Electrosorption-Driven Remediation of PFAS-Contaminated Water Using a MXene Nanosheet-PEDOT:PSS Adsorbent

Perfluoroalkyl substances (PFAS), widely used for their chemical and thermal stability in various industrial applications, have raised environmental and health concerns due to their ubiquitous presence in water sources. Stringent regulations targeting long-chain PFAS have been enacted, but emerging evidence indicates health risks associated with short-chain PFAS. Adsorption stands out as a viable remediation technology for PFAS-containing water. Electric-field-aided adsorption (electrosorption) emerges as a technique that has demonstrated that it can adsorb PFAS from water and enable on-demand desorption of the retained PFAS upon alternating the applied voltage. Effective electrosorption demands adsorbents with significant specific surface area, capacitance, and durability. Two-dimensional transition metal carbides and nanotrides (MXene) are competitive candidates. MXene, in conjunction with poly(3,4-ethylene dioxythiophene) polystyrenesulfonate (PEDOT:PSS), can exhibit increased surface area and capacitance. This study develops a titanium carbide (Ti3C2Tx) MXene-PEDOT:PSS adsorbent for PFAS electrosorption. Acid etching enhances the adsorbent's specific surface area and pore characteristics, resulting in an approximately 400% increase in volumetric capacitance for various PFAS compared to untreated counterparts. The adsorption capacity for perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) is measured at 45.6, 51.1, and 54.9 mg/g, respectively, at an initial concentration of 750 ppb upon application of +1.0 V. The reversible adsorption–desorption cycles demonstrate the potential for repeated use of the adsorbent. We envision that the adsorbent can contribute to the development of efficient and sustainable technologies for addressing PFAS contamination in water sources.