The Effect of Pluronic 123 Surfactant concentration on The N2 Adsorption Capacity of Mesoporous Silica SBA-15: Dubinin-Astakhov Adsorption Isotherm Analysis

NASA Astrophysics Data System (ADS)

Dhaneswara, Donanta; Siti Agustina, A. A. A.; Dewantoro Adhy, P.; Delayori, Farhan; Fajar Fatriansyah, Jaka

2018-04-01

Mesoporous SBA-15 has been successfully synthesized at various concentration of Pluronic 123 surfactant (7mM, 50 mM, 54 mM, 60 mM and 66 mM) and the effect of these various concentrations on the N2 adsorption capacity has been investigated. The adsorption analysis was conducted using Dubinin-Astakhov isotherm model for multilayer adsorption phenomenon. It was found that etryat low concentration of Pluronic 123, the system exhibits type I adsorption isotherm while at high concentration, the system exhibits type IV adsorption with H1 hysteresis curve which indicates the existence of pores with cylindrical geometry, relatively uniform pore size and possibility of pore network effects. It also was found that, by using D-A isotherm model fitting, at 60 mM concentration of Pluronic 123, SBA-15 has the highest adsorption capacity which stands at 421 cm3/gram.

Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

USGS Publications Warehouse

Sun, Jielun; Chen, S.; Rostam-Abadi, M.; Rood, M.J.

1998-01-01

A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

Enhancement of p-nitrophenol adsorption capacity through N2-thermal-based treatment of activated carbons

NASA Astrophysics Data System (ADS)

Álvarez-Torrellas, S.; Martin-Martinez, M.; Gomes, H. T.; Ovejero, G.; García, J.

2017-08-01

In this work several activated carbons showing different textural and chemical properties were obtained by chemical and physical activation methods, using a lignocellulosic material (peach stones) as precursor. The activated carbon resulting from the chemical activation, namely as CAC, revealed the best textural properties (SBET = 1521 m2 g-1, pore volume = 0.90 cm3 g-1) and an acidic character. It was found that the activated carbon obtained at 300 °C (under air atmosphere, PAC_air), and those synthesized at 750 °C in presence of N2 flow with bubbling of water/12 M H3PO4 solution (PAC_N2(H2O)/PAC_N2(H3PO4)), respectively, revealed worse textural properties, compared to CAC. Two functionalization treatments, by using sulphuric acid at boiling temperature (PACS) and nitric acid-urea-N2 heating at 800 °C (PAC-NUT), were applied to PAC_air, in order to enhance the adsorption ability of the carbon material. Several techniques were carried out to characterize the physical and chemical properties of the obtained carbon materials. The modification treatments had influence on the carbon surface properties, since the nitric acid-urea-N2 heating treatment led to a carbon material with highly-improved properties (SBET = 679 m2 g-1, pHIEP = 5.3). Accordingly, the original and modified-carbon materials were tested as adsorbents to remove 4-nitrophenol (4-NP), assessing batch and fixed-bed column adsorption tests. PAC-NUT carbon offered the best adsorption behavior (qe = 234 mg g-1), showing a high ability for the removal of 4-NP from water.

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performance.

PubMed

Elvira, Gutiérrez-Bonilla; Francisco, Granados-Correa; Víctor, Sánchez-Mendieta; Alberto, Morales-Luckie Raúl

2017-07-01

A series of MgO-based adsorbents were prepared through solution-combustion synthesis and ball-milling process. The prepared MgO-based powders were characterized using X-ray diffraction, scanning electron microscopy, N 2 physisorption measurements, and employed as potential adsorbents for CO 2 adsorption. The influence of structural and textural properties of these adsorbents over the CO 2 adsorption behaviour was also investigated. The results showed that MgO-based products prepared by solution-combustion and ball-milling processes, were highly porous, fluffy, nanocrystalline structures in nature, which are unique physico-chemical properties that significantly contribute to enhance their CO 2 adsorption. It was found that the MgO synthesized by solution combustion process, using a molar ratio of urea to magnesium nitrate (2:1), and treated by ball-milling during 2.5hr (MgO-BM2.5h), exhibited the maximum CO 2 adsorption capacity of 1.611mmol/g at 25°C and 1atm, mainly via chemisorption. The CO 2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area, total pore volume, pore size distribution and crystallinity. The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO 2 adsorption-desorption times, without any significant loss of performance, that supports the potential of MgO-based adsorbent. The results confirmed that the special features of MgO prepared by solution-combustion and treated by ball-milling during 2.5hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO 2 capture technologies. Copyright © 2016. Published by Elsevier B.V.

Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

PubMed

Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

2017-02-08

We demonstrate that the complex adsorption behavior of H 2 O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H 2 O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H 2 O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H 2 O adsorbates forming surface recombination centers and multiple H 2 O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H 3 O + and OH - ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

The adsorption of Run (n = 1-4) on γ-Al2O3 Surface: A DFT study

NASA Astrophysics Data System (ADS)

Liu, Zhe; Guo, Yafei; Chen, Yu; Shen, Rong

2018-05-01

The density functional theory (DFT) was adopted to study the adsorption and growth of Run (n = 1-4) clusters on γ-Al2O3 surface, which is of great significances for the design of many important catalysts, especially for carbon dioxide methanation. It is found that both the Rusbnd Ru bond length and adsorption energy Eads of Ru clusters with the surface increase with the Run clusters increasing. The growth ability of the supported Run cluster is weaker than the gas phase Run clusters through comparing their respective growth process, which ascribes to the stabilization of γ-Al2O3 support. An interesting discovery is that the basin structure was supposed to be the most favorable adsorption geometry for Run clusters. Additionally, the distances between Ru atoms in the adsorbed clusters are longer than that in their isolated counterparts. Bader charge analysis was conducted for the most stable configurations of Run (n = 1-4) clusters on γ-Al2O3 surface as well. And the results suggest that Run (n = 1-4) clusters serve as the electron donators. The result of projected density of states (PDOS) shows that strong adsorption of Ru atom on the γ-Al2O3 surface correlates with strong interaction between d orbital of Ru atom and p orbital of Al or O atom of the Al2O3 support.

Adsorption of the natural protein surfactant Rsn-2 onto liquid interfaces.

PubMed

Brandani, Giovanni B; Vance, Steven J; Schor, Marieke; Cooper, Alan; Kennedy, Malcolm W; Smith, Brian O; MacPhee, Cait E; Cheung, David L

2017-03-22

To stabilize foams, droplets and films at liquid interfaces a range of protein biosurfactants have evolved in nature. Compared to synthetic surfactants, these combine surface activity with biocompatibility and low solution aggregation. One recently studied example is Rsn-2, a component of the foam nest of the frog Engystomops pustulosus, which has been predicted to undergo a clamshell-like opening transition at the air-water interface. Using atomistic molecular dynamics simulations and surface tension measurements we study the adsorption of Rsn-2 onto air-water and cyclohexane-water interfaces. The protein adsorbs readily at both interfaces, with adsorption mediated by the hydrophobic N-terminus. At the cyclohexane-water interface the clamshell opens, due to the favourable interaction between hydrophobic residues and cyclohexane molecules and the penetration of cyclohexane molecules into the protein core. Simulations of deletion mutants showed that removal of the N-terminus inhibits interfacial adsorption, which is consistent with the surface tension measurements. Deletion of the hydrophilic C-terminus also affects adsorption, suggesting that this plays a role in orienting the protein at the interface. The characterisation of the interfacial behaviour gives insight into the factors that control the interfacial adsorption of proteins, which may inform new applications of this and similar proteins in areas including drug delivery and food technology and may also be used in the design of synthetic molecules showing similar changes in conformation at interfaces.

The adsorption of NO, NH3, N2 on carbon surface: a density functional theory study.

PubMed

Wang, Jiayong; Yang, Mo; Deng, Debing; Qiu, Shuxia

2017-08-11

To explore the adsorption mechanism of NO, NH 3 , N 2 on a carbon surface, and the effect of basic and acidic functional groups, density functional theory was employed to investigate the interactions between these molecules and carbon surfaces. Molecular electrostatic potential, Mulliken population analyses, reduced density gradient, and Mayer bond order analyses were used to clarify the adsorption mechanism. The results indicate that van der Waals interactions are responsible for N 2 physisorption, and N 2 is the least likely to adsorb on a carbon surface. Modification of carbon materials to decorate basic or acidic functional groups could enhance the NH 3 physisorption because of hydrogen bonding or electrostatic interactions, however, NO physisorption on a carbon surface is poor. Zig-zag sites are more reactive than armchair sites when these gas molecules absorb on the edge sites of carbon surface. Graphical abstract NH 3 , N 2 , NO adsortion on carbon surface.

Effect of heat treatment on CO2 adsorption of KOH-activated graphite nanofibers.

PubMed

Meng, Long-Yue; Park, Soo-Jin

2010-12-15

In this work, graphite nanofibers (GNFs) were successfully expanded intercalating KOH followed by heat treatment in the temperature range of 700-1000 °C. The aim was to improve the CO(2) adsorption capacity of the GNFs by increasing the porosity of GNFs. The effects of heat treatment on the pore structures of GNFs were investigated by N(2) full isotherms, XRD, SEM, and TEM. The CO(2) adsorption capacity was measured by CO(2) isothermal adsorption at 25 °C and 1 atm. From the results, it was found that the activation temperature had a major influence on CO(2) adsorption capacity and textural properties of GNFs. The specific surface area, total pore volume, and mesopore volume of the GNFs increased after heat treatment. The CO(2) adsorption isotherms showed that G-900 exhibited the best CO(2) adsorption capacity with 59.2 mg/g. Copyright © 2010 Elsevier Inc. All rights reserved.

Adsorptive separation of CO 2 in sulfur-doped nanoporous carbons: Selectivity and breakthrough simulation

DOE PAGES

Saha, Dipendu; Orkoulas, Gerassimos; Chen, Jihua; ...

2017-03-01

In this research, we have synthesized two sulfur functionalized nanoporous carbons by post-synthesis modifications with sulfur bearing activating agents that simultaneously enhanced the surface area and introduced sulfur functionalities on the carbon surface. The Brunauer–Emmett–Teller (BET) surface areas of these materials were 2865 and 837 m 2/g with total sulfur contents of 8.2 and 12.9 %, respectively. The sulfur-functionalized carbons were characterized with pore textural properties, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and electron microscopy (SEM and TEM). In both the carbons, CO 2 adsorption isotherms and kinetics were measured in three different temperatures of 298, 288 and 278more » K and pressures up to 760 torr. The gravimetric CO 2 uptake followed the trend with BET surface area but the surface area-based uptake was reversed and it followed the trend of sulfur content. The heat of adsorption of CO 2 in low uptake was 60-65 kJ/mol, which is the highest for CO 2 adsorption in porous carbons. In order to investigate the adsorptive separation of CO 2, N 2 and CH 4 adsorption isotherms were also measured at 298 K and 760 torr. The selectivity of separation for CO 2/N 2 and CO 2/CH 4 was calculated based on the Ideal Adsorbed Solution Theory (IAST) and all the results demonstrated the high CO 2 selectivity for the carbon with higher sulfur content. The adsorption isotherms were combined with mass balances to calculate the breakthrough behavior of the binary mixtures of CO 2/N 2 and CO 2/CH 4. The simulation results demonstrated that the dimensionless breakthrough time is a decreasing function of the mole fraction of CO 2 in the feed stream. The overall results suggest that the sulfurfunctionalized carbons can be employed as potential adsorbents for CO 2 separation.« less

Simultaneous laboratory measurements of CO2 and H2O adsorption on palagonite: Implications for the Martian climate and volatile reservoir

NASA Technical Reports Server (NTRS)

Zent, A. P.; Quinn, R.

1993-01-01

We are measuring the simultaneous adsorption of H2O and CO2 on palagonite materials in order to improve the formulation of climate models for Mars. We report on the initial co-adsorption data. Models of the Martian climate and volatile inventory indicate that the regolith serves as one of the primary reservoirs of outgassed volatiles and that it exchanges H2O and CO2 with the atmosphere in response to changes in insolation associated with astronomical cycles. Physical adsorbate must exist on the surfaces of the cold particulates that constitute the regolith, and the size of that reservoir can be assessed through laboratory measurements of adsorption on terrestrial analogs. Many studies of the independent adsorption of H2O and CO2 on Mars analog were made and appear in the literature. Empirical expressions that relate the adsorptive coverage of each gas to the temperature of the soil and partial pressure have been derived based on the laboratory data. Numerical models incorporate these adsorption isotherms into climatic models, which predict how the adsorptive coverage of the regolith and hence, the pressure of each gas in the atmosphere will vary as the planet moves through its orbit. These models suggest that the regolith holds several tens to hundreds of millibars of CO2 and that during periods of high obliquity warming of the high-latitude regolith will result in desorption of the CO2, and a consequent increase in atmospheric pressure. At lower obliquities, the caps cool and the equator warms forcing the desorption of several tens of millibars of CO2, which is trapped into quasipermanent CO2 caps.

Competitive adsorption behaviors of carbon dioxide and n-dodecane mixtures in 13X molecular sieve

NASA Astrophysics Data System (ADS)

Zhu, Chaofan; Dong, Mingzhe; Gong, Houjian

2018-01-01

The CO2 cyclic injection has been proven to be effective to enhance tight oil recovery under constant reservoir temperature and down hole pressure conditions. However, the enhance tight oil recovery mechanism was unclear, especially the adsorption of the CO2 and alkane in the surface. Therefore, it is great important to study the adsorption mechanism of CO2 and alkane mixtures in tight oil. In this study, a new experimental method and apparatus have been designed to test the change of the mole fraction of CO2 and n-C12 before and after the adsorption equilibrium. Then, the adsorption amount of CO2 and n-C12 was obtained by a mathematical method. Moreover, the adsorption character of CO2 and n-C12 mixtures in 13X molecular sieve and the effect of pressure on the adsorption and amount were studied. The results show that the adsorption of CO2 and the desorption of n-C12 follow the Langmuir adsorption. This study provides a straightforward method to experimentally determine the adsorption properties of the tight oil, which can be used to evaluate enhanced tight oil recovery by CO2 injection.

Experimental and Theoretical Studies of Gas Adsorption in Cu3(BTC)2: An Effective Activation Procedure

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

Liu, J.; Culp, J.T.; Natesakhawat, Sittichai

2007-07-05

We have improved the activation process for CuBTC [Cu3(BTC)2, BTC ) 1,3,5-benzenetricarboxylate] by extracting the N,N-dimethylformamide-solvated crystals with methanol; we identify material activated in this way as CuBTC-MeOH. This improvement allowed the activation to be performed at a much lower temperature, thus greatly mitigating the danger of reducing the copper ions. A review of the literature for H2 adsorption in CuBTC shows that the preparation and activation process has a significant impact on the adsorption capacity, surface area, and pore volume. CuBTC-MeOH exhibits a larger pore volume and H2 adsorption amount than any previously reported results for CuBTC. We havemore » performed atomically detailed modeling to complement experimentally measured isotherms. Quantum effects for hydrogen adsorption in CuBTC were found to be important at 77 K. Simulations that include quantum effects are in good agreement with the experimentally measured capacity for H2 at 77 K and high pressure. However, simulations underpredict the amount adsorbed at low pressures. We have compared the adsorption isotherms from simulations with experiments for H2 adsorption at 77, 87, 175, and 298 K; nitrogen adsorption at 253 and 298 K; and argon adsorption at 298 and 356 K. Reasonable agreement was obtained in all cases.« less

CO adsorption on small Au{sub n} (n = 1–4) structures supported on hematite. II. Adsorption on the O-rich termination of α-Fe{sub 2}O{sub 3}(0001) surface

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

Pabisiak, Tomasz; Kiejna, Adam, E-mail: kiejna@ifd.uni.wroc.pl; Winiarski, Maciej J.

2016-01-28

The adsorption of small Au{sub n} (n = 1–4) nanostructures on oxygen terminated α-Fe{sub 2}O{sub 3}(0001) surface was investigated using density functional theory in the generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) form with Hubbard correction U, accounting for strong electron correlations (PBE+U). The structural, energetic, and electronic properties were examined for two classes of the adsorbed Au{sub n} nanostructures with vertical and flattened configurations. Similarly to the Fe-terminated α-Fe{sub 2}O{sub 3}(0001) surface considered in Part I, the flattened configurations were found energetically more favored than vertical ones. The binding of Au{sub n} to the O-terminated surface is much stronger thanmore » to the Fe-termination. The adsorption bonding energy of Au{sub n} and the work function of the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) systems decrease with the increased number of Au atoms in a structure. All of the adsorbed Au{sub n} structures are positively charged. The bonding of CO molecules to the Au{sub n} structures is distinctly stronger than on the Fe-terminated surface; however, it is weaker than the binding to the bare O-terminated surface. The CO molecule binds to the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) system through a peripheral Au atom partly detached from the Au{sub n} structure. The results of this work indicate that the most energetically favored sites for adsorption of a CO molecule on the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) systems are atoms in the Au{sup 0.5+} oxidation state.« less

Insights into the Hydrothermal Stability of Triamine-Functionalized SBA-15 Silica for CO2 Adsorption.

PubMed

Jahandar Lashaki, Masoud; Ziaei-Azad, Hessam; Sayari, Abdelhamid

2017-10-23

The hydrothermal stability of triamine-grafted, large-pore SBA-15 CO 2 adsorbents was studied by using steam stripping. Following two 3 h cycles of steam regeneration, lower CO 2 uptakes, lower CO 2 /N ratios, and slower adsorption kinetics were observed relative to fresh samples, particularly at the lowest adsorption temperature (25 °C). CO 2 adsorption measurements for a selected sample exposed to 48 h of steam stripping depicted that after the initial loss during the first exposure to steam (3-6 h), the adsorptive properties stabilized. For higher adsorption temperatures (i.e., 50 and 75 °C), however, all adsorptive properties remained almost unchanged after steaming, indicating the significance of diffusional limitations. Thermogravimetric analysis and FTIR spectroscopy on grafted samples before and after steam stripping showed no amine leaching and no change in the chemical nature of the amine groups, respectively. Also, a six-cycle CO 2 adsorption/desorption experiment under dry conditions showed no thermal degradation. However, N 2 adsorption measurement at 77 K showed significant reductions in the BET surface area of the grafted samples following steaming. Based on the pore size distribution of calcined, grafted samples before and after steaming, it is proposed that exposure to steam restructured the grafted materials, causing mass transfer resistance. It is inferred that triamine-grafted, large-pore SBA-15 adsorbents are potential candidates for CO 2 capture at relatively high temperatures (50-75 °C; for example, flue gas) combined with steam regeneration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption properties of AlN on Si(111) surface: A density functional study

NASA Astrophysics Data System (ADS)

Yuan, Yinmei; Zuo, Ran; Mao, Keke; Tang, Binlong; Zhang, Zhou; Liu, Jun; Zhong, Tingting

2018-04-01

In the process of preparing GaN on Si substrate by MOCVD, an AlN buffer layer is very important. In this study, we conducted density functional theory calculations on the adsorption of AlN molecule on Si(111)-(2 × 2) surface, with the AlN molecule located horizontally or vertically above Si(111) surface at different adsorption sites. The calculations revealed that the lowest adsorption energy was at the N-top-Al-bridge site in the horizontal configuration, with the narrowest band gap, indicating that it was the most preferential adsorption growth status of AlN. In the vertical configurations, N adatom was more reactive and convenient to form bonds with the topmost Si atoms than Al adatom. When the N-end of the AlN molecule was located downward, the hollow site was the preferred adsorption site; when the Al-end was located downward, the bridge site was the most energetically favorable. Moreover, we investigated some electronic properties such as partial density of states, electron density difference, Mulliken populations, etc., revealing the microscale mechanism for AlN adsorption on Si(111) surface and providing theoretical support for adjusting the processing parameters during AlN or GaN production.

UiO-66-NH2/GO Composite: Synthesis, Characterization and CO2 Adsorption Performance

PubMed Central

Cao, Yan; Zhang, Hongmei; Song, Fujiao; Huang, Tao; Ji, Jiayu; Zhong, Qin; Chu, Wei; Xu, Qi

2018-01-01

In this work, a new composite materials of graphene oxide (GO)-incorporated metal-organic framework (MOF)(UiO-66-NH2/GO) were in-situ synthesized, and were found to exhibit enhanced high performances for CO2 capture. X-ray diffraction (XRD), scanning electron microscope (SEM), N2 physical adsorption, and thermogravimetric analysis (TGA) were applied to investigate the crystalline structure, pore structure, thermal stability, and the exterior morphology of the composite. We aimed to investigate the influence of the introduction of GO on the stability of the crystal skeleton and pore structure. Water, acid, and alkali resistances were tested for physical and chemical properties of the new composites. CO2 adsorption isotherms of UiO-66, UiO-66-NH2, UiO-66/GO, and UiO-66-NH2/GO were measured at 273 K, 298 K, and 318 K. The composite UiO-66-NH2/GO exhibited better optimized CO2 uptake of 6.41 mmol/g at 273 K, which was 5.1% higher than that of UiO-66/GO (6.10 mmol/g). CO2 adsorption heat and CO2/N2 selectivity were then calculated to further evaluate the CO2 adsorption performance. The results indicated that UiO-66-NH2/GO composites have a potential application in CO2 capture technologies to alleviate the increase in temperature of the earth’s atmosphere. PMID:29641476

Cation-Exchanged Zeolitic Chalcogenides for CO2 Adsorption.

PubMed

Yang, Huajun; Luo, Min; Chen, Xitong; Zhao, Xiang; Lin, Jian; Hu, Dandan; Li, Dongsheng; Bu, Xianhui; Feng, Pingyun; Wu, Tao

2017-12-18

We report here the intrinsic advantages of a special family of porous chalcogenides for CO 2 adsorption in terms of high selectivity of CO 2 /N 2 , large uptake capacity, and robust structure due to their first-ever unique integration of the chalcogen-soft surface, high porosity, all-inorganic crystalline framework, and the tunable charge-to-volume ratio of exchangeable cations. Although tuning the CO 2 adsorption properties via the type of exchangeable cations has been well-studied in oxides and MOFs, little is known about the effects of inorganic exchangeable cations in porous chalcogenides, in part because ion exchange in chalcogenides can be very sluggish and incomplete due to their soft character. We have demonstrated that, through a methodological change to progressively tune the host-guest interactions, both facile and nearly complete ion exchange can be accomplished. Herein, a series of cation-exchanged zeolitic chalcogenides (denoted as M@RWY) were studied for the first time for CO 2 adsorption. Samples were prepared through a sequential ion-exchange strategy, and Cs + -, Rb + -, and K + -exchanged samples demonstrated excellent CO 2 adsorption performance. Particularly, K@RWY has the superior CO 2 /N 2 selectivity with the N 2 adsorption even undetected at either 298 or 273 K. It also has the large uptake of 6.3 mmol/g (141 cm 3 /g) at 273 K and 1 atm with an isosteric heat of 35-41 kJ mol -1 , the best among known porous chalcogenides. Moreover, it permits a facile regeneration and exhibits an excellent recyclability, as shown by the multicycling adsorption experiments. Notably, K@RWY also demonstrates a strong tolerance toward water.

Overcoming double-step CO2 adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg2(dobpdc).

PubMed

Milner, Phillip J; Martell, Jeffrey D; Siegelman, Rebecca L; Gygi, David; Weston, Simon C; Long, Jeffrey R

2018-01-07

Alkyldiamine-functionalized variants of the metal-organic framework Mg 2 (dobpdc) (dobpdc 4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) are promising for CO 2 capture applications owing to their unique step-shaped CO 2 adsorption profiles resulting from the cooperative formation of ammonium carbamate chains. Primary , secondary (1°,2°) alkylethylenediamine-appended variants are of particular interest because of their low CO 2 step pressures (≤1 mbar at 40 °C), minimal adsorption/desorption hysteresis, and high thermal stability. Herein, we demonstrate that further increasing the size of the alkyl group on the secondary amine affords enhanced stability against diamine volatilization, but also leads to surprising two-step CO 2 adsorption/desorption profiles. This two-step behavior likely results from steric interactions between ammonium carbamate chains induced by the asymmetrical hexagonal pores of Mg 2 (dobpdc) and leads to decreased CO 2 working capacities and increased water co-adsorption under humid conditions. To minimize these unfavorable steric interactions, we targeted diamine-appended variants of the isoreticularly expanded framework Mg 2 (dotpdc) (dotpdc 4- = 4,4''-dioxido-[1,1':4',1''-terphenyl]-3,3''-dicarboxylate), reported here for the first time, and the previously reported isomeric framework Mg-IRMOF-74-II or Mg 2 (pc-dobpdc) (pc-dobpdc 4- = 3,3'-dioxidobiphenyl-4,4'-dicarboxylate, pc = para -carboxylate), which, in contrast to Mg 2 (dobpdc), possesses uniformally hexagonal pores. By minimizing the steric interactions between ammonium carbamate chains, these frameworks enable a single CO 2 adsorption/desorption step in all cases, as well as decreased water co-adsorption and increased stability to diamine loss. Functionalization of Mg 2 (pc-dobpdc) with large diamines such as N -( n -heptyl)ethylenediamine results in optimal adsorption behavior, highlighting the advantage of tuning both the pore shape and the diamine size for the development of

Molecular adsorption of hydrogen peroxide on N- and Fe-doped titania nanoclusters

NASA Astrophysics Data System (ADS)

Mohajeri, Afshan; Dashti, Nasimeh Lari

2017-06-01

Titanium dioxide (titania) nanoparticles have been extensively investigated for photocatalytic applications such as the decomposition and adsorption of pollutant and undesirable compound in air and waste water. In this context, the present article reports the molecular adsorption of hydrogen peroxide on the surface of doped titania clusters. Density functional theory calculations were performed to investigate the structures and electronic properties of two nanoscale (TiO2)n clusters (n = 5,6) modified by nitrogen and iron dopants. The relative stability of all possible N-doped and Fe-doped isomers has been compared with each other and with the parent cluster. It was found that the Fe-doped clusters are in general more stable than the N-doped counterparts. Moreover, after N/Fe doping an enhanced in the magnetization of the clusters is observed. In the second part, we have investigated different modes of H2O2 adsorption on the lowest-energy isomers of doped clusters. In almost all the cases, the adsorptions on the doped clusters are found to be less exothermic than on the corresponding undoped parent cluster. Our results highlight the essential role of charge transfer into the interaction between H2O2 and doped (TiO2)n clusters, especially for Fe-doped clusters.

Overcoming double-step CO 2 adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg 2(dobpdc)

DOE PAGES

Milner, Phillip J.; Martell, Jeffrey D.; Siegelman, Rebecca L.; ...

2017-10-26

Alkyldiamine-functionalized variants of the metal–organic framework Mg 2(dobpdc) (dobpdc 4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) are promising for CO 2 capture applications owing to their unique step-shaped CO 2 adsorption profiles resulting from the cooperative formation of ammonium carbamate chains. Primary,secondary (1°,2°) alkylethylenediamine-appended variants are of particular interest because of their low CO 2 step pressures (≤1 mbar at 40 °C), minimal adsorption/desorption hysteresis, and high thermal stability. Herein, we demonstrate that further increasing the size of the alkyl group on the secondary amine affords enhanced stability against diamine volatilization, but also leads to surprising two-step CO 2 adsorption/desorption profiles. This two-step behaviormore » likely results from steric interactions between ammonium carbamate chains induced by the asymmetrical hexagonal pores of Mg 2(dobpdc) and leads to decreased CO 2 working capacities and increased water co-adsorption under humid conditions. To minimize these unfavorable steric interactions, we targeted diamine-appended variants of the isoreticularly expanded framework Mg 2(dotpdc) (dotpdc 4- = 4,4''-dioxido-[1,1':4',1''-terphenyl]-3,3''-dicarboxylate), reported here for the first time, and the previously reported isomeric framework Mg-IRMOF-74-II or Mg 2(pc-dobpdc) (pc-dobpdc 4- = 3,3'-dioxidobiphenyl-4,4'-dicarboxylate, pc = para-carboxylate), which, in contrast to Mg 2(dobpdc), possesses uniformally hexagonal pores. By minimizing the steric interactions between ammonium carbamate chains, these frameworks enable a single CO 2 adsorption/desorption step in all cases, as well as decreased water co-adsorption and increased stability to diamine loss. Functionalization of Mg 2(pc-dobpdc) with large diamines such as N-(n-heptyl)ethylenediamine results in optimal adsorption behavior, highlighting the advantage of tuning both the pore shape and the diamine size for the development of new

N-doping effectively enhances the adsorption capacity of biochar for heavy metal ions from aqueous solution.

PubMed

Yu, Wenchao; Lian, Fei; Cui, Guannan; Liu, Zhongqi

2018-02-01

N-doping was successfully employed to improve the adsorption capacity of biochar (BC) for Cu 2+ and Cd 2+ by direct annealing of crop straws in NH 3 . The surface N content of BC increased more than 20 times by N-doping; meanwhile the content of oxidized-N was gradually diminished but graphitic-N was formed and increased with increasing annealing temperature and duration time. After N-doping, a high graphitic-N percentage (46.4%) and S BET (418.7 m 2 /g) can be achieved for BC. As a result, the N-doped BC exhibited an excellent adsorption capacity for Cu 2+ (1.63 mmol g -1 ) and Cd 2+ (1.76 mmol g -1 ), which was up to 4.0 times higher than that of the original BC. Furthermore, the adsorption performance of the N-doped BC remained stable even at acidic conditions. A positive correlation can be found between adsorption capacity with the graphitic N content on BC surface. The surface chemistry of N-doped BC before and after the heavy metal ions adsorption was carefully examined by XPS and FTIR techniques, which indicated that the adsorption mechanisms mainly included cation-π bonding and complexation with graphitic-N and hydroxyl groups of carbon surfaces. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

PubMed

Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

2015-12-30

This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Adsorption of n-butane on graphene/Ru(0001)—A molecular beam scattering study

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

Sivapragasam, Nilushni; Nayakasinghe, Mindika T.; Burghaus, Uwe, E-mail: uwe.burghaus@ndsu.edu

2016-07-15

Adsorption kinetics/dynamics of n-butane on graphene, physical vapor deposited on Ru(0001) (hereafter G/Ru), and bare Ru(0001) (hereafter Ru) are discussed. The chemical activity of the supported-graphene as well as the support was probed by thermal desorption spectroscopy (adsorption kinetics). In addition and to the best of our knowledge, for the first time, molecular beam scattering data of larger molecules were collected for graphene (probing the adsorption dynamics). Furthermore, samples were inspected by x-ray photoelectron spectroscopy and Auger electron spectroscopy. At the measuring conditions used here, n-butane adsorption kinetics/dynamics are molecular and nonactivated. Binding energies of butane on Ru and G/Rumore » are indistinguishable within experimental uncertainty. Thus, G/Ru is “kinetically transparent.” Initial adsorption probabilities, S{sub 0}, of n-butane decrease with increasing impact energy (0.76–1.72 eV) and are adsorption temperature independent for both Ru and G/Ru, again consistent with molecular adsorption. Also, S{sub 0} of Ru and G/Ru are indistinguishable within experimental uncertainty. Thus, G/Ru is “dynamically transparent.” Coverage dependent adsorption probabilities indicate precursor effects for graphene/Ru.« less

Development of a field-deployable method for simultaneous, real-time measurements of the four most abundant N2O isotopocules.

PubMed

Ibraim, Erkan; Harris, Eliza; Eyer, Simon; Tuzson, Béla; Emmenegger, Lukas; Six, Johan; Mohn, Joachim

2018-03-01

Understanding and quantifying the biogeochemical cycle of N 2 O is essential to develop effective N 2 O emission mitigation strategies. This study presents a novel, fully automated measurement technique that allows simultaneous, high-precision quantification of the four main N 2 O isotopocules ( 14 N 14 N 16 O, 14 N 15 N 16 O, 15 N 14 N 16 O and 14 N 14 N 18 O) in ambient air. The instrumentation consists of a trace gas extractor (TREX) coupled to a quantum cascade laser absorption spectrometer, designed for autonomous operation at remote measurement sites. The main advantages this system has over its predecessors are a compact spectrometer design with improved temperature control and a more compact and powerful TREX device. The adopted TREX device enhances the flexibility of the preconcentration technique for higher adsorption volumes to target rare isotope species and lower adsorption temperatures for highly volatile substances. All system components have been integrated into a standardized instrument rack to improve portability and accessibility for maintenance. With an average sampling frequency of approximately 1 h -1 , this instrumentation achieves a repeatability of 0.09, 0.13, 0.17 and 0.12 ‰ for δ 15 N α , δ 15 N β , δ 18 O and site preference of N 2 O, respectively, for pressurized ambient air. The repeatability for N 2 O mole fraction measurements is better than 1 ppb (parts per billion, 10 -9 moles per mole of dry air).

Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method.

PubMed

Nguyen, Huong Giang T; Horn, Jarod C; Thommes, Matthias; van Zee, Roger D; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO 2 and supercritical N 2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Microporous metal organic framework [M2(hfipbb)2(ted)] (M=Zn, Co; H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine): Synthesis, structure analysis, pore characterization, small gas adsorption and CO2/N2 separation properties

NASA Astrophysics Data System (ADS)

Xu, William W.; Pramanik, Sanhita; Zhang, Zhijuan; Emge, Thomas J.; Li, Jing

2013-04-01

Carbon dioxide is a greenhouse gas that is a major contributor to global warming. Developing methods that can effectively capture CO2 is the key to reduce its emission to the atmosphere. Recent research shows that microporous metal organic frameworks (MOFs) are emerging as a promising family of adsorbents that may be promising for use in adsorption based capture and separation of CO2 from power plant waste gases. In this work we report the synthesis, crystal structure analysis and pore characterization of two microporous MOF structures, [M2(hfipbb)2(ted)] (M=Zn (1), Co (2); H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine). The CO2 and N2 adsorption experiments and IAST calculations are carried out on [Zn2(hfipbb)2(ted)] under conditions that mimic post-combustion flue gas mixtures emitted from power plants. The results show that the framework interacts with CO2 strongly, giving rise to relatively high isosteric heats of adsorption (up to 28 kJ/mol), and high adsorption selectivity for CO2 over N2, making it promising for capturing and separating CO2 from CO2/N2 mixtures.

SeO2 adsorption on CaO surface: DFT and experimental study on the adsorption of multiple SeO2 molecules

NASA Astrophysics Data System (ADS)

Fan, Yaming; Zhuo, Yuqun; Li, Liangliang

2017-10-01

SeO2 adsorption mechanisms on CaO surface were firstly investigated by both density functional theory (DFT) calculations and adsorption experiments. Adsorption of multiple SeO2 on the CaO (001) surface was investigated using slab model. Based on the results of adsorption energy and surface property, a double-layer adsorption mechanisms were proposed. In experiments, the SeO2 adsorption products were prepared in a U-shaped quartz reactor at 200 °C. The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The superficial and total SeO2 mass fractions were measured by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The surface valence state and bulk structure are determined by XPS and X-Ray Diffraction (XRD). The experimental results are in good agreement with the DFT results. In conclusion, the fundamental SeO2 chemisorption mechanisms on CaO surface were suggested.

Measuring water adsorption on mineral surfaces in air, CO2, and supercritical CO2 with a quartz-crystal microbalance

NASA Astrophysics Data System (ADS)

Bryan, C. R.; Wells, R. K.; Burton, P. D.; Heath, J. E.; Dewers, T. A.; Wang, Y.

2011-12-01

Carbon sequestration via underground storage in geologic formations is a proposed approach for reducing industrial CO2 emissions. However, current models for carbon injection and long-term storage of supercritical CO2 (scCO2) do not consider the development and stability of adsorbed water films at the scCO2-hydrophilic mineral interface. The thickness and properties of the water films control the surface tension and wettability of the mineral surface, and on the core scale, affect rock permeability, saturation, and capillary properties. The film thickness is strongly dependent upon the activity of water in the supercritical fluid, which will change as initially anhydrous scCO2 absorbs water from formation brine. As described in a companion paper by the coauthors, the thickness of the adsorbed water layer is controlled by the disjoining pressure; structural and van der Waals components dominate at low water activity, while electrostatic forces become more important with increasing film thickness (higher water activities). As scCO2 water activity and water layer thickness increase, concomitant changes in mineral surface properties and reservoir/caprock hydrologic properties will affect the mobility of the aqueous phase and of scCO2. Moreover, the development of a water layer may be critical to mineral dissolution reactions in scCO2. Here, we describe the use of a quartz-crystal microbalance (QCM) to monitor adsorption of water by mineral surfaces. QCMs utilize a piezoelectrically-stimulated quartz wafer to measure adsorbed or deposited mass via changes in vibrational frequency. When used to measure the mass of adsorbed liquid films, the frequency response of the crystal must be corrected for the viscoelastic, rather than elastic, response of the adsorbed layer. Results are presented for adsorption to silica in N2 and CO2 at one bar, and in scCO2. Additional data are presented for water uptake by clays deposited on a QCM wafer. In this case, water uptake occurs by the

CO{sub 2} adsorption-based separation by metal organic framework (Cu-BTC) versus zeolite (13X)

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

Zhijian Liang; Marc Marshall; Alan L. Chaffee

2009-05-15

The potential for the metal organic framework (MOF) Cu-BTC to selectively adsorb and separate CO{sub 2} is considered. Isotherms for CO{sub 2}, CH{sub 4}, and N{sub 2} were measured from 0 to 15 bar and at temperatures between 25 and 105{sup o}C. The isotherms suggest a much higher working capacity (x4) for CO{sub 2} adsorption on Cu-BTC relative to the benchmark zeolite 13X over the same pressure range. Higher CO{sub 2}/N{sub 2} and CO{sub 2}/CH{sub 4} selectivities in the higher pressure range (1-15 bar) and with lower heats of adsorption were also demonstrated. Cu-BTC was observed to be stable inmore » O{sub 2} at 25{sup o}C, but its crystallinity was reduced in humid environments. The CO{sub 2} adsorption capacity was progressively reduced upon cyclic exposure to water vapor at low relative humidity (<30%), but leveled out at 75% of its original value after several water adsorption/desorption cycles. 27 refs., 1 fig.« less

Pentaethylenehexamine-Loaded Hierarchically Porous Silica for CO2 Adsorption

PubMed Central

Ji, Changchun; Huang, Xin; Li, Lei; Xiao, Fukui; Zhao, Ning; Wei, Wei

2016-01-01

Recently, amine-functionalized materials as a prospective chemical sorbent for post combustion CO2 capture have gained great interest. However, the amine grafting for the traditional MCM-41, SBA-15, pore-expanded MCM-41 or SBA-15 supports can cause the pore volume and specific surface area of sorbents to decrease, significantly affecting the CO2 adsorption-desorption dynamics. To overcome this issue, hierarchical porous silica with interparticle macropores and long-range ordering mesopores was prepared and impregnated with pentaethylenehexamine. The pore structure and amino functional group content of the modified silicas were analyzed by scanning electron microscope, transmission electron microscope, N2 adsorption, X-ray powder diffraction, and Fourier transform infrared spectra. Moreover, the effects of the pore structure as well as the amount of PEHA loading of the samples on the CO2 adsorption capacity were investigated in a fixed-bed adsorption system. The CO2 adsorption capacity reached 4.5 mmol CO2/(g of adsorbent) for HPS−PEHA-70 at 75 °C. Further, the adsorption capacity for HPS-PEHA-70 was steady after a total of 15 adsorption-desorption cycles. PMID:28773956

Adsorption properties and photocatalytic activity of TiO2/activated carbon fiber composite

NASA Astrophysics Data System (ADS)

Yao, Shuhua; Song, Shuangping; Shi, Zhongliang

2014-06-01

Photocatalysts of titanium dioxide (TiO2) and TiO2/activated carbon fiber (TiO2/ACF) composite were prepared by sol-gel method, followed by calcining the pure TiO2 sols and the TiO2/ACF sols at 500°C for 2 h in a N2 atmosphere, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms measurement. Batch experiments were conducted to study the adsorption property of TiO2/ACF composite using methylene blue as adsorbate. The adsorption data obtained from different batch experiments were analyzed using pseudo-second-order kinetic model, the experimental data can be adequately described by the pseudo-second-order equation. The photodecomposition behavior of TiO2/ACF was investigated in aqueous solution using methylene blue as target pollutant. It was found that methylene blue could be removed rapidly from water by TiO2/ACF, the photocatalytic decomposition was obviously improved when the photocatalyst was used. Kinetics analysis revealed that the photocatalytic decomposition reaction can be described well by a first-order rate equation.

