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Investigation of the effect of cyanidation after microwave roasting treatment on refractory gold/silver ores by characterization studies

Yoğurtcuoğlu Emine

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 1

art. no. 157487

EN

In this article, the efficiency of microwave pretreatment, which is an environmentally friendly, low-energy consuming method for recovery from refractory gold-silver ores, was investigated. The ore sample belonged to the oxidized Bolkardağ deposit, which contains carbonate (calcite, dolomite, smithsonite, hydrozincite), silicate (quartz, hemimorphite), sulfate (beudantite, plumbo-jarosite), and iron oxy/oxyhydroxide (hematite, limonite) minerals. Sulfur/sulfate-bearing silver and gold minerals are found either together with gangue minerals or in inclusions. Approximately 90% gold and 48% silver recovery efficiencies were achieved with the cyanide process after microwave preroasting from the ore. Additionally, the ore, heat treatment product, and waste samples were investigated by characterization studies. In these studies, bond structures, mineral content, sample mass losses, element percentage content differences, and mineral percentage content differences in the samples were determined. As a result, the microwave pretreatment application in cyanidation was presented as a new research topic in terms of its application in the valuable refractory content of this type of oxide.

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Diagnostic gold deportment studies and leaching behaviour of small-scale gold mining tailings from eastern region, Ghana

Quaicoe Ishmael, Beyuo Martin, Quaicoe Solomon, Lasidzi Nikao A.

Journal of Sustainable Mining

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2023

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Vol. 22. iss. 2

81--88

EN

Artisanal and small-scale gold mining (ASGM) sector employs about 80% of the mining workforce but only contributes about 20-30% of Ghana's gold production. The low gold production is linked to low recoveries associated with the activities because of inadequate understanding of the chemical, mineralogical and metallurgical characteristics of the ores. This study examined the metallurgical characteristics of typical small-scale gold mining tailings to understand their grinding characteristics, gold deportment and cyanidation behaviour. The gold deportment results showed that 96.1% of the gold in the samples is free milling (can be leached directly with cyanide and recovered through carbon adsorption), whilst the remaining 3.9% of the gold in the samples is associated/locked up with other mineral phases (carbonates, sulphides, carbonaceous matter and quartz). The gold-by-size distribution also indicated that 73.1% of the gold is contained in coarser size fractions (+150 mm), 14.96% is from -150 mm to +75 mm size range, and 11.83% is contained in the finer size distribution (-75 mm). This suggests that incorporating a gravity recovery system during processing will be highly advantageous. The leaching kinetics results showed that gold recoveries achieved within 8, 16 and 24 h were 68, 73.8 and 76.4%, respectively. The corresponding total cyanide consumption rates after 8, 16 and 24 h of leaching were 550, 580 and 600 ppm, respectively. Generally, the gold recoveries and the cyanide consumption rates agree with industrial practices/results. Overall, the outcomes of the study support the view that some small-scale gold mining tailings are economically viable, and hence can be re-processed through efficient processes such as carbon-in-leach/carbon-in-pulp.

3

Atomic scale study of silver sulfide leaching with cyanide and thiourea

Bernaola-Flores Roxana, Silva-Quiñones Dhamelyz, Balbuena Perla B., Rodríguez-Reyes Juan Carlos F., Tarazona-Vasquez Francisco

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 4

969--980

EN

Understanding of atomic scale interactions of molecular species with mineral surfaces is needed to bring about mineral processing innovation. In this regard, Density Functional Theory (DFT) methods are well suited. In this work, the outcome of leaching synthetic acanthite –a surrogate for a silver-containing sulfide ore- with both cyanide ion and thiourea are studied with DFT considering solvent effects. The results are correlated to the experimental percentage of silver extracted with each of the leaching agents under similar conditions of molar concentration, temperature and percentage of solids. Our calculations show both leaching reactions to be exergonic and of the same order of magnitude in Gibbs energy of reaction than values determined from thermodynamic tables. Also, less favorable Gibbs reaction energies are obtained for cyanidation in absence of oxygen and thioureation in absence of Fe(II) highlighting the impact of oxidants on the exergonicity of the respective global leaching reactions. Finally, analyzing the percentage of silver extracted from acanthite and the absolute value of Gibbs energies of the respective reaction, we conclude that the more exergonic a leaching reaction, the higher percentage of silver is extracted from acanthite, provided that there is no kinetic control of each of the leaching reactions.

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The influence of pre-aeration on cyanide leaching of a non-refractory sulphide gold and silver ore

Aydin B., Basturkcu H., Gul A.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 2

647--660

EN

The leaching behaviour of a sulphide gold-silver ore was investigated in terms of a relationship between gold and silver extractions and cyanide consumption. Ninity five Au % and 88.0% Ag extractions were obtained under the determined conditions of 24 h leaching duration, -74 μm particle size, 40% solids ratio, 4 g/dm3 NaCN concentration, and 450 rpm stirring speed with NaCN consumption of 3.35 g/dm3. Since the NaCN consumption was higher than in industrial applications, Pb(NO3)2 and H2O2 additions and aeration using an air pump were tested during leaching in order to decrease the consumption. While Pb(NO3)2 addition with aeration caused a decrease in the metal extractions, the individual or combined additions of H2O2 and aeration could not provide a reduction in the cyanide consumption. Therefore, the effect of the pre-aeration followed by cyanidation was tested. Eventually, applying 4 h of pre-aeration before a shorter leaching duration of 12 h provided 92.0% Au and 90.5% Ag extractions with a reduced NaCN consumption of 2.44 g/dm3.