Synthesis Of Photocatalytic Hydrogel Microbeads With Bi OBr_xI_1-x Solid Solution As The Core And Its Adsorption-photocatalytic Performance Study

The wide application of oxytetracycline in medical treatment and biological growth promoters has brought a lot of convenience to human life,and also led to the formation of new pollution sources.Photocatalytic degradation technology has the advantages of high degradation efficiency,non-toxic and harmless.It is a green and efficient advanced oxidation process for the degradation of organic compounds.It has an excellent performance in the degradation of oxytetracycline.However,the existing photocatalysts still have some problems,such as high recombination rate of photogenerated carriers,insufficient utilization of visible light and low energy conversion efficiency.BiOBr and BiOI are new Photocatalysts in BiOX（x=Cl,Br,I）that can realize visible light response without any modification.However,BiOBr and BiOI have some defects,such as easy agglomeration,fast photogenerated carrier recombination and so on.Therefore,the modification of BiOX to obtain better photocatalytic materials is of great significance for the removal of refractory organics.The aim of this study is to remove the oxytetracycline efficiently.First,the BiOBr_xI_1-x solid solution was synthesized by hydrothermal method.After the optimal ratio was selected through the controlled variable method,the BOBI was encapsulated in CA by the alginate hydrogel,and then the CA-BOBI photocatalytic water gel system was constructed.Secondly,based on the synergistic effect of adsorption and photocatalysis,supplemented by a variety of characterization methods to preliminarily reveal the adsorption and degradation mechanism of BOBI and CA-BOBI,so as to realize the efficient removal of oxytetracycline and the renewable utilization of photocatalyst.The main research contents are as follows:（1）A series of BiOBr_xI_1-x solid solutions were synthesized by adjusting the temperature of solvothermal method and the ratio of Br and I.A variety of characterization methods were used to compare and analyze the samples combined with changing the influencing factors of photocatalysis.It was found that when the more Br elements in the BiOBr_xI_1-x solid solution,the wider the band gap,the stronger the oxidation performance and the denser the morphological structure of the BiOBr_xI_1-x solid solution;When the I element is more,the visible light response range of BiOBr_xI_1-x solid solution is wider,the specific surface area is larger,and the adsorption performance is stronger.Among them,160℃-BiOBr_0.75I_0.25（BOBI）shows the best removal performance and has good performance in various characterization.Its more appropriate band gap width,visible light response range and nano flower structure enable BOBI to inhibit the recombination of photogenerated carriers and accelerate the migration of electrons after being excited by light,so as to realize efficient photocatalytic oxidation.Finally,combined with energy band calculation and free radical capture experiment,the photocatalytic mechanism of BOBI for oxytetracycline was explored.（2）using alginate hydrogel beads as carrier,a series of CA-BOBI photocatalytic beads were synthesized by ionic gel method.The microstructure and BOBI loading of CA-BOBI were investigated by means of various characterization methods.At the same time,taking the removal rate of oxytetracycline and the economy of synthetic materials as the standard,the optimal ratio of SA and BOBI is selected as 3:1,which can not only adsorb and degrade more than 90%of oxytetracycline in 90 minutes,but also maintain 85%degradation rate in the fifth cycle.In addition,the adsorption kinetic models of BOBI and CA-BOBI were also investigated.It was found that the adsorption process of the synthesized sample in oxytetracycline solution was more in line with the process of chemical adsorption,and the adsorption rate was affected by the surface chemical properties of oxytetracycline...