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− | ==PFAS Ex Situ Water Treatment== | + | ==Munitions Constituents – Sample Extraction and Analytical Techniques== |
− | Well-developed ''ex situ'' treatment technologies applicable to treatment of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | perfluoroalkyl and polyfluoroalkyl substances (PFAS)]] in drinking water and non-potable groundwater include membrane filtration (reverse osmosis and nanofiltration), activated carbon adsorption (granular and powdered), and anion exchange. There are also a variety of separation and destructive technologies in developmental stages. Some of these processes may also be applicable to more complex matrices including wastewater and landfill leachate.
| + | Munitions Constituents, including [[Wikipedia: Insensitive munition | insensitive munitions]] (IM), are a broad category of compounds which, in areas where manufactured or used, can be found in a variety of environmental matrices (waters, soil, and tissues). This presents an analytical challenge when a variety of these munitions are to be quantified. This article discusses sample extraction methods for each typical sample matrix (high level water, low level water, soil and tissue) as well as the accompanying [[Wikipedia: High-performance liquid chromatography | HPLC]]-UV analytical method for 27 compounds of interest (legacy munitions, insensitive munitions, and surrogates). |
| + | |
| <div style="float:right;margin:0 0 2em 2em;">__TOC__</div> | | <div style="float:right;margin:0 0 2em 2em;">__TOC__</div> |
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| '''Related Article(s):''' | | '''Related Article(s):''' |
| | | |
− | * [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] | + | *[[Munitions Constituents]] |
− | * [[PFAS Transport and Fate]]
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− | * [[PFAS Sources]]
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− | * [[PFAS Soil Remediation Technologies]]
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| | | |
− | '''Contributor(s):''' [[Dr. Scott Grieco]] and [[James Hatton]] | + | '''Contributor(s):''' |
| + | |
| + | *Dr. Austin Scircle |
| | | |
| '''Key Resource(s):''' | | '''Key Resource(s):''' |
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− | *[https://www.waterrf.org/resource/treatment-mitigation-strategies-poly-and-perfluorinated-chemicals Water Research Foundation (Drinking Water): Treatment Mitigation Strategies for PFAS]<ref name="Dickenson2016">Dickenson, E. and Higgins, C., 2016. Treatment Mitigation Strategies for Poly- and Perfluoroalkyl Substances, Report Number 4322. Water Research Foundation, Denver, Colorado. 123 pages. ISBN 978-1-60573-234-3</ref> | + | *[https://www.epa.gov/sites/default/files/2015-07/documents/epa-8330b.pdf USEPA Method 8330B]<ref name= "8330B">United States Environmental Protection Agency (USEPA), 2006. EPA Method 8330B (SW-846) Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Revision 2. [https://www.epa.gov/esam/epa-method-8330b-sw-846-nitroaromatics-nitramines-and-nitrate-esters-high-performance-liquid USEPA Website] [[Media: Epa-2006-method-8330b.pdf | EPA Method 8330b]]</ref> |
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− | *[https://pfas-1.itrcweb.org/12-treatment-technologies/#12_2 Interstate Technical and Regulatory Council: PFAS Liquids Treatment Technologies]<ref name="ITRC2020">Interstate Technology and Regulatory Council (ITRC), 2020. PFAS Technical and Regulatory Guidance Document and Fact Sheets, PFAS-1. PFAS Team, Washington, DC. [https://pfas-1.itrcweb.org/ Website] [[Media: ITRC_PFAS-1.pdf | Report.pdf]]</ref> | + | *Methods for simultaneous quantification of legacy and insensitive munition (IM) constituents in aqueous, soil/sediment, and tissue matrices<ref name="CrouchEtAl2020">Crouch, R.A., Smith, J.C., Stromer, B.S., Hubley, C.T., Beal, S., Lotufo, G.R., Butler, A.D., Wynter, M.T., Russell, A.L., Coleman, J.G., Wayne, K.M., Clausen, J.L., Bednar, A.J., 2020. Methods for simultaneous determination of legacy and insensitive munition (IM) constituents in aqueous, soil/sediment, and tissue matrices. Talanta, 217, Article 121008. [https://doi.org/10.1016/j.talanta.2020.121008 doi: 10.1016/j.talanta.2020.121008] [[Media: CrouchEtAl2020.pdf | Open Access Manuscript.pdf]]</ref> |
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− | *[https://www.sciencedirect.com/science/article/pii/S0301479717307934 Novel treatment technologies for PFAS compounds: A critical review.]<ref name="Kucharzyk2017"> Kucharzyk, K.H., Darlington, R., Benotti, M., Deeb, R. and Hawley, E., 2017. Novel treatment technologies for PFAS compounds: A critical review. Journal of Environmental Management, 204(2), pp. 757-764. [https://doi.org/10.1016/j.jenvman.2017.08.016 DOI: 10.1016/j.jenvman.2017.08.016] Manuscript available from: [https://www.researchgate.net/profile/Katarzyna_kate_Kucharzyk/publication/319125507_Novel_treatment_technologies_for_PFAS_compounds_A_critical_review/links/5a06590b4585157013a3be77/Novel-treatment-technologies-for-PFAS-compounds-A-critical-review.pdf ResearchGate].</ref>
| + | ==Introduction== |
| + | {| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;" |
| + | |+Table 1. Analyte list with acronyms and CAS numbers. |
| + | |- |
| + | !Compound |
| + | ! Acronym |
| + | !CAS Number |
| + | |- |
| + | | 1,2-Dinitrobenzene (surrogate) ||'''1,2-DNB (surr.)''' || 528-29-0 |
| + | |- |
| + | | 1,3-Dinitrobenzene || 1,3-DNB || 99-65-0 |
| + | |- |
| + | | 1,3,5-Trinitrobenzene || 1,3,5-TNB || 99-35-4 |
| + | |- |
| + | | 1,4-Dinitrobenzene || '''1,4-DNB (surr.)''' || 100-25-4 |
| + | |- |
| + | | 2-Amino-4,6-dinitrotoluene || 2-Am-4,6-DNT || 35572-78-2 |
| + | |- |
| + | | 2-Nitrophenol || '''2-NP''' || 88-75-5 |
| + | |- |
| + | | 2-Nitrotoluene || 2-NT || 88-72-2 |
| + | |- |
| + | | 2,4-Dinitrophenol || '''2,4-DNP''' || 51-28-5 |
| + | |- |
| + | | 2,4-Dinitrotoluene || 2,4-DNT || 121-14-2 |
| + | |- |
| + | | 2,4,6-Trinitrophenol || '''Picric Acid (PA)''' || 88-89-1 |
| + | |- |
| + | | 2,4,6-Trinitrotoluene || 2,4,6-TNT || 118-96-7 |
| + | |- |
| + | | 2,6-Dinitrotoluene || 2,6-DNT || 606-20-2 |
| + | |- |
| + | | 3-Nitrotoluene || 3-NT || 99-08-1 |
| + | |- |
| + | | 3,5-Dinitroaniline || 3,5-DNA || 618-87-1 |
| + | |- |
| + | | 4-Amino-2,6-dinitrotoluene || 4-Am-2,6-DNT || 19406-51-0 |
| + | |- |
| + | | 4-Nitrophenol || '''4-NP''' || 100-02-7 |
| + | |- |
| + | | 4-Nitrotoluene || 4-NT || 99-99-0 |
| + | |- |
| + | | 2,4-Dinitroanisole || '''DNAN''' || 119-27-7 |
| + | |- |
| + | | Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine || HMX || 2691-41-0 |
| + | |- |
| + | | Nitrobenzene || NB || 98-95-3 |
| + | |- |
| + | | Nitroglycerine || NG || 55-63-0 |
| + | |- |
| + | | Nitroguanidine || '''NQ''' || 556-88-7 |
| + | |- |
| + | | 3-Nitro-1,2,4-triazol-5-one || '''NTO''' || 932-64-9 |
| + | |- |
| + | | ''ortho''-Nitrobenzoic acid || '''''o''-NBA (surr.)''' || 552-16-9 |
| + | |- |
| + | | Pentaerythritol tetranitrate || PETN || 78-11-5 |
| + | |- |
| + | | Hexahydro-1,3,5-trinitro-1,3,5-triazine || RDX || 121-82-4 |
| + | |- |
| + | | N-Methyl-N-(2,4,6-trinitrophenyl)nitramide || Tetryl || 479-45-8 |
| + | |- |
| + | | colspan="3" style="background-color:white;" | Note: Analytes in '''bold''' are not identified by EPA Method 8330B. |
| + | |} |
| + | [[File: ScircleFig1.png | thumb | 400px | Figure 1. Primary Method labeled chromatograms]] |
| + | [[File: ScircleFig2.png | thumb | 400px | Figure 2. Secondary Method labeled chromatograms]] |
