An investigation into alternative eluants from activated carbon at atmospheric pressure

One of the slowest steps in the extraction of gold by CIP/CIL techniques is the desorption of the metal from the loaded activated carbon. This paper seeks to examine ways of improving the kinetics of this desorption in an economic way through the use of organic additives to the traditional NaClNaOH elution solutions. Several organic agents such as propylene glycol, ethanolamine, urea, N,N-dimethylformamide, acetonitrile and ethanol were trialed. This was done in laboratory bench scale tests, and tests also carried out using an electrowinning cell in tandem with the elution column. Comparisons are made with previous work and results compared with the Zadra elution system which serves as a benchmark. It is shown that a solution of 3.0% w/w thiourea, 2.0% w/w NaOH, and 0.05% w/w NaCN represents the best prospects for greatly improved throughput in industrial cells. A subsequent paper will report pilot and commercial scale tests. The procedure is now standard alternative practice at the gold heap leaching complex of Perseverance Exploration in Fosterville.