Adsorption and Kinetics Studies of Heavy Metals Removal by MnO2 Modified Zeolite

Zeolites can be used as one of natural adsorbents for the removal of heavy metals. Treatment of natural zeolites with various chemicals enhances their removal capacity. In this study, manganese dioxide was used to activate the natural zeolite. The modified zeolite sample and several combinations of the synthetic wastewater were contacted together to adsorb heavy metals. The wastewater used contained heavy metal ions with various concentrations such as Cu2+, Cd2+, Zn2+, Co2+, Pb2+, and Ni2+. The adsorption isotherms of Langmuir, Freundlich, BET, and Temkin, as well as adsorption kinetic models, were used to develop models imaging the behavior of adsorption. The BET isotherm provides a model being more acceptable than the other isotherms; however, in term of the prediction of adsorption amounts (qe), its description is weaker than the Langmuir isotherm. Maximum adsorption capacities with respect to Langmuir parameters were obtained under optimal conditions as follows: Ni2+ (10.51 mg/g), Co2+ (14.87 mg/g), Zn2+ (8.97 mg/g), Cu2+ (10.59 mg/g), Cd2+ (13.69 mg/g) and Pb2+(40.65 mg/g). In addition, the pseudo-second kinetic model is more accurate than the pseudo-first order. Thus, the pseudo-second kinetic model was selected to describe the adsorption kinetics.