Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/006—Wet processes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
  • C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
  • C02F1/4678—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction of metals
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/36—Regeneration of waste pickling liquors
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46123—Movable electrodes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4616—Power supply
  • C02F2201/46175—Electrical pulses
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to a method and a device for the effective cathodic deposition and recovery of metals from process solutions and waste water, e.g. from exhausted pickling solutions, preferably also in combination with anodic oxidation processes.
• the maximum possible cathodic current density remains limited with a low final concentration of the metal to be removed in order to achieve a coating which is still firmly adhering.
• the current densities used in practice on the rotating cathodes are generally between 2 and a maximum of 5 A / dm 2 , depending on the type of metal to be deposited, the composition of the catholyte solution and the desired final concentration.
• the shape of the pulses used for the pulsating direct current ranges from a sinusoidal shape to a rectangular shape. Steep edges of the pulse with short-term power interruptions have a particularly favorable effect. A brief pulse reversal can also be very advantageous for special applications. A more uniform layer thickness distribution is achieved, since metals that deposit more and more at corners and edges (e.g. in the form of dendrites) also preferentially dissolve again due to the subsequent anodic impulse.
• the pulsating direct current can achieve a better leveling of the metal deposition.
• the application of this principle also promises better adhesion of the deposited metal coating in the border area of low residual concentrations for metal recovery. This would make it possible to achieve a higher average current density with the same achievable metal depletion or to obtain a larger depletion with the same current density.
• the additional expenditure in terms of apparatus for realizing a pulsating direct current is, however, not too great for the economy of metal recovery neglecting factor.
• the acquisition costs can be 3 to ⁇ times that of conventional rectifiers.
• the present invention therefore aims to make the illustrated advantageous effects of a pulsating direct current usable for metal recovery from process solutions and waste water, without at the same time the disadvantages shown with regard to the increased expenditure for generating a pulsating direct current and the negative effects on the To have to accept anodes or in combination processes on the course of the anode reactions.
• this objective is achieved by a method according to the invention.
• the electrolysis is carried out by means of a non-pulsed direct current in an electrolysis cell equipped with cathodes and anodes, whereby the cathodes and anodes can be divided by separators and the pulsating cathodic currents are generated by dividing the anodes into strips from 2 to 100 mm wide and arranged individually or in groups parallel or concentrically to the cathode surface, while the undivided cathode surface is guided at a speed of 1 to 10 m / s past the anode strips in a direction perpendicular to their longitudinal extent and the distance between the side walls of two adjacent individual ones Anode strips or the groups of anode strips is at least 1.5 times the vertical distance between the center of the individual anode strips or the group of anode strips and the cathode.
• each point of the moving cathode surface successively traverses areas of high and low current density with a current density maximum at the smallest distance from the next anode strip and a current density minimum at the greatest distance from the next anode strip.
• the anode strips can either be individually distributed uniformly over the entire anode surface or can be combined in groups with uniformly smaller distances within the groups and larger distances between the groups. It was found that the minimum distance between the individual anode strips or the groups of anode strips must be 1, ⁇ times the vertical distance between the anode and cathode in order to achieve a sufficiently large pulsation effect.
• the alternative or additional arrangement of internals for potential shielding between individual or grouped anode strips as so-called current screens has proven to be particularly advantageous.
• anode strips or the groups of anode strips are preferably arranged in holders with edges projecting laterally in the direction of the moving cathode, hereinafter called pockets.
• FIG. 1 Various geometrical arrangements and the current density pulses that form from them on the cathode are shown schematically in FIG.
• the illustration applies to the case of stationary anode strips aligned parallel to the cathode surface, past which the cathode moves linearly. It should be taken into account that, as is known, the current density distribution not only depends on the geometry of the electrode arrangement, but also on the electrolyte composition (scatterability) and on the
• Electrode potential is dependent. Therefore, this representation should and can only serve to illustrate the principle of the invention. Shown are: a) Geometry and current density-time function for the arrangement of individual anode strips, the distance of which is 1.5 times the distance from the anode -
• the method according to the invention can be carried out in various constructive variants of undivided or divided electrolysis cells.
• the use of an electrolysis cell (device) with rotating cylinder cathodes is particularly advantageous.
• the device according to claims 6 to 16 consists of one or more rotating cylinder cathodes arranged in a housing. Concentric around this are vertical, 2 to 100 mm wide anode strips arranged individually or in groups in anode pockets.
• the distance between the individual anode pockets is at least 1.5 times the vertical distance between the anode strips and the cathode.
• the side walls of the anode pockets also serve as current apertures and baffles with the following effects: As current diaphragms they provide potential shielding for the formation of steep flanks of the cathodic current pulses which form on the cathode surface,
• the anode pockets on the side facing the cathode are open.
