Hydrophobic behavior of fluorite surface in alkaline solution and it's application in flotation

摘要

Normally fluorite was collected by fatty acid collectors at ph 5-11, rendering the surface to be hydrophobic. In this study, we found fluorite surface was naturally hydrophobic at high pH without any surfactant, which is beneficial for the selective flotation separation of fluorite from calcite. In flotation test, the recovery of fluorite remains a decreasing trend at alkalescent pH while increasing at high pH values. The results of contact angle show the hydrophobicity obviously increase at pH 13. X-ray photoelectron spectroscopy and atomic force microscopy analyses clearly indicated that fluorite surface is eroded by hydroxide ions or affected by hydroxylation. SFG spectrum confirmed that the orientation and hydrogen bonding structure of the water molecules are dramatically changed. Moreover, a new signal peak, 3657 cm~(-1), appeared at strongly alkaline condition, which is normally identified to be free -OH and indicated the surface to be hydrophobic. Therefore, the surface structure of fluorite must undergo some significant changes, which will play an important role in the flotation of fluorite.