Adsorption Of Perfluorooctanoic Acid Research Articles

Fluorinated Nonporous Adaptive Cages for the Efficient Removal of Perfluorooctanoic Acid from Aqueous Source Phases.

Per- and polyfluoroalkyl substances (PFAS) accumulate in water resources and pose serious environmental and health threats due to their nonbiodegradable nature and long environmental persistence times. Strategies for the efficient removal of PFAS from contaminated water are needed to address this concern. Here, we report a fluorinated nonporous adaptive crystalline cage (F-Cage 2) that exploits electrostatic interaction, hydrogen bonding, and F-F interactions to achieve the efficient removal of perfluorooctanoic acid (PFOA) from aqueous source phases. F-Cage 2 exhibits a high second-order kobs value of approximately 441,000 g mg-1 h-1 for PFOA and a maximum PFOA adsorption capacity of 45 mg g-1. F-Cage 2 can decrease PFOA concentrations from 1500 to 6 ng L-1 through three rounds of flow-through purification, conducted at a flow rate of 40 mL h-1. Elimination of PFOA from PFOA-loaded F-Cage 2 is readily achieved by rinsing with a mixture of MeOH and saturated NaCl. Heating at 80 °C under vacuum then makes F-Cage 2 ready for reuse, as demonstrated across five successive uptake and release cycles. This work thus highlights the potential utility of suitably designed nonporous adaptive crystals as platforms for PFAS remediation.

Apple Pomace-Derived Cationic Cellulose Nanocrystals for PFAS Removal from Contaminated Water

Per- and poly-fluoroalkyl substances (PFAS) are concerning contaminants due to their ubiquity, persistence, and toxicity. Conventional PFAS water treatments such as granular activated carbon are limited by low adsorption rates and capacities. Carbon-based nano-adsorbents with enhanced surface areas address these limitations but are hindered by their high cost and toxicity. Cellulose nanocrystals (CNC) are promising PFAS adsorbents due to sustainable sourcing, large surface areas, and amenable surface properties. In this study, CNC was synthesized from the agro-food waste, apple pomace (APCNC), and coated with Moringa oleifera cationic protein (MOCP) aqueous extract to produce MOCP/APCNC for the removal of perfluorooctanoic acid (PFOA) from water. APCNC and MOCP/APCNC were manufactured, characterized, and utilized in PFOA batch adsorption kinetics and equilibrium trials. APCNC was successfully produced from apple pomace (AP) and determined through characterization and comparison to commercial CNC (CCNC). APCNC and MOCP/APCNC exhibited rapid PFOA adsorption, approaching equilibrium within 15 min. MOCP coatings inverted the MOCP/CNC surface charge to cationic (−15.07 to 7.38 mV) and enhanced the PFOA adsorption rate (2.65 × 10−3 to 5.05 × 10−3 g/mg/s), capacity (47.1 to 61.1 mg/g), and robustness across varied water qualities. The sustainable sourcing of APCNC combined with a green surface coating to produce MOCP/CNC provides a highly promising environmentally friendly approach to PFAS remediation.

Exploring PFOA adsorption isotherm in the presence of NOM using DBD plasma-modified GAC

Perfluorooctanoic acid (PFOA), a widely used perfluorinated alkyl substance (PFAS), poses significant environmental and health risks. This study investigates PFOA adsorption in the existence of natural organic matter (NOM) using granular activated carbon (GAC) modified with dielectric barrier discharge (DBD) plasma. PFOA’s amphiphilic structure, characterized by a hydrophilic carboxyl group head and a hydrophobic perfluorinated tail, contributes to its versatility and persistence. The selection of the Chao Phraya River (CPR) water as the NOM source, captures the complexity of a major water body subjected to diverse pollution sources. The results were analyzed through the Toth and Temkin isotherm models. Application of the Toth isotherm model reveals enhanced PFOA adsorption capacity in CPR water compared to DI water, emphasizing the influence of NOM. The Temkin isotherm analysis further characterizes the strength and efficiency of the adsorption process, highlighting a stronger interaction between PFOA and plasma-modified GAC in CPR water. The study indicates that the adsorption process in CPR water may be more influenced by PFOA surface coverage on the GAC surface in the presence of NOM. Overall, this research contributes valuable insights into pollutant removal strategies, highlighting the potential of DBD plasma-modified GAC in addressing PFOA contamination challenges in water systems.

