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 Ni2+ 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 PO43- and CO32- exhibited obvious suppression on the total As removal, while the presence of Cl- and NO3- 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. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrated the successful preparation of heterogeneous NiS/NiSe/3D porous biochar using exhausted biochar adsorbing Ni2+ as a precursor. The composites showed excellent performance in As(III) removal through both adsorption and photocatalysis processes. Factors influencing the oxidation of As(III) in the reactive suspensions were investigated, with initial pH and coexisting anions playing significant roles.