| + | The primary intention of the analytical methods presented here is to support the monitoring of legacy and insensitive munitions contamination on test and training ranges, however legacy and insensitive munitions often accompany each other at demilitarization facilities, manufacturing facilities, and other environmental sites. Energetic materials typically appear on ranges as small, solid particulates and due to their varying functional groups and polarities, can partition in various environmental compartments<ref>Walsh, M.R., Temple, T., Bigl, M.F., Tshabalala, S.F., Mai, N. and Ladyman, M., 2017. Investigation of Energetic Particle Distribution from High‐Order Detonations of Munitions. Propellants, Explosives, Pyrotechnics, 42(8), pp. 932-941. [https://doi.org/10.1002/prep.201700089 doi: 10.1002/prep.201700089]</ref>. To ensure that contaminants are monitored and controlled at these sites and to sustainably manage them a variety of sample matrices (surface or groundwater, process waters, soil, and tissues) must be considered. (Process water refers to water used during industrial manufacturing or processing of legacy and insensitive munitions.) Furthermore, additional analytes must be added to existing methodologies as the usage of IM compounds changes and as new degradation compounds are identified. Of note, relatively new IM formulations containing [[Wikipedia: Nitrotriazolone | NTO]], [[Wikipedia: 2,4-Dinitroanisole | DNAN]], and [[Wikipedia: Nitroguanidine | NQ]] are seeing use in [[Wikipedia: IMX-101 | IMX-101]], IMX-104, Pax-21 and Pax-41 (Table 1)<ref>Mainiero, C. 2015. Picatinny Employees Recognized for Insensitive Munitions. U.S. Army, Picatinny Arsenal Public Affairs. [https://www.army.mil/article/148873/picatinny_employees_recognized_for_insensitive_munitions Open Access Press Release]</ref><ref>Frem, D., 2022. A Review on IMX-101 and IMX-104 Melt-Cast Explosives: Insensitive Formulations for the Next-Generation Munition Systems. Propellants, Explosives, Pyrotechnics, 48(1), e202100312. [https://doi.org/10.1002/prep.202100312 doi: 10.1002/prep.202100312]</ref>. |
| | | |
− | *[https://www.liebertpub.com/doi/abs/10.1089/ees.2016.0233 Degradation and removal methods for perfluoroalkyl and polyfluoroalkyl substances in water]<ref name="Merino2016">Merino, N., Qu, Y., Deeb, R.A., Hawley, E.L., Hoffmann, M.R., and Mahendra, S., 2016. Degradation and Removal Methods for Perfluoroalkyl and Polyfluoroalkyl Substances in Water. Environmental Engineering Science, 33(9), pp. 615-649. [https://doi.org/10.1089/ees.2016.0233 DOI: 10.1089/ees.2016.0233]</ref>
| + | Sampling procedures for legacy and insensitive munitions are identical and utilize multi-increment sampling procedures found in USEPA Method 8330B Appendix A<ref name= "8330B"/>. Sample hold times, subsampling and quality control requirements are also unchanged. The key differences lie in the extraction methods and instrumental methods. Briefly, legacy munitions analysis of low concentration waters uses a single cartridge reverse phase [[Wikipedia: Solid-phase extraction | SPE]] procedure, and [[Wikipedia: Acetonitrile | acetonitrile]] (ACN) is used for both extraction and [[Wikipedia: Elution | elution]] for aqueous and solid samples<ref name= "8330B"/><ref>United States Environmental Protection Agency (USEPA), 2007. EPA Method 3535A (SW-846) Solid-Phase Extraction (SPE), Revision 1. [https://www.epa.gov/esam/epa-method-3535a-sw-846-solid-phase-extraction-spe USEPA Website] [[Media: epa-3535a.pdf | Method 3535A.pdf]]</ref>. An [[Wikipedia: High-performance_liquid_chromatography#Isocratic_and_gradient_elution | isocratic]] separation via reversed-phase C-18 column with 50:50 methanol:water mobile phase or a C-8 column with 15:85 isopropanol:water mobile phase is used to separate legacy munitions<ref name= "8330B"/>. While these procedures are sufficient for analysis of legacy munitions, alternative solvents, additional SPE cartridges, and a gradient elution are all required for the combined analysis of legacy and insensitive munitions. |
| | | |
− | ==Established PFAS Treatment Technologies==
| + | Previously, analysis of legacy and insensitive munitions required multiple analytical techniques, however the methods presented here combine the two munitions categories resulting in an HPLC-UV method and accompanying extraction methods for a variety of common sample matrices. A secondary HPLC-UV method and a HPLC-MS method were also developed as confirmatory methods. The methods discussed in this article were validated extensively by single-blind round robin testing and subsequent statistical treatment as part of ESTCP [https://serdp-estcp.mil/projects/details/d05c1982-bbfa-42f8-811d-51b540d7ebda ER19-5078]. Wherever possible, the quality control criteria in the Department of Defense Quality Systems Manual for Environmental Laboratories were adhered to<ref>US Department of Defense and US Department of Energy, 2021. Consolidated Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.4. 387 pages. [https://www.denix.osd.mil/edqw/denix-files/sites/43/2021/10/QSM-Version-5.4-FINAL.pdf Free Download] [[Media: QSM-Version-5.4.pdf | QSM Version 5.4.pdf]]</ref>. Analytes included in the methods presented here are found in Table 1. |
− | Three technologies are well demonstrated for removal of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] from drinking water and non-potable groundwater (as described below):
| |
− |
| |
− | * membrane filtration including [[wikipedia: Reverse osmosis | reverse osmosis (RO)]] and [[Wikipedia: Nanofiltration | nanofiltration (NF)]]
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− | * granular [[Wikipedia: Activated carbon | activated carbon]] (GAC) and powdered activated carbon (PAC) adsorption
| |
− | * [[wikipedia: Ion_exchange | anion exchange (IX)]]
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| | | |
− | However, these technologies are less demonstrated for removal of PFAS from more complex matrices such as wastewater and leachate.
| + | The chromatograms produced by the primary and secondary HPLC-UV methods are shown in Figure 1 and Figure 2, respectively. Chromatograms for each detector wavelength used are shown (315, 254, and 210 nm). |
− | Site-specific considerations that affect the selection of optimum treatment technologies for a given site include water chemistry, required flow rate, treatment criteria, waste residual generation, residual disposal options, and operational complexity. Treatability studies with site water are highly recommended because every site has different factors that may affect engineering design for these technologies.
| |
| | | |
− | ===Membrane Filtration=== | + | ==Extraction Methods== |
− | [[File: revOsmosisPlant.png | thumb | 500px | Figure 1. A RO municipal drinking water plant in Arizona]] | + | [[File: ScircleFig3.PNG |thumb|400px|Figure 3. Triple cartridge SPE setup]] |
− | Given their ability to remove dissolved contaminants at a molecular size level, RO and some NF membranes can be highly effective for PFAS removal. For RO systems (Figure 1), several studies have demonstrated effective removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature) from drinking water with removal rates well above 90%<ref name="Tang2006">Tang, C.Y., Fu, Q.S., Robertson, A.P., Criddle, C.S., and Leckie, J.O., 2006. Use of Reverse Osmosis Membranes to Remove Perfluorooctane Sulfonate (PFOS) from Semiconductor Wastewater. Environmental Science and Technology, 40(23), pp. 7343-7349. [https://doi.org/10.1021/es060831q DOI: 10.1021/es060831q]</ref><ref name="Flores2013">Flores, C., Ventura, F., Martin-Alonso, J., and Caixach, J., 2013. Occurrence of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in NE Spanish surface waters and their removal in a drinking water treatment plant that combines conventional and advanced treatments in parallel lines. Science of the Total environment, 461, 618-626. [https://doi.org/10.1016/j.scitotenv.2013.05.026 DOI: 10.1016/j.scitotenv.2013.05.026]</ref><ref name="Appleman2014">Appleman, T.D., Higgins, C.P., Quiñones, O., Vanderford, B.J., Kolstad, C., Zeigler-Holady, J.C., and Dickenson, E.R., 2014. Treatment of poly- and perfluoroalkyl substances in US full-scale water treatment systems. Water Research, 51, pp. 246-255. [https://doi.org/10.1016/j.watres.2013.10.067 DOI: 10.1016/j.watres.2013.10.067]</ref>. RO potable water reuse treatment systems implemented in California have also demonstrated effective PFOS and PFOA removal as reported by the Water Research Foundation (WRF)<ref name="Dickenson2016"/>. Analysis of permeate at both sites referenced by the WRF confirmed that short and long chain PFAS concentrations in the treated water were reduced to levels below test method reporting limits.
