DD211129B1 - CIRCULAR PROCESS FOR COATING COPPER AND COPPER ALLOYS - Google Patents

Description

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Field of application of the invention

The invention relates to a cyclic process for pickling copper and copper alloys with simultaneous recovery of the copper and regeneration of the pickling solution. This is to produce oxide-free, metallically bright surfaces, the prerequisite for the use of these materials in many industries, e.g. in refrigeration, in plant and mechanical engineering is.

Characteristic of the known technical solutions

Due to their special properties (electrical conductivity, thermal conductivity, chemical resistance), copper and copper alloys find a wide range of applications in industry. To improve surface finish and durability, special surface treatments are required

 Common methods of surface treatment are:

- Mechanical processes, such as polishing with Al ₂ O ₃ suspensions or pastes, blasting with glass microspheres or application of ultrasound in sulfuric acid baths.

- Use of cleaning and degreasing solutions such as organic solvents or alkaline cleaners, such. As sodium hydroxide, carbonates, phosphates, silicates or surfactants.

- Non-oxidizing mordants such as sulfuric acid, potassium cyanide, salts of hydroxy or amino carboxylic acids, eg. Gluconates, tartrates, citrates, EDTA.

- Oxidizing pickling such as sulfuric acid / nitric acid (yellow spirit), chromic acid, peroxo compounds (hydrogen peroxide, Caro's acid, peroxodisulfates) in admixture with sulfuric acid, ferric chloride / hydrochloric acid, iron sulfate / sulfuric acid or copper-ll-chloride / hydrochloric acid.

- Anodic pickling in the presence of sodium hydroxide solution, phosphoric acid (also with butyl alcohol additive), nitric acid / methanol (or glycerol) or sulfamic acid (Benninghoff, H .: Galvanotechnik61 [1970], pp. 1009-1018 and Benninghoff, H .: Finish Digest 3 [1974], pp. 291-303).

All of these methods have disadvantages. Nitric acid and nitrites, which require additional wastewater treatment, form during nitric acid / sulfuric acid pickling.

Although stained with chromic acid surfaces are clean and bright metallic, the separation of chromate from the wastewater is known to be very expensive.

Similar problems occur when using peroxodisulfate - sulfuric acid mixtures. The chemical treatment of wastewater is particularly associated with the use of ammonium peroxodisulfate due to formation of stable copper tetramine complexes with difficulties.

Chemical and electrochemical processes for the complete and partial regeneration of peroxodisulfate pickling solutions have heretofore been proposed exclusively for etching baths for the production of printed circuits. Since metallic bright surfaces are treated in this case, in contrast to the pickling process treated here, etching solutions are used which contain no or only small amounts of sulfuric acid. It is always assumed that a Peroxodisulfatlösung in the case of ammonium peroxodisulfate in the etching process according to the equation

Cu + (NH ₄ J ₂ S ₂ O ₈ -) CuSO ₄ + (NH ₄ J ₂ SO ₄

depleted in ammonium peroxodisulfate and enriched with copper sulfate and ammonium sulfate. An incomplete regeneration of such exhausted etching solutions is possible by crystallization and separation of CuSO _4. (NH ₄ ) ₂ SO ₄ .6H ₂ O and subsequent enrichment of the mother liquor with solid ammonium peroxodisulfate (GB-P 1104497). s OS 4S2.1 "? 4b"

