Magnetic Adsorbents/Photocatalysts for Water Purification: Progress and Challenges

Photocatalysis requires the activation of photocatalytic materials by light to produce a redox system able to oxidize/reduce (in)organic pollutants. Photocatalysts in suspension form provide excellent oxidation of pollutants in water due to excellent mass transfer. However, the recovery of photocatalyst particles is challenging and costly at large scale. To solve this, numerous studies on the immobilization of photocatalysts on substrates have been reported, to avoid treatment steps or/and for better recovery of particles. This approach suffers from slow kinetics due to less mass transfer, and is not competitive with existing technologies. Magnetically recoverable photocatalysts for water treatment are innovative materials that can be used for high efficiency and ease of handling: they can be used as suspensions, ensuring maximum mass transfer, and recovered by external magnetic force. This chapter aims to discuss recent progress in the design and application of magnetic-based materials for water treatment. Their synthesis and performance in water treatment are clarified. Their catalytic role to catalyse Fenton agents and NaBH4 for organic pollutant oxidation is addressed. In addition, their photocatalytic mechanistic pathways and (photo)catalytic role are discussed. Since magnetic materials exhibit low stability and high charge, recombination as magnetic nanoparticles that can play the roles of recombination center and insulator are discussed, emphasizing the mechanisms and synthesis conditions.