Thiosulfate-copper-ammonia leaching of pure gold and pressure oxidized concentrate

Antti Porvali, Lotta Rintala, Jari Aromaa, Tommi Kaartinen, Olof Forsen, Mari Lundstrom

    Research output: Contribution to journalArticleScientificpeer-review

    6 Citations (Scopus)

    Abstract

    In this research cyanide-free leaching of pure gold and pressure oxidized refractory gold concentrate by thiosulfate-copper-ammonia solutions were examined. A quartz crystal microbalance (QCM) was used to study gold leaching as a factorial series where the best gold leaching rate (2.987 mg/(cm2·h)) was achieved with a solution consisting of 0.2 M (NH4)2S2O3, 1.2 M NH3, 0.01 M CuSO4 and 0.4 M Na2SO4. Temperature had the greatest effect on the gold leaching rate. An increase in thiosulfate concentration (0.1-0.2 M) increased gold dissolution. The combined effect of temperature and ammonia concentration had a statistically significant effect on the gold leaching rate at 0.1 M M2S2O3. Combination of applied potential and NH3:S2O3 ratio had a statistically significant effect on the gold leaching rate at 0.2 M M2S2O3. An increase in applied potential decreased the gold dissolution rate at low ammonia concentrations but increased it at high concentrations. A pressure oxidized gold concentrate was leached for 6 hours in the batch reactor leaching experiments. The effect of rotative velocity (1.26-1.56 m/s) and slurry density (10-30 wt%) was investigated at the following leaching parameters: 0.2 M Na2S2O3, 0.6 M NH3, 0.01 M CuSO4, 0.4 M Na2SO4. Lower slurry density (10 wt%) resulted in a higher Au leaching efficiency. An increase in the rotation rate did not have an effect on the final Au leaching recovery. The best Au leaching efficiency (89%) was achieved with 590 rpm mixing, 1.56 m/s rotative velocity and 10 wt% slurry density.
    Original languageEnglish
    Pages (from-to)1079-1091
    Number of pages13
    JournalPhysicochemical Problems of Mineral Processing
    Volume53
    Issue number2
    DOIs
    Publication statusPublished - 1 Jan 2017
    MoE publication typeA1 Journal article-refereed

    Keywords

    • gold leaching
    • quartz crystal microbalance
    • thiosulfate

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