The objective of this study is to evaluate and optimize an eco-friendly bioash-ground granulated blast furnace slag (GGBFS) binder for solidification/stabilization (S/S) of contaminated sandy-silt soil by identifying formulations that provide both mechanical strength and effective multi-element immobilization across curing time and carbonation aging. The soil contained elevated trace elements (As 403 mg/kg, Pb 806 mg/kg, Zn 398 mg/kg, Cu 526 mg/kg), exceeding Swedish guideline values for sensitive land use and requiring stabilization. A design-of-experiments (DoE) approach was used to define binder formulations. Mixtures were prepared at optimum moisture content (from Proctor compaction) and evaluated using unconfined compressive strength (UCS) testing and standardized batch leaching (SS-EN 12,457-2, L/S = 10). Leachates were analyzed for pH, electrical conductivity (EC), total organic carbon (TOC), inorganic carbon (IC), and dissolved trace elements. The dataset was analyzed using principal component analysis (PCA) and response-surface mapping to identify formulation regions that balance strength and leaching performance. Formulations (bioash 10-35%; GGBFS 5-15%) were cured for 28, 56, and 115 days. Carbonation aging was conducted for three weeks in sealed containers at laboratory temperature (19-24 degrees C) under CO2 exposure. The formulation 35% bioash:15% GGBFS achieved the highest UCS (1438 +/- 111 kPa at 56 days; n = 2) and strongly reduced leaching of cationic metals. Zn and Cd were below analytical limits (Zn < 2 & micro;g/L; Cd < 0.05 & micro;g/L), and Pb decreased by 99% relative to untreated soil. Arsenic leaching decreased by up to 43% after 28 and 115 days but increased transiently (20%) at 56 days. This increase coincided with CaCO3 formation and lower-pH eluates with elevated Ca and IC, consistent with carbonation-driven changes in As retention. Compared with a cement-based binder, the bioash-GGBFS system moderated alkalinity while maintaining strength and improving Pb and As immobilization. Overall, the bioash-GGBFS system shows strong potential for sustainable remediation of metal-contaminated soils, although Cu and Ni require further optimization.

Per- and polyfluoroalkyl substances (PFASs) include thousands of fluorinated organic compounds of anthropogenic origin. Their extensive use, combined with their high stability, has led to the widespread contamination of water and soil resources. Here, single-step foam fractionation enhanced soil washing was carried out for the remediation of PFAS-contaminated soil. Concentrations of target Perfluoroalkyl Carboxylic Acids (PFCAs) and Perfluoroalkane Sulfonic Acids (PFSAs) were monitored in foam and leachate along the duration of the treatment. Among PFCAs, only long-chain compounds peaked in foam at the beginning of the treatment. This was consistent with the increase in the sorption affinity to the air-water interface with chain length. The same behavior was observed also in PFSAs by comparing PFHXs, PFHpS and PFOS. The fraction of PFCAs still in the leachate after 40 min of treatment was found to decrease with chain length, with PFSAs showing a similar trend. PFAS removal significantly increased with soil particle size, ranging from 48.2 +/- 3.2% (fraction < 0.063 & micro;m) to 64.1 +/- 1.9% (fraction > 2 mm). Final mass balance analyses detail PFAS distribution among soil, leachate, and foam, providing valuable information for the additional treatment required to destroy the PFAS load extracted from the contaminated soil.

