Abstract
Photocatalytic water treatment using nanocrystalline titanium dioxide (NTO) is a well-known advanced oxidation process (AOP) for environmental remediation. With the in situ generation of electron-hole pairs upon irradiation with light, NTO can mineralize a wide range of organic compounds into harmless end products such as carbon dioxide, water, and inorganic ions. Photocatalytic degradation kinetics of pollutants by NTO is a topic of debate and the mostly reporting Langmuir-Hinshelwood kinetics must accompanied with proper experimental evidences. Different NTO morphologies or surface treatments on NTO can increase the photocatalytic efficiency in degradation reactions. Wisely designed photocatalytic reactors can decrease energy consumption or can avoid post-separation stages in photocatalytic water treatment processes. Doping NTO with metals or non-metals can reduce the band gap of the doped catalyst, enabling light absorption in the visible region. Coupling NTO photocatalysis with other water-treatment technologies can be more beneficial, especially in large-scale treatments. This review describes recent developments in the field of photocatalytic water treatment using NTO.
Highlights
Realizing the importance of keeping our planet clean, researchers are actively working for eco-friendly alternative technologies for all areas of daily life
Selective degradation could be useful for mixtures of highly toxic pollutants in low concentrations and less harmful compounds in higher concentrations [17,18]. The former can be degraded by means of Nanocrystalline titanium dioxide (NTO) photocatalysis, whereas the latter can be removed by less-expensive biological wastewater treatments [18]
These findings show that the photocatalytic degradation of aqueous pollutants is initiated mainly by ·
Summary
Realizing the importance of keeping our planet clean, researchers are actively working for eco-friendly alternative technologies for all areas of daily life. Cheaper sources of TiO2, such as bulk-synthesized TiO2 pigment [14] and iron-containing industrial TiO2 by-products [15], have been explored for the photocatalytic degradation of phenol and humic acids Their activities were found to be comparable with those of the commercially available Degussa P25 TiO2 photocatalyst, the benchmark TiO2 photocatalyst for all applications. A report by Kim et al describes the successful, elegant, and simultaneous use of NTO as both an energy and an environmental photocatalyst [16] Their surface-fluorinated and -platinized NTO catalyst generated hydrogen gas when degrading 4-chlorophenol and bisphenol compounds. Selective degradation could be useful for mixtures of highly toxic pollutants in low concentrations and less harmful compounds in higher concentrations [17,18] The former can be degraded by means of NTO photocatalysis, whereas the latter can be removed by less-expensive biological wastewater treatments [18]. The second catalyst, TAH60, with negative surface charge, showed selective adsorption of the cationic dye methylene blue, followed by its degradation, from an aqueous mixture containing methyl orange and methylene blue dyes
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