Life After Adsorption: Regeneration, Management, and Sustainability of PFAS Adsorbents in Water Treatment

Abstract

Per- and polyfluoroalkyl substances (PFASs) represent one of the most challenging classes of persistent organic pollutants, and adsorption is currently one of the most widely deployed method for their removal from water. However, the long-term sustainability of adsorption-based treatment depends on how adsorbents are regenerated, managed after exhaustion, and integrated into broader environmental and regulatory frameworks. This review synthesises recent advances in regeneration strategies for PFAS-saturated adsorbents, including thermal, solvent-based, chemical, hybrid, and emerging methods, and provides a targeted analysis of policy and regulatory frameworks governing PFAS management in water. Evidence from the literature is critically assessed with attention to regeneration efficiencies, adsorbent stability, secondary waste generation, and long-term reuse potential. Life cycle assessment (LCA) studies are also examined to evaluate the environmental and cost implications of different management options. The analysis highlights that while solvent and chemical regeneration achieve high short-term recovery, thermal processes offer partial destructive potential, and electrochemical methods are emerging as promising but unproven alternatives. Persistent challenges include incomplete PFAS desorption, performance decline over multiple cycles, energy intensity, and secondary waste burdens. Advancing sustainable PFAS treatment requires integrated evaluation frameworks linking technical performance with environmental impact and cost, supported by policy drivers that incentivize regeneration and safe end-of-life management.

1. Introduction

In recent decades, an increasing global focus on developing advanced and effective wastewater treatment technologies capable of removing persistent substances from the aquatic environment, which are resistant to conventional water treatment processes, has been observed [1,2]. Of particular note are per- and polyfluoroalkyl substances (PFASs), of which, despite years of regulatory efforts, contamination across Europe remains alarmingly ubiquitous. From 2018 to 2022, between 51% and 60% of European river samples and up to 100% of transitional and coastal water samples exceeded environmental quality standards for PFOS (perfluorooctane sulfonate) alone, strongly indicating broader PFAS pollution trends [3]. Moreover, studies have documented significant contamination hotspots, particularly at sites with known PFAS use, such as airports and industrial facilities, where surface and groundwater have become heavily burdened with these persistent chemicals [4]. PFAS contamination poses an increasing challenge to environmental quality, water resource management, and especially public health. For example, a study of pregnant women in Barcelona found that PFASs such as PFOA (perfluorooctanoic acid), PFNA (perfluorononanoic acid), PFDA (perfluorodecanoic acid), PFHxS (perfluorohexane sulfonic acid), and PFOS were detected in over 98% of participants’ plasma samples, demonstrating near-universal exposure [5,6]. The chemical characteristics underpinning this ubiquity, such as extreme persistence due to strong carbon–fluorine bonds, high aqueous mobility, and potential for long-range atmospheric and hydrological transport, make PFASs uniquely challenging to contain once released into the environment [7].

The environmental behaviour of PFASs is characterised by a combination of persistence, toxicity, and mobility. These substances do not readily degrade under natural conditions and are resistant to conventional water treatment processes. Their mobility allows them to migrate from point sources into rivers, aquifers, and even remote ecosystems, while their bioaccumulative potential leads to enrichment in food chains [8,9]. Health impacts are increasingly well-documented, with epidemiological and toxicological studies linking exposure to developmental impairments, immune system suppression, liver and thyroid dysfunction, and carcinogenic effects [10,11]. Given their widespread detection in surface water, groundwater, and even treated drinking water supplies, PFASs have been categorised by the European Chemicals Agency (ECHA) as substances of very high concern [12]. The most popular PFASs, along with their sources and occurrence in the environment, are presented in

Table 1. Types of PFAS and their occurrence in the environment.

PFAS	Typical Sources/Uses	Occurrence in Environment
PFOS (Perfluorooctane sulfonate) [10,13,14,15]	Formerly used in firefighting foams (AFFFs), stain- and water-resistant coatings for textiles, leather and paper, metal plating, and pesticides. Phased out in EU by 2010 under the Stockholm Convention on Persistent Organic Pollutants (listed as a persistent organic pollutant) but still present in legacy materials.	Widespread in EU surface waters, often exceeding quality standards. High persistence and bioaccumulation in rivers, lakes, sediments and biota (fish, wildlife), especially near airports and industrial sites.
PFOA (Perfluorooctanoic acid) [10,14,15,16,17]	Processing aid in fluoropolymer manufacturing (e.g., Teflon/PTFE), non-stick cookware, waterproof textiles and coatings, and some AFFFs. Listed under the Stockholm Convention in 2019; production and use in the EU have ceased, with industry substituting alternative PFASs (e.g., GenX).	Common in EU groundwater and surface water near chemical plants and former production areas. Persists and travels long distances; frequently detected in drinking water and food.
PFHxS (Perfluorohexane sulfonate) [10,14,15]	Used in some AFFFs, textiles and leather coatings; also an impurity in PFOS products. PFHxS and its salts were added to the Stockholm Convention in 2022 due to their extreme persistence (notably long human half-life) and bioaccumulative properties.	Found with PFOS at contaminated sites (airports, fire training areas). Detected in EU groundwater and human serum; mobile in water and accumulates in top predators.
PFNA (Perfluorononanoic acid) [14,16]	Surfactant/processing aid in some fluoropolymers (e.g., to polymerise vinylidene fluoride for PVDF plastic); also a degradation product of other PFASs. Limited EU production but present via imports and precursors breakdown.	Detected at lower levels than PFOS/PFOA but still notable in EU water and wildlife. Long-chain and bioaccumulative; contributes to dietary PFAS exposure.
PFBS (Perfluorobutane sulfonate) [14,16,18]	PFOS replacement used in water- and stain-resistant coatings for textiles, carpets, and paper, and as an industrial surfactant. It yields a much lower bioaccumulation potential in humans.	Increasingly detected in EU rivers and groundwater, especially near textile and waste facilities. Highly mobile and can reach drinking water despite lower bioaccumulation.
GenX (Hexafluoropropylene oxide dimer acid, HFPO-DA) [14,15,16,17]	PFOA replacement in fluoropolymer production (e.g., making Teflon-like coatings). Used as processing emulsifier. Came into use in the EU after PFOA was phased out. GenX was added to the EU Substances of Very High Concern list in 2019.	High levels found downstream of manufacturing plants; also detected in groundwater, rainwater and crops. Persistent but less bioaccumulative than PFOA.

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Among available water treatment methods, adsorption has emerged as one of the most widely implemented technologies. Its success lies in its relative operational simplicity, adaptability to diverse treatment scales, and capacity to achieve high removal efficiencies for a range of chemistries [19,20,21,22]. A variety of adsorbents have been developed and optimised specifically for PFAS removal. Carbon-based materials, including granular activated carbon [23], powdered activated carbon [24], and engineered biochars [25], are the most established, offering strong hydrophobic and electrostatic interactions with PFAS molecules. Mineral-based adsorbents, such as modified clays [26], zeolites [27], and metal oxides [28], provide tuneable surface chemistries that can target specific PFAS functional groups. Polymeric resins [29], including ion exchange materials [30], are increasingly used for selective PFAS removal, particularly for shorter-chain compounds. More recently, waste-derived [31] and hybrid composite materials [32] have been proposed as cost-effective, lower-carbon alternatives, reflecting a trend toward integrating circular economy principles into water treatment.

Despite some preliminary work on the removal of PFASs by adsorption having started over 20 years ago [33,34,35], with increased interest in the last few years [36], the subsequent fate of PFAS-saturated adsorbents remains an underexplored but critical issue. Once an adsorbent reaches its breakthrough capacity, operators face a choice: regenerate it for reuse, destroy the adsorbed PFAS, or dispose of it in a manner that prevents environmental release. Each of these pathways has technical, economic, and environmental trade-offs. Ineffective regeneration may result in incomplete PFAS desorption and reduced adsorbent performance, while certain disposal methods risk leaching contaminants into soils or landfill leachates. Destructive approaches, such as high-temperature incineration or advanced oxidation, can be energy-intensive, costly, and subject to uncertain regulatory acceptance. Neglecting these challenges risks undermining the benefits of PFAS removal, driving up lifecycle costs, and creating new sources of pollution [9,37].