Despite advances in reactor-based process intensification, the influence of hydrodynamic conditions on PFAS removal remains poorly understood. In particular, rotating bed reactors (RBRs), which are designed to enhance mass transfer, have not been systematically evaluated for PFAS removal or compared with conventional batch and fixed-bed column systems. This lack of comparative understanding limits the ability to assess their practical relevance for PFAS remediation. In this study, PFAS removal was investigated under intensified hydrodynamic conditions using an RBR and compared with batch and small-scale column systems with special focus on short-chain PFAS compounds. The RBR significantly enhanced adsorption kinetics, with pseudo-first-order rate constants increasing by 3 to 16-fold across PFAS, particularly for short-chain PFAS. For instance, PFBA exhibited near-complete removal within 12 h in the RBR, whereas only similar to 50% removal was achieved in batch conditions. However, faster kinetics did not translate into superior long-term breakthrough performance compared to the column treatment system. After 50 treatment cycles using ion exchange resin, PFBA reached approximately 40% C/C-0 in the RBR, while the column system maintained C/C-0 below 5%; similar trends were observed for PFPeA (15% vs. similar to 0.5%) and PFHxA (6.2% vs. similar to 0.2%). These findings reveal a fundamental trade-off between kinetic intensification and long-term treatment performance. The results highlight distinct design roles, with RBR systems enabling rapid and intensified treatment (e.g., staged or parallel configurations), while conventional column systems perform better for continuous operation and compliance control in PFAS remediation.

Conventional validation of low-carbon stabilization binders often relies on short curing periods and batch leaching tests, which do not adequately capture long-term durability or transport-controlled contaminant release. In this study, a bioash-GGBFS binder was evaluated for stabilization/solidification of metalcontaminated soil from Na & uml;sudden, Sweden, using an integrated program of extended curing, wet-dry and freeze-thaw cycling, and standardized percolation and diffusion leaching tests. The treated mixture (50% soil, 35% bioash, and 15% GGBFS) developed unconfined compressive strength in the MPa range and maintained high strength after durability exposure, with 1635 +/- 308 kPa after wet-dry cycling and 2047 +/- 100 kPa after freeze-thaw cycling. Percolation testing at L/S = 10 showed strong reductions in leaching compared with untreated soil, including 96% for As, 98% for Cd, 90% for Pb, 92% for Zn, 88% for Ni, and 65% for Cu. Diffusion testing confirmed low release for most elements, while Cu showed the highest cumulative release and mobility, indicating an element-specific limitation. Overall, the results demonstrate that the bioash-GGBFS binder can provide both durable mechanical performance and sustained immobilization of most priority contaminants under transport-relevant conditions. The findings support its potential as a low-carbon alternative for stabilization and reuse of contaminated soils, although additional measures may be needed where Cu governs compliance

Per- and polyfluoroalkyl substances (PFAS) are persistent and mobile contaminants that are increasingly detected in groundwater. Their strong resistance to degradation and continuous release from contaminated source zones necessitate effective remediation strategies. Sorptive reactive barriers represent a promising approach for PFAS retention in groundwater. However, the accumulation of PFAS within the barrier poses challenges related to sorption capacity exhaustion and long-term material management. Therefore, sustainable strategies are needed to enhance long-term PFAS remediation performance. In the present study, a reactive barrier composed of powdered peat coated with iron oxyhydroxides (Fe-P) was evaluated for PFAS retention under conditions simulating groundwater flow. Experiments were conducted using horizontal flow-through reactors operated at different seepage velocities to represent groundwater flow across varying soil structures. At the lowest seepage velocity, the Fe-P barrier effectively retained long-chain PFAS, including perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluoroheptanesulfonic acid (PFHpS), as well as perfluorohexanesulfonamide (FHxSA), achieving retention exceeding C/C0 = 0.3 at a bed volume of 280. Following PFAS loading, electrokinetic treatment was applied to assess the potential for the regeneration of the spent reactive barrier. Electro-assisted regeneration promoted the displacement of sorbed PFAS toward the anode, resulting in the relocation of approximately 80% of PFAS into the first 40% of the reactive barrier. The process required an energy consumption of about 2.1 kWh kg-1, indicating its potential for scaling up for regeneration. However, PFOS and PFHxSA exhibited limited migration under the applied electrical conditions, indicating that optimized electrokinetic parameters may be required to effectively address all PFAS classes.

