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 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 Perfluoroalkyl Substances in the Environment written by David M. Kempisty and published by CRC Press. This book was released on 2018-08-06 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: Per- and polyfluorinated alkyl substances (PFAS), often referred to as per- (and poly) fluorinated compounds (PFCs), have been used for years in many everyday3⁄4 and some lifesaving3⁄4 products. However, their use has been linked to adverse health effects in humans, a problem compounded by their persistence in the environment. This book discusses the various challenges of PFAS in our environment today, including their historical use as well as their chemical and toxicological properties. It also presents robust discussion of analytical challenges and special considerations in sampling. The work goes on to give practical recommendations for dealing with these compounds in today's dynamic regulatory landscape and includes several chapters on various remediation techniques. Key Features: Comprehensive overview of per- and polyfluorinated alkyl substances (PFAS) historical use and chemical/physical properties which help us understand their persistence, transport, and transformation pathways in the environment In-depth analysis of PFAS toxicology Detailed descriptions of conventional and state-of-the-art remediation technologies Practical recommendations for dealing with PFAS in a dynamic regulatory landscape Robust discussion of important sampling and analytical considerations Perfluoroalkyl Substances in the Environment: Theory, Practice, and Innovation explores the challenges across the topical areas of regulation and management, toxicology, environmental remediation, and analytical sampling and analysis.Readers will find this text helpful in understanding complexities associated with PFAS and informing management strategies to effectively protect this and future generations.

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 Removal of Perfluorooctanoic Acid Using Zerovalent Iron Based Materials written by Wasiu Adedapo Lawal and published by . This book was released on 2019 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perfluorinated alkyl substances (PFASs) are highly persistent organic contaminants that have become a global health concern. Few studies so far have demonstrated successful decomposition of PFASs under ambient condition. As a result, this feasibility study aimed to quickly examine whether or not zerovalent iron (ZVI)-based materials, in particular palladium-doped nanoscale ZVI (so-called nZVI/Pd) known to dehalogenate many halogenated chemicals, can remove perfluorooctanoic acid (PFOA) in water, one of the most widely used PFASs. Batch experiments were performed to evaluate the effects of various operating parameters including reaction pH, nZVI/Pd dose, and PFOA concentration, and thus to find best treatment options for PFOA. Significant removal of PFOA was observed at low pH and high nZVI/Pd dosage while nZVI/Pd was superior to micron-size ZVI and nZVI without Pd. However, decrease in total organic carbon was very similar to PFOA removal, negligible amounts of fluoride ions were detected in water, and mass spectrometry analysis indicated no significant formation of reaction intermediates. The results implied that the observed PFOA removal was more closely associated with adsorption than reaction (i.e., defluorination). Kinetic models and adsorption isotherm models were employed to explain the PFOA removal and obtain insights on the physicochemical processes around nZVI/Pd interacting with PFOA.

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 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 Degradation of Toxaphene in the Presence of Zero valent Iron written by Seethu Mariam Babu and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Removal of contaminants by pump and treat technology has been found to be an inefficient process. Little investigation about the treatment of the effluent produced by the pump and treat technology has been conducted. Dechlorination of chlorinated compounds to reduce its toxicity is a significant priority in the environmental field. Additionally, the dechlorination in the presence of metallic compounds has been successfully tested. The purpose of this research was to evaluate the effectiveness of zero-valent iron (Fe0) in treating toxaphene in aqueous solution. The disappearance rate of toxaphene showed a linear logarithmic trend. Toxaphene dechlorination adsorption displayed first order kinetics following the Freundlich Isotherm. The highest disappearance rate for the batch study was found to be 0.226 h-1 for 5 ppm. The Kd value was found to be 0.817 mL/g. The disappearance rates increased with the increase in the concentration of toxaphene. It was seen that with the increase of concentration of toxaphene, the amount of adsorption on the iron surface also increased. Therefore, this provided as an effective way of reducing toxaphene in hazardous sites.

