Enhanced degradation of tetracycline using ferrihydrite-decorated g-C3N4 via photocatalytic activation of peroxymonosulfate

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While antibiotics benefit human health, their misuse and improper disposal harm ecosystems and human health. Thus, a novel Fh/N-g-C3N4 composite photocatalyst was prepared by in situ growing of ferrihydrite (Fh) nanoparticles on the surface of nitrogen-doped g-C3N4 (NCN) for the activation of peroxymonosulfate (PMS), to efficiently photo-degrade tetracycline. In this composite, the separation and transfer efficiency of photo-generated electron-hole pairs were significantly improved, while their recombination was effectively inhibited. The performance of the Fh/NCN-PMS system in degrading tetracycline under visible light demonstrated that 20%Fh/NCN composite photocatalyst, when coupled with PMS at a concentration of 200 mg/L, resulted in a degradation efficiency of 96.9 % for tetracycline at a concentration of 20 mg/L within 30 min. Mechanism investigation revealed that 4 main active species (SO4−, O2−, 1O2 and h+) were involved in tetracycline degradation, with 1O2 and h+ playing a predominant role. Moreover, the Fh/NCN composite demonstrated superior and consistent catalytic performance in activating PMS within a pH range of 4.5 to 10. Notably, the tetracycline degradation efficiency diminished by merely 7.1 % after four cycles of use. This study introduces a new strategy for fabrication of novel photocatalytic-PMS system, providing an efficient and highly stable treatment solution for antibiotic wastewater.