Utilization of Bacillus thuringiensis MC28 as a biosorbent for mercury in groundwaters from some selected gold mining communities in the Wassa West District of the Western Region of Ghana

Abstract

In this study, Bacillus thuringiensis MC28 was investigated for its utilization as a potential adsorbent for mercury in aqueous solutions. The batch adsorption procedure was used to optimize the method. At optimal conditions of pH 8, 3.5 mL of organism, contact time of six days and 35 °C, 99.94–99.98% of mercury in groundwater samples were removed. The Langmuir isotherm parameters estimated by nonlinear method best fitted the adsorption data. The maximum monolayer coverage of the organism, the Langmuir constant, and the Langmuir separation factor (RL) were found to be 6.23E + 00 mg/mL, 253.82E + 03 L/mg and 3.94E − 07 respectively. The mercury removal was found to have occurred by chemisorption. The Elovich kinetic model best fitted the data and the rate determining step of the process was found to be bulk diffusion process. The thermodynamic properties viz: ΔH°, ΔS° and ΔG° of the mercury – B. thuringiensis MC28 adsorption system were estimated to be −114.80 kJ/mol, 391.42 kJ/mol and −506.22 kJ/mol respectively. Under the optimum physico – chemical conditions, the minimum energy required to initiate mercury removal was estimated to be 167.50E − 03 kJ/mol. The findings showed that, mercury removal process was exothermic, spontaneous, thermodynamically feasible, and the B. thuringiensis MC28 demonstrated remarkable affinity for mercury. Therefore, B. thuringiensis MC28 could be used as an adsorbent in water treatment procedure to remove mercury and restore mercury contaminated waters to their pristine.