Recovery of Gold and Silver from Non-Ferrous Metal Ore

The separation of non-ferrous metals primarily relies on flotation. For polymetallic non-ferrous ores, the standard flotation process encompasses priority flotation, total mixed flotation, partial mixed flotation, and asynchronous flotation. The selection of these processes requires comprehensive assessment of ore properties, mineral composition, useful mineral content, and product specifications, each possessing distinct applicability and unique advantages.

Flotation effectively separates sulphide concentrates containing gold and silver. However, smelting extraction of gold and silver from copper concentrates or lead concentrates proves simpler, more cost-effective, and achieves higher recovery rates. Consequently, for polymetallic non-ferrous ores where gold and silver predominantly occur as separate minerals, priority should be given to concentrating them into copper or lead concentrates. For polymetallic ores such as copper-sulphide, copper-iron, and copper-zinc ores containing associated gold and silver, processes like copper priority flotation, lead priority flotation, mixed copper-lead priority flotation, and asynchronous flotation are particularly advantageous for separating these metals.

Priority flotation separates useful minerals sequentially based on their flotation properties, from easier to harder to process. This minimises surface inhibition or contamination of gold and silver minerals, prevents prolonged circulation losses during processing, and facilitates their enrichment in copper and lead concentrates. Asynchronous flotation exploits differences in mineral floatability and flotation velocity. By applying distinct reagents in sequential stages within the same circuit, it creates optimal conditions to enhance the recovery of associated gold and silver.

For coarse-grained gold and silver minerals with high density that are difficult to process via flotation or cyanide leaching, a combined flotation-gravity separation process may be employed. Gravity separation offers simplicity, low cost, and minimal pollution, serving as a supplementary method within grinding circuits, before or after flotation, and in concentrate dressing. Common equipment includes Nelson separators and centrifugal concentrators. Within integrated beneficiation-metallurgical processes, flotation and gravity separation enrich valuable minerals while removing undesirable components. Metallurgical treatment predominantly employs the well-established cyanide leaching technique, though gold and silver minerals resistant to cyanide leaching require specialised treatment. Cyanide processing of beneficiation concentrates can reduce overall costs.

In summary, by selecting appropriate flotation, combined flotation-gravity, or integrated beneficiation-metallurgy processes tailored to ore characteristics—prioritising primary metal minerals while addressing associated free gold and silver minerals—the recovery rate of associated gold and silver in non-ferrous metal ores can be effectively enhanced.