Abstract
As a pre-treatment method of refractory gold ore, carbonaceous matter (C-matter) flotation was investigated with multi-stage flotation by rougher, scavenger, and cleaner stages. Different dosages of kerosene and MIBC (4-Methyl-2-pentanol) were applied and the optimum dosage was selected by testing in each flotation stage. With the combination of each stage, four circuit designs were suggested, which were a single-stage rougher flotation (R), rougher-scavenger flotation (R+S), rougher-scavenger-scavenger cleaner flotation (R+S+SC), and rougher-rougher cleaner-scavenger-scavenger cleaner flotations (R+S+RC+SC). The results indicated that the scavenger flotation increased C-matter recovery but reduced C-matter grade compared with single-stage rougher flotation. Cleaning of the scavenger flotation concentrate improved C-matter grade significantly, but reduced recovery slightly. Cleaning of the rougher flotation concentrate achieved overall improved selectivity in flotation. A combination of rougher-scavenger flotation followed by cleaning of both concentrates (R+S+RC+SC) resulted in 73% C-matter recovery and a combined cleaner concentrate grade of 4%; the final tailings C-matter grade was 0.9%, where the C-matter remaining in the tailings was locked, and fine grained. The results demonstrate the need for the multi-stage flotation of C-matter from refractory gold ore to achieve selective separation and suggested the potential of C-matter flotation as the pre-treatment for efficient gold production.
Highlights
Refractory gold ore, which shows poor gold recovery by cyanidation, typically contains one or all of the following: (1) carbonaceous matter (C-matter), which causes pregrobbing; (2) locked gold in sulfides/silicates, and (3) cyanide/oxygen consumable matter, such as copper or sulfidic material [1,2,3]
The ore is treated by alkaline pressure oxidation (POX) to liberate gold from sulfides, followed by thiosulfate gold leaching to avoid the preg-robbing effect caused by the presence of C-matter
Flotation, chemical oxidation, pressure oxidation, bio-oxidation, and ultrafine grinding have been investigated as pre-treatment processes for refractory gold ore [4,5]
Summary
Refractory gold ore, which shows poor gold recovery by cyanidation, typically contains one or all of the following: (1) carbonaceous matter (C-matter), which causes pregrobbing; (2) locked gold in sulfides/silicates, and (3) cyanide/oxygen consumable matter, such as copper or sulfidic material [1,2,3]. The ore is treated by alkaline pressure oxidation (POX) to liberate gold from sulfides, followed by thiosulfate gold leaching to avoid the preg-robbing effect caused by the presence of C-matter. The mass of the C-matter concentrate must be low, while removing as much C-matter as possible from the feed to pressure oxidation; the flotation tailing can be treated in an autoclave to oxidize sulfides and liberate more gold, followed by the thiosulfate leaching for gold extraction. The gold recovery from the tailing may not be improved because it is treated by the same procedure of alkaline POX, followed by thiosulfate gold leaching; the finer particle size for the flotation than the present process (P80 size of Alkaline POX discharge: 56.5 μm) could result in greater liberation of sulfide and gold, leading to higher oxidation efficiency and gold recovery. All gold in the ore is processed, but this is carried out separately by each effective treatment on the concentrate and tailings
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