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Chemical force microscopy study on the interactions of COOH functional groups with kaolinite surfaces : implications for enhanced oil recovery.

Santha, Nipada and Cubillas, Pablo and Saw, Adrian and Brooksbank, Harry and Greenwell, Hugh Christopher (2017) 'Chemical force microscopy study on the interactions of COOH functional groups with kaolinite surfaces : implications for enhanced oil recovery.', Minerals., 7 (12). p. 250.


Clay–oil interactions play a critical role in determining the wettability of sandstone oil reservoirs, which, in turn, governs the effectiveness of enhanced oil recovery methods. In this study, we have measured the adhesion between –COOH functional groups and the siloxane and aluminol faces of kaolinite clay minerals by means of chemical force microscopy as a function of pH, salinity (from 0.001 M to 1 M) and cation identity (Na+ vs. Ca2+). Results from measurements on the siloxane face show that Ca2+ displays a reverse low-salinity effect (adhesion decreasing at higher concentrations) at pH 5.5, and a low salinity effect at pH 8. At a constant Ca2+ concentration of 0.001 M, however, an increase in pH leads to larger adhesion. In contrast, a variation in the Na+ concentration showed less effect in varying the adhesion of –COOH groups to the siloxane face. Measurements on the aluminol face showed a reverse low-salinity effect at pH 5.5 in the presence of Ca2+, whereas an increase in pH with constant ion concentration resulted in a decrease in adhesion for both Ca2+ and Na+. Results are explained by looking at the kaolinite’s surface complexation and the protonation state of the functional group, and highlight a more important role of the multicomponent ion exchange mechanism in controlling adhesion than the double layer expansion mechanism

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Publisher statement:© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Date accepted:12 December 2017
Date deposited:12 January 2018
Date of first online publication:19 December 2017
Date first made open access:12 January 2018

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