Silver leaching from jarosite-type compounds using cyanide and non-cyanide lixiviants: A kinetic approach. (1st December 2021)

• Record Type: Journal Article
• Authors: Islas, Hernán; Flores, Mizraim U.; Juárez, Julio C.; Reyes, Martín; Blanco, Alien; Gutiérrez, Emmanuel J.; Aguilar, Javier; Nolasco, Mary C.; Rodríguez, Israel; Reyes, Iván A.
• Is Part Of: Minerals engineering. Volume 174(2021)
• Publication Date: 2021-12-01
• Subjects: Jarosites -- Silver leaching -- Cyanide -- Thiosulfate -- Thiocyanate -- Kinetic analysis; Mines and mineral resources -- Periodicals; Ressources minérales -- Périodiques; Mines and mineral resources; Periodicals; Electronic journals; 622
• DOI: 10.1016/j.mineng.2021.107250
• Languages: English
• ISSNs: 0892-6875

Abstract

Highlights: S2 O3 2− and SCN − can be alternatives in the silver leaching from jarosites. Recoveries and leaching rates are compared with those obtained with cyanide. Silver extraction depending on the complexing agent used. The kinetics of leaching is similar for the complexing agents employed. Jarosite dissolution is the controlling stage in the three systems used. Abstract: Precipitation of jarosite-type compounds (jarosites) is widely used in hydrometallurgical processes to control metal impurities in solution. During this process, economically valuable elements like silver may co-precipitate. Due to the toxicity of cyanide, used for silver leaching, alternative complexing agents are needed. These agents should have low human and environmental toxicity and efficiently extract silver from ores. In this study, thiosulfate (S2 O3 2− ) and thiocyanate (SCN − ) were used as alternatives to cyanide in silver extraction from jarosites. The silver extraction and leaching rates obtained with these leaching agents were compared with those obtained with cyanide. Sodium jarosite containing silver was synthesized by the hydrothermal method and characterized by different analytical techniques. Experimental data obtained from batch leaching experiments were fitted with the chemical reaction-controlled shrinking core kinetic model based on studies reported in the literature for similar systems. The effects of pH, temperature, concentration, and the type of leaching agent on the leaching rates were studied. It was found that, under the same temperature and pH conditions, the best extraction efficiency of silver with S2 O3 2− and cyanide were 99.6 % and 97.2%, respectively, but there was a noticeable higher consumption of reagent with S2 O3 2− . The best silver extraction with SCN − was only 35.4 %. However, the leaching rates and the kinetic parameters obtained were very similar, indicating that the kinetics of the jarosite dissolution and the silver complexation could be similar, independent of the complexing agent used. The global kinetic models obtained for extraction of silver from jarosites are useful for evaluating the viability of new complexing agents.