![]() ![]() After the required temperature was reached, the oxygen supply and time countdown began. Then, the resulting pulp was heated in an autoclave with constant stirring. A portion of the raw material weighing 100 g was added to a prepared solution of NaOH (300 g/dm 3) or NH 4OH and (NH 4) 2SO 4 (with solution concentrations of 0.5 mol/dm 3 (NH 4) 2SO 4 and 7 mol/dm 3 NH 3) the L/S ratio in all the experiments was 5 to 1. The materials were stirred using an overhead mixer at 700 rpm, which ensured a uniform density of the pulp and eliminated diffusion limitations. Laboratory experiments for NaOH and NH 4OH leaching were carried out using a 0.6 dm 3 autoclave reactor (Parr Instrument, Moline, IL, USA), equipped with sample collection vessel. In this case, copper recovery was 86.2% under optimal conditions. It was revealed that the process was controlled by the diffusion kinetics, with an activation energy of 37.37 kJ/mol. investigated the kinetics of leaching with ammonium sulfate solutions of complex covellite ore mined in Nigeria. It was also revealed that copper recovery reaches 77.8% and 88.1% at ammonia concentrations of 1.0 mol/dm 3 and 2.5 mol/dm 3, respectively, and that an increase in the concentration of ammonium persulfate from 0.5 mol/dm 3 to 2.0 mol/dm 3 effects an increase in copper recovery from 80.9% to 90.3%. The study showed that copper recovery rises from 82.7 to 90.3% as the temperature increases from 303.15 to 333.15 K. studied the leaching of calcareous bornite ore in a solution containing ammonia and ammonium persulfate. ![]() ![]() Since that time, a large number of studies have been carried out to study the kinetics of leaching various copper ores and copper-containing wastes in ammonia media at atmospheric and high pressure. The first industrial application of an ammonia leaching process related to the hydrometallurgical recovery of copper from oxidized ores was put into operation in 1916. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. ![]()
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