Photocatalytic and photoelectrocatalytic degradation of perfluorooctanoic acid by immobilised ZnO nanoparticles using electrophoretic deposition

This research represented the first study of perfluorooctanoic acid (PFOA) decomposition using immobilized ZnO nanoparticles by electrophoretic deposition in photocatalysis and photoelectrocatalysis. Overall, considering process performance, application under visible light exposure, and cost-effectiveness, ZnO nanoparticles are highly promising for PFOA degradation. The effect of the probable production of sulfate radicals on PFOA photocatalytic decomposition over ZnO films was investigated by the addition of different concentrations of peroxymonosulfate (PMS). Notably, ∼42% of PFOA was decomposed within 2 hours (rate constant = 0.287 h⁻¹) under UV irradiation in the presence of 0.27 g L⁻¹ PMS. Importantly, the same amount of PMS initiated PFOA degradation under visible light exposure with the rate constant of 0.125 h⁻¹. In photoelectrocatalysis, the optimal ZnO film demonstrated an excellent degradation performance of ∼49% within 2 hours at V = 0 (under UV irradiation). Overall, ZnO was highly promising in both photoelectrocatalysis and PMS-assisted photocatalysis, although PMS could enhance ZnO corrosion. In addition to the sulfate radicals, the photogenerated holes and superoxide radicals were among the main active species responsible for PFOA decomposition.