Degradation of perfluorooctanoic acid by zero-valent iron nanoparticles under ultraviolet light

Perfluorooctanoic acid (PFOA) is ubiquitous in the environment because of its wide applications in aqueous film forming foam, food packing, waterproof breathable fabrics, and Teflon products. Though it is resistant to biodegradation, photocatalytic degradation has been proven possible. In this study, zero-valent iron nanoparticles (Fe0 NPs), with or without 1% polyvinylpyrrolidone (PVP) coating, were used for PFOA degradation under ultraviolet C (UVC) light for the first time. PFOA was degraded faster initially (e.g., < 13 h) with Fe0 NPs than without Fe0 NPs under UVC light. In addition, the degradation rate using Fe0 NPs without coating was higher than that with 1% PVP coating in the initial 6 h, although the difference was diminished afterwards. Both Fe2+ and Fe3+ ions were detected during the process. Shorter-chain perfluorocarboxylic acids (PFCAs), i.e., PFHpA, PFHxA, PFPeA, and PFBA, were detected as main intermediates; fluoride ions (F−) were also detected. Rapid consumption of Fe3+ (plus the lower UV–vis absorption intensity observed for a mixture of PFOA and FeCl3 compared to the intensity observed for FeCl3 alone) indicated the possible formation of [C7F15COO-Fe]2+—a degradable complex. The UV/Fe0 system is superior, with low toxicity of iron and no introduction of other chemicals. Additionally, the cost of Fe0 NPs is low, and the recycle of Fe0 NPs is easy from the treated water by their magnetic properties. The study provided an innovative, environment-friendly, and low-cost method for PFOA degradation by Fe0 NPs under UVC light, which could be potentially applied for treatment of surface water and groundwater contaminated by PFOA.