Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System
Manganese (Mn2+) oxidation is an important phenomena in environmental and industrial processes. This study aims to shed light on the mechanism by which NaClO oxidizes Mn2+ to precipitate MnO2 in the presence of HCl. Experiments at pH = 1.5 indicated that the autocatalytic formation and the BET surfa...
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Taylor & Francis Group
2024-12-01
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| Series: | Journal of Chemical Engineering of Japan |
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| Online Access: | https://www.tandfonline.com/doi/10.1080/00219592.2024.2366409 |
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| author | Mauricio Córdova-Udaeta Bowen Cheng Shigeshi Fuchida Yutaro Takaya Keishi Oyama Chiharu Tokoro |
| author_facet | Mauricio Córdova-Udaeta Bowen Cheng Shigeshi Fuchida Yutaro Takaya Keishi Oyama Chiharu Tokoro |
| author_sort | Mauricio Córdova-Udaeta |
| collection | DOAJ |
| description | Manganese (Mn2+) oxidation is an important phenomena in environmental and industrial processes. This study aims to shed light on the mechanism by which NaClO oxidizes Mn2+ to precipitate MnO2 in the presence of HCl. Experiments at pH = 1.5 indicated that the autocatalytic formation and the BET surface area of the MnO2 precipitates are influenced by NaClO addition speed, while further tests suggested that highly acidic conditions may promote the redissolution of the initial MnO2 crystals formed after oxidant addition. Based on these observations, a completely novel kinetic mechanism for Mn2+ oxidation with NaClO in HCl solutions was proposed. Namely: the formation of MnO2 crystal nuclei by direct oxidation, the formation of an intermediary of the MnO2•HOCl type, and the disappearance of said intermediary, which can take two competing reaction pathways. The first pathway is thought to be the autocatalytic formation of MnO2 which ultimately precipitates, whereas the second one is proposed to be the redissolution of MnO2 back into Mn2+. To validate the proposed mechanism, the experimental setup was modeled as a semi batch reactor with pulsed NaClO addition, and the ensuing system of ordinary differential equations (ODEs) was solved numerically, yielding a reasonable fitting with experimental data. |
| format | Article |
| id | doaj-art-30f3c8bfae1c4e38967883c28449f70a |
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| issn | 0021-9592 1881-1299 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | Taylor & Francis Group |
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| series | Journal of Chemical Engineering of Japan |
| spelling | doaj-art-30f3c8bfae1c4e38967883c28449f70a2025-08-20T01:58:18ZengTaylor & Francis GroupJournal of Chemical Engineering of Japan0021-95921881-12992024-12-0157110.1080/00219592.2024.2366409Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE SystemMauricio Córdova-Udaeta0Bowen Cheng1Shigeshi Fuchida2Yutaro Takaya3Keishi Oyama4Chiharu Tokoro5Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, JapanSchool of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, JapanDepartment of Marine Resources and Environment, Tokyo University of Marine Science and Technology, Konan 4-5-7, Minato, Tokyo 108-8477, JapanDepartment of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-8656, JapanFaculty of Science and Engineering, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo, 169-8555, JapanDepartment of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-8656, JapanManganese (Mn2+) oxidation is an important phenomena in environmental and industrial processes. This study aims to shed light on the mechanism by which NaClO oxidizes Mn2+ to precipitate MnO2 in the presence of HCl. Experiments at pH = 1.5 indicated that the autocatalytic formation and the BET surface area of the MnO2 precipitates are influenced by NaClO addition speed, while further tests suggested that highly acidic conditions may promote the redissolution of the initial MnO2 crystals formed after oxidant addition. Based on these observations, a completely novel kinetic mechanism for Mn2+ oxidation with NaClO in HCl solutions was proposed. Namely: the formation of MnO2 crystal nuclei by direct oxidation, the formation of an intermediary of the MnO2•HOCl type, and the disappearance of said intermediary, which can take two competing reaction pathways. The first pathway is thought to be the autocatalytic formation of MnO2 which ultimately precipitates, whereas the second one is proposed to be the redissolution of MnO2 back into Mn2+. To validate the proposed mechanism, the experimental setup was modeled as a semi batch reactor with pulsed NaClO addition, and the ensuing system of ordinary differential equations (ODEs) was solved numerically, yielding a reasonable fitting with experimental data.https://www.tandfonline.com/doi/10.1080/00219592.2024.2366409Manganese oxidationAcidic conditionsAutocatalytic precipitationKinetic mechanismNumerical ODE fitting |
| spellingShingle | Mauricio Córdova-Udaeta Bowen Cheng Shigeshi Fuchida Yutaro Takaya Keishi Oyama Chiharu Tokoro Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System Journal of Chemical Engineering of Japan Manganese oxidation Acidic conditions Autocatalytic precipitation Kinetic mechanism Numerical ODE fitting |
| title | Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System |
| title_full | Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System |
| title_fullStr | Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System |
| title_full_unstemmed | Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System |
| title_short | Insights on the Mechanism of Manganese Oxide Precipitation from Mn2+ Solutions Using NaClO Under Highly Acidic Conditions, via Experimental Observations and Numerical Fitting of the Kinetic ODE System |
| title_sort | insights on the mechanism of manganese oxide precipitation from mn2 solutions using naclo under highly acidic conditions via experimental observations and numerical fitting of the kinetic ode system |
| topic | Manganese oxidation Acidic conditions Autocatalytic precipitation Kinetic mechanism Numerical ODE fitting |
| url | https://www.tandfonline.com/doi/10.1080/00219592.2024.2366409 |
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