Surface Free Energy Components of Calcium Carbonate and Their Changes Due to Radiofrequency Electric Field Treatment
✍ Scribed by Lucyna Holysz; Emil Chibowski
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 277 KB
- Volume
- 164
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
Surface free energy components for calcium carbonate were determined using a thin-layer wicking technique based on Washburn's equation. It was found that the Lifshitz-van der Waals interaction for this solid, (\gamma \mathrm{s}^{\mathrm{Lw}}), is (48.0 \mathrm{~mJ} / \mathrm{m}^{2}), and the acid-base electron donor parameter, (\gamma \bar{s}), equals (79.0 \mathrm{~mJ} / \mathrm{m}^{2}), while no value for the electron acceptor parameter, (\gamma_{\mathrm{s}}^{+}), was detected. These results show that calcium carbonate possesses a strong monopolar surface. After the thin layer of calcium carbonate was treated with a radiofrequency electric field ((44 \mathrm{MHz}), (60 \mathrm{~V}) nonloaded peak-to-peak amplitude) for 15 or (25 \mathrm{~min}), the electron donor parameter decreased to 40.7 and (63.9 \mathrm{~mJ} / \mathrm{m}^{2}), and small electron acceptor parameters appeared, 1.34 and 1.77 (\mathrm{mJ} / \mathrm{m}^{2}), respectively. At present, no idea can be put forward for the smaller changes in the (\gamma) s parameter for the surface treated for the longer time with the RF field. However, it is postulated that the observed changes in acid-base interactions (hydrogen bonding) are due to some rearrangements of the surface hydroxyl groups and/or the adsorbed water molecules, leading to their partial mutual saturation, as this type of interaction is complementary. 1994 Academic Press, Inc.