Adsorption Of Perfluorooctanoic Acid Research Articles

Adsorption of perfluorooctanoic acid from aqueous matrices onto chitosan-modified magnetic biochar: Response surface methodology-based modeling, performance, and mechanism.

Perfluorooctanoic acid (PFOA) removal has gained significant attention due to its environmental stability and potential toxicity. This study aims to synthesize a chitosan-modified magnetic biochar (CS_MBC) for efficient PFOA removal from aqueous solutions. Various CS loading ratios (0.25:1, 0.5:1, and 1:1) were explored to determine the optimal adsorbent, with preliminary experiments exhibiting superior performance of CS1_MBC. To explore the impact of various experimental conditions (pH, adsorbent dose, time, and initial PFOA concentrations) on PFOA removal and optimize these parameters, central composite design of response surface methodology was applied. Statistical analysis of variance was conducted to assess the model's adequacy, which demonstrated a strong correlation between experimental results and the model. The predicted optimal conditions for achieving maximum PFOA removal (∼94%) were pH 4, 120mg/L dose, 60min time, and 20mg/L PFOA concentration. The kinetics and isotherm studies revealed that the pseudo-second-order (R2=0.9996) and Redlich-Peterson (R2=0.999) models better described PFOA adsorption, with Langmuir maximum adsorption capacity of ∼517mg/g. Thermodynamic study confirmed the spontaneous, endothermic, and physisorptive nature of PFOA adsorption, with electrostatic and hydrophobic interactions and hydrogen bonding governing the process. Further, the fixed-bed column experiment was conducted to evaluate the effectiveness of CS1_MBC for practical applications, which demonstrated the maximum experimental adsorption capacity of 39.63mg/g. The breakthrough data showed an excellent fit with both the Thomas and Yoon-Nelson models, with a high correlation coefficient (R2=0.99). Therefore, this research underscores the potential of CS_MBC as an efficient adsorbent for mitigating PFOA contamination in aqueous environments.

A novel biochar adsorbent for treatment of perfluorooctanoic acid (PFOA) contaminated water: Exploring batch and dynamic adsorption behavior

Perfluoroalkyl substances (PFAS), like perfluorooctanoic acid (PFOA), are of concern worldwide given they are ubiquitous in the environment. In this study, the treatment of PFOA-contaminated water was assessed using biochar adsorbents produced from raw canola straw (RCS) through chemical activation with H3PO4 and ZnCl2 and microwave-assisted pyrolysis (MWP). MWP conditions were evaluated to create optimal H3PO4-treated (PBC) and ZnCl2-treated (ZnBC) biochar adsorbents with treatments determined using a central composite design (CCD) based on the response surface methodology (RSM) considering activator concentration, and microwave heating time and power. The highest PFOA removal efficiency for PBC (3.0 mol/L) was achieved at 92 % (368 μg/g), while for ZnBC (0.55 mol/L) it was 84 % (336 μg/g). In contrast, untreated biochar and RCS had markedly lower PFOA removals of 5 % and 1 %, respectively. Activation of biochar under optimal pyrolysis conditions (6 min at 600 W) led to increased chemical functional groups, porosity, and surface area, as confirmed by FT-IR, XPS, and BET. The kinetic study indicated that chemisorption was the primary PFOA adsorption mechanism, while the Freundlich isotherm model suggested heterogeneous multilayer adsorption for PFOA removal. Further, background salts enhanced PFOA adsorption through divalent bridges and salting-out mechanisms. PBC and ZnBC adsorbents performed well over a broad pH range of 3 to 9. Lastly, Yan and Yoon-Nelson models were used to assess adsorption breakthrough for a model fixed-bed adsorption system. This study exhibits that PBC and ZnBC adsorbents, derived from accessible biomass, offer an environmentally friendly solution to remove PFOA from contaminated water.

Modeling the Influence of Coastal Site Characteristics on PFAS in Situ Remediation.

