The application and mechanism of iron sulfides in arsenic removal from water and wastewater: A critical review

Over the last decades, a large amount of arsenic-containing wastewater discharged by industries has seriously polluted groundwater and drinking water, resulting in the number of arsenicosis patients increasing day by day. Iron sulfides are considered promising for effective arsenic removal from water/wastewater due to their exclusive physical and chemical properties. The applications of various iron sulfides materials, including natural pyrite and pyrrhotite, modified pyrite, nanostructure FeS and FeS2, in arsenic removal from aqueous solution are summarized. The present review paper mainly analyzes the performance and influencing factors of iron sulfides in arsenic removal, the synthetic conditions of nanoparticles, and their limitations. pH and temperature are the two main factors affecting the removal efficiency of arsenic in low arsenic-containing water. It is necessary to modify natural iron sulfide or synthesize FeS, which will significantly enhance the reactivity of iron sulfides in high concentration arsenic-containing wastewater. The mechanisms behind the arsenite and arsenate removal by iron sulfides are discussed in detail. Adsorption and precipitation are the primary removal mechanisms of low concentration and high concentration arsenic-containing wastewater, respectively. Future needs in arsenic removal technology using iron sulfides are also proposed. Overall, iron sulfides offer considerable potential towards powerfully removing arsenic in both low and high concentrations of water/wastewater.