Nanoscale Zero-Valent Iron Supported on Carbon Nitride as a Peroxymonosulfate Activator for the Efficient Degradation of Paraxylene

Nanoscale zero-valent iron (nZVI) supported on polymeric graphitic carbon nitride (CN) composite (nZVI@CN) was synthesized via liquid phase reduction method as peroxymonosulfate (PMS) activator, and had been achieved efficient degradation of paraxylene (PX) in this study. The physicochemical properties of nZVI@CN were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, Scanning electron microscopy and Brunauer–Emmett–Teller. The results indicated that catalyst prepared with 1:1 of nZVI and CN mass ration showed the best catalytic performance for the PX degradation. The removal efficiency of PX was 90.9% within 30 min treatment with the optimal reaction conditions (1 mM PMS, 0.1 g/L nZVI@CN, 20 mg/L PX and pH 6.86), and the mineralization rate measured by the removal of total organic carbon had reached 82.6%. Radical quenching and Electron paramagnetic resonance detection confirmed that sulfate and hydroxyl radicals generated by PMS activation were responsible for the degradation of PX, and sulfate radicals were the dominant active species. In addition, the possible reaction mechanism was proposed based on the experimental results. The nZVI@CN can not only be suitable for wide pH range (3–9) to effectively remove PX, but also has good stability and reusability. The removal efficiency of PX was higher than 60% in the fifth reuse experiment, which indicated that nZVI@CN was a stable PMS activator for efficiently PX removal in water.