Acid — base reactions of the TiO2 (Anatase) — water interface and the point of zero charge of TiO2 suspensions

Schindler, P.; Gamsjäger, Heinz

doi:10.1007/bf01498568

Cited by 244 publications

(114 citation statements)

References 4 publications

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“…Th e simpler constant capacitance model was introduced later by Schindler and Gamsjäger (1972), and the triple layer model was introduced by and . A good review of the construction of these models was given by Goldberg (1995).…”

Section: Models Involving Potential Determining Ionsmentioning

confidence: 99%

Historical Perspective on the Tools That Helped Shape Soil Chemistry

Schulthess

2011

Soil Science Society of America Journal

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SSSA 75 th Anniversary Paper T he tools of soil chemistry include instruments, mathematics, models, and software. Th ere is also the mind and imagination. Th roughout the history of our science, we have been shift ing away from a very labor-intensive laboratory environment, where long hours of concentration on tedious tasks was the norm. Th is change in the way we work has been accelerating, particularly since the 1950s. We are accomplishing more work but with less eff ort and more time to contemplate what the data are trying to tell us. Th e essence of our research activity has changed dramatically.Numerous laboratory tools have been used in soil chemistry during the last 200 yr, and the major changes that have occurred are highlighted here. It is hoped that the picture presented will help us decide how to better train our students for the future. By knowing how we have changed in the past and how we appear to be changing in the present, we can perhaps trace the path that we are taking, at least in the near future.Eight major themes are addressed here:1. Th e early years reviews the research environment of the 1800s up to the early 1900s. It marks the beginning years of soil chemistry that shaped many of our ideas for the decades that followed.2. Th e age of electronics covers the early part of the 1900s and the origins of the fi rst portable meters on the market.3. Spectroscopy is at the core of most of our modern methods of analysis. While the development of only a few tools are described here, the impact of spectroscopy on our current research activity cannot be understated.

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Section: Models Involving Potential Determining Ionsmentioning

confidence: 99%

Historical Perspective on the Tools That Helped Shape Soil Chemistry

Schulthess

2011

Soil Science Society of America Journal

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“…The original mechanistic explanation of these observed data was the 2-pK surface complexation model that describes chemical reactions between bound surficial metal oxide sites (4SOH) and the hydronium ion (e.g., Parks and deBruyn, 1962;Schindler and Kamber, 1969;Stumm et al, 1970;Boehm, 1971;Schindler and Gamsjager, 1972;Huang and Stumm, 1973;Chan et al, 1975;Huang, 1981):…”

Section: Historical Metal Oxide Acidity Reaction Formulationsmentioning

confidence: 99%

Extending the diffuse layer model of surface acidity behaviour: III. Estimating bound site activity coefficients

Loux

2009

Chemical Speciation & Bioavailability

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Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in application these terms are ignored based on one or more of the following assumptions: (1) bound site activity coefficients cancel out in the mass action quotients; (2) bound sites display ideal behaviour; andyor (3) these energies are already included in the exponential Boltzmann terms. In this work it is demonstrated that the bound site charging energy terms discussed in the two previous papers in this series have both conceptual and computational analogies to the charging energy contribution to the activity coefficients obtained from the Debye -Huckel Limiting Law. On high charge density colloidal particles at constant counterion condensation (t), these charging energies can be related to the surface potential (C) by: DG charging ¼ ð1 À tÞFC (where F is the Faraday constant). If one assumes a maximum practical accuracy of AE 10% in experimental estimates of C, then it is suggested that charging energies are likely to be experimentally indiscernible under conditions where t ! 0:9. These findings support the historical practice of ignoring bound site activity coefficients with the 2-pK diffuse layer surface complexation model in the following situations: for spherical particles with a radius ! 0.1 mm at ionic strengths ! 0.001 M (1 : 1), and for spherical particles with a radius 40.01 mm at an ionic strength 40.1 M (1 : 1). In contrast, charging energies (and non-ideal behaviour) are predicted to be significant at all charge densities and ionic strengths for spherical particles with a radius of 0.001 mm.

