Study On The Photo Catalytic Of Typical Drugs In Water By Dolomite And Its Mechanisms

In recent years,photocatalytic oxidation technology(AOP)has been widely used in the treatment of water and indoor air pollution.Effective use of AOP technology for pollution control is inseparable from an efficient,economical,and pollution-free photocatalyst.At present,a large number of studies have reported the use of semiconductor photocatalysts and some synthetic new photocatalysts for pollution control,but in general,although these photocatalysts have high catalytic efficiency,they have high cost of use and may cause secondary pollution.Thus limiting its application in pollution control and environmental remediation.Therefore,it is particularly important to find an economical and environmentally friendly photocatalyst.A large number of natural minerals exist on the surface,and the required raw materials can be obtained through simple physical processing.It has the characteristics of easy availability,low cost and environmental friendliness.If the photocatalytic properties of natural minerals can be used for pollution control,it will have very good application prospects.Based on this,this research proposes to study the photocatalytic properties of natural minerals and try to apply them to the treatment of polluted wastewater.We chose dolomite as the research object to study its photocatalytic degradation activity of diphenhydramine,a pharmaceutical pollutant in water,and on this basis,explore its photocatalytic mechanism through first-principles calculations.The main findings of the thesis are as follows:(1)The photocatalytic degradation of an aqueous solution of diphenhydramine with a concentration of 40 mg/L in the presence of 1.5 g of dolomite under simulated sunlight(350W,310-800nm)was studied.The results showed that,compared with the pure water phase photolysis,the addition of dolomite significantly improved the degradation rate and photolysis rate of diphenhydramine,showing better photocatalytic activity.After 150 min of light,the degradation rate of diphenhydramine increased from 10%to 60%,and the corresponding photolysis rate constant increased from 0.16×10-2 min-1 to 1.29×10-2 min-1.In addition,the total organic carbon(TOC)content of the solution after photolysis decreased by about 13%,indicating that the target pollutants can be completely mineralized under the photocatalysis of dolomite.Electron spin resonance(ESR)analysis and free radical quenching experiments show that dolomite in the solution induces three kinds of active oxygen free radicals:1O2,O2-· and ·OH under simulated sunlight irradiation.These active free radicals further react with diphenhydramine,leading to accelerated degradation of diphenhydramine.In contrast,O2-· and ·OH play a leading role in the photocatalytic degradation of diphenhydramine,while the role of 1O2 is relatively weak.Deoxygenation experiments show that the oxygen in the solution can promote the photodegradation of diphenhydramine.During the photolysis process,the analysis results of the photolysis products showed that the oxidation of alkylamine side chains induced by hydroxyl radicals is the main degradation mode of diphenhydramine molecules.(2)Based on first-principles calculations,combined with UV-Vis and photocurrent analysis,the photocatalytic mechanism of natural dolomite is discussed.The calculation results show that in natural dolomite,the isomorphic substitution of Fe to Mg leads to the emergence of new energy bands in the energy band structure of dolomite,which in turn reduces the band gap of dolomite from 5.02 eV to 1.63 eV,thus Exhibits semiconductor characteristics.Combining the analysis results of UV-Vis and photocurrent,we infer that the photocatalytic mechanism of natural dolomite is as follows:natural dolomite with semiconductor properties absorbs photons and generates photogenerated electrons and holes.Among them,the electrons migrate to the surface of the dolomite and interact with water molecules.Dissolved oxygen molecules react further to generate active free radicals.Active oxygen radicals with strong oxidizing properties react with diphenhydramine and cause its degradation.This study shows that natural dolomite has good photocatalytic activity,which can significantly promote the photodegradation of organic pollutants and mineralize them.The research results will provide a valuable reference for the application of dolomite in the field of photocatalytic degradation of pollutants.