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.
Highlights
IntroductionThe discharge of chromium (VI) into aquatic ecosystems has become a matter of concern in all the tannery areas
The discharge of chromium (VI) into aquatic ecosystems has become a matter of concern in all the tannery areasConventionally, chromium (VI) containing industrial effluent is treated by physico-chemical methods such as reduction, precipitation, ion exchange, reverse osmosis and electrodialysis
The main focus was hexavalent chromium removal potential of cyanobacterial mat collected from the local environment at relatively higher pH 5.5–6.2
Summary
The discharge of chromium (VI) into aquatic ecosystems has become a matter of concern in all the tannery areas. The work has been carried out using a cyanobacterial mat (collected from tannery effluent disposal site) to remove chromium (VI) from tannery effluent at relatively higher pH, i.e., 5.5–6.2. The main focus was hexavalent chromium removal potential of cyanobacterial mat collected from the local environment at relatively higher pH 5.5–6.2. This is the first report where chromium (VI) removal has been carried out at relatively higher pH so efficiently, it is known that at low pH (0–2) the biosorption of chromium (VI) is more predominant than bioreduction of chromium (VI) to (III).
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