• the anode pockets are equipped with separators and separate inlets and outlets for the anolyte solutions. They therefore form individual anode spaces through which the anolyte flows and which are liquid-tight and gas-tight with respect to the catholyte.
• this division into individual anode pockets has a number of advantages.
• the constructive design of the anode pockets results in far greater possible variations than is the case with the coherent anode compartment that has been customary up to now. This means that extremely short dwell times can be achieved with high anodic current densities, such as e.g. are required for the anodic regeneration of peroxodisulfate pickling solutions.
• the division of the entire anode compartment into individual anode pockets is also very easy to service. Individual anode pockets can be easily replaced in the event of defects on the anodes or the separators without having to remove the other anode pockets.
• Another advantage of the division into individual anode pockets is that several anode pockets can be hydrodynamically connected in series. This results in the flow behavior of a reactor cascade, which in some applications contributes to achieving a higher current efficiency in the anode reaction. For some applications it has proven to be advantageous to run through larger sections on the rotating cathode where the current density approaches zero. This can be achieved in a simple manner by an uneven distribution of the anode pockets around the cylinder cathode, with individual distances between the anode pockets being a multiple of the distances between the other anode pockets. For example, individual anode pockets can be omitted in an otherwise symmetrical division.
• a frequency-controlled drive is particularly advantageous for larger and heavier cylinder cathodes. It is not only possible that To start the cell smoothly with a slowly increasing speed, the working speed can also be varied and optimally adapted to the respective electrolysis process.
• the cylinder cathode is preferably made of stainless steel.
• a slightly conical design has an advantageous effect on the detachment of the deposited metal.
• the anodes or the anode pockets are arranged with a slope which is adapted to the cone of the cylinder cathode.
• the anode strips preferably consist of valve metals coated with precious metals, precious metal mixed oxides or with doped diamond, titanium, niobium, tantalum or zirconium. Ion exchange membranes or microporous plastic films serve as separators.
• FIG. 2 shows a preferred embodiment of the proposed one
• Electrolysis cell with rotating cylinder cathode shown in the form of two differently equipped half cells.
• the left half cell a corresponds to an undivided cell variant
• the right half cell b corresponds to a cell variant divided by separators.
• the electrolyte container 1 is located on a support tube 2 with ventilation openings.
• a protective inner space, in which the drive 4 is located, is formed by an inner protective tube which is connected in a liquid-tight manner to the bottom of the electrolyte container.
• the drive shaft is guided in a liquid-tight and gas-tight manner through the interior cover 6 and is connected to the cylinder cathode 5 with a fastening element 7.
• the strip anodes are arranged and held in the anode pockets 11 which are fastened to the wall and open to the cathode side.
• the current leads 10 to the anodes are guided laterally through the container wall.
• the strip anodes 9 are arranged in the anode pockets 8, which are closed on all sides.
• the side of the anode pockets facing the cathode contains the separators 13. While the inlet and outlet for the catholyte lead directly through the wall of the electrolyte container, the anolyte is distributed to the individual anolyte inlets 16 via an outer ring line 17 and via the anolyte outlets 18 and one Ring line 19 discharged again. Between the wall of the
• the cooler 12 is arranged in the electrolyte container and the anode pockets.
• the current supply 20 to the cylinder cathode takes place by means of the sliding contacts 21.
• the electrolyte container is closed by the cover 22.
• the cylinder cathode rotates at such a speed that a circumferential speed of between 2 and 10 m / s results.
• the achievable apparent pulsation frequency on the cathode surface depends on this peripheral speed and the number of anode pockets arranged around the rotating cylinder cathode. With an even distribution, the apparent pulsation frequencies given in Table I result depending on the number of anode pockets.
• Copper particles can be completely or partially redissolved there by the oxidizing agent that is still present. This is practically the same effect that is achieved in pulse-plating with pulse reversal by briefly reversing the polarity of the electrolysis current. There is a partial redissolution due to brief anodic stress.
• the electrolysis current is "temporarily” switched off, metal particles are partially redissolved by the remaining oxidizing agent.
• pulse-plating with pulse reversal there is no loss of current efficiency due to the redissolution of already deposited metal.
• Strip anodes have also been used in some cases in the previously known electrolytic cells with rotating cathodes for metal recovery.
• vertical rods or sheet segments have been used in such anode materials that are not suitable for conventional use as expanded metal, e.g. B. coal or lead.
