Fabrication and characterization of hydrophilic corn stalk biochar-supported nanoscale zero-valent iron composites for efficient metal removal.

Pyrolyzing low-cost agro-waste into biochar is a promising means for waste biomass utilization. This study engineers corn stalk-derived biochar with abundant hydrophilic functional groups as a support material for iron nanoparticles impregnation (nZVI-HCS). Surface chemistry and morphology of nZVI-HCS composites is characterized by SEM, TEM, TG, XRD, FTIR, XPS, and BET techniques, which helps to elucidate the mechanisms of Pb2+, Cu2+ and Zn2+ removal from single and mixed-metal solutions in batch experiments. Equilibrium adsorption capacities can reach 195.1, 161.9 and 109.7 mg·g-1 for Pb2+, Cu2+ and Zn2+ at neutral medium after 6-h process, respectively. The engineered biochar with hierarchical pores can impregnate iron nanoparticles, serve as an adsorbent, and enhance metal reduction/precipitation. Rapid removal and high performance can be maintained after five regeneration/reuse cycles. Multiple interaction mechanisms including adsorption, precipitation, reduction and complexation are responsible for metal removal by nZVI-HCS composites, which can be a novel biowaste-derived material for wastewater treatment.