These concerns are magnified by tightening regulatory frameworks. In the European Union, the revised Drinking Water Directive [38], effective from January 2026, will set stringent parametric values for PFASs: a limit of 0.1 µg/L for any individual PFAS (including PFOS) and a 0.5 µg/L total PFAS limit. The REACH Regulation [39] (Registration, Evaluation, Authorization, and Restriction of Chemicals) continues to advance restrictions on PFAS manufacture, use, and release, while the Water Framework Directive [40] establishes environmental quality standards for priority hazardous substances, including selected PFASs. At the global level, similar tightening is observed: Australia has introduced national PFAS standards for drinking water [41], while Canada is implementing province-wide PFAS monitoring programmes [42]. These measures collectively increase the urgency for treatment strategies that not only remove PFASs effectively but also manage used adsorbents in ways that are compliant, sustainable, and publicly acceptable.

The growing recognition of PFASs as a persistent threat has led to numerous reviews on PFAS occurrence, fate, and removal technologies [8,43,44]. However, few have addressed the post-adsorption phase in a comprehensive, integrated manner [45]. Existing literature tends to treat regeneration, destruction, and disposal of PFAS adsorbents as marginal issues, often reporting them as brief secondary findings to removal efficiency studies. Moreover, there is limited work linking the technical feasibility of these end-of-life options with LCA, TEA (techno-economic analysis), and regulatory frameworks. This omission is significant. Without understanding the operational costs, environmental trade-offs, and compliance requirements associated with end-of-life management, decision-makers risk implementing PFAS treatment systems that are unsustainable in the long term. In response, this review systematically examines regeneration and reuse strategies for PFAS adsorbents, evaluating their technical performance, economic viability, and environmental implications where such analyses have been conducted. By uniquely integrating these technical, economic, and policy dimensions, the review fills a critical knowledge gap and establishes a comprehensive framework to guide environmental engineers, water utilities, and policymakers in developing PFAS treatment strategies that are both effective and sustainable.

2. Materials and Methods

This review was undertaken in two complementary stages: first, a systematic synthesis of the scientific literature on PFAS adsorption with emphasis on regeneration strategies, and second, a targeted analysis of policy and regulatory frameworks governing PFAS management in water. This approach was selected to ensure that technical evidence could be evaluated in the context of real-world legislative constraints, a linkage that is often missing in PFAS-focused reviews.

A structured literature review was carried out using the PRISMA 2020 elements (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) as a methodological reference point [46]. The PRISMA-based method was chosen to enhance transparency, reproducibility, and methodological rigour. Searches were performed across Elsevier ScienceDirect, Scopus, Google Scholar, and the Multidisciplinary Digital Publishing Institute (MDPI), as these databases together provide extensive coverage of environmental science, materials engineering, and water treatment research. The search strategy employed predefined search strings comprising keywords such as “PFAS”, “perfluoroalkyl”, “polyfluoroalkyl”, “PFOA”, “PFOS”, “adsorption”, “adsorbent”, “regeneration”, “desorption”, “reuse”, “spent adsorbent”, with Boolean operators (AND, OR) applied to refine and target results. An iterative search strategy was adopted to capture emerging terminology and ensure that relevant studies were not excluded due to narrow keyword definitions. The temporal boundary of 2000–2025 was selected to capture developments from early PFAS treatment studies to the most recent innovations in adsorbent regeneration.

Inclusion was restricted to peer-reviewed journal articles in English that provided experimental data on regeneration or disposal of PFAS adsorbents. Grey literature (theses, reports, conference proceedings) was excluded to maintain the quality and comparability of data, given the potential for such sources to lack peer review or full methodological disclosure. Studies without direct experimental evidence on post-adsorption management were also excluded to maintain focus on the central theme of this review. Relevant data were extracted manually and organised in Microsoft Excel to enable thematic comparison across adsorbent types, regeneration approaches, performance metrics, and environmental implications. The complete process is illustrated in the literature review flow diagram (Figure 1).

The second stage involved a targeted review of policy and regulatory frameworks, focusing primarily on the European Union. Searches were conducted in official repositories such as EUR-Lex, FAOLEX (Food, Agriculture, and Renewable Natural Resources Legislation Database), and the United Nations databases. The keyword strategy mirrored that used in the technical review but was adapted to include regulatory terminology such as “water treatment regulation”, “PFAS limit values” and “waste classification”. Boolean operators were used to refine searches to relevant legislative and policy documents. Only authoritative legislative texts, official directives, and institutional reports were included. Non-English documents were excluded due to the potential for misinterpretation during translation and to maintain consistency in legal terminology.

3. Policy and Regulatory Context

The European Union has established one of the most comprehensive and stringent regulatory frameworks globally for the management of PFASs, reflecting growing scientific evidence of their persistence, mobility, and potential toxicity. Over the past two decades, EU policy has evolved from regulating individual PFAS compounds, such as PFOS and PFOA, to adopting measures aimed at restricting the entire class of PFASs. This progression is closely aligned with increasing monitoring data that reveal widespread PFAS contamination in surface water, groundwater, and, in some cases, treated drinking water across Europe.

Table 2. Summary of key EU legislative instruments regulating PFASs in the environment.

Regulation	Summary of Key PFAS-Related Aspects	Practical Implications
Drinking Water Directive (2020/2184) [38]	▪ Sets 0.1 µg/L limit for any single PFAS and 0.5 µg/L total PFASs in drinking water. ▪ Effective January 2026. ▪ Requires regular monitoring of PFASs in water supplies.	Adsorbent systems must achieve very low PFAS residual concentrations; regeneration or disposal methods must ensure compliance with strict limits.
Water Framework Directive (2000/60/EC) [40]	▪ Establishes framework for protecting and improving water quality. ▪ PFOS listed as a priority hazardous substance. ▪ Requires achieving good chemical status in water bodies.	Indirectly drives reduction in PFASs in aquatic environments; promotes safe disposal to prevent leaching.
Environmental Quality Standards Directive (2008/105/EC) [47]	▪ Establishes EQSs for PFOS: 0.00065 µg/L (inland waters) and 0.00013 µg/L (other surface waters). ▪ Targets control of PFAS discharges.	Encourages end-of-life management methods that prevent PFAS release to meet EQS values.
REACH Regulation (1907/2006) [39]	▪ Lists of several PFASs as SVHCs. ▪ Restricts manufacture, use, and marketing. ▪ Ongoing proposal to restrict all PFASs in EU.	May restrict use of certain adsorbents if they contain or degrade to PFASs; impacts choice of regeneration chemicals.
ECHA SVHCs Candidate List [12]	▪ Includes PFOS, PFOA, long-chain PFCAs, and other PFASs as SVHCs. ▪ Forms the basis for future restrictions. ▪ Recognises persistence, bioaccumulation, and toxicity.	Identifies high-risk PFASs to be prioritised in treatment and end-of-life strategies.
POPs Regulation (2019/1021) [48]	▪ Lists PFOS and PFOA as POPs. ▪ Bans production and use with limited exceptions. ▪ Applies to products, waste, and emissions.	Disposal and destruction strategies must eliminate PFASs to meet POPs requirements; limits landfill disposal options.

summarises the most relevant EU-level policies, directives, and regulations governing PFASs in the environment, with emphasis on provisions relevant to water quality and the management of PFAS adsorbents and highlights, practical implications for adsorbent regeneration strategies.

