Hexavalent chromium removal from aqueous solutions by biosorbents (non-living activated sludge)

Abstract

AbstractThe removal of hexavalent chromium from aqueous solution was examined by the adsorption process using non-living activated sludge as an absorbent. The kinetics of the hexavalent chromium removal were examined in batch experiments for the concentrations between 1 and 20 mg/L hexavalent chromium solutions. The adsorbent dosage applied was 0.1 g dry weight of adsorbent/250 mL for the non-living activated sludge. Four different mixing times ranging from 30 to 120 min and six different pH values between 2 and 7 were assessed to find out the optimum mixing time and pH value. The removal efficiencies were above 56% for all hexavalent chromium concentrations and mixing times. The 250-rpm shaker speed at pH 2 gave the highest removal efficiency. The adsorption kinetics can be described by the pseudo-first-order and pseudo-second-order kinetic models. The rate constants were evaluated for all hexavalent chromium concentrations. This study showed that the hexavalent chromium adsorption kinetics of the non-li...