Construction Of CeO₂/g-C₃N₄/PMS System With Visible Light Response And Photocatalytic Performance Study

In this work,type-II heterojunction CeO₂/g-C₃N₄ composites were constructed and their performance in photocatalytic degradation of rhodamine B（Rh B）and microcystin（MC-LR）,and killing of Methicillin-resistant Staphylococcus aureus（MRSA）under the synergistic action of peroxymonosulfate（PMS）was investigated.The main content and results are shown as follows:1.CeO₂/g-C₃N₄ type-II heterojunction was constructed for the efficient degradation of Rh B via PMS assisted-visible light-driven photocatalytic process.The scanning and transmission electron microscopy（SEM and TEM）,X-ray diffraction（XRD）,UV-vis diffuse reflectance spectroscopy（UV-vis DRS）and photoluminescence emission spectroscopy（PL）were used to characterize the microstructure and optoelectronic properties of CeO₂/g-C₃N₄.The experimental results showed that there is a suitable matching energy level between CeO₂ and g-C₃N₄,and they have constructed type-II heterojunction by compounding.The effects of CeO₂ content,PMS dosage,initial solution p H value,and aqueous matrix composition on the performance of CeO₂/g-C₃N₄/PMS/Vis system for Rh B degradation were investigated in the work.Within 50 min,the degradation rate of Rh B was 92%in the 10%CeO₂/g-C₃N₄/PMS/Vis system,which was 3.8 times higher than that of 10%CeO₂/g-C₃N₄.In addition,the CeO₂/g-C₃N₄/PMS/Vis system showed more excellent degradation performance in acidic environment,and mainly showing the gradual increase in the degradation performance of Rh B with the decrease of p H value.The CeO₂/g-C₃N₄ composite has good stability,and the photocatalytic degradation performance remains almost unchanged after 5 cycles of repeated experiments.Finally,the results of radical quenching experiments and EPR radical capture experiments show that the CeO₂/g-C₃N₄/PMS/Vis system produces SO₄^·-,O₂^·-,h⁺and ¹O₂.2.MC-LR has neurotoxicity and hepatotoxicity.In this work,the photocatalytic degradation of MC-LR was studied by CeO₂/g-C₃N₄/PMS/Vis system.The effects of variables such as PMS content and initial solution p H value in the degradation of MC-LR were investigated.And the effect of p H on the generation of reactive species was further investigated by radical quenching experiments.The experimental results of this study showed that the increase of PMS content promoted the photocatalytic performance of the system,and SO₄^·-,O₂^·-,h⁺and ¹O₂ were produced by CeO₂/g-C₃N₄/PMS/Vis under acidic and neutral environments.Finally,the intermediates（m/z=1045,1029,812,734,550,387）produced via the degradation of MC-LR by CeO₂/g-C₃N₄/PMS/Vis system were analyzed by UPLC-MS,and their possible degradation routes and degradation mechanisms were proposed.3.In this work,MRSA was selected as the target strain,and the preliminary investigation of the killing effect of CeO₂/g-C₃N₄/PMS/Vis system on drug-resistant pathogenic bacteria was carried out,and its antibacterial performance was analyzed by plate counting method.It was found that the antibacterial rate of MRSA in the CeO₂/g-C₃N₄/PMS was as high as 80%within 2 h of visible light irradiation.And the stability of the CeO₂/g-C₃N₄/PMS/Vis system in terms of antibacterial performance was demonstrated by four cycles of repeated experiments.In addition,in vitro cytotoxicity experiments were conducted for CeO₂/g-C₃N₄ toxicity,and the results showed that it did not adversely affect the normal cell growth and reproduction.