Adsorption of CO2 on amine-functionalised MCM-41: experimental and theoretical studies.

PubMed

dos Santos, Thiago Custódio; Bourrelly, Sandrine; Llewellyn, Philip L; Carneiro, José Walkimar de M; Ronconi, Célia Machado

2015-04-28

Adsorption of CO2 on MCM-41 functionalised with [3-(2-aminoethylamino)propyl]trimethoxysilane (MCM-41-N2), N(1)-(3-trimethoxysilylpropyl)diethylenetriamine (MCM-41-N3), 4-aminopyridine (MCM-41-aminopyridine), 4-(methylamino)pyridine (MCM-41-methylaminopyridine) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (MCM-41-guanidine) was investigated. The amine-functionalised materials were characterised by (29)Si and (13)C solid-state nuclear magnetic resonance, N2 adsorption/desorption isotherms, X-ray diffraction and transmission electron microscopy. CO2 adsorption at 1.0 bar and 30 °C showed that the amount of CO2 (nads/mmol g(-1)) adsorbed on MCM-41-N2 and MCM-41-N3 is approximately twice the amount adsorbed on MCM-41. For MCM-41-aminopyridine, MCM-41-methylaminopyridine and MCM-41-guanidine, the CO2 adsorption capacity was smaller than that of MCM-41 at the same conditions. The proton affinity (computed with wB97x-D/6-311++G(d,p)) of the secondary amino groups is higher than that of the primary amino groups; however, the relative stabilities of the primary and secondary carbamates are similar. The differential heat of adsorption decreases as the number of secondary amino groups increases.

Adsorption of acetanilide herbicides on soil and its components. II. Adsorption and catalytic hydrolysis of diethatyl-ethyl on saturated Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite.

PubMed

Liu, W P; Fang, Z; Liu, H J; Yang, W C

2001-04-01

Adsorption and catalytic hydrolysis of the herbicide diethatyl-ethyl [N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester] on homoionic Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite clays were investigated in water solution. The Freundlich adsorption coefficient, Ki, got from isotherms on clay followed the order of Na+ approximately K+ > Mg2+ approximately Ca2+. Analysis of FT-IR spectra of diethatyl-ethyl adsorbed on clay suggests probable bonding at the carboxyl and amide carbonyl groups of the herbicide. The rate of herbicide hydrolysis in homoionic clay suspensions followed the same order as that for adsorption, indicating that adsorption may have preceded and thus caused hydrolysis. Preliminary product identification showed that hydrolysis occurred via nucleophilic substitution at the carboxyl carbon, causing the cleavage of the ester bond and formation of diethatyl and its dechlorinated derivative, and at the amide carbon, yielding an ethyl ester derivative and its acid. These pathways also suggest that hydrolysis of diethatyl-ethyl was catalyzed by adsorption on the clay surface.

Oxygen adsorption on the Al0.25Ga0.75N (0001) surface: A first-principles study

NASA Astrophysics Data System (ADS)

Fu, Jiaqi; Song, Tielei; Liang, Xixia; Zhao, Guojun

2018-04-01

To understand the interaction mechanism for the oxygen adsorption on AlGaN surface, herein, we built the possible models of oxygen adsorption on Al0.25Ga0.75N (0001) surface. For different oxygen coverage, three kinds of adsorption site are considered. Then the favorable adsorption sites are characterized by first principles calculation for (2 × 2) supercell of Al0.25Ga0.75N (0001) surface. On basis of the optimal adsorption structures, our calculated results show that all the adsorption processes are exothermic, indicating that the (0001) surface orientation is active towards the adsorption of oxygen. The doping of Al is advantage to the adsorption of O atom. Additionally, the adsorption energy decreases with reducing the oxygen coverage, and the relationship between them is approximately linear. Owing to the oxygen adsorption, the surface states in the fundamental band gap are significant reduced with respect to the free Al0.25Ga0.75N (0001) surface. Moreover, the optical properties on different oxygen coverage are also discussed.

Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method

NASA Astrophysics Data System (ADS)

Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO2 and supercritical N2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Adsorption of NH4+-N on Chinese loess: Non-equilibrium and equilibrium investigations.

PubMed

Xie, Haijian; Wang, Shaoyi; Qiu, Zhanhong; Jiang, Jianqun

2017-11-01

NH 4 + -N is a crucial pollutant in landfill leachate and can be in high concentrations for a long period of time due to anaerobic condition of landfills. The adsorption properties of NH 4 + -N on the Chinese loess were investigated using Batch test. The influences of ammonium concentration, temperature, reaction time, slurry concentration, and pH on the adsorption process are evaluated. Adsorption kinetics and isotherm behaviors were studied by applying different models to the test data to determine the adsorption parameters. The equilibrating duration was shown to be less than 60 min. The data on adsorption kinetics can be well fitted by the pseudo-second-order kinetics model. According to the Langmuir isotherm model, the adsorption capacity of Chinese loess about NH 4 + -N was predicted to be 72.30 mg g -1 . The uptake of NH 4 + -N by Chinese loess was considered to be the type of physical adsorption on the basis of D-R isotherm analysis. The optimal pH and slurry concentration are 4 and 2 g/50 ml, respectively. According to the calculated values of free energy, enthalpy and entropy change, the adsorption process is determined to be exothermic. The disorder of the system appeared lowest at temperature of 308.15 K. The predicted Gibb's free energies also indicate the adsorption process is endothermic and spontaneous. The FTIR spectrum and EDX analysis showed the adsorption process of NH 4 + involves cation exchange and dissolution of calcite. Copyright © 2017 Elsevier Ltd. All rights reserved.

First-principles investigation of CO adsorption on pristine, C-doped and N-vacancy defected hexagonal AlN nanosheets

NASA Astrophysics Data System (ADS)

Ouyang, Tianhong; Qian, Zhao; Ahuja, Rajeev; Liu, Xiangfa

2018-05-01

The optimized atomic structures, energetics and electronic structures of toxic gas CO adsorption systems on pristine, C-doped and N-vacancy defected h-AlN nanosheets respectively have been investigated using Density functional theory (DFT-D2 method) to explore their potential gas detection or sensing capabilities. It is found that both the C-doping and the N-vacancy defect improve the CO adsorption energies of AlN nanosheet (from pure -3.847 eV to -5.192 eV and -4.959 eV). The absolute value of the system band gap change induced by adsorption of CO can be scaled up to 2.558 eV or 1.296 eV after C-doping or N-vacancy design respectively, which is evidently larger than the value of 0.350 eV for pristine material and will benefit the robustness of electronic signals in potential gas detection. Charge transfer mechanisms between CO and the AlN nanosheet have been presented by the Bader charge and differential charge density analysis to explore the deep origin of the underlying electronic structure changes. This theoretical study is proposed to predict and understand the CO adsorption properties of the pristine and defected h-AlN nanosheets and would help to guide experimentalists to develop better AlN-based two-dimensional materials for efficient gas detection or sensing applications in the future.

Adsorption and separation of binary and ternary mixtures of SO2, CO2 and N2 by ordered carbon nanotube arrays: grand-canonical Monte Carlo simulations.

PubMed

Rahimi, Mahshid; Singh, Jayant K; Müller-Plathe, Florian

2016-02-07

The adsorption and separation behavior of SO2-CO2, SO2-N2 and CO2-N2 binary mixtures in bundles of aligned double-walled carbon nanotubes is investigated using the grand-canonical Monte Carlo (GCMC) method and ideal adsorbed solution theory. Simulations were performed at 303 K with nanotubes of 3 nm inner diameter and various intertube distances. The results showed that the packing with an intertube distance d = 0 has the highest selectivity for SO2-N2 and CO2-N2 binary mixtures. For the SO2-CO2 case, the optimum intertube distance for having the maximum selectivity depends on the applied pressure, so that at p < 0.8 bar d = 0 shows the highest selectivity and at 0.8 bar < p < 2.5 bar, the highest selectivity belongs to d = 0.5 nm. Ideal adsorbed solution theory cannot predict the adsorption of the binary systems containing SO2, especially when d = 0. As the intertube distance is increased, the ideal adsorbed solution theory based predictions become closer to those of GCMC simulations. Only in the case of CO2-N2, ideal adsorbed solution theory is everywhere in good agreement with simulations. In a ternary mixture of all three gases, the behavior of SO2 and CO2 remains similar to that in a SO2-CO2 binary mixture because of the weak interaction between N2 molecules and CNTs.

Factors Influencing NO2 Adsorption/Reduction on Microporous Activated Carbon: Porosity vs. Surface Chemistry

PubMed Central

Ghouma, Imen; Limousy, Lionel; Bennici, Simona

2018-01-01

The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 °C. The main properties of the parent and modified activated carbons were analyzed by N2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO2. PMID:29670008

Effect of pH and Electrolytes on Adsorption of 2,4-D onto Kaolinite

NASA Astrophysics Data System (ADS)

Sharma, A.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

2006-12-01

The fate and transport of pesticides in soil can be greatly influenced by adsorption onto clay minerals such as kaolinite. The ionic pesticide 2,4-D (2,4-dichlorophenoxyacetic acid) is one of the most commonly used herbicides. The purpose of this study is to investigate the effect of electrolytes and pH on the adsorption of 2,4- D onto kaolinite. The adsorption coefficient (Kd) of 2,4-D on two types of kaolinite was measured in batch experiments using water and 4 different electrolytes (0.005M CaSO4, 0.005M CaCl2, 0.01M KCl, and 0.01M NaCl). The experiments were carried out with 0.5 g kaolinite at a solid:liquid ratio of 1:20 and at different pH (1.9-6.3). The pH of the solution was controlled by addition of 0.2N of HCl. X-ray diffraction analysis of both kaolinite with and without adsorbed 2,4-D was also done to understand the location of 2,4-D adsorption. The effects of pH and electrolytes on Kd were compared and possible adsorption mechanisms were revealed for 2,4-D adsorption onto the two different types of kaolinite. The results implied that 2,4-D adsorption was higher for an electrolyte solution with monovalent cation than with divalent cation for one type of kaolinite, while no such trend was observed for the other kaolinite. The adsorption of 2,4-D increased significantly with decreasing pH for both types of kaolinite.

Adsorption of methyl orange on mesoporous γ-Fe2O3/SiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Deligeer, W.; Gao, Y. W.; Asuha, S.

2011-02-01

Mesoporous γ-Fe2O3/SiO2 nanocomposite containing 30 mol% of γ-Fe2O3 was prepared by a template-free sol-gel method, and its removal ability for methyl orange (MO) was investigated. The nanocomposite was characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) absorption measurements, nitrogen adsorption-desorption measurements, and magnetic measurements. The synthesized γ-Fe2O3/SiO2 nanocomposite has a mesoporous structure with an average pore size of 3.5 nm and a specific surface area of 245 m2/g, and it exhibits ferrimagnetic characteristics with the maximum saturation magnetization of 20.9 emu/g. The adsorption of MO on the nanocomposite reaches the maximum adsorbed percentage of ca. 80% within a few minutes, showing that most of MO can be removed in a short time. The MO adsorption data fit well with both Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity of MO is estimated to be 476 mg/g.

Adsorption mechanism of 2,4-dichlorophenoxyacetic acid onto nitric-acid-modified activated carbon fiber.

PubMed

Li, Qun; Sun, Jie; Ren, Tianhao; Guo, Lin; Yang, Zhilin; Yang, Qi; Chen, Hai

2018-04-01

Adsorption by carbon materials is one of the relatively fast methods in present research, which is widely used in emergency events. Activated carbon fiber (ACF) modified by nitric acid (N-ACF) was studied in this research to determine the adsorption performance for 2,4-dichlorophenoxyacetic acid (2,4-D). Subsequently, influence factors, adsorption isotherm models, kinetics and thermodynamic were investigated in a batch system to realize this adsorption. Experimental results showed that ACF modified by 0.1M nitric acid had a better removal ability than 2,4-D. Removal rate of 2,4-D by N-ACF was greatly influenced by pH with the optimum pH at 2. The superiority of the Langmuir isotherm model in describing the adsorption equilibrium was revealed by correlation coefficients R2 (R 2  ≥ 0.997). Furthermore, adsorption kinetics was well described by pseudo-second-order model. The results of thermodynamic showed that adsorption was a spontaneous, endothermic process with randomness increasing. Additionally, surface structure properties of adsorbent were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, Specific surface area analysis of Brunauer, Emmett and Teller and Boehm's titration. It turned out that the micropore structure and functional groups on N-ACF all can contribute to the removal of 2,4-D.

Molecular simulation of CH4/CO2/H2O competitive adsorption on low rank coal vitrinite.

PubMed

Yu, Song; Bo, Jiang; Wu, Li

2017-07-21

The competitive adsorptions of CH 4 /CO 2 /H 2 O on coal vitrinite (DV-8, C 214 H 180 O 24 N 2 ) were computed based on density function theory (DFT) and grand canonical Monte Carlo (GCMC). The adsorption process reaches the saturation state after adsorbing 17 CH 4 s, 22 CO 2 s, and 35 H 2 Os per C 214 H 180 O 24 N 2 respectively. The optimal configurations of CH 4 -vitrinite, CO 2 -vitrinite, and H 2 O-vitrinite respectively manifest as aromatic 1 /T 2 /rT 3 (1 adsorption location, 2 adsorption sites and T here represents sites above the carbon atom and the heteroatom, 3 adsorption orientation and rT here means the orientations of three hydrogen atoms pointing to vitrinite), aromatic/T/v (v represents the orientations perpendicular to the plane of vitrinite), and aromatic/rV/T (rV represents an oxygen atom pointing to the vitrinite surface). The GCMC results show that high temperature is not conducive to the vitrinite's adsorption of adsorbates and the adsorption capacity order is H 2 O > CO 2 > CH 4 (263-363 K) in the one-component, binary, and ternary adsorbate systems. The optimal configurations of vitrinite are similar to graphite/graphene, while ΔE is significantly lower than graphite/graphene. Simulation data are in good agreement with the experimental results.

Cysteine and cystine adsorption on FeS2(100)

NASA Astrophysics Data System (ADS)

Suzuki, Teppei; Yano, Taka-aki; Hara, Masahiko; Ebisuzaki, Toshikazu

2018-08-01

Iron pyrite (FeS2) is the most abundant metal sulfide on Earth. Owing to its reactivity and catalytic activity, pyrite has been studied in various research fields such as surface science, geochemistry, and prebiotic chemistry. Importantly, native iron-sulfur clusters are typically coordinated by cysteinyl ligands of iron-sulfur proteins. In the present paper, we study the adsorption of L-cysteine and its oxidized dimer, L-cystine, on the FeS2 surface, using electronic structure calculations based density functional theory and Raman spectroscopy measurements. Our calculations suggest that sulfur-deficient surfaces play an important role in the adsorption of cysteine and cystine. In the thiol headgroup adsorption on the sulfur-vacancy site, dissociative adsorption is found to be energetically favorable compared with molecular adsorption. In addition, the calculations indicate that, in the cystine adsorption on the defective surface under vacuum conditions, the formation of the S-Fe bond is energetically favorable compared with molecular adsorption. Raman spectroscopic measurements suggest the formation of cystine molecules through the S-S bond on the pyrite surface in aqueous solution. Our results might have implications for chemical evolution at mineral surfaces on the early Earth and the origin of iron-sulfur proteins, which are believed to be one of the most ancient families of proteins.

Micropore Formation of [Zn2(Oxac) (Taz)2]·(H2O)2.5 via CO2 Adsorption.

PubMed

Zubir, Moondra; Hamasaki, Atom; Iiyama, Taku; Ohta, Akira; Ohki, Hiroshi; Ozeki, Sumio

2017-01-24

As-synthesized [Zn 2 (Oxac) (Taz) 2 ]·(H 2 O) 2.5 , referred to as ZOTW 2.5 , was prepared from aqueous methanol solutions of Zn 5 (CO 3 ) 2 (OH) 6 and two kinds of ligands of 1,2,4-triazole (Taz) and oxalic acid (Oxac) at 453 K for 12 h. The crystal structure was determined by the Rietveld method. As-synthesized ZOTW 2.5 was pretreated at 383 K and 1 mPa for t pt h, ZOTW x (t pt h). ZOTW x (≥3h) showed a type I adsorption isotherm for N 2 at 77 K having a saturation amount (V s ) of 180 mg/g, but that pretreated shortly showed only 1/10 in V s . CO 2 was adsorbed at 303 K in sigmoid on nonporous ZOTW x (≤2h) and in Langmuir-type on ZOTW x (≥3h) to reach the adsorption amount of 120 mg/g at 700 Torr. N 2 adsorption on ZOTW x (≤2h)deCO 2 , degassed after CO 2 adsorption on ZOTW x (≤2h), was promoted 5-fold from 180 mg/g on ZOTW x (t pt h) and ZOTW x (≥3h)deCO 2 up to ca. 1000 mg/g. The interaction of CO 2 and H 2 O molecules in micropores may lead to a new route for micropore formation.

Methylamine adsorption and decomposition on B12N12 nanocage: A density functional theory study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Nurazar, Roghaye

2014-08-01

Density functional theory calculations are performed to investigate the adsorption and decomposition of methylamine (CH3NH2) on the surface of a B12N12 fullerene-like nanocage. Two adsorption types and two reaction channels are identified. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3NH2. The pathways of CH3NH2 decomposition via bond scission of the Csbnd N and Nsbnd H bonds are examined. The results indicate that Nsbnd H bond scission is the most favorable pathway on the B12N12 surface. The side reaction that generates CH3 and NH2 fragments is endothermic by 15.6 kcal/mol with an energy-barrier height of 81.5 kcal/mol. For the CH3NH2 decomposition on the B12N12 surface, the rate-determining step appears to be as the following reaction: CH3NH → CH3N + H.

Dopant Adsorption and Incorporation at Irradiated GaN Surfaces

NASA Astrophysics Data System (ADS)

Sun, Qiang; Selloni, Annabella; Myers, Thomas; Doolittle, W. Alan

2006-03-01

Mg and O are two of the common dopants in GaN, but, in spite of extensive investigation, the atomic scale understanding of their adsorption and incorporation is still incomplete. In particular, high-energy electron irradiation, such as occurring during RHEED, has been reported to have an important effect on the incorporation of these impurities, but no study has addressed the detailed mechanisms of this effect yet. Here we use DFT calculations to study the adsorption and incorporation of Mg and O at the Ga- and N-polar GaN surfaces under various Ga, Mg and O coverage conditions as well as in presence of light or electron beam-induced electronic excitation. We find that the adsorption and incorporation of the two impurities have opposite surface polarity dependence: substitutional Mg prefers to incorporate at the GaN(0001) surface, while O prefers to adsorb and incorporate at the N-polar surface. In addition, our results indicate that in presence of light irradiation the tendency of Mg to surface-segregate is reduced. The O adsorption energy on the N-polar surface is also significantly reduced, consistent with the experimental observation of a much smaller concentration of oxygen in the irradiated samples.

Adsorption and separation of n/iso-pentane on zeolites: A GCMC study.

PubMed

Fu, Hui; Qin, Hansong; Wang, Yajun; Liu, Yibin; Yang, Chaohe; Shan, Honghong

2018-03-01

Separation of branched chain hydrocarbons and straight chain hydrocarbons is very important in the isomerization process. Grand canonical ensemble Monte Carlo simulations were used to investigate the adsorption and separation of iso-pentane and n-pentane in four types of zeolites: MWW, BOG, MFI, and LTA. The computation of the pure components indicates that the adsorption capacity is affected by physical properties of zeolite, like pore size and structures, and isosteric heat. In BOG, MFI and LTA, the amount of adsorption of n-pentane is higher than iso-pentane, while the phenomenon is contrary in MWW. For a given zeolite, a stronger adsorption heat corresponds to a higher loading. In the binary mixture simulations, the separation capacity of n-and iso-pentane increases with the elevated pressure and the increasing iso-pentane composition. The adsorption mechanism and competition process have been examined. Preferential adsorption contributions prevail at low pressure, however, the size effect becomes important with the increasing pressure, and the relatively smaller n-pentane gradually competes successfully in binary adsorption. Among these zeolites, MFI has the best separation performance due to its high shape selectivity. This work helps to better understand the adsorption and separation performance of n- and iso-pentane in different zeolites and explain the relationship between zeolite structures and adsorption performance. Copyright © 2017 Elsevier Inc. All rights reserved.

Single-component and binary CO2 and H2O adsorption of amine-functionalized cellulose.

PubMed

Gebald, Christoph; Wurzbacher, Jan A; Borgschulte, Andreas; Zimmermann, Tanja; Steinfeld, Aldo

2014-02-18

A fundamental analysis of single-component and binary CO2 and H2O adsorption of amine-functionalized nanofibrillated cellulose is carried out in the temperature range of 283-353 K and at CO2 partial pressures in the range of 0.02-105 kPa, where the ultralow partial pressure range is relevant for the direct capture of CO2 from atmospheric air. Single-component CO2 and H2O adsorption experimental data are fitted to the Toth and Guggenheim-Anderson-de Boer models, respectively. Corresponding heats of adsorption, derived from explicit solutions of the van't Hoff equation, are -50 kJ/mol CO2 and -48.8 kJ/mol H2O. Binary CO2/H2O adsorption measurements for humid air reveal that the presence of H2O at 2.55 kPa enhances CO2 adsorption, while the presence of CO2 at 0.045 kPa does not influence H2O adsorption. The energy demand of the temperature-vacuum-swing adsorption/desorption cycle for delivering pure CO2 from air increases significantly with H2O adsorption and indicates the need to reduce the hygroscopicity of the adsorbent.

Adsorption behavior of thorium on N,N,N',N'-tetraoctyldiglycolamide (TODGA) impregnated graphene aerogel.

PubMed

Chen, Mumei; Li, Zheng; Geng, Yiyun; Zhao, Haogui; He, Shuhua; Li, Qingnuan; Zhang, Lan

2018-05-01

As a kind of three-dimensional graphene architecture material with superhydrophobic, low density, high specific surface area and porosity, graphene aerogel (GA) can be used to immobilize extractant to constitute the solvent impregnated adsorbent. In this paper, the N,N,N',N'-tetraoctyldiglycolamide impregnated graphene aerogel ( GA-TODGA) was prepared to remove the thorium from aqueous solution. It is found that the adsorption of thorium on GA-TODGA is strongly dependent on the concentration of TODGA in GA and HNO 3 in aqueous solution. Compared with other solvent impregnated adsorbents, the adsorption capacity of GA-TODGA is much higher due to the high immobilization capacity of GA for TODGA. Furthermore, the GA-TODGA also possesses excellent stability and reusability, ensuring the application potential of using GA-TODGA in large scale. Copyright © 2018 Elsevier B.V. All rights reserved.

Adsorption of small hydrocarbons on rutile TiO 2(110)

DOE PAGES

Chen, Long; Smith, R. Scott; Kay, Bruce D.; ...

2015-11-21

Here, temperature programmed desorption and molecular beam scattering were used to study the adsorption and desorption of small hydrocarbons (n-alkanes, 1-alkenes and 1-alkynes of C 1–C 4) on rutile TiO 2(110). We show that the sticking coefficients for all the hydrocarbons are close to unity (> 0.95) at an adsorption temperature of 60 K. The desorption energies for hydrocarbons of the same chain length increase from n-alkanes to 1-alkenes and to 1-alkynes. This trend is likely a consequence of additional dative bonding of the alkene and alkyne π system to the coordinatively unsaturated Ti 5c sites. Similar to previous studiesmore » on the adsorption of n-alkanes on metal and metal oxide surfaces, we find that the desorption energies within each group (n-alkanes vs. 1-alkenes vs. 1-alkynes) from Ti 5c sites increase linearly with the chain length. The absolute saturation coverages of each hydrocarbon on Ti 5c sites were also determined. The saturation coverage of CH 4, is found to be ~ 2/3 monolayer (ML). The saturation coverages of C 2–C 4 hydrocarbons are found nearly independent of the chain length with values of ~ 1/2 ML for n-alkanes and 1-alkenes and 2/3 ML for 1-alkynes. This result is surprising considering their similar sizes.« less

Titanium-incorporated organic–inorganic hybrid adsorbent for improved CO{sub 2} adsorption performance

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

Zhang, Xiaoyun; Qin, Hongyan; Zhang, Sisi

2015-02-15

Highlights: • Titanium-incorporated organic–inorganic hybrid adsorbent was prepared. • The incorporation of Ti to the adsorbent showed significant effect. • The sorbent shows high CO{sub 2} capture capacity both in pure and diluted CO{sub 2} at RT. • The sorbent exhibits a high recycling stability after 15 cycling runs. - Abstract: The CO{sub 2} adsorption performance of acrylonitrile (AN)–tetraethylenepentamine (TEPA) adduct (hereafter referred to as TN) impregnated adsorbent was greatly enhanced by introduction of Titanium atom into the silica matrix. The adsorbents were characterized by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), N{sub 2} adsorption/desorption, UV–vismore » spectroscopy, Fourier transform infrared (FTIR) spectroscopy. The adsorption experiments together with the physicochemical characterization demonstrated that these adsorbents containing an optimal amount of Titanium (Ti/Si ≈ 0.1) remarkably reinforced the CO{sub 2} adsorption capacity and recycling stability. The highest CO{sub 2} uptakes reached 4.65 and 1.80 mmol CO{sub 2}/g adsorbent at 25 °C under 90% CO{sub 2} (CO{sub 2}/N{sub 2}, 90:10 V/V) and 1% CO{sub 2} (CO{sub 2}/N{sub 2}, 1:99 V/V) conditions for sample Ti(0.1)-DMS-TN, respectively. Repeated adsorption/desorption cycles revealed that the Ti-incorporated adsorbent showed only a tiny decrease in adsorption capacity (1.778 mmol CO{sub 2}/g adsorbent after 15 cycles, decreased by 0.95%), significantly enhanced the adsorbent recycling stability.« less

Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp)

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

Sun, Xiuquan; Wick, Collin D.; Thallapally, Praveen K.

Molecular dynamic simulations were carried out to study the sorption, structural properties, and diffusivities of n-hexane and cyclohexane adsorbed in Ni2(dhtp). The results indicated strong interactions between the alkanes and the host material. The free energy perturbation method was employed to investigate the adsorption free energies of methane, ethane, n-butane, n-hexane and cyclohexane. For linear alkanes, the free energy lowered as the length of the carbon chain increased. Also, the adsorption of n-hexane was preferred over cyclohexane, due to its ability to rearrange its structure to maximize contacts with the host. Furthermore, due to the large pore size of Ni2(dhtp),more » higher loadings of alkanes did not significantly affect the alkane structure, and enhanced the free energy of adsorption for subsequent alkanes being loaded. According to our studies, Ni2(dhtp) has a very promising potential for adsorption and storage of alkanes. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

Adsorption properties of congo red from aqueous solution onto N,O-carboxymethyl-chitosan.

PubMed

Wang, Li; Wang, Aiqin

2008-03-01

N,O-carboxymethyl-chitosans (N,O-CMC) with different degree of substitution (DS) were synthesized under heterogeneous conditions by controlling the reaction temperature. The factors influencing adsorption capacity of N,O-CMC such as the DS of N,O-CMC, initial pH value of the dye solution and adsorption temperature for anionic dye congo red (CR) were investigated. Compared with chitosan (78.90 mg/g), N,O-CMC with the DS of 0.35 exhibited much higher adsorption capacity (330.62 mg/g) for CR at the same adsorption conditions. The adsorption kinetics and isotherms showed that the sorption processes were better fitted by pseudo-second-order equation and the Langmuir equation, respectively. The adsorption mechanism of N,O-CMC was also discussed by means of IR and XPS spectra. The results in this study indicated that N,O-CMC was an attractive candidate for removing CR from the dye wastewater.

Adsorption of SO2 on bituminous coal char and activated carbon fiber

USGS Publications Warehouse

DeBarr, Joseph A.; Lizzio, Anthony A.; Daley, Michael A.

1997-01-01

The SO2 adsorption behaviors of activated carbons produced from Illinois coal and of commercially prepared activated carbon fibers (ACFs) were compared. There was no relation between surface area of coal-based carbons and SO2 adsorption, whereas adsorption of SO2 on the series of ACFs was inversely proportional to N2 BET surface area. Higher surface area ACFs had wider pores and adsorbed less SO2; thus, pore size distribution is thought to play a significant role in SO2 adsorption for these materials. Oxidation with HNO3 and/or H2SO4, followed by heat treatment at 700−925°C to remove carbon−oxygen complexes, resulted in increased SO2 adsorption for both coal chars and ACFs. This behavior was explained by an increase in the available number of free sites, previously occupied by oxygen and now available for SO2 adsorption. The use of nitrogen-containing functional groups on ACFs of proper pore size shows promise for further increasing SO2 adsorption capacities. Knowledge of the relationship among the number of free sites, pore size, and surface chemistry on corresponding SO2 adsorption should lead to the development of more efficient adsorbents prepared from either coal or ACFs.

Tailoring pore properties of MCM-48 silica for selective adsorption of CO2.

PubMed

Kim, Sangil; Ida, Junichi; Guliants, Vadim V; Lin, Jerry Y S

2005-04-07

Four different types of amine-attached MCM-48 silicas were prepared and investigated for CO(2) separation from N(2). Monomeric and polymeric hindered and unhindered amines were attached to the pore surface of the MCM-48 silica and characterized with respect to their CO(2) sorption properties. The pore structures and amino group content in these modified silicas were investigated by XRD, FT-IR, TGA, N(2) adsorption/desorption at 77 K and CHN/Si analysis, which confirmed that in all cases the amino groups were attached to the pore surface of MCM-48 at 1.5-5.2 mmol/g. The N(2) adsorption/desorption analysis showed a considerable decrease of the pore volume and surface area for the MCM-48 silica containing a polymeric amine (e.g., polyethyleneimine). The CO(2) adsorption rates and capacities of the amine-attached MCM-48 samples were studied employing a sorption microbalance. The results obtained indicated that in addition to the concentration of surface-attached amino groups, specific interactions between CO(2) and the surface amino groups, and the resultant pore structure after amine group attachment have a significant impact on CO(2) adsorption properties of these promising adsorbent materials.

Investigation of Zn2+ and Cd2+ Adsorption Performanceby Different Weathering Basalts

NASA Astrophysics Data System (ADS)

Xue, Q.; Shuo, Q.; Chen, H.

2016-12-01

Geological barriers play an important role in preventing pollution of groundwater. Basalts are common geological media; however, there have not been any studies that report the effect of basalt type on the metal ion adsorption performance. In this study, we explored the metal ion (Zn2+ and Cd2+) adsorption ability of two kinds of weathering basalts: the origin weathering basalt (WB) and the eluvial deposit (ED), both of which were derived from same basaltic formation. Characteristics of the sediments were examined by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Barrett-Joyner-Halenda (BJH) measurement and the rapid potentiometric titration (RPT) method. Batch experiments were performed to evaluate the Zn2+ and Cd2+ adsorption performance of WB and ED and how adsorption was affected by contact time, initial metal ion concentration, pH and ionic strength. Despite WB and ED having similar chemical compositions, WB exhibited better adsorption than ED likely due to the fact that WB was rougher and had more small-sized spherical structures and stronger electrostatic forces. The adsorption process fit the Freundlich isotherm model well. The adsorption efficiency decreased with a decrease of pH (from 4 to 2) and with increasing ionic strength. These results suggest that a geological barrier composed of WB media might be able to effectively sequester metallic contaminants to prevent them from reaching groundwater.

Total N-nitrosamine Precursor Adsorption with Carbon Nanotubes: Elucidating Controlling Physiochemical Properties and Developing a Size-Resolved Precursor Surrogate

NASA Astrophysics Data System (ADS)

Needham, Erin Michelle

As drinking water sources become increasingly impaired with nutrients and wastewater treatment plant (WWTP) effluent, formation of disinfection byproducts (DBPs)--such as trihalomethanes (THMs), dihaloacetonitriles (DHANs), and N-nitrosamines--during water treatment may also increase. N-nitrosamines may comprise the bulk of the chronic toxicity in treated drinking waters despite forming at low ng/L levels. This research seeks to elucidate physicochemical properties of carbon nanotubes (CNTs) for removal of DBP precursors, with an emphasis on total N-nitrosamines (TONO). Batch experiments with CNTs were completed to assess adsorption of THM, DHAN, and TONO precursors; physiochemical properties of CNTs were quantified through gas adsorption isotherms and x-ray photoelectron spectroscopy. Numerical modeling was used to elucidate characteristics of CNTs controlling DBP precursor adsorption. Multivariate models developed with unmodified CNTs revealed that surface carboxyl groups and, for TONO precursors, cumulative pore volume (CPV), controlled DBP precursor adsorption. Models developed with modified CNTs revealed that specific surface area controlled adsorption of THM and DHAN precursors while CPV and surface oxygen content were significant for adsorption of TONO precursors. While surrogates of THM and DHAN precursors leverage metrics from UV absorbance and fluorescence spectroscopy, a TONO precursor surrogate has proved elusive. This is important as measurements of TONO formation potential (TONOFP) require large sample volumes and long processing times, which impairs development of treatment processes. TONO precursor surrogates were developed using samples that had undergone oxidative or sorption treatments. Precursors were analyzed with asymmetric flow field-flow fractionation (AF4) with inline fluorescence detection (FLD) and whole water fluorescence excitation-emission matrices (EEMs). TONO precursor surrogates were discovered, capable of predicting changes in

Adsorption of small hydrocarbons on rutile TiO2(110)

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

Chen, Long; Smith, R. Scott; Kay, Bruce D.

2016-08-01

Temperature programmed desorption and molecular beam scattering were used to study the adsorption and desorption of small hydrocarbons (n-alkanes, 1-alkenes and 1-alkynes with 1 - 4 carbon atoms of C1-C4) on rutile TiO2(110). We show that the sticking coefficients for all the hydrocarbons are close to unity (> 0.95) at an adsorption temperature of 60 K. The desorption energies for hydrocarbons of the same chain length increase from n-alkanes to 1-alkenes and to 1-alkynes. This trend is likely a consequence of an additional dative bonding of the alkene and alkyne π system to the coordinatively unsaturated Ti5c sites. Similar tomore » previous studies on the adsorption of n-alkanes on metal and metal oxide surfaces, we find the desorption energies within each group (n-alkanes vs. 1-alkenes vs. 1-alkynes) from Ti5c sites increase linearly with the chain length. The absolute saturation coverages of each hydrocarbon on Ti5c sites were also determined. The saturation coverage of CH4, is found to be ~ 2/3 monolayer (ML). The saturation coverages of C2-C4 hydrocarbons are found nearly independent of the chain length with values of ~1/2 ML for n-alkanes and 1-alkenes and 2/3 ML for 1-alkynes. This result is surprising considering their similar sizes.« less

Adsorption behavior of Cr(VI) on modified natural zeolite by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent.

PubMed

Noroozifar, M; Khorasani-Motlagh, M; Gorgij, M N; Naderpour, H R

2008-07-15

The demand for effective adsorbents is to increase in response to the widespread recognition of the deleterious health effects of Cr(VI)-oxyanions exposure through drinking water. In this study, Cr(VI)-oxyanions uptake from aqueous solutions by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent-modified natural zeolitic materials from Zahedan, Iran, was investigated using batch technique. Spectrophotometry method was used for Cr determination. The Cr(VI)-solution concentration varied between 2 and 104 mg L(-1). It was shown that the Cr(VI) uptake strongly depended on pH. The maximum removal of Cr(VI) occurred in acidic media at pH<1.5. The amounts of Cr(VI) adsorbed increased with increase in dose of both adsorbents and their contact time. Based on results an adsorption mechanism has been suggested. The adsorption data for modified zeolite using the amine was consistent with Langmuir isotherm equation and the equilibrium data was analyzed using the Langmuir isotherm.

Cs/NF3 adsorption on [001]-oriented GaN nanowire surface: A first principle calculation

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Kong, Yike

2017-11-01

In this study, the adsorption mechanism of Cs/NF3 on the [001]-oriented GaN nanowire surface is investigated by using the density function theory based on first-principles. In the Cs/NF3 co-activation process, the system is inclined to form NF3-in structure. Through the calculation results of adsorption energy, NF3 molecule adsorption tends to take an orientation with F atoms on top and the most favorable adsorption site is BGa-N. The NF3 activation process can further cut down the work function of the Cs-covered nanowire surface only when Cs coverage is 0.75 ML and 1 ML, which can be explained by the double dipole moment theory. With increasing Cs coverage, the valence band and conduction band both shift to lower energy side, contributing to the appearance of a downward band bending region and promoting the escape of surface photoelectrons. After NF3 molecule adsorption, the peak of total density of states near Fermi level increase due to the orbital hybridization between NF3-2s, Cs-5s states and N-2p states, which strengthen the conductivity of the nanowire surface and leads to the metallic properties. All these calculations may direct the Cs/NF3 activation process of GaN nanowire optoelectronic devices.

Post-combustion CO2 capture with activated carbons using fixed bed adsorption

NASA Astrophysics Data System (ADS)

Al Mesfer, Mohammed K.; Danish, Mohd; Fahmy, Yasser M.; Rashid, Md. Mamoon

2018-03-01

In the current work, the capturing of carbon dioxide from flue gases of post combustion emission using fixed bed adsorption has been carried out. Two grades of commercial activated carbon (sorbent-1 and sorbent-2) were used as adsorbent. Feed consisting of CO2 and N2 mixture was used for carrying out the adsorption. The influence of bed temperature, feed rate, equilibrium partial pressure and initial % CO2 in feed were considered for analyzing adsorption-desorption process. It was found that the total adsorption-desorption cycle time decreases with increased column temperature and feed rates. The time required to achieve the condition of bed saturation decreases with increased bed temperature and feed rates. The amount of CO2 adsorbed/Kg of the adsorbent declines with increased bed temperature with in studied range for sorbent-1 and sorbent-2. It was suggested that the adsorption capacity of the both the sorbents increases with increased partial pressure of the gas.

Adsorption and desorption of SO2, NO and chlorobenzene on activated carbon.

