Anglo Asian Mining plc has selected the Mintek-developed DOWEX™ MINIX™ ion-exchange resin for gold recovery at its Gedabek (Gädäbäy) gold-copper project in Azerbaijan.
Gedabek, which is the first operating gold mine in the south-west Asian country, was officially opened and produced its first gold in May 2009. The operation consists of an open pit mine and heap-leach facility, with gold recovery by resin-in-solution and electrowinning. Copper production will begin shortly. The mine is expected to produce more than 300 000 ounces of gold during its initial six-year mine life.
Owing to the substantial copper grade of the ore, the copper concentration in the leach solution is about 100 times that of gold. “An ordinary ion-exchange resin would become loaded with copper, with very little capacity remaining for gold,” explained Dr Roger Paul, Mintek’s General Manager of Technology, who visited the mine in June to assist with optimising the gold recovery circuit. “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. The Gedabek plant is the first application of the resin in a leach solution containing such high copper concentrations, and we are very pleased with its performance.”
Several important classes of gold deposit contain appreciable quantities of cyanide-soluble copper minerals that can build up in the 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, is not practicable to remove the copper by flotation or acid leaching prior to cyanidation,” said Dr Paul.
Gold recovery from cyanide leach solutions with anion exchange resins is commonly practiced in the CIS countries, 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.
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 carbonaceous 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. The resin, designated XZ 91419, is manufactured and supplied under licence by the Dow Chemical Company.