Recent advances in photocatalytic oxidation techniques for decontamination of water

Pollutants in water resources (such as heavy metal ions and organic dyes) are presently causing critical issues for human health and the environment. Among such pollutants, organic dyes represent a significant class of contaminants. They are generally discharged into water from dyeing textiles and/or other industrial strategies. Removing these pollutants from wastewater is an important and vital task owing to the toxic impacts of organic dyes on animals, plants, and human health. In this paper, we outline and highlight recent reports on synthetic organic dyes and approaches for removing them (including photocatalytic degradation). We discuss the kinetics of the photodegradation of organic dye pollutants from wastewater using metal oxide-, metal organic framework-, metal sulphide-, halide-, polymer-, carbon-nitride-, carbon-based-, oxynitride-, and layered double hydroxide-based (LDH) photocatalysts. The applications considered the most significant for degrading organic dyes (such as catalysis) are attributed to different mechanisms. Notably, the aromatic structures of organic dyes cause several difficulties in the process of water treatment and affect human health. For example, the azo dye colour is dependent on azo bonds and their associated auxochromes and chromophores (molecular components responsible for the absorption or reflection of the falling light). These components are harmful to the respiratory system, cause skin irritation, and (in the case of direct contact with the eyes) may cause permanent damage. In addition to physical hazards of such effluent materials, they may also cause mutagenic effects in microorganisms and rats, including DNA damage. Ultimately, we summarise the challenges and prospects for managing pollutants (such as those from organic dyes) in wastewater.