Journal of Fuel Chemistry and Technology•2026•DOI: 10.3724/2097-213X.2025.JFCT.0021
Red mud, an industrial solid waste from alumina production, poses severe environmental challenges. This study presents a resource-efficient strategy to convert red mud into high-performance microwave absorbing materials. FexOy/TiO2/C composites were synthesized via a sol-gel method using starch as carbon source, followed by carbothermal reduction. The phase composition and microstructure were optimized by adjusting calcination temperature and raw material ratio. The optimal sample, RmCT-5.4-700, exhibited a minimum reflection loss (RLmin) of -30.2 dB at 14.0 GHz with an effective absorption bandwidth (EAB) of 5.3 GHz at a coating thickness of 2.0 mm. The superior absorption performance is attributed to the synergistic effects of dielectric components (TiO2, graphitized carbon) and magnetic components (Fe3O4/Fe). Carbothermal reduction introduces defects that induce dipole polarization, while the conductive network formed by graphitized carbon and Fe3O4/Fe particles enhances conductive loss. Heterogeneous interfaces between Fe3O4, Fe, TiO2, and the red mud matrix promote interfacial polarization. The magnetic loss of Fe3O4/Fe improves impedance matching, facilitating electromagnetic wave penetration and absorption. This work not only provides a novel route for red mud valorization but also contributes to the high-value utilization of solid wastes.
Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202510034
Phosphonate wastewater, characterized by stable C–P bonds, poses significant environmental risks due to its resistance to degradation and potential to contribute to eutrophication. This study developed a chloride-enhanced Fe(II)/PMS/H2O2 system for the oxidative degradation of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) and simultaneous recovery of phosphorus as iron phosphate (FePO4). Under optimal conditions (0.1 mmol/L PBTC, 1.0 mmol/L Fe(II), 0.5 mmol/L PMS, 0.5 mmol/L H2O2, 10 mmol/L NaCl, initial pH 3.0, 60 min), total phosphorus (TP) removal reached 100%, with phosphorus nearly completely recovered as FePO4 precipitate. Increasing NaCl concentration and temperature enhanced TP removal, while pH significantly influenced removal efficiency and product speciation; acidic conditions (pH < 4.3) favored FePO4 precipitation. Coexisting Ca2+ and Mg2+ had negligible effects, whereas HCO3− and humic acid (HA) inhibited TP removal in a concentration-dependent manner. Radical quenching and electron spin resonance (ESR) analyses identified hydroxyl radicals (•OH), ferryl ion (Fe(IV)=O), sulfate radicals (SO4•−), and chlorine radicals (Cl•) as primary reactive species, with •OH playing a dominant role. Chloride introduction promoted the generation of multiple reactive species, and Cl• and its derivative Cl2•− directly attacked the C–P bond and phosphonate group, facilitating phosphorus release as PO43− and subsequent FePO4 formation. The system's feasibility was validated using actual industrial circulating cooling water. This study provides a novel approach for phosphonate wastewater treatment and phosphorus recovery.
Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202511005
To enhance the adsorption performance of volcanic rock for nitrogen in water, an α-Fe2O3/volcanic rock composite was successfully prepared via ferric citrate impregnation and calcination. Its adsorption characteristics for NH4+-N and NO3−-N and application in tidal flow constructed wetlands (TFCWs) were systematically investigated. Results showed that the adsorption kinetics of both nitrogen forms followed a pseudo-second-order model, indicating chemisorption dominance. Langmuir and Freundlich isotherm models both fitted the data, suggesting coexistence of monolayer and multilayer adsorption. The saturated adsorption capacities of α-Fe2O3/volcanic rock for NH4+-N and NO3−-N were 0.055 mg·g−1 and 0.067 mg·g−1, respectively. In TFCWs using this composite as substrate, average removal efficiencies for NH4+-N and NO3−-N reached 72.51% and 68.13%, respectively. Furthermore, microbial community abundance and diversity in the wetland system significantly increased, indicating that α-Fe2O3 introduction effectively enhanced microbial activity, thereby improving nitrogen removal efficiency.