Biochar-supported nanosized zero-valent iron (nZVI/BC) composites for removal of nitro and chlorinated contaminants

Organic, particularly nitro and chlorinated, contaminants are of great concern in ecosystem for their contribution to environmental problems worldwide. Nitro contaminants are mostly explosives in nature and harmful to ecosystem, and polychlorinated contaminants are main water pollution cause. Nanosized zero-valent iron (nZVI) could remove and degrade organic contaminants through chemical reduction and activated oxidation. To address short-term activity and agglomeration concerns of nZVI, biochar (BC)-supported nZVI (nZVI/BC) composite could be a feasible choice for practical reductive and oxidative removal of nitro and chlorinated contaminants. Carbonaceous BC has been successfully applied in removing contaminants from water and soil, but few research results led to less operation success due to low removal efficiency. Thus, BC and nZVI could compensate for one another’s shortcomings, and the synergistic features of nZVI/BC are beneficial to interaction with contaminants and enhanced removal efficiency. The purpose of this study is a comprehensive overview of nZVI/BC synthesis, characterization, and specified application for nitro and chlorinated contaminants removal. This review focuses, relates, and evaluates literature dedicated to nitro and chlorinated contaminants in the environment, their distribution and adverse effects, nZVI/BC synthesis and characterization, effect of influencing factors during remediation process, aging, and reusability of nZVI/BC on contaminants removal, and outcomes of reductive and oxidative degradation mechanisms. Also, it overviews cost and environmental implications of nZVI/BC synthesis and contaminant remediation processes. Finally, this review ends with future research prospects of nZVI/BC applications in progressive environmental remediation.