Why are chemical reagents added during molybdenum flotation?

During molybdenum processing, chemical reagents are added during the flotation process to separate metallic minerals from gangue minerals, or to separate molybdenum from copper.1

These reagents play a critical role in the initial stages of refining. When the resulting molybdenite concentrate is later processed in multiple-hearth furnaces to be converted into technical molybdic oxide, the residual flotation reagents ignite in the first hearth, which helps initiate the exothermic transformation of molybdenum disulfide ($Mo{S}_2$) into molybdenum trioxide ($Mo{O}_3$).2