Selective perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) adsorption by nanoscale zero-valent iron (nZVI): performance and mechanisms

This study investigated the adsorption of PFOA and PFOS by nanoscale zero-valent iron, revealing the adsorption mechanism and enriching the understanding of environmental remediation.

Supramolecular imprinted cellulose-based N-doped biomass carbon fiber for visual detection and specific degradation of perfluorooctanoic acid

In this study, we successfully synthesized SMIP@N-CF, a nitrogen-doped biomass carbon fiber, using supramolecular imprinting technology. This material has good perfluorooctanoic acid (PFOA) adsorption properties and excellent photocatalytic ability. Therefore, it is possible to apply SMIP@N-CF to the detection system of PFOA for visual detection and to the photocatalytic process based on peroxymonosulfate (PMS) for the degradation of PFOA. The Independent Gradient Model (IGM) explains that visual detection relies on the rapid adsorption of PFOA by functional monomers, covering the catalytic site and resulting in a color change. Experimental evidence verifies its good linear response within the 0.07–90 µM range. Density Functional Theory (DFT) elucidates that charge transfer between pyridine N and C atoms activated PMS to produce reactive oxygen species to degrade PFOA, and the final degradation rate reached 94.3 %. The successful application of SMIP@N-CF provides a new idea for further understanding nitrogen-doped biomass materials and provides a scientific basis for detecting and degrading PFOA in water.

Photothermal porphyrin-based covalent organic framework for efficient removal of perfluoroalkyl substances

Temperature is vital to the removal ability of adsorbent materials. The application of convenient and energy-efficient light-induced heating to promote the removal of emerging contaminants is rarely reported. Here, we report synthesis of a photothermal porphyrin-based covalent organic framework (COF) called Por-MA for efficient removal of perfluoroalkyl substances (PFASs) in environment water. The crystalline Por-MA with rich nitrogen and ordered structure can provide electrostatic and hydrogen bonding interactions for adsorption of PFASs, further give a large adsorption capacity (686.6 mg g−1) and rapid adsorption kinetics (equilibrium time < 10 min) for perfluorooctanoic acid (PFOA) at 25 °C, outperforming several other COF-based sorbents. Moreover, endothermic adsorption of PFOA on Por-MA made promoting adsorption of PFASs on photothermal Por-MA with facile illumination possible. Removal efficiencies of PFASs on Por-MA in environmental water samples also significantly improved with LED irradiation, indicating the high potential of photothermal COFs for removal of contaminants in practical water.

Graphene Oxide and Its Derivatives as Adsorbents for PFOA Molecules.

Effective, low-cost adsorbents are needed to remove perfluoroalkyl and polyfluoroalkyl substances (PFAS) from water sources. Carbon-based materials are promising PFAS adsorbents. Here, we explore the potential of graphite oxide (GO) and its derivatives as PFAS adsorbents by studying the adsorption of perfluorooctanoic acid (PFOA), a model PFAS molecule, on GO surfaces with O/C ratios up to 16.7% using molecular dynamics simulations. An adsorption free energy of approximately -30 kJ/mol (or -310 meV) is obtained for pristine graphene in pure water, and adsorbed PFOA molecules diffuse rapidly. As the O/C ratio increases, hydrophobic interactions' contribution to PFOA adsorption diminishes, but that by electrostatic interactions becomes important. Overall, adsorption is weakened, but favorable adsorption still occurs at an O/C ratio of 16.7%. The in-plane diffusion coefficient of adsorbed PFOA molecules decreases by more than 45 times as the O/C ratio increases to 8.3% but increases significantly when the O/C ratio increases further to 16.7%. Adding salt improves the adsorption owing to the salting-out and screening effects but slows the diffusion of adsorbed PFOA molecules, and these effects are more pronounced at low O/C ratios. These results show that GOs are effective PFOA adsorbents. Such effectiveness, along with GO's potentially low cost and the possibility of regenerating spent GO by removing adsorbed PFOA molecules through a mild electrical potential, makes GO a promising adsorbent for PFOA and similar molecules. The insights from the present study can help the rational design of GOs to realize their full potential.

