Download or read book Per and Polyfluoroalkyl Substances PFAS Degradation by Nanoscale Zero valent Iron Under Light for Water Reuse written by Chunjie Xia and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wastewater reclamation and reuse have been increasingly practiced as sustainable strategies to meet water demands, particularly in regions threatened by water shortages. However, one of the biggest challenges for reusing wastewater effluents (WEs) as irrigation water is to remove emerging organic contaminants such as persistent and potentially bioaccumulated per- and polyfluoroalkyl substances (PFAS), whose presence may result in adverse impacts on crops, soils, aqueous ecosystems, and human health. Photocatalysis is an effective and promising technique to remediate PFAS in aqueous media. This dissertation aims to: i) Develop a novel, environmental-friendly, and low-cost treatment process for PFAS removal and degradation for water reuse; ii) Optimize the experimental conditions and investigate the removal mechanisms of PFAS with different structures in this novel process; iii) Scale up this treatment process and apply it to treatment of WEs in a point-of-use (POU) system. First, ultraviolet (UV) C /nanoscale zero-valent iron (nZVI, Fe0 nanoparticles (NPs)) system is used for the first time to induce PFAS photocatalytic removal from aqueous solution. Oxidative and/or reductive degradation of three representative PFAS - perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS) was achieved using Fe0 NPs under UVC light both with and without presence of oxygen. However, no PFAS removal was observed either under visible light and in the dark, and much lower PFAS degradation was achieved under UVA light. Higher degradation and defluorination efficiencies were obtained for longer chain PFNA compared to PFOA, and higher degradation and defluorination of PFAS were achieved without presence of O2 compared to with O2. The degradation of PFOA and PFOS followed first order reaction kinetics with the highest efficiencies achieved of 97.6, >99.9, and 98.5% without presence of O2 for PFOA, PFNA, and PFOS, respectively. The degradation efficiencies increased with the increase of nZVI concentrations in the range of 1-100 mg/L. The degradation efficiency of PFOA using bare Fe0 NPs was higher than that using 1% PVP-coated Fe0 NPs in the initial 6 h. Second, the removal mechanism of PFAS in UVC/Fe0 NPs system was obtained by testing the concentrations of iron ions (Fe2+/Fe3+), intermediate products, and reactive oxygen species (ROS, e.g., ·O2- and ·OH) generated, and conducting ROS quenching experiments. The proposed degradation pathway of PFCAs (PFNA and PFOA) was initiated from PFOA/PFNA oxidation by transferring an electron of the carboxylate terminal group of PFOA/PFNA to the Fe(III)-carboxylate complex, then followed by decarboxylation−hydroxylation−elimination−hydrolysis (DHEH) pathway and the accompanying CO2 and F− release. The generated shorter chain PFCAs also underwent degradation with time in the system. This proposed degradation pathway was confirmed by the formation of shorter chain PFCAs, e.g. PFHpA, PFHxA, PFPeA, and PFBA, F- ions, and rapid consumption of Fe3+. For PFOS, besides H/F exchange pathway and chain-shortening (DHEH pathway) to form short chain PFAS during PFCA degradation, desulfonation to form PFOA followed by PFOA degradation also happened. These pathways were suggested by the formation of intermediates -- trace amount of shorter chain PFCAs, 6:2 FTS, PFHpS, and F- ions. ·O2- and ·OH were not involved in PFOA degradation in the UVC/Fe0 NPs system with presence of O2, while they may be involved in PFOS degradation, e.g., desulfonation to form PFOA, which were suggested by the results of quenching experiments. And introducing H2O2 into the UVC/Fe0 NPs system resulted in lower PFOA degradation efficiency and defluorination efficiency, which also indicated that ·OH may not be involved in PFOA degradation. Hydrated electrons e-aq that can be involved in desulfonation, defluorination, and C-C bond scission processes were likely quenched by the presence of oxygen to reduce the degradation and defluorination efficiencies; plus, presence of Fe0 NPs may promote the generation of hydrated electrons. Last, UVC/Fe0 NPs system was used to degrade PFAS from WEs in both bench scale and in a scale up POU system. The degradation efficiencies of PFAS in WEs from both wastewater treatment plants (WWTP) were lower than that in deionized water, likely reflecting the complex compositions in the environmental media. Optimal degradation efficiencies of 90±1%, 88±1%, and 46±2% were obtained for PFNA, PFOS, and PFOA, respectively, each starting from 0.5 μg/L using bare Fe0 at pH 3.0 after 2 h. PFAS removal and bacterial inactivation were achieved simultaneously in the POU system using Fe0 NPs without and with rGO support under UVC irradiation in WEs, although the PFAS levels were still above the regulation levels for discard. These pilot tests provided more data and experiences for the real applications of UVC/Fe0 NP system to PFAS contaminated wastewater or other water matrix treatment.Overall, this research demonstrated a cost-effective and environment-friendly method -- UVC/Fe0 NPs method for PFAS (i.e., PFOA, PFNA, and PFOS) degradation from WEs for water reuse both with and without presence of oxygen. The possible degradation mechanisms of PFAS with different structures were obtained by testing the concentrations of iron ions, intermediate products, and reactive oxygen species (ROS) involved in the reactions. The developed technology can be potentially applied to treat other environmental media (e.g., groundwater, landfill leachate) that are contaminated by PFAS from previous anthropogenic activities.