For complete electrochemical regeneration, it has been proposed (GB-P 1141407) to add the double salt CuSO ₄ (NH ₄ I ₂ SO ₄ .6H ₂ O dissolved in water, brought to water and crystallized by cooling) to a divided recovery cell, while the remaining mother liquor, enriched with NH ₄ HSO _4, is fed to the peroxodisulfate in the anode chamber. the exiting anolyte is the regenerated pickling solution while the catholyte after deposition of the copper is evaporated and the NH obtained ₄ HSO ₄ is supplied again during the next cycle of the anolyte As a result of the various interlinked cycles, this process is very expensive in terms of apparatus and energy, and the efficiencies are only given as 30-40% To overcome these disadvantages, it has already been proposed to regenerate the spent etching solution in divided electrolysis cells with cation-exchange membranes s to perform separation systems while working with a circulating, stationary catholyte of ammonium bisulfate solution (GB-P. 1191034). The case of the anode space supplied exhausted etching solution is enriched with consumption of Ammoniumsulf at and sulfuric acid with peroxodisulfate, while Cu ²⁺ ions migrate through the cation exchange membrane into the cathode space and deposited at the cathode. However, this very simple process apparatus has the distinct disadvantage that in addition to the Cu ²⁺ ions and H ⁺ and NH ₄ ⁺ ions migrate through the membrane in the cathode compartment, whereby only an insufficient reduction of the copper sulfate content is achieved in the anolyte. The depletion of the catholyte on H ⁺ ions due to hydrogen deposition at the cathode and enrichment with ammonium ions also decreases the acid content as the ammonium sulfate content increases. It is therefore necessary to continuously add sulfuric acid to the process and remove ammonium sulfate from the spent catholyte, which requires additional expense. It has also been proposed (US Pat. No. 3,843,504) to carry out the regeneration in a specially constructed, undivided cell using an etching solution which, in addition to sodium, also contains potassium peroxodisulfate.

By special flow and temperature control in the cell should be achieved that the sparingly soluble potassium peroxodisulfate precipitates and sediments towards the anode. As a result, the peroxodisulfate content in the cathode region is kept low and, as a result, the reduction loss is reduced. In view of the very complicated cell construction, u. a. With a rotatable cathode and the required fairly large distance anode-cathode, this process, both from the expenditure on equipment, as well as from the electrical energy consumption her seen no advantages over the other proposed methods.

Overall, it has to be estimated that the regeneration processes known for sulfuric acid etching solutions adhere to the following fundamental disadvantages:

- high electrical energy consumption of about 3-4kWh / kg formed peroxodisulfate, due to the low current yields and the high cell voltages,

- High effort by the required special cell designs and / or by the necessary combination of multiple circuits, partly with separation and recycling of solids.

However, the situation is different when strongly sulfuric acid solutions, as they are indispensable during pickling, to be regenerated, because on the one hand due to the high migration rate of hydrogen ions sufficient depletion of copper ions is achieved and on the other hand copper is not eliminated in a compact form. In the case of divided electrolysis cells, the removal of the deposited copper complicates matters.

Object of the invention

The aim of the invention is an environmentally friendly circulation process for pickling copper and copper compounds by means of peroxodisulfate-sulfuric acid solutions to produce oxide-free, bright metallic surfaces at high current efficiency.

Explanation of the essence of the invention

The invention has for its object to find a for the pickling and regeneration process equally favorable composition of the pickling solutions, the exhausted solutions are regenerated immediately at the site

and the copper removed during pickling is recovered, and high current yields can be achieved by the process.

According to the invention this is achieved in that for pickling 0.15 to 1.0 mol / l of sodium and / or ammonium peroxodisulfate and 2 to 4mol / l sulfuric acid containing solutions are brought at temperatures of 20 to 50 ° C in contact with the workpieces to be treated and the spent pickling solutions containing 1 to 0.5 mol / l copper sulfate and 0.1 to 0.65 mol / l residual persulfate are first subjected to cathodic treatment to deposit at least 60% of the copper and to reduce the persulfates to then enrich them by anodic treatment in a conventional manner with peroxodisulfate to initial concentration.

Surprisingly, it has been found that the current yields of the anodic formation of peroxodisulfate in the exhausted pickling solution after prior destruction of the remaining persulfate, ie still present peroxodisulfates and peroxymonosulfate formed due to acid hydrolysis, by cathodic treatment is substantially greater than in direct anodic treatment, that is, the persulfates responsible for the very low power yields. On the other hand, all previously proposed electrochemical recovery processes boiled down to carrying out the regeneration of the etching solutions while retaining the residual content of persulfate from the previous etching. For this reason, the exhausted etching solution was fed directly or after previous crystallization of CuSO ₄ (NH ₄ J ₂ SO _{4) to} the anode compartment of the recovery cell the stain is brought into contact with the regenerated solution in a suitable pickling tank with the workpieces to be treated.The exposure time and the pickling temperature within the specified range are determined in a known manner by the material itself, the nature and degree of contamination, the type and Component geometry, the desired etching effect and the surface quality Both peroxodisulfates of sodium and ammonium, as well as mixtures of both, can be used, especially mixtures with a molar ratio of 1: 0.5 to 1: 2 can be with the sen mixtures higher solubilities for the reaction products CuSO ₄ , (NH ₄ ) ₂ SO ₄ or Na ₂ SO ₄ obtained. This makes it possible to achieve higher degrees of utilization of the peroxodisulfate formed, without causing a disturbing crystal formation during the pickling process, which has a very favorable effect on the economy of the overall process. The lower limit of the peroxodisulfate content of 0.15 mol / l in the regenerated pickling solution to be observed in accordance with the invention is primarily determined by still achieving a sufficient pickling rate.

