Application of photochemical treatments in the removal of perfluorooctanoic acid (PFOA) from aqueous solutions

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant (POP) whose harmful effects on the environment and human health, as well as its presence in different environmental matrices, have been studied. In this way, there is evidence of the presence of PFOA in wastewater, drinking water, treated water, and surface water, and in some aquatic species and human fluids such as blood. In this sense, the main objective of this research was to evaluate the potential application of different photochemical treatments in the removal of PFOA present in aqueous matrices. The effect of operational parameters such as the concentrations of the contaminant and the oxidizing agents, the type of the incident light (UV or solar), and the type of matrix were analyzed. The experimental results showed that processes such as photolysis, hydrolysis, the UV light/H2O2 and UV light/Fe2+ combinations, and the oxidation with H2O2 are not able to remove the contaminant. On the contrary, the application of photo-Fenton, solar photo-Fenton, and Fenton treatments allowed removals higher than 80.0% to be achieved. The best performance was showed by the photo-Fenton treatment under the irradiation of ultraviolet light with a wavelength of 254 nm, which conducted to the elimination of similar to 99.0% of PFOA in only 60 min of reaction. Despite these findings, the results associated with the degree of mineralization of the organic matter and the toxicity (using Vibrio fischeri bacteria) of the samples indicated that it is likely that the oxidation of the contaminant leads to the formation of by-products of a much more resistant organic nature and that depending on their concentrations may also represent a risk to the human health and the ecosystems.