Insight into photo-fenton catalytic degradation of tetracycline by environmental friendly nanocomposite 1T-2H hybrid phases MoS2/Fe3O4/g-C3N4

Photogenerated charge recombination is a bottleneck in the field of photocatalysis. Polycrystalline materials may be an actual way to solve this problem. In this study, a novel 1T-2H hybrid phases MoS2/Fe3O4/g-C3N4 nanocomposite (MFG) was synthesized to improve the photo-Fenton degradation under visible light on tetracycline whose emergence in water environment had attracted great public attention. We got an insight into the photo-Fenton catalytic effect on tetracycline via detailed investigation and discussion. MFG was synthesized by calcination, hydrothermal and coprecipitation. The successful synthesis of 1T-2H hybrid phases MoS2 (HP–MoS2), as a polycrystalline material, was proved by XRD and XPS. After HNO3 treatment, the grain size of bulk g-C3N4 decreased obviously, and the photocatalytic effect was also improved. It showed stable performance and significant photo-Fenton catalytic activity when H2O2 was at low concentration. Especially, the best degradation efficiency of tetracycline had been more than 80% at 0.003M H2O2 within 30min. HCO3− had an obvious inhibition effect on the reaction compared with SO42−, Cl−, and NO3−, and a reasonable explanation was proposed that HCO3− reacts with •OH to form less reactive free radicals. Free radical quenching experiments and EPR proved that •OH and •O2− were the dominant free radicals. The LC-MS was employed to identified the intermediate products of TC. The synergistic effect of HP-MoS2 and acid-treated g-C3N4(HCN) improved the transfer efficiency of photogenerated charges and promoted the reduction of Fe3+, which accelerated the photo-Fenton reaction. Moreover, the reusability of the composite was observed up to four cycles and showed good recycling performance during the degradation of tetracycline.