Utilization of iron sulfides for wastewater treatment: a critical review

Acid mine drainage due to weathering of iron sulfide minerals is one of the biggest global environmental issues. However, due to the unique physicochemical properties of natural and synthesized iron sulfides (i.e. pyrite, pyrrhotite, and mackinawite), they can be effectively used for wastewater treatment. These properties, such as ≡SH functional groups as Lewis bases, reducibility of surface Fe and S species, dissolved Fe²⁺ as a catalyst, and dissolved S^2? as an electron donor, are extensively reviewed in this article. The target water pollutants include toxic metals (i.e. lead, mercury, cadmium, and hexavalent chromium) and metalloid (i.e. arsenic), radionuclides (i.e. uranium and selenium), organic contaminants (i.e. chlorinated organic pollutants, benzene and polycyclic aromatic hydrocarbons), and nutrients (i.e. nitrogen and phosphorus). The dominant interaction mechanisms between iron sulfides and these contaminants, and the removal efficiencies are elucidated. This article focuses on the role of iron sulfides as functional materials for wastewater treatment. A recent development of nanostructured pyrrhotite with a high specific surface area for wastewater treatment is also highlighted.