Asian gold-mining junior Anglo Asian Mining is using the Dowex Minix ion-exchange resin technology developed by South African minerals research organisaiton Mintek for gold recovery at its Gedabek gold/copper project, in Azerbaijan.

Gedabek, the first operating gold mine in the south-western Asian country, produced its first gold in May this year. The operation consists of an openpit mine and a heap-leach facility, with gold recovery by resin-in- solution and electrowinning.

Copper production at the project will begin shortly. The mine is expected to produce more than 300 000 oz of gold during its initial six-year life-of-mine.

Owing to the substantial copper grade of the ore, the copper concentration in the leach solution is about 100 times that of gold.

Mintek GM for technology Dr Roger Paul says that an ordinary ion-exchange resin would become loaded with copper, with very little capacity remaining for gold. He adds that the Dowex Minix strong base resin, however, is extremely selective for gold over all other metal cyanide complexes, and is able to achieve high gold loadings under these conditions, resulting in a greatly improved gold recovery rate. “The Gedabek plant is the first application of the resin in a leach solution containing such high copper concentrations, and the company is pleased with its performance,” says Paul.

Several important classes of gold deposit contain appreciable quantities of cyanide- soluble copper minerals that can build up in metallurgical process solutions, resulting in gold lock-up in the circuit and reduced recoveries.

“The Dowex Minix resin makes low- cost heap leaching viable where, due to technological or economic considerations, it is not practicable to remove the copper by flotation or acid leaching prior to cyanidation,” says Paul.

Gold recovery from cyanide leach solutions with anion exchange resins is commonly practised in the Commonwealth of Independent States, and western gold-mining companies are now beginning to realise the economic benefits of ion exchange.

“Resins are more versatile than activated carbon because they can be customised to improve features such as selectivity, loading capacity and resistance to poisoning. They can also be eluted at much lower temperatures and, unlike activated carbon, do not require thermal regeneration,” says Paul.

Originally envisaged as an alternative to granular active carbon for gold recovery, the Dowex Minix resin found its first niche application in recovering gold from carbon-aceous preg-robbing ores. It is used in this role at Avocet Mining’s Penjom mine, in Malaysia, and formerly at the Barbrook gold plant, near Barberton, in South Africa.

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