Download or read book Reverse Osmosis and Nanofiltration written by American Water Works Association and published by Amer Water Works Assn. This book was released on 1998 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explains the processes of membrane technologies applications, used in the treatment of water sources and by medical professionals for kidney dialysis, and is a helpful research tool for engineers, scientists, administrators, and educators seeking an introduction to these processes. Covers history and theory, design and equipment, regulations, and more.

Download or read book Stantec s Water Treatment written by John C. Crittenden and published by John Wiley & Sons. This book was released on 2022-11-08 with total page 1956 pages. Available in PDF, EPUB and Kindle. Book excerpt: The updated third edition of the definitive guide to water treatment engineering, now with all-new online content Stantec's Water Treatment: Principles and Design provides comprehensive coverage of the principles, theory, and practice of water treatment engineering. Written by world-renowned experts in the field of public water supply, this authoritative volume covers all key aspects of water treatment engineering, including plant design, water chemistry and microbiology, water filtration and disinfection, residuals management, internal corrosion of water conduits, regulatory requirements, and more. The updated third edition of this industry-standard reference includes an entirely new chapter on potable reuse, the recycling of treated wastewater into the water supply using engineered advanced treatment technologies. QR codes embedded throughout the book connect the reader to online resources, including case studies and high-quality photographs and videos of real-world water treatment facilities. This edition provides instructors with access to additional resources via a companion website. Contains in-depth chapters on processes such as coagulation and flocculation, sedimentation, ion exchange, adsorption, and gas transfer Details membrane filtration technologies, advanced oxidation, and potable reuse Addresses ongoing environmental concerns, pharmacological agents in the water supply, and treatment strategies Describes reverse osmosis applications for brackish groundwater, wastewater, and other water sources Includes high-quality images and illustrations, useful appendices, tables of chemical properties and design data, and more than 450 exercises with worked solutions Stantec's Water Treatment: Principles and Design, Updated Third Edition remains an indispensable resource for engineers designing or operating water treatment plants, and is an essential textbook for students of civil, environmental, and water resources engineering.

Download or read book Analysis of Perfluoroalkyl Substances in Food and Environmental Matrices written by Marta Llorca-Casamayor and published by . This book was released on 2012 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Removal of Picric Acid from Aqueous Solution Using Zero Valent Iron written by Roderquita K. Moore and published by . This book was released on 2002 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Removal Rates of Aqueous Cr VI by Zero Valent Iron Measured Under Flow Conditions written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies were undertaken to measure the rate of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as Fe(0). The pseudo-first-order rate coefficients measured under flow conditions were comparable to those previously measured under batch conditions that had significantly greater ratios of solution volume to Fe(0) surface area. Between the range of 20 and 100 weight percent Fe(0), there was little measurable change in the reaction kinetics. Thus, it may be possible to include sand into the reactive filter packs in the event it is necessary to increase filter pack porosity or to decrease the accumulation of secondary reaction products that may lead to filter pack plugging. Background water chemistry had only marginal effects on reaction rate coefficients. The reaction rates measured in this study indicated that an Fe(0) filter pack could be used to lower Cr(VI) concentrations by several orders of magnitude in a once-through mode of operation of the Reactive Well Technology.