Adsorption of Model Polyfluoroalkyl Substances on Gold Electrodes for Electroanalytical Applications

AbstractElectrochemical methods can detect trace amounts of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the environment to help their management. PFAS adsorption on electrodes is an essential step in these methods, but is poorly understood. Here, we study the adsorption of perfluorooctanoic acid (PFOA), a model PFAS molecule, on gold substrates using metadynamics and equilibrium molecular dynamics simulations. The two‐dimensional free energy landscape obtained from metadynamics reveals that a PFOA molecule can adsorb on a neutral gold surface with the lowest free energy of −83.9 kJ/mol by adopting a co‐planar orientation, indicating a strong enrichment of PFOA occurs near the electrode. Spontaneous adsorption in other configurations, e. g., only a PFOA molecule‘s head attaches to the electrode, also occurs. However, a PFOA molecule generally must overcome energy barriers to become adsorbed. We show that energetic effects, particularly those associated with van der Waals PFOA‐gold interactions, are the primary driver for PFOA adsorption, and entropic effects associated with interfacial water molecules are the secondary driver. The implications of these results for the electrochemical detection and analysis of PFAS molecules are discussed.

Machine learning screening based strategy for the synthesis of a molecularly imprinted ionic liquid polymer for specific adsorption of perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant that poses a significant environmental threat due to its resistance to degradation in both aquatic and terrestrial environments. Ionic liquids (ILs) are a type of salt that is liquid at or near room temperature and have been widely used in separation science, as well as showing great potential in environmental applications. However, the large number and variety of ILs make them impractical to assess the suitability of all possible ILs for PFOA adsorption using purely experimental methods. To address this issue, a high-throughput machine learning method was employed in this study to screen more than a thousand ILs and identify the most appropriate molecular for designing IL based molecularly imprinted polymer (MIP) with high affinity and selectivity of PFOA. The synthesized MIP, (Vim)C3(L-Pro)@MIP, has been proven to effectively and specifically recognize and adsorb PFOA in water. It has a maximum adsorption capacity of 568.18 mg g−1 and removal efficiency of over 99%, making it a highly efficient and selective option for PFOA removal in environmental remediation applications. This study showcases the promising potential of integrating high-throughput computer screening with experimental verification in the initial stages of MIP material design and development. By doing so, it is possible to create MIP materials that can effectively remove various pollutants, and potentially extend to other IL doped materials and applications.

The role of surface thermodynamics and kinetics in the removal of PFOA from aqueous solutions

Perfluorooctanoic acid (PFOA) has been extensively used as surfactant in industrial applications. Human exposure to PFOA through contaminated water has been linked to serious adverse health effects. In this work, the removal of PFOA from water in all-silica zeolites, which are hydrophobic materials with diverse pore geometries and exceptional hydrothermal stability, is studied. Molecular scale structure, dynamics, kinetics, and free energy landscapes associated with PFOA adsorption are characterized. Interfacial adsorption constitutes the rate limiting step and the adsorption of PFOA is orientation competitive. The PFOA orientation where the hydrophobic perfluorinated methyl group is adsorbed first on the zeolite surface is thermodynamically favored; whereas the adsorption kinetics is faster when the hydrophilic carboxyl group is adsorbed first. Furthermore, the adsorption of PFOA in deprotonated state in hydrophobic pores is thermodynamically prohibitive. Based on computed permeabilities in the pores and kinetic rates associated with the adsorption of PFOA from water, three zeolites, MTW, VET and GON, are estimated to exhibit several orders of magnitude better PFOA removal performance compared to the benchmark material, zeolite Beta (BEA).