PubMed

Li, Yuran; Guo, Yangyang; Zhu, Tingyu; Ding, Song

2016-05-01

Activated carbon (AC) is very effective for multi-pollutant removal; however, the complicated components in flue gas can influence each other's adsorption. A series of adsorption experiments for multicomponents, including SO2, NO, chlorobenzene and H2O, on AC were performed in a fixed-bed reactor. For single-component adsorption, the adsorption amount for chlorobenzene was larger than for SO2 and NO on the AC. In the multi-component atmosphere, the adsorption amount decreased by 27.6% for chlorobenzene and decreased by 95.6% for NO, whereas it increased by a factor of two for SO2, demonstrating that a complex atmosphere is unfavorable for chlorobenzene adsorption and inhibits NO adsorption. In contrast, it is very beneficial for SO2 adsorption. The temperature-programmed desorption (TPD) results indicated that the binding strength between the gas adsorbates and the AC follows the order of SO2>chlorobenzene > NO. The adsorption amount is independent of the binding strength. The presence of H2O enhanced the component effects, while it weakened the binding force between the gas adsorbates and the AC. AC oxygen functional groups were analyzed using TPD and X-ray photoelectron spectroscopy (XPS) measurements. The results reveal the reason why the chlorobenzene adsorption is less affected by the presence of other components. Lactone groups partly transform into carbonyl and quinone groups after chlorobenzene desorption. The chlorobenzene adsorption increases the number of C=O groups, which explains the positive effect of chlorobenzene on SO2 adsorption and the strong NO adsorption. Copyright © 2015. Published by Elsevier B.V.

The fabrication of porous N-doped carbon from widely available urea formaldehyde resin for carbon dioxide adsorption.

PubMed

Liu, Zhen; Du, Zhenyu; Song, Hao; Wang, Chuangye; Subhan, Fazle; Xing, Wei; Yan, Zifeng

2014-02-15

N-doped carbon material constitutes abundant of micropores and basic nitrogen species that have potential implementation for CO2 capture. In this paper, porous carbon material with high nitrogen content was simply fabricated by carbonizing low cost and widely available urea formaldehyde resin, and then followed by KOH activation. CO2 capture experiment showed high adsorption capacity of 3.21 mmol g(-1) at 25 °C under 1 atm for UFCA-2-600. XRD, SEM, XPS and FT-IR analysis confirmed that a graphitic-like structure was retained even after high temperature carbonization and strong base activation. Textural property analysis revealed that narrow micropores, especially below 0.8 nm, were effective for CO2 adsorption by physical adsorption mechanism. Chemical evolved investigation revealed that graphitic-like embedded basic nitrogen groups are generated from bridged and terminal amines of urea formaldehyde resin from thermal carbonization and KOH activation treatment, which is responsible for the enrichment of CO2 capacity by chemical adsorption mechanism. The relationship between CO2 adsorption capacity and pore size or basic N species was also studied, which turned out that both of them played crucial role by physical and chemical adsorption mechanism, respectively. Copyright © 2013 Elsevier Inc. All rights reserved.

Adsorption and molecular siting of CO2, water, and other gases in the superhydrophobic, flexible pores of FMOF-1 from experiment and simulation.

PubMed

Moghadam, Peyman Z; Ivy, Joshua F; Arvapally, Ravi K; Dos Santos, Antonio M; Pearson, John C; Zhang, Li; Tylianakis, Emmanouil; Ghosh, Pritha; Oswald, Iain W H; Kaipa, Ushasree; Wang, Xiaoping; Wilson, Angela K; Snurr, Randall Q; Omary, Mohammad A

2017-05-01

FMOF-1 is a flexible, superhydrophobic metal-organic framework with a network of channels and side pockets decorated with -CF 3 groups. CO 2 adsorption isotherms measured between 278 and 313 K and up to 55 bar reveal a maximum uptake of ca. 6.16 mol kg -1 (11.0 mol L -1 ) and unusual isotherm shapes at the higher temperatures, suggesting framework expansion. We used neutron diffraction and molecular simulations to investigate the framework expansion behaviour and the accessibility of the small pockets to N 2 , O 2 , and CO 2 . Neutron diffraction in situ experiments on the crystalline powder show that CO 2 molecules are favourably adsorbed at three distinct adsorption sites in the large channels of FMOF-1 and cannot access the small pockets in FMOF-1 at 290 K and oversaturated pressure at 61 bar. Stepped adsorption isotherms for N 2 and O 2 at 77 K can be explained by combining Monte Carlo simulations in several different crystal structures of FMOF-1 obtained from neutron and X-ray diffraction under different conditions. A similar analysis is successful for CO 2 adsorption at 278 and 283 K up to ca. 30 bar; however, at 298 K and pressures above 30 bar, the results suggest even more substantial expansion of the FMOF-1 framework. The measured contact angle for water on an FMOF-1 pellet is 158°, demonstrating superhydrophobicity. Simulations and adsorption measurements also show that FMOF-1 is hydrophobic and water is not adsorbed in FMOF-1 at room temperature. Simulated mixture isotherms of CO 2 in the presence of 80% relative humidity predict that water does not influence the CO 2 adsorption in FMOF-1, suggesting that hydrophobic MOFs could hold promise for CO 2 capture from humid gas streams.

H2O Adsorption Kinetics on Smectites

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard C.; Howard, Jeanie; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

The adsorptive equilibration of H2O a with montomorillonite, a smectite clay has been measured. At low temperatures and pressures, equilibration can require many hours, effectively preventing smectites at the martian surface from responding rapidly to diurnal pressure and temperature variations.

Isoelectric point and adsorption activity of porous g-C3N4

NASA Astrophysics Data System (ADS)

Zhu, Bicheng; Xia, Pengfei; Ho, Wingkei; Yu, Jiaguo

2015-07-01

The isoelectric point (IEP) is an important physicochemical parameter of many compounds, such as oxides, hydroxides, and nitrides, and can contribute to estimation of the surface charges of compound particles at various pH conditions. In this work, three types of graphitic carbon nitrides (g-C3N4) were synthesized by directly heating melamine, thiourea, and urea. The prepared samples showed different microstructures and IEPs that influenced their adsorption activity. Differences in microstructure resulted from the various precursors used during synthesis. The IEPs of the obtained g-C3N4 were measured to be approximately 4-5, which is due to the equilibrium of chemical reactions between hydrogen ions, hydroxyl ions, and amine groups on the g-C3N4 surface. The IEP of g-C3N4 prepared from thiourea was lower than those of the corresponding samples prepared from melamine and urea. The adsorption activity of methylene blue on g-C3N4 prepared from urea and thiourea was excellent, which indicates that g-C3N4 is a promising adsorbent. This work provides a useful reference for choosing precursors with which to prepare g-C3N4 and combining g-C3N4 with other compounds in solution.

Simultaneous adsorption and degradation of Zn(2+) and Cu (2+) from wastewaters using nanoscale zero-valent iron impregnated with clays.

PubMed

Shi, Li-Na; Zhou, Yan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

2013-06-01

Clays such as kaolin, bentonite and zeolite were evaluated as support material for nanoscale zero-valent iron (nZVI) to simultaneously remove Cu(2+) and Zn(2+) from aqueous solution. Of the three supported nZVIs, bentonite-supported nZVI (B-nZVI) was most effective in the simultaneous removal of Cu(2+) and Zn(2+) from a aqueous solution containing a 100 mg/l of Cu(2+) and Zn(2+), where 92.9 % Cu(2+) and 58.3 % Zn(2+) were removed. Scanning electronic microscope (SEM) revealed that the aggregation of nZVI decreased as the proportion of bentonite increased due to the good dispersion of nZVI, while energy dispersive spectroscopy (EDS) demonstrated the deposition of copper and zinc on B-nZVI after B-nZVI reacted with Cu(2+) and Zn(2+). A kinetics study indicated that removing Cu(2+) and Zn(2+) with B-nZVI accorded with the pseudo first-order model. These suggest that simultaneous adsorption of Cu(2+)and Zn(2+) on bentonite and the degradation of Cu(2+)and Zn(2+) by nZVI on the bentonite. However, Cu(2+) removal by B-nZVI was reduced rather than adsorption, while Zn(2+) removal was main adsorption. Finally, Cu(2+), Zn(2+), Ni(2+), Pb(2+) and total Cr from various wastewaters were removed by B-nZVI, and reusability of B-nZVI with different treatment was tested, which demonstrates that B-nZVI is a potential material for the removal of heavy metals from wastewaters.

Adsorption of Ca2+ on single layer graphene oxide.

PubMed

Terracciano, Amalia; Zhang, Jianfeng; Christodoulatos, Christos; Wu, Fengchang; Meng, Xiaoguang

2017-07-01

Graphene oxide (GO) holds great promise for a broad array of applications in many fields, but also poses serious potential risks to human health and the environment. In this study, the adsorptive properties of GO toward Ca 2+ and Na + were investigated using batch adsorption experiments, zeta potential measurements, and spectroscopic analysis. When pH increased from 4 to 9, Ca 2+ adsorption by GO and the zeta potential of GO increased significantly. Raman spectra suggest that Ca 2+ was strongly adsorbed on the GO via -COOCa + formation. On the other hand, Na + was adsorbed into the electrical diffuse layer as an inert counterion to increase the diffuse layer zeta potential. While the GO suspension became unstable with increasing pH from 4 to 10 in the presence of Ca 2+ , it was more stable at higher pH in the NaCl solution. The findings of this research provide insights in the adsorption of Ca 2+ on GO and fundamental basis for prediction of its effect on the colloidal stability of GO in the environment. Copyright © 2017. Published by Elsevier B.V.

Investigation of the adsorption of ozone molecules on TiO2/WSe2 nanocomposites by DFT computations: Applications to gas sensor devices

NASA Astrophysics Data System (ADS)

Abbasi, Amirali; Sardroodi, Jaber Jahanbin

2018-04-01

The adsorption of O3 molecule on the undoped and N-doped TiO2/WSe2 nanocomposites was studied using first principles density functional theory calculations. O3 interaction with TiO2/WSe2 nanocomposites is considered so as to investigate WSe2 effects on the adsorption process. WSe2 favors the adsorption of O3 on TiO2 particles. In other words, WSe2 is conducive to the interaction of O3 molecule with fivefold coordinated titanium sites of TiO2. The effects of vdW interactions were taken into account in order to obtain equilibrium geometries of O3 molecules at TiO2/WSe2 interfaces. For all adsorption configurations, the binding site was positioned on the fivefold coordinated titanium atoms. The results show that the interactions between O3 and TiO2 in TiO2/WSe2 nanocomposites are stronger than those between O3 and bare TiO2, suggesting that WSe2 helps to strengthen the interaction of ozone molecule with TiO2 particles. The results also indicate that the adsorption of the O3 molecule on the N-doped TiO2/WSe2 nanocomposite is more energetically favorable than the adsorption of O3 on the pristine one, representing that the N-doped nanocomposites are more sensitive than the undoped ones. Our DFT results clearly show that the N-doped TiO2/WSe2 nanocomposite would be a promising O3 gas sensor. The electronic structure of the adsorption system was also investigated, including analysis of the total and projected density of states, and charge density differences of the TiO2/WSe2 with adsorbed O3 molecules. The charge density difference calculations indicate that the charges were accumulated over the adsorbed O3 molecule. Besides, the N-doped nanocomposites have better sensing response than the pristine ones. This work was devoted to provide the theory basis for the design and development of novel and advanced O3 sensors based on modified TiO2/WSe2 nanocomposites.

Study of Cs/NF3 adsorption on GaN (0 0 1) surface

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Kong, Yike

2017-03-01

To investigate the optoelectronics properties of Cs/NF3 adsorption on GaN (0 0 1) photocathode surface, different adsorption models of Cs-only, Cs/O, Cs/NF3 adsorption on GaN clean surface were established, respectively. Atomic structures, work function, adsorption energy, E-Mulliken charge distribution, density of states and optical properties of all these adsorption systems were calculated using first principles. Compared with Cs/O co-adsorption, Cs/NF3 co-adsorption show better stability and more decline of work function, which is more beneficial for photoemission efficiency. Besides, surface band structures of Cs/NF3 co-adsorption system exhibit metal properties, implying good conductivity. Meanwhile, near valence band minimum of Cs/NF3 co-adsorption system, more acceptor levels emerges to form a p-type emission surface, which is conductive to the escape of photoelectrons. In addition, imaginary part of dielectric function curve and absorption curve of Cs/NF3 co-adsorption system both move towards lower energy side. This work can direct the optimization of activation process of NEA GaN photocathode.

Comparative adsorption of Pb2+ and Cd2+ by cow manure and its vermicompost.

PubMed

Zhu, Weiqin; Du, Wenhui; Shen, Xuyang; Zhang, Hangjun; Ding, Ying

2017-08-01

Organic waste has great potential for use as an amendment to immobilize heavy metals in the environment. Therefore, this study investigates various properties of cow manure (CM) and its derived vermicompost (CV), including the pH, cationic exchangeable capacity (CEC), elemental composition and surface structure, to determine the potential of these waste products to remove Pb 2+ and Cd 2+ from solution. The results demonstrate that CV has a much higher pH, CEC and more irregular pores than CM and is enriched with minerals and ash content but has a lower C, H, O and N content. Adsorption isotherms studies shows that the adsorption of Pb 2+ and Cd 2+ onto either CM or CV follows a Langmuir model and presents maximum Pb 2+ and Cd 2+ adsorption capacities of 102.77 mg g -1 and 38.11 mg g -1 onto CM and 170.65 and 43.01 mg g -1 onto CV, respectively. Kinetic studies show that the adsorption of Pb 2+ onto CM and CV fits an Elovich model, whereas the adsorption of Cd 2+ onto CM and CV fits a pseudo-second-order model. Desorption studies indicate that CV is more effective than CM in removing Pb 2+ and Cd 2+ . FTIR analysis demonstrates that the adsorption of Pb 2+ and Cd 2+ onto CM mainly depends on existed aliphatic alcohol, aromatic acid as well as new produced carbonates, whereas that onto CV may be contributed by the existed aliphatic alcohol, aromatic acids as well as some carbonates and phosphates. Thus, vermicomposting disposal of cow manure with destination mineral addition may broaden the way of its recycle and environmental usage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption kinetics of SO2 on powder activated carbon

NASA Astrophysics Data System (ADS)

Li, Bing; Zhang, Qilong; Ma, Chunyuan

2018-02-01

The flue gas SO2 adsorption removal by powder activated carbon is investigated based on a fixed bed reactor. The effect of SO2 inlet concentration on SO2 adsorption is investigated and the adsorption kinetics is analyzed. The results indicated that the initial SO2 adsorption rate and the amount of SO2 adsorbed have increased with increased in SO2 inlet concentration. Gas diffusion, surface adsorption and catalytic oxidation reaction are involved in SO2 adsorption on powder activated carbon, which play a different role in different stage. The Bangham kinetics model can be used to predict the kinetics of SO2 adsorption on powder activated carbon.

Theoretical study on adsorption and dissociation of NO2 molecules on BNNT surface

NASA Astrophysics Data System (ADS)

Singla, Preeti; Singhal, Sonal; Goel, Neetu

2013-10-01

The adsorption of NO2 molecules on (8,0) zigzag single-walled boron nitride nanotube surface is investigated using density functional theory calculations. Two interaction modes, nitro (interacting atom is N) and nitrite (O interacts with BNNT) have been studied with increase in number of NO2 molecules. The adsorption of single NO2 molecule in both configurations is observed to be exothermic and physical in nature. However, in nitrite configuration, NO2 molecules are chemisorbed on the surface leading to the dissociation of NO2 molecules into NO and O. The density of states, natural bond orbital analysis and frontier orbital pictures provide rational understanding of the charge transfer involved in the process and predict significant enhancement in the conductivity of the BNNT after NO2 adsorption. The DFT calculations show that NO2 adsorption introduces new impurity states in the band gap of bare BNNT and expand their applications as NO2 molecule gas sensor and catalytic surface for Nsbnd O dissociation depending upon the mode of adsorption.

Adsorption of bis(2-hydroxy-3-chloropropyl) dodecylamine on quartz surface and its implication on flotation

NASA Astrophysics Data System (ADS)

Liu, Wengang; Liu, Wenbao; Dai, Shujuan; Wang, Benying

2018-06-01

In order to clarify the effect of polar group modification on flotation performance of amine collector, flotation properties of quartz and hematite using bis(2-hydroxy-3-chloropropyl) dodecylamine (N23) as a collector were investigated. And the adsorption mechanism of N23 on quartz surface was established by zeta potential measurements, SEM/EDS measurements, and molecular structure analysis. Single mineral flotation results indicated that N23 showed stronger collecting ability on quartz and hematite than DDA-CH3COOH. However, starch could depress the flotation of hematite. Flotation recovery of 98.10% for quartz could be achieved, when N23 concentration was 43.33 mg/L and starch concentration was 16.67 mg/L at natural slurry pH. Separation of artificially mixed minerals of hematite and quartz was achieved effectively using N23 as the collector. The optimized separation result with 66.29% iron grade and 90.06% iron recovery in concentrate was obtained when slurry pH was 7.34 with 43.33 mg/L N23 and 23.33 mg/L starch. The interaction energies of N23 with mineral surface also showed well consistency with flotation results. SEM/EDS analyses and zeta potential measurements revealed that N23 could absorb on quartz surface in the forms of strong electrostatic and hydrogen bonding interaction. Compared with DDA, N23 had a higher HLB value and better water-solubility, which resulted in better dispersion in water and stronger adsorption on mineral surface.

Light Hydrocarbon Adsorption Mechanisms in Two Calcium-Based Microporous Metal Organic Frameworks

DOE PAGES

Plonka, Anna M.; Chen, Xianyin; Wang, Hao; ...

2016-01-25

The adsorption mechanism of ethane, ethylene, and acetylene (C 2H n; n = 2, 4, 6) on two microporous metal organic frameworks (MOFs) is described here that is consistent with observations from single crystal and powder X-ray diffraction, calorimetric measurements, and gas adsorption isotherm measurements. Two calcium-based MOFs, designated as SBMOF-1 and SBMOF-2 (SB: Stony Brook), form three-dimensional frameworks with one-dimensional open channels. As determined from single crystal diffraction experiments, channel geometries of both SBMOF-1 and SBMOF-2 provide multiple adsorption sites for hydrocarbon molecules through C–H···π and C–H···O interactions, similarly to interactions in the molecular and protein crystals. In conclusion,more » both materials selectively adsorb C 2 hydrocarbon gases over methane as determined with IAST and breakthrough calculations as well as experimental breakthrough measurements, with C 2H 6/CH 4 selectivity as high as 74 in SBMOF-1.« less

Adsorption of sugar surfactants at the air/water interface.

PubMed

Varga, Imre; Mészáros, Róbert; Stubenrauch, Cosima; Gilányi, Tibor

2012-08-01

The adsorption isotherms of n-decyl-β-D-glucoside (β-C(10)G(1)) as well as various n-alkyl-β-D-maltosides (β-C(n)G(2)) with n=8, 10, 12 and 14 were determined from surface tension measurements. Based on the analysis of the adsorption isotherms, the total free energy change of adsorption was determined and a novel method was proposed to determine the maximum adsorbed amount of surfactant. It can be concluded that the driving force for adsorption first increases with increasing adsorbed amount of the sugar surfactants and then levels off in a plateau. This peculiar behaviour is interpreted as formation of a thin liquid-like alkane film of overlapping alkyl chains at the air/water interface once a certain adsorbed amount is exceeded. The driving force of adsorption depends on the alkyl chain length only and is not affected by the type of the head group. The hydrophobic contribution to the standard free energy change of adsorption was compared with the values of sodium alkylsulfate and alkyltrimethylammonium bromide surfactants. This comparison reveals that the hydrophobic driving force of adsorption is the largest for the sodium alkylsulfates, whereas it is the same for the sugar surfactants and the alkyltrimethylammonium bromides. Copyright © 2012 Elsevier Inc. All rights reserved.

CO₂ adsorption on amine-functionalized periodic mesoporous benzenesilicas.

PubMed

Sim, Kyohyun; Lee, Nakwon; Kim, Joonseok; Cho, Eun-Bum; Gunathilake, Chamila; Jaroniec, Mietek

2015-04-01

CO2 adsorption was investigated on amine-functionalized mesoporous silica (SBA-15) and periodic mesoporous organosilica (PMO) samples. Hexagonally (p6mm) ordered mesoporous SBA-15 and benzene-PMO (BPMO) samples were prepared in the presence of Pluronic P123 block copolymer template under acidic conditions. Three kinds of amine-containing organosilanes and polyethylenimine were used to functionalize SBA-15 and BPMO. Small-angle X-ray scattering and nitrogen adsorption isotherms showed that these samples featured ordered mesostructure, high surface area, and narrow pore size distributions. Solid-state (13)C- and (29)Si cross-polarization magic-angle spinning NMR spectra showed chemical linkage between amine-containing modifiers and the surface of mesoporous materials. The chemically linked amine-containing modifiers were found to be on both the inner and outer surfaces. N-[3-(trimethoxysilyl)propyl]ethylenediamine-modified BPMO (A2-BPMO) sample exhibited the highest CO2 uptake (i.e., ∼3.03 mmol/g measured on a volumetric adsorption analyzer) and the fastest adsorption rate (i.e., ∼13 min to attain 90% of the maximum amount) among all the samples studied. Selectivity and reproducibility measurements for the A2-BPMO sample showed quite good performance in flowing N2 gas at 40 mL/min and CO2 gas of 60 mL/min at 25 °C.

2-Hydroxypropyltrimethylammonium xylan adsorption onto rod-like cellulose nanocrystal.

PubMed

Sim, Jae Hyun; Dong, Shuping; Röemhild, Katrin; Kaya, Abdulaziz; Sohn, Daewon; Tanaka, Keiji; Roman, Maren; Heinze, Thomas; Esker, Alan R

2015-02-15

Chemical incompatibility and relatively weak interaction between lignocellulosic fibers and synthetic polymers have made studies of wood fiber-thermoplastic composite more challenging. In this study, adsorption of 2-hydroxypropyltrimethylammonium xylans onto rod-like cellulose nanocrystals are investigated by zeta-potential measurements, and polarized and depolarized dynamic light scattering as a factor for better understanding of lignocellulosic fibers and cellulose nanocrystals. Zeta-potential measurements show xylan derivative adsorption onto cellulose nanocrystals. Decay time distributions of the ternary system and binary system from dynamic light scattering show that aggregates exist in the binary system and they disappear in the ternary system. At low 2-hydroxypropyltrimethylammonium xylan concentrations relative to that of cellulose nanocrystal, xylan derivatives adsorbed onto some of the cellulose nanocrystal. Hence, more xylan derivatives adsorbed onto cellulose nanocrystal increased with increasing xylan derivative concentration. Also, the concentration dependence of the ratio of the rotational diffusion coefficient to the translational diffusion coefficient revealed a strong adsorptive interaction between xylan derivatives and the cellulose nanocrystals. Copyright © 2014 Elsevier Inc. All rights reserved.

Analyzing adsorption characteristics of CO2, N2 and H2O in MCM-41 silica by molecular simulation

NASA Astrophysics Data System (ADS)

Chang, Shing-Cheng; Chien, Shih-Yao; Chen, Chieh-Li; Chen, Cha'o.-Kuang

2015-03-01

The adsorption characteristics of carbon dioxide, nitrogen and water molecules in MCM-41 mesoporous molecular sieve have been investigated by the molecular simulation. We evaluate the pressure-adsorption isotherms and adsorption density profiles under variant gas pressure, operating temperature and mesopore radius of MCM-41 by the grand canonical Monte Carlo simulation. According to the calculated adsorption energy distributions, the adsorption mechanisms of gas in MCM-41 are mainly divided into three types, namely "surface adsorption" on the pore wall, "multilayer adsorption" on the adsorbed gas molecules and "molecular self-aggregation" near the pore center. In addition, the adsorption characteristics of water molecules in MCM-41 are found to be quite different from those of carbon dioxide and nitrogen due to the hydrogen bonds effect. The results indicate that the MCM-41 is practicable in engineering application for the capture, storage, and re-use of water molecules, since it is temperature-sensitive and can achieve significant adsorption loadings within a small range of pressure values via the capillary condensation phenomena.

Enhanced role of Al or Ga-doped graphene on the adsorption and dissociation of N2O under electric field.

PubMed

Lv, Yong-an; Zhuang, Gui-lin; Wang, Jian-guo; Jia, Ya-bo; Xie, Qin

2011-07-21

To find an effective strategy for the capture and decomposition of nitrous oxide (N(2)O) is very important in order to protect the ozone layer and control the effects of global warming. Based on first-principles calculations, such a strategy is proposed by the systemic study of N(2)O interaction with pristine and Al (or Ga)-doped graphene, and N(2)O dissociation on the surface of Al (or Ga)-doped graphene in an applied electric field. The calculated adsorption energy value shows the N(2)O molecule more firmly adsorbs on the surface of Al (or Ga)-doped graphene than that of pristine graphene, deriving from a stronger covalent bond between the N(2)O molecule and the Al (or Ga) atom. Furthermore, our study suggests that N(2)O molecules can be easily decomposed to N(2) and O(2) with the appropriate electric field, which reveals that Al-doped graphene may be a new candidate for control of N(2)O. This journal is © the Owner Societies 2011

Optimization of CO2 adsorption capacity and cyclical adsorption/desorption on tetraethylenepentamine-supported surface-modified hydrotalcite.

PubMed

Thouchprasitchai, Nutthavich; Pintuyothin, Nuthapol; Pongstabodee, Sangobtip

2018-03-01

The objective of this research was to investigate CO 2 adsorption capacity of tetraethylenepentamine-functionalized basic-modified calcined hydrotalcite (TEPA/b-cHT) sorbents at atmospheric pressure formed under varying TEPA loading levels, temperatures, sorbent weight to total gaseous flow rate (W/F) ratios and CO 2 concentrations in the influent gas. The TEPA/b-cHT sorbents were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA), Brunauer-Emmet-Teller (BET) analysis of nitrogen (N 2 ) adsorption/desorption and carbon-hydrogen-nitrogen (CHN) elemental analysis. Moreover, a full 2 4 factorial design with three central points at a 95% confidence interval was used to screen important factor(s) on the CO 2 adsorption capacity. It revealed that 85.0% variation in the capacity came from the influence of four main factors and the 15.0% one was from their interactions. A face-centered central composite design response surface method (FCCCD-RSM) was then employed to optimize the condition, the maximal capacity of 5.5-6.1mmol/g was achieved when operating with a TEPA loading level of 39%-49% (W/W), temperature of 76-90°C, W/F ratio of 1.7-2.60(g·sec)/cm 3 and CO 2 concentration of 27%-41% (V/V). The model fitted sufficiently the experimental data with an error range of ±1.5%. From cyclical adsorption/desorption and selectivity at the optimal condition, the 40%TEPA/b-cHT still expressed its effective performance after eight cycles. Copyright © 2017. Published by Elsevier B.V.

Synergic mechanism of adsorption and metal-free catalysis for phenol degradation by N-doped graphene aerogel.

PubMed

Ren, Xiaohua; Guo, Huanhuan; Feng, Jinkui; Si, Pengchao; Zhang, Lin; Ci, Lijie

2018-01-01

3D porous N-doped reduced graphene oxide (N-rGO) aerogels were synthesized by a hydrothermal reduction of graphene oxide (GO) with urea and following freeze-drying process. N-rGO aerogels have a high BET surface of 499.70 m 2 /g and a high N doping content (5.93-7.46 at%) including three kinds of N (graphitic, pyridinic and pyrrolic). Their high catalytic performance for phenol oxidation in aqueous solution was investigated by catalytic activation of persulfate (PS). We have demonstrated that N-rGO aerogels are promising metal-free catalysts for phenol removal. Kinetics studies indicate that phenol degradation follows first-order reaction kinetics with the reaction rate constant of 0.16799 min -1 for N-rGO-A(1:30). Interestingly, the comparison of direct catalytic oxidation with adsorption-catalytic oxidation experiments indicates that adsorption plays an important role in the catalytic oxidation of phenol by decreasing the phenol degradation time. Spin density and adsorption modeling demonstrates that graphitic N in N-rGO plays the most important role for the catalytic performance by inducing high positive charge densities to adjacent carbon atoms and facilitating phenol adsorption on these carbon sites. Furthermore, the activation mechanism of persulfate (PS) on N-rGO was first investigated by DFT method and PS can be activated to generate strongly oxidative radical (SO 4 · - ) by transferring electrons to N-rGO. Copyright © 2017 Elsevier Ltd. All rights reserved.

Overcoming double-step CO2 adsorption and minimizing water co-adsorption in bulky diamine-appended variants of Mg2(dobpdc)† †Electronic supplementary information (ESI) available: Additional experimental details, and full characterization (powder X-ray diffraction, infrared spectra, diamine loadings, dry N2 decomposition profiles, and CO2 adsorption data) for all new adsorbents. CCDC 1577354. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04266c

PubMed Central

Milner, Phillip J.; Martell, Jeffrey D.; Siegelman, Rebecca L.; Gygi, David; Weston, Simon C.

2017-01-01

Alkyldiamine-functionalized variants of the metal–organic framework Mg2(dobpdc) (dobpdc4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) are promising for CO2 capture applications owing to their unique step-shaped CO2 adsorption profiles resulting from the cooperative formation of ammonium carbamate chains. Primary,secondary (1°,2°) alkylethylenediamine-appended variants are of particular interest because of their low CO2 step pressures (≤1 mbar at 40 °C), minimal adsorption/desorption hysteresis, and high thermal stability. Herein, we demonstrate that further increasing the size of the alkyl group on the secondary amine affords enhanced stability against diamine volatilization, but also leads to surprising two-step CO2 adsorption/desorption profiles. This two-step behavior likely results from steric interactions between ammonium carbamate chains induced by the asymmetrical hexagonal pores of Mg2(dobpdc) and leads to decreased CO2 working capacities and increased water co-adsorption under humid conditions. To minimize these unfavorable steric interactions, we targeted diamine-appended variants of the isoreticularly expanded framework Mg2(dotpdc) (dotpdc4– = 4,4′′-dioxido-[1,1′:4′,1′′-terphenyl]-3,3′′-dicarboxylate), reported here for the first time, and the previously reported isomeric framework Mg-IRMOF-74-II or Mg2(pc-dobpdc) (pc-dobpdc4– = 3,3′-dioxidobiphenyl-4,4′-dicarboxylate, pc = para-carboxylate), which, in contrast to Mg2(dobpdc), possesses uniformally hexagonal pores. By minimizing the steric interactions between ammonium carbamate chains, these frameworks enable a single CO2 adsorption/desorption step in all cases, as well as decreased water co-adsorption and increased stability to diamine loss. Functionalization of Mg2(pc-dobpdc) with large diamines such as N-(n-heptyl)ethylenediamine results in optimal adsorption behavior, highlighting the advantage of tuning both the pore shape and the diamine size for the development

First-principles study of adsorption and diffusion of oxygen on surfaces of TiN, ZrN and HfN

NASA Astrophysics Data System (ADS)

Guo, Fangyu; Wang, Jianchuan; Du, Yong; Wang, Jiong; Shang, Shun-Li; Li, Songlin; Chen, Li

2018-09-01

Using first-principles calculations based on density functional theory, we systematically study the adsorption and diffusion behaviors of single oxygen (O) atom on the (0 0 1) surfaces of TiN, ZrN and HfN nitride coatings. The top of N site (top(N)) is the most energetic favorable site for O atom and followed by the hollow site for all the three nitrides. O atom tends to diffuse on the (0 0 1) surfaces of the nitrides from the top of transition metal top(TM) sites to a neighboring top(TM) sites by avoiding N sites. The adsorption of O on ZrN and HfN is more stable than that on TiN. Our findings could explain the experimental phenomenon that the oxide thickness of TiN is smaller than that of ZrN under the same oxidation conditions.

Wastewater remediation by TiO2-impregnated chitosan nano-grafts exhibited dual functionality: High adsorptivity and solar-assisted self-cleaning.

PubMed

Essawy, Amr A; Sayyah, S M; El-Nggar, A M

2017-08-01

This work provides a very infrequent and unique avenue of a novel bio-based nanografted polymeric composites achieving encouraging results in green management of dye contaminants in wastewater. A chitosan-grafted-polyN-Methylaniline (Ch-g-PNMANI) and chitosan-grafted-polyN-Methylaniline imprinted TiO 2 nanocomposites (Ch-g-PNMANI/TiO 2 ) were prepared and efficiently applied in wastewater remediation. The nanocomposites were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and Brunauer-Emmett-Teller surface area (BET) measurements. The prepared composites exhibit higher adsorptivity in removing remazol red RB-133 (RR RB-133) dye compared to other adsorbents reported in literature. The effects of TiO 2 loadings, initial dye concentration, contact time, and pH on dye adsorption were investigated. The maximum adsorption of dye was found at low pH values. Furthermore, Ch-g-PNMANI/TiO 2 of the optimum TiO 2 loading has higher adsorption capacity (116.3mg/g) than the pristine Ch-g-PNMANI (108.7mg/g). Moreover, the prepared adsorbents are photoactive under sunlight-irradiation. The study addresses a nanocomposite of considerable adsorption and in the same time has the fastest self-cleaning photoactivity (t 1/2 =31.5min.) under sunlight irradiation where a plausible photodegradation mechanism was proposed. Interestingly, the presented photoactive adsorbents are still effective in removing dye after five adsorption/sunlight-assisted self-cleaning photoregeneration cycles and therefore, they can be potentially applied to the rapid, "green" and low-cost remediation of RR RB-133 enriched industrial printing and dyeing wastewater. Copyright © 2017 Elsevier B.V. All rights reserved.

Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption.

PubMed

Song, Guanling; Cao, Lijing; Chen, Xiao; Hou, Wenhua; Wang, Qunhui

2012-01-01

A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

Influence of vacancy defect on surface feature and adsorption of Cs on GaN(0001) surface.

PubMed

Ji, Yanjun; Du, Yujie; Wang, Meishan

2014-01-01

The effects of Ga and N vacancy defect on the change in surface feature, work function, and characteristic of Cs adsorption on a (2 × 2) GaN(0001) surface have been investigated using density functional theory with a plane-wave ultrasoft pseudopotential method based on first-principles calculations. The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect. The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface. The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at B(Ga) site on N vacancy defect surface. The E(ads) of Cs on GaN(0001) vacancy defect surface increases compared with that of intact surface; this illustrates that the adsorption of Cs on intact surface is more stable.

Synthesis of N-doped microporous carbon via chemical activation of polyindole-modified graphene oxide sheets for selective carbon dioxide adsorption.

PubMed

Saleh, Muhammad; Chandra, Vimlesh; Kemp, K Christian; Kim, Kwang S

2013-06-28

A polyindole-reduced graphene oxide (PIG) hybrid was synthesized by reducing graphene oxide sheets in the presence of polyindole. We have shown PIG as a material for capturing carbon dioxide (CO2). The PIG hybrid was chemically activated at temperatures of 400-800 °C, which resulted in nitrogen (N)-doped graphene sheets. The N-doped graphene sheets are microporous with an adsorption pore size of 0.6 nm for CO2 and show a maximum (Brunauer, Emmet and Teller) surface area of 936 m(2) g(-1). The hybrid activated at 600 °C (PIG6) possesses a surface area of 534 m(2) g(-1) and a micropore volume of 0.29 cm(3) g(-1). PIG6 shows a maximum CO2 adsorption capacity of 3.0 mmol g(-1) at 25 °C and 1 atm. This high CO2 uptake is due to the highly microporous character of the material and its N content. The material retains its original adsorption capacity on recycling even after 10 cycles (within experimental error). PIG6 also shows high adsorption selectivity ratios for CO2 over N2, CH4 and H2 of 23, 4 and 85 at 25 °C, respectively.

Adsorption/Desorption Measurements of Nitroglycerin and Dinitrotoluene in Camp Edwards, Massachusetts Soil

DTIC Science & Technology

2010-02-01

87 8 References...without biocide to K7 soil. ................................................ 31 Figure 8 . The 2,4-DNT concentration in the measured aqueous phase (C...28 Table 8 . Adsorption and desorption partitioning

Probing adsorption sites of carbon dioxide in metal organic framework of [Zn(bdc)(dpds)]n: A molecular simulation study

NASA Astrophysics Data System (ADS)

Lu, Shih-I.; Liao, Jian-Min; Huang, Xiao-Zhuang; Lin, Chia-Hsun; Ke, Szu-Yu; Wang, Chih-Chieh

2017-11-01

We used force-field based grand-canonical Monte Carlo simulation method and density functional theory to study adsorption characteristics of carbon dioxide (CO2) molecules in a metal-organic framework (MOF) compound, [Zn(bdc)(dpds)]n. The studied MOF include a metal ion (Zn(II)), an anion organic linker (dianion of benzene dicarboxylicacid, bdc2-) and a neutral organic linker (4,4‧-dipyridyldisulfide, dpds). Results from calculated adsorption isotherms and enthalpies of adsorption agree with the experimental data. The interactions between the adsorbed CO2 and the organic linkers were examined in simulations. Calculated results show available absorption sites are surrounded by two dpds ligands in which an S-S bond as an N-N‧ spacer connect two pyridines. In contrast, the bdc2- ligand does not give a significant contribution to the substantial adsorption amount even though it contains the carboxylate group that provides available bonding site to CO2.

Measurement of Critical Adsorption of Nitrogen near Its Liquid-vapor Critical Point

NASA Technical Reports Server (NTRS)

Chan, Moses

2003-01-01

The density profile of a critical fluid near a solid surface is expected to show an universal shape. This is known as critical adsorption. The measurement of this effect, especially close to the critical point, is often obscured by gravity. We were able to separate the gravitational effect from critical adsorption by using two capacitors, one with a large gap and one with a small gap of approximately 2 m. Within the uncertainty in the measurement, our data, which ranges between 10(exp -3) to 2 x 10(exp -6) in reduced temperatures, is consistent with the predicted power law dependence. This work is carried out in collaboration with Rafael Garcia, Sarah Scheidemantel and Klaus Knorr. It is funded by NASA's office of Biological and Physical Researchunder.

Different effects of surface heterogeneous atoms of porous and non-porous carbonaceous materials on adsorption of 1,1,2,2-tetrachloroethane in aqueous environment.

PubMed

Chen, Weifeng; Ni, Jinzhi

2017-05-01

The surface heterogeneous atoms of carbonaceous materials (CMs) play an important role in adsorption of organic pollutants. However, little is known about the surface heterogeneous atoms of CMs might generate different effect on adsorption of hydrophobic organic compounds by porous carbonaceous materials - activated carbons (ACs) and non-porous carbonaceous materials (NPCMs). In this study, we observed that the surface oxygen and nitrogen atoms could decrease the adsorption affinity of both ACs and NPCMs for 1,1,2,2-tetrachloroethane (TeCA), but the degree of decreasing effects were very different. The increasing content of surface oxygen and nitrogen ([O + N]) caused a sharper decrease in adsorption affinity of ACs (slope of lg (k d /SA) vs [O + N]: -0.098∼-0.16) than that of NPCMs (slope of lg (k d /SA) vs [O + N]: -0.025∼-0.059) for TeCA. It was due to the water cluster formed by the surface hydrophilic atoms that could block the micropores and generate massive invalid adsorption sites in the micropores of ACs, while the water cluster only occupied the surface adsorption sites of NPCMs. Furthermore, with the increasing concentration of dissolved TeCA, the effect of surface area on adsorption affinity of NPCMs for TeCA kept constant while the effect of [O + N] decreased due to the competitive adsorption between water molecule and TeCA on the surface of NPCMs, meanwhile, both the effects of micropore volume and [O + N] on adsorption affinity of ACs for TeCA were decreased due to the mechanism of micropore volume filling. These findings are valuable for providing a deep insight into the adsorption mechanisms of CMs for TeCA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Particle Association on 2,2'-Bipyridyl Adsorption onto Kaolinite.

