RU2152448C1 - Precious metal recovery method - Google Patents

Abstract

FIELD: precious metal technology. SUBSTANCE: cinder mixture from heat and power stations utilized as adsorbent, prior to be mixed with solutions containing gold and silver to be recovered, is subjected to wet magnetic separation at magnetic field intensity 1000-2000 Oe. EFFECT: increased degree of recovery and mechanical strength of adsorbent. 7 ex

Description

 The invention relates to a technology for the extraction of precious metals, namely gold and silver, and can be used in adsorption technologies for their extraction, in particular for the extraction of gold and silver from ore pulps.

 A known method of extracting gold and silver from ore pulps [1], including the sorption of precious metals from their cyanide solutions by activated carbon, followed by separation of the adsorbent from the solution by screening. The disadvantages of this method include the difficulty of separating coal from the pulp and the loss of gold with a crushed fraction of coal, which is due to the abrasion of activated carbon due to their low mechanical strength.

 Closest to the claimed method according to the technical essence is the method of extraction of precious metals [2], in which the ash and slag mixture is used as a sorbent - waste from burning coal in thermal power plants. The disadvantage of this method is the low degree of separation of gold and silver, due to the insufficient adsorption capacity of the sorbent in relation to gold and silver, the difficulty of separating the adsorbent from the pulp and its low mechanical strength.

 The objective of the present invention is to increase the degree of extraction of precious metals and the mechanical strength of the adsorbent.

 The technical result is achieved by the fact that before mixing with solutions containing gold and silver, the ash and slag mixture of thermal power plants is subjected to wet magnetic separation at a magnetic field strength of 1000-2000 E.

In this case, a magnetic fraction is isolated from the ash and slag mixture, in which the content of aluminosilicate part is significantly reduced compared to the initial object and, accordingly, the content of iron oxides increases sharply. According to X-ray diffraction analysis, the main amount of silicon in the magnetic fraction is represented by quartz, and iron is represented mainly by magnetite and, to a lesser extent, hematite. That is, minerals with high hardness are concentrated in the magnetic fraction (quartz - 7.0; magnetite - 6.0; hematite - 6.5) [3]. The residue after magnetic separation is concentrated aluminosilicate part of the initial ash and slag mixture, which is mainly a mixture of clay minerals with low mechanical strength. For example, kaolinite Al ₂ O ₃ • 2SiO ₂ • 2H ₂ O has a hardness of 1.0 [4]. This part, which constitutes 85-90% of the initial ash and slag mixture, in addition, has a much lower adsorption capacity for gold, not only in comparison with the magnetic fraction, but also in comparison with the original ash and slag mixture. That is, the active component of the ash and slag mixture, which determines its adsorption properties, is the magnetic fraction. Obtained using the proposed method, the sorbent has a higher adsorption capacity relative to gold compared to the initial ash and slag mixture. The mechanical strength of the sorbent obtained using the proposed method is higher than that of the analogue and prototype, and the presence of the obtained sorbent ferromagnetic properties makes it possible to simplify the process of separating the sorbent from the pulp.

Examples of specific performance of the method
Example 1. Ash and slag mixture of thermal power plants with a content (wt.%): Si - 35.77; Fe - 4.0; Al - 13.4; subjected to wet magnetic separation at a magnetic field of 1000 E. The output of the magnetic fraction is 7.5%. The content of the main elements in it (wt.%): Fe - 54.0; Si 8.3; Al is 0.5.

 Example 2. Ash-slag mixture of thermal power plants, as in example 1, is subjected to wet magnetic separation at a magnetic field of 2000 E. The yield of magnetic fraction is 8.0%. The content of the main elements in it (wt.%): Fe - 50.0; Si - 9.8; Al is 1.5.

Example 3. 24 g of the product (sorbent) obtained according to example 1, is stirred for 2 hours with 250 cm ^{3 of a} cyanide solution with a gold concentration of 3.44 mg / dm ³ . Then the sorbent is filtered off from the solution and the concentration of gold is determined in the latter. It is 0.008 mg / dm ³ , which corresponds to a gold recovery of 99.77%.

Example 4. 24 g of the residue obtained after removal of the magnetic fraction from the ash-slag mixture according to example 1, is stirred for 2 hours with 250 cm ^{3 of a} cyanide solution with a gold concentration of 0.574 mg / DM ³ . The sorbent is filtered off from the solution and the concentration of gold is determined in the latter. It is 0.480 mg / dm ³ , which corresponds to a degree of gold recovery of 16.38%.

Example 5. 20 g of the product (sorbent) obtained according to example 1, is stirred for 2 hours with 200 cm ^{3 of a} thiourea solution with a gold concentration of 0.052 mg / dm ³ . Then the sorbent is filtered off from the solution and the concentration of gold is determined in the latter. It is 0.0001 mg / dm ³ , which corresponds to a degree of gold recovery of 99.8%.

Example 6 (prototype). 20 g of ash-slag mixture of thermal power plants are mixed with 200 cm ^{3 of a} thiourea solution with a gold concentration of 0.052 mg / dm ³ . Then the sorbent is filtered off from the solution and the concentration of gold is determined in the latter. It is 0.0091 mg / dm ³ , which corresponds to a degree of gold recovery of 82.5%.

Example 7. 14.5 g of the sorbent obtained according to example 1, is stirred for 2 hours with 250 cm ^{3 of a} cyanide solution with a silver concentration of 460 mg / DM ³ . Then the sorbent is filtered from the solution and the silver concentration is determined in the latter. It is 20 mg / dm ³ , which corresponds to a degree of silver recovery of 95.66%.

 Thus, the use of the proposed method allows to obtain a sorbent, which in contrast to the ash and slag mixture has a higher adsorption capacity with respect to gold and silver, higher mechanical strength. The presence of ferromagnetic properties in the obtained sorbent makes it possible to simplify the procedure for separating the sorbent from the pulp, in particular, due to the use of magnetic separators.

List of sources taken into account
1. Korostyshevsky NB Metallurgy of gold and silver. / Metallurgy of non-ferrous metals. - t. 17, (Results of science and technology VINITI AN USSR) .- M .: 1987. - S. 1-74.

 2. The method for the excelled in the noble metal: A.S. 33816 NRB, MKI C 22 B 11/04 / Alekseeva S.S., Gaydarzhiev S.S., Takova V.K., Valeva V.M., Ivanova T.G. - N 55590; Claim 03/01/83; Publ. 05.16.83 (prototype).

 3. Shtrubel G., Zimmer Z.Kh. Mineralogical Dictionary: Per. with him. - M .: Nedra, 1987 .-- 494 p.

 4. Yurovsky A.3. Mineral components of solid fossil fuels. - M.: Nedra, 1968 .-- 214 p.

Claims (1)

 A method of extracting precious metals from solutions by adsorption on an ash and slag mixture - waste from burning coal at thermal power plants, characterized in that the ash and slag mixture is preliminarily subjected to wet magnetic separation at a magnetic field strength of 1000 - 2000 E.