Phosphate removal using natural and Al/Cu modified Ethiopian zeolites

Abstract In the current study, Phosphate removal from aqueous solutions was studied using bimetallic Al/Cu modified natural zeolites (Z-Al/Cu). The Z-Al/Cu was synthesized in situ using simple chemical reduction and impregnation methods. The morphologies and structures of natural zeolites (NZ) and Z-Al/Cu were characterized by SEM, XRD, FTIR, and BET. Batch sorption experiments were carried out using various factors that can potentially influence the removal efficiency (initial pH, initial solution concentration, and adsorbent dosage). Experimental results showed higher adsorption of Z-Al/Cu as compared to NZ, indicating that the Al/Cu impregnation provides more adsorption sites to phosphate. The maximum adsorption of phosphate by the adsorbent was 99.32% at optimum pH 2, contact time of 60 min, and phosphate concentration of 25 mg/L. When the contact time between the adsorbent and adsorbate increased above the optimum time, the adsorption efficiency decreased due to the onset of the desorption process. Characterization results indicated that Al/Cu was successfully supported on the zeolites. Adsorption of phosphate by Z-Al/Cu adsorbent fitted well with Langmuir adsorption isotherm and pseudo-second-order kinetics within R2 = 0.913 and 0.999 respectively, which suggested that the adsorption process was a surface chemical reaction and mainly in a monolayer coverage manner. Reduction of removal efficiency, with regeneration cycles and in the presence of SO4 2-, was observed.