File Download
There are no files associated with this item.
Links for fulltext
(May Require Subscription)
- Publisher Website: 10.1016/j.gca.2016.10.032
- Scopus: eid_2-s2.0-85007303419
- WOS: WOS:000390987900017
- Find via
Supplementary
- Citations:
- Appears in Collections:
Article: Magnesium bicarbonate and carbonate interactions in aqueous solutions: An infrared spectroscopic and quantum chemical study
Title | Magnesium bicarbonate and carbonate interactions in aqueous solutions: An infrared spectroscopic and quantum chemical study |
---|---|
Authors | |
Keywords | Aqueous carbon speciation Density functional calculations Infrared spectroscopy Ion pair |
Issue Date | 2017 |
Publisher | Pergamon. The Journal's web site is located at http://www.elsevier.com/locate/gca |
Citation | Geochimica et Cosmochimica Acta, 2017, v. 198, p. 271-284 How to Cite? |
Abstract | The interaction of magnesium with bicarbonate and carbonate ions in aqueous solutions was studied using infrared spectroscopy and quantum chemical calculations. Using the infrared vibrational bands for and at 1200–1450 cm−1 (δC-OH, vS and v3) together with their molar absorptivity (ε), the concentrations of the and ions and the corresponding Mg ion pairs have been determined. In the absence of Mg2+, measured spectra were accurately reproduced assuming that only and were present in solution. Upon addition of Mg2+ at fixed pH, infrared spectra were observed to shift indicating presence of the and ion pairs. From measurements, the second ionization constant of carbonic acid and the and ion pair formation constants have been obtained, these being logK2 = −10.34 ± 0.04, = 1.12 ± 0.11 and = 2.98 ± 0.06, respectively. To support our experimental infrared measurements and to gain further insight into the molecular nature of the ion pair formation, density functional theory (DFT) calculations with VPT2 anharmonic correction were conducted. The most stable geometries predicted for the and ion pairs were a bi-dentate [MgHCO3]+(H2O)n and a monodentate [MgHCO3]+(OH)(H2O)n complexes, respectively. The predicted frequencies for , and were found to shift toward those experimentally measured with an increasing H2O solvation number where possible band shifts were predicted for relative to , this being dependent on the exact structure and hydration of the bulk ion pair. Experimentally, the ion pair formations were found to have insignificant effects on the δC-OH, vS and v3 vibrational frequencies. The speciation of dissolved inorganic carbon may be significantly influenced by ion pair formation, particularly in alkaline solutions where they may be the predominant species. |
Persistent Identifier | http://hdl.handle.net/10722/247354 |
ISSN | 2023 Impact Factor: 4.5 2023 SCImago Journal Rankings: 2.278 |
ISI Accession Number ID |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Stefánsson, A | - |
dc.contributor.author | Lemke, KH | - |
dc.contributor.author | Bénézeth, P | - |
dc.contributor.author | Schott, J | - |
dc.date.accessioned | 2017-10-18T08:26:01Z | - |
dc.date.available | 2017-10-18T08:26:01Z | - |
dc.date.issued | 2017 | - |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2017, v. 198, p. 271-284 | - |
dc.identifier.issn | 0016-7037 | - |
dc.identifier.uri | http://hdl.handle.net/10722/247354 | - |
dc.description.abstract | The interaction of magnesium with bicarbonate and carbonate ions in aqueous solutions was studied using infrared spectroscopy and quantum chemical calculations. Using the infrared vibrational bands for and at 1200–1450 cm−1 (δC-OH, vS and v3) together with their molar absorptivity (ε), the concentrations of the and ions and the corresponding Mg ion pairs have been determined. In the absence of Mg2+, measured spectra were accurately reproduced assuming that only and were present in solution. Upon addition of Mg2+ at fixed pH, infrared spectra were observed to shift indicating presence of the and ion pairs. From measurements, the second ionization constant of carbonic acid and the and ion pair formation constants have been obtained, these being logK2 = −10.34 ± 0.04, = 1.12 ± 0.11 and = 2.98 ± 0.06, respectively. To support our experimental infrared measurements and to gain further insight into the molecular nature of the ion pair formation, density functional theory (DFT) calculations with VPT2 anharmonic correction were conducted. The most stable geometries predicted for the and ion pairs were a bi-dentate [MgHCO3]+(H2O)n and a monodentate [MgHCO3]+(OH)(H2O)n complexes, respectively. The predicted frequencies for , and were found to shift toward those experimentally measured with an increasing H2O solvation number where possible band shifts were predicted for relative to , this being dependent on the exact structure and hydration of the bulk ion pair. Experimentally, the ion pair formations were found to have insignificant effects on the δC-OH, vS and v3 vibrational frequencies. The speciation of dissolved inorganic carbon may be significantly influenced by ion pair formation, particularly in alkaline solutions where they may be the predominant species. | - |
dc.language | eng | - |
dc.publisher | Pergamon. The Journal's web site is located at http://www.elsevier.com/locate/gca | - |
dc.relation.ispartof | Geochimica et Cosmochimica Acta | - |
dc.rights | Posting accepted manuscript (postprint): © <year>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ | - |
dc.subject | Aqueous carbon speciation | - |
dc.subject | Density functional calculations | - |
dc.subject | Infrared spectroscopy | - |
dc.subject | Ion pair | - |
dc.title | Magnesium bicarbonate and carbonate interactions in aqueous solutions: An infrared spectroscopic and quantum chemical study | - |
dc.type | Article | - |
dc.identifier.email | Lemke, KH: kono@hku.hk | - |
dc.identifier.authority | Lemke, KH=rp00729 | - |
dc.identifier.doi | 10.1016/j.gca.2016.10.032 | - |
dc.identifier.scopus | eid_2-s2.0-85007303419 | - |
dc.identifier.hkuros | 280926 | - |
dc.identifier.volume | 198 | - |
dc.identifier.spage | 271 | - |
dc.identifier.epage | 284 | - |
dc.identifier.isi | WOS:000390987900017 | - |
dc.publisher.place | United Kingdom | - |
dc.identifier.issnl | 0016-7037 | - |