Transforming Waste into Value: Eco-Friendly Synthesis of MOFs for Sustainable PFOA Remediation

In response to the need for sustainable solutions to address perfluorooctanoic acid (PFOA) contamination, we have developed an eco-friendly approach for synthesizing two types of metal-organic frameworks (MOFs) using waste polyethylene terephthalate (PET) bottles via a one-pot microwave-assisted strategy. Our innovative method not only avoids the initial depolymerization of PET bottles but also promotes environmental conservation by recycling waste materials. The La-MOF and Zr-MOF materials exhibit remarkable surface areas of 76.90 and 293.50 m2/g, respectively, with La-MOF demonstrating greater thermal stability than Zr-MOF. The maximum experimental PFOA adsorption for La-MOF and Zr-MOF was obtained at 310 and 290 mg/g, respectively. Both MOFs follow the Langmuir isotherm closely, with the adsorption of PFOA following a pseudo-2nd-order kinetic model. In packed-bed column tests, breakthrough positions of 174 and 150 min were observed for La-MOF and Zr-MOF, respectively, with corresponding bed volumes of 452 mL and 522 mL based on the PFOA limit of 0.07 µg/L in drinking water. These findings indicate that these MOFs can be used in industrial packed-bed columns to remove PFOA from contaminated water sources in an efficient and cost-effective manner. Importantly, the sorption performance of the fabricated MOFs for PFOA remained stable, decreasing by less than 10% over seven cycles. This study underscores the potential of recycled PET bottles and the one-pot microwave-assisted synthesis of MOFs as an effective and environmentally friendly solution for PFOA remediation. This innovative approach has several managerial implications, such as the use of waste materials as a feedstock, which can reduce the cost of production and minimize environmental impact by promoting recycling and repurposing, enhancing the reputation of companies operating in the chemical industry, and improving their sustainability metrics. By integrating sustainability principles and waste recycling, our approach offers promising avenues for addressing PFOA contamination while promoting resource efficiency and environmental conservation.

Amine-Functionalized A-Center Sphalerite for Selective and Efficient Destruction of Perfluorooctanoic Acid.

Perfluorochemicals (PFCs), especially perfluorooctanoic acid (PFOA), have contaminated the ground and surface waters throughout the world. Efficient removal of PFCs from contaminated waters has been a major challenge. This study developed a novel UV-based reaction system to achieve fast PFOA adsorption and decomposition without addition of sacrificial chemicals by using synthetic photocatalyst sphalerite (ZnS-[N]) with sufficient surface amination and defects. The obtained ZnS-[N] has the capability of both reduction and oxidation due to the suitable band gap and photo-generated hole-trapping properties created by surface defects. The cooperated organic amine functional groups on the surface of ZnS-[N] play a crucial role in the selective adsorption of PFOA, which guarantee the efficient destruction of PFOA subsequently, and 1 μg L-1 PFOA could be degraded to <70 ng L-1 after 3 h in the presence of 0.75 g L-1 ZnS-[N] under 500 W UV irradiation. In this process, the photogenerated electrons (reduction) and holes (oxidation) on the ZnS-[N] surface work in a synergistic manner to achieve complete defluorination of PFOA. This study not only provides promising green technology for PFC-pollution remediation but also highlights the significance of developing a target system capable of both reduction and oxidation for PFC degradation.

Electrosorption, Desorption, and Oxidation of Perfluoroalkyl Carboxylic Acids (PFCAs) via MXene-Based Electrocatalytic Membranes.

MXenes exhibit excellent conductivity, tunable surface chemistry, and high surface area. Particularly, the surface reactivity of MXenes strongly depends on surface exposed atoms or terminated groups. This study examines three types of MXenes with oxygen, fluorine, and chlorine as respective terminal atoms and evaluates their electrosorption, desorption, and oxidative properties. Two perfluorocarboxylic acids (PFCAs), perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) are used as model persistent micropollutants for the tests. The experimental results reveal that O-terminated MXene achieves a significantly higher adsorption capacity of 215.9 mg·g-1 and an oxidation rate constant of 3.9 × 10-2 min-1 for PFOA compared to those with F and Cl terminations. Electrochemical oxidation of the two PFCAs (1 ppm) with an applied potential of +6 V in a 0.1 M Na2SO4 solution yields >99% removal in 3 h. Moreover, PFOA degrades about 20% faster than PFBA on O-terminated MXene. The density functional theory (DFT) calculations reveal that the O-terminated MXene surface yielded the highest PFOA and PFBA adsorption energy and the most favorable degradation pathway, suggesting the high potential of MXenes as highly reactive and adsorptive electrocatalysts for environmental remediation.