Download or read book Exploring the Factors that Determine the Adsorption of Per and Polyfluoroalkyl Substances on Conventional Adsorbents and Novel Cyclodextrin Polymers with Different Surface Properties written by Ri Wang and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the concerns over the ubiquity and toxicity of per- and polyfluoroalkyl substances (PFASs) grow, research has focused on finding both technically and financially efficient PFAS remediation technologies. When evaluating certain technologies, research has focused on the removal of perfluoroalkyl acids from water, but contaminated groundwater often contains complex mixtures of diverse groups of PFASs. Utilizing a more comprehensive method to evaluate the performance of different PFAS treatment technologies involving the consideration of environmental matrix complexity can bring more useful insights into practical application. Adsorption-based processes are among the most promising technologies available for PFAS removal from water. The conventional adsorbents including activated carbon (AC) and anion exchange (AE) resins have been implemented in pilot or full-scale processes targeting PFAS removal from water. Emerging adsorbents, including novel β-cyclodextrin polymers (CDPs), have also exhibited potential for PFAS removal from water. The efficacy of CDPs on PFAS removal and the importance of varying surface properties of different CDPs on determining the affinity and selectivity to contaminants have been demonstrated. However, the mechanisms by which adsorbates bind to CDPs remains poorly understood. More research is needed to elucidate the mechanisms about the relative contributions of hydrophobic and electrostatic interactions for the adsorption of PFASs on CDPs.Two studies were designed to systematically explore the potential of conventional adsorbents and novel CDPs to remove mixtures of PFASs from contaminated groundwater and probe the adsorption binding mechanisms for anionic PFAS removal on CDPs. The first study aimed to evaluate the performance of five adsorbents including one AC, one AE resin and three different CDPs with varying surface charges to remove 68 PFASs in contaminated groundwater integrating a suspect screening approach. The PFAS removal performance of the adsorbents was evaluated with respect to adsorption affinity, kinetics, and selectivity. This evaluation provided insights on the factors that determine PFASs adsorption, which can be associated with the increasing length of the perfluorinated tail or could be more strongly related to properties of the head group. The second study aimed to evaluate the relative contributions of hydrophobic and electrostatic interactions on the adsorption of anionic PFASs by CDPs under controlled experimental conditions in nanopure water and different salt-amended nanopure water matrices. This study provided new insights into the adsorption binding mechanisms between anionic PFASs and CDPs as a function of chain length, and revealed the effects of different types and concentrations of inorganic constituents on the adsorption mechanisms. Together, the research described in this thesis furthers the understanding of different PFAS removal patterns by different adsorbents, and the understanding of anionic PFAS adsorption mechanisms on CDPs. These findings can serve as guidance and knowledge support on the future development and practical application of CDPs for different PFAS species under a range of environmental conditions.

Download or read book Membrane Separations Technology written by R.D. Noble and published by Elsevier. This book was released on 1995-01-17 with total page 737 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of membrane separation technology is presently in a state of rapid growth and innovation. Many different membrane separation processes have been developed during the past half century and new processes are constantly emerging from academic, industrial, and governmental laboratories. While new membrane separation processes are being conceived with remarkable frequency, existing processes are also being constantly improved in order to enhance their economic competitiveness. Significant improvements are currently being made in many aspects of membrane separation technology: in the development of new membrane materials with higher selectivity and/or permeability, in the fabrication methods for high-flux asymmetric or composite membranes, in membrane module construction and in process design. Membrane separation technology is presently being used in an impressive variety of applications and has generated businesses totalling over one billion U.S. dollars annually.The main objective of this book is to present the principles and applications of a variety of membrane separation processes from the unique perspectives of investigators who have made important contributions to their fields. Another objective is to provide the reader with an authoritative resource on various aspects of this rapidly growing technology. The text can be used by someone who wishes to learn about a general area of application as well as by the knowledgeable person seeking more detailed information.

Download or read book Groundwater Geochemistry written by Sughosh Madhav and published by John Wiley & Sons. This book was released on 2021-06-14 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains both practical and theoretical aspects of groundwater resources relating to geochemistry. Focusing on recent research in groundwater resources, this book helps readers to understand the hydrogeochemistry of groundwater resources. Dealing primarily with the sources of ions in groundwater, the book describes geogenic and anthropogenic input of ions into water. Different organic, inorganic and emerging contamination and salinity problems are described, along with pollution-related issues affecting groundwater. New trends in groundwater contamination remediation measures are included, which will be particularly useful to researchers working in the field of water conservation. The book also contains diverse groundwater modelling examples, enabling a better understanding of water-related issues and their management. Groundwater Geochemistry: Pollution and Remediation offers the reader: An understanding of the quantitative and qualitative challenges of groundwater resources An introduction to the environmental geochemistry of groundwater resources A survey of groundwater pollution-related issues Recent trends in groundwater conservation and remediation Mathematical and statistical modeling related to groundwater resources Students, lecturers and researchers working in the fields of hydrogeochemistry, water pollution and groundwater will find Groundwater Geochemistry an essential companion.