Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study
Prior aerosol chamber experiments show that the ligand-to-metal charge transfer absorption in iron(III) chlorides can lead to the production of chlorine (Cl2/Cl). Based on this mechanism, the photocatalytic oxidation of chloride (Cl−) in mineral dust–sea spray aerosols was recently shown to be the l...
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2024
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ftcopenhagenunip:oai:pure.atira.dk:publications/677982c7-2ddb-43e5-b73c-3ad4dd7f429c 2024-09-15T18:24:03+00:00 Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study Mikkelsen, Marie K. Liisberg, Jesper B. Van Herpen, Maarten M. J. W. Mikkelsen, Kurt V. Johnson, Matthew S. 2024 application/pdf https://curis.ku.dk/portal/da/publications/photocatalytic-chloridetochlorine-conversion-by-ionic-iron-in-aqueous-aerosols(677982c7-2ddb-43e5-b73c-3ad4dd7f429c).html https://doi.org/10.5194/ar-2-31-2024 https://curis.ku.dk/ws/files/397614879/ar_2_31_2024.pdf eng eng info:eu-repo/semantics/openAccess Mikkelsen , M K , Liisberg , J B , Van Herpen , M M J W , Mikkelsen , K V & Johnson , M S 2024 , ' Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols : a combined experimental, quantum chemical, and chemical equilibrium model study ' , Aerosol Research , vol. 2 , no. 1 , pp. 31-47 . https://doi.org/10.5194/ar-2-31-2024 article 2024 ftcopenhagenunip https://doi.org/10.5194/ar-2-31-2024 2024-07-15T14:56:02Z Prior aerosol chamber experiments show that the ligand-to-metal charge transfer absorption in iron(III) chlorides can lead to the production of chlorine (Cl2/Cl). Based on this mechanism, the photocatalytic oxidation of chloride (Cl−) in mineral dust–sea spray aerosols was recently shown to be the largest source of chlorine over the North Atlantic. However, there has not been a detailed analysis of the mechanism that includes the aqueous formation equilibria and the absorption spectra of the iron chlorides nor has there been an analysis of which iron chloride is the main chromophore. Here we present the results of experiments measuring the photolysis of FeCl3 ⋅ 6H2O in specific wavelength bands, an analysis of the absorption spectra of FeCl (n=1 … 4) made using density functional theory, and the results of an aqueous-phase model that predicts the abundance of the iron chlorides with changes in pH and iron concentrations. Transition state analysis is used to determine the energy thresholds of the dissociations of the species. Based on a speciation model with conditions extending from dilute water droplets and acidic seawater droplets to brine and salty crust, as well as the absorption rates and dissociation thresholds, we find that FeCl is the most important species for chlorine production for a wide range of conditions. The mechanism was found to be active in the range of 400 to 530 nm, with a maximum around 440 nm. We conclude that iron chlorides will form in atmospheric aerosols from the combination of iron(III) cations with chloride and that they will be activated by sunlight, generating chlorine (Cl2/Cl) from chloride (Cl−) in a process that is catalytic in both chlorine and iron. Article in Journal/Newspaper North Atlantic University of Copenhagen: Research Aerosol Research 2 1 31 47 |
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Open Polar |
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University of Copenhagen: Research |
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ftcopenhagenunip |
language |
English |
description |
Prior aerosol chamber experiments show that the ligand-to-metal charge transfer absorption in iron(III) chlorides can lead to the production of chlorine (Cl2/Cl). Based on this mechanism, the photocatalytic oxidation of chloride (Cl−) in mineral dust–sea spray aerosols was recently shown to be the largest source of chlorine over the North Atlantic. However, there has not been a detailed analysis of the mechanism that includes the aqueous formation equilibria and the absorption spectra of the iron chlorides nor has there been an analysis of which iron chloride is the main chromophore. Here we present the results of experiments measuring the photolysis of FeCl3 ⋅ 6H2O in specific wavelength bands, an analysis of the absorption spectra of FeCl (n=1 … 4) made using density functional theory, and the results of an aqueous-phase model that predicts the abundance of the iron chlorides with changes in pH and iron concentrations. Transition state analysis is used to determine the energy thresholds of the dissociations of the species. Based on a speciation model with conditions extending from dilute water droplets and acidic seawater droplets to brine and salty crust, as well as the absorption rates and dissociation thresholds, we find that FeCl is the most important species for chlorine production for a wide range of conditions. The mechanism was found to be active in the range of 400 to 530 nm, with a maximum around 440 nm. We conclude that iron chlorides will form in atmospheric aerosols from the combination of iron(III) cations with chloride and that they will be activated by sunlight, generating chlorine (Cl2/Cl) from chloride (Cl−) in a process that is catalytic in both chlorine and iron. |
format |
Article in Journal/Newspaper |
author |
Mikkelsen, Marie K. Liisberg, Jesper B. Van Herpen, Maarten M. J. W. Mikkelsen, Kurt V. Johnson, Matthew S. |
spellingShingle |
Mikkelsen, Marie K. Liisberg, Jesper B. Van Herpen, Maarten M. J. W. Mikkelsen, Kurt V. Johnson, Matthew S. Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
author_facet |
Mikkelsen, Marie K. Liisberg, Jesper B. Van Herpen, Maarten M. J. W. Mikkelsen, Kurt V. Johnson, Matthew S. |
author_sort |
Mikkelsen, Marie K. |
title |
Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
title_short |
Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
title_full |
Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
title_fullStr |
Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
title_full_unstemmed |
Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
title_sort |
photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols:a combined experimental, quantum chemical, and chemical equilibrium model study |
publishDate |
2024 |
url |
https://curis.ku.dk/portal/da/publications/photocatalytic-chloridetochlorine-conversion-by-ionic-iron-in-aqueous-aerosols(677982c7-2ddb-43e5-b73c-3ad4dd7f429c).html https://doi.org/10.5194/ar-2-31-2024 https://curis.ku.dk/ws/files/397614879/ar_2_31_2024.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Mikkelsen , M K , Liisberg , J B , Van Herpen , M M J W , Mikkelsen , K V & Johnson , M S 2024 , ' Photocatalytic chloride-to-chlorine conversion by ionic iron in aqueous aerosols : a combined experimental, quantum chemical, and chemical equilibrium model study ' , Aerosol Research , vol. 2 , no. 1 , pp. 31-47 . https://doi.org/10.5194/ar-2-31-2024 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/ar-2-31-2024 |
container_title |
Aerosol Research |
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2 |
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1 |
container_start_page |
31 |
op_container_end_page |
47 |
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1810464335902801920 |