Natural Pyrite as a Catalyst for a Fenton Reaction to Enhance Xanthate Degradation in Flotation Tailings Wastewater

The efficient treatment of mineral-processing wastewater has attracted soaring interest recently. This study’s objective was to degrade xanthate from flotation tailings wastewater using a pyrite-catalyzed Fenton system. A sodium butyl xanthate (SBX) removal rate of more than 96% was achieved via the method under optimal conditions (a H2O2 concentration of 0.5 mM, a FeS2 concentration of 0.5 g/L, an initial SBX concentration of 100 mg/L, and a natural pH of 9.36 ± 0.5), which is 12.85% higher than with a H2O2 system. An appropriate concentration of natural pyrite can act as a catalyst to significantly improve the oxidation capacity of H2O2. Additionally, the results of electron paramagnetic resonance and quenching measurements suggest that hydroxyl radicals (•OH) are the main active species in the H2O2-FeS2 system. The possible reaction mechanism is proposed. The H2O2 adsorbs onto the pyrite surfaces and reacts with Fe2+, triggering the formation of •OH and Fe3+. The •OH most likely attacks the SBX that adsorbs on the pyrite surface or exists in the solution and promotes the transformation of the SBX anion (C4H9OCS2−) into the intermediate butyl xanthate peroxide (BPX, C4H9OCS2O−). Finally, BPX intermediates are likely further oxidized to smaller products such as SO42−, CO2, and H2O under the ongoing attack of •OH.