12-01

The use of indoor ozone generators as air purifiers has steadily increased over the past decade. Many ozone generators are marketed to consumers for their ability to eliminate odors and microbial agents and to improve health. In addition to the harmful effects of ozone, recent studies have shown that heterogeneous and homogeneous reactions between ozone and some unsaturated hydrocarbons can be an important source of indoor secondary pollutants, including free radicals, carbonyls, carboxylic acids, and fine particles. Experiments were conducted in one apartment and two detached single-family dwellings in Austin, TX, to assess the effects of an ozone generator on indoor secondary organic aerosol concentrations in actual residential settings. Ozone was generated using a commercial ozone generator marketed as an air purifier, and particle measurements were recorded before, during, and after the release of terpenes from a pine oil-based cleaning product. Particle number concentration, ozone concentration, and air exchange rate were measured during each experiment. Particle number and mass concentrations increased when both terpenes and ozone were present at elevated levels. Experimental results indicate that ozone generators in the presence of terpene sources facilitate the growth of indoor fine particles in residential indoor atmospheres. Human exposure to secondary organic particles can be reduced by minimizing the intentional release of ozone, particularly in the presence of terpene sources. Past studies have shown that ozone-initiated indoor chemistry can lead to elevated concentrations of fine particulate matter, but have generally been completed in controlled laboratory environments and office buildings. We explored the effects of an explicit ozone generator marketed as an air purifier on the formation of secondary organic aerosol mass in actual residential indoor settings. Results indicate significant increases in number and mass concentrations for particles <0

Effectiveness of air purifier on health outcomes and indoor particles in homes of children with allergic diseases in Fresno, California: A pilot study.

PubMed

Park, Hye-Kyung; Cheng, Kai-Chung; Tetteh, Afua O; Hildemann, Lynn M; Nadeau, Kari C

2017-05-01

Epidemiologic studies indicate that indoor air pollution is correlated with morbidity caused by allergic diseases. We evaluated the effectiveness of reducing the levels of indoor fine particulate matter <2.5 micrometer diameter (PM 2.5 ) in Fresno, California using air purifiers on health outcomes in children with asthma and/or allergic rhinitis. The active group (with air purifiers) and the control group consisted of eight houses each. Air purifiers were installed in the living rooms and bedrooms of the subjects in the active group during the entire 12-week study duration. Childhood asthma control test, peak flow rate monitoring, and nasal symptom scores were evaluated at weeks 0, 6, and 12. At 12 weeks, the active group showed a trend toward an improvement of childhood asthma control test scores and mean evening peak flow rates, whereas the control group showed deterioration in the same measures. Total and daytime nasal symptoms scores significantly reduced in the active group (p = 0.001 and p = 0.011, respectively). The average indoor PM 2.5 concentrations reduced by 43% (7.42 to 4.28 μg/m 3 ) in the active group (p = 0.001). Intervention with air purifiers reduces indoor PM 2.5 levels with significant improvements in nasal symptoms in children with allergic rhinitis in Fresno.

Effect of an ozone-generating air-purifying device on reducing concentrations of formaldehyde in air

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

Esswein, E.J.; Boeniger, M.F.

1994-02-01

Formaldehyde, an air contaminant found in many indoor air investigations, poses distinct occupational exposure hazards in certain job categories (e.g., mortuary science) but is also of concern when found or suspected in office buildings and homes. A variety of air-purifying devices (APDs) are currently available or marketed for application to reduce or remove concentrations of a variety of indoor air pollutants through the use of ozone as a chemical oxidant. An investigation was conducted to determine if concentrations of formaldehyde similar to those found in industrial hygiene evaluations of funeral homes could be reduced with the use of an ozone-generatingmore » APD. An ozone-generating APD was placed in an exposure chamber and formaldehyde-containing embalming solution was allowed to evaporate naturally, creating peak and mean chamber concentrations of 2.5 and 1.3 ppm, respectively. Continuous-reading instruments were used to sample for formaldehyde and ozone. Active sampling methods were also used to sample simultaneously for formaldehyde and a possible reactant product, formic acid. Triplicate measurements were made in each of three evaluations: formaldehyde alone, ozone alone, and formaldehyde and ozone combined. Concentrations of formaldehyde were virtually identical with and without 0.5 ppm ozone. No reduction in formaldehyde concentration was found during a 90-minute evaluation using ozone at this concentration with peak and average concentrations of approximately 2.5 and 1.3 ppm formaldehyde, respectively. The results of this investigation suggest that the use of ozone is ineffective in reducing concentrations of formaldehyde. Because ozone has demonstrated health hazards, and is a regulated air contaminant in both the occupational and ambient environment, the use of ozone as an air purification agent in indoor air does not seem warranted. 25 refs., 5 figs., 4 tabs.« less

Heterogeneous Reactivity of NO2 with Photocatalytic Paints: A Possible Source of Nitrous Acid (HONO) in the Indoor Environment

NASA Astrophysics Data System (ADS)

Gligorovski, S.; Bartolomei, V.; Gandolfo, A.; Gomez Alvarez, E.; Kleffmann, J.; Wortham, H.

2014-12-01

There is an increasing concern about the indoor air environment, where we spend most of our time. Common methods of improving indoor air quality include controlling pollution sources, increasing ventilation rates or using air purifiers. Photocatalytic remediation technology was suggested as a new possibility to eliminate indoor air pollutants instead of just diluting or disposing them. In the present study, heterogeneous reactions of NO2 were studied on photocatalytic paints containing different size and quantity of TiO2. The heterogeneous reactions were conducted in a photo reactor under simulated atmospheric conditions. The flat pyrex rectangular plates covered with the paint were inserted into the reactor. These plates have been sprayed with the photocatalytic paints at our industrial partner's (ALLIOS) facilities using a high precision procedure that allowed the application of a thin layer of a given thickness of the paint. This allows a homogeneous coverage of the surface with the paint and an accurate determination of the exact amount of paint exposed to gaseous NO2. We demonstrate that the indoor photocatalytic paints which contain TiO2 can substantially reduce the concentrations of nitrogen dioxide (NO2). We show that the efficiency of nitrogen dioxide (NO2) removal increase with the quantity of TiO2 in the range 0 - 7 %. The geometric uptake coefficients increase from 5 · 10-6 to 1.6 · 10-5 under light irradiation of the paints. On the other hand, during the reactions of NO2 with this paint (7 % of TiO2) nitric oxide (NO) and nitrous acid (HONO) are formed. Nitrous acid (HONO) is an important harmful indoor pollutant and its photolysis leads to the formation of highly reactive OH radicals (Gomez Alvarez et al., 2013). Maximum conversion efficiencies of NO2to HONO and NO of 15 % and 33 % were observed at 30 % RH, respectively. Thus, the quantity of TiO2 embedded in the paint is an important parameter regarding the nitrogen oxides (NOx = NO + NO2

Workplace performance of a loose-fitting powered air purifying respirator during nanoparticle synthesis

NASA Astrophysics Data System (ADS)

Koivisto, Antti J.; Aromaa, Mikko; Koponen, Ismo K.; Fransman, Wouter; Jensen, Keld A.; Mäkelä, Jyrki M.; Hämeri, Kaarle J.

2015-04-01

Nanoparticle (particles with diameter ≤100 nm) exposure is recognized as a potentially harmful size fraction for pulmonary particle exposure. During nanoparticle synthesis, the number concentrations in the process room may exceed 10 × 106 cm-3. During such conditions, it is essential that the occupants in the room wear highly reliable high-performance respirators to prevent inhalation exposure. Here we have studied the in-use program protection factor (PPF) of loose-fitting powered air purifying respirators, while workers were coating components with TiO2 or Cu x O y nanoparticles under a hood using a liquid flame spray process. The PPF was measured using condensation particle counters, an electrical low pressure impactor, and diffusion chargers. The room particle concentrations varied from 4 × 106 to 40 × 106 cm-3, and the count median aerodynamic diameter ranged from 32 to 180 nm. Concentrations inside the respirator varied from 0.7 to 7.2 cm-3. However, on average, tidal breathing was assumed to increase the respirator concentration by 2.3 cm-3. The derived PPF exceeded 1.1 × 106, which is more than 40 × 103 times the respirator assigned protection factor. We were unable to measure clear differences in the PPF of respirators with old and new filters, among two male and one female user, or assess most penetrating particle size. This study shows that the loose-fitting powered air purifying respirator provides very efficient protection against nanoparticle inhalation exposure if used properly.

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

Integral Design Methodology of Photocatalytic Reactors for Air Pollution Remediation.

PubMed

Passalía, Claudio; Alfano, Orlando M; Brandi, Rodolfo J

2017-06-07

An integral reactor design methodology was developed to address the optimal design of photocatalytic wall reactors to be used in air pollution control. For a target pollutant to be eliminated from an air stream, the proposed methodology is initiated with a mechanistic derived reaction rate. The determination of intrinsic kinetic parameters is associated with the use of a simple geometry laboratory scale reactor, operation under kinetic control and a uniform incident radiation flux, which allows computing the local superficial rate of photon absorption. Thus, a simple model can describe the mass balance and a solution may be obtained. The kinetic parameters may be estimated by the combination of the mathematical model and the experimental results. The validated intrinsic kinetics obtained may be directly used in the scaling-up of any reactor configuration and size. The bench scale reactor may require the use of complex computational software to obtain the fields of velocity, radiation absorption and species concentration. The complete methodology was successfully applied to the elimination of airborne formaldehyde. The kinetic parameters were determined in a flat plate reactor, whilst a bench scale corrugated wall reactor was used to illustrate the scaling-up methodology. In addition, an optimal folding angle of the corrugated reactor was found using computational fluid dynamics tools.

The effectiveness of photocatalytic ionisation disinfection of filter materials.

PubMed

Pietrzak, Katarzyna; Gutarowska, Beata

2013-01-01

The purpose of this study was to determine the effectiveness of photocatalytic ionisation as a disinfection method for filter materials contaminated by microorganisms, and to assess how air relative humidity (RH), time and microbe type influence the effectiveness of this disinfection. In the quantitative analysis of a used car air filter, bacterial contamination equalled 1.2 x 10(5) cfu/cm2, fungal contamination was 3.8 x 10(6) cfu/cm2, and the isolated microorganisms were Aspergillus niger, Bacillus megaterium, Cladosporium herbarum, Cryptococcus laurenti, Micrococcus sp., Rhodotorula glutinis and Staphylococcus cohnii. In the model experiment, three isolates (C. herbarum, R. glutinis, S. cohnii) and 3 ATCC species (A. niger, E. coli, S. aureus) were used for photocatalytic ionisation disinfection. The conditions of effective photocatalytic ionisation disinfection (R > or = 99.9%) were established as 2-3 h at RH = 77% (bacteria) and 6-24 h at RH = 53% (fungi). RH has an influence on the effectiveness of the photocatalytic disinfection process; the highest effectiveness was obtained for bacteria at RH = 77%, with results 5% higher than for RH = 49%. The studies show that the sensitivity of microorganisms to photocatalytic ionisation disinfection is ordered as follows: Gram-positive bacteria (S. cohnii, S. aureus), Gram-negative bacteria (E. coli), yeasts (R. glutinis), and moulds (C. herbarum, A. niger). Of all the mathematical models used for the description of death dynamics after photocatalytic ionisation disinfection, the Chick-Watson model is the most useful, but for more resistant microorganisms, the delayed Chick-Watson model is highly recommended. It therefore seems, that the presented disinfection method of photocatalytic ionisation can be successfully used to clean filtration materials.

Control of aerosol contaminants in indoor air: combining the particle concentration reduction with microbial inactivation.

PubMed

Grinshpun, Sergey A; Adhikari, Atin; Honda, Takeshi; Kim, Ki Youn; Toivola, Mika; Rao, K S Ramchander; Reponen, Tiina

2007-01-15

An indoor air purification technique, which combines unipolar ion emission and photocatalytic oxidation (promoted by a specially designed RCI cell), was investigated in two test chambers, 2.75 m3 and 24.3 m3, using nonbiological and biological challenge aerosols. The reduction in particle concentration was measured size selectively in real-time, and the Air Cleaning Factor and the Clean Air Delivery Rate (CADR) were determined. While testing with virions and bacteria, bioaerosol samples were collected and analyzed, and the microorganism survival rate was determined as a function of exposure time. We observed that the aerosol concentration decreased approximately 10 to approximately 100 times more rapidly when the purifier operated as compared to the natural decay. The data suggest that the tested portable unit operating in approximately 25 m3 non-ventilated room is capable to provide CADR-values more than twice as great than the conventional closed-loop HVAC system with a rating 8 filter. The particle removal occurred due to unipolar ion emission, while the inactivation of viable airborne microorganisms was associated with photocatalytic oxidation. Approximately 90% of initially viable MS2 viruses were inactivated resulting from 10 to 60 min exposure to the photocatalytic oxidation. Approximately 75% of viable B. subtilis spores were inactivated in 10 min, and about 90% or greater after 30 min. The biological and chemical mechanisms that led to the inactivation of stress-resistant airborne viruses and bacterial spores were reviewed.

Cardiopulmonary Benefits of Reducing Indoor Particles of Outdoor Origin: a Randomized Double-Blind Crossover Trial of Air Purifiers

PubMed Central

Chen, Renjie; Zhao, Ang; Chen, Honglei; Zhao, Zhuohui; Cai, Jing; Wang, Cuicui; Yang, Changyuan; Li, Huichu; Xu, Xiaohui; Ha, Sandie; Li, Tiantian; Kan, Haidong

2017-01-01

Background Indoor exposure to fine particulate matter (PM2.5) from outdoor sources is a major health concern, especially in highly polluted developing countries, such as China. Few studies have evaluated the effectiveness of indoor air purification on the improvement of cardiopulmonary health in these areas. Objectives To evaluate whether a short-term indoor air purifier intervention improves cardiopulmonary health. Methods We conducted a randomized double-blind crossover trial among 35 healthy college students in Shanghai, China in 2014. These students lived in dormitories that were randomized into 2 groups and alternated the use of true or sham air purifiers for 48 h with a 2-week washout interval. We measured 14 circulating biomarkers of inflammation, coagulation and vasoconstriction, lung function, blood pressure (BP), and fractional exhaled nitric oxide (FeNO). We applied linear mixed-effect models to evaluate the effect of the intervention on health outcome variables. Results On average, air purification resulted in a 57% reduction in PM2.5 concentration from 96.2 to 41.3 μg/m3 within hours of operation. Air purification was significantly associated with decreases in geometric means of several circulating inflammatory and thrombogenic biomarkers, including 17.5% in monocyte chemoattractant protein-1, 68.1% in interleukin-1β, 32.8% in myeloperoxidase and 64.9% in soluble CD40 ligand. Further, systolic BP, diastolic BP, and FeNO were significantly decreased by 2.7%, 4.8%, and 17.0% in geometric mean, respectively. The impacts on lung function and vasoconstriction biomarkers were beneficial, but not statistically significant. Conclusion This intervention study demonstrated clear cardiopulmonary benefits of indoor air purification among young, healthy adults in a Chinese city with severe ambient particulate air pollution. (Intervention Study on the Health Impact of Air Filters in Chinese Adults; NCT02239744) PMID:26022815

Cardiopulmonary benefits of reducing indoor particles of outdoor origin: a randomized, double-blind crossover trial of air purifiers.

PubMed

Chen, Renjie; Zhao, Ang; Chen, Honglei; Zhao, Zhuohui; Cai, Jing; Wang, Cuicui; Yang, Changyuan; Li, Huichu; Xu, Xiaohui; Ha, Sandie; Li, Tiantian; Kan, Haidong

2015-06-02

Indoor exposure to fine particulate matter (PM2.5) from outdoor sources is a major health concern, especially in highly polluted developing countries such as China. Few studies have evaluated the effectiveness of indoor air purification on the improvement of cardiopulmonary health in these areas. This study sought to evaluate whether a short-term indoor air purifier intervention improves cardiopulmonary health. We conducted a randomized, double-blind crossover trial among 35 healthy college students in Shanghai, China, in 2014. These students lived in dormitories that were randomized into 2 groups and alternated the use of true or sham air purifiers for 48 h with a 2-week washout interval. We measured 14 circulating biomarkers of inflammation, coagulation, and vasoconstriction; lung function; blood pressure (BP); and fractional exhaled nitric. We applied linear mixed-effect models to evaluate the effect of the intervention on health outcome variables. On average, air purification resulted in a 57% reduction in PM2.5 concentration, from 96.2 to 41.3 μg/m3, within hours of operation. Air purification was significantly associated with decreases in geometric means of several circulating inflammatory and thrombogenic biomarkers, including 17.5% in monocyte chemoattractant protein-1, 68.1% in interleukin-1β, 32.8% in myeloperoxidase, and 64.9% in soluble CD40 ligand. Furthermore, systolic BP, diastolic BP, and fractional exhaled nitrous oxide were significantly decreased by 2.7%, 4.8%, and 17.0% in geometric mean, respectively. The impacts on lung function and vasoconstriction biomarkers were beneficial but not statistically significant. This intervention study demonstrated clear cardiopulmonary benefits of indoor air purification among young, healthy adults in a Chinese city with severe ambient particulate air pollution. (Intervention Study on the Health Impact of Air Filters in Chinese Adults; NCT02239744). Copyright © 2015 American College of Cardiology Foundation

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.

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.

Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process.

PubMed

Gholami, Mitra; Nassehinia, Hamid Reza; Jonidi-Jafari, Ahmad; Nasseri, Simin; Esrafili, Ali

2014-02-05

Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries.Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions.

Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process

PubMed Central

2014-01-01

Background Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries. Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. Results The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Conclusions Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions. PMID:24499601

Photocatalytic equipment with nitrogen-doped titanium dioxide for air cleaning and disinfecting

NASA Astrophysics Data System (ADS)

Son Le, Thanh; Buu Ngo, Quoc; Dung Nguyen, Viet; Chau Nguyen, Hoai; Hien Dao, Trong; Tin Tran, Xuan; Kabachkov, E. N.; Balikhin, I. L.

2014-03-01

Nitrogen-doped TiO2 nanoparticle photocatalysts were synthesized by a sol-gel procedure using tetra-n-butyl orthotitanate as a titanium precursor and urea as a nitrogen source. Systematic studies for the preparation parameters and their impact on the material's structure were carried out by multiple techniques: thermogravimetric and differential scanning calorimetric analysis, x-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive x-ray spectroscopy and UV-Vis diffuse reflectance spectrophotometry showed that the nitrogen-doped TiO2 calcined at 500 °C for 3 h exhibited a spherical form with a particle size about 15-20 nm and crystal phase presented a mixture of 89.12% anatase. The obtained product was deposited on a porous quartz tube (D = 74 mm l = 418 mm) to manufacture an air photocatalytic cleaner as a prototype of the TIOKRAFT company's equipment. The created air cleaner was able to remove 60% of 10 ppm acetone within 390 min and degrade 98.5% of bacteria (total aerobic bacteria and fungi, 300 cfu m-3) within 120 min in a 10 m3 box. These photodegradation activities of N-TiO2 are higher than that of the commercial nano-TiO2 (Skyspring Inc., USA, particle size of 5-10 nm).

Parametric Evaluation of an Innovative Ultra-Violet PhotocatalyticOxidation (UVPCO) Air Cleaning Technology for Indoor Applications

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

Hodgson, Alfred T.; Sullivan, Douglas P.; Fisk, William J.

2005-10-31

An innovative Ultra-Violet Photocatalytic Oxidation (UVPCO) air cleaning technology employing a semitransparent catalyst coated on a semitransparent polymer substrate was evaluated to determine its effectiveness for treating mixtures of volatile organic compounds (VOCs) representative of indoor environments at low, indoor-relevant concentration levels. The experimental UVPCO contained four 30 by 30-cm honeycomb monoliths irradiated with nine UVA lamps arranged in three banks. A parametric evaluation of the effects of monolith thickness, air flow rate through the device, UV power, and reactant concentrations in inlet air was conducted for the purpose of suggesting design improvements. The UVPCO was challenged with three mixturesmore » of VOCs. A synthetic office mixture contained 27 VOCs commonly measured in office buildings. A building product mixture was created by combining sources including painted wallboard, composite wood products, carpet systems, and vinyl flooring. The third mixture contained formaldehyde and acetaldehyde. Steady state concentrations were produced in a classroom laboratory or a 20-m{sup 3} chamber. Air was drawn through the UVPCO, and single-pass conversion efficiencies were measured from replicate samples collected upstream and downstream of the reactor. Thirteen experiments were conducted in total. In this UVPCO employing a semitransparent monolith design, an increase in monolith thickness is expected to result in general increases in both reaction efficiencies and absolute reaction rates for VOCs oxidized by photocatalysis. The thickness of individual monolith panels was varied between 1.2 and 5 cm (5 to 20 cm total thickness) in experiments with the office mixture. VOC reaction efficiencies and rates increased with monolith thickness. However, the analysis of the relationship was confounded by high reaction efficiencies in all configurations for a number of compounds. These reaction efficiencies approached or exceeded 90% for alcohols

Ligand interaction with the purified serotonin transporter in solution and at the air/water interface

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

Faivre, V.; Manivet, P.; Callaway, J.C.

2000-06-01

The purified serotonin transporter (SERT) was spread at the air/water interface and the effects both of its surface density and of the temperature on its interfacial behavior were studied. The recorded isotherms evidenced the existence of a stable monolayer undergoing a lengthy rearrangement. SERT/ligand interactions appeared to be dependent on the nature of the studied molecules. Whereas an unrelated drug (chlorcyclizine) did not bind to the spread SERT, it interacted with its specific ligands. Compared to heterocyclic drugs, for which binding appeared to be concentration-dependent, a 'two-site' mechanism was evidenced for pinoline and imipramine.

Photocatalytic activity of silver oxide capped Ag nanoparticles constructed by air plasma irradiation

NASA Astrophysics Data System (ADS)

Fang, Yingcui; Wu, Qingmeng; Li, Huanhuan; Zhang, Bing; Yan, Rong; Chen, Junling; Sun, Mengtao

2018-04-01

We construct a kind of structure of silver oxide capped silver nanoparticles (AgNPs) by cost-efficient air plasma irradiation, and study its visible-light driven photocatalytic activity (PA). By controlling the oxidization time, the relationship between the intensity of the localized surface plasmon resonance (LSPR) and the PA is well established. The PA reaches the maximum when the LSPR of AgNPs is nearly completely damped (according to absorption spectra); however, under this condition, the LSPR still works, confirmed with the high efficient selective transformation of p-Aminothiophenol (PATP) to p, p'-dimercaptoazobenzene (DMAB) under visible light. The mechanism of the LSPR damping induced PA improvement is discussed. We not only provide a cost-efficient approach to construct a LSPR strong damping structure but also promote the understanding of LSPR strong damping and its relationship with photocatalysis.

Experimental investigation of photocatalytic effects of concrete in air purification adopting entire concrete waste reuse model.

PubMed

Xu, Yidong; Chen, Wei; Jin, Ruoyu; Shen, Jiansheng; Smallbone, Kirsty; Yan, Chunyang; Hu, Lei

2018-07-05

This research investigated the capacities of recycled aggregate concrete adopting entire concrete waste reuse model in degrading NO 2. Two major issues within environmental sustainability were addressed: concrete waste reuse rate and mitigation of hazards substances in the polluted air. The study consisted of two stages: identification of proper replacement rates of recycled concrete wastes in new concrete mixture design, and the evaluation of photocatalytic performance of recycled aggregate concrete in degrading NO 2 . It was found that replacement rates up to 3%, 30%, and 50% for recycled power, recycled fine aggregate, and recycled coarse aggregate respectively could be applied in concrete mixture design without deteriorating concrete strength. Recycled aggregates contained both positive attributes ("internal curing") and negative effects (e.g., lower hardness) to concrete properties. It was found that 30%-50% of natural coarse aggregate replaced by recycled coarse aggregates coated with TiO 2 would significantly improve the photocatalytic performance of concrete measured by degradation rate of NO 2 . Micro-structures of recycled aggregates observed under microscope indicated that soaking recycled aggregates in TiO 2 solution resulted in whiskers that filled the porosity within recycled aggregates which enhanced concrete strength. Copyright © 2018 Elsevier B.V. All rights reserved.

Fabrication of photocatalytically active vanadium oxide nanostructures via plasma route

NASA Astrophysics Data System (ADS)

Kajita, Shin; Yoshida, Tomoko; Ohno, Noriyasu; Ichino, Yusuke; Yoshida, Naoaki

2018-05-01

Plasma irradiation was used to create nanostructured vanadium oxide with potential commercial and industrial applications. Morphology changes were induced at the nano- and micro-meter scale, accompanied by the growth of helium nanobubbles. Micrometer-sized pillars, cube-shaped nanostructures, and fuzzy fiberform nanostructures were grown on the surface; the necessary conditions in terms of the incident ion energy and the surface temperature for those morphology changes were revealed. Hydrogen production experiments using a photocatalytic reaction with aqueous methanol solution were conducted on the fabricated samples. Enhanced H2 production was confirmed with the plasma irradiated nanostructured sample that had been oxidized in air atmosphere. Photocatalytically inactive vanadium oxide exhibited a high photocatalytic activity after nanostructurization of the surface by helium plasma irradiation.

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.

Synthesis of hectorite-TiO2 and kaolinite-TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

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

Destaillats, Hugo; Kibanova, D.; Trejo, M.

2008-03-01

We studied the synthesis and photocatalytic activity of small-sized TiO{sub 2} supported on hectorite and kaolinite. Deposition of TiO{sub 2} on the clay mineral surface was conducted by using a sol-gel method with titanium isopropoxide as precursor. Anatase TiO{sub 2} particles formation was achieved by hydrothermal treatment at 180 C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. Efficiency in synthesizing clay-TiO{sub 2} composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed bymore » important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite-TiO{sub 2}, as compared with the untreated material. Photocatalytic performance of clay-TiO{sub 2} composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay-TiO{sub 2} composites was comparable to that observed using pure commercial TiO{sub 2} (Degussa P25).« less

Efficiency of clay--TiO2 nanocomposites on the photocatalytic elimination of a model hydrophobic air pollutant.

PubMed

Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

2009-03-01

Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a benchtop photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (lamda(max) = 365 nm) or UVC (lamda(max) = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-Ti02 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of approximately 170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33, and 66% relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA sorbent tubes downstream of the reactor, with subsequent thermal desorption--GC/MS analysis. The fraction of toluene removed, %R, and the reaction rate, Tr, were calculated for each experimental condition from the concentrations measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/Ilamda,the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but notfor Kao-TiO2. In all

Efficiency of clay-TiO2 nanocomposites on the photocatalytic eliminationof a model hydrophobic air pollutant

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

Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

2009-01-01

Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (gamma max = 365 nm) or UVC (gamma max = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation ofmore » ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of ~;;170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33 and 66percent relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA (R) sorbent tubes downstream of the reactor, with subsequent thermal desorption -- GC/MS analysis. The fraction of toluene removed, percentR, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/I gamma, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not

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.

Self-Powered Electrostatic Filter with Enhanced Photocatalytic Degradation of Formaldehyde Based on Built-in Triboelectric Nanogenerators.

PubMed

Feng, Yawei; Ling, Lili; Nie, Jinhui; Han, Kai; Chen, Xiangyu; Bian, Zhenfeng; Li, Hexing; Wang, Zhong Lin

2017-12-26

Recently, atmospheric pollution caused by particulate matter or volatile organic compounds (VOCs) has become a serious issue to threaten human health. Consequently, it is highly desirable to develop an efficient purifying technique with simple structure and low cost. In this study, by combining a triboelectric nanogenerator (TENG) and a photocatalysis technique, we demonstrated a concept of a self-powered filtering method for removing pollutants from indoor atmosphere. The photocatalyst P25 or Pt/P25 was embedded on the surface of polymer-coated stainless steel wires, and such steel wires were woven into a filtering network. A strong electric field can be induced on this filtering network by TENG, while both electrostatic adsorption effect and TENG-enhanced photocatalytic effect can be achieved. Rhodamine B (RhB) steam was selected as the pollutant for demonstration. The absorbed RhB on the filter network with TENG in 1 min was almost the same amount of absorption achieved in 15 min without using TENG. Meanwhile, the degradation of RhB was increased over 50% under the drive of TENG. Furthermore, such a device was applied for the degradation of formaldehyde, where degradation efficiency was doubled under the drive of TENG. This work extended the application for the TENG in self-powered electrochemistry, design and concept of which can be possibly applied in the field of haze governance, indoor air cleaning, and photocatalytic pollution removal for environmental protection.

Cardiorespiratory responses of air filtration: A randomized crossover intervention trial in seniors living in Beijing: Beijing Indoor Air Purifier StudY, BIAPSY.

PubMed

Shao, Danqing; Du, Yipeng; Liu, Shuo; Brunekreef, Bert; Meliefste, Kees; Zhao, Qian; Chen, Jie; Song, Xiaoming; Wang, Meng; Wang, Juan; Xu, Hongbing; Wu, Rongshan; Wang, Tong; Feng, Baihuan; Lung, Candice Shih-Chun; Wang, Xian; He, Bei; Huang, Wei

2017-12-15

In this Beijing Indoor Air Purifier StudY (BIAPSY), we conducted a randomized crossover intervention trial in a panel of 35 non-smoking senior participants with free-living, with and without chronic obstructive pulmonary disease (COPD). Portable air filtration units were randomly allocated to active-(filter in) for 2weeks and sham-mode (filter out) for 2weeks in the households. We examined the differences in indoor air pollutant concentrations in 20 study homes and a suite of cardio-respiratory biomarker levels in study participants between filtration modes, with and without adjustment for potential confounders. Following active filtration, we observed significant reductions from 60±45 to 24±15μg/m 3 in ten-day averages of indoor PM 2.5 and reductions from 3.87±1.65 to 1.81±1.19m -1 .10 -5 in ten-day averages of indoor BC, compared to sham-mode filtration. The major components of indoor PM 2.5 , including water soluble organics, NO 3 - , SO 4 2- , Zn 2+ , Pb 2+ and K + , were also reduced significantly by 42% to 63%. However, following active filtration, we only observed significant reductions on systemic inflammation measured as of IL-8 at 58.59% (95% CI: -76.31, -27.64) in the total group of participants and 70.04% (95% CI: -83.05, -47.05) in the subset of COPD patients, with adjustments. We were not able to detect improvements on lung function, blood pressure, and heart rate variability, following short-term intervention of two-week active air filtration. In conclusion, our results showed that indoor air filtration produced clear improvement on indoor air quality, but no demonstrable changes in the cardio-respiratory outcomes of study interest observed in the seniors living with real-world air pollution exposures. Copyright © 2017 Elsevier B.V. All rights reserved.

Improvement of Linde Kryotechnik's internal purifier

NASA Astrophysics Data System (ADS)

Decker, Lutz; Meier, Albert; Wilhelm, Hanspeter

2014-01-01

With the recent shortage in supply of helium, recovery solutions have experienced a new focus with a tendency to recover streams with higher impurity content. This development calls for purifier systems operating efficiently and with low impact on liquefaction capacity for helium streams with impurity levels in the percentage range. Linde Kryotechnik has answered this demand by improving the performance of its purifier technology. Since 1983, its standardized helium liquefiers of the L- and former TCF-series type contain an internal purifier which already allows efficient impurity removal with minimized space demand. Along with a line dryer to absorb humidity, it is designed to remove air impurities up to 5 mol%. However, with increasing impurity level, liquefaction capacity reduced significantly being furthermore restricted to an upper level of approx. 180 l/h and continuous purification became limited in time. With the current redesign of this purifier, the impact on liquefaction capacity is now minimized without any limitation within the capacity range of the L-series plants. Continuous purification is hence ensured beyond previous maximum impurity content. This paper provides the key design changes and the achievable performance, which has been verified in the recent L-series plants delivered to customers.

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.

Facile synthesis of polyaniline-modified CuS with enhanced adsorbtion and photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Xiufang; Chen, Shaohua; Shuai, Ying

2016-10-01

Novel hierarchical polyaniline-modified CuS (PANI-CuS) has been synthesized by simple assembling PANI on the surface of flower-like CuS spheres. The PANI modification enhances the adsorption properties of flower-like CuS. The prepared PANI-CuS composites exhibit higher visible-light-driven photocatalytic activities in degradation of rhodamine B (RhB) than that of neat CuS. The unusual photocatalytic activity could be attributed to the great adsorptivity of dyes, the extended photoresponse range, and the high migration efficiency of photoinduced electrons, which may effectively suppress the charge recombination. This work not only provides a simple strategy for fabricating highly efficient and stable CuS-based composites, but also proves that these unique structures are excellent platforms for significantly improving their visible- light-driven photoactivities, holding great promise for their applications in the field of purifying polluted water resources.

Deposition of Visible Light Active Photocatalytic Bismuth Molybdate Thin Films by Reactive Magnetron Sputtering

PubMed Central

Ratova, Marina; Kelly, Peter J.; West, Glen T.; Xia, Xiaohong; Gao, Yun

2016-01-01

Bismuth molybdate thin films were deposited by reactive magnetron co-sputtering from two metallic targets in an argon/oxygen atmosphere, reportedly for the first time. Energy dispersive X-ray spectroscopy (EDX) analysis showed that the ratio of bismuth to molybdenum in the coatings can be effectively controlled by varying the power applied to each target. Deposited coatings were annealed in air at 673 K for 30 min. The crystalline structure was assessed by means of Raman spectroscopy and X-ray diffraction (XRD). Oxidation state information was obtained by X-ray photoelectron spectroscopy (XPS). Photodegradation of organic dyes methylene blue and rhodamine B was used for evaluation of the photocatalytic properties of the coatings under a visible light source. The photocatalytic properties of the deposited coatings were then compared to a sample of commercial titanium dioxide-based photocatalytic product. The repeatability of the dye degradation reactions and photocatalytic coating reusability are discussed. It was found that coatings with a Bi:Mo ratio of approximately 2:1 exhibited the highest photocatalytic activity of the coatings studied; its efficacy in dye photodegradation significantly outperformed a sample of commercial photocatalytic coating. PMID:28787867

Advantages for passengers and cabin crew of operating a gas-phase adsorption air purifier in 11-h simulated flights.

PubMed

Strøm-Tejsen, P; Zukowska, D; Fang, L; Space, D R; Wyon, D P

2008-06-01

Experiments were carried out in a three-row, 21-seat section of a simulated aircraft cabin installed in a climate chamber to evaluate the extent to which passengers' perception of cabin air quality is affected by the operation of a gas-phase adsorption (GPA) purification unit. A total of 68 subjects, divided into four groups of 17 subjects took part in simulated 11-h flights. Each group experienced four conditions in balanced order, defined by two outside air supply rates (2.4 and 3.3 l/s per person), with and without the GPA purification unit installed in the recirculated air system, a total of 2992 subject-hours of exposure. During each flight the subjects completed questionnaires five times to provide subjective assessments of air quality, cabin environment, intensity of symptoms, and thermal comfort. Additionally, the subjects' visual acuity, finger temperature, skin dryness, and nasal peak flow were measured three times during each flight. Analysis of the subjective assessments showed that operating a GPA unit in the recirculated air provided consistent advantages with no apparent disadvantages. Operating a gas-phase adsorption (GPA) air purifier unit in the recirculated air in a simulated airplane cabin provided a clear and consistent advantage for passengers and crew that became increasingly apparent at longer flight times. This finding indicates that the expense of undertaking duly blinded field trials on revenue flights would be justified.

Studies on the treatment of urine by the biological purification-UV photocatalytic oxidation

NASA Astrophysics Data System (ADS)

Liu, Ch. Ch; Liu, R. D.; Liu, X. S.; Chen, M.; Bian, Z. L.; Hu, J. Ch.

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

Studies on urine treatment by biological purification using Azolla and UV photocatalytic oxidation

NASA Astrophysics Data System (ADS)

Liu, Xiaofeng; Chen, Min; Bian, Zuliang; Liu, Chung-Chu

The amount of water consumed in space station operations is very large. In order to reduce the amount of water which must be resupplied from Earth, the space station needs to resolve the problems of water supply. For this reason, the recovery, regeneration and utilization of urine of astronauts are of key importance. Many investigations on this subject have been reported. Our research is based on biological absorption and, purification using UV photocatalytic oxidation techniques to achieve comprehensive treatment for urine. In the treatment apparatus we created, the urine solution is used as part of the nutrient solution for the biological components in our bioregenerative life support system. After being absorbed, the nutrients from the urine were then decomposed, metabolized and purified which creates a favorable condition for the follow-up oxidation treatment by UV photocatalytic oxidation. After these two processes, the treated urine solution reached Chinese national standards for drinking water quality (GB5749-1985).

Composite TiO2/clays materials for photocatalytic NOx oxidation

NASA Astrophysics Data System (ADS)

Todorova, N.; Giannakopoulou, T.; Karapati, S.; Petridis, D.; Vaimakis, T.; Trapalis, C.

2014-11-01

TiO2 photocatalyst received much attention for air purification applications especially for removal of air pollutants like NOx, VOCs etc. It has been established that the activity of the photocatalyst can be significantly enhanced by its immobilization onto suitable substrates like inorganic minerals, porous silica, hydroxyapatite, adsorbent materials like activated carbon, various co-catalysts such as semiconductors, graphene, reduced graphite oxide, etc. In the present work, photocatalytic composite materials consisted of mineral substrate and TiO2 in weight ratio 1:1 were manufactured and examined for oxidation and removal of nitric oxides NOx (NO and NO2). Commercial titania P25 (Evonik-Degussa) and urea-modified P25 were used as photocatalytically active components. Inorganic minerals, namely kunipia, talk and hydrotalcite were selected as supporting materials due to their layered structure and expected high NOx adsorption capability. Al3+ and Ca2+ intercalation was applied in order to improve the dispersion of TiO2 and its loading into the supporting matrix. The X-ray diffraction analysis and Scanning Electron Microscopy revealed the binary structure of the composites and homogeneous dispersion of the photocatalyst into the substrates. The photocatalytic behavior of the materials in NOx oxidation and removal was investigated under UV and visible light irradiation. The composite materials exhibited superior photocatalytic activity than the bare titania under both types of irradiation. Significant visible light activity was recorded for the composites containing urea-modified titania that was accredited to the N-doping of the semiconductor. Among the different substrates, the hydrotalcite caused highest increase in the NOx removal, while among the intercalation ions the Ca2+ was more efficient. The results were related to the improved dispersion of the TiO2 and the synergetic activity of the substrates as NOx adsorbers.

TiO₂-Based Photocatalytic Geopolymers for Nitric Oxide Degradation.

PubMed

Strini, Alberto; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Messina, Francesco; Schiavi, Luca; Corsaro, Davide; Cioffi, Raffaele

2016-06-24

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO₂ by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features.

Valorization of Flue Gas by Combining Photocatalytic Gas Pretreatment with Microalgae Production.

PubMed

Eynde, Erik Van; Lenaerts, Britt; Tytgat, Tom; Blust, Ronny; Lenaerts, Silvia

2016-03-01

Utilization of flue gas for algae cultivation seems to be a promising route because flue gas from fossil-fuel combustion processes contains the high amounts of carbon (CO2) and nitrogen (NO) that are required for algae growth. NO is a poor nitrogen source for algae cultivation because of its low reactivity and solublilty in water and its toxicity for algae at high concentrations. Here, we present a novel strategy to valorize NO from flue gas as feedstock for algae production by combining a photocatalytic gas pretreatment unit with a microalgal photobioreactor. The photocatalytic air pretreatment transforms NO gas into NO2 gas and thereby enhances the absorption of NOx in the cultivation broth. The absorbed NOx will form NO2(-) and NO3(-) that can be used as a nitrogen source by algae. The effect of photocatalytic air pretreatment on the growth and biomass productivity of the algae Thalassiosira weissflogii in a semicontinuous system aerated with a model flue gas (1% CO2 and 50 ppm of NO) is investigated during a long-term experiment. The integrated system makes it possible to produce algae with NO from flue gas as the sole nitrogen source and reduces the NOx content in the exhaust gas by 84%.

Solutions Network Formulation Report. NASA's Potential Contributions for Using Solar Ultraviolet Radiation in Conjunction with Photocatalysis for Urban Air Pollution Mitigation and Increasing Air Quality

NASA Technical Reports Server (NTRS)

Underwood, Lauren; Ryan, Robert E.

2007-01-01

This Candidate Solution is based on using NASA Earth science research on atmospheric ozone and aerosols data as a means to predict and evaluate the effectiveness of photocatalytically created surfaces (building materials like glass, tile and cement) for air pollution mitigation purposes. When these surfaces are exposed to near UV light, organic molecules, like air pollutants and smog precursors, will degrade into environmentally friendly compounds. U.S. EPA (Environmental Protection Agency) is responsible for forecasting daily air quality by using the Air Quality Index (AQI) that is provided by AIRNow. EPA is partnered with AIRNow and is responsible for calculating the AQI for five major air pollutants that are regulated by the Clean Air Act. In this Solution, UV irradiance data acquired from the satellite mission Aura and the OMI Surface UV algorithm will be used to help understand both the efficacy and efficiency of the photocatalytic decomposition process these surfaces facilitate, and their ability to reduce air pollutants. Prediction models that estimate photocatalytic function do not exist. NASA UV irradiance data will enable this capability, so that air quality agencies that are run by state and local officials can develop and implement programs that utilize photocatalysis for urban air pollution control and, enable them to make effective decisions about air pollution protection programs.

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.

Photocatalytic destruction of automobile exhaust emissions

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

Kaviranta, P.D.; Peden, C.H.F.

1996-10-01

Hydrocarbons, carbon monoxide, and nitrogen oxides contained in automobile exhaust emissions are among the major atmospheric air pollutants. During the first few minutes of a cold start of the engine, the emission levels of unburned hydrocarbon and CO pollutants are very high due to the inefficiency of the cold engine and the poor activity of the catalysts lower temperatures. Therefore, it is necessary to provide an alternative approach to deal with this specific problem in order to meet near-term regulatory requirements. Our approach has been to use known photocatalytic reactions obtainable on semiconducting powders such as titanium dioxide. In thismore » presentation we describe our recent studies aimed at the photocatalytic reduction of unburned hydrocarbons and carbon monoxide in automobile exhaust emissions. Our results demonstrate the effective destruction of propylene into water and carbon dioxide. The conversion was found to be dependent on the propylene flow rate. The reaction rate was studied as a function of time, humidity and temperature. The effect of the power of the UV source on conversion will also be presented.« less

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.

TiO2-Based Photocatalytic Geopolymers for Nitric Oxide Degradation

PubMed Central

Strini, Alberto; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Messina, Francesco; Schiavi, Luca; Corsaro, Davide; Cioffi, Raffaele

2016-01-01

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO2 by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features. PMID:28773634

Influence of thermodynamic mechanism of inter- facial adsorption on purifying air-conditioning engineering under intensification of electric field

NASA Astrophysics Data System (ADS)

Chen, Yun-Yu

2016-12-01

As a kind of mass transfer process as well as the basis of separating and purifying mixtures, interfacial adsorption has been widely applied to fields like chemical industry, medical industry and purification engineering in recent years. Influencing factors of interfacial adsorption, in addition to the traditional temperature, intensity of pressure, amount of substance and concentration, also include external fields, such as magnetic field, electric field and electromagnetic field, etc. Starting from the point of thermodynamics and taking the Gibbs adsorption as the model, the combination of energy axiom and the first law of thermodynamics was applied to boundary phase, and thus the theoretical expression for the volume of interface absorption under electric field as well as the mathematical relationship between surface tension and electric field intensity was obtained. In addition, according to the obtained theoretical expression, the volume of interface absorption of ethanol solution under different electric field intensities and concentrations was calculated. Moreover, the mechanism of interfacial adsorption was described from the perspective of thermodynamics and the influence of electric field on interfacial adsorption was explained reasonably, aiming to further discuss the influence of thermodynamic mechanism of interfacial adsorption on purifying air-conditioning engineering under intensification of electric field.

Ozone Air Purifiers: Can They Improve Asthma Symptoms?

MedlinePlus

... and cleaner. However, ozone generators don't actually filter out the small particles that trigger asthma. Inhaling ... air — but they may generate unwanted ozone. Air filters that remove small particles — such as high-efficiency ...

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 degradation of NOx in a pilot street canyon configuration using TiO2-mortar panels.

PubMed

Maggos, Th; Plassais, A; Bartzis, J G; Vasilakos, Ch; Moussiopoulos, N; Bonafous, L

2008-01-01

Titanium dioxide is the most important photocatalysts used for purifying applications. If a TiO2- containing material is left outdoors as a form of flat panels, it is activated by sunlight to remove harmful NOx gases during the day. The photocatalytic efficiency of a TiO2-treated mortar for removal of NOx was investigated in the frame of this work. For this purpose a fully equipped monitoring system was designed at a pilot site. This system allows the in situ evaluation of the de-polluting properties of a photocatalytic material by taking into account the climatologic phenomena in street canyons, accurate measurements of pollution level and full registration of meteorological data The pilot site involved three artificial canyon streets, a pollution source, continuous NOx measurements inside the canyons and the source as well as background and meteorological measurements. Significant differences on the NOx concentration level were observed between the TiO2 treated and the reference canyon. NOx values in TiO2 canyon were 36.7 to 82.0% lower than the ones observed in the reference one. Data arising from this study could be used to assess the impact of the photocatalytic material on the purification of the urban environment.

Gas stream purifier

NASA Technical Reports Server (NTRS)

Adam, Steven J.

1994-01-01

A gas stream purifier has been developed that is capable of removing corrosive acid, base, solvent, organic, inorganic, and water vapors as well as particulates from an inert mixed gas stream using only solid scrubbing agents. This small, lightweight purifier has demonstrated the ability to remove contaminants from an inert gas stream with a greater than 99 percent removal efficiency. The Gas Stream Purifier has outstanding market and sales potential in manufacturing, laboratory and science industries, medical, automotive, or any commercial industry where pollution, contamination, or gas stream purification is a concern. The purifier was developed under NASA contract NAS9-18200 Schedule A for use in the international Space Station. A patent application for the Gas Stream Purifier is currently on file with the United States Patent and Trademark Office.

