Enhanced activation of peroxymonosulfate by ZIF-67/g-C3N4 S-scheme photocatalyst under visible light assistance for degradation of polyethylene terephthalate

Photocatalyst-activated peroxymonosulfate (PMS) degradation of pollutants is already widely used for wastewater treatment under visible light. Polyethylene terephthalate (PET) is widely used in daily life, but waste plastics have an irreversible negative impact on the environment. In this paper, the ZIF-67/g-C3N4 S-scheme heterojunction catalyst was synthesized as a photocatalyst to achieve a good effect on PET degradation in coordination with PMS. The results indicated that PET could be degraded up to 60.63 ± 2.12 % under the combined effect of catalyst, PMS, and light. In this experiment, the influence of catalyst-to-plastic ratio, PMS concentration, aqueous pH, and inorganic anions on plastic degradation by the photocatalytic synergistic PMS system was discussed, and the excellent performance of this system for degrading PET was highlighted through a comparative test. Electron spin resonance (ESR) and free radical quenching experiments demonstrated that SO4•− contributes the largest amount to the PET degradation performance. Furthermore, results from gas chromatography and liquid chromatography-mass spectrometry (LC-MS) indicated that the plastic degradation products include CO, CH4, and organic small-molecule liquid fuels. Finally, a possible mechanism for the light/PMS system to degrade PET in water was suggested. This paper provides a feasible solution to treat waste microplastics in water.