Electrokinetic remediation for removal of per- and polyfluoroalkyl substances (PFASs) from contaminated soil

Uncontrolled use and disposal of per-and polyfluoroalkyl substances (PFASs) in recent decades has resulted in extensive soil and groundwater contamination, necessitating counteraction. Electrokinetic remediation (EKR) offers a promising approach to in-situ soil remediation. Two novel modifications to conventional EKR were tested for the first time in a laboratory-scale study, to explore the capacity of EKR for PFAS removal. The first modi-fication was a two-compartment setup designed for PFAS extraction from soil to an electrolyte-filled chamber. The second was a single-compartment setup designed to transport and confine contaminants in a chamber filled with granular activated carbon (GAC), thus, combining extraction with stabilisation. Electromigration varied for individual compounds, based mainly on perfluorocarbon chain length and functional group. The results indicated up to 89% concentration and extraction of n-ary sumation PFASs for the two-compartment setup, with removal efficiency reaching 99% for individual PFASs with C <= 6. Removed PFASs were concentrated adjacent to the anode at the anion exchange membrane, while short-chain compounds were extracted in the anolyte. The single-compartment setup achieved 75% extraction and accumulation of n-ary sumation PFASs in GAC. This demonstrates, for the first time, good effectiveness of coupling EKR with AC stabilisation for PFAS removal from soil. Perfluorocarbon chain length was a dominant factor affecting treatment efficiency in both setups, with very high removal rates for short-chain PFASs

Per- and polyfluoroalkyl substance (PFAS) retention by colloidal activated carbon (CAC) using dynamic column experiments

Developing effective remediation methods for per- and polyfluoroalkyl substance (PFAS)-contaminated soils is a substantial step towards counteracting their widespread occurrence and protecting our ecosystems and drinking water sources. Stabilisation of PFAS in the subsurface using colloidal activated carbon (CAC) is an innovative, yet promising technique, requiring better understanding. In this study, dynamic soil column tests were used to assess the retardation of 10 classical perfluoroalkyl acids (PFAAs) (C-5-C-11 perfluoroalkyl carboxylic acids (PFCAs) and C-4, C-6, C-8 perfluoroalkane sulfonates (PFSAs)) as well as two alternative PFAS (6:2 and 8:2 fluorotelomer sulfonates) using CAC at 0.03% w/w, to investigate the fate and transport of PFAS under CAC treatment applications. Results showed high retardation rates for long-chain PFAS and eight times higher retardation for the CAC-treated soil compared to the non-treated reference soil for the Sigma PFAS. Replacement of shorter chain perfluorocarboxylic acids (PFCAs), such as perfluoropentanoic acid (PFPeA), by longer chained PFAS was observed, indicating competition effects. Partitioning coefficients (K-d values) were calculated for the CAC fraction at similar to 10(3)-10(5) L kg(-1) for individual PFAS, while there was a significant positive correlation (p < 0.05) between perfluorocarbon chain length and K-d. Mass balance calculations showed 37% retention of Sigma PFAS in treated soil columns after completion of the experiments and 99.7% higher retention rates than the reference soil. Redistribution and elution of CAC were noticed and quantified through organic carbon analysis, which showed a 23% loss of carbon during the experiments. These findings are a step towards better understanding the extent of CAC's potential for remediation of PFAS-contaminated soil and groundwater and the limitations of its applications

