Optimization and mechanistic study on bioremediation of Cr (VI) using microbial cell immobilized sugarcane bagasse biochar

Hexavalent chromium (Cr (VI)), a highly toxic heavy metal, contaminates water bodies due to its heavy usage in industrial processes. The present study proposes an environmentally friendly strategy for the bioremediation of Cr (VI) from water systems. Bacillus sp. was immobilized onto sugarcane bagasse biochar (BSCB) to remediate Cr (VI). The Cr (VI) removal process was optimized through one-factor-at-a-time (OFAT) and response surface methodology (RSM). Results showed that BSCB effectively removed 93.56 % of Cr (VI), with optimum conditions of 100 mg L−1 initial Cr (VI) concentration, 12 h incubation time, 40 °C temperature, pH 7.0, and 0.1 % BSCB dosage. The study also investigated reusability of BSCB across five consecutive cycles for the removal of Cr (VI) under optimized operating conditions, showcasing its consistent high performance compared to both sugarcane bagasse biochar (SCB) and free cells. BSCB maintained an average removal efficiency of 88.2 % across three cycles, outperforming SCB (56.67 %) and free cells (82.24 %). This immobilization approach enables better recovery of bacterial cells from water bodies and presents a sustainable, cost-effective bioremediation solution for Cr (VI) removal.