Cement-free stabilization/solidification systems based on biomass ash and slag can reduce reliance on Portland cement for contaminated-soil remediation, but their high alkalinity may increase transition-metal mobility in organic-rich soils. This study evaluated a wood ash-ground granulated blast furnace slag (WA-GGBFS) binder for treating metal-contaminated sandy-silt soil from the Näsudden area in northern Sweden and tested activated carbon (AC) and zero-valent iron (ZVI) as targeted amendments to improve retention of the DOC-sensitive metals Cu and Ni. Early-age leaching was assessed using one-week conditioned loose mixtures before compaction and solidification, while UCS, hydraulic conductivity, batch leaching, and monolithic diffusion tests evaluated cured solidified specimens. The one-week results showed rapid development of strong alkaline conditions and increased dissolved organic carbon (DOC) release, indicating that Cu mobility was promoted from the early reaction stage. AC reduced the dissolved organic fraction and improved Cu and Ni retention. The WA-GGBFS matrix developed MPa-range strength, with UCS increasing from 1.44 MPa at 56 days to 1.67 MPa at 90 days, while the AC-amended mixture reached 2.10 MPa and low hydraulic conductivity. Batch leaching showed strong retention of Cd, Co, Pb, Zn, and Cr, whereas Cu and, to a lesser extent, Ni remained comparatively mobile in the unamended system because of alkaline speciation and DOC complexation. AC reduced DOC release and improved Cu and Ni retention, whereas ZVI provided no consistent additional benefit. Diffusion testing indicated mainly diffusion-controlled long-term release, with Cu and As remaining the controlling elements. Findings show that DOC control is critical when designing alkaline ash-slag stabilization systems for low-load reuse applications.

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals found worldwide in several industrial and consumer products. The extensive use of these fluorinated organic compounds, together with their high stability, has led to a broad contamination of water and soil resources. Among the technologies under development for their remediation, sonochemistry stands out. Propagation of ultrasounds in aqueous media results in sonophysical and sonochemical effects, able to collaboratively mineralize most of PFAS. Oxidative additives, as well as surfactants, may enhance the performance of the technique, which is also affected by organic matter, residual solvents, pH and temperature of the solution. PFAS concentration is a crucial factor in terms of treatment efficiency since it defines the rate order, while differences in functional group, chain length, and extent of fluorination affect hydrophobicity, surface activity and thermal activation energy of PFAS. Reaction pathways, solution chemistry, reactor configuration, and operational parameters including flowrate, atmosphere condition, US frequency and power density are discussed within this critical review, with the aim of boosting the implementation of this technology for PFAS remediation.

Risk-based land management emphasises remediation to manage risks from land contamination, aiming to reduce human and environmental risks while enabling site reuse and redevelopment. Since the mid-2000s, sustainable remediation has gained prominence, driven by global sustainability agendas such as the United Nations 2030 Agenda and the European Green Deal. These frameworks encourage integrated approaches that maximise remediation benefits and minimise negative impacts. Low-input remediation techniques (LIRT) represent a family of approaches characterised by lower energy and resource demands, often leveraging natural processes, renewable resources, or energy sources. Examples include methods using biochar, photosynthesis, or renewable energy systems. LIRT overlap with concepts like gentle remediation options (GRO) and nature-based solutions (NBS), which employ natural processes to address contamination while delivering environmental and societal benefits. While LIRT are typically effective for pathway management rather than source control, they offer sustainable outcomes such as stabilisation, containment, and destruction of biodegradable contaminants. They also contribute to broader sustainability goals, such as reducing carbon footprints and preserving soil functionality, and can support site reuse for biofeedstocks, habitats, or amenity spaces. LIRT are particularly valuable for stalled or economically unviable sites, offering cost-effective and flexible solutions. However, achieving sustainable outcomes depends on site-specific factors, and LIRT often work best when integrated into a broader remedial strategy combining intensive and low-input methods. This paper explores LIRT's potential applications, technical characteristics, and challenges, alongside their benefits for sustainable land management and the restoration of underutilised sites.