Electrodialytic Remediation of PFAS-Contaminated Soil

Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic aliphatic compounds, widelyknown for their environmental persistence and toxicity to living beings. While they are ubiquitous in theenvironment, interest has been focused on contaminated soil, which can act as a primary recipient andsource of groundwater contamination. Electrokinetic technology is based on the movement of ionsunder the effect of an electric field. This could be a promising remediation solution, since PFASs areusually present in their anionic form. The contaminants can then be concentrated towards the anode,thus reducing a plume’s volume and possibly extracting the substances from soil. The preliminary aimof the present study was to evaluate the potential of using electrodialysis for the remediation of PFAScontaminatedsoil for the first time. Experiments were run with natural contaminated soil samples,originating from a fire-fighting training site at Arlanda Airport, and at Kallinge, Sweden, as well as inartificially spikedsoil. Electrodes were placed in electrolyte-filled chambers and separated by the soilwith ion-exchange membranes for pH-control. In total, five experiments were conducted. Two differentsetups were tested, a typical 3-compartment EKR cell and a 2-compartment setup, to allow for pHincrease and facilitate PFAS desorption. Two different current densities were tested; 0.19 mA cm-2 and0.38 mA cm-2. After twenty-one days, soil was cut in ten parts lengthwise and triplicate samples wereanalysed for PFAS concentrations, with HPLC-MS/MS. Sixteen out of the twenty-six screened PFASswere detected above MDL in the natural soil samples. The majority of the detected PFASs showed apositive trend of electromigration towards the anode, under both current densities, with only longerchainedcompounds (c&gt;8) being immobile. This can be attributed to the stronger sorption potential oflong-chained PFAS molecules, as has been reported in previous sorption studies. Mass balancedistribution for a high current density (0.38 mA cm-2) experiment revealed that 73.2% of Σ26PFAS wasconcentrated towards the anode, with 59% at the soil closer to the anode, 5.7% at the anion exchangemembrane and 8.5% at the anolyte. It also showed higher mobility for short-chained molecules (c≤6),as they were the only compounds to be extracted from soil and be concentrated in the anolyte. Highercurrent densities were not directly correlated with higher electromigration rates, as to the lack of massbalance data for the low current density experiments. Regardless, electrodialysis could be a viable optionfor PFAS soil remediation and further research to encourage the understanding of the migrationmechanism, as well as combination with other treatment methods is encouraged.Per- och polyfluoralkylsubstanser (PFAS) är en grupp av antropogena alifatiska föreningar, allmäntkända för sin miljöpåverkan och toxicitet för levande varelser. Medan de är allestädes närvarande imiljön har intresset varit inriktat på förorenad mark, som kan fungera som primär mottagare och källatill grundvattenförorening. Elektrokinetisk teknik är baserad på jonernas rörelse under effekten av ettelektriskt fält. Detta kan vara en lovande lösningsmedel, eftersom PFAS är vanligtvis närvarande i sinanjoniska form. Föroreningarna kan sedan koncentreras mot anoden, vilket reducerar en plums volymoch eventuellt extraherar ämnena från jorden. Det preliminära målet med den föreliggande studien varatt utvärdera potentialen att använda elektrodialys för sanering av PFAS-förorenad jord för förstagången. Experimenten kördes med naturliga förorenade jordprover, härrörande från enbrandbekämpningsplats vid Arlanda flygplats, och i Kallinge, Sverige, samt i konstgjort spikedsol.Elektroder placerades i elektrolytfyllda kamrar och separerades av jorden med jonbytesmembran förpH-kontroll. Totalt genomfördes fem experiment. Två olika inställningar testades, en typisk 3-facksEKR-cell och en 2-facksinställning, vilket möjliggör pH-ökning och underlättar PFAS-desorption. Tvåolika strömtätheter testades; 0,19 mA cm-2 och 0,38 mA cm-2. Efter tjugo dagar skärs jorden i tio delari längdriktningen och trippelprover analyserades för PFAS-koncentrationer, med HPLC-MS / MS.Sexton av de tjugosex screenade PFAS: erna detekterades över MDL i de naturliga markproverna.Majoriteten av de upptäckta PFAS-värdena visade en positiv trend av elektromigration mot anodenunder båda strömtätheten, varvid endast längre kedjiga föreningar (c&gt; 8) var immobila. Detta kanhänföras till den starkare sorptionspotentialen hos långkedjiga PFAS-molekyler, vilket har rapporteratsi tidigare sorptionsstudier. Massbalansfördelning för ett experiment med hög strömtäthet (0,38 mA cm-2) visade att 73,2% av Σ26PFAS koncentrerades mot anoden, med 59% vid jorden närmare anoden, 5,7%vid anjonbytarmembranet och 8,5% vid anolyten. Det visade också högre rörlighet för kortkedjigamolekyler (c≤6), eftersom de var de enda föreningarna som skulle extraheras från jord och koncentrerasi anolyten. Högre strömtätheter var inte direkt korrelerade med högre elektromigrationshastigheter,avseende bristen på massbalansdata för experimenten med låg strömtäthet. Oavsett elektrodialys kandet vara ett lönsamt alternativ för PFAS-markrening och ytterligare forskning för att uppmuntraförståelsen för migrationsmekanismen, liksom kombinationen med andra behandlingsmetoder främjas