Synthesis and photocatalytic activity of electrospun niobium oxide nanofibers

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

Qi, Shishun; Zuo, Ruzhong, E-mail: piezolab@hfut.edu.cn; Liu, Yi

2013-03-15

Graphical abstract: Different morphologies are obtained for the electrospun niobium oxide nanofibers with different phase structures. The nanofibers of the two phase structures present different band gap value and the light absorption. Hexagonal phase nanofibers show better photocatalytic activity compared with the orthorhombic nanofibers. Highlights: ► Niobium oxide nanofibers of two phase structures were fabricated by electrospinning. ► Photocatalytic properties of the niobium oxide nanofibers were first explored. ► Nanofibers of different phase structures showed different photocatalytic activities. ► Reasons for the differences in the photocatalysis were carefully discussed. - Abstract: Niobium oxide (Nb{sub 2}O{sub 5}) nanofibers have been synthesizedmore » by sol–gel based electrospinning technique. Pure hexagonal phase (H-Nb{sub 2}O{sub 5}) and orthorhombic phase (O-Nb{sub 2}O{sub 5}) nanofibers were obtained by thermally annealing the electrospun Nb{sub 2}O{sub 5}/polyvinylpyrrolidone composite fibers in air at 500 °C and 700 °C, respectively. The fibers were characterized using the X-ray diffraction, scanning electron microscopy, specific surface area analyzer and UV–vis diffuse reflectance spectroscopy. Photocatalytic activities of the obtained nanofibers were evaluated depending on the degradation of methyl orange. The results indicate that the heat-treatment temperature, the crystalline structure and the morphology affected the physical and chemical properties of the as-prepared Nb{sub 2}O{sub 5} nanofibers. The H-Nb{sub 2}O{sub 5} nanofibers obtained at lower temperature showed better potential for the application as a promising photocatalyst.« less

Synthesis, Structural Property, Photophysical Property, Photocatalytic Property of Novel ZnBiErO4 under Visible Light Irradiation

PubMed Central

Zhuang, Yan

2018-01-01

A novel photocatalyst ZnBiErO4 was firstly synthesized by solid-state reaction method and its structural and photocatalytic properties were analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance. The results demonstrated that ZnBiErO4 crystallized with tetragonal crystal structure with space group I41/A. The lattice parameters for ZnBiErO4 were proved to be a = b = 10.255738 Å and c = 9.938888 Å. The band gap of ZnBiErO4 was estimated to be about 1.69 eV. Compared with nitrogen doped TiO2, ZnBiErO4 showed excellent photocatalytic activities for degrading methyl blue during visible light irradiation. The photocatalytic degradation of methyl blue with ZnBiErO4 or N-doped TiO2 as catalyst followed the first-order reaction kinetics. Moreover, the apparent first-order rate constant of ZnBiErO4 or N-doped TiO2 was 0.01607 min−1 or 0.00435 min−1. The reduction of total organic carbon, formation of inorganic products, such as SO42− and NO3− and the evolution of CO2 revealed the continuous mineralization of methyl blue during the photocatalytic process. ZnBiErO4 photocatalyst had great potential to purify textile industry wastewater. PMID:29463016

Are TiO2 nanotubes worth using in photocatalytic purification of air and water?

PubMed

Pichat, Pierre

2014-09-19

Titanium dioxide nanotubes (TNT) have mainly been used in dye sensitized solar cells, essentially because of a higher transport rate of electrons from the adsorbed photo-excited dye to the Ti electrode onto which TNT instead of TiO2 nanoparticles (TNP) are attached. The dimension ranges and the two main synthesis methods of TNT are briefly indicated here. Not surprisingly, the particular and regular texture of TNT was also expected to improve the photocatalytic efficacy for pollutant removal in air and water with respect to TNP. In this short review, the validity of this expectation is checked using the regrettably small number of literature comparisons between TNT and commercialized TNP referring to films of similar thickness and layers or slurries containing an equal TiO2 mass. Although the irradiated geometrical area differed for each study, it was identical for each comparison considered here. For the removal of toluene (methylbenzene) or acetaldehyde (ethanal) in air, the average ratio of the efficacy of TNT over that of TiO2 P25 was about 1.5, and for the removal of dyes in water, it was around 1. This lack of major improvement with TNT compared to TNP could partially be due to TNT texture disorders as seems to be suggested by the better average performance of anodic oxidation-prepared TNT. It could also come from the fact that the properties influencing the efficacy are more numerous, their interrelations more complex and their effects more important for pollutant removal than for dye sensitized solar cells and photoelectrocatalysis where the electron transport rate is the crucial parameter.

Purifying Nanomaterials

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh (Inventor); Hurst, Janet (Inventor)

2014-01-01

A method of purifying a nanomaterial and the resultant purified nanomaterial in which a salt, such as ferric chloride, at or near its liquid phase temperature, is used to penetrate and wet the internal surfaces of a nanomaterial to dissolve impurities that may be present, for example, from processes used in the manufacture of the nanomaterial.

Photocatalytic surface reactions on indoor wall paint.

PubMed

Salthammer, T; Fuhrmann, F

2007-09-15

The reduction of indoor air pollutants by air cleaning systems has received considerable interest, and a number of techniques are now available. So far, the method of photocatalysis was mainly applied by use of titanium dioxide (TiO2) in flow reactors under UV light of high intensity. Nowadays, indoor wall paints are equipped with modified TiO2 to work as a catalyst under indoor daylight or artificial light. In chamber experiments carried out under indoor related conditions itwas shown thatthe method works for nitrogen dioxide with air exchange and for formaldehyde without air exchange at high concentrations. In further experiments with volatile organic compounds (VOCs), a small effect was found for terpenoids with high kOH rate constants. For other VOCs and carbon monoxide there was no degradation at all or the surface acted as a reversible sink. Secondary emissions from the reaction of paint constituents were observed on exposure to light. From the results it is concluded that recipes of photocatalytic wall paints need to be optimized for better efficiency under indoor conditions.

Self-Assembly of ZnO Nanoplatelets into Hierarchical Mesocrystals and Their Photocatalytic Property

NASA Astrophysics Data System (ADS)

Yang, Yongqiang; Wang, Qinsheng; Liu, Zheng; Jin, Ling; Ou, Bingxian; Han, Pengju; Wang, Qun; Cheng, Xiaobao; Liu, Wenjun; Wen, Yu; Liu, Yuan; Zhao, Weifang

2018-03-01

In this work, a simple chemical procedure was developed for the preparation of mesocrystals consisiting of ZnO nanoplateletes. By simple mixing the aqueous solutions Zn(NO3)2, NaOH and ethanol at certain temperatures, the hierarchical mesocrystals with big at both ends but small in the middle were obtained. After being annealed in air at certain temperatures, the same structured ZnO mesocrystals were generated. The morphology, crystalline structure and chemical composition were characterized using SEM, XRD FT-IR and Raman. The photocatalytic properties of the ZnO mesocrystals were also investigated. It was illustrated that the ZnO mesocrystals show decent photocatalytic performance to the photodegradation of methyl blue.

The influence of ZnO-SnO2 nanoparticles and activated carbon on the photocatalytic degradation of toluene using continuous flow mode.

PubMed

Rangkooy, Hossein Ali; Tanha, Fatemeh; Jaafarzadeh, Neamat; Mohammadbeigi, Abolfazl

2017-01-01

The present study examined the gas-phase photocatalytic degradation of toluene using ZnO-SnO 2 nanocomposite supported on activated carbon in a photocatalytic reactor. Toluene was selected as a model pollutant from volatile organic compounds to determine the pathway of photocatalytic degradation and the factors influencing this degradation. The ZnO-SnO 2 nanocomposite was synthesized through co-precipitation method in a ratio of 2:1 and then supported on activated carbon. The immobilization of ZnO-SnO 2 nanocomposite on activated carbon was determined by the surface area and scanning electron micrograph technique proposed by Brunauer, Emmett, and Teller. The laboratory findings showed that the highest efficiency was 40% for photocatalytic degradation of toluene. The results also indicated that ZnO-SnO 2 nano-oxides immobilization on activated carbon had a synergic effect on photocatalytic degradation of toluene. Use of a hybrid photocatalytic system (ZnO/SnO 2 nano coupled oxide) and application of absorbent (activated carbon) may be efficient and effective technique for refinement of toluene from air flow.

The influence of ZnO-SnO2 nanoparticles and activated carbon on the photocatalytic degradation of toluene using continuous flow mode

PubMed Central

Rangkooy, Hossein Ali; Tanha, Fatemeh; Jaafarzadeh, Neamat; Mohammadbeigi, Abolfazl

2017-01-01

The present study examined the gas-phase photocatalytic degradation of toluene using ZnO-SnO2 nanocomposite supported on activated carbon in a photocatalytic reactor. Toluene was selected as a model pollutant from volatile organic compounds to determine the pathway of photocatalytic degradation and the factors influencing this degradation. The ZnO-SnO2 nanocomposite was synthesized through co-precipitation method in a ratio of 2:1 and then supported on activated carbon. The immobilization of ZnO-SnO2 nanocomposite on activated carbon was determined by the surface area and scanning electron micrograph technique proposed by Brunauer, Emmett, and Teller. The laboratory findings showed that the highest efficiency was 40% for photocatalytic degradation of toluene. The results also indicated that ZnO-SnO2 nano-oxides immobilization on activated carbon had a synergic effect on photocatalytic degradation of toluene. Use of a hybrid photocatalytic system (ZnO/SnO2 nano coupled oxide) and application of absorbent (activated carbon) may be efficient and effective technique for refinement of toluene from air flow. PMID:29497487

42 CFR 84.179 - Non-powered air-purifying particulate respirators; filter identification.

Code of Federal Regulations, 2011 CFR

2011-10-01

...; filter identification. 84.179 Section 84.179 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH...-purifying particulate respirators; filter identification. (a) The respirator manufacturer, as part of the application for certification, shall specify the filter series and the filter efficiency level (i.e., “N95...

42 CFR 84.179 - Non-powered air-purifying particulate respirators; filter identification.

Code of Federal Regulations, 2013 CFR

2013-10-01

...; filter identification. 84.179 Section 84.179 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH...-purifying particulate respirators; filter identification. (a) The respirator manufacturer, as part of the application for certification, shall specify the filter series and the filter efficiency level (i.e., “N95...

42 CFR 84.179 - Non-powered air-purifying particulate respirators; filter identification.

Code of Federal Regulations, 2010 CFR

2010-10-01

...; filter identification. 84.179 Section 84.179 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH...-purifying particulate respirators; filter identification. (a) The respirator manufacturer, as part of the application for certification, shall specify the filter series and the filter efficiency level (i.e., “N95...

42 CFR 84.179 - Non-powered air-purifying particulate respirators; filter identification.

Code of Federal Regulations, 2012 CFR

2012-10-01

...; filter identification. 84.179 Section 84.179 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH...-purifying particulate respirators; filter identification. (a) The respirator manufacturer, as part of the application for certification, shall specify the filter series and the filter efficiency level (i.e., “N95...

42 CFR 84.179 - Non-powered air-purifying particulate respirators; filter identification.

Code of Federal Regulations, 2014 CFR

2014-10-01

...; filter identification. 84.179 Section 84.179 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH...-purifying particulate respirators; filter identification. (a) The respirator manufacturer, as part of the application for certification, shall specify the filter series and the filter efficiency level (i.e., “N95...

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.

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.

Oxidation of gas phase trichloroethylene and toluene using composite sol-gel TiO2 photocatalytic coatings.

PubMed

Keshmiri, Mehrdad; Troczynski, Tom; Mohseni, Madjid

2006-02-06

The previously developed composite sol-gel (CSG) process is proposed for the deposition of thick (10-50 microm) porous films of photocatalytic TiO2. The CSG titania was developed by binding pre-calcined TiO2 particles with TiO2 sol. It had relatively high surface area (15-35 m2/g) and good resistance against mechanical stress and abrasion. Photocatalytic activity tests were carried out on trichloroethylene (TCE) and toluene, and compared with those of standard Degussa P-25 titania. The CSG photocatalyst provided good photo-efficiency in removing both pollutants from contaminated air streams. When compared with P-25 titania, the CSG photocatalyst showed a similar photo-efficiency with first-order kinetic rate constants not significantly different from that of P-25. For both photocatalysts the rate of photocatalytic oxidation of TCE was significantly greater than that obtained for toluene. Overall, the combination of better mechanical integrity, resistance against abrasion, and comparable photocatalytic efficiency of the CSG titania versus that of P-25 titania, make the composite sol-gel (CSG) photocatalyst a viable alternative for industrial applications where long term stability, superior mechanical properties, and good photo-efficiency are of critical value.

Role of dissolved oxygen on the degradation mechanism of Reactive Green 19 and electricity generation in photocatalytic fuel cell.

PubMed

Lee, Sin-Li; Ho, Li-Ngee; Ong, Soon-An; Wong, Yee-Shian; Voon, Chun-Hong; Khalik, Wan Fadhilah; Yusoff, Nik Athirah; Nordin, Noradiba

2018-03-01

In this study, a membraneless photocatalytic fuel cell with zinc oxide loaded carbon photoanode and platinum loaded carbon cathode was constructed to investigate the impact of dissolved oxygen on the mechanism of dye degradation and electricity generation of photocatalytic fuel cell. The photocatalytic fuel cell with high and low aeration rate, no aeration and nitrogen purged were investigated, respectively. The degradation rate of diazo dye Reactive Green 19 and the electricity generation was enhanced in photocatalytic fuel cell with higher dissolved oxygen concentration. However, the photocatalytic fuel cell was still able to perform 37% of decolorization in a slow rate (k = 0.033 h -1 ) under extremely low dissolved oxygen concentration (approximately 0.2 mg L -1 ) when nitrogen gas was introduced into the fuel cell throughout the 8 h. However, the change of the UV-Vis spectrum indicates that the intermediates of the dye could not be mineralized under insufficient dissolved oxygen level. In the aspect of electricity generation, the maximum short circuit current (0.0041 mA cm -2 ) and power density (0.00028 mW cm -2 ) of the air purged photocatalytic fuel cell was obviously higher than that with nitrogen purging (0.0015 mA cm -2 and 0.00008 mW cm -2 ). Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of intelligent monitoring purifier for indoor PM 2.5

NASA Astrophysics Data System (ADS)

Lou, Guanting; Zhu, Rong; Guo, Jiangwei; Wei, Yongqing

2018-03-01

The particulate matter 2.5 (PM2.5) refers to tiny particles or droplets in the air that are two and one half microns or less in width. PM2.5 is an air pollutant that is a concern for people’s health when levels in air are high. The intelligent monitoring purifier was developed to detect indoor PM2.5 concentration before and after purification and the monitoring data could be displayed on the LCD screen, displaying different color patterns according to the concentrations. Through the Bluetooth transport module, real-time values could also display on the mobile phone and voice broadcast PM2.5 concentration level in the air. When PM2.5 concentration is higher than the setting threshold, the convection fan rotation and the speed can be remote controlled with mobile phone through the Bluetooth transport. Therefore, the efficiency and scope of the purification could be enhanced and further better air quality could be achieved.

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.

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.

Water Purifier

NASA Technical Reports Server (NTRS)

1992-01-01

The Floatron water purifier combines two space technologies - ionization for water purification and solar electric power generation. The water purification process involves introducing ionized minerals that kill microorganisms like algae and bacteria. The 12 inch unit floats in a pool while its solar panel collects sunlight that is converted to electricity. The resulting current energizes a specially alloyed mineral electrode below the waterline, causing release of metallic ions into the water. The electrode is the only part that needs replacing, and water purified by the system falls within EPA drinking water standards.

Photocatalytic Activity of Nanotubular TiO2 Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

PubMed Central

Sanabria Arenas, Beatriz Eugenia; Schiavi, Luca; Russo, Valeria; Pedeferri, MariaPia

2018-01-01

The availability of immobilized nanostructured photocatalysts is of great importance in the purification of both polluted air and liquids (e.g., industrial wastewaters). Metal-supported titanium dioxide films with nanotubular morphology and good photocatalytic efficiency in both environments can be produced by anodic oxidation, which avoids release of nanoscale materials in the environment. Here we evaluate the effect of different anodizing procedures on the photocatalytic activity of TiO2 nanostructures in gas and liquid phases, in order to identify the most efficient and robust technique for the production of TiO2 layers with different morphologies and high photocatalytic activity in both phases. Rhodamine B and toluene were used as model pollutants in the two media, respectively. It was found that the role of the anodizing electrolyte is particularly crucial, as it provides substantial differences in the oxide specific surface area: nanotubular structures show remarkably different activities, especially in gas phase degradation reactions, and within nanotubular structures, those produced by organic electrolytes lead to better photocatalytic activity in both conditions tested. PMID:29587360

The Structural, Photocatalytic Property Characterization and Enhanced Photocatalytic Activities of Novel Photocatalysts Bi2GaSbO7 and Bi2InSbO7 during Visible Light Irradiation

PubMed Central

Luan, Jingfei; Shen, Yue; Li, Yanyan; Paz, Yaron

2016-01-01

In order to develop original and efficient visible light response photocatalysts for degrading organic pollutants in wastewater, new photocatalysts Bi2GaSbO7 and Bi2InSbO7 were firstly synthesized by a solid-state reaction method and their chemical, physical and structural properties were characterized. Bi2GaSbO7 and Bi2InSbO7 were crystallized with a pyrochlore-type structure and the lattice parameter of Bi2GaSbO7 or Bi2InSbO7 was 10.356497 Å or 10.666031 Å. The band gap of Bi2GaSbO7 or Bi2InSbO7 was estimated to be 2.59 eV or 2.54 eV. Compared with nitrogen doped TiO2, Bi2GaSbO7 and Bi2InSbO7, both showed excellent photocatalytic activities for degrading methylene blue during visible light irradiation due to their narrower band gaps and higher crystallization perfection. Bi2GaSbO7 showed higher catalytic activity compared with Bi2InSbO7. The photocatalytic degradation of methylene blue followed by the first-order reaction kinetics and the first-order rate constant was 0.01470 min−1, 0.00967 min−1 or 0.00259 min−1 with Bi2GaSbO7, Bi2InSbO7 or nitrogen doped TiO2 as a catalyst. The evolution of CO2 and the removal of total organic carbon were successfully measured and these results indicated continuous mineralization of methylene blue during the photocatalytic process. The possible degradation scheme and pathway of methylene blue was also analyzed. Bi2GaSbO7 and Bi2InSbO7 photocatalysts both had great potential to purify textile industry wastewater. PMID:28773922

Enhanced TiO2 Photocatalytic Processing of Organic Wastes for Green Space Exploration

NASA Technical Reports Server (NTRS)

Udom, I.; Goswami, D. Y.; Ram, M. K.; Stefanakos, E. K.; Heep, A. F.; Kulis, M. J.; McNatt, J. S.; Jaworske, D. A.; Jones, C. A.

2013-01-01

The effect of transition metal co-catalysts on the photocatalytic properties of TiO2 was investigated. Ruthenium (Ru), palladium, platinum, copper, silver, and gold, were loaded onto TiO2 powders (anatase and mixed-phase P25) and screened for the decomposition of rhodamine B (RhB) under broad-band irradiation. The morphology and estimated chemical composition of photocatalysts were determined by scanning electron microscopy and energy dispersive spectroscopy, respectively. Brunhauer, Emmett and Teller (BET) analysis measured mass-specific surface area(s). X-ray diffraction analysis was performed to confirm the identity of titania phase(s) present. The BET surface area of anatase TiO2/Ru 1% (9.2 sq m/gm) was one of the highest measured of all photocatalysts prepared in our laboratory. Photolyses conducted under air-saturated and nitrogen-saturated conditions revealed photodegradation efficiencies of 85 and 2 percent, respectively, after 60 min compared to 58 percent with no catalyst. The cause of low photocatalytic activity under an inert atmosphere is discussed. TiO2/Ru 1% showed a superior photocatalytic activity relative to P25-TiO2 under broad-band irradiation. A potential deployment of photocatalytic technologies on a mission could be a reactor with modest enhancement in solar intensity brought about by a trough-style reactor, with reactants and catalyst flowing along the axis of the trough and therefore being illuminated for a controlled duration based on the flow rate.

Formation of combustible hydrocarbons and H2 during photocatalytic decomposition of various organic compounds under aerated and deaerated conditions.

PubMed

Mozia, Sylwia; Kułagowska, Aleksandra; Morawski, Antoni W

2014-11-26

A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of "green energy" production.

Application of nano-TiO2/LDPE composite film on photocatalytic oxidation degradation of dichloromethane.

PubMed

Suwannahong, Kowit; Liengcharernsit, Winai; Sanongraj, Wipada; Kruenate, Jittiporn

2012-09-01

This study focused on the photocatalytic destruction of dichloromethane (DCM) in indoor air using the nano-TiO2/LDPE composite film as an economical photocatalyst. The nano-TiO2 was dispersed in a polyethylene matrix to form composite film. The photocatalytic activity of the nano-TiO2/LDPE composite films was evaluated through the degradation of dichloromethane(DCM) under UV-C irradiance at specific wavelength of 254 nm. The percentage of nano-TiO2 contents varied from 0, 5, and 10% (wt cat./wt LDPE composite film). The results derived from the kinetic model revealed that the photocatalytic rates of 5 and 10 wt.% nano-TiO2/ LDPE composite films follow the first order reaction while the rate of the film without TiO2 followed the zero order reaction. At low concentration of DCM, the rate of photocatalytic degradation of the DCM was slower than that at high DCM concentration. The 10 wt.% of TiO2 content of the nano-TiO2/LDPE composite film yielded the highest degradation efficiency of 78%, followed by the removal efficiency of 55% for the 5 wt.% of TiO2 content of the nano-TiO2/LDPE composite film. In contrast with the composite film containing nano-TiO2, the LDPE film without adding nano-TiO2 expressed the degradation efficiency of 28%.

Graphene oxide as a photocatalytic material

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

Krishnamoorthy, Karthikeyan; Mohan, Rajneesh; Kim, S.-J.

2011-06-13

The photocatalytic characteristics of graphene oxide (GO) nanostructures synthesized by modified Hummer's method were investigated by measuring reduction rate of resazurin (RZ) into resorufin (RF) as a function of UV irradiation time. The progress of the photocatalytic reaction was monitored by change in color from blue (RZ) into pink (RF) followed by absorption spectra. It exhibited excellent photocatalytic activity, leading to the reduction of RZ in UV irradiation. The fitting of absorbance maximum versus time suggests that the reduction of RZ follow the pseudo first-order reaction kinetics. These results indicate that GO have great potential for use as a photocatalyst.

Facet‐Engineered Surface and Interface Design of Photocatalytic Materials

PubMed Central

Wang, Lili; Li, Zhengquan

2016-01-01

The facet‐engineered surface and interface design for photocatalytic materials has been proven as a versatile approach to enhance their photocatalytic performance. This review article encompasses some recent advances in the facet engineering that has been performed to control the surface of mono‐component semiconductor systems and to design the surface and interface structures of multi‐component heterostructures toward photocatalytic applications. The review begins with some key points which should receive attention in the facet engineering on photocatalytic materials. We then discuss the synthetic approaches to achieve the facet control associated with the surface and interface design. In the following section, the facet‐engineered surface design on mono‐component photocatalytic materials is introduced, which forms a basis for the discussion on more complex systems. Subsequently, we elucidate the facet‐engineered surface and interface design of multi‐component photocatalytic materials. Finally, the existing challenges and future prospects are discussed. PMID:28105398

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.

Porphyrin-Based Nanostructures for Photocatalytic Applications

PubMed Central

Chen, Yingzhi; Li, Aoxiang; Huang, Zheng-Hong; Wang, Lu-Ning; Kang, Feiyu

2016-01-01

Well-defined organic nanostructures with controllable size and morphology are increasingly exploited in optoelectronic devices. As promising building blocks, porphyrins have demonstrated great potentials in visible-light photocatalytic applications, because of their electrical, optical and catalytic properties. From this perspective, we have summarized the recent significant advances on the design and photocatalytic applications of porphyrin-based nanostructures. The rational strategies, such as texture or crystal modification and interfacial heterostructuring, are described. The applications of the porphyrin-based nanostructures in photocatalytic pollutant degradation and hydrogen evolution are presented. Finally, the ongoing challenges and opportunities for the future development of porphyrin nanostructures in high-quality nanodevices are also proposed. PMID:28344308

Enhanced photocatalytic performance of Er-doped Bi{sub 24}O{sub 31}Br{sub 10}: Facile synthesis and photocatalytic mechanism

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

Liu, Zhang Sheng, E-mail: lzsliu2008@hotmail.com; Liu, Zhi Lin; Liu, Jin Long

2016-04-15

Highlights: • Er-doped Bi{sub 24}O{sub 31}Br{sub 10} have been prepared via a one-pot solvothermal method. • Er doping drastically improves the photocatalytic activity of Bi{sub 24}O{sub 31}Br{sub 10}. • The enhanced activity is attributed to effective electron trapping and up-conversion process resulting from Er{sup 3+}. • Holes and super-oxide radicals are main active species. - Abstract: Erbium (Er) doped Bi{sub 24}O{sub 31}Br{sub 10} samples were successfully prepared by using a solvothermal method. The samples were characterized by XRD, XPS, SEM, TEM, BET, DRS, PL and EIS. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) and methylmore » orange (MO) under visible light irradiation. The result shows that Er dopant induces a significant improvement in the photocatalytic activity. 1.0% Er–Bi{sub 24}O{sub 31}Br{sub 10} sample exhibits the best photocatalytic performance. The enhanced photocatalytic activity is attributed to the effective trapping of photogenerated electron by Er{sup 3+} ion and the up-conversion process resulting from Er dopant. In addition, it is found that holes and super-oxide radicals play main role in the photocatalytic degradation of RhB and MO.« less

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.

Ceramic ultrafiltration membranes with photocatalytic properties

NASA Astrophysics Data System (ADS)

Bell, Deborah Wildman

The photocatalytic properties of ceramic ultrafilters have been utilized in the development of a novel in-situ membrane cleaning process for ultrafiltration membranes fabricated from titania. The use of the photoactive membrane layer mitigates the effects of foulants in the system, thereby yielding an increase in the observed overall flux without sacrificing rejection of the solute by the membrane. Photocatalytic membranes of titania supported on porous tubes of alpha-alumina were fabricated using sol-gel techniques. These membranes were developed on the basis of the results of two-level factorial experimental designs. Electron microscopy and x-ray spectrometry were employed to evaluate coverage of the support by the membrane, the thickness of the membrane, and the presence of defects in the membrane. The photocatalytic membrane system was characterized to determine both morphological and performance parameters. Morphological parameters included the pore diameters, Darcy coefficients, and the individual resistances associated with each of the porous layers comprising the composite photocatalytic membrane. Performance parameters included the nominal molecular weight cutoff values of the ceramic membranes, the rate of permeation of pure solvent in the presence and the absence of UV illumination through the porous layers of interest, and the ability of the photocatalytic membrane to resist fouling and maintain permselectivity in the presence of UV illumination. The photocatalytic membranes were used to ultrafilter aqueous solutions of polymeric organic foulants present at an initial concentration of 1 x 10-3 M. Formation of a gel layer of foulant on the surface of the membrane was observed in the presence and in the absence of UV radiation; however, the results of permeability experiments indicated that formation of this foulant layer was significantly retarded (by a factor of two) in the presence of UV radiation. Improvement in the flow rate of permeate through the

Photocatalytic selective hydroxylation of phenol to dihydroxybenzene by BiOI/TiO2 p-n heterojunction photocatalysts for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Li, Bin; Chen, Xingwei; Zhang, Tianyong; Jiang, Shuang; Zhang, Guanghui; Wu, Wubin; Ma, Xiaoyuan

2018-05-01

The BiOI/TiO2 heterostructures with different Bi/Ti molar ratios were synthesized by biomimetic synthesis and simple hydrothermal method. XRD, SEM, TEM, N2 adsorption-desorption isotherms, XPS, UV-vis diffuse reflection spectra and photoluminescence spectra (PL) were employed to characterize the as-prepared photocatalysts and confirm the presence of p-n heterojunction. The photocatalytic activities of these photocatalysts were measured by photocatalytic selective hydroxylation of phenol with high concentration under simulated solar light irradiation. The results showed that BiOI/TiO2 heterostructure exhibited more excellent photocatalytic performance than the pure TiO2 and BiOI. Moreover, 20% BiOI/TiO2 heterostructure exhibited the highest photocatalytic performance, which can be ascribed to the exposed reactive facets, narrow band gap and effective separation of the photogenerated electrons and holes because of p-n heterojunction between BiOI and TiO2. The results of reusability tests indicated that the as-prepared photocatalysts have excellent photochemical stability. Furthermore, active-species trapping experiments were conducted to confirm the formation of radOH, which played a chief role in the process of photocatalytic selective hydroxylation of phenol. The charge transfer process of BiOI/TiO2 heterostructure and a possible mechanism for photocatalytic selective hydroxylation of phenol were proposed.

Photocatalytic silver enhancement reaction for gravimetric immunosensors.

PubMed

Seo, Hyejung; Joo, Jinmyoung; Ko, Wooree; Jung, Namchul; Jeon, Sangmin

2010-12-17

A novel microgravimetric immunosensor has been developed using TiO(2) nanoparticle-modified immunoassay and silver enhancement reaction. An antibody-conjugated TiO(2) nanoparticle is bound to the AFP antigen immobilized on a quartz resonator. When the nanoparticles are exposed to UV light in a silver nitrate solution, the photocatalytic reduction of silver ions results in the formation of metallic silver onto the nanoparticles and induces a decrease in the resonance frequency. The frequency change by this photocatalytic reduction reaction is three orders of magnitude larger than the change by antigen binding alone. The efficiency of the photocatalytic reaction has been found to increase with the fraction of anatase crystallites in the nanoparticles and the concentration of the AgNO(3) solution. The results highlight the potential of the photocatalytic nanoparticles for the detection of low concentrations of target molecules using gravimetric sensors.

Nitrogen removal from purified swine wastewater using biogas by semi-partitioned reactor.

PubMed

Waki, Miyoko; Yokoyama, Hiroshi; Ogino, Akifumi; Suzuki, Kazuyoshi; Tanaka, Yasuo

2008-09-01

Nitrate and ammonium removal from purified swine wastewater using biogas and air was investigated in continuous reactor operation. A novel type of reactor, a semi-partitioned reactor (SPR), which enables a biological reaction using methane and oxygen in the water phase and discharges these unused gases separately, was operated with a varying gas supply rate. Successful removal of NO(3)(-) and NH(4)(+) was observed when biogas and air of 1L/min was supplied to an SPR of 9L water phase with a NO(2,3)(-)-N and NH(4)(+)-N removal rate of 0.10 g/L/day and 0.060 g/L/day, respectively. The original biogas contained an average of 77.2% methane, and the discharged biogas from the SPR contained an average of 76.9% of unused methane that was useable for energy like heat or electricity production. Methane was contained in the discharged air from the SPR at an average of 2.1%. When gas supply rates were raised to 2L/min and the nitrogen load was increased, NO(3)(-) concentration was decreased, but NO(2)(-) accumulated in the reactor and the NO(2,3)(-)-N and NH(4)(+)-N removal activity declined. To recover the activity, lowering of the nitrogen load and the gas supply rate was needed. This study shows that the SPR enables nitrogen removal from purified swine wastewater using biogas under limited gas supply condition.

Effects of a powered air-purifying respirator intervention on indium exposure reduction and indium related biomarkers among ITO sputter target manufacturing workers.

PubMed

Liu, Hung-Hsin; Chen, Chang-Yuh; Lan, Cheng-Hang; Chang, Cheng-Ping; Peng, Chiung-Yu

2016-01-01

This study aimed to evaluate the efficacy of powered air-purifying respirators (PAPRs) worn by the workers, and to investigate the effect of this application on exposure and preclinical effects in terms of workplace measuring and biomarker monitoring in ITO sputter target manufacturing plants and workers, respectively. Fifty-four workers were recruited and investigated from 2010-2012, during which PAPRs were provided to on-site workers in September 2011. Each worker completed questionnaires and provided blood and urine samples for analysis of biomarkers of indium exposure and preclinical effects. Area and personal indium air samples were randomly collected from selected worksites and from participants. The penetration percentage of the respirator (concentration inside respirator divided by concentration outside respirator) was 6.6%. Some biomarkers, such as S-In, SOD, GPx, GST, MDA, and TMOM, reflected the decrease in exposure and showed lower levels, after implementation of PAPRs. This study is the first to investigate the efficacy of PAPRs for reducing indium exposure. The measurement results clearly showed that the implementation of PAPRs reduces levels of indium-related biomarkers. These findings have practical applications for minimizing occupational exposure to indium and for managing the health of workers exposed to indium.

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.

Porphyrin-based Photocatalytic Nanolithography

PubMed Central

Bearinger, Jane P.; Stone, Gary; Dugan, Lawrence C.; El Dasher, Bassem; Stockton, Cheryl; Conway, James W.; Kuenzler, Tobias; Hubbell, Jeffrey A.

2009-01-01

Nanoarray fabrication is a multidisciplinary endeavor encompassing materials science, chemical engineering, and biology. We formed nanoarrays via a new technique, porphyrin-based photocatalytic nanolithography. The nanoarrays, with controlled features as small as 200 nm, exhibited regularly ordered patterns and may be appropriate for (a) rapid and parallel proteomics screening of immobilized biomolecules, (b) protein-protein interactions, and/or (c) biophysical and molecular biology studies involving spatially dictated ligand placement. We demonstrated protein immobilization utilizing nanoarrays fabricated via photocatalytic nanolithography on silicon substrates where the immobilized proteins are surrounded by a non-fouling polymer background. PMID:19406753

Synthesis of LaVO4/TiO2 heterojunction nanotubes by sol-gel coupled with hydrothermal method for photocatalytic air purification.

PubMed

Zou, Xuejun; Li, Xinyong; Zhao, Qidong; Liu, Shaomin

2012-10-01

With the aim of improving the effective utilization of visible light, the LaVO(4)/TiO(2) heterojunction nanotubes were fabricated by sol-gel coupled with hydrothermal method. The photocatalytic ability was demonstrated through catalytic removal of gaseous toluene species. The nanotube samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface photovoltage (SPV), Raman spectra and N(2) adsorption-desorption measurements. The characterization results showed that the samples with high specific surface areas were of typical nanotubular morphology, which would lead to the high separation and transfer efficiency of photo induced electron-hole pairs. The as-prepared nanotubes exhibited high photocatalytic activity in decomposing toluene species under visible light irradiation with fine photochemical stability. The enhanced photocatalytic performance of LaVO(4)/TiO(2) nanotubes might be attributed to the matching band potentials, the interconnected heterojunction of LaVO(4) versus TiO(2), and the large specific surface areas of nanotubes. Copyright © 2012 Elsevier Inc. All rights reserved.

Efficient photocatalytic degradation of gaseous N,N-dimethylformamide in tannery waste gas using doubly open-ended Ag/TiO2 nanotube array membranes

NASA Astrophysics Data System (ADS)

Zhao, Yang; Ma, Lin; Chang, Wenkai; Huang, Zhiding; Feng, Xugen; Qi, Xiaoxia; Li, Zenghe

2018-06-01

Gaseous N,N-dimethylformamide (DMF), typical volatile organic compound exhausted from manufacturing factories, may damage the health of workers under long-term exposure even at low levels. The defined geometry, porous surface and highly ordered channels make the free-standing anodic TiO2 nanotube (TiNT) arrays particularly suitable for applications of practical air purification by flow-through photocatalysis. In the present work, crystallized doubly open-ended Ag/TiNT array membranes were designed and prepared by employing a lift-off process based on an anodization-annealing-anodization-etching sequence, followed by uniform Ag nanoparticles decoration. For the photocatalytic degradation of gaseous DMF at low concentration levels close to that found in realistic pollutant air, an analytical methodology for the monitoring and determination of degradation process was developed based on the coupling of headspace sampling with gas chromatography mass spectrometry (HS-GC-MS). The doubly open-ended Ag/TiNT arrays exhibited higher removal efficiency of gaseous DMF from air compared with conventional bottom-closed Ag/TiNT arrays and pure bottomless TiNT arrays. These results indicated that the photocatalytic properties of TiNT arrays were improved with the open-bottom morphology and the Ag nanoparticles decoration. Based on the analysis with GC-MS and high performance ion chromatography (HPIC), it was found that demethylation is the main pathway of DMF degradation in photocatalytic reactions. Furthermore, decontamination of actual polluted tannery waste gas collected in leather factory proved that the photocatalysis on doubly open-ended Ag/TiNT array membrane is an efficient way and a promising application to treat air contaminated by DMF despite the complexity of various volatile organic compounds.

Purified silicon production system

DOEpatents

Wang, Tihu; Ciszek, Theodore F.

2004-03-30

Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

Photochemical and photocatalytic degradation of trans-resveratrol.

PubMed

Silva, Cláudia Gomes; Monteiro, Judith; Marques, Rita R N; Silva, Adrián M T; Martínez, Cristina; Canle, Moisés; Faria, Joaquim Luís

2013-04-01

Photochemical and photocatalytic degradation of the emerging pollutant trans-resveratrol has been studied under different irradiation wavelengths and using different TiO2 catalysts. trans-Resveratrol was more easily degraded when irradiated using the whole spectral range (UV-Vis) rather than with UV and near-UV to visible irradiation. The main intermediate of trans-resveratrol phototransformation was identified as its isomer cis-resveratrol. Different TiO2 catalysts were used to carry out the photocatalytic degradation of trans-resveratrol. Catalysts properties such as crystallite dimensions, surface area and presence of hydroxy surface groups are shown to be crucial to the photocatalytic efficiency of the materials tested. From the point of view of trans-resveratrol abatement, the photocatalytic process was more efficient than the pure photochemical one resulting in higher degradation rates and higher organic content removal. Six photoproducts of trans-resveratrol phototransformation were identified mainly resulting from the attack of the hydroxyl radical to the organic molecule.

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.

Enhanced photocatalytic degradation of dyes under sunlight using biocompatible TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Bharati, B.; Sonkar, A. K.; Singh, N.; Dash, D.; Rath, Chandana

2017-08-01

As TiO2 is one of the most popular photocatalysts, we have studied here the photocatalytic degradation of the most common dyestuffs like rhodamine B (RhB), congo red (CR) and methylene blue (MB), which mainly come from the textile and photographic industries using nanoparticles of TiO2. Nanoparticles of TiO2 synthesized through a simple and cost effective sol-gel technique crystallizes in the anatase phase, showing a band gap less than that of bulk value. Particles consisting of coherently scattered domains of size 33 nm are found to be agglomerated and polycrystalline in nature. While the degradation rates of MB, CR and RhB after irradiating with a renewable source of energy, i.e. sunlight, show 100% degradation, TiO2 irradiated with UV light of 4.8 eV shows a much slower degradation rate. To use the waste water after photocatalysis, we examine further the biocompatibile nature of the TiO2 nanoparticles by platelet interaction activity, hemolysis effect and MTT assay. It is worth mentioning here that TiO2 nanoparticles are found to be highly hemocompatible, show no platelet aggregation, and the level of intracellular ROS in human platelets does not show significant change in ROS level. We conclude that TiO2 nanoparticles constitute an excellent photocatalyst and biocompatible material, and that after photocatalytic degradation of dye effluents obtained from textile industries, purified water can be used in agriculture and domestic sectors.

Preparation and enhanced daylight-induced photocatalytic activity of C,N,S-tridoped titanium dioxide powders.

PubMed

Zhou, Minghua; Yu, Jiaguo

2008-04-15

A simple method for preparing highly daylight-induced photoactive nanocrystalline C,N,S-tridoped TiO2 powders was developed by a solid-phase reaction. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra, N2 adsorption-desorption measurements and transmission electron microscopy (TEM). The photocatalytic activity was evaluated by the photocatalytic oxidation of formaldehyde under daylight irradiation in air. The results show that daylight-induced photocatalytic activities of the as-prepared TiO2 powders were improved by C,N,S-tridoping. The C,N,S-tridoped TiO2 powders exhibited stronger absorption in the near UV and visible-light region with red shift in the band-gap transition. When the molar ratio of CS(NH2)2 to xerogel TiO2 powders (prepared by hydrolysis of Ti(OC4H9)4 in distilled water) (R) was kept in 3, the daylight-induced photocatalytic activities of the as-prepared C,N,S-tridoped TiO2 powders were about more than six times greater than that of Degussa P25 and un-doped TiO2 powders. The high activities of the C,N,S-tridoped TiO2 can be attributed to the results of the synergetic effects of strong absorption in the near UV and visible-light region, red shift in adsorption edge and two phase structures of un-doped TiO2 and C,N,S-tridoped TiO2.

Photocatalytic degradation of NO/NO2 gas injected into a 10-m3 experimental chamber.

PubMed

Hot, Julie; Martinez, T; Wayser, B; Ringot, E; Bertron, A

2017-05-01

This paper investigates a new test method to assess the photocatalytic activity of plasterboards coated with a TiO 2 dispersion under real-world conditions. The degradation of nitrogen oxides NO x (NO and NO 2 ) is studied and the photocatalytic efficiency under UV illumination is evaluated in a 10-m 3 room after a constant gas injection. Two ultrafine TiO 2 dispersions are used: 0.85% TiO 2 and 5% TiO 2 , and three types of gas are tested: an NO/NO 2 mixture (8/8 mol-ppm), NO (45 mol-ppm) and NO 2 (45 mol-ppm). The test method presented here is midway between laboratory and real-scale procedures and allows better control of the experimental parameters than a real field experiment. Testing a mixture of NO and NO 2 is a way to get closer to real-world conditions as air is polluted by various gases. This study focuses on the degradation of NO and NO 2 under UV illumination when two types of TiO 2 dispersions are used and highlights the difference in behaviour between these two molecules in terms of photocatalytic degradation. The results show that photocatalytic activity does not appear to be efficient to degrade NO 2 molecules. Another mechanism seems to be responsible for the reduction of the concentration of NO 2 , namely adsorption. Encouraging results are obtained with NO molecules, which can be degraded by photocatalysis. The degradation observed is even greater with the more concentrated TiO 2 dispersion.

Photocatalytic activity of ZnWO₄: band structure, morphology and surface modification.

PubMed

Zhang, Cuiling; Zhang, Hulin; Zhang, Kaiyou; Li, Xiaoyan; Leng, Qiang; Hu, Chenguo

2014-08-27

Photocatalytic degradation of organic contaminants is an important application area in solar energy utilization. To improve material photocatalytic properties, understanding their photocatalytic mechanism is indispensable. Here, the photocatalytic performance of ZnWO4 nanocrystals was systematicly investigated by the photodegradation of tetraethylated rhodamine (RhB) under simulated sunlight irradiation, including the influence of morphology, AgO/ZnWO4 heterojunction and comparison with CoWO4 nanowires. The results show that the photocatalytic activity of ZnWO4 is higher than that of CoWO4, and the ZnWO4 nanorods exhibit better photocatalytic activity than that of ZnWO4 nanowires. In addition, the mechanism for the difference of the photocatalytic activity was also investigated by comparison of their photoluminescence and photocurrents. AgO nanoparticles were assembled uniformly on the surface of ZnWO4 nanowires to form a heterojunction that exhibited enhanced photocatalytic activity under irradiation at the initial stage. We found that a good photocatalyst should not only have an active structure for electrons directly to transfer from the valence band to the conduction band without the help of phonons but also a special electronic configuration for the high mobility, to ensure more excited electrons and holes in a catalytic reaction.

Enhanced photocatalytic performance and degradation pathway of Rhodamine B over hierarchical double-shelled zinc nickel oxide hollow sphere heterojunction

NASA Astrophysics Data System (ADS)

Zhang, Ying; Zhou, Jiabin; Cai, Weiquan; Zhou, Jun; Li, Zhen

2018-02-01

In this study, hierarchical double-shelled NiO/ZnO hollow spheres heterojunction were prepared by calcination of the metallic organic frameworks (MOFs) as a sacrificial template in air via a one-step solvothermal method. Additionally, the photocatalytic activity of the as-prepared samples for the degradation of Rhodamine B (RhB) under UV-vis light irradiation were also investigated. NiO/ZnO microsphere comprised a core and a shell with unique hierarchically porous structure. The photocatalytic results showed that NiO/ZnO hollow spheres exhibited excellent catalytic activity for RhB degradation, causing complete decomposition of RhB (200 mL of 10 g/L) under UV-vis light irradiation within 3 h. Furthermore, the degradation pathway was proposed on the basis of the intermediates during the photodegradation process using liquid chromatography analysis coupled with mass spectroscopy (LC-MS). The improvement in photocatalytic performance could be attributed to the p-n heterojunction in the NiO/ZnO hollow spheres with hierarchically porous structure and the strong double-shell binding interaction, which enhances adsorption of the dye molecules on the catalyst surface and facilitates the electron/hole transfer within the framework. The degradation mechanism of pollutant is ascribed to the hydroxyl radicals (rad OH), which is the main oxidative species for the photocatalytic degradation of RhB. This work provides a facile and effective approach for the fabrication of porous metal oxides heterojunction with high photocatalytic activity and thus can be potentially used in the environmental purification.

Enhanced Photocatalytic Property of Cu Doped Sodium Niobate

DOE PAGES

Xu, Jianbin; Zhang, Feng; Sun, Bingyang; ...

2015-01-01

Here, we investigate the photocatalytic activity of Cu doped NaNbO 3 powder sample prepared by the modified polymer complex method. The photocatalytic activity of hydrogen evolution from methanol aqueous solution was improved by Cu 2.6 at% doping. The photocatalytic degradation of rhodamine B (RhB) under visible light irradiation was enhanced in comparison with pristine NaNbO 3. Cu introduction improved the adsorption property of NaNbO 3, judging from the Fourier transform infrared spectra. Moreover, the ultraviolet light excitation in Cu doped sample would accelerate the mineralized process.

