Difference between revisions of "User:Jhurley/sandbox"

From Enviro Wiki
Jump to: navigation, search
(→‎Application of High-Pressure Membranes for Treatment of PFAS Contaminated Water)
(→‎State of the Practice)
 
(273 intermediate revisions by the same user not shown)
Line 1: Line 1:
−
==Reverse Osmosis and Nanofiltration Systems for PFAS Removal==  
+
==PFAS Destruction by Ultraviolet/Sulfite Treatment==  
−
[[Wikipedia: Nanofiltration | Nanofiltration (NF)]] or [[Wikipedia: Reverse osmosis | reverse osmosis (RO)]] are engineered polymeric filters designed to remove solutes down to the atomic and molecular size scale<ref name="Wilf2019">Wilf, M., 2019. Basic Terms and Definitions, Chapter 3 in Desalination: Water from Water, 2nd Edition, J. Kucera, Editor. John Wiley & Sons. ISBN: 978-1-119-40774-4 [https://doi.org/10.1002/9781119407874.ch3 doi: 10.1002/9781119407874.ch3]</ref><ref name="BellonaEtAl2004">Bellona, C., Drewes, J., Xu, P., Amy, G., 2004. Factors affecting the rejection of organic solutes during NF/RO treatment—a literature review. Water Research, 38(12), p. 2795-2809. [https://doi.org/10.1016/j.watres.2004.03.034 doi: 10.1016/j.watres.2004.03.034]</ref><ref name="BazarganSalgado2018">Bazargan, A., Salgado, B., 2018. Fundamentals of Desalination Technology, in A Multidisciplinary Introduction to Desalination, A. Bazargan, Editor.  River Publishers. p. 41-66. ISBN 9788793379541. [https://doi.org/10.1201/9781003336914 doi: 10.1201/9781003336914]</ref>. RO, and to a lesser extent NF, has been implemented in a variety of water treatment applications including seawater and brackish water desalination, surface water treatment, industrial process water separation, and purification applications<ref name="Wilf2019"/><ref name="BellonaEtAl2004"/><ref name="BazarganSalgado2018"/><ref name="TurekEtAl2017">Turek, M., Mitko, K., Piotrowski, K., Dydo, P., Laskowska, E., Jakóbik-Kolon, A., 2017. Prospects for high water recovery membrane desalination. Desalination, 401, p. 180-189. [https://doi.org/10.1016/j.desal.2016.07.047 doi: 10.1016/j.desal.2016.07.047]</ref><ref name="PanagopoulosEtAl2019">Panagopoulos, A., Haralambous, K.-J., Loizidou, M., 2019. Desalination brine disposal methods and treatment technologies - A review. Science of The Total Environment, 693, Article 133545. [https://doi.org/10.1016/j.scitotenv.2019.07.351 doi: 10.1016/j.scitotenv.2019.07.351]</ref><ref name="WarsingerEtAl2018">Warsinger, D.M., Chakraborty, S., Tow, E.W., Plumlee, M.H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A.M., Achilli, A., Ghassemi, A., Padhye, L.P., Snyder, S.A., Curcio, S., Vecitis, C.D., Arafat, H.A., Lienhard, J.H., 2018. A review of polymeric membranes and processes for potable water reuse. Progress in Polymer Science, 81, p. 209-237. [https://doi.org/10.1016/j.progpolymsci.2018.01.004 doi: 10.1016/j.progpolymsci.2018.01.004]</ref><ref name="Yan2017">Yan, D., 2017. Membrane Desalination Technologies, Chapter 6 in A Multidisciplinary Introduction to Desalination, A. Bazargan, Editor. River Publishers, p. 155-199. ISBN: 9788793379541</ref><ref name="Bellona2019">Bellona, C., 2019. Nanofiltration - Theory and Application, Chapter 4 in Desalination: Water from Water, 2nd Edition, J. Kucera, Editor. John Wiley & Sons. ISBN: 978-1-119-40774-4. [https://doi.org/10.1002/9781118904855.ch4 doi: 10.1002/9781118904855.ch4]</ref>. RO and NF use semi-permeable membranes that limit diffusion of solutes into the product water (i.e., permeate) through [[Wikipedia: Steric effects | steric]] and electrostatic exclusion from the membrane polymer<ref name="BellonaEtAl2004"/>. Due to the molecular size and ionic character of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], past research has demonstrated that both RO and NF membranes can achieve a high degree of separation (i.e., rejection) of PFAS<ref name="ApplemanEtAl2013">Appleman, T.D., Dickenson, E.R.V., Bellona, C., Higgins, C.P., 2013. Nanofiltration and granular activated carbon treatment of perfluoroalkyl acids. Journal of Hazardous Materials, 260, p. 740-746. [https://doi.org/10.1016/j.jhazmat.2013.06.033 doi: 10.1016/j.jhazmat.2013.06.033]</ref><ref name="Steinle-DarlingReinhard2008">Steinle-Darling, E., 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), p. 5292-5297. [https://doi.org/10.1021/es703207s doi: 10.1021/es703207s]</ref><ref name="SafulkoEtAl2023">Safulko, A., Cath, T.Y., Li, F., Tajdini, B., Boyd, M., Huehmer, R.P., Bellona, C., 2023. Rejection of perfluoroalkyl acids by nanofiltration and reverse osmosis in a high-recovery closed-circuit membrane filtration system. Separation and Purification Technology, 326, Article 124867. [https://doi.org/10.1016/j.seppur.2023.124867  doi: 10.1016/j.seppur.2023.124867]  [[Media: SafulkoEtAl2023.pdf | Open Access Manuscript]]</ref>.  
+
The ultraviolet (UV)/sulfite based reductive defluorination process has emerged as an effective and practical option for generating hydrated electrons (''e<sub><small>aq</small></sub><sup><big>'''-'''</big></sup>'' ) which can destroy [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] in water. It offers significant advantages for PFAS destruction, including significant defluorination, high treatment efficiency for long-, short-, and ultra-short chain PFAS without mass transfer limitations, selective reactivity by hydrated electrons, low energy consumption, low capital and operation costs, and no production of harmful byproducts. A UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor">Haley and Aldrich, Inc. (commercial business), 2024. EradiFluor. [https://www.haleyaldrich.com/about-us/applied-research-program/eradifluor/ Comercial Website]</ref>) has been demonstrated in two field demonstrations in which it achieved near-complete defluorination and greater than 99% destruction of 40 PFAS analytes measured by EPA method 1633.
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
Line 8: Line 8:
 