| + | [[File: ScircleFig4.PNG |thumb|400px|Figure 4. A flow chart of the soil extraction procedure]] |
− |
| + | ===High Concentration Waters (> 1 ppm)=== |
− | Full-scale studies using larger effective pore size NF membranes for PFAS removal are limited in number but are promising since NF systems are somewhat less costly than RO and may be nearly as effective in removing PFAS. Recent laboratory or pilot studies have shown good performance of NF membranes<ref name="Steinle-Darling2008">Steinle-Darling, E., and Reinhard, M., 2008. Nanofiltration for Trace Organic Contaminant Removal: Structure, Solution, and Membrane Fouling Effects on the Rejection of Perfluorochemicals. Environmental Science and Technology, 42(14), pp. 5292-5297. [https://doi.org/10.1021/es703207s DOI: 10.1021/es703207s] Free download from: [https://d1wqtxts1xzle7.cloudfront.net/48926882/es703207s20160918-21142-1xmqco5.pdf?1474189169=&response-content-disposition=inline%3B+filename%3DNanofiltration_for_Trace_Organic_Contami.pdf&Expires=1613000850&Signature=N-ZvvjOJX3TSOQzg7od3Q0LulNSZOqqjfummVEUfmiYlC3VasS4FuBHOgY52Xy~7FrKbOLhx0xx8QHdUsR~fbRTMQNXhiqbEslnU2gda2EcZHMMJj0mf-01wIA3jFIywA7IIabmTd3uMUGsIfT1D0PrGY00RmprYIQBoG3Dg~KjoizdfxYfvEgdZw2C~7D47pPiwMSnavZiGuvO0~dbRF8nawL7Prg91xt5BFTNUQQiIrIlMWc4PhVjzE5Su2CUZqnNlYdAW5Ck7B9lKmmVMPiOgz07vFnyp7m-q4UK3woa~aBFW9Wp~hjqN6vfohn8Hocv5oMpZNamhu8vBbPilKw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA Academia].</ref><ref name="Appleman2013">Appleman, T.D., Dickenson, E.R., Bellona, C., and Higgins, C.P., 2013. Nanofiltration and granular activated carbon treatment of perfluoroalkyl acids. Journal of Hazardous Materials, 260, 740-746. [https://doi.org/10.1016/j.jhazmat.2013.06.033 DOI: 10.1016/j.jhazmat.2013.06.033]</ref><ref name="Soriano2017">Soriano, Á., Gorri, D., and Urtiaga, A., 2017. Efficient treatment of perfluorohexanoic acid by nanofiltration followed by electrochemical degradation of the NF concentrate. Water Research, 112, 147-156. [https://doi.org/10.1016/j.watres.2017.01.043 DOI: 10.1016/j.watres.2017.01.043] [[Media: Soriano2017.pdf | Author’s Manuscript.]]</ref><ref name="Zeng2017">Zeng, C., Tanaka, S., Suzuki, Y., Yukioka, S., and Fujii, S., 2017. Rejection of Trace Level Perfluorohexanoic Acid (PFHxA) in Pure Water by Loose Nanofiltration Membrane. Journal of Water and Environment Technology, 15(3), pp. 120-127. [https://doi.org/10.2965/jwet.16-072 DOI: 10.2965/jwet.16-072] Free download from: [https://www.jstage.jst.go.jp/article/jwet/15/3/15_16-072/_pdf J-STAGE]</ref><ref name="Wang2018">Wang, J., Wang, L., Xu, C., Zhi, R., Miao, R., Liang, T., Yue, X., Lv, Y. and Liu, T., 2018. Perfluorooctane sulfonate and perfluorobutane sulfonate removal from water by nanofiltration membrane: The roles of solute concentration, ionic strength, and macromolecular organic foulants. Chemical Engineering Journal, 332, pp. 787-797. [https://doi.org/10.1016/j.cej.2017.09.061 DOI: 10.1016/j.cej.2017.09.061]</ref>.
| + | Aqueous samples suspected to contain the compounds of interest at concentrations detectable without any extraction or pre-concentration are suitable for analysis by direct injection. The method deviates from USEPA Method 8330B by adding a pH adjustment and use of MeOH rather than ACN for dilution<ref name= "8330B"/>. The pH adjustment is needed to ensure method accuracy for ionic compounds (like NTO or PA) in basic samples. A solution of 1% HCl/MeOH is added to both acidify and dilute the samples to a final acid concentration of 0.5% (vol/vol) and a final solvent ratio of 1:1 MeOH/H<sub><small>2</small></sub>O. The direct injection samples are then ready for analysis. |
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− | Although membrane RO and NF processes are generally capable of providing uniform removal rates relative to short and long chain PFAS compounds (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature), other aspects of these treatment technologies are more challenging:
| + | ===Low Concentration Waters (< 1 ppm)=== |
| + | Aqueous samples suspected to contain the compounds of interest at low concentrations require extraction and pre-concentration using solid phase extraction (SPE). The SPE setup described here uses a triple cartridge setup shown in Figure 3. Briefly, the extraction procedure loads analytes of interest onto the cartridges in this order: Strata<sup><small>TM</small></sup> X, Strata<sup><small>TM</small></sup> X-A, and Envi-Carb<sup><small>TM</small></sup>. Then the cartridge order is reversed, and analytes are eluted via a two-step elution, resulting in 2 extracts (which are combined prior to analysis). Five milliliters of MeOH is used for the first elution, while 5 mL of acidified MeOH (2% HCl) is used for the second elution. The particular SPE cartridges used are noncritical so long as cartridge chemistries are comparable to those above. |
| | | |
− | * Membranes must be flushed and cleaned periodically, such that overall water recovery rates (process water volumes consumed, wasted, and lost vs. treated water volumes produced) are much lower than those for GAC and IX processes. Membrane fouling can be slowed or avoided depending on operating conditions, membrane modifications, and feed modifications<ref name="LeRoux2005">Le Roux, I., Krieg, H.M., Yeates, C.A. and Breytenbach, J.C., 2005. Use of chitosan as an antifouling agent in a membrane bioreactor. Journal of Membrane Science, 248(1-2), pp. 127-136. [https://doi.org/10.1016/j.memsci.2004.10.005 DOI: 10.1016/j.memsci.2004.10.005]</ref>. Typically, 70-90% of the water supplied into a membrane RO process is recoverable as treated water. The remaining 10-30% is reject containing approximately 4 to 8 times the initial PFAS concentration (depending on recovery rate).
| + | {| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;" |
| + | |+Table 2. Primary HPLC-UV mobile phase gradient method concentrations |
| + | |- |
| + | | colspan="5" style="background-color:white;"| Method run time = 48 minutes; Column temperature = 25°C<br>Injection volume = 50 μL; Flow rate = 1.0 mL/min<br>Detector wavelengths = 210, 254, and 310 nm |
| + | |- |
| + | ! Time<br>(min) |
| + | ! Reagent Water<br>(%) |
| + | ! MeOH<br>(%) |
| + | ! 0.1% TFA/Water<br>(%) |
| + | ! ACN<br>(%) |
| + | |- |
| + | | 0.00 || 89 || 3 || 3 || 5 |
| + | |- |
| + | | 2.00 || 89 || 3 || 3 || 5 |
| + | |- |
| + | | 2.20 || 52 || 40 || 3 || 5 |
| + | |- |
| + | | 12.5 || 52 || 40 || 3 || 5 |
| + | |- |
| + | | 19.0 || 57 ||35 || 3 || 5 |
| + | |- |
| + | | 28.0 || 48 || 44 || 3 || 5 |
| + | |- |
| + | | 32.0 || 48 || 44 || 3 || 5 |
| + | |- |
| + | | 44.0 || 32 || 60 || 3 || 5 |
| + | |- |
| + | | 44.1 || 89 || 3 || 3 || 5 |
| + | |- |
| + | | 48.0 || 89 || 3 || 3 || 5 |
| + | |} |
| | | |
− | * These cleaning and flushing processes create a continuous liquid waste stream, which periodically includes harsh membrane cleaning chemicals as well as a continuous flow of concentrated membrane reject chemicals (i.e., PFAS) that must be properly managed and disposed of. Management often includes further treatment to remove PFAS from the liquid waste.
| + | ===Soils=== |
| + | Soil collection, storage, drying and grinding procedures are identical to the USEPA Method 8330B procedures<ref name= "8330B"/>; however, the solvent extraction procedure differs in the number of sonication steps, sample mass and solvent used. A flow chart of the soil extraction procedure is shown in Figure 4. Soil masses of approximately 2 g and a sample to solvent ratio of 1:5 (g/mL) are used for soil extraction. The extraction is carried out in a sonication bath chilled below 20 ⁰C and is a two-part extraction, first extracting in MeOH (6 hours) followed by a second sonication in 1:1 MeOH:H<sub><small>2</small></sub>O solution (14 hours). The extracts are centrifuged, and the supernatant is filtered through a 0.45 μm PTFE disk filter. |
| | | |
− | * RO and NF systems are inherently more expensive and complicated systems to implement, operate, and maintain compared to adsorption processes. Treatment system operator certification and process monitoring requirements are correspondingly markedly higher for RO and NF than they are for GAC and IX.
| + | The solvent volume should generally be 10 mL but if different soil masses are required, solvent volume should be 5 mL/g. The extraction results in 2 separate extracts (MeOH and MeOH:H<sub><small>2</small></sub>O) that are combined prior to analysis. |
| | | |
− | * Water feed pressures required to drive flow through membrane RO and NF processes are considerably higher than those involved with GAC and IX processes. This results in reduced process efficiency and higher pumping and electrical operating costs.
| + | ===Tissues=== |
| | | |
− | * Membrane systems can also be subject to issues with irreversible membrane fouling, clogging, and scaling or other physical membrane damage and failures. Additional water pretreatment and higher levels of monitoring and maintenance are then required, further adding to the higher costs of such systems.
| + | Tissue matrices are extracted by 18-hour sonication using a ratio of 1 gram of wet tissue per 5 mL of MeOH. This extraction is performed in a sonication bath chilled below 20 ⁰C and the supernatant (MeOH) is filtered through a 0.45 μm PTFE disk filter. |
− | ===Activated Carbon Adsorption===
| |
− | [[File: GAChouse.JPG | thumb| 500px | Figure 2. Typical private water supply well GAC installation for removal of VOCs and PFAS. Pressure gages and sample ports installed before the first (or lead) vessel, at the midpoint, and after the second (or lag) vessel allow monitoring for pressure drop due to fouling and for contaminant breakthrough.]]
