How photocatalyst work on environmental pollution?
Answers
In recent years, semiconductor photocatalytic technology has been demonstrated to be one of the “green” and effective strategies for solving environmental pollution problems. Therefore, environmental photocatalysis, including water disinfection, hazardous waste remediation, air and water purification, deodorization, antibacterial, and self-cleaning, has caused more and more attention in recent years (see the work of J. G. Yu et al. “ photocatalytic materials” [1–9]). However, owing to low photocatalytic efficiency and activity of photocatalytic materials, the environmental applications of various photocatalytic technologies and materials are still very limited. Thus, more investigations are highly required from the viewpoint of practical use and commerce.
This special issue contains eighteen papers, which mainly deal with environmental photocatalysis. Among them eight papers are related to preparation, characterization, and photocatalytic performance of photocatalytic materials including CeO2-SiO2, BiVO4, mesoporous TiO2, Bi2WO6, Bi2O3-Bi2CrO6, H3PW12O40/SiO2, Mn-C-codoped TiO2, ZnO, and N-doped TiO2, three papers, are devoted to decolorization and treatment of industrial wastewater, three papers present photocatalytic degradation of dyes, one paper reports on indoor air purification, two papers are related to photo-Fenton and photoelectron-Fenton reactions, and the remaining one deals with photocatalytic degradation of nitrobenzene. Furthermore, in this special issue, 16 papers are research articles and two papers are review articles. We wish to express our thanks to all the authors who have made this special issue possible. A brief summary of all eighteen papers is presented below.
The article entitled “Comparison between solar and artificial photocatalytic decolorization of textile industrial wastewater” mainly reported the photocatalytic decolorization of industrial wastewater by using TiO2 and ZnO photocatalysts. Heterogeneous photocatalysis applied under natural weathering conditions, in the presence of solar radiation, shows a promising degradation capability. The complete removal of color was achieved in a relatively short time of about 20 minutes when ZnO was used, and about 100 minutes when TiO2 was used under solar irradiation. The results indicated that the photocatalytic decolorization of textile industrial wastewater was obviously influenced by different factors including mass and type of catalyst, reactor, dye concentration, and temperature.
In the article entitled “Synthesis and characterization of nanoparticles by microwave-assisted irradiation method for photocatalytic oxidation of methylene blue dye,” CeO2-SiO2 nanoparticles were prepared for the first time by a facile microwave-assisted irradiation process. The photocatalytic activities were evaluated by the decomposition of methylene blue dye under UV light irradiations. The results showed that all solid samples exhibited mesoporous textures with high specific surface areas, relatively small pore size diameters, and large pore volume. The sample prepared by 30 min microwave irradiation time exhibited the best photocatalytic activity. The photocatalytic activity of CeO2-SiO2 nanoparticles prepared by 30 min irradiation times was found to have better performance than commercial reference P25.
In the paper entitled “Electrochemical techniques in textile processes and wastewater treatment,” the authors review the electrochemical techniques applied to textile industry. In particular, they are an efficient method to remove color of textile effluents. The reuse of the discolored effluent is possible, which implies an important saving of salt and water (i.e., by means of the “UVEC Cell”). Electrochemical reduction reactions are mostly used in sulfur and vat dyeing, but, in some cases, they are applied to effluents discoloration. However, the main applications of electrochemical treatments in the textile sector are based on oxidation reactions. Most of electrochemical oxidation processes involve indirect reactions which imply the generation of hypochlorite or hydroxyl radical in situ. These electrogenerated species are able to bleach indigo-dyed denim fabrics and to degrade dyes in wastewater in order to achieve the effluent color removal.