Further lowering of the persulfate content of the regenerated pickling solution leads to insufficient pickling results both with regard to the quality of the pickled surfaces and the low possible space-time yield. In contrast, exceeding the upper limit of 1.0 mol / l peroxodisulfate with overall good space-time yields due to the solubility of the sulfates formed also leads to unacceptably low levels of utilization. Particularly favorable bating results are obtained using equimolar sodium and ammonium persulfate solutions having a starting content of about 0.6 mol / l. In order to enable approximately the same removal rates for the workpieces to be machined despite the decreasing pickling rate as the persulfate consumption increases, either the exposure times can be extended or the pickling rate is maintained at the required level by simultaneous temperature increase. The latter procedure allows for higher space-time yields and the subsequent copper recovery process can proceed immediately in the favorable temperature range.

For the electrochemical regeneration process, it has also proved to be advantageous if the pickling solutions contain additional amounts of sodium and / or ammonium sulfate. At the end of the anodic enrichment with peroxodisulfate, sufficient sulphate ion concentrations should still be present to obtain high current yields. Expediently, a degree of conversion of 80%, based on the total sulphate mixture present, should not be exceeded in the peroxodisulfate formation.

The cathodic and subsequent anodic treatment to be carried out according to the invention for the regeneration of the used pickling solution can be carried out both in the cathode and anode compartments of a divided electrolytic cell and in two electrolysis cells to be passed in succession.

The coupling of an undivided copper recovery cell with a divided cell for peroxodisulfate electrolysis according to a further feature of the present invention has proved to be particularly advantageous. For this purpose, it is expedient to comply with the conditions known from copper electrolysis in the recovery cell for the smoothest possible, fine-grained cathodic deposition of copper. In particular, at current densities of 50 to 200 A / m ² and temperatures of 5O ⁰ C to work while bringing the bulk of the copper for deposition. The smooth copper deposition favoring additives known inhibitors such. As gelatin, glue, thiourea, urea, etc. can be added to the pickling solution to be regenerated. Subsequently, the stripping solution freed from the bulk of the copper and a large part of the persulfates is first fed to the cathode spaces of the persulfate line, in which the deposition of further small amounts of copper takes place and the reduction of persulfates is continued. In contrast to the copper recovery cell, cathodic work is carried out here in the diffusion limiting current region with simultaneous evolution of hydrogen, wherein current densities of 500 to 2000 A / m ^{2 are to be} maintained according to the invention.

According to the invention, this copper is removed from the cathode by periodic backwashing with depleted pickling solutions still containing residual persulfate. In this way, the cell is regenerated without having to open it and mechanically free from the copper. The depleted pickling solution used for backwashing is returned to the copper recovery cell at the following cycle. This makes it possible in a simple manner to recover this copper content in a pure form suitable for direct further processing.

The electrolyte freed after passage through the copper recovery cell and the cathode compartments of the cell for the peroxodisulfate electrolysis of at least 60% of the copper is then fed for anodic treatment of anode compartments of these cells, electrolysis is carried out at current densities of 4000 to 7,000 A / m ² and temperatures from 15-35 ° C. For this it is necessary to cool the cells.

