Photocatalytic Activity Enhancement of Titanium Dioxide Nanoparticles: Degradation of Pollutants in Wastewater

Advanced oxidation processes (AOPs) with UV irradiation and photocatalyst titanium dioxide (TiO2) are gaining growing acceptance as an effective wastewater treatment method. A comprehensive study of the UV/visible-TiO2 photocatalytic oxidation process was conducted with an insight into the mechanism involved, catalyst TiO2, irradiation sources, types of reactors, comparison between effective modes of TiO2 application as immobilized on surface or as suspension. Photocatalytic degradation technique with TiO2 is generally applied for treating wastewater containing organic contaminants due to its ability to achieve complete mineralization of the organic contaminants under mild conditions such as ambient temperature and ambient pressure. TiO2 is highly stable in aqueous media and is tolerant to both acidic and alkaline solutions. It is inexpensive, recyclable, reusable, and relatively simple to produce. The large band gap of TiO2 lies in the UV range, which allows for only 5–8 % of sunlight to be useful for the activation of the catalyst. Therefore, a visible light activated catalyst is desired that can take advantage of a larger fraction of the solar spectrum and would be much more effective in environmental cleanup. Several competing effects inherently limit catalyst efficiency. The positively charged holes and negatively charged electrons tend, by nature, to recombine to yield a neutral state, through emission of photons or phonons. This can occur via volumetric or surface recombination. There are several known ways to increase the efficiency of a photocatalyst. The effects of particle size reduction, anion doping with nitrogen ions, and cations, e.g., Nd, Pd, Pt, Co doping have been