The potential performance of a hypothetical colloidal-activated carbon (CAC) in situ remedy for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater in coastal zones was evaluated using estimated hydrogeologic and geochemical parameters for a coastal site in the United States. With these parameters, a reactive transport model (ISR-MT3DMS) was used to assess the effects of tidal fluctuations and near-shore geochemistry on CAC performance. The average near-shore ionic strength of 84 mM at the site was conservatively estimated to result in an increase in the adsorption of PFOA to CAC by about 50% relative to non-coastal sites with ionic strength <10 mM. The modeling also confirmed the hypothesis that tidally induced groundwater flow reversals near the shore would result in the accumulation of PFOA at the downgradient edge of the CAC zone. Slow desorption of PFOA from this downgradient CAC boundary may sustain downgradient plume concentrations above a strict cleanup criterion (e.g., USEPA MCL of 0.004 μg/L), for decades; however, there was still a large PFOA mass flux reduction (>99.9%) achieved after several decades at the shore. CAC longevity was substantially greater for PFOS with a similar source concentration; however, the higher PFOS distribution coefficient (Kd) in soil downgradient from the CAC zone resulted in substantially longer flushing times. It is recommended that short-term remedial action objectives for CAC remedies at coastal sites be based on mass flux reduction targets over a period of several decades, given the demonstrated challenges in trying to achieve very low cleanup criteria downgradient of a CAC zone in the short term.

Efficient separation of per- and polyfluoroalkyl substances (PFAS) from water by aminated polyacrylamide hydrogel foam

Emerging per- and polyfluoroalkyl substances (PFAS) are highly toxic chemicals with extraodinary stability in the aquatic environment. Highly efficient adsorbents are in urgent need to address the environmental challenges caused by PFAS. Herein, we developed a novel aminated foam adsorbent with high affinity for PFAS adsorption through polymerization, amination and pyrolyzation. For initial 1 μg/L perfluorooctanoic acid (PFOA) solution, more than 97.9 % removal efficiency could be obatined with a rapid equilibration time of ∼ 15 min. The elevated adsorption efficiency could be explained by the synergetic effect of electrostatic/hydrogen bonding and hydrophobic interaction, while the increase of specific surface area (SSA) also has a positive effect on PFOA adsorption. Furthermore, the sythesized polyacrylamide-polyaniline material (pyrolyzed at 301℃, PAM-PANI-2) exhibited high adaptability to different environmental influencing factors, including pH and co-existed organic matters, and presented excellent adsorption removal ability for other common PFAS except for PFOA. Moreover, it is worth noting that this foam material has advantages in regeneration compared to traditional powder adsorbents, without complicated procedures such as centrifugation and filtration. These results indicate that aminated PAM polymers are promising adsorbents in remediations of trace PFAS-contaminated water, which can give new insights to the design and application of novel polymer materials of PFAS treatments.

Efficient removal of perfluorooctanoic acid from aqueous matrices using cationic surfactant functionalized graphene oxide nanocomposite: RSM and ANN modeling, and adsorption behaviour

Perfluorooctanoic acid (PFOA), a persistent and recalcitrant emerging organic contaminant, has garnered worldwide attention due to its pervasiveness and strong bioaccumulation, emphasizing the urgent necessity for effective removal strategies. To address PFOA contamination in the global aquatic environment, this study prepared cetyltrimethylammonium bromide (CTAB)-functionalized graphene oxide (GO-C) nanocomposites. The functionality of GO-C is controlled by varying loading ratios of CTAB to achieve satisfactory performance. After preliminary experiments that confirmed the superior performance of GO-C0.5 in PFOA removal, the response surface methodology (RSM) revealed the effects of different process parameters, which followed the sequence: adsorbent dose > pH > time. The optimum PFOA removal of 98.5 % was achieved at adsorbent dose: 200 mg/L, pH: 3.5, and time: 50 min, at an experimental temperature of 298 K. Furthermore, a predictive model using an artificial neural network was developed for PFOA adsorption, which closely aligns with the experimental data (R2: 0.9999). The PFOA adsorption was most accurately represented by Freundlich isotherm (R2: 0.9747) and pseudo-second-order kinetics (R2: 0.9995), with a maximum experimental adsorption capacity of ~709.94 mg/g under RSM optimized conditions. The adsorption mechanism involves electrostatic and hydrophobic interactions and hydrogen bonding, as confirmed by the spectroscopic and zeta potential analyses. Lastly, the competitive adsorption and regeneration experiments underscore the potential of GO-C nanocomposite in removing PFOA. Overall, this study provides insights into the development and application of sustainable and promising adsorbent for the removal of PFOA in wastewater stream.

