Removal of toxic cations and Cr(Vi) from aqueous solution by hazelnut shell

Removal of ions such as Cd2+, Zn2+, three- and hexavalent chromium from aqueous solutions using hazelnut shell as biosorbent substrate has been performed. Batch equilibrium tests showed that the metal sorption was dependent on both pH and surface loading. For Cd2+, Cr3+ and Zn2+ ions the maximum removal was observed only into a specific pH range. The metal ion sorption obeyed both the Langmuir and Freundlich isotherms. Experiments by mixed solutions showed that more Cr3+ ions were removed than both Cd2+ and Zn2+ ions. The binding capacities acid the affinities observed were consistent with the HSAB theory on hard and soft acid base. The Cr(VI) removal was pH dependent and fitted with the Langmuir isotherm model. It was proceeding effectively into a short acid pH interval (2.5-3.5) where both processes of Cr (VI) reduction and (Cr III) sorption are maximized. Mechanisms for removal of anions and cations studied have been proposed. The observed sorption data showed similarity with that of other fresh cellulosic materials found in literature. (C) 2000 Elsevier Science Ltd. All rights reserved.