| Автор | Apperley, David C. |
| Автор | Hudson, Michael J. |
| Автор | Keene, Matthew T. J. |
| Автор | Knowles, James A. |
| Дата выпуска | 1995 |
| dc.description | Kanemite, NaHSi2O5·3H2O, is able to exchange metal cations directly from aqueous solution. However, the degree of extraction is dependent upon whether kanemite or its hydrogen-exchanged form is the exchanger. Zinc cations, for example, are exchanged from basic solutions but the equilibrium extraction decreases with increasing acidity (at an equilibrium pH of 11.2, Kd=1070 cm<sup>3</sup> g<sup>â 1</sup>, whereas at an equilibrium pH of 4.88, Kd=70 cm<sup>3</sup> g<sup>â 1</sup>). Kanemite acts as an effective ion exchanger but the hydrogen-exchanged form is less effective, exchanging only by surface sorption at pH 2. In order to explain these and other properties, high-resolution solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) has been used to probe the structure of kanemite and its hydrogen-exchanged form. In kanemite there are only Q<sup>3</sup> silicon-containing groups with extensive hydrogen bonding, and the interlamellar water molecules interact strongly with the silicate layers. In the hydrogen form, there is a dominance of Q<sup>3</sup>, but there are also Q<sup>2</sup> and Q<sup>4</sup> silicons. There is no NMR evidence for extensive hydrogen bonding and the SiO-H group is essentially undissociated. There are Bipolar interactions between the protons and the Q<sup>3</sup> silicon atoms with weaker interactions with the Q<sup>2</sup> and Q<sup>4</sup>. When the H-form is heated to 400 °C, some of the Q<sup>3</sup> groups are involved in dehydroxylation reactions, as evidenced by the formation of Q<sup>4</sup> silicons, but there are still some Q<sup>3</sup> silicons remaining, and hence there are OH groups in the resulting material both from interlamellar water and Si-OH groups. |
| Формат | application.pdf |
| Издатель | Royal Society of Chemistry |
| Название | Kanemite (NaHSi2O5·3H2O) and its hydrogen-exchanged form |
| Тип | research-article |
| DOI | 10.1039/JM9950500577 |
| Electronic ISSN | 1364-5501 |
| Print ISSN | 0959-9428 |
| Журнал | Journal of Materials Chemistry |
| Том | 5 |
| Первая страница | 577 |
| Последняя страница | 582 |
| Выпуск | 4 |
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