RU2301287C2 - Method of the electrochemical purification of the zinc water solution from manganese - Google Patents

Abstract

FIELD: nonferrous metallurgy; other branches of industry and economy; methods of the electrochemical purification of the zinc and other nonferrous metals water solutes, the industrial and household waste waters from impurities.

SUBSTANCE: the invention is pertaining to the field of the nonferrous metallurgy and may be used for extraction of the substances by the method of the electrochemical extraction and also for purification of the industrial and household waste waters. Metallic zinc is extracted from the sulfate-chloride solution on the titanium cathode and manganese is settled in the composition of the anode sludge formed on the lead-silver anode. The solution is fed into the anode sell made in the form of a sack from the tight filtering cloth with the anode located in it, and it is withdrawn from the cathode space separated from the anode space by the porous partition. The molar ratio between the ion Mn²⁺ in the initial solution and the ion MnO^- ₄ in the anolyte compounds Mn²⁺ : MnO^- ₄ ≥ 3/2. The invention is characterized by the high degree of purification of the zinc solutions from manganese, the high quality of the surface of the cathode zinc, the lack of limitations on the contents of the ions of manganese in the initial solution, the possibility to create the wasteless technology at the anode sludge salvaging and also it is characterized by the environmental safety of the production process.

EFFECT: the invention ensures the high degree of purification of the zinc solutions from manganese, the high quality of the surface of the cathode zinc, the lack of limitations on the contents of the ions of manganese in the initial solution, the possibility to create the wasteless technology at the anode sludge salvaging and it is characterized by the environmental safety of the production process.

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Description

The electrochemical method of purification of zinc solutions from manganese relates to the field of extraction of substances by electroextraction and can be used in non-ferrous and ferrous metallurgy, as well as for the treatment of industrial and domestic wastes.

Known methods for cleaning solutions of non-ferrous metals from manganese [Khudyakov I.O., Klein S.E., Ageev N.G. Metallurgy of copper, nickel, related elements and design of workshops. M .: Metallurgy, 1993, p.166-167] by precipitation of the last of the heated acidic solutions in the presence of oxidizing agents.

The disadvantage of the methods is that along with manganese a significant amount of non-ferrous metal is precipitated, in addition, a large number of processing steps are necessary to obtain a metal that does not contain manganese impurities.

The closest technical solution is a method for the electrochemical production of zinc from solutions, including the separation of metallic zinc on a titanium cathode and the deposition of manganese in the composition of the anode sludge formed on a lead-silver anode [A.P. Snurnikov. Zinc hydrometallurgy. Moscow, metallurgy, 1981, p.237-266].

The disadvantage of this method is that the conditions for obtaining zinc, purified from manganese impurities, are not defined, especially at high concentrations of manganese impurities in the electrolyte.

The objective of the invention is to provide an effective method for purification of zinc solutions from manganese in the technology for producing metallic zinc without restrictions on the content of manganese ions in the initial solution.

The technical result that can be achieved by carrying out the invention is to obtain metallic zinc of high purity.

This technical result is achieved by the fact that in the known method of electrolytic extraction of zinc from a solution, including the separation of metallic zinc on a titanium cathode and the deposition of manganese in the composition of the anode sludge formed on a lead-silver anode, zinc is extracted from a sulfate and chloride-sulfate solution, which is supplied into the anode cell, made in the form of a bag of dense filter cloth with an anode placed in it, and removed from the cathode space separated from the anode space by a porous orodkoy, wherein the molar ratio between the compliance Mn ²⁺ ion in the original solution and ion MnO ₄ ^- in the anolyte Mn ^2+: MnO ₄ ^- ≥3: 2.

The essence of the method is illustrated by the design diagram of the electrolyzer, shown in the drawing and the data of table 1-7, which indicate the conditions for electroextraction (table 1-2), the results of spectral (table 3) and x-ray phase (table 4-5) cathodic analyzes zinc, the phase composition of the anode sludge (table 6-7).

It is known that zinc is electrolytically released from solution. According to the reference data, the standard electrode potential of the reaction

Zn ²⁺ + 2e → Zn

equal to E ⁰ = -0.763 Century

Mn ²⁺ cation is oxidized at the anode by reactions

Mn ²⁺ -2e + 6H ₂ O = MnO ₂ + H ₃ O ⁺ ,

Mn ²⁺ -5e + 2O ₂ = MnO ₄ ^- .

Anion MnO ₄ ^{- is} reduced at the cathode by the reaction

but Mn ²⁺ at the cathode is not restored, because electrode potential E (Mn ²⁺ / Mn ⁰ ) = - 1.18 B.

Manganese anions go to the anode and stand out on the lead anode as part of the anode sludge.

Chloride-sulfate solutions were prepared by adding ZnCl ₂ or NaCl chlorides to the zinc sulfate solution, while the amount of chlorion did not exceed the concentration at which chlorine formed during electrolysis could be released as a gas; the calculation was carried out taking into account the fact that chlorine released during the experiment is in the dissolved state in the electrolyte.

