Effect of electron shuttles on typical perfluoroalkyl substance removal via iron oxide reduction in wetland sediment

Perfluoroalkyl substance (PFAS) had been widely detected in water environment and caused extremely toxicity. The Fe(Ⅲ) reduction process had been confirmed with potential effect on organic pollutants removal. Many substances can be served as electron shuttles that played important role in Fe(Ⅲ) reduction and the removal or distribution of PFAS. Considering the complex organic characteristics in wetland sediment, this study explored the effect of diverse electron shuttles, including activated carbon (AC), sucrose, humic acid (HA), organic acid (OA) and NH4+, on typical PFAS (PFOA and PFOS) removal under the Fe(Ⅲ) reduction conditions. Results showed that, the Fe(Ⅲ) contents reduced with the removal of PFAS. The addition of NH4+, AC and sucrose enhanced PFOA and PFOS removal in sediment. And the addition of NH4+ achieved best PFOA removal, which had 30.2% lower content than that in control. The characteristics of organic carbon changed with these electron shuttles and thus influenced the performance and distribution of PFAS. Among the organic matter components, the proportions of fulvic acid-like and humic-like materials increased, which could promote Fe(Ⅲ) reduction. Increased proportions of Firmicutes, Proteobacteria and Pseudomonas were detected with various electron shuttles. These microbes could survival under PFAS pollution and have potential to defluorination of PFAS. The electron shuttles highly improved the proportions of iron-reduction bacteria, which were more than 86.0% higher than that in control. This study provided a key information for better understanding the role of electron shuttles in PFAS removal via Fe(Ⅲ) reduction process, which could be useful for effective PFAS remediation in sediment.