4.4.1. Photocatalytic Treatments

Photocatalysis can be described as an advanced oxidation process able to fully mineralize the contamination in liquid as well as the gas phase under room pressure and temperature [92]. Its efficiency is mainly due to the capability to generate powerful oxidizing agents [14,15,93,94]. In this way, the chemical transformation rate is enhanced by the chosen photocatalyst under light irradiation [95]. Following these perspectives, photocatalysis has found a successful application in the water decontamination field [96], providing promising results in the removal of a large variety of contaminants (e.g., aromatics, pesticides, drugs, oils) [97].

In this context, photocatalytic treatments can be applied in the field of OMWW degradation using both homogeneous and heterogeneous photocatalysts in the presence of UV, visible and solar light irradiation. In this class of treatments, photo-Fenton and solar-Fenton processes are also included [18,98,99].

In the following paragraphs, deeper insights into the current approaches used in the literature are reported with the aim of fully describing the scenarios related to these technologies.