A central pillar of the EU’s regulatory approach is the Drinking Water Directive [38], which will apply fully from January 2026. For the first time, this legislation sets binding parametric values for PFASs in drinking water, requiring compliance with a 0.1 µg/L limit for any single PFAS and a 0.5 µg/L limit for the sum of all PFASs. These ambitious thresholds are expected to necessitate advanced water treatment technologies, most prominently adsorption-based systems, and impose strict demands on the management of PFAS adsorbents to prevent recontamination. In parallel, the REACH Regulation [39] provides the legal basis for controlling the manufacture, use, and placing on the market of chemicals, including PFASs. Several PFASs are listed on the Candidate List of Substances of Very High Concern (SVHCs) [12], and in 2023 a joint proposal by five EU Member States was submitted to the ECHA to restrict the manufacture, use, and placing on the market of over 10,000 PFASs. If adopted, this would represent one of the most sweeping chemical bans in EU history, with significant implications for industries reliant on PFAS-containing products or processes.

The Water Framework Directive [40] and its daughter legislation, the Environmental Quality Standards Directive [47], complement these measures by setting Environmental Quality Standards (EQSs) for PFOS in surface waters (0.00065 µg/L annual average in inland waters; 0.00013 µg/L in other surface waters). Although these limits focus on environmental concentrations rather than product regulation, they indirectly mandate safe handling and disposal of PFAS-containing wastes to avoid breaches. Additional controls are provided under the Persistent Organic Pollutants Regulation (POPs) [48], which prohibits the production and use of PFOS and PFOA, with limited exemptions, and applies to products, waste streams, and emissions. Together, these instruments create a multi-layered regulatory environment in which PFAS contamination is addressed from source control to environmental remediation.

4. Regeneration and Management of PFAS-Saturated Adsorbents

The regeneration and management of PFAS-saturated adsorbents are pivotal for advancing sustainable water treatment technologies. Although the studies reviewed here vary widely in experimental designs, operational conditions and reporting practices, they converge on one critical point: regeneration can extend the lifespan of adsorption media, reduce operational costs, and lower the environmental burden associated with solid waste disposal and the production of virgin materials [49,50]. The effectiveness of regeneration is strongly influenced by the chemical structure and adsorption mechanism of each material. In this review, adsorbents are categorised into four major groups—carbon-based, polymeric, mineral-based and emerging/hybrid—and each group’s representative materials, functional groups and adsorption mechanisms are described alongside their regeneration performance. Detailed operational parameters and specific experimental conditions are not reproduced here in full; readers are strongly encouraged to consult the original publications for complete methodological information.

Table 3. Characteristics of selected adsorbents.

Category	Adsorbent	Chemical Structure	Functional Groups	Main Adsorption Mechanisms	Adsorption Efficiency
Carbon-based	Biochar loaded with sulfobetaine–acrylamide copolymer [51]	Wood-derived biochar (BET 22.8 m2/g) coated with SBMA–acrylamide copolymer (BET 167.3 m2/g).	Quaternary ammonium groups (SBMA), –SO3− groups, amide (–CONH2) groups from polyacrylamide, N- and S-containing groups on biochar surface.	Combined hydrophobic interaction (fluorocarbon chain–polymer), electrostatic attraction of anionic PFASs to cationic groups, pore diffusion and complexation.	~265–635 mg/g
	Bituminous granular activated carbon (Filtrasorb 400, F400) [52]	Microporous bituminous coal-based GAC commonly used in water treatment plants; BET area ~1000 m2/g.	Surface oxygen-containing groups; high microporosity; PFASs trapped in pores with 65–70% moisture content.	Primarily hydrophobic adsorption of long-chain PFASs; electrostatic interactions for short-chain PFASs; pore-filling and aggregation inside micropores.	~0.2 mg/g
	Bamboo-derived mesoporous biochar [53]	Highly porous carbon with micropores (0.6–1.3 nm) and mesopores (2–4 nm); SBET 1085 m2/g, pore volume 0.670 cm3/g, O/C 0.09, H/C 0.27.	Predominantly aromatic carbon with reduced oxygen-containing groups (C–O, C=O); some oxygen groups reintroduced during steam activation; very low surface polarity; near-neutral zeta potential at pH 7.5.	Hydrophobic interactions (favouring long-chain PFASs), electrostatic attraction for anionic PFASs, pore-filling (pores ~1–3× PFOS size), enrichment at air bubbles on the surface.	~640 mg/g
Polymeric	Carbon-dot-modified polyacrylonitrile fibre (PAN-g-CD) [54]	Polyacrylonitrile fibre grafted with amine-functionalised carbon dots (CDs)—fibrous, low surface area (15–16 m2 g−1), average pore radius ~1.6 nm.	Zwitterionic with amine groups (pH-responsive), carboxylate groups, anchored carbon dots providing hydrophobic domains.	Combined electrostatic attraction/repulsion depending on PFOS derivative head group; hydrophobic interactions between CDs and fluorocarbon chains; chemisorption on energetically heterogeneous surface.	~640–1055 mg/g
	Anion exchange resin (AER) [29]	Strong-base anion exchange resin with quaternary ammonium functional groups on a cross-linked polystyrene matrix (gel-type).	Quaternary ammonium groups (Cl− form initially); hydrophobic polymer backbone.	Ion exchange (replacement of Cl− with PFAS anions), hydrophobic interactions, semi-micellar adsorption in presence of long-chain PFASs, enhanced by pre-treatment to remove competing anions.	~775 mg/g
Mineral-based	Calcined beta zeolite (BEA) [55]	Ion exchange (replacement of Cl− with PFAS anions), hydrophobic interactions, semi-micellar adsorption in presence of long-chain PFASs, enhanced by pre-treatment to remove competing anions.	Bronsted-acid sites (Si–O(H)–Al) and Lewis-acid sites inside micropores; hydrophilic external surface, internal hydrophobic channels; converted to hydrogen form after calcination at 550 °C.	Size-selective molecular sieving; electrostatic interactions with cations; hydrophobic adsorption inside pores; minimal effect of pH 6–9 and natural organic matter at high loading.	~100 mg/g
	Magnetic surfactant-modified clay (MMC) [56]	Montmorillonite (2:1 layered aluminosilicate) intercalated with CTAC, then co-precipitated with Fe2+/Fe3+ to form magnetite nanoparticles; particle size ~3.6 µm; BET surface area 48 m2/g.	Quaternary ammonium groups from CTAC impart positive charge; Fe–O groups from magnetite; Si–O framework from clay.	Electrostatic attraction of anionic PFASs to positively charged CTAC-modified clay; hydrophobic interactions between PFAS fluorocarbon chains and CTAC tails; ion exchange and complexation with Fe3+ sites.	~35 mg/g
	Zn–Al LDH (nitrate intercalated) [57]	Layered double hydroxides with brucite-like positively charged layers and exchangeable nitrate anions; Zn/Al ratio 3:1 and Mg/Al ratio 3:1.	Abundant hydroxyl groups within LDH layers; interlayer nitrate ions; high positive surface charge (pHpzc ~10 for Zn–Al).	Mainly electrostatic interactions between positively charged layers and anionic PFASs; fast uptake (Zn–Al LDH removes ~95% PFOA in 1 h); enhanced affinity with longer chain PFASs.	~625 mg/g
Emerging/hybrid	β-Cyclodextrin polymer coated on silica [58]	Silica particles (40 × 100 mesh) coated with β-cyclodextrin crosslinked by hexamethylene diisocyanate (HMDI) in DMSO; ~32% w/w polymer loading; core–shell morphology.	β-CD with abundant hydroxyl groups; carbamate linkages from HMDI; silanol groups from silica.	Inclusion complexation (β-CD cavity trapping PFOA), hydrophobic interactions and hydrogen bonding between PFASs and β-CD hydroxyl rims; host–guest complexation stabilised by hydrogen bonding.	~0.3 mg/g
	POP-4F (fluorine and amine porous organic polymer) [59]	Mainly electrostatic interactions between positively charged layers and anionic PFASs; fast uptake (Zn–Al LDH removes ~95% PFOA in 1 h); enhanced affinity with longer-chain PFASs.	Triazine nitrogen, secondary amines (protonated at pH < 6), fluorine atoms providing hydrophobic domains.	Strong electrostatic attraction between protonated amines and deprotonated PFOA carboxylate; hydrophobic interactions from fluorinated framework; rapid uptake due to high surface area.	~100 mg/g
	AMSN (mesoporous silica nanoparticles APTES only) [60]	Dendritic mesoporous silica nanoparticles (average 177 nm) with ~14.4 nm pores; functionalised solely with APTES.	Protonated amine groups (–NH3+ at pH < 9) on silica surface; silanol groups partly capped.	Predominantly electrostatic attraction to anionic PFASs; limited hydrophobic interaction compared to OAMSN; slower kinetics.	~80 mg/g

summarises the representative adsorbents, their functional groups, and reported adsorption efficiencies to provide a comparative overview.

