A Review of Treatment Techniques for Short-Chain Perfluoroalkyl Substances

Abstract

In recent years, an increasing amount of short-chain perfluoroalkyl substance (PFAS) alternatives has been used in industrial and commercial products. However, short-chain PFASs remain persistent, potentially toxic, and extremely mobile, posing potential threats to human health because of their widespread pollution and accumulation in the water cycle. This study systematically summarized the removal effect, operation conditions, treating time, and removal mechanism of various low carbon treatment techniques for short-chain PFASs, involving adsorption, advanced oxidation, and other practices. By the comparison of applicability, pros, and cons, as well as bottlenecks and development trends, the most widely used and effective method was adsorption, which could eliminate short-chain PFASs with a broad range of concentrations and meet the low-carbon policy, although the adsorbent regeneration was undesirable. In addition, advanced oxidation techniques could degrade short-chain PFASs with low energy consumption but unsatisfied mineralization rates. Therefore, combined with the actual situation, it is urgent to enhance and upgrade the water treatment techniques to improve the treatment efficiency of short-chain PFASs, for providing a scientific basis for the effective treatment of PFASs pollution in water bodies globally.

Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

“…For decades, per- and polyfluoroalkyl substances (PFAS) chemicals have been widely used in various consumer, medical, and industrial products. − Owing to environmental persistence and being notoriously hazardous, the long-chain PFAS chemicalsperfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS)have been prohibited under international regulations. , However, many short-chain fluorinated alternatives remain in use, and they could also be accumulated via physicochemical degradation pathways of longer-chain PFAS. − Even though the use of hydrated electron (e aq – )-based advanced reductive technology (e aq – -ART) has recently shown to be effective to destruct both perfluoroalkyl carboxylates (PFxA, x = number of carbons comprising the hydrophobic tail) and perfluoroalkyl sulfonates (PFxS), − PFxS with short fluoroalkyl chains such as PFBS (C 4 F 9 SO 3 – ) remains an exceptional case and displays very sluggish reactivity . To date, the abundance of short-chain PFAS from numerous sources has already been detected in most locations on the planet. − Recent toxicological studies revealed that the potential threats to human health posed by analogs had been underestimated due to increased solubility, mobility, and inertness. − Thus, their complete removal and decomposition from the aquatic environment has become an urgent concern.…”

Substitution and Orientation Effects on the Crystallinity and PFAS Adsorption of Olefin-Linked 2D COFs

“…Two key factors that control PFAS absorption are the electrostatic interactions between anionic headgroups of the PFASs with cationic amine groups on the sorbents and the hydrophobic interactions between the sorbents and the PFAS molecules. ,, The porosity, shape, and particle size of the sorbents are other parameters that affect the affinity and efficacy of adsorbents toward the PFAS molecules. ,, To find which factor impacts the PFOA removal mechanism, we first measured the contact angle to show the hydrophobicity and hydrophilicity of each COF’s surface (Figure S26, Movie S1). COF-I showed the most hydrophobic surface, while the hydroxy groups made COF-II more hydrophilic; as a result, the affinity of COF-II for the PFOA removal decreased dramatically (Table S1).…”

“…Among these COFs, COF-I showed the best removal performance toward PFOA from these solutions, 36% from 10 mg L −1 and 85% from 1 mg L −1 solution within 24 h. Two key factors that control PFAS absorption are the electrostatic interactions between anionic headgroups of the PFASs with cationic amine groups on the sorbents and the hydrophobic interactions between the sorbents and the PFAS molecules. 15,16,65 The porosity, shape, and particle size of the sorbents are other parameters that affect the affinity and efficacy of adsorbents toward the PFAS molecules. 15,16,65 To find which factor impacts the PFOA removal mechanism, we first measured the contact angle to show the hydrophobicity and hydrophilicity of each COF's surface (Figure S26, Movie S1).…”

“…Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are the two most common PFAS forms used and spread in the environment for decades . These types of PFASs have been widely detected in different parts of the environment and even in human blood. − Using solid adsorbents for PFAS removal, especially from water, is one of the most efficient, environmentally friendly, and economically feasible techniques that have been reported. ,− Carbonaceous materials, anion-exchange resins, porous organic and molecular imprinted polymers, minerals, and metal–organic frameworks (MOFs) are the reported adsorbents used for the removal of PFASs from water. ,,− Most of these materials exhibit large specific surface areas with suitable pore sizes and particular functional groups for the enhanced adsorption capacity of PFASs. However, these adsorbents suffer drawbacks such as slow adsorption rate, poor regeneration ability, and structural change at different pH levels.…”

Low-Carbon Water Treatment and Energy Recovery

“…In the first paper authored by Liu et al, the persistence, toxicity, mobility, and widespread pollution of short-chain PFASs in the water cycle are discussed. The study compares how various treatment techniques, such as the adsorption, electrochemical oxidation, and photocatalytic degradation have certain removal effects on short-chain PFASs [5]. Among these techniques, adsorption proves to be the most widely applied technique for the effective removal of short-chain PFASs, suitable for a wide concentration range of pollution and aligning with low-carbon policies.…”