Peroxymonosulfate activation by iron-sulfur tailings doped with SiO₂ for efficient degradation of tetracycline

Developing suitable peroxymonosulfate (PMS) catalysts for activation in purification processes is challenging. The high-performance PMS activation catalyst, PTSi, was successfully synthesized by incorporating SiO₂ nanoparticles into nanoscale iron-sulfide tailings through a co-precipitation and calcination method. Under optimal conditions, PTSi achieved a tetracycline (TC) removal efficiency of 95.46% in aqueous solutions within 60 min. After three reuses, the catalyst maintained its strong performance. The active oxygen species (ROS) involved in the degradation of TC were confirmed through electron paramagnetic resonance (EPR) and radical quenching experiments. These experiments demonstrated that SiO₂ doping enhanced the formation of oxygen vacancies (OVs) on the catalyst surface. Based on X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) characterization data, it was found that Fe²⁺ and OVs on the surface of the PTSi catalyst rapidly generate ¹O₂ after activating PMS, thereby accelerating the degradation of TC. The potential degradation pathways of TC within the PTSi/PMS system were examined through liquid chromatography-mass spectrometry (LC-MS) analysis. This study proposes a novel approach to treat one type of waste using another, aiming to prepare reusable PMS catalysts from mineral processing residues. This method demonstrates significant potential for water pollution control and the utilization of iron-sulfur tailings.