Perfluorooctanoic Acid Removal Research Articles

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.

Dispersive solid phase extraction of perfluorooctanoic acid from wastewater using chromium-doped CoFe layered double hydroxide for determination by LC-MS/MS

Polyfluoroalkyl substances (PFAS) are persistently dangerous substances in the environment, threatening human health even in very low concentrations. This work introduced a dispersive solid phase extraction (DSPE) based on Cr-doped CoFe layered double hydroxide (LDH), which was used as the extraction phase for the effective removal of perfluorooctanoic acid (PFOA) from wastewater samples. Cr-doped CoFe LDH was synthesized using the facile co-precipitation method. Successful partial substitution of Fe3+ by Cr3+ cations in the crystalline lattice of CoFe LDH was affirmed by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and elemental dot-mapping analysis. Layered morphology was observed for both bare and Cr-doped CoFe LDH in scanning and transmission electron microscopy images. The influence of diverse parameters, including sorbent mass, eluent solvent type, volume of eluent, agitation mode, adsorption time, and pH, was assessed on the extraction of PFOA by Cr-doped CoFe LDH. The experimental data from the effective DSPE followed by liquid chromatography–tandem mass spectrometry exhibited a low limit of detection of 0.03 µg/L, broad linear range (0.1–300 µg/L and R2 ≥ 0.997), and good repeatability (6.7 %, n = 5 intraday) for the enrichment and determination of PFOA in wastewater samples.

Enhanced removal of perfluorooctanoic acid by VUV/sulfite/iodide: efficiencies, influencing factors, and decomposition mechanism

Perfluoroalkyl acids (PFAAs) such as perfluorooctanoic acid (PFOA) have been referred to as “forever chemicals” and are toxic and bioaccumulative.

Enhance electrocoagulation-flotation (ECF) removal efficiency perfluorohexanoic acid (PFHxA) by adding surfactants

This research focuses on the application of electrocoagulation-flotation (ECF) in the removal of perfluorooctanoic acid (PFHxA), a prevalent short-chain perfluoroalkyl substance in semiconductor manufacturing, especially at concentrations of industrial wastewater levels. We explored the effectiveness of ECF, which employs sacrificial electrodes to create metal ions and bubbles for pollution extraction. The study particularly examines the role of various surfactants in augmenting PFHxA removal. We observed that at an initial PFHxA concentration of 1 mM, both anionic and cationic surfactants modestly increased removal efficiency, with limited impact from electrostatic repulsion. Significantly, at a higher concentration of 5.0 mM, cationic surfactants, notably DTAB with its short carbon chain, markedly enhanced PFHxA elimination. The superior performance of DTAB is attributed to its facilitation in Al(OH)3 crystal formation, promoting PFHxA adsorption, efficient micelle or bubble formation with PFHxA, and the stability of resulting flocs. Our findings underscore the efficacy of DTAB as a surfactant in ECF for high-concentration PFHxA scenarios, emphasizing the importance of surfactant and electrode material selection in optimizing PFAS treatment in wastewater systems. This study contributes valuable insights into refining PFAS remediation strategies in real industrial wastewater applications.

Enhanced removal of perfluoroalkyl substances using MMO-TiO2 visible light photocatalyst

Exploration of easily produced visible light photocatalysts is still necessary. Thus, this study investigated the catalytic performance of a mixed metal oxide-titanium dioxide (MMO-TiO2) to remove perfluorooctanoic acid (PFOA), a typical and harmful perfluoroalkyl substance, under visible light conditions. Analysis of degradation efficiencies revealed that MMO-TiO2 exhibited a remarkable removal efficiency of 95.99 ± 1.49 %, surpassing other catalysts, including TiO2, ZnAl, MMO, and ZnAl-TiO2. MMO-TiO2, derived from ZnAl-TiO2 calcination, displayed a 5.66-fold higher apparent degradation rate constant (1.07 × 10−2 min−1) compared to ZnAl-TiO2 (1.89 × 10−3 min−1). These materials were characterized via X-ray powder diffractometry, Fourier transform infrared-attenuated total reflectance, N2 adsorption-desorption analysis, and field emission-scanning electron microscopy. Results revealed that O2•- radicals play a pivotal role as the predominant species that mediate PFOA removal. Comparative experiments using probe compounds confirmed increased O2•- production during MMO-TiO2 photoreaction under visible light. In addition, this study explored the effect of operational parameters, such as catalyst dose, initial PFOA concentration, solution pH, and water matrices on the photocatalytic removal process. These findings provide insight into the removal of PFOA using MMO-TiO2, highlighting the potential of this visible light catalyst for the eco-friendly removal of persistent organic pollutants in aquatic systems.