| |
− | Activated carbon is a form of carbon processed to have small pores that increase the surface area available for adsorption of constituents from water. Activated carbon is derived from many source materials, including coconut shells, wood, lignite, and bituminous coal. Different types of activated carbon base materials have varied adsorption characteristics such that some may be better suited to removing certain contaminant compounds than others. Results from laboratory testing, pilot evaluations, and full-scale system operations suggest that bituminous coal-based GAC is generally the best performing carbon for PFAS removal<ref name="McNamara2018">McNamara, J.D., Franco, R., Mimna, R., and Zappa, L., 2018. Comparison of Activated Carbons for Removal of Perfluorinated Compounds from Drinking Water. Journal‐American Water Works Association, 110(1), pp. E2-E14. [https://doi.org/10.5942/jawwa.2018.110.0003 DOI: 10.5942/jawwa.2018.110.0003]</ref><ref name="Westreich2018">Westreich, P., Mimna, R., Brewer, J., and Forrester, F., 2018. The removal of short‐chain and long‐chain perfluoroalkyl acids and sulfonates via granular activated carbons: A comparative column study. Remediation Journal, 29(1), pp. 19-26. [https://doi.org/10.1002/rem.21579 DOI: 10.1002/rem.21579]</ref>.
| |
| | | |
− | The removal efficiency of individual PFAS compounds using GAC is a function of both the PFAS functional group (carboxylic acid versus sulfonic acid) and also the perfluoro-carbon chain length<ref name="McCleaf2017">McCleaf, P., Englund, S., Östlund, A., Lindegren, K., Wiberg, K., and Ahrens, L., 2017. Removal efficiency of multiple poly-and perfluoroalkyl substances (PFASs) in drinking water using granular activated carbon (GAC) and anion exchange (AE) column tests. Water Research, 120, pp. 77-87. [https://doi.org/10.1016/j.watres.2017.04.057 DOI: 10.1016/j.watres.2017.04.057]</ref><ref name="Eschauzier2012">Eschauzier, C., Beerendonk, E., Scholte-Veenendaal, P., and De Voogt, P., 2012. Impact of Treatment Processes on the Removal of Perfluoroalkyl Acids from the Drinking Water Production Chain. Environmental Science and Technology, 46(3), pp. 1708-1715. [https://doi.org/10.1021/es201662b DOI: 10.1021/es201662b]</ref>(see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature):
| + | Due to the complexity of tissue matrices, an additional tissue cleanup step, adapted from prior research, can be used to reduce interferences<ref name="RussellEtAl2014">Russell, A.L., Seiter, J.M., Coleman, J.G., Winstead, B., Bednar, A.J., 2014. Analysis of munitions constituents in IMX formulations by HPLC and HPLC-MS. Talanta, 128, pp. 524–530. [https://doi.org/10.1016/j.talanta.2014.02.013 doi: 10.1016/j.talanta.2014.02.013]</ref><ref name="CrouchEtAl2020"/>. The cleanup procedure uses small scale chromatography columns prepared by loading 5 ¾” borosilicate pipettes with 0.2 g activated silica gel (100–200 mesh). The columns are wetted with 1 mL MeOH, which is allowed to fully elute and then discarded prior to loading with 1 mL of extract and collecting in a new amber vial. After the extract is loaded, a 1 mL aliquot of MeOH followed by a 1 mL aliquot of 2% HCL/MeOH is added. This results in a 3 mL silica treated tissue extract. This extract is vortexed and diluted to a final solvent ratio of 1:1 MeOH/H<sub><small>2</small></sub>O before analysis. |
− | * perfluoro-sulfonate acids (PFSAs) are more efficiently removed than perfluoro-carboxylic acids (PFCAs) of the same chain length
| |
− | * long chain compounds of the same functional group are removed better than the shorter chains
| |
− | Activated carbon may be applied in drinking water systems as GAC or PAC<ref name="Dudley">Dudley, L.A., Arevalo, E.C., and Knappe, D.R., 2015. Removal of Perfluoroalkyl Substances by PAC Adsorption and Anion Exchange. Water Research Foundation Project #4344. Free download of Executive Summary from: [https://www.waterrf.org/system/files/resource/2019-04/4344_ProjectSummary.pdf Water Research Foundation (Public Plus account)]</ref><ref name="Qian2017">Qian, J., Shen, M., Wang, P., Wang, C., Li, K., Liu, J., Lu, B. and Tian, X., 2017. Perfluorooctane sulfonate adsorption on powder activated carbon: Effect of phosphate (P) competition, pH, and temperature. Chemosphere, 182, pp. 215-222. [https://doi.org/10.1016/j.chemosphere.2017.05.033 DOI: 10.1016/j.chemosphere.2017.05.033]</ref>. GAC has larger granules and is reusable, while PAC has much smaller granules and is not typically reused. To-date, PAC is most often used as a temporary treatment as costs associated with disposal and replacement of the used PAC may preclude using PAC for long-term treatment. A typical GAC installation for a private drinking water well is shown in Figure 2.
| |
− | Contrary to PAC, GAC used to treat PFAS can be reactivated by the manufacturer, driving the PFAS from the GAC and into off-gas. The extracted gas is then treated with thermal oxidation (temperatures often 1200°C to 1400°C). The reactivated GAC is then brought back to the site and reused. Thus, GAC can ultimately be a destructive treatment technology.
| |
| | | |
− | ===Anion Exchange=== | + | ==HPLC-UV and HPLC-MS Methods== |
− | Anion exchange has also been demonstrated for the adsorption of PFAS, and published results note higher sorption per pound than GAC<ref name="McCleaf2017"/><ref name=" Senevirathna2010">Senevirathna, S.T.M.L.D., Tanaka, S., Fujii, S., Kunacheva, C., Harada, H., Shivakoti, B.R., and Okamoto, R., 2010. A comparative study of adsorption of perfluorooctane sulfonate (PFOS) onto granular activated carbon, ion-exchange polymers and non-ion-exchange polymers. Chemosphere, 80(6), pp. 647-651. [https://doi.org/10.1016/j.chemosphere.2010.04.053 DOI: 10.1016/j.chemosphere.2010.04.053] Free download from: [https://www.researchgate.net/profile/Chinagarn_Kunacheva/publication/44672056_A_comparative_study_of_adsorption_of_perfluorooctane_sulfonate_PFOS_onto_granular_activated_carbon_ion-exchange_polymers_and_non-ion-exchange_polymers/links/5a3380510f7e9b2a288a2b21/A-comparative-study-of-adsorption-of-perfluorooctane-sulfonate-PFOS-onto-granular-activated-carbon-ion-exchange-polymers-and-non-ion-exchange-polymers.pdf ResearchGate]</ref><ref name="Woodard2017">Woodard, S., Berry, J., and Newman, B., 2017. Ion exchange resin for PFAS removal and pilot test comparison to GAC. Remediation Journal, 27(3), pp. 19-27. [https://doi.org/10.1002/rem.21515 DOI: 10.1002/rem.21515]</ref>. The higher capacity is believed to be due to combined hydrophobic and ion exchange adsorption mechanisms, whereas GAC mainly relies on hydrophobic attraction. Anion exchange resins can be highly selective, or they can also remove other contaminants based on design requirements and water chemistry. Resins have greater affinity for PFAS subgroup PFSA than for PFCA, and affinity increases with carbon chain length.
| + | {| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;" |
− | [[Wikipedia: Ion-exchange resin | Anion exchange resins]] are a viable alternative to GAC for ex situ treatment of PFAS anions, and several venders sell resins capable of removing PFAS. Resins available for treating PFAS include regenerable resins that can be used multiple times (Figure 3) and single-use resins that must be disposed or destroyed after use<ref name=" Senevirathna2010"/>. Regenerable resins generate a solvent and brine solution, which is distilled to recover the solvent prior to the brine being adsorbed onto a small quantity of GAC or resin for ultimate disposal. This use of one treatment technology (GAC, IX) to support another (RO) is sometimes referred to as a “treatment train” approach. Single-use resins can be more fully exhausted than regenerable resins can and may be a more cost-effective solution for low concentration PFAS contamination, while regenerable resins may be more cost effective for high concentration contamination.