A novel ammonia complex-assisted ion-exchange strategy to fabricate heterostructured PdO/TiO2 nanorods with enhanced photocatalytic activities

NASA Astrophysics Data System (ADS)

Shi, Liang; Han, Qian; Cao, Lixin; Zhao, Fenghuan; Xia, Chenghui; Dong, Bohua; Xi, Yaoning

2016-12-01

Heterojunctions have been often employed to improve the photocatalytic behavior of titania-based materials. Herein, we propose a novel strategy to fabricate PdO/TiO2 heterostructured nanorods, as PdO was proved to be an efficient co-catalyst in photocatalytic reactions. Primarily, ammonia complex-assisted ion-exchange method was used to store Pd(II) ions in protonated titanate nanotubes, as which cannot be replaced by metallic cations via traditional route. Then, PdO/TiO2 heterojunctions formed through calcination in air, as nanotubes dehydrated and shrank into nanorods. X-ray diffraction, Raman spectra, and X-ray photoelectron spectroscopy were used to demonstrate the formation of PdO component, and transmission electron microscopy was employed to prove the successful connection between TiO2 nanorods and PdO nanoparticles. Moreover, inductive coupled plasma proved excellent compositional gradient of Pd(II) in the PdO/TiO2 heterostructured nanorods. In the present work, the photocatalytic activities of PdO/TiO2 heterostructured nanorods were investigated by decoloring several dyes under UV illumination. Our research revealed appropriate PdO loading (1.0 wt%) enhanced photocatalytic performance compared with bare TiO2 nanorods, where PdO/TiO2 heterojunctions were responsible for the prohibitive photogenerated carries recombination.

Atmospheric nanoparticles in photocatalytic and thermal production of atmospheric pollutants

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

Chianelli, R.R.; Yacaman, M.J.

1997-12-31

Atmospheric aerosols which occur above heavily polluted areas such as Mexico City are characterized and found to be complex materials which have the potential to accelerate important ozone-forming reactions photocatalytically and thermocatalytically. In addition, because the particles are respirable, they represent a considerable health hazard. The aerosols consist of two intermixed components. The first component consists of amorphous carbonaceous materials of variable composition with fullerene like materials dispersed throughout. The second component is an inorganic material consisting of nanoparticles of oxides and sulfides supported on clay minerals. This inorganic component has all of the characteristics of an airborne photocatalyst. Nanoparticlesmore » of Fe{sub 2}O{sub 3}, MnO{sub 2} and FeS{sub 2} have demonstrated catalytic properties, particularly when occurring in the nanoparticle range as they do in the subject aerosol materials. These materials have band-gaps which occur in the broad solar spectrum enhancing the photocatalytic adsorption of solar radiation beyond that of the wider band-gap aluminosilicate and titanate materials which also occur in the aerosols. In addition, the materials are acidic and probably are coated with moisture when suspended in air, further enhancing the catalytic ability to crack hydrocarbons and create free radicals.« less

Rose-like monodisperse bismuth subcarbonate hierarchical hollow microspheres: one-pot template-free fabrication and excellent visible light photocatalytic activity and photochemical stability for NO removal in indoor air.

PubMed

Dong, Fan; Lee, S C; Wu, Zhongbiao; Huang, Yu; Fu, Min; Ho, Wing-Kei; Zou, Shichun; Wang, Bo

2011-11-15

Rose-like monodisperse hierarchical (BiO)(2)CO(3) hollow microspheres are fabricated by a one-pot template-free method for the first time based on hydrothermal treatment of ammonia bismuth citrate and urea in water. The microstructure and band structure of the as-prepared (BiO)(2)CO(3) superstructure are characterized in detail by X-ray diffraction, Raman spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The monodisperse hierarchical (BiO)(2)CO(3) microspheres are constructed by the self-assembly of single-crystalline nanosheets. The aggregation of nanosheets result in the formation of three dimensional hierarchical framework containing mesopores and macropores, which is favorable for efficient transport of reaction molecules and harvesting of photo-energy. The result reveals the existence of special two-band-gap structure (3.25 and 2.0 eV) for (BiO)(2)CO(3). The band gap of 3.25 eV is intrinsic and the formation of smaller band gap of 2.0 eV can be ascribed to the in situ doped nitrogen in lattice. The performance of hierarchical (BiO)(2)CO(3) microspheres as efficient photocatalyst are further demonstrated in the removal of NO in indoor air under both visible light and UV irradiation. It is found that the hierarchical (BiO)(2)CO(3) microspheres not only exhibit excellent photocatalytic activity but also high photochemical stability during long term photocatalytic reaction. The special microstructure, the high charge separation efficiency due to the inductive effect, and two-band-gap structure in all contribute to the outstanding photocatalytic activities. The discovery of monodisperse hierarchical nitrogen doped (BiO)(2)CO(3) hollow structure is significant because of its potential applications in environmental pollution control, solar energy conversion, catalysis and other related

Methods for Purifying Enzymes for Mycoremediation

NASA Technical Reports Server (NTRS)

Cullings, Kenneth W. (Inventor); DeSimone, Julia C. (Inventor); Paavola, Chad D. (Inventor)

2014-01-01

A process for purifying laccase from an ectomycorrhizal fruiting body is disclosed. The process includes steps of homogenization, sonication, centrifugation, filtration, affinity chromatography, ion exchange chromatography, and gel filtration. Purified laccase can also be separated into isomers.

Cleaner Air for Home and Office

NASA Technical Reports Server (NTRS)

1989-01-01

Increased insulation has led to higher concentrations in homes and offices of toxic chemicals caused by emissions from synthetic building components. Recent NASA research regarding future interplanetary manned spacecraft has shown that certain plants can absorb gasses, reducing indoor air pollution. After working with water purifying water hyacinths, Dr. B. C. Wolverton at NSTL developed a carbon/plant filter system to remove chemicals, smoke, etc. Two companies have commercialized the system. Bio-safe provides plants, a bed of activated carbon and an air pump installed near the plant's roots. Pollutants are trapped by the charcoal and either digested by the roots or broken down by microorganisms. Purified air is then directed back into the room. Applied Indoor Resource Company markets Bio-Pure, which includes plants on a layer of patented soil medium with activated carbon. Legumes and mosses filter the air; a blower moves air through the filtering system for cleansing by microorganisms. Research at NSTL continues, and the system may eventually be enlarged.

[Preparation and Photocatalytic Properties of Supported TiO2 Photocatalytic Material].

PubMed

Guo, Yu; Jin, Yu-jia; Wu, Hong-mei; Li, Dong-xin

2015-06-01

Titanium dioxide (TiO2) supported on spherical alumina substrate was prepared by using sol-gel method combined with dip-coating process. The surface morphology and structure of the synthesized samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) pattern. The results show that the morphology of the supported TiO2 composite material was obviously different from that of the original support. It reveals a layer formed by anatase TiO2 nanoparticles of 10-20 nm was deposited on the alumina substrate. Energy dispersive X-ray spectroscopy (EDX) analyses on the spherical alumina substrate and the resulting TiO2 composite catalyst were performed to determine the TiO2 loading content in the samples. It indicates that the TiO2 loading content on alumina substrate could be effectively increased by increasing the times of dip-coating alumina support in TiO2 sol. When dip-coating times increased to 5, the TiO2 loading content increased from 3.8 Wt. % to 15.7 Wt. %. In addition, the photocatalytic performances of the supported TiO2 materials prepared by different dip-coating times have been investigated by degrading methylene blue. It was found that the surface morphology of the supported TiO2 material was not only improved, but also the photocatalytic activity could be promoted significantly by increasing the dip-coating times. When the alumina substrate was dip-coated in TiO2 sol from 1 to 4 times, the degradation rate of methylene blue increased from 40% to 83.1%. However, after dip-coating the alumina support in TiO2 sol for 5 times, the degradation of methylene blue was only up to 85.6%. This indicates that the photocatalytic activity increased slowly when the TiO2 content in the supported catalyst was up to some extent. It is attributed to the continuous dip-coating resulted in less opportunities and weak intensity of illumination for the TiO2 nano-particles that under lower layer. The photocatalytic activity was relatively stable

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).

Synthesis and visible light photocatalytic property of polyhedron-shaped AgNbO3.

PubMed

Li, Guoqiang; Yan, Shicheng; Wang, Zhiqiang; Wang, Xiangyan; Li, Zhaosheng; Ye, Jinhua; Zou, Zhigang

2009-10-28

Polyhedron-shaped AgNbO3 photocatalysts were synthesized by solvothermal and liquid-solid methods. Their photocatalytic properties were evaluated from the photocatalytic O2 evolution under visible light irradiation. The polyhedron-shaped AgNbO3 was induced to grow by shaped silver particles followed by the free-growth model. The photocatalytic results indicate that the polyhedron-shaped morphology is favourable for the photocatalytic O2 evolution under visible light irradiation in comparison with the spherical one. Furthermore, the Cu doping on the surface would enhance the visible light photocatalytic activity significantly.

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

Core-Shell Photonic Nanoparticles for Enhanced Solar-to-Fuel Photocatalytic Conversion

DTIC Science & Technology

2017-10-11

photocatalytic activity of semiconducting materials. They synthesized and functionalized titanium dioxide nanoparticles with a partial shell of gold...Their research also characterized the photocatalytic activity . The second area was the tuning the dielectric environment of the nanoparticles with think...successful investigation of bimetallic nanoshells that enhance the photocatalytic activity of semiconducting materials. Our earlier work focused on the

Photocatalytic and Photoelectrochemically Degradation of Chlorsulfuron herbicide

NASA Astrophysics Data System (ADS)

Guo, Xu; Liu, Hongwei; Miao, Jinjie; Ma, Zhen

2017-12-01

Photocatalytic and photo electrochemical (PEC) degradation of chlorsulfuron herbicide were studied. Two novel PEC electrodes Ti/IrO2-Pt-WO3 (TIW) and Ti/IrO2-Pt-Ag3PO4 (TIA) were designed and some important factors were studied. Lower current density showed lower removal efficiency than higher conditions by electrochemical method. Furthermore, PEC showed higher degradation efficiency than the sum of individual EO and photocatalytic methode.

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

Hydrogen purifier module with membrane support

DOEpatents

A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

2012-07-24

A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

Site remediation using photocatalytic VOC destruction of chlorinated hydrocarbons

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

Brunet, R.A.H.; Pearcey, R.; Kittrell, J.R.

1999-07-01

An innovative environmental technology has been developed and demonstrated for cost-effective control of toxic air emissions, such as trichloroethylene (TCE) and perchloroethylene (PCE), found in soil and groundwater at hazardous waste sites and in industrial effluents. The technology uses UV light and a proprietary photocatalyst to adsorb and destroy pollutants at ambient conditions, even with high humidity. Air stripping and soil vapor extraction efficiently transfer the pollutants to the gas phase, where they can be economically treated by photocatalysis without the risk of hazardous by-product formation. The AIR2000 photocatalytic technology was successfully installed at the Stamina Mills Superfund site inmore » Rhode Island, where a commercial scale unit is treating 700 cfm of up to 1,000 ppm TCE, mixed with PCE, dichloroethylene (DCE), trichloroethane (TCA), and vinyl chloride (VC) produced through a combination of soil vapor extraction (SVE) and air stripping. As part of the EPA SITE program, the system was monitored for overall destruction removal efficiency (DRE) and hazardous by-product formation. A DRE in excess of 99% was reported over the first four months of operation, with greater than 99.99% DRE achieved, without production of hazardous by-products. The operating cost of the system is approximately 20% of activated carbon adsorption, which provides approximately $1,500,000 in cost savings over the life of the Stamina Mills project. The Adsorption Integrated Reaction (AIR) process is the recipient of the 1997 SBIR Technology of the Year award, the 1998 EPA Environmental Technology Innovator Award, and the 1998 R and D 100 Award.« less

Photocatalytic fluoroalkylation reactions of organic compounds.

PubMed

Barata-Vallejo, Sebastián; Bonesi, Sergio M; Postigo, Al

2015-12-14

Photocatalytic methods for fluoroalkyl-radical generation provide more convenient alternatives to the classical perfluoroalkyl-radical (Rf) production through chemical initiators, such as azo or peroxide compounds or the employment of transition metals through a thermal electron transfer (ET) initiation process. The mild photocatalytic reaction conditions tolerate a variety of functional groups and, thus, are handy to the late-stage modification of bioactive molecules. Transition metal-photocatalytic reactions for Rf radical generation profit from the redox properties of coordinatively saturated Ru or Ir organocomplexes to act as both electron donor and reductive species, thus allowing for the utilization of electron accepting and donating fluoroalkylating agents for Rf radical production. On the other hand, laboratory-available and inexpensive photoorgano catalysts (POC), in the absence of transition metals, can also act as electron exchange species upon excitation, resulting in ET reactions that produce Rf radicals. In this work, a critical account of transition metal and transition metal-free Rf radical production will be described with photoorgano catalysts, studying classical examples and the most recent investigations in the field.

A novel experimental technology for testing efficacy of air purifiers on pollen reduction.

PubMed

Bergmann, Karl-Christian; Sehlinger, Torsten; Gildemeister, Julia; Zuberbier, Torsten

2017-01-01

Allergenic pollen exposure is mostly seen as an outdoor phenomenon but studies have shown an indoor exposure: different pollen species including birch and grass pollen in houses, schools, and shops are leading to long-lasting symptoms even after the pollen season because pollen settle on surfaces and re-enter the indoor air depending on ventilation. To reduce indoor pollen load, windows need to be closed and devices should be used: as pure wiping and cleaning of surfaces is mostly not sufficient, air cleaners may be helpful in reducing pollen counts in indoor environment. The efficacy of an air cleaner is usually described by the filtration rate of standard dust particle sizes which is not necessarily related to clinical efficacy. A novel study design was developed using the technical equipment of a new mobile exposure chamber to investigate participants with allergic rhinitis (individual observational, controlled, prospective, single arm study). The tested air cleaner reduced the grass pollen-induced (4000 grass pollen/m 3 over 90 min) nasal symptoms (total nasal symptom score) significantly from 6 and 4 points (1st and 2nd exposure in sham run) to less than 1 point when air cleaner was activated. The novel study protocol is suitable for testing efficacy of air cleaners and the tested air cleaner is effective in reducing clinical symptoms due to grass pollen in an indoor environment.

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

21 CFR 880.6710 - Medical ultraviolet water purifier.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Medical ultraviolet water purifier. 880.6710... Miscellaneous Devices § 880.6710 Medical ultraviolet water purifier. (a) Identification. A medical ultraviolet water purifier is a device intended for medical purposes that is used to destroy bacteria in water by...

21 CFR 880.6710 - Medical ultraviolet water purifier.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Medical ultraviolet water purifier. 880.6710... Miscellaneous Devices § 880.6710 Medical ultraviolet water purifier. (a) Identification. A medical ultraviolet water purifier is a device intended for medical purposes that is used to destroy bacteria in water by...

21 CFR 880.6710 - Medical ultraviolet water purifier.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Medical ultraviolet water purifier. 880.6710... Miscellaneous Devices § 880.6710 Medical ultraviolet water purifier. (a) Identification. A medical ultraviolet water purifier is a device intended for medical purposes that is used to destroy bacteria in water by...

21 CFR 880.6710 - Medical ultraviolet water purifier.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Medical ultraviolet water purifier. 880.6710... Miscellaneous Devices § 880.6710 Medical ultraviolet water purifier. (a) Identification. A medical ultraviolet water purifier is a device intended for medical purposes that is used to destroy bacteria in water by...

Air/Water Purification

NASA Technical Reports Server (NTRS)

1992-01-01

After 18 years of research into air/water pollution at Stennis Space Center, Dr. B. C. Wolverton formed his own company, Wolverton Environmental Services, Inc., to provide technology and consultation in air and water treatment. Common houseplants are used to absorb potentially harmful materials from bathrooms and kitchens. The plants are fertilized, air is purified, and wastewater is converted to clean water. More than 100 U.S. communities have adopted Wolverton's earlier water hyacinth and artificial marsh applications. Catfish farmers are currently evaluating the artificial marsh technology as a purification system.

Enhanced visible light photocatalytic property of red phosphorus via surface roughening

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

Li, Weibing, E-mail: lwbing@qust.edu.cn; Yue, Jiguang; Hua, Fangxia

Highlights: • Photocatalytic RhB degradation of red phosphorus was studied for the first time. • Surface rough can increase the photocatalysis reaction active sites. • Surface rough red phosphorus possesses high photocatalytic performance. • Surface rough red phosphorus has high industrial application value. - Abstract: Red phosphorus with rough surface (SRP) was prepared by catalyst-assisted hydrothermal synthesis using Co{sup 2+} catalyst. The photocatalytic Rhodamine B (RhB) degradation of red phosphorus (RP) and SRP was studied for the first time in this work. Rough surface can enhance the dye adsorption ability of RP. About 75% RhB was absorbed by SRP aftermore » 30-min adsorption in 100 ml RhB solution with concentration of 10 mg l{sup −1} in dark. After only 10 min of illumination by visible light, more than 95% RhB was degraded, indicating that SRP has a great application potential in the area of photocatalysis. The photocatalytic RhB degradation properties of RP are much weaker than those of SRP. The increase of the number of the active sites for the photocatalytic reactions, the electron mobility and the lifetime of the photogenerated electrons cause the significant improvement of the photocatalytic performance of SRP based on the experimental results obtained.« less

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).

Room-temperature in situ fabrication of Bi2O3/g-C3N4 direct Z-scheme photocatalyst with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

He, Rongan; Zhou, Jiaqian; Fu, Huiqing; Zhang, Shiying; Jiang, Chuanjia

2018-02-01

Constructing direct Z-scheme heterojunction is an effective approach to separating photogenerated charge carriers and improving the activity of semiconductor photocatalysts. Herein, a composite of bismuth(III) oxide (Bi2O3) and graphitic carbon nitride (g-C3N4) was in situ fabricated at room temperature by photoreductive deposition of Bi3+ and subsequent air-oxidation of the resultant metallic Bi. Quantum-sized ω-Bi2O3 nanoparticles approximately 6 nm in diameter were uniformly distributed on the surface of mesoporous g-C3N4. The as-prepared Bi2O3/g-C3N4 composite exhibited higher photocatalytic activity than pure Bi2O3 and g-C3N4 for photocatalytic degradation of phenol under visible light. Reactive species trapping experiments revealed that superoxide radicals and photogenerated holes played important roles in the photocatalytic degradation of phenol. The enhanced photocatalytic activity, identification of reactive species and higher rate of charge carrier recombination (as indicated by stronger photoluminescence intensity) collectively suggest that the charge migration within the Bi2O3/g-C3N4 composite followed a Z-scheme mechanism. Photogenerated electrons on the conduction band of Bi2O3 migrate to the valence band of g-C3N4 and combine with photogenerated holes therein. At the cost of these less reactive charge carriers, the Z-scheme heterojunction enables efficient charge separation, while preserving the photogenerated electrons and holes with stronger redox abilities, which is beneficial for enhanced photocatalytic activity.

Recent developments in photocatalytic water treatment technology: a review.

PubMed

Chong, Meng Nan; Jin, Bo; Chow, Christopher W K; Saint, Chris

2010-05-01

In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align with the "zero" waste scheme in the water/wastewater industry. The ability of this advanced oxidation technology has been widely demonstrated to remove persistent organic compounds and microorganisms in water. At present, the main technical barriers that impede its commercialisation remained on the post-recovery of the catalyst particles after water treatment. This paper reviews the recent R&D progresses of engineered-photocatalysts, photoreactor systems, and the process optimizations and modellings of the photooxidation processes for water treatment. A number of potential and commercial photocatalytic reactor configurations are discussed, in particular the photocatalytic membrane reactors. The effects of key photoreactor operation parameters and water quality on the photo-process performances in terms of the mineralization and disinfection are assessed. For the first time, we describe how to utilize a multi-variables optimization approach to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency. Both photomineralization and photo-disinfection kinetics and their modellings associated with the photocatalytic water treatment process are detailed. A brief discussion on the life cycle assessment for retrofitting the photocatalytic technology as an alternative waste treatment process is presented. This paper will deliver a scientific and technical overview and useful information to scientists and engineers who work in this field.

Water Purifiers

NASA Technical Reports Server (NTRS)

1992-01-01

Technology developed to purify the water aboard manned spacecraft has led to a number of spinoff applications. One of them is the Ambassador line of bacteriostatic water treatment systems, which employ high grade, high absorption media to inhibit bacteria growth and remove the medicinal taste and odor of chlorine. Company President, Ray Ward, originally became interested in the technology because of the "rusty" taste of his water supply.

Bismuth Oxysulfide and Its Polymer Nanocomposites for Efficient Purification

PubMed Central

Luo, Yidong; Qiao, Lina; Wang, Huanchun; Lan, Shun; Shen, Yang; Lin, Yuanhua; Nan, Cewen

2018-01-01

The danger of toxic organic pollutants in both aquatic and air environments calls for high-efficiency purification material. Herein, layered bismuth copper oxychalcogenides, BiCuSO, nanosheets of high photocatalytic activity were introduced to the PVDF (Polyvinylidene Fluoride). The fibrous membranes provide an easy, efficient, and recyclable way to purify organic pollutant. The physical and photophysical properties of the BiCuSO and its polymer composite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (EPR). Photocatalysis of Congo Red reveals that the BiCuSO/PVDF shows a superior photocatalytic activity of a 55% degradation rate in 70 min at visible light. The high photocatalytic activity is attributed to the exposed active {101} facets and the triple vacant associates VBi‴VO••VBi‴. By engineering the intrinsic defects on the surface of bismuth oxysulfide, high solar-driven photocatalytic activity can be approached. The successful fabrication of the bismuth oxysulfide and its polymer nanocomposites provides an easy and general approach for high-performance purification materials for various applications. PMID:29562701

Substrate-Coated Illumination Droplet Spray Ionization: Real-Time Monitoring of Photocatalytic Reactions

NASA Astrophysics Data System (ADS)

Zhang, Hong; Li, Na; Zhao, Dandan; Jiang, Jie; You, Hong

2017-09-01

Real-time monitoring of photocatalytic reactions facilitates the elucidation of the mechanisms of the reactions. However, suitable tools for real-time monitoring are lacking. Herein, a novel method based on droplet spray ionization named substrate-coated illumination droplet spray ionization (SCI-DSI) for direct analysis of photocatalytic reaction solution is reported. SCI-DSI addresses many of the analytical limitations of electrospray ionization (ESI) for analysis of photocatalytic-reaction intermediates, and has potential for both in situ analysis and real-time monitoring of photocatalytic reactions. In SCI-DSI-mass spectrometry (MS), a photocatalytic reaction occurs by loading sample solutions onto the substrate-coated cover slip and by applying UV light above the modified slip; one corner of this slip adjacent to the inlet of a mass spectrometer is the high-electric-field location for launching a charged-droplet spray. After both testing and optimizing the performance of SCI-DSI, the value of this method for in situ analysis and real-time monitoring of photocatalytic reactions was demonstrated by the removal of cyclophosphamide (CP) in TiO2/UV. Reaction times ranged from seconds to minutes, and the proposed reaction intermediates were captured and identified by tandem mass spectrometry. Moreover, the free hydroxyl radical (·OH) was identified as the main radicals for CP removal. These results show that SCI-DSI is suitable for in situ analysis and real-time monitoring of CP removal under TiO2-based photocatalytic reactions. SCI-DSI is also a potential tool for in situ analysis and real-time assessment of the roles of radicals during CP removal under TiO2-based photocatalytic reactions. Graphical Abstract[Figure not available: see fulltext.

Visible-light-driven N-(BiO)2CO3/Graphene oxide composites with improved photocatalytic activity and selectivity for NOx removal

NASA Astrophysics Data System (ADS)

Chen, Meijuan; Huang, Yu; Yao, Jie; Cao, Jun-ji; Liu, Yuan

2018-02-01

N-doped (BiO)2CO3 (NBOC)/graphene oxide (GO) composite obtained from three-dimensional hierarchical microspheres is successfully synthesized by one-pot hydrothermal method for the first time. In this synthesis, citrate ion plays a critical role in N doping. The obtained samples are used to degrade gaseous nitrogen oxides (NOx) at parts-per-billion (ppb) level under visible-light irradiation. NBOC-GO composite with 1.0 wt% graphene oxide (GO) displays the highest photocatalytic NO removal efficiency, which is 4.3 times higher than that of pristine (BiO)2CO3. Moreover, NBOC-GO composite significantly inhibits toxic NO2 intermediate production, indicating its high selectivity for NO conversion. Compared with regular GO, N doping considerably improves the catalytic performance of NBOC-GO composite, which increases NO removal by 74.6% and fully inhibits NO2 generation. The improved photocatalytic activity is mainly ascribed to extended optical absorption ability and enhanced separation efficiency of photogenerated charge carriers over NBOC-GO composite. Both results of electron spin resonance and theoretical analysis of band structure indicate that NO removal is dominated by oxidation with rad OH and rad O2- radicals. The photocatalytic activity improvement mechanism over the NBOC-GO composite is proposed accordingly based on systematic characterizations. This study demonstrates a feasible route to fabricating Bi-containing composites with high selectivity and stability for air pollution control and provides a new insight into the associated photocatalytic mechanisms.

Food-Growing, Air- And Water-Cleaning Module

NASA Technical Reports Server (NTRS)

Sauer, R. L.; Scheld, H. W.; Mafnuson, J. W.

1988-01-01

Apparatus produces fresh vegetables and removes pollutants from air. Hydroponic apparatus performs dual function of growing fresh vegetables and purifying air and water. Leafy vegetables rooted in granular growth medium grow in light of fluorescent lamps. Air flowing over leaves supplies carbon dioxide and receives fresh oxygen from them. Adaptable to production of food and cleaning of air and water in closed environments as in underwater research stations and submarines.

A Method of Effective Quarry Water Purifying Using Artificial Filtering Arrays

NASA Astrophysics Data System (ADS)

Tyulenev, M.; Garina, E.; Khoreshok, A.; Litvin, O.; Litvin, Y.; Maliukhina, E.

2017-01-01

The development of open pit mining in the large coal basins of Russia and other countries increases their negative impact on the environment. Along with the damage of land and air pollution by dust and combustion gases of blasting, coal pits have a significant negative impact on water resources. Polluted quarry water worsens the ecological situation on a much larger area than covered by air pollution and land damage. This significantly worsens the conditions of people living in cities and towns located near the coal pits, and complicates the subsequent restoration of the environment, irreversibly destroying the nature. Therefore, the research of quarry wastewater purifying is becoming an important mater for scholars of technical colleges and universities in the regions with developing open-pit mining. This paper describes the method of determining the basic parameters of the artificial filtering arrays formed on coal pits of Kuzbass (Western Siberia, Russia), and gives recommendations on its application.

Investigation of polypyrrole/polyvinyl alcohol-titanium dioxide composite films for photo-catalytic applications

NASA Astrophysics Data System (ADS)

Cao, Shaoqiang; Zhang, Hongyang; Song, Yuanqing; Zhang, Jianling; Yang, Haigang; Jiang, Long; Dan, Yi

2015-07-01

Polypyrrole/polyvinyl alcohol-titanium dioxide (PPy/PVA-TiO2) composite films used as photo-catalysts were fabricated by combining TiO2 sol with PPy/PVA solution in which PPy was synthesized by in situ polymerization of pyrrole (Py) in polyvinyl alcohol (PVA) matrix and loaded on glass. The prepared photo-catalysts were investigated by X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectra and photoluminescence (PL). The results indicate that the composites have same crystal structure as the TiO2 and extend the optic absorption from UV region to visible light region. By detecting the variation ratio, detected by ultraviolet-vis spectroscopy, of model pollutant rhodamine B (RhB) solution in the presence of the composite films under both UV and visible light irradiation, the photo-catalytic performance of the composite films was investigated. The results show that the PPy/PVA-TiO2 composite films show better photo-catalytic properties than TiO2 film both under UV and visible light irradiation, and the photo-catalytic degradation of RhB follows the first-order kinetics. The effects of the composition of composite films and the concentration of RhB on the photo-catalytic performance, as well as the possible photo-catalytic mechanism, were also discussed. By photo-catalytic recycle experiments, the structure stability of the PPy/PVA-TiO2 composite film was investigated and the results show that the photo-catalytic activity under both UV and visible light irradiation have no significant decrease after four times of recycle experiments, suggesting that the photo-catalyst film is stable during the photo-catalytic process, which was also confirmed by the XRD pattern and FT-IR spectra of the composite film before and after photo-catalytic.

METHOD FOR PURIFYING URANIUM

DOEpatents

Knighton, J.B.; Feder, H.M.

1960-04-26

A process is given for purifying a uranium-base nuclear material. The nuclear material is dissolved in zinc or a zinc-magnesium alloy and the concentration of magnesium is increased until uranium precipitates.

Real-time spectroscopic monitoring of photocatalytic activity promoted by graphene in a microfluidic reactor

PubMed Central

Li, Yifan; Lin, Beichen; Ge, Likai; Guo, Hongchen; Chen, Xinyi; Lu, Miao

2016-01-01

Photocatalytic microreactors have been utilized as rapid, versatile platforms for the characterization of photocatalysts. In this work, a photocatalytic microreactor integrated with absorption spectroscopy was proposed for the real-time monitoring of photocatalytic activity using different catalysts. The validity of this method was investigated by the rapid screening on the photocatalytic performance of a titanium oxide (TiO2)-decorated graphene oxide (GO) sheet for the degradation of methylene blue under monochromatic visible irradiation. The sampling interval time could be minimized to 10 s for achieving real-time detection. The best photocatalytic activity was observed for an optimized TiO2/GO weight mixing ratio of 7:11, with a reaction rate constant up to 0.067 min−1. The addition of GO into TiO2 enhances photocatalytic activity and adsorption of MB molecules. The synthetic reaction rate constant was up to approximately 0.11 min−1, which was also the highest among the catalysts. The microreactor exhibited good sensitivity and reproducibility without weakening the performance of the photocatalysts. Consequently, the photocatalytic microreactor is promising as a simple, portable, and rapid screening tool for new photocatalysts. PMID:27346555

Real-time spectroscopic monitoring of photocatalytic activity promoted by graphene in a microfluidic reactor

NASA Astrophysics Data System (ADS)

Li, Yifan; Lin, Beichen; Ge, Likai; Guo, Hongchen; Chen, Xinyi; Lu, Miao

2016-06-01

Photocatalytic microreactors have been utilized as rapid, versatile platforms for the characterization of photocatalysts. In this work, a photocatalytic microreactor integrated with absorption spectroscopy was proposed for the real-time monitoring of photocatalytic activity using different catalysts. The validity of this method was investigated by the rapid screening on the photocatalytic performance of a titanium oxide (TiO2)-decorated graphene oxide (GO) sheet for the degradation of methylene blue under monochromatic visible irradiation. The sampling interval time could be minimized to 10 s for achieving real-time detection. The best photocatalytic activity was observed for an optimized TiO2/GO weight mixing ratio of 7:11, with a reaction rate constant up to 0.067 min-1. The addition of GO into TiO2 enhances photocatalytic activity and adsorption of MB molecules. The synthetic reaction rate constant was up to approximately 0.11 min-1, which was also the highest among the catalysts. The microreactor exhibited good sensitivity and reproducibility without weakening the performance of the photocatalysts. Consequently, the photocatalytic microreactor is promising as a simple, portable, and rapid screening tool for new photocatalysts.

The highly efficient photocatalytic and light harvesting property of Ag-TiO2 with negative nano-holes structure inspired from cicada wings.

PubMed

Zada, Imran; Zhang, Wang; Zheng, Wangshu; Zhu, Yuying; Zhang, Zhijian; Zhang, Jianzhong; Imtiaz, Muhammad; Abbas, Waseem; Zhang, Di

2017-12-08

The negative replica of biomorphic TiO 2 with nano-holes structure has been effectively fabricated directly from nano-nipple arrays structure of cicada wings by using a simple, low-cost and highly effective sol-gel ultrasonic method. The nano-holes array structure was well maintained after calcination in air at 500 °C. The Ag nanoparticles (10 nm-25 nm) were homogeneously decorated on the surface and to the side wall of nano-holes structure. It was observed that the biomorphic Ag-TiO 2 showed remarkable photocatalytic activity by degradation of methyl blue (MB) under UV-vis light irradiation. The biomorphic Ag-TiO 2 with nano-holes structure showed superior photocatalytic activity compared to the biomorphic TiO 2 and commercial Degussa P25. This high-performance photocatalytic activity of the biomorphic Ag-TiO 2 may be attributed to the nano-holes structure, localized surface plasmon resonance (LSPR) property of the Ag nanoparticles, and enhanced electron-hole separation. Moreover, the biomorphic Ag-TiO 2 showed more absorption capability in the visible wavelength range. This work provides a new insight to design such a structure which may lead to a range of novel applications.

An Advanced Semimetal-Organic Bi Spheres-g-C3N4 Nanohybrid with SPR-Enhanced Visible-Light Photocatalytic Performance for NO Purification.

PubMed

Dong, Fan; Zhao, Zaiwang; Sun, Yanjuan; Zhang, Yuxin; Yan, Shuai; Wu, Zhongbiao

2015-10-20

To achieve efficient photocatalytic air purification, we constructed an advanced semimetal-organic Bi spheres-g-C3N4 nanohybrid through the in-situ growth of Bi nanospheres on g-C3N4 nanosheets. This Bi-g-C3N4 compound exhibited an exceptionally high and stable visible-light photocatalytic performance for NO removal due to the surface plasmon resonance (SPR) endowed by Bi metal. The SPR property of Bi could conspicuously enhance the visible-light harvesting and the charge separation. The electromagnetic field distribution of Bi spheres involving SPR effect was simulated and reaches its maximum in close proximity to the Bi particle surface. When the Bi metal content was controlled at 25%, the corresponding Bi-g-C3N4 displayed outstanding photocatalytic capability and transcended those of other visible-light photocatalysts. The Bi-g-C3N4 exhibited a high structural stability under repeated photocatalytic runs. A new visible-light-induced SPR-based photocatalysis mechanism with Bi-g-C3N4 was proposed on the basis of the DMPO-ESR spin-trapping. The photoinduced electrons could transfer from g-C3N4 to the Bi metal, as revealed with time-resolved fluorescence spectra. The function of Bi semimetal as a plasmonic cocatalyst for boosting visible light photocatalysis was similar to that of noble metals, which demonstrated a great potential of utilizing the economically feasible Bi element as a substitute for noble metals for the advancement of photocatalysis efficiency.

Ionic liquid-assisted synthesis of highly dispersive bowknot-like ZnO microrods for photocatalytic applications

NASA Astrophysics Data System (ADS)

Zhao, Shuo; Zhang, Yiwei; Zhou, Yuming; Zhang, Chao; Sheng, Xiaoli; Fang, Jiasheng; Zhang, Mingyu; Yang, Yong

2017-04-01

Here we present a facile method for the preparation of highly dispersive ZnO materials by using ionic liquid 1-methyl-3-[3‧-(trimethoxysilyl) propyl] imidazolium chloride as the template. The influence of ionic liquid concentration and calcined atmosphere on the photoactivity is studied. The samples were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), scanning electron microscope (SEM), N2 gas sorption and ultraviolet-visible diffuse reflectance spectroscopy. The results showed that the as-fabricated ZnO materials consisted of individual microrods with self-assembled bowknot-like architecture whose size was about 1 μm. The formation mechanism of the bowknot-like ZnO materials which is based on the self-assembly of ionic liquid is tentatively elucidated. Moreover, the ZnO-2.6N sample exhibited the higher activity for the photodegradation of MB than the photodegradation of MO and RhB. Furthermore, it was found that the ZnO materials calcined under air atmosphere showed the better photocatalytic activities than that of samples calcined under nitrogen atmosphere in the degradation of methylene blue (MB) under UV irradiation. And the special structure, surface area, adsorption capability of dye, the separation rate of photogenerated electron-hole pairs and band gap had effects on the photocatalytic activity of ZnO photocatalysts. O2rad - was the main active species for the photocatalytic degradation of MB. It is valuable to develop this facile route preparing the highly dispersive bowknot-like ZnO materials and the ZnO materials can be beneficial for environmental protection.

Method of photocatalytic nanotagging

DOEpatents

Shelnutt, John A [Tijeras, NM; Medforth, Craig J [Winters, CA; Song, Yujiang [Albuquerque, NM

2010-04-27

A nanotagged chemical structure comprising a chemical structure with an associated photocatalyst and a tagging nanoparticle (a nanotag) grown in proximity to the photocatalyst, and a method for making the nanotagged chemical structure. The nanoparticle is grown in proximity to the photocatalyst by using a photocatalytic reduction reaction.

Solar or UVA-Visible Photocatalytic Ozonation of Water Contaminants.

PubMed

Beltrán, Fernando J; Rey, Ana

2017-07-14

An incipient advanced oxidation process, solar photocatalytic ozonation (SPO), is reviewed in this paper with the aim of clarifying the importance of this process as a more sustainable water technology to remove priority or emerging contaminants from water. The synergism between ozonation and photocatalytic oxidation is well known to increase the oxidation rate of water contaminants, but this has mainly been studied in photocatalytic ozonation systems with lamps of different radiation wavelength, especially of ultraviolet nature (UVC, UVB, UVA). Nowadays, process sustainability is critical in environmental technologies including water treatment and reuse; the application of SPO systems falls into this category, and contributes to saving energy and water. In this review, we summarized works published on photocatalytic ozonation where the radiation source is the Sun or simulated solar light, specifically, lamps emitting radiation to cover the UVA and visible light spectra. The main aspects of the review include photoreactors used and radiation sources applied, synthesis and characterization of catalysts applied, influence of main process variables (ozone, catalyst, and pollutant concentrations, light intensity), type of water, biodegradability and ecotoxicity, mechanism and kinetics, and finally catalyst activity and stability.

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.

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.

Effect of doping on the photocatalytic, electronic and mechanical properties of sol-gel titanium dioxide films

NASA Astrophysics Data System (ADS)

Kurtoglu, Murat

Heterogeneous photocatalysis has been an active research area over the last decade as a promising solution for energy generation and environmental problems which has led to promising applications from air and water purification systems, self-cleaning and self-sterilizing surfaces to solar cells and hydrogen production from water dissociation reaction. Titanium dioxide (TiO2), an abundant material with a high photocatalytic efficiency and chemical stability, is undoubtedly the most widely studied and used among all photocatalytic materials. Although titanium dioxide has been used in powder form, its immobilized form (film) is necessary from practical application standpoint. However, there are several shortcomings of titanium dioxide films that need to be addressed to realize a wide range of successful applications: lack of visible light activity, poisoning of the catalytic performance by the substrate and the low surface area compared to powder forms. In addition, mechanical properties of such films have not been investigated thoroughly, which may be critical when abrasion and weathering resistance are necessary. To address each of these issues, a systematic experimental and theoretical investigation of doping titanium dioxide films with a variety of elements were conducted. Utilizing theoretical calculations to filter elements for experimental studies as well as interpretation of the experimental results, several dopant or dopant combinations were found to remedy some of the issues of photocatalytic titanium dioxide films. Doping with 32 metals, nitrogen and 11 metal-nitrogen combinations are investigated theoretically and the results are used as guideline for the experimental studies. Particular attention is given to certain metal dopants such as Cr, V, Mo, Ta and Ga not just because of their relatively modest cost but also their non-toxicity and wide availability of their compatible compounds for sol-gel synthesis. While metal-dopants improved the overall

Photocatalytic Activity of Vanadium-Substituted ETS-10

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

Nash,M.; Rykov, S.; Lobo, R.

2007-01-01

Various amounts of vanadium have been isomorphously substituted for titanium in ETS-10, creating samples with V/(V+Ti) ratios of 0.13, 0.33, 0.43, and 1.00 and characterized experimentally using Raman, near-edge X-ray absorption fine structure (NEXAFS), X-ray powder diffraction, N{sub 2} adsorption, scanning electron microscopy (SEM), UV/vis spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Raman spectra reveal a disordered chain structure that contains different V-O bonds along with the presence of a V-O-Ti peak. The UV/vis spectra of the vanadium samples have three new absorption features in the visible region at 450, 594, and 850 nm, suggesting both V{sup 4+}more » and V{sup 5+} are present in the samples. NEXAFS results confirm the presence of both V{sup 5+} and V{sup 4+} in the vanadium samples, with a fraction of V{sup 4+} within the range of 0.2-0.4. The addition of vanadium lowers the band gap energy of ETS-10 from 4.32 eV to a minimum of 3.58 eV for the 0.43ETVS-10 sample. Studies of the photocatalytic polymerization of ethylene show that the 594 nm transition has no photocatalytic activity. The visible transition around 450 nm in the vanadium-incorporated samples is photocatalytically active, and the lower-concentration vanadium samples have higher photocatalytic activity than that of ETS-10 and AM-6, the all-vanadium analogue of ETS-10.« less

Study on Photocatalytic Properties of TiO2 Nanoparticle in various pH condition

NASA Astrophysics Data System (ADS)

Nasikhudin; Diantoro, M.; Kusumaatmaja, A.; Triyana, K.

2018-04-01

Titanium dioxide has been widely studied for its ability to photocatalytic and applications have high performance for photovoltaic applications. In this paper TiO2 nanoparticle was investigated for the degradation of methylene blue under UV light in various pH condition. The TiO2 nanoparticle was characterized by SEM and XRD. The results showed that TiO2 nanoparticle has the structure of anatase and have a particle size of 27 nm. The photocatalytic activity of TiO2 nanoparticle show that the degradation of methylene blue under UV light have dye removal of 97% dye was degraded in 3 h, but the degradation of methylene blue without UV light have dye removal of 15% dye was degraded in 3 h. It indicated that The photocatalytic activity of TiO2 nanoparticle could occur if there the UV light. If not UV light the photocatalytic activity cannot occurs, the degradation of Methylene Blue 15% is not a photocatalytic activity but it is adsorption of Methylene Blue by TiO2 nanoparticle. The photocatalytic activity of TiO2 nanoparticle has pH-sensitive. The photocatalytic activity of TiO2 nanoparticle in acid condition (pH 4.1) is 40%, in neutral condition (pH 7.0) is 90%, and in base condition (pH 9.7) is 97%. The highest photocatalytic activity occurs in base condition, it causes in base condition OH- can be direct reaction with a hole to produce hydroxyl radical (OH*).

Synthesis process and photocatalytic properties of BiOBr nanosheets for gaseous benzene.

PubMed

Liu, Yu; Yin, Yongquan; Jia, Xueqing; Cui, Xiangyu; Tian, Canrui; Sang, Yuanhua; Liu, Hong

2016-09-01

A series of nano-BiOBr were prepared by an effective hydrothermal method in the presence of cetyltrimethyl ammonium bromide (CTAB) and ethanol at different calcination temperatures. The as-prepared nano-BiOBr samples were characterized by measuring the specific area (S BET), UV-Vis diffuse reflectance spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results show that the calcination temperature has an important impact on the morphology and microstructure of BiOBr. The nano-BiOBr calcined at 120 °C showed excellent photocatalytic degradation properties for benzene, with photocatalytic degradation rate of 75 % for benzene under UV irradiation for 90 min, and removal efficiency of benzene was significantly enhanced by using nano-BiOBr catalyst compared to UV irradiation alone. BiOBr catalyst possessed good photocatalytic activity even after three consecutive photocatalytic reaction cycles, illustrating its excellent stability. The photocatalytic degradation of benzene followed the first-order kinetics, and the good catalytic capability of nano-BiOBr catalyst can be attributed to its crystalline, hierarchical nanostructure and nanosheet thickness.

Methods for purifying carbon materials

DOEpatents

Dailly, Anne [Pasadena, CA; Ahn, Channing [Pasadena, CA; Yazami, Rachid [Los Angeles, CA; Fultz, Brent T [Pasadena, CA

2009-05-26

Methods of purifying samples are provided that are capable of removing carbonaceous and noncarbonaceous impurities from a sample containing a carbon material having a selected structure. Purification methods are provided for removing residual metal catalyst particles enclosed in multilayer carbonaceous impurities in samples generate by catalytic synthesis methods. Purification methods are provided wherein carbonaceous impurities in a sample are at least partially exfoliated, thereby facilitating subsequent removal of carbonaceous and noncarbonaceous impurities from the sample. Methods of purifying carbon nanotube-containing samples are provided wherein an intercalant is added to the sample and subsequently reacted with an exfoliation initiator to achieve exfoliation of carbonaceous impurities.

[Spectroscopic study of photocatalytic mechanism of methanol and CO2].

PubMed

Hai, Feng; Zhang, Qian-cheng; Bai, Feng-rong; Wang, A-nan; Wang, Zhi-wei; Jian, Li

2011-12-01

Ni-Ti-O/SiO2 catalyst was prepared by impregnation method, and its photocatalytic performance for carbonylation of methanol with CO2 was investigated under UV light. The in-situ IR, XPS and MS were carried out to analyze the possible photocatalytic reaction mechanism. Results indicated that the Ni-Ti-O/SiO2 exhibited good photocatalytic performance for carbonylation of methanol with CO2, the methanol conversion reached up to 24.9%, and the selectivity for the carbonylated products was more than 60% within 180 min reaction time. The catalyst characterization results showed that the O==C .--O- and CH3OC(O)* might be important intermediate in the carbonylation of methanol with CO2.

Biomolecule-assisted construction of cadmium sulfide hollow spheres with structure-dependent photocatalytic activity.

