isotherm and kinetic studies on adsorption of pb, zn and cu by kaolinite

the feasibility of kaolinite used as a low-cost adsorbent for the removal of pb(ii), zn(ii) and cu(ii) from aqueous solutions was investigated. during the removal process, batch technique was used, and the effects of heavy metal concentration and contact time on adsorption efficiency at ph of 4.5, under a constant temperature of 20?1 ?c were studied. the experimental results were analyzed using four adsorption isotherm models; freundlich, langmuir, temkin and redlich-peterson. evaluating the correlation coefficients showed that the redlich-peterson isotherm described the data appropriable than others. the adsorption capacities (qm) from the langmuir isotherm for pb(ii), zn(ii) and cu(ii) are found as 7.75 mg/g, 4.95 mg/g and 4.42 mg/g respectively. the effectiveness of kaolinite in the sorption of the three metals from aqueous system was pb(ii) > zn(ii) > cu(ii). kinetic studies showed that a pseudo-second order model was more suitable than the pseudo first order model. it is concluded that kaolinite can be used as an effective adsorbent for removing pb(ii), zn(ii) and cu(ii) from aqueous solutions.