In recent years, alarm has been raised due to the presence of chemical contaminants of emerging concern (CECs) in water. This concern is due to the risks associated with their exposure, even in small amounts. These complex compounds cannot be removed or degraded by existing technologies in wastewater treatment plants. Therefore, advanced oxidation processes have been studied, with the objective of developing a technology capable of complementing the conventional water treatment plants. Heterogenous photocatalysis stands out for being a cost-effective and environmentally friendly process. However, its most common form (with suspended catalytic particles) requires time-consuming and costly downstream processes. Therefore, the heterogeneous photocatalysis process with a supported catalyst is preferable. Among the available supports, polymeric ones stand out due to their favorable characteristics, such as their transparency, flexibility and stability. This is a relatively novel process; therefore, there are still some gaps in the scientific knowledge. Thus, this review article aims to gather the existing information about this process and verify which questions are still to be answered.

Wastewaters from the olive oil industry are a regional environmental problem. Their phenolic content provides inherent toxicity, which reduces the treatment potential of conventional biological systems. In this study, Sulfate Radical based Advanced Oxidation Processes (SRbAOPs) are compared with advanced oxidation processes (namely Fenton’s peroxidation) as a depuration alternative. Synthetic olive mill wastewaters were submitted to homogeneous and heterogeneous SRbAOPs using iron sulfate and solid catalysts (red mud and Fe-Ce-O) as the source of iron (II). The homogenous process was optimized by testing different pH values, as well as iron and persulfate loads. At the best conditions (pH 5, 300 mg/L of iron and 600 mg/L of persulfate), it was possible to achieve 39%, 63% and 37% COD, phenolic compounds and TOC removal, respectively. The catalytic potential of a waste (red mud) and a laboratory material (Fe-Ce-O) was tested using heterogenous SRbAOPs. The best performance was achieved by Fe-Ce-O, with an optimal load of 1600 mg/L. At these conditions, 27%, 55% and 5% COD, phenolic compounds and TOC removal were obtained, respectively. Toxicity tests on A. fischeri and L. sativum showed no improvements in toxicity from the treated solutions when compared with the original one. Thus, SRbAOPs use a suitable technology for synthetic OMW.

Heterogenous-photocatalysis is suitable for the removal of contaminants of emerging concern from wastewaters. Usually, photocatalysts are used in suspension, which requires time-consuming and costly down-stream processes. Thus, supported-photocatalysis gained interest in the scientific community. To develop a supported photocatalyst, TiO₂ (P25) was immobilized, by dip-coating, in polyethylene terephthalate (PET). This photocatalyst was used to degrade parabens, under UV radiation. Plastic wastes were use as the source of PET, to reduce the amount of plastic sent to landfill and its environmental impact and to obtain revaluated residues, through the production of a higher-grade product. To enhance the photocatalytic activity of the modified sheets, the concentration of the P25 dispersion and the number of immersions were optimized. Dipping PET sheets in a P25 dispersion (20 g/L) five times allowed to achieve parabens removals of ~30%. Also, the developed material can be reused four times without a significant decrease in its photocatalytic activity. <!----> <!----> <!----> <!---->