Per- and polyfluoroalkyl substances (PFAS) have emerged as a class of important pollutants in various environmental media such as water, soil/sediment and landfill leachates. Due to the unique chemical structure, PFAS are extremely recalcitrant to environmental degradation, and thus, may pose long-term risks to the environment and human health. Yet, cost-effective technology has been lacking to treat PFAS. To address this technology need, this study aimed to develop a new adsorptive photocatalyst for efficient adsorption and photocatalytic degradation of PFAS. Building upon our previous study of activated charcoal supported titanate nanotubes (TNTs@AC), we developed a new adsorptive photocatalyst, Fe-doped TNTs@AC (or Fe/TNTs@AC). First, TNTs@AC was prepared based on low-cost commercial activated charcoal/carbon and TiO2 through a one-step hydrothermal method under alkaline conditions. Fe/TNTs@AC was then prepared by first loading Fe2+ onto the TNTs@AC through ion exchange, and then, upon proper drying, calcined at 550 oC under nitrogen flow. The effectiveness of the material was tested through batch adsorption and photocatalytic degradation experiments using perfluorooctanoic acid (PFOA) as a model PFAS. Fe/TNTs@AC was able to highly effectively adsorb PFOA (~99% PFOA was adsorbed within 20 min, PFOA = 100 ppb, material dosage = 1 g/L). Subsequently, the pre-sorbed PFOA was completely photodegraded under UV irradiation within 3 h, and 76% of fluorine in PFOA was completely converted into fluoride (defluorinated) under UV irradiation for 4 h. The defluorination efficiency was about 7 times higher than that of TNTs@AC. The photo-regenerated Fe/TNTs@AC can then be reused for more than another 10 adsorption-photodegradation cycles without significant loss in adsorption capacity or photodegradation activity. Mechanistically, photo-generated holes were the dominant oxidative species for PFOA degradation and the doped Fe(III) facilitated electron transfer and inhibited hole-electron recombination. Besides, more and large crystallite anatases were observed after calcination, further improving the photocatalytic activity. Fe/TNTs@AC hold the promise to be a low-cost, eco-friendly and efficient material for treating PFAS in contaminated water.

New adsorptive photocatalyst for highly efficient adsorption and degradation of perfluorooctanoic acid (PFOA)

2019 Spring National Meeting

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