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

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.

Per- and Polyfluoroalkyl Substance (Pfas) Retention by Colloidal Activated Carbon (CAC) Using Dynamic Column Experiments

“…Specifically, PFOS had a complete breakthrough at 400 PV, much later than its analogous PFNA, which showed a complete breakthrough at 234 PV. Stronger sorption of PFSAs than PFCAs has similarly been reported before for sorption to soils (Campos Pereira et al, 2018) and activated carbons (Park et al, 2020;Son et al, 2020). This can be explained by the stronger hydrophobicity of PFSAs than their analogous PFCAs due to the larger size of the sulphonate moiety (Higgins and Luthy, 2006).…”

Adsorption of perfluorooctanoic acid from water by pH-modulated Brönsted acid and base sites in mesoporous hafnium oxide ceramics

“…Mesoporous hafnium oxide, a group IV transition metal oxide, is an attractive PFOA adsorption candidate. Mesoporous materials lead to increased PFOA adsorption as the diameter of PFOA is about 2 nm ( Xiang et al., 2018 ), and previous work has shown that microporous materials (<2 nm) are not ideal for PFOA adsorption ( Son et al., 2020 ). The high thermal (700°C) and chemical stability (active sites on the surface) of MHO ceramic, results from its highly coordinated hafnium.…”

A Review on Removal and Destruction of Per- and Polyfluoroalkyl Substances (PFAS) by Novel Membranes

“…It also addresses factors affecting PFAS removal via membrane filtration and delineates research gaps and key future research directions. In recent years, a growing number of studies have addressed the environmental occurrence, fate, and transport of PFAS in potable water and wastewater treatment plants, as well as varying treatment approaches [2,[27][28][29][30][31]. Therefore, it is necessary to systematically review and critically analyze the state of knowledge and determine research gaps for suitable and economically viable technology leading to PFAS removal from water.…”