Ion Exchange MIEX® GOLD Resin as a Promising Sorbent for the Removal of PFAS Compounds

Per- and polyfluoroalkyl substances (PFASs) are synthetic compounds, which have been widely produced, used, and recently identified as extremely toxic chemicals, and are responsible for serious environmental and human health risks. In this study, the removal efficiency of MIEX® GOLD resin was tested against six PFAS compounds including perfluorobutanoic acid (PFBA), perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). The removal of PFASs and the regeneration of resin (NaCl-saturated methanol) were achieved via adsorption and desorption mechanisms. In all cases, the removal efficiency was greater than 99% where the volume ratio of 1 ppm PFAS to resin was maintained at 50-bed volume. Furthermore, the adsorption capacity of MIEX® GOLD resin was studied for PFOA and PFHxS and achieved 1.05 ± 0.01 g PFOA adsorption and 1.01 ± 0.04 g PFHxS adsorption per gram of resin. In addition, a detailed study on the interference of natural organic matter (NOM) and inorganic matter was carried out against PFHxA, PFOA, and PFOS. The presence of 10 ppm NOM (5 ppm tannic acid + 5 ppm humic acid) and 25 ppm inorganic matter (5 ppm nitrate + 20 ppm sulfate) showed no noticeable interference in the removal of selected PFAS compounds. Compared to sulfonic acid-containing PFASs, the interference of organic and inorganic matter on carboxylic acid-containing PFASs was slightly higher. The regeneration of PFAS-adsorbed resin was studied using a mixed solution containing 70% methanol and saturated NaCl. Desorption of PFHxS, PFOS, and PFOA was found to be 98.3, 100, and 43.3%, respectively. The results again indicate that the resin regeneration is strongly affected by the functional group of PFASs; i.e., resin with sulfonic acid-containing PFAS is much easier to regenerate than carboxylic acid-containing PFAS compounds. All the PFAS analyses were performed by using mass spectroscopy and liquid chromatography–mass spectroscopy. In conclusion, this study confirms the remarkable efficiency of MIEX® GOLD resin in removing PFAS compounds, even in the presence of a high concentration of organic and inorganic interferences, and its capacity to be regenerated for repeated usage. These advantages make MIEX® GOLD a promising product for the remediation of PFAS-contaminated water. This study in the broader sense proves that MIEX® GOLD is a promising adsorbent and provides the ground for future study to treat contaminated groundwater.

Investigation into Cationic Surfactants and Polyelectrolyte-Coated β-Zeolites for Rapid and High-Capacity Adsorption of Short- and Long-Chain PFAS

Per- and polyfluoroalkyl substances (PFASs) are aqueous contaminants associated with serious health consequences. Conventional PFAS adsorbents are limited by slow kinetics and low short-chain PFAS uptake, driving interest in high-performing alternatives. Here, β-zeolites were investigated for short- (<C8) and long-chain (≥C8) PFAS removal. β-zeolites with high (CP811C) and low (CP814E) silica/alumina ratios were coated with cetyltrimethylammonium bromide (CTAB) or poly(diallyldimethylammonium chloride) (PDADMAC) to enhance short- and long-chain PFAS retention, represented by heptafluorobutyric acid (PFBA) and perfluorooctanoic acid (PFOA). PFAS rapidly adsorbed onto β-zeolites, reaching equilibrium within 1–2 h. Greater PFOA uptake (91.87 vs 57.77 mg/g) was reported onto the silica-rich β-zeolite, CP811C. While the CTAB coatings reduced PFOA adsorption capacity by 58.7%, the PDADMAC coatings increased PFBA adsorption capacity by 51.3%. On unmodified CP811C, PFOA and PFBA exhibited maximum adsorption capacities of 181.87 and 27.89 mg/g, respectively. Fast and high-capacity adsorption make β-zeolites highly promising PFAS adsorption technology.

