Detection of Chromium in surface and groundwater and its bio-absorption using bio-wastes and vermiculite

Abstract

Unnao has a large number of tanneries and huge amount of waste water is generated and there effluents contain Chromium, which infiltrates and percolates below the ground and contaminate the surface and subsurface water, thereby creating a possibility of becoming a potent carcinogenic. Chromium is present in different forms, trivalent and hexavalent being the prevalent ones. Cr(III) has low solubility whereas Cr(VI) has high solubility and can easily move through the groundwater and get mixed with it. Present paper is based upon the collection of 47 samples from Unnao district of Uttar Pradesh (India), which were tested for pH, Electrical Conductivity, hexavalent Chromium and total Chromium. The concentration of Cr(VI) for one of the sites (Dharamkata) was found to be 2070 µg/l; which has a high efficacy to contaminate the unlined channels, thereby causing contamination of surface and groundwater. In order to remediate the problem, different bio-waste materials were used for the removal of Cr(VI). The concentration of Cr(VI) and total Chromium were determined by Diphenylcarbazide method and ICP-OES. Hexavalent Chromium is highly oxidizing in nature and requires electron donor materials for reduction. The research utilized bio-wastes like coir pith, sawdust, rice husk and vermiculite (natural mineral) to reduce Chromium. An effluent sample having Chromium concentration, 184.8 mg/l was passed through columns having different bio-absorbent medium, out of which bio-absorbents and vermiculite combination was found to be more capable of reducing hexavalent Chromium from the sample. An outstanding decrease in concentration of total Chromium (184.8–4.48 mg/l) is accomplished by the combination of vermiculite and coir pith. This shows that natural wastes are very likely the absorbents of Cr(VI), which can be used to decrease the concentrations of Chromium from the contaminated water.