The electrolyte can be added in the concentration range from 0.05 to 0.5 g / l, in the concentration range of 0.05 to 0.5 g / l, prior to entering the anode space known polarizers usual in peroxodisulfate electrolysis, whereby the current yields are favorably influenced. Advantageously, thiocyanate, chloride, urea, thiourea, cyanamide u.a. used singly or in admixture. It is particularly advantageous to use those polarizers which at the same time serve as inhibitors for copper deposition

act, ζ. As thiourea and urea. On the one hand, to be able to meet the favorable conditions for copper deposition in the recovery cell and, on the other hand, to minimize electrical energy consumption, the current capacity of the copper recovery cell can be reduced to 50 to 90% of the current capacity for persulfate electrolysis. This is advantageous because the current yield of the copper deposit is greater than that of persulfate formation and a portion of the copper deposit is laid in the Persulfatzelle. This makes it possible to optimally adapt both the anode and the cathode processes to the achievable different current yields. It is particularly advantageous for the process according to the invention to use peroxodisulfate electrolysis cells according to DD-P 99548 with which current yields of 70-80% at 4.2 V cell voltage can be achieved. When coupled with a technically conventional copper recovery cell with anodes of unleaded lead with about 70% of the current capacity of persulphates (cell voltage about 2.2 V), a specific electric energy consumption (electrolysis DC) of 41OkWh based on 11 to be regenerated pickling solution with 1 mol / l peroxodisulfate. In contrast, 813 kWh / l are required in the known method for the regeneration of etching solutions at a specified mean current efficiency of about 30% and a cell voltage of 6.5 V and a residual content of 0.3 mol / l persulfate from the previous etching solution. It is clear that in the procedure of the present invention, only approximately half of the electrical energy is required as in conventional methods, although according to the invention, the residual persulfate must first be destroyed.

The overall sequence of the pickling and regeneration process in the embodiment of two separate cells is to be summarized on the basis of the flowchart FIG.

The workpieces are brought into contact with the regenerated electrolyte at the selected exposure times and temperatures in the pickling tank 1. The exhausted pickling solution is discharged into the intermediate vessel 2 and the pickling tank 1 is refilled from the intermediate vessel 3. From the intermediate vessel 2, the exhausted pickling solution is first conveyed by means of metering pump 4 for electrochemical regeneration in the copper recovery cell 5. From there, the partially decuperated solution enters the cathode space K of the cell for the peroxodisulfate electrolysis 6, in order to transfer from there into the anode space. When entering the anode compartment potential-increasing additives are added from the storage vessel 7. After anodic regeneration, the regenerated pickling solution returns to the intermediate vessel 3. After several cycles, the exhausted pickling solution from the tundish 2 is fed by means of the metering pump 4 via the bypass line 8 directly to the cathode chambers of the peroxodisulfate electrolysis cell in order to dissolve the deposited there copper in the de-energized state. The solution then passes into the intermediate vessel 3, is fed from there via the connecting line 9 directly to the intermediate vessel 2 and the next regeneration cycle is ready to start. Lost solution losses are compensated periodically by adding Na ₂ SO ₄ , (NH ₄ ) ₂ SO ₄ , H ₂ SO ₄ and water over 10.

The pickling and regeneration process according to the features of the present invention is in no way limited only to workpieces of pure copper. In an analogous manner, those of copper alloys, eg. B. brass, treat. It should be noted, however, that less noble metals z. As zinc, do not precipitate cathodically under the conditions of copper electrolysis. There is an accumulation in the electrolyte, which does not adversely affect the quality of the treated workpieces. It is therefore quite possible to use the same pickling solution over several cycles. Thereafter, the entire amount or a abzukreisender after passing through the copper recovery cell portion of the exhausted, enriched with zinc sulfate pickling solution must be removed by known methods of zinc. For this purpose, for example, the remaining copper can be removed by cementation with zinc and the electrolyte can be supplied to a zinc electrolysis. The freed from the bulk of the zinc solution can be fed back to the process via the anode compartments of the cell for the peroxodisulfate electrolysis. The copper powder precipitated by cementation can also be supplied to the regeneration process after dissolution in the exhausted pickling solution and recovered in the form of electrolytic copper.

embodiments

example 1

A partially exhausted pickling solution, as obtained from a peroxodisulfate content of 0.6 mol / l during the pickling process after 50% utilization, was prepared in the following composition:

sulfuric acid 3.0 mol / l Natriu mperoxodisu Ifat 0.15mol / l ammonium 0.15 mol / l sodium sulphate 0.35 mol / l ammonium sulfate 0.35 mol / l copper sulphate 0.30 mol / l

The newly used each solution was heated at 30.40 and 50 ⁰ C for several hours and hourly determines the levels of peroxodisulfate and Peroxomonosulfat by titration by known methods. The proportions of peroxomonosulfate in the total persulfate content (degree of conversion) are summarized in Table 1 as a function of time.