*[[PFAS Ex Situ Water Treatment]]
 
*[[PFAS Ex Situ Water Treatment]]
 
*[[PFAS Sources]]
 
*[[PFAS Sources]]
−
*[[PFAS Transport and Fate]]
+
*[[PFAS Treatment by Electrical Discharge Plasma]]
 +
*[[Supercritical Water Oxidation (SCWO)]]
 +
*[[Photoactivated Reductive Defluorination - PFAS Destruction]]
  
−
'''Contributors:''' Christopher Bellona, Nicole Masters, Stephen Richardson
+
'''Contributors:''' John Xiong, Yida Fang, Raul Tenorio, Isobel Li, and Jinyong Liu
  
−
'''Key Resource(s):'''
+
'''Key Resources:'''
−
 
+
*Defluorination of Per- and Polyfluoroalkyl Substances (PFAS) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management<ref name="BentelEtAl2019">Bentel, M.J., Yu, Y., Xu, L., Li, Z., Wong, B.M., Men, Y., Liu, J., 2019. Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management. Environmental Science and Technology, 53(7), pp. 3718-28. [https://doi.org/10.1021/acs.est.8b06648 doi: 10.1021/acs.est.8b06648]&nbsp; [[Media: BentelEtAl2019.pdf | Open Access Article]]</ref>
−
*Interstate Technology Regulatory Council (ITRC), PFAS – Per- and Polyfluoroalkyl Substances: [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_2 12.2 Field-Implemented Liquids Treatment Technologies] and [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_5 12.5 Limited Application and Developing Liquids Treatment Technologies]
+
*Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies<ref>Liu, Z., Chen, Z., Gao, J., Yu, Y., Men, Y., Gu, C., Liu, J., 2022. Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies. Environmental Science and Technology, 56(6), pp. 3699-3709. [https://doi.org/10.1021/acs.est.1c07608 doi: 10.1021/acs.est.1c07608]&nbsp; [[Media: LiuZEtAl2022.pdf | Open Access Article]]</ref>
 +
*Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment<ref>Tenorio, R., Liu, J., Xiao, X., Maizel, A., Higgins, C.P., Schaefer, C.E., Strathmann, T.J., 2020. Destruction of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment. Environmental Science and Technology, 54(11), pp. 6957-67. [https://doi.org/10.1021/acs.est.0c00961 doi: 10.1021/acs.est.0c00961]</ref>
 +
*EradiFluor<sup>TM</sup><ref name="EradiFluor"/>
  
 
==Introduction==
 
==Introduction==
−
[[File:RichardsonFig1.png|thumb|500px|Figure 1. Basic schematic of cross-flow operation of high-pressure membranes. The feed water flows parallel to the membrane becoming more concentrated and then leaves the system as retentate. The permeate is water forced through the membrane by applying pressure. Q is flowrate and C is concentration of the solute of interest. F is the feed, P is the permeate, and R is the retentate.]]
+
The hydrated electron (''e<sub><small>aq</small></sub><sup><big>'''-'''</big></sup>'' ) can be described as an electron in solution surrounded by a small number of water molecules<ref name="BuxtonEtAl1988">Buxton, G.V., Greenstock, C.L., Phillips Helman, W., Ross, A.B., 1988. Critical Review of Rate Constants for Reactions of Hydrated Electrons, Hydrogen Atoms and Hydroxyl Radicals (⋅OH/⋅O-) in Aqueous Solution. Journal of Physical and Chemical Reference Data, 17(2), pp. 513-886. [https://doi.org/10.1063/1.555805 doi: 10.1063/1.555805]</ref>. Hydrated electrons can be produced by photoirradiation of solutes, including sulfite, iodide, dithionite, and ferrocyanide, and have been reported in literature to effectively decompose per- and polyfluoroalkyl substances (PFAS) in water. The hydrated electron is one of the most reactive reducing species, with a standard reduction potential of about −2.9 volts. Though short-lived, hydrated electrons react rapidly with many species having more positive reduction potentials<ref name="BuxtonEtAl1988"/>.  
−
High-pressure membrane filtration such as nanofiltration (NF) or reverse osmosis (RO) is a filtration process that separates dissolved inorganic and organic solutes from liquid solvents, typically water<ref name="Wilf2019"/>. As opposed to porous and more permeable low-pressure membranes (i.e., microfiltration and ultrafiltration), NF and RO membranes are widely considered semi-permeable and therefore require higher operating pressures to force water against an [[Wikipedia: Osmosis | osmotic gradient]] to produce a purified permeate stream<ref name="BellonaEtAl2004"/><ref name="BazarganSalgado2018"/>. The semi-permeable nature and properties of RO and NF membranes results in  significantly lower solute diffusive flux across the membranes compared to water<ref name="BellonaEtAl2004"/>.
 
−
 
 
−
To optimize solute separation and minimize accumulation of solutes on the membrane, these systems are almost exclusively operated in a cross-flow configuration where feed water flows parallel to the membrane surface and is forced across the membrane through the application of pressure (Figure 1). In a cross-flow configuration, NF and RO systems are separation processes that yield two streams: the treated permeate and the concentrated retentate. 
 
