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Yu M, Dong H, Zheng Y, Liu W. Ternary metal oxide embedded carbon derived from metal organic frameworks for adsorption of methylene blue and acid red 73. CHEMOSPHERE 2021; 280:130567. [PMID: 33945901 DOI: 10.1016/j.chemosphere.2021.130567] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 04/05/2021] [Accepted: 04/10/2021] [Indexed: 06/12/2023]
Abstract
Organic dyes can enter water bodies through industrial wastes and may pose a threat to the health of aquatic organisms and human. Metal organic framework derived carbon materials (CMOFs) have shown excellent performance for aqueous dye adsorption. However, few have studied multimetallic CMOFs for dye removal. Herein, a ternary metal oxide embedded carbon derived from amino-modified metal organic framework (CMOF(Fe/Al/Ni 8/7/5)-NH2) has been developed as an efficient adsorbent to remove aqueous methylene blue (MB) and acid red 73 (AR-73). CMOF(Fe/Al/Ni 8/7/5)-NH2 reached adsorption equilibrium for both MB and AR-73 within 30 min at neutral pH condition. It also achieved 18 and 24 times higher adsorption than commercial activated carbon (AC) in 10 min for MB and AR-73, respectively. Compared to other CMOFs-NH2, CMOF(Fe/Al/Ni 8/7/5)-NH2 had the highest adsorption capacity for both cationic MB and anionic AR-73. In addition, CMOF(Fe/Al/Ni 8/7/5)-NH2 had < 0.15% metal leaching in 90 min in the pH range of 4-10, and it also maintained 89% and 95% adsorption capacity for MB and AR-73 in five consecutive adsorption batches, respectively. Electrostatic interaction was identified as the primary interaction between CMOFs-NH2 and the dyes, and the embedded crystalline metal oxides with different points of zero charge (PZCs) were identified to be the key adsorption sites. A uniformly distributed surface charge model was proposed to explain the exceptional adsorption capacity of CMOF(Fe/Al/Ni 8/7/5)-NH2. With fast kinetics, high adsorption capacity, wide applicability and good stability, CMOF(Fe/Al/Ni 8/7/5)-NH2 may be an effective adsorbent for many other ionic organic pollutants.
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Affiliation(s)
- Menglin Yu
- College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Linde + Robinson Laboratories, California Institute of Technology, Pasadena, CA, 91125, United States
| | - Heng Dong
- Linde + Robinson Laboratories, California Institute of Technology, Pasadena, CA, 91125, United States
| | - Yingdie Zheng
- College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China
| | - Weiping Liu
- College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China.
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Ahmed MG, Zhang M, Tay YF, Chiam SY, Wong LH. Surface Modification of Hematite Photoanodes with CeO x Cocatalyst for Improved Photoelectrochemical Water Oxidation Kinetics. CHEMSUSCHEM 2020; 13:5489-5496. [PMID: 32776429 DOI: 10.1002/cssc.202001135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 08/05/2020] [Indexed: 06/11/2023]
Abstract
Hematite is a promising photoanode for solar water splitting by photoelectrochemical (PEC) cells, but its performance is limited by the slow kinetics of water oxidation reaction or oxygen evolution reaction (OER). Surface modification of hematite photoanodes with a suitable water oxidation cocatalyst is a key strategy for improving the kinetics of water oxidation. In this study, a CeOx overlayer is deposited on the surface of the hematite photoanode by a water-based solution method with ceric ammonium nitrate (CAN) followed by heat treatment. The photocurrent of CeOx -modified hematite is 3 times higher than that of pristine hematite (at 1.23 V vs. RHE) under AM 1.5G, 1 sun conditions. Through hole-scavenger measurements, Tafel plot analysis, and electrochemical impedance spectroscopy, it is concluded that CeOx overlayer increases the hole injection efficiency, improves the surface catalytic activity, and enhances charge transfer across the photoanode/electrolyte interface. These observations are attributed to the synergistic effects of Ce3+ /Ce4+ redox species in CeOx and the oxygen vacancies. This work elucidates the role of CeOx as an efficient cocatalyst overlayer to improve the OER kinetics of photoanodes.