Advanced Polymer Composites for Effective Removal of Perfluorooctanoic Acid (PFOA) Pollutants From Aqueous Solutions.

Perfluorooctanoic acid (PFOA) is extensively utilized in industrial applications, posing significant environmental and health risks because of its persistence and toxicity. Effective elimination methods are vital to mitigate its adverse effects on ecosystems and human health. In this study, we investigate the potential of biomass-derived polymer composite for PFOA adsorption in aqueous solution. Due to its unique surface interaction and porosity, the polymer-based composite derived from sustainable biomass sources exhibits favorable adsorption characteristics. The physicochemical properties of polymer composites were characterized using FTIR, XRD, SEM-EDS, XPS, and BET analysis. The polymer composites reached a maximum PFOA adsorption efficiency about 93.3% under optimized conditions determined by Box Behnken Design. The Langmuir isotherm model revealed and provided an adsorption capacity of PFOA about 13.98 mg g-1. Moreover, the polymer-based composites demonstrated reusability, with removal rates of PFOA ranging from 93.3% to 52% over the course of four cycles after desorption. Our findings underscore the possibility of biomass-derived polymer composites as long-term and effective adsorbents for PFOA removal from aqueous environments.

Transport and competitive interfacial adsorption of PFOA and PFOS in unsaturated porous media: Experiments and modeling

Among emerging contaminants, per- and polyfluoroalkyl substances (PFAS) have captured public attention based upon their environmental ubiquity and potential risks to human health. Due to their typical surface release conditions and amphiphilic properties, PFAS tend to sorb to soil and accumulate at the air-water interface within the vadose zone. These processes can result in substantial plume attenuation. Although there is a growing body of literature on vadose zone transport, few studies have explored PFAS mixture transport, particularly under conditions where nonlinear sorption processes are important. The present study aims to advance our understanding of PFAS transport in variably saturated porous media through integration of experiments and mathematical modeling. Experiments include batch studies to quantify sorption to the solid phase, interfacial tension (IFT) measurements to estimate adsorption at the air-water interface (AWI), and column studies with F-70 Ottawa sand at 100 % and ca. 50 % water saturation to explore transport mechanisms. Employed PFAS solutions encompass individual solutes and binary mixtures of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentration levels spanning four orders of magnitude to assess competitive and nonlinear sorption at the AWI. Observations demonstrate that concentration levels and competitive effects substantially influence PFAS transport in unsaturated systems. In the presence of PFOS, PFOA experienced less retention than would be anticipated based on single-solute behavior, and effluent breakthrough curves exhibited chromatographic peaking. The presented mathematical model for simultaneous flow and transport of PFAS was able to capture experimental observations with a consistent set of parameters and minimal curve fitting. These results demonstrate the robustness of the model formulation that included rate-limited interfacial mass transfer, an extended Langmuir-Szyszkowski model for adsorption at the AWI, and a scaled Leverett thermodynamic model to predict the AWI specific area. Overall, the results of this work underscore the importance of the AWI in PFAS transport and highlight the relevance of competition effects in adsorption formulations.