PubMed

Wei, Chengzhen; Zang, Wenzhe; Yin, Jingzhou; Lu, Qingyi; Chen, Qun; Liu, Rongmei; Gao, Feng

2013-02-25

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure-dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution-reprecipitation mechanism. Their visible-light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible-light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Defect engineering in atomically-thin bismuth oxychloride towards photocatalytic oxygen evolution

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

Di, Jun; Chen, Chao; Yang, Shi -Ze

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds,more » defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.« less

Defect engineering in atomically-thin bismuth oxychloride towards photocatalytic oxygen evolution

DOE PAGES

Di, Jun; Chen, Chao; Yang, Shi -Ze; ...

2017-06-26

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds,more » defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.« less

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.

Bactericidal effect of photocatalytically-active nanostructured TiO2 surfaces on biofilms of the early oral colonizer, Streptococcus oralis.

PubMed

Westas, Emma; Hayashi, Mariko; Cecchinato, Francesca; Wennerberg, Ann; Andersson, Martin; Jimbo, Ryo; Davies, Julia R

2017-08-01

This study evaluated the photocatalytic bactericidal effect of nanostructured anatase-rich titanium dioxide (TiO 2 ) on microbial biofilms. Commercially pure titanium discs were spin-coated with photocatalytic TiO 2 nanoparticles (P25). Uncoated discs were used as control (CTRL). Half of the CTRL and half of the P25-coated surfaces were coated with purified saliva (SAL) to give four different groups (CTRL, CTRL + SAL, P25 and P25 + SAL). Streptococcus oralis were allowed to form biofilms on the discs for 18 h and non-adherent cells were rinsed off. Bacterial viability was assessed at time 0 with Live/Dead BacLight staining and epifluorescence microscopy. The remaining discs were divided into a non-UV group and UVA-irradiated (+UV) group (irradiation time, 6 or 24 h). Thereafter, viability was assessed as above. Viability at time 0 was high and no dead cells were seen on any of the surfaces, even after 24 h, in the absence of UVA. However, after 24 h of exposure, the proportion of viable cells was reduced by 40% on the P25 discs compared to 0 and 6 h, and this effect was enhanced with a salivary pellicle. Members of mixed species biofilms differ in their susceptibility to the bactericidal effect of the surfaces tested and further investigations are needed to optimize the conditions. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2321-2328, 2017. © 2017 Wiley Periodicals, Inc.

Evaluation of Ultra-Violet Photocatalytic Oxidation (UVPCO) forIndoor Air Applications: Conversion of Volatile Organic Compounds at LowPart-per-Billion Concentrations

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

Hodgson, Alfred T.; Sullivan, Douglas P.; Fisk, William J.

2005-09-30

Efficient removal of indoor generated airborne particles and volatile organic compounds (VOCs) in office buildings and other large buildings may allow for a reduction in outdoor air supply rates with concomitant energy savings while still maintaining acceptable indoor air quality in these buildings. Ultra-Violet Photocatalytic Oxidation (UVPCO) air cleaners have the potential to achieve the necessary reductions in indoor VOC concentrations at relatively low cost. In this study, laboratory experiments were conducted with a scaled, prototype UVPCO device designed for use in a duct system. The experimental UVPCO contained two 30 by 30-cm honeycomb monoliths coated with titanium dioxide andmore » 3% by weight tungsten oxide. The monoliths were irradiated with 12 UVC lamps arranged in four banks. The UVPCO was challenged with four mixtures of VOCs typical of mixtures encountered in indoor air. A synthetic office mixture contained 27 VOCs commonly measured in office buildings. A cleaning product mixture contained three cleaning products with high market shares. A building product mixture was created by combining sources including painted wallboard, composite wood products, carpet systems, and vinyl flooring. A fourth mixture contained formaldehyde and acetaldehyde. Steady-state concentrations were produced in a classroom laboratory or a 20-m{sup 3} environmental chamber. Air was drawn through the UVPCO, and single pass conversion efficiencies were measured from replicate air samples collected upstream and downstream of the reactor section. Concentrations of the mixtures were manipulated, with concentrations of individual VOCs mostly maintained below 10 ppb. Device flow rates were varied between 165 and 580 m{sup 3}/h. Production of formaldehyde, acetaldehyde, acetone, formic acid, and acetic acid as reaction products was investigated. Conversion efficiency data were generated for 48 individual VOCs or groups of closely related compounds. Alcohols and glycol ethers were

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

Asymmetric radical alkylation of N-sulfinimines under visible light photocatalytic conditions.

PubMed

Garrido-Castro, Alberto F; Choubane, Houcine; Daaou, Mortada; Maestro, M Carmen; Alemán, José

2017-07-06

In this communication, a new photocatalytic strategy for the addition of alkyl-radical derivatives to N-sulfinimines with complete diastereoselectivity and moderate to good yields is presented. This is the first asymmetric photocatalytic addition to N-sulfinimines under visible light irradiation with smooth conditions and functional group tolerance.

Improving indoor air quality through botanical air filtration in energy efficient residences

NASA Astrophysics Data System (ADS)

Newkirk, Daniel W.

According to the U.S. EPA, the average American spends 90% of their time indoors where pollutants are two to five times more prevalent than outside. The consequences of these pollutants are estimated to cost the U.S. 125 billion dollars in lost health and productivity. Background literature suggests botanical air filtration may be able to solve this problem by leveraging the natural ability of plants to purify indoor air. By improving indoor air quality, energy consumption can also be reduced by bringing in less outside air to dilute contaminants within the space. A botanical air filter, called the Biowall, was designed and grown aeroponically in a sealed environmental chamber. Precise measurements of air temperature, air humidity, air quality and energy consumption were made under various lighting levels, plant species and watering strategies to optimize its performance. It was found to reduce indoor air pollutants 60 percent and has the potential to reduce heating and cooling energy consumption by 20 to 30 percent.

Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

NASA Astrophysics Data System (ADS)

Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

2015-09-01

Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

Photocatalytic reduction of CO₂: from molecules to semiconductors.

PubMed

Yui, Tatsuto; Tamaki, Yusuke; Sekizawa, Keita; Ishitani, Osamu

2011-01-01

We are facing three serious problems related to fossil resources, i.e., shortage of energy, shortage of carbon resources, and the global worming problem. Development of practical systems for converting CO₂ to useful chemicals using solar light, i.e., photocatalytic CO₂ reduction systems, should be one of the best solutions for these problems. In this article, we review photocatalytic CO₂ reduction systems, which are classified in two categories: (1) homogeneous reaction systems mainly using transition metal complexes, and (2) heterogeneous systems mainly using inorganic semiconductor as a light absorber.

Synthesis, characterization and photocatalytic performance of chemically exfoliated MoS2

NASA Astrophysics Data System (ADS)

Prabhakar Vattikuti, S. V.; Shim, Jaesool

2018-03-01

Two-dimensional (2D) layered structure transition metal dichalcogenides (TMDs) has gained huge attention and importance for photocatalytic energy conversion because of their unique properties. Molybdenum disulfide (MoS2) nanosheets were synthesized via one-pot method and exfoliated in (dimethylformamide) DMF solution. Subsequent exfoliated MoS2 nanosheets (e-MoS2) were used as photocatalysts for degradation of Rhodamine B (RhB) pollutant under solar light irradiation. The e-MoS2 nanosheets exhibited excellent photocatalytic activity than that of pristine MoS2, owing to high specific surface area with enormous active sites and light absorption capacity. In addition, e-MoS2 demonstrated remarkable photocatalytic stability.

Synthesis and Photocatalytic Property of ZnO/TiO2 Inverse Opals Films with Controllable Composition and Topology

NASA Astrophysics Data System (ADS)

Xu, Jiao; Yang, Bei-fang; Fu, Zheng-ping; Wen, Mei-wang; Zhao, Yong-xun

2012-04-01

A novel method to fabricate composition- and topology-controlled ZnO/TiO2 inverse opals (IO) films using a positive sacrificial ZnO IO template has been developed. This method includes a two-step process, preparation of ZnO IO by a simple electrochemical deposition using a self-assembly polystyrene colloidal crystal template and preparation of ZnO/TiO2 IO by a liquid phase deposition (LPD) process at room temperature. The composition and topology of ZnO/TiO2 IO can be easily controlled by changing the duration of the LPD. After 20 min LPD process, a ZnO/TiO2 composite IO with non-close-packed face-centered cubic air sphere array was obtained. Prolonging the duration to 60 min, a pure TiO2 IO (TIO-LPD60) with obviously thickened walls was formed. The formation mechanism for the compositional and topological variation was discussed. A preliminary study on UV photocatalytic property of the samples for degradation of methylene blue reveals that the composition and topology significantly influenced the photocatalytic activity of the IO film. The ZnO/TiO2 composite IO demonstrates a higher degree of activity than both pure ZnO and pure TiO2 IO, although they have a similar IO wall thickness. Moreover, with increasing IO wall thickness from ~52 nm to ~90 nm, TIO-LPD60 exhibits the highest level of photocatalytic performance.

Thermostable photocatalytically active TiO2 anatase nanoparticles

NASA Astrophysics Data System (ADS)

Qi, Fei; Moiseev, Anna; Deubener, Joachim; Weber, Alfred

2011-03-01

Anatase is the low-temperature (300-550 °C) crystalline polymorph of TiO2 and it transforms to rutile upon heating. For applications utilizing the photocatalytic properties of nanoscale anatase at elevated temperatures (over 600 °C) the issue of phase stabilisation is of major interest. In this study, binary TiO2/SiO2 particles were synthesized by a flame aerosol process with TiCl4 and SiCl4 as precursors. The theoretical Si/Ti ratio was varied in the range of 0.7-1.3 mol/mol. The synthesized TiO2/SiO2 samples were heat treated at 900 and 1,000 °C for 3 h to determine the thermostability of anatase. Pyrogenic TiO2 P25 (from Evonik/Degussa, Germany) widely applied as photocatalyst was used as non-thermostabilized reference material for comparison of photocatalytic activity of powders. Both the non-calcinated and calcinated powders were characterized by means of XRD, TEM and BET. Photocatalytic activity was examined with dichloroacetic acid (DCA) chosen as a model compound. It was found that SiO2 stabilized the material retarding the collapse of catalyst surface area during calcination. The weighted anatase content of 85% remains completely unchanged even after calcination at 1,000 °C. The presence of SiO2 layer/bridge as spacer between TiO2 particles freezes the grain growth: the average crystallite size increased negligibly from 17 to 18 nm even during the calcination at 1,000 °C. Due to the stabilizing effect of SiO2 the titania nanoparticles calcinated at 900 and 1,000 °C show significant photocatalytic activity. Furthermore, the increase in photocatalytic activity with calcination temperature indicates that the titania surface becomes more accessible either due to intensified cracking of the SiO2 layer or due to enhanced transport of SiO2 into the necks thus releasing additional titania surface.

Controlled Synthesis and Photocatalytic Antifouling Properties of BiVO4 with Tunable Morphologies

NASA Astrophysics Data System (ADS)

Xiang, Zhenbo; Wang, Yi; Ju, Peng; Zhang, Dun

2017-02-01

Monoclinic BiVO4 with different nanostructures were prepared via a facile and rapid route by adding different surfactants. Ethylenediaminetetraacetic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate surfactants were selected as morphology controlling agents. The crystal phase, morphology, and diffuse reflectance spectra of BiVO4 were characterized by x-ray diffraction, scanning electron microscopy, and UV-visible diffuse reflectance spectra techniques, respectively. The photocatalytic activities of BiVO4 were investigated by killing the typical marine fouling bacteria Pseudomonas aeruginosa ( P. aeruginosa) under visible light irradiation. BiVO4 with grape-like nanostructure exhibited the best photocatalytic bactericidal activity. The sterilization rate of P. aeruginosa could reach up to 99.9% in 120 min. The photocatalytic mechanism was studied by captive species trapping experiments. The result revealed that photogenerated hole (h+) is the main reactive specie for killing P. aeruginosa under visible light irradiation. In addition, after five recycles, BiVO4 does not exhibit significant loss of photocatalytic sterilization activity. The results confirm that the synthesized BiVO4 photocatalyst has long-time reusability and good photocatalytic stability.

Influence of carbon content on photocatalytic performance of C@ZnO hollow nanospheres

NASA Astrophysics Data System (ADS)

Jin, Changqing; Zhu, Kexin; Jian, Zengyun; Wei, Yongxing; Gao, Ling; Zhang, Zhihong; Zheng, Deshan

2018-02-01

Mesoporous C@ZnO hollow spheres were successfully synthesized through a carbon-sphere template combined hydrothermal method. The photocatalytic activities of the samples to rhodamine B (RhB) were investigated, and the sample of 3 wt% carbon has the best photocatalytic activity to RhB. The excellent photocatalytic performance could come from both enhanced photogenerated electron-hole pair separation, and the larger specific surface area induced by mesoporous hollow nanostructure. The photocatalytic performance sensitively depends upon content of amorphous carbon. Too much or too little carbon content decreases sample performance. The changes in performance according to carbon content are probably a result of the competing mechanism: the increasing rate of separation efficiency of photogenerated carriers and the decreasing contact area of ZnO with RhB according to the carbon content. This work would help us to better understand the important roles of carbon content in the fabricated nano-heterojunctions and also provide us with a feasible route to improve UV photocatalytic activities of ZnO and other metal oxides greatly.

Investigation of the effect of Anodized Duration toward Photocatalytic Performance of Nb2O5

NASA Astrophysics Data System (ADS)

Sabirin Zoolfakar, Ahmad; Atiqah Mokhtar, Nurul; Rani, Rozina Abdul; Samihah Khairir, Nur; Aqma Abu Talip, Mahzaton; Hafiz Mamat, Mohamad; Kadir, Rosmalini Abdul; Rusop, M.

2018-03-01

Highly oriented Nb2O5 nanoporous network produced via anodization for photocatalytic activity of methyl orange (MO) is presented. The anodization duration was varies from 0.5 to 2 hours and the photocatalytic performance is observed by degradation of MO solution. The Nb2O5 nanoparticles were added in MO solution and were exposed to the solar simulator for 3 hours. The morphology of Nb2O5 nanoporous and the photocatalytic performance are characterized in Field Emission Scanning Electron Microscopy (FESEM) and UV-Vis spectrophotometer, respectively. The result shows that different duration of anodized produce different sizes of nanoporous diameter that will significantly affect the photocatalytic performance. The 1.5 hours of anodized has the largest diameter size of nanoporous and exhibited the best photocatalytic performance

Effects of indoor air purification by an air cleaning system (Koala technology) on semen parameters in male factor infertility: results of a pilot study.

PubMed

Paradisi, R; Vanella, S; Barzanti, R; Cani, C; Battaglia, C; Seracchioli, R; Venturoli, S

2009-06-01

A number of studies indicated a clear decline in semen quality in the past 30-50 years and there is accumulating evidence that this decline might result from exposure to high levels of air pollution. To examine the impact of environment on male reproductive ability, we undertook for the first time a pilot study on semen quality of infertile men exposed to purification of indoor air. Ten subjects with a history of unexplained male infertility and poor semen quality were exposed for at least 1 year to a cleaning indoor air system (Koala technology). The key feature of this air purifier is the unique innovative multiple filtering system. The treatment of total purification of indoor air showed neither improvements in semen parameters nor variation in reproductive hormones (P = N.S.), but induced an evident increase (P < 0.03 and more) in seminal leucocytic concentrations. Within the limits due to the small sample of subjects recruited, the sole purification of indoor air does not seem enough to improve semen quality, although the increase in leucocytic concentrations could indicate an activation of the role of immunosurveillance in a purified indoor air environment.

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.

Preparation of sustainable photocatalytic materials through the valorization of industrial wastes.

PubMed

Sugrañez, Rafael; Cruz-Yusta, Manuel; Mármol, Isabel; Morales, Julián; Sánchez, Luis

2013-12-01

A new value-added material was developed from wastes to aim for appropriate waste management and sustainable development. This paper reports the valorization of industrial sandblasting operation wastes (SOWs) as new photocatalytic materials. This waste is composed of Fe2 O3 (60.7 %), SiO2 (29.1 %), and Al2 O3 (3.9 %) as the main components. The high presence of iron oxides was used to develop photocatalytic properties through their thermal transformation into α-Fe2 O3 . The new product, SOW-T, exhibited a good behavior towards the photochemical degradation of organic dyes. The preparation of advanced photocatalytic materials that exhibit self-cleaning and depolluting properties was possible by the inclusion of SOW-T and TiO2 in a cement-based mortar. The synergy observed between both materials enhanced their photocatalytic action. To the best of our knowledge, this is the first report that describes the use of transformed wastes based on iron oxide for the photochemical oxidation of NOx gases. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Purifying Water by Imbibition

NASA Technical Reports Server (NTRS)

Lawton, E. A.

1986-01-01

Concept for purifying water uses absorbent material to remove organic substances. Entire bulk of material employed, not just surface. Proposed purification process uses inexpensive equipment and low energy. Material is methyl acrylate polymer. Material cheap and regenerated by rinsing with methanol or by allowing absorbed compounds to evaporate from it.

Method of purifying isosaccharinate

DOEpatents

Rai, Dhanpat; Moore, Robert C.; Tucker, Mark D.

2010-09-07

A method of purifying isosaccharinate by mixing sodium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide with calcium isosaccharinate, removing the precipitated calcium carbonate and adjusting the pH to between approximately 4.5 to 5.0 thereby removing excess carbonate and hydroxide to provide an acidic solution containing isosaccharinate.

Controlled Defects of Zinc Oxide Nanorods for Efficient Visible Light Photocatalytic Degradation of Phenol

PubMed Central

Al-Sabahi, Jamal; Bora, Tanujjal; Al-Abri, Mohammed; Dutta, Joydeep

2016-01-01

Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO) nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC) was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region. PMID:28773363

Controlled Defects of Zinc Oxide Nanorods for Efficient Visible Light Photocatalytic Degradation of Phenol.

PubMed

Al-Sabahi, Jamal; Bora, Tanujjal; Al-Abri, Mohammed; Dutta, Joydeep

2016-03-28

Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO) nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC) was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.

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.

[BiOBr promoted the photocatalytic degradation of beta-cypermethrin under visible light].

PubMed

Peng, Yi-Zhu; Zhao, Xiao-Rong; Jia, Man-Ke; Zhou, Wei; Huang, Ying-Ping

2014-05-01

As a visible light photocatalyst, bismuth oxide bromide (BiOBr) was used to catalyze the degradation of beta-cypermethrin (beta-CP). The photocatalytic degradation of beta-CP was studied with gas chromatography. The effects of pH and catalyst dose on the photocatalytic degradation efficiency were discussed. The oxidization and mineralization of beta-CP were detected by chemical oxygen demand (COD) analyzer. The results showed that beta-CP could be effectively degraded under visible light irradiation using BiOBr as the catalyst. At given experimental conditions, the degradation rate of beta-CP reached 94. 68% after 10 h and the COD removal rate reached 67. 99% after 36 h. With the increase of catalyst dose and pH value, the degradation rate was improved. The photocatalytic oxidation species was determined by peroxidase method and terephthalic acid fluorescence method. These results suggested that the photocatalytic degradation process mainly referred to hydroxyl radical ( OH) mechanism.

Photocatalytic activity of silicon-based nanoflakes for the decomposition of nitrogen monoxide.

PubMed

Itahara, Hiroshi; Wu, Xiaoyong; Imagawa, Haruo; Yin, Shu; Kojima, Kazunobu; Chichibu, Shigefusa F; Sato, Tsugio

2017-07-04

The photocatalytic decomposition of nitrogen monoxide (NO) was achieved for the first time using Si-based nanomaterials. Nanocomposite powders composed of Si nanoflakes and metallic particles (Ni and Ni 3 Si) were synthesized using a simple one-pot reaction of layered CaSi 2 and NiCl 2 . The synthesized nanocomposites have a wide optical absorption band from the visible to the ultraviolet. Under the assumption of a direct transition, the photoabsorption behavior is well described and an absorption edge of ca. 1.8 eV is indicated. Conventional Si and SiO powders with indirect absorption edges of 1.1 and 1.4 eV, respectively, exhibit considerably low photocatalytic activities for NO decomposition. In contrast, the synthesized nanocomposites exhibited photocatalytic activities under irradiation with light at wavelengths >290 nm (<4.28 eV). The photocatalytic activities of the nanocomposites were confirmed to be constant and did not degrade with the light irradiation time.

Photocatalytic activity of Fe-doped CaTiO₃ under UV-visible light.

PubMed

Yang, He; Han, Chong; Xue, Xiangxin

2014-07-01

The photocatalytic degradation of methylene blue (MB) over Fe-doped CaTiO₃ under UV-visible light was investigated. The as-prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system, Fourier transform infrared spectra (FT-IR), and UV-visible diffuse reflectance spectroscopy (DRS). The results show that the doping with Fe significantly promoted the light absorption ability of CaTiO₃ in the visible light region. The Fe-doped CaTiO₃ exhibited higher photocatalytic activity than CaTiO₃ for the degradation of MB. However, the photocatalytic activity of the Fe-doped CaTiO₃ was greatly influenced by the calcination temperature during the preparation process. The Fe-doped CaTiO₃ prepared at 500°C exhibited the best photocatalytic activity, with degradation of almost 100% MB (10ppm) under UV-visible light for 180 min. Copyright © 2014. Published by Elsevier B.V.

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.

Improvement of the BiOI photocatalytic activity optimizing the solvothermal synthesis

NASA Astrophysics Data System (ADS)

Mera, Adriana C.; Moreno, Yanko; Contreras, David; Escalona, Nestor; Meléndrez, Manuel F.; Mangalaraja, Ramalinga Viswanathan; Mansilla, Héctor D.

2017-01-01

BiOI nanostructured microspheres were obtained from the solvothermal synthesis route in the presence of ethylene glycol and KI as solvent and source of iodide, respectively. Optimal conditions for the synthesis were obtained by using multivariate analysis and choosing the photocatalytic oxidation rate constant of 3,4,5-trihydroxybenzoic acid (gallic acid) as response factor under simulated solar radiation. Response surface methodology (RSM) was used to determine the optimum values of the reaction time and temperature which were 18 h and 126 °C, respectively, to obtain the most active catalyst. In addition, BiOI synthesis using ionic liquid 1-butyl-3-methylimidazolium iodide ([bmim]I) as iodide source was also carried out for the comparison of microstructure and its photocatalytic efficiency. The obtained BiOI nanostructures were characterized by scanning electron microscopy (SEM) attached with energy dispersive spectrometer (EDS), nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), Fourier transform infrared (FTIR) spectrometry, diffuse reflectance spectroscopy (DRS) and cyclic voltammetry (CV) analyses for their changes in morphological and structural behaviors. It was observed that the synthesis temperature of BiOI nanostructures strongly influenced the morphology, crystalline phase, surface area and electrochemical behavior, and thus affecting the photocatalytic efficiency. The higher photocatalytic removal of gallic acid (60%) was reached within 30 min of irradiation with UV-A on microspheres obtained with ionic liquid. The (1 1 0) crystal phase of BiOI influenced the photocatalytic efficiency.

Photocatalytic Oxidation of Low-Level Airborne 2-Propanol and Trichloroethylene over Titania Irradiated with Bulb-Type Light-Emitting Diodes.

PubMed

Jo, Wan-Kuen

2013-01-18

This study examined the photocatalytic oxidation of gas-phase trichloroethylene (TCE) and 2-propanol, at indoor levels, over titanium dioxide (TiO₂) irradiated with light-emitting diodes (LED) under different operational conditions. TiO₂ powder baked at 450 °C exhibited the highest photocatalytic decomposition efficiency (PDE) for TCE, while all photocatalysts baked at different temperatures showed similar PDEs for 2-propanol. The average PDEs of TCE over a three hour period were four, four, five, and 51% for TiO₂ powders baked at 150, 250, 350, and 450 °C, respectively. The average PDEs of 2-propanol were 95, 97, 98, and 96% for TiO₂ powders baked at 150, 250, 350, and 450 °C, respectively. The ratio of anatase at 2θ = 25.2° to rutile at 2θ = 27.4° was lowest for the TiO₂ powder baked at 450 °C. Although the LED-irradiated TiO₂ system revealed lower PDEs of TCE and 2-propanol when compared to those of the eight watt, black-light lamp-irradiated TiO₂ system, the results for the PDEs normalized to the energy consumption were reversed. Other operational parameters, such as relative humidity, input concentrations, flow rate, and feeding type were also found to influence the photocatalytic performance of the UV LED-irradiated TiO₂ system when applied to the cleaning of TCE and 2-propanol at indoor air levels.

An introduction to photocatalysis through methylene blue photodegradation

NASA Astrophysics Data System (ADS)

Petit, Matthieu; Michez, Lisa; Raimundo, Jean-Manuel; Malinowski, Tuhiti; Dumas, Philippe

2016-11-01

We described a simple experimental set-up for lab work on the photocatalytic degradation of methylene blue by TiO2 nanoparticles. The photocatalysis process can be used for many applications. Treatments for diluted wastewater industries, air purifying in underground car parks, and preventing fouling on glass surfaces, are some of the potential applications of this phenomenon. The described experiment is easy to perform and the interpretation can be easily adapted to different levels of students, from high school students demonstrating their interest in sustainable development, to students obtaining a Masters in science departments who want to propose a full explanation for all phenomena of the photocatalytic process. Starting with a description of the experimental set-up, we analysed the photocatalyst nanoparticles and applied the Langmuir-Hinshelwood model to our experimental data. Finally we briefly discussed the respective energetic levels of the photocatalyst semiconductor and methylene blue.

Plasmonic Ag coated Zn/Ti-LDH with excellent photocatalytic activity

NASA Astrophysics Data System (ADS)

Zhu, Yanping; Zhu, Runliang; Zhu, Gangqiang; Wang, Miaomiao; Chen, Yannan; Zhu, Jianxi; Xi, Yunfei; He, Hongping

2018-03-01

Nowadays, two-dimensional (2D) nanosheets, such as layered double hydroxides (LDH), have received considerable attention for their potential to meeting clean energy demand and solving environmental problems. In this work, novel and efficient photocatalysts of plasmonic Ag nanoparticles coated Zn/Ti-LDH nanosheets have been synthesized through low-temperature reduction method. The structural characteristics of the as-prepared products were investigated by a series of characteristic methods The scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed that Ag nanoparticles were distributed on the surface of Zn/Ti-LDH uniformly. The UV-vis diffuse reflectance spectra (DRS) showed that the absorbance of Ag/LDH in visible-light region enhanced markedly and presented a broad band at 500-600 nm, which was resulted from the surface plasmon resonance (SPR) effect of Ag nanoparticles. The photocatalytic activities of Ag/LDH were evaluated by degradation of Rhodamine-B (RhB) and NO. The photocatalytic experiments showed that Ag/LDH had higher photocatalytic activity than that of pure LDH, and 2%Ag/LDH exhibited the highest photocatalytic activity. In addition, the 2%Ag/LDH exhibited high photochemical stability after multiple reaction runs. The obtained results from photoluminescence (PL) spectroscopic measurement and transient photocurrent (I-V) analysis both revealed the existence of Schottky barriers between LDH and Ag nanoparticles. The electron spin resonance (ESR) showed that rad OH were the dominant active species in the photo-degradation process. The enhanced photocatalytic performance of the composite should be ascribed to both the SPR effect of Ag nanoparticles in visible light and the Schottky barriers between LDH and Ag nanoparticles.

Synthesis of graphene oxide-copper molybdate (GO-CuM) nanocomposites for photocatalytic application

NASA Astrophysics Data System (ADS)

Singh, Gajendar; Bhargava, V. Sai; Sharma, Manu

2018-05-01

Transition metal molybdates (TMBs) MMoO4 (M=Ni, Cu, Fe, Zn, Co, etc.) based nanocomposites have been considered as remarkable materials in the field of electronics, optics, catalysis, supercapicitors and energy storage devices. Nanocomposites of TMBs with graphene oxide have also been chosen as an effective material in photocatalytic application. GO-CuM nanocomposites were synthesized by ultra-sonication method at RT, followed by reflux route for preparation of CuM and GO by modified Hemmer's method. As prepared nanocomposites were characterized using analytical techniques such as PXRD, SEM, FT-IR and UV-Visible spectroscopy. The enhanced photocatalytic activity of Methylene blue (MB) dye was observed by GO-CuM nanocomposites as compared to pure copper molybdate. GO-CuM nanocomposites show high photodegradation rate (0.094 min-1) whereas CuM was degraded only 30 % with the rate of 0.0029 min-1. The high photocatalytic efficiency is due to the presence of graphene oxide that helps to delay the charge recombination in photocatalytic reaction The effect of the different amount of graphene oxide on the photocatalytic activity of as prepared photocatalyst has also been investigated.

Nanocomposite film of TiO{sub 2} nanotube and polyoxometalate towards photocatalytic degradation of nitrobenzene

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

Sun, Zhixia; Zhao, Mingliang; Li, Fengyan, E-mail: lify525@nenu.edu.cn

2014-12-15

Highlights: • The film of POMs and TiO{sub 2} nanotubes was prepared by electrodeposition. • The photocatalytic activity of the composite film for nitrobenzene was investigated. • The composite film showed higher photocatalytic activity than pure TiO{sub 2} nanotubes. • The introduction of POMs into TiO{sub 2} could retard electron–hole recombination. - Abstract: The composite film based on polyoxometalates (POMs)-modified TiO{sub 2} nanotubes was prepared by electrodeposition method for the photocatalytic degradation of nitrobenzene. The composite film was characterized by field-emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, which indicated that the POMs weremore » well introduced into the TiO{sub 2} nanotubes. Furthermore, the photocatalytic properties of the TiO{sub 2} nanotubes and POMs-modified TiO{sub 2} nanotubes were evaluated by the decomposition of nitrobenzene. POMs-modified TiO{sub 2} nanotubes showed much higher photocatalytic activity than pure TiO{sub 2} nanotubes. These results provide a promising route to effectively photocatalytic degradation of nitrobenzene by POMs-modified TiO{sub 2} nanotubes.« less

Influences of the (NH2)2CO concentration on magnetic photocatalytic composites

NASA Astrophysics Data System (ADS)

Liŭ, Dan; Li, Ziheng; Wang, Wenquan; Liú, Dan; Wang, Guoqiang; Lin, Junhong; He, Yingqiao; Li, Xiangru

2016-11-01

Magnetic photocatalytic Fe3O4@TiO2 composites have been fabricated by changing the concentration of (NH2)2CO. Samples were named as low (NH2)2CO concentration group which the (NH2)2CO concentration in the synthesis process was below 2.25 mol/L and high (NH2)2CO concentration group which the (NH2)2CO concentration was above 2.5 mol/L. Photocatalytic degradation experiments of methyl orange showed that the final degradation rates of low (NH2)2CO concentration group samples were higher than that of high (NH2)2CO concentration group, even better than P25 at the same test conditions. And it was interesting that samples of low (NH2)2CO concentration group had smaller values of BET surface areas than that of high (NH2)2CO concentration group. It indicated that the improvement of photocatalytic activity which was effected by BET surface areas was not obvious. There were two main factors enhancing the photocatalytic property of low (NH2)2CO concentration group: First, diffusing reflection spectra showed that the low (NH2)2CO concentration group samples had lower reflectivity, this suggested that the structure improved the efficiency of light absorption; Second, NH4+ would take up the active sites on the surface of the TiO2 particles, the FT-IR test results showed that the samples of the low (NH2)2CO concentration group samples bonded less NH4+, thus leading to the higher photocatalytic activity. It had enlightenment role for optimizing the performance of photocatalytic materials.

Photocatalytic degradation of diethyl phthalate using TiO{sub 2} nanoparticles

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

Singla, Pooja, E-mail: pooja.singla@thapar.edu; Pandey, O. P., E-mail: pooja.singla@thapar.edu; Singh, K., E-mail: pooja.singla@thapar.edu

2014-04-24

TiO{sub 2} nanoparticles predominantly in rutile phase are synthesized by ultrasonication assisted sol-gel method. TiO{sub 2} powder is characterized using X-ray powder diffraction and UV-vis diffuse reflectance. TiO{sub 2} is used as catalyst in photocatalytic degradation of Diethyl Phthalate. TiO{sub 2} exhibits good photocatalytic activity for the degradation of diethyl phthalate.

Room temperature synthesis and highly enhanced visible light photocatalytic activity of porous BiOI/BiOCl composites nanoplates microflowers.

PubMed

Dong, Fan; Sun, Yanjuan; Fu, Min; Wu, Zhongbiao; Lee, S C

2012-06-15

This research represents a highly enhanced visible light photocatalytic removal of 450 ppb level of nitric oxide (NO) in air by utilizing flower-like hierarchical porous BiOI/BiOCl composites synthesized by a room temperature template free method for the first time. The facile synthesis method avoids high temperature treatment, use of organic precursors and production of undesirable organic byproducts during synthesis process. The result indicated that the as-prepared BiOI/BiOCl composites samples were solid solution and were self-assembled hierarchically with single-crystal nanoplates. The aggregation of the self-assembled nanoplates resulted in the formation of 3D hierarchical porous architecture containing tri-model mesopores. The coupling to BiOI with BiOCl led to down-lowered valence band (VB) and up-lifted conduction band (CB) in contrast to BiOI, making the composites suitable for visible light excitation. The BiOI/BiOCl composites samples exhibited highly enhanced visible light photocatalytic activity for removal of NO in air due to the large surface areas and pore volume, hierarchical structure and modified band structure, exceeding that of P25, BiOI, C-doped TiO(2) and Bi(2)WO(6). This research results could provide a cost-effective approach for the synthesis of porous hierarchical materials and enhancement of photocatalyst performance for environmental and energetic applications owing to its low cost and easy scaling up. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of calcination temperatures on microstructures and photocatalytic activity of tungsten trioxide hollow microspheres.

PubMed

Yu, Jiaguo; Qi, Lifang; Cheng, Bei; Zhao, Xiufeng

2008-12-30

Tungsten trioxide hollow microspheres were prepared by immersing SrWO4 microspheres in a concentrated HNO3 solution, and then calcined at different temperatures. The prepared tungsten oxide samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, differential thermal analysis-thermogravimetry, UV-visible spectrophotometry, scanning electron microscopy, N2 adsorption/desorption measurements. The photocatalytic activity of the samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, on the contrary, Brunauer-Emmett-Teller-specific surface areas decreased. However, pore volume and porosity increased firstly, and then decreased. Increasing calcination temperatures resulted in the changes of surface morphology of hollow microspheres. The un-calcined and 300 degrees C-calcined samples showed higher photocatalytic activity than other samples. At 400 degrees C, the photocatalytic activity decreased greatly due to the decrease of specific surface areas. At 500 degrees C, the photocatalytic activity of the samples increased again due to the junction effect of two phases.

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.

Morphological driven photocatalytic activity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Abbas, Khaldoon N.; Bidin, Noriah

2017-02-01

Using a simple combination of pulse laser ablation in liquid and hydrothermal (PLAL-H) approaches, we control the morphology of ZnO nanostructures (ZNSs) to determine the feasibility of their photocatalytic efficacy. These ZNSs are deposited on Si (100) substrates and two different morphologies are achieved. In this synergistic approach, PLAL synthesized NSs are used as a nutrient solution with different pH for further hydrothermal treatment at 110 °C under varying growth time (5, 30 and 60 min). Surface morphology, structure, composition, and optical characteristics of the prepared ZNSs are determined using FESEM, XRD, FTIR and Photoluminescence (PL) and UV-vis absorption measurements. The morphology revealed remarkable transformation from nanorods (NRs)/nanoflowers (NFs) (at pH 7.6) to nanoparticles (NPs)-like (at pH 10.5) structure. XRD patterns showed better polycrystallinity for NPs with enlarged band gap than NR/NF-like structures. Both PL and UV-vis spectral analysis of ZNPs exhibited higher surface area and deep level defects density dependent morphology, where the nutrient pH and growth time variation are found to play a significant role towards structural evolution. Furthermore, the photocatalytic activities of, such ZNSs are evaluated via sunlight driven photo-degradation of methylene blue (MB) dye. The photocatalytic efficiency of ZNPs is demonstrated to be much superior (97.4%) than ZNRs/ZNFs-like morphology (86%). Such enhanced photocatalytic activities of as-synthesized ZNPs is attributed to the synergism of the improved surface area and defects density, which is useful for promoting the adsorption of the MB dye and suppressed surface recombination of photo-generated charge carriers.

Ag modified LaCoO3 perovskite oxide for photocatalytic application

NASA Astrophysics Data System (ADS)

Jayapandi, S.; Prakasini, V. Anitha; Anitha, K.

2018-04-01

The present investigation has been carried out to develop a novel photocatalytic material based on lanthanum cobaltite (LaCoO3) and silver (Ag) doped LaCoO3 perovskite oxide. Pure LaCoO3 and 5 Mol% Ag doped LaCoO3 (Ag-LaCoO3) have been synthesized by simple co-precipitation method and characterized by X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) and photoluminescence (PL) techniques and its photocatalytic activity was evaluated by photodegradation of methylene blue under sunlight irradiation. The observed XRD, UV and PL results indicate that Ag influences on the crystallite size and absorption coefficient of LaCoO3 perovskite oxide. The percentage of dye degradations was calculated as 60% and 99 % for LaCoO3 and 5 Mol% Ag-LaCoO3 pervoskite oxides respectively for 10 minutes (10 min) exposure to sunlight, which indicates that 5 mol% of Ag-LaCoO3, has better photodegradation activity. Hence, the present investigation confirms that Ag influences the photocatalytic activity of a material and the observations will be helpful for further developing new photocatalytic materials.

Insights into the relationship between the color and photocatalytic property of attapulgite/CdS nanocomposites

NASA Astrophysics Data System (ADS)

Wang, Xiaowen; Mu, Bin; An, Xingcai; Wang, Aiqin

2018-05-01

Attapulgite/CdS (APT/CdS) nanocomposites were fabricated by hydrothermal decomposition of the cadmium-thiourea complex in the presence of APT. The incorporating of APT not only adjusted the color of APT/CdS nanocomposites and controlled the growth of CdS nanoparticles on the surface of APT without the free agglomeration, but also changed the band-gap energy of nanocomposites to affect their photocatalytic property for degradation of organic dyes. Interestingly, there was a close relationship between the color and the photocatalytic property of APT/CdS nanocomposites. The as-prepared nanocomposites with the optimal color properties exhibited the optimal photocatalytic performance for degradation of methylene blue, methyl violet and congo red within 70 min. The key bridge between the color and the photocatalytic activity was mainly band-gap energy. Therefore, it was presumed that the photocatalytic activity of APT/CdS nanocomposites could be evaluated directly from their color property.

Surface modification of nanoporous anodic alumina photonic crystals for photocatalytic applications

NASA Astrophysics Data System (ADS)

Lim, Siew Yee; Law, Cheryl Suwen; Santos, Abel

2018-01-01

Herein, we report on the development of a rationally designed composite photocatalyst material by combining nanoporous anodic alumina-rugate filters (NAA-RFs) with photo-active layers of titanium dioxide (TiO2). NAA-RFs are synthesised by sinusoidal pulse anodisation and subsequently functionalised with TiO2 by sol-gel method to provide the photonic structures with photocatalytic properties. We demonstrate that the characteristic photonic stopband (PSB) of the surface-modified NAA-RFs can be precisely tuned across the UV-visible-NIR spectrum to enhance the photon-toelectron conversion of TiO2 by `slow photon effect'. We systematically investigate the effect of the anodisation parameters (i.e. anodisation period and pore widening time) on the position of the PSB of NAA-RFs as well as the photocatalytic performances displayed by these photonic crystal structures. When the edges of the PSB of surfacemodified NAA-RFs are positioned closely to the absorption peak of the model organic dye (i.e. methyl orange - MO), the photocatalytic performance of the system to degrade these molecules is enhanced under simulated solar light irradiation due to slow photon effect. Our investigation also reveals that the photocatalytic activity of surface-modified NAA-RFs is independent of slow photon effect and enhances with increasing period length (i.e. increasing anodisation period) of the photonic structures when there is no overlap between the PSB and the absorption peak of MO. This study therefore provides a rationale towards the photocatalytic enhancement of photonic crystals by a rational design of the PSB, creating new opportunities for the future development of high-performance photocatalysts.

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

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production.

PubMed

Reynal, Anna; Pastor, Ernest; Gross, Manuela A; Selim, Shababa; Reisner, Erwin; Durrant, James R

2015-08-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye ( RuP ) and a nickel bis(diphosphine) electrocatalyst ( NiP ) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H 2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP - NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP , which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP - NiP photocatalytic system, which can be widely applied to other photocatalytic systems.

Effects of Ag doping on the photocatalytic disinfection of E. coli in bioaerosol by Ag-TiO₂/GF under visible light.

PubMed

Pham, Thanh-Dong; Lee, Byeong-Kyu

2014-08-15

Ag doped TiO2/glass fibers (Ag-TiO2/GF) were prepared and used for photocatalytic disinfection of Escherichia coli (E. coli) in an indoor air environment. The prepared photocatalysts were characterized using scanning electron microscope (SEM) for morphology, X-ray diffraction (XRD) for microstructure, UV-Visible diffuse reflectance spectra (DRS) for optical properties and X-ray photoelectron spectroscopy (XPS) to determine elemental state. The optimized weight fraction of TiO2 in the TiO2/glass fiber (TiO2/GF) was 3%. The silver content in Ag/TiO2 was altered from 1% to 10% to investigate the optimal ratio of Ag doped on the TiO2/GF for the photocatalytic disinfection of E. coli. Doped Ag enhanced the electron-hole separation as well as charge transfer efficiency between the valance band and the conduction band of TiO2. The generated electron-hole pairs reacted with water and molecular oxygen to form strong oxidative radicals, which participated in the oxidation of organic components of E. coli, resulting in bacterial death. The photocatalytic disinfection activity under visible light increased with the increase in silver content up to 7.5% and then decreased slightly with further increasing Ag content. Among the three humidity conditions used in this study (40±5%, 60±5%, 80±5%), the highest disinfection ratio of E. coli by the photocatalytic system was observed in the intermediate humidity level followed by the high humidity level. Using the 7.5% Ag-TiO2/GF and the intermediate level of humidity (60±5%), the highest disinfection ratio and disinfection capacity of E. coli were 93.53% and 26 (CFU/s cm(2)), respectively. Copyright © 2014 Elsevier Inc. All rights reserved.

An LED Approach for Measuring the Photocatalytic Breakdown of Crystal Violet Dye

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; Underwood, Lauren W.; ONeal, Duane; Pagnutti, Mary; Davis, Bruce A.

2009-01-01

A simple technique to assess the reactivity of photocatalytic coatings sprayed onto transmissive glass surfaces was developed. This new method uses ultraviolet (UV) gallium nitride (GaN) light-emitting diodes (LEDs) to drive a photocatalytic reaction (the photocatalytic breakdown of a UV-resistant dye applied to a surface coated with the semiconductor titanium dioxide); and then a combination of a stabilized white light LED and a spectrometer to track the dye degradation as a function of time. Simple, standardized evaluation techniques that assess photocatalytic materials over a variety of environmental conditions, including illumination level, are not generally available and are greatly needed prior to in situ application of photocatalytic technologies. To date, much research pertaining to this aspect of photocatalysis has been limited and has focused primarily on laboratory experiments using mercury lamps. Mercury lamp illumination levels are difficult to control over large ranges and are temporally modulated by line power, limiting their use in helping to understand and predict how photocatalytic materials will behave in natural environmental settings and conditions. The methodology described here, using steady-state LEDs and time series spectroradiometric techniques, is a novel approach to explore the effect of UV light on the photocatalytic degradation of a UV resistant dye (crystal violet). GaN UV LED arrays, centered around 365 nm with an adjustable DC power supply, are used to create a small, spatially uniform light field where the steady state light level can be varied over three to four orders of magnitude. For this study, a set of glass microscope slides was custom coated with a thinly sprayed layer of photocatalytic titanium dioxide. Crystal violet was then applied to these titanium-dioxide coated slides and to uncoated control slides. The slides were then illuminated at various light levels from the dye side of the slide by the UV LED array. To monitor

Enhanced photocatalytic activity of hydrogenated and vanadium doped TiO2 nanotube arrays grown by anodization of sputtered Ti layers

NASA Astrophysics Data System (ADS)

Motola, Martin; Satrapinskyy, Leonid; Čaplovicová, Mária; Roch, Tomáš; Gregor, Maroš; Grančič, Branislav; Greguš, Ján; Čaplovič, Ľubomír; Plesch, Gustav

2018-03-01

TiO2 nanotube (TiNT) arrays were grown on silicon substrate via electrochemical anodization of titanium films sputtered by magnetron. To improve the photocatalytic activity of arrays annealed in air (o-TiNT), doping of o-TiNT with vanadium was performed (o-V/TiNT). These non-doped and doped TiNT arrays were also hydrogenated in H2/Ar atmosphere to r-TiNT and r-V/TiNT samples, respectively. Investigation of composition and morphology by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and X-ray photoelectron spectroscopy (XPS) showed the presence of well-ordered arrays of anatase nanotubes with average diameter and length of 100 nm and 1.3 μm, respectively. In both oxidized and reduced V-doped samples, vanadium is partly dissolved in the structure of anatase and partly deposited in form of oxide on the nanotube surface. Vanadium-doped and reduced samples exhibited higher rates in the photodegradation of organic dyes (compared to non-modified o-TiNT sample) and this is caused by limitation of electron-hole recombination rates and by shift of the energy gap into visible region. The photocatalytic activity was measured under UV, sunlight and visible irradiation, and the corresponding efficiency increased in the order (o-TiNT) < (r-TiNT) < (o-V/TiNT) < (r-V/TiNT). Under visible light, only r-TiNT and r-V/TiNT showed significant photocatalytic activity.

Three-dimensional assembly structure of anatase TiO2 hollow microspheres with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Tang, Yihao; Zhan, Shuai; Wang, Li; Zhang, Bin; Ding, Minghui

The pure anatase TiO2 hollow microspheres are synthesized by a one-step template-free hydrothermal route. By defining temperature and time limits, we produce TiO2 hollow microspheres with a fluoride-mediated self-transformation. The surface morphology of TiO2 hollow microspheres was studied by SEM. The hollow microspheres have diameters of about 800 nm and are remarkably uniform. The UV-light photocatalytic activity and the stability/multifunction of TiO2 hollow microspheres structure were evaluated by photocatalytic degradation of methylene blue and photocatalytic hydrogen evolution. The excellent photocatalytic activity is attributed to large specific surface area, more active sites, unique hollow structures, and improved light scattering.