Effective removal of per- and polyfluoroalkyl substances (PFAS) form contaminated waters remains a significant treatment challenge in remediation facilities due to their structural heterogenicity, high aqueous mobility, and frequent occurrence as complex multi-component mixtures. Although granular activated carbon (GAC) and ion exchange resins (IER) are widely used for PFAS treatment, their performance is strongly influenced by water-matrix composition and competitive adsorption among PFAS, which can accelerate breakthrough and reduce adsorption capacity. Consequently, treatment performance assessments and capacity estimates may remain uncertain under multi-component conditions. Accordingly, this study evaluates how structurally diverse PFAS compete during adsorption and displacement in single- and multi-solute systems. This unified comparison clarifies how GAC and IER chemistry influence PFAS competitive behavior. Coexisting organic and inorganic constituents, dissolved organic matter (DOM) and phosphate, were incorporated to simulate realistic water matrices and to quantify their influence on PFAS competition and displacement. Results revealed that PFAS chain length and functional group chemistry governed the competitive hierarchy, with sulfonates generally exhibiting greater surface stability and removal efficiency than carboxylates. In addition, the results demonstrated distinct surface-dependent competitive behavior across the studied sorbents. GAC exhibited pronounced inhibition and displacement of PFAS in the presence of dissolved organic matter, whereas IER maintained relatively higher selectivity toward PFAS but was more susceptible to phosphate-induced displacement, highlighting the distinct matrix sensitivities of the two sorbents. These findings provide critical insight into PFAS treatment in multi-component systems and emphasize the importance of water-matrix specific design considerations to improve treatment efficiency, particularly for short-chain PFAS.

Remediation of former wood treatment sites is challenging due to the presence of contaminants with distinct physicochemical properties, such as arsenic (As) and polycyclic aromatic hydrocarbons (PAHs). This study evaluated a low-voltage electricity-induced soil remediation method designed to immobilize As while simultaneously degrading PAH in situ. A field pilot experiment was conducted at a highly contaminated site using iron (Fe) electrodes supplying pulsed direct current to promote PAH oxidation and Fe release from electrodes for As immobilization. Groundwater in five wells was monitored for concentrations of contaminants, their degradation byproducts, and microbial and fungal community structures. Over two years, dissolved PAH16 concentrations decreased by 62-94% across wells, with no accumulation of oxygenated or nitrogen-containing PAH. Dissolved As concentrations declined by up to 88% at low PAH levels, but reductions were weaker (55-57%) and more variable at very high PAH concentrations (hundreds to thousands μg L-1). Microbial communities, both prokaryotic and fungal, were characterized by taxa often found in contaminated aquifers and soils, with enrichment of PAH-degrading and As-tolerant Pseudomonas, Rugosibacter, and Duganella, but showed no adverse effect of the treatment. Overall, the method promoted concurrent PAH degradation and As immobilization with minimal secondary impacts, demonstrating potential for remediation of mixed-pollutant soils.

Swedish environmental practice exhibits a paradox where excavation and landfilling dominate per- and polyfluoroalkyl substances (PFAS) remediation despite evidence that in situ stabilisation achieves equivalent exposure risk reduction at substantially lower cost. This article examines whether legal uncertainty rather than technical or economic factors drives this pattern. Through traditional legal method, the analysis identifies structural ambiguities in the Swedish Environmental Code (SFS 1998:808) (SEC) that systematically favour technically inferior approaches. Two distinct gaps create legal uncertainty: Swedish law provides no clear criteria for distinguishing between preventive measures under Chapter 2 and remediation under Chapter 10 when stabilisation requires long-term active management. Additionally, Chapter 10 establishes no framework for determining when remediation obligations are fulfilled if contaminants remain in place under indefinite management while risks are adequately controlled. These gaps create asymmetric liability exposure where stabilisation achieves superior environmental outcomes but generates indefinite legal obligations, whereas excavation provides definitive liability termination despite relocating rather than managing contamination. The findings demonstrate that operators may rationally optimise individual liability management rather than environmental protection when legal frameworks cannot accommodate technical realities. Resolving this paradox does not require untested legal innovation. Swedish law’s nuclear waste and mining liability structures demonstrate that indefinite management can be operationalised through financial assurance and graduated responsibility. While PFAS present a distinct challenge requiring tailored statutory design, these frameworks suggest structural principles for enabling regulatory closure without assuming complete remediation.

