Study On Photocatalytic Selective Degradation Of Malachite Green By Molecular Imprinting

Malachite green is a kind of synthetic dye with triphenylmethane structure.It is often detected in the water environment and poses potential health risks to human and ecological environment.It is of great significance to study efficient and safe dye wastewater treatment technology.In actual water,low concentration dyes usually exist together with other high concentration pollutants or organic matter.The complex interaction between compound pollution and organic matter affects the catalytic oxidation efficiency of traditional catalysts in the process of advanced oxidation.How to realize selective oxidation is the current bottleneck problem,and molecular imprinting technology may be a good solution.Therefore,in this study,powdered activated carbon-supported Bi₂O₃-doped Ti O₂ was used as catalyst and malachite green was used as target pollutant.Based on the molecular imprinting technology,starting from the selective adsorption characteristics of the catalyst,the surface structure of the catalyst was accurately adjusted,the molecularly imprinted catalyst with recognition effect on malachite green pollutants was studied,and the mechanism of selective adsorption of malachite green in oxidized water environment by molecularly imprinted catalyst was analyzed.This study can provide a theoretical basis for the study of molecularly imprinted photocatalysts and the selective oxidation of pollutants in water environment.The specific results are as follows:（1）A molecularly imprinted Bi/Ti/activated carbon photocatalyst（MG-MI）was firstly synthesised by using surface molecular imprinting.MG-MI showed the synergistic effect of strong specific recognition and photocatalysis due to the existence of MG imprinted cavities on the surface of MG-MI.The selectivity of MG-MI was evaluated by adsorption and degradation of CV and MG solutions.Compared with the nonimprinted material photocatalytic composite（MG-NI）,MG-MI showed superior selectivity coefficient（5.17）,higher adsorption capacity（75.23 mg/g）,and faster degradation kinetic rate(0.054 min^-1).This study confirmed that the perfect combination of surface MIT and photocatalyst has great potential and can be a promising solution for the treatment of low concentration pollutants in wastewater.（2）Novel malachite green molecularly imprinted polymer microspheres（MIP-MGs）were first synthesised using a modified powdered activated carbon-supported Bi₂O₃-doped Ti O₂ to stabilise Pickering emulsion polymerisation for removal of malachite green（MG）.Adsorption,catalytic properties and effects of p H and dosage on MIP-MGs were studied.The adsorption capacity of MIP-MGs reached 38.20 mg/L,which was about 1.8times higher than that of non-molecularly imprinted polymer microspheres（NIP-MGs）and a higher selection coefficient K,of 4.26 and 3.75 for MG was exhibited.MIP-MGs had the best photocatalytic activity（98.25%）under the optimal conditions of 0.8 g/L of MIP-MGs and p H 8.In addition,photo-induced·O₂^-and h⁺were considered to be the main active substances in MG photodegradation.According to the research results,the possible photocatalytic reaction mechanism of MIP-MGs was proposed and discussed in detail.