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.

Preparation and analysis of zero gases for the measurement of trace VOCs in air monitoring

NASA Astrophysics Data System (ADS)

Englert, Jennifer; Claude, Anja; Demichelis, Alessia; Persijn, Stefan; Baldan, Annarita; Li, Jianrong; Plass-Duelmer, Christian; Michl, Katja; Tensing, Erasmus; Wortman, Rina; Ghorafi, Yousra; Lecuna, Maricarmen; Sassi, Guido; Sassi, Maria Paola; Kubistin, Dagmar

2018-06-01

Air quality observations are performed globally to monitor the status of the atmosphere and its level of pollution and to assess mitigation strategies. Regulations of air quality monitoring programmes in various countries demand high-precision measurements for harmful substances often at low trace concentrations. These requirements can only be achieved by using high-quality calibration gases including high-purity zero gas. For volatile organic compound (VOC) observations, zero gas is defined as being hydrocarbon-free and can be, for example, purified air, nitrogen or helium. It is essential for the characterisation of the measurement devices and procedures, for instrument operation as well as for calibrations. Two commercial and one self-built gas purifiers were tested for their VOC removal efficiency following a standardised procedure. The tested gas purifiers included one adsorption cartridge with an inorganic media and two types of metal catalysts. A large range of VOCs were investigated, including the most abundant species typically measured at air monitoring stations. Both catalysts were able to remove a large range of VOCs whilst the tested adsorption cartridge was not suitable to remove light compounds up to C4. Memory effects occurred for the adsorption cartridge when exposed to higher concentration. This study emphasises the importance of explicitly examining a gas purifier for its intended application before applying it in the field.

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.

Urban air quality measurements using a sensor-based system

NASA Astrophysics Data System (ADS)

Ródenas, Mila; Hernández, Daniel; Gómez, Tatiana; López, Ramón; Muñoz, Amalia

2017-04-01

Air pollution levels in urban areas have increased the interest, not only of the scientific community but also of the general public, and both at the regional and at the European level. This interest has run in parallel to the development of miniaturized sensors, which only since very recently are suitable for air quality measurements. Certainly, their small size and price allows them to be used as a network of sensors capable of providing high temporal and spatial frequency measurements to characterize an area or city and with increasing potential, under certain considerations, as a complement of conventional methods. Within the frame of the LIFE PHOTOCITYTEX project (use of photocatalytic textiles to help reducing air pollution), CEAM has developed a system to measure gaseous compounds of importance for urban air quality characterization. This system, which allows an autonomous power supply, uses commercial NO, NO2, O3 and CO2 small sensors and incorporates measurements of temperature and humidity. A first version, using XBee boards (Radiofrequency) for communications has been installed in the urban locations defined by the project (tunnel and school), permitting the long-term air quality characterization of sites in the presence of the textiles. An improved second version of the system which also comprises a sensor for measuring particles and which uses GPRS for communications, has been developed and successfully installed in the city center of Valencia. Data are sent to a central server where they can be accessed by citizens in nearly real time and online and, in general, they can be utilized in the air quality characterization, for decision-making related to decontamination (traffic regulation, photocatalytic materials, etc.), in air quality models or in mobile applications of interest for the citizens. Within this work, temporal trends obtained with this system in different urban locations will be shown, discussing the impact of the characteristics of the

Method of decontaminating a contaminated fluid by using photocatalytic particles

NASA Technical Reports Server (NTRS)

Cooper, Gerald (Inventor); Ratcliff, Matthew A. (Inventor)

1994-01-01

A system for decontaminating the contaminated fluid by using photocatalytic particles. The system includes a reactor tank for holding the contaminated fluid and the photocatalytic particles suspended in the contaminated fluid to form a slurry. Light irradiates the surface of the slurry, thereby activating the photocatalytic properties of the particles. The system also includes stirring blades for continuously agitating the irradiated fluid surface and for maintaining the particles in a suspended state within the fluid. The system also includes a cross flow filter for segregating the fluid (after decomposition) from the semiconductor powder. The cross flow filter is occasionally back flushed to remove any semiconductor powder that might have caked on the filter. The semiconductor powder may be recirculated back to the tank for reuse, or may be stored for future use. A series of such systems may be used to gradually decompose a chemical in the fluid. Preferably, the fluid is 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 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. A method of decontaminating a contaminated fluid is also disclosed.

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.

Boron oxynitride nanoclusters on tungsten trioxide as a metal-free cocatalyst for photocatalytic oxygen evolution from water splitting

NASA Astrophysics Data System (ADS)

Xie, Ying Peng; Liu, Gang; Lu, Gao Qing (Max); Cheng, Hui-Ming

2012-02-01

Here we show that B2O3-xNx nanoclusters can be formed on the surface of WO3 particles by a combination of thermal oxidation of tungsten boride (WB) in air and the subsequent nitriding process in gaseous ammonia. The resultant nanoclusters are found to play an apparent role in improving the photocatalytic oxygen evolution of WO3 by promoting the surface separation of photoexcited charge-carriers.Here we show that B2O3-xNx nanoclusters can be formed on the surface of WO3 particles by a combination of thermal oxidation of tungsten boride (WB) in air and the subsequent nitriding process in gaseous ammonia. The resultant nanoclusters are found to play an apparent role in improving the photocatalytic oxygen evolution of WO3 by promoting the surface separation of photoexcited charge-carriers. Electronic supplementary information (ESI) available: (1) Experimental section. (2) XRD patterns, FT-IR and Raman spectra of B2O3@WO3 and B2O3-xNx@WO3. (3) Time course of O2 evolution from water splitting using B2O3@WO3 and B2O3-xNx@WO3. (4) XRD pattern and SEM image of pure WO3, UV-visible absorption spectra of pure WO3 and N-WO3. (5) UV-visible absorption spectra of bulk B2O3 and schematic of band edges of WO3, bulk B2O3, and B2O3-xNx nanocluster. See DOI: 10.1039/c2nr11846g

Phase change liquid purifier and pump

DOEpatents

Steinhour, Leif Alexi

2017-05-23

Systems, methods, and apparatus are provided for purifying and pumping liquids, and more particularly, for purifying and pumping water. The apparatus includes a chamber including a top portion and a bottom portion. A surface configured to be heated is proximate the bottom portion of the chamber. A baffle is disposed within the chamber and above the surface. The baffle is disposed at an angle relative to a vertical direction. The chamber further includes an inlet and a first outlet. The surface heats a liquid in the chamber, causing the liquid to boil. In operation, bubbles rise from the surface and are forced in a horizontal direction by the baffle disposed in the chamber.

Sunlight-driven photocatalytic degradation of non-steroidal anti-inflammatory drug based on TiO₂ quantum dots.

PubMed

Kaur, Amandeep; Umar, Ahmad; Kansal, Sushil Kumar

2015-12-01

This paper reports the facile synthesis, characterization and solar-light driven photocatalytic degradation of TiO2 quantum dots (QDs). The TiO2 QDs were synthesized by a facile ultrasonic-assisted hydrothermal process and characterized in terms of their structural, morphological, optical and photocatalytic properties. The detailed studies confirmed that the prepared QDs are well-crystalline, grown in high density and exhibiting good optical properties. Further, the prepared QDs were efficiently used as effective photocatalyst for the sun-light driven photocatalytic degradation of ketorolac tromethamine, a well-known non-steroidal anti-inflammatory drug (NSAID). To optimize the photocatalytic degradation conditions, various dose-dependent, pH-dependent, and initial drug-concentration dependent experiments were performed. The detailed solar-light driven photocatalytic experiments revealed that ∼99% photodegradation of ketorolac tromethamine drug solution (10 mg L(-1)) was observed with optimized amount of TiO2 QDs and pH (0.5 g L(-1) and 4.4, respectively) under solar-light irradiations. The observed results demonstrate that simply synthesized TiO2 QDs can efficiently be used for the solar-light driven photocatalytic degradation of harmful drugs and chemicals. Copyright © 2015 Elsevier Inc. All rights reserved.

UV-induced photocatalytic degradation of aqueous acetaminophen: the role of adsorption and reaction kinetics.

PubMed

Basha, Shaik; Keane, David; Nolan, Kieran; Oelgemöller, Michael; Lawler, Jenny; Tobin, John M; Morrissey, Anne

2015-02-01

Nanostructured titania supported on activated carbon (AC), termed as integrated photocatalytic adsorbents (IPCAs), were prepared by ultrasonication and investigated for the photocatalytic degradation of acetaminophen (AMP), a common analgesic and antipyretic drug. The IPCAs showed high affinity towards AMP (in dark adsorption studies), with the amount adsorbed proportional to the TiO2 content; the highest adsorption was at 10 wt% TiO2. Equilibrium isotherm studies showed that the adsorption followed the Langmuir model, indicating the dependence of the reaction on an initial adsorption step, with maximum adsorption capacity of 28.4 mg/g for 10 % TiO2 IPCA. The effects of initial pH, catalyst amount and initial AMP concentration on the photocatalytic degradation rates were studied. Generally, the AMP photodegradation activity of the IPCAs was better than that of bare TiO2. Kinetic studies on the photocatalytic degradation of AMP under UV suggest that the degradation followed Langmuir-Hinshelwood (L-H) kinetics, with an adsorption rate constant (K) that was considerably higher than the photocatalytic rate constant (k r), indicating that the photocatalysis of AMP is the rate-determining step during the adsorption/photocatalysis process.

Photocatalytic wastewater purification with simultaneous hydrogen production using MoS2 QD-decorated hierarchical assembly of ZnIn2S4 on reduced graphene oxide photocatalyst.

PubMed

Zhang, Shuqu; Wang, Longlu; Liu, Chengbin; Luo, Jinming; Crittenden, John; Liu, Xia; Cai, Tao; Yuan, Jili; Pei, Yong; Liu, Yutang

2017-09-15

It is attractive to photocatalytically purify wastewater and simultaneously convert solar energy into clean hydrogen energy. However, it is still a challenge owing to the relatively low photocatalytic efficiency of photocatalysts. In this study, we synthesized a molybdenum disulfide (MoS 2 ) quantum dot-decorated 3D nanoarchitecture (MoS 2 QDs) of indium zinc sulfide (ZnIn 2 S 4 ) and reduced grapheme oxide (MoS 2 QDs@ZnIn 2 S 4 @RGO) photocatalyst using a simple solvothermal method. The RGO promotes the electron transfer, and the highly dispersed MoS 2 QDs provides numerous catalytic sites. The photocatalytic purification of rhodamine B (RhB), eosin Y (EY), fulvic acid (FA), methylene blue (MB) and p-nitrophenol (PNP) in simulated wastewaters were further tested. The degradation efficiencies and TOC removal were 91% and 75% for PNP, 92.2% and 72% for FA, 98.5% and 80% for MB, 98.6% and 84% for EY, and 98.8% and 88% for RhB, respectively (C organics  = 20 mg/L, C catalyst  = 1.25 g/L, t = 12 h, I light  = 3.36 × 10 -5  E L -1  s -1 ). Among these tests, the highest hydrogen production was achieved (45 μmol) during RhB degradation. Both experimental and calculational results prove that lower LUMO (lowest unoccupied molecular orbit) level of organic molecules was available for transferring electrons to catalysts, resulting in more efficient hydrogen production. Significantly, the removal efficiencies of natural organic substances in actual river water reached 76.3-98.4%, and COD reduced from 32 to 16 mg/L with 13.8 μmol H 2 production after 12 h. Copyright © 2017 Elsevier Ltd. All rights reserved.

A high efficiency microfluidic-based photocatalytic microreactor using electrospun nanofibrous TiO2 as a photocatalyst

NASA Astrophysics Data System (ADS)

Meng, Zhaoxu; Zhang, Xu; Qin, Jianhua

2013-05-01

We present a novel microfluidic-based photocatalytic microreactor by using electrospun nanofibrous TiO2 as a photocatalyst for the first time. The microreactor exhibits not only a simple fabrication process, but also much higher photocatalytic activity than that achieved by a TiO2 film microreactor.We present a novel microfluidic-based photocatalytic microreactor by using electrospun nanofibrous TiO2 as a photocatalyst for the first time. The microreactor exhibits not only a simple fabrication process, but also much higher photocatalytic activity than that achieved by a TiO2 film microreactor. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00775h

Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

NASA Astrophysics Data System (ADS)

Pan, Xiaoyang; Yang, Min-Quan; Fu, Xianzhi; Zhang, Nan; Xu, Yi-Jun

2013-04-01

Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the

Adsorption performance of titanium dioxide (TiO2) coated air filters for volatile organic compounds.

PubMed

Zhong, Lexuan; Lee, Chang-Seo; Haghighat, Fariborz

2012-12-01

The photocatalytic oxidation (PCO) technology as an alternative method for air purification has been studied for decades and a variety of PCO models indicate that the adsorption of reactants on the catalyst surface is one of the major physical and chemical processes occurring at a heterogeneous photocatalytic reaction. However, limited study explored the adsorption effect of a photocatalyst. This study carried out a systematic evaluation of adsorption performance of titanium dioxide (TiO(2)) coated fiberglass fibers (FGFs), TiO(2) coated carbon cloth fibers (CCFs), and original CCFs air filters at various relative humidity conditions for nine volatile organic compounds. TiO(2)/FGFs, TiO(2)/CCFs, and CCFs were characterized by SEM for morphology and N(2) adsorption isotherm for BET surface area and pore structure. A bench-scale adsorption test setup was constructed and adsorption tests were performed at various relative humidity conditions and four different injected concentrations for each compound. The isothermal adsorption curves at low concentration levels were obtained and they were well described by Langmuir isotherm model. It was noticed that there were significant differences between the adsorption behaviors and photocatalytic activities of TiO(2)/FGFs and TiO(2)/CCFs. It was concluded that adsorption performance is closely related to the characteristics of substrates and therefore, the development of a substrate with high adsorption ability is a promising trend for improving the performance of the UV-PCO technology. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Engineering titania nanostructure to tune and improve its photocatalytic activity

PubMed Central

Cargnello, Matteo; Montini, Tiziano; Smolin, Sergey Y.; Priebe, Jacqueline B.; Delgado Jaén, Juan J.; Doan-Nguyen, Vicky V. T.; McKay, Ian S.; Schwalbe, Jay A.; Pohl, Marga-Martina; Gordon, Thomas R.; Lu, Yupeng; Baxter, Jason B.; Brückner, Angelika; Murray, Christopher B.

2016-01-01

Photocatalytic pathways could prove crucial to the sustainable production of fuels and chemicals required for a carbon-neutral society. Electron−hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, we show the efficacy of anisotropy in improving charge separation and thereby boosting the activity of a titania (TiO2) photocatalytic system. Specifically, we show that H2 production in uniform, one-dimensional brookite titania nanorods is highly enhanced by engineering their length. By using complimentary characterization techniques to separately probe excited electrons and holes, we link the high observed reaction rates to the anisotropic structure, which favors efficient carrier utilization. Quantum yield values for hydrogen production from ethanol, glycerol, and glucose as high as 65%, 35%, and 6%, respectively, demonstrate the promise and generality of this approach for improving the photoactivity of semiconducting nanostructures for a wide range of reacting systems. PMID:27035977

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

Photocatalytic Degradation of Organic Contaminants in Water

EPA Science Inventory

Photocatalytic treatment of organics, including regulated and contaminants of emerging concern, has been an important area of this field. Details are provided on the mechanism of degradation, reaction intermediates, kinetics, and nanointerfacial adsorption phenomena. The degradat...

Electrospinning Fabrication of SrTiO3 Nanofibers and Their Photocatalytic Activity

NASA Astrophysics Data System (ADS)

Xu, Lei; Zhao, Yiping; Wang, Wei; Liu, Hao; Wang, Rui

2018-06-01

SrTiO3 nanofibers were fabricated by an electrospinning process. The phase, microstructure and photocatalytic activity of the obtained SrTiO3 nanofibers were investigated. The XRD patterns and the SEM images suggest that SrTiO3 nanofibers with perovskite phase and rough surface have been fabricated in the current work. The SrTiO3 nanofibers show a high efficiency decomposition of RhB under ultraviolet light irradiation. The high photocatalytic activity of SrTiO3 nanofibers results from the large specific surface area. The large specific surface area provides more surface active sits and makes an easier charge carrier transport. On the basis of the photocatalytic performance of SrTiO3 nanofibers, the possible photocatalysis mechanism was proposed.

Effect of platinum dispersion on photocatalytic performance of Pt-TiO2

NASA Astrophysics Data System (ADS)

Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-03-01

Noble metal Pt nanoparticles have been considered as the most effective co-catalyst to improve the photocatalytic hydrogen production activity of TiO2. In this study, the effect of the dispersion of Pt nanoparticles on the photoactivity of TiO2 nanotubes was investigated. Compared with the samples that the co-catalyst of Pt nanoparticles agglomerated or freely dispersed, the sample with the uniformly dispersion of Pt nanoparticles showed a higher performance for photocatalytic hydrogen production. The photocatalysts were characterized systematically by TEM, BET, UV-Vis, XPS, and PL techniques, and the relationship between the structure and the photoactivity was investigated in detail. The results demonstrated that the dispersion status of Pt nanoparticles had a crucial effect on the photocatalytic activity.

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.

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.

Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity.

PubMed

Faraji, Masoud; Mohaghegh, Neda; Abedini, Amir

2018-01-01

A series of g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plates were fabricated via simple dipping of TiO 2 nanotubes/Ti in a solution containing SnCl 2 and g-C 3 N 4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C 3 N 4 -SnO 2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO 2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis illuminations. Detailed characterization and results of photocatalytic and antibacterial activity tests revealed that semiconductor coupling significantly affected the photocatalyst properties synthesized and hence their photocatalytic and antibacterial activities. Modification of TiO 2 nanotubes/Ti plates with g-C 3 N 4 -SnO 2 deposits resulted in enhanced photocatalytic activities in both chemical and microbial systems. The g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate exhibited the highest photocatalytic and antibacterial activity, probably due to the heterojunction between g-C 3 N 4 -SnO 2 and TiO 2 nanotubes/Ti in the ternary composite plate and thus lower electron/hole recombination rate. Based on the obtained results, a photocatalytic and an antibacterial mechanism for the degradation of E. coli bacteria and chemical pollutants over g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate were proposed and discussed. Copyright © 2017 Elsevier B.V. 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.

Plant leaves as indoor air passive samplers for volatile organic compounds (VOCs).

PubMed

Wetzel, Todd A; Doucette, William J

2015-03-01

Volatile organic compounds (VOCs) enter indoor environments through internal and external sources. Indoor air concentrations of VOCs vary greatly but are generally higher than outdoors. Plants have been promoted as indoor air purifiers for decades, but reports of their effectiveness differ. However, while air-purifying applications may be questionable, the waxy cuticle coating on leaves may provide a simple, cost-effective approach to sampling indoor air for VOCs. To investigate the potential use of plants as indoor air VOC samplers, a static headspace approach was used to examine the relationship between leaf and air concentrations, leaf lipid contents and octanol-air partition coefficients (Koa) for six VOCs and four plant species. The relationship between leaf and air concentrations was further examined in an actual residence after the introduction of several chlorinated VOC emission sources. Leaf-air concentration factors (LACFs), calculated from linear regressions of the laboratory headspace data, were found to increase as the solvent extractable leaf lipid content and Koa value of the VOC increased. In the studies conducted in the residence, leaf concentrations paralleled the changing air concentrations, indicating a relatively rapid air to leaf VOC exchange. Overall, the data from the laboratory and residential studies illustrate the potential for plant leaves to be used as cost effective, real-time indoor air VOC samplers. Copyright © 2014 Elsevier Ltd. All rights reserved.

Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

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

Adraider, Y.; Pang, Y.X., E-mail: F6098038@tees.ac.uk; Nabhani, F.

2014-06-01

Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surfacemore » morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.« less

Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

NASA Astrophysics Data System (ADS)

Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

2018-06-01

TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

Photocatalytic oxidation of aqueous ammonia over microwave-induced titanate nanotubes.

PubMed

Ou, Hsin-Hung; Liao, Ching-Hui; Liou, Ya-Hsuan; Hong, Jian-Hao; Lo, Shang-Lien

2008-06-15

Characterizations of microwave-induced titanate nanotubes (NaxH(2-x)Ti3O7, TNTs) were conducted by the determinations of specific surface area (S(BET)), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), ionic coupled plasma-atomic emission spectrometry(ICP-AES), scanning electron microscopy/ energy dispersive X-ray (SEM/EDX), and high-resolution transmission electron microscopy (HR-TEM). The applied level of microwave irradiation during the fabrication process is responsible for both the intercalation intensity of Na atoms into TNTs and the type of crystallization phase within TNTs, which dominate the efficiency of photocatalytic NH3/NH4+. A pure TNT phase presents no powerful ability toward photocatalytic NH3/ NH4+, while the photocatalytic efficiency can be enhanced with the presence of a rutile phase within TNTs. In addition, the mixture of anatase and rutile phase within P25 TiO2 prefers forming NO3-, whereas TNTs yield higher NO2- amount Regarding the effect of acid-washing treatment on TNTs, the acid-treated TNTs with enhanced ion exchangeability considerably improve the NH3/NH4+ degradation and NO2-/NO3- yields. This result is likely ascribed to the easy intercalation of NH3/ NH4+ into the structure of acid-washing TNTs so that the photocatalytic oxidation of intercalated NH3/NH4+ is not limited to the shielding effect resulting from the overload of TNTs.

Oxidative esterification via photocatalytic C-H activation

EPA Science Inventory

Direct oxidative esterification of alcohol via photocatalytic C-H activation has been developed using VO@g-C3N4 catalyst; an expeditious esterification of alcohols occurs under neutral conditions using visible light as the source of energy.

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.

Enhanced photocatalytic performances of ultrafine g-C3N4 nanosheets obtained by gaseous stripping with wet nitrogen

NASA Astrophysics Data System (ADS)

Fan, Chengkong; Feng, Qiang; Xu, Guangqing; Lv, Jun; Zhang, Yong; Liu, Jiaqin; Qin, Yongqiang; Wu, Yucheng

2018-01-01

Graphitic carbon nitride (g-C3N4) is a promising heterogeneous photocatalyst for organics pollutants degradation and water splitting. Herein, we highlight an available pathway to prepare the ultrafine g-C3N4 nanosheets by gaseous stripping of bulk g-C3N4 in wet nitrogen. As comparison, g-C3N4 treated in air and nitrogen atmospheres are also prepared. The obtained products are characterized with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectra, respectively. Well dispersed g-C3N4 nanosheets can be obtained by this gaseous stripping process in wet nitrogen, which possess much higher specific surface area (211.2 m2 g-1) than that of bulk g-C3N4 (15.3 m2 g-1). Both RhB degradation and water splitting are applied to characterize the photocatalytic performances of the ultrafine g-C3N4 nanosheets. The g-C3N4 (w-N2) nanosheets can degrade 20 mg/L RhB completely within 12 min under visible light illumination, which is 5.32 times faster than that of bulk g-C3N4. Also, the g-C3N4 (w-N2) nanosheets possess the highest photocatalytic hydrogen evolution rate of 1113.48 μmol h-1 g-1 under visible light illumination, which is 6 times that of bulk g-C3N4. The mechanisms of enhancing the photocatalytic performance are discussed to be the higher oxidation ability of VB and higher specific surface area (211.2 m2/g) of the ultrafine g-C3N4 nanosheets.

Photocatalytic degradation of acetaminophen in modified TiO2 under visible irradiation.

PubMed

Dalida, Maria Lourdes P; Amer, Kristine Marfe S; Su, Chia-Chi; Lu, Ming-Chun

2014-01-01

This study investigated the photocatalytic degradation of acetaminophen (ACT) in synthetic titanium dioxide (TiO2) solution under a visible light (λ >440 nm). The TiO2 photocatalyst used in this study was synthesized via sol-gel method and doped with potassium aluminum sulfate (KAl(SO4)2) and sodium aluminate (NaAlO2). The influence of some parameters on the degradation of acetaminophen was examined, such as initial pH, photocatalyst dosage, and initial ACT concentration. The optimal operational conditions were also determined. Results showed that synthetic TiO2 catalysts presented mainly as anatase phase and no rutile phase was observed. The results of photocatalytic degradation showed that LED alone degraded negligible amount of ACT but with the presence of TiO2/KAl(SO4)2, 95% removal of 0.10-mM acetaminophen in 540-min irradiation time was achieved. The synthetic TiO2/KAl(SO4)2 presented better photocatalytic degradation of acetaminophen than commercially available Degussa P-25. The weak crystallinity of synthesized TiO2/NaAlO2 photocatalyst showed low photocatalytic degradation than TiO2/KAl(SO4)2. The optimal operational conditions were obtained in pH 6.9 with a dose of 1.0 g/L TiO2/KAl(SO4)2 at 30 °C. Kinetic study illustrated that photocatalytic degradation of acetaminophen fits well in the pseudo-first order model. Competitive reactions from intermediates affected the degradation rate of ACT, and were more obvious as the initial ACT concentration increased.

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.

Effect of bath temperature on surface morphology and photocatalytic activity of ZnO nanorods

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

Sriharan, N.; Senthil, T. S., E-mail: tssenthi@gmail.com; Muthukumarasamy, N.

2016-05-06

ZnO nanorods were prepared by using simple hydrothermal method using four different bath temperatures. All the prepared ZnO nanorods are annealed at 450°C and are characterized by using various techniques such as X-ray diffraction, UV spectra and scanning electron microscopy. Photocatalytic activity of the prepared ZnO nanorods is analyzed. A novel photocatalytic reactor designed with ZnO nanorods prepared at 90°C shows enhanced catalytic efficiency. The role of light irradiation time, bath temperature and surface morphology of the ZnO nanorods on the performance of photocatalytic reaction is analyzed.

Advances in Photocatalytic CO₂ Reduction with Water: A Review.

PubMed

Nahar, Samsun; Zain, M F M; Kadhum, Abdul Amir H; Hasan, Hassimi Abu; Hasan, Md Riad

2017-06-08

In recent years, the increasing level of CO₂ in the atmosphere has not only contributed to global warming but has also triggered considerable interest in photocatalytic reduction of CO₂. The reduction of CO₂ with H₂O using sunlight is an innovative way to solve the current growing environmental challenges. This paper reviews the basic principles of photocatalysis and photocatalytic CO₂ reduction, discusses the measures of the photocatalytic efficiency and summarizes current advances in the exploration of this technology using different types of semiconductor photocatalysts, such as TiO₂ and modified TiO₂, layered-perovskite Ag/ALa₄Ti₄O 15 (A = Ca, Ba, Sr), ferroelectric LiNbO₃, and plasmonic photocatalysts. Visible light harvesting, novel plasmonic photocatalysts offer potential solutions for some of the main drawbacks in this reduction process. Effective plasmonic photocatalysts that have shown reduction activities towards CO₂ with H₂O are highlighted here. Although this technology is still at an embryonic stage, further studies with standard theoretical and comprehensive format are suggested to develop photocatalysts with high production rates and selectivity. Based on the collected results, the immense prospects and opportunities that exist in this technique are also reviewed here.

Modelling studies for photocatalytic degradation of organic dyes using TiO2 nanofibers.

PubMed

Singh, Narendra; Rana, Mohit Singh; Gupta, Raju Kumar

2017-09-05

In this work, modelling of the photocatalytic degradation of para-nitrophenol (PNP) using synthesized electrospun TiO 2 nanofibers under UV light illumination is reported. A dynamic model was developed in order to understand the behaviour of operating parameters, i.e. light intensity and catalyst loading on the photocatalytic activity. This model was simulated and analysed for both TiO 2 solid nanofibers and TiO 2 hollow nanofibers, applied as photocatalysts in the Langmuir-Hinshelwood kinetic framework. The entire photocatalytic degradation rate follows pseudo-first-order kinetics. The simulated results obtained from the developed model are in good agreement with the experimental results. At a catalyst loading of 1.0 mg mL -1 , better respective degradation rates were achieved at UV light irradiance of 4 mW cm -2 , for both the TiO 2 solid and hollow nanofibers. However, it was also observed that TiO 2 hollow nanofibers have a higher adsorption rate than that of TiO 2 solid nanofibers resulting in a higher photocatalytic degradation rate of PNP.

Kinetic study of gold nanoparticle mediated photocatalytic degradation of Victoria blue.

PubMed

Jishma, P; Roshmi, Thomas; Snigdha, S; Radhakrishnan, E K

2018-02-01

In the study, biogenic gold nanoparticles (AuNPs) were used for the photocatalytic degradation of triphenylmethane dyes Victoria blue B (VBB) and R (VBR). The process was found to result in an approximate degradation of 65 and 52%, respectively, for VBB and VBR within a period of 8 h. The relative rate of photocatalytic degradation of VBB and VBR was identified to be 0.0195 ± 0.0031/min and 0.0295 ± 0.0025/min, respectively, by using the Langmuir-Hinshelwood model. By using the Vigna unguiculata model system, the degradation products were demonstrated to have non-toxic effect. Moreover, the less toxic nature of AuNPs used for dye removal highlights its feasibility for large-scale application. Hence, the AuNPs-based photocatalytic dye degradation as described in the study is cost-effective, rapid and environment-friendly.

2. View of Liquified Propane Air Plant (New), former Exhaust ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. View of Liquified Propane Air Plant (New), former Exhaust and Compressor Building and former Purifying Plant in background. - Concord Gas Light Company, South Main Street, Concord, Merrimack County, NH

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.

Understanding Mechanism of Photocatalytic Microbial Decontamination of Environmental Wastewater

PubMed Central

Regmi, Chhabilal; Joshi, Bhupendra; Ray, Schindra K.; Gyawali, Gobinda; Pandey, Ramesh P.

2018-01-01

Several photocatalytic nanoparticles are synthesized and studied for potential application for the degradation of organic and biological wastes. Although these materials degrade organic compounds by advance oxidation process, the exact mechanisms of microbial decontamination remains partially known. Understanding the real mechanisms of these materials for microbial cell death and growth inhibition helps to fabricate more efficient semiconductor photocatalyst for large-scale decontamination of environmental wastewater or industries and hospitals/biomedical labs generating highly pathogenic bacteria and toxic molecules containing liquid waste by designing a reactor. Recent studies on microbial decontamination by photocatalytic nanoparticles and their possible mechanisms of action is highlighted with examples in this mini review. PMID:29541632

MWCNT/CdS hybrid nanocomposite for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Chaudhary, Deepti; Khare, Neeraj; Vankar, V. D.

2016-05-01

Multi-walled carbon nanotubes (MWCNT)/CdS hybrid nanocomposite were synthesized by one step hydrothermal method. MWCNTs were used as a substrate for the growth of CdS nanoparticles. MWCNT/CdS nanocomposite and pure CdS were characterized by XRD, TEM, UV-vis and photoluminescence spectroscopy. HRTEM study confirms the intimate contact of CdS with MWCNT. The photocatalytic activity of nanocomposite was studied for the degradation of methylene blue dye under UV irradiation. The enhanced photocatalytic activity of MWCNT/CdS nanocomposite as compared to pure CdS has been attributed to reduced recombination of photogenerated charge carriers due to interfacial electron transfer from CdS to MWCNT.

Enhanced Visible-Light Photocatalytic H2 Evolution in Cu2O/Cu2Se Multilayer Heterostructure Nanowires Having {111} Facets and Physical Mechanism.

PubMed

Liu, Bin; Ning, Lichao; Zhang, Congjie; Zheng, Hairong; Liu, Shengzhong Frank; Yang, Heqing

2018-06-21

It is rather challenging to develop photocatalysts based on narrow-band-gap semiconductors for water splitting under solar irradiation. Herein, we synthesized the Cu 2 O/Cu 2 Se multilayer heterostructure nanowires exposing {111} crystal facets by a hydrothermal reaction of Se with Cu and KBH 4 in ethanol amine aqueous solution and subsequent annealing in air. The photocatalytic H 2 production activity of Cu 2 O/Cu 2 Se multilayer heterostructure nanowires is dramatically improved, with an increase on the texture coefficient of Cu 2 O(111) and Cu 2 Se(111) planes, and thus the exposed {111} facets may be the active surfaces for photocatalytic H 2 production. On the basis of the polar structure of Cu 2 O {111} and Cu 2 Se {111} surfaces, we presented a model of charge separation between the Cu-Cu 2 Se(111) and O-Cu 2 O(1̅ 1̅ 1̅) polar surfaces. An internal electric field is created between Cu-Cu 2 Se(111) and O-Cu 2 O(1̅ 1̅ 1̅) polar surfaces, because of spontaneous polarization. As a result, this internal electric field drives the photocreated charge separation. The oxidation and reduction reactions selectively occur at the negative O-Cu 2 O(1̅ 1̅ 1̅) and the positive Cu-Cu 2 Se(111) surfaces. The polar surface-engineering may be a general strategy for enhancing the photocatalytic H 2 -production activity of semiconductor photocatalysts. The charge separation mechanism not only can deepen the understanding of photocatalytic H 2 production mechanism but also provides a novel insight into the design of advanced photocatalysts, other photoelectric devices, and solar cells.

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.

Synthesis of CdS/BiOBr nanosheets composites with efficient visible-light photocatalytic activity

NASA Astrophysics Data System (ADS)

Cui, Haojie; Zhou, Yawen; Mei, Jinfeng; Li, Zhongyu; Xu, Song; Yao, Chao

2018-01-01

The efficient charge separation action and visible-light responding could enhance the photocatalytic property of photocatalysts. In the present study, novel CdS/BiOBr nanosheets composites were synthesized by a three-step process. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), diffuse reflection spectroscopy (DRS), Raman spectroscopy and photoluminescence (PL). Under visible-light irradiation, the as-prepared CdS nanoparticles decorated BiOBr nanosheets exhibited the excellent photocatalytic activity and high stability for malachite green (MG) degradation. The photodegradation achieved maximum degradation efficiency (99%) using CdS/BiOBr-3 composites as photocatalyst. Furthermore, the possible photocatalytic mechanism upon CdS/BiOBr composites was also discussed through radical and holes trapping experiments. The heterostructure between CdS and BiOBr improved photocatalytic activity dramatically, which greatly promoted migration rate of the photoinduced electrons besides limiting the recombination of photogenerated electron-hole pairs.

Metal-free hybrids of graphitic carbon nitride and nanodiamonds for photoelectrochemical and photocatalytic applications.

PubMed

Zhou, Li; Zhang, Huayang; Guo, Xiaochen; Sun, Hongqi; Liu, Shaomin; Tade, Moses O; Wang, Shaobin

2017-05-01

Graphitic carbon nitride (g-C 3 N 4 ) has been considered as a metal-free, cost-effective, eco-friendly and efficient catalyst for various photoelectrochemical applications. However, compared to conventional metal-based photocatalysts, its photocatalytic activity is still low because of the low mobility of carriers restricted by the polymer nature. Herein, a series of hybrids of g-C 3 N 4 (GCN) and nanodiamonds (NDs) were synthesized using a solvothermal method. The photoelectrochemical performance and photocatalytic efficiency of the GCN/NDs were investigated by means of the generation of photocurrent and photodegradation of methylene blue (MB) solutions under UV-visible light irradiations. In this study, the sample of GCN/ND-33% derived from 0.1g GCN and 0.05g NDs displayed the highest photocatalytic activity and the strongest photocurrent density. The mechanism of enhanced photoelectrochemical and photocatalytic performances was also discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

Photocatalytic degradation of commercial phoxim over La-doped TiO2 nanoparticles in aqueous suspension.

PubMed

Dai, Ke; Peng, Tianyou; Chen, Hao; Liu, Juan; Zan, Lin

2009-03-01

Photocatalytic degradation of commercial phoxim emulsion in aqueous suspension was investigated by using La-doped mesoporous TiO2 nanoparticles (m-TiO2) as the photocatalyst under UV irradiation. Effects of La-doping level, calcination temperature, and additional amount of the photocatalyst on the photocatalytic degradation efficiency were investigated in detail. Experimental results indicate that 20 mg L(-1) phoxim in 0.5 g L(-1) La/m-TiO2 suspension (the initial pH 4.43) can be decomposed as prolonging the irradiation time. Almost 100% phoxim was decomposed after 4 h irradiation according to the spectrophotometric analyses, whereas the mineralization rate of phoxim just reached ca. 80% as checked by ion chromatography (IC) analyses. The elimination of the organic solvent in the phoxim emulsion as well as the formation and decomposition of some degradation intermediates were observed by high-performance liquid chromatography-mass spectroscopy (HPLC-MS). On the basis of the analysis results on the photocatalytic degradation intermediates, two possible photocatalytic degradation pathways are proposed under the present experimental conditions, which reveal that both the hydrolysis and adsorption of phoxim under UV light irradiation play important roles during the photocatalytic degradation of phoxim.

Bi2WO6 nanoflowers: An efficient visible light photocatalytic activity for ceftriaxone sodium degradation

NASA Astrophysics Data System (ADS)

Zhao, Yanyan; Wang, Yongbo; Liu, Enzhou; Fan, Jun; Hu, Xiaoyun

2018-04-01

The morphology-controlled synthesis of nano-structure photocatalyst have leaded a new possibility to improve their physical and chemical properties. Herein, Bi2WO6 nanocrystals (BWO) with nano-flower, nano plates, knot shape, rod like and irregular morphologies have been successfully synthesized through a highly facile hydrothermal process by simply adjusting pH values, reactive solvents and temperature. Photocatalytic activity of the as-prepared samples were evaluated by degradation of Ceftriaxone sodium under visible light irradiation (λ > 420 nm), the results indicated that all the BWO samples exhibit morphology-associated photocatalytic activity, and the 3D flowerlike-structure of BWO composed of well-ordered nano plates (BWO-D-5) displayed the outstanding photocatalytic activity. Through getting insight into the mechanism, h+ and rad O2- play major roles compared with rad OH in photocatalytic degradation process. The possible pathway of Ceftriaxone sodium and the intermediates were proposed to better understand the reaction process. Moreover, this work not only provides an example of morphology-dependent photocatalytic activity of BWO but also provides an illustrative example for removing organic pollutant molecules according to practical requirements.

Photocatalytic degradation of NOx gases using TiO2-containing paint: a real scale study.

PubMed

Maggos, Th; Bartzis, J G; Liakou, M; Gobin, C

2007-07-31

An indoor car park was appropriately equipped in order to test the de-polluting efficiency of a TiO(2)-containing paint in an indoor polluted environment, under real scale configuration. Depollution tests were performed in an artificially closed area of the parking, which was polluted by a car exhaust during the testing period. The ceiling surface of the car park was covered with white acrylic TiO(2)-containing paint (PP), which was developed in the frame of the EU project 'PICADA' (Photocatalytic Innovative Coverings Application for Depollution Assessment). The closed area was fed with car exhaust gases. As soon as the system reached steady state, the UV lamps were turned on for 5h. The difference between the final and the initial steady state concentration indicates the removal of the pollutants due to both the photocatalytic paint and car emission reduction. Results showed a significant photocatalytic oxidation of NO(x) gases. The photocatalytic removal of NO and NO(2) was calculated to 19% and 20%, respectively, while the photocatalytic rate (microgm(-2)s(-1)) ranged between 0.05 and 0.13 for NO and between 0.09 and 0.16 for NO(2).

Photocatalytic Hybrid Semiconductor-Metal Nanoparticles; from Synergistic Properties to Emerging Applications.

PubMed

Waiskopf, Nir; Ben-Shahar, Yuval; Banin, Uri

2018-04-14

Hybrid semiconductor-metal nanoparticles (HNPs) manifest unique combined and often synergetic properties stemming from the materials combination. These structures exhibit spatial charge separation across the semiconductor-metal junction upon light absorption, enabling their use as photocatalysts. So far, the main impetus of photocatalysis research in HNPs addresses their functionality in solar fuel generation. Recently, it was discovered that HNPs are functional in efficient photocatalytic generation of reactive oxygen species (ROS). This has opened the path for their implementation in diverse biomedical and industrial applications where high spatially temporally resolved ROS formation is essential. Here, the latest studies on the synergistic characteristics of HNPs are summarized, including their optical, electrical, and chemical properties and their photocatalytic function in the field of solar fuel generation is briefly discussed. Recent studies are then focused concerning photocatalytic ROS formation with HNPs under aerobic conditions. The emergent applications of this capacity are then highlighted, including light-induced modulation of enzymatic activity, photodynamic therapy, antifouling, wound healing, and as novel photoinitiators for 3D-printing. The superb photophysical and photocatalytic properties of HNPs offer already clear advantages for their utility in scenarios requiring on-demand light-induced radical formation and the full potential of HNPs in this context is yet to be revealed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A visible light-induced photocatalytic silver enhancement reaction for gravimetric biosensors.

PubMed

Ko, Wooree; Yim, Changyong; Jung, Namchul; Joo, Jinmyoung; Jeon, Sangmin; Seo, Hyejung; Lee, Soo Suk; Park, Jae Chan

2011-10-07

We have developed a novel microgravimetric immunosensor using a WO(3) nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e.  AgNO(3)) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO(2) nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO(3) nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO(3) nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone.

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.

Heterogeneous photocatalytic degradation of toluene in static environment employing thin films of nitrogen-doped nano-titanium dioxide

NASA Astrophysics Data System (ADS)

Kannangara, Yasun Y.; Wijesena, Ruchira; Rajapakse, R. M. G.; de Silva, K. M. Nalin

2018-04-01

Photocatalytic semiconductor thin films have the ability to degrade volatile organic compounds (VOCs) causing numerous health problems. The group of VOCs called "BTEX" is abundant in houses and indoor of automobiles. Anatase phase of TiO2 has a band gap of 3.2 eV and UV radiation is required for photogeneration of electrons and holes in TiO2 particles. This band gap can be decreased significantly when TiO2 is doped with nitrogen (N-TiO2). Dopants like Pd, Cd, and Ag are hazardous to human health but N-doped TiO2 can be used in indoor pollutant remediation. In this research, N-doped TiO2 nano-powder was prepared and characterized using various analytical techniques. N-TiO2 was made in sol-gel method and triethylamine (N(CH2CH3)3) was used as the N-precursor. Modified quartz cell was used to measure the photocatalytic degradation of toluene. N-doped TiO2 nano-powder was illuminated with visible light (xenon lamp 200 W, λ = 330-800 nm, intensity = 1 Sun) to cause the degradation of VOCs present in static air. Photocatalyst was coated on a thin glass plate, using the doctor-blade method, was inserted into a quartz cell containing 2.00 µL of toluene and 35 min was allowed for evaporation/condensation equilibrium and then illuminated for 2 h. Remarkably, the highest value of efficiency 85% was observed in the 1 μm thick N-TiO2 thin film. The kinetics of photocatalytic degradation of toluene by N-TiO2 and P25-TiO2 has been compared. Surface topology was studied by varying the thickness of the N-TiO2 thin films. The surface nanostructures were analysed and studied with atomic force microscopy with various thin film thicknesses.

PROCESS OF PURIFYING URANIUM

DOEpatents

Seaborg, G.T.; Orlemann, E.F.; Jensen, L.H.

1958-12-23

A method of obtaining substantially pure uranium from a uranium composition contaminated with light element impurities such as sodium, magnesium, beryllium, and the like is described. An acidic aqueous solution containing tetravalent uranium is treated with a soluble molybdate to form insoluble uranous molybdate which is removed. This material after washing is dissolved in concentrated nitric acid to obtaln a uranyl nitrate solution from which highly purified uranium is obtained by extraction with ether.

The kinetics of photocatalytic degradation of aliphatic carboxylic acids in an UV/TiO2 suspension system.

PubMed

Chen, Q; Song, J M; Pan, F; Xia, F L; Yuan, J Y

2009-10-01

Kinetic studies on the photocatalytic degradation of aliphatic carboxylic acids were carried out in a slurry photoreactor with in-situ monitoring, employing artificial UV light as the source of energy and nano-TiO2 powder as the catalyst. The influences on the photocatalytic degradation such as the initial concentration of reactant (C0), catalyst dosage (CTiO2), UV intensity (Ia) and pH value have been investigated. Good agreement has been obtained between the value calculated by Langmuir-Freundlich-Hinshelwood (L-F-H) model and experimental data, with coefficient of multiple determination (R2) varying from 0.880 to 0.999. The L-F-H model has been proven to be feasible in describing the kinetic characteristic of the photocatalytic degradation of aliphatic carboxylic acids. Moreover, the apparent reaction rate constant (k) of the photocatalytic degradation of dicarboxylic acids is higher than that of monocarboxylic acids with the same carbon atoms. This shows that the photocatalytic degradation rate is favoured by different chemical structure.

Synthesis of ZnO-Pt nanoflowers and their photocatalytic applications.

PubMed

Yuan, Jiaquan; Choo, Eugene Shi Guang; Tang, Xiaosheng; Sheng, Yang; Ding, Jun; Xue, Junmin

2010-05-07

The photocatalytic behaviors of ZnO nanoparticles have been intensively studied recently. However, the photocatalytic efficiency of pure ZnO nanoparticles always suffers from the quick recombination of photoexcited electrons and holes. In order to suppress the electron-hole recombination and then raise the photocatalytic efficiency of ZnO, metal nanoparticles have been combined with ZnO to form ZnO-metal heterostructures. In this work, the feasibility of synthesizing ZnO-Pt composite nanoflowers for optimized catalytic properties was studied. Three different Pt nanocrystals, i.e. cubic Pt nanocrystals enclosed by {100} facets, octahedral Pt nanocrystals enclosed by {111} facets, and truncated octahedral Pt nanocrystals enclosed by both {111} and {100} facets, were selected as seeds for epitaxial growth of ZnO. A ZnO-Pt flowerlike nanostructure was formed by selective growth of ZnO nanolobes at {111} facets of the truncated octahedral Pt nanocrystals. The resultant nanoflowers had well defined ZnO-Pt interfaces and exposed Pt {100} facets, as confirmed by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) measurements. The photocatalytic behaviors of the resultant ZnO-Pt nanoflowers were demonstrated in the photodegradation of ethyl violet. In comparison with the commercial TiO(2) photocatalyst P25, the ZnO-Pt flowerlike nanostructures showed improved catalytic efficiency. Notable ferromagnetism of the obtained ZnO-Pt flowerlike nanostructures was also observed. It is believed that the ZnO-Pt interface played an important role in the enlarged magnetic coercivity of the ZnO-Pt nanoflowers.

