Trends in photocatalytic degradation of organic dye pollutants using nanoparticles: A review

The development of the textile industry is a major concern due to the effluents of organic dyes. These organic dyes contaminate the drinking water and cause a carcinogenic risk to humans. Nanomaterials such as semiconductors can be used for the degradation of dye pollutants through photocatalysis. Several parameters, including catalyst dosage, irradiation time, light sources, initial concentration of dyes, temperature, and pH, significantly influence the degradation of the dyes. Single metal nanoparticles such as Ag, Au, Fe, and Cu NPs were also used for the degradation of organic dyes. Photocatalytic nanomaterials can be classified into three different generations. The first-generation catalysts consist of single-component materials such as metal oxide Fe₃O₄, ZnO, SnO₂, TiO₂, and metal nanoparticles such as silver nanoparticles (AgNPs), CuNPs, and gold nanoparticles (AuNPs). The second-generation catalysts consist of binary metal oxides, such as ZnO-SnO₂, PbO-Al₂O₃, Fe₃O₄-CeO₂, WO₃-ZnO, and ternary metal oxides, such as ZnO-CuO-Ag₂O, Fe₃O₄-TiO₂-CoMoO₄. The third-generation catalysts comprise photocatalysts spread on inert solid substrates, such as Ce/TiO₂ and Al/ZnO. This review describes different types of nanoparticles (NPs) used for dye degradation, including metal nanoparticles, metal oxides, and their doping with other metals, semiconductors, binary metal oxides, and ternary metal oxide nanocomposites.