To the Problem of Reducing the Amount of Harmful Emissions when Refining Silver

Abstract:

The work is devoted to the study of the possibilities of minimizing the release of nitrogen oxides during the dissolution of silver in nitric acid solutions during refining of the gold and silver alloy. Using a rotating disk, the maximum concentration of nitric acid is determined, at which the oxidation potential of the system is insufficient for the oxidation of silver. It has been established that at a temperature of 363 K and a concentration of HNO₃ = 50 g/l, the dissolution rate of silver does not exceed 0.00022∙10^-5 mol/(cm²∙s), and such conditions can be considered as background for an environmentally friendly process. To initiate dissolution, hydrogen peroxide was used as an alternative oxidizing agent. As a criterion for the rational use of the oxidant and the ecological purity of the process, the excess pressure over the solution was evaluated. The influence of the initial and current composition of the solution, temperature, and conditions of oxidant supply to the reactor on the kinetics of the target process was studied. It is shown that at a silver dissolution rate of 2.7∙10^-6 mol/(cm²∙s), no release of nitrogen oxides was observed.

• Periodical: Solid State Phenomena (Volume 284)
• Pages: 877-881
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.284.877
• Online since: October 2018
• Authors: S.E. Polygalov*, S.A. Mastugin, E.A. Shadrina
• Keywords: Ecological Purity, Hydrogen Peroxide, Nitric Acid, Silver

References

[1] M.A. Meretukov, A.M. Orlov. Metallurgy of precious metals, Metallurgy, Moscow, (1991) 356-357.

[2] RU Patent 2312911.

[3] A.N. Kirintsev, L.I. Trushnikov, V.G. Lavrentyeva, Solubility of inorganic substances in water, Directory, Leningrad: Chemistry, (1972).

[4] I.N. Maslenitsky, L.V. Chugayev and others, Metallurgy of precious metals, textbook, Moscow (1987).

[5] RU Patent 2265673.

[6] RU Patent 2185452.

[7] RU Patent 2535266.

[8] RU Patent 2100484.

[9] L.L. Martínez, M. Segarra, M. Fernández, F. Espiell, Kinetics of the dissolution of pure silver and silver-gold alloys in nitric acid solution, Metallurgical Transactions B. 24(5) (1993) 827-837.

DOI: 10.1007/bf02663143

[10] Y. Yanagisava, H. Nishimura, H. Matsuki, F. Osaka, Personalexposure to nitrogen dioxide and it's effect in human health, 6 Congress mond.Jualite air. Paris.1605.1983, Adian Institute mining and metallurgy. NY, (1987).

[11] L.B. Borisova, A.I. Burkhanov, Experimental study of the toxicity of nitric oxide, Gig. and the nurse, 4 (1985) 65-68.

[12] The denitrification of the flue gas: pat. 54-37095 Japan. 52-102677.

[13] Semi-dry flue gas desulphurization process with end product CaS04 and simultaneous NOx removal: pat. 3318407 Germany. РЗЗ 18407.0.

[14] Verfahren zur Verminderung des Stickstoffdioxidgehaltes von Gasgemischen: pat. 3326639 Deutschland. P3326639.5.

[15] V.M. Sizyakov, A.S. Kukolevsky, A.M. Belenky, Thermodynamics of the process of chemical dissolution of silver-containing wastes of jewelry production. Non-ferrous metals. 1 (2010) 49-51.

[16] A.S. Kukolevsky, I.B. Elkin, Recycling of jewelry industry waste containing gold, silver and palladium, Notes of the Mining Institute,169 (2006).

[17] Sposob odzysku i rafinacji srebra ze zlomow: pat. 145399 Polska. 250704.

[18] RU Patent 2280086.

[19] Sposob odzysku srebra ze zlomow srebronosnych: pat. 163664 Polska. № 289732.

[20] V.A. Krasitsky, Interaction of nitric acid with metals; Journal of Chemistry and Chemistry, 6 (2009).