RU2280106C2 - Method for preparing electrolyte for electrolytic refining of copper - Google Patents

Abstract

FIELD: hydraulic metallurgy of non-ferrous metals, namely electrolytic refining of copper, possibly electroplating metallurgy.

SUBSTANCE: method comprises steps of introducing into electrolyte complex of surface active matters including such as thiocarbomide. The last is preliminarily dissolved in copper sulfate solution at mass relation of ions of copper and sulfur (contained in thiocarbomide) in range 20 - 600 at temperature 40 - 70°C during 10 - 70 h. Initial electrolyte is used as copper sulfate solution for treating thiocarbomide. Invention allows produce smooth cathode copper with high helical elongation characterizing copper capability to rolling.

EFFECT: possibility for producing cathode copper with smooth surface, low content of sulfur, high physical and mechanical properties.

2 cl, 1 tbl, 8 ex

Description

The invention relates to the field of hydrometallurgy of non-ferrous metals, in particular to electrolytic refining of copper, and can be used in electroplating.

A known method of preparing an electrolyte for electrolytic refining of copper, comprising introducing into a sulfate electrolyte a complex of surface-active substances (surfactants), including thiocarbamide (thiourea). Surfactant additives are dissolved in water and introduced into the electrolyte in the form of aqueous solutions into the electrolysis baths. The consumption of thiocarbamide is 90 g per ton of copper obtained by electrolysis. The method allows in the process of electrorefining at a current density of 310-320 A / m ² to obtain copper cathodes of the brand M0k, characterized by a fine crystalline structure, a grooved surface and a relatively high sulfur content [1].

The disadvantage of this method is the increased sulfur content in the cathode copper, due to the significant consumption of thiocarbamide sulfur-containing compounds used as additives for surfactants, because when an aqueous solution of thiocarbamide is added to the electrolyte, its sulfur goes into cathodic copper immediately before electrolysis. In turn, the sulfur contained in the cathode copper has a negative effect on the physicomechanical properties of copper, in particular, worsens the spiral elongation. Spiral elongation is the main indicator used in world practice, along with the chemical composition for assessing the suitability of cathode copper in the production of wire rod by continuous casting and rolling, that is, characterizing the rolling of cathode copper. Another disadvantage of the method is the insufficiently high grade of cathode copper M0k, guaranteed to be obtained as a result of the electrorefining process using the prepared electrolyte. The next disadvantage of this method is the increased energy costs for the production of cathode copper in the process of electrorefining of copper, due to the significant consumption of thiocarbamide used as an additive surfactant.

A known method of preparing an electrolyte for electrolytic deposition of copper, including the introduction of a surfactant complex into a sulfate electrolyte, including thiocarbamide (thiourea). Each surfactant additive is dissolved in water and introduced into the electrolyte in the form of aqueous solutions entering the electrolysis baths. The consumption of thiocarbamide is 70 g per ton of copper obtained by electrolysis. The method allows in the process of electrolytic refining to obtain copper cathodes of the grades M00k and M0k, characterized by a fine-crystalline structure [2].

The disadvantage of this method is the increased sulfur content in the cathode copper, due to the significant consumption of thiocarbamide sulfur-containing compounds used as additives for surfactants, since when an aqueous solution of thiocarbamide is added to the electrolyte, its sulfur goes into cathode copper immediately before electrolysis. In turn, the sulfur contained in the cathode copper has a negative effect on the physicomechanical properties of copper, in particular, worsens the spiral elongation. Spiral elongation is the main indicator used in world practice, along with the chemical composition for assessing the suitability of cathode copper in the production of wire rod by continuous casting and rolling, that is, characterizing the rolling of cathode copper. Another disadvantage of this method is the insufficiently high grade of cathode copper M0k obtained as a result of the electrorefining process using the prepared electrolyte. The next disadvantage is the increased cost of electricity for the production of cathode copper in the process of copper electrorefining, due to the significant consumption of thiocarbamide used as a surfactant additive.

