COMPETITIVE ADSORPTION OF CR(VI), K(I) AND NH4(I) IONS ONTO NATURAL ZEOLITES AND BENTONITES

Abstract

Chromium, ammonium, and potassium compounds are pollutants in the environment released mainly by industrial wastewater and they can negatively influence the quality of surface water. Zeolites and bentonites are commonly used adsorbents for removal of pollutant from water. In the study, the adsorbents were used in their natural form, without chemical modification for adsorption of Cr(VI), K(I) and NH4(I) from K2CrO4, K2Cr2O7 and (NH4)2CrO4 in a single compound system for each adsorbate separately. The Langmuir isotherm provided the best correlation for the adsorption onto the zeolites and bentonites. The adsorption capacities of bentonites were higher than the adsorption capacities of zeolites from all the used adsorbates. The maximum sorption capacities of K(I) from K2CrO4 were approximately the same. The maximum sorption capacities of K(I) from K2Cr2O7 and NH4(I) from (NH4)2CrO4 were higher for zeolites than for bentonites. The adsorption of Cr(VI) in the form of anions is preferred to the adsorption of cations. The zeolites and bentonites were found to be suitable adsorbents for removal of Cr(VI) from aqueous solutions.