Using the electrochemical method, cathode metal was obtained from sulfate and chloride-sulfate solutions of zinc (II) and manganese (II), which, according to spectral and X-ray phase analysis, contains manganese in an amount not exceeding 1 wt.%.

During the electrochemical separation of cathode zinc from solutions, manganese is selectively released in the composition of the anode sludge.

The drawing shows a diagram of the electrolyzer. The anode was placed in a cell from a dense filter cloth - an anode bag, the solution was fed into the anode cell - an anode bag and removed from the cathode space, the cathode and anode space were separated by a porous septum.

With this method of electroextraction, manganese anions MnO ₄ ^- formed on the anode cannot appear in the cathode space, since, for example, Mn ²⁺ cations contained in the initial solution can interact with MnO ₄ ^- by the reaction

Thus, manganese is discharged into the anode sludge in the form of MnO ₂ by reaction (2), while MnO ₄ ^{- is} excluded from entering the cathode space, which excludes the reduction of the MnO ₄ ^- anion on the cathode by reaction (1). MnO ₂ and other sparingly soluble manganese compounds in the anode sludge are accumulated in the cell from a dense filter cloth - the anode bag and do not enter the cathode space, and the presence of a porous septum also prevents the passage of anode sludge particles to the cathode.

This method of supplying the initial solution to the electrolyzer and withdrawing the spent electrolyte improves the surface quality of the cathode zinc, reduces the content of manganese in it. The content of manganese ions in the original solution is not limited, particularly if, according to the reaction (2), the following molar ratio is observed between the Mn ²⁺ ion in the original solution and ion MnO ₄ ^- in the anolyte Mn ^2+: MnO ₄ ^- ≥3: 2.

The concentration of zinc (II) ions in the initial solution was in the range of 15-40 g / dm ³ in Zn, manganese (II) ions in the range of 0.05-15 g / dm ³ in Mn, the current strength was 0.5-1, 5 A, current density 200-300 A / m ² , flow rate 2-3 cm ³ / min.

Examples of practical application.

Table 1-7 presents the results of electroextraction from sulfate and chloride-sulfate solutions of nickel.

Lead anode containing 1% silver, titanium cathode.

Tables 1 and 2 give the main parameters of the electrolysis process from a solution of sulfates (Table 1) and from solutions of sulfates and chlorides (Table 2).

The zinc released at the cathode had a shiny, even surface and contained a small amount of manganese impurity.

Table 3 gives the concentration of manganese in the samples of cathodic zinc of table 1 and 2.

The results of spectral analysis indicate a high degree of selectivity of zinc extraction at the cathode during its electrochemical purification from manganese (II) ions, the manganese content in cathode zinc did not exceed 0.98%.

Table 4-5 shows the phase compositions of the surface layers of zinc from the side of the titanium cathode (Table 4) and from the side of the electrolyte solution (Table 5) according to the X-ray phase analysis. From the data in Tables 4-5 it follows that the surface layers are contaminated with electrolyte, and in the surface layer facing the titanium cathode, the amount of oxide and salt contaminants is less than in the surface layer facing the electrolyte solution.

Table 6 gives the phase composition of the anode sludge obtained under the conditions of the experiments of Tables 1-2, according to x-ray phase analysis.

Table 7 gives the phase composition of the anode sludge of OJSC “Electrozinc”, Vladikavkaz, North Ossetia-Alania, while the composition of the cathode zinc corresponds to the zinc compositions presented in tables 4-5.

Sulphates of lead, manganese, zinc and silver, oxides and hydroxides of these metals of various degrees of oxidation, oxide phases of complex composition containing various metals in different valence states were found in the anode sludge.

According to chemical analysis, the composition of the anode sludge obtained by electrolysis of a solution of zinc sulfate of OJSC “Electrozinc”, Vladikavkaz, North Ossetia-Alania, wt.%: MnO ₂ - 53.9; PbO ₂ - 15; Ag ₂ O - 0.06; impurities - the rest.

In the production of zinc metal, the electrochemical method for cleaning zinc solutions from manganese in comparison with the prototype has several advantages, including a high degree of zinc purification from manganese, good surface quality of cathode zinc, no restrictions on the content of manganese ions in the initial solution, the possibility of creating a waste-free technology for the disposal of anode sludge, environmental safety of the process.

With the electrolytic release of zinc, there is no need to organize special stages of cleaning zinc solutions from manganese impurities, which reduces the number of staff.

The developed method of supplying the initial solution and withdrawing the spent electrolyte allows us to make the process continuous, automated, which increases the productivity, extraction and quality of the metal.

