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A Cyanide Alternative: Flotation

The cyanide process(1) has allowed the development of large, low grade precious metal deposits more than any other process.   The reasons for its widespread acceptance are economic as well as metallurgical. It usually obtains a higher gold recovery than other processes, especially for fine gold.  Cyanidation is also easier to operate than other leaching processes.   But with increasing concern for the transport and use of cyanide a lot of work is being done on alternatives.

 We seem to get in the habit of forgetting what we have done in the past.  And if it is not new it is not worth looking at.  With alternatives to cyanide a hot topic, with proposals from glycine to fish sperm to thio-urea and others it may be time for a fresh look at an old (relatively) process, flotation.  While gravity separation is often touted (include by yours truly) it does have its limitation, especially for fine gold and also for large tonnages. 

 Often over looked is that gold and silver (as native metals) are readily floatable using xanthates.  And when they are of a more refractory nature (sulfide ores, telluride ores, and carbonaceous ores) or ores that contain cyanicides flotation can be used to recover the mineral or to remove the cyanicides.

 When gold or silver are a secondary mineral (copper ores, lead-zinc ores, or such) the selectivity of flotation can be used (and has been used) for recovery.

 There have been several successful operations that have used flotation for gold recovery in the past and the present:

·       Bjorkdal, Sweden uses flotation for free-milling ore that was not recoverable by gravity process. It does use gravity for coarse gold recovery.

·       Pamour Porcupine Mines, Schumacher Division uses flotation for copper sulfifed recover and to reduce the load on the leach circuit.

·       El Indio, Chile used a primary flotation to remove cyanicides during grinding, and followed grinding by flotation to reduce the load on the leach circuit.

 Flotation is more complex than a straight cyanide leach, and takes more operational control.  So why is flotation more complex than cyanidation?  First the agitator is different as the goal is to mix and introduce air bubbles not just mix.  Depending on the type of agitator you may (probably) need some low pressure blowers/compressors to supply the air bubbles.  Then a froth collection system (launderers) is required at the top of the tank.  But, compared to other processes, flotation is fairly simple.

Flotation is a proven method of recovering low grade ores (see copper) and as an alternative to cyanide it can work.  So for your next large project try flotation!

 For more information on cyanidation and flotations see:

(1)  An Introduction to Cyandidation

(2)  An Introduction to Flotation

 

 

o   40+ years’ experience in the mining industry with strong mineral processing experience in precious metals, copper, industrial minerals, coal, and phosphate

o   Operational experience in precious metals, coal, and phosphate plus in petrochemicals.

o   Extensive experience performing studies and determining feasibility in the US and international (United States, Canada, Mexico, Ecuador, Columbia, Venezuela, Chile, China, India, Indonesia, and Greece).

o    E-mail:  info@smartdogmining.com