A known method of preparing a sulfate electrolyte for electrolytic refining of copper, including the introduction of a surfactant complex into the electrolyte, including thiocarbamide, (thiourea). Surfactant additives, including thiocarbamide, are dissolved in water at room temperature and introduced into the electrolyte entering the electrolysis baths. The consumption of each surfactant additive is 50-150 g per ton of copper obtained by electrolysis [3]. The method allows to obtain copper cathodes characterized by a fine crystalline structure in the process of electrolytic refining.

The disadvantage of this method is the increased sulfur content in the cathode copper, due to the significant consumption of thiocarbamide (sulfur-containing compounds), introduced as an additive surfactant. In turn, the sulfur contained in the cathode copper negatively affects the physicomechanical properties of copper, in particular, worsens the spiral elongation index characterizing the rolling of the cathode copper. Another disadvantage of the method is the insufficiently high grade of cathode copper M0k, guaranteed to be obtained as a result of the electrorefining process using the prepared electrolyte. Another drawback is the increased cost of electricity for the production of cathode copper in the process of electrorefining, due to the significant consumption of thiocarbamide introduced into the sulfate electrolyte as an additive surfactant.

Closest to the claimed method according to the set of essential features is a method of electrolytic refining of copper from sulfate electrolytes, comprising introducing into the electrolyte 2-5 mg / l of a condensation product of thiourea and fatty acid aminoamides. Surfactant additives, including the condensation product of thiourea and fatty acid aminoamides, are dissolved in water at 60-70 ° C and introduced into the electrolyte entering the electrolysis baths. In this case, the concentration of the condensation product of thiourea and fatty acid aminoamides is 2-5 g / l [4]. The method allows to obtain dense dendritic copper cathodes during electrolytic refining.

The disadvantage of this prototype method is the increased (0.001%) sulfur content in the cathode copper. In turn, the sulfur contained in the cathode copper negatively affects the physicomechanical properties of copper, in particular, worsens the spiral elongation index characterizing the rolling of the cathode copper. Another disadvantage of this method is the insufficiently high grade of cathode copper M0k obtained as a result of the electrorefining process using the prepared electrolyte. Another drawback is the increased cost of electricity for the production of cathode copper in the process of electrorefining.

The objective of the invention is to improve the quality of the cathode copper and reduce the specific energy consumption for its production.

The technical result from the use of the invention is to obtain cathode copper having a smooth surface without dendrites, low sulfur content, high physical and mechanical properties, in particular spiral elongation, characterizing the ability of copper to rolling.

The essence of the invention lies in the fact that a complex of surfactant additives is introduced into a sulfate electrolyte for electrolytic refining of copper, including thiocarbamide. In this case, thiocarbamide is pre-dissolved in copper sulfate solution at a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 20-600, at a temperature of 40-70 ° C and kept at a temperature of 40-70 ° C for 10-70 hours. Another difference of the method is that the source electrolyte is used as a sulfate solution of copper for the treatment of thiocarbamide.

It was experimentally established that the method according to claim 1 or claim 2 of preparing an electrolyte for electrolytic refining of copper allows to obtain cathode copper characterized by preliminary dissolution of thiocarbamide in a copper sulfate solution and holding the solution at a temperature of 40-70 ° C for 10-70 hours smooth surface, fine crystalline structure and low sulfur content. In addition, the proposed method for the preparation of electrolyte can reduce the energy consumption for the production of 1 ton of electrolyte copper.

In the methods of preparing an electrolyte for electrolytic refining of copper, including the introduction of a complex of surfactant additives into the electrolyte, including thiocarbamide, these analogues and prototype do not pre-dissolve thiocarbamide in copper sulfate solution and hold this solution at a temperature of 40-70 ° С for 10- 70 hours.

In the absence of preliminary dissolution of thiocarbamide in copper sulfate solution and exposure of this solution at a temperature of 40-70 ° C for 10-70 hours, in order to obtain cathode copper, having a smooth surface and a fine crystalline structure, as a result of electrorefining, it is necessary to increase the consumption of thiocarbamide (description of analogues) or introduce another surfactant (prototype). In turn, an increase in the consumption of thiocarbamide leads to an increase in the sulfur content in the cathode copper, a decrease in its physical and mechanical properties, and an increase in the specific energy consumption for its production.

