Model for Competitive Adsorption of Organic Cations on Clays

Margulies, L.

doi:10.1346/ccmn.1988.0360309

Cited by 127 publications

(102 citation statements)

References 23 publications

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“…According to the Gouy-Chapman equation, Y0 should increase in this case with an increase in ionic strength. Experimental results confirmed the prediction of the model that the adsorbed amounts of certain monovalent organic cations should increase with ionic strength for adsorption beyond the CEC (Margulies et al 1988;Rytwo et al 1995a). We agree with Maes and Cremers (1977) that the GouyChapman equation is strictly applicable only for isolated surfaces.…”

Section: Application Of the Adsorption Model To The Experimental Resultssupporting

confidence: 77%

Exchange Reactions in the Ca-Mg-Na-Montmorillonite System

Rytwo

Banin

Nir

1996

Clays and clay miner.

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Abstract--The exchange reactions of Na, Ca and Mg on montmorillonite are revisited employing recently developed analytical and theoretical approaches. The fractional adsorption of the cations has been determined by displacing them from the adsorbed state in one step, using a low concentration of an organic cation of large binding affinity. The analysis of displaced and solution cations employed inductively coupled plasma emission spectrometry. An adsorption model was employed in the analysis of the data. The procedure consists of solving the electrostatic Gouy-Chapman equations and calculating adsorbed amounts of the cations as the sum of the cations residing in the double layer region, and the cations chemically bound to the surface, in a closed system. The model also accounts explicitly for cation complexation in solution. Thus the calculations also considered the adsorption of CaC1 + and MgCI +, which eliminated the apparent increase of the cation exchange capacity (CEC) with divalent cation concentration. The model could explain and yield predictions for our measured adsorbed amounts as well as previously published data, in the binary and ternary systems of Ca/Mg/Na, provided that the fraction of surface sites occupied by calcium did not exceed 0.4. For a larger coverage of surface sites by calcium, a fit of the experimental data required an order of magnitude increase in the binding coefficients of the divalent cations in the binary system Ca/Na and in the ternary system Ca/Mg/Na.

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Section: Application Of the Adsorption Model To The Experimental Resultssupporting

confidence: 77%

Exchange Reactions in the Ca-Mg-Na-Montmorillonite System

Rytwo

Banin

Nir

1996

Clays and clay miner.

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“…Essas potencialidades são decorrentes das propriedades físico-químicas que as mesmas apresentam, como capacidade de troca de cátions (CTC), natureza dos cátions trocáveis, distribuição granulométrica das partículas, área específica, porosidade, potencial eletrocinético, viscosidade em suspensão aquosa e plasticidade 3 , que podem ser alteradas visando aumentar a sua eficiência 4,5 . Devido à variedade de combinações dos minerais precursores, tem sido freqüente a presença de certas espécies minerais, que se constitui num problema para as aplicações das argilas, principalmente como catalisadores ou adsorventes.…”

Section: Introductionunclassified

Influência da calcinação sobre a remoção de ferro da caulinita e ilita e seus efeitos sobre a acidez

