Simultaneous removal of NH4+, H2PO4- and Ni2+ from aqueous sMark solution by thermally activated combinations of steel converter slag and spent alumina catalyst

Abstract

Industrial wastes (spent alumina catalyst and steel converter slag) were utilized to prepare low-cost inorganic sorbents by thermal activation at temperatures ranging from 500 to 1000 degrees C. According to the results of X-ray diffraction analysis, high-temperature thermal activation of mixtures of spent alumina catalyst and steel converter slag in different ratios leads to the formation of new crystalline phases. The Ni2+, H2PO4- and NH4+ sorption properties of the prepared samples were investigated in separate batch experiments, employing initial analyte concentration of 10 mmol L-1. The steel converter slag samples calcined at 500 degrees C and 900 degrees C and the mixed sample (70% spent alumina catalyst and 30% steel converter slag) calcined at 1000 degrees C exhibited maximum ion sorption capacities of 3.56 mmol Ni2+ g(-1), 3.28 mmol H-2 PO4+ g(-1) and 2.21 mmol NH4+ g(-1), respectively. The principal mechanisms of Ni2+ sorption were the substitution of Ca2+ ions by Ni2+ ions, precipitation at high pH and sorption on Fe3O4 and SiO2 surfaces present in the samples. The H2PO4-sorption was due mainly to the formation of calcium phosphates and sorption on Fe2O3 and SiO2 surfaces, whereas the removal of NH4+ involved sorption on Al2O3 surfaces of the prepared samples. The results of the kinetics calculations showed that a second-order kinetic model offers a good fit for the present experimental data. The materials prepared from low-cost industrial wastes in this work have the ability to simultaneously remove NH4+, H-2 PO(4)(-)and Ni2+ ions from aqueous solution.