Mechanism Of Fe/TiO_2-X Visible Light Activated Persulfate Degradation Of Bisphenol A

In view of the problems such as low catalytic efficiency and complex preparation process in the catalyst for activating persulfate,this study optimized the modification of TiO ₂ by iron quantum point embedding composite and surface modification.In order to improve the efficiency of visible light activated persulfate in the degradation of organic pollutants,its microstruct ure and degradation efficiency were analyzed and evaluated.Furthermore,the factors affecting the degradation effect,the composition of active species and the reaction mechanism were systematically analyzed and compared.The main contents and conclusions of this paper are as follows:（1）Using TiO₂ and Fe Cl₃ as the main raw materials,a new type of Fe/TiO_2-Xcatalyst with high visible light catalytic activity was successfully prepared by water bath heating-anoxic calcination method,and the reaction unit of visible light catalytic activation of persulfate for degradation of organic pollutants in water was constructed.The microstructure of Fe/TiO_2-X was characterized and analyzed by transmission electron microscope,XRD,XPS and so on.It is clear that there are Ti³⁺self-doped energy levels,iron quantum dots and oxygen vacancies in Fe/TiO_2-X.At the same time,the maximum absorption wavelength of Fe/TiO_2-X is broadened from 398 nm of TiO₂ to 783 nm,the band gap is reduced to 1.58 e V,the fluorescence lifetime is extended to 10.339 ns,and the performance of visible light absorption and carrier separation is greatly improved.（2）The optimal reaction conditions are determined as follows:self-doping of Ti³⁺in the catalyst,relative content of iron oxide 47%,catalyst dosage 0.5g.L^-1,PS concentration 1mmol.L^-1.Based on the above optimization,the degradation efficiency of bisphenol A by Fe/TiO_2-X visible light activated PS reached 100%in 50 min,and the salinity reached 68.92%.Compared with TiO₂,the degradation rate was increased by 8 times.At the same time,it is further confirmed that PS is the best oxidant and CO₃^2-can inhibit the degradation efficiency of the system.Combined with the determination results of p H and solid ZETA potential in different environments,it is found that the surface of the catalyst will carry a large amount of negative charge in alkaline environment,resulting in electrostatic repulsion between PS and Bisphenol A,thus reducing the reaction efficiency.（3）Through the addition of Humic Acid（HA）and the selection of ultra-pure water,tap water and secondary effluent as the background water quality,the effects of actual water environmental factors on the degradation efficiency of BPA were investigated.The reaction unit has a good anti-interference ability and the degradation efficiency of organic matter is more than 70%under a variety of water quality background.the results of five continuous cycle experiments show that the reaction unit can degrade Bisphenol A at 100%.It is proved that it has high stability.The degradation rate of the reaction unit for five typical organic pollutants can reach more than 80%,and the salinity can reach more than 40%,which has a certain universal applicability.（4）Free radical quenching experiments and electron paramagnetic resonance（EPR）tests show that the visible light reaction unit of Fe/TiO_2-X/PS produces active oxidation species dominated by·OH and SO₄^-·,the iron oxides and TiO_2-X on the surface of the catalyst participate in the activation process of PS,and the target pollutants are degraded under the action of the absolute main body of free radical path.Through a variety of characterization methods,it is further confirmed that the excellent visible light absorption capacity,photoelectron separation performance of Fe/TiO_2-X and the strong redox ability of Fe³⁺/Fe²⁺improve the efficiency of activating persulfate.In addition,Fe/TiO_2-X can also realize the cycle of trivalent iron and bivalent iron by autogenic photoelectron reduction of Fe³⁺.