Table 1

Temperature conversion rates as a function of time (h)

⁰ C 0.5 1 2 3

30 0.06 0.12 0.19 0.25 0.34 0.47 40 0.14 0.25 0.40 0.53 0.63 0.83 50 0.31 0.49 0.77 0.87 0.91 -

It is clear that at 50 ⁰ C is already present approximately half of the persulfate for a -hour as peroxymonosulfate. At 40 ° C

This is the case after about 3 hours, at 30 ⁰ C after about 7 hours. It follows that even at low pickling temperatures after 24 hours of service life of the bath, most of the Peroxodisulfates has converted to Peroxomonosulfat.

Example 2

In a given time for Peroxodisulfatelektrolyse with platinum anodes and copper cathodes 250 ml of exhausted pickling solutions were anodized (2 hours, 4.8 A, 6000 A / m ² , 25 ⁰ C). 0.2 g / l of ammonium thiocyanate and 0.1 g / l of hydrochloric acid were added as polarizers at the beginning of the electrolysis. The catholyte used was 3 molar sulfuric acid. The anolyte solutions had the following compositions:

ABC

sulfuric acid minor 3.0 3.0 3.0 Sulfates (Na ⁺ ; NH ₄ ⁺ ) minor 1.0 0.8 1.0 Persulfates (Na ⁺ ; NH ₄ ⁺ ) minor - 0.2 - copper sulphate minor 0.2 0.2 0.2 zinc sulfate minor - - 0.3

Solution A corresponds to a pickling solution freed from residual persulfates by cathodic treatment according to the invention, but which still has a residual content of 0.2 mol / l of copper. In comparison, solution B still contains 0.2 mol / l of unspent persulfate, of which 0.15 mol / l is present as peroxomonosulfate. Solution C corresponds to solution A, but additionally contains 0.3 mol / l zinc sulfate, as is the case with pickling of brass.

The following results were obtained:

Persulfate content after minor 0.61 0.41 0.55 electrolysis Increase in persulfate minor 0.61 0.21 0.55 current yield % 85.1 29.3 76.8

It follows that compared to the comparative solution B in the procedure according to the invention larger Persulfatgehalte and significantly higher current efficiencies are obtained.

In the case of solution B, the peroxomonosulphuric acid present has a strong reduction in yield. It is also clear that not completely deposited copper (0.2 mol / l = about 40% of the initial amount) has no negative influence on the current efficiency. Even with the additional presence of zinc sulfate still sufficiently high current yields are obtained.

Example 3

Pickling solutions of varying degrees of exhaustion, as produced using a 0.1 mol / l peroxodisulfate, 0.25 mol / l excess sulfate and 3 mol / l sulfuric acid-containing starting solution, were prepared. Both peroxodisulfates or sulfates of sodium or ammonium, as well as equimolar mixtures of both were used. After standing at room temperature (23 ° C ± 1 ° C) for 48 hours, it was checked whether soil bodies had formed. The results obtained are shown in Table 2.

Table 2

Utilization of electrolyte composition in mol / l

(NH ₄ J ₂ S ₂ O ₈ Na ₂ S ₂ O ₈ (NH ₄ ) ₂ SO ₄

Na ₂ SO ₄

CuSO ₄

H ₂ SO ₄

Crystallization phenomena

0.40 0.40 0.40 0.60 0.30 0.30 0.60 0.65 0.325 0.325 0.65 0.40 0.40 0.40 3.0 3.0 3.0 medium little bit 0.35 0.35 0.35 0.65 0.325 0.325 0.65 0.6 0.3 0.3 0.6 0.35 0.35 0.35 3.0 3.0 3.0 little no very little 0.30 0.30 0.30 0.70 0.35 0.35 0.70 0.55 0.275 0.275 0.55 0.30 0.30 0.30 о о о со со со very little no very little

It is clear that higher efficiencies of the peroxodisulfates can be achieved with equimorphic mixtures without over saturation.

Example 4

There were pickling solutions of varying degrees of exhaustion, as obtained using different peroxodisulfate starting concentrations, each with 25% excess of sulfates and a content of 3 mol / l sulfuric acid,

manufactured.