PubMed

Helmy, A. K.; Ferreiro, E. A.; de Bussetti, S. G.

2000-05-15

The effect of particle concentration, in kaolin suspensions, on the adsorption of 2,2'-bipyridyl was studied. Adsorption expressed in units of micromoles per gram decreased as a result of the increase in particle concentration and also as a result of the presence of coagulant (0.25 M NaCl). Dispersion treatment with sodium hexametaphosphate increased the adsorption of bipyridyl. The decrease in adsorption with the increase in particle concentration suggests a possible relation between adsorption and flocculation phenomena. On the basis of classic flocculation theory a straight-line relation was obtained between the square root of the adsorption maximum (mmol/L) and particle concentration (g/L). It is concluded that particle association, which is a function of particle concentration, reduces the surface/aqueous interface and consequently the adsorption of bipyridyl. Copyright 2000 Academic Press.

Statistical inference in single molecule measurements of protein adsorption

NASA Astrophysics Data System (ADS)

Armstrong, Megan J.; Tsitkov, Stanislav; Hess, Henry

2018-02-01

Significant effort has been invested into understanding the dynamics of protein adsorption on surfaces, in particular to predict protein behavior at the specialized surfaces of biomedical technologies like hydrogels, nanoparticles, and biosensors. Recently, the application of fluorescent single molecule imaging to this field has permitted the tracking of individual proteins and their stochastic contribution to the aggregate dynamics of adsorption. However, the interpretation of these results is complicated by (1) the finite time available to observe effectively infinite adsorption timescales and (2) the contribution of photobleaching kinetics to adsorption kinetics. Here, we perform a protein adsorption simulation to introduce specific survival analysis methods that overcome the first complication. Additionally, we collect single molecule residence time data from the adsorption of fibrinogen to glass and use survival analysis to distinguish photobleaching kinetics from protein adsorption kinetics.

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.

Infrared spectroscopic study of radiation-induced adsorption of n-hexane on a beryllium surface

NASA Astrophysics Data System (ADS)

Gadzhieva, N. N.

2017-07-01

Radiation-stimulated adsorption on a beryllium surface is studied by IR reflection-absorption spectroscopy. It is found that γ-irradiation at room temperature leads to the appearance of n-hexane adsorption centers on a beryllium surface according to molecular and dissociation mechanisms. The kinetics of n-hexane adsorption in a Be- n-hexane system is studied; activated dissociative chemisorption accompanied by formation of beryllium alkyls and surface hydrides is observed at absorbed doses 15 kGy ≤ Vγ ≤ 35 kGy. A possible mechanism of this process is suggested.

Energetic investigation of the adsorption process of CH4, C2H6 and N2 on activated carbon: Numerical and statistical physics treatment

NASA Astrophysics Data System (ADS)

Ben Torkia, Yosra; Ben Yahia, Manel; Khalfaoui, Mohamed; Al-Muhtaseb, Shaheen A.; Ben Lamine, Abdelmottaleb

2014-01-01

The adsorption energy distribution (AED) function of a commercial activated carbon (BDH-activated carbon) was investigated. For this purpose, the integral equation is derived by using a purely analytical statistical physics treatment. The description of the heterogeneity of the adsorbent is significantly clarified by defining the parameter N(E). This parameter represents the energetic density of the spatial density of the effectively occupied sites. To solve the integral equation, a numerical method was used based on an adequate algorithm. The Langmuir model was adopted as a local adsorption isotherm. This model is developed by using the grand canonical ensemble, which allows defining the physico-chemical parameters involved in the adsorption process. The AED function is estimated by a normal Gaussian function. This method is applied to the adsorption isotherms of nitrogen, methane and ethane at different temperatures. The development of the AED using a statistical physics treatment provides an explanation of the gas molecules behaviour during the adsorption process and gives new physical interpretations at microscopic levels.

CO2 Adsorption in Low-Rank Coals: Progress Toward Assessing the National Capacity to Store CO2 in the Subsurface

NASA Astrophysics Data System (ADS)

Stanton, R. W.; Burruss, R. C.; Flores, R. M.; Warwick, P. D.

2001-05-01

Subsurface environments for geologic storage of CO2 from combustion of fossil fuel include saline formations, depleted oil and gas reservoirs, and unmineable coalbeds. Of these environments, storage in petroleum reservoirs and coal beds offers a potential economic benefit of enhanced recovery of energy resources. Meaningful assessment of the volume and geographic distribution of storage sites requires quantitative estimates of geologic factors that control storage capacity. The factors that control the storage capacity of unmineable coalbeds are poorly understood. In preparation for a USGS assessment of CO2 storage capacity we have begun new measurements of CO2 and CH4 adsorption isotherms of low-rank coal samples from 4 basins. Initial results for 13 samples of low-rank coal beds from the Powder River Basin (9 subbituminous coals), Greater Green River Basin (1 subbituminous coal), Williston Basin (2 lignites) and the Gulf Coast (1 lignite) indicate that their adsorption capacity is up to 10 times higher than it is for CH4. These values contrast with published measurements of the CO2 adsorption capacity of bituminous coals from the Fruitland Formation, San Juan basin, and Gates Formation, British Columbia, that indicate about twice as much carbon dioxide as methane can be adsorbed on coals. Because CH4 adsorption isotherms are commonly measured on coals, CO2 adsorption capacity can be estimated if thecorrect relationship between the gases is known. However, use a factor to predict CO2 adsorption that is twice that of CH4 adsorption, which is common in the published literature, grossly underestimates the storage capacity of widely distributed, thick low-rank coal beds. Complete petrographic and chemical characterization of these low-rank coal samples is in progress. Significant variations in adsorption measurements among samples are depicted depending on the reporting basis used. Properties were measured on an "as received" (moist) basis but can be converted to a

Investigation of protein adsorption performance of Ni2+-attached diatomite particles embedded in composite monolithic cryogels.

PubMed

Ünlü, Nuri; Ceylan, Şeyda; Erzengin, Mahmut; Odabaşı, Mehmet

2011-08-01

As a low-cost natural adsorbent, diatomite (DA) (2 μm) has several advantages including high surface area, chemical reactivity, hydrophilicity and lack of toxicity. In this study, the protein adsorption performance of supermacroporous composite cryogels embedded with Ni(2+)-attached DA particles (Ni(2+)-ADAPs) was investigated. Supermacroporous poly(2-hydroxyethyl methacrylate) (PHEMA)-based monolithic composite cryogel column embedded with Ni(2+)-ADAPs was prepared by radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm) as cross-linker directly in a plastic syringe for affinity purification of human serum albumin (HSA) both from aqueous solutions and human serum. The chemical composition and surface area of DA was determined by XRF and BET method, respectively. The characterization of composite cryogel was investigated by SEM. The effect of pH, and embedded Ni(2+)-ADAPs amount, initial HSA concentration, temperature and flow rate on adsorption were studied. The maximum amount of HSA adsorption from aqueous solution at pH 8.0 phosphate buffer was very high (485.15 mg/g DA). It was observed that HSA could be repeatedly adsorbed and desorbed to the embedded Ni(2+)-ADAPs in poly(2-hydroxyethyl methacrylate) composite cryogel without significant loss of adsorption capacity. The efficiency of albumin adsorption from human serum before and after albumin adsorption was also investigated with SDS-PAGE analyses. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular simulation of methane adsorption characteristics on coal macromolecule

NASA Astrophysics Data System (ADS)

Yang, Zhiyuan; He, Xiaoxiao; Meng, Zhuoyue; Xue, Wenying

2018-02-01

In this paper, the molecular model of anthracite named Wender2 was selected to study the adsorption behaviour of single component CH4 and the competitive adsorption of CH4/CO2, CH4/H2O and CH4/N2. The molecular model of anthracite was established by molecular simulation software (Materials Studio 8.0), and Grand Canonical Monte Carlo (GCMC) simulations were carried out to investigate the single and binary component adsorption. The effects of pressure and temperature on the adsorption position, adsorption energy and adsorption capacity were mainly discussed. The results show that for the single component adsorption, the adsorption capacity of CH4 increases rapidly with the pressure ascending, and then tends to be stable after the first step. The low temperature is favourable for the adsorption of CH4, and the high temperature promotes desorption quantity of CH4 from the coal. Adsorbent molecules are preferentially adsorbed on the edge of coal macromolecules. The order of adsorption capacity of CH4/CO2, CH4/H2O and CH4/N2 in the binary component is H2O>CO2>CH4>N2. The change of pressure has little effect on the adsorption capacity of the adsorbent in the competitive adsorption, but it has a great influence on the adsorption capacity of the adsorbent, and there is a positive correlation between them.

SAPO-34 Membranes for N-2/CH4 separation: Preparation, characterization, separation performance and economic evaluation

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

Li, SG; Zong, ZW; Zhou, SJ

2015-08-01

SAPO-34 membranes were synthesized by several routes towards N-2/CH4 separation. Membrane synthesis parameters including water content in the gel, crystallization time, support pore size, and aluminum source were investigated. High performance N-2-selective membranes were obtained on 100-nm-pore alumina tubes by using Al(i-C3H7O)(3) as aluminum source with a crystallization time of 6 h. These membranes separated N-2 from CH, with N-2 permeance as high as 500 GPU with separation selectivity of 8 at 24 degrees C. for a 50/50 N-2/CH4 mixture. Nitrogen and CH, adsorption isotherms were measured on SAPO-34 crystals. The N-2 and CH, heats of adsorption were 11 andmore » 15 kJ/mol, respectively, which lead to a preferential adsorption of CE-H-4 over N-2 in the N-2/CH4 mixture. Despite this, the SAPO-34 membranes were selective for N-2 over CH4 in the mixture because N-2 diffuses much faster than CH4 and differences in diffusivity played a more critical role than the competitive adsorption. Preliminary economic evaluation indicates that the required N-2/CH4 selectivity would be 15 in order to maintain a CH4 loss below 10%. For small nitrogen-contaminated gas wells, our current SAPO-34 membranes have potential to compete with the benchmark technology cryogenic distillation for N-2 rejection. (C) 2015 Elsevier B.V. All rights reserved,« less

Influence of Vacancy Defect on Surface Feature and Adsorption of Cs on GaN(0001) Surface

PubMed Central

Ji, Yanjun; Du, Yujie; Wang, Meishan

2014-01-01

The effects of Ga and N vacancy defect on the change in surface feature, work function, and characteristic of Cs adsorption on a (2 × 2) GaN(0001) surface have been investigated using density functional theory with a plane-wave ultrasoft pseudopotential method based on first-principles calculations. The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect. The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface. The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at BGa site on N vacancy defect surface. The E ads of Cs on GaN(0001) vacancy defect surface increases compared with that of intact surface; this illustrates that the adsorption of Cs on intact surface is more stable. PMID:25126599

Adsorption of CO2 on KOH activated, N-enriched carbon derived from urea formaldehyde resin: kinetics, isotherm and thermodynamic studies

NASA Astrophysics Data System (ADS)

Tiwari, Deepak; Bhunia, Haripada; Bajpai, Pramod K.

2018-05-01

High surface area nitrogen enriched carbon adsorbents were prepared from a low cost and widely available urea-formaldehyde resin using a standard chemical activation with KOH and characterized using different characterization techniques for their porous structure and surface functional groups. Maximum surface area and total pore volume of 4547 m2 g-1 and 4.50 cm3 g-1 were found by controlling the activation conditions. Nitrogen content of this sample was found to be 5.62%. Adsorption of CO2 uptake for the prepared carbon adsorbents was studied using a dynamic fixed bed adsorption system at different adsorption temperatures (30-100 °C) and at different CO2 concentrations (5-12.5%), relevant from the flue gas point application. Maximum CO2 uptake of 1.40 mmol g-1 for UFA-3-700 at 30 °C under 12.5% CO2 flow was obtained. Complete regenerability of the adsorbents over multiple adsorption-desorption cycles was obtained. Fractional order kinetic model provided best description over all adsorption temperatures and CO2 concentrations. Heterogeneity of the adsorbent surface was confirmed from Temkin adsorption isotherm model fit and isosteric heat of adsorption values. Negative value of ΔG° and ΔH° confirms spontaneous, feasible nature and exothermic nature of adsorption process. Overall, very high surface area of carbon adsorbent makes this adsorbent a new promising carbon material for CO2 capture from power plant flue gas and for other relevant applications.

Ti, Al and N adatom adsorption and diffusion on rocksalt cubic AlN (001) and (011) surfaces: Ab initio calculations

NASA Astrophysics Data System (ADS)

Mastail, C.; David, M.; Nita, F.; Michel, A.; Abadias, G.

2017-11-01

We use ab initio calculations to determine the preferred nucleation sites and migration pathways of Ti, Al and N adatoms on cubic NaCl-structure (B1) AlN surfaces, primary inputs towards a further thin film growth modelling of the TiAlN alloy system. The potential energy landscape is mapped out for both metallic species and nitrogen adatoms for two different AlN surface orientations, (001) and (110), using density functional theory. For all species, the adsorption energies on AlN(011) surface are larger than on AlN(001) surface. Ti and Al adatom adsorption energy landscapes determined at 0 K by ab initio show similar features, with stable binding sites being located in, or near, epitaxial surface positions, with Ti showing a stronger binding compared to Al. In direct contrast, N adatoms (Nad) adsorb preferentially close to N surface atoms (Nsurf), thus forming strong N2-molecule-like bonds on both AlN(001) and (011). Similar to N2 desorption mechanisms reported for other cubic transition metal nitride surfaces, in the present work we investigate Nad/Nsurf desorption on AlN(011) using a drag calculation method. We show that this process leaves a Nsurf vacancy accompanied with a spontaneous surface reconstruction, highlighting faceting formation during growth.

Study of CO2 adsorption capacity of mesoporous carbon and activated carbon modified by triethylenetetramine (TETA)

NASA Astrophysics Data System (ADS)

Sulistianti, I.; Krisnandi, Y. K.; Moenandar, I.

2017-04-01

Mesoporous carbon was synthesized by soft template method using phloroglucinol and formaldehyde as a carbon source; and Pluronic F-127 as a mesoporous template. The synthesized mesoporous carbon and commercial activated carbon were modified with triethylenetetramine (TETA) to increase CO2 adsorption capacity. Based on FTIR characterization, the synthesized mesoporous carbon and the activated carbon without modification process has similarity pattern. After the modification, both of them showed absorption peaks in the area around 1580 to 1650 cm-1 which is known as N-H bending vibration and absorption peaks in the area around 3150 to 3380 cm-1 which is known as N-H stretching vibration. The XRD results showed two peaks at 2θ = 24.21° and 2θ = 43.85°, according to JCPDS index No. 75-1621 those peak are the typical peaks for hexagonal graphite carbon. In BET analysis, the synthesized mesoporous carbon and activated carbon modified TETA have surface area, pore volume and pore diameter lower than without modification process. In carbon dioxide adsorption testing, the synthesized mesoporous carbon showed better performance than the commercial activated carbon for CO2 adsorption both without modification and by modification. The synthesized mesoporous carbon obtained CO2 adsorption of 9.916 mmol/g and the activated carbon of 3.84 mmol/g for on 3.5 hours of adsorption. It is three times better than activated carbon for adsorption of carbon dioxide. The modified mesoporous carbon has the best performance for adsorption of gas CO2 if compared by unmodified.

Assessment of the role of micropore size and N-doping in CO2 capture by porous carbons.

PubMed

Sevilla, Marta; Parra, Jose B; Fuertes, Antonio B

2013-07-10

The role of micropore size and N-doping in CO2 capture by microporous carbons has been investigated by analyzing the CO2 adsorption properties of two types of activated carbons with analogous textural properties: (a) N-free carbon microspheres and (b) N-doped carbon microspheres. Both materials exhibit a porosity made up exclusively of micropores ranging in size between <0.6 nm in the case of the pristine materials and up to 1.6 nm for the highly activated carbons (47% burnoff). The N-doped carbons possess ~3 wt % of N heteroatoms that are incorporated into several types of functional groups (i.e., pyrrole/pyridone, pyridine, quaternary, and pyridine-N-oxide). Under conventional operation conditions (i.e., T ~ 0-25 °C and P(CO2) ~ 0-1 bar), CO2 adsorption proceeds via a volume-filling mechanism, the size limit for volume-filling being ~0.7-0.8 nm. Under these circumstances, the adsorption of CO2 by nonfunctionalized porous carbons is mainly determined by the volume of the micropores with a size below 0.8 nm. It was also observed that the CO2 capture capacities of undoped and N-doped carbons are analogous which shows that the nitrogen functionalities present in these N-doped samples do not influence CO2 adsorption. Taking into account the temperature invariance of the characteristic curve postulated by the Dubinin theory, we show that CO2 uptakes can be accurately predicted by using the adsorption data measured at just one temperature.

Comparison of nitrogen adsorption and transmission electron microscopy analyses for structural characterization of carbon nanotubes

NASA Astrophysics Data System (ADS)

Abbaslou, Reza Malek; Vosoughi, Vahid; Dalai, Ajay K.

2017-10-01

Carbon nanotubes (CNTs) are different from other porous substrates such as activated carbon due to their high external surfaces. This structural feature can lead in some uncertainties in the results of nitrogen adsorption analysis for characterization of CNTs. In this paper, the results of microscopic analyses and nitrogen adsorption method for characterization of carbon nanotubes were compared. Five different types of CNTs with different structures were either synthesized or purchased. The CNT samples were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and N2 adsorption analysis. The comparisons between the results from the microscopic analyses and N2 adsorption showed that the total pore volume and BET surface measurements include the internal and external porosity of CNTs. Therefore, the interpretation of N2 adsorption data required accurate TEM analysis. In addition, the evaluation of pore size distribution curves from all CNT samples in this study and several instances in the literature revealed the presence of a common peak in the range of 2-5 nm. This peak does not explain the inner pore size distribution. The presence of this common peak can be attributed to the strong adsorption of N2 on the junction of touched and crossed nanotubes.

Adsorption Characteristics of Pb(2+) onto Wine Lees-Derived Biochar.

PubMed

Zhu, Qihong; Wu, Jun; Wang, Lilin; Yang, Gang; Zhang, Xiaohong

2016-08-01

Biochar has great advantages in soil amendment and polluted soil remediation. Herein, the pore and adsorption properties of wine lees-derived biochar were explored. Specifically, the adsorption isotherm and kinetics of Pb(2+) onto wine lees-derived biochar were examined. Experimental results revealed that wine lees-derived biochar featured large specific surface area and total pore volume, and high contents of -COOH and -OH on its surface. Adsorption of Pb(2+) onto wine lees-derived biochar proceeded via a multilayer adsorption mechanism, as described by the Freundlich adsorption model. Adsorption kinetics followed the Lagergren pseudo-second-order kinetics model; adsorption equilibrium was achieved within 30-60 min. Furthermore, the effect of solution pH on the adsorption of Pb(2+) was investigated. Within the studied pH range of 3-6, the adsorption capacity increased with increasing pH. Under established optimized conditions, wine lees-derived biochar achieved a Pb(2+) adsorption capacity of 79.12 mg/g.

Two-step adsorption on jungle-gym-type porous coordination polymers: dependence on hydrogen-bonding capability of adsorbates, ligand-substituent effect, and temperature.

PubMed

Uemura, Kazuhiro; Yamasaki, Yukari; Onishi, Fumiaki; Kita, Hidetoshi; Ebihara, Masahiro

2010-11-01

A preliminary study of isopropanol (IPA) adsorption/desorption isotherms on a jungle-gym-type porous coordination polymer, [Zn(2)(bdc)(2)(dabco)](n) (1, H(2)bdc = 1,4-benzenedicarboxylic acid, dabco =1,4-diazabicyclo[2.2.2]octane), showed unambiguous two-step profiles via a highly shrunk intermediate framework. The results of adsorption measurements on 1, using probing gas molecules of alcohol (MeOH and EtOH) for the size effect and Me(2)CO for the influence of hydrogen bonding, show that alcohol adsorption isotherms are gradual two-step profiles, whereas the Me(2)CO isotherm is a typical type-I isotherm, indicating that a two-step adsorption/desorption is involved with hydrogen bonds. To further clarify these characteristic adsorption/desorption behaviors, selecting nitroterephthalate (bdc-NO(2)), bromoterephthalate (bdc-Br), and 2,5-dichloroterephthalate (bdc-Cl(2)) as substituted dicarboxylate ligands, isomorphous jungle-gym-type porous coordination polymers, {[Zn(2)(bdc-NO(2))(2)(dabco)]·solvents}(n) (2 ⊃ solvents), {[Zn(2)(bdc-Br)(2)(dabco)]·solvents}(n) (3 ⊃ solvents), and {[Zn(2)(bdc-Cl(2))(2)(dabco)]·solvents}(n) (4 ⊃ solvents), were synthesized and characterized by single-crystal X-ray analyses. Thermal gravimetry, X-ray powder diffraction, and N(2) adsorption at 77 K measurements reveal that [Zn(2)(bdc-NO(2))(2)(dabco)](n) (2), [Zn(2)(bdc-Br)(2)(dabco)](n) (3), and [Zn(2)(bdc-Cl(2))(2)(dabco)](n) (4) maintain their frameworks without guest molecules with Brunauer-Emmett-Teller (BET) surface areas of 1568 (2), 1292 (3), and 1216 (4) m(2) g(-1). As found in results of MeOH, EtOH, IPA, and Me(2)CO adsorption/desorption on 2-4, only MeOH adsorption on 2 shows an obvious two-step profile. Considering the substituent effects and adsorbate sizes, the hydrogen bonds, which are triggers for two-step adsorption, are formed between adsorbates and carboxylate groups at the corners in the pores, inducing wide pores to become narrow pores. Interestingly, such

CO2/H2O adsorption equilibrium and rates on metal-organic frameworks: HKUST-1 and Ni/DOBDC.

PubMed

Liu, Jian; Wang, Yu; Benin, Annabelle I; Jakubczak, Paulina; Willis, Richard R; LeVan, M Douglas

2010-09-07

Metal-organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO(2), H(2)O vapor, and their mixtures and also rates of CO(2) adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO(2)/H(2)O binary adsorption equilibria were studied using a volumetric system. The effects of H(2)O adsorption on CO(2) adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive measurements of H(2)O and CO(2)/H(2)O mixture equilibria were also studied. CO(2) adsorption rates from helium for the MOF samples were investigated by using a unique concentration-swing frequency response (CSFR) system. Mass transfer into the MOFs is rapid with the controlling resistance found to be macropore diffusion, and rate parameters were established for the mechanism.

Synthesis, characterization, and application of Zn(NH 3)(CO3) for selective adsorptive separation of CO2

NASA Astrophysics Data System (ADS)

Khazeni, Naasser

This study explores the potential of Zn(NH3)(CO3) for selective CO2 separation. It develops a novel, highly controllable, single-pot synthesis approach based on urea hydrolysis and solvothermal aging to increase the feasibility of synthesizing Zn(NH3)(CO3), determines the structure of Zn(NH3)(CO3) in detail through single crystal X-ray diffraction and powder X-ray diffraction analyses, and performs adsorption analyses for the compound using CO2, N 2, H2, O2, and CH4 as adsorptives. Through adsorptive characterization, a systematic adsorbent selection screening is performed to assess the potential application of Zn(NH3)(CO 3) for adsorptive separation of CO2 from an upstream gas mixture of power generation, hydrogen production, and natural gas industries. Structural analysis shows Zn(NH3)(CO3) to have an inorganic helical framework that consists of a small helix of (ZnOCO) 2 and a large helix of (ZnOCO)4 with two ammines (NH 3) pendant from every other zinc. In terms of adsorption capacity and CO2 selectivity, Zn(NH3)(CO3) adsorbed 0.550 mmole/g CO2 at 293 K and 4500 mmHg, but only 0.047 mmole/g N 2, 0.084 mmole/g H2, 0.207 mmole/g 02, and 0.060 mmole/g CH4 at the same temperature and pressure. This behavior demonstrates considerable equilibrium selectivities - 36, 31, 63, and 11 - for separating CO2 from CH4, CO2 from H 2, CO2 from N2, and CO2 from 02, respectively. During adsorption, the pendant ammines act as the gates of check-valves: applied pressure opens the gates for adsorption; and during desorption, the gates are closed, trapping the adsorbates, until a reduction of pressure to near-atmospheric levels. Therefore, Zn(NH3)(CO3) exhibits low-pressure H3 or H4 hysteresis, indicating that the Zn(NH3)(CO3) framework can achieve gas storage at near-atmospheric pressures. Additionally, the compound proves structurally stable, with an adsorption decrease of 0.8% after 20 adsorption/desorption cycles - a factor that, considered with the other characteristics of Zn

Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

PubMed Central

Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

2015-01-01

Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

Removal of binary dyes mixtures with opposite and similar charges by adsorption, coagulation/flocculation and catalytic oxidation in the presence of CeO2/H2O2 Fenton-like system.

PubMed

Issa Hamoud, Houeida; Finqueneisel, Gisèle; Azambre, Bruno

2017-06-15

In this study, the removal of binary mixtures of dyes with similar (Orange II/Acid Green 25) or opposite charges (Orange II/Malachite Green) was investigated either by simple adsorption on ceria or by the heterogeneous Fenton reaction in presence of H 2 O 2 . First, the CeO 2 nanocatalyst with high specific surface area (269 m 2 /g) and small crystal size (5 nm) was characterized using XRD, Raman spectroscopy and N 2 physisorption at 77 K. The adsorption of single dyes was studied either from thermodynamic and kinetic viewpoints. It is shown that the adsorption of dyes on ceria surface is highly pH-dependent and followed a pseudo-second order kinetic model. Adsorption isotherms fit well the Langmuir model with a complete monolayer coverage and higher affinity towards Orange II at pH 3, compared to other dyes. For the (Orange II/Acid Green 25) mixture, both the amounts of dyes adsorbed on ceria surface and discoloration rates measured from Fenton experiments were decreased by comparison with single dyes. This is due to the adsorption competition existing onto the same surface Ce x+ sites and the reaction competition with hydroxyl radicals, respectively. The behavior of the (Orange II/Malachite Green) mixture is markedly different. Dyes with opposite charges undergo paired adsorption on ceria as well as homogeneous and heterogeneous coagulation/flocculation processes, but can also be removed by heterogeneous Fenton process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of Na+ impregnated activated carbon on the adsorption of NH4(+)-N from aqueous solution.

PubMed

Shi, Mo; Wang, Zhengfang; Zheng, Zheng

2013-08-01

Two kinds of activated carbons modified by Na+ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid (denoted as AC/N-Na and AC/HCl-Na, respectively), were used as adsorbents to remove NH4(+)-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4(+)-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na+ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4(+)-N. Na(+)-impregnated ACs had a higher removal capability in removing NH4(+)-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4(+)-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

PubMed

Manga, Mohamed S; Hunter, Timothy N; Cayre, Olivier J; York, David W; Reichert, Matthew D; Anna, Shelly L; Walker, Lynn M; Williams, Richard A; Biggs, Simon R

2016-05-03

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher

Highly Permeable AlPO-18 Membranes for N 2 /CH 4 Separation

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

Zong, Zhaowang; Elsaidi, Sameh K.; Thallapally, Praveen K.

Herein we demonstrate that AlPO-18 membranes can separate N2/CH4 gas mixtures at unprecedented N2 permeances. The best membranes separated N2/CH4 mixtures with N2 permeances as high as 3076 GPU and separation selectivities as high as 4.6. Gas mixture separation data, N2 and CH4 adsorption isotherms, ideal adsorbed solution theory (IAST), and breakthrough experiments were collected to understand the separation mechanisms. Competitive adsorption and differences in diffusivities were identified as the prevailing separation mechanisms. Differences in diffusivity played a more dominant role than the competitive adsorption, and led to nitrogen selective membranes.

Thermodynamic properties of adsorption and micellization of n-oktyl-β-D-glucopiranoside.

PubMed

Mańko, Diana; Zdziennicka, Anna; Jańczuk, Bronisław

2014-02-01

Measurements of the surface tension, density and viscosity of aqueous solutions of n-oktyl-β-D-glucopiranoside (OGP) were made at 293 K. From the obtained results the Gibbs surface excess concentration of OGP at the water-air interface and its critical micelle concentration were determined. The Gibbs surface excess concentration of OGP used in the Gu and Zhu isotherm equation allowed us to determine the Gibbs standard free energy of OGP adsorption at the water-air interface. The Gibbs standard free energy of OGP adsorption was also determined on the basis of the Langmuir, Szyszkowski, Gamboa and Olea equations as well the surface tension of "hydrophobic" part of OGP and "hydrophobic" part-water interface tension. It appeared that there is an agreement between the values of Gibbs standard free energy of OGP adsorption at the water-air interface determined by using all the above mentioned methods. It also proved that standard free energy of OGP micellization determined from CMC is consistent with that obtained on the basis of the free energy of the interactions between the "hydrophobic" part of the OPG through the water phase. Copyright © 2013 Elsevier B.V. All rights reserved.

Water adsorption on goethite: Application of multilayer adsorption models

NASA Astrophysics Data System (ADS)

Hatch, C. D.; Tumminello, R.; Meredith, R.

2016-12-01

Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

Li-adsorption on doped Mo2C monolayer: A novel electrode material for Li-ion batteries

NASA Astrophysics Data System (ADS)

Mehta, Veenu; Tankeshwar, K.; Saini, Hardev S.

2018-04-01

A first principle calculation has been used to study the electronic and magnetic properties of pristine and N/Mn-doped Mo2C with and without Li-adsorption. The pseudopotential method implemented in SIESTA code based on density functional theory with generalized gradient approximation (GGA) as exchange-correlation (XC) potential has been employed. Our calculated results revealed that the Li gets favorably adsorbed on the hexagonal centre in pristine Mo2C and at the top of C-atom in case of N/Mn-doped Mo2C. The doping of Mn and N atom increases the adsorption of Li in Mo2C monolayer which may results in enhancement of storage capacity in Li-ion batteries. The metallic nature of Li-adsorbed pristine and N/Mn-doped Mo2C monolayer implies a good electronic conduction which is crucial for anode materials for its applications in rechargeable batteries. Also, the open circuit voltage for single Li-adsorption in doped Mo2C monolayer comes in the range of 0.4-1.0 eV which is the optimal range for any material to be used as an anode material. Our result emphasized the enhanced performance of doped Mo2C as an anode material in Li-ion batteries.

Molecular adsorption properties of CO and H2O on Au-, Cu-, and AuxCuy-doped MoS2 monolayer

NASA Astrophysics Data System (ADS)

Kadioglu, Yelda; Gökoğlu, Gökhan; Üzengi Aktürk, Olcay

2017-12-01

In this study, we investigate the adsorption properties of Au, Cu, and AuxCuy nanoclusters on MoS2 sheet and the interactions of the adsorbed systems with CO and H2O molecules by using first principles calculations. Results indicate that Au, Cu, or AuxCuy strongly binds to MoS2 monolayer resulting in enhanced chemical activity and sensitivity toward CO and H2O molecules compared to bare MoS2 monolayer. Although both CO and H2O molecules bind weakly to pristine MoS2 monolayer, CO strongly binds to MoS2 sheet in the presence of Au, Cu atoms or AuxCuy clusters. Semiconductor MoS2 monolayer turns into metal upon Au or Cu adsorption. AuxCuy nanocluster adsorption decreases the band gap of MoS2 monolayer acting as a n-type dopant. AuxCuy-doped MoS2 systems have improved adsorption properties for CO and H2O molecules, so the conclusions provided in this study can be useful as a guide for next generation device modeling.

Adsorption of polyethyleneimine and polymethacrylic acid onto synthesized hematite.

PubMed

Chibowski, S; Patkowski, J; Grzadka, E

2009-01-01

An influence of different functional groups of polymer, its molecular weight, polydispersity ratio (M(w)/M(n)) and presence of impurities on its adsorption in different pH values (3, 6 and 9) onto synthesized hematite (Fe(2)O(3)) was measured. A structure of adsorbed macromolecules of PMA and PEI was obtained according to S-F theory. Two polymers were used: polymethacrylic acid (PMA) of 6500 and 75,100 molecular weight as well as polyethyleneimine (PEI) 25,000 commercial and fractionated. Electrokinetic properties of the interface oxide-polymer solution (surface charge density and zeta potential) were also measured as well as adsorption layer thicknesses (with use of viscosimetric measurements). Obtained data show, that all above-mentioned factors do influence not only the adsorption process itself but also a surface charge, zeta potential and structure of adsorbed polymer layers on polymer/hematite interface.

A flow-pulse adsorption-microcalorimetry system for studies of adsorption processes on powder catalysts

NASA Astrophysics Data System (ADS)

You, Rui; Li, Zhaorui; Zeng, Hongyu; Huang, Weixin

2018-06-01

A pulse chemisorption system combining a Tian-Calvet microcalorimeter (Setaram Sensys EVO 600) and an automated chemisorption apparatus (Micromeritics Autochem II 2920) was established to accurately measure differential adsorption heats of gas molecules' chemisorption on solid surfaces in a flow-pulse mode. Owing to high sensitivity and high degree of automation in a wide range of temperatures from -100 to 600 °C, this coupled system can present adsorption heats as a function of adsorption temperature and adsorbate coverage. The functions of this system were demonstrated by successful measurements of CO adsorption heats on Pd surfaces at various temperatures and also at different CO coverages by varying the CO concentration in the pulse dose. Key parameters, including adsorption amounts, integral adsorption heats, and differential adsorption heats of CO adsorption on a Pd/CeO2 catalyst, were acquired. Our adsorption-microcalorimetry system provides a powerful technique for the investigation of adsorption processes on powder catalysts.

Adsorption mechanism of SF6 decomposed species on pyridine-like PtN3 embedded CNT: A DFT study

NASA Astrophysics Data System (ADS)

Cui, Hao; Zhang, Xiaoxing; Chen, Dachang; Tang, Ju

2018-07-01

Metal-Nx embedded CNT have aroused considerable attention in the field of gas interaction due to their strong catalytic behavior, which provides prospective scopes for gas adsorption and sensing. Detecting SF6 decomposed species in certain devices is essential to guarantee their safe operation. In this work, we performed DFT method and simulated the adsorption of three SF6 decomposed gases (SO2, SOF2 and SO2F2) onto the PtN3 embedded CNT surface, in order to shed light on its adsorption ability and sensing mechanism. Results suggest that the CNT embedded with PtN3 center has strong interaction with these gas molecules, leading to high hybridization between Pt dopant and active atoms inner gas molecules. These interactions are assumed to be chemisorption due to the remarkable Ead and QT, thus resulting in dramatic deformations in electronic structure of PtN3-CNT near the Fermi level. Furthermore, the electronic redistribution cause the conductivity increase of proposed material in three systems, based on frontier molecular orbital theory. Our calculations attempt to suggest novel sensing material that are potentially employed in detection of SF6 decomposed components.

Measurements of VOC adsorption/desorption characteristics of typical interior building materials

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

An, Y.; Zhang, J.S.; Shaw, C.Y.

2000-07-01

The adsorption/desorption of volatile organic compounds (VOCs) on interior building material surfaces (i.e., the sink effect) can affect the VOC concentrations in a building, and thus need to be accounted for an indoor air quality (IAQ) prediction model. In this study, the VOC adsorption/desorption characteristics (sink effect) were measured for four typical interior building materials including carpet, vinyl floor tile, painted drywall, and ceiling tile. The VOCs tested were ethylbenzene, cyclohexanone, 1,4-dichlorobenzene, benzaldehyde, and dodecane. These five VOCs were selected because they are representative of hydrocarbons, aromatics, ketones, aldehydes, and chlorine substituted compounds. The first order reversible adsorption/desorption model wasmore » based on the Langmuir isotherm was used to analyze the data and to determine the equilibrium constant of each VOC-material combination. It was found that the adsorption/desorption equilibrium constant, which is a measure of the sink capacity, increased linearly with the inverse of the VOC vapor pressure. For each compound, the adsorption/desorption equilibrium constant, and the adsorption rate constant differed significantly among the four materials tested. A detailed characterization of the material structure in the micro-scale would improve the understanding and modeling of the sink effect in the future. The results of this study can be used to estimate the impact of sink effect on the VOC concentrations in buildings.« less

Adsorptive removal of 2-chlorophenol by low-cost coir pith carbon.

PubMed

Namasivayam, C; Kavitha, D

2003-03-17

Adsorption of 2-chlorophenol (2-CP) by coir pith carbon was carried out by varying the parameters such as agitation time, 2-CP concentration, adsorbent dose, pH and temperature. Adsorption equilibrium reached at 40, 60, 80 and 100 min for 2-CP concentration of 10, 20, 30 and 40 mg/l, respectively. Adsorption followed second-order kinetics. The adsorption equilibrium data obeyed Freundlich isotherm. Acidic pH was favorable for the adsorption of 2-CP. Desorption studies showed that chemisorption plays a major role in the adsorption process. Copyright 2003 Elsevier Science B.V.

Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology

NASA Technical Reports Server (NTRS)

Megaridis, Constantine M.; Bellizia, Giulio; McNallan, Michael; Wallace, David B.

2003-01-01

Surface tension forces play a critical role in fluid dynamic phenomena that are important in materials processing. The surface tension of liquid metals has been shown to be very susceptible to small amounts of adsorbed oxygen. Consequently, the kinetics of oxygen adsorption can influence the capillary breakup of liquid-metal jets targeted for use in electronics assembly applications, where low-melting-point metals (such as tin-containing solders) are utilized as an attachment material for mounting of electronic components to substrates. By interpreting values of surface tension measured at various surface ages, adsorption and diffusion rates of oxygen on the surface of the melt can be estimated. This research program investigates the adsorption kinetics of oxygen on the surface of an atomizing molten-metal jet. A novel oscillating capillary jet method has been developed for the measurement of dynamic surface tension of liquids, and in particular, metal melts which are susceptible to rapid surface degradation caused by oxygen adsorption. The experimental technique captures the evolution of jet swells and necks continuously along the jet propagation axis and is used in conjunction with an existing linear, axisymmetric, constant-property model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated so far focus on a time window of 2-4ms from the jet orifice. The surface properties of the eutectic 63%Sn-37%Pb solder alloy have been investigated in terms of their variation due to O2 adsorption from a N2 atmosphere containing controlled amounts of oxygen (from 8 ppm to 1000 ppm). The method performed well for situations where the oxygen adsorption was low in that time window. The value of surface tension for the 63Sn-37Pb solder in pure nitrogen was found to be 0.49 N/m, in good agreement with previously published work. A characteristic

Development of chemically activated N-enriched carbon adsorbents from urea-formaldehyde resin for CO2 adsorption: Kinetics, isotherm, and thermodynamics.

PubMed

Tiwari, Deepak; Bhunia, Haripada; Bajpai, Pramod K

2018-07-15

Nitrogen enriched carbon adsorbents with high surface areas were successfully prepared by carbonizing the low-cost urea formaldehyde resin, followed by KOH activation. Different characterization techniques were used to determine the structure and surface functional groups. Maximum surface area and total pore volume of 4547 m 2  g -1 and 4.50 cm 3  g -1 were found by controlling activation conditions. The optimized sample denoted as UFA-3-973 possesses a remarkable surface area, which is found to be one of the best surface areas achieved so far. Nitrogen content of this sample was found to be 22.32%. Dynamic CO 2 uptake capacity of the carbon adsorbents were determined thermogravimetrically at different CO 2 concentrations (6-100%) and adsorption temperatures (303-373 K) which have a much more relevance for the flue gas application. Highest adsorption capacity of 2.43 mmol g -1 for this sample was obtained at 303 K under pure CO 2 flow. Complete regenerability of the adsorbent over four adsorption-desorption cycles was obtained. Fractional order kinetic model provided best description of adsorption over all adsorption temperatures and CO 2 concentrations. Heterogeneity of the adsorbent surface was confirmed from the Langmuir and Freundlich isotherms fits and isosteric heat of adsorption values. Exothermic, spontaneous and feasible nature of adsorption process was confirmed from thermodynamic parameter values. The combination of high surface area and large pore volume makes the adsorbent a new promising carbon material for CO 2 capture from power plant flue gas and for other relevant applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fe-doped graphene nanosheet as an adsorption platform of harmful gas molecules (CO, CO2, SO2 and H2S), and the co-adsorption in O2 environments

NASA Astrophysics Data System (ADS)

Cortés-Arriagada, Diego; Villegas-Escobar, Nery; Ortega, Daniela E.

