Use of General Purpose Adsorption Isotherms for Heavy Metal–Clay Mineral Interactions

• Published in: Journal of colloid and interface science 1998-02, Vol.198 (1), p.130-140
• Main Authors: Altın, Orhan, Özbelge, H.Önder, Doğu, Timur
• Format: Article
• Language: English
• Subjects: adsorption isotherms; Chemistry; clay minerals; Exact sciences and technology; General and physical chemistry; heavy metals; Solid-liquid interface; Surface physical chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1997.5246

General purpose adsorption isotherm equations were fitted to the sorption data of lead and cadmium on both unmodified and Ca-saturated kaolinite and montmorillonite. Langmuir–Freundlich, Redlich–Petersen, Toth, Dubinin–Radushkevich, competitive Langmuir, and some modified forms of these isotherms were fitted to experimental data, and their goodnesses of fit are compared. The adjustable parameters of the Langmuir- and Freundlich-based isotherms were estimated by nonlinear least-squares analysis. The application of these two isotherms which allow for the effect of surface heterogeneity for both multiple and single desorbing ions during the sorption process was also studied. It was concluded that Redlich–Petersen, Toth, and original and modified forms of Dubinin–Radushkevich isotherms perform superior to the others both in high and low concentration regions for both unmodified and Ca-saturated clays. Competitive Langmuir adsorption isotherm for Ca-saturated clays fitted well for Pb adsorption, while a change of slope was observed for Cd adsorption.