Perfluorooctanoic Acid Removal Research Articles

Electrochemical Advanced Oxidation of PFOA by Ti4O7 Reactive Electrochemical Membrane Anode

In recent years, per and polyfluoroalkyl substances (PFAS) have garnered significant attention due to their persistent and harmful effects on the environment and human health. Traditional treatment methods often fall short of effectively removing PFAS from water, prompting the need for innovative techniques. One promising approach is electrochemical advanced oxidation, based on highly reactive chemical species generated through electrochemical reactions to degrade organic pollutants. In this study, a specific reactive electrochemical membrane (REM) anode was used to degrade perfluorooctanoic acid (PFOA). The anode is a tubular Ti4O7-based REM (mixture of Ti4O7 and Ti5O9 Magneli phases) with a water permeability of 3300Lm-2 h-1 bar-1. The impact of various operating parameters, including current density, flux through REM, and feed concentration, on PFOA degradation efficiency was investigated. It was found that higher current densities, feed concentrations and lower flux through REM led to increased PFOA removal rates. With this type of REM, a total degradation of PFOA was observed at PFOA flux (passing throw the REM) under 0.2gh-1 m-2 even at the lowest current density (71A/m2). The degradation mechanism was investigated by evaluating the generated by-products after several degradation cycles, and the results confirmed that the degradation occurs via the decomposition cycle of CF2. Energy consumption has been taken into account, as it is the major limitation of advanced oxidation processes, exhibiting value under 5 kWh/g for the lowest current density and the highest PFOA flux. The originality of this study relies on the use of a specific anode; a tubular shape Ti4O7-based REM (by Saint Gobain Company). Such concentric REM reactor is optimal for the treatment of recalcitrant effluent containing PFOA as it significantly improved mass transfer leading to a very interesting energy efficient system that can easily be scale up.

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.

Adsorptive removal of perfluorooctanoic acid from aqueous matrices using peanut husk-derived magnetic biochar: Statistical and artificial intelligence approaches, kinetics, isotherm, and thermodynamics

Removal of perfluorooctanoic acid (PFOA) from water matrices is crucial owing to its pervasiveness and adverse ecological and human health effects. This study investigates the adsorptive removal of PFOA using magnetic biochar (MBC) derived from FeCl3-treated peanut husk at different temperatures (300, 600, and 900 °C). Preliminary experiments demonstrated that MBC600 exhibited superior performance, with its characterization confirming the presence of γ-Fe2O3. However, efficient PFOA removal from water matrices depends on determining the optimum combination of inputs in the treatment approaches. Therefore, optimization and predictive modeling of the PFOA adsorption were investigated using the response surface methodology (RSM) and the artificial intelligence (AI) models, respectively. The central composite design (CCD) of RSM was employed as the design matrix. Further, three AI models, viz. artificial neural network (ANN), support vector machine (SVM), and adaptive neuro-fuzzy inference system (ANFIS) were selected to predict PFOA adsorption. The RSM-CCD model applied to optimize three input process parameters, namely, adsorbent dose (100–400 mg/L), pH (3–10), and contact time (20–60 min), showed a statistically significant (p < 0.05) effect on PFOA removal. Maximum PFOA removal of about 98.3% was attained at the optimized conditions: adsorbent dose: 400 mg/L, pH: 3.4, and contact time: 60 min. Non-linear analysis showed PFOA adsorption was best fitted by pseudo-second-order kinetics (R2 = 0.9997). PFOA adsorption followed Freundlich isotherm (R2 = 0.9951) with a maximum adsorption capacity of ∼307 mg/g. Thermodynamics and spectroscopic analyses revealed that PFOA adsorption is a spontaneous, exothermic, and physical phenomenon, with electrostatic interaction, hydrophobic interaction, and hydrogen bonding governing the process. A comparative analysis of the statistical and AI models for PFOA adsorption demonstrated high R2 (>0.99) for RSM-CCD, ANN, and ANFIS. This research demonstrates the applicability of the statistical and AI models for efficient prediction of PFOA adsorption from water matrices using MBC (MBC600).

Co-Removal of Perfluorooctanoic Acid and Nitrate from Water by Coupling Pd Catalysis with Enzymatic Biotransformation.

