Efficient degradation of tetracycline hydrochloride by activation of peroxomonosulfate on a magnetic steel slag/MoS₂ composite <i>via</i> ball milling

The dual environmental challenges of solid waste magnetic steel slag (MSS) utilization and antibiotic pollution treatment require novel environmental remediation strategies. Herein, a novel MSS@MoS₂ composite catalyst was prepared for the first time by an alkali pretreatment of MSS followed by one-step high-speed ball milling functionalization with MoS₂. The optimized MSS@MoS₂-50 catalyst showed outstanding peroxomonosulfate (PMS) activation capability, enabling efficient tetracycline hydrochloride (TCH) degradation across a broad pH range (2-11). Mechanistic investigations revealed the generation of multiple reactive species (¹O₂, ˙O₂^-, ˙OH, and SO₄˙^-) through synergistic Fe²⁺/Fe³⁺ redox cycling and multi-valent Mo-mediated electron transfer. The catalytic activity of MSS@MoS₂-50 showed only a 12% decrease after five cycles but almost recovered to its initial level <i>via</i> simple regeneration, showing good stability and renewability. The leaching of iron ions (<0.2 mg L^-1) after the reaction was below the standard for surface water. Additionally, it has good magnetic separability, showing good application potential. The three possible degradation pathways were proposed by combining the results of LC-MS and active species analysis. The toxicity of TCH can be effectively reduced after degradation by the T.E.S.T. toxicity analysis.