Sorption of Pb2+ on mercapto functionalized sepiolite.

Mercapto functionalized sepiolite (MSEP) was prepared by nanotexturization method and applied for the sorption of Pb(2+) from aqueous solution. These samples before and after sorption were characterized through XRD, FT-IR, (29)Si and (13)C CP/MAS NMR and XPS. The sorption behaviors including thermodynamic and kinetic parameters, effect factors and mechanisms of Pb(2+) sorption on MSEP were studied. The maximum sorption amounts of 97 mg g(-1). The parameters ΔH(0) and ΔS(0) were 33.637 kJ mol(-1) and 202.697 J mol(-1) K(-1), respectively. Freundlich isotherm was proved to describe the sorption data better than other isotherms and pseudo second order kinetic model could fit the sorption kinetic processes well. The pH influenced the sorption of Pb(2+) on MSEP significantly but background electrolytes have relative weak effect. Based on hard and soft acids and bases theory and the results analyzed from XPS, the sorption mechanisms could be explained as primarily chemical adsorption and secondary physical adsorption.