Photo-catalyst for wastewater treatment: A review of modified Fenton, and their reaction kinetics

Persistent organic substances in wastewater are creating serious problems to the living world as well as to the environment, thereby creating a hugely detrimental impact on the ecosystem. Given the critical situation, the removal of the persistent organic substances from wastewater effluent holds a great promise to balance the ecosystem and sustain societal impact value. Among the several wastewater treatment techniques, the advanced oxidation processes (AOPs) employing solar energy is the acceptable one and is considered one of the promising alternative methods to work on. Organic pollutants like dye-contaminated wastewater, pharmaceutical waste-water, petroleum wastewater, municipality wastewater, etc. are treated for purification purposes by these techniques. This review article aims to provide an overview on the importance of the above techniques, from their origin to their recent modification, progress, and the probable scopes for further improvement. The modification of the Fenton process has been processed to overcome several weaknesses including high bandgap, recombination of electron-hole pair, lower light intensity in solar light, operation under visible light, and natural pH conditions. The photo-catalysts with novel properties are functioning as an emergent class of smart materials with recently introduced promising materials like graphene, g-C3N4, metal-organic framework, quantum dots, etc. The review will spark the kinetic study and role of scavengers to investigate the mechanistic insights for the development of value-added photo-catalysts. The study also evaluates the prospects and future challenges to follow strict regulations.