Surface ionization and complexation at the oxide/water interface

Davis, James A.; James, R.; Leckie, James O.

doi:10.1016/s0021-9797(78)80009-5

Cited by 1,397 publications

(649 citation statements)

References 42 publications

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“…Because hydronium has a uniquely high mobility, a factor of ∼ 5 higher than common salt ions, in bulk solutions, it is found that hydronium ions begin to dominate the electrical conductivity when the salt concentration is lower than ∼ 5 × 10 −6 M. Furthermore, hydronium is also known to interact with the confining walls of the electrolyte. For oxide walls, most prominently silica, numerous studies have shown how hydronium affects the electrical properties of the wall-electrolyte interface and leads to a wall surface charge that depends on salt concentration [33][34][35][36][37][38][39][40][41][42][43][44] including our own recent study [26]. Finally, at sufficiently low salt concentration, this surface charge is found to dominate the conductance of electrolyte-filled nanochannels [8,11,19,24,27,28,32,45].…”

Section: Introductionsupporting

confidence: 50%

“…8 in a recent review paper [2]. However, this is in contrast to the observed nonmonotonic conductance graphs with a minimum, and therefore, we choose to base our analysis on the other well-known class of modeling, where the surface charge is governed dynamically by chemical reaction constants of the proton dissociation processes in the bulk electrolyte and at the wall [26,[32][33][34][35][36][37][38][39][40][41][42][43][44].…”

Section: Modelmentioning

confidence: 99%

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Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

et al. 2011

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Section: Introductionsupporting

confidence: 50%

Section: Modelmentioning

confidence: 99%

Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

et al. 2011

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“…Observe that K^ varies by about one order of magnitude for each order of magnitude change in the background ionic strength. The ion-exchange equilibria were inter preted using an extension of the sitebinding model of Davies, James and Leckie [1]. This model predicted correctly the effect of ionic strength on ion sorption, as well as multi-ion sorption.…”

Section: Methodsmentioning

confidence: 99%

Electrolyte Diffusion in Compacted Montmorillonite Engineered Barriers

Jahnke

Radke

1987

Coupled Processes Associated With Nuclear Waste Repositories

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The bentonite-based engineered bar rier or packing is a proposed component of several designs conceived to dispose of high-level nuclear waste in geologic reposi tories. Once radionulcides escape the waste package, they must first diffuse through the highly impermeable day-rich barrier before they reach the host repository. To deter mine the effectiveness of the packing as a sorption barrier in the transient release period and as a mass-transfer barrier in the steady release period over the geologic time scales involved in nuclear waste disposal, a fundamental understanding of the diffusion of electrolytes in compacted clays is required. We present, and compare with laboratory data, a model quantifying the diffusion rates of cationic cesium and uncharged tritium in compacted mont morillonite clay. Neutral tritium character izes the geometry (Le., tortuosity) of the particulate gel. After accounting for cation exchange, we find that surface diffusion is the-dominant mechanism of cation tran sport, with an approximate surface diffusion coefficient of 2xl0~6 cm 2 /s for cesium. This value increases slightly with increasing background ionic strength.The implications of this work for the packing as a migration barrier are twofold. During the transient release period, K4 values are of little importance in retarding ion migration. Tbii is because sorption also gives rise to a surface diffusion path, and it is surface diffusion which controls the diffusion rate of highly sorbing cations in compacted montmorillonite. During the steady release period, the presence of sur face diffusion leads to a flux through the packing which is greatly enhanced. In either case, if surface diffusion is neglected, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommen dations. IntroductionHigh-level nuclear wastes will be stared in underground repositories. To aid the host formation in protecting the bio sphere from the harmful, long-lived radioisotopes contained in the waste pack age, use of an engineered barrier or packing is being considered [6]. This barrier, based upon the day mineral montmorillonite, is envisaged as an impermeable barrier sur rounding the waste canisters which retards the migration of ions in the transient release period due to its high cation exchange capadty [3] and low hydraulic permeability [7]. As time passes and steady-state diffusion through the packing is established, it further serves as a masstransfer resistance retarding the escape of ions from the canister to the fluid percolat ing around the waste package. To deter mine the steady-state plume of radionu clides eminating from the waste repository in the steady-state period and the protec tion an engineered barrier affords the waste disposal scheme in the transient release period, the diffusion rate of ions in com pacted montmorillonite clay must be deter mined.