Carbon-based adsorbents are the most widely used class of PFAS sorbents. These materials, including granular activated carbon, biochars and engineered mesoporous carbons, are characterised by a graphitic backbone interspersed with micro- and mesoporous domains [51,52,53,61,62,63,64,65]. Their surfaces possess oxygenated functional groups such as hydroxyl, carboxyl and carbonyl moieties, which can be further modified with cationic polymers, iron oxides or nitrogen functionalities to improve interaction with anionic PFASs [63,65,66,67,68,69,70]. The combination of extended porosity and large surface chemistry enables strong hydrophobic partitioning of fluorocarbon tails into carbon pores and electrostatic attraction between PFAS head groups and positively charged or neutral sites [62,64,66,71,72,73]. Such mechanisms give rise to a wide range of adsorption capacities, from sub-mg/g loadings [52,74] to hundreds of mg/g [51,53,67]. However, it should be noted that, due to inconsistent reporting and different experimental conditions, comparing the adsorption effectiveness of various adsorbents may be hindered and carry errors. The high thermal stability of carbonaceous materials makes them particularly compatible with high-temperature regeneration, typically at 500–850 °C in steam, inert or oxidative atmospheres, where PFAS desorption from the carbon matrix is often effective and, in some cases, surface chemistry is renewed through mild activation that can increase adsorption capacity in subsequent cycles [51,63,72,73,75,76,77,78,79]. Nonetheless, repeated exposure to high temperatures may gradually induce micropore collapse, surface oxidation or partial gasification, diminishing adsorption performance over time, and at higher temperature the carbon itself may begin to decompose, limiting practical upper temperature thresholds [23,78,80,81]. Lower-temperature regeneration can be achieved using polar organic solvents such as methanol or ethanol, or alkaline solutions (e.g., methanol–NaCl or methanol–NaOH), which disrupt hydrophobic and electrostatic interactions and can desorb a substantial fraction of PFASs, especially short-chain species [61,82]. However, solvent regeneration of carbonaceous materials is frequently less effective for long-chain PFASs strongly bound within micropores, and these approaches generate PFAS-laden liquid waste streams requiring downstream treatment or recovery processes to ensure environmental compliance [71,83,84,85]. To overcome the limitations of single approaches, hybrid strategies such as microwave-assisted heating, electro-assisted desorption and solvent washing combined with mild oxidative polishing have been developed and show promise for partially restoring capacity without severe structural damage [52,86,87]. These techniques operate at lower temperatures than conventional thermal regeneration but may achieve higher desorption than solvents alone, and although still at an early stage of development they may allow regeneration of carbon-based adsorbents while reducing energy use and extending their operational lifetime [88,89]. Overall, carbon-based PFAS adsorbents exhibit a unique combination of high adsorption capacity and robust regeneration potential, but the trade-offs between thermal efficiency, solvent waste management and structural stability highlight the need for integrated assessment of regeneration strategies before full-scale implementation.

Polymeric adsorbents constitute another important category of PFAS sorbents. These materials, including anion-exchange resins, functionalised polymeric fibres and molecularly imprinted polymers, consist of cross-linked organic backbones bearing quaternary ammonium, amine, zwitterionic or cyclodextrin groups [29,54,90,91,92,93,94,95,96,97]. This architecture allows simultaneous ion exchange between anionic PFAS head groups and positively charged sites, hydrophobic partitioning of fluorocarbon chains into the polymer matrix, and in some cases host–guest inclusion or molecular imprinting for selective binding [29,30,54,71,98]. Such synergistic mechanisms enable high adsorption capacities, ranging from around 100 mg/g [93,99] to above 1000 mg/g for carbon-dot modified PAN fibres [54]. These materials are highly compatible with solvent and mild chemical regeneration, which can efficiently desorb PFASs without damaging the matrix. Typical methods include methanol, ethanol, and mixed solvent systems such as methanol plus NaCl or alkaline brines, often achieving more than 90% desorption over several cycles [29,100,101,102,103]. Multi-cycle studies demonstrate that such mild solvent systems combined with moderate ionic strength offer the most viable pathways for long-term use [29,104]. In contrast, polymeric matrices are inherently susceptible to degradation under high-temperature or oxidative conditions, and thermal regeneration is rarely applied because it can cause irreversible changes in resin structure and loss of functional groups [98,105]. Some emerging oxidative hybrid methods can partially regenerate polymeric sorbents by coupling solvent washing with mild oxidants, but these approaches risk damaging the polymer backbone or functional sites over repeated cycles and remain at an experimental stage [106,107]. Overall, polymeric PFAS adsorbents exhibit a favourable balance of high capacity, tuneable chemistry and gentle regeneration potential, but their heat and oxidant sensitivity necessitate careful choice of regenerant conditions to preserve long-term performance.

Mineral-based adsorbents, including zeolites, clays, layered double hydroxides and graphite-based materials, offer rigid crystalline or layered frameworks with abundant exchangeable cations and hydroxyl groups [27,55,56,57,108,109,110,111,112,113]. They adsorb PFASs through a combination of electrostatic attraction to positively charged framework layers or surfactant modifiers, size-selective molecular sieving in microporous channels and hydrophobic interactions within modified interlayers [27,55,56,57,108,109,110,111,112,113,114]. The adsorption capacities vary substantially among different minerals and functionalisation methods, ranging from only a few milligrams per gram to as high as 250 mg/g [28,109,115]. Because of their structural diversity, mineral-based adsorbents display mixed regeneration outcomes. Mild solvent or ammonium solutions can desorb PFASs and restore surface activity, but repeated cycles may leach framework cations or gradually reduce crystallinity [56,110,111,114]. Thermal regeneration at moderate temperatures has shown partial success for some zeolites (e.g., Ag-modified forms) but often risks phase changes and micropore collapse when the upper temperature limits are approached [27,55,60]. Some emerging or hybrid strategies using tailored chemistries, such as mild oxidants combined with surfactant exchange or low-temperature catalytic treatments, have been proposed to improve regeneration, but these approaches remain at an early stage and stability issues persist [116,117]. Taken together, the evidence shows that although mineral-based adsorbents provide a robust and versatile platform for PFAS capture, their regeneration is highly dependent on both the structural integrity of the mineral framework and the nature of the modifying agents, necessitating careful optimisation of regeneration conditions to balance performance recovery against long-term stability.

