Journal
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
Volume 609, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.colsurfa.2020.125661
Keywords
Fluorite; Hydrophobic; Sum-frequency generation spectroscopy; Alkaline solution; Flotation
Categories
Funding
- National Natural Science Foundation of China (NSFC) [51804340]
- State Key Laboratory of Mineral Processing
- Innovation Driven Plan of Central South University [2018CX036]
- National Project 111 [B14034]
- Collaborative Innovation Center for Clean and Efficient
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Fluorite surfaces are naturally hydrophobic at high pH without the need for surfactants, aiding in selective flotation separation from calcite. Water molecules undergo significant changes in orientation and hydrogen bonding structure at the fluorite/water interface, with increased hydrophobicity observed at pH 13, which plays a crucial role in the flotation of fluorite.
Normally fluorite was collected by fatty acid collectors at pH 5-11, rendering the surface to be hydrophobic. In this study, we found that fluorite surfaces are naturally hydrophobic at high pH without any surfactant, which is beneficial for the selective flotation separation of fluorite from calcite. In a flotation test, fluorite recovery showed a decreasing trend at alkalescent pH but increased at high pH. Sum-frequency generation spectroscopy spectrum confirmed that the orientation and hydrogen bonding structure of the water molecules are dramatically changed at fluorite/water interface. Moreover, a new signal peak, wavenumber of 3657 cm(-1), appeared under strongly alkaline conditions; this peak is normally attributed to free OH stretching region and indicates a hydrophobic surface. Meanwhile, the results of contact angle and atomic force microscopy measurements show that the hydrophobicity obviously increases at pH 13. Therefore, the surface structure of fluorite must undergo some significant changes, which will play an important role in the flotation of fluorite.
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