Removal of Cr(VI) from aqueous solution by adsorption onto low cost non-conventional adsorbents

Adsorption behavior of chromium, Cr(VI) from wastewater has been investigated using clarified sludge (a steel plant waste material), rice husk ash and sawdust as non-conventional adsorbents. The studies were carried out at room temperature (30C) following batch adsorption technique in a reciprocating shaker. Factors affecting the adsorption characteristics such as agitation time, initial metal ion concentration, adsorbent dose and pH were studied. Maximum adsorption of Cr(VI) was observed at pH 3. The experimental data fitted to Langmuir and Freundlich isotherms. The adsorption process found to follow Lagergren first order kinetics model. Adsorption capacity has been observed to follow the order clarified sludge > rice husk ash > sawdust. At pH 3 and initial Cr(VI) concentration of 3 mg/L more than 99% removal of Cr(VI) may be possible. The maximum amount of adsorbed metal (qmax) value is significantly influenced by liquid/solid ratio and by the pH values of the metal solutions.