Preparation Of Molecularly Imprinted BiOBr And Study On Selective Photocatalytic Properties

At present,Pharmaceutical and Personal Care Products(PPCPs)are ubiquitous in China's natural water environment,causing various extent damage to the ecological environment and human health,how to treat PPCPs residual wastewater effectively has become a research hotspot of experts and scholars at home and abroad.Photocatalytic technology is an efficient and environmentally friendly water treatment technology that theoretically degrades all pollutants in wastewater,however,when a variety of high-concentration contaminants are present in the solution,the degradation of trace contaminants on the surface of the photocatalyst will be restricted.In order to improve the removal rate of trace contaminants,it is necessary to improve the selective adsorption and photocatalytic degradation ability of materials.Molecular imprinting technology refers to the process of preparing molecularly imprinted polymers(MIPs)that are selective for a specific target molecule.MIPs have specific selectivity,good stability,long service life and strong adaptability,such advantages make MIPs have important application prospects in the field of removing trace contaminants in water.This paper aims to combine molecular imprinting technology with photocatalytic technology,using norfloxacin(NOR)as template molecule and bismuth oxybromide(BiOBr)as carrier material to prepare molecular imprinted species with high photocatalytic activity and selective removal of target contaminants.The selective adsorption and photocatalytic degradation effects of the imprinted material on NOR were investigated and the cyclic regeneration performance of the imprinted material was discussed.The mechanism of molecularly imprinted photocatalytic degradation was mastered to provide effective removal of other trace organic pollutants in the environment,which provided theory and practice basis for effective removal of other trace organic pollutants in the environment.The main experimental contents and results are as follows:Norfloxacin molecularly imprinted materials(MIPs)were prepared by surface molecular imprinting with BiOBr as carrier.The orthogonal experimental method was adopted to analyze the preparation conditions of imprinted materials,and its microstructure was characterized and analyzed.Observations show that the crystal form of MIPs is consistent with BiOBr,but the specific surface area and pore size are larger,which makes the imprinted material MIPs have better adsorption and photocatalytic properties.A series of photocatalytic reactions were designed to evaluate the adsorption properties of MIPs under dark reaction and the photocatalytic properties under photoreaction.The recycling performance and stability of MIPs were investigated by cycle experiments.It was found that the MIPs had poor stability and low cycle utilization.The mechanism of molecularly imprinted photocatalytic degradation was investigated by free radical trapping experiments.The results show that the main functions of the degradation process are superoxide radicals(O2·-)and holes(h~?).In order to detect the selective adsorption performance of MIPs,a unitary,binary and ternary adsorption system were designed.Tetracycline(TC)and ciprofloxacin(CIP)were used as interfering molecules to test the selective adsorption properties of the materials.The imprinted material has good selective adsorption and anti-interference ability.After photocatalytic degradation,the residual quantity of NOR in water can be as low as 3.8%.Even in binary system and ternary system,the final removal rate of NOR can be reached 87%and 74.2%.In order to study the practicability of the materials prepared in the natural environment,the solvent influence experiment and the common anion-cation interference experiment were designed.The results show that the material still has the selective adsorption and photocatalytic properties in the tap water and the effect of cations on the degradation of NOR by MIPs is greater.In order to improve the photocatalytic and regenerative cycling properties of MIPs,graphene oxide(GO)was prepared by modified Hummers method,and the loading of GO on the surface of MIPs was controlled to produce modified composite molecularly imprinted materials(GO/MIP).GO/M]P were observed and analyzed by various characterization methods.The results show that GO/MIP have larger specific surface area and pore size than MIPs,and have better adsorption and photocatalytic properties,theoretically.Compared with MIPs,the adsorption performance of GO/MIP under dark reaction is slightly lower than that of MIPs,but the photocatalytic performance is obviously improved.It is verified by cyclic experiments that the recycled performance of the modified imprinted material is significantly improved,and the GO/MIP have a certain degree of practical value.The free radical capture test proved that the major active substances in the degradation process of GO/MIP and MIPs are O2·-and h~+.For comparison and doing parallel experiments,the selective adsorption and photocatalytic degradation experiments,solvent influence experiment and common anion-cation experiment were designed to be consistent with MIPs.The results show that GO/MIP have better selective adsorption and photocatalytic properties than MIPs.The total removal rate can reach 98.1%in unitary system,and the data in both binary and ternary mixture systems were higher than MIPs.