Preparation of trifunctional magnetic ZnO-based biochar for pollutions removal from wastewater

The trifunctional magnetic Fe3O4/ZnO-based biochar (ZF-BC) was prepared for the removal of levofloxacin and Cr6+ from wastewater in single and binary contaminant systems. The physical and chemical properties of the ZF-BC were characterized and analyzed. The adsorption amounts of levofloxacin and Cr6+ for ZF-BC are 332.11 and 34.40 mg/g in a single contaminant system based on Hill model calculation, respectively. Levofloxacin slightly contributes to Cr6+, while levofloxacin adsorption on ZF-BC is restrained at high Cr6+ concentration in the binary contaminant system. The levofloxacin and Cr6+ adsorption mechanism were investigated and analyzed, combined with density functional theory calculations. ZF-BC also has excellent reusability and stability for levofloxacin and Cr6+ adsorption. Using the photocatalytic degradation system, 97.60% of levofloxacin and 79.43% of Cr6+ were removed. The photocatalytic degradation mechanism analysis indicates that levofloxacin is first adsorbed on ZF-BC and then used as the hole sacrificial agent to release more electrons/holes to participate in the Cr6+ redox reaction.