Table 1
The electrolysis parameters of a solution of zinc (II) sulfates and manganese (II). The volume of the solution is 1 dm ³ , t = 20-40 ° C No. p / p The concentration of the initial solution, g / DM ³ Process parameters Weight g Zn Mn Current strength, A Current density, A / m ² Time min Voltage Flow rate, cm ³ / min Cathode Zinc Anode sludge one 40 10 1,0 278 395 18-12 2,5 6.63 2.80 2 40 10 0.5 139 365 16-14 2.7 2,53 2,51 3 40 one 1,0 278 380 29-14 2.6 6.06 2.66 four 40 one 0.5 139 337 20-12 3.0 2.48 2.48

table 2
The electrolysis parameters of a solution of sulfates and chlorides of zinc (II) and manganese (II)
The volume of the solution is 1 dm ³ , t = 20-40 ° C No. p / p The concentration of the initial solution, g / DM ³ Process parameters Weight g Zn Mn Current strength, A Current density, A / m ² Time min Voltage Flow rate, cm ³ / min Cathode Zinc Anode sludge one 40 10 one 278 500 19-12 2.0 10.09 9.01 2 40 10 0.5 139 335 17-14 3.0 3.12 6.45 3 40 one one 278 390 22-12 2.6 7.45 6.71 four 40 one 0.5 139 415 18-10 2,4 4.25 5.78

Table 3
Manganese concentration in cathode zinc samples, Tables 1 and 2
according to spectral analysis. Sample No. The concentration of Mn, wt.% Samples of table 1 one 0.98 2 0.94 3 0.96 four 0.96 Samples of table 2 one 0.93 2 0.92 3 0.91 four 0.93

Table 6
Phase composition of the anode sludge according to x-ray phase analysis Sample No. Phase composition, wt.% PbSO ₄ ZnSO ₄ H ₂ O Zno Zn ₂ MnO ₄ Pbo PbO ₂ Samples of the table. one one 8.14 8.17 10.94 3.12 12.07 31.26 2 9.80 12.41 14.77 5.87 20.26 20,23 3 11.82 10.63 4.61 2.05 18.32 30.71 four 11.30 14.04 11.85 5.14 25.33 18.30 Samples of the table. 2 one 9.84 8.61 14.53 - - 39.37 2 7.43 10.81 10.29 - - 33.34 3 7.86 9.07 12.85 - 4.91 32.37 four 10.15 9.91 - - 12.07 34.81 Table 6 continued Sample No. Phase composition, wt.% ZnSO ₄ Na ₂ Zn ₃ (SO ₃ ) ₄ 4H ₂ O ZnMnO ₃ MnSO ₄ Mn ₂ O ₃ Ag ₂ SO ₄ Samples of table 1 one 25.13 - - - - - 2 17.63 - - - - - 3 21.27 - - - - - four 14.04 - - - Samples of table 2 one 18.87 1,08 5.92 - 0.98 0.23 2 13.23 9.40 5.48 6.69 3.66 - 3 25.38 - - 4.91 2.05 0.15 four 20.96 - 11.77 - 1.05 0.08

Table 7
The phase composition of the anode sludge according to the XRD. Phase Interplanar distances, d Intensity,% Mn (OH) ₄ 2.39 3.11 2.15 100 60 60 MnO (OH) ₂ 2.39 3.11 2.15 100 60 60 PbSO ₄ 3.00 4.26 3.33 100 87 86 MnO ₂ 3.14 2.41 1.63 100 50 50 MnO _1.88 2.39 3.13 2.15 100 75 75 Pb (OH) ₂ 3.23 3.05 2.70 100 100 80 β-PbO ₂ 3.50 2.46 2.79 100 90 80 Zn (OH) ₂ 6.97 3.09 2.97 100 30 30 Pb ₄ O ₃ SO ₄ nH ₂ O 3.25 3.13 3.07 100 80 80 MnPbMn ₆ O ₁₄ 3.11 3.46 2.40 100 45 40 Pb ₂ Mn ₈ O ₁₆ 3.13 6.99 2.40 100 60 45 MnPbMn ₆ O ₁₄ 3.10 3.47 1.54 100 60 50 HZnMn ₂ O ₄ 2.47 2.66 3.02 100 80 70 AgMn ₂ O ₄ 3.06 2.72 2.40 100 100 100 Ag ₅ Pb ₂ O ₆ 2.97 2.73 2.38 100 100 100 Mn ₂ O ₃ 2.72 1.66 3.85 100 25 25 ZnSO ₄ · H ₂ O 3.42 4.77 3.07 100 55 45 Ago 2.80 2.78 2.42 100 80 65 Ag ₂ SO ₄ 2.84 2.64 3.17 100 85 75 pyrochlore 3.00 1.84 1.57 100 60 50 pyrochlore 3.00 1.83 1.56 100 80 60 spinel 2.44 2.02 1.43 100 58 58

Claims (1)

The method of electrolytic extraction of zinc from a solution, including the separation of metallic zinc on a titanium cathode and the deposition of manganese in the composition of the anode sludge formed on a lead-silver anode, characterized in that the zinc is extracted from a sulfate or chloride-sulfate solution, which is fed into the anode cell made in the form of a bag of dense filter cloth with an anode placed in it, and removed from the cathode space separated from the anode space by a porous septum, while observing the molar the ratio between the Mn ²⁺ ion in the original solution and ion MnO ₄ ^- in the anolyte Mn ^2+: MnO ₄ ^- ≥3: 2.