An investigation into the role of froth height and depressant dosage in the recovery of chromite in the flotation of UG2 ore using a laboratory column

• Depressant (guar) moderately affects the recovery of chromite.
• Concentrate grade improves with guar due to the depression of naturally floatable gangue.
• Increase of froth height does not seem to improve grade.
• Rather, entrainment seems to be the main mechanism of chromite recovery.

The control of chromite during the flotation of UG2 ore is of critical importance since its presence affects the downstream pyrometallurgical treatment. It has been reported that the main mechanism for chromite recovery is entrainment (Hay and Roy, 2010 and Ekmekçi et al., 2003) and hence monitoring the mass of solids and water recovered is important in such an investigation. It is also well known that the froth phase plays a key role in the control of entrained gangue (Neethling and Cilliers, 2009 and Kirjavainen, 1992). In the present investigation a laboratory scale column cell was used to determine the mass of solids and water recovered in the concentrate as a function of different froth heights, superficial gas velocity and depressant dosages. Chromite assays were also carried out on all streams. Tests were carried out at two different froth heights (viz., 30 cm and 60 cm) and in the absence of depressant, using 100 g/t and 500 g/t of guar. Superficial gas velocity was set at three different values, 1 cm/s, 1.5 cm/s and 2 cm/s. The collector was SIBX (80 g/t) and the frother was Dow 200 (100 g/t). The column attained operational steady state. Samples of feed, concentrate and tailings were taken to determine solids and water recoveries, particle size distributions of all streams and chromite grades of the bulk feed material as well as of each stream on a size by size basis. Also, mineralogical examination using QEMSCAN were performed on selected concentrates samples. It was found that froth height had no significant effect on the water, solids recovered or on the chromite grade of the concentrate. However the higher depressant dosage resulted in an increase in chromite grade in the concentrate which is ascribed to the effect of the guar in depressing the recovery of gangue minerals. The paper will present the detailed results of the investigation.