−
 
 
−
Typical parameters used to describe operational performance of high-pressure membrane systems include solvent ''recovery'' and solute ''rejection''. Recovery is defined as the percentage of feed water that becomes permeate, which can be calculated as:
 
−
 
 
−
:::[[File: RichardsonEq1.png]]
 
−
 
 
−
where ''Q<sub>P</sub>'' is the permeate flow rate, and ''Q<sub>F</sub>'' is the feed flow rate. The recovery of a high-pressure membrane system is dependent upon the RO system configuration and feed water quality. For feed waters containing relatively low [[Wikipedia: Total dissolved solids | total dissolved solids (TDS)]] concentrations, in conventional RO and NF membrane applications, recovery is typically between 75% and 85%. However, several novel membrane configurations have been developed to increase membrane recoveries to 90% and greater depending on feed water quality.
 
−
 
 
−
Solute rejection is defined as the percent of concentrated feed water retained by the membrane and can be calculated as:
 
−
 
 
−
:::[[File: RichardsonEq2.png]]
 
−
 
 
−
where ''C<sub>p</sub>'' and ''C<sub>f</sub>'' are the concentration of a solute in the permeate and feed water, respectively. Because the retentate stream contains high concentrations of all solutes rejected by the membrane, minimization of retentate volume is a focus of ongoing research and development<ref name="TurekEtAl2017"/><ref name="PanagopoulosEtAl2019"/>.
 
−
 
 
−
[[File:RichardsonFig2.png|thumb|650px|Figure 2. (Left) Spiral-wound membrane element with the feed side of the element and permeate collection tube in the middle visible. (Right) 1-million gallon per day membrane system with multiple pressure vessels.]]
 
−
Significant advancements in membrane material development have led to development of NF and RO membranes with varying pressure requirements and solute rejection characteristics<ref name="BellonaEtAl2004"/><ref name="WarsingerEtAl2018"/>. RO utilizes very tight and selective membrane material (typically [[Wikipedia: Polyamide | polyamide]]) that can achieve high rejection of most dissolved solutes but requires relatively high pressures, typically >150 psi depending on TDS concentration and RO membrane type (e.g., requiring up to 1000 psi when treating seawater with RO membrane elements optimized for seawater)<ref name="Yan2017"/>. RO is used in a variety of applications where a high degree of solute separation is desired including seawater and brackish water desalination, potable water reuse applications, industrial water treatment, and separation applications<ref name="Wilf2019"/>. NF is fundamentally similar to RO; however, NF has been engineered to provide selective separation of solutes and often operate at lower pressures than RO (<150 psi). NF membranes have a range of rejection characteristics with some NF membranes being ‘tighter’ with lower permeability similar to RO (i.e., high salt and organic solute rejection) and others being ‘looser’ with high permeability (i.e., lower salt and organic solute rejection)<ref name="Bellona2019"/>.
 
−
 
 
−
High-pressure NF and RO membranes are commonly found in a spiral-wound configuration<ref name="Wilf2019"/>. Spiral-wound elements come in standardized sizes that are then loaded into a series of pressure vessels. An example of a spiral-wound element and a membrane system comprised of multiple pressure vessels is shown in Figure 2. Large-scale membrane systems are typically comprised of several membrane “stages” to increase recovery. Each stage contains multiple pressure vessels containing several individual spiral-wound elements each.
 
−
 
 
−
==Application of High-Pressure Membranes for Treatment of PFAS Contaminated Water==
 
−
[[File:RichardsonFig3.png|thumb|450px|Figure 3. Rejection of nine PFAAs by four available membrane products at the pilot-scale. Rejection data shown above was generated from permeate samples collected at 97% recovery.]]
 
−
[[File:RichardsonFig4.png|thumb|600px|Figure 4. Mobile high-pressure membrane treatment trailer (left) and pilot-scale closed-circuit membrane filtration system (right).]]
 