Download or read book Remediation of Per and Polyfluoroalkyl Substances and Comingled Chlorinated Solvents Using Reduced Graphene Oxide nanoscale Zero valent Iron written by Sushmita Regmi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lack of biodegradability of PFAS, or per- and polyfluoroalkyl substances, is due to the presence of many strong carbon-fluorine bonds. Two common PFAS that are found in the environment are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). This work first studied an innovative pathway for PFAS removal through the adsorption of PFOA and PFOS (pre-concentrating the contaminants) by nanoscale zero-valent iron/reduced graphene oxide (rGO-nZVI) and their subsequent degradation via photocatalysis under UVC light. The GO that was later reduced in nanohybrid production was made utilizing a modified Hummer's method. The rGO-nZVI nanohybrid was prepared for the first time via thermal reduction at high temperatures. Additionally, the nanohybrid was prepared using the wet chemistry method for comparison. LC/MS/MS analysis was conducted to determine the adsorption efficiencies for PFOA and PFOS using the nanohybrids and their successive removal under UVC light. Chlorinated hydrocarbons are another group of contaminants of concern that should be removed from the subsurface due to their harmful effects. In this study, a more complex mixture of the contaminants including PFAS and chlorinated hydrocarbons was investigated, which is usually found in the superfund and other contaminated sites. Considering the effectiveness of nZVI to remove chlorinated hydrocarbons from the subsurface, engineered nZVI coupled with rGO was utilized to enhance the removal efficiency of the mixture of contaminants, i.e., PFAS comingled with chlorinated hydrocarbons. The synthesized rGO-nZVI nanoparticle showed high adsorption efficiencies for both PFOA and PFOS, i.e., removal of 55.3%, 98.2%, and >99.9% of PFOA of 10, 1, and 0.1 mg/L, and 94.9%, 97.6%, and 85.0% of PFOS of 10, 1, and 0.1 mg/L, respectively, in 3 h. Later degradation of pre-concentrated PFAS under UVC light was also achieved. Using extracted rGO-nZVI, 55.1%, 77.6% of preconcentrated PFOS was degraded starting from 10, and 1 mg/L of initial concentrations before adsorption in the photoreactor at the end of 24 h. In comparison, 68.5% and 47.2% of PFOS and PFOA (starting from 1 mg/L each) was degraded, respectively, using rGO-nZVI directly under UVC light after 24 h. Moreover, it was found that rGO-nZVI had high adsorption capacity of 69.4% and 68.7% respectively for TCE and PFOA in a mixture of these contaminants. Under UVC irradiation, the preconcentrated mixture of TCE and PFOA were both degraded to below the detection limit in 21 h. It was also found that PFOA concentration dropped by 64.3% at 5 h and by 88.7% at 24 h by fresh rGO-nZVI in presence of 10 mg/L TCE. Short-chained PFCAs like PFHpA and PFHxA were found as the intermediates for PFOA degradation using rGO-nZVI under UVC light. Also, under UVC irradiation of a mixture of TCE and PFOA, TCE degradation was supported by the formation of intermediates during the reaction. Because of its composition, photocatalytic activity, large surface area, magnetic properties, and environmental friendliness, the thermal reduced rGO-nZVI particle demonstrated its potential to successfully remove PFAS and comingled chlorinated hydrocarbon from pre-concentration followed by degradation under UVC light. The nanohybrid is promising to be used to repair PFAS-contaminated water bodies.

Download or read book Development of Reductive oxidative Treatment Strategy for the Removal of Per and Polyfluoroalkyl Substances PFAS in Water written by Akshay Chandrashekar Parenky and published by . This book was released on 2020 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The detrimental health effects of halogenated compounds in humans has been well documented, and the frequent occurrence of per- and polyfluoroalkyl substances (PFAS)in the water environment is a recent global concern. Feasible and sensible treatment strategies are in dire need for environmental remediation and water treatment. Currently, efficient treatment is only obtained at a small scale and at a high energy cost. This research is presented in three subsections, where decomposition of selected PFAS was evaluated under advanced oxidation techniques. The first study involved decomposition of a polyfluoroalkyl substance, 6:2 fluorotelomer sulfonate (6:2 FTS), in which 2 carbons of the alkyl chain are hydrogenated making the molecule more vulnerable to degradation. The 6:2 FTS was tested against some of the common oxidants such aspersulfate (PS), peroxymonosulfate and hydrogen peroxide. Interestingly, 6:2 FTS was degraded by PS alone under ambient conditions. Several byproducts and fluoride release were observed and quantified. A decomposition pathway was proposed, and certain reaction intermediates were identified. Upon achieving successful degradation of 6:2 FTS, a highly oxidized perfluorinated compound, perfluoroctanesulfonic acid (PFOS) was investigated. The absence of C-H bonds makes the molecule more resilient to conventional oxidation, hence a synergistic approach of using reduction combined with advanced oxidation was envisioned. This strategy involved the use of electrons generated by zero valent iron as the reductive source in combination with highly reactive radical species such as sulfate radical and hydroxyl radicals as the oxidizing species. This combination of oxidation and reduction was evaluated under several conditions by changing factors such as concentration, pH, and temperature. Significant removal of PFOS was observed in most cases but no transformation was observed. However, when this system was tested for perfluorooctanoic acid (PFOA), decomposition byproducts were observed consisting of short chain compounds demonstrating the potential for this treatment strategy. Although decomposition of PFOA was achieved through the synergistic approach, the constraints of heat requirement reduce the practical applicability of the system. Since oxidants can be activated efficiently by transition metals, several different combinations of metal-oxidants were evaluated. Amongst these combinations, silver-PS was successful in decomposing a variety of carboxylic PFAS under ambient conditions without the use of any external energy source such as heat, ultra-violet or microwave. Significant byproduct and fluoride release were observed upon decomposition of selected PFAS. This system shows great potential for in situ application of PFAS remediation. The reaction mechanism for the system is complex and future studies should: i) investigate the role of silver and identify the reactive species responsible for the reaction, ii) identify an appropriate metal-oxidant pair capable of decomposing sulfonic PFAS, and iii) evaluate the efficacy of these systems for a wider range of PFAS.

