Relationship between flotation operational factors and froth behaviour
This study utilised laboratory-scale column flotation experiments to investigate froth stability, with respect to, water recovery and top-of-froth bubble burst rate. Tests were conducted at different froth heights, superficial air rates and depressant dosages in a 2 m high Plexiglass column, using a PGM bearing UG2 ore from the Bushveld Igneous Complex. Four concentrate and tailings samples were simultaneously collected and solids and water recoveries were determined. Assays of the concentrates were conducted to establish the amount of platinum, palladium and chromite that was recovered under each operating condition. Video footage of the top of the froth was recorded and was used to measure the top-of-froth bubble burst rate. The stability of the froth was analysed qualitatively by comparing the relationship between water recovery and the bubble burst rate at the different operating conditions. A key finding from this study was that the concentration of particles had a large effect on the stability of the froth. The maximum concentration of particles was obtained when the tests were conducted in the absence of depressant. Under these conditions it was established that the froth produced was so stable that increasing the air rate only showed minor changes in the stability of the froth phase. This stability has been attributed to the presence of hydrophobic gangue, which stabilised the froth phase by embedding between adjacent bubbles and preventing bubble coalescence. Conversely, when a high depressant dosage was used the froth became unstable such that no trends could be established when either air rate or froth height were altered. The instability of the froth has been attributed to the depression of the majority of the froth stabilising gangue, which resulted in increased bubble coalescence.
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