−
The effectiveness of RO and NF membranes for dissolved solute rejection has led to high-pressure membranes being regarded as one of the best available technologies for PFAS removal for over a decade<ref name="ApplemanEtAl2013"/><ref name="Steinle-DarlingReinhard2008"/>. Several studies have evaluated aspects of PFAS removal by NF and RO membranes including evaluating different membrane products, the impact of operating conditions and water quality, and the influence of physicochemical characteristics of PFAS<ref name="ApplemanEtAl2013"/><ref name="SafulkoEtAl2023"/><ref name="LiuStrathmannBellona2021">Liu, C.J., Strathmann, T.J., Bellona, C., 2021. Rejection of per- and polyfluoroalkyl substances (PFASs) in aqueous film-forming foam by high-pressure membranes. Water Research, 188, Article 116546. [https://doi.org/10.1016/j.watres.2020.116546 doi: 10.1016/j.watres.2020.116546]</ref><ref name="WangEtAl2018">Wang, J., Wang, L., Xu, C., Zhi, R., Miao, R., Liang, T., Yue, X., Lv, Y., 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, p. 787-797.  [https://doi.org/10.1016/j.cej.2017.09.061 doi: 10.1016/j.cej.2017.09.061]</ref><ref name="ZhaoEtAl2016">Zhao, C., Tang, C.Y., Li, P., Adrian, P., Hu, G., 2016. Perfluorooctane sulfonate removal by nanofiltration membrane—the effect and interaction of magnesium ion / humic acid. Journal of Membrane Science, 503, p. 31-41. [https://doi.org/10.1016/j.memsci.2015.12.049 doi: 10.1016/j.memsci.2015.12.049]</ref><ref name="ZhaoEtAl2013">Zhao, C., Zhang, J., He, G., Wang, T., Hou, D., Luan, Z., 2013. Perfluorooctane sulfonate removal by nanofiltration membrane the role of calcium ions. Chemical Engineering Journal, 233, p. 224-232. [https://doi.org/10.1016/j.cej.2013.08.027 doi: 10.1016/j.cej.2013.08.027]</ref><ref name="Steinle-DarlingEtAl2010">Steinle-Darling, E., Litwiller, E., Reinhard, M., 2010. Effects of Sorption on the Rejection of Trace Organic Contaminants During Nanofiltration. Environmental Science and Technology, 44(7), p. 2592-2598. [https://doi.org/10.1021/es902846m doi: 10.1021/es902846m]</ref>. Most studies have focused on anionic (at neutral pH) [[Perfluoroalkyl_and_Polyfluoroalkyl_Substances_(PFAS)#Nomenclature | perfluoroalkyl acid (PFAA)]] rejection and reported greater than 90% separation of PFAAs by available NF and RO membranes due to electrostatic and steric exclusion from the membrane polymer<ref name="ApplemanEtAl2013"/><ref name="Steinle-DarlingReinhard2008"/><ref name="LiuStrathmannBellona2021"/>. Water quality constituents such as organic matter and cations including calcium and magnesium have been shown to reduce rejection of PFAS<ref name="LiuStrathmannBellona2021"/>. However, little is known about how fouling and membrane aging impact rejection of PFAS by NF and RO membranes and additional data are needed. A recent Department of Defense [https://serdp-estcp.mil/ ESTCP] pilot scale project ([https://serdp-estcp.mil/projects/details/0aa2fb20-b851-4b5b-ac64-e72795986b8a ER20-5369]) conducted at Colorado School of Mines (Mines) systematically evaluated the rejection of nine PFAAs by four available NF and RO products using full scale spiral-wound membrane elements in a high recovery membrane system which achieved up to 97% recovery<ref name="SafulkoEtAl2023"/>. Tight NF and the two RO membranes evaluated exhibited greater than 98% rejection of all PFAAs evaluated even at high recovery conditions (Figure 3). The loose NF membrane product evaluated provided lower than expected (based on literature) rejection of investigated PFAAs particularly at higher recovery values. These findings indicate that tight NF and RO membranes can be effective at separating PFAAs from contaminated source waters regardless of PFAA chain length. Energy requirements modeled from these experiments varied from 0.14 kWh/m<sup>3</sup> for loose NF to 0.57 kWh/m<sup>3</sup> for seawater RO<ref name="SafulkoEtAl2023"/>.
 
−
 
 
−
Mines researchers have developed a mobile high-recovery closed-circuit membrane filtration system (Figure 4) that has been successfully deployed for treating groundwater at a fire training area of Wright-Patterson Air Force Base ([https://serdp-estcp.mil/projects/details/be0417c9-aaa4-4fd6-9007-7de0cdbffb85 ESTCP ER21-5136]), groundwater at Peterson Space Force Base (AFCEC BAA-031), and firetruck rinsate at Tyndall Air Force Base ([https://serdp-estcp.mil/projects/details/0aa2fb20-b851-4b5b-ac64-e72795986b8a ESTCP ER20-5369]) during recent ESTCP and AFCEC funded research projects. In these projects, NF or RO was implemented to produce a permeate stream containing low concentrations of PFAS and to concentrate PFAS into smaller volumes of retentate for subsequent destructive PFAS treatment. While NF and RO membranes have demonstrated effective rejection of PFAS, PFAS are subsequently concentrated in the membrane concentrate, or retentate stream. This concentrate stream is increasingly paired with PFAS destruction technologies, as PFAS destruction is often considered viable only for concentrated solutions of PFAS. Ongoing ESTCP funded projects include using high-recovery NF and RO to treat and concentrate groundwater leading to PFAS destruction using [[PFAS Treatment by Electrical Discharge Plasma | plasma based treatment]]<ref name="Richardson2021"> Richardson, S., 2021. Nanofiltration Followed by Electrical Discharge Plasma for Destruction of PFAS and Co-occurring Chemicals in Groundwater: A Treatment Train Approach. [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/be0417c9-aaa4-4fd6-9007-7de0cdbffb85/er21-5136-project-overview Project ER21-5136]</ref> or [[Hydrothermal Alkaline Treatment (HALT) | hydrothermal alkaline treatment (HALT)]]<ref name="Bellona2023">Bellona, C., 2023. Cradle to Grave PFAS Treatment Using Membrane and Foam Fractionation Concentration Followed by Hydrothermal Alkaline Treatment. [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/5cf08cdb-b86a-45d2-98d3-f747ba97d293 Project ER23-8367]</ref>.
 
−
 
 
−
==Advantages and Limitations of the Technology for PFAS Removal==
 
−
<u>Advantages:</u>
 
−
*Robust, high throughput treatment
 
−
*Mature technology with well documented solute separation performance
 
−
*High rejection of PFAS and other contaminants
 
−
*Removes solutes at the molecular scale
 
−
 
 
−
<u>Limitations:</u>
 
−
*Complex and often expensive pretreatment requirements for certain waters
 
−
*Energy intensive
 
−
*High capital costs
 
−
*Membrane fouling requiring high chemical usage for cleaning
 
−
*Concentrated waste stream requiring disposal or destruction
 
−
*Permeate quality depends on feed water concentration
 
−
*Greater operation complexity than most water treatment processes
 
−
*Water loss due to membrane separation
 
−
 
 
−
==Summary==
 
  
 +
Among the electron source chemicals, sulfite (SO<sub>3</sub><sup>2−</sup>) has emerged as one of the most effective and practical options for generating hydrated electrons to destroy PFAS in water. The mechanism of hydrated electron production in a sulfite solution under ultraviolet is shown in Equation 1 (UV is denoted as ''hv, SO<sub>3</sub><sup><big>'''•-'''</big></sup>'' is the sulfur trioxide radical anion):
 +
</br>
 +
::<big>'''Equation 1:'''</big>&nbsp;&nbsp; [[File: XiongEq1.png | 200 px]]
  