| + | |+Table 3. Secondary HPLC-UV mobile phase gradient method concentrations |
− | ==Developing PFAS Treatment Technologies==
| + | |- |
− | Numerous separation and destructive technologies are in the developmental stages of bench-scale testing or limited field-scale demonstrations. Some of these are listed in Table 1:
| + | | colspan="5" style="background-color:white;" | Method run time = 43 minutes; Column temperature = 25°C<br>Injection volume = 50 μL; Flow rate = 0.8 mL/min<br>Detector wavelengths = 210, 254, and 310 nm |
− | | + | |- |
− | {| class="wikitable" style="float:right; margin-left:10px;" | + | ! Time<br>(min) |
− | |+ Table 1. Developmental Technologies | + | ! Reagent Water<br>(%) |
| + | ! MeOH<br>(%) |
| + | ! 0.1% TFA/Water<br>(%) |
| + | ! ACN<br>(%) |
| + | |- |
| + | | 0.00 || 75 || 10 || 10 || 5 |
| + | |- |
| + | | 2.50 || 75 || 10 || 10 || 5 |
| + | |- |
| + | | 2.60 || 39 || 46 ||10 || 5 |
| + | |- |
| + | | 9.00 || 39 || 46 ||10 || 5 |
| + | |- |
| + | | 9.10 || 33.5 || 51.5 || 10 || 5 |
| + | |- |
| + | | 15.00 || 35 || 50 || 10 || 5 |
| + | |- |
| + | | 15.10 || 43 || 42 || 10 || 5 |
| + | |- |
| + | | 33.00 || 30 || 55 || 10 || 5 |
| + | |- |
| + | | 33.10 || 75 || 10 || 10 || 5 |
| + | |- |
| + | | 43.00 || 75 || 10 || 10 || 5 |
| + | |} |
| + | {| class="wikitable mw-collapsible" style="float:right; margin-left:20px; text-align:center;" |
| + | |+Table 4. Ionization source and detector parameters |
| + | |- |
| + | ! Parameter |
| + | ! Value |
| + | |- |
| + | | Ionization Source || APCI |
| + | |- |
| + | | Ionization Mode || Negative |
| + | |- |
| + | | Drying Gas Temperature (°C) || 350 |
| + | |- |
| + | | Vaporizer Temperature (°C) || 325 |
| + | |- |
| + | | Drying Gas Flow (L/min) || 4.0 |
| + | |- |
| + | | Nebulizer Pressure (psig) || 40 |
| + | |- |
| + | | Corona Current (μA) || 10 |
| + | |- |
| + | | Capillary Potential (V) || 1500 |
| + | |- |
| + | | Mass Range || 40 – 400 |
| + | |- |
| + | | Fragmentor || 100 |
| + | |- |
| + | | Gain || 1 |
| |- | | |- |
− | ! Stage
| + | | Threshold || 0 |
− | ! Separation/Transfer
| |
− | ! Destructive*
| |
| |- | | |- |
− | | Developing | + | | Step Size || 0.20 |
− | | | + | |- |
− | * Biochar (20, 21, 22)
| + | | Speed (μ/sec) || 743 |
− | * Modified Zeolites (23, 24)
| |
− | * Specialty adsorbents
| |
− | | | |
− | * Electro-oxidation (32, 33, 34)
| |
− | * Heat activated persulfate (35)
| |
− | * Alkaline perozone (36)
| |
− | * Sonolysis (37, 38, 39, 40)
| |
− | * Super Critical Water Oxidation
| |
| |- | | |- |
− | | Maturing and</br>Demonstrated | + | | Peak Width (min) || 0.06 |
− | |
| |
− | * Chemical coagulation (28)
| |
− | * Electrocoagulation (29)
| |
− | * Foam fractionation (30, 31)
| |
− | | | |
− | * Low temperature plasma (41, 42)
| |
| |- | | |- |
− | | colspan="3" style="background:white;" | * There are several other destructive technologies such as alternative oxidants, and activation</br>methods of oxidants, but for the purpose of this article, the main categories are presented here. | + | | Cycle Time (sec/cycle) || 0.57 |
| |} | | |} |
| | | |
− | ==Conclusions==
| + | The Primary HPLC-UV method uses a Phenomenex Synergi 4 µm Hydro-RP column (80Å, 250 x 4.6 mm), or comparable, and is based on both the HPLC method found in USEPA 8330B and previous work<ref name= "8330B"/><ref name="RussellEtAl2014"/><ref name="CrouchEtAl2020"/>. This separation relies on a reverse phase column and uses a gradient elution, shown in Table 2. Depending on the analyst’s needs and equipment availability, the method has been proven to work with either 0.1% TFA or 0.25% FA (vol/vol) mobile phase. Addition of a guard column like a Phenomenex SecurityGuard AQ C18 pre-column guard cartridge can be optionally used. These optional changes to the method have no impact on the method’s performance. |
− | The well established processes for removing PFAS from water all produce residuals that require management, and it is likely that newer processes under development will also produce some residuals. Often, it is the residuals that limit the usefulness of the process. For instance, RO and NF may currently provide the most complete treatment of water, but the production of a relatively high volume of PFAS-containing liquid reject (the portion of the liquid that retains the contaminants and is “rejected” from the process) limits their application. Often, a second treatment technology such as an adsorbent is required to support the main technology by concentrating or treating the residuals. | |
− | As more testing and operational data on adsorbents are generated, it is becoming evident that no adsorbent technology outperforms the others in all cases. Whether GAC, ion exchange or another technology is the most technically efficient and cost effective long term option for a given site depends on influent water geochemistry and contaminant concentrations, treatment standards, co-contaminants, duration of treatment, and required flow rates. New generation adsorbents are rapidly being introduced into the market at “evaluation scale” which may provide advantages over commercially available adsorbents.
| |
− | Several newer technologies are being evaluated in the lab and in the field which include electro-oxidation, heat-activated persulfate, sonolysis, electrocoagulation, low temperature plasma, super critical water oxidation, and foam fractionation. These and other potential treatments for PFAS are still largely in the developmental stage. Several technologies show promise for improved management of PFAS sites. However, it is unlikely that a single technology will be adequate for full remediation at many sites. A multi-technology treatment train approach may be necessary for effective treatment of this complicated group of compounds.
| |
| | | |
− | ==Soil Treatment==
| + | The Secondary HPLC-UV method uses a Restek Pinnacle II Biphenyl 5 µm (150 x 4.6 mm) or comparable column and is intended as a confirmatory method. Like the Primary method, this method can use an optional guard column and utilizes a gradient elution, shown in Table 3. |
− | [[File: DiGuiseppi1w2Fig1.PNG |thumb|600px| Figure 1. A full scale PFAS-impacted soil stabilization project at a military base in Australia. Image courtesy of RemBind™.]]
| + | |
− | Addressing recalcitrant contaminants in soil has traditionally been done through containment/capping or excavation and off-site disposal or treatment. Containment/capping may be an acceptable solution for PFAS in some locations. However, containment/capping is not considered ideal given the history of releases from engineered landfills and restrictions on use of land containing capped soils. Innovative treatment approaches for PFAS include stabilization with amendments and thermal treatment.
| + | For instruments equipped with a mass spectrometer (MS), a secondary MS method is available and was developed alongside the Primary UV method. The method was designed for use with a single quadrupole MS equipped with an atmospheric pressure chemical ionization (APCI) source, such as an Agilent 6120B. A majority of the analytes shown in Table 1 are amenable to this MS method, however nitroglycerine (which is covered extensively in USEPA method 8332) and 2-,3-, and 4-nitrotoluene compounds aren’t compatible with the MS method. MS method parameters are shown in Table 4. |
| | | |
− | ===Excavation and Disposal=== | + | ==Summary== |
− | Excavation and off-site disposal or treatment of PFAS-impacted soils is the only well-developed treatment technology option and may be acceptable for small quantities of soil, such as those generated during characterization activities (i.e., investigation derived waste, IDW). Disposal in non-hazardous landfills is allowable in most states. However, some landfill operators are choosing to restrict acceptance of PFAS-containing waste and soils as a protection against future liability. In addition, the US EPA and some states are considering or have designated PFOA and PFOS as hazardous substances, which would reduce the number of facilities where disposal of PFAS-contaminated soil would be allowed<ref name="EPA2019">US Environmental Protection Agency (EPA), 2019. EPA’s Per- and Polyfluoroalkyl Substances (PFAS) Action Plan: EPA 823R18004. Washington, DC. [https://www.epa.gov/pfas/epas-pfas-action-plan Website] [[Media: EPA823R18004.pdf | Report.pdf]] [[Media: EPA100K20002.pdf | 2020 Update]]</ref>. Treatment of excavated soils is commonly performed using incineration or other high temperature thermal methods<ref name="ITRC2020"/>. Recent negative publicity regarding incomplete combustion of PFAS in incinerators<ref name="Hogue2020">Cheryl Hogue, 2020. Incineration may spread, not break down PFAS. Chemical and Engineering News, American Chemical Society. [https://cen.acs.org/environment/persistent-pollutants/Incincerators-spread-break-down-PFAS/98/web/2020/04 Website] [[Media: Hogue2020.pdf | Report.pdf]]</ref> has caused some states to ban PFAS incineration<ref name="NYSS2020">New York State Senate, 2020. An ACT prohibiting the incineration of aqueous film-forming foam containing perfluoroalkyl and polyfluoroalkyl substances in certain cities. [https://www.nysenate.gov/legislation/bills/2019/s7880/amendment/b Website] [[Media: NYsenate2020.pdf | Report.pdf]]</ref>.
| + | The extraction methods and instrumental methods in this article build upon prior munitions analytical methods by adding new compounds, combining legacy and insensitive munitions analysis, and expanding usable sample matrices. These methods have been verified through extensive round robin testing and validation, and while the methods are somewhat challenging, they are crucial when simultaneous analysis of both insensitive and legacy munitions is needed. |
− | | |
− | ===Stabilization===
| |
− | [[File:DiGuiseppi1w2Fig2.PNG|thumb|600px| Figure 2. A portable infrared thermal treatment unit for PFAS-impacted soils<ref name="DiGuiseppi2019"/>.]]