Download or read book Oxidative Degradation of Organic Contaminants Using Nanoscale Zero valent Iron written by Sung Hee Joo and published by . This book was released on 2005 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of the Removal of Perfluoroalkyl Substances from Aqueous Matrices in the Presence of Zerovalent Iron written by Janis Rachel Baldwin and published by . This book was released on 2018 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Per- and polyfluoroalkyl substances (PFASs) are a class of persistent organic pollutants present in the environment that pose a threat to human health. PFASs primarily reside within aqueous phases and are present in groundwater environments. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most predominant PFASs. Remediation techniques focus on oxidation and sorption methods, both of which lack efficacy for all PFASs. There are few studies on reduction treatments such as zerovalent iron (ZVI), which demonstrate potential for both PFOS and PFOA removal and can be applied in subsurface environments. This thesis describes laboratory batch experiments that evaluate PFOS and PFOA removal in the presence of ZVI under a range of physical and geochemical conditions. Mechanisms of removal are explored utilizing PFAS mass balances based on a series of analyses that include aqueous phase fluoride and PFAS short chains, and PFAS extractions from the iron surface. Solid iron phase characterization provides supporting information regarding PFAS interaction with the iron surface. Laboratory batch experiments with PFOS in the presence of granular ZVI were conducted under combinations of initial pH (pH 2.0 and 6.6), temperature (~22°C and 60°C) and ZVI dosage (179 and 1792 mM). PFOS removal was enhanced under low initial pH likely due to a greater abundance of iron oxides compared to higher pH conditions. Higher temperatures also enhanced PFOS removal. PFOS removal by sorption generally increased under low pH and high ZVI dosed conditions, suggesting the abundance of iron oxides and surface area may play an important role. Laboratory batch experiments of PFOS and PFOA in the presence of zerovalent iron nanoparticles (nZVI) were conducted under combinations of initial pH (pH 2.0 and 8.3) and coating (uncoated and palladium-coated). The iron phase likely changed over time, as there was some release of PFOS and PFOA into aqueous solution compared to earlier sampling times. The presence of a palladium coating appeared to minimize the effects of iron corrosion, as PFOS and PFOA were released to a lesser degree at later time points compared to uncoated nZVI. PFOS and PFOA removal is likely dominated by electrostatic interaction, however functional group interaction with the iron surface may also play an important role.

Download or read book Accelerated Degradation of Chlorinated Solvents by Nanoscale Zero Valent Iron Coated with Iron Monosolfide and Stabilized with Carboxymethyl Cellulose written by Shirin Ghahghaei Nezamabadi and published by . This book was released on 2016 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoscale zero-valent iron (nZVI) injections have proven to be a promising approach for the remediation of aquifers contaminated by chlorinated organic pollutants. This study compares the efficacy of nZVI in sulfidated and unamended forms in degrading selected chlorinated hyrocarbons (CHCs). Results show that nZVI amended with iron monosulfide (FeS) increases the rate of dechlorination of CT, CF and 1,1,1-TCA compared to that by unamended nZVI. The focus of this research was to characterize degradation kinetics and degradation byproduct distributions of CT, CF and 1,1,1-TCA by nZVI coated by iron monosulfide, which is represented as nZVI/FeS. To prevent nZVI particles from agglomerating, carboxymethylcellulose (CMC) was used as a stabilizer in all experiments. Results indicated that the nZVI/FeS system was faster and produced less toxic byproducts than nZVI for all CHCs studied. a-elimination in nZVI/FeS system was an important degradation pathway for CF and 1,l,1-TCA: it produces reactive carbene intermediates capable of degrading into benign products such as methane, ethane, and ethene. The effect of sulfide loading on degradation was evaluated with all CHCs studied. Regardless of CHC type, the rate constant (kobs) increased with increasing sulfide loading, reaching the highest amount at 1 wt% sulfide, and then decreased with higher sulfide loading. An additional study focused on the effects of varying of the concentration of nZVI and CMC, and particle longevity on the degradation of 1,1,1-TCA in the nZVI/FeS system with 1 wt.% sulfide. Particle longevity experiments showed that reactivity with 1,1,1-TCA decreases as particles age. nZVI/FeS particles showed a rapid power function decline in reactivity with time. Increasing the amount of iron-reducing chemical during nZVI/FeS synthesis improved reactivity by 43%. The addition of a polyelectrolyte stabilizer at an optimized concentration of 4.0 g/L further increased nZVI/FeS reactivity by 350%. nZVI/FeS shows great potential for treating certain CHCs.

Download or read book Degradation of Per and Polyfluoroalkyl Substances with Nonthermal Plasma in a Gas Liquid Film Reactor written by Rachel Olivia Gallan and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perfluorinated carbons are hazardous molecules that have contaminated ground water systems and become a prevalent environmental issue. One group of perfluorinated carbons is a class of molecules referred to as per- and polyfluoroalkyl substances (PFAS), which have been used for decades in applications such as firefighting foams, waterproof coatings, nonstick cookware, carpets, and many others. The wide use of PFAS has led to their large accumulation in the environment. Due to this accumulation and the release into the aquifer, PFAS has become a concern in most water purification systems. Recently developed methods to degrade PFAS include advanced oxidation and reduction techniques such as photocatalysis, sonolysis, electrochemical reduction, and nonthermal plasma. Our work focuses on the degradation of PFAS with nonthermal plasma. Two example PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are not only major pollutants but they are often used as model PFAS compounds, and they are the focus for this work. In this study, we use a nonthermal plasma reactor with flowing liquid and gas phases and a nanosecond pulsed power supply to degrade PFAS compounds in water. The plasma is generated with a pulsed power supply capable of variation of the input voltage, frequency, and pulse width. Through changing the input electrical pulse forming properties, we can change the plasma characteristics such as electron density, electron energy, and plasma gas temperature. The non-thermal plasma generates many different reactive chemical species such as OH, H, e-, and eaq- that may degrade PFOA and PFOS. This work shows that PFOA and PFOS are degraded into several daughter products of smaller carbon chains, and mineralization products including carbon dioxide and fluoride (F-). This work shows that PFOA and PFOS degradation are affected by concentration and pulse frequency. PFOA and PFOA are surfactants and have large surface activities. Higher surface activity leads to higher degradation and mineralization because of increased adsorption at the interface where the plasma occurs. The input frequency of the power supply changes the plasma properties and therefore PFOA and PFOS were shown to have maximum degradation percentages of 89.6% and 96%, respectively, at 2 kHz frequency. Because the degradation is dependent on initial concentration and the input frequency, these setting can be used to optimize the reactor. For comparison with other methods, the values of energy yield and EE/O are used to describe the system efficiency. Energy yield is the molar amount of the compound degraded or produced (depending on the target compound) per joule of energy. EE/O is the amount of energy used per volume per log order reduction of contaminant. The best-case energy yield and EE/O values are 6.61x10-10 mol/J and 2.5 kWh/m3(order) for PFOA and 6.691x10-10 mol/J and1.7 kWh/m3(order) for PFOS, which are better or comparable to the best reported methods for PFAS degradation. Ground water and leachate samples from field sites were treated to demonstrate the applicability of the reactor. The ground water towards the higher chain compounds, and will degrade them in order of decreasing chain length. PFOA mass transfer and reaction rates were modeled in the reactor to analyze the factors affecting the frequency and concentration effects. The model shows that the upper limit of PFOA degradation is likely mass transfer limited, but it fails to show the drop-in degradation with increasing frequency or the shift in optimal degradation with decreasing concentration.These results are encouraging for the practical application of this plasma reactor in real world remediation processes. This study furthers the understanding of non-thermal degradation of PFAS, and leads to its future use in water purification systems.

