Adsorption of four perfluorinated acids on non ion exchange polymer sorbents

Perfluorinated compounds (PFCs) have attracted global concern due to their ubiquitous distribution and properties of persistence, bio accumulation and toxicity. The process of adsorption has been identified as an effective technique to remove PFCs in water. Different non ion-exchange polymeric adsorbents were tested with regard to their sorption kinetics and isotherms at low PFCs concentrations. Selected PFCs were perfluorobutanoic acid (PFBA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) and the tested polymers were three types of Dowex optopores (V-493, V503, and L493), Amberlite XAD-4, and Filtrasorb 400 (Granular Activated Carbon-GAC). We observed the selective adsorption of PFCs on synthetic polymers. For PFDA, Amberlite XAD-4 gave the Freundlich adsorption constant of 2,965 (μg PFCs/g sorbent)(μg PFCs/L)⁻ⁿ, which was higher than that of GAC (121.89 (μg PFCs/g sorbent) (μg PFCs/L)⁻ⁿ). In the case of PFBA, GAC showed better performance (13.36) (μg PFCs/g sorbent) μg PFCs/L)⁻ⁿ than synthetic polymers (0.62–5.23) (μg PFCs/g sorbent) (μg PFCs/L)⁻ⁿ. Adsorption kinetics of all adsorbents were well described (R²=0.85–1) by pseudosecond order kinetic model. Sorption capacity was influenced by initial PFCs concentration for all adsorbents. GAC reached the equilibrium concentration within 4 hours, Amberlite XAD 4 reached it within 10 hours and other polymers took more than 70 hours. Key words 9 adsorption, non ion-exchange polymers, PFCs, sorption isotherm, sorption kinetics