RU2233893C1 - Method of cleaning sulfate zinc solutions from admixtures - Google Patents

Abstract

FIELD: non-ferrous metallurgy; cleaning sulfate zinc solutions from admixtures.

SUBSTANCE: proposed method consists in two-stage cleaning of sulfate zinc solutions from copper and cadmium; cleaning of solution from cadmium is performed at first stage to residual content not exceeding 30 mg/l; second stage is performed due to additional delivery of solution of copper sulfate at content of sum of ions of copper and cadmium within 70-100 mg/l at temperature of solution of 75-80 C and pH= 4.6-4.9.

EFFECT: improved quality of cleaned solution.

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Description

The invention relates to ferrous metallurgy and can be used in the purification of zinc sulfate solutions from impurities.

A known method of purification of zinc sulfate solutions from impurities, including a two-stage purification with filing of zinc dust containing, wt.%: Cobalt and nickel from the 2nd stage;

lead 0.6-0.9

iron 0.003-0.5

other impurities less than 0.01

zinc rest

(see Russian patent No. 2186131, publ. Bull. No. 21 dated 07/27/2002).

The disadvantage of this method is the high consumption of zinc dust in total at all stages of cementation treatment.

A known method for the purification of zinc sulfate solutions from impurities, comprising a two-stage purification with supply to the 2nd stage of zinc dust containing,%: aluminum 0.001-0.03; lead 0.05-1 and sometimes copper 0.02-0.1 for cleaning from cobalt and nickel with the return of part of the cement deposit with excess zinc dust to the 1st stage of cleaning solutions (see Canadian Patent No. 1133228, publ. 12.10. 82, MKI C 01 G 9/06).

The disadvantage of this method is the high yield of copper-cadmium cake (solid residue of the 1st stage of purification) due to the increased content of zinc in it, which requires an increase in capital and current costs for filtering and processing it.

The closest in technical essence and the achieved result is a method of purification of zinc sulfate solutions from impurities, including a two-stage purification with the supply of spent electrolyte, antimony-containing additives, with the purification of the solution at the 1st stage from copper to 0.19 mg / l and cadmium to 34, 5-68 mg / l with zinc dust and pulp, consisting of a reverse cake, a neutral solution and spent electrolyte with a weight ratio of 1: (2.6-4.1) :( 0.24-0.6) (see author certificate of the USSR No. 876760, class C 22 V 19/26, publ. 30.01.81, Bull. No. 40).

The disadvantage of this method is the high content of cobalt and cadmium and other impurities in the purified solution ((see example, Table 2 ed. Certificate. No. 876760) of cobalt 0.7-1.02 and cadmium 0.9-1.3 mg / l).

The technical result of this invention is to improve the quality of the purified solution and thereby reduce the specific energy consumption for zinc electrolysis and reduce the content of impurities in the cathode zinc. This result is achieved by the fact that in the method of purification of zinc sulfate solutions from impurities, including two-stage purification with the supply of spent electrolyte, antimony additives, zinc dust containing lead, purification of the solution in the first stage from copper to a residual content of less than 0.5 mg / l and from cadmium, the cadmium solution is cleaned in the first stage to a residual content of not more than 30 mg / l, and the second stage of purification is carried out by additional supply of copper sulfate solution with the amount of io s cadmium and copper in the feed solution in the range 70-100 mg / l at a solution temperature of 75-80 ° C and pH 4.6-4.9.

The method is as follows.

