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Fennell B, Fowler D, Mezyk SP, McKay G. Reactivity of Dissolved Organic Matter with the Hydrated Electron: Implications for Treatment of Chemical Contaminants in Water with Advanced Reduction Processes. Environ Sci Technol 2023; 57:7634-7643. [PMID: 37141499 PMCID: PMC10862553 DOI: 10.1021/acs.est.3c00909] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/17/2023] [Accepted: 04/18/2023] [Indexed: 05/06/2023]
Abstract
Advanced reduction processes (ARP) have garnered increasing attention for the treatment of recalcitrant chemical contaminants, most notably per- and polyfluoroalkyl substances (PFAS). However, the impact of dissolved organic matter (DOM) on the availability of the hydrated electron (eaq-), the key reactive species formed in ARP, is not completely understood. Using electron pulse radiolysis and transient absorption spectroscopy, we measured bimolecular reaction rates constant for eaq- reaction with eight aquatic and terrestrial humic substance and natural organic matter isolates ( kDOM,eaq-), with the resulting values ranging from (0.51 ± 0.01) to (2.11 ± 0.04) × 108 MC-1 s-1. kDOM,eaq- measurements at varying temperature, pH, and ionic strength indicate that activation energies for diverse DOM isolates are ≈18 kJ mol-1 and that kDOM,eaq- could be expected to vary by less than a factor of 1.5 between pH 5 and 9 or from an ionic strength of 0.02 to 0.12 M. kDOM,eaq- exhibited a significant, positive correlation to % carbonyl carbon for the isolates studied, but relationships to other DOM physicochemical properties were surprisingly more scattered. A 24 h UV/sulfite experiment employing chloroacetate as an eaq- probe revealed that continued eaq- exposure abates DOM chromophores and eaq- scavenging capacity over a several hour time scale. Overall, these results indicate that DOM is an important eaq- scavenger that will reduce the rate of target contaminant degradation in ARP. These impacts are likely greater in waste streams like membrane concentrates, spent ion exchange resins, or regeneration brines that have elevated DOM concentrations.
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Affiliation(s)
- Benjamin
D. Fennell
- Zachry
Department of Civil & Environmental Engineering, Texas A&M University, College Station, Texas 77845, United States
| | - Douglas Fowler
- Department
of Chemistry and Biochemistry, California
State University Long Beach, Long Beach, California 90840, United States
| | - Stephen P. Mezyk
- Department
of Chemistry and Biochemistry, California
State University Long Beach, Long Beach, California 90840, United States
| | - Garrett McKay
- Zachry
Department of Civil & Environmental Engineering, Texas A&M University, College Station, Texas 77845, United States
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Conrad JK, Mezyk SP, Isherwood LH, Baidak A, Pilgrim CD, Whittaker D, Orr RM, Pimblott SM, Horne GP. Gamma Radiation-Induced Degradation of Acetohydroxamic Acid (AHA) in Aqueous Nitrate and Nitric Acid Solutions Evaluated by Multiscale Modelling. Chemphyschem 2023; 24:e202200749. [PMID: 36470592 DOI: 10.1002/cphc.202200749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/11/2022] [Indexed: 12/12/2022]
Abstract
Acetohydroxamic acid (AHA) has been proposed for inclusion in advanced, single-cycle, used nuclear fuel reprocessing solvent systems for the reduction and complexation of plutonium and neptunium ions. For this application, a detailed description of the fundamental degradation of AHA in dilute aqueous nitric acid is required. To this end, we present a comprehensive, multiscale computer model for the coupled radiolytic and hydrolytic degradation of AHA in aqueous sodium nitrate and nitric acid solutions. Rate coefficients for the reactions of AHA and hydroxylamine (HA) with the oxidizing nitrate radical were measured for the first time using electron pulse radiolysis and used as inputs for the kinetic model. The computer model results are validated by comparison to experimental data from steady-state gamma ray irradiations, for which the agreement is excellent. The presented model accurately predicts the yields of the major degradation products of AHA: acetic acid, HA, nitrous oxide, and molecular hydrogen.
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Affiliation(s)
- Jacy K Conrad
- Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Ave., 83415, Idaho Falls, ID, USA
| | - Stephen P Mezyk
- Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd, 90840, Long Beach, CA, USA
| | - Liam H Isherwood
- Dalton Cumbrian Facility, The University of Manchester, West Lakes Science Park, CA24 3HA, Moor Row, U. K.,Department of Chemistry, The University of Manchester, Oxford Rd, M13 9PL, Manchester, U.K
| | - Aliaksandr Baidak
- Dalton Cumbrian Facility, The University of Manchester, West Lakes Science Park, CA24 3HA, Moor Row, U. K.,Department of Chemistry, The University of Manchester, Oxford Rd, M13 9PL, Manchester, U.K
| | - Corey D Pilgrim
- Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Ave., 83415, Idaho Falls, ID, USA
| | - Daniel Whittaker
- National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, CA20 1PG, Cumbria, U.K
| | - Robin M Orr
- National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, CA20 1PG, Cumbria, U.K
| | - Simon M Pimblott
- Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Ave., 83415, Idaho Falls, ID, USA
| | - Gregory P Horne
- Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Ave., 83415, Idaho Falls, ID, USA
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