Removal of Bismuth from Water by Orange Peel Biochar

The dissemination of bismuth (Bi) into the environment has become a significant concern due to its wide application. The low-cost orange peel was used as a bio-sorbent to remove Bi from water. Influence of pH (4 similar to 12), biochar dosage (5 similar to 12.5 g L-1), temperature (25 similar to 55 degrees C), and coexisting ions (Mg2+ and Zn2+) on Bi adsorption were investigated. The removal rate was 91.90% when 10 g L-1 adsorbent was added at 25 degrees C in 40 mL Bi solution with an initial concentration of 50 mg L-1. The pseudo-second-order kinetic model could better describe the adsorption process than pseudo-first-order model, demonstrating that the adsorption of Bi by the orange peel biochar was predominantly chemisorption. Analytical techniques such as SEM, FTIR, XRD, and XPS indicated that the adsorption mechanism concerned electrostatic attraction, ion exchange, pi-pi electron donor-acceptor interaction, - OH and - COOH complexation, and pore filling. Orange peel biochar demonstrated a sustained performance, maintaining over 65% removal efficiency for Bi after three regeneration cycles. Orange peel biochar has a good application prospect as a cost-effective bio-sorbent for the treatment of Bi removal from water.