Microbial sorption studies for removal of trivalent chromium from model tanning bath

Abstract

Out of the industrial waste streams/effluents entering in the aquatic system containing metallic species, tanneries release high amounts of chromium, an anthropogenic pollutant because of use of basic chromium sulphate in the tanning processes. Trivalent chromium, Cr(III) is the targeted ionic species for removal by biosorption on a fungal species in this work, as the technique has inherent merit of easy adsorbent regeneration and lower capital costs. The study involves the use of Aspergillus niger (A. niger), to remediate chromium from a model tanning bath with Cr(III) concentration of 500 mg L-1. The fungal species was grown in Czapek Dox media at pH 2.5 and 35oC temperature and its biomass was used in various forms such as live, autoclaved and alkali treated. With 1% (w/v) alkali treated biomass, the biosorption of chromium reached a maximum of 91% for a feed concentration of 500 mg L-1 in 2 h time at pH 2.5, temp 35oC and A/R (adsorbent : solution volume) ratio of 1/100. The lower biosorption of metal (42 - 44%) was observed with live and autoclaved biomass. The biosorption of chromium (III) on the fungal biomass was explained with various isotherms and fitted to the kinetic model involving first order expression. The study focuses on establishing the mechanism of bioremediation of chromium on A. niger.