Interaction of calcium dioleate collector colloids with calcite and fluorite surfaces as revealed by AFM force measurements and molecular dynamics simulation |
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| Authors: | Keqing Fa Anh V Nguyen Jan D Miller |
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| Institution: | 1. Department of Metallurgical Engineering, University of Utah, 135 South 1460 East, Salt Lake City, Utah 84112, USA;2. Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA;3. Discipline of Chemical Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia |
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| Abstract: | Spherical calcium dioleate particles (∼ 10 μm in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has a longer range than the DLVO (Derjaguin–Landau–Verwey–Overbeek) prediction. The repulsive AFM force between the calcium dioleate sphere and the fluorite surface does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at fluorite– and calcite–water interfaces as revealed by the numerical computation experiments using molecular dynamics simulation. The density of interfacial water at the fluorite surface is low and the fluorite surface is not strongly wetted by water molecules. In contrast to the water at the fluorite surface, water molecules at the calcite surface form tightly packed monolayer structures and the calcite surface is extensively hydrated by water molecules. The interfacial water structure agrees with the AFM force measurements and the flotation recovery data. The strong attraction between the calcium dioleate colloid and the fluorite surface, and the moderately wetted fluorite surface by water molecules explain the better flotation response of fluorite with the oleate collector colloid. |
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| Keywords: | Flotation collectors Flotation reagents Froth flotation Atomic force microscopy Molecular dynamics simulation Oleate Calcium dioleate Collector colloids Fluoride Calcite Interfacial water structure |
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