In all cases, an equimolar mixture of ammonium and sodium peroxodisulfates or sulfate was used. The efficiencies of the persulfate were determined, exceeding 48 hours at 25 ⁰ C just a beginning crystallization was detected. The thus determined limit concentrations or the utilization rates at room temperatures

are summarized in Table 3.

Table 3

Ausgangskonz.

at peroxodisulfate mol / l

Cu ²⁺ mol / l utilization -6- 211 129 0.35 maximum Limit concentration for crystallization 0.36 0.35 usable S ₂ O ₈ ² "mol / l 0.38 0.40 0.35 0.65 0.40 0,475 0.40 0.54 0.44 0.57 0,475 0.42 0.5 0.73 0.57 0.30 0.5 1.0 0.73 0.16 0.5 1.0 0.70 0 1.0 0.63 0 0.50 0

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3

It can be seen that the maximum utilization rate given by the solubility increases greatly with decreasing persuidate starting concentration. At an initial concentration S 0.5 mol / l, no more crystal formation occurs, but then the usable utilization rate is limited by the achievable etching rate. The usable degree of utilization relating to a minimum limit concentration of 0.15 mol / l of peroxodisulfate reaches a maximum at the peroxodisulfate concentration of 0.6 mol / l preferred according to the invention.

Example 5

After each degreasing, the hot and cold rinsing, a tube sample of copper with dimensions of 12 χ 1 χ 125 (surface 8.63 × 10 ^-3 m ² ), each 10min at 25 ⁰ C both freshly regenerated with 250ml, as well brought into contact with 250ml of differently used pickling solutions. All electrolyte concentrations refer to a starting solution containing 0.6 mol / l peroxodisulfate, 0.15 mol / l excess sulfate (both in equimolar mixture of NH ₄ and Na salts) and 3 mol / l sulfuric acid. After pickling has been carried out, the increase in the copper content of the solution and from this the removal rate in mol / l Cu was determined as a measure of the pickling rate. The values summarized in Table 4 were obtained.

Table 4

Composition of the pickling solution mol / l sulfate CuSO ₄ H ₂ SO ₄ Utilization of the Cu mol / l Abtra persulfate persulfate transfer rate to cumol / 0.15 0.0 0.3 m ² 0.6 0.25 0.1 3.0 0,000 0.0167 0.484 0.5 0.35 0.2 3.0 0.167 0.0129 0.374 0.4 0.45 0.3 3.0 0.333 0.0116 0,336 0.3 0.55 0.4 3.0 0,500 0.0099 0.287 0.2 0.65 0.45 3.0 0,667 0.0065 0,189 0.15 0,750 0.0038 0,110

When using the pickling solution with 0.15 mol / l of persulfate, as expected, incipient crystal formation was observed. All other solutions remained clear.

Example 6

To determine the temperature dependence of the pickling rate, pickling at 50% was carried out at different temperatures under the same conditions of Example 5 using a pickling solution which still contained 0.3 mol / l of peroxodisulfate and was used to 50%. The results are summarized in Table 5.

Table S

middle Cu excavation pickling temperature minor rate of Cu X mol / m ² 21.0 0.0078 0.226 27.8 0.0097 0.281 32.5 0.0121 0.351 38.8 0.0153 0.444 45.0 .0191 0.554

The evaluation showed that by increasing the temperature from 20 to 50 ⁰ C to about a 3-fold increased pickling rate is achieved. Since, on the other hand, according to the results of Example 5, the pickling rate drops to about one third with a utilization rate increasing to 80%, this rate drop can be approximately compensated for by a corresponding increase in temperature.

Example 7

The pickling and the electrochemical regeneration of the pickling solution were carried out in a technical plant, analogously to the flow chart shown in FIG. The copper recovery cell used was a technically common construction with copper cathodes and lead anodes in monopolar circuit. There were used 4 flowed through in succession by the electrolyte of individual cells with 7 pairs of electrodes and an electrode area of 5.6 m ^J per cell. The cell used for the peroxodisulfate electrolysis was a filter press electrolyzer type EZ II according to DO-P 99548 with 6 bipolar cells with Pt-Ta strip electrodes and cathodes made of impregnated graphite.

