GOLD RECOVERY WITH ION EXCHANGE RESIN Process Summary

During the last years have been done important developments on the application of ion exchange resins in gold recovery from solutions or pulps obtaine d in a cyanidation process. The resins employed have been strong/weak base and the trials were initiated in small scale.

Strong base resins give high capacity and good kinetic during the loading stage, but offer poor selectivity. These resins present difficult elution and could be necessary carry out selective elution of several metal before recovering precious metals. Some eluants are zinc cyanide and ammonium thiocyanate.

Weak base resins present good selectivity, but its capacity is very low. However, its elution is easy and simple. The preferred eluant is sodium hydroxide.

Strong base resins have shown good results during pilot tests and industrial scale.

Resins are superior to activated carbon in several aspects: loading, kinetic, organic compounds don’t affect its capacity, and reactivation is according to the process to be chosen. Consequently, resin inventories will be lower and the capital and operating cost are lower too.

An interesting advantage under ecological and economical points of view is on the possibility of recycling free cyanide to the leaching circuit, and consequently reduces the consumption of cyanide.

The resin to be chosen must show easy elution, resistance to attrition, resistance to osmotic shock [17], porosity, and high capacity. Ideally must exist a specific resin for each ore.

Methods and reagents employed during elution must be improved so that the process can be dynamic and the resins to be chosen give the best results.

Ion exchange resins can be used in the treatment of gold ores with low and high grades. [18] Organic compounds are not a problem for the process. Clayey ores affect activated carbon but not resins.

Resins apparently have greater mechanical durability in agitated pulps than activated carbon [19, 20]. However, seems that the major engineering problems in a RIP process include transporting and mixing the pulp and resin damaging the resin.

The development of new resins and the advances in elution methods must lead to the application of ion exchange resins on an industrial scale for the treatment of gold ores.