A novel biochar-copolymer composite for rapid Cr(VI) removal: Adsorption-reduction performance and mechanism

In this work, a novel biochar-copolymer composite (CPBC) that can efficiently remove Cr(VI) from water was successfully synthesized. The physicochemical properties of CPBC were fully characterized by various characterization techniques. The removal performance and mechanisms of Cr(VI) by CPBC were systematically studied. The results of characterization showed that CPBC possessed a considerable pore structure and abundant oxygen-containing and nitrogen-containing functional groups. The results of experiments demonstrated that CPBC had excellent performance for Cr(VI) removal. CPBC could remove 99.7% of Cr(VI) in half an hour, with the maximum removal capacity of 491.3 mg/g, and it could effectively resist the interference of various coexisting ions and organics. Through the analysis of the removal mechanism, it was found that the process of Cr(VI) removal by CPBC involved the synergy of adsorption and reduction. Different functional groups in CPBC played different roles. Among them, hydroxyl groups could reduce Cr(VI) to Cr(III) with the participation of hydrogen ions, protonated N combined with negatively charged Cr(VI) through electrostatic interaction, and other oxygen-containing nitrogen-containing groups remove Cr(VI) and Cr(III) through complexation. Furthermore, the practical application potential of CPBC was evaluated from generality, reusability, and actual water treatment capacity. It was found that the removal efficiency of CPBC for various pollutants exceeded 97.2%, it could be recycled for more than three times, and the removal efficiency of Cr(VI) in several actual water samples exceeded 91.7%, demonstrating that the good practical application potential of CPBC.