Resumo

MA, J.; TANG, Y.; YANG, D.Q.  e  PEI, P.. Kinetics of advanced oxidative leaching of pyrite in a potassium peroxy-disulphate solution. J. S. Afr. Inst. Min. Metall. [online]. 2020, vol.120, n.2, pp.165-172. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/710/2020.

This study investigates the leaching kinetics of gold-bearing pyrite in the potassium peroxydisulphate system and the potassium peroxydisulphate-ferrous sulphate combined system, using potassium peroxydisulphate as an oxidizing agent. Experimental results indicate that the pyrite leaching rate is roughly proportional to the potassium sulphate concentration. The pyrite leaching rate also increases with temperature, and is 48.19% faster at 70°C than at 30°C. Additionally, the pyrite leaching rate is inversely proportional to the particle size; the leaching rate of < 0.038 mm particles is 44.31% greater than that of 0.180-0.120 mm particles. At 70°C, the concentration of ferrous sulphate has no effect. However, at the more typical leaching temperature of 30°C, the addition of ferrous sulphate and hydrogen peroxide can increase the rate of leaching. Therefore, the kinetics of pyrite leaching in the potassium peroxydisulphate system at 70°C and in the potassium peroxydisulphate-ferrous sulphate combined system at normal temperatures were investigated in detail. Pyrite leaching kinetics follows the formula kt = 1 - 2/3x - (1 - x)²'³ where solid film diffusion is the limiting process. The effective activation energy of pyrite leaching in the temperature range 30-70°C was 65.30 kJ/mol. Pyrite had a regular crystal habit prior to leaching, but exhibited faviform holes after leaching. These results provide a basis for effective leaching of gold from gold-bearing pyrite ores using the advanced oxidative leaching system.

Palavras-chave : gold-bearing pyrite; high-grade oxidation; leaching dynamics; activation energy.

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