2018-01-01

The adsorption of pollutant gases (CO, CO2, SO2 and H2S) onto Fe-doped graphene nanosheets (FeG) is studied on the basis of density functional theory calculations at the PBE/Def2-SVP level of theory. The most stable adsorption configurations, binding characteristics, electronic properties and stability at room temperature of the FeG-Gas interactions is fully analyzed. The gas molecules are chemisorbed onto FeG with adsorption energies in the range of 0.54-1.8 eV, with an enhanced adsorption strength compared to intrinsic graphene. The stability of the FeG-Gas interactions is dominated by Lewis-acid-base interactions, and its strength is sorted as SO2 > CO > H2S > CO2. The adsorption stability is also retained at room temperature (300 K). Due to the strong interaction of SO2, CO, and H2S, FeG could catalyze or activate these gas molecules, suggesting the possibility of FeG as a catalyst substrate. The electron acceptor/donor character of CO, CO2, SO2 and H2S molecules when adsorbed onto FeG causes charge transfer processes that are responsible for the change in conductance of FeG; thus, the response of the HOMO-LUMO gap of FeG under gas adsorption could be useful for sensing applications. Furthermore, the analysis of the co-adsorption in O2 environments shows that the CO2 interaction turns unstable onto FeG, while the sensing response towards H2S is suppressed. Finally, these results give new insights into the emerging applications of Fe-doped graphene in gas capture/filtration devices, solid-state gas sensors or as a catalyst substrate.

Adsorption of drugs onto a pH responsive poly(N,N-dimethyl aminoethyl methacrylate) grafted anion-exchange membrane in vitro.

PubMed

Karppi, Jouni; Akerman, Satu; Akerman, Kari; Sundell, Annika; Nyyssönen, Kristiina; Penttilä, Ilkka

2007-06-29

The influence of charge and lipophilicity of acidic and basic model drugs on their adsorption onto poly(N,N-dimethyl aminoethyl methacrylic acid) grafted poly(vinylidene fluoride) (DMAEMA-PVDF) membranes was evaluated. The effect of serum proteins (albumin, IgG) and hormones (cortisol, free thyroxine (T(4)F) and thyrotropin (TSH)) on drug adsorption was also studied. Acidic model drugs (antiepileptics and benzodiazepies) adsorbed to a greater extent onto the membrane from Hepes buffer at ionic strength of 25mM and pH 7.0 than basic drugs (antidepressants) did. Adsorption of acidic model drugs was based on electrostatic interactions between positively charged tertiary amino groups of DMAEMA side-chain and acidic negatively charged drug. Albumin diminished the adsorption of drugs from serum onto the membrane. Lipophilicity was related to the adsorption of acidic model drugs from serum onto the membrane. The degree of grafting had the greatest effect on adsorption of lipophilic drugs, but no influence was observed on adsorption of hydrophilic drugs. The present results showed that acidic drugs and albumin adsorbed onto the membrane, which suggests that the PVDF-DMAEMA membrane may be suitable for separating acidic drugs from protein-free substances for subsequent monitoring and evaluation.

Adsorption of phenol and hydrazine upon pristine and X-decorated (X = Sc, Ti, Cr and Mn) MoS2 monolayer

NASA Astrophysics Data System (ADS)

Wang, Meiyan; Wang, Wei; Ji, Min; Cheng, Xinlu

2018-05-01

Using density functional theory (DFT), we present a theoretical investigation of phenol (C6H5OH) and hydrazine (N2H4) on pristine and decorated MoS2 monolayer. In our work, we first focus on the interactions between several metal atoms and MoS2 monolayer and then choose the MoS2 nanosheet decorated by Sc, Ti, Cr and Mn to be the substrate. Furthermore, the properties of phenol and N2H4 on pure and X-doped (X = Sc, Ti, Cr and Mn) MoS2 base materials are discussed in terms of adsorption energy, adsorption distance, charge transfer, charge density difference, HOMO and LUMO molecular orbitals and density of states (DOS). The results predict that the adsorption of phenol and hydrazine upon X-decorated MoS2 monolayers are more favorable than the adsorption on isolated ones, which demonstrating that Sc, Ti, Cr and Mn doping help to improve the adsorption abilities. Calculations also show shorter adsorption distance and more charge transfer for Sc-, Ti-, Cr- and Mn-doped systems than the pristine one. The results confirm that X-doped MoS2 monolayer can be used as effective and potential adsorbents for toxic phenol and hydrazine.

Adsorption of 4-n-Nonylphenol and Bisphenol-A on Magnetic Reduced Graphene Oxides: A Combined Experimental and Theoretical Studies.

PubMed

Jin, Zhongxiu; Wang, Xiangxue; Sun, Yubing; Ai, Yuejie; Wang, Xiangke

2015-08-04

Adsorption of 4-n-nonylphenol (4-n-NP) and bisphenol A (BPA) on magnetic reduced graphene oxides (rGOs) as a function of contact time, pH, ionic strength and humic acid were investigated by batch techniques. Adsorption of 4-n-NP and BPA were independent of pH at 3.0- 8.0, whereas the slightly decreased adsorption was observed at pH 8.0-11.0. Adsorption kinetics and isotherms of 4-n-NP and BPA on magnetic rGOs can be satisfactorily fitted by pseudo-second-order kinetic and Freundlich model, respectively. The maximum adsorption capacities of magnetic rGOs at pH 6.5 and 293 K were 63.96 and 48.74 mg/g for 4-n-NP and BPA, respectively, which were significantly higher than that of activated carbon. Based on theoretical calculations, the higher adsorption energy of rGOs + 4-n-NP was mainly due to π-π stacking and flexible long alkyl chain of 4-n-NP, whereas adsorption of BPA on rGOs was energetically favored by a lying-down configuration due to π-π stacking and dispersion forces, which was further demonstrated by FTIR analysis. These findings indicate that magnetic rGOs is a promising adsorbent for the efficient elimination of 4-n-NP/BPA from aqueous solutions due to its excellent adsorption performance and simple magnetic separation, which are of great significance for the remediation of endocrine-disrupting chemicals in environmental cleanup.

Energetics of CO2 and H2O adsorption on zinc oxide.

PubMed

Gouvêa, Douglas; Ushakov, Sergey V; Navrotsky, Alexandra

2014-08-05

Adsorption of H2O and CO2 on zinc oxide surfaces was studied by gas adsorption calorimetry on nanocrystalline samples prepared by laser evaporation in oxygen to minimize surface impurities and degassed at 450 °C. Differential enthalpies of H2O and CO2 chemisorption are in the range -150 ±10 kJ/mol and -110 ±10 kJ/mol up to a coverage of 2 molecules per nm(2). Integral enthalpy of chemisorption for H2O is -96.8 ±2.5 kJ/mol at 5.6 H2O/nm(2) when enthalpy of water condensation is reached, and for CO2 is -96.6 ±2.5 kJ/mol at 2.6 CO2/nm(2) when adsorption ceases. These values are consistent with those reported for ZnO prepared by other methods after similar degas conditions. The similar energetics suggests possible competition of CO2 and H2O for binding to ZnO surfaces. Exposure of bulk and nanocrystalline ZnO with preadsorbed CO2 to water vapor results in partial displacement of CO2 by H2O. In contrast, temperature-programmed desorption (TPD) indicates that a small fraction of CO2 is retained on ZnO surfaces up to 800 °C, under conditions where all H2O is desorbed, with adsorption energies near -200 kJ/mol. Although molecular mechanisms of adsorption were not studied, the thermodynamic data are consistent with dissociative adsorption of H2O at low coverage and with several different modes of CO2 binding.

Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp).

PubMed

Sun, Xiuquan; Wick, Collin D; Thallapally, Praveen K; McGrail, B Peter; Dang, Liem X

2011-03-31

Enhancing the efficiency of the Rankine cycle, which is utilized for multiple renewable energy sources, requires the use of a working fluid with a high latent heat of vaporization. To further enhance its latent heat, a working fluid can be placed in a metal organic heat carrier (MOHC) with a high heat of adsorption. One such material is Ni\\DOBDC, in which linear alkanes have a higher heat of adsorption than cyclic alkanes. We carried out molecular dynamics simulations to investigate the structural, diffusive, and adsorption properties of n-hexane and cyclohexane in Ni\\DOBDC. The strong binding for both n-hexane and cyclohexane with Ni\\DOBDC is attributed to the increase of the heat of adsorption observed in experiments. Our structural results indicate the organic linkers in Ni\\DOBDC are the primary binding sites for both n-hexane and cyclohexane molecules. However, at all temperatures and loadings examined in present work, n-hexane clearly showed stronger binding with Ni\\DOBDC than cyclohexane. This was found to be the result of the ability of n-hexane to reconfigure its structure to a greater degree than cyclohexane to gain more contacts between adsorbates and adsorbents. The geometry and flexibility of guest molecules were also related to their diffusivity in Ni\\DOBDC, with higher diffusion for flexible molecules. Because of the large pore sizes in Ni\\DOBDC, energetic effects were the dominant force for alkane adsorption and selectivity.

DFT study on the adsorption behavior and electronic response of AlN nanotube and nanocage toward toxic halothane gas

NASA Astrophysics Data System (ADS)

Mohammadi, R.; Hosseinian, A.; Khosroshahi, E. Saedi; Edjlali, L.; Vessally, E.

2018-04-01

We have investigated the adsorption of a halothane molecule on the AlN nanotube, and nanocage using density functional theory calculations. We predicted that the halothane molecule tends to be physically adsorbed on the surface of AlN nanotube with adsorption energy (Ead) of -4.2 kcal/mol. The electronic properties of AlN nanotube are not affected by the halothane, and it is not a sensor. But the AlN nanocage is more reactive than the AlN nanotube because of its higher curvature. The halothane tends to be adsorbed on a hexagonal ring, an Alsbnd N bond, and a tetragonal ring of the AlN nanocage. The adsorption ability order is as follows: tetragonal ring (Ead = -14.7 kcal/mol) > Alsbnd N bond (Ead = -12.3 kcal/mol) > hexagonal ring (Ead = -10.1 kcal/mol). When a halothane molecule is adsorbed on the AlN nanocage, its electrical conductivity is increased, demonstrating that it can yield an electronic signal at the presence of this molecule, and can be employed in chemical sensors. The AlN nanocage benefits from a short recovery time of about 58 ms at room temperature.

Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

NASA Astrophysics Data System (ADS)

Tzvetkov, George; Kaneva, Nina; Spassov, Tony

2017-04-01

A new core-shell nano-ZnO/pollen grain (n-ZnO/PG) biocomposite has been successfully synthesized via simple and low-temperature two-step liquid precipitation method. The synthetic strategy consists of grafting the surface of pine pollen grains (PG) with Zn2+-organic complexes followed by a treatment in Zn(CH3COO)2/NaOH solution, thus producing a closed n-ZnO shell around the organic core, with a thickness of ∼450 nm. Scanning electron microscopy, X-ray diffraction, FTIR, XPS and UV-vis spectroscopy measurements along with N2 adsorption/desorption were used to characterize the resulting n-ZnO/PG biocomposite. The as-prepared core-shell microparticles are meso-/macro-porous with BET surface area of 25 m2 g-1 and total pore volume of 0.26 cm3 g-1. The adsorption properties of n-ZnO/PG were evaluated through adsorption of Malachite Green (MG) from aqueous medium at room temperature (25 °C). For the sake of comparison, the physico-chemical and adsorptive properties of the raw PG and pure n-ZnO were also examined. Results indicate that n-ZnO/PG is the most favorable for the adsorption of MG under the conditions used in this study. The adsorption kinetic data for PG, n-ZnO and n-ZnO/PG follow the pseudo-second order equation and the maximum adsorption capacity follows an order of n-ZnO/PG > n-ZnO > PG. For n-ZnO/PG an adsorption uptake up to 145.9 mg g-1 is observed. The as-prepared core-shell biocomposite material is a promising cost-effective and environmentally friendly adsorbent due to its textural properties, surface chemistry, adsorption capacity and recyclability.

Adsorption of radionuclides on the monolayer MoS2

NASA Astrophysics Data System (ADS)

Zhao, Qiang; Zhang, Zheng; Ouyang, Xiaoping

2018-04-01

How to remove radionuclides from radioactive wastewater has long been a difficult problem, especially in nuclear accidents. In this paper, the adsorption of radionuclides Cs, Sr, and Ba on the monolayer MoS2 was investigated by using the first principles calculation method. Through the calculation of adsorption energy and Hirshfeld charge of the radionuclides on the monolayer MoS2 at six adsorption sites, the results show that all of the radionuclides chemisorbed on the monolayer MoS2, and the adsorption strength of these three kinds of radionuclides on the monolayer MoS2 is Ba > Sr > Cs. This work might shed some light on the treatment of the radioactive wastewater.

Optical regulation of protein adsorption and cell adhesion by photoresponsive GaN nanowires.

PubMed

Li, Jingying; Han, Qiusen; Zhang, Ying; Zhang, Wei; Dong, Mingdong; Besenbacher, Flemming; Yang, Rong; Wang, Chen

2013-10-09

Interfacing nanowires with living cells is attracting more and more interest due to the potential applications, such as cell culture engineering and drug delivery. We report on the feasibility of using photoresponsive semiconductor gallium nitride (GaN) nanowires (NWs) for regulating the behaviors of biomolecules and cells at the nano/biointerface. The GaN NWs have been fabricated by a facile chemical vapor deposition method. The superhydrophobicity to superhydrophilicity transition of the NWs is achieved by UV illumination. Bovine serum albumin adsorption could be modulated by photoresponsive GaN NWs. Tunable cell detachment and adhesion are also observed. The mechanism of the NW surface responsible for modulating both of protein adsorption and cell adhesion is discussed. These observations of the modulation effects on protein adsorption and cell adhesion by GaN NWs could provide a novel approach toward the regulation of the behaviors of biomolecules and cells at the nano/biointerface, which may be of considerable importance in the development of high-performance semiconductor nanowire-based biomedical devices for cell culture engineering, bioseparation, and diagnostics.

Adsorption of CO2 from flue gas streams by a highly efficient and stable aminosilica adsorbent.

PubMed

Liu, Shou-Heng; Lin, Yuan-Chung; Chien, Yi-Chi; Hyu, Han-Ren

2011-02-01

Three ordered mesoporous silicas (OMSs) with different pore sizes and pore architectures were prepared and modified with amine functional groups by a postgrafting method. The carbon dioxide (CO2) adsorption on these amine-modified OMSs was measured by using microbalances at 348 K, and their adsorption capacities were found to be 0.2-1.4 mmol g(-1) under ambient pressure using dry 15% CO2. It was found experimentally that the CO2 adsorption capacity and adsorption rate were attributed to the density of amine groups and pore volume, respectively. A simple method is described for the production of densely anchored amine groups on a solid adsorbent invoking direct incorporation of tetraethylenepentamine onto the as-synthesized OMSs. Unlike conventional amine-modified OMSs, which typically show CO2 adsorption capacity less than 2 mmol g(-1), such organic template occluded amine-OMS composites possessed remarkably high CO2 uptake of approximately 4.6 mmol g(-1) at 348 K and 1 atm for a dry 15% CO2/nitrogen feed mixture. The enhancement of 8% in CO2 adsorption capacity was also observed in the presence of 10.6% water vapor. Durability tests done by cyclic adsorption-desorption revealed that these adsorbents also possess excellent stability.

A Biomedical Application of Activated Carbon Adsorption: An Experiment Using Acetaminophen and N-Acetylcysteine.

ERIC Educational Resources Information Center

Rybolt, Thomas R.; And Others

1988-01-01

Illustrates an interesting biomedical application of adsorption from solution and demonstrates some of the factors that influence the in vivo adsorption of drug molecules onto activated charcoal. Uses acetaminophen and N-acetylcysteine for the determination. Suggests several related experiments. (MVL)

Adsorption calorimetry during metal vapor deposition on single crystal surfaces: Increased flux, reduced optical radiation, and real-time flux and reflectivity measurements

NASA Astrophysics Data System (ADS)

Sellers, Jason R. V.; James, Trevor E.; Hemmingson, Stephanie L.; Farmer, Jason A.; Campbell, Charles T.

2013-12-01

Thin films of metals and other materials are often grown by physical vapor deposition. To understand such processes, it is desirable to measure the adsorption energy of the deposited species as the film grows, especially when grown on single crystal substrates where the structure of the adsorbed species, evolving interface, and thin film are more homogeneous and well-defined in structure. Our group previously described in this journal an adsorption calorimeter capable of such measurements on single-crystal surfaces under the clean conditions of ultrahigh vacuum [J. T. Stuckless, N. A. Frei, and C. T. Campbell, Rev. Sci. Instrum. 69, 2427 (1998)]. Here we describe several improvements to that original design that allow for heat measurements with ˜18-fold smaller standard deviation, greater absolute accuracy in energy calibration, and, most importantly, measurements of the adsorption of lower vapor-pressure materials which would have previously been impossible. These improvements are accomplished by: (1) using an electron beam evaporator instead of a Knudsen cell to generate the metal vapor at the source of the pulsed atomic beam, (2) changing the atomic beam design to decrease the relative amount of optical radiation that accompanies evaporation, (3) adding an off-axis quartz crystal microbalance for real-time measurement of the flux of the atomic beam during calorimetry experiments, and (4) adding capabilities for in situ relative diffuse optical reflectivity determinations (necessary for heat signal calibration). These improvements are not limited to adsorption calorimetry during metal deposition, but also could be applied to better study film growth of other elements and even molecular adsorbates.

Adsorption calorimetry during metal vapor deposition on single crystal surfaces: increased flux, reduced optical radiation, and real-time flux and reflectivity measurements.

PubMed

Sellers, Jason R V; James, Trevor E; Hemmingson, Stephanie L; Farmer, Jason A; Campbell, Charles T

2013-12-01

Thin films of metals and other materials are often grown by physical vapor deposition. To understand such processes, it is desirable to measure the adsorption energy of the deposited species as the film grows, especially when grown on single crystal substrates where the structure of the adsorbed species, evolving interface, and thin film are more homogeneous and well-defined in structure. Our group previously described in this journal an adsorption calorimeter capable of such measurements on single-crystal surfaces under the clean conditions of ultrahigh vacuum [J. T. Stuckless, N. A. Frei, and C. T. Campbell, Rev. Sci. Instrum. 69, 2427 (1998)]. Here we describe several improvements to that original design that allow for heat measurements with ~18-fold smaller standard deviation, greater absolute accuracy in energy calibration, and, most importantly, measurements of the adsorption of lower vapor-pressure materials which would have previously been impossible. These improvements are accomplished by: (1) using an electron beam evaporator instead of a Knudsen cell to generate the metal vapor at the source of the pulsed atomic beam, (2) changing the atomic beam design to decrease the relative amount of optical radiation that accompanies evaporation, (3) adding an off-axis quartz crystal microbalance for real-time measurement of the flux of the atomic beam during calorimetry experiments, and (4) adding capabilities for in situ relative diffuse optical reflectivity determinations (necessary for heat signal calibration). These improvements are not limited to adsorption calorimetry during metal deposition, but also could be applied to better study film growth of other elements and even molecular adsorbates.

SO2 Adsorption on CeO2(100) and CeO2(111)

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

Mullins, David R.

2016-09-13

The adsorption and reaction of sulfur dioxide, SO2, was studied on oxidized and reduced CeOX(100) and compared to previous results on CeOX(111). SO2 adsorbs on oxidized CeO2(100) as sulfite, SO32-, at 200 K and sulfite is the only adsorbate observed on the surface at any temperature. The sulfite desorbs monotonically from 200 to 700 K. The adsorption and desorption of SO2 does not result in any change in the Ce4+ oxidation state. SO2 also adsorbs as sulfite on reduced CeO1.7(100) at 200 K. There is also a small amount of elemental sulfur, S0, formed. As the sample is heated themore » sulfite decomposes into sulfide, S2-. Roughly 25 % of the adsorbed S either desorbs or diffuses into the bulk of the reduced ceria. The decomposition, and resulting formation of S2- and O2-, re-oxidize some of the Ce3+ to Ce4+. Unlike what has been observed following the adsorption and reaction of many other molecules, the adsorption and reaction of SO2 is virtually identical on CeOX(100) and CeOX(111).« less

Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium—Thermodynamic of adsorption process

NASA Astrophysics Data System (ADS)

Guerra, Denis Lima; Pinto, Alane Azevedo; Airoldi, Claudio; Viana, Rúbia Ribeiro

2008-12-01

Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298±1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic (Δ intH=-4.15-5.98 kJ mol -1) accompanied by increase in entropy (Δ intS=41.32-62.20 J k -1 mol -1) and Gibbs energy (Δ intG=-22.44-24.56 kJ mol -1). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid-liquid interface in the spontaneous process.

Syntheses, structures and selective dye adsorption of five formic-based coordination polymers prepared by in-situ hydrolysis of N, N‧-dimethylformamide

NASA Astrophysics Data System (ADS)

Zhu, Zheng; Meng, Xiang-min; Zhang, Dong-mei; Zhang, Xia; Wang, Mei; Jin, Fan; Fan, Yu-hua

2017-04-01

Five functional coordination polymers (formic-based CPs) namely: {[Cu2(CHOO)3(bibp)2]·CHOO}n (1), {[Co2(CHOO)3(bibp)2]·NO3·H2O}n (2), {[Ni2(CHOO)3(bibp)2]·NO3·H2O}n (3) [Co(CHOO)2(bbibp)]n (4) and [Zn(CHOO)2(bbibp)]n (5) (bibp=4,4‧-bis(imidazolyl)biphenyl, bbibp=4,4‧-bis(benzoimidazo-1-yl)biphenyl) have been successfully hydrothermally synthesized using the in-situ hydrolysis of N, N‧-dimethylformamide (DMF) as the source of formate. All of these five polymers were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complexes 1-3 have the similar three-dimensional 3D kag topological framework built from the bibp ligand as the support member between the neighboring formic planes. Both complexes 4 and 5 have the similar one-dimensional 1D linear chain which is further assembled into 3D supermolecular structure by C-H…O hydrogen bonds. The dyes adsorption experiments have also been investigated systematically. The results show that complexes 2 and 3 exhibit high selective adsorption ability towards anionic dyes in their aqueous solution. Moreover, complex 2 displays good reversibility in the process of the dyes adsorption-release. Meanwhile, the unusual blocking phenomenon was firstly observed when complex 2 was in MO/OIV aqueous solutions with different concentration.

Understanding Electrocatalytic Activity Enhancement of Bimetallic Particles to Ethanol Electro-oxidation: (1) Water Adsorption and Decomposition on PtnM (n=2,3 and 9; M=Pt, Ru, Sn)

PubMed Central

Wang, Yixuan; Mi, Yunjie; Redmon, Natalie; Holiday, Jessica

2009-01-01

The fundamental assumption of the bi-functional mechanism for PtSn alloy to catalyze ethanol electro-oxidation reaction (EER) is that Sn facilitates water dissociation and EER occurs over Pt site of the PtSn alloy. To clarify this assumption and achieve a good understanding about the EER, H2O adsorption and dissociation over bimetallic clusters PtM (M=Pt, Sn, Ru, Rh, Pd, Cu and Re) are systematically investigated in the present work. To discuss a variety of effects, PtnM (n=2, and 3; M=Pt, Sn and Ru), one-layer Pt6M (M=Pt, Sn and Ru), and two-layer (Pt6M)Pt3 (M=Pt, Sn, Ru, Rh, Pd, Cu and Re) clusters are used to model the PtM bimetallic catalysts. Water exhibits atop adsorption on Pt and Ru sites of the optimized clusters PtnM (n=2, and 3; M=Pt and Ru), yet bridge adsorption on Sn sites of Pt2Sn as well as distorted tetrahedral Pt3Sn. However, in the cases of one-layer Pt6M and two-layer Pt9M cluster models water preferentially binds to all of investigated central atom M of surface layer in atop configuration with the dipole moment of water almost parallel to the cluster surface. Water adsorption on the Sn site of PtnSn (n=2 and 3) is weaker than those on the Pt site of Ptn (n=3 and 4) and the Ru site of PtnRu (n=2 and 3), while water adsorptions on the central Sn atom of Pt6Sn and Pt9Sn are enhanced so significantly that they are even stronger than those on the central Pt and Ru atoms of PtnM (n=6 and 9; M=Pt and Ru). For all of the three cluster models, energy barrier (Ea) for the dissociation of adsorbed water over Sn is lower than over Ru and Pt atoms (e.g., Ea: 0.78 vs 0.96 and 1.07 eV for Pt9M), which also remains as external electric fields were added. It is interesting to note that the dissociation energy on Sn site is also the lowest (Ediss: 0.44 vs 0.61 and 0.67eV). The results show that from both kinetic and thermodynamic viewpoints Sn is more active to water decomposition than pure Pt and the PtRu alloy, which well supports the assumption of the bi

Measurement of the adsorption energy difference between ortho- and para-D2 on an amorphous ice surface.

PubMed

Amiaud, L; Momeni, A; Dulieu, F; Fillion, J H; Matar, E; Lemaire, J-L

2008-02-08

Molecular hydrogen interaction on water ice surfaces is a major process taking place in interstellar dense clouds. By coupling laser detection and classical thermal desorption spectroscopy, it is possible to study the effect of rotation of D(2) on adsorption on amorphous solid water ice surfaces. The desorption profiles of ortho- and para-D(2) are different. This difference is due to a shift in the adsorption energy distribution of the two lowest rotational states. Molecules in J''=1 rotational state are on average more strongly bound to the ice surface than those in J''=0 rotational state. This energy difference is estimated to be 1.4+/-0.3 meV. This value is in agreement with previous calculation and interpretation. The nonspherical wave function J'' =1 has an interaction with the asymmetric part of the adsorption potential and contributes positively in the binding energy.

Chemical looping of metal nitride catalysts: low-pressure ammonia synthesis for energy storage† †Electronic supplementary information (ESI) available: Experimental and computational details, free energy plots for the NH3 evolution and N2 reduction with Co3N/Co, Fe4N/Fe, Mn5N2/Mn4N, Mo2N/Mo, CrN/Cr2N, TaN/Ta2N, NbN/Nb2N, Li3N/LiH, Ba3N2/BaH2, Sr3N2/SrH2, and Ca3N2/CaH2, surface oxidation energetics, ΔGvac[NH*x, yH*] based on gas phase H2 as hydrogen source, NH3 evolution with Fe-doped Mn4N, NH3 evolution with Mn6N2.58, Ca3N2 and Sr2N after correcting for partial nitride hydrolysis, NH3 yield from Ca3N2vs. time and H2 gas flow rate. See DOI: 10.1039/c5sc00789e

PubMed Central

Avram, A. M.; Peterson, B. A.; Pfromm, P. H.; Peterson, A. A.

2015-01-01

The activity of many heterogeneous catalysts is limited by strong correlations between activation energies and adsorption energies of reaction intermediates. Although the reaction is thermodynamically favourable at ambient temperature and pressure, the catalytic synthesis of ammonia (NH3), a fertilizer and chemical fuel, from N2 and H2 requires some of the most extreme conditions of the chemical industry. We demonstrate how ammonia can be produced at ambient pressure from air, water, and concentrated sunlight as renewable source of process heat via nitrogen reduction with a looped metal nitride, followed by separate hydrogenation of the lattice nitrogen into ammonia. Separating ammonia synthesis into two reaction steps introduces an additional degree of freedom when designing catalysts with desirable activation and adsorption energies. We discuss the hydrogenation of alkali and alkaline earth metal nitrides and the reduction of transition metal nitrides to outline a promoting role of lattice hydrogen in ammonia evolution. This is rationalized via electronic structure calculations with the activity of nitrogen vacancies controlling the redox-intercalation of hydrogen and the formation and hydrogenation of adsorbed nitrogen species. The predicted trends are confirmed experimentally with evolution of 56.3, 80.7, and 128 μmol NH3 per mol metal per min at 1 bar and above 550 °C via reduction of Mn6N2.58 to Mn4N and hydrogenation of Ca3N2 and Sr2N to Ca2NH and SrH2, respectively. PMID:29218166

Particle-scale CO2 adsorption kinetics modeling considering three reaction mechanisms

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

Suh, Dong-Myung; Sun, Xin

2013-09-01

In the presence of water (H2O), dry and wet adsorptions of carbon dioxide (CO2) and physical adsorption of H2O happen concurrently in a sorbent particle. The three reactions depend on each other and have a complicated, but important, effect on CO2 capturing via a solid sorbent. In this study, transport phenomena in the sorbent were modeled, including the tree reactions, and a numerical solving procedure for the model also was explained. The reaction variable distribution in the sorbent and their average values were calculated, and simulation results were compared with experimental data to validate the proposed model. Some differences, causedmore » by thermodynamic parameters, were observed between them. However, the developed model reasonably simulated the adsorption behaviors of a sorbent. The weight gained by each adsorbed species, CO2 and H2O, is difficult to determine experimentally. It is known that more CO2 can be captured in the presence of water. Still, it is not yet known quantitatively how much more CO2 the sorbent can capture, nor is it known how much dry and wet adsorptions separately account for CO2 capture. This study addresses those questions by modeling CO2 adsorption in a particle and simulating the adsorption process using the model. As adsorption temperature changed into several values, the adsorbed amount of each species was calculated. The captured CO2 in the sorbent particle was compared quantitatively between dry and wet conditions. As the adsorption temperature decreased, wet adsorption increased. However, dry adsorption was reduced.« less

Selective adsorption of bovine hemoglobin on functional TiO2 nano-adsorbents: surface physic-chemical properties determined adsorption activity

NASA Astrophysics Data System (ADS)

Guo, Shiguang; Zhang, Jianghua; Shao, Mingxue; Zhang, Xia; Liu, Yufeng; Xu, Junli; Meng, Hao; Han, Yide

2015-04-01

Surface functionalized nanoparticles are efficient adsorbents which have shown good potential for protein separation. In this work, we chose two different types of organic molecules, oleic acid (OA) and 3-glycidoxypropyltrimethoxy silane (GPTMS), to functionalize the surface of TiO2 nanoparticles, and we studied the effects of this modification on their surface physicochemical properties in correlation with their selective adsorption of proteins. The results showed that the surface zeta potential and the surface water wettability of the modified TiO2 were significantly changed in comparison with the original TiO2 nanoparticles. The adsorption activities of bovine hemoglobin (BHb) and bovine serum albumin (BSA) on these functionalized TiO2 samples were investigated under different conditions, including pH values, contact time, ion strength, and initial protein concentration. In comparison with the non-specific adsorption of original TiO2, however, both the OA-TiO2 and GPTMS-TiO2 exhibited increased BHb adsorption and decreased BSA adsorption at the same time. Using a binary protein mixture as the adsorption object, a higher separation factor (SF) was obtained for OA-TiO2 under optimum conditions. The different adsorption activities of BHb and BSA on the modified TiO2 were correlated with different interactions at the protein/solid interface, and the chemical force as well as the electrostatic force played an important role in the selective adsorption process.

Dye adsorption mechanisms in TiO2 films, and their effects on the photodynamic and photovoltaic properties in dye-sensitized solar cells.

PubMed

Hwang, Kyung-Jun; Shim, Wang-Geun; Kim, Youngjin; Kim, Gunwoo; Choi, Chulmin; Kang, Sang Ook; Cho, Dae Won

2015-09-14

The adsorption mechanism for the N719 dye on a TiO2 electrode was examined by the kinetic and diffusion models (pseudo-first order, pseudo-second order, and intra-particle diffusion models). Among these methods, the observed adsorption kinetics are well-described using the pseudo-second order model. Moreover, the film diffusion process was the main controlling step of adsorption, which was analysed using a diffusion-based model. The photodynamic properties in dye-sensitized solar cells (DSSCs) were investigated using time-resolved transient absorption techniques. The photodynamics of the oxidized N719 species were shown to be dependent on the adsorption time, and also the adsorbed concentration of N719. The photovoltaic parameters (Jsc, Voc, FF and η) of this DSSC were determined in terms of the dye adsorption amounts. The solar cell performance correlates significantly with charge recombination and dye regeneration dynamics, which are also affected by the dye adsorption amounts. Therefore, the photovoltaic performance of this DSSC can be interpreted in terms of the adsorption kinetics and the photodynamics of oxidized N719.

Synthesis of Hierarchically Structured Hybrid Materials by Controlled Self-Assembly of Metal-Organic Framework with Mesoporous Silica for CO2 Adsorption.

PubMed

Chen, Chong; Li, Bingxue; Zhou, Lijin; Xia, Zefeng; Feng, Nengjie; Ding, Jing; Wang, Lei; Wan, Hui; Guan, Guofeng

2017-07-12

The HKUST-1@SBA-15 composites with hierarchical pore structure were constructed by in situ self-assembly of metal-organic framework (MOF) with mesoporous silica. The structure directing role of SBA-15 had an obvious impact on the growth of MOF crystals, which in turn affected the morphologies and structural properties of the composites. The pristine HKUST-1 and the composites with different content of SBA-15 were characterized by XRD, N 2 adsorption-desorption, SEM, TEM, FT-IR, TG, XPS, and CO 2 -TPD techniques. It was found that the composites were assembled by oriented growth of MOF nanocrystals on the surfaces of SBA-15 matrix. The interactions between surface silanol groups and metal centers induced structural changes and resulted in the increases in surface areas as well as micropore volumes of hybrid materials. Besides, the additional constraints from SBA-15 also restrained the expansion of HKUST-1, contributing to their smaller crystal sizes in the composites. The adsorption isotherms of CO 2 on the materials were measured and applied to calculate the isosteric heats of adsorption. The HS-1 composite exhibited an increase of 15.9% in CO 2 uptake capacity compared with that of HKUST-1. Moreover, its higher isosteric heats of CO 2 adsorption indicated the stronger interactions between the surfaces and CO 2 molecules. The adsorption rate of the composite was also improved due to the introduction of mesopores. Ten cycles of CO 2 adsorption-desorption experiments implied that the HS-1 had excellent reversibility of CO 2 adsorption. This study was intended to provide the possibility of assembling new composites with tailored properties based on MOF and mesoporous silica to satisfy the requirements of various applications.

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

PubMed

Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

2016-08-25

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5

PubMed Central

Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

2016-01-01

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example. PMID:27585356

Revisiting the adsorption of copper-phthalocyanine on Au(111) including van der Waals corrections.

PubMed

Lüder, Johann; Eriksson, Olle; Sanyal, Biplab; Brena, Barbara

2014-03-28

We have studied the adsorption of copper-phthalocyanine on Au(111) by means of van der Waals corrected density functional theory using the Tkatchenko-Scheffler method. We have compared the element and site resolved adsorption distances to recent experimental normal-incident X-ray standing wave measurements. The measured adsorption distances could be reproduced within a deviation of 1% for the Cu atom, 1% for the C atoms, and 2% for the N atoms. The molecule was found to have a magnetic moment of 1 μB distributed over the Cu and the N atoms of the pyrrole ring. Simulated scanning tunnel microscopy images based on the total and on the spin-resolved differential charge densities are provided for bias voltages of -1.45 and 1.45 eV.

Revisiting the adsorption of copper-phthalocyanine on Au(111) including van der Waals corrections

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

Lüder, Johann; Eriksson, Olle; Sanyal, Biplab

2014-03-28

We have studied the adsorption of copper-phthalocyanine on Au(111) by means of van der Waals corrected density functional theory using the Tkatchenko-Scheffler method. We have compared the element and site resolved adsorption distances to recent experimental normal-incident X-ray standing wave measurements. The measured adsorption distances could be reproduced within a deviation of 1% for the Cu atom, 1% for the C atoms, and 2% for the N atoms. The molecule was found to have a magnetic moment of 1 μ{sub B} distributed over the Cu and the N atoms of the pyrrole ring. Simulated scanning tunnel microscopy images based onmore » the total and on the spin-resolved differential charge densities are provided for bias voltages of −1.45 and 1.45 eV.« less

Analysis of (n,2n) cross-section measurements for nuclei up to mass 238

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

Davey, W.G.; Goin, R.W.; Ross, J.R.

All suitable measurements of the energy dependence of (n,2n) cross sections of all isotopes up to mass 238 have been analyzed. The objectives were to display the quality of the measured data for each isotope and to examine the systematic dependence of the (n,2n) cross section upon N, Z, and A. Graphs and tables are presented of the ratio of the asymptotic (n,2n) and nonelastic cross section to the neutron-asymmetry parameter (N--Z)/A. Similar data are presented for the derived nuclear temperature, T, and level-density parameter, $alpha$, as a function of N, Z, and A. This analysis of the results ofmore » over 145 experiments on 61 isotopes is essentially a complete review of the current status of (n,2n) cross-section measurements. (auth)« less

NH3 adsorption on anatase-TiO2(101)

NASA Astrophysics Data System (ADS)

Koust, Stig; Adamsen, Kræn C.; Kolsbjerg, Esben Leonhard; Li, Zheshen; Hammer, Bjørk; Wendt, Stefan; Lauritsen, Jeppe V.

2018-03-01

The adsorption of ammonia on anatase TiO2 is of fundamental importance for several catalytic applications of TiO2 and for probing acid-base interactions. Utilizing high-resolution scanning tunneling microscopy (STM), synchrotron X-ray photoelectron spectroscopy, temperature-programmed desorption (TPD), and density functional theory (DFT), we identify the adsorption mode and quantify the adsorption strength on the anatase TiO2(101) surface. It was found that ammonia adsorbs non-dissociatively as NH3 on regular five-fold coordinated titanium surface sites (5f-Ti) with an estimated exothermic adsorption energy of 1.2 eV for an isolated ammonia molecule. For higher adsorbate coverages, the adsorption energy progressively shifts to smaller values, due to repulsive intermolecular interactions. The repulsive adsorbate-adsorbate interactions are quantified using DFT and autocorrelation analysis of STM images, which both showed a repulsive energy of ˜50 meV for nearest neighbor sites and a lowering in binding energy for an ammonia molecule in a full monolayer of 0.28 eV, which is in agreement with TPD spectra.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

NASA Astrophysics Data System (ADS)

Al-Alwani, Mahmoud A. M.; Mohamad, Abu Bakar; Kadhum, Abd. Amir H.; Ludin, Norasikin A.

2015-03-01

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

Theoretical study on the gas adsorption capacity and selectivity of CPM-200-In/Mg and CPM-200-In/Mg-X (-X = -NH2, -OH, -N, -F).