The increase in the proposed method, the number of copper ions in the sulfate copper solution is more than necessary to ensure the upper limit of the proposed range of ratios of copper and sulfur ions contained in thiocarbamide, equal to 20-600, will create performance difficulties associated with a significant increase in the intermediate equipment for dissolution and aging at preparation of an additive of thiocarbamide, and will require an unjustified additional consumption of energy resources to maintain the required temperature of the solution.

A decrease in the amount of copper ions in a sulfate copper solution in the proposed method is less than necessary to ensure the lower limit of the proposed range of ratios of copper and sulfur ions contained in thiocarbamide, equal to 20-600, will lead to the formation of limited soluble compounds that impede the execution of the method and can negatively affect the process of electrolytic refining of copper.

A decrease below 40 ° C of the temperature of the solution maintained during preliminary dissolution and aging of the thiocarbamide solution will not allow to achieve the goal, namely, by electrolytic refining, to obtain cathode copper, characterized by a smooth surface and a fine crystalline structure while reducing the consumption of thiocarbamide used as a complex of surfactant additives .

An increase above 70 ° C of the temperature of the solution, maintained during preliminary dissolution and aging of the thiocarbamide solution, leads to its decomposition, which negatively affects the surface-active properties and does not allow to achieve the goal, namely, electrolytic refining to obtain cathode copper, characterized by a smooth surface and a fine-crystalline structure, while reducing the consumption of thiocarbamide used as a complex of surfactant additives.

Reducing the duration of preliminary exposure less than 10 hours will not allow to achieve the goal, namely, as a result of electrolytic refining, to obtain cathode copper, characterized by a smooth surface and a fine crystalline structure, while reducing the consumption of thiocarbamide introduced as a surfactant additive complex.

An increase in the duration of preliminary exposure of a thiocarbamide solution to more than 70 hours creates performance difficulties associated with a significant increase in the intermediate equipment for preparing a thiocarbamide solution and will require unjustified additional energy consumption to maintain the required temperature of the solution.

Information about the fame of the distinguishing feature of the proposed technical solution in the study of patent and technical literature has not been identified, which indicates the compliance of the claimed object with the criterion of "inventive step".

The method is as follows.

Thiocarbamide is pre-dissolved at a temperature of 40-70 ° C in a copper sulfate solution with a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 20-600, and the thiocarbamide solution is maintained at a temperature of 40-70 ° C for 10-70 hours. The prepared solution is introduced, among other solutions included in the complex of surfactant additives, into the flow of electrolyte entering the electrolysis baths for the implementation of the process of electrolytic refining of copper.

The process of electrolytic refining of copper is as follows. In electrolysis baths, the corresponding electrodes are hung on the current-carrying anode and cathode buses. As anodes, cast plates made of fire-refined copper are used; as cathodes, thin sheets of electrolyte copper (base) or a matrix of titanium (or stainless steel) are used. A direct electric current is supplied to the electrolysis bath based on a cathode current density of 250-360 A / m ² .

Electrochemical dissolution of copper anodes and cathodic deposition of copper from a sulfate electrolyte is carried out at its constant circulation and a temperature of 60-65 ° C.

The effectiveness of the method is estimated by the results of electrolysis in terms of specific energy consumption and obtaining cathode copper having a smooth surface, a fine crystalline structure, low sulfur content and a high value of spiral elongation characterizing the rolling of copper. The proposed method is described in specific examples and table 1.

Example 1 (table 1, experiment 1) is the implementation of the prototype method.

The specified amount of surfactant additives calculated by flow rate, g / t _Cu : glue - 70 (1.6 g / dm ³ ); the condensation product of thiocarbamide (thiourea) and fatty acid aminoamides - 85 (2.0 g / dm ³ ) was dissolved in distilled water at a temperature of 70 ° C. The prepared solutions of each surfactant were introduced into a sulfate electrolyte for electrolytic refining of copper entering the electrolysis bath. For the experiment we used a sulfate electrolyte of the following composition, g / dm ³ : copper - 50-55; nickel - 19-22; sulfuric acid - 155-161; chlorine ion - 0.045-0.050.

