TiO 2 films on a capillary column were prepared using tetrabutoxytitanium as a source of TiO 2 via the sol-gel method. The film thickness showed a linear increase with tetrabutoxytitanium concentration. The specific surface area of the film was improved by adding polyethylene glycol with different molecular weights.Under optimal conditions, the prepared film had a good mesoporous structure with specific surface area of 47.72 m 2 g À1, and showed nearly spherical nanoparticles with a 10 nm diameter and anatase phase.Influences of the thickness, specific surface area, and initial solution concentration on photodegradation of rhodamine B using TiO 2 films as a catalyst were investigated. The results showed that the photodegradation efficiency increased with an increasing thickness and specific surface area of TiO 2 films. For a rhodamine B solution of 15 mg L À1, the photodegradation efficiency was 98.33% in 30 min under the optimal conditions. The catalysts could be reused up to eight times with almost the same efficiency, indicating a firm immobilization of films on the inner wall of the capillary. Therefore, TiO 2 films are promising for the treatment of wastewater.

While modern industry has contributed to the prosperity of an increasingly urbanized society, it has also led to serious pollution problems, with discharged wastewater and exhaust gases causing significant environmental harm. Titanium dioxide (TiO2), which is an excellent photocatalyst, has received extensive attention because it is inexpensive and able to photocatalytically degrade pollutants in an environmentally friendly manner. TiO2 has many advantages, including high chemical stability, low toxicity, low operating costs, and environmental friendliness. TiO2 is an N-order semiconductor material with a bandgap of 3.2 eV. Only when the wavelength of ultraviolet light is less than or equal to 387.5 nm can the valence band electrons obtain the energy of the photons and pass through the conduction band and form photoelectrons, while the valence band, correspondingly, forms photogenerated holes, and light in other areas will not be generated. The most common methods used to improve the photocatalytic efficiency of TiO2 involve increasing its photoresponse range and reducing photogenerated-carrier coupling. The morphology, size, and structure of a heterojunction can be altered through element doping, leading to improved photocatalytic efficiency. Mainstream methods for preparing TiO2 are reviewed in this paper, with several excellent preparation schemes for improving the photocatalytic efficiency of TiO2 introduced. TiO2 is mainly prepared using sol-gel, solvothermal, hydrothermal, anodic oxidation, microwave-assisted, CVD and PVD methods, and TiO2 nanoparticles with excellent photocatalytic properties can also be prepared. Ti-containing materials are widely used to purify harmful gases, as well as contaminants from building materials, coatings, and daily necessities. Therefore, the preparation and applications of titanium materials have become globally popular research topics.