RU2238993C1 - Method of refining sulfate zinc solutions to remove impurities - Google Patents

Abstract

FIELD: nonferrous metallurgy.

SUBSTANCE: method comprises two-step refining, which involves first feeding into incoming solution of exhausted electrolyte antimony-containing additive and second-step cement sediment separated from refined solution and simultaneously zinc powder including 0.1-0.5% lead and having particle size above 63 mcm. Antimony-containing additive is antimony trioxide used in amount selected from condition that ratio of antimony to summary content of cobalt and nickel in incoming solution is (1-2):1.

EFFECT: improved quality of refined solution when solutions with content of cobalt 5-7 mg/l and higher are processed.

2 cl, 1 tbl

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 Else

(see. Patent of Russia No. 2186131, publ. Bulletin No. 21 of July 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 of purification of zinc sulfate solutions from impurities, including a two-stage purification with precipitation of impurities with zinc dust and reverse cake with the supply of spent electrolyte to the second stage (see ed. 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 that it does not provide the necessary purification from impurities in the first stage of purification and does not improve the quality of the resulting copper-cadmium cake.

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 introduction of an antimony-containing additive in the first stage of the spent electrolyte solution and a second-stage cement deposit separated from the purified solution (ed. Certificate of the USSR No. 1043177, class C 22 V 19/26, publ. 23.09.83, bull. No. 35).

The disadvantage of this method is the high content of cobalt in the purified solution, which affects the quality of the cathode zinc.

The technical result of this invention is to reduce the cobalt content in the purified solution without increasing the consumption of zinc dust. This result is achieved by the fact that in the method of purification of zinc sulfate solutions from impurities, comprising a two-stage purification with the introduction of an antimony-containing additive in the first stage of the spent electrolyte solution and the second stage cement cake separated from the purified solution, zinc dust is fed to the first stage together with the cement cake with a lead content of 0.1-0.5% and as an antimony-containing additive, antimony trioxide in an amount based on the ratio of antimony to the sum of cobalt and nickel in the incoming solution ore 1-2: 1. Zinc dust containing 0.1-0.5% lead is fed with a particle size of more than 63 microns.

The method is as follows.

Neutral sulfate zinc solution with an impurity content, mg / l: copper 200-800, cadmium 300-700, cobalt 5-15, nickel 3-10, enters the two-stage cement cleaning of solutions from impurities. At the first stage, zinc dust is purified, containing 0.1-0.5% lead, mainly from copper and cadmium to residual copper contents of less than 0.5 mg / l and cadmium not more than 30 mg / l. Together with zinc dust, cement slurry of the composition is dosed at stage 1,%: zinc 60-70, cadmium 0.8-1.5, copper 1.5-2.5, cobalt 0.05-0.15, obtained by filtering the solution 2 stages of purification, as well as antimony trioxide in an amount based on the mass ratio of antimony to the total (cobalt + nickel) in the incoming solution 1-2: 1. The temperature of the solution at the 1st stage of purification is maintained at 55-60 ° C, and the duration is 1-2 hours, the pH of the solution is 4.6-4.9, which is controlled 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 ratio of antimony to total (cobalt + nickel) 0.2-1: 1 in the solution entering stage 2. The temperature of the solution in 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 purified solid solution of the 2nd stage of cleaning, separated on the filter presses, is sent to electrolysis.

The proposed method is tested in an industrial environment.

Tests have shown that the purification of zinc sulfate solutions from impurities by feeding zinc dust with a lead content of 0.1-0.5% and antimony trioxide in an amount of 1 based on the mass ratio of antimony to the sum of cobalt and nickel along with cement sludge 2 stages of zinc dust in an incoming solution of 1-2: 1 allows to reduce the cobalt content in the purified solution without increasing the consumption of zinc dust.

The limits of change in the content of lead in zinc dust from 0.1 to 0.5% are associated with its activity (reactivity) in solutions of the first stage of purification. So, with a decrease in the lead content in dust of less than 0.1%, the dust activity decreases, which is reflected in an increase in the cobalt content in the solution entering the 2nd stage of purification, and thereby its content in the purified solution increases. An increase in lead content above 0.5% practically does not increase the activity of used dust with a particle size of more than 63 microns. The total activity of lead-containing zinc dust with respect to cobalt cementation increases when the third component of antimony is added to the 1st complex stage of purification (from copper, cadmium, and partially from cobalt and nickel). The dosage of antimony trioxide in an amount based on the mass ratio of antimony to the total (cobalt + nickel) in the incoming solution is less than 1: 1 does not affect the increase in the cementation efficiency of cobalt, and when the dosage is more than 2: 1, the cadmium content in the solution entering the 2-stage cleaning increases . At the 1st stage of cleaning, the use of zinc dust with a particle size of less than 63 microns increases its consumption in comparison with the use of coarser dust, since unreacted finely dispersed metallic zinc, which is part of the cement residue, will be used in this case to a lesser extent.

The verification of the method is as follows.

At the first stage of purification, a sulfate zinc solution was supplied with a content, mg / l: copper 520, cadmium 480, cobalt 7.5, nickel 5.2. The temperature of the solution was 60 ° C, pH 4.8. The consumption of zinc dust containing 0.25% lead, particle size above 63 microns amounted to 1 g / l. Cement residue, composition,%: zinc 65.8, cadmium 1.5, copper 2.1, cobalt 0.1, obtained in 2 stages, in an amount of 2.8 g / l was loaded with zinc dust. The consumption of antimony trioxide is 20 mg / l. The cleaning time is 2 hours. The solution was separated from the solid in a filter press and a filtrate was obtained with a content, mg / l: copper 0.5, cadmium 17.8, cobalt 2.8, nickel 2.0, which was subjected to the 2nd stage of purification. At the second stage, potassium tartrate (per liter of 1.5 mg solution) was introduced into the filtrate. The temperature of the solution at 2 stages was maintained at 78 ° C, and a pH of 4.7. The consumption of zinc dust in 2 stages was 3.1 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 obtained data, the use of the proposed method for purification of zinc sulfate solutions allows, in comparison with the known method, to reduce the cobalt content in the solution entering the 2 stage of purification from 8.9 to 2.8 mg / l and thereby improve the quality of the purified solution. For a deeper cleaning of cobalt by a known method, it would be necessary to increase the consumption of zinc dust.

Claims (2)

1. The method of purification of zinc sulfate solutions from impurities, comprising a two-stage purification with the supply of spent electrolyte, an antimony-containing additive and a second-stage cement deposit separated from the purified solution in the first stage, characterized in that zinc dust is supplied to the first stage with zinc dust with a lead content of 0.1-0.5% and as an antimony-containing additive, antimony trioxide in an amount based on the ratio of antimony to the sum of cobalt and nickel in the incoming solution is 1-2: 1. 2. The method according to claim 1, characterized in that the zinc dust containing 0.1-0.5% lead is fed with a particle size of more than 63 microns.