Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, to facilitate their application and reduce costs. TiO₂ is a reference material, and it has been greatly optimized. However, in its typical configuration, it is known to be mainly active under ultraviolet radiation. Thus, multiple alternative visible light driven (VLD) materials have been intensively studied recently. WO₃ and g-C₃N₄ are currently attractive VLD catalysts, with WO₃ possessing similarities with TiO₂ as a metal oxide, allowing correlations between the knowledge regarding the reference catalyst, and g-C₃N₄ having an interesting and distinct non-metallic polymeric structure with the benefit of easy production. In this review, recent developments towards CECs degradation in TiO₂ based photocatalysis are discussed, as reference catalyst, alongside the selected alternative materials, WO₃ and g-C₃N₄. The aim here is to evaluate the different techniques more commonly explored to enhance catalyst photo-activity, specifically doping with multiple elements and the formation of composite materials. Moreover, the possible combination of photocatalysis and ozonation is also explored, as a promising route to potentialize their individual efficiencies and overcome typical drawbacks.

The main drawback of Fenton′s process is the formation of ferric sludge. In this work, ion exchange (IE) appears as a complement to the Fenton process, allowing, on the one hand, to remove the iron excess present in the sludge, as well as reduce the COD of the real olive oil industry extraction wastewater (OOIEW) from the Fenton process. The Fenton process uses iron (II) sulfate as catalyst, therefore concentrations of iron up to 2 g L⁻¹ could be present in the treated OOIEW. The iron and COD adsorption equilibrium behavior has been modelized by Langmuir, Freundlich and Temkin isotherms. Moreover, the resin efficiency was tested in a continuous fixed-bed column. It was concluded that the resin maintains iron adsorption capacity over at least three reuse cycles. Overall Fenton’s process followed by ion exchange seems to be a promising approach for the treatment of cumbersome industrial wastewaters.