Removal of Persistent Organic Pollutants Using Redox Active Metal Oxide Nanocatalysts via Advanced Oxidation Process

Abstract

Improvement of water quality involves the detection and removal of synthetic organic pollutants and naturally occurring toxic substances from industrial and municipal wastewater. This can be effectively done by adopting advanced oxidation processes (AOPs) that were designed to remove organic or inorganic contaminants of wastewater by the process of oxidation. AOPs involves adequate production of hydroxyl radical (OH•) that can oxidize pollutants into mineral end-products, CO2 and inorganic ions. Oxide nanoparticles with different morphologies and sizes have attracted enormous attention due to their unique physical and chemical properties.We focussed mainly on the application of oxide nanomaterials of Cu, Fe, Ce and Co for removal of persistent organic pollutants in wastewater via AOPs. Many reports have shown the use of copper oxides as effective nanocatalysts for degradation of organic dyes such as methylene blue, methyl orange, rhodamine B etc. The use of iron oxides (mainly Fe+3 ions) in Fenton reaction is very common as they are magnetically separable, inexpensive, environmental friendly and less toxic which makes them a good contender for the practical application in wastewater treatment. Again, the unique characteristics of cerium oxides/ceria like reducibility, oxygen storage capacity, resistance to sintering, acid-base and redox properties which makes it a promising catalyst as well as promoter for a variety of catalytic reactions. Moreover, ceria also affects the thermal stability of supports, oxidation and reduction of noble metals and the dispersion of noble metals. Similarly, cobalt oxide based nanomaterials are very important for generation of PMS (peroxymonosulfate salt) to obtain SO4− radical. Numerous strategies have been established to get diversity of redox active oxide nanomaterials of Cu, Co, Fe, Ce and their mixed oxides.