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“…Developed for oxide surfaces at the interface with aqueous solutions by Paul W. Schindler and Werner Stumm, along with several collaborators (Schindler & Gamsjager, 1972;Schindler et al, 1976;Stumm et al, 1976;1980), this model is based on the following assumptions; (i) all surface complexes are considered inner-sphere complexes, and adsorption occurs by ligand exchanges; (ii) no surface complex are formed with the electrolyte ions; (iii) a plan of charges represents the surface; (iv) surface density charge (σ) is proportional to (ψ o ) at the particle surface, or σ = C.ψ o , where σ is expressed in C m -2 (coulombs per square meter); C is the capacitance in F m -2 (Farad per square meter,) and ψ o is in V (volts).…”

Section: Constant Capacitance Model (Ccm)mentioning

confidence: 99%

Electrochemical attributes and availability of nutrients, toxic elements, and heavy metals in tropical soils

Fontes¹,

Alleoni²

2006

Sci. agric. (Piracicaba, Braz.)

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Electrochemical properties of soils are very important for the understanding of the physico-chemical phenomena which affect soil fertility and the availability of nutrients for plants. This review highlights the electrochemical properties of tropical soils, the behavior and the availability of nutrients, toxic elements and heavy metals in the soil, especially for soils with predominant variable charge minerals. Availability of the elements is related to ionic exchange, solution speciation, and electrostatic and specific adsorptive soil properties. Empirical and surface complexation models are briefly described, and some results of their application in tropical soils are presented. A better understanding of the role of the double diffuse layer of charges and CEC on nutrient cation availability for highly weathered soils is required, as well as a solid comprehension of surface complexation models, in order to improve the knowledge regarding the behavior of anions in soils. More studies have to be conducted to generate results that enable the use of chemical speciation concepts and calculation of several constants used in surface complexation models, especially for highly weathered soils from the humid tropics. There has to be a continuing development and use of computer softwares that have already incorporated the concepts of chemical speciation and adsorption models in the study of nutrients, toxic elements and heavy metal availability in the soil-plant system. Key words: electric charge, adsorption, model, ionic exchange, speciation ATRIBUTOS ELETROQUÍMICOS E DISPONIBILIDADE DE NUTRIENTES, ELEMENTOS TÓXICOS E METAIS PESADOS EM SOLOS TROPICAISRESUMO: As propriedades eletroquímicas dos solos tropicais são muito importantes para entendimento dos fenômenos físico-químicos que afetam a fertilidade do solo e a disponibilidade dos nutrientes das plantas. Essa revisão destaca os atributos eletroquímicos de solos e o comportamento e a disponibilidade de nutrientes, elementos tóxicos e metais pesados no solo, especialmente aqueles com predominância de minerais com cargas variáveis. A disponibilidade dos elementos é relacionada com a troca iônica, especiação da solução e propriedades adsortivas eletrostáticas e específicas do solo. Modelos empíricos e de complexação de superfície são brevemente descritos, e são apresentados resultados de sua aplicação em solos tropicais. É necessário um melhor entendimento do papel da dupla camada difusa de cargas e da CTC na disponibildade de nutrientes em solos altamente intemperizados, assim como uma melhor compreensão dos modelos de complexação de superfície, a fim de melhorar o entendimento do comportamento dos ânions no solo. Mais estudos devem ser conduzidos para gerar resultados que tornem possível o uso de conceitos de especiação química e o cálculo de diversas constantes usadas em modelos de complexação, especialmente para solos altamente intemperizados do trópico úmido. Deve haver um contínuo desenvolvimento de programas computacionais que já tenham incorporado os conc...

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Acid — base reactions of the TiO2 (Anatase) — water interface and the point of zero charge of TiO2 suspensions

Cited by 244 publications

References 4 publications

Historical Perspective on the Tools That Helped Shape Soil Chemistry

Historical Perspective on the Tools That Helped Shape Soil Chemistry

Extending the diffuse layer model of surface acidity behaviour: III. Estimating bound site activity coefficients

Electrochemical attributes and availability of nutrients, toxic elements, and heavy metals in tropical soils

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