Investigation of the effect of different frother blends on the flotation of selected PGM bearing ores

Concentrators processing platinum group mineral (PGM) bearing ores use polysaccharide depressants to reduce the recovery of the naturally floatable gangue minerals (mainly silicates) present in the ores. Recent work has shown that high depressant dosage can completely depress the naturally floatable gangue from reporting to the concentrate. Unfortunately, this high dosage of depressant can have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the negative effects of depressant addition, frothers are normally added. The optimum frother provides a balance between the pulp kinetics and the froth recovery (through the effect of the frother on the bubble size and froth stability, respectively) over the range of frother addition. Usually one frother is added to accomplish this but using only one frother gives only one unique hydrodynamic relationship. It would be preferable to have independent control over the bubble size and froth stability, but unfortunately this cannot be achieved because changing the concentration of the frother changes both responses. An alternative strategy for gaining more independent control over the froth characteristics and bubble size would be to use a blend of frothers, such as a weak and a stronger frother. Such a system would give an additional degree of freedom so that changing the ratio of the two frothers would provide more independent control of bubble Sauter mean diameter and froth stability. Little research work has been conducted on frother blends and none suggests the mechanism of blended frother action. This study investigates through the use of batch flotation tests how blending low molecular weight alcohols with commercially available high molecular weight frothers impacts the solids and water recovery, as well as the valuable mineral recovery and concentrate grade, in different PGM ores. The results are compared with laboratory batch flotation tests using single frothers only. Two ores from the Merensky Reef in the Bushveld Igneous Complex, South Africa, were used .The frothers were selected to cover a range of polyglycols and alcohols, and included Senfroth 516, DOW 200 and DOW 250 (all polyglycols), and 1-butanol, 1-pentanol, 1-hexanol and MIBC (all low molecular weight alcohols). The frothers were used individually and as v blends at a total dosage of 50 g/t. Two phase tests were also carried out to measure the bubble sizes produced at different concentrations of both single frother and blends