Heterogeneous NiS/NiSe/3D porous biochar for As removal from water by interface engineering-induced nickel lattice distortion

Biochar has been widely used in the removal of heavy metals from wastewater due to its obligate adsorption properties. The reutilization of exhausted biochar has become a challenge for chemical researchers. In this study, diazotization-modified biochar adsorbing Ni 2+ was used as a precursor to prepare heterogeneous NiS/NiSe/3D porous biochar (DAC-Ni/NiS/NiSe) using vulcanization followed by in situ competitive hydrogen reduction. The composites exhibited excellent performance in As(III) removal from water via both adsorption and photocatalysis processes, removing 100% of 10 mg/L As(III) within 110 min with 20 mg catalyst, and 90% removal rate was maintained even after five recyclability runs. The influencing factors of As(III) oxidation in reactive DAC-Ni/NiS/NiSe suspensions were also investigated. The photocatalytic oxidation efficiency of As(III) was susceptible to initial pH. The coexisting species of PO 4 3− and CO 3 2− exhibited obvious suppression on the total As removal, while the presence of Cl − and NO 3 − exhibited no obvious effect on the oxidation efficiency of As. This study provides a feasible and simple strategy for reclaiming waste biochar after adsorbing nickel to prepare energy-intensive materials and implies the possibility and necessity of biowaste applications for environmental remediation.