Recent literature review of Cerium-containing photocatalysts used for methylene blue degradation

Methylene blue is being used in several applications including textile, medical diagnostics, and surgical procedures, and its concentration in wastewater is increasing significantly globally with time, posing high health hazards for humans and other living organisms. Research studies are in progress worldwide to eliminate methylene blue and other related pollutants using several methods, including adsorption, photolysis, photocatalytic degradation, and photoelectrocatalytic degradation and elimination. Methylene blue can be degraded and eliminated proficiently from wastewater using photocatalytic degradation or photolysis. Several semiconductor nanomaterials are being utilized to degrade methylene blue and other related drugs in wastewater. This is a review conducted for the research papers published in early 2024 on cerium-containing catalysts for the photodegradation of methylene blue. These studies have used a variety of reaction conditions that include radiation types (UV, solar, and visible), pH of the solution, concentration of methylene blue, concentration of nanomaterials used, and presence of other additives and activators such as H₂O₂ on the photodegradation efficiency. The cerium has been used in these photocatalysts in different forms; oxide forms, oxides mixed with other metal oxides or metals, cerium salt containing nanomaterials, or as a dopant to other oxides or other metals. The metals used with cerium include zinc, tin, tellurium, magnesium, molybdenum, iron, titanium, aluminum, nickel, copper, and manganese. A summary of the reported literature showing the type of catalysts used, reaction conditions, and degradation efficiency has been presented in tabulated form. A discussion is made on the comparative and relative effects of different parameters on the photocatalytic performance of cerium-based catalysts. Some of the earlier published reviews are also presented.