Preparation Of WO₃-MOFs Composites And Its Degradation Performance Of PPCPs

Pharmaceuticals and personal care products（PPCPs）are a kind of emerging pollutants,which are widespread in the natural environment.With the abuse of PPCPs,it may pose a huge threat to the natural ecological environment and human health.Because of its low content in the environment and poor biodegradability,traditional environmental remediation technology cannot solve the problem.Advanced oxidation processes include Fenton oxidation,activated persulfate oxidation,ozone oxidation,etc.,which can generate a large number of free radicals with strong oxidizing ability under reaction conditions such as light,electricity,and catalysts,which can convert refractory organic matter into small molecular organic matter or even completely mineralized to CO₂.Iron-based metal-organic framework materials（Fe-MOFs）are widely used in AOPs because of their excellent visible light absorption properties and abundant Fe-O clusters.However,Fe-MOFs still have disadvantages such as poor stability and easy recombination of photogenerated electrons and holes.In order to further improve the photocatalytic activity and oxidation performance of Fe-MOFs,it is considered to introduce WO₃to modify Fe-MOFs to form a heterojunction structure with better performance.In this study,a variety of MIL-100（Fe）and WO₃were used to compound with different methods,and a variety of advanced oxidation technologies such as photo Fenton and activated persulfate were used to degrade two representative PPCPs,bisphenol A and sulfamethoxazole.The optimal reaction conditions and stability of WO₃/MIL-100（Fe）composites were explored.The reaction mechanism was proposed and verified.The main work is as follows:1.Series WO₃/MIL-100（Fe）composites were prepared by in-situ method and characterized by multiple methods.Under the irradiation of visible light,the photo-Fenton degradation performance of the composites was explored,and the results showed that the composites had a significant improvement in BPA degradation compared with WO₃and MIL-100（Fe）.Among them,MW2 showed outstanding BPA degradation performance,which could degrade 5 mg L^-1BPA within 15 min.At the same time,the effects of initial p H,H₂O₂dosage,inorganic anions and other factors on BPA degradation were also explored.By means of capturing active substances,it was determined that MW2 was a Z-type heterojunction structure and the mechanism of BPA degradation was clarified.However,MW2 had a poor reusability.The possible reason was that the size of photocatalyst was too large,which could reach the micron level;rod-shaped WO₃had weak visible light absorption capacity and low photocatalytic activity.The next chapter will focus on solving the above problems and further improve the oxidation performance of WO₃/MIL-100（Fe）composites.2.In order to solve the problems of low reactivity and poor circulation of MW2,WO₃nanosheets with stronger photocatalytic ability and spherical MIL-100（Fe）were used to compound by a more green and convenient ball milling method.Series Z-scheme WO₃/MIL-100（Fe）（Mx Wy）composites were prepared and affirmed by various characterization techniques.All the as-prepared Mx Wy composites displayed superior photo-Fenton bisphenol A（BPA）degradation performances under LED visible light,in which the M80W120 could accomplish 100%BPA degradation with the aid of photo-Fenton process in 20 min.The influences of different initial p H,co-existing foreign ions and H₂O₂dosage on photo-Fenton performances were clarified.Moreover,M80W120 displayed outstanding stability and reusability during five successive cycling experiments on BPA degradation.Also,the possible degradation pathway of BPA degradation over M80W120 was clarified.Finally,a Z-scheme mechanism was put forward,which was further confirmed by active species capture,photo-deposition of Pb O₂along with electron spin-resonance spectroscopy determination.However,the leaching Fe ions concentration of M80W120 was slightly high,which was likely to cause secondary pollution and hinder the practical application of M80W120.The next chapter will focus on solving this problem and reducing the dissolution of Fe ions.3.Series WO₃/MIL-100（Fe）composites were prepared by a gentle solvent evaporation method and affirmed by various characterization techniques.Under the irradiation of visible light,the WO₃/MIL-100（Fe）composites showed excellent SMX degradation activity by the activation of persulfate.Compared with the pure WO₃and MIL-100（Fe）,the degradation performance of the composites was significantly improved.M1W4 showed best SMX degradation efficiency,which could 100%degraded 10 mg L^-1SMX within 20 min.M1W4 performed well in the acidic condition and PDS concentration of 1-2 m M.HCO₃^-and SO₄^2-had strong negative effects on SMX degradation.The cyclability and stability of M1W4 were also explored.After 5 cycling experiments,M1W4 could still maintain 100%SMX degradation efficiency,and the Fe ion leaching concentration was only 0.2-0.3 mg L^-1.Finally,sulfate radical was determined to the main active species by the capture of active species and ESR analysis.According to electrochemical tests and photo deposition experiments,the reaction mechanism of M1W4 activation of PDS to degrade SMX is proposed and confirmed.