Use of General Purpose Adsorption Isotherms for Heavy Metal–Clay Mineral Interactions
✍ Scribed by Orhan Altın; H.Önder Özbelge; Timur Doğu
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 241 KB
- Volume
- 198
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
the surfaces, and soil organic matter content (6). In the General purpose adsorption isotherm equations were fitted to modeling of metal ion adsorption, effects of surface heterothe sorption data of lead and cadmium on both unmodified and geneity have been taken into account (7, 8) in the last de-Ca-saturated kaolinite and montmorillonite. Langmuir-Freundcade. Adsorption phenomena has been modeled on semiemlich, Redlich-Petersen, Toth, Dubinin-Radushkevich, competipirical grounds so far. Although, there has been modeling
tive Langmuir, and some modified forms of these isotherms were efforts based on thermodynamic principles (9-16). fitted to experimental data, and their goodnesses of fit are com-The Langmuir and Freundlich models are widely used pared. The adjustable parameters of the Langmuir-and Freundsince they are simple and have an ability to describe experilich-based isotherms were estimated by nonlinear least-squares
mental results in wide ranges of concentrations. Both isoanalysis. The application of these two isotherms which allow for the effect of surface heterogeneity for both multiple and single therm models can be easily transformed into linear forms to desorbing ions during the sorption process was also studied. It obtain adjustable parameters just by graphical means or by was concluded that Redlich-Petersen, Toth, and original and linear regression analysis. The Langmuir isotherm is used modified forms of Dubinin-Radushkevich isotherms perform sufor homogeneous surfaces, and to handle nonhomogeneous perior to the others both in high and low concentration regions for surfaces new isotherms were derived starting with Langmuir both unmodified and Ca-saturated clays. Competitive Langmuir isotherms. The models, having more than two adjustable adsorption isotherm for Ca-saturated clays fitted well for Pb adparameters, are not easily fitted to the experimental data by sorption, while a change of slope was observed for Cd adsorption. linear regression or graphical means. In this case, it is neces-᭧ 1998 Academic Press sary to apply nonlinear least-squares (NLLS) analysis.