Removal mechanism and effects of aqueous chemistry on rapid adsorption of perfluorooctanoic and perfluorooctanesulfonic acids by microscale zero valent magnesium

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as the two most typical perfluorinated compounds, their effective and rapid removal are still facing enormous challenges. In this study, the adsorption performance and mechanism of PFOA and PFOS by ball milled micrometer zero valent magnesium (mZVMg) were revealed firstly through the adsorption kinetics and isothermal, ions coexisting competitive adsorption and extraction experiments. Rapid adsorption equilibrium within 0.5 h was observed in the mZVMg system, and the higher adsorption affinities at 1.9 and 6.5 L/mg for PFOA and PFOS respectively were approximately 4.4–110 times higher than those of the carbon materials, layered double hydroxide and magnetite reported in the literature. Correspondingly, high removal efficiencies for PFOS were observed even under a wide pH ranging from 3.0 to 11.0. In the meantime, negligible influences on the PFOS adsorption were identified from the coexisting PFOA, perfluorobutanoic acid (PFBA), perfluorobutanoic sulfonic acid (PFBS), anions of Cl−, NO3− and SO42−. Reversely, the PFOA adsorption was adversely influenced by enhanced electrostatic repulsion under the increased pH and the presence of the abovementioned anions. Additionally, the original removal efficiency of 67.18 % for PFOA in the absence of any cations and anions was decreased to 7.98 %, 31.08 % and 39.65 % respectively in the presence of humic acid, HCO3− and CO32−. Similarly, the removal efficiency of 94.41 % for PFOS was declined to 40.01 %, 70.04 % and 80.58 % respectively when humic acid, HCO3− and CO32− were added to the solution. However, in the presence of respective Mg2+ and Ca2+, the original removal efficiencies were increased from 67.18 % to 75.78 % and 74.68 % for PFOA, and from 84.99 % to 93.23 % and 92.49 % for PFOS, likely due to the cation’s bridge effect. Consequently, the hydrophobic adsorption and electrostatic interaction accounted for 71.3 % and 19.75 % for PFOA, while 86.26 % and 5.85 % for PFOS removal, respectively through the solvent extraction and long-term effective removal experiments. Overall, this study provided an alternative, promising and environmental-friendly mZVMg for rapid adsorption of PFOA and PFOS.

Enhanced adsorption of aqueous perfluorooctanoic acid on iron-functionalized biochar: elucidating the roles of inner-sphere complexation

Perfluorooctanoic acid (PFOA) is ubiquitously detected in various water bodies, which raises the urgent need for developing effective and economic remediation methods in response to its health risks. The adsorptive removal of PFOA by biochar (BC) is regarded as a simple, effective, and economical technique. However, engineered BCs, including FeCl3-activated BC, for PFOA removal and adsorption mechanisms have been ill-studied. In this study, a FeCl3-activated dairy manure-derived biochar (Fe@MBC) was prepared via one-step pyrolysis/activation, and its properties and adsorption characteristics were compared with a pristine manure-derived biochar (P-MBC). The FeCl3 activation largely increased the surface area of Fe@MBC and the deposition of FexOy minerals on surface of Fe@MBC while significantly elevating the surface roughness of Fe@MBC. The maximum adsorption capacity of Fe@MBC for PFOA (233 mg·g−1) was five times higher than that of P-MBC (46 mg·g−1). PFOA adsorption was favorable at low solution pH and was independent on ionic strength, which supported the major contribution by inner-sphere complexation rather than out-sphere complexation. This mechanism was further confirmed by the disappearance of FeO peak on Fourier transform infrared spectrum and the blue-shift of Fe binding energies on X-ray photoelectron Fe 2p spectrum of Fe@MBC after PFOA adsorption. Fe@MBC maintained a near 100% adsorption capacity for PFOA after 4 cycles of chemical regeneration. Fe@MBC also exhibited efficient removal for PFOA and other PFAS compounds at trace levels in the lake water and wastewater treatment plant effluent. Thus, this study highlights a promising insight for selectively eliminating PFASs from water.

