Froth flotation is a vital mineral concentration process, utilised to recover a vast array of diverse minerals holding valuable commodities. Such commodities include copper, lead, zinc, nickel, molybdenum, tungsten, silver, gold, phosphate and potash. In the flotation process, ore is ground to a size sufficient to adequately liberate desired minerals from the waste rock (gangue); it is conditioned as a slurry by using precise chemicals, widely denoted as ‘collectors’, that adsorb to the surfaces of the desired minerals. This makes these mineral surfaces hydrophobic and gives them the tendency to attach to air bubbles. The conditioned mineral slurry is then processed in flotation cells, which are fundamentally distressed tanks into which finely-dispersed air bubbles are introduced. The desired hydrophobic mineral will then attach to the air bubbles and float to the top of the flotation cell, where it will be skimmed off as a mineral-laden froth. The remaining un-floated mineral slurry will be discharged as tailings.
Most flotation circuits include an initial stage of rougher flotation, tailed by a scavenger stage of flotation in order to maximise recovery of the desired minerals into relatively low grade concentrates that may typically contain 5-15 weight percent of the ore feed. Depending on the specific mineral liberation characteristics of the rougher and scavenger concentrates, before upgrading in subsequent stages of cleaner flotation these concentrates may be subjected to further grinding .
Test work necessary to define the design parameters for a flotation circuit normally includes:
- Grindability studies to establish grinding power requirements
- Chemical and mineralogical analyses of test composites to establish ore grades, mineral associations and liberation characteristics
Chemical evaluations required for rougher and cleaner flotation, include:
- Slurry pH
- Collector dosages and types
- Mineral depressants and activators
It is important to acknowledge that flotation retention determined by laboratory testing are generally scaled-up by a factor (depending on the mineral in question) to establish the retention requirements needed in a commercial concentrator.