Foam fractionation is emerging as a promising option to remove and concentrate PFAS from polluted water and soil resources. Here, we investigate the electrochemical treatment of foamate resulting from the simultaneous application of soil washing and foam fractionation for the remediation of PFAS-contaminated soil. The effect of the applied current density, flowrate, initial PFAS concentration and organic matter content was first assessed on a synthetic solution. Fractionated foam was then treated, and concentration profiles of detected C4-C8 perfluoroalkane sulfonic acids (PFSAs), the fluorotelomer sulfonate 6:2 FTS, and C4-C8 perfluoroalkyl carboxylic acids (PFCAs) were investigated. Electrochemical degradation of the fractionated foam proceeded through the generation of short chain intermediates. Most of PFOS degradation occurred within the first 10 min of treatment, with a resulting reduction of ∼68% of the initial total PFAS content. However, no further significant reduction of PFOS was observed within 5 h, concentration of C < 8 PFSAs did not decrease, while PFCAs concentration increased likely due to their generation as degradation intermediates. Electrochemical treatment of fractionated foam must be further studied to extend the degradation performance to several PFSAs, as well as to ensure complete mineralization of PFCAs within a reasonable timeframe. To this aim, matrix-specific interferences demand investigation. Furthermore, advancement in reactor configuration may guarantee enhanced performance driven by maximized PFAS contact with the electrode surface.

Improper management of wood impregnation chemicals and treated wood has led to soil contamination at many wood treatment sites, particularly with toxic substances like creosote oil and chromated copper arsenate (CCA). The simultaneous presence of these pollutants complicates the choice of soil remediation technologies, especially if they are to be applied in situ. In this laboratory study, we attempted to immobilise arsenic (As) and simultaneously degrade polycyclic aromatic hydrocarbons (PAHs) (constituents of creosote oil) by applying a modified electrochemical oxidation method. The supply of iron (Fe) amendments in contaminated soil was done using corroding Fe electrodes as an Fe source and applying an alternating polarity electrical current. Soil with a large fraction of organic matter (25

This study investigates the remediation of PFAS-contaminated soil by single-step foam fractionation enhanced soil washing, with special focus on compounds with the highest Relative Potency Factors among those listed in the upcoming EU legislation. The experimental setup involved a small-scale reactor filled with water, PFAS-contaminated soil, and a diluted mixture of surfactants. Mechanical stirring and air injection were provided by a vertical propeller. Design of experiments (DOE) and Response Surface Methodology (RSM) were applied. Liquid to Solid ratio (L/S), stirring rate, and the amount of surfactant were varied simultaneously over a set of planned experiments. Stirring rate was observed to play the dominant role in the process. The lowest removal efficiencies increased with decreasing chain length for both Perfluoroalkyl Carboxylic Acids and Perfluoroalkane Sulfonic Acids, consistent with observations in soil washing processes. Since aeration was linked to the propeller rotation, foam fractionation was enhanced by increasing the stirring rate, resulting in removal efficiencies reaching similar levels. This led to some response surfaces overlapping, reflecting the higher sorption affinity of longer chain compounds to the air-water interface of bubbles compared to short chain PFAS. Final trials successfully validated the suggested optimum operating conditions, achieving 90% PFAS removal at L/S 7. These findings confirm the promising potential of foam fraction for the remediation of PFAS contaminated soil applied as a single-step treatment. Modeling and optimization are suggested as precious tools to explore operative conditions, with the aim to maximize treatment performance according to multiple targets in view of future scale-up.