Curcumin-mediated balsa wood-derived 3D magnetic biochar with dual active sites to activate peroxymonosulfate for PFOA removal

Perfluorooctanoic acid (PFOA) is one of the most commonly detected perfluorinated compounds, and now poses a significant threat to animal, plant and human health as an emerging pollutant. Using balsa wood as a natural template and potassium ferrocyanide as a precursor, curcumin-mediated Fe3C/N-embedded 3D magnetic biochar (Fe3C/N@BsB) was obtained in this study via a facile in-situ pyrolysis method. Featured with dual metallic and non-metallic active centers, Fe3C/N@BsB was then utilized for activating peroxymonosulfate (PMS) to degrade PFOA in water. The experimental data indicated that a degradation efficiency of 82.9% and defluorination efficiency of 71.4% were achieved for PFOA at room temperature and pH 3.0. Coexisting 50 mM Cl− in water had no significant impact, while HCO3− and HA showed inhibitory effects on PFOA degradation. By the identification and quantification of free radicals, SO4− was predominant in the Fe3C/N@BsB + PMS system with its maximum accumulation concentration of 29.6 μM. Under the attack of active species, PFOA degradation occurred gradually to produce short-chain by-products for subsequent mineralization. Finally, the recyclability of Fe3C/N@BsB and its catalytic degradability in tap water and Yellow River water were also evaluated. This study not only demonstrates the enormous potential of Fe3C/N@BsB + PMS system for the removal of emerging PFOA in water, but also provides good theoretical support for the resource utilization of balsa wood.

Fe3S4/persulfate-based pre-oxidation for mitigating membrane fouling and enhancing synergistic perfluorooctanoic acid removal: Influence of pH and persulfate types

Aerobic granular sludge membrane system (AGSMS) represents a new wastewater reuse treatment technology. However, the challenges of membrane fouling and limited micropollutant removal efficiency significantly impact its potential for further application. Consequently, this study aimed to address these concerns by employing Fe3S4/persulfate pretreatment to mitigate membrane fouling and enhance perfluorooctanoic acid (PFOA) removal in AGSMS. The effects of pH and persulfate types were investigated by assessing membrane flux, fouling resistance, membrane characterization, and effluent properties. Results showed that optimal mitigation of membrane fouling and removal of PFOA were achieved using Fe3S4-activated PMS at a pH of 6. The primary mechanism for Fe3S4-activated PMS involved the generation of SO4•− and 1O2. Moreover, the fouling mechanism transitioned from cake layer fouling and intermediate blocking fouling to complete blocking fouling in the presence of Fe3S4/PMS. The application of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory revealed that at pH 6.0, there was a significant increase in the energy barrier for both foulant-membrane and foulant-foulant interactions, leading to an effective mitigation of membrane fouling. Correlation analysis demonstrated a significant influence of polysaccharides and total phosphorus concentration on mitigating membrane fouling. Furthermore, pH played a crucial role in mitigating membrane fouling as well as pollutant removal by influencing both coexisting ion states in solution and catalyst properties. This study offers valuable insights for future research and provides essential theoretical guidance for large-scale applications of AGSMS technology in wastewater treatment.