Humidity Sensing Properties of Paper Substrates and Their Passivation with ZnO Nanoparticles for Sensor Applications

In this paper, we investigated the effect of humidity on paper substrates and propose a simple and low-cost method for their passivation using ZnO nanoparticles. To this end, we built paper-based microdevices based on an interdigitated electrode (IDE) configuration by means of a mask-less laser patterning method on simple commercial printing papers. Initial resistive measurements indicate that a paper substrate with a porous surface can be used as a cost-effective, sensitive and disposable humidity sensor in the 20% to 70% relative humidity (RH) range. Successive spin-coated layers of ZnO nanoparticles then, control the effect of humidity. Using this approach, the sensors become passive to relative humidity changes, paving the way to the development of ZnO-based gas sensors on paper substrates insensitive to humidity

Remediation of per- and polyfluoroalkyl substance-contaminated soil and groundwater, using electrokinetic and stabilisation methods

Per- and polyfluoroalkyl substances, commonly known as PFAS, are emerging contaminants with a worldwide environmental distribution and a concerning (eco)toxicological profile. The omnipresence of PFAS in various environmental media poses risks to the quality of our drinking water sources. Soils can act as inventories of PFAS plumes, which can slowly find their way into water resources. There is an imperative need for treatment applications at the pollution hotspots to prevent the spreading of PFAS into water bodies. This thesis aimed to investigate the potential of two technologies for treating PFAS-contaminated soils and groundwater: one focused on PFAS removal using electrokinetics and the other on their immobilisation in the subsurface using stabilisation with colloidal activated carbon (CAC). The findings of this thesis show that both methods can be promising; however, their effectiveness depends on compound-specific parameters and field considerations at the contaminated sites. The electrokinetic removal was highly effective for short-chain PFAS, with up to 99% removal for PFAS with C≤6 in their perfluorocarbon chain. Electrokinetic removal was also coupled with immobilisation by transporting and entrapping 75% of ∑PFAS to GAC. Conversely, stabilisation with CAC was more successful for long-chain PFAS and more for perfluoroalkyl sulfonates (PFSAs) than perfluoroalkyl carboxylic acids (PFCAs), with lab tests indicating an average of eight times retardation of PFAS in CAC-treated soils. Desorption from CAC was not significant, signifying that immobilisation with CAC can be effective in the long term. Challenges in applying both methods were also identified; electrokinetic remediation can be limited due to the low solubility of certain PFAS and the depletion of ions from the soil matrix, which might increase the complexity of the treatment and its costs. Stabilisation with CAC did not prove viable for the treatment of short-chain PFAS. Moreover, CAC was partially flushed out of the soil, with column tests showing a loss of 22% of the added CAC. These aspects must be considered in full-scale treatment applications to ensure optimal treatment. The PFAS composition is another critical parameter in stabilisation treatment, as the results showed competition among PFAS for sorption sites, with FOSA dominating its counterparts and short-chain PFAS being outcompeted by their long-chain homologues at higher concentrations. Immobilisation was also tested in a field study, which confirmed the results of the lab experiments, exhibiting the potential for PFAS contamination and highlighting the challenges. Nonetheless, the effectiveness of the stabilisation methods needs to be contextualised within the requirements and limitations of each contaminated site. In the future, optimising the technologies studied in this thesis can likely lead to higher efficiency, while combining these methods with other technologies, such as degradation, can be beneficial for the holistic management of PFAS-impacted sites.