−
This investigation proposes that PCMs can affect the thermodynamics and kinetics of hydrolysis reactions by confining the reaction species near PCM surfaces, thus making them less accessible to solvent molecules and creating an environment with a weaker dielectric constant that favors nucleophilic substitution reactions. The addition of QA groups on the PCM surface can further accelerate MC hydrolysis. The performance of PCM toward DNAN hydrolysis was evaluated by comparing the MC decay kinetics across various PCM types, including unmodified PCMs such as almond shell char or activated carbon (AC)), and modified PCMs with physical or chemically attached QA groups. The results suggest that QA-modified activated carbon performed the best by reducing the half-life of DNAN to 2.5 days at pH 11.5 and 25°C while maintaining its reactivity over ten consecutive additions of DNAN<ref name="SeenthiaEtAl2024"/>. TNT exhibited faster decay in samples containing QA-modified AC than unmodified AC, with an estimated half-life of 0.2 days and 1 day, respectively<ref name="Li"/>. Nitrite was observed as one of the transformation products for both DNAN and TNT, suggesting the presence of PCM favored the denitration pathway. By contrast, demethylation, the preferred pathway in homogeneous solution, produces [[Wikipedia: 2,4-Dinitrophenol | 2,4-dinitrophenol (DNP)]]. Denitration catalyzed by PCM was advantageous when compared to demethylation because nitrite is less toxic than DNAN and DNP. Overall, the results suggest that further improvement of the PCM performance could be expected by tailoring its surface to increase the abundance of QA while decreasing the presence of -NH<sub>2</sub> or -OH groups for the hydrolysis of MCs.  
+
The hydrated electron has demonstrated excellent performance in destroying PFAS such as [[Wikipedia:Perfluorooctanesulfonic acid | perfluorooctanesulfonic acid (PFOS)]], [[Wikipedia:Perfluorooctanoic acid|perfluorooctanoic acid (PFOA)]]<ref>Gu, Y., Liu, T., Wang, H., Han, H., Dong, W., 2017. Hydrated Electron Based Decomposition of Perfluorooctane Sulfonate (PFOS) in the VUV/Sulfite System. Science of The Total Environment, 607-608, pp. 541-48. [https://doi.org/10.1016/j.scitotenv.2017.06.197 doi: 10.1016/j.scitotenv.2017.06.197]</ref> and [[Wikipedia: GenX|GenX]]<ref>Bao, Y., Deng, S., Jiang, X., Qu, Y., He, Y., Liu, L., Chai, Q., Mumtaz, M., Huang, J., Cagnetta, G., Yu, G., 2018. Degradation of PFOA Substitute: GenX (HFPO–DA Ammonium Salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite? Environmental Science and Technology, 52(20), pp. 11728-34. [https://doi.org/10.1021/acs.est.8b02172 doi: 10.1021/acs.est.8b02172]</ref>. Mechanisms include cleaving carbon-to-fluorine (C-F) bonds (i.e., hydrogen/fluorine atom exchange) and chain shortening (i.e., [[Wikipedia: Decarboxylation | decarboxylation]], [[Wikipedia: Hydroxylation | hydroxylation]], [[Wikipedia: Elimination reaction | elimination]], and [[Wikipedia: Hydrolysis | hydrolysis]])<ref name="BentelEtAl2019"/>.
  
−
[[File:XuFig3.png | thumb |400px| Figure 3. (a) Ball-and-stick model of TNT confined between four layers of graphene with quaternary ammonium groups with a 4-nm distance, black = graphite, green = TNT, purple = ammonium groups, orange = chloride ions, blue = hydroxide oxygens<ref name="SeenthiaEtAl2024"/>. (b) (Top) Molecular snapshot from an AIMD/MM simulation: DNAN + [OH<sup>-</sup>] → DNAN-2-OH + nitrite in a nano-pore, containing DNAN,  hydroxide, Na<sup>+</sup> counter-ion, and  43 H<sub>2</sub>O, at a concentration of 1.3 M. (Bottom) Reaction pathways: Nucleophilic aromatic reaction of DNAN + [OH<sup>-</sup>] → DNAN-2-OH + Nitrite in solution and within a nano-pore, investigated using PBE and PBE0 AIMD/MM free energy simulations with WHAM. Each pathway used approximately 0.5 ns of simulation time<ref name="Li"/>.]]
+
==Process Description==
−
Further mechanistic insights were obtained by performing non-reactive molecular dynamics simulations on idealized pore structures. Upon the introduction of positively charged QA groups, the structure changed dramatically at the PCM interface. As the number of surface groups increased, the resulting density of OH<sup>-</sup> at the PCM surface increased by a factor of four relative to the density in the middle of the pore. Hence, the impact of the surface-bound cations was to attract OH<sup>-</sup> in competition with the neutralizing anions in the environment. In addition to driving the accumulation of OH<sup>-</sup>, the surface QA groups also impacted the distribution of TNT in the pore. At low QA surface coverage, TNT sought to adsorb on the exposed graphene. However, at sufficiently high QA surface coverage, TNT was blocked from lying flat on the graphene sheet and instead aggregated in the fluid away from the pore wall. The observation of TNT surface layering at intermediate charge densities was intriguing because it demonstrated the collection of TNT molecules close to the surface in the same spatial region where hydroxide was likewise accumulating relative to its concentration in the interstitial fluid. The molecular dynamics simulations provided evidence that the presence of the surface groups can play a role in accelerating TNT hydrolysis by acting to concentrate both TNT and hydroxide near the pore wall<ref name="Li"/>.
+
A commercial UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>) includes an optional pre-oxidation step to transform PFAS precursors (when present) and a main treatment step to break C-F bonds by UV/sulfite reduction. The effluent from the treatment process can be sent back to the influent of a pre-treatment separation system (such as a [[Wikipedia: Foam fractionation | foam fractionation]], [[PFAS Treatment by Anion Exchange | regenerable ion exchange]], or a [[Reverse Osmosis and Nanofiltration Membrane Filtration Systems for PFAS Removal | membrane filtration system]]) for further concentration or sent for off-site disposal in accordance with relevant disposal regulations. A conceptual treatment process diagram is shown in Figure 1. [[File: XiongFig1.png | thumb | left | 600 px | Figure 1: Conceptual Treatment Process for a Concentrated PFAS Stream]]<br clear="left"/>
  
