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Molybdenite (MoS2) is the only major commercial molybdenum mineral being recovered by flotation. Ores that contain molybdenum as the chief value are being worked by very few mines. A large quantity is produce, however, as a by-product in the concentration of copper ores.
Molybdenite is one of the most easily floatable minerals, and generally no collector other than the frother-fuel oil combination is required for good recovery. However, despite this high mineral floatability, copper-molybdenum ores often present a number of problems.
As with all ores, good concentrate grade and recovery require a sufficiently fine grind to substantially liberate the mineral from the gangue. This is especially important with copper-molybdenum ores since a high-grade concentrate is required and small amounts of middlings or locked particles in the concentrate would either greatly reduce their value or make them unsalable. Regrinding of the molybdenum concentrate is, therefore, quite common and any middlings or locked particles are rejected in the “moly” circuit tailing rather than being included in the final product.
The grinding problem is further complicated by the fact that “moly” production is of secondary importance in the treatment of most such ores. The mill grind is therefore usually regulated to obtain optimum copper recovery at the lowest
cost. The standard practice is to float both copper and molybdenum at the same time, and then clean the bulk concentrate to reject the gangue minerals before making the copper-molybdenum separation. Such cleaning operations frequently reject an appreciable quantity of the molybdenum, most of which is probably still locked with gangue particles. |