The electrolytic refining of copper was carried out in a laboratory setup consisting of an electrolysis bath with a capacity of 4 dm ³ and a pressure tank with a capacity of 10 l. The bath was provided with an individual circulation system and equipped with anode and cathode buses connected through a laboratory autotransformer (LATR) to the BCA-5 rectifier. One cathode, two copper anodes were hung on a cathode and anode busbars of the electrolysis bath at a distance of 4 cm and direct current was passed. The cathodic current density was 310 A / m ² . Surfactant additives were administered at equal intervals during the tests. During the experiment, the electrolyte temperature was maintained at 60-65 ° C, and the circulation rate was 4 dm ³ / h. The duration of the experiment was 94 hours.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- fine crystalline structure;

- the presence of small rounded growths;

- sulfur content - 10 g / t;

- low rate of spiral elongation equal to 368 mm

The specific energy consumption was 336 kWh / t _Cu .

Example 2 (table 1, experiment 2) is the implementation of the prototype method.

The experiment was carried out under the same conditions as Example 1. Example 2 differed from Example 1 by the consumption of the condensation product of thiocarbamide (thiourea) and fatty acid aminoamides per ton of cathode copper, which was 200 (5.0 g / dm ³ ).

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- fine crystalline structure;

- slight furrow;

- sulfur content - 12 g / t;

- spiral elongation equal to 351 mm.

The specific energy consumption was 371 kWh / t _Cu .

Example 3 (table 1, experiment 3) - implementation of the prototype method

The experiment was carried out under the same conditions as Example 1. Example 3 differed from Example 1 by the consumption of the condensation product of thiocarbamide (thiourea) and fatty acid aminoamides per ton of cathode copper, which was 200 (5.0 g / dm ³ ), and the concentration nickel (25 g / dm ³ ) and sulfuric acid (120 g / dm ³ ).

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- fine crystalline structure;

- slight furrow;

- sulfur content - 14 g / t;

- a low spiral elongation rate of 339 mm.

The specific energy consumption was 445 kWh / t _Cu .

Example 4 (table 1, experiment 4) - implementation of the proposed method

The experiment on electrolytic refining of copper was carried out under the same conditions as Example 1. Example 4 differed from Example 1 by the introduction of surfactant solutions calculated by flow rate as additives, g / t _Cu : glue - 70 and thiocarbamide - 30 g. In this case, the solution thiocarbamide was previously prepared.

Thiocarbamide was dissolved at a temperature of 40 ° C in a copper sulfate solution at a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 20, and the thiocarbamide solution was kept at a temperature of 40 ° C for 10 hours.

The prepared solution was introduced, among other solutions included in the complex of surfactant additives, into the electrolyte stream entering in the process of electrolytic refining of copper into electrolysis baths during the process of electrolytic refining of copper.

Surfactant additives were administered at equal intervals during the tests. During the experiment, the electrolyte temperature was maintained at 60-65 ° C, and the circulation rate was 4 dm ³ / h. The duration of the experiment was 94 hours.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- finely crystalline structure and smooth surface of the cathode;

- sulfur content - 6 g / t;

- a high spiral elongation rate of 419 mm.

The specific energy consumption was 284 kWh / t _Cu .

Example 5 (table 1, experiment 5) - implementation of the proposed method

The experiment was carried out under the same conditions as example 4. Example 5 differed from example 4 in terms of the preparation of a thiocarbamide solution.

The preparation of thiocarbamide solution contained the following operations:

- dissolution at a temperature of 70 ° C in a sulfate solution of copper with a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 600;

- exposure of the prepared solution for no more than 70 hours at a temperature of 70 ° C.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- finely crystalline structure and smooth surface of the cathode;

- sulfur content - 5 g / t;

- a high spiral elongation rate of 424 mm.

