Coupling system application in photocatalytic degradation of methylorange by TiO2, TiO2/SiO2 and TiO2/SiO2/Ag

Three different photocatalysts including TiO2,TiO2/SiO2 and TiO2/SiO2/Ag were synthesized via sol-gel growth method,in which colloidal silica was used as Si source,titanium tetra iso-propoxide（TTiP） as titanium source,Ag+ as dopant ion and hydroxypropyl cellulose（HPC） as dispersant.The purpose was to study the enhancement of photocatalytic activity of TiO2 by deposition on SiO2 colloids and also doping with Ag ion.The catalysts were characterized using X-ray diffraction（XRD）,transmission electron microscopy（TEM）,X-ray fluorescence（XRF）,Fourier transform infrared spectroscopy（FT-IR）and Brunauer-Emmett-Teller（BET） methods.It is confirmed that the major phase in all catalysts is anatase.Photocatalytic activity was studied in various conditions for degradation of methylorange（as a model pollutant） to evaluate the effect of some parameters on degradation efficiency.Studying the degradation process in various pH values reveals that the degradation is more efficient in acidic solution than alkaline condition.Coupling the photocatalytic process with some fields called electro-photochemical（EP）,magnetic-photochemical（MP） and ultrasonic-photochemical（UP） was studied at two pH values which were compared with photochemical（P） alone.It is concluded that in most cases,the EP is the best coupled system and has the maximum efficiency.Liquid chromatography-mass spectrometry（LC-MS）analysis was used to check the complete decomposition of methylorange at the end of process.