Reductive degradation mechanism of perfluorooctanoic acid (PFOA) during vacuum ultraviolet (VUV) reactions combining with sulfite and iodide

In this study, PFOA removal and defluorination were examined during vacuum ultraviolet (VUV) photolysis in the presence of sulfite and sulfite/iodide conditions. PFOA (24 μM) degradation rate constant (kobs) and defluorination amount in VUV photolysis, and VUV/sulfite, and VUV/sulfite/iodide reactions under nitrogen-purging condition were 5.50 × 10−3, 7.26 × 10−2, 1.60 × 10−1 min−1, and 34.6, 72.7, 73.9% in 6 h, respectively. When tert-butanol (t-BuOH), NO2−, and NO3− ions were added as radical scavengers, hydrated electrons (eaq−) was confirmed as the main species responsible for degrading PFOA and mediating defluorination in VUV-based reactions. While, during VUV photolysis, short-chain perfluoroalkyl carboxylic acids (PFCAs), such as PFHpA, PFHxA, PFPeA, and PFBA, were mainly produced as transformation products (TPs) by the chain-shortening mechanism, additional 14 and 15 TPs were identified in the VUV/sulfite and VUV/sulfite/iodide reactions by LC-QTOF/MS, respectively. The main degradation mechanisms in these reactions are H–F exchange (e.g., TP395 (m/z = 394.9739) and TP377 (m/z = 376.9838)), •SO3−–F exchange (TP474, m/z = 474.9323), carbon double bond formation by defluorination (e.g., TP392 (m/z = 392.9455), TP410 (m/z = 410.9355), and TP436 (m/z = 436.9347)), and H–F exchange followed by hydration reaction (TP393, m/z = 392.9773), respectively. PFOA degradation pathways were proposed for these VUV-based reactions based on the identified TPs, their time profiles, and the density functional theory (DFT). Finally, the toxicity of PFOA and its TPs produced during three reactions were assessed using ECOSAR simulation.

Will iron-promotion on ecological factors continue with its dosage increasing over time under long-term perfluorooctanoic acid exposure?

Considering the potential threat of perfluorooctanoic acid (PFOA) on constructed wetlands (CWs), nano zero valent iron (nZVI) has been employed to promote ecological factors in CWs to enhance the operation performance. Nevertheless, effectiveness of iron-promotion on carbon and phosphorous metabolism with nZVI at various dosage should be investigated. In this study, the most significant enhancement on TP removal was found by 30 mg/L nZVI, with removal efficiency 1.46–12.89% higher than control level. It was consistent to the highest phosphatase activity on this condition. Whereas, lower abundance of key phyla involved in phosphorous metabolism like Proteobacteria, Actinobacteria and Chloroflexi with 30 mg/L nZVI indicated that microbial stimulation was not the dominant manner for strengthening phosphorous removal. In contrast to phosphorous metabolism, the highest increase of PFOA removal by 11.56% was uncovered with 10 mg/L nZVI, and such promotion was reduced by 2.76% since nZVI dosing rising to 30 mg/L. Analogously, inhibition on COD removal was even observed due to higher nZVI concentration. Lower dosage of nZVI generally contributed to more reinforcement on secreting polysaccharide and humus. As for plants, the most obvious improvement of chlorophyll (increased by 33.34–36.85%) and the highest reduction on catalase and malondialdehyde (declined by 221.16% and 45.24% in maximum) were all discovered with 30 mg/L nZVI introduction. It revealed the more potential of nZVI at higher concentration to restore plants under PFOA stress. Information in this study enriched investigation on iron-promoted CWs for treating wastewater containing per- and perfluoroalkyl substances.

Degradation of perfluorooctanoic acid (PFOA) using multiphase fenton-like technology by reduced graphene oxide aerogel (rGAs) combined with BDD electrooxidation

