Free gold flotation fundamentally is not possible because gold is a noble element which means it is a chemically nonreactive metallic. Since sulphide flotation collectors chemisorb to the target mineral surfaces, because noble metals do not react, collector adsorption on a pure gold surface is not possible. Use of cresylic based dithiophosphates does provide some collection of gold particularly in gold-silver ore flotation. Alternatively, if there is significant metallic gold association with silver metal, because silver has a reactive
surface for collector bonding, collectors for silver indirectly also result in gold recovery.
Consequently, gold flotation recovery requires a focus on floating the associated base metals (predominantly lead, copper) and often pyrite minerals. While lime is often used in base sulphide mineral flotation, because excess lime also tends
to depress gold flotation, a balance must be maintained between good base metal metallurgy and gold recoveries. Natural pH is recommended for gold flotation. Alternatively using soda ash for pH adjustment can reduce gold depression.
Where gold is associated with pyrite in base metal ores where iron sulphides are depressed and report to the tailings, a separate tailings pyrite flotation concentrate should be considered. Producing a pyrite concentrate with associated gold maximizes gold recovery.
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The following Danafloat™ collectors should be initially considered for gold-pyrite ore flotation: