Improving Gold Recovery
A gold mine located in Quebec, Canada processes ore through a flotation circuit followed by cyanidation. Prior to 2016, the main sulfide collector used was potassium amyl xanthate (PAX).
During winter when pulp temperature reached below 10℃, overall gold recovery decreased from ~93% to as low as 90%. As a result, 800-900 oz/year were lost to the tailings. Flotation performed steadily throughout the year, so the ~3% drop likely happened during cyanidation downstream. The metallurgical team suspected that PAX passivated (coated) gold particles.
Lab Testing and Short-Term Plant Trial
COREM conducted lab tests to determine the effect of PAX on gold particles at various temperatures and to select a substitute collector. At <10℃, PAX formed stable multilayers (dixanthogen dimers) through physisorption which lowered the efficiency of dissolution, whereas novel methods in electrochemistry and spectroscopy showed that a Danafloat specialty collector did not.
On-site tests/trials compared the flotation performance of PAX with that of the Danafloat specialty collector. At equal dosage, gold recoveries were on par, but iron recoveries were slightly in favor of PAX: iron monitoring makes it possible to check the efficiency of the flotation circuit as well as to limit the quantity of sulfides (acid generators) sent to the tailings pond.
Further tests/trials on the flotation concentrate confirmed that Danafloat did not prevent cyanidation and that fluctuations in particle size distribution and mineralogy had no significant impact on the metallurgical performances.
Long-Term Plant Trial
In 2017, Quadra Chemicals’ personnel worked closely with the metallurgical team to trial the Danafloat specialty collector. The dosage was adjusted progressively. The following graph shows its industrial validation:
The plant substituted 70% of PAX with the Danafloat specialty collector; the remaining 30% is used to mitigate iron recovery loss. Overall gold recovery was maintained between 93 and 94% throughout the year (especially during winter).
- Increased gold production by 800-900 oz/year (valued at CA $1.3-1.5M/year)
- Reduced health and safety risks associated with the preparation of PAX such as dust control
- Reduced environmental impact: fewer bags and boxes of PAX to destroy
- Easy handling: Danafloat’s specialty collector is a liquid product which requires no preparation