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 aqu eous solutions using hazelnut shell as biosorbent substrate has been perfor med. Batch equilibrium tests showed that the metal sorption was dependent o n both pH and surface loading. For Cd2+, Cr3+ and Zn2+ ions the maximum rem oval was observed only into a specific pH range. The metal ion sorption obe yed both the Langmuir and Freundlich isotherms. Experiments by mixed soluti ons showed that more Cr3+ ions were removed than both Cd2+ and Zn2+ ions. T he binding capacities acid the affinities observed were consistent with the HSAB theory on hard and soft acid base. The Cr(VI) removal was pH dependen t and fitted with the Langmuir isotherm model. It was proceeding effectivel y into a short acid pH interval (2.5-3.5) where both processes of Cr (VI) r eduction and (Cr III) sorption are maximized. Mechanisms for removal of ani ons and cations studied have been proposed. The observed sorption data show ed similarity with that of other fresh cellulosic materials found in litera ture. (C) 2000 Elsevier Science Ltd. All rights reserved.