PubMed

Liu, Xiao-le; Chen, Guang-Hui; Wang, Xiu-Jun; Li, Peng; Song, Yi-Bing; Li, Rui-Yan

2017-11-15

The adsorption capacities of a heterometallic metal-organic framework (CPM-200-In/Mg) to VOCs (HCHO, C 2 H 4 , CH 4 , C 2 H 2 , C 3 H 8 , C 2 H 6 , C 2 H 3 Cl, C 2 H 2 Cl 2 , CH 2 Cl 2 and CHCl 3 ) and some inorganic gas molecules (HCN, SO 2 , NO, CO 2 , CO, H 2 S and NH 3 ), as well as its selectivity in ternary mixture systems of natural gas and post-combustion flue gas are theoretically explored at the grand canonical Monte Carlo (GCMC) and density functional theory (DFT) levels. It is shown that CPM-200-In/Mg is suitable for the adsorption of VOCs, particularly for HCHO (up to 0.39 g g -1 at 298 K and 1 bar), and the adsorption capacities of some inorganic gas molecules such as SO 2 , H 2 S and CO 2 match well with the sequence of their polarizability (SO 2 > H 2 S > CO 2 ). The large adsorption capacities of HCN and HCHO in the framework result from the strong interaction between adsorbates and metal centers, based on analyzing the radial distribution functions (RDF). Comparing C 2 H 4 and CH 4 molecules interacting with CPM-200-In/Mg by VDW interaction, we speculate that the high adsorption capacities of their chlorine derivatives in the framework could be due to the existence of halogen bonding or strong electrostatic and VDW interactions. It is found that the basic groups, including -NH 2 , -N and -OH, can effectively improve both the adsorption capacities and selectivity of CPM-200-In/Mg for harmful gases. Note that the adsorption capacity of CPM-200-In/Mg-NH 2 (site 2) (245 cm 3 g -1 ) for CO 2 exceeded that of MOF-74-Mg (228 cm 3 g -1 ) at 273 K and 1 bar and that for HCHO can reach 0.41 g g -1 , which is almost twice that of 438-MOF and nearly 45 times of that in active carbon. Moreover, for natural gas mixtures, the decarburization and desulfurization abilities of CPM-200-In/Mg-NH 2 (site 2) have exceeded those of the MOF-74 series, while for post-combustion flue gas mixtures, the desulfurization ability of CPM-200-In/Mg-NH 2 (site 2) is still

Experimental studies on equilibrium adsorption isosteres and determination of the thermodynamic quantities of polar media on alumina Al2O3

NASA Astrophysics Data System (ADS)

Yonova, Albena

2017-03-01

The present work is a revieif of theoretical and experimental study on the adsorption performance of the adsorbent Alumina (Al2O3) used in the adsorption system. An experimental investigation on the equilibrium adsorption isosteres at low pressure (< 1 atm) of working pairs Al2O3/H2O and Al2O3/C2H6O2 is carried out. The isovolume measurement method is adopted in the test setup to directly measure the saturated vapor pressures of working pairs at vapor-liquid equilibrium (dG=0 and dμi=0). Quantity adsorbed is determined from pressure, volume and temperature using gas law. The isosteric heat of adsorption is calculated from the slope of the plot of lnP versus 1/T different amounts of adsorbate onto adsorbent as follows: 0,01 vol% Al2O3/H2O; 0,03 vol% Al2O3/H2O; 0,1 vol% Al2O3/H2O; 0,01 vol% Al2O3/C2H6O2; 0,03 vol% Al2O3/C2H6O2; 0,1 vol% Al2O3/C2H6O2. This study shows that adsorption working pair Al2O3 C2H6O2 has better adsorption performances than those of the A2O3/H2O. Surface acidity! is a most important property! far both adsorption and catalysis and therefore is examined structure of active sites of alumina surface. Thermodynamic parameters such as isosteric heat of adsorption, isosteric enthalpy and entropy of adsorption are critical design variables in estimating the performance and predicting the mechanism of an adsorption process and are also one of the basic requirements for the characterization and optimization of an adsorption process

Final report of CCQM-K136 measurement of porosity properties (specific adsorption, BET specific surface area, specific pore volume and pore diameter) of nanoporous Al2O3

NASA Astrophysics Data System (ADS)

Sobina, E.; Zimathis, A.; Prinz, C.; Emmerling, F.; Unger, W.; de Santis Neves, R.; Galhardo, C. E.; De Robertis, E.; Wang, H.; Mizuno, K.; Kurokawa, A.

2016-01-01

CCQM key comparison K-136 Measurement of porosity properties (specific adsorption, BET specific surface area, specific pore volume and pore diameter) of nanoporous Al2O3 has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of specific adsorption, BET specific surface area, specific pore volume and pore diameter) of nanoporous substances (sorbents, catalytic agents, cross-linkers, zeolites, etc) used in advanced technology. In this key comparison, a commercial sorbent (aluminum oxide) was supplied as a sample. Five NMIs participated in this key comparison. All participants used a gas adsorption method, here nitrogen adsorption at 77.3 K, for analysis according to the international standards ISO 15901-2 and 9277. In this key comparison, the degrees of equivalence uncertainties for specific adsorption, BET specific surface area, specific pore volume and pore diameter was established. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The studies on gas adsorption properties of MIL-53 series MOFs materials

NASA Astrophysics Data System (ADS)

Jiao, Yuqiu; Li, Zhenyu; Ma, Yue; Zhou, Guanggang; Wang, Shuangxi; Lu, Guiwu

2017-08-01

Molecular dynamics (MD), grand canonical Monte Carlo (GCMC) and ideal adsorbed solution theory (IAST) were used to study the structures and gas adsorption properties of MIL-53(M)[M=Cr, Fe, Sc, Al] metal organic framework (MOF) materials. The results show that the volumes of those MOF materials increase significantly at high temperature. By analyzing the adsorption isotherms, we found that the temperature had a paramount effect on the gas adsorption behaviors of these MOF materials. For MIL-53(Cr), the orders of the quantities of adsorbed gases were CH4>N2>CO2>H2S, CH4>H2S>CO2>N2 and CH4>CO2>H2S>N2 at 100K, 293K and 623K, respectively. We also calculated the adsorption of several combinations of two gases by MIL-53(Cr) at 293K, the results indicate that the material had selective adsorption of CH4 over CO2, H2S and N2. Our calculations provide microscopic insights into the gas adsorption performances of these MOFs and may further guide the practice of gas separation.

Application of activated carbon modified by acetic acid in adsorption and separation of CO2 and CH4

NASA Astrophysics Data System (ADS)

Song, Xue; Wang, Li'ao; Zeng, Yunmin; Zhan, Xinyuan; Gong, Jian; Li, Tong

2018-03-01

Compared with the methods to modify the activated carbons by alkalis for gas adsorption, fewer studies of that by organic acids have been reported. The acid modified activated carbons are usually utilized to treat wastewater, whereas the application in the separation of CO2/CH4 has less been studied. In this study, acetic acid was used to modify activated carbon. N2 adsorption/desorption isotherms and FT-IR were adopted to describe the properties of the samples. According to the adsorption data of pure gas component at 298 K, the gas adsorbed amount and the selectivity on the modified samples were larger than that on the raw sample. Besides, the adsorbed amount of CO2 and the selectivity on 15H-AC in the adsorption breakthrough experiments showed better performance. The results confirm that the method to modify the activated carbons with acetic acid is feasible to improve the adsorption capacity and the separation effect of CO2/CH4.

Magnetometory Measurement of AlGaN/GaN 2DEG

NASA Astrophysics Data System (ADS)

Tsubaki, K.; Maeda, N.; Saitoh, T.; Kobayashi, N.

2004-03-01

AlGaN/GaN heterostructure devices have been attracting much attention because of their potential for high-performance microwave applications. Therefore, the electronic properties of a 2DEG in AlGaN/GaN heterostructures have recently been discussed. In this paper, we performed the magnetometory measurement of AlGaN/GaN 2DEG at low temperature. The AlGaN/GaN heterostructures were grown by low-pressure metal-organic chemical vapour phase epitaxy on (0001) SiC substrate using AlN buffers. The electron mobility and electron concentration at 4.2 K are 9,540 cm^2/Vs and 6.6 × 10^12 cm-2, respectively. When the temperature is lower than 4.5 K the hysteresis of magnetometric data is observed near zero magnetic field. At the temperature larger than 4.5 K, the hysteresis of magnetometric data disappears and the slope of magnetometric data with respect to magnetic field becomes lower as obeying Currie-Weiss law. In general the hysteresis and Currie-Weiss law behavior in magnetometric data imply the possibility of the ferromagnetism, but the conformation of the ferromagnetism of AlGaN/GaN heterostructure is still difficult and the detailed physical mechanism is still unclear.

Adenovirus type 5 intrinsic adsorption rates measured by surface plasmon resonance.

PubMed

Roper, D Keith; Nakra, Shamit

2006-01-01

Intrinsic adsorption rates of whole adenovirus type 5 (Ad5) onto a diethylaminoethyl (DEAE) anion exchange surface are measured for the first time by surface plasmon resonance (SPR). Fitting SPR sensorgrams to a two-compartment mass transport reaction model distinguishes intrinsic adsorption rates from slow diffusive Ad5 mass transport. Ad5 is a widely used viral vector for gene therapy that binds electrostatically to surfaces of cells and synthetics such as membranes, chromatographic resins, and glass. Increasing NaCl concentration from 4.8 to 14.4mM shifts binding of whole Ad5 from diffusion control to a regime where both sorption and diffusion affect binding. Intrinsic adsorption rates for Ad5-DEAE interaction are 16 times faster than intrinsic adsorption rates for Ad5 fiber knob interacting with soluble extracellular domain of coxsackievirus adenovirus receptors (s-CAR).

A density functional theory study on the adsorption and decomposition of methanol on B12N12 fullerene-like nanocage

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Nurazar, Roghaye

2014-03-01

The adsorption and dissociative reaction of methanol on B12N12 fullerene-like nanocage is investigated by using density functional calculations. Equilibrium geometries, adsorption energies, and electronic properties of CH3OH adsorption on the surface of the B12N12 were identified. The calculated adsorption energies range from -1.3 to -34.9 kcal/mol. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3OH. The mechanism of methanol decomposition via CO and OH bond scissions is also studied. The results indicate that OH bond scission is the most favorable pathway on the B12N12 surface.

Temporal changes in nitrogen adsorption properties of single-walled carbon nanotubes

USGS Publications Warehouse

Agnihotri, S.; Rostam-Abadi, M.; Rood, M.J.

2004-01-01

Temporal evolution of N2 adsorption (77 K) properties of as-produced and purified single-walled nanotubes (SWNTs) samples is described here. The N2 adsorption isotherms are used to characterize the samples' surface areas and porosities. The as-produced samples demonstrate a temporal increase in surface area and pore volumes for up to 16 months. The purified samples, however, reached their stable values of surface area and pore volumes within four to seven months. N2 adsorption capacity of the purified SWNTs also increased when the fresh samples were subjected to thermal pre-processing, with diminishing changes in adsorption capacity with increased age. These observations indicate that the freshly prepared SWNTs, both as-produced and purified, were in an unstable state with their porosity changing with increasing sample age and thermal treatments. It is hypothesized that SWNTs undergo slow but progressive changes in their surface chemistry which causes their N2 adsorption properties to change over several months. ?? 2004 Elsevier Ltd. All rights reserved.

The adsorption features between insecticidal crystal protein and nano-Mg(OH)2.

PubMed

Pan, Xiaohong; Xu, Zhangyan; Zheng, Yilin; Huang, Tengzhou; Li, Lan; Chen, Zhi; Rao, Wenhua; Chen, Saili; Hong, Xianxian; Guan, Xiong

2017-12-01

Nano-Mg(OH) 2 , with low biological toxicity, is an ideal nano-carrier for insecticidal protein to improve the bioactivity. In this work, the adsorption features of insecticidal protein by nano-Mg(OH) 2 have been studied. The adsorption capacity could reach as high as 136 mg g -1 , and the adsorption isotherm had been fitted with Langmuir and Freundlich models. Moreover, the adsorption kinetics followed a pseudo-first or -second order rate model, and the adsorption was spontaneous and an exothermic process. However, high temperatures are not suitable for adsorption, which implies that the temperature would be a critical factor during the adsorption process. In addition, FT-IR confirmed that the protein was adsorbed on the nano-Mg(OH) 2 , zeta potential analysis suggested that insecticidal protein was loaded onto the nano-Mg(OH) 2 not by electrostatic adsorption but maybe by intermolecular forces, and circular dichroism spectroscopy of Cry11Aa protein before and after loading with nano-Mg(OH) 2 was changed. The study applied the adsorption information between Cry11Aa and nano-Mg(OH) 2 , which would be useful in the practical application of nano-Mg(OH) 2 as a nano-carrier.

Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

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

Kempisty, Paweł; Krukowski, Stanisław; Interdisciplinary Centre for Materials Modelling, Warsaw University, Pawińskiego 5a, 02-106 Warsaw

Adsorption of ammonia at NH{sub 3}/NH{sub 2}/H-covered GaN(0001) surface was analyzed using results of ab initio calculations. The whole configuration space of partially NH{sub 3}/NH{sub 2}/H-covered GaN(0001) surface was divided into zones of differently pinned Fermi level: at the Ga broken bond state for dominantly bare surface (region I), at the valence band maximum (VBM) for NH{sub 2} and H-covered surface (region II), and at the conduction band minimum (CBM) for NH{sub 3}-covered surface (region III). The electron counting rule (ECR) extension was formulated for the case of adsorbed molecules. The extensive ab intio calculations show the validity of themore » ECR in case of all mixed H-NH{sub 2}-NH{sub 3} coverages for the determination of the borders between the three regions. The adsorption was analyzed using the recently identified dependence of the adsorption energy on the charge transfer at the surface. For region I ammonia adsorbs dissociatively, disintegrating into a H adatom and a HN{sub 2} radical for a large fraction of vacant sites, while for region II adsorption of ammonia is molecular. The dissociative adsorption energy strongly depends on the Fermi level at the surface (pinned) and in the bulk (unpinned) while the molecular adsorption energy is determined by bonding to surface only, in accordance to the recently published theory. Adsorption of Ammonia in region III (Fermi level pinned at CBM) leads to an unstable configuration both molecular and dissociative, which is explained by the fact that broken Ga-bonds are doubly occupied by electrons. The adsorbing ammonia brings 8 electrons to the surface, necessitating the transfer of these two electrons from the Ga broken bond state to the Fermi level. This is an energetically costly process. Adsorption of ammonia at H-covered site leads to the creation of a NH{sub 2} radical at the surface and escape of H{sub 2} molecule. The process energy is close to 0.12 eV, thus not large, but the direct

Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium-Thermodynamic of adsorption process

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

Lima Guerra, Denis; Azevedo Pinto, Alane; Airoldi, Claudio

2008-12-15

Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298{+-}1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic ({delta}{sub int}H=-4.15-5.98 kJ mol{sup -1}) accompanied by increase in entropy ({delta}{sub int}S=41.32-62.20 J k{sup -1} mol{sup -1}) and Gibbs energy ({delta}{sub int}G=-22.44-24.56 kJmore » mol{sup -1}). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid-liquid interface in the spontaneous process. - Grapical Abstract: The results suggest that the adsorption capacities increased with an increase of reactive basic centers in the pendant organic chains of the intercalated agent.« less

Adsorption characteristics of hexavalent chromium on HCB/TiO2

NASA Astrophysics Data System (ADS)

Zhang, Li; Zhang, Yonggang

2014-10-01

Sol-gel method was adopted to prepare HCB/TiO2 and its adsorption ability of hexavalent chromium, Cr(VI), and removal from aqueous solution were investigated. The samples were characterized by Power X-ray diffraction (XRD) and a transmission electron microscope (TEM) which showed that the TiO2 was deposited on the surface of HCB. FTIR was used to identify the changes of the surface functional groups before and after adsorption. Potentiometric titration method was used to characterize the zero charge (pHpzc) characteristics of the surface of HCB/TiO2 which showed more acidic functional groups containing. Batch experiments showed that initial pH, absorbent dosage, contact time and initial concentration of Cr(VI) were important parameters for the Cr(VI) adsorption studies. The Freundlich isotherm model better reflected the experimental data better. Cr(VI) adsorption process followed the pseudo-second order kinetic model, which illustrated chemical adsorption. The thermodynamic parameters, such as Gibbs free energy (ΔG), changes in enthalpy change (ΔH) and changes in entropy change (ΔS) were also evaluated. Negative value of free energy occurred at temperature range of 25-45 °C, so Cr(VI) adsorption by HCB/TiO2 is spontaneous. Desorption results showed that the adsorption capacity could maintain 80% after five cycles. The maximum adsorption capacity for Cr(VI) was at 27.33 mg g-1 in an acidic medium, of which the value is worth comparable with other low-cost adsorbents.

Simultaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard

1994-01-01

The Martian regolith is the most substantial volatile reservoir on the planet; it holds CO2 as adsorbate, and can exchange that CO2 with the atmosphere-cap system over timescales of 10(exp 5) to 10(exp 6) years. The climatic response to insolation changes caused by obliquity and eccentricity variations depends in part on the total reservoir of adsorbed CO2. Previous estimates of the adsorbate inventory have been made by measuring the adsorptive behavior of one or more Mars-analyog materials, and deriving an empirical equation that described that adsorption as a function of the partial pressure of CO2 and the temperature of the regolith. The current CO2 inventory is that which satisfies adsorptive equilibrium, observed atmospheric pressure, and no permanent CO2 caps. There is laboratory evidence that H2O poisons the CO2 adsorptive capacity of most materials. No consideration of CO2 - H2O co-adsorption was given in previous estimates of the Martian CO2 inventory, although H2O is present in the vapor phase, and so as adsorbate, throughout the regolith.

Phase 2 Methyl Iodide Deep-Bed Adsorption Tests

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

Soelberg, Nick; Watson, Tony

2014-09-01

Nuclear fission produces fission products (FPs) and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Research, demonstrations, and some reprocessing plant experience have indicated that diatomic iodine can be captured with efficiencies high enough to meet regulatory requirements. Research on the capture of organic iodides has also been performed, but to a lesser extent. Several questions remain open regarding the capture of iodine bound in organic compounds. Deep-bed methyl iodide adsorption testing has progressed according to a multi-laboratory methylmore » iodide adsorption test plan. This report summarizes the second phase of methyl iodide adsorption work performed according to this test plan using the deep-bed iodine adsorption test system at the Idaho National Laboratory (INL), performed during the second half of Fiscal Year (FY) 2014. Test results continue to show that methyl iodide adsorption using AgZ can achieve total iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) above 1,000, until breakthrough occurred. However, mass transfer zone depths are deeper for methyl iodide adsorption compared to diatomic iodine (I2) adsorption. Methyl iodide DFs for the Ag Aerogel test adsorption efficiencies were less than 1,000, and the methyl iodide mass transfer zone depth exceeded 8 inches. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption under various conditions specified in the methyl iodide test plan, and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.« less

N2O reduction over a fullerene-like boron nitride nanocage: A DFT study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.

2017-07-01

We study, for the first time, the adsorption and catalytic decomposition of N2O molecule over a fullerene-like boron nitride nanocage (B12N12) using density functional theory calculations. It is found that the electron donating property of the cage plays an important role in the adsorption and activation of N2O. By the incorporation of a carbon atom into B12N12 cluster, our results indicate that the adsorption of N2O over B11N12C or B12N11C is more stronger than over pristine B12N12. The decomposition of N2O into N2 and O species over the C-doped clusters is energetically more favorable than that on B12N12. Moreover, the C-doping plays an important role in reducing the activation barrier for the CO + O* reaction over B12N12 surface.

Study on the enhanced adsorption properties of lysozyme on polyacrylic acid modified TiO2 nano-adsorbents

NASA Astrophysics Data System (ADS)

Liu, Yufeng; Jin, Zu; Meng, Hao; Zhang, Xia

2018-01-01

The adsorption and immobilization of enzymes onto solid carriers has been focused on due to their many advantages, such as improved stability against a thermal or organic solvent and a good cycle usability. TiO2 nanoparticles is one of excellent nano-adsorbents owing to its excellent biocompatibility, non-inflammatory, and abundant surface hydroxyl groups, which are convenient to be combined with various functional groups. In this paper polyacrylic acid (PAA) modified TiO2 nanoparticles were synthesized through an in situ light-induced polymerization of acrylic acid on the surface of TiO2 nanoparticles. The structure and surface physicochemical properties of the PAA/TiO2 nanoparticles were characterized by TEM, XRD, FT-IR, Zeta potential measurements and TG-DSC. The experimental results showed that the isoelectric point of PAA/TiO2 significantly reduced to 1.82 compared with that of pure TiO2 nanoparticles (6.08). In the adsorption tests of lysozyme (Lyz), the PAA/TiO2 nanoparticles displayed enhanced adsorption activity compared with pristine TiO2. The maximum adsorption capacity of PAA/TiO2 for Lyz was 225.9 mg g-1 under the optimum conditions where the initial concentration of Lyz was 300 mg ml-1, the addition amount of PAA/TiO2 was 6.4 mg, the adsorption time was 30 min and the pH value was 7.0. The sodium dodecyl sulfate (SDS, 0.5%) presented the best efficiency (76.86%) in the removal of adsorbed Lyz, and the PAA/TiO2 nanoparticles showed excellent adsorption stability based on five cyclic adsorption-desorption tests. The fitting calculation results of the adsorption isotherm and the thermodynamics indicated the adsorption was an exothermic, entropy increasing, spontaneous and monomolecular layer adsorption process.

Amine–mixed oxide hybrid materials for carbon dioxide adsorption from CO2/H2 mixture

NASA Astrophysics Data System (ADS)

Ravi, Navin; Aishah Anuar, Siti; Yusuf, Nur Yusra Mt; Isahak, Wan Nor Roslam Wan; Shahbudin Masdar, Mohd

2018-05-01

Bio-hydrogen mainly contains hydrogen and high level of carbon dioxide (CO2). High concentration of CO2 lead to a limitation especially in fuel cell application. In this study, the amine-mixed oxide hybrid materials for CO2 separation from bio-hydrogen model (50% CO2:50% H2) have been studied. Fourier-transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) characterizations showed that the amine–mixed oxide hybrid materials successfully adsorbed CO2 physically with no chemical adsorption evidence. The dry gas of CO2/H2 mixture adsorbed physically on amine–CuO–MgO hybrid material. No carbonates were detected after several times of adsorption, which indicated the good recyclability of adsorbents. The adsorbent system of diethanolamine (DEA)/15% CuO–75% MgO showed the highest CO2 adsorption capacity of 21.2 wt% due to the presence of polar substance on MgO surface, which can adsorb CO2 at ambient condition. The alcohol group of DEA can enhance the CO2 solubility on the adsorbent surface. In the 20% CuO–50% MgO adsorbent system, DEA as amine type showed a high CO2 adsorption of 19.4 wt%. The 10% amine loading system showed that the DEA adsorption system provided high CO2 adsorption. The BET analysis confirmed that a high amine loading contributed to the decrease in CO2 adsorption due to the low surface area of the adsorbent system.

Syntheses, structures and selective dye adsorption of five formic-based coordination polymers prepared by in-situ hydrolysis of N, N′-dimethylformamide

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

Zhu, Zheng; Meng, Xiang-min; Zhang, Dong-mei

Five functional coordination polymers (formic-based CPs) namely: ([Cu{sub 2}(CHOO){sub 3}(bibp){sub 2}]·CHOO){sub n} (1), ([Co{sub 2}(CHOO){sub 3}(bibp){sub 2}]·NO{sub 3}·H{sub 2}O)n (2), ([Ni{sub 2}(CHOO){sub 3}(bibp){sub 2}]·NO{sub 3}·H{sub 2}O){sub n} (3) [Co(CHOO){sub 2}(bbibp)]{sub n} (4) and [Zn(CHOO){sub 2}(bbibp)]{sub n} (5) (bibp=4,4′-bis(imidazolyl)biphenyl, bbibp=4,4′-bis(benzoimidazo-1-yl)biphenyl) have been successfully hydrothermally synthesized using the in-situ hydrolysis of N, N′-dimethylformamide (DMF) as the source of formate. All of these five polymers were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complexes 1–3 have the similar three-dimensional 3D kag topological framework built from the bibp ligand as the support member betweenmore » the neighboring formic planes. Both complexes 4 and 5 have the similar one-dimensional 1D linear chain which is further assembled into 3D supermolecular structure by C–H…O hydrogen bonds. The dyes adsorption experiments have also been investigated systematically. The results show that complexes 2 and 3 exhibit high selective adsorption ability towards anionic dyes in their aqueous solution. Moreover, complex 2 displays good reversibility in the process of the dyes adsorption-release. Meanwhile, the unusual blocking phenomenon was firstly observed when complex 2 was in MO/OIV aqueous solutions with different concentration.« less

Adsorption of selected volatile organic vapors on multiwall carbon nanotubes.

PubMed

Shih, Yang-hsin; Li, Mei-syue

2008-06-15

Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. This study examines the adsorption behaviors of volatile organic compounds (VOCs), n-hexane, benzene, trichloroethylene and acetone on two multiwall carbon nanotubes (MWCNTs), CNT1 and CNT2. Among these VOCs, acetone exhibits the highest adsorption capacity. The highest adsorption enthalpies and desorption energies of acetone were also observed. The strong chemical interactions between acetone and both MWCNTs may be the result from chemisorption on the topological defects. The adsorption heats of trichloroethylene, benzene, and n-hexane are indicative of physisorption on the surfaces of both MWCNTs. CNT2 presents a higher adsorption capacity than CNT1 due to the existence of an exterior amorphous carbon layer on CNT2. The amorphous carbon enhances the adsorption capacity of organic chemicals on carbon nanotubes. The morphological and structure order of carbon nanotubes are the primary affects on the adsorption process of organic chemicals.

Adsorption and catalytic properties of sulfated aluminum oxide modified with cobalt ions

NASA Astrophysics Data System (ADS)

Lanin, S. N.; Bannykh, A. A.; Vlasenko, E. V.; Krotova, I. N.; Obrezkov, O. N.; Shilina, M. I.

2017-01-01

The adsorption properties of sulfated aluminum oxide (9% SO 4 2- /γ-Al2O3) and a cobalt-containing composite (0.5%Co/SO 4 2- /γ-Al2O3) based on it are studied via dynamic sorption. The adsorption isotherms of such test adsorbates as n-hydrocarbons (C6-C8), benzene, ethylbenzene, chloroform, and diethyl ether are measured, and their isosteric heats of adsorption are calculated. It is shown that the surface sulfation of aluminum oxide substantially improves its electron-accepting properties, and so the catalytic activity of SO 4 2- /γ-Al2O3 in the liquid-phase alkylation of benzene with octene-1 at temperatures of 25-120°C is one order of magnitude higher than for the initial aluminum oxide. It is established that additional modification of sulfated aluminum oxide with cobalt ions increases the activity of this catalyst by 2-4 times. It is shown that adsorption sites capable of strong specific adsorption with both donating (aromatics, diethyl ether chemosorption) and accepting molecules (chloroform) form on the surface of sulfated γ-Al2O3 promoted by cobalt salt.

Competitive adsorption of Pb2+, Cu2+, and Cd2+ ions on microporous titanosilicate ETS-10.

PubMed

Lv, Lu; Hor, Mei Peng; Su, Fabing; Zhao, X S

2005-07-01

In the present study, the competitive adsorption characteristics of binary and ternary heavy metal ions Pb2+, Cu2+, and Cd2+ on microporous titanosilicate ETS-10 were investigated in batch systems. Pure microporous titanosilicate ETS-10 was synthesized with P25 as the Ti source and characterized by the techniques of X-ray diffraction (XRD), field emission-scanning electron microscope (FESEM), nitrogen adsorption, and zeta-potential. Equilibrium and kinetic adsorption data showed that ETS-10 displays a high selectivity toward one metal in a two-component or a three-component system with an affinity order of Pb2+ > Cd2+ > Cu2+. The equilibrium behaviors of heavy metals species with stronger affinity toward ETS-10 can be described by the Langmuir equation while the adsorption kinetics of the metals can be well fitted to a pseudo-second-order (PSO) model.

Fabrication of carbon/SiO2 composites from the hydrothermal carbonization process of polysaccharide and their adsorption performance.

PubMed

Li, Yinhui; Li, Kunyu; Su, Min; Ren, Yanmei; Li, Ying; Chen, Jianxin; Li, Liang

2016-11-20

In this work, carbon/SiO2 composites, using amylose and tetraethyl orthosilicate (TEOS) as raw materials, were successfully prepared by a facial hydrothermal carbonization process. The carbon/SiO2 composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), transmission electron microscope (TEM), N2 adsorption and Thermogravimetric (TG) analysis. The composites, which were made up of amorphous SiO2 and amorphous carbon, were found to have hierarchical porous structures. The mass ratios of amylose and SiO2 and the hydrothermal carbonization time had significant effects on the morphology of the composites, which had three shapes including monodispersed spheres, porous pieces and the nano-fibers combined with nano-spheres structures. The adsorption performance of the composites was studied using Pb(2+) as simulated contaminants from water. When the mass ratio of amylose and SiO2 was 9/1, the hydrothermal time was 30h and the hydrothermal temperature was 180°C, the adsorption capacity of the composites achieved to 52mg/g. Experimental data show that adsorption kinetics of the carbon/SiO2 composites can be fitted well by the Elovich model, while the isothermal data can be perfectly described by the Langmuir adsorption model and Freundlich adsorption model. The maximum adsorption capacity of the carbon/SiO2 composites is 56.18mgg(-1). Copyright © 2016 Elsevier Ltd. All rights reserved.

Adsorption kinetics of ion of Pb2+ using Tricalcium Phosphate particles

NASA Astrophysics Data System (ADS)

Fadli, A.; Yenti, S. R.; Akbar, F.; Maihendra; Mawarni, F.

2018-04-01

One of the heavy metals that can pollute water is Pb2+. The concentration of ion Pb2+ can be removed using the adsorption method. The purpose of this research is to determine the adsorption kinetics model of ions Pb2+ using tricalcium phosphate (TCP) particles with variation of the temperature and adsorbent dosage. Five hundred mililiter Pb2+ solution with of 3 mg/L were added 0,5 gr, 1 gr and 1,5 gr of TCP in a glass beaker and stirred with rate of 300 rpm at a temperature of 30 °C, 40 °C and 50 °C. Pb2+ concentration in solution was analyzed by AAS (Atomic Adsorption Spectroscopy). The results showed that the rate of adsorption increased with the increasing of the temperature and adsorbent dosage. Minimum constant value of adsorption kinetic was 1,720 g/mg.min obtained at temperature of 30 °C and adsorbent dosageof 0,5 gr. The maximum value of adsorption kinetic constant was 9,755 g/mg.min obtained at temperature of 50 °C and adsorbent dosage of 1,5 gr. The appropriate model for adsorption kinetics followed the pseudo second order.

Surface rheology of saponin adsorption layers.

PubMed

Stanimirova, R; Marinova, K; Tcholakova, S; Denkov, N D; Stoyanov, S; Pelan, E

2011-10-18

Extracts of the Quillaja saponaria tree contain natural surfactant molecules called saponins that very efficiently stabilize foams and emulsions. Therefore, such extracts are widely used in several technologies. In addition, saponins have demonstrated nontrivial bioactivity and are currently used as essential ingredients in vaccines, food supplements, and other health products. Previous preliminary studies showed that saponins have some peculiar surface properties, such as a very high surface modulus, that may have an important impact on the mechanisms of foam and emulsion stabilization. Here we present a detailed characterization of the main surface properties of highly purified aqueous extracts of Quillaja saponins. Surface tension isotherms showed that the purified Quillaja saponins behave as nonionic surfactants with a relatively high cmc (0.025 wt %). The saponin adsorption isotherm is described well by the Volmer equation, with an area per molecule of close to 1 nm(2). By comparing this area to the molecular dimensions, we deduce that the hydrophobic triterpenoid rings of the saponin molecules lie parallel to the air-water interface, with the hydrophilic glucoside tails protruding into the aqueous phase. Upon small deformation, the saponin adsorption layers exhibit a very high surface dilatational elasticity (280 ± 30 mN/m), a much lower shear elasticity (26 ± 15 mN/m), and a negligible true dilatational surface viscosity. The measured dilatational elasticity is in very good agreement with the theoretical predictions of the Volmer adsorption model (260 mN/m). The measured characteristic adsorption time of the saponin molecules is 4 to 5 orders of magnitude longer than that predicted theoretically for diffusion-controlled adsorption, which means that the saponin adsorption is barrier-controlled around and above the cmc. The perturbed saponin layers relax toward equilibrium in a complex manner, with several relaxation times, the longest of them being around 3

Orientation and temperature dependent adsorption of H 2S on GaAs: Valence band photoemission

NASA Astrophysics Data System (ADS)

Ranke, W.; Kuhr, H. J.; Finster, J.

A cylindrically shaped GaAs single crystal was used to study the adsorption of H 2S on the six inequivalent orientations (001), (113), (111), (110), (111) and (113) by angle resolved valence band photoelectron spectroscopy and surface dipole measurements. Adsorption at 150 K on the surface prepared by molecular beam epitaxy (MBE) yields similar adsorbate induced emission on all orientations which were ascribed to SH radicals. On (110), where preferential adsorption occurs additional features from molecular H 2S are observed. The adsorbate spectra at 720 K are ascribed to atomic sulphur. On the surface prepared by ion bombardment and annealing, defect enhanced adsorption occurs in the range (111)-(113). The adsorbate spectra are very similar to those on the MBE surface at 720 K. Thus, no new species are adsorbed on defects but only sticking probability and penetration capability are increased.

Measurements of d 2 n and A 1 n : Probing the neutron spin structure

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

Flay, D.; Posik, M.; Parno, D. S.

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d(2) of the neutron (d(2)(n)) was conducted. The quantity d(2)(n) represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the He-3 spin structure functions, g(1) and g(2), after nuclear corrections had been applied to these moments. The structure functions were obtained frommore » a measurement of the unpolarized cross section and of double-spin asymmetries in the scattering of a longitudinally polarized electron beam from a transversely and a longitudinally polarized He-3 target. The measurement kinematics included two average Q(2) bins of 3.2 GeV2 and 4.3 GeV2, and Bjorken-x 0.25 <= x <= 0.90 covering the deep inelastic and resonance regions. We have found that d(2)(n) is small and negative for < Q(2)> = 3.2 GeV2, and even smaller for < Q(2)> = 4.3 GeV2, consistent with the results of a lattice QCD calculation. The twist-4 matrix element f(2)(n) was extracted by combining our measured d(2)(n) with the world data on the first moment in x of g(1)(n), Gamma(n)(1). We found f(2)(n) to be roughly an order of magnitude larger than d(2)(n). Utilizing the extracted d(2)(n) and f(2)(n) data, we separated the Lorentz color force into its electric and magnetic components, F-E(y,n) and F-B(y,n), and found them to be equal and opposite in magnitude, in agreement with the predictions from an instanton model but not with those from QCD sum rules. Furthermore, using the measured double-spin asymmetries, we have extracted the virtual photon-nucleon asymmetry on the neutron A(1)(n), the structure function ratio g(1)(n)/F-1(n), and the quark ratios (Delta u + Delta(u) over bar)/(u + (u) over bar) and (Delta d + Delta(d) over

A study in the adsorption of Fe(2+) and NO(3)(-) on pine needles based hydrogels.

PubMed

Chauhan, Ghanshyam S; Chauhan, Sandeep; Kumar, Sunil; Kumari, Anita

2008-09-01

Novel supports for use as cation and anion adsorbents were prepared from lignocellulosics using pine needles and their carboxymethylated forms by network/hydrogel formation with acrylamide and N,N-methylene bisacrylamide. The hydrogels thus prepared were further functionalized by partial alkaline hydrolysis with 0.5 N NaOH and were characterized by FTIR, SEM and nitrogen analysis. Adsorption of Fe(2+) on these hydrogels was carried as a function of time, temperature, pH and ionic strength. The hydrogel having the maximum adsorption capacity was loaded with Fe(2+) at the conditions those afforded maximum uptake and was used as novel anionic adsorbent for NO(3)(-). The water uptake capacities and biodegradability of the hydrogels before and after the ion loading was studied to evaluate the possible end-uses of these hydrogels as alternate materials in the removal of ionic species from water.

Charge-controlled switchable CO adsorption on FeN4 cluster embedded in graphene

NASA Astrophysics Data System (ADS)

Omidvar, Akbar

2018-02-01

Electrical charging of an FeN4 cluster embedded in graphene (FeN4G) is proposed as an approach for electrocatalytically switchable carbon monoxide (CO) adsorption. Using density functional theory (DFT), we found that the CO molecule is strongly adsorbed on the uncharged FeN4G cluster. Our results show that the adsorption energy of a CO molecule on the FeN4G cluster is dramatically decreased by introducing extra electrons into the cluster. Once the charges are removed, the CO molecule is spontaneously adsorbed on the FeN4G absorbent. In the framework of frontier molecular orbital (FMO) analysis, the enhanced sensitivity and reactivity of the FeN4G cluster towards the CO molecule can be interpreted in terms of interaction between the HOMO of CO molecule and the LUMO of FeN4G cluster. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the FeN4G nanomaterial is an excellent absorbent for controllable and reversible capture and release of the CO.

Adsorptive separation studies of ethane-methane and methane-nitrogen systems using mesoporous carbon.

PubMed

Yuan, Bin; Wu, Xiaofei; Chen, Yingxi; Huang, Jianhan; Luo, Hongmei; Deng, Shuguang

2013-03-15

Adsorptive separations of C(2)H(6)/CH(4) and CH(4)/N(2) binary mixtures are of paramount importance from the energy and environmental points of view. A mesoporous carbon adsorbent was synthesized using a soft template method and characterized with TEM, TGA, and nitrogen adsorption/desorption. Adsorption equilibrium and kinetics of C(2)H(6), CH(4), and N(2) on the mesoporous carbon adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. The adsorption capacities of C(2)H(6) and CH(4) on the mesoporous carbon adsorbent at 298 K and 100 kPa are 2.20 mmol/g and 1.05 mmol/g, respectively. Both are significantly higher than those of many adsorbents including pillared clays and ETS-10 at a similar condition. The equilibrium selectivities of C(2)H(6)/CH(4) and CH(4)/N(2) at 298 K are 19.6 and 5.8, respectively. It was observed that the adsorption of C(2)H(6), CH(4), and N(2) gases on the carbon adsorbent was reversible with modest isosteric heats of adsorption, which implies that this carbon adsorbent can be easily regenerated in a cyclic adsorption process. These results suggest that the mesoporous carbon studied in this work is a promising alternative adsorbent for the separations of C(2)H(6)/CH(4) and CH(4)/N(2) gas mixtures. Copyright © 2012 Elsevier Inc. All rights reserved.

