The Adsorption Selectivity of Short and Long Per- and Polyfluoroalkyl Substances (PFASs) from Surface Water Using Powder-Activated Carbon

Heejong Son,Dongye Zhao,Byungryul An,Hoon-Sik Yoom,Taehoon Kim

doi:10.3390/w12113287

Abstract

Nine per- and polyfluoroalkyl substances (PFASs), including six perfluoroalkyl carboxylic acids (PFCAs) and three perfluoroalkyl sulfonic acids (PFSAs), were tested to find their adsorption selectivity from surface water and the feasibility of the powder activated carbon (PAC) process between the perchlorination and coagulation processes by operating parameters such as mixing intensity, dosage, contact time, initial pH, and concentration of perchlorination. The removal efficiency of four types of PAC revealed that the coal-based activated carbon was clearly advanced for all of the PFASs, and the thermal regenerated PAC did not exhibit a significant reduction in adsorption capacity. The longer carbon chain or the higher molecular weight (MW) obtained a higher adsorption capacity and the MW exhibited a more proportional relationship with the removal efficiency than the carbon chain number, regardless of the PFCA and PFSA species. Approximately 80% and 90% equilibria were accomplished within 60 and 120 min for the long chain carbon PFAS, respectively, while for the short chain PFAS, 240 min was required to reach 85% equilibrium. The effect of mixing intensity (rpm) was not considered for the removal of the PFAS, although it was relatively influenced in the short PFAS species. Due to the surface charge of the PAC and the properties of protonation of the PFASs, the acid condition increased the PFASs’ adsorption capacity. The prechlorination decreased the removal efficiency, and the reduction rate was more significantly influenced for the short chain PFAS than for the long chain PFAS.

Highlights

Poly- and perfluoroalkyl substances (PFASs) are one class of fluorinated substances that contain at least one fluorine atom (-F) replacing one or all of the hydrogen atoms on the carbon skeleton and a terminal functional group on the organic and inorganic compound [1]
A standard solution containing six perfluoroalkyl carboxylic acids (PFCAs) and three perfluoroalkyl sulfonic acids (PFSAs) among polyfluoroalkyl substances (PFASs) was purchased from Wellington Laboratories (Guelph, ON, Canada) and was used without further purification
Four types of powder activated carbon (PAC) were investigated to determine the feasibility in water treatment plants (WTPs) by comparing the removal of various PFAS species in different conditions, such as PAC dosage, mixing contact time, mixing intensity, pH, and concentration of chlorination

Summary

Introduction

Poly- and perfluoroalkyl substances (PFASs) are one class of fluorinated substances that contain at least one fluorine atom (-F) replacing one or all of the hydrogen atoms on the carbon skeleton and a terminal functional group on the organic and inorganic compound [1]. Buck et al (2011) divided them into polymeric and non-polymeric PFASs, and each PFAS includes three sub-groups and four sub-families, respectively [1]. Polymeric PFASs are fluoropolymers, sidechain fluorinated polymers, and perfluoropolyethers and non-polymeric PFASs are perfluoroalkyl acids (PFAAs), fluorotelomers (FT), per- and polyfluroalkyl ethers, and perfluoroalkane sulfonlyl fluorides [2]. Current target PFASs belong either to perfluoroalkyl carboxylic acids (PFCAs) or perfluoroalkyl sulfonic acids (PFSAs), and these are the most significant of the PFAAs. Due to a PFAS containing one or more carbon atoms, it can usually be sorted with long and short carbon chains depending on the carbon length (number).

Methods

Results

Conclusion