A critical review of environmental remediation via iron-mediated sulfite advanced oxidation processes

In response to the increasingly serious environmental pollution problem, iron-based sulfite activation has been considered as an effective option for environmental remediation. This article aims to make a scientific review of the recent progress on sulfite activation by iron-based materials, as well as the detailed activation mechanism. Advanced oxidation processes (AOPs) via sulfite activation by homogeneous and heterogeneous iron-based materials for the pollutant removal during the environmental remediation depended on various reactive species such as HO•, SO3•-, SO4•-, SO5•-, and high-valent iron-oxo species was proposed due to the dual property of sulfite as an oxidability and reducibility. The introduction of extra energy into the iron-based activated sulfite process, especially the most adopted photo-irradiation, strengthens the oxidation performance. Importantly, the favorable application in organic compounds degradation, heavy metal removal, oxidation disinfection, and pretreatment of waste activated sludge indicated the promising potential of iron-based materials activated sulfite process. Water chemistry involving initial pH, iron-based materials dosage, sulfite concentration, dissolved oxygen concentration, and water matrices on the treatment efficiency was analyzed. Finally, the potential challenge and future research prospect in the sulfite activation through iron-based materials have been proposed.