Analysis of the reasons for molybdenite losses and improvement of recirculating water conditioning regimes in the process of copper-molybdenum ore flotation

Abstract

Copper-molybdenum ore flotation at closed water circulation system is accompanied by significant losses of molybdenum, recovery of which often does not exceed 50%. The losses are often caused by changing ion composition of the pulp aqueous phase, and primarily accumulation of copper and calcium ions, causing the change in the state of mineral surface. The probability of molybdenite activation by copper cations under conditions of copper-molybdenum ore milling was determined by thermodynamic calculations and confirmed by spectral studies. It was demonstrated that the activation of molybdenite by copper ions increases floatability in the bulk flotation circuit, but causes depression and increase in molybdenite losses in the selective flotation circuit, that leads to decreasing the recovery into commercial concentrates. Kinetic parameters of the interaction of molybdenite with copper cations under milling conditions were experimentally determined, and the boundary concentration of copper cations (0.175 mg/l) was determined. The reasons for molybdenite flotability decline at elevated concentrations of calcium ions and molybdate ions were determined: the formation of calcium molybdate on the mineral surface under conditions of bulk flotation, which is transformed to hydrophilic calcium carbonate at pH above 9.5. The flotation studies established the maximum permissible concentration of copper ions (0.6 mg/l) and calcium (350 mg/l) in recirculating water, exceeding of which leads to deterioration of the process performance. Regime of joint conditioning of filtrates saturated with copper and utility fluids was developed, at the medium pH maintained at 7.5–7.8 by lime adding, providing reducing concentration of dissolved copper and technical fatty acids in the purified recirculating water to 0.4 mg/l and 0.55 mg/l, respectively. The developed conditioning regime for heavily polluted effluents of Erdenet GOK industrial cluster made it possible to increase the recovery of copper and molybdenum by 0.35% and 0.5%, respectively, when the effluents are involved in the water circulation system.