Bioremediation of hexavalent chromium by a cyanobacterial mat

Abstract

The study comprises the use of cyanobacterial mat (collected from tannery effluent site) to remove hexavalent chromium. This mat was consortium of cyanobacteria/blue-green algae such as Chlorella sp., Phormidium sp. and Oscillatoria sp. The adsorption experiments were carried out in batches using chromium concentrations 2–10, 15–30 and 300 ppm at pH 5.5–6.2. The adsorption started within 15 min; however, 96 % reduction in metal concentration was observed within 210 min. The adsorption phenomenon was confirmed by Fourier transform–infrared spectroscopy and energy dispersive X-ray analysis. This biosorption fitted Freundlich adsorption isotherm very well. It was observed that the best adsorption was at 4 ppm, and at 25 ppm in the chosen concentration ranges. Scanning electron micrograph showed the physiology of mat, indicating sites for metal uptake. The main focus was collection of the cyanobacterial mat from local environments and its chromium removal potential at pH 5.5–6.2.