| |
− | Various amendments have been manufactured to sorb PFAS to reduce leaching from soil. Although this is a non-destructive approach, stabilization can reduce mass flux from a source area or allow soils to be placed in landfills with reduced potential for leaching. Amendments sorb PFAS through hydrophobic and electrostatic interactions and are applied to soil through ''in situ'' soil mixing or ''ex situ'' stabilization (Figure 1). Effectiveness of amendments varies depending on site conditions, PFAS types present, and mixing conditions<ref name="ITRCwNs2020"/>. Good results have been observed in bench and field scale tests with a variety of cationic clays (natural or chemically modified) and zeolites<ref name="OchoaHerrera2008">Ochoa-Herrera, V., and Sierra-Alvarez, R., 2008. Removal of perfluorinated surfactants by sorption onto granular activated carbon, zeolites and sludge. Chemosphere, 72(10), pp. 1588-1593. [https://doi.org/10.1016/j.chemosphere.2008.04.029 DOI: 10.1016/j.chemosphere.2008.04.029]</ref><ref name="Rattanaoudom2012">Rattanaoudom, R., Visvanathan, C., and Boontanon, S.K., 2012. Removal of Concentrated PFOS and PFOA in Synthetic Industrial Wastewater by Powder Activated Carbon and Hydrotalcite. Journal of Water Sustainability, 2(4), pp. 245-248. [http://www.jwsponline.com/uploadpic/Magazine/pp%20245-258.pdf Open access article.] [[Media: Rattanaoudom2012.pdf | Report.pdf]]</ref><ref name="Ziltek2017">Ziltek, 2017. RemBind: Frequently Asked Questions. [https://static1.squarespace.com/static/5c5503db4d546e22f6d2feb2/t/5c733787f9619ae6c84674c9/1551054727451/RemBind+FAQs.pdf Free download] [[Media: RemBind2017.pdf | Report.pdf]]</ref>. Bench-scale tests have shown that activated carbon sorbents reduce leachability of PFAS from soils<ref name="Du2014">Du, Z., Deng, S., Bei, Y., Huang, Q., Wang, B., Huang, J. and Yu, G., 2014. Adsorption behavior and mechanism of perfluorinated compounds on various adsorbents – A review. Journal of Hazardous Materials, 274, pp. 443-454. [https://doi.org/10.1016/j.jhazmat.2014.04.038 DOI: 10.1016/j.jhazmat.2014.04.038]</ref><ref name="Yu2009">Yu, Q., Zhang, R., Deng, S., Huang, J. and Yu, G., 2009. Sorption of perfluorooctane sulfonate and perfluorooctanoate on activated carbons and resin: Kinetic and isotherm study. Water Research, 43(4), pp. 1150-1158. [https://doi.org/10.1016/j.watres.2008.12.001 DOI: 10.1016/j.watres.2008.12.001]</ref><ref name="Szabo2017">Szabo, J., Hall, J., Magnuson, M., Panguluri, S., and Meiners, G., 2017. Treatment of Perfluorinated Alkyl Substances in Wash Water Using Granular Activated Carbon and Mixed Media, EPA/600/R-17/175. US Environmental Protection Agency (EPA), Washington, DC. [https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NHSRC&direntryid=337098 Website] [[Media: EPA600R17175.PDF | Report.pdf]]</ref>. A commercial product developed in Australia ([https://rembind.com/ RemBind™]) combines the cation exchange binding capability of clays, the hydrophobic sorption and [[Wikipedia: Van der Waals force | van der Waals]] attraction of organic material, and the electrostatic interactions of aluminum hydroxide to create a highly effective soil stabilizer. This material has been mixed into soil at 1 to 5% ratio by weight in ''ex situ'' applications and been demonstrated to reduce leachability by greater than 99 percent<ref name="Nolan2015">Nolan, A., Anderson, P., McKay, D., Cartwright, L., and McLean, C., 2015. Treatment of PFCs in Soils, Sediments and Water, WC35. Program and Proceedings, CleanUp Conference 2015. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC Care), Melbourne, Australia. pp. 374-375. [https://www.crccare.com/files/dmfile/CLEANUP_2015_PROCEEDINGS-web.pdf Free download] [[Media: CRCCare2015.pdf | Report.pdf]]</ref>.
| |
− | | |
− | ===Thermal Treatment===
| |
− | [[File:DiGuiseppi1w2Fig3.PNG|thumb|600px| Figure 3. A full scale PFAS-impacted soil washing plant in Australia<ref name="Grimison2020"/>.]]
| |
− | ''Incineration:'' Incineration is a well-developed technology for organics destruction, including PFAS-impacted soils. Incineration is generally defined as high temperature (>1,100°C) thermal destruction of waste, and PFAS are thought to mineralize at high temperatures. Generally, incinerators treat off-gasses by thermal oxidation with temperatures as high as 1,400°C, and vaporized combustion products can be captured using condensation and wet scrubbing<ref name="ITRCwNs2020"/>. Some regulatory officials have expressed concern about possible PFAS emissions in off-gas from these incinerators, and the authors are not aware of any published evidence demonstrating complete mineralization of multiple PFAS in incinerators at the time of this posting. In general, incineration is designed to provide “5 nines of destruction” – destruction of 99.999% of the contaminants, although incinerators are not designed to specifically treat PFAS to this standard. In the absence of approved industry standard test methods, the US EPA is developing off-gas/stack testing procedures capable of detecting PFAS at the levels considered to be harmful<ref name="EPA2018">US Environmental Protection Agency (EPA), 2018. PFAS Research and Development, Community Engagement in Fayetteville, North Carolina. [https://www.epa.gov/pfas/pfas-community-engagement-north-carolina-meeting-materials Website] [[Media: EPAFayetteville2018.pdf | Report.pdf]]</ref>.
| |
− | | |
− | ''Thermal Desorption:'' Thermal Desorption of PFAS from soil has been demonstrated at the field scale in Australia and the US (Alaska)<ref name="Nolan2015"/> using a rotary kiln operating at temperatures in the range of 900°C or less with treatment times of 10-15 minutes<ref name="Burke2015">Burke, Jill, 2019. Fairbanks incinerator shows promise for cleaning toxic soil. Channel 2-KTUU, October 8. [https://www.ktuu.com/content/news/Fairbanks-incinerator-shows-promise-for-cleaning-toxic-soil-562593631.html Website]</ref>. At these temperatures, some PFAS are mineralized, releasing fluorine that must be captured in off-gas treatment systems. Some PFAS would not be destroyed at these temperatures and therefore must be captured in off-gas treatment systems. Several bench-scale tests have been performed that have narrowed down the optimal temperature for desorption to between 350°C and 400°C<ref name="Hatton2019">Hatton, J., Dasu, K., Richter, R., Fitzpatrick, T., and Higgins, C., 2019. Field Demonstration of Infrared Thermal Treatment of PFAS-impacted Soils from Subsurface Investigations. Strategic Environmental Research and Development Program (SERDP), Project ER18-1603, Alexandria, VA. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/ER18-1603 Website] [[Media: SERDP ER18-1603.pdf | Report.pdf]]</ref><ref name="DiGuiseppi2019">DiGuiseppi, W., Richter, R., and Riggle, M., 2019. Low Temperature Desorption of Per- and Polyfluoroalkyl Substances. The Military Engineer, 111(719), pp. 52-53. Society of American Military Engineers, Washington, DC. [http://online.fliphtml5.com/fedq/sdoo/#p=54 Open access article.] [[Media: DiGuiseppi2019.pdf | Report.pdf]]</ref>. A US Department of Defense (DoD) Strategic Environmental Research and Development Program (SERDP) field-scale demonstration was performed in Oregon, where thermal desorption was conducted at 400°C over several days, and the PFAS were captured on vapor-phase activated carbon and incinerated<ref name="Hatton2019"/>. An ''in situ'' thermal desorption project has been funded under the US DoD’s Environmental Security Technology Certification Program (ESTCP) to demonstrate that vadose zone soil can be heated to the requisite 350°C and held there for the appropriate length of time to desorb and capture PFAS from soil source areas<ref name="Iery2020">Iery, R., 2020. In Situ Thermal Treatment of PFAS in the Vadose Zone. US Department of Defense, Environmental Security Technology Certification Program (ESTCP), Project ER20-5250. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER20-5250 Website]</ref>.