PFAS (poly- and per-fluorinated alkyl substances) represent a large family of recalcitrant organic compounds that are widely used and pose serious threats to human and ecosystem health. Here, palladium (Pd0)-catalyzed defluorination and microbiological mineralization were combined in a denitrifying H2-based membrane biofilm reactor to remove co-occurring perfluorooctanoic acid (PFOA) and nitrate. The combined process, i.e., Pd-biofilm, enabled continuous removal of ∼4 mmol/L nitrate and ∼1 mg/L PFOA, with 81% defluorination of PFOA. Metagenome analysis identified bacteria likely responsible for biodegradation of partially defluorinated PFOA: Dechloromonas sp. CZR5, Kaistella koreensis, Ochrobacterum anthropic, and Azospira sp. I13. High-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and metagenome analyses revealed that the presence of nitrate promoted microbiological oxidation of partially defluorinated PFOA. Taken together, the results point to PFOA-oxidation pathways that began with PFOA adsorption to Pd0, which enabled catalytic generation of partially or fully defluorinated fatty acids and stepwise oxidation and defluorination by the bacteria. This study documents how combining catalysis and microbiological transformation enables the simultaneous removal of PFOA and nitrate.

Fixed-bed adsorption of perfluorooctanoic acid from water by a polyamine-functionalized polychlorotrifluoroethylene-ethylene polymer coated on activated carbon

Perfluorooctanoic acid (PFOA) has received extensive attention because of its ubiquitous presence in the aqueous environmental phase and concerns of its impact on human health. An economical and effective adsorption method is in demand to help resolve the issue. In this study, a polyamine-functionalized polychlorotrifluoroethylene-ethylene polymer coated activated carbon (AC) was synthesized via a two-step reaction. The fluoropolymer based on the repeating unit ethylene-chlorotrifluoroethylene (ECTFE) was applied as the binding medium to connect activated carbon with polyethyleneimine (PEI). Hence a dual grafted activated carbon-based sorbent AC-ECTFE-PEI was generated. Through the adsorption evaluation of packed columns by on-line detection flow analysis, the optimum synthetic stoichiometry parameters to produce AC-ECTFE-PEI, based on the longest adsorption breakthroughs, were determined to be the 5:2 AC/ECTFE and 1:1 AC-ECTFE/PEI mass ratios. The new adsorbent has shown a strongly enhanced initial adsorption breakthrough to PFOA compared to AC, 270 min vs. 110 min, under the same adsorption conditions. AC-ECTFE-PEI was also characterized by attenuated total reflectance infrared spectroscopy, BET surface area analysis, and scanning electron microscopy. The functional group alterations during the reactions and the morphology information of the sorbent have also been elucidated. The Thomas, Adams-Bohart, and Yoon-Nelson models respectively were used to describe the adsorption behavior, indicating an PFOA adsorption capacity of 380 mg/g sorbent, 120 mg/L sorbent column, and a 50% average breakthrough time of 350 min for 100 mg/L PFOA removal, under a 1 mL/min flow rate and a 2 cm bed height. The regeneration study of AC-ECTFE-PEI of more than five adsorption-desorption cycles indicates good sustainability and stability. Both electrostatic and hydrophobic interactions of PFOA were justified using selective solvent compositon of the mobile phase as the two main adsorption mechanisms. The electrostatic forces of PFOA on AC-ECTFE-PEI, AC-ECTFE, and AC were also evaluated by their zeta-potential values.

Application of electric potential and Fe(Ⅲ) to stimulate perfluorooctanoic acid (PFOA) degradation using mixed culture anammox granules

Pollution by perfluorooctanoic acid (PFOA), a highly persistent and toxic substance, is commonly addressed with several approaches, but the need for post-treatment affects their environmental and economic sustainability. Biodegradation, which can efficiently degrade micropollutants in water under optimal conditions, offers a promising solution, but faces challenges from the persistence of the C-F bond and the high reactivity of F-. Despite recent use of various microorganisms for PFOA degradation, performance issues persist. In this study, we aimed to simulate PFOA degradation while mixed culture anammox granules oxidize NH4+ and to confirm the effects of electric potential and Fe(Ⅲ) applications on PFOA degradation. A control reactor containing only anammox granules exhibited NH4+ and PFOA removal efficiencies of 11.52% and 19.2%, respectively, with traceable biodegradation at 3.7%. In contrast, a reactor that applied both electric potential and Fe(Ⅲ) demonstrated enhanced removal efficiencies of 41.98% and 50.93%, with traceable biodegradation at 35.03%. Bio-electrochemical properties also improved, showing an average current generation of 331.95 μA and Coulombic efficiency of 141.79 ± 7.6%. This study shows that mixed-culture anammox granules with electric potential and Fe(Ⅲ) can be introduced for efficient PFOA biodegradation and provides the basis for further studies on overcoming the limitations of PFOA biodegradation.

