Heavy metal removal from water by sorption using surfactant-modified montmorillonite

Removal of Cu²⁺ and Zn²⁺ from aqueous solutions by sorption on the montmorillonite modified with sodium dodecylsulfate (SDS) was investigated. Experiments were carried out as a function of solution pH, solute concentration, and temperature (25-55°C). The Dubinin-Kaganer-Radushkevick model was adopted to describe the single-solute sorption isotherms. Also, the binary-solute sorption equilibria could be reasonably predicted by the competitive Langmuir model, in which the Langmuir parameters were directly taken from those obtained in single-solute systems. The thermodynamic parameters (ΔH^o and ΔS^o) for Cu²⁺ and Zn²⁺ sorption on the modified clay were also determined from the temperature dependence. The kinetics of metal ions sorption was examined and the pseudo-first-order rate constant was finally evaluated.