Preparation Of Amorphous TiO₂ And Its Catalystic Degradation Of Typical PPCPs Under Visible Light

In the past two decades,Pharmaceuticals and Personal Care Products?PPCPs?have attracted more and more attention due to their potential impact on human beings and ecosystems.Advanced Oxidation Process?AOPs?has been used to treat PPCPs in various water substrates.Among these oxidation methods,visible light photocatalysis is mild,low-cost and environmentally friendly.Titanium dioxide?TiO2?has been widely studied as the most widely applied photocatalyst,but its application under visible light is seriously restricted because of its wide band gap and fast photogenerated electron-hole pair recombination.In this study,S-doped amorphous titanium dioxide?S-TiO₂?and S-TiO₂/C₃N₄visible-light photocatalytic materials were synthesized for the degradation of Methyl orange?MO?and typical carboxylic acid PPCPs pollutants.The specific research work is as follows:?1?A method for preparing S-doped amorphous titanium dioxide?S-TiO₂?visible-light photocatalyst was proposed,and S-TiO₂ visible-light photocatalyst was successfully prepared.The samples were characterized by XRD,SEM,TEM,XPS,FTIR and TG.The results showed that the TiO₂ was amorphous and S existed in the form of S⁶⁺.The band gap of the S-TiO₂ catalyst was calculated to be 2.91 eV by UV-vis DRS test results.The change of preparation conditions can affect the catalytic performance of S-TiO₂ catalyst.3%?S:Ti molar ratio?S-TiO₂ catalyst has better photocatalytic degradation effect under visible light.While the dosage of catalyst is 0.4g·L^-1 and the concentration of methyl orange is 5mg·L^-1,the degradation rate of methyl orange can reach 90%in 240 minutes.The S-TiO₂ catalyst can effectively degrade FLBP under visible light.The degradation rate of FLBP can reach 91.7%within 4 hours(Conditions:FLBP concentration is 10mg·L^-1 and catalyst concentration is0.6g·L^-1).Free radical trapping experiments showed that the main active species in the degradation process were photogenic holes?h⁺?,a small amount of hydroxyl radicals?·OH?and superoxide radicals?O₂^-?.The intermediate products in the process of FLBP degradation were analyzed based on LC-MS,and the degradation pathway of FLBP was analyzed.?2?S-TiO₂/C₃N₄ visible light catalyst was prepared by sol-gel method and low temperature calcination method.The catalysts were characterized by XRD,TEM,XPS,FTIR and TG.The results showed that S-TiO₂ and layered C₃N₄ formed composite photocatalyst materials.The change of preparation conditions can affect the catalytic performance of S-TiO₂/C₃N₄ catalyst.When the molar ratio of Ti:C₃N₄ is 1/1,S-TiO₂/C₃N₄ catalyst has better photocatalytic degradation effect under visible light.While the dosage of catalyst is 0.6g·L^-1and the concentration of methyl orange is 5 mg·L^-1,the degradation rate of methyl orange can reach 97.9%in 120 minutes.The S-TiO₂/C₃N₄ catalyst can effectively degrade FLBP under visible light.The degradation rate of FLBP can reach 99.1%within 90 minutes(Conditions:FLBP concentration is 10mg·L^-1 and catalyst concentration is 0.6g·L^-1),which is much better than that of S-TiO₂ catalyst.It shows that S-TiO₂ and C3N4 have synergistic effect.The results of free radical trapping experiments showed that the main active species in the degradation process were photogenerated holes?h⁺?and hydroxyl radicals?·OH?,which indicated that S-TiO₂/C₃N₄ catalyst could produce more hydroxyl radicals?·OH?than S-TiO₂catalyst under visible light excitation for the degradation of organic pollutants.