Can the photocatalyst TiO2 be incorporated into a wastewater treatment method? Background and prospects

This brief non-exhaustive review article aims to highlight first and foremost, what we consider to be, some of the milestones of photocatalysis and of titanium dioxide as the workhorse among metal-oxide photocatalysts, in particular, and metal chalcogenides, in general, together with some of the attempts at using titania in wastewater treatment systems. In this regard, over half a century has passed since the initial research on water treatment using TiO2 as the preferred photocatalyst. During that period, the decomposition of water pollutants, the mechanisms of photocatalytic reactions, the development of a method to immobilize TiO2 on suitable support substrates, reactor designs, and engineering scale-ups have all been addressed worldwide. Unfortunately, the use of titania as the photocatalyst in current water treatment methods appears to have little consequences in Advanced Oxidation Technologies (AOT), although its prospects are not to be discounted. Consequently, first we briefly examine the historical background of what was achieved in the first 50 years of the 20th century with regard to photocatalysis, and then the second 50 years of the 20th century and beyond about implementing photocatalysis and TiO2 as a photocatalyst in the treatment of wastewaters contaminated with organics, followed by probing some of the features of various reactor designs in scale-ups to treat large volumes of wastewaters.