Progress in the application of ionic liquids and deep eutectic solvents for the separation and quantification of per- and polyfluoroalkyl substances

Abstract

Per- and polyfluoroalkyl substances (PFASs), often labeled as "forever chemicals," earned this moniker due to their widespread presence in the environment, bioaccumulative tendencies, and resistance to remediation efforts. Employed for decades in various applications, spanning from stain-resistant fabrics to grease-proof food containers and fire-fighting foams, PFASs have evolved into an anthropogenic nightmare. Their adverse impact on human health, including immune dysfunction, infertility, and a spectrum of cancers, is alarming. Conventional water treatment methods, notably in the case of short-chain congeners, struggle to effectively eliminate PFASs, underscoring the pressing need for enhanced adsorbents. In recent years, there has been a prominent surge in the exploration of innovative techniques centered around ionic liquids (ILs) and deep eutectic solvents (DESs) for the removal of PFASs from various sources, including food samples like cooking oil, as well as environmental waters. In this Review, we delve into key advancements and discoveries related to the utilization of ILs and DESs as media for the liquid-liquid extraction of PFASs, as well as their applications as sorbents on solid-state or nanoscale supports. Our exploration encompasses groundbreaking approaches, including the utilization of dicationic ILs for ultra-sensitive mass spectrometric PFAS detection, alongside the innovative application of fluorinated ILs and hydrophobic DESs, enabling highly efficient PFAS sequestration. The landscape of existing PFAS extraction methods is riddled with formidable challenges, including limited selectivity, matrix interferences, subpar extraction efficiency, exorbitant costs, laborious procedures, ecological consequences, and a lack of standardization. Given these challenges, our review unequivocally asserts the pivotal role ILs and DESs will play in shaping the next generation of PFAS remediation strategies. Rigorous characterization of water solubility, toxicity, and biodegradation, along with improved recyclability and thorough techno-economic analyses, are essential for further progress. Future focus must also extend to addressing short-chain PFASs (such as PFBS) and PFAS alternatives (including ADONA, GenX, F-53B), which often pose higher toxicity risks than the compounds they aim to replace. A forward-thinking approach will integrate cutting-edge data-driven techniques, such as machine learning, to enhance our understanding and response to PFAS-related issues. Finally, we advocate seamless integration of PFAS separation with advanced treatment, efficiently isolating and destroying these compounds for a lasting solution to contamination challenges.

Keywords: Deep eutectic solvents; Ionic liquids; PFAS; PFCs.