Combination of adsorption/desorption and photocatalytic reduction processes for PFOA removal from water by using an aminated biosorbent and a UV/sulfite system

Per- and polyfluoroalkyl substances (PFAS) are stable organic chemicals, which have been used globally since the 1940s and have caused PFAS contamination around the world. This study explores perfluorooctanoic acid (PFOA) enrichment and destruction by a combined method of sorption/desorption and photocatalytic reduction. A novel biosorbent (PG-PB) was developed from raw pine bark by grafting amine groups and quaternary ammonium groups onto the surface of bark particles. The results of PFOA adsorption at low concentration suggest that PG-PB has excellent removal efficiency (94.8%–99.1%, PG-PB dosage: 0.4 g/L) to PFOA in the concentration range of 10 μg/L to 2 mg/L. The PG-PB exhibited high adsorption efficiency regarding PFOA, being 456.0 mg/g at pH 3.3 and 258.0 mg/g at pH 7 with an initial concentration of 200 mg/L. The groundwater treatment reduced the total concentration of 28 PFAS from 18 000 ng/L to 9900 ng/L with 0.8 g/L of PG-PB. Desorption experiments examined 18 types of desorption solutions, and the results showed that 0.05% NaOH and a mixture of 0.05% NaOH + 20% methanol were efficient for PFOA desorption from the spent PG-PB. More than 70% (>70 mg/L in 50 mL) and 85% (>85 mg/L in 50 mL) of PFOA were recovered from the first and second desorption processes, respectively. Since high pH promotes PFOA degradation, the desorption eluents with NaOH were directly treated with a UV/sulfite system without further adjustment. The final PFOA degradation and defluorination efficiency in the desorption eluents with 0.05% NaOH + 20% methanol reached 100% and 83.1% after 24 h reaction. This study proved that the combination of adsorption/desorption and a UV/sulfite system for PFAS removal is a feasible solution for environmental remediation.

Enhanced adsorption of PFOA with nano MgAl2O4@CNTs: influence of pH and dosage, and environmental conditions

Perfluorooctanoic acid (PFOA) has received extensive attention due to its widespread distribution in the environment and concerns of its exposure to human health. Nano-MgAl2O4 modified carbon nanotubes (CNTs) were synthesized, characterized, and used as nanoadsorbents to remove ppb (μg/L)-levels of PFOA from drinking water and brackish groundwater. Nano-MgAl2O4@CNTs composite materials were characterized by UV-Vis, FT-IR, DLS, p-XRD, BET, and SEM with EDX. The adsorption isotherms and kinetic studies were fitted to a Freundlich and to a pseudo-second-order models, respectively. Composite nano-MgAl2O4@CNTs remove over 99% of PFOA (100 ppb) from water in 3 hours, and completely (100%) in 3.5 hours. The optimal pH range is under mild alkaline conditions (pH = 7.5-9.0). Electrostatic and hydrophobic interactions drive the PFOA adsorption onto MgAl2O4@CNTs. The adsorption data of ground and drinking water samples indicated that nano-MgAl2O4@CNTs is an efficient nanoadsorbent for PFOA removal.

Effects of trace PFOA on microbial community and metabolisms: Microbial selectivity, regulations and risks

Perfluorooctanoic acid (PFOA), a "forever chemical", is continuously discharged and mitigated in the environment despite its production and use being severely restricted globally. Due to the transformation, attachment, and adsorption of PFOA in aquatic environments, PFOA accumulates in the porous media of sediments, soils, and vadose regions. However, the impact of trace PFOA in the porous media on interstitial water and water safety is not clear. In this work, we simulated a porous media layer using a sand column and explored the effects of µg-level PFOA migration on microbial community alternation, microbial function regulation, and the generation and spread of microbial risks. After 60 days of PFOA stimulation, Proteobacteria became the dominant phylum with an abundance of 91.8%, since it carried 71% of the antibiotic resistance genes (ARGs). Meanwhile, the halogen-related Dechloromonas abundance increased from 0.4% to 10.6%. In addition, PFOA significantly stimulated protein (more than 1288%) and polysaccharides (more than 4417%) production by up-regulating amino acid metabolism (p< 0.001) and membrane transport (p < 0.001) to accelerate the microbial aggregation. More importantly, the rapidly forming biofilm immobilized and blocked PFOA. The more active antioxidant system repaired the damaged cell membrane by significantly up-regulating glycerophospholipid metabolism and peptidoglycan biosynthesis. It is worth noting that PFOA increased the abundance of antibiotic resistance genes (ARGs) and human bacterial pathogens (HBPs) in porous media by 30% and 106%. PFOA increased the proportion of vertical transmission ARGs (vARGs), and co-occurrence network analysis (r ≥ 0.8, p ≤ 0.01) verified that vARGs were mainly mediated by HBPs. A comprehensive understanding of PFOA interactions with its microecological environment is provided.

