Abstract
The dissolution of both copper and arsenic from a copper concentrate was investigated in oxidative ammonia/ammonium solutions at moderate temperatures and atmospheric pressure. The main parameters studied were temperature, pH, concentrations of different ammonia salts, the presence of sodium hypochlorite, pretreatment with sodium chloride, and curing period. In all ammoniacal solutions studied, increasing the temperature enhanced the dissolution of copper, but the dissolution of arsenic remained marginal. Mixing the copper concentrate with sodium chloride and leaving it to rest for 72 h before leaching in ammoniacal solutions significantly increased the dissolution of copper and slightly increased the dissolution of arsenic from the concentrate. A maximum of 35% of Cu and 3.3% of As were extracted when ammonium carbonate was used as the lixiviant. The results show relatively rapid dissolution of the concentrate with the addition of sodium hypochlorite in ammonium carbonate solution, achieving a dissolution of up to 50% and 25% of copper and arsenic, respectively. A copper dissolution with a non-linear regression model was proposed, considering the effect of NaClO and NH4Cl at 25 °C. These findings highlight the importance of using the correct anionic ligands for the ammonium ions and temperature to obtain a high dissolution of copper or arsenic. The results also showed that the curing time of the packed bed before the commencement of leaching appeared to be an important parameter to enhance the dissolution of copper and leave the arsenic in the residues.
Highlights
According to [1], more than 300 arsenic (As) minerals are known to occur in nature
In order to minimize the problems associated with the arsenic content in copper concentrate, this paper presents results from a study on the leaching of enargite in ammoniacal solutions at various alkaline pH, anionics ligands, chloride ions, using a strong oxidizing (OCl− ), variation of temperature and curing time
It can be seen that as the pH increases, the ammonia concentrations increase, while the ammonium concentrations decrease. This is due to the transformation that occurs from ammonium to ammonia
Summary
According to [1], more than 300 arsenic (As) minerals are known to occur in nature. Of these, approximately 60% are arsenates, 20% are sulfides and sulfosalts, 10% are oxides, and the rest are arsenite, arsenide, native elements, and metal alloys. Another process described as one of the first industrial-scale processes corresponds to the method developed by Sherritt-Gordon in a plant in Fort Saskatchewan, Canada, in 1953 In this process, the ammoniacal leaching of sulphate ores containing Cu, Ni and Co was carried out in autoclaves at high pressures and temperatures using oxygen as an oxidizing agent [27]. In order to minimize the problems associated with the arsenic content in copper concentrate, this paper presents results from a study on the leaching of enargite in ammoniacal solutions at various alkaline pH, anionics ligands, chloride ions, using a strong oxidizing (OCl− ), variation of temperature and curing time
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