Surface-engineered coal gasification fine slag supported with highly dispersed FeS nanoparticles to enhanced peroxymonosulfate activation for Azo pollutant degradation

Background Coal gasification fly ash (CGFS) poses severe environmental threats due to its massive discharge, necessitating urgent treatment and valorization. Methods This study developed a facile chemical precipitation method to synthesize CGFS-supported iron sulfide catalyst (FeS@CGFS) for activating persulfate to treat coal chemical wastewater. Significant findings FeS@CGFS exhibited a unique coral-like structure with well-dispersed FeS nanoparticles on CGFS, effectively suppressing aggregation. The catalyst demonstrated exceptional Rhodamine B degradation activity across a broad pH range (3–9), achieving 98.64% removal of 20 mg/L RhB within 10 min under optimal conditions (pH 6, 0.060 g/L catalyst, 0.05 mM potassium persulfate). Mechanistic studies identified sulfate radicals (SO₄•⁻) and hydroxyl radicals (•OH) as primary reactive species. The coral-like structure enhanced pollutant adsorption and electron transfer, while S²⁻ facilitated Fe³⁺/Fe²⁺ cycling to sustain reactive species generation. This work provides a strategic blueprint for the high-value utilization of CGFS, and also offers a representative case for implementing the "waste-treats-waste" strategy and on-site treatment of coal chemical wastewater.