Download or read book Assessment of Water Treatment Technologies for Per and Polyfluoroalkyl Substances PFAS in Multiple Matrices written by Vanessa Maldonado and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ubiquitous presence of per-and polyfluoroalkyl substances (PFAS) in the environment resulted in extensive water contamination that poses a significant risk to human health and biota. Continuous research efforts aim to develop efficient treatment technologies to treat PFAS in water, break the PFAS accumulation cycle in the environment, and improve the efficiency of emerging technologies. In this thesis work, selected treatment technologies including electrochemical oxidation and dielectrophoresis-enhanced adsorption were used to assess and advance the state-of-the-art for PFAS remediation in multiple matrices, not previously addressed.A boron-doped diamond (BDD) flow-through cell was used to evaluate the electrochemical oxidation of perfluoroalkyl acids (PFAAs) in landfill leachates. Multiple leachates with a concentration of individual PFAAs in the range of 102 -104 ng/L were treated. The effect of current density and variability of the composition of leachates was investigated. Non-detect levels and >90% removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were reached for all leachates tested after electrochemical treatment. Although high removal efficiencies for long-chain PFAAs were obtained, high concentrations of short-chain PFAAs were generated and associated with the transformation of perfluoroalkyl acid (PFAA) precursor compounds.In the second part of this thesis research, the oxidative transformation of PFAA-precursors typically present in leachates was addressed for the first time. Target and suspect PFAS were identified in a landfill leachate and their concentrations during electrochemical treatment were quantified over time. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF) measurements of the leachate identified 53 PFAS compounds and 19 PFAS classes. Multiple PFAS were reported for the first time in landfill leachates. The evaluation of the intermediate and final products generated during the electrochemical treatment showed evidence of known electrochemical degradation pathways.Coupling destructive technologies (e.g., electrochemical oxidation) with concentration technologies (e.g., ion exchange (IX), adsorption) in a treatment train approach could reduce the treatment cost of destructive technologies and increase their feasibility. Therefore, in the next part of this work, electrochemical oxidation of PFAAs from the concentrated waste of IX still bottoms was assessed at laboratory and semi-pilot scales. The concentrated waste resulted from the treatment of PFAAs-impacted groundwater with IX resins. Multiple current densities were evaluated at laboratory scale and the optimum current density was used at the semi-pilot scale. The results at the laboratory and semi-pilot scales allowed for >99% and >94% removal of total PFAAs with 50 mA/cm2, respectively. Defluorination values, energy consumption, and implications were discussed.The third matrix addressed for PFAS remediation was drinking water. Dielectrophoresis-enhanced adsorption was used for the removal of low concentrations of PFOA. This study introduced a coaxial-electrode cell (CEC) that allowed for the generation of a non-uniform electric field to enhance the adsorption of PFOA. Experiments were performed in batch and continuous-flow modes. The dielectrophoretic-enhanced adsorption in batch mode resulted in a 4, 7, and 8-fold increase in the removal of PFOA with 5, 25, and 50 V when compared to adsorption only. The performance of the CEC in continuous-flow mode allowed for an increase of up to 2.4-fold in the PFOA removal with 25 V. The results highlighted the benefits of using a dielectrophoresis-enhanced adsorption process for the removal of PFOA from water. Overall, results from this thesis contribute to the understanding of the electrochemical degradation of PFAS in multiple matrices and introduce an alternative process to enhance the widely used adsorption technology for PFAS removal. Treatment implications of each matrix are discussed and provide a clear baseline for future research, development, and scale-up of treatment technologies for PFAS remediation.