Between ethnicity, religion and politics : foreign policy and the treatment of minorities in Greece and Turkey, 1923-1974

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Electrodialytic Remediation of PFAS-Contaminated Soil

Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic aliphatic compounds, widelyknown for their environmental persistence and toxicity to living beings. While they are ubiquitous in theenvironment, interest has been focused on contaminated soil, which can act as a primary recipient andsource of groundwater contamination. Electrokinetic technology is based on the movement of ionsunder the effect of an electric field. This could be a promising remediation solution, since PFASs areusually present in their anionic form. The contaminants can then be concentrated towards the anode,thus reducing a plume’s volume and possibly extracting the substances from soil. The preliminary aimof the present study was to evaluate the potential of using electrodialysis for the remediation of PFAScontaminatedsoil for the first time. Experiments were run with natural contaminated soil samples,originating from a fire-fighting training site at Arlanda Airport, and at Kallinge, Sweden, as well as inartificially spikedsoil. Electrodes were placed in electrolyte-filled chambers and separated by the soilwith ion-exchange membranes for pH-control. In total, five experiments were conducted. Two differentsetups were tested, a typical 3-compartment EKR cell and a 2-compartment setup, to allow for pHincrease and facilitate PFAS desorption. Two different current densities were tested; 0.19 mA cm-2 and0.38 mA cm-2. After twenty-one days, soil was cut in ten parts lengthwise and triplicate samples wereanalysed for PFAS concentrations, with HPLC-MS/MS. Sixteen out of the twenty-six screened PFASswere detected above MDL in the natural soil samples. The majority of the detected PFASs showed apositive trend of electromigration towards the anode, under both current densities, with only longerchainedcompounds (c&gt;8) being immobile. This can be attributed to the stronger sorption potential oflong-chained PFAS molecules, as has been reported in previous sorption studies. Mass balancedistribution for a high current density (0.38 mA cm-2) experiment revealed that 73.2% of Σ26PFAS wasconcentrated towards the anode, with 59% at the soil closer to the anode, 5.7% at the anion exchangemembrane and 8.5% at the anolyte. It also showed higher mobility for short-chained molecules (c≤6),as they were the only compounds to be extracted from soil and be concentrated in the anolyte. Highercurrent densities were not directly correlated with higher electromigration rates, as to the lack of massbalance data for the low current density experiments. Regardless, electrodialysis could be a viable optionfor PFAS soil remediation and further research to encourage the understanding of the migrationmechanism, as well as combination with other treatment methods is encouraged.Per- och polyfluoralkylsubstanser (PFAS) är en grupp av antropogena alifatiska föreningar, allmäntkända för sin miljöpåverkan och toxicitet för levande varelser. Medan de är allestädes närvarande imiljön har intresset varit inriktat på förorenad mark, som kan fungera som primär mottagare och källatill grundvattenförorening. Elektrokinetisk teknik är baserad på jonernas rörelse under effekten av ettelektriskt fält. Detta kan vara en lovande lösningsmedel, eftersom PFAS är vanligtvis närvarande i sinanjoniska form. Föroreningarna kan sedan koncentreras mot anoden, vilket reducerar en plums volymoch eventuellt extraherar ämnena från jorden. Det preliminära målet med den föreliggande studien varatt utvärdera potentialen att använda elektrodialys för sanering av PFAS-förorenad jord för förstagången. Experimenten kördes med naturliga förorenade jordprover, härrörande från enbrandbekämpningsplats vid Arlanda flygplats, och i Kallinge, Sverige, samt i konstgjort spikedsol.Elektroder placerades i elektrolytfyllda kamrar och separerades av jorden med jonbytesmembran förpH-kontroll. Totalt genomfördes fem experiment. Två olika inställningar testades, en typisk 3-facksEKR-cell och en 2-facksinställning, vilket möjliggör pH-ökning och underlättar PFAS-desorption. Tvåolika strömtätheter testades; 0,19 mA cm-2 och 0,38 mA cm-2. Efter tjugo dagar skärs jorden i tio delari längdriktningen och trippelprover analyserades för PFAS-koncentrationer, med HPLC-MS / MS.Sexton av de tjugosex screenade PFAS: erna detekterades över MDL i de naturliga markproverna.Majoriteten av de upptäckta PFAS-värdena visade en positiv trend av elektromigration mot anodenunder båda strömtätheten, varvid endast längre kedjiga föreningar (c&gt; 8) var immobila. Detta kanhänföras till den starkare sorptionspotentialen hos långkedjiga PFAS-molekyler, vilket har rapporteratsi tidigare sorptionsstudier. Massbalansfördelning för ett experiment med hög strömtäthet (0,38 mA cm-2) visade att 73,2% av Σ26PFAS koncentrerades mot anoden, med 59% vid jorden närmare anoden, 5,7%vid anjonbytarmembranet och 8,5% vid anolyten. Det visade också högre rörlighet för kortkedjigamolekyler (c≤6), eftersom de var de enda föreningarna som skulle extraheras från jord och koncentrerasi anolyten. Högre strömtätheter var inte direkt korrelerade med högre elektromigrationshastigheter,avseende bristen på massbalansdata för experimenten med låg strömtäthet. Oavsett elektrodialys kandet vara ett lönsamt alternativ för PFAS-markrening och ytterligare forskning för att uppmuntraförståelsen för migrationsmekanismen, liksom kombinationen med andra behandlingsmetoder främjas