Emerging and hybrid adsorbents represent a rapidly developing class of PFAS sorbents that combine inorganic supports with organic functional layers or entirely new porous frameworks. Examples include functionalised metal–organic frameworks, β-cyclodextrin polymers coated on silica, nanotubes, hydrogels and aerogels, polyacrylonitrile-based functional fibres and photocatalyst–adsorbent composites [118,119,120,121,122,123,124]. These materials exploit multiple adsorption mechanisms simultaneously, including dual-mode binding by electrostatic and hydrophobic interactions, host–guest inclusion via cyclodextrin cavities and shape-selective molecular imprinting [58,59,60,118,119,120,121,122,123,124]. This synergy produces high adsorption capacities, typically in the range of about 100 mg/g to over 1100 mg/g [59,125,126,127], although lower efficiencies have also been reported for some materials [58]. Available data on regeneration indicate that many of these materials are compatible with organic solvent or mild alkaline washing, which effectively desorbs PFASs from amine or quaternary ammonium groups while operating under conditions that minimise structural damage [32,121,124,128,129]. In addition, several studies have demonstrated the feasibility of combining regeneration with oxidative polishing, for instance through UV-assisted persulfate or catalytic oxidation, to reduce PFAS concentrations in regenerant streams [118,120,127,130]. While limited data exist for thermal regeneration, some high-stability frameworks may tolerate moderate heat, although no large-scale or long-term evaluations have yet been reported. In most laboratory-scale tests, emerging and hybrid adsorbents maintained adsorption and desorption performance over multiple cycles with minimal loss, suggesting good intrinsic durability under mild conditions [123,128,129,131]. Nevertheless, long-term stability, large-scale implementation and cost-effectiveness remain largely untested, and their relatively high production costs make efficient regeneration essential to overall feasibility [121,122,123]. Collectively, these findings point to the potential of emerging and hybrid adsorbents as next-generation PFAS treatment materials, while also underscoring the need for systematic pilot-scale and life-cycle assessments to confirm their performance under operational conditions.

The reviewed literature reveals five principal regeneration categories: thermal regeneration, solvent-based regeneration, chemical regeneration, hybrid approaches, and emerging methods (Table 4). Thermal regeneration remains the most established and widely studied approach for restoring PFAS adsorbents, particularly carbon-based materials such as granular activated carbon, biochar, and carbon nanotubes. In this method, elevated temperatures in the range of 400–900 °C promote desorption of PFASs from the adsorbent surface, while temperatures above approximately 1000 °C usually initiate partial to complete thermal decomposition of the adsorbent itself [23,25,27,28,31,52,53,55,60,61,77,78,79,80,81,105,116,132,133,134,135]. Several studies analysing carbonaceous materials demonstrated that reactivation at 500–800 °C under inert or oxidative atmospheres restored between 75% and 99% of the initial adsorption capacity after a single cycle, with occasional reports of efficiencies increasing in the subsequent cycles due to in situ activation effects that increase surface area or modify surface chemistry [52,61,79]. In biochar systems, retention rates above 80% were often maintained for up to five cycles, whereas some granular activated carbons showed declines, primarily due to irreversible micropore collapse, partial gasification, and surface oxidation [25,53,78,79,80]. Catalytically assisted thermal treatments, such as using metal-doped carbons, have also been reported to lower the decomposition temperature threshold for PFASs, improving energy efficiency while achieving high regeneration yields [79,132]. Thermal regeneration performance varies with adsorbent type and operating conditions. While carbonaceous materials generally withstand repeated high-temperature treatments with minimal structural damage, mineral and composite adsorbents often suffer more extensive heat-induced degradation, resulting in pore loss, brittleness, or decomposition of functional coatings [27,61,80,133]. Certain mineral adsorbents, such as Ag-exchanged zeolites, retained high PFAS removal capacity after regeneration at 500–700 °C, though crystallinity loss was observed at the upper end of this range [27]. From an operational standpoint, the high energy demand of thermal systems remains a major limitation, particularly for large-scale applications. Nonetheless, their unique capacity to both regenerate adsorbents and, under sufficiently high temperatures, approach full PFAS destruction makes them an attractive option where infrastructure and energy resources permit [23,52,53,55,60,61,77,79,80,133,134]. Hybrid approaches, combining moderate-temperature thermal reactivation with subsequent chemical polishing, have been suggested to reduce energy costs while achieving regulatory compliance in demanding contexts [61,105,116]. Overall, thermal regeneration occupies a middle ground in the trade-off between regeneration efficiency, cycle stability, and environmental risk, making it particularly suited to durable carbon-based adsorbents but less so for heat-sensitive materials.

Organic solvent-based regeneration employs polar organic solvents, most commonly methanol, ethanol, acetone, or tailored solvent mixtures, often supplemented with salts (e.g., NaCl) or bases (e.g., NaOH) to enhance desorption efficiency. The underlying mechanism is the disruption of hydrophobic and electrostatic interactions between PFAS molecules and the adsorbent surface, making it especially effective for both long- and short-chain PFASs that are strongly bound to functionalised surfaces. Across the reviewed studies, methanol was by far the most frequently used solvent, followed by ethanol, with occasional use of binary systems such as methanol–NaCl or methanol–NaOH to improve ion exchange and reduce solvent polarity for stronger PFAS displacement [32,59,69,70,76,84,94,100,101,115,119,121,136,137,138,139,140,141,142,143,144]. Performance data consistently place solvent-based regeneration among the top-performing strategies in terms of short-term recovery, with first-cycle restoration rates commonly exceeding 90% of the initial adsorption capacity. For example, polymeric anion-exchange resins regenerated with methanol–NaCl solutions maintained over 80% removal efficiency for up to five consecutive cycles [104,108,117,145,146,147,148], while fluorous-functionalised polyacrylonitrile (PAN) fibres and carbon-dot hydrogels retained 85–95% of their initial capacity over similar regeneration periods [123,128]. Even bio-based adsorbents, such as lignin-derived amine-functionalised carbon, showed high stability in solvent washing tests, preserving >94% retention after five cycles [131]. This method’s strong performance was particularly evident for polymeric materials and carbon-based adsorbents targeting short-chain PFASs such as PFBA (perfluorobutanoic acid), PFBS (perfluorobutane sulfonate), and PFHxA (perfluorohexanoic acid), where hydrophobic and electrostatic interactions can be effectively disrupted by polar solvents [30,64,66,71,91,114,129,149,150,151]. Solvent systems were generally applied at ambient temperatures with moderate contact times (e.g., 30–60 min), which helps reduce energy costs and preserves the physical integrity of heat-sensitive adsorbents. Morphological analyses across multiple studies reported negligible changes in pore structure or surface area after repeated solvent treatments, further supporting their suitability for delicate or composite materials [29,58,71,117,128,145,152,153]. However, performance stability can be compromised over more extended reuse, where gradual fouling of micropores and incomplete desorption of tightly bound PFASs begins to accumulate [131,147,154,155]. From a sustainability perspective, solvent-based regeneration faces one major drawback: the generation of PFAS solvent waste streams [65,96,103,125,156,157,158,159]. These require further treatment, typically via high-temperature incineration or advanced oxidation processes, to ensure safe disposal and regulatory compliance. In large-scale operations, solvent recovery systems (e.g., distillation) have been proposed to reduce waste volumes and operating costs, but more studies are needed to analyse full life-cycle assessments to evaluate their environmental benefits versus impacts [30,63,160]. Overall, solvent-based regeneration offers a highly effective, relatively low-energy, and material-friendly route for the short-term reuse of PFAS adsorbents, particularly in applications where high initial recovery is prioritised over long-term cycle stability. Its main trade-off lies in balancing the operational simplicity and strong regeneration performance against the environmental and logistical challenges of managing PFAS-contaminated solvent wastes.

