Sulfite activation by oxidized pyrite for dye degradation assisted by oxygen

Abstract

Because pyrite is easily oxidized, the catalytic performance of a pyrite-peroxymonosulfate (PMS) or peroxydisulfate (PDS) activation system will be significantly affected due to the low activation of PMS or PDS by Fe³⁺ in practical applications. Herein, sulfite was selected to react with oxidized pyrite (OP) to generate radicals for the degradation of dye wastewater in the presence of oxygen because both Fe²⁺ and Fe³⁺ can be used as efficient activators of sulfite. Under the optimal conditions, an OP/sodium sulfite (SS) system achieved high-efficiency removal of rhodamine B (RB) in the wide pH range of 4.0–9.0. In the OP/SS system, sulfite was mainly activated by dissolved iron. Moreover, by comparison with an acid-washed pyrite (AWP)/SS system, Fe(III) on the surface of pyrite, instead of Fe(II), acted as the active site of sulfite activation in the heterogeneous reaction of the OP/SS system. In addition, good reusability of OP and high decolorization of different dye pollutants made the OP/SS system possibly suitable for application in dye wastewater treatment.