Biosorptive performance of Escherichia coli supported on Waste tea biomass (WTB) for removal of Cr(VI) to avoid the contamination of ground water: A comparative study between biosorption and SBB system

Abstract

The present study deals with simultaneous biosorption and bioaccumulation (SBB) batch system for the removal of hexavalent chromium Cr(VI) from aqueous solution using biofilm of Escherichia coli immobilized onto the surface of WTB. For comparison purpose the same study was carried out without bacterial biofilm using WTB as biosorbent. The effect of process parameters like pH, adsorbent dose, contact time, initial concentration of adsorbate on to the percentage removal of Cr(VI) has been determined for both SBB system and biosorption using WTB. The maximum percentage removal was found at pH 6–7 and temperature 37°C. The adsorbent dose in case of SBB system was 15g/L while in case of adsorption using WTB was 30g/L at pH 7 and temperature 37°C. A 99.99% removal of Cr(VI) at an initial concentration of 150mg/L was obtained in both SBB system and biosorption using WTB but for the concentration greater than 150mg/L, maximum percentage removal was obtained in SBB system which shows that SBB system at higher concentration of toxic pollutant is better than biosorption using WTB. Kinetic and equilibrium isotherm studies were performed to know the nature of biosorption. It was found that pseudo-second order model is followed in both cases with and without E. coli biofilm supported on WTB (SBB system and biosorption using WTB) indicating that chemisorption is the mechanism of biosorption. Here equilibrium isotherm study was also performed which shows that Langmuir isotherm was followed in case of SBB while Freundlich isotherm was followed in case of biosorption using WTB.