Preparation And Photocatalytic Properties Of Chitin/BiOX（X=Cl、Br、I） Composites

With the accelerated industrialization and the improvement of people’s living standard,energy shortage and environmental pollution problems are becoming more and more serious.BiOX（X=Cl,Br,I）is a binary bismuth oxide,and its high anisotropy and special electronic structure make it a hot research topic.However,the shortcomings such as electron-hole complexation of BiOX is very easy to lead to low photocatalytic efficiency.Chitin,as a biomolecule with good biocompatibility,is often used as a carrier for photocatalysts.In this paper,the hydrolysis method was chosen to prepare BiOX based on further compounding it with chitin to produce a new photocatalyst chitin/BiOX composite,and the main research is as follows.BiOX was prepared by hydrolysis method.By XRD analysis,the BiOX obtained under different preparation conditions was pure phase;by XPS and FT-IR analysis,the preparation conditions had no effect on the composition and structure of BiOX photocatalysts;by BET,it can be seen that the specific surface areas of the products under different preparation conditions were significantly different;UV-Vis DRS showed that the absorption band edges of photocatalysts under different preparation conditions were significantly different.The photocatalytic performance tests showed that the degradation rates of Bi OI,Bi OBr and Bi OCl on methyl orange were 71.15%,38.79%and 13.89% under 120 min visible light irradiation,respectively.Based on the above work,the chitin/BiOX composites were synthesized and characterized and tested for photocatalytic performance in this thesis.XRD results showed that the physical structure of the composites was similar to that of BiOX;XPS and FT-IR results showed that different preparation conditions had no significant effect on the composition and structure of the composites;UV-Vis DRS results showed that The UV-Vis DRS results showed that the composites had enhanced light absorption ability and broadened the light response range compared with BiOX;the BET results showed that the specific surface area of the composites was higher that of BiOX;the photocatalytic performance tests showed that the degradation rates of methyl orange under the same light conditions were 88.83%,79.83% and 65.53% for7wt%-CBI,20wt%-CBBr and 25wt%-CBCl,respectively.The stability and active material of the photocatalyst were investigated by cycling experiments and capture experiments.It is shown that the composite has partial loss during cycling,which is tentatively considered as partial chitin shedding,but the photocatalytic activity of the composite during cycling is still better than that of BiOX.Preliminary investigation of the photocatalytic mechanism.It was demonstrated that hydroxyl radicals（·OH）play a dominant role in the degradation of methyl orange in BiOX and chitin/BiOX composites.