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Affiliation(s)
- Mahmoud G Ahmed
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798, Singapore
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Mengyuan Zhang
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798, Singapore
| | - Ying Fan Tay
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798, Singapore
| | - Sing Yang Chiam
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Lydia H Wong
- School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798, Singapore
- Campus for Research Excellence and Technological Enterprise, 1 Create Way, Singapore, Singapore, 139602, Singapore
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Koopal L, Tan W, Avena M. Equilibrium mono- and multicomponent adsorption models: From homogeneous ideal to heterogeneous non-ideal binding. Adv Colloid Interface Sci 2020; 280:102138. [PMID: 32387754 DOI: 10.1016/j.cis.2020.102138] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/30/2020] [Accepted: 03/04/2020] [Indexed: 01/19/2023]
Abstract
Aqueous sorption processes play an important role in, for example, pollutant binding to natural nanoparticles, colloid stability, separation and enrichment of components and remediation processes. In this article, which is a tribute to Hans Lyklema, models of localized (ad)sorption of molecules and ions from aqueous solution on homogeneous and heterogeneous nanoparticles are presented. The discussed models range from ideal monocomponent sorption on homogeneous (Langmuir) and heterogeneous sites, to multicomponent ideal sorption on homogeneous and heterogeneous sites, multicomponent multisite ion complexation with charge distribution (CD-MUSIC) and non-ideal competitive adsorption on heterogeneous sites (NICA). Attention is also paid to lateral interaction, site-induced aggregation, binding stoichiometry and multilayer formation. Electrical double layer models are discussed in relation to ion binding on impermeable and permeable nanoparticles. Insight in models that can describe sorption of molecules and ions on nanoparticles leads to awareness of the limitations of using simple models for complex systems and is needed for the selection and application of an appropriate model for a given system. This is relevant for all practical sorption processes and for a better understanding of the role of natural nanoparticles in the binding of nutrients and pollutants.
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Affiliation(s)
- Luuk Koopal
- Physical Chemistry and Soft Matter, Wageningen University and Research, Wageningen, the Netherlands; College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Wenfeng Tan
- College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Marcelo Avena
- INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Bahía Blanca, Argentina.
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Opportunities and constraints of using the innovative adsorbents for the removal of cobalt(II) from wastewater: A review. ACTA ACUST UNITED AC 2018. [DOI: 10.1016/j.enmm.2018.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Kosmulski M. Isoelectric points and points of zero charge of metal (hydr)oxides: 50years after Parks' review. Adv Colloid Interface Sci 2016; 238:1-61. [PMID: 27890403 DOI: 10.1016/j.cis.2016.10.005] [Citation(s) in RCA: 178] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 10/27/2016] [Accepted: 10/28/2016] [Indexed: 02/06/2023]
Abstract
The pH-dependent surface charging of metal (hydr)oxides is reviewed on the occasion of the 50th anniversary of the publication by G.A. Parks: "Isoelectric points of solid oxides, solid hydroxides, and aqueous hydroxo complex systems" in Chemical Reviews. The point of zero charge (PZC) and isoelectric point (IEP) became standard parameters to characterize metal oxides in aqueous dispersions, and they define adsorption (surface excess) of ions, stability against coagulation, rheological properties of dispersions, etc. They are commonly used in many branches of science including mineral processing, soil science, materials science, geochemistry, environmental engineering, and corrosion science. Parks established standard procedures and experimental conditions which are required to obtain reliable and reproducible values of PZC and IEP. The field is very active, and the number of related papers exceeds 300 a year, and the standards established by Parks remain still valid. Relevant experimental techniques improved over the years, especially the measurements of electrophoretic mobility became easier and more reliable, are the numerical values of PZC and IEP compiled by Parks were confirmed by contemporary publications with a few exceptions. The present paper is an up-to-date compilation of the values of PZC and IEP of metal oxides. Unlike in former reviews by the same author, which were more comprehensive, only limited number of selected results are presented and discussed here. On top of the results obtained by means of classical methods (titration and electrokinetic methods), new methods and correlations found over the recent 50years are presented.
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Ahmed MG, Kretschmer IE, Kandiel TA, Ahmed AY, Rashwan FA, Bahnemann DW. A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting. ACS APPLIED MATERIALS & INTERFACES 2015; 7:24053-62. [PMID: 26488924 DOI: 10.1021/acsami.5b07065] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm(-2) vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm(-2) vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.
