Properties Of Rare Earth Ions Doped Tio₂ Sol And Its Application

Title: Preparation of Rare Earth Ions doped TiO₂ Sol and its ApplicationName: Xu MeiProfessor: Wang ChaoxiaMajor: Textile EngineeringSince TiO₂ has better photocatalytic activity and degrades organic pollutants with speed, non-selective and completely oxidation. TiO₂ can make full use of renewable solar energy, oxygen molecules in the air and the operation is easy to control.Therefore it has broad applications of environmental governance, such as air purification, health care and wastewater treatment. In the area of self-cleaning products, such as ceramics, glass, lighting and textiles have been studied and applied. Photocatalytic activity TiO₂ doped with rare earth ion is synthesized in this paper. The factors of preparation conditions, photo-induced activity are investigated, and the modified TiO₂ is applied to photodegradation of organic pollutants on the fabric under visible light irradiation.Tm/TiO₂ pholocatalyst loaded cotton fabric is prepared by sol-gel deposition. The crystal grains, visible light response range of Tm/TiO₂ as well as its distribution on the cotton fibers were characterized by XRD, UV-Vis and SEM. The influences of preparation and photocatalytic process on fabric self-cleaning performance, durability, tensile property, permeability, hand feel and whiteness are discussed. According to the experimental results, the mechanism of rare earth doped TiO₂ as well as degradation of organic pollutants are analyzed in detail.Tm/TiO₂ powders prepared by sol-gel method are the mixture of anatase and rutile phases from the XRD analysis, the average crystallite sizes of anatase decrease from 13.7nm to 11.4 nm, and rutile decrease from 15.3nm to 12.9nm, respectively.With the increase of Tm-doping, the particle size of TiO₂ sol decreases, which can be reduced to 35.7nm. The Zeta potential of TiO₂ sol increases with Tm-doped increase and achieves to 27.0mV. UV-visible absorption spectroscopy of pure TiO₂ and Tm/TiO₂ sol indicates that the optical absorption extends towards the visible spectrum and a red-shift absorption edge (0.13eV) exists. With the increase of Tm doped ratio, red shift in the band-gap transition increases. Under an irradiation intensity of 21mW/cm² for180min, Tm-doped molar ratio is 2 mol%, dosage of sol aged for 5 days is 0.5g/L, the photocatalytic activity for capsicum red pigment degradation can achieve around 94%. The improvement mechanisms are due to the higher visible light adsorption and the special 4f12 electron configuration of Tm. Tm-doping leads to the formation of energy levels and the bandgap narrowing. The degradation of capsicum red pigment is caused by photocatalytic and photosensitized degradation.The major degradation pathway for capsanthin is dealkylation from FT-IR analysis, the carbochain and carboxide bonds in the capsanthin chain are broken by oxidation process with the pholocatalyst. The degradation rate of organic pollutants on treated fabric is 80% after 20 times washing, which indicates that the self-cleaning property of treaded fabric has an excellent washing fastness. The crease recovery oftreated fabric improves, while the tensile property, permeability, hand feel and whiteness decline slightly. Therefore Tm/TiO₂ sol loaded cotton fabric has self-cleaning function on the photodegradation of capsicum red pigment under visible light irradiation.