SULFIDE COLLECTOR MINERAL BONDING AND THE MECHANISM OF FLOTATION

Preliminary concentration of sulphide minerals by froth flotation requires nascent bubble formation for particle capture, and sulphide collectors which chemisorb selectively on the mineral. The amount of collector absorbed is such that at the optimum flotation conditions, bubble contact angle values are zero, or minimal, i.e., the mineral surface is not hydrophobic, which means that the mineral carrying capacity of the bubble should be calculated from bonding energy, and not from surface tension forces. Based on Linus Pauling's argononic sulphur atom theory, which postulates surplus electrons on the metal in sulphide mineral crystals, it can be shown that the collector bond is not sulphur-to-metal, but rather sulphur-to-sulphur. The use of bubble contact angle experiments, and Hallimond tube data, to interpret sulphydryl collector behaviour in sulphide mineral flotation systems is questionable in light of the lack of surface hydrophobicity, when normal amounts of collector are used. As most thiol collectors for six- and seven-coordination complexes with metal cations, it is unlikely that the spectroscopic data on surface compounds formed during sulphide flotation can be interpreted as dithiolate formation, and considering that the more common xanthates and dithiophosphates form insoluble solid dimers it is unlikely that dithiolates, per se, play a dominant role in sulphide ore flotation.