SORPTION STUDIES ON CHROMIUM(VI) REMOVAL BY GREEN ALGAE

Abstract

The presence of inorganic contaminants in surface water continues to be one of the most pervasive environmental issues of present time. Although control technologies have been applied to many industrial and municipal sources, the total quantity of these agents released to the environment i.e. water, air and soil etc. remains staggering which makes the environment unusable. Chromium is one of such contaminants which exists either in hexavalent form or in trivalent form. Hexavalent chromium is more toxic than trivalent chromium, hence requires more concern. There are various methods available for the removal of chromium from wastewater such as chemical reduction and precipitation, ion exchange, evaporative recovery, adsorp-tion on activated carbon etc. Though biosorptive processes have been reported in literature, not much work has been done on removal of chromium by these processes. In the present study, effort has been made to investigate the metal sorptive property of Spirogyra sp., a green and filamentous type of algae commonly found in polluted water. It was observed that algal binding of chromium (VI) is highly pH-dependent. At optimum pH of 2.0, removal of Cr(VI) was found to be more than 95% at a concentration of 5 nig/1. Also, chromium (VI) binding to algal cells was effectively reversed by increasing pH to 8.0. Though 100% reversal was not achieved, it holds the promise for future work. Thus, algal sorbents offer an attractive means for treatment of metal laden industrial wastewater and recovery of selective metal ions.