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Affiliation(s)
- Mahmoud G Ahmed
- Department of Chemistry, Faculty of Science, Sohag University , Sohag 82524, Egypt
| | - Imme E Kretschmer
- Photocatalysis and Nanotechnology Research Unit, Institut für Technische Chemie, Leibniz Universität Hannover , Callinstrasse 3, D-30167 Hannover, Germany
| | - Tarek A Kandiel
- Department of Chemistry, Faculty of Science, Sohag University , Sohag 82524, Egypt
| | - Amira Y Ahmed
- Department of Chemistry, Faculty of Science, Sohag University , Sohag 82524, Egypt
| | - Farouk A Rashwan
- Department of Chemistry, Faculty of Science, Sohag University , Sohag 82524, Egypt
| | - Detlef W Bahnemann
- Photocatalysis and Nanotechnology Research Unit, Institut für Technische Chemie, Leibniz Universität Hannover , Callinstrasse 3, D-30167 Hannover, Germany
- Laboratory for Nanocomposite Materials, Department of Photonics, Faculty of Physics, Saint-Petersburg State University , Ulianovskaia street 3, Peterhof, Saint Petersburg 198504, Russia
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Kulyukhin SA, Krasavina EP, Rumer IA, Klimovich IV. Sorption of 60Co from aqueous solutions onto layered double hydroxides of various compositions. RADIOCHEMISTRY 2015. [DOI: 10.1134/s1066362215020071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Wang T, Hung HT, Wang W, Li PC, Hsieh YK, Dong Y, Wang CF. Application of surface complexation modeling on modification of hematite surface with cobalt cocatalysts: a potential tool for preparing homogeneously distributed catalysts. RSC Adv 2015. [DOI: 10.1039/c5ra08588h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The knowledge to synthesize homogeneously distributed catalysts on the support is rather identical to understand the interactions between pollutants and adsorbents in the environmental chemistry.
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Affiliation(s)
- TsingHai Wang
- Biomedical Engineering and Environment Sciences
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Hsin-Ting Hung
- Biomedical Engineering and Environment Sciences
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Wei Wang
- School of Material Sciences and Engineering
- Harbin Institute of Technology
- Shenzhen Graduate School
- Shenzhen
- PR China
| | - Po-Chieh Li
- Department of Chemical Engineering
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Yi-Kong Hsieh
- Biomedical Engineering and Environment Sciences
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Yingchao Dong
- Institute of Urban Environment
- Chinese Academy of Science
- Xiamen
- China
| | - Chu-Fang Wang
- Biomedical Engineering and Environment Sciences
- National Tsing Hua University
- Hsinchu
- Taiwan
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Hankin A, Alexander JC, Kelsall GH. Constraints to the flat band potential of hematite photo-electrodes. Phys Chem Chem Phys 2014; 16:16176-86. [DOI: 10.1039/c4cp00096j] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reasons are discussed for the widely disparate, reported flat band potentials for semiconducting hematite (photo-) electrodes in aqueous solutions.
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Affiliation(s)
- A. Hankin
- Department of Chemical Engineering
- Imperial College London
- South Kensington, UK
| | - J. C. Alexander
- Department of Materials
- Imperial College London
- South Kensington, UK
| | - G. H. Kelsall
- Department of Chemical Engineering
- Imperial College London
- South Kensington, UK
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11
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Ren X, Yang S, Tan X, Chen C, Wang X. Investigation of radionuclide 60Co(II) binding to TiO2 by batch technique, surface complexation model and DFT calculations. Sci China Chem 2012. [DOI: 10.1007/s11426-012-4694-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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12
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Kulyukhin SA, Krasavina EP, Rumer IA, Gredina IV. Sorption of 60Co from aqueous solutions on layered double hydroxides of Mg, Al, and Nd. RADIOCHEMISTRY 2012. [DOI: 10.1134/s106636221203006x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Guo Z, Xu D, Zhao D, Zhang S, Xu J. Influence of pH, ionic strength, foreign ions and FA on adsorption of radiocobalt on goethite. J Radioanal Nucl Chem 2010. [DOI: 10.1007/s10967-010-0706-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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14