The wood preservation industry has contaminated numerous sites with polycyclic aromatic hydrocarbons (PAH). The aim of this study was to investigate the use of electrochemical oxidation (EO), without chemical additives, for in situ degradation of PAHs in soil co-contaminated with arsenic. Two 1 m3 boxes, each containing a 20 cm layer of contaminated sand overlaid with 20 cm of peat, were equipped with iron electrodes and placed outdoors. EO was applied using a pulsating direct current with alternating polarity, and its impact on PAH concentrations in soil and soil solution, as well as on the associated microbial community was assessed. Soil solution was sampled from the boxes over two seasons and analysed for PAH16 concentrations, showing an average decrease of 82 % by the end of the second season. This reduction was mainly observed in the medium and high molecular weight PAH fractions, suggesting that EO can effectively degrade more recalcitrant PAH compounds. The least reduction was seen in the low molecular weight PAH16, likely due to the replenishment from PAHs sorbed to the soil. Soil samples were taken from 12 different locations within the boxes, showing that PAH16 concentrations significantly decreased in 10 out of 12 sampling points, with a greater average reduction in sand (84 % decrease) compared to peat (69 % decrease). Microbial analyses of the soil samples revealed no significant changes in DNA concentrations across all taxa over time, with Gammaproteobacteria remaining the most abundant microorganisms in all samples, suggesting its ability to persist complex contamination.

The global accumulation of per- and polyfluoroalkyl substances (PFAS) in soils raises concerns about soil quality. While PFAS sorption may depend on the quality of soil organic matter (SOM), their unique properties may also affect SOM dynamics in complex and poorly understood ways, impacting long-term soil quality. Literature provides vague conclusions about how SOM, particularly its quality, influences PFAS–soil interactions and whether PFAS can modify SOM characteristics. The present study aims to enhance both the qualitative and quantitative understanding of the reciprocal impact that PFAS and SOM have on each other’s environmental fate. Sorption of three PFAS molecules and simultaneous mobilization of dissolved organic matter (DOM) in three distinct soils were studied. PFOS had the highest sorption by ranging 61–98

The remediation of per-and polyfluorinated alkyl substances (PFAS) has received increasing attention because of their toxicity at even low concentration and their ubiquitous presence in water and soil resources. Electrochemical treatment with Boron Doped Diamond (BDD) electrodes has emerged as a powerful technology for PFAS removal and destruction from surface water, groundwater, and wastewater, including streams originating from the remediation of contaminated soils. Impressive removal rates and full mineralization can be achieved for several classes of PFAS with minimum demand of chemicals, an extremely low amount of waste generation and reduced energy requirements compared to other destruction technologies. Within this critical review, reaction pathways, solution chemistry and operational parameters are discussed, and recent advances of the electrochemical cell are summarized. Finally, synergic combination with other remediation techniques is presented, with the aim to promote the development of a robust approach to tackle PFAS contamination.

Per- and polyfluoroalkyl substances (PFAS) are frequently found in soil, groundwater, and landfill leachate, in the vicinity where materials containing PFAS have been disposed of, or in areas where activities involving the use of aqueous film-forming foams (AFFF) have been executed. Removing PFAS via adsorption is a cost-effective and practical method to clean PFAS from contaminated waters. However, challenges arise with the inefficient adsorption of short-chain PFAS and the breakthrough of the contaminant, demanding further advancement. The current study investigates the removal of PFAS using a byproduct generated during the production of Float Adsorb (GP) in combination with electrochemical oxidation (EO). The byproduct was modified by incorporating iron oxyhydroxides. Batch experiments were conducted to assess PFAS adsorption onto the iron-modified material (Fe-P) and (GP), followed by column experiments simulating upscaled treatment. Electrochemical oxidation was then applied to degrade PFAS that broke through the adsorbent. Results showed that iron-coated adsorbent (Fe-P) had a higher capability to retain PFAS than uncoated material (GP). The removal of PFAS in groundwater on batch mode reached an average of 84.5 +/- 1.1 % using GP and 94.5 +/- 0.3 %& sum;11PFAS using Fe-P with an L/S ratio of 10. The EO following column treatment effectively degraded PFAS not adsorbed by the Fe-P adsorbent, showing promising potential for PFAS treatment in solutions. Up to 94 % of & sum;11 PFAS were removed in contaminated groundwater and 76 % in leachate. Our study highlighted the potential of combined sorption and electrochemical oxidation methods to remediate PFAS in contaminated waters.