| |
− | | |
− | ===Soil Washing===
| |
− | Soil washing has been applied to PFAS in a handful of pilot projects<ref name="Torneman2012">Torneman, N., 2012. Remedial Methods and Strategies for PFCs. Fourth Joint Nordic Meeting on Remediation of Contaminated Sites, NORDROCS 2012, Oslo, Norway. [http://nordrocs.org/wp-content/uploads/2012/09/Session-VI-torsdag-1-Torneman-short-paper.pdf Free download.] [[Media: Torneman2012.pdf | Report.pdf]]</ref><ref name="Toase2018">Toase, D., 2018. Application of enhanced soil washing techniques to PFAS contaminated source zones. Emerging Contaminants Summit 2018, Westminster, Colorado.</ref><ref name="Grimison2018">Grimison, C., Barthelme, S., Nolan, A., Cole, J., Morrell, C., 2018. Integrated Soil and Water System for Treatment of PFAS Impacted Source Areas, 18E138P. Australasian Land and Groundwater Association (ALGA), Sydney, Australia. [https://landandgroundwater.com/media/18E138P_-_Charles_Grimison.pdf Free download.] [[Media: Grimison2018.pdf | Report.pdf]]</ref> and one full-scale implementation in Australia. This approach requires a large-scale engineered plant to handle the various liquid and solid waste streams generated. Soil washing is less suitable for clay-rich soils, where aggregation of the particulates occurs and is difficult to prevent or mitigate. Treatment of the liquid rinse water waste stream is required, which would then rely on conventional water treatment technologies such as granular activated carbon (GAC) or ion exchange. Additionally, in some cases flocculated sludge is generated, which would require treatment or disposal offsite. At present, the only full-scale soil washing demonstration is occurring in Australia, where a vendor has constructed and is operating a 10 million AUD$ treatment plant in anticipation of future treatment of soils generated from remedial actions at Australian Defense installations. Some Australian installations are stockpiling soils due to the lack of cost-effective soil treatment options. According to the vendor, this system generates no solid waste, instead feeding any solids back into the front end of the process for further removal of PFAS<ref name="Grimison2020">Grimison, C., Brookman, I., Hunt, J., and Lucas, J., 2020. Remediation of PFAS-related impacts – ongoing scrutiny and review, Ventia Submission to PFAS Subcommittee of the Joint Standing Committee on Foreign Affairs, Defence and Trade, Australia. [https://www.aph.gov.au/DocumentStore.ashx?id=a209e924-2b7e-4727-bccf-30bef5304bba&subId=691428 Free download.] [[Media: Grimison2020.pdf | Report.pdf]]</ref>.
| |
− | | |
− | ==Conclusions==
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− | Several well-developed remedial technologies have been applied to address soil contaminated with PFAS. Unfortunately, none of the available techniques are ideal, with some reducing leachability but leaving the PFAS-impacted soil in place, while others result in destruction of the contaminants but require high energy inputs with associated high cost.
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| ==References== | | ==References== |
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| <references /> | | <references /> |
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| ==See Also== | | ==See Also== |
| + | *[[Media: ERDC_TR-21-12.pdf | Preparative, Extraction, and Analytical Methods for Simultaneous Determination of Legacy and Insensitive Munition (IM) Constituents in Aqueous, Soil or Sediment, and Tissue Matrices]] |
| + | *[https://serdp-estcp.mil/focusareas/9f7a342a-1b13-4ce5-bda0-d7693cf2b82d/uxo#subtopics SERDP/ESTCP Focus Areas – UXO – Munitions Constituents] |
| + | *[https://denix.osd.mil/edqw/home/ Environmental Data Quality Workgroup] |
Munitions Constituents – Sample Extraction and Analytical Techniques
Munitions Constituents, including insensitive munitions (IM), are a broad category of compounds which, in areas where manufactured or used, can be found in a variety of environmental matrices (waters, soil, and tissues). This presents an analytical challenge when a variety of these munitions are to be quantified. This article discusses sample extraction methods for each typical sample matrix (high level water, low level water, soil and tissue) as well as the accompanying HPLC-UV analytical method for 27 compounds of interest (legacy munitions, insensitive munitions, and surrogates).
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Contributor(s):
Key Resource(s):
- Methods for simultaneous quantification of legacy and insensitive munition (IM) constituents in aqueous, soil/sediment, and tissue matrices[2]
Introduction
Table 1. Analyte list with acronyms and CAS numbers.
Compound
|
Acronym
|
CAS Number
|
1,2-Dinitrobenzene (surrogate) |
1,2-DNB (surr.) |
528-29-0
|
1,3-Dinitrobenzene |
1,3-DNB |
99-65-0
|
1,3,5-Trinitrobenzene |
1,3,5-TNB |
99-35-4
|
1,4-Dinitrobenzene |
1,4-DNB (surr.) |
100-25-4
|
2-Amino-4,6-dinitrotoluene |
2-Am-4,6-DNT |
35572-78-2
|
2-Nitrophenol |
2-NP |
88-75-5
|
2-Nitrotoluene |
2-NT |
88-72-2
|
2,4-Dinitrophenol |
2,4-DNP |
51-28-5
|
2,4-Dinitrotoluene |
2,4-DNT |
121-14-2
|
2,4,6-Trinitrophenol |
Picric Acid (PA) |
88-89-1
|
2,4,6-Trinitrotoluene |
2,4,6-TNT |
118-96-7
|
2,6-Dinitrotoluene |
2,6-DNT |
606-20-2
|
3-Nitrotoluene |
3-NT |
99-08-1
|
3,5-Dinitroaniline |
3,5-DNA |
618-87-1
|
4-Amino-2,6-dinitrotoluene |
4-Am-2,6-DNT |
19406-51-0
|
4-Nitrophenol |
4-NP |
100-02-7
|
4-Nitrotoluene |
4-NT |
99-99-0
|
2,4-Dinitroanisole |
DNAN |
119-27-7
|
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine |
HMX |
2691-41-0
|
Nitrobenzene |
NB |
98-95-3
|
Nitroglycerine |
NG |
55-63-0
|
Nitroguanidine |
NQ |
556-88-7
|
3-Nitro-1,2,4-triazol-5-one |
NTO |
932-64-9
|
ortho-Nitrobenzoic acid |
o-NBA (surr.) |
552-16-9
|
Pentaerythritol tetranitrate |
PETN |
78-11-5
|
Hexahydro-1,3,5-trinitro-1,3,5-triazine |
RDX |
121-82-4
|
N-Methyl-N-(2,4,6-trinitrophenyl)nitramide |
Tetryl |
479-45-8
|
Note: Analytes in bold are not identified by EPA Method 8330B.
|
Figure 1. Primary Method labeled chromatograms
Figure 2. Secondary Method labeled chromatograms
The primary intention of the analytical methods presented here is to support the monitoring of legacy and insensitive munitions contamination on test and training ranges, however legacy and insensitive munitions often accompany each other at demilitarization facilities, manufacturing facilities, and other environmental sites. Energetic materials typically appear on ranges as small, solid particulates and due to their varying functional groups and polarities, can partition in various environmental compartments[3]. To ensure that contaminants are monitored and controlled at these sites and to sustainably manage them a variety of sample matrices (surface or groundwater, process waters, soil, and tissues) must be considered. (Process water refers to water used during industrial manufacturing or processing of legacy and insensitive munitions.) Furthermore, additional analytes must be added to existing methodologies as the usage of IM compounds changes and as new degradation compounds are identified. Of note, relatively new IM formulations containing NTO, DNAN, and NQ are seeing use in IMX-101, IMX-104, Pax-21 and Pax-41 (Table 1)[4][5].
Sampling procedures for legacy and insensitive munitions are identical and utilize multi-increment sampling procedures found in USEPA Method 8330B Appendix A[1]. Sample hold times, subsampling and quality control requirements are also unchanged. The key differences lie in the extraction methods and instrumental methods. Briefly, legacy munitions analysis of low concentration waters uses a single cartridge reverse phase SPE procedure, and acetonitrile (ACN) is used for both extraction and elution for aqueous and solid samples[1][6]. An isocratic separation via reversed-phase C-18 column with 50:50 methanol:water mobile phase or a C-8 column with 15:85 isopropanol:water mobile phase is used to separate legacy munitions[1]. While these procedures are sufficient for analysis of legacy munitions, alternative solvents, additional SPE cartridges, and a gradient elution are all required for the combined analysis of legacy and insensitive munitions.
Previously, analysis of legacy and insensitive munitions required multiple analytical techniques, however the methods presented here combine the two munitions categories resulting in an HPLC-UV method and accompanying extraction methods for a variety of common sample matrices. A secondary HPLC-UV method and a HPLC-MS method were also developed as confirmatory methods. The methods discussed in this article were validated extensively by single-blind round robin testing and subsequent statistical treatment as part of ESTCP ER19-5078. Wherever possible, the quality control criteria in the Department of Defense Quality Systems Manual for Environmental Laboratories were adhered to[7]. Analytes included in the methods presented here are found in Table 1.
The chromatograms produced by the primary and secondary HPLC-UV methods are shown in Figure 1 and Figure 2, respectively. Chromatograms for each detector wavelength used are shown (315, 254, and 210 nm).
Figure 3. Triple cartridge SPE setup
Figure 4. A flow chart of the soil extraction procedure
High Concentration Waters (> 1 ppm)
Aqueous samples suspected to contain the compounds of interest at concentrations detectable without any extraction or pre-concentration are suitable for analysis by direct injection. The method deviates from USEPA Method 8330B by adding a pH adjustment and use of MeOH rather than ACN for dilution[1]. The pH adjustment is needed to ensure method accuracy for ionic compounds (like NTO or PA) in basic samples. A solution of 1% HCl/MeOH is added to both acidify and dilute the samples to a final acid concentration of 0.5% (vol/vol) and a final solvent ratio of 1:1 MeOH/H2O. The direct injection samples are then ready for analysis.
