Tungsten carbide induced acceleration of Fe3+/Fe2+ cycle in Fe2+/PMS process for rapid degradation of tetracycline hydrochloride

Metal sulfides have gained significant attention as cocatalysts for Fenton/Fenton-like processes in recent years due to their ability to reduce trivalent iron (Fe3+). Nevertheless, the issue of hydrogen sulfide (H2S) formation as a secondary contaminant is a significant concern. In this work, tungsten carbide (WC) was innovatively introduced into the Fenton-like process based on ferrous ion/peroxymonosulfate (Fe2+/PMS). The results showed that the WC/Fe2+/PMS system had a significantly higher degradation efficiency and rate for tetracycline hydrochloride (TC) than the Fe2+/PMS system. The WC/Fe2+/PMS system can work efficiently over a wide pH range (2.8–8.5), and WC has excellent reusability with negligible metal leaching. X-ray photoelectron spectrum analysis proved that the presence of W(Ⅳ) on the WC surface contributes to its excellent co-catalytic performance. Electrochemical characterization indicated that WC can facilitate the electron transfer of the system. Electron Paramagnetic Resonance analysis demonstrated that WC significantly improves the generation of four oxidative species by the Fe2+/PMS system as a result of the enhanced PMS activation due to the continuous reduction of Fe(Ⅲ) by WC. Moreover, the WC/Fe2+/PMS system can work effectively under a complex water matrix and has an excellent degradation effect on other pollutants. In summary, this study provides a novel and eco-friendly cocatalyst to accelerate the Fe3+/Fe2+ cycle and activate PMS for TC degradation.