Download or read book Destruction of PFOA on Ion exchange Resin with Advanced Reduction Processes to Regenerate Resins for Addressing PFOA Pollution in Drinking Water written by Junkui Cui and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Per- and polyfluoroalkyl substances (PFAS) have been globally incorporated into various industrial and consumer products since the 1940s. However, concerns about PFAS have gradually grown because of their prevalence, mobility, persistence, bioaccumulation, and adverse impacts on human and environmental health. Unfortunately, traditional water treatment processes inefficiently remove PFAS. Therefore, there is an urgent research need to develop innovative, technically viable, and low cost-treatment processes for the removal of PFAS in water. Among the established PFAS treatment technologies, ion-exchange (IX) has been extensively applied to drinking water treatment practices due to its adsorption capability and technology maturity. However, IX is highly cost-inefficient and environmentally unfriendly because of the expenses associated with off-site regeneration, no PFAS detoxification, and the production of harmful PFAS-containing regenerant waste required for careful disposal. In contrast, advanced reduction processes (ARPs) have demonstrated technical viability for PFAS degradation due to the powerful reducing potential of hydrated electron (eaq−) generated. Nevertheless, ARPs are restricted in realistic water treatment, particularly drinking water treatment, due to increased total dissolved solids in effluent, operational requirements in pH adjustment, and depletion of dissolved oxygen. The primary objective of this dissertation is to advance the fundamental understanding of the interactions of eaq − and PFAS-laden IX resins, thereby providing a scientific basis for the development of an innovative on-site ARP-based IX resin regeneration method capable of recovering spent resins and degrading PFAS in drinking water treatment. Specifically, the design comprises repeated IX adsorption - ARP regeneration phases. In the first adsorption phase, trace PFAS in water is captured by IX resins until saturation. Subsequently, ARPs are launched to decompose PFAS laden on the resins for adsorption recovery before reuse. In the dissertation research, perfluorooctanoic acid (PFOA) was chosen as a model PFAS species owing to its prevalence in the aquatic environment, while ultraviolet (UV)/sulfite was selected as the representative ARP to generate eaq −. Five tasks were sequentially completed in this dissertation to achieve the primary objective. In Task 1, a critical review of the destruction of aqueous PFAS with ARPs was conducted to retrospect the state-of-the-art knowledge on the emerging PFAS treatment technology and identify the critical knowledge gaps toward applications to drinking water treatment. In Task 2, bench-scale tests were performed to screen for a potentially durable resin to demonstrate the technical feasibility of eaq −-driven ARPs for mitigation and degradation of PFAS laden on resins. Specifically, IRA67 resins were selected among eight commercially available resins for the subsequent dissertation studies because of their excellent PFOA adsorption capability and durable physical/chemical properties for consistently high PFOA. In Task 3, bench-scale tests were carried out to elucidate the interactions of eaq− and PFOA sorbed on the PFOA/NOM-laden IRA67 resins and assess the role of NOM co-sorbed on the IX resins in the proposed PFAS treatment approach. Results showed that PFOA, regardless of sorbed or aqueous states, could be effectively degraded by eaq−. However, UV/SO32− ARP treatment could not effectively decompose co-sorbed NOM to substantially recover the resin adsorption effectively. The buildup of NOM on the resins finally led to the loss of the resin capacity for capturing PFOA in water with the increasing cycle number. Therefore, two pretreatment strategies (i.e., coagulation and UV/hydrogen peroxide (H2O2)-based advanced oxidation process (AOP)) were assessed in Task 4 to alleviate NOM loading on PFOA/NOM-laden IRA67 and to evaluate the effect of pH on desorption of co-sorbed NOM during the IRA67 regeneration processes, respectively. Moreover, the optimized cyclic adsorption-regeneration tests combined with the NOM mitigation strategies were evaluated for the repeated removal of PFOA in water. Results showed that alum coagulation at the optimized operational conditions (i.e., alum 60.0 mg/L; pH 6.0) significantly alleviated the NOM loading on IRA67, but the UV/H2O2-based AOP could not further reduce the PFOA loading on IRA67. The continuous adsorption of PFOA by IRA67 in the cyclic adsorption-regeneration process was ascribed to NOM desorption at pH 10.0 during the ARP regeneration process to release more occupied sites on IRA67. Therefore, the UV/SO32− process operated at an alkaline condition, if jointly used with alum coagulation as a pretreatment step, can enable a promising on-site regeneration process for the PFOA/NOM-laden IRA67 in drinking water. The information will be input to Task 5 in which the implications of the proposed ARP-based resin regeneration technologies were discussed in terms of economic, environmental, and social aspects, major conclusions were summarized, and future research directions were identified. The dissertation builds a basis for an innovative ARP-enabled on-site IX regeneration approach to PFAS pollution in drinking water treatment. The resin adsorption capacity can be substantially recovered, accompanied by the PFAS degradation and the production of a small volume of easily managed regenerant waste.

Download or read book Effect of Zero Valent Iron and Chemical Interactions by Trichloroethene on Perchlorate Biodegradation in Contaminated Groundwater written by Kun Yang and published by . This book was released on 2007 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sorption mediated Chemical Processes for the Versatile Treatment of Per and Polyfluoroalkyl Substances PFAS in Complex Media written by Naomi Gevaerd de Souza and published by . This book was released on 2022 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, per- and polyfluoroalkyl substances (PFAS) have gained notoriety due to environmental and health concerns. These molecules are chemically stable which contributes to their persistence in biological systems and their increased detections in surface waters. Treatment of highly persistent PFAS has been a challenging but significant task. The most practical technique for removal of PFAS is through adsorption onto granular activated carbon (GAC) or other novel materials. Meanwhile, PFAS are resistant to simple oxidation, and although decomposition of specific PFAS has been reported through advanced oxidation technologies, often energy-intense technologies capable of generating electrons such as ultraviolet radiation, microwave, or high temperatures are required when coupled with an oxidant to generate highly reactive radical species. The use of such technologies increases the cost and lowers its practical applicability. Hence, in an effort to develop a practical treatment technology, an adsorption-based decomposition technology was envisioned. The high surface area of GAC poses a unique opportunity of housing reactive materials inside the pores. To achieve this, zero valent iron (ZVI), previously demonstrated to reductively delahogenate other persistent pollutants, was incorporated into the pores of the GAC, so called reactive activated carbon (RAC). Additionally, to generate highly oxidizing radical species per sulfate (PS) was injected. Hence, once PFAS are encapsulated inside the pores, a combination of both reductive and oxidative species is present in close proximity to decompose the much recalcitrant PFAS. To demonstrate its effectiveness and understand its behavior, 6 PFAS of different functional groups and carbon chain lengths were investigated. An adsorption isotherm was first developed to test the affinity of the selected GAC. Then, the effects of reaction temperature, injection of PS, and presence of soil on removal of PFAS in water by RAC were evaluated. Results showed that RAC conjugated with PS at 60 °C exhibited decomposition of PFAS, exclusively all 3 carboxylic PFAS tested, obviously producing various identifiable short chain PFAS. Carboxylic PFAS were removed via physical adsorption combined with chemical decomposition while sulfonic PFAS were removed via solely adsorption mechanism. The presence of soil particles did not greatly affect the overall removal of PFAS. Carbon mass balance suggested that chemical oxidation by radical mechanisms mutually influences, in a complex manner, PFAS adsorption to GAC, ZVI and its iron derivatives, and soil particles. Nonetheless, all tested 6 PFAS were removed significantly. If successfully developed, the adsorption-mediated decomposition strategy may work for treatment of complex media containing PFAS and co-contaminants under different environmental settings. Future studies are required, to ensure the decomposition of PFAS exclusively inside the pores of RAC, additionally the synthesis of RAC containing different types of reactive metals and oxidants should be investigated. Pilot scale studies should also be conducted to simulate treatment beds and evaluate the effectiveness of the system.

