Biosorption of Cr(VI) by Calcium Alginate-Encapsulated Enterobacter aerogenes T2, in a Semi-Batch Plug Flow Process

Abstract

Carcinogenic heavy metal chromium, in its hexavalent form Cr(VI) is spuriously used in various industrial operations because of its hardness and stability. Due to lack of proper remediation processes, effluents contain Cr(VI) in large excess of WHO’s statutory limit of 50 μg l−1. In this study, a biosorption-based remediation strategy is proposed for the remediation of Cr(VI) from contaminated samples. The novel bacterial strain Enterobacter aerogenes T2 (GU265554, NII 1111) was isolated from Cr(VI)-contaminated tannery effluent and used for bioremediation studies. The cell-free extract (CFE) was prepared and encapsulated in spherical calcium alginate biopolymeric beads. A semi-batch plug-flow-packed bed made of these beads was used for biosorption of Cr(VI). A remediation rate of 932 mg Cr(VI) m−3 water per day with a sorption efficiency of 93.2 % was achieved. The method exhibited the best results when compared to those reported in the literature. Various isotherm models of adsorption such as Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) were studied. The results predicted adsorption in a multi-layered fashion via physisorption. The developed technology could be considered as green since no synthetic chemical was used for sorption of Cr(VI).