Natural hydrobhobicity and flotation of fluorite
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Institute of Catalysis and Surface Chemistry Polish Academy of Sciences
Wroclaw University of Technology
Publication date: 2007-01-01
Physicochem. Probl. Miner. Process. 2007;41(1):5–11
The free ascending bubble–fluorite surface collision test showed that the three phase contact (TPC) was formed and time of the TPC formation was strongly affected by the roughness of the fluorite surface. The time of the TPC formation varied by an order of magnitude, from ca. 20 to 200ms, depending on the fluorite origin and surface roughness. The fact that the TPC was formed shows that fluorite can be considered as a naturally hydrophobic material. The contact angle formed by the bubble attached to fluorite plate was found to be 40o in comparison to 10-25o measured by flotometry and 55o by sessile drop. Thus, the macroscopic contact angle of fluorite depends on the method of measurement as well as its origin and color since colorless fluorites float better. Hydrophobicity of fluorite and the time of the three phase contact formation influence its flotation. The best flotation is observed in Hallimond tubes while flotation is significantly reduced or absent in laboratory flotation machines. This is very likely a result of relatively long time of the TPC formation and/or low hydrophobicity of fluorite, which is not enough to withstand the detachment force during enhanced hydrodynamics of larger flotation devices.