Titania–Montmorillonite for the Photocatalytic Removal of Contaminants from Water: Adsorb & Shuttle Process

Recently, TiO2–Montmorillonite-based composites have attracted a great deal of attention as efficient photocatalysts for the degradation/reduction of organic contaminants and heavy metals in waters and wastewaters. It can be claimed that the most popular benefits of using TiO2–Montmorillonite photocatalysts are an enhancement in the photocatalytic removal of contaminants due to their high adsorption capacity, high photocatalytic activity of nanoscaled TiO2 deposited on Montmorillonite surface and low costs. Otherwise, the use of naked nanoscaled TiO2 is not recommended because of its low adsorption ability, fast agglomeration in water and due to the issue of recovery of such small particles from water. Differently from naked TiO2, the photocatalytic removal of contaminants by TiO2–Montmorillonite is enhanced through the mechanism so-called Adsorb & Shuttle (A&S) which is based on the use of highly adsorbing domains to increase the quantity of contaminants near TiO2 photocatalytic sites. Adsorb & Shuttle process can be affected by TiO2–Montmorillonite characteristics (i.e. TiO2 loading, surface area, pore size and degree of TiO2 crystallinity) as well as the type of contaminant. In this chapter, the following points will be highlighted: (i) mechanisms of TiO2 photocatalysis for the removal of organic contaminants and heavy metals, (ii) recent progress on synthesis of TiO2–Montmorillonite photocatalysts via different methods and (iii) recent discussions regarding the photocatalytic removal of contaminants by TiO2–Montmorillonite composites.