Download or read book Per and Polyfluoroalkyl Substances PFAS Resources for Small Public Water Systems written by Drinking Water Program (Mass.) and published by . This book was released on 2021 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Degradation of 1 2 Dichloroethane with Nano scale Zero Valent Iron Particles written by Ambareen Atisha and published by . This book was released on 2011 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxidative Transformation of Perfluoroalkyl and Polyfluoroalkyl Substances PFAS written by Eniola Oye-Bamgbose and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Perfluoroalkyl and Polyfluoroalkyl substances (PFAS) are anthropogenic chemicals with unique properties and wide applications in industrial and consumer products. However, studies have shown that the once highly valued PFAS are persistent pollutants, ubiquitous in the environment, and are developmental and reproductive toxins. To meet the stringent drinking water guidelines for PFAS, technologies that can destroy PFAS are urgently sought for. As multiple carbon-fluorine bonds render many conventional destruction processes ineffective, advanced oxidation-based treatment methods are some of the very promising methods for the destruction of PFAS in contaminated environmental matrices. Nevertheless, if effective oxidation-based treatment methods are to be developed, it is essential to know all the transformations PFAS can undergo during oxidation. This thesis focused on PFAS oxidation with and without the addition of external oxidants divided into two studies. The first study focused on the non-additive oxidation and degradation of perfluorooctanoic acid (PFOA) using nonthermal plasma, and the second on the additive oxidation of unknown PFAS using persulfate-based total oxidizable precursor assay.The first study was centered on plasma-based water treatment of perfluorooctanoic acid, which relies on only an electrical discharge to convert water and gas molecules to a mixture of highly reactive oxidative species. The objective was to achieve a complete mass balance of PFOA after treatment by performing a total fluorine mass balance analysis. A 16 [mu]M PFOA solution was treated with a nonthermal plasma generated in nanosecond long pulses. After 30 min of treatment, a 42% reduction in PFOA concentration was achieved. The degradation of PFOA also led to the generation of shorter chain perfluorocarboxylic acids. Specifically, 0.08 [mu]M of perfluorobutanoic acid, 0.2 [mu]M of perfluoropentanoic acid, 0.5 [mu]M of perfluorohexanoic acid, 1.5 [mu]M of perfluoroheptanoic acid and 9.1 [mu]M of free fluoride ions were produced. Total fluorine mass balance analysis using combustion ion chromatography suggested that in addition to the measured degradation products, other unmeasured compounds possibly such as gaseous fluorinated products, trifluoroacetic acid, and perfluoropropionic acid were also produced. In the second study, conventional uses of persulfate oxidation process, which degrades selected PFAS under very restrictive conditions, was repurposed for the measurement of many unidentifiable PFAS, through the total oxidizable precursor assay. The study was aimed at investigating how the presence of co-contaminants affects PFAA precursor oxidation and finding solutions to improve precursor oxidation during the assay. Seventy aqueous film-forming foam impacted groundwater samples received from Environment and Climate Change Canada were subjected to the assay. Initial analysis of the groundwater samples showed a diverse range of PFAS levels with the maximum sum of concentrations measured to be 2.33 mg/L, and several PFAA precursors were detected. The results after oxidation showed a direct correlation between matrix complexities (i.e. the presence of co-contaminants) and the extent of PFAA precursor oxidation. There was incomplete oxidation of PFAA precursors in samples with a high concentration of co-contaminants. The implementation of a previously developed clean-up procedure improved precursor oxidation during TOP assay by an average of +52%.To further investigate how the presence of co-contaminants affect PFAA precursor oxidation during the TOP assay, mixtures of 6:2 FTSA or 6:2 FTAB and natural organic matter were prepared respectively. Only at low and intermediate COD levels of no more than 230 mgO2/L, 100% loss of the precursors can be largely accounted for by the generation of C3-C7 PFCAs. The results showed that the presence of co-contaminants in TOP assay not only affects the oxidation loss of precursors but also the type of products generated"--

Download or read book Investigation of the Efficacy of in Situ Degradation Methods for Perfluorooctanoic Acid PFOA and Perfluorooctane Sulfonic Acid PFOS in Groundwater written by Janice Marie Cooper and published by . This book was released on 2018 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Per- and polyfluoroalkyl substances (PFASs) are a group of emerging contaminants that include perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). PFASs can be released into groundwater through the application of fire-fighting foam, or effluent from industrial locations, wastewater facilities, and landfill leachate. Human exposure to PFASs should be limited due to the potential for human health implications; PFOA and PFOS are linked to liver, gastrointestinal, and thyroid toxic effects. Removal of PFASs from aqueous solutions can occur through capture, oxidation, reduction, or thermolysis. One of the most popular recent methods for the removal of aqueous PFOA in groundwater is thermally-activated persulfate. The goals of this thesis were to (1) evaluate the performance of a fluoride-selective electrode (FSE) in different matrix combinations that were representative of in situ groundwater remediation activities (2) investigate the removal of PFOA and PFOS with the addition of permanganate to thermally-activated or ambient persulfate, and (3) compare the removal of PFOA by thermally-activated or ambient persulfate in different sediment-slurry experiments. A systematic investigation of the impacts of oxidant-based reagents and a quenching agent, aqueous geochemistry, and the presence of sediments was conducted for the FSE, in order to provide guidance on the use of this analytical tool. The hypothesis was that the quantification of fluoride (F-) using an ultrapure water calibration curve would be inaccurate in some of the combinations tested. Using matrix spike recovery and electrode slope measured in the various matrices as indicators, permanganate, ascorbic acid, and sediments were flagged as components of concern. While either a matrix-matched calibration curve or the standard addition method could be used for samples containing permanganate, the presence of sediments or ascorbic acid should be avoided for F- quantification with the FSE. Matrix spike recovery was within the acceptable bounds defined by the USEPA, and the electrode slopes were consistent with the slope of the calibration curve in the presence of persulfate and in different geochemical aqueous phases. The impact of adding permanganate to both thermally-activated (60 °C) and ambient (20 °C) persulfate treatment systems for the removal of PFOA and PFOS was investigated using a 1:100 molar ratio of permanganate: persulfate. It was hypothesized that permanganate, or the manganese dioxide produced from permanganate in the presence of water, might be able to activate persulfate. Sacrificial, aqueous batch reactors prepared in the laboratory were used in this experiment. Analysis was conducted