−
[[Wikipedia: Molecular dynamics#Potentials in ab initio methods | ''Ab Initio'' Molecular Dynamics/Molecular Mechanics (AIMD/MM)]] free energy simulations using expanded slabs and unit cells were also performed, focusing on the interaction of DNAN, hydroxide ions, Na<sup>+</sup>, and multiple water molecules sandwiched between two graphene layers<ref name="SeenthiaEtAl2024"/>. The upper panel of Figure 3(b) provides a molecular snapshot from the AIMD/MM simulation, showcasing the intermediate stage of DNAN reacting with a hydroxide ion within a nano-pore structure. The lower panel depicts the reaction energy profiles for the hydrolysis of DNAN, both in bulk aqueous solution and within the nano-pore environment. The x-axis represents the reaction coordinate, a schematic representation of the progression from reactants to products through various transition states and intermediates. The y-axis corresponds to the [[Wikipedia: Gibbs free energy| Gibbs free energy]] changes (ΔG), providing insights into the thermodynamic favorability of each step in the pathway. Lower barriers corresponded to more kinetically accessible reactions. In the nano-pore environment, the energy barriers were significantly reduced, suggesting a catalytic effect due to confinement. This reduction was quantified by a decrease in ΔG of approximately 8 kcal/mol compared to the bulk solution, indicating that the reactions were not only more thermodynamically favorable but also kinetically accelerated in the nano-pore. In conclusion, the results demonstrate that nano-pore environments can significantly alter the hydrolysis mechanism of DNAN, leading to potentially less toxic products.  
+
==Advantages==
 +
A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by ''e<sub><small>aq</small></sub><sup><big>'''-'''</big></sup>'', low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:
 +
*'''High efficiency for short- and ultrashort-chain PFAS:''' While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies<ref>Singh, R.K., Brown, E., Mededovic Thagard, S., Holson, T.M., 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, Article 124452. [https://doi.org/10.1016/j.jhazmat.2020.124452 doi: 10.1016/j.jhazmat.2020.124452]</ref><ref>Singh, R.K., Multari, N., Nau-Hix, C., Woodard, S., Nickelsen, M., Mededovic Thagard, S., Holson, T.M., 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21), pp. 13973-80. [https://doi.org/10.1021/acs.est.0c02158 doi: 10.1021/acs.est.0c02158]</ref><ref>Nau-Hix, C., Multari, N., Singh, R.K., Richardson, S., Kulkarni, P., Anderson, R.H., Holsen, T.M., Mededovic Thagard S., 2021. Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater. American Chemical Society’s Environmental Science and Technology (ES&T) Water, 1(3), pp. 680-87. [https://doi.org/10.1021/acsestwater.0c00170 doi: 10.1021/acsestwater.0c00170]</ref>, the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including [[Wikipedia: Trifluoroacetic acid | trifluoroacetic acid (TFA)]] and [[Wikipedia: Perfluoropropionic acid | perfluoropropionic acid (PFPrA)]].
 +
*'''High defluorination ratio:''' As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
 +
*'''No harmful byproducts:''' While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.  
 +
*'''Ambient pressure and low temperature:''' The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS. 
 +
*'''Low energy consumption:''' The electrical energy per order values for the degradation of [[Wikipedia: Perfluoroalkyl carboxylic acids | perfluorocarboxylic acids (PFCAs)]] by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., [[Supercritical Water Oxidation (SCWO) | supercritical water oxidation]])<ref>Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A Review. Critical Reviews in Environmental Science and Technology, 49(10), pp. 866-915. [https://doi.org/10.1080/10643389.2018.1542916 doi: 10.1080/10643389.2018.1542916]</ref>.
 +
*'''Co-contaminant destruction:''' The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride<ref>Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. [https://doi.org/10.1016/j.jece.2015.07.026 doi: 10.1016/j.jece.2015.07.026]</ref><ref>Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. [https://doi.org/10.1016/j.cej.2012.11.086 doi: 10.1016/j.cej.2012.11.086]</ref><ref>Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. [https://doi.org/10.1021/es3008535 doi: 10.1021/es3008535]</ref><ref>Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. [https://doi.org/10.1016/j.watres.2014.05.051 doi: 10.1016/j.watres.2014.05.051]</ref>.
  
−
[[File:XuFig4.png | thumb |500px| Figure 4. Proposed formation of charge-assisted hydrogen bond between NTO and weak acid functional groups on the carbon surface<ref name="Abdelraheem"/>.]]
+
==Limitations==
−
Results from this project suggest that NTO was chemically stable for up to at least a week in NaOH solution at pH 13.8<ref name="Abdelraheem">Abdelraheem, W., Meng, L., Pignatello, J.J., Seenthia, N.I., Xu, W., 2024. Participation of Strong H-Bonding to Acidic Groups Contributes to the Intense Sorption of the Anionic Munition, Nitrotriazolone (NTO) to the Carbon, Filtrasorb 400. Environmental Science and Technology, 58(46), pp. 20719-20728. [https://doi.org/10.1021/acs.est.4c07055 doi: 10.1021/acs.est.4c07055]</ref>. Despite its highly polar and anionic character (''pK<sub>a</sub>'' = 3.78), NTO exhibited unexpectedly strong sorption toward PCM at environmentally relevant pH conditions. This high affinity was partly due to the formation of an exceptionally strong negative charge-assisted hydrogen bond, or (−)CAHB, with weak acid functional groups on the carbon surface. The CAHB was identified by evaluating adsorption isotherms, pH adsorption edge plots, competitive sorption experiments, and pH drift experiments. The findings contradict the conventional view that polar organic anions have little affinity for or are even repelled by hydrophobic carbonaceous sorbents. The results call attention to the need for new models or modification of existing models for the sorption of ionizable compounds that consider CAHB formation with sorbents. The findings also have potential implications for the use of carbons in environmental remediation and catalysis, particularly for the design of strategies for the retention and degradation of highly mobile contaminants.
+
Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.
 +
*Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
 +
*Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
 +
*The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and [[Wikipedia: Perfluorobutanesulfonic acid | perfluorobutanesulfonate (PFBS)]] exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.
  