A review of engineering development of aqueous phase solar photocatalytic detoxification and disinfection processes

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

Goswami, D.Y.

1997-05-01

Scientific research on photocatalytic oxidation of hazardous chemicals has been conducted extensively over the last three decades. Use of solar radiation in photocatalytic detoxification and disinfection has only been explored in the last decade. Developments of engineering scale systems, design methodologies, and commercial and industrial applications have occurred even more recently. A number of reactor concepts and designs including concentrating and nonconcentrating types and methods of catalyst deployment have been developed. Some commercial and industrial field tests of solar detoxification systems have been conducted. This paper reviews the engineering developments of the solar photocatalytic detoxification and disinfection processes, including systemmore » design methodologies.« less

Method for purifying bidentate organophosphorus compounds

DOEpatents

Schulz, Wallace W.

1977-01-01

Bidentate organophosphorus compounds useful for extracting actinide elements from acidic nuclear waste solutions are purified of undesirable acidic impurities by contacting the compounds with ethylene glycol which preferentially extracts the impurities found in technical grade bidentate compounds.

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.

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

Purifying Aluminum by Vacuum Distillation

NASA Technical Reports Server (NTRS)

Du Fresne, E. R.

1985-01-01

Proposed method for purifying aluminum employs one-step vacuum distillation. Raw material for process impure aluminum produced in electrolysis of aluminum ore. Impure metal melted in vacuum. Since aluminum has much higher vapor pressure than other constituents, boils off and condenses on nearby cold surfaces in proportions much greater than those of other constituents.

Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

NASA Astrophysics Data System (ADS)

Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

2013-07-01

Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

Nd/TiO2 Anatase-Brookite Photocatalysts for Photocatalytic Decomposition of Methanol.

PubMed

Kočí, Kamila; Troppová, Ivana; Reli, Martin; Matějová, Lenka; Edelmannová, Miroslava; Drobná, Helena; Dubnová, Lada; Rokicińska, Anna; Kuśtrowski, Piotr; Čapek, Libor

2018-01-01

Neodymium enriched TiO 2 anatase-brookite powders were prepared by unconventional method via using pressurized hot fluids for TiO 2 crystallization and purification. The photocatalysts were tested in the CH 3 OH photocatalytic decomposition and they were characterized with respect to the textural (nitrogen adsorption), structural (XRD, XPS, and Raman spectroscopies), chemical (XRF), and optical (DR UV-Vis spectroscopy) and photoelectrochemical measurement. All prepared materials were nanocrystalline, had biphasic (anatase- brookite) structure and relatively large specific surface area (125 m 2 .g -1 ). The research work indicates that the doping of neodymium on TiO 2 photocatalysts significantly enhances the efficiency of photocatalytic reaction. The photocatalytic activity increased with increasing portion of hydroxyl oxygen to the total amount of oxygen species. It was ascertained that the optimal amount of 1 wt% Nd in TiO 2 accomplished the increasing of hydrogen production by 70% in comparison with pure TiO 2 . The neodymium doped on the titanium dioxide act as sites with accumulation of electrons. The higher efficiency of photocatalytic process was achieved due to improved electron-hole separation on the modified TiO 2 photocatalysts. This result was confirmed by electrochemical measurements, the most active photocatalysts proved the highest photocurrent responses.

Nd/TiO2 Anatase-Brookite Photocatalysts for Photocatalytic Decomposition of Methanol

PubMed Central

Kočí, Kamila; Troppová, Ivana; Reli, Martin; Matějová, Lenka; Edelmannová, Miroslava; Drobná, Helena; Dubnová, Lada; Rokicińska, Anna; Kuśtrowski, Piotr; Čapek, Libor

2018-01-01

Neodymium enriched TiO2 anatase-brookite powders were prepared by unconventional method via using pressurized hot fluids for TiO2 crystallization and purification. The photocatalysts were tested in the CH3OH photocatalytic decomposition and they were characterized with respect to the textural (nitrogen adsorption), structural (XRD, XPS, and Raman spectroscopies), chemical (XRF), and optical (DR UV-Vis spectroscopy) and photoelectrochemical measurement. All prepared materials were nanocrystalline, had biphasic (anatase- brookite) structure and relatively large specific surface area (125 m2.g−1). The research work indicates that the doping of neodymium on TiO2 photocatalysts significantly enhances the efficiency of photocatalytic reaction. The photocatalytic activity increased with increasing portion of hydroxyl oxygen to the total amount of oxygen species. It was ascertained that the optimal amount of 1 wt% Nd in TiO2 accomplished the increasing of hydrogen production by 70% in comparison with pure TiO2. The neodymium doped on the titanium dioxide act as sites with accumulation of electrons. The higher efficiency of photocatalytic process was achieved due to improved electron-hole separation on the modified TiO2 photocatalysts. This result was confirmed by electrochemical measurements, the most active photocatalysts proved the highest photocurrent responses. PMID:29552558

Ecotoxic effect of photocatalytic active nanoparticles (TiO2) on algae and daphnids.

PubMed

Hund-Rinke, Kerstin; Simon, Markus

2006-07-01

Due to their large potential for manifold applications, the use of nanoparticles is of increasing importance. As large amounts of nanoparticles may reach the environment voluntarily or by accident, attention should be paid on the potential impacts on the environment. First studies on potential environmental effects of photocatalytic TiO2 nanoparticles have been performed on the basis of widely accepted, standardized test systems which originally had been developed for the characterization of chemicals. The methods were adapted to the special requirements of testing photocatalytic nanoparticles. Suspensions of two different nanoparticles were illuminated to induce their photocatalytic activity. For testing, the growth inhibition test with the green alga Desmodesmus subspicatus and the immobilization test with the daphnid Daphnia magna were selected and performed following the relevant guidelines (algae: ISO 8692, OECD 201, DIN 38412-33; daphnids: ISO 6341, OECD 202, DIN 38412-30). The guidelines were adapted to meet the special requirements for testing photocatalytic nanoparticles. The results indicate that it is principally possible to determine the ecotoxicity of nanoparticles. It was shown that nanoparticles may have ecotoxicological effects which depend on the nature of the particles. Both products tested differ in their toxicity. Product 1 shows a clear concentration-effect curve in the test with algae (EC50: 44 mg/L). It could be proven that the observed toxicity was not caused by accompanying contaminants, since the toxic effect was comparable for the cleaned and the commercially available product. For product 2, no toxic effects were determined (maximum concentration: 50 mg/L). In the tests with daphnids, toxicity was observed for both products, although the concentration effect-curves were less pronounced. The two products differed in their toxicity; moreover, there was a difference in the toxicity of illuminated and non-illuminated products. Both products

Purified discord and multipartite entanglement

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

Brown, Eric G.; Webster, Eric J.; Martín-Martínez, Eduardo, E-mail: emmfis@gmail.com

2013-10-15

We study bipartite quantum discord as a manifestation of a multipartite entanglement structure in the tripartite purified system. In particular, we find that bipartite quantum discord requires the presence of both bipartite and tripartite entanglement in the purification. This allows one to understand the asymmetry of quantum discord, D(A,B)≠D(B,A) in terms of entanglement monogamy. As instructive special cases, we study discord for qubits and Gaussian states in detail. As a result of this we shed new light on a counterintuitive property of Gaussian states: the presence of classical correlations necessarily requires the presence of quantum correlations. Finally, our results alsomore » shed new light on a protocol for remote activation of entanglement by a third party. -- Highlights: •Bipartite quantum discord as a manifestation of multipartite entanglement. •Relevance of quantum discord as a utilizable resource for quantum info. tasks. •Quantum discord manifests itself in entanglement in the purified state. •Relation between asymmetry of discord and entanglement monogamy. •Protocol for remote activation of entanglement by a third party.« less

Negative impact of surface Ti3+ defects on the photocatalytic hydrogen evolution activity of SrTiO3

NASA Astrophysics Data System (ADS)

Chen, Haidong; Zhang, Feng; Zhang, Weifeng; Du, Yingge; Li, Guoqiang

2018-01-01

Defects play an important and in many cases dominant role in the physical and chemical properties of many oxide materials. In this work, we show that the surface Ti3+ defects in SrTiO3 (STO), characterized by electron paramagnetic resonance and X-ray photoelectron spectroscopy, directly impact the photocatalytic activity of STO. O2 species are found to absorb preferentially on Ti3+ defect sites. Hydrogen evolution under ambient air diminishes with the increase in the concentration of surface Ti3+. This is explained by the over-accumulation of Pt cocatalysts on the site of surface Ti3+ defects after the removal of adsorbed O2.

Use of photovoltaic detector for photocatalytic activity estimation

NASA Astrophysics Data System (ADS)

Das, Susanta Kumar; Satapathy, Pravakar; Rao, P. Sai Shruti; Sabar, Bilu; Panda, Rudrashish; Khatua, Lizina

2018-05-01

Photocatalysis is a very important process and have numerous applications. Generally, to estimate the photocatalytic activity of newly grown material, its reaction rate constant w.r.t to some standard commercial TiO2 nanoparticles like Degussa P25 is evaluated. Here a photovoltaic detector in conjunction with laser is used to determine this rate constant. This method is tested using Zinc Orthotitanate (Zn2TiO4) nanoparticles prepared by solid state reaction and it is found that its reaction rate constant is six times higher than that of P25. The value is found to be close to the value found by a conventional system. Our proposed system is much more cost-effective than the conventional one and has the potential to do real time monitoring of the photocatalytic activity.

NASA's Potential Contributions for Using Solar Ultraviolet Radiation in Conjunction with Photocatalysis for Urban Air Pollution Mitigation

NASA Technical Reports Server (NTRS)

Ryan, robert E.; Underwood, Lauren W.

2007-01-01

More than 75 percent of the U.S. population lives in urban communities where people are exposed to levels of smog or pollution that exceed the EPA (U.S. Environmental Protection Agency) safety standards. Urban air quality presents a unique problem because of a number of complex variables, including traffic congestion, energy production, and energy consumption activities, all of which can contribute to and affect air pollution and air quality in this environment. In environmental engineering, photocatalysis is an area of research whose potential for environmental clean-up is rapidly developing popularity and success. Photocatalysis, a natural chemical process, is the acceleration of a photoreaction in the presence of a catalyst. Photocatalytic agents are activated when exposed to near UV (ultraviolet) light (320-400 nm) and water. In recent years, surfaces coated with photocatalytic materials have been extensively studied because pollutants on these surfaces will degrade when the surfaces are exposed to near UV light. Building materials, such as tiles, cement, glass, and aluminum sidings, can be coated with a thin film of a photocatalyst. These coated materials can then break down organic molecules, like air pollutants and smog precursors, into environmentally friendly compounds. These surfaces also exhibit a high affinity for water when exposed to UV light. Therefore, not only are the pollutants decomposed, but this superhydrophilic nature makes the surface self-cleaning, which helps to further increase the degradation rate by allowing rain and/or water to wash byproducts away. According to the Clean Air Act, each individual state is responsible for implementing prevention and regulatory programs to control air pollution. To operate an air quality program, states must adopt and/or develop a plan and obtain approval from the EPA. Federal approval provides a means for the EPA to maintain consistency among different state programs and ensures that they comply with the

Effect of photocatalytic oxidation technology on GaN CMP

NASA Astrophysics Data System (ADS)

Wang, Jie; Wang, Tongqing; Pan, Guoshun; Lu, Xinchun

2016-01-01

GaN is so hard and so chemically inert that it is difficult to obtain a high material removal rate (MRR) in the chemical mechanical polishing (CMP) process. This paper discusses the application of photocatalytic oxidation technology in GaN planarization. Three N-type semiconductor particles (TiO2, SnO2, and Fe2O3) are used as catalysts and added to the H2O2-SiO2-based slurry. By optical excitation, highly reactive photoinduced holes are produced on the surface of the particles, which can oxidize OH- and H2O absorbed on the surface of the catalysts; therefore, more OH* will be generated. As a result, GaN MRRs in an H2O2-SiO2-based polishing system combined with catalysts are improved significantly, especially when using TiO2, the MRR of which is 122 nm/h. The X-ray photoelectron spectroscopy (XPS) analysis shows the variation trend of chemical composition on the GaN surface after polishing, revealing the planarization process. Besides, the effect of pH on photocatalytic oxidation combined with TiO2 is analyzed deeply. Furthermore, the physical model of GaN CMP combined with photocatalytic oxidation technology is proposed to describe the removal mechanism of GaN.

A new route for synthesis of spherical NiO nanoparticles via emulsion nano-reactors with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Fazlali, Farnaz; Mahjoub, Ali reza; Abazari, Reza

2015-10-01

This study has sought to draw a comparison among the nickel oxide nanostructures (NSs) with multiple shapes in terms of their photocatalytic properties. These NSs have been synthesized using a set of wet chemical methods (thermal-decomposition, sol-gel, hydrothermal, and emulsion nano-reactors), for which a similar precursor has been considered. For evaluation of the photocatalytic properties of the suggested NSs, methyl orange (MeO) solution photocatalytic degradation has been estimated based on UV-Vis spectroscopy. As shown by our results, the photocatalytic efficiency of the prepared NSs is highly dependent upon the shape of the corresponding structures. In this context, the emulsion nano-reactors (ENRs) method has been developed for the synthesis of pure nickel oxide nanoparticles (NPs) with unaggregated, quite spherical, and homogeneous NPs at environmental conditions. Compared with the other methods in this work, ENRs method shows high photocatalytic efficiency in the MeO dye decomposition.

Photocatalytic removal of phenol over titanium dioxide- reduced graphene oxide photocatalyst

NASA Astrophysics Data System (ADS)

Shuhada Alim, Nor; Lintang, Hendrik O.; Yuliati, Leny

2016-02-01

Titanium dioxide (TiO2) has been one of the most investigated semiconductors due to its high activity for the removal of organic pollutants. In order to improve the efficiency of the TiO2, series of TiO2-reduced graphene oxide (rGO) composites with various loading amounts of graphene oxide (GO), which were 0.5, 1, 3 and 5 wt% were prepared by UV- assisted photocatalytic reduction method. The X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed that all the TiO2-rGO composites samples were successfully synthesized without disrupting the structure of the TiO2. Fluorescence spectroscopy revealed the role of the rGO to reduce the electron-hole recombination on the TiO2, while the transmission electron microscopy-energy dispersive X- ray spectroscopy (TEM-EDS) confirmed the morphology and the presence of both TiO2 and rGO. In the photocatalytic removal of phenol, all the TiO2-rGO composites showed better photocatalytic activities than the TiO2 under UV light irradiation. The activity of the TiO2 was enhanced by more than two times with the addition of the GO with the optimum amount (3 wt%). It was proposed that the good photocatalytic performance obtained on the composites were caused by the successful suppression of electron-hole recombination by the rGO on the TiO2.

Fluorescence analysis of NOM degradation by photocatalytic oxidation and its potential to mitigate membrane fouling in drinking water treatment.

PubMed

Nerger, Bryan A; Peiris, Ramila H; Moresoli, Christine

2015-10-01

This study examined the photocatalytic oxidation of natural organic matter (NOM) as a method to mitigate membrane fouling in drinking water treatment. ZnO and TiO2 photocatalysts were tested in concentrations ranging from 0.05 g L(-1) to 0.5 g L(-1). Fluorescence peaks were used as the primary method to characterize the degradation of three specific NOM components - fulvic acid-like humic substances, humic acid-like humic substances, and protein-like substances during photocatalytic oxidation. Fluorescence peaks and Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis indicated that higher NOM degradation was obtained by photocatalytic oxidation with ZnO than with TiO2. Treatment of the feed water by ZnO photocatalytic oxidation was successful in reducing considerably the extent of hydraulically reversible and irreversible membrane fouling during ultrafiltration (UF) compared to feed water treatment with TiO2. Fouling during UF of water subjected to photocatalytic oxidation appeared to be caused by low molecular weight constituents of NOM generated during photocatalytic oxidation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photocatalytic activity of nanostructured ZnO-ZrO2 binary oxide using fluorometric method

NASA Astrophysics Data System (ADS)

Ibrahim, M. M.

2015-06-01

Evaluation of the photocatalytic activity of ZnO-ZrO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, ZnO-ZrO2 mixed oxides coupled with various ZnO dosages (0, 10, 30, 50, 70 wt%) were prepared by impregnation method. These nanomaterials were characterized by studying their structural, surface and optical properties. The photocatalytic activity in term of quantitative determination of the active oxidative species (radOH) produced on the surface of binary oxide was evaluated using fluorescent probe method. The interaction between ZnO and ZrO2 was affected on the photocatalytic efficiency of mixture. The results show that, the addition of ZnO to ZrO2 decreased the electron-hole recombination and increased the rate of radOH radicals formation. 50 wt% ZnO-ZrO2 photocatalyst exhibited much higher photocatalytic activity. The profound effect of binary oxide catalyst was generally considered due to the high surface area, small particle size, high monoclinic phase of ZrO2 content, low band gap and the presence of surface OH groups.

Increased photocatalytic activity induced by TiO2/Pt/SnO2 heterostructured films

NASA Astrophysics Data System (ADS)

Testoni, Glaucio O.; Amoresi, Rafael A. C.; Lustosa, Glauco M. M. M.; Costa, João P. C.; Nogueira, Marcelo V.; Ruiz, Miguel; Zaghete, Maria A.; Perazolli, Leinig A.

2018-02-01

In this work, a high photocatalytic activity was attained by intercalating a Pt layer between SnO2 and TiO2 semiconductors, which yielded a TiO2/Pt/SnO2 - type heterostructure used in the discoloration of blue methylene (MB) solution. The porous films and platinum layer were obtained by electrophoretic deposition and DC Sputtering, respectively, and were both characterized morphologically and structurally by FE-SEM and XRD. The films with the Pt interlayer were evaluated by photocatalytic activity through exposure to UV light. An increase in efficiency of 22% was obtained for these films compared to those without platinum deposition. Studies on the reutilization of the films pointed out high efficiency and recovery of the photocatalyst, rendering the methodology favorable for the construction of fixed bed photocatalytic reactors. A proposal associated with the mechanism is discussed in this work in terms of the difference in Schottky barrier between the semiconductors and the electrons transfer and trapping cycle. These are fundamental factors for boosting photocatalytic efficiency.

Synthesis and characterization of TiO2/graphitic carbon nanocomposites with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Wanag, Agnieszka; Kusiak-Nejman, Ewelina; Kowalczyk, Łukasz; Kapica-Kozar, Joanna; Ohtani, Bunsho; Morawski, Antoni W.

2018-04-01

In this paper titanium dioxide carbon modification with benzene as a carbon source is presented. A TiO2/graphitic carbon nanocomposites were synthesized by thermal modification in the presence of benzene vapours at different temperature (300-700 °C). The new materials were characterized by a various techniques, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-vis/DR), surface-enhanced Raman spectroscopy. BET specific surface area was also measured. The photocatalytic activity of obtained nanocomposites was measured by the decomposition of acetic acid and methylene blue under UV-vis irradiation. The results show that photocatalytic activity increasing with increase in carbon concentration and temperature of modification. It can be noted that adsorption degree has a very high impact on methylene blue decomposition. The highest photocatalytic activity was found for the photocatalyst modified at 600 °C contains 1.13 wt% of carbon. It should be noted that, the influence of crystallite size, crystal structure changes and specific surface area for photocatalytic activity are presented.

Effect of Ag nanoparticles deposition on photocatalytic activity of Ag{sub 2}SO{sub 3}

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

Zhang, Xuan, E-mail: xzhang@dhu.edu.cn; Wang, Qi; Hu, Jin-Wen

Highlights: • Ag{sub 2}SO{sub 3} was developed as novel photocatalyst. • The effect of Ag nanoparticles deposition on photocatalytic activity was investigated. • The activation and deactivation mechanism was proposed. - Abstract: A novel photocatalyst Ag{sub 2}SO{sub 3} was prepared and the effect of Ag nanoparticles, photo-deposited on the surface of Ag{sub 2}SO{sub 3}, on its photocatalytic activity was investigated. The as-prepared photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflection spectroscopy (DRS). The photocatalytic activity was evaluated by photo-degradation of rhodamine B dye under UV light irradiation. It was found that the photocatalyticmore » activity of Ag{sub 2}SO{sub 3} was initially enhanced with deposition of Ag nanoparticles, but subsequently declined with Ag nanoparticles overloaded. The possible mechanism was proposed based on experimental results. These findings may contribute to developing novel photocatalysts and understanding of fundamentals of Ag-based photocatalytic materials.« less

A Gallium Oxide-Graphene Oxide Hybrid Composite for Enhanced Photocatalytic Reaction

PubMed Central

Kim, Seungdu; Han, Kook In; Lee, In Gyu; Park, Won Kyu; Yoon, Yeojoon; Yoo, Chan Sei; Yang, Woo Seok; Hwang, Wan Sik

2016-01-01

Hybrid composites (HCs) made up of gallium oxide (GaO) and graphene oxide (GO) were investigated with the intent of enhancing a photocatalytic reaction under ultraviolet (UV) radiation. The material properties of both GaO and GO were preserved, even after the formation of the HCs. The incorporation of the GO into the GaO significantly enhanced the photocatalytic reaction, as indicated by the amount of methylene blue (MB) degradation. The improvements in the reaction were discussed in terms of increased surface area and the retarded recombination of generated charged carriers. PMID:28335255

Black Hydroxylated Titanium Dioxide Prepared via Ultrasonication with Enhanced Photocatalytic Activity

PubMed Central

Fan, Chenyao; Chen, Chao; Wang, Jia; Fu, Xinxin; Ren, Zhimin; Qian, Guodong; Wang, Zhiyu

2015-01-01

The amorphous TiO2 derived from hydroxylation has become an effective approach for the enhancement of photocatalytic activity of TiO2 since a kind of special black TiO2 was prepared by engineering disordered layers on TiO2 nanocrystals via hydrogenation. In this contribution, we prepared totally amorphous TiO2 with various degrees of blackness by introducing hydroxyls via ultrasonic irradiation, through which can we remarkably enhance the photocatalytic activity of TiO2 with improved light harvesting and narrowed band gap. PMID:26133789

Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light

PubMed Central

2011-01-01

WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3. PMID:21774800

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.

The preparation and characterization of La doped TiO 2 nanoparticles and their photocatalytic activity

NASA Astrophysics Data System (ADS)

Liqiang, Jing; Xiaojun, Sun; Baifu, Xin; Baiqi, Wang; Weimin, Cai; Honggang, Fu

2004-10-01

In this paper, pure and La doped TiO2 nanoparticles with different La content were prepared by a sol-gel process using Ti (OC4H9)4 as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra. We mainly investigated the effects of calcining temperature and La content on the properties and the photocatalytic activity for degrading phenol of as-prepared TiO2 samples, and also discussed the relationships between PL spectra and photocatalytic activity as well as the mechanisms of La doping on TiO2 phase transformation. The results showed that La3+ did not enter into the crystal lattices of TiO2 and was uniformly dispersed onto TiO2 as the form of La2O3 particles with small size, which possibly made La dopant have a great inhibition on TiO2 phase transformation; La dopant did not give rise to a new PL signal, but it could improve the intensity of PL spectra with a appropriate La content, which was possibly attributed to the increase in the content of surface oxygen vacancies and defects after doping La; La doped TiO2 nanoparticles calcined at 600°C exhibited higher photocatalytic activity, indicating that 600°C was an appropriate calcination temperature. The order of photocatalytic activity of La doped TiO2 samples with different La content was as following: 1>1.5>3>0.5>5>0 mol%, which was the same as the order of their PL intensity, namely, the stronger the PL intensity, the higher the photocatalytic activity, demonstrating that there were certain relationships between PL spectra and photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing the photoinduced electrons during the process of photocatalytic reactions.

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

Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Xie, Yi; Heo, Sung Hwan; Yoo, Seung Hwa; Ali, Ghafar; Cho, Sung Oh

2010-03-01

A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV-visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.

Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

PubMed Central

2010-01-01

A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2. PMID:20671780

Fast photocatalytic degradation of methylene blue dye using a low-power diode laser.

PubMed

Liu, Xianhua; Yang, Yulou; Shi, Xiaoxuan; Li, Kexun

2015-01-01

This study focused on the application of diode lasers as alternative light sources for the fast photocatalytic degradation of methylene blue. The photocatalytic decomposition of methylene blue in aqueous solution under 443 nm laser light irradiation was found to be technically feasible using Ag/AgCl nanoparticles as photocatalysts. The effects of various experimental parameters, such as irradiation time, light source, catalyst loading, initial dye concentration, pH, and laser energy on decolorization and degradation were investigated. The mineralization of methylene blue was confirmed by chemical oxygen demand analysis. The results demonstrate that the laser-induced photocatalytic process can effectively degrade methylene blue under the optimum conditions (pH 9.63, 4 mg/L MB concentration, and 1.4 g/L Ag/AgCl nanoparticles). Copyright © 2014 Elsevier B.V. All rights reserved.

Measuring the Photocatalytic Breakdown of Crystal Violet Dye using a Light Emitting Diode Approach

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; Underwood, Lauren W.; O'Neal, Duane; Pagnutti, Mary; Davis, Bruce A.

2009-01-01

A simple method to estimate the photocatalytic reactivity performance of spray-on titanium dioxide coatings for transmissive glass surfaces was developed. This novel technique provides a standardized method to evaluate the efficiency of photocatalytic material systems over a variety of illumination levels. To date, photocatalysis assessments have generally been conducted using mercury black light lamps. Illumination levels for these types of lamps are difficult to vary, consequently limiting their use for assessing material performance under a diverse range of simulated environmental conditions. This new technique uses an ultraviolet (UV) gallium nitride (GaN) light emitting diode (LED) array instead of a traditional black light to initiate and sustain photocatalytic breakdown. This method was tested with a UV-resistant dye (crystal violet) applied to a titanium dioxide coated glass slide. Experimental control is accomplished by applying crystal violet to both titanium dioxide coated slides and uncoated control slides. A slide is illuminated by the UV LED array, at various light levels representative of outdoor and indoor conditions, from the dye side of the slide. To monitor degradation of the dye over time, a temperature-stabilized white light LED, whose emission spectrum overlaps with the dye absorption spectrum, is used to illuminate the opposite side of the slide. Using a spectrometer, the amount of light from the white light LED transmitted through the slide as the dye degrades is monitored as a function of wavelength and time and is subsequently analyzed. In this way, the rate of degradation for photocatalytically coated versus uncoated slide surfaces can be compared. Results demonstrate that the dye absorption decreased much more rapidly on the photocatalytically coated slides than on the control uncoated slides, and that dye degradation is dependent on illumination level. For photocatalytic activity assessment purposes, this experimental configuration and

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.

ZnO nanostructures with different morphology for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Peter, I. John; Praveen, E.; Vignesh, G.; Nithiananthi, P.

2017-12-01

ZnO nanomaterials of different morphologies have been synthesized and the effect of morphology on Photocatalytic activity on natural dye has been investigated. Crystalline size and lattice strain of the synthesized particles are determined by XRD analysis and Williamson-Hall (W-H) method respectively. All other important physical parameters such as strain, stress and energy density values are also calculated using W-H analysis using different models such as uniform deformation model, uniform deformation stress model and uniform deformation energy density model. A shift in the peak of FTIR spectrum of ZnO is observed due to morphology effects. The SEM analysis reveals that the synthesized ZnO nanoparticles appear as flake, rod and dot. ZnO quantum dot exhibits higher photocatalytic activity comparing to the other morphologies. Larger surface area, high adsorption rate, large charge separation and the slow recombination of electrons/holes in ZnO dots establish dots as favorable morphology for good photocatalysis. Among the three, ZnO quantum dot shows three-times enhancement in the kinetic rate constants of photocatalysis. The results confirm that availability of specific (active) surface area, photocatalytic potential and quantum confinement of photo-induced carriers differ with morphology.

TiO2-graphene oxide nanocomposite as advanced photocatalytic materials.

PubMed

Stengl, Václav; Bakardjieva, Snejana; Grygar, Tomáš Matys; Bludská, Jana; Kormunda, Martin

2013-02-27

Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer-Emmett-Teller surface area and Barrett-Joiner-Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light.

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.

TiO2-graphene oxide nanocomposite as advanced photocatalytic materials

PubMed Central

2013-01-01

Background Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. Results TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer–Emmett–Teller surface area and Barrett–Joiner–Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. Conclusions The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light. PMID:23445868

76 FR 66687 - Purified Carboxymethylcellulose From the Netherlands: Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-27

... antidumping duty administrative review of purified carboxymethylcellulose (CMC) from the Netherlands, covering...) (Preliminary Results). The merchandise covered by the order is purified CMC, as described in the ``Scope of the... duty order on purified CMC from the Netherlands. See Preliminary Results. The respondent under review...

High photocatalytic activity of mixed anatase-rutile phases on commercial TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ruu Siah, Wai; Lintang, Hendrik O.; Shamsuddin, Mustaffa; Yuliati, Leny

2016-02-01

Titanium dioxide (TiO2) is well-known as an active photocatalyst for degradation of various organic pollutants. Over the years, a wide range of TiO2 nanoparticles with different phase compositions, crystallinities, and surface areas have been developed. Due to the different methods and conditions used to synthesize these commercial TiO2 nanoparticles, the properties and photocatalytic performance would also be different from each other. In this study, the photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) was investigated on commercial Evonik P25, Evonik P90, Hombikat UV100 and Hombikat N100 TiO2 nanoparticles. Upon photocatalytic tests, it was found that overall, the photocatalytic activities of the P25 and the P90 were higher than the N100 and the UV100 for the removal of both 2,4-D and 2,4,5-T. The high activities of the P25 and the P90 could be attributed to their phase compositions, which are made up of a mixture of anatase and rutile phases of TiO2. Whereas, the UV100 and the N100 are made up of 100% anatase phase of TiO2. The synergistic effect of the anatase/rutile mixture was reported to slow down the recombination rate of photogenerated electron-hole pairs. Consequently, the photocatalytic activity was increased on these TiO2 nanoparticles.

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.

Photocatalytic degradation of pentachlorophenol in aqueous solution by visible light sensitive N-F-codoped TiO{sub 2} photocatalyst

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

Govindan, Kadarkarai, E-mail: govindanmu@gmail.com; Water Chemistry Lab, Water Institute, Karunya University, Coimbatore 641 114; Murugesan, Sepperumal

Graphical abstract: Schematic representation for the visible light photocatalytic process of N and F codoped TiO{sub 2}. Highlights: ► Visible light sensitive N-F-codoped TiO{sub 2}. ► Photocatalytic degradation of pentachlorophenol. ► Effect of oxidants on photocatalytic degradation of pentachlorophenol. ► PMS is a more efficient oxidant for the photodegradation of PCP. - Abstract: In this present study, N-F-codoped titanium dioxide nanocatalyst (NFTO) has been synthesized by simple sol–gel assisted solvothermal method for the effective utilization of visible light in photocatalytic reactions. Structural characterization of the photocatalyst is analyzed by XRD, UV–vis diffuse reflectance spectra (DRS), SEM and TEM. Moreover themore » chemical statuses of NFTO are gathered by X-ray photoelectron spectroscopy (XPS). The results show that a high surface area with photoactive anatase phase crystalline is obtained. In addition, nitrogen and fluorine atoms are doped into TiO{sub 2} crystal lattice to extend the visible light absorption and higher photocatalytic activity. The photocatalytic degradation of pentachlorophenol in aqueous solution is examined under visible light irradiation, the addition of oxidants such as PMS, PDS and H{sub 2}O{sub 2} is analyzed in detail. The rate of photocatalytic degradation of pentachlorophenol is obtained in the following order: PMS > PDS > H{sub 2}O{sub 2}.« less

Black phosphorus quantum dots/attapulgite nanocomposite with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Li, Xiazhang; Li, Feihong; Lu, Xiaowang; Zuo, Shixiang; Zhuang, Ziheng; Yao, Chao

Novel black phosphorus quantum dots/attapulgite (BPQDs/ATP) nanocomposites were prepared via a facile hydrothermal-deposition method. TEM showed that BPQDs dispersed evenly on the surface of ATP with uniform particle size about 5nm. UV-Vis revealed that the BPQDs/ATP composite showed wider visible light absorption range as compared with pure ATP. The photocatalytic activity was evaluated by degradation of bisphenol A (BPA). Results showed that BPQDs/ATP reached 90% degradation rate under solar light irradiation for 180min. The coherent heterostructure formed by BPQDs and ATP was responsible for the enhanced photocatalytic performance, due to the sensitization effect of BPQDs and the facilitation of charges separation.

Iron-based catalysts for photocatalytic ozonation of some emerging pollutants of wastewater.

PubMed

Espejo, Azahara; Beltrán, Fernando J; Rivas, Francisco J; García-Araya, Juan F; Gimeno, Olga

2015-01-01

A synthetic secondary effluent containing an aqueous mixture of emerging contaminants (ECs) has been treated by photocatalytic ozonation using Fe(3+) or Fe3O4 as catalysts and black light lamps as the radiation source. For comparative purposes, ECs have also been treated by ultraviolet radiation (UVA radiation, black light) and ozonation (pH 3 and 7). With the exception of UVA radiation, O3-based processes lead to the total removal of ECs in the mixture. The time taken to achieve complete degradation depends on the oxidation process applied. Ozonation at pH 3 is the most effective technique. The addition of iron based catalysts results in a slight inhibition of the parent compounds degradation rate. However, a positive effect is experienced when measuring the total organic carbon (TOC) and the chemical oxygen demand (COD) removals. Photocatalytic oxidation in the presence of Fe(3+) leads to 81% and 88% of TOC and COD elimination, respectively, compared to only 23% and 29% of TOC and COD removals achieved by single ozonation. The RCT concept has been used to predict the theoretical ECs profiles in the homogeneous photocatalytic oxidation process studied. Treated wastewater effluent was toxic to Daphnia magna when Fe(3+) was used in photocatalytic ozonation. In this case, toxicity was likely due to the ferryoxalate formed in the process. Single ozonation significantly reduced the toxicity of the treated wastewater.

Combination of photocatalytic and membrane distillation hybrid processes for reactive dyes treatment.

PubMed

Yatmaz, H Cengiz; Dizge, Nadir; Kurt, Merve Sezen

2017-11-01

In this study, the degradation of azo dye solutions (Reactive Red 180 and Reactive Orange 16) of textile industry wastewater was investigated for using innovative hybrid process of photocatalytic and membrane distillation (MD) processes. Photocatalytic oxidation was conducted with semiconductor catalysts (ZnO and TiO2) and their mixture under UVA and UVC irradiation. More effective results were obtained under UVA at the initial stages of the reactions for both dye solutions. ZnO and TiO2 catalysts have given similar efficient results, but results with ZnO were better at initial stages. For the next stage, hybrid design of MD and photocatalytic processes was performed sequentially. Initially, the photocatalytic process was conducted for at least 1 h at initial values of 100 mg/L RR-180 dye solutions and 1 g/L ZnO catalyst loading under UVA irradiation and then treated solution was run through the distillation module at different temperatures (30°C and 40°C) and flow rates (210, 425, and 665 mL/min). Three types of membranes (polypropylene, polytetrafluoroethylene, and polyvinylidene fluoride) with different pore sizes (0.45 and 0.22 μm) were used in the module. Increasing temperature on the side of treated solution and decreasing the temperature on the other side has increased the distillate efficiency.

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.

75 FR 57815 - Purified Carboxymethylcellulose From Finland, Mexico, Netherlands, and Sweden

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-22

... INTERNATIONAL TRADE COMMISSION [Investigations Nos. 731-TA-1084-1087 (Review)] Purified Carboxymethylcellulose From Finland, Mexico, Netherlands, and Sweden AGENCY: United States International Trade Commission. ACTION: Scheduling of full five-year reviews concerning the antidumping duty orders on purified...

Near-infrared light controlled photocatalytic activity of carbon quantum dots for highly selective oxidation reaction

NASA Astrophysics Data System (ADS)

Li, Haitao; Liu, Ruihua; Lian, Suoyuan; Liu, Yang; Huang, Hui; Kang, Zhenhui

2013-03-01

Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize the transformation from benzyl alcohol to benzaldehyde with high selectivity (100%) and conversion (92%) under NIR light irradiation. HO&z.rad; is the main active oxygen specie in benzyl alcohol selective oxidative reaction confirmed by terephthalic acid photoluminescence probing assay (TA-PL), selecting toluene as the substrate. Such metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes with high conversion, demonstrating a potential application of accessing traditional alcohol oxidation chemistry.Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize

Photocatalytic degradation of organic dyes by a stable and biocompatible Zn(II) MOF having ferulic acid: Experimental findings and theoretical correlation

NASA Astrophysics Data System (ADS)

Zhou, En-Hong; Li, Bao-Hong; Chen, Wei-Xin; Luo, Zhidong; Liu, Jianqiang; Singh, Amita; Kumar, Abhinav; Jin, Jun-Cheng

2017-12-01

The photocatalytic properties of d10-based metal-organic frameworks (MOFs) have been developed as a potential technology in the photo-degradation of organic dyes. Herein, a biocompatible metal-organic framework (MOF) {[Zn2(fer)2]•0.5H2O}n (1) (fer = ferulic acid) has been selected which shows photocatalytic activity for the degradation of methyl violet (MV) and Rhodamine B (Rh B) in aqueous solution under UV irradiation. The photocatalytic results indicated the 1 exhibit 88% photocatalytic efficiency against Rh B in 100 min, while its against MV was only 54% under the identical experimental conditions. Moreover, a possible mechanism for the photocatalytic activity has proposed by density of states (DOS) calculations.

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

Manifestation of weak ferromagnetism and photocatalytic activity in bismuth ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Sakar, M.; Balakumar, S.; Saravanan, P.; Jaisankar, S. N.

2013-02-01

Bismuth ferrite (BFO) nanoparticles were synthesized by auto-ignition technique with and without adding ignition fuel such as citric acid. The presence of citric acid in the reaction mixture yielded highly-magnetic BFO/γ-Fe2O3 nanocomposite. When this composite was annealed to 650°C, a single phase BFO was formed with average crystallite size of 50 nm and showed weak ferromagnetic behavior. Conversely, the phase pure BFO prepared without adding citric acid exhibited antiferromagnetism because of its larger crystallite size of around 70 nm. The visible-light driven photocatalytic activity of both the pure BFO and BFO/γ-Fe2O3 nanocomposite were examined by degrading methyl orange dye. The pure BFO showed a moderate photocatalytic activity; while BFO/γ-Fe2O3 nanocomposite showed enhanced activity. This could be probably due to the optimal band gap ratio between BFO and γ-Fe2O3 phases reduced the recombination of electron-hole pairs which aided in the enhancement of photocatalytic activity.

Photocatalytic Coatings for Exploration and Spaceport Design

NASA Technical Reports Server (NTRS)

2008-01-01

This project developed self-cleaning photocatalytic coatings that remove contamination without human intervention. The coatings chemically remove organic contaminants and leave no residue. The photocatalyst will not negatively affect other coating properties, especially corrosion resistance. Titanium dioxide, TiO2, is an extremely popular photocatalyst because of its chemical stability, nontoxicity, and low cost. TiO2 is commonly used in the photocatalytic oxidation of organic matter or pollutants in the gas and liquid phases. However, TiO2 does have some drawbacks. It has limited light absorption because of its large band-gap and suffers from a photonic efficiency of less than 10 percent for organic degradation. Dopants can lower the band-gap and improve efficiency. Since the photocatalytically active form of TiO2 is a nanocrystalline powder, it can be difficult to make a robust coating with enough catalyst loading to be effective. Photocatalysts become active when certain light energy is absorbed. When photons with an energy greater than the band-gap, Eg, (wavelengths shorter than 400 nm) impinge upon the surface of the TiO2, an electron-hole pair is formed. The electron-hole pair oxidizes adsorbed substances either directly or via reactive intermediates that form on the surface, such as hydroxyl radicals (OH) or superoxide ions (O2-). Several factors can influence the band-gap energy of TiO2, two of which are crystal structure and impurities. TiO2 exists as three crystal structures brookite, anatase, and rutile that can be controlled via heat treatment. Anatase is the most photocatalytically active crystal form of TiO2. Doping TiO2 with impurities can alter its band-gap energy, as well as its effectiveness as a catalyst. Depending on their size, dopant atoms can occupy either the substitutional or interstitial lattice positions. Atoms that are relatively large will assume the interstitial positions and create a much greater energy disturbance in the crystal than

First-principles investigation on the mechanism of photocatalytic properties for cubic and orthorhombic KNbO3

NASA Astrophysics Data System (ADS)

Xu, Yong-Qiang; Wu, Shao-Yi; Ding, Chang-Chun; Wu, Li-Na; Zhang, Gao-Jun

2018-03-01

The geometric structures, band structures, density of states and optical absorption spectra are studied for cubic and orthorhombic KNbO3 (C- and O-KNO) crystals by using first-principles calculations. Based on the above calculation results, the mechanisms of photocatalytic properties for both crystals are further theoretically investigated to deepen the understandings of their photocatalytic activity from the electronic level. Calculations for the effective masses of electron and hole are carried out to make comparison in photocatalytic performance between cubic and orthorhombic phases. Optical absorption in cubic phase is found to be stronger than that in orthorhombic phase. C-KNO has smaller electron effective mass, higher mobility of photogenerated electrons, lower electron-hole recombination rate and better light absorption capacity than O-KNO. So, the photocatalytic activity of cubic phase can be higher than orthorhombic one. The present work may be beneficial to explore the series of perovskite photocatalysts.

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.

Reusable photocatalytic titanium dioxide-cellulose nanofiber films

Treesearch

Alexandra Snyder; Zhenyu Bo; Robert Moon; Jean-Christophe Rochet; Lia Stanciu

2013-01-01

Titanium dioxide (TiO2) is a well-studied photocatalyst that is known to break down organic molecules upon ultraviolet (UV) irradiation. Cellulose nanofibers (CNFs) act as an attractive matrix material for the suspension of photocatalytic particles due to their desirable mechanical and optical properties. In this work, TiO2...

Bacterial disinfection in a sunlight/visible-light-driven photocatalytic reactor by recyclable natural magnetic sphalerite.

PubMed

Peng, Xingxing; Ng, Tsz Wai; Huang, Guocheng; Wang, Wanjun; An, Taicheng; Wong, Po Keung

2017-01-01

A 5-L reactor was designed and used to enhance the sunlight/visible-light-driven (VLD) photocatalytic disinfection efficiency towards Gram-negative bacterium (Escherichia coli). Natural magnetic sphalerite (NMS) was used as the photocatalyst, which could be easily recycled by applying a magnetic field. Results showed that NMS with irradiation by the blue light emitting diode (LED) lamp could completely inactivate 1.5 × 10 5  cfu/mL of E. coli within 120 min in the first three runs. However, the inactivation efficiency of E. coli started to decrease in the 4th Run, while in the 5th run, the E. coli with the initial concentration of 5 logs was inactivated to 3.3 (blue-light) and 3.5 logs (sunlight), respectively. Moreover, the stability and deactivation mechanism of NMS during subsequent runs were also studied. The results showed that the decline of the photocatalytic activity was possibly attributed to adsorption of the bacterial decomposed compounds on the active sites. In addition, photocatalytic bactericidal mechanism of the NMS in the photocatalytic system was investigated by using multiple scavengers to remove the specific reactive species. Moreover, various Gram-positive bacteria including Staphylococcus aureus, Microbacterium barkeri, and Bacillus subtilis could also be efficiently inactivated in the photocatalytic system. Copyright © 2016 Elsevier Ltd. All rights reserved.

Room temperature synthesis and enhanced photocatalytic property of CeO2/ZnO heterostructures

NASA Astrophysics Data System (ADS)

Wang, Chao; Fan, Huiqing; Ren, Xiaohu; Fang, Jiawen

2018-02-01

To achieve better photocatalytic performance, we proposed a facile solid-state reaction method to produce CeO2/ZnO heterostructures. Ceria and zinc oxide were synthesized simultaneously by thoroughly grinding the mixture of zinc acetate dihydrate, cerium nitrate hexahydrate and sodium hydroxide. The morphology of the as-prepared heterostructures varies dramatically as different amount of ceria was introduced in the composition. The photocatalytic performance of CeO2/ZnO heterojunctions was 4.6 times higher than that of pure ZnO. The enhanced photocatalytic activity could be ascribed to that more electrons and holes could transport to the surface of catalysts and react with the pollution due to the extended light-responsive range, accelerated migration, increased specific surface area and suppressed recombination of photogenerated carriers.