First, the cathode chambers, then the anode chambers, were successively passed through by the electrolyte. The current capacity of the copper recovery cell was 4,400A at 2400A, and the 6X 600A persulfate cell at 3600A. The cathodic current density at the recovery cell was 107 A / m ² and that of the peroxodisulfate cell was 1200 A / m ² . The anodic current density at the platinum electrodes was 5400 A / m ² .

A pickling solution with a starting concentration of 0.6 mol / l and a residual copper content of 0.03 mol / l was used and up to a residual content of 0.2 mol / l of persulfate and 0.43 mol / l of CuSO ₄ 45 ° C used for pickling. The exhausted pickling solution was conveyed through the cells at a metering rate of 89 l / h. Thus, the initial concentration of about 0.6 mol / l of peroxodisulfate and about 0.43 mol / l of CuSO _{4 was} reached in the exiting from the peroxodisulfate anolyte. This results in an average current yield of peroxodisulfate formation of 79.5%. At the same time, 76% of the copper in the form of electrolytic copper was deposited in the recovery cell and 17% in the persulfate cell, for a total of 93% of the copper present.

Since the cell voltage of the copper recovery cell was 2.1V, that of the persulfate cell was 4.2V, the electric power consumption per hour was 20.14kWh. Based on the anodically newly formed peroxodisulfate of 0.4 mol / l, this results in a specific electric energy consumption of 2.48 kWh / kg.

The regeneration of the cathodes of the Persulfatzelle was carried out after several cycles by backwashing with exhausted electrolyte solution.

Claims (11)

Invention claim: 1. Circulation method for pickling copper and copper alloys with peroxodisulfate and sulfuric acid-containing aqueous solutions and the simultaneous recovery of the copper by cathodic deposition and the peroxodisulfate by anodic formation, characterized in that 0.15 to 1.0 mol / l of sodium and / or Ammoniumperoxodisulfat and 2 to 4 mol / l sulfuric acid containing solutions at temperatures of 20 to 5O ⁰ C are brought into contact with the workpieces to be treated and the exhausted pickling solutions containing 0.1 to 0.5 mol / l copper sulfate and a residual content of 0, Contain 1 to 0.65 mol / l of persulfates, cathodically treated until the deposition of at least 60% of the copper and then anodized peroxodisulfate is produced to initial concentration. 2. The method according to item 1, characterized in that the regenerated pickling solutions sodium and ammonium peroxydisulfate in a molar ratio of 1: 0.5 to 1: 2. 3. The method according to points 1 and 2, characterized in that preferably pickling solutions are used with a starting content of peroxodisulfate of about 0.6 mol / l. 4. The method according to points 1 to 3, characterized in that the pickling solutions additionally contain sodium and / or ammonium sulfate. 5. The method according to points 1 to 4, characterized in that the pickling process is started at room temperature and extends the pickling time with increasing degree of exhaustion and / or the temperature of the pickling solution is increased. 6. The method according to the items 1 to 5, characterized in that the cathodic treatment takes place in undivided copper recovery cells and / or in the cathode compartments divided cells for Peroxodisulfateiektrolyse. 7. The method according to the items 1 to 6, characterized in that the main amount of copper to be cathodically regenerated in a copper recovery cell at cathodic current densities of 50 to 200 A / m ² , the rest in the cell for Peroxodisulfateiektrolyse at cathodic current densities of 500 to 2000 A / m ^{2 is} deposited. 8. The method according to items 1 to 7, characterized in that the copper deposited at the cathodes of the cells for Peroxodisulfateiektrolyse periodically detached by rinsing with exhausted pickling solutions and the copper recovery cell is supplied. 9. The method according to points 1 to 8, characterized in that the anodic treatment in the anode compartments divided cells for Peroxodisulfateiektrolyse at current densities of 4000 to 7000 A / m ² and temperatures of 15 to 35 ⁰ C. 10. The method according to points 1 to 9, characterized in that the pickling solution to be regenerated before the anodic treatment 0.05 to 0.5 g / l suitable polarizers, for. As thiocyanate, chloride, urea, thiourea, cyanamide u.a. be added individually or in a mixture. 11. The method according to items 1 to 10, characterized in that the current capacity of the copper recovery cell is reduced to 50 to 90% of the current capacity of the cell for Peroxodisulfateiektrolyse.