• this was not done with the aim of generating a pulsating cathodic current in the sense of the present invention. For this reason, no targeted action was taken in these cells by choosing an appropriate one
• the new method and the device for metal recovery by means of pulsating cathodic currents according to the present invention not only make it possible to recover metals more effectively than with the known methods and devices described at the beginning. There are also new ones
• peroxosulfates When metals are recovered from etching or pickling solutions, the remaining oxidizing agents, predominantly peroxomonosulfate and peroxodisulfates (hereinafter referred to as peroxosulfates) and hydrogen peroxide are additionally reduced cathodically. This can prevent the destruction of these oxidizing agents by adding suitable reducing agents during wastewater treatment. At the same time, metals that cannot or cannot be completely deposited in metallic form under the set electrolysis conditions are converted from a higher valence level to a lower one. This is e.g. B. of importance in the presence of toxic chromium VI compounds, which are reduced cathodically to chromium III compounds and are then easily precipitated as hydroxides.
• Oxygen is predominantly developed from chloride-free solutions in metal recovery. Combination processes in which the anode reaction is used to generate or regenerate oxidizing agents and pickling agents or to completely or partially oxidatively decompose inorganic and / or organic pollutants have proven to be particularly advantageous. Electrolysis can then be carried out in undivided cells if the anodically oxidized compounds cannot be cathodically reduced again, as is the case, for example, with oxidative ones Degradation of cyanides in metal cyanide solutions is the case. In contrast, in the presence of reversible redox systems, the use of a divided electrolytic cell is usually essential.
• Anodically degradable pollutants in the broadest sense are considered to be inorganic or organic compounds that either have a toxic effect themselves and therefore must not get into the wastewater, or bind the heavy metals in a complex manner, which not only complicates their almost complete recovery, but also in wastewater treatment prevent compliance with specified limit values or additional treatment steps, e.g. B. require a precipitation with organosulfur compounds.
• complexing agents play a particularly important role in the surface technology of metals, the preferred field of application of the present invention.
• inorganic and organic complexing agents such as e.g. B. cyanides, thiocyanates, thiourea, dicarboxylic acids, EDTA, sulfur compounds such as. B. sulfides, sulfur dioxide, thiosulfates and dithionites, nitrogen compounds such. B. nitrites and amines u. a. be oxidatively degraded.
• Hydrogen peroxide as an oxidizing agent in pickling solutions can not only be reduced cathodically, but can also be degraded anodically by oxidation to oxygen.
• peroxodisulfate formation has included special platinum anodes with a smooth, shiny surface and high anodic current densities of at least 40 A / dm 2 and also the highest possible anodic
• Metal recovery cells with plate electrodes require a low current density in the range of 1 to 2 A / dm 2 .
• the anodic current density would have to be 20 to 40 times the cathodic current density in order on the one hand to achieve a sufficiently high current efficiency in the formation of peroxodisulfate and on the other hand to enable almost complete metal recovery in a compact form.
• the electrolysis is carried out in a divided persulfate regeneration electrolysis cell at high anodic and also cathodic current densities.
• the copper is deposited in powder form on the cathode in the area of hydrogen evolution. It requires complex rinsing and release processes in order to discharge the copper powder as completely as possible and to prevent clogging of the cathode compartments with spongy copper coatings on the cathode.
• the dissolved metals are first completely or partially separated cathodically from the exhausted peroxodisulfate pickling solutions and at the same time the unconverted peroxosulfates are reduced to sulfates, and then the used peroxodisulfates are anodically completely or partially at the anodes coated with platinum or doped diamond at current densities in the range of 20 up to 100 A / dm 2 and current concentrations of 50 to 500 A / l.
• the maximum current density to be observed for compact metal deposition is determined both by the pulsation effect and by the partial redissolution of dendritically deposited metal components between the pulses unreacted peroxosulfates present further approximated the anodically required high current density.
• the subdivision of the anode compartment into individual anode pockets according to the invention also makes it easy to maintain the required high anodic current concentrations.
• anodes that are coated with doped diamond it is possible to minimize the current densities required for optimum current yields in the formation of peroxodisulfate and thus to achieve a further approximation to the cathodically required current density.
• the pickling solutions regenerated in this way are preferably metered continuously into the pickling bath in such an amount that a pickling rate that is as constant as possible can be maintained.
• the peroxodisulfate formation is not limited solely to the sodium peroxodisulfate that is usually used as a mordant.
• Peroxodisulfates of the metals magnesium, zinc, nickel and even iron can also be reoxidized alone or in a mixture with sodium peroxodisulfate and used for pickling.
• the required metal sulfates are either added to the pickling solution or they form when alloys are pickled due to alloying components that accumulate in the pickling bath, e.g. Zinc sulfate when pickling brass.
• the cathodically pretreated pickling solutions preferably have a sulfate concentration (as the sum of the metal sulfate and sulfuric acid concentration) of 2 to 5 mol / l in order to achieve sufficiently high current yields for the formation of peroxodisulfate.
• potential-increasing substances e.g. Thiocyanates can be added.
