A study of mechanisms affecting molybdenite recovery in a bulk copper/molybdenum flotation circuit

Molybdenite flotation in the bulk copper/molybdenum flotation circuit at Kennecott Utah Copper was studied by means of a combination of plant metallurgical surveys, laboratory flotation tests, mineralogical analysis (QEM-Scan), surface analysis (ToF-SIMS) and contact angle measurements. It was demonstrated that molybdenite recovery is influenced by flotation feed solids percent and by the mineralogy of the host rock. Molybdenite recovery was consistently higher at reduced flotation feed solids percent. Furthermore, the recovery of molybdenite was significantly lower from flotation feeds with high limestone skarn ore content. The major factors affecting the flotation recovery of molybdenite from both porphyry and skarn copper ores are discussed. It is suggested that the lower flotation recovery of molybdenite compared to the copper sulphide is determined by several factors, including particle morphology, inherent hydrophobicity and possible formation of slime coatings in the presence of gangue minerals typical of skarn ores. Implications on plant performance are discussed, and solutions to restore molybdenite recovery presented.