Synergistic contributions of plant growth-promoting rhizobacteria and exogenous fulvic acid to enhance phytoremediation efficiency of perfluorooctanoic acid (PFOA)-contaminated soils: Boosting PFOA bioavailability and elevating pak choi tolerance

Perfluorooctanoic acid (PFOA), a synthetic perfluoroalkyl compound, has caused extensive soil contamination over several decades, posing serious health risks to humans through bioaccumulation in plants and subsequent transfer via the food chain. Due to the durability of PFOA in soil and its propensity to migrate and accumulate in plants, phytoremediation has been recognized as an effective remediation method. However, the phytotoxicity of PFOA and the adsorption of PFOA by soil hindered the efficiency of traditional phytoremediation. Therefore, this research employed plant growth-promoting rhizobacteria (PGPR)-assisted phytoremediation, augmented with the bio-stimulant fulvic acid (FA), to devise an effective soil remediation strategy tailored for PFOA contamination removal. The results indicated that Rhizobium sp. strain ZY2, endowed with PGP traits, significantly increased the root weight and shoot weight of pak choi by 194.67 % and 37.38 %, respectively, versus the non-inoculation treatment. Furthermore, inoculation with strain ZY2 enhanced soil alkaline phosphatase, protease, and cellulase activities, bolstering soil nutrient cycling and resource availability. On the other hand, compared to treatment with strain ZY2 alone, additional exogenous FA drastically reduced the residual fraction of PFOA in soil from 34.1 % to 1.9 %, likely mediated by complex electrostatic and hydrophobic interactions between FA and soil components. Ultimately, FA addition increased PFOA concentration in pak choi by 8.1-fold. Furthermore, FA could increase the relative abundance of beneficial rhizosphere bacteria (Actinobacterota and Methylotener, etc.), thereby creating a more favorable microenvironment for plant growth. In conclusion, the combined use of strain ZY2 and FA in phytoremediation notably strengthened plant resilience to PFOA, minimized soil sorption, and achieved high remediation efficacy, offering an effective system to mitigate PFOA-soil pollution's environmental and health risks.

Fast Perfluorooctanoic Acid (PFOA) Removal with Honeycomb-like Nitrogen-Doped Carbon Nanosheets: Mechanisms for the Selective Adsorption of PFOA over Competing Contaminants/Water Matrix

Fast Perfluorooctanoic Acid (PFOA) Removal with Honeycomb-like Nitrogen-Doped Carbon Nanosheets: Mechanisms for the Selective Adsorption of PFOA over Competing Contaminants/Water Matrix

Removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) by coagulation: Influence of coagulant and dosing conditions

Per- and polyfluoroalkyl substances (PFAS) pose significant risks to the environment and human health. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are two of the most frequently detected PFAS in the environment. In most surface water drinking water treatment works (WTW), coagulation is the first processes exposed to a range of contaminants, including PFAS. While not designed to be a process for removal of micropollutants, it is important to understand the fate of PFAS in coagulation processes, intended or otherwise, to determine whether water treatment sludge can be a significant sink for this group of micropollutants. This work advances understanding of PFAS removal in coagulation processes by comparing the removal of PFOA and PFOS by four metal coagulants (Zr, Zn, Fe, and Al) from real water matrices. The coagulant performance followed the order Al > Fe > Zr > Zn. Al was taken forward for further evaluation, with significant removal of PFAS (>15 % for PFOA and > 30 % for PFOS) being observed when the pH<5.5 and the dose was > 5 mg Al·L-1. The adsorption of PFOA and PFOS onto flocs through hydrophobic interaction was the primary removal route. The impacts of background matrix on the mechanisms of coagulation for PFAS were explored using five organic compounds. Macromolecular organic compounds contributed to an increase in removal due to the sorption of PFAS and subsequent removal of the organic-PFAS aggregate during coagulation. Low molecular weight organic matter inhibited the removal of PFAS due to the ineffective removal of these compounds during coagulation.

Removal of per- and polyfluoroalkyl substances (PFAS) from water using magnetic cetyltrimethylammonium bromide (CTAB)-modified pine bark