Comparison of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutane sulfonate (PFBS) removal in a combined adsorption and electrochemical oxidation process

This study focused on three of the most studied PFAS molecules, namely perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutane sulfonate (PFBS). They were compared in terms of their adsorption capacity onto graphite intercalated compound (GIC), a low surface area, highly conductive and cheap adsorbent. The adsorption on GIC followed a pseudo second order kinetics and the maximum adsorption capacity using Langmuir was 53.9 μg/g for PFOS, 22.3 μg/g for PFOA and 0.985 μg/g for PFBS due to electrostatic attraction and hydrophobic interactions. GIC was added into an electrochemical oxidation reactor and >100 μg/L PFOS was found to be fully degraded (<10 ng/L) leaving degradation by-products such as PFHpS, PFHxS, PFPeS, PFBS, PFOA, PFHxA and PFBA below 100 ng/L after 5 cycles of adsorption onto GIC for 20 min followed by regeneration at 28 mA/cm2 for 10 min. PFBS was completely removed due to degradation by aqueous electrons on GIC flakes. Up to 98 % PFOA was removed by the process after 3 cycles of adsorption onto GIC for 20 min followed by regeneration at 25 mA/cm2 for 10 min. When PFBS was spiked individually, only 17 % was removed due to poor adsorption on GIC. There was a drop of 3–40 % by treating PFOS, PFOA and smaller sulfonates in a real water matrix under the same electrochemical conditions (20 mA/cm2), but PFOS and PFOA removal percentage were 95 and 68 % after 20 min at 20 mA/cm2.

Simultaneous removal of perfluorooctanoic acid and thiocyanate by modified activated carbon fiber/persulfate system

In this study, NaOH-modified activated carbon fiber (NaOH-ACF) was used as a catalyst to activate persulfate (PS) for the removal of perfluorooctanoic acid (PFOA) and thiocyanate (SCN−) from wastewater. The effects of the crucial parameters in the NaOH-ACF/PS process, including NaOH-ACF dosage, PS concentration and initial pH, were investigated and optimized using response surface methodology. The experimental results indicated showed that under the optimal reaction conditions of NaOH-ACF dosage (0.40 g/L), PS concentration (2.0 mmol/L), pH (3.0), and temperature (25 °C), the removal efficiencies for PFOA and SCN− reached 93.63 % and 95.17 %, respectively, within 60 min of reaction. When PFOA and SCN− coexisted in the reaction system, it was observed that PFOA had minimal effect on the removal of SCN−, while SCN− actually enhanced the removal of PFOA. Free radical identification experiments demonstrated that the NaOH-ACF/PS system generated free radicals (O2−, SO4−, OH) and non-free radicals (1O2), which cooperatively facilitated the degradation of PFOA and SCN−. Furthermore, Liquid Chromatograph-Mass Spectrometer (LC-MS) analysis results have been used to speculate on the possible degradation pathways and intermediates of PFOA. The material characterization results indicated that NaOH-ACF possesses abundant surface functional groups with excellent adsorption and catalytic properties. Thus, the NaOH-ACF-activated PS advanced oxidation process offered a promising approach for the simultaneous removal of Perfluorinated compounds and thiocyanates.

Superb green cycling strategies for microbe-Fe0 neural network-type interaction: Harnessing eight key genes encoding enzymes and mineral transformations to efficiently treat PFOA

