Organic Degradation Mechanism Of Titanate Photocatalysts

In this paper,two kinds of porous La₂Ti₂O₇ photocatalysts synthesized using PEG2000 and CTAB as the template.A sol-gel method was used to prepare the photocatalysts.The photocatalysts were characterized through XRD,SEM,FT-IR,UV-Vis DRS,BET,BJH and FS measurements.The effects of template amount on photocatalytic activity of porous La₂Ti₂O₇ were investigated.At the same time,the paper also studied degradation mechanism of azophloxine and ofloxacine with different photocatalysts which had different amount of template on it,and these were extensively analyzed through UV-Vis,FT-IR and IC analysis method.The main results are as follows:1.The porous La₂Ti₂O₇ photocatalysts were prepared by sol-gel method with PEG2000 as a template.The crystallite size decreases along with the increasing proper amount of PEG2000.Compared with La₂Ti₂O₇,the porous La₂Ti₂O₇ photocatalysts own bigger specific surface area,more mesoporous structure.And the porous La₂Ti₂O₇can produce more hydroxyl radicals.Hence,the photocatalytic activity of porous La₂Ti₂O₇ with PEG2000 as a template is much higher than pure La₂Ti₂O₇.2.The porous La₂Ti₂O₇ photocatalysts were prepared with CTAB as a template.The results of XRD show that crystal size and crystal cell volume of La₂Ti₂O₇ are affected by CTAB.At the same time the specific surface area,porous structure and adsorption capacity of the porous La2Ti2O7 increase significantly than pure La2Ti2O7.The photocatalytic activity of samples with the amount of CTAB 4 g is the best.3.Using the two types of photocatalysts to degrade azophloxine,hydroxyl radicals first attack the N atoms of N=N in the conjugated system.The amide group break down from the molecule of the azophloxine.NH₄⁺and N₂ were generated in the aqueous solution.R-SO₃^-turn into SO₄^2-.Benzene and naphthalene were oxidized into quinone that can be further degraded into small molecule acids.4.Using the two types of photocatalysts to degrade ofloxacine,most organofluorines changes into F^-.Hydroxyl radicals attack conjugated system of quinolone substituents.The C-N of piperazynel substituents was turned into NH₄⁺and NO₂^-;C-O of oxazynel substituents was cracked.Oxazynel substituents break down from the molecule of ofloxacine.Benzene was oxidized into quinone that can be further degraded into small molecule acids.