Sulfidation of zero-valent iron for enhanced reduction of chlorinated contaminants: A review on the reactivity, selectivity, and interference resistance

Chlorinated hydrocarbons (CHCs) are of worldwide concerns for posing environmental and health issues, especially in soil and groundwater systems. The emergence of sulfidized zero-valent iron (S-ZVI) has boosted the development of remediation techniques for the removal of CHCs. Recent studies summarized a state-of-the-art understanding of the fundamental characteristics for enhanced reactivity of S-ZVI, which provide valuable insights into the mechanisms for sulfidation enhanced reactivity, selectivity, and interference resistance. These aspects are significant in advancing the rational design and field application of S-ZVI for groundwater remediation. This review aims to comprehensively apprehend the key aspects of S-ZVI, focusing on the sulfidation induced physicochemical properties for enhanced dechlorination performance of ZVI. The CHCs treatment and dechlorination pathways were summarized. The mechanisms of sulfidation enhanced dechlorination were explored with a particular emphasis on selectivity, and the comparison of dechlorination performance was made with other modifications, including the ZVI particles modified by transition metals, nitride, and carbon materials. In addition, a better understanding of the impacts of aging and potential interference in actual groundwater, notably co-existing ions and contaminants, on the dechlorination by S-ZVI are provided. Hopefully, this review will inspire the development of groundwater remediation by S-ZVI-based materials.