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Kay A, Cesar I, Grätzel M. New benchmark for water photooxidation by nanostructured alpha-Fe2O3 films. J Am Chem Soc 2007; 128:15714-21. [PMID: 17147381 DOI: 10.1021/ja064380l] [Citation(s) in RCA: 654] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thin films of silicon-doped Fe2O3 were deposited by APCVD (atmospheric pressure chemical vapor deposition) from Fe(CO)5 and TEOS (tetraethoxysilane) on SnO2-coated glass at 415 degrees C. HRSEM reveals a highly developed dendritic nanostructure of 500 nm thickness having a feature size of only 10-20 nm at the surface. Real surface area determination by dye adsorption yields a roughness factor of 21. XRD shows the films to be pure hematite with strong preferential orientation of the [110] axis vertical to the substrate, induced by silicon doping. Under illumination in 1 M NaOH, water is oxidized at the Fe2O3 electrode with higher efficiency (IPCE = 42% at 370 nm and 2.2 mA/cm2 in AM 1.5 G sunlight of 1000 W/m2 at 1.23 VRHE) than at the best reported single crystalline Fe2O3 electrodes. This unprecedented efficiency is in part attributed to the dendritic nanostructure which minimizes the distance photogenerated holes have to diffuse to reach the Fe2O3/electrolyte interface while still allowing efficient light absorption. Part of the gain in efficiency is obtained by depositing a thin insulating SiO2 interfacial layer between the SnO2 substrate and the Fe2O3 film and a catalytic cobalt monolayer on the Fe2O3 surface. A mechanistic model for water photooxidation is presented, involving stepwise accumulation of four holes by two vicinal iron or cobalt surface sites.
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Affiliation(s)
- Andreas Kay
- Institut des sciences et ingénierie chimiques, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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Duc M, Lefèvre G, Fédoroff M. Sorption of selenite ions on hematite. J Colloid Interface Sci 2006; 298:556-63. [PMID: 16483595 DOI: 10.1016/j.jcis.2006.01.029] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 01/13/2006] [Accepted: 01/14/2006] [Indexed: 10/25/2022]
Abstract
The sorption of selenite from aqueous solutions onto hematite was investigated as a function of pH (2-12), ionic strength (0.01-0.1 M), and concentration of selenium (10(-7)-10(-2) M). The sorption may proceed according to two processes: surface complexation, followed by the precipitation of ferric selenite starting at approximate [Se] = 4 x 10(-4) M (surface coverage>ca. 2 at nm(-2)). The sorption isotherms have been fitted by a Tempkin equation. A surface complexation model (2-pK/Constant Capacitance Model) was used to fit the sorption data. The nature of the surface species of selenite cannot be determined by modeling since monodentate >FeOSe(O)O- or >FeOSe(O)OH and bidentate (>FeO)2SeO surface complexes are both able to fit the experimental data. The reversibility and kinetics of sorption were also studied. The affinity of selenite ions toward hematite, expressed as the distribution coefficient with respect to the surface area (K(D) in L m(-2)), was compared with results published for other ferric oxides (goethite and amorphous ferric oxide). It was found that the reactivity toward selenite is similar, contrary to acid-base properties which depend on the nature of the oxide and its level of purity.
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Affiliation(s)
- M Duc
- Laboratoire d'Electrochimie et de Chimie Analytique (ENSCP-CNRS UMR7575), 11, Rue Pierre et Marie Curie, F75231 Paris Cedex 05, France
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Lefèvre G, Duc M, Fédoroff M. Effect of solubility on the determination of the protonable surface site density of oxyhydroxides. J Colloid Interface Sci 2004; 269:274-82. [PMID: 14654384 DOI: 10.1016/s0021-9797(03)00653-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The impact of the dissolved quantity of aluminum on the calculation of surface charge from titration experiments of hydrated gamma-alumina was investigated. Two methods were developed to correct this effect: direct determination of aluminum in solution in batch titration experiments and application of a dissolution rate model in continuous titration experiments. There is a large effect of dissolution on surface charge determination for pH>10 and pH < 4.5. Application of these correction methods to these pH ranges lead to apparent saturation surface charges of 1.3 and 2.3 at nm(-2), respectively. The last value seems to be the real proton-active site density, while the hydroxyl-active site density cannot be reached for easily achievable basic pH values.
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Affiliation(s)
- G Lefèvre
- Centre d'Etudes de Chimie Métallurgique, CNRS UPR2801, 15, rue Georges Urbain, 94407, Vitry-sur-Seine, France.
