RU2048612C1 - Gold bearing alloy processing method - Google Patents

Abstract

FIELD: gold bearing alloys processing and gold extraction. SUBSTANCE: method provides for electrolytic solution of initial alloy under application of alternating asymmetric current with half-cycles of positive and negative signs. Process is carried out under voltage of 0.9 1.1 V, current intensity correspondingly of 330 350 and 30 50 A and definite ration of number of positive and negative sign half-cycles. EFFECT: method allows to process effectively gold alloys with high degree of silver, bismuth, lead and tin impurities.

Description

 The invention relates to the field of hydrometallurgy of precious metals, in particular to methods for processing gold-containing alloys and extracting gold from them.

 During electrolytic refining of gold, soluble anodes, in addition to gold, contain silver, platinum and base metals, in particular non-ferrous metals, as impurities. During the electrolysis of gold, an impurity of silver is oxidized at the anode with the formation of insoluble silver chloride, which covers the anode with a film. Compounds of lead and bismuth have an even greater passivating effect. In this case, the dissolution of the anode stops. Gold alloys with a high content of impurities are not electrolyzable at all.

A known method of processing a gold-bearing alloy by electrolysis, in which an asymmetric current is used to overcome the passivation effect. At the same time, direct current with an anode density of 0.08-8 A / dm ³ and a voltage of 1-12 V and an alternating current with a frequency of 30-70 Hz at a ratio of AC and DC potentials of 0.5-0.75: 1 are simultaneously transmitted.

 The closest technical solution to the invention is a method for processing a gold-containing alloy containing up to 12% silver impurities by electrolysis, which is carried out under alternating asymmetric current, containing half periods of a positive sign and shorter half periods of a negative sign.

 With this mode of current transmission, the formation of a layer of silver chloride on the anode and its peeling and falling from the anode to the bottom of the electrolysis bath alternate in the form of sludge.

 The disadvantage of this method is the low efficiency of processing gold-silver alloys with a high content of bismuth and lead compounds. A film of compounds of these metals adheres so tightly to the anode that it lends itself only to mechanical removal (tearing).

 The technical result is to increase the degree of dissolution of the gold-containing alloy containing, in addition to silver, more than 3% impurities of bismuth, lead and tin, as well as simplifying the process.

 To do this, the process is carried out at a bath voltage of 0.9-1.1 V and an asymmetric current with a certain ratio of the number of pulses of positive and negative signs, which is 20: 1. In this case, the current strength of the half-periods of the positive sign is 330-350 A, and the current strength of the half-cycle of the negative sign is 30-50 A. Carrying out the process in the indicated mode at this ratio of pulses allows you to periodically clean the anode of a dense film of non-ferrous metal compounds, which was previously unsuccessful.

 The essence of the current supply by pulses is as follows. In the forward direction of the current (the positive sign of the pulse), the anode dissolves and a passivating film forms. During the reverse current pulse, the gold-containing alloy acquires the function of a cathode and there the reaction of restoration of the discharge of hydrogen ions proceeds. Hydrogen ions have a minimum ionic radius of all elements, so they can reach the surface of the metal of the anode, passing through a layer of passivator. The resulting gaseous hydrogen "peels" the film of compounds passivating the anode).

 The ratio of the number of current pulses of positive and negative sign, the alternating current strength in the bath is directed, on the one hand, to the deposition of a relatively more loose layer of metal chloride impurities, and on the other hand, to obtain enough hydrogen to penetrate the passivator film, to loosen it up before dropping.

PRI me R. Anodes, content, 70 Au; 13Ag; 10 cu; 4 sums of Bi, Pb, Sn; 3Ni, pour in an electrolyte with a concentration of 140 g / dm ^{3 of} gold and 80 g / dm ^{3 of} hydrochloric acid. The current is supplied to the electrolysis bath through a rectifier equipped with a reversing device, which allows 20 positive pulses (half-cycle) to be applied to the bath, and then one negative sign pulses, during which the current flows in the opposite direction. The voltage on the bath is 1.0 V. The current strength with direct current supply is 335 A, with a reverse pulse of 45 A. Anode dissolution of 80% is achieved in 3 days, while the prototype dissolves the anode after 12 hours at a dissolution rate of 10% The pulse current mode and the corresponding current strength in the bath were selected experimentally and going beyond the specified parameters leads to a sharp decrease in the dissolution rate until its complete cessation.

Claims (1)

 METHOD FOR PROCESSING GOLD-CONTAINING ALLOY, containing impurities of silver and non-ferrous metals, including electrolytic dissolution of the initial alloy by applying alternating asymmetric current, containing half-periods of positive and negative signs, characterized in that the process is carried out at a voltage of 0.9 1.1 V, current strength of the half-cycle of positive sign 330 350 A, the current strength of the half-cycle of the negative sign 30 50 A, with the ratio of the number of half-periods of the positive and negative sign 20 1.