Remediation of per- and polyfluoroalkyl substance-contaminated soil and groundwater, using electrokinetic and stabilisation methods

Per- and polyfluoroalkyl substances, commonly known as PFAS, are emerging contaminants with a worldwide environmental distribution and a concerning (eco)toxicological profile. The omnipresence of PFAS in various environmental media poses risks to the quality of our drinking water sources. Soils can act as inventories of PFAS plumes, which can slowly find their way into water resources. There is an imperative need for treatment applications at the pollution hotspots to prevent the spreading of PFAS into water bodies. This thesis aimed to investigate the potential of two technologies for treating PFAS-contaminated soils and groundwater: one focused on PFAS removal using electrokinetics and the other on their immobilisation in the subsurface using stabilisation with colloidal activated carbon (CAC). The findings of this thesis show that both methods can be promising; however, their effectiveness depends on compound-specific parameters and field considerations at the contaminated sites. The electrokinetic removal was highly effective for short-chain PFAS, with up to 99% removal for PFAS with C≤6 in their perfluorocarbon chain. Electrokinetic removal was also coupled with immobilisation by transporting and entrapping 75% of ∑PFAS to GAC. Conversely, stabilisation with CAC was more successful for long-chain PFAS and more for perfluoroalkyl sulfonates (PFSAs) than perfluoroalkyl carboxylic acids (PFCAs), with lab tests indicating an average of eight times retardation of PFAS in CAC-treated soils. Desorption from CAC was not significant, signifying that immobilisation with CAC can be effective in the long term. Challenges in applying both methods were also identified; electrokinetic remediation can be limited due to the low solubility of certain PFAS and the depletion of ions from the soil matrix, which might increase the complexity of the treatment and its costs. Stabilisation with CAC did not prove viable for the treatment of short-chain PFAS. Moreover, CAC was partially flushed out of the soil, with column tests showing a loss of 22% of the added CAC. These aspects must be considered in full-scale treatment applications to ensure optimal treatment. The PFAS composition is another critical parameter in stabilisation treatment, as the results showed competition among PFAS for sorption sites, with FOSA dominating its counterparts and short-chain PFAS being outcompeted by their long-chain homologues at higher concentrations. Immobilisation was also tested in a field study, which confirmed the results of the lab experiments, exhibiting the potential for PFAS contamination and highlighting the challenges. Nonetheless, the effectiveness of the stabilisation methods needs to be contextualised within the requirements and limitations of each contaminated site. In the future, optimising the technologies studied in this thesis can likely lead to higher efficiency, while combining these methods with other technologies, such as degradation, can be beneficial for the holistic management of PFAS-impacted sites.

Design and fabrication of an energy harvesting microgenerator for mechanical vibrations