for pH using a pH probe, aqueous F- using the FSE, and aqueous PFASs using solid-phase extraction preparation and liquid-chromatography tandem mass spectrometry. PFASs with carbon chain lengths from four to eight were quantified. PFOA was successfully removed (> 99 %) in the thermally-activated persulfate with permanganate (dual-oxidant) and thermally-activated persulfate systems in both ultrapure and sodium bicarbonate simulated groundwater after seven days. Both short-chain PFCAs and aqueous F- were generated and indicated that PFOA was degraded in these experiments. The removal of PFOA was not evident in the ambient dual-oxidant and heated permanganate systems. The mass balance calculations for the PFOA systems accounted for nearly all of the initial PFOA (81 - 142 %). There was no indication of removal of PFOS by any combination of oxidants, and no degradation products were generated. Removal of PFOA or PFOS was not improved in the thermally-activated or ambient persulfate systems with the addition of permanganate at the tested ratio. The challenges for the implementation of thermally-activated persulfate for the removal of PFOA in groundwater settings include the interaction of persulfate and PFOA with the aquifer sediments. The hypothesis of this experiment was that PFOA would be removed and converted into PFCAs and F- with thermally-activated persulfate treatment, even in the presence of sediments. The removal of PFOA by thermally-activated (60 °C) persulfate (50 mM, 9.6 g L-1) was compared using three different sediments in sacrificial sediment-slurry batch reactors. For each reactor, pH, aqueous F-, and aqueous PFCAs were determined, similar to the dual-oxidant experiment. In addition, liquid-solid extraction was used to quantify the sorbed PFASs in the solid phase. At least 60 % of the initial PFOA was removed after seven days in all three sediment slurries using thermally-activated persulfate. Removal of PFOA in all slurry reactors was lower than in aqueous reactors (99 % after 7 days). The detection of degradation products (short-chain PFCAs and F-) was also altered in sediment slurries compared to aqueous reactors. Short-chain PFCAs were retained within the systems longer when sediments were present. The decreased amount of PFCA removal led to the production of less F-. Furthermore, less F- could be measured in the sediments with high carbonate or organic carbon content. PFOA was extracted at higher concentrations from the sediment with the highest organic carbon content under acidic pH conditions. No removal of PFOA was measured under ambient persulfate treatment conditions. Thermally-activated persulfate was still effective for the removal of PFOA from soil-slurry reactors, but at decreased removal efficiency. Thermally-activated persulfate can be considered as a potential remediation method for use in the removal of PFOA in groundwater settings. At the ratio tested, permanganate did not improve the effectiveness of persulfate under thermally-activated or ambient conditions. However, the investigation of a wider range of persulfate to permanganate ratios could provide further information. PFOS removal was not observed in thermally-activated or ambient persulfate treatment conditions. The quantification of degradation products, such as short-chain PFASs and F-, should be included in the analytical suite for any PFAS degradation project. The FSE is a valuable tool for the measurement of aqueous F- concentrations.

Download or read book Spatial and Temporal Patterns of PFAS Occurrence at a Wastewater Beneficial Reuse Site in Central Pennsylvania written by Olivia Mroczko and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Per- and polyfluoroalkyl substances (PFAS) is a collective name for a growing range of synthetic fluorinated compounds that have been produced to enhance both consumer and industrial products since the 1940s. Due to their chemical composition, PFAS do not easily degrade and can persist in the environment, negatively impacting ecosystem and human health. With recent advances in analytical technology, the fate and transport of PFAS in the environment is becoming better understood, as are the risks they pose to human and environmental health. Because PFAS persist in treated wastewater, reusing wastewater effluent as an irrigation source can inadvertently introduce PFAS into agroecosystems. The Pennsylvania State University has been spray-irrigating all of its treated wastewater at a site known as the "Living Filter" since the early 1980s. The site contains ~250 ha of mixed use agricultural and forested land and 13 monitoring wells. To understand the effects of this long-term irrigation on the occurrence and the spatial and temporal patterns of PFAS at the site, groundwater water samples were collected bimonthly from October 2019 to February 2021 from the wastewater influent and effluent and from each of the groundwater monitoring wells, with all samples analyzed for 20 PFAS compounds. Additionally, crop tissue samples were collected at the time of harvest for corn silage and fescue to determine the potential impacts of spray-irrigation activities on PFAS occurrence in the crops harvested as livestock feed. To better understand potential human health impacts of PFAS occurrence at the Living Filter site, aqueous PFAS concentrations were compared to national and international drinking water policies, including throughout the United Kingdom, to determine if the long-term spray irrigation activities associated with beneficial reuse are significant enough to warrant human-health related concerns under different policy regimes. Data from the monitoring wells demonstrated that of the 20 analyzed PFAS compounds, 10 PFAS compounds were found to be present in the ground water. Concentrations of total measured PFAS ranged from below the detection limit to 155 ng/L, with concentrations increasing in the direction of groundwater flow. PFOA and PFOS across the Living Filter were detected at concentrations above the drinking water standards proposed by US Environmental Protection Agency (USEPA) at 10 of the 13 monitoring wells and above the Pennsylvania Department of Environmental Protection's drinking water standards in 7 wells. However, all but 3 of the 13 wells met UK policy standards. Because the Living Filter is operated to maintain groundwater concentrations below the USEPA's primary drinking water standard of nitrate of 10 mg NO3-N/L (USEPA, 2009), strict regulations for PFAS in potable water could limit the long- term feasibility of beneficial reuse of treated wastewater. However, these wells do not serve as supply wells for potable water and therefore do not pose a direct risk to human health. Research results provide insight into potential impacts of beneficial reuse of treated wastewater on groundwater and crop tissue quality. Crop tissue was also found to contain detectable levels of PFAS, with short chain compounds being the largest contributor (>84%). These results were used to estimate the amount of PFAS ingested by dairy cattle through their feed, which was found to range from 2.46 -- 7.67 mg/animal/yr. These results suggest that beneficial reuse of wastewater effluent can impact groundwater and feed quality; however, the results to livestock and human health are not yet fully understood. Without these beneficial reuse programs, the treated wastewater would be discharged to surface water. Therefore, additional research is needed to better understand the risks and benefits associated with beneficial reuse programs as they relate to PFAS fate and transport in agroecosystems.

