Perfluorooctane sulfonic acid (PFOS) degradation by optimized heterogeneous photocatalysis (TiO2/UV) using the response surface methodology (RSM)

Abstract

Perfluorinated compounds (PFCs) are chemical substances widely used in industry, especially in textile coatings, often detected in waters all around the world. Those are persistent, bioaccumulative, and endocrine disruptors, causing damage to human health and the environment. Thus, this work aimed at evaluating the degradation of aqueous perfluorooctane sulfonic acid (PFOS), one of the most used PFCs, at near environmental concentrations (initially 100 μg L−1) by heterogeneous photocatalysis (TiO2/UV). At optimized conditions (CTiO2= 1.45 g L−1 and pH= 4.0), which were determined by the response surface methodology (RSM), 83 % PFOS removal was achieved in 8 h at 25 °C. A pseudo-first-order kinetic model was adjusted to the experimental data and the initial rate constant (k) was estimated as 0.64 h−1 with maximum oxidation capacity (MOC) of 86 %. No significant degradation was observed by direct UV-photolysis. Furthermore, the degradation products (DPs) were identified by high performance liquid chromatography coupled to high resolution mass spectrometry (HPLC-MS), acute and chronic ecotoxicities for three classes of organisms (fishes, daphnids, and green algae) and lipophilicity (log D, pH 7.4) of the DPs were estimated using the ECOSAR 1.11 and Chemicalize software, respectively. The main finding was that PFOS could be degraded by an advanced oxidation process under mild conditions and reasonable times, and that the lipophilicity of the formed DPs affects acute and chronic ecotoxicities of the organisms studied.