Per- and polyfluoroalkyl substances (PFAS) have gained global attention in recent years due to their adverse effect on environment and human health. In this study, a novel and cost-effective sorbent was developed utilizing forestry by-product pine bark and tested for the removal of PFAS compounds from both synthetic solutions and contaminated groundwater. The synthesis of the adsorbent included two steps: 1) loading of cetyltrimethylammonium bromide (CTAB) onto the pine bark and followed by 2) a simple coating of magnetite nanoparticles. The developed sorbent (MC-PB) exhibited 100 % perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal from synthetic solution (10 µg/L PFOA and PFOS) and enabled quick magnetic separation. A rapid removal of PFOA (> 80 %) by MC-PB was observed within 10 min from synthetic PFOA solution and the adsorption equilibrium was reached within 4 h, achieving > 90 % removal of PFOA (dosage 2 g/L, PFOA 10 mg/L, initial pH 4.2). The PFOA adsorption kinetics fitted well to an optimized pseudo-order model (R2=0.929). Intra-particle diffusion and Boyd models suggested that the adsorption process was not governed by pore diffusion. The maximum PFOA adsorption capacity was found to be 69 mg/g and the adsorption isotherm was best described by the Dual Mode Model (R2=0.950). The MC-PB demonstrated > 90 % PFOA and PFOS removal from contaminated groundwater. Furthermore, both short- and long-chain perfluorosulfonic acids and 6:2 fluorotelomer sulfonate were efficiently removed resulting in 83.9 % removal towards total PFAS (2 g/L dosage).

Removal of PFOA from water by activated carbon adsorption: Influence of pore structure

Activated carbon (AC) adsorption is a practical process for the removal of perfluorooctanoic acid (PFOA) in aquatic environments, but the relationship between its pore structure and adsorption performance is not well understood. In this study, the KOH-activated carbons (KACs) with different tailored pore structures were prepared, and presented a 2.61-fold higher adsorption capacity and a 2.21-fold higher adsorption rate than the raw AC. An in situ characterization method and a modified adsorption model were introduced to investigate the impact of pore size, which demonstrated that the ultra-micropores (<1.2 nm) and small mesopores (2.0–3.0 nm) contributed significantly to the adsorption of PFOA, with the highest mean contribution factor (k) of 0.45 and the second highest of 0.39, respectively. Molecular dynamics simulations revealed that PFOA molecules tend to attach to the pore walls at various pore sizes. The adsorption of PFOA in the ultra-micropores was dominated by enhanced interactions due to the overlapping potentials of the bilateral pore walls (maximum of −567.32 Kcal·mol−1) and hydrophobic interactions. PFOA micelles or hemi-micelles could be formed in the small mesopores, allowing them to function as both the molecule transportation channels and strong adsorption sites. This study would guide the development of activated carbon tailored for the selective adsorption of PFOA from water.

3D-printed indium oxide monoliths for PFAS removal

More efficient removal methods for per- and polyfluoroalkyl substances (PFAS), anthropogenic compounds with high persistence in the environment, are urgently needed due to their significant adverse health effects. Current technologies for PFAS removal in water are limited by incomplete degradation or practical concerns about the use of slurry-based adsorbents. In this study, self-supported indium oxide (In2O3) monoliths were produced via extrusion-based 3D printing and used for the removal of perfluorooctanoic acid (PFOA) via adsorption in a recirculating flow system. A detailed study of the sintering temperature, monolith geometry, and flow rate allowed maximising PFOA adsorption due to the improvement of PFOA diffusion and the increased number of active sites on the monolith, resulting in 53 % of PFOA removal with fast adsorption kinetics in 3 h. Additionally, a low-temperature pyrolysis process at 500 °C effectively regenerated the In2O3 monoliths, allowing reusing the monoliths for three adsorption cycles, while also improving the PFOA removal to 75 % in 3 h. The regenerated In2O3 monoliths not only have a high adsorption capacity (0.16 mg g−1), but also required a much shorter time to reach the adsorption equilibrium compared with other adsorbents reported in the literature. The effectiveness, robustness and reusability of the 3D printed In2O3 monoliths highlight their potential as an efficient and sustainable adsorbent for PFAS removal. The approach presented here represents an effective strategy for the fabrication of complex adsorbents, which are reusable and can be easily handled, eliminating the expensive downstream removal required for slurries while offering a clear route for scale-up towards industrial use.

