Photocatalytic Degradation Of Perfluorooctanoic Acid In Water By Bismuth Oxychloride-nanodiamond

Perfluorooctanoic acid（PFOA）has been widely detected in worldwide water environment and has a variety of toxic effects,and it would seriously threaten the ecological environment and human health.Therefore,it is very important to carry out research on the degradation of PFOA in water.The existing PFOA degradation technologies have some limitations,such as limited treatment effect,high cost and complicated process,which restrict their further applications.Photocatalytic oxidation has a broad prospect for the degradation of PFOA in water,due to its technical superiority.Moreover,the key to ensure treatment effect is to develop efficient and stable photocatalysts.In this study,PFOA was taken as the treatment object and the efficient removal of PFOA in water was achieved by adopting photocatalytic oxidation technology and optimizing the preparation of high-efficiency,stable and environmentally friendly BiOCl-ND catalyst by hydrothermal method.Further discussion was proposed about the degradation mechanism of PFOA in the UV photocatalytic system and the catalytic activity enhancement mechanism of BiOCl-ND composite catalyst.It was expected to provide a novel technical path and theoretical basis for the pollution control of PFOA in water.The main results were as follows:The BiOCl-ND composite photocatalyst with high catalytic activity was successfully synthesized by hydrothermal method.The physicochemical properties of the photocatalytic materials were analyzed by scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,photoluminescence spectroscopy and photoelectrochemical test,and the successful synthesis of BiOCl-ND heterostructure was identified.The effect of enhanced charge transfer by using BiOCl-ND 10:1 was confirmed compared with pure BiOCl.Moreover,BiOCl-ND 10:1 was selected as the best photocatalyst by constructing a catalytic degradation system of PFOA by BiOCl-ND driven by UV lightAdditionally,single factor experiment was carried out,and the optimizing conditions were used to determine the highest degradation efficiency of PFOA when the additive amount of photocatalyst was 0.3 g/L and the initial concentration of PFOA was 50 mg/L.The photocatalytic degradation rate and defluorination rate of PFOA by using BiOCl-ND 10:1 reached 100%and 74.6%respectively after 60 min reaction under the optimal conditions,BiOCl-ND 10:1 could act as an efficient photocatalytic material for PFOA degradation.The analysis of the PFOA photocatalytic degradation path and the toxicity of the intermediate products was performed.It was found that the photocatalytic degradation of PFOA was a progressive decarboxylation process accompanied by the release of fluoride ions,and the toxic environmental effect of PFOA was effectively reduced with the gradual degradation.The reusability and stability of BiOCl-ND 10:1 photocatalytic material was confirmed by cycled degradation and metal ion leaching experiments.The radical quenching experiment and EPR test showed that the main active species in the degradation of PFOA by BiOCl-ND 10:1 under UV light irradiation were holes（h⁺）and superoxide radicals（·O₂^-）.Furthermore,the photocatalytic degradation of PFOA was further enhanced because of the great concentration increase of oxygen vacancy（OVs）after the combination of BiOCl and ND.The electron transfer path and band structure of BiOCl-ND were determined by UV-visible diffuse reflection and Motschottky test,and the catalytic degradation mechanism on PFOA by BiOCl-ND10:1 heterojunction was revealed under UV light irradiation.