The specific energy consumption was 300 kWh / t _Cu .

Example 6 (table 1, experiment 6) - implementation of the proposed method

The experiment was carried out under the same conditions as example 4. Example 6 differed from example 4 in terms of the preparation of a thiocarbamide solution.

The preparation of a thiourea solution contained the following operations:

- dissolution at a temperature of 60 ° C in a sulfate solution of copper with a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 300;

- exposure of the prepared solution for 24 hours at a temperature of 60 ° C.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- finely crystalline structure and smooth surface of the cathode;

- sulfur content - 4 g / t;

- a high spiral elongation rate of 431 mm.

The specific energy consumption was 292 kWh / t _Cu .

Example 7 (table 1, experiment 7) - implementation outside the range of the proposed method

The experiment was carried out under the same conditions as example 4. Example 7 differed from example 4 in terms of the preparation of a thiocarbamide solution.

The preparation of a thiourea solution contained the following operations:

- dissolution at a temperature of 30 ° C in a sulfate solution of copper at a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 18;

- exposure of the prepared solution for 8 hours at a temperature of 30 ° C.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- the presence of small dendritic growths on the surface of the cathode;

- sulfur content - 8 g / t sulfur;

- the spiral elongation was 348 mm.

The specific energy consumption was 314 kWh / t _Cu .

The results, namely, a decrease in the quality of the cathode copper in appearance, an increase in its sulfur content, a decrease in the physico-mechanical index of spiral elongation, and an increase in the specific energy consumption as compared to Examples 4-6, show that the conditions for the preparation of thiocarbamide are not optimal.

Example 8 (table 1, experiment 8) - the implementation of the method outside the claimed range.

The experiment was carried out under the same conditions as Example 4. Example 8 differed from Example 4 in the preparation conditions of the thiocarbamide solution.

The preparation of a thiourea solution contained the following operations:

- dissolution at a temperature of 80 ° C in a sulfate solution of copper with a mass ratio of copper and sulfur ions contained in thiocarbamide equal to 650;

holding the prepared solution for 80 hours at a temperature of 90 ° C.

The use, in this case, of a significant mass ratio of copper and sulfur ions contained in thiocarbamide led to an unjustified increase in the volumes of the thiocarbamide solution with a corresponding increase in intermediate capacities and to a significant increase in the duration of the equipment (thermostat) that maintains the given temperature of the solution.

As a result of electrolytic refining, cathode copper was obtained, characterized by the following indicators:

- the presence of small dendritic growths;

- sulfur content was 9 g / t sulfur;

- the spiral elongation was 343 mm.

The specific energy consumption was 324 kWh / t _Cu .

The results of the experiment, namely, a decrease in the quality of the cathode copper in appearance, a decrease in the physicomechanical index of spiral elongation, and an increase in the specific energy consumption relative to Examples 4-6, confirm that the conditions for the preparation of thiocarbamide used in this example are not optimal.

According to the obtained experimental data (experiments 4-6), the proposed method according to claim 1 or claim 2 for preparing an electrolyte for electrolytic refining of copper in the presence of a complex of surface-active substances, including thiocarbamide, including its preliminary treatment with copper sulfate solution, is really effective. The implementation of the method of preparing the electrolyte for electrolytic refining of copper according to examples 4-6 allows to improve the quality of the cathode copper, reduce the sulfur content in it, improve the spiral elongation rate characterizing the suitability of cathode copper for the production of wire rod by continuous casting and rolling, and reduce by 18-57% specific energy consumption for the production of cathode copper relative to the prototype (examples 1-3). The presented experimental results confirm that the selected boundaries for the conditions of electrolyte preparation within the limits proposed by the formula are correct.

When the values of the parameters of the preparation of the electrolyte outside the declared ranges (experiments 7-13), the main technological indicators deteriorate, approaching the results obtained by the prototype method. This confirms that the selected boundaries for the conditions of electrolyte preparation within the limits proposed by the formula are correct.

