UBC Theses and Dissertations
The modes of gold loss in the calcium thiosulfate leaching system Daenzer, Renaud
The processing of gold is becoming more complicated due to the increasingly complex nature of the remaining gold-bearing ore bodies. This worldwide phenomenon is the driving force for the development of alternative technologies for the leaching and recovery of gold from so-called double refractory ores. Barrick Gold recently commercialized a unique calcium thiosulfate leaching plant to treat these problematic ores after an autoclave pre-treatment with simultaneous recovery of the dissolved gold-thiosulfate complex onto anion exchange resins. Nonetheless, this new process can experience unexpected losses in gold from solution. It is hypothesized that the reagent’s degradation products known as polythionates and various mineral additions could adversely affect soluble gold stability along with their known detrimental effect on gold recovery. This dissertation aims to understand the possible causes of gold losses by means of a thorough investigation of the effects of polythionate and mineral additions into synthetic calcium thiosulfate leaching solutions. A series of batch leaching experiments were subsequently conducted on actual preg-robbing ores to further elucidate the effects of polythionates on the stability soluble gold complexes in the calcium thiosulfate system. A subsequent study on the rates of polythionate species loading on the resin and their competitive loading behaviour was made and extended to include their effects on the displacement of gold from the resin. This was demonstrated in the form of gold loading isotherms tailored to the calcium thiosulfate leaching system. Ultimately, the processes of gold leaching from refractory ores and gold recovery by resin loading in the presence of polythionates were tied together in a last study to quantify their harmful outcomes on overall gold extraction.
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