Hydrated Electron Degradation of PFOA Laden on Ion-Exchange Resins in the Presence of Natural Organic Matter

This study aimed to probe the interactions of hydrated electrons (eaq–) and perfluorooctanoic acid (PFOA)-laden ion-exchange (IX) resins in the presence of natural organic matter (NOM). PFOA and Suwannee River NOM-loaded resins were prepared through the removal of PFOA in simulated natural water with weak-base anion (WBA) resins (IRA67). Adsorption tests reveal that sorbed NOM was much more abundant than cosorbed PFOA, highlighting the role of NOM in resin saturation. Ensuing UV/SO32– treatment of PFOA/NOM-laden resins (pH 10.0) under a dissolved oxygen-free condition indicates that eaq– generated could effectively degrade sorbed and aqueous PFOA, the latter of which derived from desorption of PFOA due to pH increase. Finally, cyclic adsorption-UV/SO32– treatment tests demonstrate that the PFOA sorbed on the WBA resins could be mostly degraded over six cycles. However, eaq– could not effectively decompose cosorbed NOM, resulting in a gradual decrease in the recovered PFOA adsorption capability with the cycle number. This study spotlights that eaq– can decompose PFOA sorbed on the WBA resins in the presence of NOM. The UV/SO32– process, when jointly used with appropriate strategies for mitigating cosorbed NOM, can enable a promising on-site resin regeneration process with PFOA degradation while producing a relatively small volume of regenerant waste.

Removal of perfluorooctanoic acid via polyethyleneimine modified graphene oxide: Effects of water matrices and understanding mechanisms

This research aimed to evaluate the adsorption behaviors and mechanisms of perfluorooctanoic acid (PFOA) onto polyethyleneimine modified graphene oxide (GO-PEI) from aqueous solutions. The adsorption capacity was significantly improved by doping polyethyleneimine (PEI) onto graphene oxide (GO). The Brunauer-Emmett-Teller (BET) isotherm model was considered as the best isotherm model in describing the PFOA adsorption onto GO-PEI3 (wPEI/wGO = 3). GO-PEI3 exhibited high adsorption capacity (qe = 368.2 mg/g, calculated from BET isotherm model) and excellent stability. The maximum monolayer amount of PFOA adsorption onto GO-PEI3 (qm = 231.2 mg/g) was successfully evaluated. The calculated saturated concentration (Cs = 169.9 mg/L) of PFOA on GO-PEI3 closely agrees with its critical micelle concentration (CMC = 157.0 mg/L), suggesting the formation of multilayer hemi-micelles or micelles PFOA structures on the surface of GO-PEI3. PFOA adsorption onto GO-PEI3 was inhibited by several factors including: the presence of humic acid (HA) by competing with the adsorption sites, background salts through the double-layer compression effect, and the competition from soluble ions for the amine or amide functional groups on GO-PEI3. Finally, both the FT-IR and XPS results confirmed that the adsorption of PFOA onto GO-PEI3 was through electrostatic attraction and hydrophobic interaction (physical adsorption), but not chemical adsorption. This work provides fundamental knowledge both in understanding the adsorption behavior through the BET isotherm model and in developing a stable adsorbent for PFOA adsorption. In addition, the findings highlight the potential of PFOA remediation from wastewater systems using GO-PEI in engineering applications.