Preparation And Properties Of Composite Photocatalyst Based On Bismuth Oxyiodide And Their Degradation Performance Of Typical PPCPs

Pharmaceuticals and personal care products（PPCPs）have been widespread in the acquatic ecosysystems,such as groundwater,surface water and sewage treatment plant tail water,due to the random disposal of drugs and inappropriate and imperfect treatment of sewage treatment plants.It increasingly threatened the ecological environment and human health with a increasing number of species and concentration of PPCPs.Among various treatmental technology,photocatalysis,taking renewable light energy as driving force,with high-efficiency and low-energy consumption can achieve the purpose of degrading PPCPs using the redox effect of active groups.Bismuth oxyiodide,a typical photocatalyst,has attracted wide attention in photocatalytic degradation because of its high photochemical stability,non-toxicity,low cost,good light absorption ability and strong redox ability.However,in application,bismuth oxyiodide still has some disadvantages such as easy recombination of electrons and holes,which limit the photocatalytic ability.At present,there are many methods for modifying bismuth oxyiodide,including morphology control,composition regulation,ion doping and heterojunction structure,etc.Among them,the method of doping and compound have become the widely used modification technologies due to their simple operation and easy preparation conditions.Therefore,in this study,bismuth oxyiodide was modified by introducing alkaline earth metal ions as well as oxygen vacancies and loading carbon quantum dots to prepare compounds with higher photocatalytic activity,which was applied to the photocatalytic degradation of PPCPs.The specific research content and results are as follows:（1）Prepared the bismuth oxyiodide complex doped with alkaline earth metal Sr²⁺（Sr BiOI）by the simple precipitation method,and explored its degradation activity to indomethacin（IDM）under visible light.The experimental results showed that the composite was conducive to high-efficiency degradation of IDM,and the degradation effect was the best when the Sr²⁺doping amount is 0.45 g.Furthermore,the first-order degradation rate was about 10 times than that of pure BiOI.The enhancement of photocatalytic ability was mainly due to the doping of Sr²⁺causing the generation of oxygen vacancies and thereby synergistically promoting the reaction.Both the existences of metal ion and oxygen vacancies were beneficial to the capture of electrons,thereby promoting the separation of electrons and holes.The experiments and characterization of active species showed that O₂^·-,¹O₂ and h⁺were main active substances in the photocatalytic degradation process of0.45-Sr BiOI composite.Additionally,the identification of degradation products of indomethacin were conducted to propose the possible degradation pathways of indomethacin.The main degradation reaction is decarboxylation,addition reactions and demethylation.（2）The bismuth oxyiodide with{110}crystal faces loaded by different amounts of carbon quantum dot（CDs-BiOI）were prepared by hydrothermal method.Through transmission electron microscopy（TEM）characterization,it can be seen that the carbon quantum dots were uniformly dispersed on the flower cluster-shaped bismuth oxyiodide.The CDs-BiOI composites were applied to the degradation effect of diclofenac（DCF）under visible light and showed the elevated photocatalytic efficiency contrast to pure bismuth oxyiodide.When the loading of carbon quantum dots is 0.5 mL,0.5-CDs-BiOI showed the best activity in the degradation of diclofenac,which can degrade 92%of diclofenac,and the degradation rate is four times than that of pure bismuth oxyiodide.Additionally,through the diclofenac degradation experiment under different influencing factors,it can be concluded that 0.5-CDs-BiOI has high activity.