Chemical regeneration employs alkaline, acidic, or oxidative reagents to reverse adsorption mechanisms, typically by breaking ionic bonds and disrupting hydrophobic interactions that retain PFASs on the adsorbent surface. Strong bases such as NaOH, KOH, or ammonia solutions are particularly effective for polymeric anion-exchange resins, where base-driven ion exchange can displace strongly bound long-chain PFASs such as PFOA and PFOS [30,51,71,102,104,107,146,147,149,161,162,163,164,165,166,167,168,169,170]. For example, mesoporous melamine–formaldehyde resin microspheres regenerated with dilute ammonia maintained >85% of initial capacity after multiple cycles, highlighting the potential for long-term operational stability without significant structural degradation [168]. Acidic regenerants (e.g., HCl, H₂SO₄) are less common but have been applied successfully to mineral-based adsorbents, such as nano-ceramic clays, where they help dissolve surface-bound PFAS salts and restore adsorption sites [51,72,76,169]. Oxidative reagents such as Na₂S₂O₈ and O₃ have also been employed, offering the added advantage of partial PFAS degradation during desorption [134,171]. In combined approaches, chemical desorption is followed by in-solution oxidation (e.g., UV/sulfite or heat-activated persulfate), reducing the PFAS load in the regenerant waste. This integrated regeneration–destruction concept has been demonstrated for both resins and carbon-based adsorbents, producing regenerant streams with significantly reduced PFAS concentrations and, in some cases, complete mineralisation of short-chain by-products [99,107]. Across the dataset, regeneration efficiencies for alkaline and oxidative systems typically ranged between 70% and 95% in the first few cycles, with many materials sustaining >80% capacity retention for multiple cycles [168]. This places chemical regeneration among the most stable methods in terms of long-term reuse potential. The energy requirements are considerably lower than those of thermal regeneration, and chemical systems can be adapted for continuous operation in fixed-bed columns, making them attractive for utilities seeking to minimise downtime [116,168]. However, aggressive reagents, especially concentrated alkalis and oxidants, can induce irreversible changes to adsorbent morphology and chemistry [135,166]. Additionally, chemical regeneration invariably produces liquid waste streams containing PFASs and, in the case of oxidative systems, partially degraded intermediates or fluoride ions. These require secondary treatment before disposal, adding operational complexity and cost [70,88,104,108,121,146,148,167,172,173,174,175]. Overall, chemical regeneration presents a balanced performance profile, combining high short-term recovery rates with strong multi-cycle stability and relatively low energy costs. Its versatility across different adsorbent classes, particularly anion-exchange resins and certain mineral-based materials, makes it a strong candidate for long-term PFAS treatment systems. However, sustainable implementation will require careful selection of regenerants, optimised reagent dosing, and integration with effective waste management solutions to prevent secondary contamination.

Emerging regeneration methods, such as electrochemical processes, are attracting increasing research attention as potential alternatives to traditional thermal, solvent, and chemical techniques. These methods share the common feature of relying on electrochemical mechanisms, often enabling simultaneous PFAS desorption and partial degradation, which can substantially reduce the burden of secondary waste treatment [74,75,87,176,177]. Electrochemical regeneration is the most extensively studied among novel approaches, typically employing boron-doped diamond anodes or graphite intercalated compounds to generate strong oxidising species (e.g., hydroxyl radicals, persulfate) capable of breaking the carbon–fluorine bonds in PFASs during regeneration. For instance, electrochemical oxidation of PFOS, PFOA, and PFBS using graphite intercalated compounds achieved >95% removal of target compounds in initial cycles, with adsorption capacities of 53.9 μg/g for PFOS and 22.3 μg/g for PFOA maintained over up to five cycles [74]. Similarly, in situ electro-regeneration of PFOA spent granular activated carbon sustained ~80% of initial capacity after three cycles while producing primarily fluoride ions and short-chain PFASs as by-products, which could be further treated [75]. A separate approach using alternating electric fields on inexpensive graphite adsorbents demonstrated reversible PFAS adsorption–desorption over multiple cycles without significant loss of capacity [87]. Emerging regeneration methods demonstrate moderate-to-high regeneration efficiencies and offer the added advantage of reducing PFAS concentrations in the regenerant stream. Nonetheless, they remain in early developmental stages, with critical uncertainties surrounding their scalability, operational costs, long-term adsorbent stability, and integration into existing treatment infrastructure. Although electrochemical approaches reduce the need for chemical regenerants or high-temperature treatment, their net environmental benefits depend strongly on the carbon intensity of the electricity used. If the electricity is produced from fossil fuels, the associated CO₂ emissions may partially offset the gains achieved through reduced chemical inputs and secondary waste generation. Future studies should therefore incorporate life cycle and techno-economic assessments that include indirect greenhouse gas emissions and explore the use of renewable or low-carbon power sources to confirm the climate advantages of electrochemical regeneration [178,179]. While these technologies may become valuable components of future PFAS management strategies, further pilot-scale studies and life-cycle assessments are essential to establish their technical and economic feasibility.

Table 4. Regeneration and management methods for PFAS-saturated adsorbents.

Method	Main Advantages	Key Drawbacks
Thermal treatment [23,25,28,52,55,60,61,132]	▪ High PFAS desorption and potential destruction (≥90% for long-chain PFASs) ▪ Applicable to carbonaceous and mineral adsorbents due to high thermal stability ▪ Established, scalable technology	▪ Very high energy demand (≥500–600 °C) ▪ Risk of pore collapse, oxidation, or crystallinity loss in adsorbents ▪ Emissions of CO2 and fluorinated gases unless controlled ▪ Costly and environmentally intensive
Organic solvent-based regeneration [69,76,84,115,119,121,142]	▪ Effective desorption (>90% for PFOA/PFOS) ▪ Maintains adsorption capacity over several cycles ▪ Operates under mild conditions ▪ Compatible with polymers, carbonaceous materials, fibres, hydrogels	▪ Produces PFAS-containing solvent waste requiring downstream treatment ▪ Solvent recovery or safe disposal needed ▪ Chemical handling issues ▪ Limited pilot/large-scale demonstrations
Chemical regeneration (salts, pH/ionic strength shifts, surfactants) [30,104,107,146,147,164]	▪ Inexpensive and widely available reagents ▪ Can selectively target PFAS–adsorbent interactions ▪ Reported recoveries of 60–90% for anion exchange resins and clays	▪ Generates brine or surfactant-rich waste streams ▪ Incomplete desorption of strongly bound PFASs (esp. short-chain) ▪ Requires additional treatment of secondary waste
Emerging and hybrid methods [74,75,87,176,177,180]	▪ Potential to couple desorption within situ PFAS degradation ▪ May reduce secondary liquid waste ▪ Growing interest at pilot scale	▪ High electricity demand ▪ Electrode fouling and material stability challenges ▪ Limited evidence for scale-up and long-term use

Table 4. Regeneration and management methods for PFAS-saturated adsorbents.

Method	Main Advantages	Key Drawbacks
Thermal treatment [23,25,28,52,55,60,61,132]	▪ High PFAS desorption and potential destruction (≥90% for long-chain PFASs) ▪ Applicable to carbonaceous and mineral adsorbents due to high thermal stability ▪ Established, scalable technology	▪ Very high energy demand (≥500–600 °C) ▪ Risk of pore collapse, oxidation, or crystallinity loss in adsorbents ▪ Emissions of CO2 and fluorinated gases unless controlled ▪ Costly and environmentally intensive
Organic solvent-based regeneration [69,76,84,115,119,121,142]	▪ Effective desorption (>90% for PFOA/PFOS) ▪ Maintains adsorption capacity over several cycles ▪ Operates under mild conditions ▪ Compatible with polymers, carbonaceous materials, fibres, hydrogels	▪ Produces PFAS-containing solvent waste requiring downstream treatment ▪ Solvent recovery or safe disposal needed ▪ Chemical handling issues ▪ Limited pilot/large-scale demonstrations
Chemical regeneration (salts, pH/ionic strength shifts, surfactants) [30,104,107,146,147,164]	▪ Inexpensive and widely available reagents ▪ Can selectively target PFAS–adsorbent interactions ▪ Reported recoveries of 60–90% for anion exchange resins and clays	▪ Generates brine or surfactant-rich waste streams ▪ Incomplete desorption of strongly bound PFASs (esp. short-chain) ▪ Requires additional treatment of secondary waste
Emerging and hybrid methods [74,75,87,176,177,180]	▪ Potential to couple desorption within situ PFAS degradation ▪ May reduce secondary liquid waste ▪ Growing interest at pilot scale	▪ High electricity demand ▪ Electrode fouling and material stability challenges ▪ Limited evidence for scale-up and long-term use

