Oil shale semi-coke-activated persulphate treatment of aniline wastewater: feasibility and reaction mechanism

This study employed oil shale semi-coke (OSSC), a solid waste from oil shale pyrolysis, as a persulphate (PS) activator for the treatment of aniline wastewater. The catalyst was characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS), etc., which revealed its porous structure along with the presence of low-valent iron and organic components. The research evaluated its catalytic performance, optimized the degradation process, and elucidated the reaction mechanisms. Under the optimized conditions of an OSSC dosage of 5 g/L, a PS concentration of 7.5 mM, an initial pH of 3, and a temperature of 80 °C, complete removal of aniline was achieved within 60 minutes. Mechanistic analysis indicated that the system operates via synergistic radical and non-radical pathways. The low-valent iron in OSSC activates PS to generate reactive oxygen species such as SO4•–, •OH, O2•–, thereby initiating the oxidative polymerisation of aniline. The resulting polyaniline-like polymers are effectively immobilized onto the OSSC matrix, forming a composite material. This work provides new insights into the reaction mechanisms of heterogeneous PS activation systems and proposes a promising waste-treats-waste strategy for the resource utilisation of OSSC and the degradation of aniline.