In this study, coal fly ash supported MnO₂ (CFA@MnO₂) was synthesized as heterocatalyst for the activation of peroxymonosulfate to degrade Acid Red 73 (AR73). The synthesized catalyst was characterized by X-Ray Fluorescence Spectrometer(XRF), X-ray powder diffraction(XRD), Scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS), and Brunauer-Emmett-Teller(BET). The composite of CFA@MnO₂ possesses a large surface area of 74.59m²·g⁻¹. In the catalytic experiment, CFA@MnO₂ exhibits excellent catalytic performance with 99.13% AR73 removed within 40 min with a high kinetic rate constant of 0.124 min^-1, 5.49 times higher than that of pure MnO₂. The operating parameters of CFA@MnO₂-based fenton catalytic system were discussed, including MnO₂ loading, solution pH, PMS dosage, and temperature. The catalyst maintained a relatively high removal rate (>85%) over 5 cycles and degradation intermediates are detected on the catalyst surface after cycled via XPS analysis. The degradation mechanism was investigated by quenching experiments and Electron Paramagnetic Resonance technology. The surface-bound ^·OH and SO4^·- are considered as the main active radicals in the degradation process. The composite of CFA@MnO₂ provides a low-cost and efficient alternative for the catalytic oxidation of organic pollutants.

The preparation of high-purity sulfur and pyrrhotite by pyrolysis holds great potential to realize the high-value utilization of pyrite concentrate (FeS₂), i.e., a by-product during the flotation of sulfide ore. In this study, the pyrrhotite obtained from the pyrolysis of pyrite concentrate was taken as the study object, and the effects of acid types, initial acidity, leaching time, leaching temperature, oxygen pressure, and liquid-to-solid ratio on the leaching behavior of pyrrhotite under oxygen pressure, were explored. The results show that elemental sulfur and hematite-based iron residue can be obtained by oxygen pressure leaching of pyrrhotite. It is found that the optimal experimental conditions for pyrrhotite oxygen pressure leaching are hydrochloric acid with 0.8 mol/L of initial acidity, 5 h of leaching time, 0.8 MPa of oxygen partial pressure, and 9:1 of liquid to solid ratio at 150 °C; moreover, the yield of sulfur reached 88.37%. Under optimal conditions, the leaching ratios of Fe, Pb, and Zn were 19.8%, 92.25%, and 99.11%, respectively. The sieved leaching residue was roasted at a low temperature of 500 °C, where the grade of Fe in the obtained hematite iron powder was 61.46%, and the grades of Pb, Zn, and S were 0.082%, 0.024%, and 0.1%. Clearly, the results meet well with the standard of the first grade of pyrite cinder, and this process realizes the comprehensive recovery of Fe and S resources in pyrolysis slag, which provides a superb technical route for the high-value utilization of pyrite concentrate.