−
Batch and column tests were conducted to evaluate the adsorption and hydrolysis of post-detonation residues of [[Wikipedia: IMX-101 | IMX-101]] in three DoD range soils amended with modified PCMs<ref name="SeenthiaEtAl2025">Seenthia, N.I., Abdelraheem, W., Beal, S.A., Pignatello, J.J., Xu, W., 2025. Simultaneous adsorption and hydrolysis of insensitive munition compounds by pyrogenic carbonaceous matter (PCM) and functionalized PCM in soils. Journal of Hazardous Materials, 494, article 138501. [https://doi.org/10.1016/j.jhazmat.2025.138501 doi: 10.1016/j.jhazmat.2025.138501]</ref>. Results indicated that adding PCMs enhanced the removal of NTO, NQ, and DNAN in soils compared to the soil controls, with enhancement factors ranging from 50 to 300. Consistent with previous results, NTO exhibited the highest partition coefficients (''K<sub>d</sub>'') in PCM-amended soils compared to DNAN and NQ despite its highly polar and anionic character. Among various PCMs, QA-modified AC performed best, followed by unmodified AC and chars. The ''K<sub>d</sub>'' values of NTO, NQ, and DNAN were slightly lower in the IMX-101 mixture than individually, possibly due to the adsorption competition from other constituents in IMX-101. The treatment was evaluated at pH 8, 10, and 12. No NTO decay was observed across the investigated pH range with or without PCM. By contrast, up to 13% of NQ was removed but only at pH > 10. Up to 90% DNAN decay occurred at pH 10 and 12 over 7 days in soils amended with modified AC. The 2% amendment dose was most effective, maintaining its adsorption capacity and reactivity over three consecutive IMX-101 additions. Column tests confirmed that 2% PCM addition significantly delayed the NTO, NQ, and DNAN breakthrough. The breakthrough volume (defined as treatment volume resulting in Concentration<sub>out</sub>=0.1*Concentration<sub>in</sub>) of NTO, NQ, and DNAN correlated with their ''K<sub>d</sub>'' values obtained from the batch tests, where no retention was observed in the absence of PCM amendments. These findings highlight the feasibility of using modified PCM to simultaneously retain and transform IMX residues, providing a strategy for using reactive amendments ''in situ'' to sustain military operation and pollutant abatement.
+
==State of the Practice==
 +
[[File: XiongFig2.png | thumb | 500 px | Figure 2. Field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.]]
 +
[[File: XiongFig3.png | thumb | 500 px | Figure 3. Field demonstration of a treatment train (SAFF + EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.]] 
 +
The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the [[Wikipedia: TOP Assay | total oxidizable precursor (TOP) assay]], adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.  
 +
*Under the [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)] [https://serdp-estcp.mil/projects/details/4c073623-e73e-4f07-a36d-e35c7acc75b6/er21-5152-project-overview Project ER21-5152], a field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an ''in situ'' foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
 +
*Another field demonstration was completed at an Air Force base in California, where a treatment train combining [https://serdp-estcp.mil/projects/details/263f9b50-8665-4ecc-81bd-d96b74445ca2 Surface Active Foam Fractionation (SAFF)] and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).
  
 
==References==
 
==References==

Latest revision as of 11:33, 29 January 2026

PFAS Destruction by Ultraviolet/Sulfite Treatment

The ultraviolet (UV)/sulfite based reductive defluorination process has emerged as an effective and practical option for generating hydrated electrons (eaq- ) which can destroy PFAS in water. It offers significant advantages for PFAS destruction, including significant defluorination, high treatment efficiency for long-, short-, and ultra-short chain PFAS without mass transfer limitations, selective reactivity by hydrated electrons, low energy consumption, low capital and operation costs, and no production of harmful byproducts. A UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluorTM[1]) has been demonstrated in two field demonstrations in which it achieved near-complete defluorination and greater than 99% destruction of 40 PFAS analytes measured by EPA method 1633.

Related Article(s):

Contributors: John Xiong, Yida Fang, Raul Tenorio, Isobel Li, and Jinyong Liu

Key Resources:

  • Defluorination of Per- and Polyfluoroalkyl Substances (PFAS) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management[2]
  • Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies[3]
  • Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment[4]
  • EradiFluorTM[1]

Introduction

The hydrated electron (eaq- ) can be described as an electron in solution surrounded by a small number of water molecules[5]. Hydrated electrons can be produced by photoirradiation of solutes, including sulfite, iodide, dithionite, and ferrocyanide, and have been reported in literature to effectively decompose per- and polyfluoroalkyl substances (PFAS) in water. The hydrated electron is one of the most reactive reducing species, with a standard reduction potential of about −2.9 volts. Though short-lived, hydrated electrons react rapidly with many species having more positive reduction potentials[5].

