Preparation Of BiOBr Based Photocatalyst And Its Performance Of Degradation For 2,4-dichlorophenoxyacetic Acid

The emergence of pesticides has facilitated the development of agricultural activities,but their over-application seriously threatens the safety of the water environment.Among various pesticide products,2,4-D is widely used to remove weeds in farmland due to its low cost and good selectivity.However,2,4-D enters the water environment via a variety of pathways due to its high water solubility and poor soil sorption.Nowadays,2,4-D is frequently detected in water bodies around the world.2,4-D in the aquatic environment can have a toxic effect on aquatic organisms.More seriously,2,4-D accumulates along the food chain and poses a threat to human health.Therefore,the development of green and efficient degradation technology for 2,4-D has become a research hotspots for researchers.Photocatalytic technology is attracting a lot of attention because of its safety and cost-effectiveness features.Among the various known photocatalysts,bismuth bromide oxide(BiOBr)has received much attention from researchers due to its special structure,stability,non-toxicity and good visible light-responsivity.However,the low light absorption efficiency and rapid recombination of photogenerated carriers limit the development and application of BiOBr,Currently,researchers generally use single modification method,which limits the development of BiOBr photocatalytic ability.To address these problems,two kinds of economic,efficient,green and stable photocatalysts were prepared by combining solid solution and heterojunction.Prepared photocatalyst can efficient removal of 2,4-D pesticide contaminants in water.The main research contents and results are as follows:1.In this study,a series of photocatalyst BiOBrxI1-x were prepared by solvothermal method.The BiOBr0.9I0.1 photocatalytic degradation capacity wass the best with the optical Br:I(9:1).The 2,4-D removal rate achieved 80.6%under the visible light irradiation within 120 min.In order to enhance the 2,4-D removal efficiency,the same crystal structure heterojunction was constructed by combining Bi2O2CO3 and BiOBr0.9I0.1 on the basis of the solid solution structure,so as to achieve a synergistic modification of BiOBr by constructing a solid solution and heterojunction.The crystal structure,microscopic morphology and elemental composition of the catalyst samples were characterized by XRD,XPS and SEM.The photoelectric properties of the materials were measured by PL,UV-vis DRS and EIS.The results of photocatalytic experiments showed that 10wt%Bi2O2CO3/BiOBr0.9I0.1 has the best photocatalytic degradation performance.2,4-D(10 mg/L)was degraded by 10wt%Bi2O2CO3/BiOBr0.9I0.1 at 120 min under visible light with an efficiency of 89.1%,which was 43.7%higher than that of BiOBr and 8.5%higher than that of BiOBr0.9I0.1.After four cycles of experiments,10wt%Bi2O2CO3/BiOBr0.9I0.1.still showed high photocatalytic activity for 2,4-D degradation.Combined with the results of the characterization,the improved photocatalytic effect of 10wt%Bi2O2CO3/BiOBr0.9I0.1 can be attributed to the fact that the solid solution can effectively improve the optical response range of BiOBr and the separation efficiency of photogenerated carriers.The construction of heterojunction can have synergistic effect with the construction of solid solution in broadening the photoresponse capacity of photocatalyst samples and the separation rate of photogenerated carriers,thus realizing the efficient degradation of 2,4-D.The results of capture experiments and ESR techniques confirmed that ·O2-and h+are the main active species in the system.The prepared BiOBr0.9I0.1 can effectively modulate the BiOBr energy band structure,and the heterojunction formed by BiOBr0.9I0.1 and Bi2O2CO3 conforms to the characteristics of a Z-type heterojunction.2.To address the problem that Bi2O2CO3/BiOBr0.9I0.1 does not effectively enhance the light adsorption capacity compared to BiOBr0.9I0.1.The BiOI,narrow-band gap semiconductor,was introduced to construct heterojunctions based on determining the optimal halogen ratio of solid solution structure.The crystal structure,microstructure and elemental composition of the catalyst samples were detected by XRD,XPS and SEM.The photoelectric properties of the materials were estimated with the aid of PL,UV-vis DRS and EIS.The photocatalytic degradation experiments showed that the best degradation efficiency of 2,4-D reached at 95%when 15wt%BiOI/BiOBr0.9I0.1 was exposed to visible light for 120 min.Reaction kinetic analysis showed that the photocatalytic degradation rate constant of 15wt%BiOI/BiOBr0.9I0.1 was 4.1 times than that of BiOBr and 1.9 times that of BiOBr0.9I0.1.After four cycles experiments,the photocatalytic activity of 15wt%BiOI/BiOBr0.9I0.1 for 2,4-D is maintained above 80%.Combined with analysis of characterization results,BiOI has a unique flower-like structure,which contributes to the adsorption of 2,4-D and utilization of visible light in the photocatalytic degradation process.The introduction of narrow-band gap photocatalyst(BiOI)significantly improves the photoresponse range of BiOBr0.9I0.1 and the separation efficiency of photogenerated carriers.Meanwhile,it is further demonstrated that heterojunctions can have a synergistic effect with solid solutions in strengthening the performance of photocatalysts.The results of capture experiments and ESR techniques confirm that ·O2-and h+are the main active species in the system.BiOBr0.9I0.1 can effectively regulate BiOBr band structure.The heterojunction formed by BiOBr0.9I0.1 and BiOI conforms to the characteristics of Z-type heterojunction.In this study,10wt%Bi2O2CO3/BiOBr0.9I0.1 and 15wt%BiOI/BiOBr0.9I0.1 were prepared for the removal of 2,4-D from water by constructing heterojunction and solid solution structure to jointly modify BiOBr.Research provides new ideas for modified photocatalytic materials and provides theoretical and technical support to deal with the ecological pollution generated by 2,4-D pesticides.