Download or read book Removal of Perchlorate in Ammunition Wastewater by Zero valent Iron and Perchlorate Respiring Bacteria written by Se Chang Ahn and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Perchlorate has recently received a great deal of attention due to high concentrations found in groundwaters and surface waters. The US Army and DoD facilities generate ammunition wastewater containing perchlorate (ClO 4 - ), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and 2,4-dinitroanisole (DNAN) (i.e. PAX-21 wastewater) from munitions manufacturing and demilitarization processes. Perchlorate is known to affect human health by interfering with the uptake of iodide into the thyroid glands. The US EPA recently set the perchlorate reference dose to 0.0007 mg/kg/day which corresponds to a drinking water equivalent level of 24.5 ppb. Aqueous perchlorate is both chemically stable in natural water and extremely soluble and mobile; as a result, many traditional wastewater treatment techniques that are commonly used for solvents and other organic pollutants are not effective for removal of perchlorate from contaminated water. Presently, most Army ammunition plants use granular activated carbon (GAC) adsorption and alkaline hydrolysis to separate and treat energetic compounds in wastewater from munitions manufacturing and demilitarization processes. GAC processes are not only expensive but generate explosive-laden spent carbon, which needs to be treated or disposed of properly to avoid secondary contamination problems. This additional treatment further increases the overall cost of wastewater treatment. The overall objective of this research was to develop a novel treatment process for the removal of perchlorate and energetic compounds from mixed ammunition wastewater. We investigated two options for effective removal of perchlorate from mixed munitions wastewater that contains both perchlorate and energetic compounds: (1) increasing the solution temperature to overcome the kinetic barrier of perchlorate reduction by zero-valent iron; and (2) integrating Fe(0)-biological process for simultaneous removal of perchlorate and energetic compounds. Perchlorate reduction by zero-valent iron at elevated temperatures was investigated with a continuous-flow system that consisted of an iron-packed pressure vessel and a heat exchanger. Results from the continuous-flow system showed that 99% of perchlorate was removed in 1 hour of contact time at 175°C. With decreasing pH to 2.5, more than 60% of perchlorate was removed with an iron contact time of 30 min at operation temperature of 95°C. Increasing the reactor temperature to 125°C resulted in 98% perchlorate removal at the same retention time of 30 min. This result demonstrated that Fe(0) technology combined with heating may be a viable option for the removal of perchlorate from Army ammunition wastewater. Biodegradation experiments using glucose as the primary sources of electrons and carbon were conducted to evaluate microbial perchlorate reduction as a practical option for the treatment of perchlorate in PAX-21 wastewater. The results indicated that the constituents in PAX-21 wastewater may be toxic to perchlorate reducing bacteria. A series of batch toxicity test was conducted to identify the toxic constituents in PAX-21 wastewater and DNAN was identified as the primary toxicant responsible for inhibiting the activity of perchlorate reducing bacteria. It was hypothesized that pretreatment of PAX-21 by zero-valent iron granules will transform toxic constituents in PAX-21 wastewater to non-toxic products. Zero-valent iron pretreatment completely removed DNAN and RDX. After a 3-day acclimation period, perchlorate in iron-treated PAX-21 wastewater was rapidly decreased to an undetectable level in 2 days, which demonstrated that iron treatment not only removed energetic compounds but also eliminated the toxic constituents that inhibited the subsequent microbial process. Finally, potential application of energetic compounds as the source of electrons for perchlorate reduction by PRB was investigated. It was hypothesized that the pretreatment of PAX-21 wastewater with Fe(0) would convert energetic compounds to products that are more amenable for biological oxidation and that these products can also serve as electron donors for PRB. Results of batch experiments showed that DNAN was completely reduced to 2,4-diaminoanisole (DAAN) and RDX was completely reduced to formaldehyde in the presence of cast iron granules within 2 h. Batch biodegradation experiments showed that formaldehyde can serve as an electron donor for perchlorate respiring bacteria. It was also demonstrated that complete reduction of perchlorate in iron-treated PAX-21 wastewater can be achieved without adding an exogenous electron donor. This study confirmed that iron pretreatment not only removed energetic compounds, but also transformed the energetic compounds to products that can serve as the source of electrons for perchlorate respiring bacteria. Based on the results, we proposed an integrated Fe(0)-biological process for simultaneous removal of perchlorate and energetic compounds, which consists of (1) a Fe(0) process for the reduction of electron-withdrawing nitro groups to biodegradable compounds and (2) an anaerobic biological treatment process containing perchlorate-respiring bacteria, which utilize Fe(0)-treated energetic compounds as electron donor and perchlorate as electron acceptor.