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

Preparation of flower-like TiO{sub 2} sphere/reduced graphene oxide composites for photocatalytic degradation of organic pollutants

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

Kim, Tae-Woong; Park, Mira; Kim, Hak Yong

In this study, novel flower-like TiO{sub 2} sphere (FTS)/reduced graphene oxide (rGO) composites (FTS-G) were synthesized via a hydrothermal method. The photocatalytic performance of the FTS-G composites was evaluated through the photodegradation of rhodamine B (Rh B) and trichloroethylene (TCE) under simulated solar light irradiation. The rGO to FTS ratio in the composites significantly affected photocatalytic activity. The photocatalytic activities of FTS-Gs in the degradation of Rh B and TCE were superior to that of pure FTS. Of all the FTS-G composites tested, FTS-G with 1 wt% rGO (FTS-G-1) had the greatest photocatalytic activity, while FTS-G composites with rGO contentsmore » over 1 wt% had lower photocatalytic activities. Additionally, it is expected that the synthesis of FTS with a high specific surface area and well-developed pore structure and simultaneous conversion of GO to graphene-like rGO without the use of strong reducing agents could be a promising strategy to prepare other carbon-based flower-like TiO{sub 2} sphere composite photocatalysts. - Graphical abstract: Schematic illustration of high photocatalytic activity for FTS-G composites. Display Omitted.« less

Microwave synthesis and photocatalytic activities of ZnO bipods with different aspect ratios

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

Sun, Fazhe; Zhao, Zengdian; Qiao, Xueliang, E-mail: xuelqiao@163.com

2016-02-15

Highlights: • We synthesized linked ZnO nanorods by a facile microwave method. • The effect of reaction parameters on ZnO was investigated. • ZnO bipods with different aspect ratios were prepared. • The photocatalytic performance of ZnO bipods was evaluated. - Abstract: Linked ZnO nanorods have been successfully prepared via a facile microwave method without any post-synthesis treatment. The X-ray diffraction (XRD) patterns indicated the precursor had completely transformed into the pure ZnO crystal. The images of field emitting scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that linked ZnO nanorods consisted predominantly of ZnO bipods. The formationmore » process of the ZnO bipods was clearly discussed. ZnO bipods with different aspect ratios have been obtained by tuning the concentrations of reagents and microwave power. Moreover, the photocatalytic performance of ZnO bipods with different aspect ratios for degradation of methylene blue was systematically evaluated. The results of photocatalytic experiments showed that the photocatalytic activity increased with the aspect ratios of ZnO bipods increased. The reason is that ZnO bipods with larger aspect ratio have higher surface area, which can absorb more MB molecules to react with ·OH radicals.« less

Gold-plasmon enhanced photocatalytic performance of anatase titania nanotubes under visible-light irradiation

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

Yang, Bingyang; He, Dawei, E-mail: dwhe@bjtu.edu.cn; Wang, Wenshuo

2016-02-15

Highlights: • APTMS/(TNTs-Au) was synthesized using a deposition-precipitation process. • APTMS/(TNTs-Au) showed superior visible light activity for the degradation of methylene blue. • The electromagnetic field distribution at the interface between TNTs and Au NPs were estimated by the 3D finite-difference time domain simulation. • The working mechanism of the photocatalytic activity of APTMS/(TNTs-Au) was illustrated. - Abstract: [3-Aminopropyl]trimethoxysilane-modified titania nanotubes decorated with Au nanoparticles (APTMS/(TNTs-Au)) nanocomposites were synthesized using a deposition-precipitation process. The results showed that Au nanoparticles (NPs) in the metallic state were firmly adhered to the surface of the anatase TNTs. APTMS/(TNTs-Au) exhibited great photocatalytic activities whichmore » were evaluated from the degradation rate of methylene blue aqueous solution under visible light irradiation. 3D finite-difference time domain simulation was performed to estimate the electromagnetic field distribution at the interface between TNTs and Au NPs. The visible photocatalytic activity of APTMS/(TNTs-Au) was largely attributed to the surface plasmon absorption of metallic Au NPs, which generated and transferred hot electrons to the CB of TNTs. In addition, the hot electrons on the surface of TNTs also suppressed the radiative electron–hole recombination and consequently enhanced the photocatalytic activity.« less

Synthesis, photoelectrochemical properties and solar light-induced photocatalytic activity of bismuth ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Pattnaik, Sambhu Prasad; Behera, Arjun; Martha, Satyabadi; Acharya, Rashmi; Parida, Kulamani

2018-01-01

Bismuth ferrite (BFO) nanoparticles prepared by solid state reaction route were characterized by various characterization techniques such as XRD, FESEM, HRTEM, UV-Vis DRS, PL etc., and their photocatalytic activities were evaluated by decolorization of aqueous solution of Congo red (CR) under solar light. The photocatalytic activity of BFO was increased by increasing the preparation temperature from 350 to 500 °C and then decreased with rise in temperature. The results of electrochemical measurements such as linear sweep voltammetry (LSV), electrochemical impedence (EIS), and Mott-Schottky analysis of BFO nanoparticles corroborated the findings of their photocatalytic activity. The enhanced photocatalytic response of the sample prepared at 500 °C is attributed to its smallest band gap, minimum crystallite size (30 nm), efficient separation, and lowest possible recombination of photo-generated charge carriers. The effects of amount of nano-BFO, irradiation time, initial CR concentration, and BFO calcination temperature on the decolorization of CR were examined. It was observed that 1 g/L nano-BFO calcined at 500 °C can decolorize up to 77% a 10-ppm CR dye solution under solar irradiation for 60 min. The studies included scavenger tests for identification of reactive species and a possible mechanism of dye decolorization.

Characterization of Purified Staphylococcal Lipase1

PubMed Central

Vadehra, D. V.; Harmon, L. G.

1967-01-01

Purified staphylococcal lipase had an optimal pH of 8.3 for activity at 37 C, and an optimal temperature of 45 C at pH 8.0. During storage, the enzyme lost less than 10% of the activity over a period of 21 days at 4 and -23 C. The enzyme retained 93% of the activity when heated for 30 min at 50 C and was 95% destroyed in 30 min at 70 C. The purified lipase was capable of hydrolyzing a variety of natural fats and oils. However, the enzyme was three times more active on nonhydrogenated soybean oil than on hydrogenated soybean oil with an iodine value of <3.0. The enzyme was also capable of hydrolyzing fatty acids on the α, β, and α′ positions of a synthetic mixed triglyceride. In general, the presence of oxidizing agents increased the activity and the presence of reducing agents decreased the activity of the lipase enzyme. PMID:6035042

Solvothermal-induced phase transition and visible photocatalytic activity of nitrogen-doped titania.

PubMed

Liu, Jianjun; Qin, Wei; Zuo, Shengli; Yu, Yingchun; Hao, Zhengping

2009-04-15

Nitrogen-doped titania nanoparticles consisting of pure anatase, pure rutile and bicrystallites (anatase+rutile and anatase+brookite) have been prepared in TiCl(3)-HMT (hexamethylene tetramine)-alcohol solution under solvothermal process. The effect of the solvent type and amount of HMT as pH adjuster on the phase composition of titania and its visible photocatalytic activity for degradation to MO (methyl orange) was investigated. It is found that anatase gradually transferred to rutile with increase of carbon chain using methanol, ethanol, 1-propanol and 1-butanol as solvent. The pure anatase formed at the pH value of 1-2, while bicrystalline titania (anatase+rutile and anatase+brookite) at that of 7-10 in the presence of methanol. The bicrystalline (anatase+brookite) titania have the best visible photocatalytic activity among all the samples. The -(NO) and -(NH) dopants with an N (1s) binding energy of 400 eV may have positive effects on the visible light photocatalytic activity.

Synthesis and visible light photocatalytic properties of iron oxide–silver orthophosphate composites

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

Febiyanto,; Eliani, Irma Vania; Riapanitra, Anung

2016-04-19

The iron oxide-silver orthophosphate composites were successfully synthesized by co-precipitation method using Fe(NO{sub 3}){sub 3}.9H{sub 2}O, AgNO{sub 3}, and Na{sub 2}HPO{sub 4}.12 H{sub 2}O, followed by calcination at 500°C for 5 hours. The Fe/Ag mole ratios of iron oxide-silver orthophosphate composites were designed at 0, 0.1, 0.2, 0.3 and 0.4. The samples were characterized using X-ray Diffraction, Diffuse Reflectance Spectroscopy, Scanning Electron Microscopy and Specific Surface Area. The photocatalytic activities were evaluated using Rhodamine B degradation under visible light irradiation. The iron oxide-silver orthophosphate composite with the Fe/Ag mole ratio of 0.2 exhibited higher photocatalytic activity compared to the puremore » Ag{sub 3}PO{sub 4} under visible light irradiation. The enhanced photocatalytic activity could be attributed to the effective separation of hole (+) and electron pairs in the iron oxide-silver orthophosphate composite.« less

Multi-branched Cu2O nanowires for photocatalytic degradation of methyl orange

NASA Astrophysics Data System (ADS)

Yu, Chunxin; Shu, Yun; Zhou, Xiaowei; Ren, Yang; Liu, Zhu

2018-03-01

Multi-branched cuprous oxide nanowires (Cu2O NWs) were prepared by one-step hydrothermal method of a facile process. The architecture of these Cu2O NWs was examined by scanning electron microscopy, and the resulting crystal nanowire consists of the trunk growing along [100] plane and the branch growing along [110] plane. Photocatalytic degradation of methyl orange (MO) in the experiment indicates that pure Cu2O NWs prepared at 150 °C have a higher photocatalytic activity (90% MO were degraded within 20 min without the presence of H2O2) compared with the samples obtained at other temperatures. In the photoelectrochemical test, pure Cu2O NWs had outstanding photoelectric response, which corresponds to the catalytic performance. The superior photocatalytic performance can be attributed to the absence of grain boundaries between the small branches and the nanowire trunk, which is conducive to the transport of photo-generated carriers, and the reduction of Cu impurities to reduce the number of recombination centers.

New Method Developed To Purify Single Wall Carbon Nanotubes for Aerospace Applications

NASA Technical Reports Server (NTRS)

Lebron, Marisabel; Meador, Michael A.

2003-01-01

their stability significantly. The onset of decomposition of the purified nanotubes (determined by thermal gravimetric analysis in air) is more than 300 C higher than that of the crude nanotubes. Transmission electron microscopy analysis of nanotubes purified by this method reveals near complete removal of iron catalyst particles. Analysis of the nanotubes using inductively coupled plasma spectroscopy revealed that the iron content of the nanotubes was reduced from 22.7 wt% in the crude nanotubes to less than 0.02 wt%. X-ray photoelectron spectroscopy revealed a decrease in iron content after purification as well as an increase in oxygen content due to the formation of carboxylic acid groups on the surface of the nanotubes. Nanotubes purified by this improved method can be readily dispersed in common organic solvents, in particular N,N-dimethylformamide, using prolonged ultrasonic treatment. These dispersions can then be used to incorporate single wall carbon nanotubes into polymer films.

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.

Study of the Photocatalytic Property of Polysulfone Membrane Incorporating TiO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Xingxing; Zhou, Weiqi; Chen, Zhe; Yao, Lei

In order to investigate the effect of the incorporated nanoparticles on the photocatalytic property of the hybrid membranes, the uncovered and covered polysulfone/TiO2 hybrid membranes were prepared. Positron annihilation γ-ray spectroscopy coupled with a positron beam was utilized to examine the depth profiles of the two membranes. The photocatalytic activities of the membranes were evaluated by the degradation of Rhodamine B (RhB) aqueous solution under the irradiation of Xe lamp. UV-Vis spectroscopy was applied to study the UV transmission through the polysulfone layer. Electrochemical impedance spectroscopy was used to detect the photo-generated charges by the covered membrane during the irradiation. It can be found that UV light can penetrate through the covered layer (about 230nm), and the incorporated nanoparticles can still generate charges under irradiation, which endows the photocatalytic ability of the covered membrane.

Plasma flame for mass purification of contaminated air with chemical and biological warfare agents

NASA Astrophysics Data System (ADS)

Uhm, Han S.; Shin, Dong H.; Hong, Yong C.

2006-09-01

An elimination of airborne simulated chemical and biological warfare agents was carried out by making use of a plasma flame made of atmospheric plasma and a fuel-burning flame, which can purify the interior air of a large volume in isolated spaces such as buildings, public transportation systems, and military vehicles. The plasma flame generator consists of a microwave plasma torch connected in series to a fuel injector and a reaction chamber. For example, a reaction chamber, with the dimensions of a 22cm diameter and 30cm length, purifies an airflow rate of 5000lpm contaminated with toluene (the simulated chemical agent) and soot from a diesel engine (the simulated aerosol for biological agents). Large volumes of purification by the plasma flame will free mankind from the threat of airborne warfare agents. The plasma flame may also effectively purify air that is contaminated with volatile organic compounds, in addition to eliminating soot from diesel engines as an environmental application.

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.

Facile preparation of well-combined lignin-based carbon/ZnO hybrid composite with excellent photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Huan; Qiu, Xueqing; Liu, Weifeng; Yang, Dongjie

2017-12-01

In this work, a novel lignin-based carbon/ZnO (LC/ZnO) hybrid composite with excellent photocatalytic performance was prepared through a convenient and environment friendly method using alkali lignin (AL) as carbon source. The morphological, microstructure and optical properties of the as-prepared LC/ZnO hybrid composite was characterized with scanning electron microscope (SEM), X-ray diffraction (XRD), Raman and UV-vis. The resulting LC/ZnO hybrid is composed of highly dispersed ZnO nanoparticles embedded on a lignin-based carbon nanosheet, showing excellent photogenerated electrons and holes separation and migration efficiency. The photocatalytic activity of LC/ZnO was much higher than the pure ZnO. The LC/ZnO hybrid composite showed different photocatalytic mechanism for degradation of negative methyl orange (MO) and positive Rhodamine B (RhB). It showed that h+ was the main photocatalytic active group during the degradation of MO, ·O2- and ·OH were the photocatalytic active groups during degradation of RhB. This reported photocatalyst with selective degradation of positive and negative organic dyes may have a great application prospect for photoelectric conversion and catalytic materials. Results of this work were of practical importance for high-valued utilization of lignin for carbon materials.

Facile synthesis and photocatalytic activity of ZnO/zinc titanate core-shell nanorod arrays

NASA Astrophysics Data System (ADS)

He, Ding-Chao; Fu, Qiu-Ming; Ma, Zhi-Bin; Zhao, Hong-Yang; Tu, Ya-Fang; Tian, Yu; Zhou, Di; Zheng, Guang; Lu, Hong-Bing

2018-02-01

ZnO/zinc titanate core-shell nanorod arrays (CSNRs) were successfully prepared via a simple synthesis process by combining hydrothermal synthesis and liquid phase deposition (LPD). The surface morphologies, crystalline characteristics, optical properties and surface electronic states of the ZnO/zinc titanate CSNRs were characterized by scanning electron microscope, transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy, PL and ultraviolet (UV)-visible absorption spectra. By controlling the reaction time of LPD, the shell thickness could vary with the reaction time. Furthermore, the impacts of the reaction time and post-annealing temperature on the crystalline structure and chemical composition of the CSNRs were also investigated. The studies of photocatalytic activity under UV light irradiation revealed that the ZnO/zinc titanate CSNRs annealed at 700 °C with 30 min deposition exhibited the best photocatalytic activity and good stability for degradation of methylene blue. It had been found that the effective separation of photogenerated electron-hole pairs in the CSNRs led to the enhanced photocatalytic activity. Moreover, the ZnO/zinc titanate CSNRs grown on quartz glass substrate could be easily recycled for reuse with almost unchanged photocatalytic activity.

Visible-light-driven Bi 2 O 3 /WO 3 composites with enhanced photocatalytic activity

DOE PAGES

Adhikari, Shiba P.; Dean, Hunter; Hood, Zachary D.; ...

2015-10-19

Semiconductor heterojunctions (composites) have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from electron–hole recombination and narrow photo-response range. We prepared a novel visible-light-driven Bi 2O 3/WO 3 composite photocatalyst by hydrothermal synthesis. The composite was characterized by scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy (EIS) to better understand the structures, compositions, morphologies and optical properties. Bi 2O 3/WO 3 heterojunction was found to exhibit significantly higher photocatalyticmore » activity towards the decomposition of Rhodamine B (RhB) and 4-nitroaniline (4-NA) under visible light irradiation compared to that of Bi 2O 3 and WO 3. A tentative mechanism for the enhanced photocatalytic activity of the heterostructured composite is discussed based on observed activity, band position calculations, photoluminescence, and electrochemical impedance data. Our study provides a new strategy for the design of composite materials with enhanced visible light photocatalytic performance.« less

Sandwiched ZnO@Au@CdS nanorod arrays with enhanced visible-light-driven photocatalytical performance

NASA Astrophysics Data System (ADS)

Ren, Shoutian; Wang, Yingying; Fan, Guanghua; Gao, Renxi; Liu, Wenjun

2017-11-01

The development of high-performance photocatalysts is central to efforts focused on taking advantage of solar energy to overcome environmental and energy crises. Integrating different functional materials artfully into nanostructures can deliver more efficient photocatalytic activity. Here, sandwiched ZnO@Au@CdS nanorod films were synthesized via successive ZnO nanorod electrodeposition, Au sputtering and CdS electrodeposition. The as-synthesized composites were characterized by UV-vis spectrophotometer, x-ray diffractometer, scanning and transmission electron microscopy. Their photocatalytic activity was assessed by degrading Rhodamine B solution under visible light irradiation. ZnO@Au@CdS exhibited better photocatalytic performance than ZnO@CdS throughout the visible light region, and the corresponding enhancement factor of Au nanoparticles was measured as a function of CdS loading amount, and it could reach 190% with CdS deposition for 1 min. The normalized rate constant could reach 0.387 h-1 for ZnO@Au@CdS-1min, which was equivalent to or better than results in reference photocatalysts. The enhancement mechanism of Au nanoparticles was estimated by comparing the monochromatic photocatalytic action spectra with the absorption spectrum of ZnO@Au@CdS, and it was mainly determined by incident photon energy. With selective excitation of Au nanoparticles by incident photons, the excited hot electrons in Au NPs are transferred to the conduction band of ZnO to boost photocatalytic reaction. With selective excitation of CdS, the enhanced interband absorption of CdS and relay station effect of Au nanoparticles should be responsible for the enhanced photocatalytic performance. Our work not only opens the door to the design of efficient supported photocatalysts, but also helps to understand the enhancement mechanism of LSPR effect on the photoelectric conversion of semiconductors.

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).

Three-dimensional hollow graphene efficiently promotes electron transfer of Ag3PO4 for photocatalytically eliminating phenol

NASA Astrophysics Data System (ADS)

Song, Shaoqing; Meng, Aiyun; Jiang, Shujuan; Cheng, Bei

2018-06-01

The effective transport of photo-induced carriers over semiconductor photocatalyst is critical for enhancing the photocatalytic performance under light excitation. Although oxidized graphene (GO) and/or reduced graphene oxide (rGO) has been used as cocatalyst to promote the transfer and utilization of electrons, however, random diffusion and transfer of photo-induced charges are inevitable from all sides over these actual graphene owing to the limitation of the preparation process and theory. Herein, we utilized three-dimensional hollow carbon graphene (HCG) to promote the efficient electron transfer of Ag3PO4 in the photocatalytic process. Owing to the confinement-induced electron field of HCG, the constructed HCG-Ag3PO4 photocatalytic system demonstrated the enhanced visible-light adsorption, improved transfer of photo-induced charges, and suitable redox potentials as revealed by transient photo-current spectroscopic, surface photovoltage spectroscopy, and electron paramagnetic resonance (EPR). EPR spectra of oxygen species and gas chromatography-mass spectra exhibited high efficiency activity over HCG-Ag3PO4 with Z-scheme photocatalytic mechanism for phenol decomposition by reaction between hexanoic acid and radOH and radO2-. It is noteworthy that photocatalytic performance over optimal HCG-Ag3PO4 is 6, 3.43, 1.92 times of pristine Ag3PO4, GO-Ag3PO4, and rGO-Ag3PO4, respectively. The results may supply a novel perspective to enhance transfer of photo-induced charges for the promotion of photocatalytic technology.

Engineering of solar photocatalytic detoxification and disinfection process

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

Goswami, D.Y.

1995-12-31

Use of solar radiation for photocatalytic detoxification and disinfection is a very fascinating and fast-developing area. Although scientific research on these processes, especially photocatalytic oxidation, has been conducted for at least the last three decades, the development of industrial/commercial applications, engineering systems and engineering design methodologies have occurred only recently. A number of reactor concepts and designs, including concentrating and non-concentrating types and various methods of catalyst deployment have been developed. Some of these reactors have been used in field demonstrations of groundwater and wastewater remediation. Recent research has been focused on improvements of catalysts to increase the reaction rates,more » as well as finding new applications of the process. This paper reviews the latest developments of solar detoxification and disinfection including catalyst development, industrial/commercial applications, reactor design and engineering system design methodologies. 80 refs., 20 figs., 3 tabs.« less

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.

Tuning the morphology, stability and photocatalytic activity of TiO{sub 2} nanocrystal colloids by tungsten doping

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

Xu, Haiping; Liao, Jianhua; School of Pharmaceutical Sciences, Gannan Medical University, Ganzhou, Jiangxi 341000

2014-03-01

Graphical abstract: - Highlights: • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids were prepared by hydrothermal methods. • The properties of TiO{sub 2} nanocrystal colloids can be tuned by tungsten doping. • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids show higher stability and dispersity. • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids show higher photocatalytic activity. - Abstract: The effects of tungsten doping on the morphology, stability and photocatalytic activity of TiO{sub 2} nanocrystal colloids were investigated. The nanostructure, chemical state of Ti, W, O, and the properties of tungsten doped TiO{sub 2} samples were investigated carefully by TEM, XRD, XPS, UV–vis, PLmore » and photocatalytic degradation experiments. And the structure–activity relationship was discussed according to the analysis and measurement results. The analysis results reveal that the morphology, zeta potential and photocatalytic activity of TiO{sub 2} nanocrystals can be easily tuned by changing the tungsten doping concentration. The tungsten doped TiO{sub 2} colloid combines the characters of high dispersity and high photocatalytic activity.« less

A high efficiency microfluidic-based photocatalytic microreactor using electrospun nanofibrous TiO2 as a photocatalyst.

PubMed

Meng, Zhaoxu; Zhang, Xu; Qin, Jianhua

2013-06-07

We present a novel microfluidic-based photocatalytic microreactor by using electrospun nanofibrous TiO2 as a photocatalyst for the first time. The microreactor exhibits not only a simple fabrication process, but also much higher photocatalytic activity than that achieved by a TiO2 film microreactor.

PHOTOCATALYTIC TIO2 FILMS AND MEMBRANES FOR THE DEVELOPMENT OF EFFICIENT WASTEWATER TREATMENT AND REUSE SYSTEMS

EPA Science Inventory

In order to develop efficient photocatalytic TiO₂ films and membranes for application in water and wastewater treatment and reuse systems, there is a great need to tailor-design the structural properties of TiO2 material and enhance its photocatalytic activity. Through...

Highly efficient photocatalytic degradation of methylene blue by PoPD/TiO2 nanocomposite

PubMed Central

Dong, Wenping; Cui, Guanwei; Ren, Zongming

2017-01-01

The poly-o-phenylenediamine (PoPD)/TiO2 nanocomposite was successfully synthesized via ‘in situ’ oxidative polymerization method. The modified photocatalysts were characterized by BET, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrarad spectra (FT-IR), thermogravimrtic analysis (TGA), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible diffuse reflectance spectrum (UV-Vis DRS) and Photocurrent Test. The results showed that the PoPD exists on the surface of TiO2, the presence of PoPD does not impact on the lattice structure and grain size of TiO2, and the presence of PoPD enhances the visible response and photoelectric property. The photocatalytic degradation of methylene blue (MB) was chosen as a model reaction to evaluate the photocatalytic activities of TiO2 and PoPD/TiO2. The optimal preparation condition was the molar ratio of oPD to TiO2 = 3:1, HCl concentration = 1.2 mol/L, the molar ratio of APS to oPD = 1:1. The apparent first-order rate constant kapp of PoPD/TiO2 nanocomposite was 0.0098 min-1, which is 6 times higher than TiO2 (0.0016 min-1). Meanwhile, the PoPD/TiO2 nanocomposites showed excellent photocatalytic stability, and the photocatalytic stability was depended on the stability of structure. At last, the photocatalytic mechanism of POPD/TiO2 nanocomposites was also proposed based on the synergetic effect between TiO2 and PoPD. PMID:28329007

Visible-light-induced Ag/BiVO4 semiconductor with enhanced photocatalytic and antibacterial performance

NASA Astrophysics Data System (ADS)

Regmi, Chhabilal; Dhakal, Dipesh; Wohn Lee, Soo

2018-02-01

An Ag-loaded BiVO4 visible-light-driven photocatalyst was synthesized by the microwave hydrothermal method followed by photodeposition. The photocatalytic performance of the synthesized samples was evaluated on a mixed dye (methylene blue and rhodamine B), as well as bisphenol A in aqueous solution. Similarly, the disinfection activities of synthesized samples towards the Gram-negative Escherichia coli (E. coli) in a model cell were investigated under irradiation with visible light (λ ≥ 420 nm). The synthesized samples have monoclinic scheelite structure. Photocatalytic results showed that all Ag-loaded BiVO4 samples exhibited greater degradation and a higher mineralization rate than the pure BiVO4, probably due to the presence of surface plasmon absorption that arises due to the loading of Ag on the BiVO4 surface. The optimum Ag loading of 5 wt% has the highest photocatalytic performance and greatest stability with pseudo-first-order rate constants of 0.031 min-1 and 0.023 min-1 for the degradation of methylene blue and rhodamine B respectively in a mixture with an equal volume and concentration of each dye. The photocatalytic degradation of bisphenol A reaches 76.2% with 5 wt% Ag-doped BiVO4 within 180 min irradiation time. Similarly, the Ag-loaded BiVO4 could completely inactivate E. coli cells within 30 min under visible light irradiation. The disruption of the cell membrane as well as degradation of protein and DNA exhibited constituted evidence for antibacterial activity towards E. coli. Moreover, the bactericidal mechanisms involved in the photocatalytic disinfection process were systematically investigated.

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.

Remarkable photo-catalytic degradation of malachite green by nickel doped bismuth selenide under visible light irradiation

NASA Astrophysics Data System (ADS)

Kulsi, Chiranjit; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

2017-01-01

Bismuth selenide (Bi2Se3) and nickel (Ni) doped Bi2Se3 were prepared by a solvothermal approach to explore the photo-catalytic performance of the materials in degradation of malachite green (MG). The presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement in doped Bi2Se3. The results showed that the nickel doping played an important role in microstructure and photo-catalytic activity of the samples. Nickel doped Bi2Se3 sample exhibited higher photo-catalytic activity than that of the pure Bi2Se3 sample under visible-light irradiation. The photo-catalytic degradation followed first-order reaction kinetics. Fast degradation kinetics and complete (100% in 5 min of visible light irradiation) removal of MG was achieved by nickel doped Bi2Se3 in presence of hydrogen peroxide (H2O2) due to modification of band gap energies leading to suppression of photo-generated electron-hole recombination.

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.

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.

Preparation of flower-like TiO2 sphere/reduced graphene oxide composites for photocatalytic degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Kim, Tae-Woong; Park, Mira; Kim, Hak Yong; Park, Soo-Jin

2016-07-01

In this study, novel flower-like TiO2 sphere (FTS)/reduced graphene oxide (rGO) composites (FTS-G) were synthesized via a hydrothermal method. The photocatalytic performance of the FTS-G composites was evaluated through the photodegradation of rhodamine B (Rh B) and trichloroethylene (TCE) under simulated solar light irradiation. The rGO to FTS ratio in the composites significantly affected photocatalytic activity. The photocatalytic activities of FTS-Gs in the degradation of Rh B and TCE were superior to that of pure FTS. Of all the FTS-G composites tested, FTS-G with 1 wt% rGO (FTS-G-1) had the greatest photocatalytic activity, while FTS-G composites with rGO contents over 1 wt% had lower photocatalytic activities. Additionally, it is expected that the synthesis of FTS with a high specific surface area and well-developed pore structure and simultaneous conversion of GO to graphene-like rGO without the use of strong reducing agents could be a promising strategy to prepare other carbon-based flower-like TiO2 sphere composite photocatalysts.

Preparation of bismuth titanate/calcium alginate composite bead and its photocatalytic degradation of dye pollutants

NASA Astrophysics Data System (ADS)

Gan, Huihui; Dong, Nanyang; Lu, Linxiao; Fu, Yan; Zhang, Huining; Qian, Yongxin; Zhang, Kefeng; Jin, Huixia

2017-08-01

In this study, the bismuth titanate/calcium alginate composite bead was synthesized by immobilizing bismuth titanate Bi4Ti3O12 particles into 1.5% sodium alginate (SA) matrix. The Bi4Ti3O12 particles were characterized by X-ray diffraction (XRD). The photocatalytic activity for the degradation of dye Rhodamine B in solution by as-prepared bismuth titanate/calcium alginate composite bead was investigated. The as-prepared composite beads CA/BTO-700 exhibited best photocatalytic efficiency for the degradation of RhB compared with CA/BTO-800 and CA/BTO-900 under simulated solar light. After 4 cycles in photocatalytic degradation of RhB, the degradation rate of the CA/BTO-700 nearly remained unchanged.

Development of a Microwave Regenerative Sorbent-Based Hydrogen Purifier

NASA Technical Reports Server (NTRS)

Wheeler, Richard R., Jr.; Dewberry, Ross H.; McCurry, Bryan D.; Abney, Morgan B.; Greenwood, Zachary W.

2016-01-01

This paper describes the design and fabrication of a Microwave Regenerative Sorbent-based Hydrogen Purifier (MRSHP). This unique microwave powered technology was developed for the purification of a hydrogen stream produced by the Plasma Pyrolysis Assembly (PPA). The PPA is a hydrogen recovery (from methane) post processor for NASA's Sabatier-based carbon dioxide reduction process. Embodied in the Carbon dioxide Reduction Assembly (CRA), currently aboard the International Space Station (ISS), the Sabatier reaction employs hydrogen to catalytically recover oxygen, in the form of water, from respiratory carbon dioxide produced by the crew. This same approach is base-lined for future service in the Air Revitalization system on extended missions into deep space where resupply is not practical. Accordingly, manned exploration to Mars may only become feasible with further closure of the air loop as afforded by the greater hydrogen recovery permitted by the PPA with subsequent hydrogen purification. By utilizing the well-known high sorbate loading capacity of molecular sieve 13x, coupled with microwave dielectric heating phenomenon, MRSHP technology is employed as a regenerative filter for a contaminated hydrogen gas stream. By design, freshly regenerated molecular sieve 13x contained in the MRSHP will remove contaminants from the effluent of a 1-CM scale PPA for several hours prior to breakthrough. By reversing flow and pulling a relative vacuum the MRSHP prototype then uses 2.45 GHz microwave power, applied through a novel coaxial antenna array, to rapidly heat the sorbent bed and drive off the contaminants in a short duration vacuum/thermal contaminant desorption step. Finally, following rapid cooling via room temperature cold plates, the MRSHP is again ready to serve as a hydrogen filter.

Comparative study of disinfectants for use in low-cost gravity driven household water purifiers.

PubMed

Patil, Rajshree A; Kausley, Shankar B; Balkunde, Pradeep L; Malhotra, Chetan P

2013-09-01

Point-of-use (POU) gravity-driven household water purifiers have been proven to be a simple, low-cost and effective intervention for reducing the impact of waterborne diseases in developing countries. The goal of this study was to compare commonly used water disinfectants for their feasibility of adoption in low-cost POU water purifiers. The potency of each candidate disinfectant was evaluated by conducting a batch disinfection study for estimating the concentration of disinfectant needed to inactivate a given concentration of the bacterial strain Escherichia coli ATCC 11229. Based on the concentration of disinfectant required, the size, weight and cost of a model purifier employing that disinfectant were estimated. Model purifiers based on different disinfectants were compared and disinfectants which resulted in the most safe, compact and inexpensive purifiers were identified. Purifiers based on bromine, tincture iodine, calcium hypochlorite and sodium dichloroisocyanurate were found to be most efficient, cost effective and compact with replacement parts costing US$3.60-6.00 for every 3,000 L of water purified and are thus expected to present the most attractive value proposition to end users.

Understanding the effect of surface/bulk defects on the photocatalytic activity of TiO2: anatase versus rutile.

PubMed

Yan, Junqing; Wu, Guangjun; Guan, Naijia; Li, Landong; Li, Zhuoxin; Cao, Xingzhong

2013-07-14

The sole effect of surface/bulk defects of TiO2 samples on their photocatalytic activity was investigated. Nano-sized anatase and rutile TiO2 were prepared by hydrothermal method and their surface/bulk defects were adjusted simply by calcination at different temperatures, i.e. 400-700 °C. High temperature calcinations induced the growth of crystalline sizes and a decrease in the surface areas, while the crystalline phase and the exposed facets were kept unchanged during calcination, as indicated by the characterization results from XRD, Raman, nitrogen adsorption-desorption, TEM and UV-Vis spectra. The existence of surface/bulk defects in calcined TiO2 samples was confirmed by photoluminescence and XPS spectra, and the surface/bulk defect ratio was quantitatively analyzed according to positron annihilation results. The photocatalytic activity of calcined TiO2 samples was evaluated in the photocatalytic reforming of methanol and the photocatalytic oxidation of α-phenethyl alcohol. Based on the characterization and catalytic results, a direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anatase TiO2 and rutile TiO2. The surface defects of TiO2, i.e. oxygen vacancy clusters, could promote the separation of electron-hole pairs under irradiation, and therefore, enhance the activity during photocatalytic reaction.

Preparation and Characterization of Surface Photocatalytic Activity with NiO/TiO₂ Nanocomposite Structure.

PubMed

Chen, Jian-Zhi; Chen, Tai-Hong; Lai, Li-Wen; Li, Pei-Yu; Liu, Hua-Wen; Hong, Yi-You; Liu, Day-Shan

2015-07-13

This study achieved a nanocomposite structure of nickel oxide (NiO)/titanium dioxide (TiO₂) heterojunction on a TiO₂ film surface. The photocatalytic activity of this structure evaluated by decomposing methylene blue (MB) solution was strongly correlated to the conductive behavior of the NiO film. A p -type NiO film of high concentration in contact with the native n -type TiO₂ film, which resulted in a strong inner electrical field to effectively separate the photogenerated electron-hole pairs, exhibited a much better photocatalytic activity than the controlled TiO₂ film. In addition, the photocatalytic activity of the NiO/TiO₂ nanocomposite structure was enhanced as the thickness of the p -NiO film decreased, which was beneficial for the migration of the photogenerated carriers to the structural surface.

Highly efficient TiO2-based microreactor for photocatalytic applications.

PubMed

Krivec, Matic; Žagar, Kristina; Suhadolnik, Luka; Čeh, Miran; Dražić, Goran

2013-09-25

A photocatalytic, TiO2-based microreactor is designed and fabricated on a metal-titanium foil. The microchannel is mechanically engraved in the substrate foil, and a double-layered TiO2 anatase film is immobilized on its inner walls with a two-step synthesis, which included anodization and a hydrothermal treatment. X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirm the presence of an approximately 10-μm-thick layer of titania nanotubes and anatase nanoparticles. The SEM and transmission electron microscopy (TEM) of the cross sections show a dense interface between the titanium substrate and the TiO2 nanotubes. An additional layer of TiO2-anatase nanoparticles on the top of the film provides a large, photocatalytic surface area. The metal-titanium substrate with a functionalized serpentine channel is sealed with UV-transparent Plexiglas, and four 0.8-mW UV LEDs combined with a power controller on a small printed-circuit board are fixed over the substrate. The photocatalytic activity and the kinetic properties for the degradation of caffeine are provided, and the longer-term stability of the TiO2 film is evaluated. The results show that after 6 months of use and 3600 working cycles the microreactor still exhibits 60% of its initial efficiency.

Advances in Photocatalytic CO2 Reduction with Water: A Review

PubMed Central

Nahar, Samsun; Zain, M. F. M.; Kadhum, Abdul Amir H.; Hasan, Hassimi Abu; Hasan, Md. Riad

2017-01-01

In recent years, the increasing level of CO2 in the atmosphere has not only contributed to global warming but has also triggered considerable interest in photocatalytic reduction of CO2. The reduction of CO2 with H2O using sunlight is an innovative way to solve the current growing environmental challenges. This paper reviews the basic principles of photocatalysis and photocatalytic CO2 reduction, discusses the measures of the photocatalytic efficiency and summarizes current advances in the exploration of this technology using different types of semiconductor photocatalysts, such as TiO2 and modified TiO2, layered-perovskite Ag/ALa4Ti4O15 (A = Ca, Ba, Sr), ferroelectric LiNbO3, and plasmonic photocatalysts. Visible light harvesting, novel plasmonic photocatalysts offer potential solutions for some of the main drawbacks in this reduction process. Effective plasmonic photocatalysts that have shown reduction activities towards CO2 with H2O are highlighted here. Although this technology is still at an embryonic stage, further studies with standard theoretical and comprehensive format are suggested to develop photocatalysts with high production rates and selectivity. Based on the collected results, the immense prospects and opportunities that exist in this technique are also reviewed here. PMID:28772988

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…

Development and characterization of silica and titania based nano structured materials for the removal of indoor and outdoor air pollutants

NASA Astrophysics Data System (ADS)

Peiris, Thelge Manindu Nirasha

Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized

Robust sparse image reconstruction of radio interferometric observations with PURIFY

NASA Astrophysics Data System (ADS)

Pratley, Luke; McEwen, Jason D.; d'Avezac, Mayeul; Carrillo, Rafael E.; Onose, Alexandru; Wiaux, Yves

2018-01-01

Next-generation radio interferometers, such as the Square Kilometre Array, will revolutionize our understanding of the Universe through their unprecedented sensitivity and resolution. However, to realize these goals significant challenges in image and data processing need to be overcome. The standard methods in radio interferometry for reconstructing images, such as CLEAN, have served the community well over the last few decades and have survived largely because they are pragmatic. However, they produce reconstructed interferometric images that are limited in quality and scalability for big data. In this work, we apply and evaluate alternative interferometric reconstruction methods that make use of state-of-the-art sparse image reconstruction algorithms motivated by compressive sensing, which have been implemented in the PURIFY software package. In particular, we implement and apply the proximal alternating direction method of multipliers algorithm presented in a recent article. First, we assess the impact of the interpolation kernel used to perform gridding and degridding on sparse image reconstruction. We find that the Kaiser-Bessel interpolation kernel performs as well as prolate spheroidal wave functions while providing a computational saving and an analytic form. Secondly, we apply PURIFY to real interferometric observations from the Very Large Array and the Australia Telescope Compact Array and find that images recovered by PURIFY are of higher quality than those recovered by CLEAN. Thirdly, we discuss how PURIFY reconstructions exhibit additional advantages over those recovered by CLEAN. The latest version of PURIFY, with developments presented in this work, is made publicly available.

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.

Surface modification of mixed-phase hydrogenated TiO2 and corresponding photocatalytic response

NASA Astrophysics Data System (ADS)

Samsudin, Emy Marlina; Hamid, Sharifah Bee Abd; Juan, Joon Ching; Basirun, Wan Jefrey; Kandjani, Ahmad Esmaielzadeh

2015-12-01

Preparation of highly photo-activated TiO2 is achievable by hydrogenation at constant temperature and pressure, with controlled hydrogenation duration. The formation of surface disorders and Ti3+ is responsible for the color change from white unhydrogenated TiO2 to bluish-gray hydrogenated TiO2. This color change, together with increased oxygen vacancies and Ti3+ enhanced the solar light absorption from UV to infra-red region. Interestingly, no band gap narrowing is observed. The photocatalytic activity in the UV and visible region is controlled by Ti3+ and oxygen vacancies respectively. Both Ti3+ and oxygen vacancies increases the electron density on the catalyst surface thus facilitates rad OH radicals formation. The lifespan of surface photo-excited electrons and holes are also sustained thus prevents charge carrier recombination. However, excessive amount of oxygen vacancies deteriorates the photocatalytic activity as it serves as charge traps. Hydrogenation of TiO2 also promotes the growth of active {0 0 1} facets and facilitates the photocatalytic activity by higher concentration of surface OH radicals. However, the growth of {0 0 1} facets is small and insignificant toward the overall photo-kinetics. This work also shows that larger role is played by Ti3+ and oxygen vacancies rather than the surface disorders created during the hydrogenation process. It also demonstrates the ability of hydrogenated TiO2 to absorb wider range of photons even though at a similar band gap as unhydrogenated TiO2. In addition, the photocatalytic activity is shown to be decreased for extended hydrogenation duration due to excessive catalyst growth and loss in the total surface area. Thus, a balance in the physico-chemical properties of hydrogenated TiO2 is crucial to enhance the photocatalytic activity by simply controlling the hydrogenation duration.

Orientation-dependent structural and photocatalytic properties of LaCoO3 epitaxial nano-thin films

PubMed Central

Zhang, Yan-ping; Hu, Hai-long; Xie, Rui-shi; Ma, Guo-hua; Huo, Ji-chuan; Wang, Hai-bin

2018-01-01

LaCoO3 epitaxial films were grown on (100), (110) and (111) oriented LaAlO3 substrates by the polymer-assisted deposition method. Crystal structure measurement and cross-section observation indicate that all the LaCoO3 films are epitaxially grown in accordance with the orientation of LaAlO3 substrates, with biaxial compressive strain in the ab plane. Owing to the different strain directions of CoO6 octahedron, the mean Co–O bond length increases by different amounts in (100), (110) and (111) oriented films compared with that of bulk LaCoO3, and the (100) oriented LaCoO3 has the largest increase. Photocatalytic degradation of methyl orange indicates that the order of photocatalytic activity of the three oriented films is (100) > (111) > (110). Combined with analysis of electronic nature and band structure for LaCoO3 films, it is found that the change of the photocatalytic activity is closely related to the crystal field splitting energy of Co3+ and Co–O binding energy. The increase in the mean Co–O bond length will decrease the crystal field splitting energy of Co3+ and Co–O binding energy and further reduce the value of band gap energy, thus improving the photocatalytic activity. This may also provide a clue for expanding the visible-light-induced photocatalytic application of LaCoO3. PMID:29515854

Orientation-dependent structural and photocatalytic properties of LaCoO3 epitaxial nano-thin films

NASA Astrophysics Data System (ADS)

Zhang, Yan-ping; Liu, Hai-feng; Hu, Hai-long; Xie, Rui-shi; Ma, Guo-hua; Huo, Ji-chuan; Wang, Hai-bin

2018-02-01

LaCoO3 epitaxial films were grown on (100), (110) and (111) oriented LaAlO3 substrates by the polymer-assisted deposition method. Crystal structure measurement and cross-section observation indicate that all the LaCoO3 films are epitaxially grown in accordance with the orientation of LaAlO3 substrates, with biaxial compressive strain in the ab plane. Owing to the different strain directions of CoO6 octahedron, the mean Co-O bond length increases by different amounts in (100), (110) and (111) oriented films compared with that of bulk LaCoO3, and the (100) oriented LaCoO3 has the largest increase. Photocatalytic degradation of methyl orange indicates that the order of photocatalytic activity of the three oriented films is (100) > (111) > (110). Combined with analysis of electronic nature and band structure for LaCoO3 films, it is found that the change of the photocatalytic activity is closely related to the crystal field splitting energy of Co3+ and Co-O binding energy. The increase in the mean Co-O bond length will decrease the crystal field splitting energy of Co3+ and Co-O binding energy and further reduce the value of band gap energy, thus improving the photocatalytic activity. This may also provide a clue for expanding the visible-light-induced photocatalytic application of LaCoO3.

Orientation-dependent structural and photocatalytic properties of LaCoO3 epitaxial nano-thin films.

PubMed

Zhang, Yan-Ping; Liu, Hai-Feng; Hu, Hai-Long; Xie, Rui-Shi; Ma, Guo-Hua; Huo, Ji-Chuan; Wang, Hai-Bin

2018-02-01

LaCoO 3 epitaxial films were grown on (100), (110) and (111) oriented LaAlO 3 substrates by the polymer-assisted deposition method. Crystal structure measurement and cross-section observation indicate that all the LaCoO 3 films are epitaxially grown in accordance with the orientation of LaAlO 3 substrates, with biaxial compressive strain in the ab plane. Owing to the different strain directions of CoO 6 octahedron, the mean Co-O bond length increases by different amounts in (100), (110) and (111) oriented films compared with that of bulk LaCoO 3 , and the (100) oriented LaCoO 3 has the largest increase. Photocatalytic degradation of methyl orange indicates that the order of photocatalytic activity of the three oriented films is (100) > (111) > (110). Combined with analysis of electronic nature and band structure for LaCoO 3 films, it is found that the change of the photocatalytic activity is closely related to the crystal field splitting energy of Co 3+ and Co-O binding energy. The increase in the mean Co-O bond length will decrease the crystal field splitting energy of Co 3+ and Co-O binding energy and further reduce the value of band gap energy, thus improving the photocatalytic activity. This may also provide a clue for expanding the visible-light-induced photocatalytic application of LaCoO 3 .

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.

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.

Synthesis of metal free ultrathin graphitic carbon nitride sheet for photocatalytic dye degradation of Rhodamine B under visible light irradiation

NASA Astrophysics Data System (ADS)

Rahman, Shakeelur; Momin, Bilal; Higgins M., W.; Annapure, Uday S.; Jha, Neetu

2018-04-01

In recent times, low cost and metal free photocatalyts driven under visible light have attracted a lot of interest. One such photo catalyst researched extensively is bulk graphitic carbon nitride sheets. But the low surface area and weak mobility of photo generated electrons limits its photocatalytic performance in the visible light spectrum. Here we present the facile synthesis of ultrathin graphitic carbon nitride using a cost effective melamine precursor and its application in highly efficient photocatalytic dye degradation of Rhodamine B molecules. Compared to bulk graphitic carbon nitride, the synthesized ultrathin graphitic carbon nitride shows an increase in surface area, a a decrease in optical band gap and effective photogenerated charge separation which facilitates the harvest of visible light irradiation. Due to these optimal properties of ultrathin graphitic carbon nitride, it shows excellent photocatalytic activity with photocatalytic degradation of about 95% rhodamine B molecules in 1 hour.

