REMOVAL OF BORRON FROM WATER BY IRANIAN NATURAL AND SOLOVOTHERMALLY TREATED ZEOLITE

摘要

Boron removal from aqueous solutions by natural and modified zeolite was studied in batch equilibrium experiments. Adsorption experiments were carried out as a function of pH, concentrations of Ca~(2+) and Mg~(2+) and boron concentrations. Boron species in equilibrium solutions was predicted by Visual MINTEQ speciation program. For both adsorbents, the adsorption amounts of boron increased with increasing equilibrium pH. Greater adsorption was observed in the presence of Ca~(2+) ions as compared with Mg~(2+) ions at the same concentrations. For natural zeolite, the amounts of B adsorbed at 0.03 M Ca~(2+) and Mg~(2+) concentrations were significantly higher than those at 0.06 M Ca~(2+) and Mg~(2+) concentrations. For solvothermally treated zeolite, effect of Ca~(2+) and Mg~(2+) concentrations on the adsorption of boron was not significantly different. The Freundlich adsorption model describes the interaction between B and the adsorbents better than Langmuir model. Maximum adsorption capacity (q_(max)) of natural zeolite (187.5 mmol/kg) was approximately 5 times higher than that of solvothermally treated-zeolite (33.1 mmol/kg). Solvothermally treated zeolite removed lesser amounts of B from the solutions as compared to natural zeolite in similar chemical conditions. This may be attributed to pores clogging and (or) structural damage in smaller particles during solvothermal treatment. The experimental data show that natural zeolite used in this study has a reasonable adsorption capacity for B, and therefore, may be useful for removal of B from polluted waters.