Perfluorooctanoic acid (PFOA) pollution in aqueous environments has attracted considerable attention. Due to its high chemical stability, PFOA is very difficult to degrade, posing potential risks to human health. Therefore, it is of significance to find an efficient and eco-friendly way to remove PFOA from the environment. In this study, reduced graphene oxide aerogel (rGA) was loaded with Fe3O4 and Cu nanoparticles (NPs) to obtain Fe3O4-rGA and Cu-rGA, which were then prepared into cathodes using the microbubble templating method. Heterogeneous Fenton-like system coupling Fe3O4/Cu-rGA cathodes and boron-doped diamond (BDD) electrodes were used to efficiently degrade PFOA in aqueous solutions. The parameters for PFOA degradation were optimized to be initial current density of 20.0 mA cm−2, initial electrolyte pH of 6, and electrolyte (Na2SO4) concentration of 10 mM. After 360 min, the Fe3O4-rGA and Cu-rGA systems achieved PFOA removal efficiencies of 98.25 % and 98.91 %, respectively, which were 16.7 % and 17.5 %, respectively, higher than that achieved by the system using a commercial graphite electrode. PFOA was completely removed, in 720 min and the F− production rates were 62.29 % and 65.48 % in the Fe3O4-rGA and Cu-rGA systems, respectively. PFOA degradation followed pseudo first-order kinetics in both systems (R2 > 0.99). The results of free radical quenching experiment and electrochemical performance experiment showed that the abundant active sites and excellent electrocatalytic properties of Fe3O4-rGA and Cu-rGAs promoted the formation of ⋅OH radicals for efficient PFOA degradation. In conclusion, coupling heterogeneous Fenton-like systems with Fe3O4 or Cu NPs-loaded rGA and BDD electrooxidation have great potential in the treatment of PFOA wastewaters in the future.

Calotropis gigantea fiber confined ZIF-67 derived Co, N in-situ assembled hollow carbon fiber to activate peroxymonosulfate for degradation of perfluorooctanoic acid

Perfluorinated compounds have serious impacts on ecosystems and threats to human health, and exploring technologies to remove them is urgently needed. Using Calotropis gigantea fiber (CGF) as the biological template, the precursor of ZIF-67 was firstly in-situ anchored in the inner/outer walls of the fiber and then pyrolyzed to yield the composite catalyst labelled as Co/C@C. In combination with peroxymonosulfate (PMS), the advanced oxidation system, i.e. Co/C@C/PMS, was constructed for the catalytic removal of perfluorooctanoic acid (PFOA) from water. The experimental results showed that under the optimized conditions of PMS dosage of 1.0 g/L, catalyst dosage of 0.5 g/L and pH 3.0, PFOA achieved the degradation efficiency of 72.2% within 4 h at ambient temperature. Combined with free radical quenching, electron paramagnetic resonance, electrochemistry and nitroblue tetrazolium dichloride-based UV-Vis analysis, the reactive oxygen species and diverse pathways were identified, including SO4•−, O2•−, O21 and electron transfer process in the Co/C@C/PMS system. The coexisting anions (HCO3−, Cl−, H2PO4− and NO3−) and real wastewaters showed no significant effects on PFOA degradation, demonstrating that the Co/C@C/PMS system has good resistance to external ions and different media. After four cycles, the degradation efficiency of PFOA was still 62.8%, indicating that Co/C@C has high stability and good reusability. The degradation products of PFOA were mainly short-chain perfluorinated carboxylic acids (C4-C7) and hydrogen-substituted perfluorinated compounds. Based on quantitative structure-activity relationship analysis, their ecotoxicity was finally evaluated via ECOSAR method. In short, natural CGF derived Co/C@C has great potential for the reduction of emerging PFOA to achieve a sustainable water environment for humans.

Can perfluorooctanoic acid be effectively degraded using β-PbO2 reactive electrochemical membrane?

Aqueous perfluorooctanoic acid (PFOA) elimination has raised significant concerns due to its persistence and bioaccumulation. Although β-PbO2 plate anodes have shown efficient mineralization of PFOA, it remains unclear whether PFOA can be effectively degraded using β-PbO2 reactive electrochemical membrane (REM). Herein, we assessed the performance of Ti/SnO2-Sb/La-PbO2 REM for PFOA removal and proposed a possible degradation mechanism. At a current density of 10 mA/cm2 and a membrane flux of 8500 (liters per square meter per hour, LMH), the degradation efficiency of 10 mg/L PFOA was merely 8.8%, whereas the degradation efficiency of 0.1 mg/L PFOA increased to 96.6%. Although the porous structure of the β-PbO2 REM provided numerous electroactive sites for PFOA, the generated oxygen bubbles in the pores could block the pore channels and adsorb PFOA molecules. These hindered the protonation process and significantly impeded the degradation of high-concentration PFOA. Quenching experiments indicated that •OH played dominant role in PFOA degradation. The electrical energy per order to remove 0.1 mg/L PFOA was merely 0.74 Wh/L, which was almost an order of magnitude lower than that of other anode materials. This study presents fresh opportunities for the electrochemical degradation of low-concentration PFOA using β-PbO2 REM.