High resolution measurements of the {sup 241}Am(n,2n) reaction cross section

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

Sage, C.; European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel; Commissariat a L'Energie Atomique Cadarache, DEN/CAD/DER/SPRC/LEPh, F-13108 St Paul-lez-Durance

Measurements of the {sup 241}Am(n,2n) reaction cross section have been performed at the Joint Research Centre (JRC) Geel in the frame of a collaboration between the European Commission (EC) JRC and French laboratories from CNRS and the Commissariat a L'Energie Atomique (CEA) Cadarache. Raw material coming from the Atalante facility of CEA Marcoule has been transformed by JRC Karlsruhe into suitable {sup 241}AmO{sub 2} samples embedded in Al{sub 2}O{sub 3} matrices specifically designed for these measurements. The irradiations were carried out at the 7-MV Van de Graaff accelerator. The {sup 241}Am(n,2n) reaction cross section was determined relative to the {supmore » 27}Al(n,alpha){sup 24}Na standard cross section. The measurements were performed in four sessions, using quasi-mono-energetic neutrons with energies ranging from 8 to 21 MeV produced via the {sup 2}H(d,n){sup 3}He and the {sup 3}H(d,n){sup 4}He reactions. The induced activity was measured by standard gamma-ray spectrometry using a high-purity germanium detector. Below 15 MeV, the present results are in agreement with data obtained earlier. Above 15 MeV, these measurements allowed the experimental investigation of the {sup 241}Am(n,2n) reaction cross section for the first time. The present data are in good agreement with predictions obtained with the talys code that uses an optical and fission model developed at CEA.« less

Enhanced adsorption and catalytic oxidation of ciprofloxacin by an Ag/AgCl@N-doped activated carbon composite

NASA Astrophysics Data System (ADS)

Nekouei, Farzin; Nekouei, Shahram; Noorizadeh, Hossein

2018-03-01

In this study, we synthesized a new nanocomposite catalyst comprising Ag/AgCl@N-doped activated carbon (Ag/AgCl@N-AC) and demonstrated its high efficiency during the enhanced adsorptive removal and catalytic oxidation of ciprofloxacin (CIP) with peroxymonosulfate (PMS) and persulfate (PS) as oxidants in aqueous solution. The efficiency of the new nanocomposite was compared with those of both pristine AC and N-AC under the same conditions. Furthermore, the effects of oxidants on the catalytic oxidation of CIP were assessed using PMS and PS. We found that the degradation efficiency of CIP with Ag/AgCl@N-AC was higher when using PS as an oxidant, whereas the use of PMS obtained relatively better results with both AC and N-AC. The adsorption processes for AC, N-AC, and Ag/AgCl@N-AC were dominated not only by electrostatic attraction but also by π-π interactions, which had higher impacts on the adsorption processes than the specific surface area.

Surface-Bound Casein Modulates the Adsorption and Activity of Kinesin on SiO2 Surfaces

PubMed Central

Ozeki, Tomomitsu; Verma, Vivek; Uppalapati, Maruti; Suzuki, Yukiko; Nakamura, Mikihiko; Catchmark, Jeffrey M.; Hancock, William O.

2009-01-01

Abstract Conventional kinesin is routinely adsorbed to hydrophilic surfaces such as SiO2. Pretreatment of surfaces with casein has become the standard protocol for achieving optimal kinesin activity, but the mechanism by which casein enhances kinesin surface adsorption and function is poorly understood. We used quartz crystal microbalance measurements and microtubule gliding assays to uncover the role that casein plays in enhancing the activity of surface-adsorbed kinesin. On SiO2 surfaces, casein adsorbs as both a tightly bound monolayer and a reversibly bound second layer that has a dissociation constant of 500 nM and can be desorbed by washing with casein-free buffer. Experiments using truncated kinesins demonstrate that in the presence of soluble casein, kinesin tails bind well to the surface, whereas kinesin head binding is blocked. Removing soluble casein reverses these binding profiles. Surprisingly, reversibly bound casein plays only a moderate role during kinesin adsorption, but it significantly enhances kinesin activity when surface-adsorbed motors are interacting with microtubules. These results point to a model in which a dynamic casein bilayer prevents reversible association of the heads with the surface and enhances association of the kinesin tail with the surface. Understanding protein-surface interactions in this model system should provide a framework for engineering surfaces for functional adsorption of other motor proteins and surface-active enzymes. PMID:19383474

The adsorption of cationic and amphoteric copolymers on glass surfaces: zeta potential measurements, adsorption isotherm determination, and FT Raman characterization.

PubMed

Tartakovsky, Alla; Drutis, Dane M; Carnali, Joseph O

2003-07-15

The adsorption of cationic and amphoteric copolymers onto controlled pore glass (CPG) powders has been studied by measurement of the powder particle zeta (zeta) potential, by determination of the adsorption isotherm, and by FT Raman measurements of the polymer-coated powder. The cationic polymers consisted chiefly of homopolymers of dimethyldiallylammonium chloride (DMDAAC) or copolymers of DMDAAC and acrylamide. The amphoteric polymers studied included copolymers of DMDAAC and acrylic acid. The comonomer ratio was varied to explore the dependence of cationic charge density on the extent and effect of adsorption. Both types of polymers adsorb onto the anionic glass surface via an ion-exchange mechanism. Consequently, a correspondingly higher mass of a low-charge-density copolymer adsorbs than of a cationic homopolymer. The presence of the anionic portion in the amphoteric polymers does not significantly alter this picture. The zeta potential, however, reflects the overall nature of the polymer. Cationic polymers effectively neutralize the glass surface, while amphoteric polymers leave the zeta potential net negative. Adsorption isotherms, determined via the depletion technique using colloidal titration, were used to "calibrate" a FT Raman method. The latter was used to determined the amount of adsorbed polymer under solution conditions in which colloidal titration could not be performed.

Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

NASA Astrophysics Data System (ADS)

Öztürk, A.; Malkoc, E.

2014-04-01

In this work, natural untreated clay (NUC) was studied for the removal of Basic Yellow 2 (BY2) from aqueous solution in batch system. The effects of initial BY2 concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

Static and Dynamic Measurement of Dopamine Adsorption in Carbon Fiber Microelectrodes Using Electrochemical Impedance Spectroscopy.

PubMed

Rivera-Serrano, Nilka; Pagan, Miraida; Colón-Rodríguez, Joanisse; Fuster, Christian; Vélez, Román; Almodovar-Faria, Jose; Jiménez-Rivera, Carlos; Cunci, Lisandro

2018-02-06

In this study, electrochemical impedance spectroscopy was used for the first time to study the adsorption of dopamine in carbon fiber microelectrodes. In order to show a proof-of-concept, static and dynamic measurements were taken at potentials ranging from -0.4 to 0.8 V versus Ag|AgCl to demonstrate the versatility of this technique to study dopamine without the need of its oxidation. We used electrochemical impedance spectroscopy and single frequency electrochemical impedance to measure different concentrations of dopamine as low as 1 nM. Moreover, the capacitance of the microelectrodes surface was found to decrease due to dopamine adsorption, which is dependent on its concentration. The effect of dissolved oxygen and electrochemical oxidation of the surface in the detection of dopamine was also studied. Nonoxidized and oxidized carbon fiber microelectrodes were prepared and characterized by optical microscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Optimum working parameters of the electrodes, such as frequency and voltage, were obtained for better measurement. Electrochemical impedance of dopamine was determined at different concentration, voltages, and frequencies. Finally, dynamic experiments were conducted using a flow cell and single frequency impedance in order to study continuous and real-time measurements of dopamine.

Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

PubMed

Kuśmierek, Krzysztof; Świątkowski, Andrzej

2016-03-01

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water.

H{sub 2} adsorption in Li-decorated porous graphene

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

Seenithurai, S.; Pandyan, R. Kodi; Kumar, S. Vinodh

Porous graphene (PG) has been decorated with Li atoms and subsequently studied the hydrogen (H{sub 2}) adsorption characteristics, by using Density Functional Theory (DFT)-based calculations. A 2×2 PG has been decorated with eight Li atoms. Upto four H{sub 2} molecules get adsorbed on each Li atom. The maximum H{sub 2} storage capacity that could be achieved in 2×2PG-8Li is 8.95 wt% which is higher than the U.S. DOE’s revised target for the on-board vehicles. The average H{sub 2} adsorption binding energy is 0.535 eV/H{sub 2}, which lies between 0.2-0.6 eV/H{sub 2} that is required for achieving adsorption and desorption atmore » near ambient conditions. Thus, Li-decorated PG could be a viable option for on-board automobile applications.« less

Adsorption behavior of methacryloyloxydecyl dihydrogen phosphate on an apatite surface at neutral pH.

PubMed

Bista, Baba; Nakashima, Syozi; Nikaido, Toru; Sadr, Alireza; Takagaki, Tomohiro; Romero, Maria J R H; Sato, Takaaki; Tagami, Junji

2016-04-01

This study aimed to quantify the adsorption affinity of neutralized 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP-N) toward hydroxyapatite (HA) and dicalcium phosphate dihydrate (DCPD) at pH 7.0 by employing the Langmuir isotherm model. Furthermore, the effects of inorganic phosphate (Pi) and fluoride (F(-) ) ions on the adsorption of 10-MDP-N onto HA and DCPD were examined. Fixed amounts of HA and DCPD powders were suspended in different concentrations of 10-MDP-N solutions and were incubated for 18 h. Equilibrated concentrations of 10-MDP-N were measured by spectrophotometry and the adsorption affinity was estimated using the Langmuir model. Moreover, the adsorption was examined by zeta-potential analysis. The results indicated that significant Langmuir correlation was noted in both substrates, along with an increasing negative zeta-potential; however, in DCPD the correlation was less strong. The addition of 1.0 mM Pi slightly delayed the adsorption of 10-MDP-N onto both substrates, whereas 3.0 mM Pi drastically delayed adsorption onto HA but completely inhibited adsorption onto DCPD. Up to 50 ppm, F(-) enhanced the adsorption onto HA, and the adsorption plateaued at higher concentrations of F(-) , whereas no obvious influence of F(-) on the adsorption onto DCPD was noted. © 2016 Eur J Oral Sci.

Selective CO2 gas adsorption in the narrow crystalline cavities of flexible peptide metallo-macrocycles.

PubMed

Miyake, Ryosuke; Kuwata, Chika; Masumoto, Yui

2015-02-21

Crystalline peptide Ni(ii)-macrocycles (BF4(-) salt) exhibited moderate CO2 gas adsorption (ca. 6-7 CO2 molecules per macrocycle) into very narrow cavities (narrowest part <2 Å), accompanied by the expansion of the cavities. The BF4(-) salt demonstrated selective uptake of CO2 gas in preference to CH4 and N2 gases.

Designed Synthesis of Mesoporous Solid-Supported Lewis Acid-Base Pairs and Their CO2 Adsorption Behaviors.

PubMed

Zakharova, Maria V; Masoumifard, Nima; Hu, Yimu; Han, Jongho; Kleitz, Freddy; Fontaine, Frédéric-Georges

2018-04-18

Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpiperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as Ti-, Al-, and Zr-SBA-15, to generate air-stable solid-supported Lewis acid-base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-Fourier transform infrared spectroscopy. Detailed characterization of the materials was achieved by solid-state 13 C and 31 P MAS NMR spectroscopy, low-temperature N 2 physisorption, X-ray photoelectron spectroscopy, and energy-dispersive X-ray mapping analyses. Study of their potential interactions with CO 2 was performed using CO 2 adsorption isotherm experiments, which provided new insights into their applicability as solid CO 2 adsorbents. A correlation between solid-supported Lewis acid-base pair strength and the resulting affinity to CO 2 is discussed based on the calculation of isosteric enthalpy of adsorption.

A flexible metal–organic framework: Guest molecules controlled dynamic gas adsorption

DOE PAGES

Mahurin, Shannon Mark; Li, Man -Rong; Wang, Hailong; ...

2015-04-13

A flexible metal–organic framework (MOF) of [Zn 3(btca) 2(OH) 2]·(guest) n (H 2btca = 1,2,3-benzotriazole-5-carboxylic acid) that exhibits guest molecule-controlled dynamic gas adsorption is reported in which carbon dioxide molecules rather than N 2, He, and Ar induce a structural transition with a corresponding appearance of additional steps in the isotherms. Physical insights into the dynamic adsorption behaviors of flexible compound 1 were detected by gas adsorption at different temperatures and different pressures and confirmed by Fourier transform infrared spectroscopy and molecular simulations. Interestingly, by taking advantage of the flexible nature inherent to the framework, this MOF material enables highlymore » selective adsorption of CO 2/N 2, CO 2/Ar, and CO 2/He of 36.3, 32.6, and 35.9, respectively, at 298 K. Furthermore, this class of flexible MOFs has potential applications for controlled release, molecular sensing, noble gas separation, smart membranes, and nanotechnological devices.« less

Adsorptive features of polyacrylamide-apatite composite for Pb2+, UO(2)2+ and Th4+.

PubMed

Ulusoy, Ulvi; Akkaya, Recep

2009-04-15

Micro-composite of polyacrylamide (PAA) and apatite (Apt) was prepared by direct polymerization of acrylamide in a suspension of Apt and characterized by means of FT-IR, XRD, SEM and BET analysis. The adsorptive features of PAA-Apt and Apt were then investigated for Pb(2+), UO(2)(2+) and Th(4+) in view of dependency on ion concentration, temperature, kinetics, ion selectivity and reusability. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. Apt in PAA-Apt had higher adsorption capacity (0.81, 1.27 and 0.69 mol kg(-1)) than bare Apt (0.28, 0.41 and 1.33 mol kg(-1)) for Pb(2+) and Th(4+), but not for UO(2)(2+). The affinity to PAA-Apt increased for Pb(2+) and UO(2)(2+) but not changed for Th(4+). The values of enthalpy and entropy changed were positive for all ions for both Apt and PAA-Apt. Free enthalpy change was DeltaG<0. Well compatibility of adsorption kinetics to the pseudo-second-order model predicated that the rate-controlling step was a chemical sorption. This was consistent with the free energy values derived from DR model. The reusability tests for Pb(2+) for five uses proved that the composite was reusable to provide a mean adsorption of 53.2+/-0.7% from 4x10(-3)M Pb(2+) solution and complete recovery of the adsorbed ion was possible (98+/-1%). The results of this investigation suggested that the use of Apt in the micro-composite form with PAA significantly enhanced the adsorptive features of Apt.

Pore size distribution calculation from 1H NMR signal and N2 adsorption-desorption techniques

NASA Astrophysics Data System (ADS)

Hassan, Jamal

2012-09-01

The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N2 adsorption-desorption and 1H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121-134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs-Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.

Influence of surface treatments on micropore structure and hydrogen adsorption behavior of nanoporous carbons.

PubMed

Kim, Byung-Joo; Park, Soo-Jin

2007-07-15

The scope of this work was to control the pore sizes of porous carbons by various surface treatments and to investigate the relation between pore structures and hydrogen adsorption capacity. The effects of various surface treatments (i.e., gas-phase ozone, anodic oxidation, fluorination, and oxygen plasma) on the micropore structures of porous carbons were investigated by N(2)/77 K isothermal adsorption. The hydrogen adsorption capacity was measured by H(2) isothermal adsorption at 77 K. In the result, the specific surface area and micropore volume of all of the treated samples were slightly decreased due to the micropore filling or pore collapsing behaviors. It was also found that in F(2)-treated carbons the center of the pore size distribution was shifted to left side, meaning that the average size of the micropores decreased. The F(2)- and plasma-treated samples showed higher hydrogen storage capacities than did the other samples, the F(2)-treated one being the best, indicating that the micropore size of the porous carbons played a key role in the hydrogen adsorption at 77 K.

Neutron Scattering Measurements of Carbon Dioxide Adsorption in Pores within the Marcellus Shale: Implications for Sequestration.

PubMed

Stefanopoulos, Konstantinos L; Youngs, Tristan G A; Sakurovs, Richard; Ruppert, Leslie F; Bahadur, Jitendra; Melnichenko, Yuri B

2017-06-06

Shale is an increasingly viable source of natural gas and a potential candidate for geologic CO 2 sequestration. Understanding the gas adsorption behavior on shale is necessary for the design of optimal gas recovery and sequestration projects. In the present study neutron diffraction and small-angle neutron scattering measurements of adsorbed CO 2 in Marcellus Shale samples were conducted on the Near and InterMediate Range Order Diffractometer (NIMROD) at the ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory along an adsorption isotherm of 22 °C and pressures of 25 and 40 bar. Additional measurements were conducted at approximately 22 and 60 °C at the same pressures on the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument at Oak Ridge National Laboratory. The structures investigated (pores) for CO 2 adsorption range in size from Å level to ∼50 nm. The results indicate that, using the conditions investigated densification or condensation effects occurred in all accessible pores. The data suggest that at 22 °C the CO 2 has liquid-like properties when confined in pores of around 1 nm radius at pressures as low as 25 bar. Many of the 2.5 nm pores, 70% of 2 nm pores, most of the <1 nm pores, and all pores <0.25 nm, are inaccessible or closed to CO 2 , suggesting that despite the vast numbers of micropores in shale, the micropores will be unavailable for storage for geologic CO 2 sequestration.

Effect of Spin Multiplicity in O2 Adsorption and Dissociation on Small Bimetallic AuAg Clusters.

PubMed

García-Cruz, Raúl; Poulain, Enrique; Hernández-Pérez, Isaías; Reyes-Nava, Juan A; González-Torres, Julio C; Rubio-Ponce, A; Olvera-Neria, Oscar

2017-08-17

To dispose of atomic oxygen, it is necessary the O 2 activation; however, an energy barrier must be overcome to break the O-O bond. This work presents theoretical calculations of the O 2 adsorption and dissociation on small pure Au n and Ag m and bimetallic Au n Ag m (n + m ≤ 6) clusters using the density functional theory (DFT) and the zeroth-order regular approximation (ZORA) to explicitly include scalar relativistic effects. The most stable Au n Ag m clusters contain a higher concentration of Au with Ag atoms located in the center of the cluster. The O 2 adsorption energy on pure and bimetallic clusters and the ensuing geometries depend on the spin multiplicity of the system. For a doublet multiplicity, O 2 is adsorbed in a bridge configuration, whereas for a triplet only one O-metal bond is formed. The charge transfer from metal toward O 2 occupies the σ* O-O antibonding natural bond orbital, which weakens the oxygen bond. The Au 3 ( 2 A) cluster presents the lowest activation energy to dissociate O 2 , whereas the opposite applies to the AuAg ( 3 A) system. In the O 2 activation, bimetallic clusters are not as active as pure Au n clusters due to the charge donated by Ag atoms being shared between O 2 and Au atoms.

Adsorption of Reactive Red M-2BE dye from water solutions by multi-walled carbon nanotubes and activated carbon.

PubMed

Machado, Fernando M; Bergmann, Carlos P; Fernandes, Thais H M; Lima, Eder C; Royer, Betina; Calvete, Tatiana; Fagan, Solange B

2011-09-15

Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N(2) adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298K was fixed at 1h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of hydration and oxygen vacancy on CO2 adsorption and activation on beta-Ga2O3(100).

PubMed

Pan, Yun-xiang; Liu, Chang-jun; Mei, Donghai; Ge, Qingfeng

2010-04-20

The effects of hydration and oxygen vacancy on CO(2) adsorption on the beta-Ga(2)O(3)(100) surface have been studied using density functional theory slab calculations. Adsorbed CO(2) is activated on the dry perfect beta-Ga(2)O(3)(100) surface, resulting in a carbonate species. This adsorption is slightly endothermic, with an adsorption energy of 0.07 eV. Water is preferably adsorbed molecularly on the dry perfect beta-Ga(2)O(3)(100) surface with an adsorption energy of -0.56 eV, producing a hydrated perfect beta-Ga(2)O(3)(100) surface. Adsorption of CO(2) on the hydrated surface as a carbonate species is also endothermic, with an adsorption energy of 0.14 eV, indicating a slightly repulsive interaction when H(2)O and CO(2) are coadsorbed. The carbonate species on the hydrated perfect surface can be protonated by the coadsorbed H(2)O to a bicarbonate species, making the CO(2) adsorption exothermic, with an adsorption energy of -0.13 eV. The effect of defects on CO(2) adsorption and activation has been examined by creating an oxygen vacancy on the dry beta-Ga(2)O(3)(100) surface. The formation of an oxygen vacancy is endothermic, by 0.34 eV, with respect to a free O(2) molecule in the gas phase. Presence of the oxygen vacancy promoted the adsorption and activation of CO(2). In the most stable CO(2) adsorption configuration on the dry defective beta-Ga(2)O(3)(100) surface with an oxygen vacancy, one of the oxygen atoms of the adsorbed CO(2) occupies the oxygen vacancy site, and the CO(2) adsorption energy is -0.31 eV. Water favors dissociative adsorption at the oxygen vacancy site on the defective surface. This process is spontaneous, with a reaction energy of -0.62 eV. These results indicate that, when water and CO(2) are present in the adsorption system simultaneously, water will compete with CO(2) for the oxygen vacancy sites and impact CO(2) adsorption and conversion negatively.

The adsorption properties of titanium dioxide

NASA Astrophysics Data System (ADS)

Lanin, S. N.; Vlasenko, E. V.; Kovaleva, N. V.; Zung, Fam Tien

2008-12-01

The adsorption properties of titanium dioxide were studied by gas chromatography. We used organic compounds from different classes, namely, n-alkanes, n-alkenes (C6-C8), and polar compounds (electron donors and acceptors) as test adsorbates. The differential heats of adsorption and the contributions of dispersion and specific intermolecular interaction energies were determined for the systems from the experimental retention data. The electron-donor and electron-acceptor characteristics of the ultimately hydroxylated surface of TiO2 were evaluated.

Dynamics of adsorption in micellar and non micellar solutions of derivatives of lysosomotropic substances.

PubMed

Dopierala, Katarzyna; Prochaska, Krystyna

2010-04-22

Dynamics of adsorption in micellar and non micellar solutions of derivatives of lysosomotropic substances was studied. The following compounds were considered in our research work: alkyl N,N-dimethyl-alaninates methobromides (DMALM-n), alkyl N,N-dimethylglycinates methobromides (DMGM-n), fatty acids N,N-dimethylaminoethylesters methobromides (DMM-n), fatty acids N,N-dimethylaminopropylesters methobromides (DMPM-n), fatty acids 1-dimethylamino-2-propyl methobromides (DMP(2)M-n), and derivatives of aminoesters with double alkyl chains (M(2)M-n). The examined compounds show interesting biological properties which can be useful, especially in medicine. The exact mechanism of interaction of such compounds with biological membrane is not fully known. However, it is supposed that the presence of micelles has an important role in biological systems. In this paper we show the results of dynamic surface tension measurements in solutions containing the investigated compounds at concentrations above and below cmc. Moreover, we analyzed the influence of the chemical structure of molecules on the diameters of the micelles formed in the solutions. It was found that adsorption dynamics for the studied compounds is strongly affected by the chemical structure of the considered derivatives, especially by the presence of the ester bond, linearity of the molecule, as well as its hydrophobicity. The obtained results show that the structure of the bromide M(2)M-n with two short hydrocarbon chains favors a faster and more efficient adsorption of the molecules at the air/water interface, compared with compounds having one long alkyl chain. Moreover, the double chained derivatives of the M(2)M-n type do not form typical spherical micelles but bilayer structures probably exist in these solutions. The micelles present in the solutions influence the dynamics of adsorption drastically. Moreover, the obtained results indicated that the compounds with especially high biological activity form

Adsorptive removal of selected pharmaceuticals by mesoporous silica SBA-15.

PubMed

Bui, Tung Xuan; Choi, Heechul

2009-09-15

The removal of five selected pharmaceuticals, viz., carbamazepine, clofibric acid, diclofenac, ibuprofen, and ketoprofen was examined by batch sorption experiments onto a synthesized mesoporous silica SBA-15. SBA-15 was synthesized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N(2) adsorption-desorption measurement, and point of zero charge (PZC) measurement. Pharmaceutical adsorption kinetics was rapid and occurred on a scale of minutes, following a pseudo-second-order rate expression. Adsorption isotherms were best fitted by the Freundlich isotherm model. High removal rates of individual pharmaceuticals were achieved in acidic media (pH 3-5) and reached 85.2% for carbamazepine, 88.3% for diclofenac, 93.0% for ibuprofen, 94.3% for ketoprofen, and 49.0% for clofibric acid at pH 3 but decreased with increase in pH. SBA-15 also showed high efficiency for removal of a mixture of 5 pharmaceuticals. Except for clofibric acid (35.6%), the removal of pharmaceuticals in the mixture ranged from 75.2 to 89.3%. Based on adsorption and desorption results, the mechanism of the selected pharmaceuticals was found to be a hydrophilic interaction, providing valuable information for further studies to design materials for the purpose. The results of this study suggest that mesoporous-silica-based materials are promising adsorbents for removing pharmaceuticals from not only surface water but also wastewater of pharmaceutical industrial manufactures.

Novel hydrophobic PDVB/R-SiO2 for adsorption of volatile organic compounds from highly humid gas stream.

PubMed

Lu, Han-feng; Cao, Jie-jing; Zhou, Ying; Zhan, De-li; Chen, Yin-fei

2013-11-15

A novel organic-inorganic hydrophobic polydivinylbenzene-silica adsorbent (PDVB/R-SiO2) was successfully prepared by introducing a specific amount of divinylbenzene and solvent (i.e., tetrahydrofuran) to SiO2pores and initiating polymerization under solvothermal conditions. New smaller structures and surface areas were formed in the SiO2 pores. The PDVB/R-SiO2-0.5 samples exhibited a bimodal pore size distribution with both SiO2 micropores/mesopores (0.5-2.0 nm) and mesopores (2.0-5.0 nm). The surface areas increased from 116 m(2)/g (SiO2) to 246 m(2)/g. The breakthrough curves of toluene adsorption indicated that the amount adsorbed on PDVB/R-SiO2-0.5 was 12 times higher than that on SiO2. The highly humid environment exhibited no effect on adsorption because the surface of PDVB was functionalized. The adsorbed toluene was easily desorbed in hot N2 stream at 100 °C. After 10 adsorption-desorption cycles, PDVB/R-SiO2-0.5 continued exhibiting excellent adsorption, indicating superior structural and regeneration abilities. Copyright © 2013 Elsevier B.V. All rights reserved.

DFT simulation on H2 adsorption over Ni-decorated defective h-BN nanosheets

NASA Astrophysics Data System (ADS)

Zhou, Xuan; Chu, Wei; Zhou, Yanan; Sun, Wenjing; Xue, Ying

2018-05-01

Nickel doped defective h-BN nanosheets and their potential application on hydrogen storage were explored by density functional theory (DFT) calculation. Three types of defective h-BN (SW defect, VB and VN substrates) were modeled. In comparison with the SW defect, the B or N vacancy can improve the interaction between Ni atom and h-BN nanosheet strikingly. Furthermore, the Ni-doped SW defect sheet shows chemisorption on H2 molecules, and the Hsbnd H bond is partially dissociated. While on the VB sheet, Ni adatom interacts with H2 in the range of physisorption. However, the Ni-functionalized VN sheet exhibits a desirable adsorption on H2, and the corresponding energy varies from -0.40 to -0.51 eV, which is favorable for H2 adsorption and release at ambient conditions. As a result, the VN substrate is expected to a desirable support for H2 storage. Our work provides an insight into H2 storage on Ni-functionalized defective h-BN monolayer.

Reactive adsorption of SO2 on activated carbons with deposited iron nanoparticles.

PubMed

Arcibar-Orozco, Javier A; Rangel-Mendez, J Rene; Bandosz, Teresa J

2013-02-15

The effect of iron particle size anchored on the surface of commercial activated carbon on the removal of SO(2) from a gas phase was studied. Nanosize iron particles were deposited using forced hydrolysis of FeCl(3) with or without H(3)PO(4) as a capping agent. Dynamic adsorption experiments were carried out on either dry or pre-humidified materials and the adsorption capacities were calculated. The surface of the initial and exhausted materials was extensively characterized by microscopic, porosity, thermogravimetric and surface chemistry. The results indicate that the SO(2) adsorption capacity increased two and half times after the prehumidification process owing to the formation of H(2)SO(4) in the porous system. Iron species enhance the SO(2) adsorption capacity only when very small nanoparticles are deposited on the pore walls as a thin layer. Large iron nanoparticles block the ultramicropores decreasing the accessibility of the active sites and consuming oxygen that rest adsorption centers for SO(2) molecules. Iron nanoparticles of about 3-4 nm provide highly dispersed adsorption sites for SO(2) molecules and thus increase the adsorption capacity of about 80%. Fe(2)(SO(4))(3) was detected on the surface of exhausted samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

PubMed

Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

2015-01-01

Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants. Copyright © 2014. Published by Elsevier B.V.

Adsorption characteristics of nano-TiO2 onto zebrafish embryos and its impacts on egg hatching.

PubMed

Shih, Yu-Jen; Su, Chia-Chi; Chen, Chiu-Wen; Dong, Cheng-Di; Liu, Wen-Sheng; Huang, C P

2016-07-01

The characteristics of nanoparticles (NPs) uptake may fundamentally alter physicochemical effects of engineered NPs on aquatic organisms, thereby yielding different ecotoxicology assessment results. The adsorption behavior of nano-TiO2 (P-25) on zebrafish embryos in Holtfreter's medium (pH 7.2, I ∼ 7.2 × 10(-2) M) and the presence of sodium alginate (100 mg/L) as dispersant was investigated. Zebrafish embryos (total 100) were exposed to nano-TiO2 at different concentrations (e.g., 0, 10, 20, 60, 120 mg/L) in batch-mode assay. The adsorption capacity of nano-TiO2 on fish eggs was determined by measuring the Ti concentration on the egg surface using ICP-OES analysis. Results showed that the adsorption capacity increased rapidly in the first hour, and then declined to reach equilibrium in 8 h. The adsorption characteristics was visualized as a three-step process of rapid initial layer formation, followed by break-up of aggregates and finally rearrangement of floc structures; the maximum adsorption capacity was the sum of an inner rigid layers of aggregates of 0.81-0.84 μg-TiO2/#-egg and an outer softly flocculated layers of 1.01 μg-TiO2/#-egg. The Gibbs free energy was 543.29-551.26 and 100.75 kJ/mol, respectively, for the inner-layer and the outer-layer aggregates. Adsorption capacity at 0.5-1.0 μg-TiO2/#-egg promoted egg hatching; but hatching was inhibited at higher adsorption capacity. Results clearly showed that the configuration of TiO2 aggregates could impact the hatching efficiency of zebrafish embryos. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surface complexation model for multisite adsorption of copper(II) onto kaolinite

NASA Astrophysics Data System (ADS)

Peacock, Caroline L.; Sherman, David M.

2005-08-01

We measured the adsorption of Cu(II) onto kaolinite from pH 3-7 at constant ionic strength. EXAFS spectra show that Cu(II) adsorbs as (CuO 4H n) n-6 and binuclear (Cu 2O 6H n) n-8 inner-sphere complexes on variable-charge ≡AlOH sites and as Cu 2+ on ion exchangeable ≡X-H + sites. Sorption isotherms and EXAFS spectra show that surface precipitates have not formed at least up to pH 6.5. Inner-sphere complexes are bound to the kaolinite surface by corner-sharing with two or three edge-sharing Al(O,OH) 6 polyhedra. Our interpretation of the EXAFS data are supported by ab initio (density functional theory) geometries of analog clusters simulating Cu complexes on the {110} and {010} crystal edges and at the ditrigonal cavity sites on the {001}. Having identified the bidentate (≡AlOH) 2Cu(OH) 20, tridentate (≡Al 3O(OH) 2)Cu 2(OH) 30 and ≡X-Cu 2+ surface complexes, the experimental copper(II) adsorption data can be fit to the reactions

Water adsorption constrained Frenkel-Halsey-Hill adsorption activation theory: Montmorillonite and illite

NASA Astrophysics Data System (ADS)

Hatch, Courtney D.; Greenaway, Ann L.; Christie, Matthew J.; Baltrusaitis, Jonas

2014-04-01

Fresh mineral aerosol has recently been found to be effective cloud condensation nuclei (CCN) and contribute to the number of cloud droplets in the atmosphere due to the effect of water adsorption on CCN activation. The work described here uses experimental water adsorption measurements on Na-montmorillonite and illite clay to determine empirical adsorption parameters that can be used in a recently derived theoretical framework (Frenkel-Halsey-Hill Activation Theory, FHH-AT) that accounts for the effect of water adsorption on CCN activation. Upon fitting the Frenkel-Halsey-Hill (FHH) adsorption model to water adsorption measurements, we find FHH adsorption parameters, AFHH and BFHH, to be 98 ± 22 and 1.79 ± 0.11 for montmorillonite and 75 ± 17 and 1.77 ± 0.11 for illite, respectively. The AFHH and BFHH values obtained from water adsorption measurements differ from values reported previously determined by applying FHH-AT to CCN activation measurements. Differences in FHH adsorption parameters were attributed to different methods used to obtain them and the hydratable nature of the clays. FHH adsorption parameters determined from water adsorption measurements were then used to calculate the critical super-saturation (sc) for CCN activation using FHH-AT. The relationship between sc and the dry particle diameter (Ddry) gave CCN activation curve exponents (xFHH) of -0.61 and -0.64 for montmorillonite and illite, respectively. The xFHH values were slightly lower than reported previously for mineral aerosol. The lower exponent suggests that the CCN activity of hydratable clays is less sensitive to changes in Ddry and the hygroscopicity parameter exhibits a broader variability with Ddry compared to more soluble aerosols. Despite the differences in AFHH, BFHH and xFHH, the FHH-AT derived CCN activities of montmorillonite and illite are quite similar to each other and in excellent agreement with experimental CCN measurements resulting from wet-generated clay aerosol

Effect of heat treatment on the efficient adsorption of Cd2+ ions by nanosized SiO2, TiO2 and their composite

NASA Astrophysics Data System (ADS)

Waseem, M.; Muntha, S. T.; Nawaz, M.; Rehman, W.; Rehman, M. A.; Shah, K. H.

2017-01-01

In this study nanosized SiO2, TiO2 and their composite were synthesized via the oil in water (o/w) microemulsion method and their thermal treatment was performed at 378, 573, 973 and 1273 K. The physicochemical properties of the samples were studied by surface area measurements, scanning electron microscopy, Fourier transform infra-red spectroscopy and x-ray diffraction analysis. The Brunauer, Emmett and Teller surface area of all the adsorbents increases from 378 to 573 K, while it decreases upon further heat treatment. The average crystallite size decreases by heating the samples from 378 to 573 K while it increases when the adsorbents were thermally heat treated at 973 and 1273 K. The intensity of a few IR bands was reduced along with the disappearance of most of the bands at higher temperatures. The appearance of the beta-cristobalite phase in SiO2 and the rutile phase in TiO2 was confirmed from the diffraction data. The heat treated samples were subjected to preliminary adsorption of Cd2+ ions from aqueous solution at 293 K. Based on the preliminary adsorption experiments, SiO2, TiO2 and their composite heat treated at 573 K were selected for further adsorption studies. The Langmuir model was found to be fitted to the sorption data of TiO2 and the nanocomposite while the adsorption of Cd2+ ions by the SiO2 nanoparticles was explained well based on the Freundlich model. In the present study, the maximum Cd2+ adsorption capacity of SiO2, TiO2 and their composite was found to be 79.72, 98.55 and 107.17 mg g-1, respectively. The q m and K f values obtained in the present study were found to be far better than those reported in the literature. The negative values of ΔG confirm the feasibility of an adsorption process at higher temperatures. The positive values of ΔH and ΔS represent the endothermic and physical nature of the adsorption process with the increased randomness of Cd2+ ions at the solid/solution interface.

Adsorption of zwitterionic surfactant on limestone measured with high-performance liquid chromatography: micelle-vesicle influence.

PubMed

Nieto-Alvarez, David Aaron; Zamudio-Rivera, Luis S; Luna-Rojero, Erick E; Rodríguez-Otamendi, Dinora I; Marín-León, Adlaí; Hernández-Altamirano, Raúl; Mena-Cervantes, Violeta Y; Chávez-Miyauchi, Tomás Eduardo

2014-10-21

Herein is presented a new methodology to determine the static adsorption of a zwitterionic surfactant on limestone in three different aqueous media [high-performance liquid chromatography (HPLC) water, seawater, and connate water] with the use of HPLC at room temperature and 70 °C. The results showed that, in both HPLC water and seawater, the surfactant adsorption followed a monolayer Langmuir tendency. In contrast, for connate water, the surfactant presented a new adsorption profile, characterized by two regions: (i) At surfactant concentrations below 1500 mg L(-1), an increase of adsorption is observed as the amount of divalent cations increases in the aqueous media. (ii) At surfactant concentrations above 1500 mg L(-1), the adsorption decreases because the equilibrium, monomer ⇆ micelle ⇆ vesicle, is shifted to the formation of vesicles, giving as a result a decrease in the concentration of monomers, thus reducing the interaction between the surfactant and the rock, and therefore, lower adsorption values were obtained. The behavior of the surfactant adsorption under different concentrations of divalent cations was well-described by the use of a new modified Langmuir model: (dΓ/dt)ads = k(ads)c(Γ∞ - Γ) - k(cmc)(c - c(cmc))(n)ΓH(c - c(cmc)). It was also observed that, as the temperature increases, the adsorption is reduced because of the exothermic nature of the adsorption processes.

Adsorption of Anionic, Cationic and Nonionic Surfactants on Carbonate Rock in Presence of ZrO 2 Nanoparticles

NASA Astrophysics Data System (ADS)

Esmaeilzadeh, Pouriya; Bahramian, Alireza; Fakhroueian, Zahra

The adsorption of surfactants at the solid-water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19 nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.

Physicochemical factors affecting ethanol adsorption by activated carbon.

PubMed

Bradley, K J; Hamdy, M K; Toledo, R T

1987-03-01

Powder and granular activated charcoal were evaluated for ethanol adsorptivity from aqueous mixtures using an adsorption isotherm. Ethanol adsorption capacity was more pronounced at 25 degrees C as compared to 5, 15, and 40 degrees C. When pH of the ethanol-buffer mixture (0.09 ionic strength) was changed from acidic (2.3) to neutral and then to alkaline (11.2), ethanol adsorption was decreased. Increasing ionic strength of the ethanol-buffer mixtures from 0.05 to 0.09 enhanced ethanol adsorption but a further increase to 0.14 showed no significant effect. Ethanol adsorption was more efficient from an aqueous ethanol mixture as compared to semidefined and nondefined fermentation worts, respectively. Heating granular charcoal to 400 degrees C for 1 h and 600 degrees C for 3 h in N(2) increased ethanol adsorptivity and heating to 1000 degrees C (1 h) in CO(2) decreased it when ethanol was removed from dilute solutions by simple pass adsorption in a carbon packed column. Granular charcoal was superior to powdered charcoal and an inverse relationship was noted between the weight of the granular carbon bed in the column and ethanol adsorbed/g carbon. Decreasing the column feed flow rate from 7.5 to 2.0 L aqueous ethanol/min increased the adsorption rate.

Identification of adsorption sites in Cu-BTC by experimentation and molecular simulation.

PubMed

García-Pérez, Elena; Gascón, Jorge; Morales-Flórez, Víctor; Castillo, Juan Manuel; Kapteijn, Freek; Calero, Sofía

2009-02-03

The adsorption of several quadrupolar and nonpolar gases on the Metal Organic Framework Cu-BTC has been studied by combining experimental measurements and Monte Carlo simulations. Four main adsorption sites for this structure have been identified: site I close to the copper atoms, site I' in the bigger cavities, site II located in the small octahedral cages, and site III at the windows of the four open faces of the octahedral cage. Our simulations identify the octahedral cages (sites II and III) and the big cages (site I') as the preferred positions for adsorption, while site I, near the copper atoms, remains empty over the entire range of pressures analyzed due to its reduced accessibility. The occupation of the different sites for ethane and propane in Cu-BTC proceeds similarly as for methane, and shows small differences for O2 and N2 that can be attributed to the quadrupole moment of these molecules. Site II is filled predominantly for methane (the nonpolar molecule), whereas for N2, the occupation of II and I' can be considered almost equivalent. The molecular sitting for O2 shows an intermediate behavior between those observed for methane and for N2. The differences between simulated and experimental data at elevated temperatures for propane are tentatively attributed to a reversible change in the lattice parameters of Cu-BTC by dehydration and by temperature, blocking the accessibility to site III and reducing that to site I'. Adsorption parameters of the investigated molecules have been determined from the simulations.