Thus, the technical result achieved by using the proposed method is as follows:

- to improve the quality of the cathode copper in appearance, chemical composition and physical and mechanical properties, in particular in the magnitude of the spiral elongation associated with a decrease in its sulfur content;

- a decrease of 18-57% in the specific energy consumption for the production of cathode copper.

Table 1 Laboratory test results for electrolytic refining of copper Test conditions: cathodic current density - 310 A / m ² ; electrolyte temperature - 60-65 ° С; the duration of each experiment is 94 hours; circulation rate - 4 dm ³ / h; electrolyte composition, g / dm ³ : copper - 50-55; nickel - 19-22; sulfuric acid - 155-161; chlorine ion - 0.045-0.050. Experience number Additional * surfactant The conditions for the preparation of thiocarbamide in copper sulfate solution Sulfur content in cathode copper, g / t Spiral elongation, mm The average voltage in the bath, V Current output,% Specific energy consumption, kW · h / t Appearance of cathode deposits Name Consumption, g / I _Cu (g / dm ³ ) Ratio Cu ²⁺ / S _{CS (NH2) 2} Duration, h Temperature ° C one 2 3 four 5 6 7 8 9 10 eleven 12 one TAJ *** 85 (2) 10 368 0.39 98.0 336 The presence of small rounded dendritic growths 2 200 (5) 12 351 0.43 97.8 371 Fine crystalline structure, slight groove 3 ** 200 (5) - - - fourteen 339 0.51 96.7 445 Also four Thiocarbamide 30 (0.7) twenty 10 40 6 419 0.33 98.1 284 Fine crystalline structure, smooth surface 5 30 (0.7) 600 70 70 5 424 0.35 98.3 300 Also 6 30 (0.7) 300 24 fifty four 431 0.34 98.2 292 " 7 30 (0.7) eighteen 8 thirty 8 348 0.36 96.8 314 The presence of small rounded growths 8 30 (0.7) 650 80 80 9 343 0.37 96.4 324 Also 9 30 (0.7) eighteen 80 80 eighteen 305 0.40 95.4 354 The presence of small rounded growths 10 30 (0.7) eighteen 8 60 16 350 0.38 95.8 334 The presence of small rounded growths eleven 30 (0.7) eighteen 10 thirty eleven 328 0.36 96.0 316 The presence of small rounded growths, friable in the upper part 12 30 (0.7) 650 80 60 5 422 0.35 97.8 302 Fine crystalline structure, smooth surface 13 30 (0.7) 650 24 80 eleven 338 0.37 96.9 322 Fine-crystalline structure, the presence of rare small roundish growths * - either thiocarbamide or the condensation product of thiocarbamide (thiourea) and fatty acid aminoamides (TAJ) was introduced as one of the (additional) surfactants; ** - in the experiment used the electrolyte recommended in the prototype composition, g / dm ³ : copper - 50; nickel - 25; sulfuric acid - 120.

Sources used

1. Report on research work // Intensification and improvement of the process of copper electrorefining at NMMC. Stage 1. Improvement and intensification of the process of electrorefining of copper in direct current / № state. Registration 79061613 / Moscow - 1979 - p.31.

2. Technological instructions for the production of electrolyte copper TI 14.55-46-99. The term for introduction of September 1, 1998 is p. 48.

3. Patent PNR, CL 40 s1 / 16, / C 22 D 1/16, No. 66979, claimed. 04/10/69, publ. 03/31/73

4. SU 907088 A (Bugaev A.V. et al.), 02/23/1982.

Claims (2)

1. A method of preparing an electrolyte for electrolytic refining of copper, comprising introducing a complex of surfactants into a sulfate electrolyte, including thiocarbamide, with preliminary dissolution of thiocarbamide, characterized in that thiocarbamide is dissolved in a sulfate solution of copper at a mass ratio of copper and sulfur ions, contained in thiocarbamide, equal to 20-600 at a temperature of 40-70 ° C and maintained at a temperature of 40-70 ° C for 10-70 hours 2. The method according to claim 1, characterized in that the source electrolyte is used as a sulfate solution of copper in the processing of thiocarbamide.