The regeneration efficiency of adsorbents is strongly modulated by the physiochemical profile of the target PFAS, especially chain length and functional group [25,53,61,128,133]. Long-chain perfluoroalkyl acids (≥C8) such as PFOS and PFOA typically show stronger hydrophobic and electrostatic binding to adsorbent surfaces than short-chain analogues [25,53,61,128,133,152]. This translates into lower desorption efficiencies under mild conditions and a greater need for aggressive or combined regeneration treatments [82,128,133]. In contrast, short-chain PFASs (e.g., PFBA, PFBS, PFHxA), owing to their higher solubility and weaker adsorption affinity, are more readily desorbed by polar solvents or dilute alkaline solutions [25,61,128,133]. The clearest PFAS-type effect is observed in solvent-based and alkaline regeneration of polymeric and carbonaceous adsorbents [128,133]. Methanol, ethanol and methanol–NaCl or methanol–NaOH mixtures consistently achieved >90% desorption of short-chain PFASs over multiple cycles, whereas efficiencies for PFOA and PFOS dropped to 60–80% under the same conditions [61,128,133]. Adding salts or bases improved the desorption of long-chain PFASs by promoting ion exchange and disrupting hydrophobic packing but rarely matched the near-quantitative recovery seen for short-chain species [61]. Alkaline regenerants such as NaOH and ammonia showed similar trends: high recovery for short-chain PFASs on anion-exchange resins and mesoporous polymers (>85% retention after 4–5 cycles) but persistent residuals of PFOA/PFOS even after extended contact times [61,128,133]. Temperature plays a decisive role for long-chain PFASs. Desorption of PFBA or PFBS was frequently observed at 400–500 °C on carbonaceous adsorbents [25,53], whereas PFOS and PFOA typically required 600–800 °C to achieve comparable removal [82]. Several studies reported partial decomposition of long-chain PFASs at ≥700 °C with simultaneous recovery of adsorption capacity, suggesting that thermal pathways may offer combined regeneration and destruction for the more recalcitrant species [61,82]. However, the higher temperatures needed for PFOS/PFOA also increased the risk of pore collapse or crystallinity loss in heat-sensitive materials such as zeolites or composites [61]. Hybrid regeneration strategies (moderate-temperature heating plus chemical polishing, or solvent washing followed by oxidative treatment) consistently improved removal of long-chain PFASs compared with single methods alone [61]. Moreover, sulfonates (PFOS, PFBS) are generally more strongly retained than carboxylates (PFOA, PFBA, PFHxA) on both carbonaceous and mineral adsorbents [25,53,61,128,133,152], which explains their more difficult desorption under identical conditions. Cationic and zwitterionic PFASs, although less extensively studied, tend to respond better to solvent-based regeneration due to weaker ionic binding at environmentally relevant pH [61].

In general, matching the regeneration method to the PFAS type and material’s stability profile is critical for maintaining both performance and economic viability. The regeneration of PFAS adsorbents offers significant potential for improving the sustainability of water treatment systems, the literature reveals persistent technical, environmental, and operational challenges that limit current implementation. These constraints are common across methods and materials, though their severity varies depending on adsorbent type, regeneration conditions, and PFAS chemistry.

Declining performance over successive cycles was one of the most consistent observations across studies. Even when first-cycle regeneration efficiencies exceeded 90%, most materials experienced cumulative losses, although these usually did not become pronounced until after multiple cycles [28,71,92,110,131,181]. This performance decay may be linked to incomplete desorption of strongly bound PFASs, particularly long-chain species such as PFOA and PFOS, which remained detectable even under aggressive solvent or alkaline treatments [95,182]. Moreover, oxidative methods could partially degrade PFASs during regeneration, but by-product formation limited their completeness and added secondary waste management challenges [74,99,106,160,171]. Secondary waste generation was a recurring environmental concern across all regeneration strategies. Solvent-based approaches consistently produced PFAS-containing liquids [68,90,97,128,140,183], while chemical regeneration generated alkaline or oxidative solutions requiring downstream treatment [102,146,161,162,163,164,170]. Thermal methods avoided liquid waste but carried risks of contaminated off-gas release, necessitating strict emission controls [23,27,55,78,79]. These findings underscore that regeneration strategies must be evaluated not only on performance metrics but also on the burden of managing secondary waste streams. Cost and energy intensity also remain critical barriers to scaling. High-temperature thermal regeneration is inherently energy-intensive, with operational costs increasing steeply at scale, whereas hybrid methods such as combined thermal–chemical approaches, while promising in laboratory studies, often require complex infrastructure and operational sophistication that may be impractical in decentralised or resource-limited settings [61,80,132,133,134].

Overall, the choice of regeneration approach is influenced by multiple factors: the physicochemical nature of the adsorbent, the target PFAS profile (chain length, functional group), site-specific operational constraints, and regulatory requirements for residual PFAS levels in treated water and secondary waste streams. While regeneration can substantially extend the service life of PFAS adsorbents, its benefits are constrained by performance decay, incomplete PFAS removal, secondary waste generation, and cost considerations. Addressing these challenges will require the development of integrated evaluation frameworks that incorporate technical performance, life cycle environmental impacts, and techno-economic analysis, coupled with the establishment of standardised testing protocols to enable meaningful cross-study comparisons.

5. Sustainability of PFAS Adsorbents

The selection of regeneration and disposal strategies for PFAS adsorbents must go beyond technical efficiency to consider economic viability and environmental sustainability. Recent advances in life cycle assessment provide valuable tools for evaluating these trade-offs, but their application to PFAS-specific treatment scenarios remains limited. Nevertheless, the emerging body of evidence highlights critical factors that influence the sustainability profile of different adsorbent systems. The summary of the existing data is presented in

Table 5. Sustainability and life-cycle assessment insights on PFAS adsorbents.

Adsorbents	Main Findings
Granular activated carbon vs. ion exchange resin [37]	▪ Both adsorbents removed 97–98% PFASs. ▪ Ion exchange resin had lower energy demand and global warming potential than granular activated carbon. ▪ Total costs were lower for ion exchange resin. ▪ Ion exchange resin assessed as more sustainable across environmental, economic, and social dimensions.
Strong-base anion exchange resin [49]	▪ Resin production was the dominant contributor to global warming potential and resource depletion. ▪ Regeneration introduced significant chemical consumption and waste burdens. ▪ Life cycle costs were largely driven by resin replacement and regeneration needs. ▪ Sustainability highly dependent on regeneration efficiency and waste handling strategies.
Reusable ion exchange resin vs. single-use resin [164]	▪ Regenerable resins reduced solid waste compared to single-use. ▪ Regeneration increased impacts from chemical use. ▪ Single-use resins generated large disposal burdens. ▪ Single-use resins more costly over long-term operation. ▪ Regenerable ion exchange resins preferable if regeneration and waste management are optimised.
Granular activated carbon, ion exchange resin, and emerging adsorbents [184]	▪ Sustainability outcomes strongly influenced by water chemistry and adsorbent use rate. ▪ High use rates increased energy demand and material consumption, especially for short-chain PFASs. ▪ Ion exchange resins generally more cost- and resource-efficient in waters with low concentrations of dissolved organic carbon. ▪ Granular activated carbon performance less predictable due to faster exhaustion. ▪ Site-specific water conditions critical for sustainability assessment.

.

