Study On The Activity Enhancement Mechanism Of Titanate Photocatalytic Materials

In this paper,two modification methods were used to prepare and study the titanate photocatalyst by sol-gel method.The Sm₂Ti₂O₇/SiO₂ photocatalyst was prepared by sol-gel method with SiO₂ as the carrier,and the effects of loading and calcination temperature on its photocatalytic activity were analyzed.The porous Sm₂Ti₂O₇ photocatalyst was prepared using PEG and TBAOH with different molecular weights as templates.The effect of 1.5 g of PEG and TBAOH with different molecular weights on the photocatalytic activity of Sm₂Ti₂O₇ was studied.With XRD,SEM,TEM,FT-IR/FIR,UV-Vis DRS,BET,BJH,FS and XPS and other characterization methods,study the effect of different modification methods on the photocatalytic degradation of RBR X-3B and Ofloxacin,The main experimental contents were as follows:（1）Samarium Titanate was supported on SiO₂ via a sol-gel route to prepare Sm₂Ti₂O₇/SiO₂ composites.The pyrochlore phase Sm₂Ti₂O₇ remained after being loaded by SiO₂,and no other impurity phases were formed.The TEM image shows that Sm₂Ti₂O₇ crystals are dispersed on the surface of SiO₂.As the content of Sm₂Ti₂O₇decreases,the absorption edge of the Sm₂Ti₂O₇/SiO₂ composite material moves to a shorter wavelength region,and the band gap of Sm₂Ti₂O₇ increases accordingly.The pore volume of 50%Sm₂Ti₂O₇/SiO₂ composite material was larger than that of Sm₂Ti₂O₇,and its pore size distribution was wider and the specific surface area was larger.The first order reaction rate constants were 0.00977 min^-1、0.0148 min^-1和0.0220 min^-1 for RBR X-3B degradation on the Sm₂Ti₂O₇、20%Sm₂Ti₂O₇/SiO₂ and 50%Sm₂Ti₂O₇/SiO₂powders.When the calcination temperature is 800℃,the 50%Sm₂Ti₂O₇/SiO₂ sample has the best photocatalytic activity,The photodegradation rates of RBR X-3B and Ofloxacin were31.6%and 47.8%when irradiated under UV light for 30 min.（2）Polyethylene glycol（PEG）was used in a sol-gel route to synthesize porous gadolinium titanate photocatalyst.The addition of PEG results in a blue shift of the absorption edge of the porous Sm₂Ti₂O₇ samples,whose bandgap energies are between3.41 e V and 3.82 e V.The N₂ adsorption-desorption isotherms of the Sm₂Ti₂O₇（PEGn）samples are IUPAC type IV of mesoporous material.The Sm₂Ti₂O₇（PEG2000）prepared using 1.5 g of PEG2000 has the maximum BET surface area of 23.22 m²/g,while the value of the Sm₂Ti₂O₇ prepared without PEG is only 2.87 m²/g.The order in photocatalytic activity of the Sm₂Ti₂O₇（PEGn）samples is as same as the orders shown in both photoluminescence intensity of the materials and hydroxyl radical production efficiency.All porous Sm₂Ti₂O₇（PEGn）samples have a significant improvement in the degradation of RBR X-3B,The Sm₂Ti₂O₇（PEG2000）sample has the best photocatalytic activity,and its photodegradation rate of RBR X-3B was 43.1%when exposed to ultraviolet light for 30 min.The first order reaction rate constants for photocatalytic degradation of RBR X-3B on Sm₂Ti₂O₇、Sm₂Ti₂O₇（PEG2000）and Sm₂Ti₂O₇（PEG10000）powder are 0.0058 min^-1、0.0300 min^-1 and 0.0136 min^-1,respectively.（3）TBAOH was used in a sol-gel route to synthesize porous gadolinium titanate photocatalyst.TBAOH in the sol can prohibit crystal growth of Sm₂Ti₂O₇.After adding different amounts of TBAOH,obvious pore structure will be left in Sm₂Ti₂O₇,and even through-type pore structure can be observed.The addition of TBAOH results in a blue shift of the absorption edge of the porous Sm₂Ti₂O₇ samples and the band gap increased.With the pore-forming properties of TBAOH,Sm₂Ti₂O₇prepared with 1.0 m L TBAOH has the largest pore volume of 0.0271 cm³/g,while the pore volume of pure Sm₂Ti₂O₇was only 0.0127 cm³/g.The photodegradation rate of Sm₂Ti₂O₇（1.0TBAOH）sample to Reactive Brilliant Red was 77.1%,and the total removal rate of Sm₂Ti₂O₇（1.0TBAOH）to Reactive Brilliant Red was 96.6%;The photodegradation rate of pure Sm₂Ti₂O₇ is only45.2%.The first order reaction rate constants for photocatalytic degradation of RBR X-3B on Sm₂Ti₂O₇、Sm₂Ti₂O₇（1.0TBAOH）and Sm₂Ti₂O₇（1.4TBAOH）powder are 0.0148min^-1、0.0487 min^-1和0.0225 min^-1,respectively.