To address time-consuming and efficiency-limited challenges in conventional zero-valent iron (ZVI, Fe0) reduction or biotransformation for perfluorooctanoic acid (PFOA) treatment, two calcium alginate-embedded amendments (biochar-immobilized PFOA-degrading bacteria (CB) and ZVI (CZ)) were developed to construct microbe-Fe0 high-rate interaction systems. Interaction mechanisms and key metabolic pathways were systematically explored using metagenomics and a multi-process coupling model for PFOA under microbe-Fe0 interaction. Compared to Fe0 (0.0076 day−1) or microbe (0.0172 day−1) systems, the PFOA removal rate (0.0426 day−1) increased by 1.5 to 4.6 folds in the batch microbe-Fe0 interaction system. Moreover, Pseudomonas accelerated the transformation of Fe0 into Fe3+, which profoundly impacted PFOA transport and fate. Model results demonstrated microbe-Fe0 interaction improved retardation effect for PFOA in columns, with decreased dispersivity a (0.48 to 0.20 cm), increased reaction rate λ (0.15 to 0.22 h−1), distribution coefficient Kd (0.22 to 0.46 cm3∙g−1), and fraction f´(52 % to 60 %) of first-order kinetic sorption of PFOA in microbe-Fe0 interaction column system. Moreover, intermediates analysis showed that microbe-Fe0 interaction diversified PFOA reaction pathways. Three key metabolic pathways (ko00362, ko00626, ko00361), eight functional genes, and corresponding enzymes for PFOA degradation were identified. These findings provide insights into microbe-Fe0 “neural network-type” interaction by unveiling biotransformation and mineral transformation mechanisms for efficient PFOA treatment.

Exceptionally High Perfluorooctanoic Acid Uptake in Water by a Zirconium-Based Metal-Organic Framework through Synergistic Chemical and Physical Adsorption.

Perfluorooctanoic acid (PFOA) is an environmental contaminant ubiquitous in water resources, which as a xenobiotic and carcinogenic agent, severely endangers human health. The development of techniques for its efficient removal is therefore highly sought after. Herein, we demonstrate an unprecedented zirconium-based MOF (PCN-999) possessing Zr6 and biformate-bridged (Zr6)2 clusters simultaneously, which exhibits an exceptional PFOA uptake of 1089 mg/g (2.63 mmol/g), representing a ca. 50% increase over the previous record for MOFs. Single-crystal X-ray diffraction studies and computational analysis revealed that the (Zr6)2 clusters offer additional open coordination sites for hosting PFOA. The coordinated PFOAs further enhance the interaction between coordinated and free PFOAs for physical adsorption, boosting the adsorption capacity to an unparalleled high standard. Our findings represent a major step forward in the fundamental understanding of the MOF-based PFOA removal mechanism, paving the way toward the rational design of next-generation adsorbents for per- and polyfluoroalkyl substance (PFAS) removal.

Evaluation of ecological impacts with ferrous iron addition in constructed wetland under perfluorooctanoic acid stress

In this study, ferrous ion (Fe(II)) had the potential to promote ecological functions in constructed wetlands (CWs) under perfluorooctanoic acid (PFOA) stress. Concretely, Fe(II) at 30 mg/L and 20–30 mg/L even led to 11.37% increase of urease and 93.15–243.61% increase of nitrite oxidoreductase respectively compared to the control. Fe(II) promotion was also observed on Nitrosomonas, Nitrospira, Azospira, and Zoogloea by 1.00–6.50 folds, which might result from higher expression of nitrogen fixation and nitrite redox genes. These findings could be explanation for increase of ammonium removal by 7.47–8.75% with Fe(II) addition, and reduction of nitrate accumulation with 30 mg/L Fe(II). Meanwhile, both Fe(II) stimulation on PAOs like Dechloromonas, Rhodococcus, Mesorhizobium, and Methylobacterium by 1.58–2.00 folds, and improvement on chemical phosphorus removal contributed to higher total phosphorus removal efficiency under high-level PFOA exposure. Moreover, Fe(II) raised chlorophyll content and reduced the oxidative damage brought by PFOA, especially at lower dosage. Nevertheless, combination of Fe(II) and high-level PFOA caused inhibition on microbial alpha diversity, which could result in decline of PFOA removal (by 4.29–12.83%). Besides, decrease of genes related to nitrate reduction demonstrated that enhancement on denitrification was due to nitrite reduction to N2 pathways rather than the first step of denitrifying process.

