Biosorption-based elimination of hexavalent chromium using Bacillus cereus F4810/72 isolated from tannery effluents

Abstract

The leather industry of West Bengal continuously discharges chromium-laden effluents, with hexavalent chromium [Cr(VI)] being particularly persistent and toxic. Hexavalent chromium released from tannery effluents poses serious environmental and public health hazards due to its high mobility, solubility, and carcinogenicity. Biosorption offers a sustainable and cost-effective alternative to conventional physicochemical remediation methods. In this study, the biosorption potential of Bacillus cereus F4810/72, a strain previously isolated from tannery wastewater, was systematically evaluated for Cr(VI) removal under varying physicochemical conditions. Batch experiments were conducted to investigate the influence of initial metal concentration (10–1000 µg/mL), contact time (10–100 min), pH (1–9), biomass concentration (1–4 g/L), temperature (10–60 °C), and agitation speed (10–120 rpm) on biosorption efficiency. Maximum Cr(VI) removal (approximately 79–80%) was achieved under optimized conditions: 250 µg/mL initial Cr(VI), 4 g/L biomass, pH 3, 50 °C, 70 min contact time, and 80 rpm agitation. Langmuir and Freundlich isotherm models were applied to elucidate adsorption behavior. Nonlinear Langmuir modeling indicated monolayer adsorption with a maximum capacity (Q<inf>max</inf>) of 28.57 mg/g, whereas the Freundlich model (R2 = 0.98) suggested adsorption onto a heterogeneous surface. Regeneration studies showed that 2 M HCl and a combined HNO₃–ascorbic acid eluent exhibited superior desorption efficiencies, maintaining high uptake–release performance across three cycles. Overall, B. cereus F4810/72 demonstrates strong Cr(VI) biosorption and regeneration potential, highlighting its viability as a low-cost, eco-friendly biosorbent for chromium-contaminated industrial wastewater systems. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.