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Dissolution characteristics of scheelite in HClC2H5OHH2O and HClC2H5OH solutions

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DOI: 10.1016/0304-386x(93)90036-d
  • Chemistry


Abstract The reaction of synthetic scheelite with hydrochloric acid, HCl-C 2H 5OH and HCl-C 2H 5OH-H 2O (with varying proportions of H 2O) solutions was studied at 70°C between HCl concentrations of 4 M and 5 M. Although the reaction product was solid tungstic acid when hydrochloric acid was used as a leachant, this behaviour was observed to change with a decrease in the amount of water in the reaction media. Complete dissolution was achieved with HCl-C 2H 5OH-H 2O (25% H 2O, v/v) and HCl-C 2H 5OH solutions. The same dissolution behaviour, with the formation of negligible or minor amounts of solid tungstic acid was observed in the leaching of Swedish scheelite (71.4% WO 3) and upgraded Turkish scheelite (65.18% WO 3) concentrates. Leach solutions were observed to be stable when hot and at room temperature in the case of HCl-C 2H 5OH leaching and only stable when hot in the case of HCl-C 2H 5OH-H 2O leaching. Selective precipitation of tungsten from solution was possible by dilution with water at a ratio of 1:1. The reaction rate was controlled chemically rather than by diffusion in HCl-alcohol solutions. This great change in the dissolution behaviour was attributed to the prevention of hydrolysis, due to the replacement of water in the media by ethyl alcohol, which is a better solvator for chloride ions and has the property of forming hydrogen bonds.

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