Experimental Study On The Photocatalytic Degradation Of Salicylic Acid By Doped Modified TiO₂

Salicylic acid wastewater has the characteristics of low concentration.However,traditional water treatment technology is difficult to effectively remove the salicylic acid wastewater.Photocatalytic technology is a hot topic in recent years because of its economic and efficient,among which TiO₂photocatalyst has advantages of simple fabrication and stable properties.However,the wide band gap of TiO₂and low utilization of UV light limit its practical application.This paper uses sol-gel method to prepare co-doped modified TiO₂catalysts.The influence factors of photocatalytic performance,reuse experiments and active species quenching experiments are also studied.The characteristic of catalysts is analyzed by XRD,BET,TEM,XPS and UV-Vis.Photocatalytic mechanism of the removal of salicylic acid by co-doped TiO₂is studied.The main research contents are as follows:The experiments results show that 0.10La-0.20N-TiO₂and 1.0La-0.15S-TiO₂catalysts achieve the optimum degradation rate of 93.78%and 96.34%respectively to the 50ml salicylic acid（p H=5）.When the calcination temperature is 500℃,the calcination time is 2h,the catalyst dosage is 50mg,the volume of salicylic acid is50m L,the degradation rate of 0.10La-0.20N-TiO₂（93.78%）is 1.08 and 1.41 times that of 0.20N-TiO₂（86.93%）and naked TiO₂（66.42%）.The degradation rate of1.0La-0.15S-TiO₂（96.34%）is 1.20 and 1.45 times that of 0.15S-TiO₂（80.61%）and naked TiO₂（66.42%）.The degradation rate of salicylic acid are 86.81%and 88.28%after La-N-TiO₂and La-S-TiO₂reuse 5 times,respectively.The photogenerated hole is the main active species in the process of La-N-TiO₂and La-S-TiO₂photocatalytic reaction,and La-S-TiO₂can produce more·OH than La-N-TiO₂catalyst.The characterization results show that the La-N-TiO₂and La-S-TiO₂are both100%anatase.The average particle size of La-N-TiO₂and La-S-TiO₂are 18.3nm and14.7nm respectively.The specific surface area of La-N-TiO₂and La-S-TiO₂are44.67m²/g and 61.67m²/g respectively.The band gap of La-N-TiO₂and La-S-TiO₂are2.96e V and 2.88e V respectively.Small average particle size of La-S-TiO₂shortens the migration path of electron-hole pairs generated by photoexcitation.Large surface area of La-S-TiO₂enhances adsorption.Small band gap of La-S-TiO₂increases photon utilization.What’s more,La-S-TiO₂catalyst can adsorb more surface hydroxyl oxygen,reduce the recombination probability of electron-hole pairs and broaden the spectrum response range of TiO₂.To sum up,both La-N and La-S co-doped modified TiO₂can significantly improve the photocatalytic activity.The photocatalytic performance of La-S-TiO₂is better than that of La-N-TiO₂.