Adsorption of Fluorotelomer Olefin (FTO) on Activated Carbon, Non-Ion and Ion Exchange Resin: Kinetics and Isotherm Studies

Fluorotelomer aroused global concern when it was introduced into industry to replace per- and polyfluoroalkyl substances (PFAS) due to its extensive dispersion and attributes of potential persistence, bioaccumulation, and toxicity. Adsorption has been known to be an efficient approach for eliminating PFAS from water. However, there is still a lack of studies regarding the removal of fluorotelomer by adsorption. Three different adsorbents: granular activated carbon (GAC), non-ion exchange resin (XAD-4), and ion exchange resin (IRA958) were investigated regarding sorption kinetics and isotherms at different adsorbent dosages, contact times, and fluorotelomer olefin (FTO) concentrations. Each of adsorbents were characterized by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). Most of the FTO adsorption on the adsorbents began to achieve equilibrium within 5 h and all adsorbents were well-described using pseudo-second-order model for adsorption kinetics; GAC (R2 = 0.9966), XAD-4 (R2 = 0.9915), and IRA958 (R2 = 0.9951). Meanwhile, the Freundlich isotherm model was preferred for FTO adsorption, with GAC exhibiting the highest adsorption capacity (Kf = 3.0853) followed by IRA958 (Kf = 3.0400) and XAD-4 (Kf = 0.0009). The study suggests that strong interactions between FTO molecules and adsorbent surfaces result in the formation of multiple FTO layers, incorporating both multilayer adsorption and chemisorption mechanism.