Removal of perfluorooctanoic acid (PFOA) in the liquid culture of Phanerochaete chrysosporium

Perfluorooctanoic acid (PFOA) is becoming a concern due to its persistence, bioaccumulation, and potential harmful effects on humans and the environment. In this study, the fungus Phanerochaete chrysosporium (P. chrysosporium) was used to remove the PFOA in liquid culture system. The results showed that the average activities of laccase (Lac), lignin peroxidase (LiP), and manganese peroxidase (MnP) enzymes secreted by P. chrysosporium were 0.0003 U/mL, 0.013 U/mL, and 0.0059 U/mL, respectively, during the incubation times of 0–75 days. The pH of 3 and incubation time of 45–55 days were the optimum parameters for the three enzymes activities. The enzyme activities in P. chrysosporium incubation system were firstly inhibited by adding PFOA and then they were enhanced after 14 days. The maximum removal efficiency of PFOA (69.23%) was achieved after 35 days in P. chrysosporium incubation system with an initial PFOA concentration of 0.002 mM and no veratryl alcohol (VA). Adsorption was not a main pathway for PFOA removal and the PFOA adsorbed in fungi mycelial mat accounted for merely 1.91%. The possible products of PFOA contained partially fluorinated aldehyde, alcohol, and aromatic ring. These partially fluorinated compounds might result from PFOA degradation via a combination of cross-coupling and rearrangement of free radicals.

Comparing the removal and fate of long and short chain per- and polyfluoroalkyl substances (PFAS) during surface water treatment via specialty adsorbents

The oleophobic and hydrophobic properties of per- and polyfluoroalkyl substances (PFAS) favoring their industrial applications have resulted in the persistence, transport, transformation, and accumulation of PFAS in environmental matrices around the globe. Specialty adsorbents comprise specialty ingredients that have wide availability tailored for scalable applications in any landscape. This study investigated 2 specialty adsorbents, Zero-Valent-Iron and Perlite-based Green Environmental Media (ZIPGEM) and Clay-Perlite and Sand sorption media (CPS) in removing long-chain and short-chain PFAS via a fixed-bed column study. The adsorption of perfluorooctane sulfonic acid (PFOS) by ZIPGEM was best explained by pseudo-second-order kinetics. The intraparticle diffusion model was a better fit for adsorption of perfluorooctanoic acid (PFOA) by both CPS and ZIPGEM. CPS exhibited a higher initial removal of PFOA (approximately 91 %) compared to that by ZIPGEM (approximately 84 %). During the initial 2-h run, the removals of perfluoropentanoic acid (PFPeA), perfluorobutanesulfonic acid (PFBS), and perfluorobutanoic acid (PFBA) by CPS were approximately 82 %, 72 %, and 54 %, respectively. The removals of PFPeA, PFBS, and PFBA by ZIPGEM were approximately 42 %, 90 %, and 36 %, respectively. In general, the order of adsorption by CPS and ZIPGEM was PFOS > PFOA > PFHxS > PFHpA > PFHxA > PFPeA > PFBS > PFBA. The preference of adsorption generally follows the media affinity initially by adsorbing larger molecules with higher molecular weights, followed by short-chain perfluorocarboxylic acids and perfluorosulfonic acids. Overall, adsorption was the dominant PFAS removal mechanism with some possible transformation of long-chain PFAS to short-chain PFAS when using CPS and ZIPGEM.

