Electrochemical Perspective on Hematite–Malonate Interactions
Organic matter (OM) interactions with minerals are essential in OM preservation against decomposition in the environment. Here, by combining potentiometric and electrophoretic measurements, we probed the mode of coordination and the role of pH-dependent electrostatic interactions between organic aci...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-10-01
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| Series: | Colloids and Interfaces |
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| Online Access: | https://www.mdpi.com/2504-5377/5/4/47 |
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| author | Karolina Kędra Marzena Łazarczyk Tajana Begović Danijel Namjesnik Karolina Lament Wojciech Piasecki Piotr Zarzycki |
| author_facet | Karolina Kędra Marzena Łazarczyk Tajana Begović Danijel Namjesnik Karolina Lament Wojciech Piasecki Piotr Zarzycki |
| author_sort | Karolina Kędra |
| collection | DOAJ |
| description | Organic matter (OM) interactions with minerals are essential in OM preservation against decomposition in the environment. Here, by combining potentiometric and electrophoretic measurements, we probed the mode of coordination and the role of pH-dependent electrostatic interactions between organic acids and an iron oxide surface. Specifically, we show that malonate ions adsorbed to a hematite surface in a wide pH window between 3 and 8.7 (point of zero charge). The mode of interactions varied with this pH range and depended on the acid and surface acidity constants. In the acidic environment, hematite surface potential was highly positive (+47 mV, pH 3). At pH < 4 malonate adsorption reduced the surface potential (+30 mV at pH 3) but had a negligible effect on the diffuse layer potential, consistent with the inner-sphere malonate complexation. Here, the specific and electrostatic interactions were responsible for the malonate partial dehydration and surface accumulation. These interactions weakened with an increasing pH and near PZC, the hematite surface charge was neutral on average. Adsorbed malonates started to desorb from the surface with less pronounced accumulation in the diffuse layer, which was reflected in zeta potential values. The transition between specific and non-specific sorption regimes was smooth, suggesting the coexistence of the inner- and outer-sphere complexes with a relative ratio that varied with pH. |
| first_indexed | 2024-03-10T04:22:59Z |
| format | Article |
| id | doaj.art-8adddd2532844052bb27b3565b140abd |
| institution | Directory Open Access Journal |
| issn | 2504-5377 |
| language | English |
| last_indexed | 2024-03-10T04:22:59Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Colloids and Interfaces |
| spelling | doaj.art-8adddd2532844052bb27b3565b140abd2023-11-23T07:46:11ZengMDPI AGColloids and Interfaces2504-53772021-10-01544710.3390/colloids5040047Electrochemical Perspective on Hematite–Malonate InteractionsKarolina Kędra0Marzena Łazarczyk1Tajana Begović2Danijel Namjesnik3Karolina Lament4Wojciech Piasecki5Piotr Zarzycki6Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, PolandInstitute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, PolandDepartment of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, CroatiaDepartment of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, CroatiaRegional Research and Development Center, Józef Piłsudski University of Physical Education in Warsaw, 21-500 Biała Podlaska, PolandFaculty of Physical Education and Health, Józef Piłsudski University of Physical Education in Warsaw, 21-500 Biała Podlaska, PolandInstitute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, PolandOrganic matter (OM) interactions with minerals are essential in OM preservation against decomposition in the environment. Here, by combining potentiometric and electrophoretic measurements, we probed the mode of coordination and the role of pH-dependent electrostatic interactions between organic acids and an iron oxide surface. Specifically, we show that malonate ions adsorbed to a hematite surface in a wide pH window between 3 and 8.7 (point of zero charge). The mode of interactions varied with this pH range and depended on the acid and surface acidity constants. In the acidic environment, hematite surface potential was highly positive (+47 mV, pH 3). At pH < 4 malonate adsorption reduced the surface potential (+30 mV at pH 3) but had a negligible effect on the diffuse layer potential, consistent with the inner-sphere malonate complexation. Here, the specific and electrostatic interactions were responsible for the malonate partial dehydration and surface accumulation. These interactions weakened with an increasing pH and near PZC, the hematite surface charge was neutral on average. Adsorbed malonates started to desorb from the surface with less pronounced accumulation in the diffuse layer, which was reflected in zeta potential values. The transition between specific and non-specific sorption regimes was smooth, suggesting the coexistence of the inner- and outer-sphere complexes with a relative ratio that varied with pH.https://www.mdpi.com/2504-5377/5/4/47ion adsorptiondicarboxylate ionsiron oxide α-Fe<sub>2</sub>O<sub>3</sub>hematiteelectrical double layersurface potential |
| spellingShingle | Karolina Kędra Marzena Łazarczyk Tajana Begović Danijel Namjesnik Karolina Lament Wojciech Piasecki Piotr Zarzycki Electrochemical Perspective on Hematite–Malonate Interactions Colloids and Interfaces ion adsorption dicarboxylate ions iron oxide α-Fe<sub>2</sub>O<sub>3</sub> hematite electrical double layer surface potential |
| title | Electrochemical Perspective on Hematite–Malonate Interactions |
| title_full | Electrochemical Perspective on Hematite–Malonate Interactions |
| title_fullStr | Electrochemical Perspective on Hematite–Malonate Interactions |
| title_full_unstemmed | Electrochemical Perspective on Hematite–Malonate Interactions |
| title_short | Electrochemical Perspective on Hematite–Malonate Interactions |
| title_sort | electrochemical perspective on hematite malonate interactions |
| topic | ion adsorption dicarboxylate ions iron oxide α-Fe<sub>2</sub>O<sub>3</sub> hematite electrical double layer surface potential |
| url | https://www.mdpi.com/2504-5377/5/4/47 |
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