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“…O efeito da força iônica (I) sobre a adsorção de metais tem sido atribuído a: 1) mudança na atividade dos íons livres (p. ex., Pb 2+ , Cd 2+ e Zn 2+ ) por causa da formação de pares iônicos, e do efeito de I sobre o pH (Davis & Leckie, 1978); 2) competição pelos sítios de adsorção entre o metal e os eletrólitos presentes no meio (Spark et al, 1995); 3) mudanças do potencial eletrostático no plano de adsorção (Barrow, 1986). Como, neste estudo, o pH das soluções e das suspensões com solo foi ajustado para 5,5, o efeito de I sobre o pH é pouco provável.…”

Section: Resultsunclassified

Efeito da força iônica da solução de equilíbrio sobre a adsorção/dessorção de chumbo em Latossolos brasileiros

Pierangeli

Guilherme

Oliveira

et al. 2001

Pesq. agropec. bras.

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Resumo A adsorção/dessorção de metais pelos solos é afetada por vários fatores, dentre os quais, a concentração salina da solução do solo. Este estudo teve o objetivo de avaliar o efeito da variação da força iônica da solução de equilíbrio (I) sobre a adsorção/dessorção de Pb por Latossolos brasileiros. Amostras do horizonte A foram colocadas para reagir com Pb(NO 3 ) 2 0,15 mmol L -1 em Ca(NO 3 ) 2 5 e 50 mmol L -1 (pH 5,5; I = 15 e 150 mmol L -1 ; relação solo:solução 1:100), durante 72 horas. Em seguida, as amostras foram colocadas para dessorver em Ca(NO 3 ) 2 5 mmol L -1 . Dos 17 Latossolos, apenas seis apresentaram diferenças significativas entre as quantidades adsorvidas nos dois valores de I. As correlações significativas obtidas entre as quantidades adsorvidas e alguns atributos dos solos (SiO 2 e Fe 2 O 3 do ataque sulfúrico, Fe d e Fe o , caulinita, hematita, CTC e superfície específica) foram as mesmas para os dois valores de I. A variação de I durante a adsorção teve pouco efeito sobre a dessorção de chumbo. A não-variação da quantidade adsorvida com a mudança de I indica que o Pb é adsorvido, na maioria dos Latossolos, como complexo de esfera interna. Conclui-se que, dentro destas condições experimentais, o Pb não fez parte do complexo de troca da maioria dos solos estudados.Termos para indexação: metal pesado, íons, processo de transporte no solo, poluição do solo. Effect of ionic strength of the equilibrium solution upon lead adsorption/desorption in Brazilian OxisolsAbstract The ionic strength of soil solution influences metal availability and mobility in soils. Laboratory experiments were conducted in order to evaluate the effect of solution ionic strength (I) upon Pb adsorption/desorption in A-horizon samples of 17 Brazilian Oxisols. The effect of I upon Pb adsorption was evaluated after a 72-hour reaction of the soil samples with 0.15 mmol L -1 Pb(NO 3 ) 2 at pH 5.5, using 5 and 50 mmol L -1 Ca(NO 3 ) 2 as background solutions (I = 15 and 150 mmol L -1 ). Lead desorption was measured after a 72-hour reaction of the soil samples with 5 mmol L -1 Ca(NO 3 ) 2 at pH 5.5. All experiments were performed with a 1:100 soil:solution ratio. Increasing I caused Pb adsorption to decrease in six soils, while no significant change in Pb adsorption was observed for the remaining 11 Oxisols. Soil properties such as specific surface area, CEC, clay and hematite content, oxalate-and DCB-Fe, and sulfuric acid digestion-Si and -Fe correlated with Pb adsorption equally for both values of solution ionic strength. Changing I had a small effect on Pb desorption. The little change in the amount of Pb adsorbed upon variation of I indicates that Pb is adsorbed as an inner-sphere complex in most Oxisols. Therefore, this experiment suggests that Pb may not be part of the exchange complex of these soils.

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Surface ionization and complexation at the oxide/water interface

Cited by 1,397 publications

References 42 publications

Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

Hydronium-dominated ion transport in carbon-dioxide-saturated electrolytes at low salt concentrations in nanochannels

Electrolyte Diffusion in Compacted Montmorillonite Engineered Barriers

Efeito da força iônica da solução de equilíbrio sobre a adsorção/dessorção de chumbo em Latossolos brasileiros

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