Efficient Removal of Perfluorooctanoic Acid by UV-Based Peroxide and Persulfate Advanced Oxidation Processes

Perfluorooctanoic acid (PFOA) challenges traditional methods of aquatic treatment and recycling from recalcitrant organic compounds, which ubiquitously persist in the environment, mainly water bodies, and cause various adverse effects on humans and the environment. Conventional water treatment technologies are proven inefficient and must focus on advanced oxidation processes. This study conducted treatability studies for removing PFOA by direct photolysis, UV/peroxide, and UV/persulfate oxidation using a lab-scale reactor. The experiment was performed with an initial concentration of 20 mg/L for 120 min for a 500 mL of sample. The oxidant dosage and pH were optimized based on the mineralization efficiency. An efficient method for PFOA degradation is based on its percentage reduction in concentration, mineralization efficiency, and reaction kinetics study. It was found that all three processes were adequate for mineralizing PFOA. Among them, UV/persulfate was more effective in mineralizing PFOA. The total organic carbon removal percentages using direct photolysis, UV/persulfate, and UV/peroxide treatments were 49%, 80%, and 66%, respectively. The pseudofirst-order kinetics for these three were 0.160, 0.489, and 0.349 h−1, respectively.

Bio-inspired interfacial micro-electric field of FeOCl nanosheets for rapid adsorption of perfluorocarboxylic acids (PFCAs)

In this study, a FeOCl adsorbent was demonstrated to rapidly remove perfluorocarboxylic acids (PFCAs). The unique coordination environment led to preferential dissociation of the Cl− in the FeOCl lattice by hydration, forming a high-intensity interfacial micro-electric field. The interfacial micro-electric field could apply an electric driving force to increase the external diffusion flux of PFCAs, thus achieving rapid adsorption (adsorption equilibrium time ∼10 min). In addition, the interfacial micro-electric field excited synergistic adsorption of multiple interactions (complexation, electrostatic interaction, and halogen-bonding interaction), being able to reach 277.01 mg/g for perfluorooctanoic acid (PFOA). Additionally, we developed a continuous flow column using FeOCl to demonstrate its potential for decontaminating drinking water with PFCAs at environmentally relevant concentrations. The FeOCl adsorbent exhibited a bed life of 125,000 BV upon reaching breakthrough concentration of breakthrough concentration of 70 ng/L in dynamic adsorption experiment, which outperformed conventional activated carbon F400D and ion exchange resin IRA67 adsorbents. Spent FeOCl absorbent could be easily regenerated in mild regeneration conditions and maintained a high PFOA removal in subsequent usage cycles. FeOCl demonstrated great potential in the purification of PFCA-contaminated water for household or municipal applications.

Important properties of anion exchange resins for efficient removal of PFOS and PFOA from groundwater

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) present in various water sources have raised a serious concern on their health risk worldwide. Anion exchange is known to be one of the effective treatment methods but the resin properties suitable for theses contaminants have not been fully understood. We examined four commercially available anion exchange resins with different properties (DIAION™ PA312, HPA25M, UBA120, and WA30) and one polymer-based adsorbent (HP20), for their PFOA and PFOS removal in the batch experiment. All or a part of the selected resins were further characterized for their functional group, surface morphology and pore size distribution. The 72 h batch experiment with the 100 mg/L PFOA or PFOS in the laboratory pure water matrix showed a superior capacity of the strong base anion exchange resins, the porous-type HPA25M and PA312, and the gel-type UBA120, for PFOA removal (92.6–97.9%). Among those resins, the high porous HPA25M was suggested most effective due to its remarkably high reaction rate and effectiveness to PFOS (99.9%). In the groundwater matrix, however, the performance of the those anion exchange resins was generally suppressed, causing up to 71% decrease in their removal rates. The least matrix impact was observed for PFOS removal by HPA25M, which indicated the resin's high selectivity to the contaminant. The physiochemical analysis indicated that the presence of relatively large pores (1 nm–10 nm) over HPA25M played an important role in the PFAS removal.

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.

