Studies on the Flotation of Molybdenite. I : Flotation of Molybdenite Ore Containing Clayey Gangue

Some points to be considered in the flotation of molybdenite containing clayey gangue were investigated, and based on the results obtained, the method of flotation operation was examined at the Daito mine, Shimane Prefecture. In the rougher flotation of molybdenite ore, high concentrate grade and recovery can be obtained by selecting the proper ratio of silica to soda and suitable concentration of sodium silicate to be added. Sodium silicate having the ratio of silica to soda 2 : 1 shows the most effective depressing action on gangue minerals. The minimum content of SiO_2 in the froth product is obtained when the conditioning time after adding sodium silicate is 10-20 minutes. It is preferable to use sodium hydroxide instead of lime to regulate the pH value of the pulp containing much primary slime. On the contraty, lime is effective for the flotation of molybdenite ore containing no primary slime. Though it is usual to use oily collectors as collecting agents for molybdenite, quantities to be added to obtain good flotation results are unexpectedly large. In some cases molybdenite can be recovered at high rates of recovery by using xanthate with oily collector, but we should be cautious of using much xanthate. However, a good flotation result cannot be expected with xanthate only. At the Daito mine, the flotation results have been improved by modifications of flotation methods : slime is treated by a separate flotation circuit and the froths are returned to the main circuit. Sodium hydroxide is used to regulate the pH value of the pulp. Thus, no difficulty has been experienced in producing a molybdenite concentrate assaying 86.3-87.4% MoS_2 with a recovery of 95.5-97.9% from a flotation feed assaying 1.06-1.13% MoS_2.