The application of phosphonium-based ionic liquids (ILs) on the selective extraction of cobalt is presented. The extraction mechanism is established, and different parameters of the process are evaluated. It has been found that it is possible to extract cobalt from aqueous solutions in sulfate media, with the addition of sodium chloride, using phosphonium ILs. The cobalt extraction was selective with respect to nickel and strongly dependent on the chloride concentration in the aqueous solution. The cobalt extraction is given by an anion exchange mechanism through an endothermic process. Cobalt extractions greater than 98% were obtained using the proposed methods. Cobalt stripping from the loaded IL phase using water was proved. Therefore, an alternative extraction process to traditional organic solvents is proposed. This alternative has additional advantages such as easy handling, lower costs in reagents and equipment, and risk reduction.
Cyanide is one of the most used reagents in the precious metal extraction process; as well as the most efficient from the point of view of the dissolution process, but it is also a toxic product that requires a lot of care in handling. Likewise, the residual solutions of the process must be followed because they can be a risk of contamination of water, animals and human health. In the artisanal processes of obtaining gold and silver, neutralization of the residual solutions is used to passivate the present cyanide. During this process ammonium cyanate is formed which decomposes rapidly in the presence of air and sunlight in carbon dioxide and ammonia gas, contributing to the greenhouse effect. In this work, the use of the ammonium cyanate obtained in the process of neutralization of the cyanide solutions as a reagent to obtain urea is proposed. Urea was obtained indirectly through the use of the reagent kit UREA/BUN-COLOR. The process is effective at pH ≤ 4.5 with a rapid increase in solution temperature and the addition of hydrogen peroxide. The urea crystals begin to form at 50°C. The cyanide/urea ratio obtained was 1/7.5.
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