Effect of pH and Precipitations on Copper–Molybdenum Rougher Flotation in Seawater

Abstract

Effect of pH and precipitations on copper–molybdenum ore rougher flotation has been investigated in seawater with flotation experiments followed by precipitation estimation with thermodynamic calculations, turbidity measurements and XRD analysis. Results of flotation experiments in seawater indicated that the effect of pH on copper and molybdenum flotation maximum recovery seems limited. On the other hand, pH drastically influences copper and molybdenum flotation kinetic constant, it decreased a lot with increasing pH, and results of pH 8.5 and 9.0 is quite similar. From thermodynamic calculation, precipitation effect on seawater less than pH 9 seems limited since CaCO3 and Mg(OH)2 does not exist on this pH region. To estimate precipitation on pH in seawater, turbidity measurements were carried out with controlled pH and results indicated even pH is less than 9, noticeable turbidity can be seen. To confirm precipitation in seawater, precipitation was collected from controlled pH seawater solution. XRD analysis of precipitation indicated that obtained precipitation at pH 8.7 is CaCO3, CaSO4 and Mg(OH)2. This result is not same as the result of thermodynamic calculation and it might be due to the activity coefficient and ionic strength effect. Although flotation kinetic is influenced with turbidity, turbidity influence on maximum recovery is limited. Effect of kinetic might be due to that precipitation exist as suspension and it prevent bubble and mineral attachments. Small effect of precipitation on maximum recovery might be due to exist of few precipitation on the surface of copper and molybdenum mineral since most of mineral in rougher flotation is gangue minerals and also most of precipitations might be on gangue minerals. These results indicated that seawater flotation have to take into account of precipitation effect more for flotation kinetic than maximum flotation recovery.