Magnetic Nanoscale Zerovalent Iron Assisted Biochar: Interfacial Chemical Behaviors and Heavy Metals Remediation Performance

It has been reported that zerovalent iron can help biochar improve efficiency in heavy metal (HM) absorption, but the surface chemical behaviors and HM removal mechanisms remain unclear. We successfully synthesized the magnetic nanoscale zerovalent iron assisted biochar (nZVI-BC). The porosity, crystal structure, surface carbon/iron atom state, and element distribution were comprehensively investigated to understand nZVI-BC's interfacial chemical behaviors and HM removal mechanisms. We clearly revealed the formation of a nanoscale Fe⁰ core-Fe₃O₄ shell on the surface/pores/channels of biochar. With the combination of iron nanoparticles and biochar, C-O/COOH groups were cracked with the formation of C=O/C=C, indicating the C-O-Fe acted as an electron acceptor during the reduction reaction. We also demonstrated that the stabilization was dramatically improved in the nZVI-BC, while more reduced iron and better homogeneity were observed. These results, showing the surface chemical behaviors of nZVI-BC, would help increase our understanding of the HM removal mechanisms. Moreover, our demonstration of the superior removal ability of multiple HM (Pb²⁺, Cd²⁺, Cr⁶⁺, Cu²⁺, Ni²⁺, Zn²⁺) from a solution can provide a breakthrough in making a feasible material for removing HM from polluted water resources.