Removal of phosphate from aqueous solution using modified zeolite clays

Abstract

Phosphate adsorption capabilities of different treated zeolite clays were assessed from aqueous solution. Natural zeolites were treated by thermal activation over 120–800 °C for 2 h, and by hydrochloric ac-id solution from 1%-9%, respectively. The mechanisms of phosphate adsorption of these modified products were also studied through adsorption isotherms and adsorption kinetics experiments. The acid activation in-creased the phosphate sorption capacity and the highest phosphate sorption capacity occurred at AZT9 (zeo-lite activated by 9% hydrochloric acid), while thermal activation did not have the same effect. AZT9 showed higher adsorption rate than natural zeolite (ZT). The phosphate adsorption isotherms of ZT, H400 and AZT9 are fitted well with Langmuir equation in terms of R2 values. It suggested that the adsorption of phosphate on zeolite was homogeneous multilayer adsorption. Based on R2 values, the kinetics of phosphate adsorption on these three zeolites can be satisfactorily described by pseudo-second-order kinetic equation. Results of this study suggested that acid modified zeolite could be potentially used as a promising adsorption media for phosphate removal.