Photocatalytic Degradation of 4-Nitrophenol by C, N-TiO2: Degradation Efficiency vs. Embryonic Toxicity of the Resulting Compounds

NASA Astrophysics Data System (ADS)

Osin, Oluwatomiwa A.; Yu, Tianyu; Cai, Xiaoming; Jiang, Yue; Peng, Guotao; Cheng, Xiaomei; Li, Ruibin; Qin, Yao; Lin, Sijie

2018-06-01

The photocatalytic activity of TiO2 based photocatalysts can be improved by structural modification and elemental doping. In this study, through rational design, one type of carbon and nitrogen co-doped TiO2 (C, N-TiO2) photocatalyst with mesoporous structure was synthesized with improved photocatalytic activity in degrading 4-nitrophenol under simulated sunlight irradiation. The photocatalytic degradation efficiency of the C, N-TiO2 was much higher than the anatase TiO2 (A-TiO2) based on absorbance and HPLC analyses. Moreover, using zebrafish embryos, we showed that the intermediate degradation compounds generated by photocatalytic degradation of 4-nitrophenol had higher toxicity than the parent compound. A repeated degradation process was necessary to render complete degradation and non-toxicity to the zebrafish embryos. Our results demonstrated the importance of evaluating the photocatalytic degradation efficiency in conjunction with the toxicity assessment of the degradation compounds.

Photocatalytic Degradation of 4-Nitrophenol by C, N-TiO2: Degradation Efficiency vs. Embryonic Toxicity of the Resulting Compounds.

PubMed

Osin, Oluwatomiwa A; Yu, Tianyu; Cai, Xiaoming; Jiang, Yue; Peng, Guotao; Cheng, Xiaomei; Li, Ruibin; Qin, Yao; Lin, Sijie

2018-01-01

The photocatalytic activity of TiO 2 based photocatalysts can be improved by structural modification and elemental doping. In this study, through rational design, one type of carbon and nitrogen co-doped TiO 2 (C, N-TiO 2 ) photocatalyst with mesoporous structure was synthesized with improved photocatalytic activity in degrading 4-nitrophenol under simulated sunlight irradiation. The photocatalytic degradation efficiency of the C, N-TiO 2 was much higher than the anatase TiO 2 (A-TiO 2 ) based on absorbance and HPLC analyses. Moreover, using zebrafish embryos, we showed that the intermediate degradation compounds generated by photocatalytic degradation of 4-nitrophenol had higher toxicity than the parent compound. A repeated degradation process was necessary to render complete degradation and non-toxicity to the zebrafish embryos. Our results demonstrated the importance of evaluating the photocatalytic degradation efficiency in conjunction with the toxicity assessment of the degradation compounds.

Enhanced photocatalytic activity of BiOCl by C70 modification and mechanism insight

NASA Astrophysics Data System (ADS)

Ma, Dongmei; Zhong, Junbo; Li, Jianzhang; Wang, Li; Peng, Rufang

2018-06-01

As an excellent photocatalyst which can compete with TiO2, BiOCl has triggered increasing attention. However, the practical application of BiOCl has been significantly limited by the fast recombination of the photoinduced electron-hole charge pairs. In this study, to further enhance the separation efficiency of photoinduced electron-hole charge pairs of BiOCl, a series of efficient BiOCl photocatalysts were prepared by C70 surface modification. The trapping experiments reveal that the main active species were determined to be superoxide radicals (O2rad -) and holes (h+) under simulated sunlight irradiation. The surface photovoltage spectroscopy (SPS) demonstrates that separation of the photoinduced electron-hole pairs has been significantly promoted, forming more radOH, proven by terephthalic acid photoluminescence probing technique. The photocatalytic evaluation results display that the C70/BiOCl photocatalysts exhibit much higher photocatalytic activity in decolorization of rhodamine B (RhB) than that of the bare BiOCl under the simulated sunlight irradiation. The excellent electron acceptability of C70 is conducive to the separation of the photogenerated carriers and results in efficient formation of O2rad -, proven by the results of SPS and electron spin-resonance (ESR), therefore the photocatalytic performance of C70/BiOCl has been greatly improved. Based on all these observations, an enhancement mechanism in photocatalytic performance of C70/BiOCl was proposed.

Novel durable bio-photocatalyst purifiers, a non-heterogeneous mechanism: accelerated entrapped dye degradation into structural polysiloxane-shield nano-reactors.

PubMed

Dastjerdi, Roya; Montazer, Majid; Shahsavan, Shadi; Böttcher, Horst; Moghadam, M B; Sarsour, Jamal

2013-01-01

This research has designed innovative Ag/TiO(2) polysiloxane-shield nano-reactors on the PET fabric to develop novel durable bio-photocatalyst purifiers. To create these very fine nano-reactors, oppositely surface charged multiple size nanoparticles have been applied accompanied with a crosslinkable amino-functionalized polysiloxane (XPs) emulsion. Investigation of photocatalytic dye decolorization efficiency revealed a non-heterogeneous mechanism including an accelerated degradation of entrapped dye molecules into the structural polysiloxane-shield nano-reactors. In fact, dye molecules can be adsorbed by both Ag and XPs due to their electrostatic interactions and/or even via forming a complex with them especially with silver NPs. The absorbed dye and active oxygen species generated by TiO(2) were entrapped by polysiloxane shelter and the presence of silver nanoparticles further attract the negative oxygen species closer to the adsorbed dye molecules. In this way, the dye molecules are in close contact with concentrated active oxygen species into the created nano-reactors. This provides an accelerated degradation of dye molecules. This non-heterogeneous mechanism has been detected on the sample containing all of the three components. Increasing the concentration of Ag and XPs accelerated the second step beginning with an enhanced rate. Further, the treated samples also showed an excellent antibacterial activity. Copyright © 2012 Elsevier B.V. All rights reserved.

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.

Sono-photocatalytic production of hydrogen by interface modified metal oxide insulators.

PubMed

Senevirathne, Rushdi D; Abeykoon, Lahiru K; De Silva, Nuwan L; Yan, Chang-Feng; Bandara, Jayasundera

2018-07-01

Dielectric oxide materials are well-known insulators that have many applications in catalysis as well as in device manufacturing industries. However, these dielectric materials cannot be employed directly in photochemical reactions that are initiated by the absorption of UV-Vis photons. Despite their insensitivity to solar energy, dielectric materials can be made sono-photoactive even for low energy IR photons by modifications of the interfacial properties of dielectric materials by noble metals and metal oxides. In this investigation, by way of interface modification of dielectric MgO nanoparticles by Ag metal and Ag 2 O nanoparticles, IR photon initiated sono-photocatalytic activity of MgO is reported. The observed photocatalytic activity is found to be the synergic action of both IR light and sonication effect and sonication assisted a multi-step, sub-bandgap excitation of electrons in the MgO is proposed for the observed catalytic activity of Ag/Ag 2 O coated MgO nanoparticles. Our investigation reveals that other dielectric materials such as silver coated SiO 2 and Al 2 O 3 also exhibit IR active sono-photocatalytic activity. Copyright © 2018 Elsevier B.V. All rights reserved.

Photocatalytic oxidation of tabun simulant-diethyl cyanophosphate: FTIR in situ investigation.

PubMed

Kolinko, P A; Kozlov, D V

2008-06-15

Gas phase photocatalytic oxidation of diethyl cyanophosphate vapor in a static reactor using TiO2 and modified TiO2 as the photocatalyst was studied with the FTIR in situ method. The transition metals Pt, Au, and Ag were used for TiO2 modification by the chemical and photochemical deposition methods as well as the mechanical mixture of TiO2 with manganese oxide to improve its adsorption and catalytic activity. Photocatalytic oxidation of diethyl cyanophosphate in a static reactor results in its complete mineralization with carbon dioxide, phosphoric and nitric acids, and water as the major final products. HCN was demonstrated to be the only toxic gaseous intermediate of diethyl cyanophosphate photocatalytic oxidation, formed as a result of diethyl cyanophosphate hydrolysis. Diethylphosphate and acetic and formic acids were registered as the surface intermediates. It was found that cyanhydric acid is oxidized slowly with the use of unmodified TiO2. The formation of surface cyanide complexes with Ag and Au ions could be responsible for the fast removal of HCN from the gas phase and its further photooxidation in the case of using TiO2 with deposited Au and Ag.

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.

Constructing MnO{sub 2}/single crystalline ZnO nanorod hybrids with enhanced photocatalytic and antibacterial activity

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

Yu, Weiwei; Liu, Tiangui, E-mail: tianguiliu@gmail.com; Cao, Shiyi

In order to improve the photocatalytic and antibacterial activity of ZnO nanorods, ZnO nanorods decorated with MnO{sub 2} nanoparticles (MnO{sub 2}/ZnO nanorod hybrids) were prepared by using microwave assisted coprecipitation method under the influence of hydrogen peroxide, and the structure, photocatalytic activity and antibacterial property of the products were studied. Experimental results indicated that MnO{sub 2} nanoparticles are decorated on the surface of single crystalline ZnO nanorods. Moreover, the resultant MnO{sub 2}/ZnO nanorod hybrids have been proven to possess good photocatalytic and antibacterial activity, which their degradated efficiency for Rhodamin B (RhB) is twice as the pure ZnO nanorods. Enhancementmore » for photocatalytic and antibacterial activity is mainly attributed to the low band gap energy and excellent electrochemical properties of MnO{sub 2} nanoparticles. - Graphical abstract: The MnO{sub 2}/single crystalline ZnO nanorods hybrids, which MnO{sub 2} nanoparticles are loaded on the surface of ZnO nanorods, were prepared by the step-by-step precipitation method under the assistance of ammonia and hydrogen peroxide. Display Omitted - Highlights: • MnO{sub 2}/ZnO nanorod hybrids were prepared by the step-by-step assembly method. • Single crystalline ZnO nanorods can be decorated by MnO{sub 2} nanoparticles. • MnO{sub 2}/ZnO nanorod hybrids possess good photocatalytic and antibacterial activity. • MnO{sub 2} can improve the photocatalytic activity of ZnO nanorods under visible light.« less

Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Cheng, Hsyi-En; Lin, Chun-Yuan; Hsu, Ching-Ming

2017-02-01

Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

New insights into how RGO influences the photocatalytic performance of BiOIO3/RGO nanocomposites under visible and UV irradiation.

PubMed

Xiong, Ting; Dong, Fan; Zhou, Ying; Fu, Min; Ho, Wing-Kei

2015-06-01

Reduced graphene oxide (RGO) has been demonstrated to be effective in enhancing the photocatalytic activity of various semiconductors. However, an important issue that has been overlooked is the role of RGO in UV-induced photocatalysis of RGO-based nanocomposites. In the present work, novel BiOIO3/RGO nanocomposites were prepared by a simple one-pot hydrothermal method, during which BiOIO3 nanoplates were formed in situ on RGO sheets resulting from partial reduction of RGO. The two components of the composite displayed intimate interfacial contact. The as-prepared BiOIO3/RGO nanocomposites exhibited highly enhanced visible photocatalytic activity, relative to that of pure BiOIO3, toward removal of NO from air. However, the BiOIO3/RGO nanocomposites showed only slightly increased photocatalytic activity, relative to pure, under UV irradiation. The limited enhancement of UV activity can be ascribed to the fact that BiOIO3 would be expected to compete with RGO with regard to absorption and utilization of UV light. Evidence shows that RGO can act as a semiconductor rather than a photosensitizer or electron reservoir in BiOIO3/RGO nano-composites. In addition, the active species responsible for photoactivity have been investigated by a DMPO spin-trapping electron spin resonance technique. Photo-generated holes were found to be the main active species inducing the photo-oxidation of NO under visible light, whereas holes and OH radicals are considered to be responsible for photo-activity under UV light. This work points to BiOIO3/RGO nano-composites as new and efficient visible light photocatalysts for environmental remediation applications, and also as a source of new insights into the pivotal role of RGO in photocatalysis of RGO-based nanocomposites under visible as well as UV light. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

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.

Below room temperature: How the photocatalytic activity of dense and mesoporous TiO2 coatings is affected

NASA Astrophysics Data System (ADS)

Cedillo-González, Erika Iveth; Riccò, Raffaele; Costacurta, Stefano; Siligardi, Cristina; Falcaro, Paolo

2018-03-01

Different parameters such as morphology, porosity, crystalline phase or doping agents affect the self-cleaning performance of photocatalytic TiO2-based coatings. However, also environmental conditions have been found to play a major role on the photocatalytic self-cleaning property. Substrate temperature is a significant environmental variable that can drastically affect this process. This variable becomes of great importance especially for outdoor applications: many self-cleaning photocatalytic materials have been designed to be exposed to outdoor environments and consequently, can be exposed to variable temperatures depending on the season of the year and the typical weather of the geographical zone. Thus, understanding the influence of the most common outdoor temperatures on the self-cleaning performance of TiO2-based coatings is essential for the fabrication of any kind of photocatalytic self-cleaning materials (fabricated by coating technology) that is expected to be subjected to outdoor environments. In this work, the photocatalytic activity was studied by Fourier Transformed Infrared (FTIR) Spectroscopy varying the temperature in the 0 to 30 °C range for dense and mesoporous TiO2 coatings. The temperature conditions at which these coatings present better performances were identified, providing a deeper insight for the practical application of TiO2-based self-cleaning coatings.

Recommended test methods and pass/fail criteria for a respirator fit capability test of half-mask air-purifying respirators

PubMed Central

Zhuang, Ziqing; Bergman, Michael; Lei, Zhipeng; Niezgoda, George; Shaffer, Ronald

2017-01-01

This study assessed key test parameters and pass/fail criteria options for developing a respirator fit capability (RFC) test for half-mask air-purifying particulate respirators. Using a 25-subject test panel, benchmark RFC data were collected for 101 National Institute for Occupational Safety and Health-certified respirator models. These models were further grouped into 61 one-, two-, or three-size families. Fit testing was done using a PortaCount® Plus with N95-Companion accessory and an Occupational Safety and Health Administration-accepted quantitative fit test protocol. Three repeated tests (donnings) per subject/respirator model combination were performed. The panel passing rate (PPR) (number or percentage of the 25-subject panel achieving acceptable fit) was determined for each model using five different alternative criteria for determining acceptable fit. When the 101 models are evaluated individually (i.e., not grouped by families), the percentages of models capable of fitting >75% (19/25 subjects) of the panel were 29% and 32% for subjects achieving a fit factor ≥100 for at least one of the first two donnings and at least one of three donnings, respectively. When the models are evaluated grouped into families and using >75% of panel subjects achieving a fit factor ≥100 for at least one of two donnings as the PPR pass/fail criterion, 48% of all models can pass. When >50% (13/25 subjects) of panel subjects was the PPR criterion, the percentage of passing models increased to 70%. Testing respirators grouped into families and evaluating the first two donnings for each of two respirator sizes provided the best balance between meeting end user expectations and creating a performance bar for manufacturers. Specifying the test criterion for a subject obtaining acceptable fit as achieving a fit factor ≥100 on at least one out of the two donnings is reasonable because a majority of existing respirator families can achieve an PPR of >50% using this criterion

Recommended test methods and pass/fail criteria for a respirator fit capability test of half-mask air-purifying respirators.

PubMed

Zhuang, Ziqing; Bergman, Michael; Lei, Zhipeng; Niezgoda, George; Shaffer, Ronald

2017-06-01

This study assessed key test parameters and pass/fail criteria options for developing a respirator fit capability (RFC) test for half-mask air-purifying particulate respirators. Using a 25-subject test panel, benchmark RFC data were collected for 101 National Institute for Occupational Safety and Health-certified respirator models. These models were further grouped into 61 one-, two-, or three-size families. Fit testing was done using a PortaCount® Plus with N95-Companion accessory and an Occupational Safety and Health Administration-accepted quantitative fit test protocol. Three repeated tests (donnings) per subject/respirator model combination were performed. The panel passing rate (PPR) (number or percentage of the 25-subject panel achieving acceptable fit) was determined for each model using five different alternative criteria for determining acceptable fit. When the 101 models are evaluated individually (i.e., not grouped by families), the percentages of models capable of fitting >75% (19/25 subjects) of the panel were 29% and 32% for subjects achieving a fit factor ≥100 for at least one of the first two donnings and at least one of three donnings, respectively. When the models are evaluated grouped into families and using >75% of panel subjects achieving a fit factor ≥100 for at least one of two donnings as the PPR pass/fail criterion, 48% of all models can pass. When >50% (13/25 subjects) of panel subjects was the PPR criterion, the percentage of passing models increased to 70%. Testing respirators grouped into families and evaluating the first two donnings for each of two respirator sizes provided the best balance between meeting end user expectations and creating a performance bar for manufacturers. Specifying the test criterion for a subject obtaining acceptable fit as achieving a fit factor ≥100 on at least one out of the two donnings is reasonable because a majority of existing respirator families can achieve an PPR of >50% using this criterion

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.

Diatomite-immobilized BiOI hybrid photocatalyst: Facile deposition synthesis and enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Li, Baoying; Huang, Hongwei; Guo, Yuxi; Zhang, Yihe

2015-10-01

A novel diatomite-immobilized BiOI hybrid photocatalyst has been prepared by a facile one-step deposition process for the first time. The structure, morphology and optical property of the products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic performance of the as-prepared BiOI/diatomite photocatalysts was studied by photodegradation of Rhodamine B (RhB) and methylene blue (MB) and monitoring photocurrent generation under visible light (λ > 420 nm). The results revealed that BiOI/diatomite composites exhibit enhanced photocatalytic activity compared to the pristine BiOI sample. This enhancement should be attributed to that diatomite can play as an excellent carrier platform to increase the reactive sites and promote the separation of photogenerated electron-hole pairs. In addition, the corresponding photocatalytic mechanism was proposed based on the active species trapping experiments. This work shed new light on facile fabrication of novel composite photocatalyst based on natural mineral.

Growth and photocatalytic properties of Sb-doped ZnO nanoneedles by hydrothermal process

NASA Astrophysics Data System (ADS)

Abaker, M.; Umar, Ahmad; Al-Sayari, S. A.; Dar, G. N.; Faisal, M.; Kim, S. H.; Hwang, S. W.

2011-10-01

This paper reports a facile hydrothermal synthesis of Sb-doped ZnO nanoneedles by using aqueous mixtures of zinc chloride, antimony (Sb) chloride, hexamethylenetetramine (HMTA) and ammonium hydroxide at low temperature of 110 °C. The morphological characterizations of as-synthesized nanoneedles were done by field emission scanning electron microscopy (FESEM) which reveals that the nanoneedles are grown in large-quantity and arranged in such a special manner that they made flower-like morphologies. The structural characterization of as-synthesized nanoneedles was investigated by X-ray diffraction (XRD) pattern which confirm the well-crystalline and wurtzite hexagonal phase of as-synthesized products. The compositional characterization of as-synthesized nanoneedles was characterized by energy dispersive spectroscopy (EDS), which verify that the synthesized nanoneedles are composed of zinc, Sb and oxygen. For application point of view, the synthesized nanoneedles were used as photocatalyst for photocatalytic degradation of methylene blue (MBB) and it was found that it exhibit good photocatalytic properties towards the photocatalytic degradation of methylene blue.

Synthesis of BiOCl nanosheets with oxygen vacancies for the improved photocatalytic properties

NASA Astrophysics Data System (ADS)

Cai, Yujie; Li, Dongya; Sun, Jingyu; Chen, Mengdie; Li, Yirui; Zou, Zhongwei; Zhang, Hua; Xu, Haiming; Xia, Dongsheng

2018-05-01

The square-sharped BiOCl nanosheets with oxygen vacancies were successfully synthesized via a facile hydrothermal route using xylitol as surfactant. The as-prepared BiOCl samples were characterized by Powder X-ray Diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), UV-Vis diffuse reflectance spectra (DRS), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and Electron spin resonance (ESR). The as-prepared samples were phase-pure with the width and the thickness were about 50-400 nm and 20-50 nm respectively. Besides, the photodegradation performances showed the BiOCl nanosheets with 0.1 g concentration of xylitol (BOC-1) had the best photocatalytic activity under visible light due to its special polycrystalline structure, grain boundary and an optimum concentration of oxygen vacancies. The h+ and radO2- were the two main active species during the photocatalytic process and the possible photocatalytic mechanism was 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.

Facile synthesis of bird's nest-like TiO2 microstructure with exposed (001) facets for photocatalytic degradation of methylene blue

NASA Astrophysics Data System (ADS)

Zhang, Guozhong; Zhang, Shuqu; Wang, Longlu; Liu, Ran; Zeng, Yunxiong; Xia, Xinnian; Liu, Yutang; Luo, Shenglian

2017-01-01

The scrupulous design of hierarchical structure and highly active crystal facets exposure is essential for the creation of photocatalytic system. However, it is still a big challenge for scrupulous design of TiO2 architectures. In this paper, bird's nest-like anatase TiO2 microstructure with exposed highly active (001) surface has been successfully synthesized by a facile one-step solvothermal method. Methylene blue (MB) is chosen as a model pollutant to evaluate photocatalytic activity of as-obtained TiO2 samples. The results show that the photocatalytic activity of the bird's nest-like sample is more excellent than P25 in the degradation of MB due to high specific surface area and highly active (001) crystal facets exposure when tested under simulated solar light. Besides, it can be readily separated from the photocatalytic system by sedimentation after photocatalytic reaction, which is a significant advantage against conventional powder photocatalyst. The bird's nest-like microspheres with novel structure may have potential application in photocatalysis and other fields.

Fabrication of a PANI/CPs composite material: a feasible method to enhance the photocatalytic activity of coordination polymers.

PubMed

Xu, Xin-Xin; Cui, Zhong-Ping; Qi, Ji; Liu, Xiao-Xia

2013-03-21

To improve the photocatalytic activity of a coordination polymer in the visible light region, polyaniline (PANI) was loaded onto its surface through a facile in situ chemical oxidation polymerization process. The resulting PANI loaded coordination polymer composite materials with excellent stability exhibit significantly higher photocatalytic activities than the pure coordination polymer photocatalyst on the degradation of methyl orange (MO) under visible light irradiation. This enhancement can be ascribed to the introduction of PANI on the surface of the coordination polymer, which leads to efficient separation of photogenerated electron-hole pairs as well as a significant expansion of the photoresponse region. Finally, we discussed the influence of acidity on the morphology and photocatalytic activity of the composite material. An optimal condition to obtain the PANI loaded coordination polymer composite material with excellent photocatalytic activity has been obtained.

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.

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.

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.

Preparation, characterization of Sb-doped ZnO nanocrystals and their excellent solar light driven photocatalytic activity

NASA Astrophysics Data System (ADS)

Nasser, Ramzi; Othmen, Walid Ben Haj; Elhouichet, Habib; Férid, Mokhtar

2017-01-01

In the present study, undoped and antimony (Sb) doped ZnO nanocrystals (NCs) were prepared by a simple and economical sol-gel method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the purity of the obtained phase and its high crystallinity. Raman analysis confirms the hexagonal Wurtzite ZnO structure. According to the diffuse reflectance results, the band gap was found to decrease up to 3% of Sb doping (ZSb3 sample). The results of X-ray photoelectron spectroscopy (XPS) measurements reveal that Sb ions occupied both Zn and interstitials sites. The successful substitution of antimony in ZnO lattice suggests the formation of the complex (SbZn-2 VZn) acceptor level above the valence band. Particularly for ZSb3 sample, the UV photoluminescence (PL) band presents an obvious red-shift attributed to the formation of this complex. Rhodamine B (RhB) was used to evaluate the photocatalytic activity of Sb-doped ZnO NCs under sunlight irradiation. It was found that oxygen vacancies play a major role in the photocatalytic process by trapping the excited electrons and inhibiting the radiative recombination. During the photocatalytic mechanism, the Sb doping, expressed through the apparition of the (SbZn-2 VZn) correspondent acceptor level, enhances the sunlight absorption within the ZnO band gap, which stimulates the generation of hydroxyl radicals and promotes the photocatalytics reaction rates. Such important contribution of the hydroxyl radicals was confirmed experimentally when using ethanol as scavenger in the photocatalytic reaction. The photodegradation experiments reveal that ZSb3 sample exhibits the highest photocatalytic activity among all the prepared samples and presents a good cycling stability and reusability. The influence of the initial pH in the photodegradation efficiency was also monitored and discussed.

Simultaneous purifying of Hg0, SO2, and NOx from flue gas by Fe3+/H2O2: the performance and purifying mechanism.

PubMed

Xing, Yi; Li, Liuliu; Lu, Pei; Cui, Jiansheng; Li, Qianli; Yan, Bojun; Jiang, Bo; Wang, Mengsi

2018-03-01

Hg 0 , SO 2 , and NOx result in heavily global environmental pollution and serious health hazards. Up to now, how to efficiently remove mercury with SO 2 and NOx from flue gas is still a tough task. In this study, series of high oxidizing Fenton systems were employed to purify the pollutants. The experimental results showed that Fe 3+ /H 2 O 2 was more suitable to purify Hg 0 than Fe 2+ /H 2 O 2 and Cu 2+ /H 2 O 2. The optimal condition includes Fe 3+ concentration of 0.008 mol/L, Hg 0 inlet concentration of 40 μg/m 3 , solution temperature of 50 °C, pH of 3, H 2 O 2 concentration of 0.7 mol/L, and O 2 percentage of 6%. When SO 2 and NOx were taken into account under the optimal condition, Hg 0 removal efficiency could be enhanced to 91.11% while the removal efficiency of both NOx and SO 2 was slightly declined, which was consistent to the analysis of purifying mechanism. The removal efficiency of Hg 0 was stimulated by accelerating the conversion of Fe 2+ to Fe 3+ , which resulted from the existence of SO 2 and NOx. The results of this study suggested that simultaneously purifying Hg 0 , SO 2 , and NOx from flue gas is feasible.

Photocatalytic Oxidation and Reduction Chemistry and a New Process for Treatment of Pink Water and Related Contaminated Water

DTIC Science & Technology

1996-10-01

Schiavello, Mario; Sclafani, Antonino ; Marchese, Leonardo; Martra, Gianmario; Miano, Fausto. "Photocatalytic Degradation of Nitrophenols in Aqueous...Photocatalytic System." Appl. Catal., A 101, no. 1 (1993): 7-13. Augugliaro, Vincenzo, Leonardo Palmisano, Mario Schiavello, Antonino Sclafani, Leonardo Marchese

Constructing TiO2 decorated Bi2WO6 architectures with enhanced visible-light-driven photocatalytic activity

NASA Astrophysics Data System (ADS)

Yang, Zhiyuan; Chen, Lu; Yang, Yun; Wang, Junjie; Huang, Yongkui; Liu, Xiaoxia; Yang, Shuijin

2017-06-01

TiO2 nanoparticles modified Bi2WO6 photocatalysts were prepared via a facile hydrothermal process. The photocatalytic activity of as-prepared TiO2/Bi2WO6 composites was investigated sufficiently by the photodegradation of rhodamine B (RhB), tetracycline hydrochloride (TC) and ciprofloxacin (CIP). The TiO2/Bi2WO6 composites, in which the molar ratio of TiO2 to Bi2WO6 is 1:1, exhibited optimum photocatalytic activity, which is found to increase by about 2.4 times more than that of pristine Bi2WO6 for the photodegradation of TC. The enhanced photocatalytic activity may be attributed to the higher surface area and the highly efficient charge separation between Bi2WO6 nanosheets and TiO2 nanoparticles. The mechanism of the photocatalysts is investigated by the determination of reactive species in the photocatalytic reactions, the photoluminescence measurement and photoelectrochemical analyses.

Degradation of endocrine disrupting chemicals in aqueous solution by interaction of photocatalytic oxidation and ferrate (VI) oxidation.

PubMed

Li, C; Li, X Z

2007-01-01

In this study, the degradation of bisphenol A in aqueous suspension by interaction of photocatalytic oxidation and ferrate(VI) oxidation was investigated under different conditions. The results indicate that the formation of Fe(V) and Fe(IV) is in the photocatalytic reduction of Fe(VI) by electron (ecb-) on the surface of TiO2. The oxidation efficiency of the photocatalytic oxidation in the presence of Fe(VI) was much greater than that without. In addition, the decomposition of Fe(VI) under different conditions was also investigated. The results indicate that the Fe(VI) reduction was accelerated by photocatalytic reaction and the adsorption capacity of Fe(VI) on TiO2 surface decreased as pH increased. The characteristics of solid potassium ferrate prepared were investigated by X-ray diffraction. It was found that the potassium ferrate solid has a tetrahedral structure with a space group of D2h (Pnma) and a = 7.705 A, b = 5.863 A, and c = 10.36 A.

Electrorefiner system for recovering purified metal from impure nuclear feed material

DOEpatents

Berger, John F.; Williamson, Mark A.; Wiedmeyer, Stanley G.; Willit, James L.; Barnes, Laurel A.; Blaskovitz, Robert J.

2015-10-06

An electrorefiner system according to a non-limiting embodiment of the present invention may include a vessel configured to maintain a molten salt electrolyte and configured to receive a plurality of alternately arranged cathode and anode assemblies. The anode assemblies are configured to hold an impure nuclear feed material. Upon application of the power system, the impure nuclear feed material is anodically dissolved and a purified metal is deposited on the cathode rods of the cathode assemblies. A scraper is configured to dislodge the purified metal deposited on the cathode rods. A conveyor system is disposed at a bottom of the vessel and configured to remove the dislodged purified metal from the vessel.

Twin defects engineered Pd cocatalyst on C3N4 nanosheets for enhanced photocatalytic performance in CO2 reduction reaction

NASA Astrophysics Data System (ADS)

Lang, Qingqing; Hu, Wenli; Zhou, Penghui; Huang, Tianlong; Zhong, Shuxian; Yang, Lining; Chen, Jianrong; Bai, Song

2017-12-01

Photocatalytic conversion of CO2 to value-added chemicals, a potential route to addressing the depletion of fossil fuels and anthropogenic climate change, is greatly limited by the low-efficient semiconductor photocatalyst. The integration of cocatalyst with light-harvesting semiconductor is a promising approach to enhancing the photocatalytic performance in CO2 reduction reaction. The enhancement is greatly determined by the catalytic active sites on the surface of cocatalyst. Herein, we demonstrate that the photocatalytic performance in the CO2 reduction reaction is greatly promoted by twin defects engineered Pd cocatalyst. In this work, Pd nanoicosahedrons with twin defects were in situ grown on C3N4 nanosheets, which effectively improve the photocatalytic performance in reduction of CO2 to CO and CH4 in comparison with Pd nanotetrahedrons without twin defects. It is proposed that the twin boundary (TB) terminations on the surface of Pd cocatalysts are highly catalytic active sites for CO2 reduction reaction. Based on the proposed mechanism, the photocatalytic activity and selectivity in CO2 reduction were further advanced through reducing the size of Pd icosahedral cocatalyst resulted from the increased surface density of TB terminations. The defect engineering on the surface of cocatalyst represents a novel route in realizing high-performance photocatalytic applications.

Twin defects engineered Pd cocatalyst on C3N4 nanosheets for enhanced photocatalytic performance in CO2 reduction reaction.

PubMed

Lang, Qingqing; Hu, Wenli; Zhou, Penghui; Huang, Tianlong; Zhong, Shuxian; Yang, Lining; Chen, Jianrong; Bai, Song

2017-12-01

Photocatalytic conversion of CO 2 to value-added chemicals, a potential route to addressing the depletion of fossil fuels and anthropogenic climate change, is greatly limited by the low-efficient semiconductor photocatalyst. The integration of cocatalyst with light-harvesting semiconductor is a promising approach to enhancing the photocatalytic performance in CO 2 reduction reaction. The enhancement is greatly determined by the catalytic active sites on the surface of cocatalyst. Herein, we demonstrate that the photocatalytic performance in the CO 2 reduction reaction is greatly promoted by twin defects engineered Pd cocatalyst. In this work, Pd nanoicosahedrons with twin defects were in situ grown on C 3 N 4 nanosheets, which effectively improve the photocatalytic performance in reduction of CO 2 to CO and CH 4 in comparison with Pd nanotetrahedrons without twin defects. It is proposed that the twin boundary (TB) terminations on the surface of Pd cocatalysts are highly catalytic active sites for CO 2 reduction reaction. Based on the proposed mechanism, the photocatalytic activity and selectivity in CO 2 reduction were further advanced through reducing the size of Pd icosahedral cocatalyst resulted from the increased surface density of TB terminations. The defect engineering on the surface of cocatalyst represents a novel route in realizing high-performance photocatalytic applications.

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.

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

Photocatalytic activity of Pt-TiO2 films supported on hydroxylated fly ash cenospheres under visible light

NASA Astrophysics Data System (ADS)

Wang, Bing; Yang, Zewei; An, Hao; Zhai, Jianping; Li, Qin; Cui, Hao

2015-01-01

TiO2 was coated on the surface of hydroxylated fly ash cenospheres (FACs) by the sol-gel method. Platinum (Pt) was then deposited on these TiO2/FAC particles by a photoreduction method to form PTF photocatalyst. The photocatalytic activity of PTF for the degradation of methylene blue (MB) under visible-light irradiation was determined. The PTF sample that was calcined at 450 °C and had a Pt/TiO2 mass ratio of 1.5% exhibited the optimal photocatalytic activity for degradation of MB with a catalyst concentration of 3 g L-1. MB was photodecomposed by PTF in aqueous solution more effectively at alkali pH than at acidic pH, because more MB molecules were adsorbed on the surface of PTF under alkaline conditions than that under acidic. The effect of various inorganic anions (HCO3-, F-, SO42-, NO3-, and Cl-) on the photodegradation of MB by PTF was also investigated. Addition of anions with a concentration of 5 mM enhanced the photocatalytic efficiency of PTF because of the improved adsorption of MB. This effect weakened as the anion concentration was increased, which was attributed to the ability of the anions to scavenge hydroxyl radicals and holes. Our results indicated that the photodegradation of MB took place mainly on the catalyst surface. The generation of hydroxyl radicals in the photocatalytic reaction was measured by the fluorescence method. KI was used to determine the participation of holes in the photocatalytic reaction. Both hydroxyl radicals and valence-band holes were detected in the PTF system. Recycling tests revealed that calcination of the used PTF helped to regain its photocatalytic activity.

Low-temperature route to metal titanate perovskite nanoparticles for photocatalytic applications

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

Alammar, Tarek; Hamm, Ines; Wark, Michael

MTiO 3 (M = Ca, Sr, Ba) nanoparticles were synthesized by a one-step room-temperature ultrasound synthesis in ionic liquid. The samples we gathered are characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, UV–vis diffuse reflectance, Raman and IR spectroscopy and their capability in photocatalytic hydrogen evolution and methylene blue degradation was tested. Powder X-ray diffraction and Raman spectroscopic investigations revealed the products to crystallize in the cubic perovskite structure. SEM observations showed that the obtained CaTiO 3 consists of nanospheres, BaTiO 3 of raspberry-like shaped particles of 20 nm in diameter. SrTiO 3 particles have cubic-like morphology with anmore » edge length varying from 100 to 300 nm. SrTiO 3 exhibited the highest catalytic activity for photocatalytic H 2 evolution using only 0.025 wt.% Rh as co-catalyst and for the degradation of methylene blue under UV irradiation. The influence of parameters such as synthesis method, calcination temperature, and doping with nitrogen on the morphology, crystallinity, chemical composition, and photocatalytic acivity of SrTiO 3 was studied. Heating the as-prepared SrTiO 3 to 700 °C for extended time leads to a decrease in surface area and catalytic activity. Ionothermal prepared SrTiO 3 exhibits a higher activity than sonochemically prepared one without co-catalyst due to a synergistic effect of anatase which is present in small amount as a by-phase. Furthermore, after photodeposition of Rh, however, the activity is lower than that of the sonochemically prepared SrTiO 3. Nitrogen-doped SrTiO 3 showed photocatalytic acivity under visible light irradiation.« less

Low-temperature route to metal titanate perovskite nanoparticles for photocatalytic applications

DOE PAGES

Alammar, Tarek; Hamm, Ines; Wark, Michael; ...

2014-11-13

MTiO 3 (M = Ca, Sr, Ba) nanoparticles were synthesized by a one-step room-temperature ultrasound synthesis in ionic liquid. The samples we gathered are characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, UV–vis diffuse reflectance, Raman and IR spectroscopy and their capability in photocatalytic hydrogen evolution and methylene blue degradation was tested. Powder X-ray diffraction and Raman spectroscopic investigations revealed the products to crystallize in the cubic perovskite structure. SEM observations showed that the obtained CaTiO 3 consists of nanospheres, BaTiO 3 of raspberry-like shaped particles of 20 nm in diameter. SrTiO 3 particles have cubic-like morphology with anmore » edge length varying from 100 to 300 nm. SrTiO 3 exhibited the highest catalytic activity for photocatalytic H 2 evolution using only 0.025 wt.% Rh as co-catalyst and for the degradation of methylene blue under UV irradiation. The influence of parameters such as synthesis method, calcination temperature, and doping with nitrogen on the morphology, crystallinity, chemical composition, and photocatalytic acivity of SrTiO 3 was studied. Heating the as-prepared SrTiO 3 to 700 °C for extended time leads to a decrease in surface area and catalytic activity. Ionothermal prepared SrTiO 3 exhibits a higher activity than sonochemically prepared one without co-catalyst due to a synergistic effect of anatase which is present in small amount as a by-phase. Furthermore, after photodeposition of Rh, however, the activity is lower than that of the sonochemically prepared SrTiO 3. Nitrogen-doped SrTiO 3 showed photocatalytic acivity under visible light irradiation.« 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.

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.

Investigation of the physical, optical, and photocatalytic properties of CeO2/Fe-doped InVO4 composite

NASA Astrophysics Data System (ADS)

Chaison, Jindaporn; Wetchakun, Khatcharin; Wetchakun, Natda

2017-12-01

The CeO2/Fe-doped InVO4 composites with various Fe concentrations (0.5, 1.0, 2.0, 5.0 and 6.0 mol%) was synthesized by homogeneous precipitation and hydrothermal methods. The as-synthesized samples were characterized by powder X-ray diffraction (XRD), Brunauer Emmett and Teller (BET)-specific surface area, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (DRS). Fe-doping into InVO4 crystal induces the distortion of the crystalline structure, the transformation of InVO4 morphology, and the new energy subband level generation of Fe between the CB and VB edge of InVO4. The electron excitation from the VB to Fe orbitals results in the decreased band gap and the extended absorption of visible-light, and thus enhances its photocatalytic performance. Visible-light-driven photocatalytic degradation of Rhodamine B (RhB) dye in water was used to evaluate the photocatalytic performance of CeO2/Fe-doped InVO4 composites. The results revealed that there is an optimum Fe (5.0 mol %) doping level. The composite with the optimum doping level obtains high photocatalytic activity of CeO2/Fe-doped InVO4 composite compared to pure CeO2 and pure InVO4 host. The increase of photocatalytic activity of CeO2/Fe-doped InVO4 composite was ascribed to the surface area, crystal defect, and band gap energy. Moreover, the photocatalytic enhancement is also because iron ions act as a trapping site, which results in the higher separation efficiency of photogenerated electrons and holes pairs in the CeO2/InVO4 composite. The evaluation of radical scavengers confirmed that hydroxyl radical was the main active species during the photodegradation of RhB. These synergistic effects are responsible for the enhanced photocatalytic activity of CeO2/Fe-doped InVO4 composite. Furthermore, the possible enhanced photocatalytic mechanism

Controlled synthesis and photocatalytic investigation of different-shaped one-dimensional titanic acid nanomaterials

NASA Astrophysics Data System (ADS)

Li, Qiuye; Lu, Gongxuan

Different-shaped one-dimensional (1D) titanic acid nanomaterials (TANs) were prepared by hydrothermal synthesis. By changing the reaction temperature (120, 170 and 200 °C), three kinds of 1D TAN, short-nanotubes (SNT), long-nanotubes (LNT), and nanorods (NR), were obtained. The obtained TANs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and solid-stated diffuse reflectance UV-vis spectra (UV-vis DRS) techniques. Based on these 1D TAN, Eosin Y-sensitized Pt-loaded TAN were prepared by the in situ impregnation and photo-reduction method. Their photocatalytic activity for hydrogen generation was evaluated in triethanolamine (TEOA) aqueous solution under visible light irradiation (λ ≥ 420 nm). The results indicated that the morphology difference led to a significant variation of photocatalytic performance for hydrogen generation, with the activity order as follows: Eosin Y-sensitized Pt-loaded LNT > Eosin Y-sensitized Pt-loaded NR > Eosin Y-sensitized Pt-loaded SNT. The experimental conditions for photocatalytic hydrogen generation such as Pt loading content, the mass ratio of Eosin Y to TAN, and so on, were optimized. As a result, the highest apparent quantum yields of hydrogen generation for Eosin Y-sensitized Pt-loaded SNT, LNT, and NR were 6.65, 17.36, and 15.04%, respectively. The stability of these photocatalysts and the reaction mechanism of the photocatalytic hydrogen generation are also discussed in detail.

ZnO-graphene quantum dots heterojunctions for natural sunlight-driven photocatalytic environmental remediation

NASA Astrophysics Data System (ADS)

Kumar, Suneel; Dhiman, Ankita; Sudhagar, Pitchaimuthu; Krishnan, Venkata

2018-07-01

In this work, we report the formation of heterojunctions comprising of graphene quantum dots (GQD) decorated ZnO nanorods (NR) and its use as efficient photocatalysts for environmental remediation. The heterojunctions has been designed to be active both in the UV and visible light regions and anticipated utilize the maximum part of the solar light spectrum. In this view, we examined the photocatalytic performance of our heterojunctions towards the degradation of colored pollutant (methylene blue (MB) dye) and a colorless pollutant (carbendazim (CZ) fungicide) under sunlight irradiation. Compared to bare photocatalyst ZnO and GQD, the heterojunction with 2 wt% of GQD (ZGQD2) showed the best photocatalytic activity by effectively degrading (about 95%) of organic pollutants (MB and CZ) from water within a short span of 70 min. The superior photocatalytic activity of these ZnO-GQD heterojunctions could be attributed to efficient charge carrier separation lead suppressed recombination rate at photocatalyst interfaces. In addition to the enhanced light absorption from UV to visible region, the high specific surface area of ZGQD2 heterojunction (353.447 m2 g-1) also imparts strong adsorption capacity for pollutants over catalyst surface, resulting in high photoactivity. Based on the obtained results, band gap alignment at ZnO-GQD heterojunction and active species trapping experiments, a plausible mechanism is proposed for photocatalytic reaction. The excellent photostability and recyclability of the ZnO-GQD heterojunctions fostering as promising photocatalyst candidate for environmental remediation applications.

Method of purifying neutral organophosphorus extractants

DOEpatents

Horwitz, E. Philip; Gatrone, Ralph C.; Chiarizia, Renato

1988-01-01

A method for removing acidic contaminants from neutral mono and bifunctional organophosphorous extractants by contacting the extractant with a macroporous cation exchange resin in the H.sup.+ state followed by contact with a macroporous anion exchange resin in the OH.sup.- state, whereupon the resins take up the acidic contaminants from the extractant, purifying the extractant and improving its extraction capability.

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.

Process for purifying geothermal steam

DOEpatents

Li, Charles T.

1980-01-01

Steam containing hydrogen sulfide is purified and sulfur recovered by passing the steam through a reactor packed with activated carbon in the presence of a stoichiometric amount of oxygen which oxidizes the hydrogen sulfide to elemental sulfur which is adsorbed on the bed. The carbon can be recycled after the sulfur has been recovered by vacuum distillation, inert gas entrainment or solvent extraction. The process is suitable for the purification of steam from geothermal sources which may also contain other noncondensable gases.

Process for purifying geothermal steam

DOEpatents

Li, C.T.

Steam containing hydrogen sulfide is purified and sulfur recovered by passing the steam through a reactor packed with activated carbon in the presence of a stoichiometric amount of oxygen which oxidizes the hydrogen sulfide to elemental sulfur which is adsorbed on the bed. The carbon can be recycled after the sulfur has been recovered by vacuum distillation, inert gas entrainment or solvent extraction. The process is suitable for the purification of steam from geothermal sources which may also contain other noncondensable gases.

ZnO:Ag nanorods as efficient photocatalysts: Sunlight driven photocatalytic degradation of sulforhodamine B

NASA Astrophysics Data System (ADS)

Raji, R.; K. S., Sibi; K. G., Gopchandran

2018-01-01

Visible light responsive highly photocatalytic ZnO:Ag nanorods with varying Ag concentration were synthesized via co-precipitation method. X-ray diffraction analysis and high resolution transmission electron microscopy investigations confirmed the hexagonal wurtzite phase for these ZnO:Ag nanorods with preferential growth along the (101) plane. Raman shift and luminescence measurements indicated that the incorporation of Ag influences the lattice vibrational modes; there by causing distortion in lattice, inducing silent vibrational modes and emission behavior by quenching of both the band edge and visible emissions respectively. The photocatalytic performance of these nanorods as catalysts was tested by observing the photodegradation of a representative dye pollutant, viz., sulforhodamine B under sunlight irradiation. Photocatalytic performance was evaluated by determining the rate of reaction kinetics, photodegradation efficiency and mineralization efficiency. A high rate constant of 0.552 min-1, chemical oxygen demand value of 5.8 ppm and a mineralization efficiency of 94% were obtained when ZnO: Ag nanorods with an Ag content of 1.5 at.% were used as catalysts. The observed increase in photocatalytic efficiency with Ag content in ZnO:Ag nanorods is attributed to the electron scavenging action of silver, Schottky barrier between the Ag and ZnO interface and the better utilization of sunlight due to enhanced absorption due to plasmons in the visible region. BET analysis indicated that silver doping causes effective surface area of nanorods to increase, which in turn increases the photocatalytic efficiency. The possible mechanism for degradation of dye under sunlight irradiation is described with a schematic and the photostability of the ZnO:Ag nanorods were also tested through five repetitive cycles. This work suggests that the prepared ZnO:Ag nanorods are excellent reusable photocatalysts for the degradation of toxic organic waste in water, which causes severe