The research conducted during this thesis involves the “Design, Fabrication and Characterization of a Vibrational Piezoelectric Microgenerator”, with use in wireless sensor networks, to make them autonomous. At the beginning, there is a review on some the latest cantileverd-based MEMS piezoelectric microgenerators and their characteristics. Also, there is a small review on the field of Piezotronics and its applications. The prototype microgenerator developed and presented in this thesis is a combination of MEMS technology and nanostructures of the piezoelectric material ZnO, able to convert low vibrations (~100Hz) into electricity. After, there is an extensive review on the basic equations that have been taken into account for the optimization of the design and fabrication processes. Arrays of vertical nanowires as well as uniform nanotextured films of ZnO were fabricated, simulated and characterized, taking into account the influence of each parameter. The MEMS microgenerators were successfully fabricated, packaged and characterized to achieve optimum results. Finally, an alternative approach on the fabrication of flexible nanogenerators is presented. Nanogenerators with either Au or Al electrodes were fabricated on flexible substrates, providing power outputs up to 30nWatts on an external load of 2MΩ.Η παρούσα διδακτορική διατριβή αφορά στο σχεδιασμό και την κατασκευή μιας μικρογεννήτριας που συλλέγει ενέργεια από τις μηχανικές δονήσεις του περιβάλλοντος. Η μετατροπή της μηχανικής ενέργειας σε ηλεκτρική καθίσταται δυνατή μέσω του πιεζοηλεκτρικού φαινομένου και ειδικής κατηγορίας υλικών που έχουν αυτή την ιδιότητα. Ιδιαίτερο ενδιαφέρον ως προς τις πιεζοηλεκτρικές του ιδιότητες και την ποικιλία δομών που μπορεί να προσφέρει παρουσιάζει το ZnO, το οποίο χρησιμοποιείται ως το ενεργό στοιχείο για την κατασκευή των μικρογεννητριών στα πλαίσια αυτής της διατριβής. Ο σκοπός μιας τέτοιας διάταξης έγκειται στη μετέπειτα ολοκλήρωσή του με ένα κύκλωμα χαμηλής ισχύος, αποτελώντας την πηγή τροφοδοσίας του, με αποτέλεσμα την ενεργειακή του αυτονόμηση. Αρχικά γίνεται μια αναφορά σε πιεζοηλεκτρικές MEMS μικρογεννήτριες που έχουν κατασκευαστεί τα τελευταία χρόνια και παρουσιάζονται τα βασικά χαρακτηριστικά τους. Επίσης, γίνεται μια εκτενής εισαγωγή στο νέο πεδίο της Πιεζοτρονικής, το οποίο ασχολείται με την εμφάνιση και τον έλεγχο πιεζοηλεκτρικού δυναμικού σε νανοδομές διαφόρων υλικών. Η πρωτοτυπία των μικρογεννητριών που παρουσιάζονται στην παρούσα διατριβή έγκειται στο συνδυασμό της τεχνολογίας MEMS με νανοδομές από ZnO ως πιεζοηλεκτρικό υλικό. Στη συνέχεια παρουσιάζονται οι βασικές εξισώσεις που διέπουν την αρχή λειτουργίας μιας πιεζοηλεκτρικής μικρογεννήτριας, με έμφαση στην πιεζοηλεκτρική πτώση τάσης σε νανοδομές ZnO, όταν αυτές υπόκεινται σε μηχανική παραμόρφωση. Παρουσιάζονται τα βέλτιστα γεωμετρικά χαρακτηριστικά για το σωστό σχεδιασμό των MEMS μικρογεννητριών τύπου αιωρούμενης προβόλου με συχνότητα φυσικής ταλάντωσης στα 100Hz. Στη συνέχεια, παρουσιάζονται τα πειραματικά αποτελέσματα της ανάπτυξης πολύπλοκων νανοδομών, αλλά και νανοδομημένων λεπτών υμενίων από ZnO, τα οποία είναι το βασικό στοιχείο των μικρογεννητριών που κατασκευάστηκαν. Στη συνέχεια οι μικρογεννήτριες χαρακτηρίστηκαν ώστε να διαπιστωθούν τα βέλτιστα ηλεκτρικά και πιεζοηλεκτρικά χαρακτηριστικά τους. Τέλος, παρουσιάζεται και μία εναλλακτική προσέγγιση κατασκευής νανογεννητριών, σε εύκαμπτα υποστρώματα με σκοπό τη χρήση αυτής της τεχνολογίας σε φορετές διατάξεις. Η τάση εξόδου κυμάνθηκε σε μερικά Volts με αντίστοιχο ρεύμα εξόδου μερικές εκατοντάδες nΑ για ελεγχόμενες μηχανικές δονήσεις. Οι τυπικές τιμές ισχύος εξόδου από τις εύκαμπτες νανογεννήτριες κυμάνθηκαν μεταξύ 3-30nW