Life cycle studies of anion exchange resins show that both regeneration efficiency and waste management strategies are decisive in determining overall sustainability. A detailed combined LCA and cost study demonstrated that regenerable resins could outperform single-use systems in both environmental impact and cost when brine solutions were recycled rather than disposed of directly [49]. However, inefficient regeneration or poor waste handling shifts the balance toward higher emissions and operational expenses. Economic considerations are equally central to treatment feasibility. Pilot-scale testing has shown that regenerable resins can treat groundwater at costs in the range of €0.20–0.35 per m³, provided that regeneration efficiencies remain high, whereas single-use resins may cost nearly double due to frequent replacement [164]. These findings emphasise that cost-effectiveness is closely tied to long-term reuse potential and practical waste management, particularly for concentrated brines containing high PFAS loads. Granular activated carbon, one of the most widely used adsorbents, presents a different set of trade-offs. Although granular activated carbon offers competitive treatment costs, its regeneration via high-temperature thermal reactivation (>1000 °C) contributes substantially to greenhouse gas emissions and energy demand [37]. In fact, LCA comparisons indicate that granular activated carbon typically shows higher climate impacts than regenerable resins, despite similar or slightly lower direct annual operating and maintenance costs. These results underscore the environmental penalty of thermal energy-intensive processes, which must be considered alongside adsorption performance [37]. Novel bio-based and functionalized adsorbents have been proposed as potentially more sustainable alternatives, especially due to lower energy demands during production. An evaluation of bio-derived materials concluded that they could reduce environmental footprints compared to conventional carbons, though scalability and regeneration methods remain uncertain [184]. While such materials may lower upfront environmental costs, their long-term feasibility will depend on whether efficient, low-impact regeneration pathways can be developed.

Taken together, these studies reveal a central tension between short-term adsorption efficiency, long-term reusability, and the downstream costs of managing concentrated PFAS-saturated adsorbents. Regenerable resins appear to provide the most balanced option, but only if regeneration is both efficient and coupled with sustainable brine management. Thermal regeneration of carbons remains a robust technology but is penalised environmentally by its energy intensity. Single-use systems, while simpler to operate, consistently emerge as the least sustainable option in both cost and environmental metrics. Looking forward, coupling TEA and LCA frameworks with pilot-scale data will be critical to identify not only the most effective adsorbents but also the most sustainable regeneration and disposal strategies across different treatment contexts.

6. Research Gaps and Future Directions

The European Union has set some of the most ambitious PFAS regulations globally, with legally binding concentration limits that will require transformative changes in water treatment practices. The Drinking Water Directive’s [38] upcoming 0.1 µg/L limit for any single PFAS and 0.5 µg/L total PFASs in drinking water, combined with environmental quality standards under the Water Framework Directive [40], and the outright bans under the POPs Regulation [48], create a compliance landscape where both removal performance and safe management of PFAS adsorbent residuals are equally critical. The REACH Regulation’s [39] move towards a group restriction on over 10,000 PFAS compounds further underscores the urgency of developing end-to-end solutions that can satisfy regulatory, environmental, and operational requirements simultaneously.

The regeneration and disposal methods demonstrate that achieving high PFAS removal efficiency from water is only one part of the challenge. Many regeneration processes, particularly solvent-based and certain chemical approaches, can achieve initial desorption efficiencies above 90%, but still leave 20–40% of the original PFAS load in the adsorbent, particularly for long-chain PFASs [25,83,104,156,182]. This residual loading can cause premature breakthrough in service, risking exceedances of the PFAS limits unless regeneration cycles are more effective or more frequent. Thermal destruction, while capable of >95% PFAS mineralisation under controlled laboratory conditions, raises concerns regarding the scalability and completeness of destruction under real-world conditions, particularly with respect to HF and other fluorinated by-products that require advanced flue gas cleaning to meet POPs Regulation requirements [23,52,78,133,134].

EU environmental policy implicitly demands that PFAS releases are prevented not only during water treatment but also during all handling, regeneration, and end-of-life management steps. However, there are significant gaps in environmental and occupational safety integration. Regeneration effluents with PFAS concentrations orders of magnitude above regulatory thresholds are still reported, and their treatment is often considered separately from the regeneration process itself [96,103,157,167]. Similarly, by-product formation in advanced oxidation processes, such as PFEAs (Per- and polyfluoroalkyl ether acids) or ultra-short-chain PFASs, is insufficiently monitored, despite their persistence and mobility [74,75,99,160]. Occupational exposure risk assessments remain rare, even though handling powdered or granular PFAS-saturated adsorbents poses known inhalation and dermal contact hazards. Closing these gaps will require policy guidance on emissions monitoring, effluent treatment standards, and workplace safety protocols tailored to PFAS adsorbent management.

The sustainability assessments highlight that high-performing PFAS destruction technologies are not automatically the most sustainable or cost-effective. Thermal regeneration and destruction are energy-intensive, with LCAs identifying energy use as the dominant environmental hotspot. Solvent-based and chemical regeneration processes can reduce energy demand but increase reagent production impacts and generate secondary waste streams requiring careful management. From an economic standpoint, TEA results show that operating costs can vary by an order of magnitude between methods, with decentralised, lower-energy options generally more feasible for small to medium-sized utilities. However, the absence of integrated LCA–TEA frameworks in most PFAS management studies makes it difficult to determine the overall sustainability of a given method under EU policy constraints. There is a clear opportunity for targeted funding and incentives to support low-footprint, high-compliance technologies, particularly for utilities without access to centralised high-temperature destruction facilities [37,49,164,185].

Bridging the gap between policy ambitions and technical capabilities will require a coordinated research and implementation agenda (Figure 2). The synthesis of EU regulatory frameworks and the technical evidence demonstrate that achieving compliance with upcoming PFAS limits will require not only high-efficiency removal technologies but also a paradigm shift in how PFAS adsorbents are regenerated, disposed of, and assessed for sustainability. Addressing the identified gaps offers a pathway to aligning EU policy objectives with practical, safe, and economically viable PFAS management strategies that protect both environmental and public health.

7. Conclusions

The long-term viability of adsorption-based treatment systems for PFAS-contaminated water depends not only on removal efficiency but also on how adsorbents are regenerated, managed and ultimately disposed of at the end of their service life. This review highlights that while notable progress has been made, no single regeneration method offers a universal solution. Thermal regeneration remains the most established approach, particularly for carbon-based adsorbents, but its high energy demand and potential structural damage constrain its wider application. Solvent- and chemical-based methods achieve strong recovery and, in some cases, good multi-cycle stability, yet their benefits are offset by the generation of PFAS-contaminated liquid wastes requiring downstream treatment. Emerging electrochemical and hybrid techniques show promise by combining desorption with partial in situ degradation, but their technical feasibility, durability and economic viability at scale remain uncertain. When regeneration is no longer viable, the disposal or destruction of PFAS-saturated adsorbents remains challenging. High-temperature incineration is currently the most reliable route for near-complete PFAS mineralisation but is limited by cost, energy demand and the risk of incomplete destruction. Alternative oxidative or chemical destruction approaches are under development but have yet to demonstrate large-scale performance, and immobilisation and stabilisation techniques offer only interim containment rather than permanent elimination. Across all methods, evidence from life-cycle and techno-economic assessments confirms that regeneration and disposal strategies must be evaluated in terms of energy demand, secondary waste generation, greenhouse gas emissions and overall costs. However, such integrated assessments remain rare, hindering meaningful comparisons between technologies. Wider uptake of standardised LCA and TEA approaches will be essential to align treatment systems with climate targets and regulatory requirements, particularly as EU and global rules impose progressively stricter PFAS limits. Future work should prioritise regeneration methods that minimise secondary waste and energy inputs, integrate regeneration within circular treatment frameworks and adopt harmonised testing protocols to enable robust cross-study comparison. Expanding the combined use of LCA and TEA will be crucial to guide decision-making and investment, ensuring that innovation in PFAS remediation supports both environmental and regulatory objectives. By linking technical evidence with policy perspectives, this review identifies pathways for developing regeneration and disposal technologies that are both technically robust and environmentally and economically viable. These insights can inform EU research agendas, such as Horizon Europe priorities on water quality, pollution control, and the circular economy, helping ensure that innovation in PFAS remediation supports broader environmental and regulatory objectives.