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Abstract
The sorption of Pu(VI) onto TiO(2) was studied as a function of pH (2-10) and Pu concentration (10(-8)-10(-4) M) under an N(2) atmosphere, in 0.016 and 0.1 M NaClO(4). A batch-wise method was used, in which pH was measured in separate experimental containers after removal of a sample to determine the amount of Pu that had been sorbed. As Pu is radioactive, it was used as a tracer and measured by liquid scintillation counting. No ionic strength dependence was discerned, which was taken as an indication of inner sphere complex formation. In the interval of pH 2-7 the system could be described by the formation of two positively charged surface complexes using a 1-pK Stern model. Sorption of the plutonyl ion (PuO(2)(2+)) and the first hydrolysis species (PuO(2)(OH)(+)) was estimated using FITEQL to logK(1)=6.9 and logK(2)=1.4, respectively.
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Affiliation(s)
- Mattias Olsson
- Department of Materials and Surface Chemistry, Nuclear Chemistry, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
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Kosmulski M, Maczka E, Jartych E, Rosenholm JB. Synthesis and characterization of goethite and goethite-hematite composite: experimental study and literature survey. Adv Colloid Interface Sci 2003; 103:57-76. [PMID: 12689760 DOI: 10.1016/s0001-8686(02)00083-0] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Aging of synthetic goethite at 140 degrees C overnight leads to a composite material in which hematite is detectable by Mössbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods.
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Affiliation(s)
- Marek Kosmulski
- Department of Electrochemistry, Technical University of Lublin, Nadbystrzycka 38 A, 20618, Lublin, Poland.
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Olsson M, Jakobsson AM, Albinsson Y. Surface Charge Densities of Two Actinide(IV) Oxides: UO2 and ThO2. J Colloid Interface Sci 2002. [DOI: 10.1006/jcis.2002.8586] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Kosmulski M, Maczka E, Rosenholm JB. Isoelectric Points of Metal Oxides at High Ionic Strengths. J Phys Chem B 2002. [DOI: 10.1021/jp013942e] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marek Kosmulski
- Department of Electrochemistry, Technical University of Lublin, 20618 Lublin, Nadbystrzycka 38A, Poland, and Department of Physical Chemistry, Åbo Akademi University, Porthansgatan 3-5, 20500 Turku, Finland
| | - Edward Maczka
- Department of Electrochemistry, Technical University of Lublin, 20618 Lublin, Nadbystrzycka 38A, Poland, and Department of Physical Chemistry, Åbo Akademi University, Porthansgatan 3-5, 20500 Turku, Finland
| | - Jarl B. Rosenholm
- Department of Electrochemistry, Technical University of Lublin, 20618 Lublin, Nadbystrzycka 38A, Poland, and Department of Physical Chemistry, Åbo Akademi University, Porthansgatan 3-5, 20500 Turku, Finland
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Gunnarsson M, Rasmusson M, Wall S, Ahlberg E, Ennis J. Electroacoustic and Potentiometric Studies of the Hematite/Water Interface. J Colloid Interface Sci 2001; 240:448-458. [PMID: 11482952 DOI: 10.1006/jcis.2001.7725] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The basic charging properties of nearly spherical hematite particles were studied by using potentiometric titration and the electroacoustic technique. Both the pH and the ionic strength dependence of the surface charge and the zeta-potential were studied in detail. For calculating the zeta-potential from mobility data a few different theories were used and obtained differences are discussed. At pH values higher than 7 and at high electrolyte concentrations (50 mM and 100 mM NaNO(3)), it was difficult to fit the mobility data by using the full mobility spectra including both magnitude and phase angle at several frequencies. In this regime the best fits were obtained by using a theory for aggregated complexes (porous particles). From potentiometric titrations in 0.01, 0.1, and 1.0 M NaNO(3), parameters for a 1-pK Basic Stern Model were determined. The model was used to examine the possibility of correlating the experimentally determined zeta-potentials to the model-calculated potentials at the Stern plane. Qualitatively, the model predicted the correct ionic strength dependence of the zeta-potentials, and there was also a rather good quantitative agreement at high ionic strengths (50 and 100 mM NaNO(3)). However, at lower ionic strengths the model predicted values up to 40% higher than those found from the electroacoustic study. Surface conduction behind the slip plane was discussed as a possible cause for this discrepancy. Copyright 2001 Academic Press.
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Affiliation(s)
- Magnus Gunnarsson
- Department of Chemistry, Göteborg University, Göteborg, SE-412 96, Sweden
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