Available online www.jocpr.com Journal of Chemical and Pharmaceutical Research, 2015, 7(10):546-554 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 546 Biosorption of hexavalent chromium in aqueous solution using water hyacinth Ashwin Shenoy*, Jagadish H. Patil and M. A. Lourdu Antony Raj Department of Chemical Engineering, R V College of Engineering, Bangalore _____________________________________________________________________________________________ ABSTRACT The current work was performed to search the likelihood of using the water menace, water hyacinth as biosorbent for the removal of hexavalent chromium ions from synthetic water containing chromium. All the biosorption experiments were carried out in batch operation mode with crude and pyrolysed water hyacinth. The impact of key physico-chemical factors pH, temperature, initial chromium ion concentration and biosorbent dosage on chromium removal has been studied. The experiments reveal that the maximum chromium removal can be achieved from an aqueous solution at low pH, less chromium concentration, moderate temperature (40 o C) and maximum biomass loading. Adsorption isotherms at equilibrium were examined. The experimental data obtained were analyzed with Langmuir, Freundlich and Temkin adsorption isotherm models. The data fits well to all the three isotherms as regression coefficient R 2 is more than 0.9 in all the cases. The crude and pyrolysed water hyacinth had mono layer adsorption with capacity of 2.7964 mg/g and 2.9438 mg/g respectively while the separation factor (S f ) for crude and pyrolysed water hyacinth is found to be 0.0102 and 0.0077 respectively. This indicatesthat performance of water hyacinth in pyrolysed form is marginally better than crude form. However taking economics in to consideration water hyacinth in crude form is better as removal of hexavalent chromium is less by 0.52%. Key words: Chromium, biosorption, pyrolysis, water hyacinth, adsorption isotherm. _____________________________________________________________________________________________ INTRODUCTION Waste water from industries containing heavy metals causes danger to human beings and other forms of fauna. Conventionalomethods used for removaloofoheavyometals from waste water are often too expensive and have poor efficienciesoat low metal ion concentrations. In the recent years the biosorption of metaloions has received considerable attention forothe development of an efficient, clean, cheap and sustainable technology for waste water treatment at low metal concentrations. Chromium in aqueous system occurs in two forms, trivalent chromium (Cr (III)) and hexavalent chromium (Cr (VI)). Chemical, biological and environmental characters exhibited by both the forms of chromium are diverse and distinct [1]. Cr (III) is essential trace metal nutrient required for microorganisms in minute quantities, whereas Cr (VI) is required for all types of fauna and flora [2-4]. Huge quantities of chromium is discharged into the water bodies from various industries such as electroplating, leather tanning, mining, paints and pigments. Due to threat caused by chromium to environment and mankind, permissible limits of chromium have been closely monitored and regulated by most of the developed and developing countries. Industrial effluents generally contain chromium concentration up to 270 mg/l, while inland surface water and potable water has chromium concentration up to 0.1 and 0.05 ppm respectively. Various technologies are employed to reduce the level of chromium in effluents such as reduction with chemical precipitation, ion exchange process, electrochemical precipitation, reduction, adsorption, solvent extraction,