Magnetically Recyclable Photocatalysts for Degradation of Organic Pollutants in Aquatic Environment

Due to effectiveness of the photocatalysis process in mineralization of organic pollutants into relatively less harmful CO2 and H2O, their application in degradation of organic pollutants in aquatic environment was explored which has limitations, such as (a) the activity of the photocatalyst in relatively higher energy light only (e.g., UV light of the solar spectrum); (b) the high recombination rate of e−–h+ pair, resulting in dissipation of the captured light energy; and (c) the recovery of photocatalysts from the suspension solution after its use. Considering recovery of photocatalysts as their main limitation, magnetic separation of photocatalysts was performed in which the magnetic material is found to be in two roles, such as (a) magnetic material as a photocatalyst and (b) magnetic material as a non-photocatalyst. The magnetic material as a photocatalyst can further play three roles, such as (a) catalyst, (b) co-catalyst, or (c) dopant. Among these roles, the application of magnetic material as a co-catalyst is found to be more promising due to its ability to extend the absorption of light in the wide range of solar spectrum (i.e., UV to NIR region). Moreover, the magnetic material in non-photocatalytic role is usually insulated from the photocatalytic material by a non-conductive reaction barrier (e.g., SiO2). However, the photocatalytic degradation of organic pollutants at large scale has certain limitations, such as (a) scale-up of the photocatalytic reaction unit with an integrated magnetic separation unit and (b) ensuring the environmental effectiveness of the photocatalysts in real aqueous environment, which requires further research.