Sustainable utilization of fly ash in crafting shell structure for the reduction of iron sludge in Fenton oxidation via enhanced core–shell interaction

The extensive production of fly ash, despite its untapped potential due to its inherent richness in Fe, Ca, Si and Al, remains significantly underutilized. Herein, we innovatively designed a core–shell catalyst, waste steel slag@fly ash (WSS@FAC). It features a Fe-rich waste steel slag core surrounded by a high-strength, porous fly ash shell, effectively utilizing these valuable resources. This design leverages not only the Fe content for catalytic activity but also the abundant Ca, Si and Al in fly ash to enhance the structural integrity of the shell. By strategically incorporating Na 2 SiO 3 , the compressive strength of the shell was significantly boosted from 12.10 MPa to 24.12 MPa, attributed to formation of a robust glass framework structure. Furthermore, modulation of NaHCO 3 content engineered Fe leaching channels with an average pore size of 14.46 nm within the shell, ensuring controlled release of Fe ions through core–shell interactions. When the initial concentration of rifampicin was 10–60 mg/L, the removal rate could be as high as 97.06 ± 1.93 % − 83.78 ± 0.47 %. Over an extended reaction period of 80 h, the leached Fe concentration for WSS@FAC was only 1.88 ± 0.11 mg/L, which was approximately one-ninth of that for the same initial mass of WSS catalyst. Remarkably, the catalytic performance of WSS@FAC decreased by only 9.23 % from its initial efficiency of 83.78 %, highlighting its exceptional long-term stability. This study presents a novel Fenton-like catalyst that not only reduces Fe sludge production but also advances the sustainable recovery of Fe-containing industrial wastes, underscoring the importance of comprehensively utilizing all components within fly ash.