Low Concentration Waters (< 1 ppm)
Aqueous samples suspected to contain the compounds of interest at low concentrations require extraction and pre-concentration using solid phase extraction (SPE). The SPE setup described here uses a triple cartridge setup shown in Figure 3. Briefly, the extraction procedure loads analytes of interest onto the cartridges in this order: StrataTM X, StrataTM X-A, and Envi-CarbTM. Then the cartridge order is reversed, and analytes are eluted via a two-step elution, resulting in 2 extracts (which are combined prior to analysis). Five milliliters of MeOH is used for the first elution, while 5 mL of acidified MeOH (2% HCl) is used for the second elution. The particular SPE cartridges used are noncritical so long as cartridge chemistries are comparable to those above.
Table 2. Primary HPLC-UV mobile phase gradient method concentrations
Method run time = 48 minutes; Column temperature = 25°C Injection volume = 50 μL; Flow rate = 1.0 mL/min Detector wavelengths = 210, 254, and 310 nm
|
Time (min)
|
Reagent Water (%)
|
MeOH (%)
|
0.1% TFA/Water (%)
|
ACN (%)
|
0.00 |
89 |
3 |
3 |
5
|
2.00 |
89 |
3 |
3 |
5
|
2.20 |
52 |
40 |
3 |
5
|
12.5 |
52 |
40 |
3 |
5
|
19.0 |
57 |
35 |
3 |
5
|
28.0 |
48 |
44 |
3 |
5
|
32.0 |
48 |
44 |
3 |
5
|
44.0 |
32 |
60 |
3 |
5
|
44.1 |
89 |
3 |
3 |
5
|
48.0 |
89 |
3 |
3 |
5
|
Soils
Soil collection, storage, drying and grinding procedures are identical to the USEPA Method 8330B procedures[1]; however, the solvent extraction procedure differs in the number of sonication steps, sample mass and solvent used. A flow chart of the soil extraction procedure is shown in Figure 4. Soil masses of approximately 2 g and a sample to solvent ratio of 1:5 (g/mL) are used for soil extraction. The extraction is carried out in a sonication bath chilled below 20 ⁰C and is a two-part extraction, first extracting in MeOH (6 hours) followed by a second sonication in 1:1 MeOH:H2O solution (14 hours). The extracts are centrifuged, and the supernatant is filtered through a 0.45 μm PTFE disk filter.
The solvent volume should generally be 10 mL but if different soil masses are required, solvent volume should be 5 mL/g. The extraction results in 2 separate extracts (MeOH and MeOH:H2O) that are combined prior to analysis.
Tissues
Tissue matrices are extracted by 18-hour sonication using a ratio of 1 gram of wet tissue per 5 mL of MeOH. This extraction is performed in a sonication bath chilled below 20 ⁰C and the supernatant (MeOH) is filtered through a 0.45 μm PTFE disk filter.
Due to the complexity of tissue matrices, an additional tissue cleanup step, adapted from prior research, can be used to reduce interferences[8][2]. The cleanup procedure uses small scale chromatography columns prepared by loading 5 ¾” borosilicate pipettes with 0.2 g activated silica gel (100–200 mesh). The columns are wetted with 1 mL MeOH, which is allowed to fully elute and then discarded prior to loading with 1 mL of extract and collecting in a new amber vial. After the extract is loaded, a 1 mL aliquot of MeOH followed by a 1 mL aliquot of 2% HCL/MeOH is added. This results in a 3 mL silica treated tissue extract. This extract is vortexed and diluted to a final solvent ratio of 1:1 MeOH/H2O before analysis.
HPLC-UV and HPLC-MS Methods
Table 3. Secondary HPLC-UV mobile phase gradient method concentrations
Method run time = 43 minutes; Column temperature = 25°C Injection volume = 50 μL; Flow rate = 0.8 mL/min Detector wavelengths = 210, 254, and 310 nm
|
Time (min)
|
Reagent Water (%)
|
MeOH (%)
|
0.1% TFA/Water (%)
|
ACN (%)
|
0.00 |
75 |
10 |
10 |
5
|
2.50 |
75 |
10 |
10 |
5
|
2.60 |
39 |
46 |
10 |
5
|
9.00 |
39 |
46 |
10 |
5
|
9.10 |
33.5 |
51.5 |
10 |
5
|
15.00 |
35 |
50 |
10 |
5
|
15.10 |
43 |
42 |
10 |
5
|
33.00 |
30 |
55 |
10 |
5
|
33.10 |
75 |
10 |
10 |
5
|
43.00 |
75 |
10 |
10 |
5
|
Table 4. Ionization source and detector parameters
Parameter
|
Value
|
Ionization Source |
APCI
|
Ionization Mode |
Negative
|
Drying Gas Temperature (°C) |
350
|
Vaporizer Temperature (°C) |
325
|
Drying Gas Flow (L/min) |
4.0
|
Nebulizer Pressure (psig) |
40
|
Corona Current (μA) |
10
|
Capillary Potential (V) |
1500
|
Mass Range |
40 – 400
|
Fragmentor |
100
|
Gain |
1
|
Threshold |
0
|
Step Size |
0.20
|
Speed (μ/sec) |
743
|
Peak Width (min) |
0.06
|
Cycle Time (sec/cycle) |
0.57
|
The Primary HPLC-UV method uses a Phenomenex Synergi 4 µm Hydro-RP column (80Å, 250 x 4.6 mm), or comparable, and is based on both the HPLC method found in USEPA 8330B and previous work[1][8][2]. This separation relies on a reverse phase column and uses a gradient elution, shown in Table 2. Depending on the analyst’s needs and equipment availability, the method has been proven to work with either 0.1% TFA or 0.25% FA (vol/vol) mobile phase. Addition of a guard column like a Phenomenex SecurityGuard AQ C18 pre-column guard cartridge can be optionally used. These optional changes to the method have no impact on the method’s performance.
The Secondary HPLC-UV method uses a Restek Pinnacle II Biphenyl 5 µm (150 x 4.6 mm) or comparable column and is intended as a confirmatory method. Like the Primary method, this method can use an optional guard column and utilizes a gradient elution, shown in Table 3.
For instruments equipped with a mass spectrometer (MS), a secondary MS method is available and was developed alongside the Primary UV method. The method was designed for use with a single quadrupole MS equipped with an atmospheric pressure chemical ionization (APCI) source, such as an Agilent 6120B. A majority of the analytes shown in Table 1 are amenable to this MS method, however nitroglycerine (which is covered extensively in USEPA method 8332) and 2-,3-, and 4-nitrotoluene compounds aren’t compatible with the MS method. MS method parameters are shown in Table 4.
Summary
The extraction methods and instrumental methods in this article build upon prior munitions analytical methods by adding new compounds, combining legacy and insensitive munitions analysis, and expanding usable sample matrices. These methods have been verified through extensive round robin testing and validation, and while the methods are somewhat challenging, they are crucial when simultaneous analysis of both insensitive and legacy munitions is needed.
References
- ^ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 United States Environmental Protection Agency (USEPA), 2006. EPA Method 8330B (SW-846) Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Revision 2. USEPA Website EPA Method 8330b
- ^ 2.0 2.1 2.2 Crouch, R.A., Smith, J.C., Stromer, B.S., Hubley, C.T., Beal, S., Lotufo, G.R., Butler, A.D., Wynter, M.T., Russell, A.L., Coleman, J.G., Wayne, K.M., Clausen, J.L., Bednar, A.J., 2020. Methods for simultaneous determination of legacy and insensitive munition (IM) constituents in aqueous, soil/sediment, and tissue matrices. Talanta, 217, Article 121008. doi: 10.1016/j.talanta.2020.121008 Open Access Manuscript.pdf
- ^ Walsh, M.R., Temple, T., Bigl, M.F., Tshabalala, S.F., Mai, N. and Ladyman, M., 2017. Investigation of Energetic Particle Distribution from High‐Order Detonations of Munitions. Propellants, Explosives, Pyrotechnics, 42(8), pp. 932-941. doi: 10.1002/prep.201700089
- ^ Mainiero, C. 2015. Picatinny Employees Recognized for Insensitive Munitions. U.S. Army, Picatinny Arsenal Public Affairs. Open Access Press Release
- ^ Frem, D., 2022. A Review on IMX-101 and IMX-104 Melt-Cast Explosives: Insensitive Formulations for the Next-Generation Munition Systems. Propellants, Explosives, Pyrotechnics, 48(1), e202100312. doi: 10.1002/prep.202100312
- ^ United States Environmental Protection Agency (USEPA), 2007. EPA Method 3535A (SW-846) Solid-Phase Extraction (SPE), Revision 1. USEPA Website Method 3535A.pdf
- ^ US Department of Defense and US Department of Energy, 2021. Consolidated Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.4. 387 pages. Free Download QSM Version 5.4.pdf
- ^ 8.0 8.1 Russell, A.L., Seiter, J.M., Coleman, J.G., Winstead, B., Bednar, A.J., 2014. Analysis of munitions constituents in IMX formulations by HPLC and HPLC-MS. Talanta, 128, pp. 524–530. doi: 10.1016/j.talanta.2014.02.013
See Also