Degradation of sodium butylxanthate in flotation wastewater by natural pyrite via visible light-assisted advanced oxidation processes: A comprehensive study

The advanced oxidation process (AOPs) based on natural pyrite (NP) as a catalyst is a promising strategy for flotation wastewater purification. However, the slow Fe(III)/Fe(II) cycle limits the number of active sites during oxidant activation. Therefore, this work attempts to accelerate Fe(III)/Fe(II) reduction on NP surface by introducing visible light irradiation. By comparing the degradation performance of sodium butylxanthate (SBX) via various oxidants (peroxydisulfate, periodate, hydrogen peroxide, and sulfite) activation under visible light, periodate was selected as the most suitable oxidant for SBX removal. Although peroxydisulfate exhibits optimal SBX degradation in acidic environments, its failure in alkaline environments and poor reusability caused by high surface oxidation limit its application. The investigation of active species suggests that O2 center dot- are the dominant active species in hydrogen peroxide and sulfite activation systems, while the electron transfer process is the dominant active species in peroxydisulfate and periodate activation systems. Electrochemistry elucidates the interaction of different oxidants on the NP surface. XPS analysis revealed that the photogenerated electrons induced by visible light irradiation accelerate the Fe(III)/Fe(II) cycle on NP surface, thereby improving the continuous activation of NP towards the oxidants. In addition, the ecotoxicity of wastewater treated by the periodate activation system is greatly reduced. This work provides a new idea towards flotation wastewater purification.