Neutral sulfate zinc solution with impurities, mg / l: copper 200-800; cadmium 300-700; cobalt 2-15; Nickel 3-10 enters the two-stage cement cleaning of solutions from impurities. At the first stage, zinc dust is purified mainly from copper and cadmium to residual copper contents of less than 0.5 mg / l and cadmium not more than 30 mg / l. The temperature of the solution at the 1st stage of purification is maintained at 60 ° C, and the duration is 1-2 hours, the pH of the solution is 4.6-4.9, which is regulated by the dosed supply of spent electrolyte to the zinc sulfate solution. The solution after the 1st stage of purification is separated from the solid on the filter presses and the filtrate enters the 2nd stage of purification. An antimony-containing additive (antimony trioxide, potassium tartrate) is added to the filtrate to maintain the antimony to total ratio (cobalt + nickel) of 0.2-1: 1 and copper sulfate solution with a copper concentration of 40-55 g / l to maintain the total ion content (copper + cadmium) in the incoming solution in the range of 70-100 mg / L. The temperature of the solution at the 2nd stage is 75-80 ° C and the pH of the solution is 4.6-4.9, which is regulated by the dosed supply of spent electrolyte. The duration of the process at the 2nd stage is from 2 to 3 hours. The cleaned 2nd stage cleaning solution separated on the filter presses is sent to electrolysis, and the cement cake is sent to receive cobalt cake.

The proposed method is tested in an industrial environment.

Tests have shown that the purification of zinc sulfate solutions from impurities by conducting the 2nd stage of purification due to the additional supply of copper sulfate solution with a total ion content (copper + cadmium) in the incoming solution within 70-100 mg / l at a solution temperature of 75-80 ° C and pH 4.6-4.9 can improve the quality of the purified solution.

The limits of the change in the content of the sum of ions (copper + cadmium) at a certain solution temperature and pH are associated with obtaining minimum concentrations of cadmium and cobalt in the purified solution. So, at contents above 100 mg / l in the temperature range of the solution 75-80 ° С and pH 4.6-4.9, the content of copper and cobalt in the purified solution increases, and when lower than 70 mg / l, the cadmium content in the purified solution increases . An increase in the temperature of the solution above 80 ° C and a pH above 4.9 when the content of the sum of ions (copper + cadmium) in the range of 70-100 mg / l increases the cadmium content in the purified solution. When the temperature drops below 75 ° C and a pH below 4.6, the activity of zinc dust decreases, which increases the cobalt content in the purified solution.

The verification of the method is as follows. At the 1st stage of purification sulphate zinc solution was supplied with a content, mg / l: copper 520; cadmium 480; cobalt 4.9; nickel 5.2. The temperature of the solution is 60 ° C, pH 4.9. The consumption of zinc dust containing 0.2% lead was 2.2 g / l. The cleaning time is 2 hours. The solution was separated from the solid in a filter press, while the filtrate was obtained with a content, mg / l: copper 0.3; cadmium 15.6; cobalt 4.0; Nickel 1.3, which was subjected to the 2nd stage of purification. Potassium tartrate (per 1 liter of 2.5 mg solution) and 1.58 ml / l of copper sulfate solution (45 g / l of copper) was introduced into the filtrate, which provided a total of 86.9 mg / l of ions (copper + cadmium) in the solution. The temperature of the solution at the 2nd stage was maintained at 78 ° C, and a pH of 4.7. The consumption of zinc dust at the 2nd stage was 2.5 g / l.

The table shows comparative verification data of the known and proposed method for purification of zinc sulfate solutions from impurities.

As can be seen from the data obtained, the use of the proposed method for purification of sulfate zinc solutions can improve the quality of the purified solution compared to the known method. So, the cadmium content decreased from 0.5 to 0.3 mg / l, and cobalt - from 0.7 to 0.15 mg / l.

Claims (1)

The method of purification of zinc sulfate solutions from impurities, including two-stage purification with the supply of spent electrolyte, antimony additives, zinc dust containing lead, purification of the solution in the first stage from copper to a residual content of less than 0.5 mg / l and cadmium, characterized in that purification of the solution from cadmium in the first stage is carried out to a residual content of not more than 30 mg / l, and the second stage is carried out by additional supply of a solution of copper sulfate with the content of the sum of copper and cadmium ions in the incoming p alignment within 70-100 mg / liter at a solution temperature of 75-80 ° C and pH 4.6-4.9.