Many environmentally relevant poly-/perfluoroalkyl substances (PFASs) including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) exist in different isomeric (branched and linear) forms in the natural environment. The isomeric distribution of PFASs in the environment and source waters is largely controlled by the source of contamination and varying physicochemical properties imparted by their structural differences. For example, branched isomers of PFOS are relatively more reactive and less sorptive compared to the linear analogue. As a result, the removal of branched and linear PFASs during water treatment can vary, and thus the isomeric distribution in source waters can influence the overall efficiency of the treatment process. In this paper, we highlight the need to consider the isomeric distribution of PFASs in contaminated matrices while designing appropriate remediation strategies. We additionally summarize the known occurrence and variation in the physicochemical properties of PFAS isomers influencing their detection, fate, toxicokinetics, and treatment efficiency.

Poly‐ and perfluoroalkyl substances (PFAS) are known as “forever chemicals” due to their ubiquitous persistence in the environment, and their negative human health effects. Among them, short‐chain PFAS are of increasing concern due to their high solubility and mobility in water, while possessing persistency and toxicity nature like their longer‐chain analogs. The most common method for PFAS removal from water is by sorption with activated carbons or ion exchange resins, but these adsorbents only exhibit limited removal efficiency against short‐chain PFAS, and they require frequent replacement leading to high operational cost. Here we review and discuss the potential of using bio‐adsorbents, which can be derived from common biomass feedstocks, as low‐cost alternatives to traditional adsorbents, while these materials can also possess good removal efficiency against short‐chain PFAS. We further provide the perspective on the designs of low‐cost, activated bio‐adsorbent systems that can be implemented for effective removal of short‐chain PFAS.

The soil-washing technique has been successfully utilized for the remediation of PFAS-contaminated soils. Prior studies have shown that the organic carbon (OC) content and grain size of soil determined the efficiency of PFAS removal during washing. However, most of the past studies have focused on soils with a low OC content, typically ranging from 0–3%. In this study, we explored the use of a novel process where soil washing was combined with air bubbling (or foam fractionation) to aid in the removal of PFAS from high OC-content soils (~4–20%). Treatment with air bubbling of high OC soil (~20%) with perfluorobutane sulfonate (PFBS) and perfluorooctanoate (PFOA) did not enhance their removal, as they featured low surface activity. However, we observed an improvement in the extraction of perfluorooctane sulfonate (PFOS) from 27% to 42% with bubbling, consistent with the higher surface activity of PFOS compared to PFOA and PFBS. Perfluorodecanoic acid (PFDA) was irreversibly adsorbed to the high OC soil and was not removed efficiently by both bubbling and soil washing. A slight improvement in PFDA removal (6–13%) was observed when a co-surfactant (cetyltrimethylammonium chloride) was added and when the OC content was reduced to ~4% by the addition of nonorganic sand to the contaminated soil prior to soil washing. This suggested that the interaction of PFDA with OC was the dominant factor determining its extraction from soil. In conclusion, our results indicated that soil washing alone was sufficient for the removal of short-chain PFAS from soil. Although bubbling had a mild effect on the removal of some long-chain PFAS from the solution, it did not help in the overall removal of PFAS from high OC soils, highlighting the difficulty in the treatment of high OC-content soils and that immobilization of PFAS would be an ideal approach in managing such contaminated sites.

Electrochemical oxidation processes (eAOP) are a promising approach for the remediation of per- and polyfluoroalkyl substance (PFAS) due to its ease of operation, low energy needs and lack of auxiliary chemicals. In this study, we designed and utilized a boron-doped diamond anode in a two-electrode system to investigate the impact of the electrolyte composition and PFAS chain length on the eAOP performance. We varied the supporting anions (Na₂SO₄, NaCl, NaNO₃) and electrical conductivity (500–2000 μS cm⁻¹, constant current), and found no effect of supporting anions on PFAS removal. Varying the supporting anions, while maintaining constant electrical conductivity did not significantly vary the anodic voltage (p value = 0.99). We found a strong correlation between PFAS removal and their log n-octanol–water partitioning coefficient (r = 0.8), suggesting that PFAS sorption onto the electrode was a critical step in the degradation of PFASs. It was also demonstrated, for the first time for eAOPs, that gas bubbles generated in the system could capture and transport PFASs from the solution to the water surface, leading to loss of PFASs by electrochemical aerosolization (2–85%) after the bursting of bubbles. Fluorine mass balance for the treatment of PFOA and 6 : 2 FTS revealed ∼68% recovery post treatment, with the inorganic fluorine (48%) released during treatment being the primary component and ∼20% fluorine, unaccounted for. Results from this study highlight the impact of the supporting electrolyte and PFAS aerosolization on the treatment efficiency and provide insight into the mechanisms and system design to improve removal of PFASs utilizing an eAOP.

The application of electron beam (e-beam) technology for water treatment has been proposed to be a faster and safer approach to decomposing persistent contaminants in water, because of its ability to rapidly generate high amounts of both oxidizing and reducing reactive species without the addition of chemicals. In this study, we utilized a lab-scale 9 MeV e-beam accelerator to investigate the feasibility of treating 1,4-dioxane in various water matrices in batches with low sample volumes (<90 mL). Very low doses (<5 kGy) and treatment times (98% of 1,4-dioxane within the range of environmentally relevant concentrations (0.1–10 mg L⁻¹), without the need for any sample modification or pH adjustment. Low dissolved oxygen in the solution enhanced the degradation efficiency by 21–23% when treating 1000 mg L⁻¹ of 1,4-dioxane, presumably because of the increased H˙ and O˙⁻ that can react with 1,4-dioxane. Although the degrading intermediates were not fully mineralized to carbon dioxide at the tested doses, the detected intermediates, such as aldehydes and organic acids, were not as persistent as 1,4-dioxane and were more vulnerable to conventional treatment methods and natural attenuation. The slowest reaction rate constant was observed when treating wastewater samples (k = 0.13–0.62 kGy⁻¹), followed by contaminated groundwater (k = 0.16–1.4 kGy⁻¹), suggesting other organics and ions could scavenge the generated reactive species. The electrical energy per order (EE/O) ranged from 0.39 (DI water) to 6.3 (wastewater) kWh m⁻³ per order, depending on the initial concentration of 1,4-dioxane and water matrix. The EE/O values were comparable to other traditional advanced oxidation processes (AOPs) to treat 1,4-dioxane, suggesting the feasibility of utilizing e-beam to treat contaminated waters. The organic carbon content of the sample positively correlated (R² >0.9) with the EE/O values and thus can be utilized to predict e-beam treatment performance. Our results show that e-beam radiolysis is a promising technology to treat 1,4-dioxane and could potentially outperform other AOPs and 1,4-dioxane disposal methods (e.g., incineration) in terms of energy consumption and treatment time, leaving no trace of oxidants.