Evaluating the efficiency of modified hydrophobic PVDF membrane for the removal of PFOA substances from water by direct contact membrane distillation

This study addresses the global issue of the contamination of water resources by per- and poly-fluoroalkyl substances (PFAS). PFAS are notoriously difficult to remove due to their resilient alkyl-fluorinated chains. We examined the potential of hydrophobic PVDF membranes in direct contact membrane distillation (DCMD) to eliminate perfluorooctanoic acid (PFOA) from Water. For desalination, both commercial and custom-made PVDF membranes exhibited a permeate flux of approximately 13 LMH, with salt rejections of 98.39 % and 99.95 %, respectively. In the case of PFOA removal, the fabricated PVDF membrane outperformed its commercial counterpart. It boasted an initial permeate flux of 16 LMH and a PFAS rejection of 95.8 %, compared to the commercial membrane's 13 LMH and 67.31 %. Furthermore, the custom membrane exhibited superior resistance to fouling, experiencing less flux decline. Employing response surface methodology (RSM), we identified the optimal combination of feed concentration (30 ppm), (60 °C), and flow rate (1.5 LPM) to yield a flux of 9 LMH and a PFOA rejection of 95.41 %. Feed temperature emerged as the most influential factor in DCMD performance. This study offers a novel approach to concentrating and removing emerging contaminants from wastewater and highlights the efficacy of tailored membrane technology in addressing pressing environmental challenges.

The Optimization of Hydrodynamic Cavitation as an Advanced Oxidation Option for the Removal of Persistent Contaminants in Wastewater

Wastewater is increasingly becoming the primary source of potable water in many cities, thanks to the development of recycling facilities. Persistent contaminants such as dyes and perfluorinated compounds from textile industries as well as other contaminants necessitate the design of removal technologies to treat wastewater to reduce these chemicals before discharge or being used as feed to a potable water plant. Several chemical treatment techniques have been reported but the most utilized advanced chemical treatments lead to high costs and further environmental concerns. This study investigated an alternative approach to wastewater treatment using a hydrodynamic cavitation pilot plant combined with a venturi as a way to remove recalcitrant compounds. The optimization of the removal process was explored by testing the effect of orifices with size 2, 3, 4, 5, or 6 mm on the decoloration of orange II dye. The impact of the catalyst: iron(II); oxidizing agent: hydrogen peroxide; and contact time was evaluated to find the ideal conditions under which the removal of perfluorooctanoic acid (PFOA) could be achieved. The decoloration of 20 ppm of orange II dye in simulated industrial textile wastewater was achieved at 90% efficiency when the pressure at the inlet was maintained at 300 kPa, the temperature at 34 °C, the pH at 2, and the orifice size at 2 mm of diameter. The kinetic study proved the decoloration reaction was pseudo first order and the rate of decolourisation of orange II was 0.23/min.Ten parts per million of PFOA could not be degraded by free radical attack using advanced oxidation processes when the inlet pressure was maintained at 300 kPa, the temperature at 34 °C, the pH of 2, and the orifice diameter of 2 mm. This resistance to removal is due to the structure of PFOA which is made up of a fluorine ion which stabilizes the compounds by inductive effects while dye is made up of nitrogen ion and is compatible with the above removal methods. The study demonstrated that the combination of venturi and orifice requires the throat size of the venturi to be similar or equal to that of the orifice for better efficiency.

Influence of water chemistry and operating parameters on PFOS/PFOA removal using rGO-nZVI nanohybrid

Graphene and zero-valent-iron based nanohybrid (rGO-nZVI NH) with oxidant H2O2 can remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) through adsorption-degradation in a controlled aquatic environment. In this study, we evaluated how and to what extent different environmental and operational parameters, such as initial PFAS concentration, H2O2 dose, pH, ionic strength, and natural organic matter (NOM), influenced the removal of PFOS and PFOA by rGO-nZVI. With the increase in initial PFAS concentration (from 0.4 to 50 ppm), pH (3 to 9), ionic strength (0 to 100 mM), and NOM (0 to 10 ppm), PFOS removal reduced by 20%, 30%, 2%, and 6%, respectively, while PFOA removal reduced by 54%, 76%, 11%, and 33% respectively. In contrast, PFOS and PFOA removal increased by 10% and 41%, respectively, with the increase in H2O2 (from 0 to 1 mM). Overall, the effect of changes in environmental and operational parameters was more pronounced for PFOA than PFOS. Mechanistically, •OH radical generation and availability showed a profound effect on PFOA removal. Also, the electrostatic interaction between rGO-nZVI NH and deprotonated PFAS compounds was another key factor for removal. Most importantly, our study confirms that rGO-nZVI in the presence of H2O2 can degrade both PFOS and PFOA to some extent by identifying the important by-products such as acetate, formate, and fluoride.

