Nitrogen-doped porous carbon encapsulating iron nanoparticles for enhanced sulfathiazole removal via peroxymonosulfate activation.

Developing novel catalyst with both high efficiency and stability presents an enticing prospect for peroxymonosulfate (PMS) activation. In this paper, nitrogen-doped porous carbon encapsulating iron nanoparticles (CN-Fe) was fabricated by a facile carbothermal reduction process using polyaniline (PANI) and α-FeO as the precursors. The stubborn antibiotics, sulfathiazole (STZ), was employed as a target pollutant, demonstrating that CN-Fe coupled with PMS could achieve 96% removal efficiency and even 57% mineralization rate of STZ within 40 min. More importantly, the rate constant of CN-Fe was calculated to be 0.07665 min, which was 6 times higher than that of the commercial α-FeO catalyst. Furthermore, CN-Fe also presented a favorable catalytic performance for removing other organic pollutants including phenolic compounds and organic dyes. Interestingly, the catalytic activity of the used CN-Fe catalyst could be regenerated after thermal treatment (600 °C) and the as-synthesized CN-Fe catalyst exhibited excellent long-term stability with almost no loss of activity after storage for three months. The catalytic mechanism in the CN-Fe/PMS system was elucidated by electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV), radical and electron trapping tests, which confirmed that sulfate radicals (SO), hydroxyl radicals (OH), superoxide radicals (O) and singlet oxygen (O) were generated in the oxidation process with the assistance of electron transfer between PMS and catalyst. To our knowledge, this was the first attempt for the application of PANI-derived CN-Fe hybrid materials as PMS activators and the findings would provide a simple and promising strategy to fabricate highly efficient and environment-benign catalysts for wastewater remediation.