Araújo

Silva

2003

Quím. Nova

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ACIDITY. Samples of natural clay composed by kaolinite, illite, goethite and quartz, were calcinated and submitted to lixiviation with citrate and chloridric acid in order to remove iron. Investigation due to extraction consequences was carried cut by analyzing its acid properties using ammonia gas as probe in infrared spectrophotometry analysis. The sample that were treated with citrate followed by acid lixiviation yield materials twice more acid than samples treated with acid only.Keywords: calcination; iron extraction; lixiviation acid; sodium citrate. INTRODUÇÃONas últimas décadas as argilas têm sido utilizadas para diversos fins científicos e tecnológicos, tais como: na catálise, nos processos de adsorção, na purificação de óleos vegetais, dentre outros 1,2 . Essas potencialidades são decorrentes das propriedades físico-químicas que as mesmas apresentam, como capacidade de troca de cátions (CTC), natureza dos cátions trocáveis, distribuição granulométrica das partículas, área específica, porosidade, potencial eletrocinético, viscosidade em suspensão aquosa e plasticidade 3 , que podem ser alteradas visando aumentar a sua eficiência 4,5 . Devido à variedade de combinações dos minerais precursores, tem sido freqüente a presença de certas espécies minerais, que se constitui num problema para as aplicações das argilas, principalmente como catalisadores ou adsorventes. A presença de ferro, por exemplo, que pode ser encontrado em diversas formas minerais (hematita, algita, goetita, hidróxido de ferro(III) amorfo, entre outros), tem sido uma preocupação imediata quando se trata da produção de catalisadores ácidos, tendo em vista que o ferro pode interferir na acidez das argilas. São encontrados na literatura métodos de eliminação dessa espécie 6,7 , bastante eficazes, e que podem contribuir positivamente para o aumento no número de sítios ácidos de Lewis e de Brönsted 8 , indispensáveis aos processos de craqueamento, isomerização, ciclização de compostos orgânicos, entre outros 9 . Tendo em vista esse problema, pretendeu-se investigar a presença do ferro e sua influência sobre as propriedades ácidas de argila sedimentar encontrada no município de Fortim, litoral leste do estado do Ceará. PARTE EXPERIMENTALPreviamente ao estudo sobre a eliminação do ferro e seus efeitos sobre a acidez, foram realizadas algumas análises físicas para caracterização da argila de partida. Foi obtido, inicialmente, um espectro de difração da fração 200 mesh, em um difratômetro modelo Universal X-ray diffractometer D/MAX 3B Rigaku, numa geometria Bragg-Brenteno, CuKa e monocromador de grafite pirolítico curvo. Uma análise posterior, foi a determinação do comportamento térmi-co das espécies minerais presentes, em um equipamento da PerkinElmer TGA-7, em fluxo de ar e velocidade de aquecimento de 10 °C/min, e algumas determinações da textura da argila, como área específica e porosidade total em um analisador BET Flowsorb 2300 Micrometric Equipaments. Quanto à determinação dos componentes químicos da argila, foram realizadas análises química...

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“…This method is simple and versatile because MB has a strong affinity for most solid surfaces (Bergmann and O'Konski, 1963;Margulies et al, 1988;Rytwo et aL, 1998). Methylene blue has a special affinity for negatively charged surfaces, and its concentration is easily quantified by spectrophotometry.…”

Section: Introductionmentioning

confidence: 99%

Methylene Blue Dimerization Does Not Interfere in Surface-Area Measurements of Kaolinite and Soils

Avena

Valenti

Pfaffen

et al. 2001

Clays and clay miner.

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Abstract--Methylene blue (MB) was adsorbed from aqueous solutions onto a kaolinite and four soil samples to determine the effects of MB dimerization on the measured surface area. Adsorption isotherms were prepared using four adsorbing solutions containing, respectively, 9, 46, 71, and 83% of MB molecules in the dimeric state. Langmuir-type isotherms were obtained in each case. The results indicate that equilibration occurs quickly. The aggregation state of MB molecules at the surface does not depend on the aggregation state in the initial adsorbing solutions, but on the final equilibrium concentration of MB. A comparison with the specific surface area measured by adsorption of ethylene glycol monoethyl ether indicates that MB adsorbs as a monomer, regardless of the aggregation number in solution. This result occurs owing to the strength of monomer-surface and monomer-monomer interactions. If monomer-surface interactions are favored, the MB dimer adsorbs in the monomeric form. If monomer-monomer interactions are favored, dimer adsorption may occur. The visible spectra of adsorbed molecules indicated that MB was present at the surface as a mixture of monomeric and dimeric species. These results suggest that dimers are formed in the contact region between two aggregating particles.

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Model for Competitive Adsorption of Organic Cations on Clays

Cited by 127 publications

References 23 publications

Exchange Reactions in the Ca-Mg-Na-Montmorillonite System

Exchange Reactions in the Ca-Mg-Na-Montmorillonite System

Influência da calcinação sobre a remoção de ferro da caulinita e ilita e seus efeitos sobre a acidez

Methylene Blue Dimerization Does Not Interfere in Surface-Area Measurements of Kaolinite and Soils

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