A stable, non-emulsifying, regenerable ionic liquid-based extraction system for safe removal of perfluorooctanoic acid from water

The main sources of polyfluoroalkyl substances (PFAS) in the environment are industrial plants at which PFAS are manufactured or used. PFAS are released from such plants in wastewater, which must be effectively decontaminated to prevent PFAS contaminating the environment. In this study, perfluorooctanoic acid (PFOA) was extracted from model aqueous solutions using a novel ionic liquid (IL) [trihexyltetradecylphosphonium][perfluotooctanoic acid] ([P6,6,6,14][PFOA]) without an emulsification problem. Liquid–liquid extraction using the IL removed 99.7% of the PFOA from a 2000 mg/L PFOA solution after 3–6 h of mixing. The IL was easily regenerated and reused, but some of the IL was lost after multiple extraction and regeneration cycles. Immobilization of the [P6,6,6,14][PFOA] IL in a poly(vinylidene fluoride-co-hexafluoropropylene) membrane system prevented the loss of the IL. The [P6,6,6,14][PFOA]/membrane system removed 79%–85% of the PFOA from a solution containing 100 mg/L PFOA solution after 24 h of mixing. The IL immobilized in the membrane system could be regenerated by washing the system with 0.25 mol/L NaOH and could be reused multiple times giving extraction efficiencies of 72%–77%.

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.

Application of photochemical treatments in the removal of perfluorooctanoic acid (PFOA) from aqueous solutions

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant (POP) whose harmful effects on the environment and human health, as well as its presence in different environmental matrices, have been studied. In this way, there is evidence of the presence of PFOA in wastewater, drinking water, treated water, and surface water, and in some aquatic species and human fluids such as blood. In this sense, the main objective of this research was to evaluate the potential application of different photochemical treatments in the removal of PFOA present in aqueous matrices. The effect of operational parameters such as the concentrations of the contaminant and the oxidizing agents, the type of the incident light (UV or solar), and the type of matrix were analyzed. The experimental results showed that processes such as photolysis, hydrolysis, the UV light/H2O2 and UV light/Fe2+ combinations, and the oxidation with H2O2 are not able to remove the contaminant. On the contrary, the application of photo-Fenton, solar photo-Fenton, and Fenton treatments allowed removals higher than 80.0% to be achieved. The best performance was showed by the photo-Fenton treatment under the irradiation of ultraviolet light with a wavelength of 254 nm, which conducted to the elimination of ∼99.0% of PFOA in only 60 min of reaction. Despite these findings, the results associated with the degree of mineralization of the organic matter and the toxicity (using Vibrio fischeri bacteria) of the samples indicated that it is likely that the oxidation of the contaminant leads to the formation of by-products of a much more resistant organic nature and that depending on their concentrations may also represent a risk to the human health and the ecosystems.

Study on Conventional Drinking Water Treatment for Removing Emerging Contaminants: A Literature Review

Emerging contaminants (ECs) are substances that can be synthetic or natural, or even microorganisms that are usually not monitored in the environment and could be harmful to the environment and human health. These chemicals can include pharmaceuticals, such as ibuprofen and acetaminophen, and industrial chemicals, e.g., perfluorooctanoic acid (PFOA). Common conventional drinking water treatment plants (CDWTP) are not designed to remove emerging contaminants, so these compounds can enter the water system and affect the drinking water treatment process. This study aims to focus on the performance of CDWTP in removing ibuprofen, acetaminophen, and PFOA parameters, as well as determine suitable water treatment units to eliminate these parameters from the system. An extensive literature review was conducted and further analysed using descriptive and qualitative analysis to understand the unit performance in removing emerging contaminants, followed by the simple simulation to determine the types of advanced drinking water treatment facilities that perform better in eliminating ECs. The results show that CDWTP could reduce ibuprofen concentration in water with 40%, 20%, and 36% efficiency through coagulation-flocculation, sand filtration, and disinfection, respectively. Acetaminophen removal is up to 67%, 51%, and 66.45% during coagulation-flocculation, sand filtration, and disinfection, respectively. However, PFOA removal is only up to 5%, 7%, and 2% during coagulation-flocculation, sand filtration, and disinfection, respectively. Membrane treatment technology with reverse osmosis could remove ibuprofen, acetaminophen, and PFOA compounds more effectively with removal efficiencies of 99.99%, 96%, and 100%, respectively.

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.

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.