Vesicles exhibit high-performance removal of per-and polyfluoroalkyl substances (PFAS) depending on their hydrophobic groups

The removal of per- and polyfluoroalkyl substances (PFAS) from drinking water is urgently needed. Here, we demonstrated high performance of vesicles on PFAS adsorption. Vesicles used in this study were enclosed amphiphile bilayers keeping their hydrophobic groups inside and their hydrophilic groups outside in water. The distribution coefficient Kd of perfluorooctane sulfonic acid (PFOS) for vesicles was 5.3 × 105 L/kg, which is higher than that for granulated activated carbon (GAC), and Kd of perfluorooctanoic acid (PFOA) for vesicles was 103–104 L/kg. The removal efficiencies of PFOA and PFOS adsorption on DMPC vesicles were 97.1 ± 0.1% and 99.4 ± 0.2%, respectively. The adsorption behaviors of PFOA and PFOS on vesicles were investigated by changing the number of cis-double bonds in the hydrophobic chains of the vesicle constituents. Moreover, vesicles formed by membranes in the different phases were also tested. The results revealed that, when vesicles are formed of a membrane in the liquid-crystalline (liquid-like) phase, the adsorption amounts of both PFOA and PFOS increased as the cis-double bond in the hydrocarbon chains decreased, which is considered due to molecular shape similarity. When vesicles are formed of a membrane in the gel (solid-like) phase, they do not adsorb PFAS as much as in the liquid-crystalline phase, even though the hydrocarbon chains do not have any cis-double bond. Our findings demonstrate that vesicles can be utilized as PFAS adsorbents by optimizing the structure of vesicle constituents and their thermodynamical phase. Indeed, the vesicles (DMPC) were demonstrated that they can adsorb PFOA and PFOS, and be coagulated by a coagulant even in environmental water. The coagulation will enable the removal of PFOA and PFOS from the water after adsorption.

Adsorption behaviors of perfluorooctanoic acid on aged microplastics.

The presence of perfluoroalkyl substances (PFAS) in the environment poses a significant threat to ecological safety and environmental health. Widespread microplastics (MPs) have been recognized as vectors for emerging contaminants due to human activities. However, the adsorption behaviors of PFAS on MPs, especially on aged MPs, have not been extensively investigated. This study aimed to investigate the adsorption behaviors of perfluorooctanoic acid (PFOA) on aged MPs (polystyrene, polyethylene, and polyethylene terephthalate) treated with UV irradiation and persulfate oxidation under salinity and dissolve organic matter (DOM) condition. Carbonyl index values of MPs increased after the aged treatment, indicating the production of oxygen-containing groups. The PFOA adsorption on aged MPs was impacted by the co-existence of Na+ ions and DOM. As PFOA adsorption onto aged MPs was mainly controlled by hydrophobic interaction, the electrostatic interaction also made a contribution, but there was no significant change in PFOA adsorption behavior between the pristine and aged MPs. While these findings provide insight into PFAS adsorption on aged MPs, further research is necessary to account for the complexity of the real environment. PRACTITIONER POINTS: Adsorption behaviors of perfluorooctanoic acid (PFOA) on aged microplastics were investigated. Hydrophobic interaction mainly controlled PFOA adsorption on aged microplastics (MPs). Co-existence dissolve organic matter and salinity influenced PFOA adsorption behaviors on aged MPs.

Zirconium-Based Metal-Organic Frameworks with Free Hydroxy Groups for Enhanced Perfluorooctanoic Acid Uptake in Water.

Perfluorooctanoic acid (PFOA) is a highly recalcitrant organic pollutant, and its bioaccumulation severely endangers human health. While various methods are developed for PFOA removal, the targeted design of adsorbents with high efficiency and reusability remains largely unexplored. Here the rational design and synthesis of two novel zirconium-based metal‒organic frameworks (MOFs) bearing free ortho-hydroxy sites, namely noninterpenetrated PCN-1001 and twofold interpenetrated PCN-1002,are presented. Single crystal analysis of the pure ligand reveals that intramolecular hydrogen bonding plays a pivotal role in directing the formation of MOFs with free hydroxy groups. Furthermore, the transformation from PCN-1001 to PCN-1002 is realized. Compared to PCN-1001, PCN-1002 displays higher chemical stability due to interpenetration, thereby demonstrating an exceptional PFOA adsorption capacity of up to 632mgg-1 (1.53mmolg-1), which is comparable to the reported record values. Moreover, PCN-1002 shows rapid kinetics, high selectivity, and long-life cycles in PFOA removal tests. Solid-state nuclear magnetic resonance results and density functional theory calculations reveal that multiple hydrogen bonds between the free ortho-hydroxy sites and PFOA, along with Lewis acid-base interaction, work collaboratively to enhance PFOA adsorption.