Among the electron source chemicals, sulfite (SO32−) has emerged as one of the most effective and practical options for generating hydrated electrons to destroy PFAS in water. The mechanism of hydrated electron production in a sulfite solution under ultraviolet is shown in Equation 1 (UV is denoted as hv, SO3•- is the sulfur trioxide radical anion):

Equation 1:   XiongEq1.png

The hydrated electron has demonstrated excellent performance in destroying PFAS such as perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA)[6] and GenX[7]. Mechanisms include cleaving carbon-to-fluorine (C-F) bonds (i.e., hydrogen/fluorine atom exchange) and chain shortening (i.e., decarboxylation, hydroxylation, elimination, and hydrolysis)[2].

Process Description

A commercial UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluorTM[1]) includes an optional pre-oxidation step to transform PFAS precursors (when present) and a main treatment step to break C-F bonds by UV/sulfite reduction. The effluent from the treatment process can be sent back to the influent of a pre-treatment separation system (such as a foam fractionation, regenerable ion exchange, or a membrane filtration system) for further concentration or sent for off-site disposal in accordance with relevant disposal regulations. A conceptual treatment process diagram is shown in Figure 1.

Figure 1: Conceptual Treatment Process for a Concentrated PFAS Stream


Advantages

A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by eaq-, low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:

  • High efficiency for short- and ultrashort-chain PFAS: While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies[8][9][10], the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA).
  • High defluorination ratio: As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
  • No harmful byproducts: While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
  • Ambient pressure and low temperature: The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS.
  • Low energy consumption: The electrical energy per order values for the degradation of perfluorocarboxylic acids (PFCAs) by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., supercritical water oxidation)[11].
  • Co-contaminant destruction: The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride[12][13][14][15].

Limitations

Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.

  • Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
  • Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
  • The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and perfluorobutanesulfonate (PFBS) exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.

State of the Practice

Figure 2. Field demonstration of EradiFluorTM[1] for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.
Figure 3. Field demonstration of a treatment train (SAFF + EradiFluorTM[1]) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluorTM[1]; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.

The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluorTM[1] system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the total oxidizable precursor (TOP) assay, adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.

  • Under the Environmental Security Technology Certification Program (ESTCP) Project ER21-5152, a field demonstration of EradiFluorTM[1] was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an in situ foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
  • Another field demonstration was completed at an Air Force base in California, where a treatment train combining Surface Active Foam Fractionation (SAFF) and EradiFluorTM[1] was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluorTM[1] was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluorTM[1]. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).

References

  1. ^ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Haley and Aldrich, Inc. (commercial business), 2024. EradiFluor. Comercial Website
  2. ^ 2.0 2.1 Bentel, M.J., Yu, Y., Xu, L., Li, Z., Wong, B.M., Men, Y., Liu, J., 2019. Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management. Environmental Science and Technology, 53(7), pp. 3718-28. doi: 10.1021/acs.est.8b06648  Open Access Article
  3. ^ Liu, Z., Chen, Z., Gao, J., Yu, Y., Men, Y., Gu, C., Liu, J., 2022. Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies. Environmental Science and Technology, 56(6), pp. 3699-3709. doi: 10.1021/acs.est.1c07608  Open Access Article
  4. ^ Tenorio, R., Liu, J., Xiao, X., Maizel, A., Higgins, C.P., Schaefer, C.E., Strathmann, T.J., 2020. Destruction of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment. Environmental Science and Technology, 54(11), pp. 6957-67. doi: 10.1021/acs.est.0c00961
  5. ^ 5.0 5.1 Buxton, G.V., Greenstock, C.L., Phillips Helman, W., Ross, A.B., 1988. Critical Review of Rate Constants for Reactions of Hydrated Electrons, Hydrogen Atoms and Hydroxyl Radicals (⋅OH/⋅O-) in Aqueous Solution. Journal of Physical and Chemical Reference Data, 17(2), pp. 513-886. doi: 10.1063/1.555805
  6. ^ Gu, Y., Liu, T., Wang, H., Han, H., Dong, W., 2017. Hydrated Electron Based Decomposition of Perfluorooctane Sulfonate (PFOS) in the VUV/Sulfite System. Science of The Total Environment, 607-608, pp. 541-48. doi: 10.1016/j.scitotenv.2017.06.197
  7. ^ Bao, Y., Deng, S., Jiang, X., Qu, Y., He, Y., Liu, L., Chai, Q., Mumtaz, M., Huang, J., Cagnetta, G., Yu, G., 2018. Degradation of PFOA Substitute: GenX (HFPO–DA Ammonium Salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite? Environmental Science and Technology, 52(20), pp. 11728-34. doi: 10.1021/acs.est.8b02172
  8. ^ Singh, R.K., Brown, E., Mededovic Thagard, S., Holson, T.M., 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, Article 124452. doi: 10.1016/j.jhazmat.2020.124452
  9. ^ Singh, R.K., Multari, N., Nau-Hix, C., Woodard, S., Nickelsen, M., Mededovic Thagard, S., Holson, T.M., 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21), pp. 13973-80. doi: 10.1021/acs.est.0c02158
  10. ^ Nau-Hix, C., Multari, N., Singh, R.K., Richardson, S., Kulkarni, P., Anderson, R.H., Holsen, T.M., Mededovic Thagard S., 2021. Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater. American Chemical Society’s Environmental Science and Technology (ES&T) Water, 1(3), pp. 680-87. doi: 10.1021/acsestwater.0c00170
  11. ^ Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A Review. Critical Reviews in Environmental Science and Technology, 49(10), pp. 866-915. doi: 10.1080/10643389.2018.1542916
  12. ^ Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. doi: 10.1016/j.jece.2015.07.026
  13. ^ Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. doi: 10.1016/j.cej.2012.11.086
  14. ^ Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. doi: 10.1021/es3008535
  15. ^ Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. doi: 10.1016/j.watres.2014.05.051

See Also

Retrieved from "https://www.enviro.wiki/index.php?title=User:Jhurley/sandbox&oldid=17890"