Left: reflectivity profile and fit (blue) for a surfactant (AOT) in water at the calcite interface compared to a bare surface (red). Right: schematic illustration of the structure deduced.
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Calcite is an extremely important mineral in sedimentary deposits and in many industrial processes. This is particularly evident in water heating where it forms ‘scale’ in hard water areas due to its retrograde solubility (solubility falls on heating).
This precipitation leads to major process difficulties including pipe blockage. We have successfully used neutron reflection on Crisp to address the surface behaviour of calcite, particularly adsorption of surface active agents including those that inhibit calcite crystal formation and growth. The adsorbents studied include surfactants and polymers of different molecular weights adsorbed from both water and oil, reflecting the wide range of systems of interest. The results are complex with mono, bi and multilayer formation together with surface dissolution in some cases. Similarly, this approach can be used to probe adsorption of biopolymers on to the surface of calcite which in nature leads to the formation of beautiful, complex calcite architectures that are still perfect single crystals.
SM Clarke, IN Stocker (Cambridge University), K Webb (BP), C Kinane, J Webster (ISIS)
Research date: January 2008
Further reading: FC Meldrum et al., Chem Rev 108 (2008) 4332
Contact: Dr SM Clarke, firstname.lastname@example.org; Ms IN Stocker, email@example.com
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