Comparison of perfluoroalkyl substance adsorption performance by inorganic and organic silicon modified activated carbon

Owing to the persistence and increasingly stringent regulations of perfluoroalkyl substances (PFAS), it is necessary to improve their adsorption capacities using activated carbon (AC). However, their adsorption capacities are suppressed by dissolved organic matter (DOM). In this study, two ACs modified with organic silicon (C-OS) and inorganic silicon (C-IS) were synthesized and used for the adsorption of PFAS in raw water (RW). The results showed that the PFAS adsorption capacity of C-IS was much less influenced by DOM than that of the original AC (C-virgin). In RW, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption capacities on C-IS were 15.08 and 3.65 times higher than those on C-virgin, respectively. DOM had less influence on the PFOA and PFOS adsorption kinetics of C-IS than C-OS and C-virgin. Under multi-PFAS condition, C-IS also exhibited slower desorption of short-chain PFAS and breakthrough in batch and column tests, respectively. Characterization of the ACs before and after adsorption and independent gradient modelling indicated that hydrogen bond interactions between the O-Si of C-IS and the –COOH or –CSO3H groups of PFAS contributed to PFAS adsorption. Density functional theory calculations demonstrated that the adsorption energy of C-IS was much lower than that of C-OS and C-virgin. The arrangement of PFAS molecules on C-OS was chaotic owing to the hydrophobic siloxane chain, whereas the arrangement of PFAS on C-IS was orderly in multi-layer or semi-micelle status and more favorable to PFAS adsorption. This study provides a new strategy for avoiding adverse effects of DOM on PFAS adsorption.

Investigation of Kinetic, Equilibrium, and Thermodynamic Modeling of Perfluorooctanoic Acid (PFOA) Adsorption in the Presence of Natural Organic Matter (NOM) by Dielectric Barrier Discharge Plasma-Modified Granular Activated Carbon (GAC)

Perfluorooctanoic acid (PFOA) contamination in water sources poses significant environmental and health concerns. The kinetic, equilibrium, and thermodynamic features of PFOA adsorption in the existence of natural organic matter (NOM) were thoroughly investigated in this work using granular activated carbon (GAC) modified by dielectric barrier discharge (DBD) plasma. The impacts of DBD plasma parameters on the adsorption process were systematically examined. The results demonstrated that GAC modified by DBD plasma exhibited enhanced adsorption performance for PFOA, even in the presence of NOM. The optimal condition for plasma-treated GAC was achieved with 20 min of plasma treatment time and 100 W of plasma power, resulting in 92% PFOA removal efficiency in deionized water (DIW) and 97% removal efficiency in Chao Phraya River water (CPRW). A kinetic investigation using the pseudo-first-order model (PFOM), the pseudo-second-order model (PSOM), and the Elovich model (EM) indicated that plasma treatment time and NOM presence influenced the adsorption capacity and rate constants of PFOA with the PSOM having emerged as the most fitting kinetic model. The Langmuir isotherm model indicates monolayer adsorption of PFOA on plasma-treated GAC, with higher maximum adsorption capacity while NOM is present. The Redlich–Peterson and Sips isotherm models indicated varying adsorption capacity and heterogeneity in the adsorption system. The Sips model was determined as the most fitting isotherm model. Furthermore, the favorable and spontaneous character of PFOA adsorption onto plasma-treated GAC was validated by thermodynamic analysis, with endothermic heat absorption during the process. Overall, this comprehensive investigation provides valuable insights into the adsorption characteristics of PFOA in the existence of NOM using GAC modified by DBD plasma.