Flotation as a separation technique in the coal gold agglomeration process

Abstract

Internationally, there is an increase in the need for safer environmental processes that can be applied to mining operations, especially on a small scale, where mercury amalgamation is the main process used for the recovery of free gold. An alternative, more environmentally acceptable, process called the Coal Gold Agglomeration (CGA) process has been investigated at the Cape Technikon. This paper explains the application of flotation as a means of separation for the CGA process. The CGA process is based on the recovery of hydrophobic gold particles from ore slurries into agglomerates formed from coal and oil. The agglomerates are separated from the slurry through scraping, screening, flotation or a combination of the aforementioned. They are then ashed to release the gold particles, after which it is smelted to form gold bullion. All components were contacted for fifty minutes after which a frother was added and after three minutes of conditioning, air, at a rate of one I/min per cell volume was introduced into the system. The addition of a collector (Potassium Amyl Xanthate) at the start of each run significantly improved gold recoveries. Preliminary experiments indicated that the use of baffles decreased the gold recoveries, which was concluded to be due to agglomerate breakage. The system was also found to be frother-selective and hence only DOW-200 was used in subsequent experiments. A significant increase or decrease in the air addition rate both had a negative effect on the recoveries; therefore, the air addition rate was not altered during further tests. The use of tap water as opposed to distilled water decreased the attainable recoveries by less than five per cent. This was a very encouraging result, in terms of the practical implementation of the CGA process.