Pb(II) and Zn(II) adsorption onto Na- and Ca-montmorillonites in acetic acid/acetate medium: Experimental approach and geochemical modeling

► Higher Zn and Pb sorption onto Na-montmorillonite than onto the calcic clay at pH 5. ► Increasing acetic acid/acetate concentration decreases Pb and Zn adsorption. ► Determination of new selectivity coefficients for PbNa and PbCa equilibria. ► Contribution of cation exchange and surface complexation onto strong and weak sites.