A comprehensive review on spinel based novel catalysts for visible light assisted dye degradation

Abstract

Removal of color-causing compounds from wastewater is one of the major issues industries face because of its toxic, carcinogenic, baleful nature. It adversely affects aquatic life and human health too. Many processes are known to humankind, such as physiochemical, biological, chemical, and electrochemical. Advanced Oxidation Processes (AOPs) are of particular interest among these processes. The current review presents spinel-type photocatalysts for dye degradation that degrades the color-causing pollutants (dyes) and converts them into molecules such as CO2, H2O, and other simpler compounds depending on the structure of dyes. At first, the basics of photocatalyst degradation and its mechanism are discussed, followed by works with different catalyst spinels. The successive sections cover the effect of doping and parameters affecting photocatalysts. Three spinels: Nickel Ferrites, Cobalt Ferrites, and Zinc Ferrites are specifically discussed. Effects of doping on A sites and B sites are both reviewed. In general, doping alters the spinels' magnetic, optical, and structural parameters. Doping induces defects in the spinel lattice and thereby increases strain which causes oxygen vacancies and higher surface area with a reduction in particle or grain size, which finally results in better photocatalytic activity and ease of separation because of magnetic properties. The current work reviews the recent works carried out for photocatalytic dye degradation using spinel-type catalysts.