Insights into the Responses of the Partial Denitrification Process to Elevated Perfluorooctanoic Acid Stress: Performance, EPS Characteristic and Microbial Community

This study aimed at investigating the potential impacts of perfluorooctanoic acid (PFOA) exposure on the partial denitrification (PD) system. Our results indicated that nitrite accumulation rates were significantly decreased to 67.94 ± 1.25%–69.52 ± 3.13% after long-term PFOA exposure (0.5–20 mg/L), while the nitrate transformation ratio was slightly impacted. The PFOA removal efficiency gradually decreased from 67.42 ± 3.39% to 6.56 ± 5.25% with an increasing PFOA dosage, indicating that the main PFOA removal pathway was biosorption. The average EPS contents increased by two folds, which suggested that exposure to PFOA significantly stimulated EPS secretion. Excitation emission matrix analysis revealed that PFOA exposure promoted the secretion of tryptophan protein-like, humic acid-like, and aromatic protein II-like substances, which may act as a protective barrier against PFOA toxicity. Moreover, significant changes in characteristic peaks after PFOA exposure were shown as indicated by Fourier transform infrared spectroscopy. High-throughput sequencing suggested that PFOA significantly decreased bacterial richness and increased evenness, indicating that toxicity effects of PFOA were more pronounced for abundant species (e.g., Thauera) than rare species. Thauera was the most dominant genus responsible for nitrite accumulation, whose abundance significantly decreased from 35.99 ± 2.67% to 18.60 ± 2.18% after PFOA exposure. In comparison, the abundances of common denitrifiers, such as Denitratisoma, Bdellovibrio, and OLB8, significantly increased, suggesting that these genera were potential PFOA-resistant bacteria. This study presents new insights into the effect of PFOA on a PD system.

Boosting PFOA photocatalytic removal from water using highly adsorptive and sunlight-responsive ZIF67/MIL-100(Fe) modified C3N4

Per- and polyfluoroalkyl substances (PFAS) are widely used in many industrial and food processes. Their discharge into the environment shows a serious threat because of their toxicity, non-biodegradability and high mobility in water and soil. Photocatalytic reaction is confirmed an effective way for the degradation of PFOA. Photocatalytic materials with multifunctional properties can boost the generation of oxidizing materials, enhance the degradation efficiency of target pollutants. Herein, we report an easy-synthesis of ZIF67@C3N4 and MIL-100(Fe)@C3N4 by in-situ hydrothermal growth route for the photocatalytic degradation of perfluorooctanoic acid (PFOA). Unlike bare g-C3N4, ZIF67@C3N4 and MIL-100(Fe)@C3N4 composites exhibit higher specific surface areas which enhanced the adsorption properties. Moreover, the formed heterojunction systems boost the visible light responsive and the separation of photo-induced electrons, allowing excellent degradation of PFOA. Besides the same response to spectrum below 420 nm as C3N4, ZIF67@C3N4 holds a certain light absorption capacity between 500 and 600 nm, proving that ZIF67@C3N4-X has better light utilization capacity than ZIF67 and C3N4. With the increase of MIL-100(Fe) addition, the red-shift becomes significant. Through the preliminary photocatalytic tests using methylene blue as a representative organic pollutant, the results showed that ZIF67@C3N4-24.4% and MIL-100(Fe)@C3N4-70% are the most effective. When ZIF67@C3N4-24.4% and MIL-100(Fe)@C3N4-70% were applied comparatively towards the photocatalytic oxidation of PFOA, the results showed that the removal rates reached 79.2% and 60.5%, respectively, which is much higher than bare C3N4. The quenching tests indicated that photo-induced h+ played a major role in the photocatalytic degradation of PFOA by ZIF67@C3N4-24.4%, while O2- and h+ participated equality towards the PFOA degradation in MIL-100(Fe)@C3N4-70% system. Besides the photonic effects, it was suggested that the adsorption and electron shuttle effect also played significant role on the excellent removal of PFOA, wherein the adsorption e behavior of catalysts help the accumulation of PFOA nearby the photoactive C3N4 area. In addition, this process promoted further mineralization of generated intermediate products, making the system more sustainable.