Agieienko, Vira and Buchner, Richard (2024) What is behind a gas stream scrubbing liquid? Monoethanolamine/water mixtures as seen by dielectric relaxation spectroscopy. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 26 (3). pp. 2312-2323. ISSN 1463-9076, 1463-9084
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High-quality dielectric data for monoethanolamine (MEA)/water mixtures covering the entire miscibility range are presented. For MEA concentrations c1 >= 1 M the obtained complex permittivity spectra, covering the frequency range from 0.05 to 89 GHz, are best described by a sum of four Debye relaxations. Modes at similar to 3 GHz and similar to 10 GHz are solute-specific. Whilst the first can be assigned to MEA aggregates, the second is a composite arising from "free" MEA dipoles with dynamically retarded water hydrating them. The relaxations at similar to 18 GHz and similar to 200 GHz essentially reflect the cooperative H-bond fluctuations of more-or-less unperturbed "bulk" water, albeit with minor solute contributions. Evaluation of the bulk-water amplitude reveals that in water-rich mixtures (c1 <= 3.5 M) Zt = 3.5 +/- 0.2 H2O molecules hydrate a MEA molecule. Then Zt drops linearly, reaching zero for neat MEA. Supported by the literature, this concentration dependence suggests that only H2O molecules H-bonded to the NH2 and OH groups of MEA contribute to Zt. At concentrations beyond hydration shell overlap (c1 >= 3.5 M) these H-bonds are gradually eliminated, while new interactions with neighboring MEA molecules are formed. From the evaluation of the MEA-specific amplitudes we conclude that for c1 >= 2 M, including neat MEA, similar to 35% of the solute molecules are in aggregates, where breaking the intermolecular NHMIDLINE HORIZONTAL ELLIPSISO hydrogen bond determines the dynamics. Dielectric spectra of monoethanolamine (MEA)/water mixtures constitute a sum of relaxations arising from MEA in a composition of its aggregates, MEA hydrates and more-or-less unperturbed water.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | MOLECULAR-DYNAMICS SIMULATION; WATER-ETHANOLAMINE MIXTURES; BINARY-MIXTURES; AQUEOUS-SOLUTIONS; COLLECTIVE DYNAMICS; EXCESS PROPERTIES; SURFACE-TENSION; PARTIAL MOLAR; POWER-PLANTS; CO2 CAPTURE; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > PD Dr. Richard Buchner |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 17 Nov 2025 09:52 |
| Last Modified: | 17 Nov 2025 09:52 |
| URI: | https://pred.uni-regensburg.de/id/eprint/65034 |
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