UTSA-16 Growth within 3D-Printed Co-Kaolin Monoliths with High Selectivity for CO2/CH4, CO2/N2, and CO2/H2 Separation.

PubMed

Lawson, Shane; Al-Naddaf, Qasim; Krishnamurthy, Anirduh; Amour, Marc St; Griffin, Connor; Rownaghi, Ali A; Knox, James C; Rezaei, Fateme

2018-06-06

Honeycomb monoliths loaded with metal-organic frameworks (MOFs) are highly desirable adsorption contactors because of their low-pressure drop, rapid mass-transfer kinetics, and high-adsorption capacity. Moreover, three-dimensional (3D)-printing technology renders direct material modification a realistic and economic prospect. In this study, 3D printing was utilized to impregnate kaolin-based monolith with UTSA-16 metal formation precursor (Co), whereupon an internal growth was facilitated via a solvothermal synthesis approach. The cobalt weight loading in the kaolin support was varied systematically to optimize the MOF growth while retaining monolith mechanical integrity. The obtained UTSA-16 monolith with 90 wt % loading exhibited similar textural features and adsorption characteristics to its powder analogue while improving upon structural integrity. In comparison to previously developed 3D-printed UTSA-16 monoliths, the UTSA-16-kaolin monolith not only showed higher MOF loading but also higher compression stress, indicative of its robust structure. Furthermore, the 3D-printed UTSA-16-kaolin monolith displayed a comparable CO 2 adsorption capacity to the UTSA-16 powder (3.1 vs 3.5 mmol/g at 25 °C and 1 bar), which was proportional to its loading. Selectivity values of 49, 238, and 3725 were obtained for CO 2 /CH 4 , CO 2 /N 2 , and CO 2 /H 2 , respectively, demonstrating good separation potential of the 3D-printed MOF monolith for various gas mixtures, as determined by both equilibrium and dynamic adsorption measurements. Overall, this study provides a novel route for the fabrication of UTSA-16-loaded monoliths, which demonstrate both high MOF loading and mechanical integrity that could be readily applied to various CO 2 capture applications.

Pb2+ and Zn2+ adsorption by a natural aluminum- and iron-bearing surface coating on an aquifer sand

USGS Publications Warehouse

Coston, J.A.; Fuller, C.C.; Davis, J.A.

1995-01-01

Pb2+ and Zn2+ adsorption was studied in batch experiments with material collected from a shallow, unconfined aquifer of glacial outwash sand and gravel in Falmouth, Massachusetts, USA. The aquifer solids contain primarily quartz with minor amounts of alkali feldspars and ferromagnetic minerals. Pb2+ and Zn2+ adsorption experiments with various grain size and mineral fractions of the aquifer solids showed that: 1) Zn2+ adsorption was independent of grain size, but Pb2+ was preferentially adsorbed by the <64 ??m size fraction and 2) Pb2+ adsorption decreased after removal of the paramagnetic, Fe-bearing mineral fraction, but Zn2+ adsorption was unaffected. Pb2+ and Zn2+ adsorption on mineral separates from the aquifer material compared with metal adsorption on a purified quartz powder indicated that adsorption of both metal ions was dominated by coatings on the quartz fraction of the sediment. Characterization of the coatings by AES, SEM-EDS, and TOF-SIMS demonstrated that the natural quartz grains were extensively coated with Al- and Fe-bearing minerals of variable composition. -from Authors

[Adsorption and removal of gas-phase Hg(0) over a V2O5/AC catalyst in the presence of SO2].

PubMed

Wang, Jun-wei; Yang, Jian-li; Liu, Zhen-yu

2009-12-01

The adsorption and removal behaviors of gas-phase Hg(0) over V2O5/AC and AC were studied under a simulated flue gas (containing N2, SO2, O2) in a fixed-bed reactor. The influences of the V2O5, loading, SO2 concentration and adsorption temperature on Hg0 adsorption were investigated. The speciation of mercury adsorbed was determined by X-ray photoelectron spectroscopy (XPS). It was found that the V2O5/AC catalyst has a much higher capability than AC for Hg(0) adsorption and removal, mainly because of the catalytic oxidation activity of V2O5. The Hg(0) adsorption capability depends on the V2O5 content of the V2O5/AC catalyst. The amounts of mercury adsorbed increase from 75.9 microg x g(-1) to 89.6 microg x g(-1) (in the absence of O2) and from 115.9 microg x g(-1) to 185.5 microg x g(-1) (in the presence of O2) as the V2O5 loading increases from 0.5% to 1.0%, which are much higher than those over AC under the same conditions (9.6 microg x g(-1) and 23.3 microg x g(-1)). SO2 in the flue gas enhances Hg(0) adsorption over the V2O5/AC catalyst, which is due to the reaction of SO2 and Hg(0) on V2O3/AC. But as the SO2 concentration increases from 500 x 10(-6) to 2000 x 10(-6), the amount of mercury adsorbed has only a slight increase. The optimal temperature for Hg(0) adsorption over the V2O5/AC catalyst is around 150 degrees C, at which the amounts of mercury adsorbed are up to 98.5 microg x g(-1) (in the absence of O2) and 187.7 microg x g(-1) (in the presence of O2). The XPS results indicate the formation of Hg(0) and HgSO4 on the surface of the V2O5/AC catalyst, which confirms the role of V2O5 and SO2.

Evaluating metal-organic frameworks for post-combustion carbon dioxide capture via temperature swing adsorption

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

Mason, JA; Sumida, K; Herm, ZR

Two representative metal-organic frameworks, Zn4O(BTB)(2)(BTB3- = 1,3,5-benzenetribenzoate; MOF-177) and Mg-2(dobdc) (dobdc(4-) = 1,4-dioxido-2,5-benzenedicarboxylate; Mg-MOF-74, CPO-27-Mg), are evaluated in detail for their potential use in post-combustion CO2 capture via temperature swing adsorption (TSA). Low-pressure single-component CO2 and N-2 adsorption isotherms were measured every 10 degrees C from 20 to 200 degrees C, allowing the performance of each material to be analyzed precisely. In order to gain a more complete understanding of the separation phenomena and the thermodynamics of CO2 adsorption, the isotherms were analyzed using a variety of methods. With regard to the isosteric heat of CO2 adsorption, Mg-2(dobdc) exhibits anmore » abrupt drop at loadings approaching the saturation of the Mg2+ sites, which has significant implications for regeneration in different industrial applications. The CO2/N-2 selectivities were calculated using ideal adsorbed solution theory (IAST) for MOF-177, Mg-2(dobdc), and zeolite NaX, and working capacities were estimated using a simplified TSA model. Significantly, MOF-177 fails to exhibit a positive working capacity even at regeneration temperatures as high as 200 degrees C, while Mg-2(dobdc) reaches a working capacity of 17.6 wt% at this temperature. Breakthrough simulations were also performed for the three materials, demonstrating the superior performance of Mg-2(dobdc) over MOF-177 and zeolite NaX. These results show that the presence of strong CO2 adsorption sites is essential for a metal-organic framework to be of utility in post-combustion CO2 capture via a TSA process, and present a methodology for the evaluation of new metal-organic frameworks via analysis of single-component gas adsorption isotherms.« less

Mechanism of Preferential Adsorption of SO 2 into Two Microporous Paddle Wheel Frameworks M(bdc)(ted) 0.5

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

Tan, Kui; Canepa, Pieremanuele; Gong, Qihan

The adsorption of a corrosive gas, SO 2, into microporous pillared paddle-wheel frameworks M(bdc)(ted) 0.5 [M = Ni, , Zn; bdc = 1,4-benzenedicarboxylate; ted=triethylenediamine] is studied by volumetric adsorption measurements and a combination of in-situ infrared spectroscopy and ab initio density functional theory (DFT) calculations. The uptake of SO 2 in M(bdc)(ted) 0.5 at room temperature is quite significant, 9.966 mol kg -1(63.8%) at room temperature/1.132 bar, which represents the highest SO 2 uptake so far observed. Two different adsorption species are identified by infrared spectroscopy: one is typical physisorbed SO 2 species, characterized by a modest red shift ofmore » S-O stretching bands (36 cm -1 for νas and 7 cm -1 for νs); the other characterized by adsorption bands at 1242 and 1105cm -1 and by a much higher (~150°C) temperature to completely remove. Theoretical calculations including van der Waals interactions (based on vdW-DF) indicate that the adsorption geometry of SO 2 involves one molecule bonding of its sulfur atom to the oxygen atom of the paddle-wheel building unit and its two oxygen atoms to the C-H groups of the organic linkers by formation of hydrogen bonds. Such a configuration results in a large distortion of benzene rings, which is consistent with the experimentally observed shift of the ring deformation mode. The simulated frequency shift of the SO 2 stretching bands by vdW-DF is in excellent agreement with spectroscopically measured value of physisorbed SO 2. The IR absorptions at 1242 and 1105 cm -1 also suggest a stronger adsorption configuration, previously observed in SO 4-like species involving two oxygen atoms of the paddle wheel building units. The adsorption configurations of SO 2 into M(bdc)(ted) 0.5 derived by infrared spectroscopy and vdW-DF calculations provide the understanding necessary to develop industrial processes for SO 2 removal using microporous paddle-wheel frameworks materials.« less

Water Adsorption on Clean and Defective Anatase TiO2 (001) Nanotube Surfaces: A Surface Science Approach.

PubMed

Kenmoe, Stephane; Lisovski, Oleg; Piskunov, Sergei; Bocharov, Dmitry; Zhukovskii, Yuri F; Spohr, Eckhard

2018-05-31

We use ab initio molecular dynamics simulations to study the adsorption of thin water films with 1 and 2 ML coverage on anatase TiO 2 (001) nanotubes. The nanotubes are modeled as 2D slabs, which consist of partially constrained and partially relaxed structural motifs from nanotubes. The effect of anion doping on the adsorption is investigated by substituting O atoms with N and S impurities on the nanotube slab surface. Due to strain-induced curvature effects, water adsorbs molecularly on defect-free surfaces via weak bonds on Ti sites and H bonds to surface oxygens. While the introduction of an S atom weakens the interaction of the surface with water, which adsorbs molecularly, the presence of an N impurity renders the surface more reactive to water, with a proton transfer from the water film and the formation of an NH group at the N site. At 2 ML coverage, a further surface-assisted proton transfer takes place in the water film, resulting in the formation of an OH - group and an NH 2 + cationic site on the surface.

Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution.

PubMed

Kazak, Omer; Eker, Yasin Ramazan; Akin, Ilker; Bingol, Haluk; Tor, Ali

2017-10-01

This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH pzc ) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L) -1/n ] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.

The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

PubMed

Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

2016-01-01

Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p < 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p < 0.05). The desorption percentages of Pb(2+) and Cd(2+) were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.

High-Precision Measurements of 15N15N, 14N15N, and 14N2 in N2 and Potential Applications to Oceanic Nitrogen Cycle Research

NASA Astrophysics Data System (ADS)

Li, S.; Yeung, L.; Young, E. D.; Ostrom, N. E.; Haslun, J. A.

2016-02-01

The balance of nitrogen fixation and nitrogen loss in the oceans is uncertain. For example, anaerobic ammonia oxidation could account for 50% or more of marine N2 production, although its global importance is still poorly known. Isotopic ratios in fixed nitrogen species (e.g., δ15N and δ18O values of NO2- and NO3-) are widely used to trace preservation and removal of N-bearing compounds and/or isotopic variations of their different sources. However, these approaches in general probe only one side of the nitrogen mass balance—the "fixed" nitrogen reservoir—so they offer few constraints on the ultimate loss of nitrogen from that pool as N2. The rare isotopologue ratio 15N15N/14N2 in N2may provide information about those nitrogen-loss processes directly. We will report the first measurements of Δ30 (the abundance of 15N15N relative to that predicted by chance alone), made on a unique high-resolution mass spectrometer (the Nu Instruments Panorama), and we will discuss the potential utility of Δ30 as an independent tracer of the nitrogen cycle. The parameter Δ30 is insensitive to the bulk 15N/14N isotopic ratio of the reservoir; instead, it reflects isotopic ordering in N2, which is altered when N-N bonds are made or broken. Our preliminary measurements of N2 from denitrifying soils and pure cultures of denitrifiers indicate large kinetic isotopic effects during N-N bond formation that favor 15N15N production during denitrification. We also observed a nonstochastic excess of 15N15N in tropospheric N2 [Δ30 = +19.05 ± 0.12‰ (1σ)]. This excess likely comes from fixed-nitrogen loss processes in the biosphere. Variations in Δ30 of N2 from pure culture experiments (+16.96 to +18.95‰) probably reflect the different isotopic signatures of the enzymes that catalyze denitrification. So, enzyme-specific Δ30 values of dissolved N2 should provide information about the importance of different biochemical pathways of fixed-nitrogen loss (e.g., denitrification vs

Neutron scattering measurements of carbon dioxide adsorption in pores within the Marcellus Shale: Implications for sequestration

USGS Publications Warehouse

Stefanopoulos, Konstantinos L.; Youngs, Tristan G. A.; Sakurovs, Richard; Ruppert, Leslie F.; Bahadur, Jitendra; Melnichenko, Yuri B.

2017-01-01

Shale is an increasingly viable source of natural gas and a potential candidate for geologic CO2sequestration. Understanding the gas adsorption behavior on shale is necessary for the design of optimal gas recovery and sequestration projects. In the present study neutron diffraction and small-angle neutron scattering measurements of adsorbed CO2 in Marcellus Shale samples were conducted on the Near and InterMediate Range Order Diffractometer (NIMROD) at the ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory along an adsorption isotherm of 22 °C and pressures of 25 and 40 bar. Additional measurements were conducted at approximately 22 and 60 °C at the same pressures on the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument at Oak Ridge National Laboratory. The structures investigated (pores) for CO2 adsorption range in size from Å level to ∼50 nm. The results indicate that, using the conditions investigated densification or condensation effects occurred in all accessible pores. The data suggest that at 22 °C the CO2 has liquid-like properties when confined in pores of around 1 nm radius at pressures as low as 25 bar. Many of the 2.5 nm pores, 70% of 2 nm pores, most of the <1 nm pores, and all pores <0.25 nm, are inaccessible or closed to CO2, suggesting that despite the vast numbers of micropores in shale, the micropores will be unavailable for storage for geologic CO2 sequestration.

From aggregative adsorption to surface depletion: Aqueous systems of C nE m amphiphiles at hydrophilic surfaces

DOE PAGES

Rother, Gernot; Müter, Dirk; Bock, Henry; ...

2017-03-27

Adsorption of a short-chain nonionic amphiphile (C 6E 3) at the surface of mesoporous silica glass (CPG-10) was studied by a combination of adsorption measurements and mesoscale simulations. Adsorption measurements covering a wide composition range of the C 6E 3 + water system show that no adsorption occurs up to the critical micelle concentration (cmc), at which a sharp increase of adsorption is observed that is attributed to ad-micelle formation at the pore walls. Intriguingly, as the concentration is increased further, the surface excess of the amphiphile begins to decrease and eventually becomes negative, which corresponds to preferential adsorption ofmore » water rather than amphiphile at high amphiphile concentrations. The existence of such a surface-azeotropic point has not previously been reported in the surfactant adsorption field. Dissipative particle dynamics (DPD) simulations were performed to reveal the structural origin of this transition from aggregative adsorption to surface depletion. Finally, the simulations indicate that this transition can be attributed to the repulsive interaction between head groups, causing amphiphilic depletion in the region around the corona of the surface micelles.« less

Utilization of Natural Zeolite from Ponorogo and Purworejo for Naphthol Substance Adsorption

NASA Astrophysics Data System (ADS)

Imandiani, Sundus; Indira, Christine; Johan, Anthony; Budiyono

2018-02-01

Indonesia has many zeolite producing areas yet untapped. Researchers developed the utilization of natural zeolites useful for the adsorption of naphthol dyes commonly found in batik waste. In this study researchers used natural zeolites from Purworejo and Ponorogo that are activated using hydrochloric acid that is used for adsorption. The purpose of this research is to know the effect of natural zeolite activation from Ponorogo and Purworejo on the effectiveness of adsorption of naphthol dyes widely used in batik industry. Natural zeolite was activated using HCl concentration of 1.3N; 1.8N; 3.2N; and 3.9N for 60 minutes. The methods are preparation of natural zeolite from Purworejo and Ponorogo, dealumination using hydrochloric acid, adsorption process of naphthol dyes using activated zeolite, and test of adsorption result with uv-vis spectrophotometry. The test results showed that the higher HCl concentration will increase adsorption capacity. This can be known from the concentration of naphthol dye which decreased both using natural zeolite Ponorogo and Purworejo. While the effectiveness of adsorption shows natural zeolite Purworejo has a greater adsorption capacity than Ponorogo with optimum conditions of dealumination using concentration HCl 3,9N.

Surface interaction of H2S, SO2, and SO3 on fullerene-like gallium nitride (GaN) nanostructure semiconductor

NASA Astrophysics Data System (ADS)

Salimifard, M.; Rad, A. Shokuhi; Mahanpoor, K.

2017-10-01

Density functional theory (DFT) using MPW1PW91 and B3LYP hybrid functionals was utilized for quantum-based investigations of three major sulfur compounds (H2S, SO2, and SO3) adsorption onto fullerene-like Ga12N12 nanocluster. All chemicals showed high chemisorption with the order of SO3>SO2>>H2S. Results of charge analysis showed that during adsorption, transfer of charge is from H2S to nanocluster while reverse direction of charge transfer is found for SO2 and SO3 molecules. Partial dissociation is found for adsorbates especially for SO2 and SO3 molecules. Results of thermochemistry analysis show negative values for enthalpy and Gibbs free energy of adsorption, confirming exothermic spontaneous process. Analysis of frontier molecular orbital (FMO) showed important role of orbital hybridizing towards formation of new bonds upon adsorption. As a result, we introduce Ga12N12 nanocluster as a strong adsorbent for sulfur compounds.

Measuring N2 Pressure Using Cyanobacteria Discipline: Geomicrobiology

NASA Technical Reports Server (NTRS)

Silverman, Shaelyn N.; Kopf, Sebastian; Gordon, Richard; Bebout, Brad M.; Som, Sanjoy

2017-01-01

The evolution of Earth's atmosphere has been governed by biological evolution. Dinitrogen (N2) has been a major constituent of Earth's atmosphere throughout the planet's history, yet only a few constraints exist for the partial pressure of N2 (pN2). In this study we evaluate two new potential proxies for pN2: the physical spacing between heterocysts and the isotopic signature of nitrogen fixation in filamentous cyanobacteria. Heterocyst-forming filamentous cyanobacteria are some of the oldest photosynthetic microorganisms on Earth, and debated fossilized specimens have been found in sedimentary rocks as old as 2 Ga. These organisms overcome nitrogen limitation in their aqueous environment through cellular differentiation along their filaments. The specialized cells that develop, known as heterocysts, fix the nitrogen and laterally distribute it to neighboring cells along the filaments. Because the concentration of the dissolved N2 available to the filaments correlates directly with pN2, any preservable physiological response of the organism to the changed N2 availability constitutes a potential proxy for pN2. In the laboratory, we have examined how pN2 is reflected in the heterocyst spacing pattern and in the isotopic signature of nitrogen fixation by subjecting the representative species Anabaena cylindrica and Anabaena variabilis to different N2 partial pressures during growth at constant temperature and lighting (in media free of combined nitrogen). We show experimentally that the distance between heterocysts and the nitrogen isotope fractionation measured in bulk biomass reflect the pN2 experienced by Anabaena cylindrica. Current work is investigating these responses in Anabaena variabilis. When heterocystous cyanobacteria fossilize, these morphological and isotopic signatures should preserve information about pN2 at that time. Application of this relationship to the rock record may provide a paleoproxy to complement the two existing geobarometers.

Measurement of 235U(n,n'γ) and 235U(n,2nγ) reaction cross sections

NASA Astrophysics Data System (ADS)

Kerveno, M.; Thiry, J. C.; Bacquias, A.; Borcea, C.; Dessagne, P.; Drohé, J. C.; Goriely, S.; Hilaire, S.; Jericha, E.; Karam, H.; Negret, A.; Pavlik, A.; Plompen, A. J. M.; Romain, P.; Rouki, C.; Rudolf, G.; Stanoiu, M.

2013-02-01

The design of generation IV nuclear reactors and the studies of new fuel cycles require knowledge of the cross sections of various nuclear reactions. Our research is focused on (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data for reactions and isotopes of interest for transmutation or advanced reactors. The present work studies the 235U(n,n'γ) and 235U(n,2nγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments were performed with the Geel electron linear accelerator GELINA, which delivers a pulsed white neutron beam. The time characteristics enable measuring neutron energies with the time-of-flight (TOF) technique. The neutron induced reactions [in this case inelastic scattering and (n,2n) reactions] are identified by on-line prompt γ spectroscopy with an experimental setup including four high-purity germanium (HPGe) detectors. A fission ionization chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods are presented and the model calculations performed with the TALYS-1.2 code are discussed.

Synthesis and Electrospraying of Nanoscale MOF (Metal Organic Framework) for High-Performance CO2 Adsorption Membrane

NASA Astrophysics Data System (ADS)

Wahiduzzaman; Allmond, Kelsey; Stone, John; Harp, Spencer; Mujibur, Khan

2017-01-01

We report the sonochemical synthesis of MOF (metal organic framework) nanoparticles of 30-200 nm in size and electrospraying of those particles on electrospun nanofibers to process a MOF-attached nanofibrous membrane. This membrane displayed significant selectivity towards CO2 and capacity of adsorbing with 4000-5000 ppm difference from a mixed gas flow of 1% CO2 and 99% N2. Applying ultrasonic waves during the MOF synthesis offered rapid dispersion and formation of crystalline MOF nanoparticles in room temperature. The MOF nanoparticles of 100-200 nm in size displayed higher surface area and adsorption capacity comparing to that of 30-60 nm in size. Nanofibrous membrane was produced by electrospinning of MOF blended PAN solution followed by electrospraying of additional MOF nanoparticles. This yielded uniform MOF deposition on nanofibers, occurred due to electrostatic attraction between highly charged nanoparticles and conductive nanofibers. A test bench for real-time CO2 adsorption at room temperature was built with non-dispersive Infrared (NDIR) CO2 sensors. Comparative tests were performed on the membrane to investigate its enhanced adsorption capacity. Three layers of the as-produced membranes displayed CO2 adsorption for approximately 2 h. Thermogravimetric analysis (TGA) of the membrane showed the thermal stability of the MOF and PAN up to 290 and 425 °C, respectively.

Synthesis and Electrospraying of Nanoscale MOF (Metal Organic Framework) for High-Performance CO2 Adsorption Membrane.

PubMed

Wahiduzzaman; Allmond, Kelsey; Stone, John; Harp, Spencer; Mujibur, Khan

2017-12-01

We report the sonochemical synthesis of MOF (metal organic framework) nanoparticles of 30-200 nm in size and electrospraying of those particles on electrospun nanofibers to process a MOF-attached nanofibrous membrane. This membrane displayed significant selectivity towards CO 2 and capacity of adsorbing with 4000-5000 ppm difference from a mixed gas flow of 1% CO 2 and 99% N 2 . Applying ultrasonic waves during the MOF synthesis offered rapid dispersion and formation of crystalline MOF nanoparticles in room temperature. The MOF nanoparticles of 100-200 nm in size displayed higher surface area and adsorption capacity comparing to that of 30-60 nm in size. Nanofibrous membrane was produced by electrospinning of MOF blended PAN solution followed by electrospraying of additional MOF nanoparticles. This yielded uniform MOF deposition on nanofibers, occurred due to electrostatic attraction between highly charged nanoparticles and conductive nanofibers. A test bench for real-time CO 2 adsorption at room temperature was built with non-dispersive Infrared (NDIR) CO 2 sensors. Comparative tests were performed on the membrane to investigate its enhanced adsorption capacity. Three layers of the as-produced membranes displayed CO 2 adsorption for approximately 2 h. Thermogravimetric analysis (TGA) of the membrane showed the thermal stability of the MOF and PAN up to 290 and 425 °C, respectively.

The role of electric field in enhancing separation of gas molecules (H2S, CO2, H2O) on VIB modified g-C3N4 (0 0 1)

NASA Astrophysics Data System (ADS)

Wang, Fang; Li, Penghui; Wei, Shiqian; Guo, Jiaxing; Dan, Meng; Zhou, Ying

2018-07-01

In this study, the first-principles calculations were performed to investigate the adsorption behaviors of gas molecules H2S, CO2 and H2O on Cr, Mo and W modified g-C3N4 (0 0 1) surface. The results show that H2S, CO2 and H2O are physically adsorbed on the pristine g-C3N4, while the adsorption becomes chemisorbed due to the introduction of transition metals which significantly improve the interfacial electron transfer and narrow the band gap of g-C3N4 (0 0 1). Furthermore, it is found that the adsorption behaviors can be greatly influenced by the applied electric field. The adsorption energy is generally arranged in the order of Eads(H2S) > Eads(H2O) > Eads(CO2), and W/g-C3N4 (0 0 1) exhibits the best separation capability. The study could provide a versatile approach to selectively capture and separate the mixed gases in the catalytic reactions by controlling the applied intensity of electric field.

Simutaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

NASA Technical Reports Server (NTRS)

Zent, Aaron P.; Quinn, Richard C.

1995-01-01

The Martian regolith is the most substantial volatile reservoir on the planet; estimates of its adsorbed inventory have been based on simple measurements of the adsorption of either water or CO2 in isolation. Under some conditions, H2O can poison adsorbate surfaces, such that CO2 uptake is greatly reduced. We have made the first measurements of the simultaneous adsorption of CO2 and H2O under conditions appropriate to the Martian regolith and have found that at H2O monolayer coverage above about 0.5, CO2 begins to be displaced into the gas phase. We have developed an empirical expression that describes our co-adsorption data and have applied it to standard models of the Martian regolith. We find that currently, H2O does not substantially displace CO2, implying that the adsorbate inventories previously derived may be accurate, not more than 3-4 kPa (30-40 mbar). No substantial increase in atmospheric pressure is predicted at higher obliquities because high-latitude ground ice buffers the partial pressure of H2O in the pores, preventing high monolayer coverages of H2O from displacing CO2. The peak atmospheric pressure at high obliquity does increase as the total inventory of exchangeable CO2 increases.

Modeling the adsorption of metal ions (Cu 2+, Ni 2+, Pb 2+) onto ACCs using surface complexation models

NASA Astrophysics Data System (ADS)

Faur-Brasquet, Catherine; Reddad, Zacaria; Kadirvelu, Krishna; Le Cloirec, Pierre

2002-08-01

Activated carbon cloths (ACCs), whose efficiency has been demonstrated for microorganics adsorption from water, were here studied in the removal of metal ions from aqueous solution. Two ACCs are investigated, they are characterized in terms of porosity parameters (BET specific surface area, percentage of microporosity) and chemical characteristics (acidic surface groups, acidity constants, point of zero charge). A first part consists in the experimental study of three metal ions removal (Cu 2+, Ni 2+ and Pb 2+) in a batch reactor. Isotherms modeling by Freundlich and Brunauer-Emmett-Teller (BET) equations enables the following adsorption order: Cu 2+>Ni 2+>Pb 2+ to be determined for adsorption capacities on a molar basis. It may be related to adsorbates characteristics in terms of electronegativity and ionic radius. The influence of adsorbent's microporosity is also shown. Adsorption experiments carried out for pH values ranging from 2 to 10 demonstrate: (i) an adsorption occurring below the precipitation pH; (ii) the strong influence of pH, with a decrease of electrostatic repulsion due to the formation of less charged hydrolyzed species coupled with a decrease of activated carbon surface charge as pH increases. The second part focuses on the modeling of adsorption versus the pH experimental data by the diffuse layer model (DLM) using Fiteql software. The model is efficient to describe the system behavior in the pH range considered. Regarding complexation constants, they show the following affinity for ACC: Pb 2+>Cu 2+>Ni 2+. They are related to initial concentrations used for the three metal ions.

Effects of Hydration and Oxygen Vacancy on CO2 Adsorption and Activation on β-Ga2O3(100)

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

Pan, Yunxiang; Liu, Chang-jun; Mei, Donghai

The effects of hydration and oxygen vacancy on CO2 adsorption on the β-Ga2O3(100) surface have been studied using density functional theory slab calculations. Adsorbed CO2 is activated on the dry perfect β-Ga2O3(100) surface, resulting in a carbonate species. This adsorption is slightly endothermic, with an adsorption energy of 0.07 eV. Water is preferably adsorbed molecularly on the dry perfect β-Ga2O3(100) surface with an adsorption energy of -0.56 eV, producing a hydrated perfect β-Ga2O3(100) surface. Adsorption of CO2 on the hydrated surface as a carbonate species is also endothermic, with an adsorption energy of 0.14 eV, indicating a slight repulsive interactionmore » when H2O and CO2 are coadsorbed. The carbonate species on the hydrated perfect surface can be protonated by the co-adsorbed H2O to a bicarbonate species, making the overall process exothermic with an adsorption energy of -0.13 eV. The effect of defects on CO2 adsorption and activation has been examined by creating an oxygen vacancy on the dry β-Ga2O3(100) surface. The formation of an oxygen vacancy is endothermic, by 0.34 eV, with respect to a free O2 molecule in the gas phase. Presence of the oxygen vacancy promoted the adsorption and activation of CO2. In the most stable CO2 adsorption configuration on the dry defective β-Ga2O3(100) surface with an oxygen vacancy, one of the oxygen atoms of the adsorbed CO2 occupies the oxygen vacancy site and the CO2 adsorption energy is -0.31 eV. Water favors dissociative adsorption at the oxygen vacancy site on the defective surface. This process is instantaneous with an adsorption energy of -0.62 eV. These results indicate that, when water and CO2 are both present in the adsorption system simultaneously, the water molecule will compete with CO2 for the oxygen vacancy sites and impact CO2 adsorption and conversion negatively. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. A portion of the computing time

Simultaneous adsorption of CO2 and H2O under Mars-like conditions and application to the evolution of the Martian climate

NASA Technical Reports Server (NTRS)

Zent, Aaron, P.; Quinn, Richard C.

1995-01-01

The Martian regolith is the most substantial volatile reservoir on the planet; estimates of its adsorbed inventory have been based on simple measurements of the adsorption of either water or CO2 in isolation. Under some conditions, H2O can poison adsorbate surfaces, such that CO2 uptake is greatly reduced. We have made the first measurements of the simultaneous adsorption of CO2 and H2O under conditions appropriate to the Martian regolith and have found that at H2O monolayer coverage above about 0.5, CO2 begins to be displaced into the gas phase. We have developed an empirical expression that describes our co-adsorption data and have applied it to standard models of the Martian regolith. We find that currently, H2O does not substantially displace CO, implying that the adsorbate inventories previously derived may be accurate, not more than 3-4 kPa (30-40 mbar). No substantial increase in atmospheric pressure is predicted at higher obliquities because high-latitude ground ice buffers the partial pressure of H2O in the pores, preventing high monolayer coverages of H2O from displacing CO2. The peak atmospheric pressure at high obliquity does increase as the total inventory of exchangeable CO2 increases.

Ab Initio Cluster Calculations for the Adsorption of Small Molecules on Oxide Surfaces - from Single Molecules to Monolayers

NASA Astrophysics Data System (ADS)

Pykavy, M.; Staemmler, V.; Rittner, F.

2000-04-01

Quantum chemical ab initio cluster calculations were performed for the adsorption of small molecules on metal oxide surfaces. Two systems were studied in detail: The adsorption of N2 on the (110) surface plane of TiO2 (rutile) and the adsorption of CO on the polar (0001) surface of Cr2O3. In both cases a full five-dimensional potential for the interaction of a single molecule with the respective surface was calculated. For N2/TiO2 (110) the minimum was found for the end-on adsorption of N2 atop a coordinately unsaturated surface Ti atom, with an adsorption energy of (35 ± 5) kJ/mol. In the case of CO/Cr2O3 (0001) the CO molecule is adsorbed strongly tilted (almost side-on) along a line connecting two Cr3+ ions at the surface; the calculated adsorption energy is 22 kJ/mol. In conjunction with empirical pair potentials for the N2/N2 and CO/CO interaction in the gas phase, Monte Carlo simulations were carried out to determine adsorption isotherms and the geometric structure of adsorbed monolayers.

First-principles characterization of formate and carboxyl adsorption on the stoichiometric CeO2(111) and CeO2(110) surfaces

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

Mei, Donghai

2013-05-20

Molecular adsorption of formate and carboxyl on the stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species aremore » not affected by using different U parameters (U=0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge whiled the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased. This work was supported by the Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL) and by a Cooperative Research and Development Agreement (CRADA) with General Motors. The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC)« less

Adsorption of Pb2+ ions on novel ternary nanocomposite of tin, iron and titania

NASA Astrophysics Data System (ADS)

Rehman, Mahfooz ur; Rehman, Wajid; Waseem, Muhammad; Haq, Sirajul; Hussain Shah, Khizar; Kang, Peng

2018-02-01

In this study, ternary nanocomposite (TNC) was synthesized by microemulsion method by taking Sn, Ti and Fe in (1:1:1) molar ratio. The BET surface area and pore size were measured by nitrogen adsorption method. The morphological features of TNC like particle size, elemental percentage and crystallite size were studied by scanning electron microscopy (SEM), energy dispersive x-rays (EDX) and x-rays diffraction (XRD) respectively, whereas the surface functional groups were detected by Fourier Transform Infrared (FTIR) spectroscopy. The crystallite size was found to be 11 nm, calculated from FWHM of diffraction peak with relative intensity 100%. For the thermal stability of TNC, thermogravimetric analysis (TGA) was performed. Batch adsorption tests were used for the removal of Pb2+ ions from aqueous solutions. The maximum adsorption capacity in this study was found to be 79.56 mg g-1 at 40 °C which is promising than the values reported in the literature. Based on the regression coefficient (r 2), the adsorption data was found well fitted to the Langmuir as compared to Freundlich model. The exchange of a single proton with every Pb2+ ion was calculated. Thermodynamic parameters were indicative for the sorption process to be endothermic and spontaneous.

Adsorption of normal pentane on the surface of rutile. Experimental results and simulations.

PubMed

Rakhmatkariev, G U; Carvalho, A J Palace; Ramalho, J P Prates

2007-07-03

Adsorption isotherms and differential heats of normal pentane adsorption on microcrystalline rutile were measured at 303 K. The heat of adsorption of n-pentane on rutile at zero occupancy is 64 kJ/mol. The differential heats have three descending segments, corresponding to the adsorption of n-pentane on three types of surfaces. At low coverage (first segment), the adsorption is restricted to the rows A of the (110) faces along the 5-fold coordinatively unsaturated (cus) Ti(4+) ions with differential heat showing a linear decrease with increasing occupancy. The second segment is attributed to bonding with atoms of the rows along the remaining faces exposed, (101) and (100). The third segment is related to a multilayer adsorption. The mean molar adsorption entropy of n-pentane is ca. -25 J/mol K less than the entropy of the bulk liquid, thus revealing a hindered state of motion of the n-pentane molecules on the surface of rutile. Simulations of the adsorption of n-pentane on the three most abundant crystallographic faces of rutile were also performed. The adsorption isotherm obtained from the combination of each face's isotherm weighted by the respective abundance was found to be in a good agreement with the experimental data. A structural characterization of n-pentane near the surface was also conducted, and it was found that the substrate, especially for the (110) face, strongly perturbs the distribution of n-pentane conformations, compared to those found for the gas phase. Adsorbed molecules are predominantly oriented with their long axes and their backbone zigzag planes parallel to the surface and are also characterized by fewer gauche conformations than observed in the bulk phase.

Water Adsorption in Porous Metal-Organic Frameworks and Related Materials

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

Furukawa, H; Gandara, F; Zhang, YB

2014-03-19

Water adsorption in porous materials is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing porous materials for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. In search of an excellently performing porous material, we have studied and compared the water adsorption properties of 23 materials, 20 of which are metal organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset ofmore » these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)(4)(-CO2)(n) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.« less

Water adsorption in porous metal-organic frameworks and related materials.

PubMed

Furukawa, Hiroyasu; Gándara, Felipe; Zhang, Yue-Biao; Jiang, Juncong; Queen, Wendy L; Hudson, Matthew R; Yaghi, Omar M

2014-03-19

Water adsorption in porous materials is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing porous materials for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. In search of an excellently performing porous material, we have studied and compared the water adsorption properties of 23 materials, 20 of which are metal-organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)4(-CO2)n secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.

Adsorption characteristics of UO(2)(2+) and Th(4+) ions from simulated radioactive solutions onto chitosan/clinoptilolite sorbents.

PubMed

Humelnicu, Doina; Dinu, Maria Valentina; Drăgan, Ecaterina Stela

2011-01-15

Adsorption features of UO(2)(2+) and Th(4+) ions from simulated radioactive solutions onto a novel chitosan/clinoptilolite (CS/CPL) composite as beads have been investigated compared with chitosan cross-linked with epichlorohydrin. The effects of contact time, the initial metal ion concentration, sorbent mass and temperature on the adsorption capacity of the CS-based sorbents were investigated. The adsorption kinetics was well described by the pseudo-second order equation, and the adsorption isotherms were better fitted by the Sips model. The maximum experimental adsorption capacities were 328.32 mg Th(4+)/g composite, and 408.62 mg UO(2)(2+)/g composite. The overall adsorption tendency of CS/CPL composite toward UO(2)(2+) and Th(4+) radiocations in the presence of Cu(2+), Fe(2+) and Al(3+), under competitive conditions, followed the order: Cu(2+)>UO(2)(2+)>Fe(2+)>Al(3+), and Cu(2+)>Th(4+)>Fe(2+)>Al(3+), respectively. The negative values of Gibbs free energy of adsorption indicated the spontaneity of the adsorption of radioactive ions on both the CS/CPL composite and the cross-linked CS. The desorption level of UO(2)(2+) from the composite CS/CPL, by using 0.1M Na(2)CO(3), was around 92%, and that of Th(4+) ions, performed by 0.1M HCl, was around 85%, both values being higher than the desorption level of radiocations from the cross-linked CS, which were 89% and 83%, respectively. Copyright © 2010 Elsevier B.V. All rights reserved.

Doping and vacancy effects of graphyne on SO2 adsorption.

PubMed

Kim, Sunkyung; Lee, Jin Yong

2017-05-01

The adsorption of sulfur dioxide (SO 2 ) on pristine and modified graphyne (including boron- or nitrogen- doping and introducing a single carbon atom defect) was investigated by density functional theory calculations. The structural, electronic, and magnetic properties of graphyne were changed according to the dopant atom site of doping and vacancy. SO 2 adsorption was obviously affected by modification of graphyne. SO 2 weakly interacted with pristine and nitrogen-doped graphynes. Boron doping at the sp-hybridized carbon site and introducing a single carbon atom vacancy in graphyne brought about a dramatic enhancement in SO 2 adsorption. The strongly chemisorbed SO 2 at these active sites caused deformation of the graphyne structure and electron redistribution, which induced changes in the conductivity and magnetism of graphynes. Copyright © 2017 Elsevier Inc. All rights reserved.

DFT study of CO2 and H2O co-adsorption on carbon models of coal surface.