Removal of heavy metals from aqueous solutions by X-type zeolite prepared from combination of oil shale ash and coal fly ash

In this paper, the zeolite was synthesized from a combination of oil shale ash and coal fly ash and was used to remove heavy metals from aqueous solution. The structural characterization of product was conducted by XRD and SEM, which proved that the ashes can be converted into zeolite. The adsorption performance of synthetic zeolite for heavy metals was evaluated by the batch experiment. The results showed that the adsorption kinetic data conformed to the pseudo-second-order kinetics model, and the Langmuir isotherm model described well the isotherm data. Based on the equilibrium studies, the selectivity sequence was in following order: Pb2+ > Cr3+ > Cu2+ > Cd2+ > Zn2+. The results of XPS indicated that the mechanism of synthetic zeolite removal of heavy metals was ion exchange.