• ion exchange membranes As separators, it is also possible to increase the efficiency of the overall process, in addition to the anodic and cathodic reactions shown, to use the mass transfer through the membranes in order to optimize the process.
• a depletion of metal cations from the anolyte or, when using anion exchange membranes, a corresponding depletion of anions from the catholyte can be used expediently.
• the complex-bound hydrofluoric acid be released into the divalent form by reducing the trivalent iron by cathodic treatment of pickling solutions with the stable FeF 3 complex
• the fluoride ions can also be depleted from the catholyte and converted into the anolyte by using anion exchange membranes become. This results in the possibility of releasing the complex-bound fluoride ions from a partial stream of the exhausted fluoride-containing iron-Ill pickling solution to be circulated via the cathode compartments and of feeding it back directly to the main stream of the pickling solution to be anodically reoxidized.
• Another possible application for different electrolyte solutions in the cathode and anode compartments is to block the transfer of undesirable ion types into the other electrode compartment. So can A metal recovery from a chloride catholyte solution can be achieved without undesired chlorine development at the anode if cation exchange membranes are used as separators and the anode compartment is charged with a chloride-free "barrier electrolyte".
• sulfuric acid or a sulfate eg sodium sulfate
• a sulfate eg sodium sulfate
• metal ions e.g. B. sodium ions is buffered (z. B. in the cathodic deposition of nickel from chloride nickel electrolytes).
• Electrode material stainless steel cathode, titanium anode, platinum-plated
• Cathode area 2500 cm 2 (effective height of the cathode cylinder 400 mm, average diameter 200 mm)
• Anode area 480 cm 2 (6 anode pockets with 2 anode strips each
• Anode-cathode distance 40 mm on average
• Anode pockets approx. 65 mm wide, side walls approx. 15 mm high.
• About ⁇ O I electrolyte solution were pumped in a circuit from the storage tank in a circuit over the electrolysis cell. Electrolysis was carried out at 100 A. Various largely chloride-free metal salt solutions were used in sulfate electrolytes. The metals were deposited in a compact form. The most important data are summarized in Table II.
• Example 1 50 l of an exhausted sulfuric acid-hydrogen peroxide pickling solution for copper were electrolyzed. Initial amount 58 I with 30, g / Cu (about 0.48 mol / I), 4.4 g / l H 2 0 2 (about 0.13 mol / I) and 115 g / l free sulfuric acid. Electrolysis was carried out at 100 A for 17 h (current input approx. 29.3 Ah / I, cell voltage 3.9 V). The electrolyzed solution still contained 0.3 g / l copper and 0.1 g / l H 2 0 2 . The deposited copper was in compact, firmly adhering form despite the low residual concentration.
• the apparent current yield based on the sum of the two cathode reactions of copper deposition and the reduction of hydrogen peroxide was 116.5%. In fact, part of the hydrogen peroxide is oxidized at the anodes, which explains the high apparent current efficiency. In relation to copper recovery, the electricity yield was still relatively high at 85.8%.
• Electrolysis cell from Example 3 1, 5 l of a cyanide waste solution from the gold processing was electrolyzed with the aim of largely oxidatively decomposing the cyanide and recovering the remaining gold.
• the starting solution contained 21 g / l free cyanide and approx. 0.8 g gold.
• Electrolysis was carried out for 15 hours at 16 A at a cell voltage of 3.5 V. After that, the largely detoxified waste solution contained only a residual content of ⁇ mg / l gold and 1 ⁇ mg / l cyanide.
• NaPS sodium peroxodisulfate
• the current efficiency of the copper deposition is then approximately 100%. Only when the copper content has dropped to about 0.01 mol / l will the copper content decrease become significantly less than it corresponds to the theory. It is only in this area that hydrogen is noticeably co-separated. After 6, ⁇ h of electrolysis, the copper concentration has dropped to approx. 0.06 g / l. The cumulative current yield for the sum of both cathode reactions is then still 83.8%.
• a technical electrolysis cell for ⁇ OO A according to example ⁇ was used, but in a split version according to FIG. 2 b. That was what they were Anode pockets sealed against the catholyte by National 450 cation exchange membranes. All 12 anode pockets were flowed through in parallel by the anolyte. The total anolyte volume (content of all 12 anode pockets) was only 1. ⁇ I, so that a high anodic current concentration of 333 A / l was achieved. An exhausted peroxodisulfate copper pickling solution was electrolyzed, which was circulated through the cathode compartment of the electrolytic cell (batch operation). The starting solution had the following composition: sulfuric acid 160 g / l sodium sulfate 290 g / l
• a pickling solution that had already been cathodically decoupled in the previous cycle was conveyed through the anode compartments at an average dosing rate of 11.3 l / h (flow-through mode). It had the following composition:
• the sum of the sulfate concentration consisting of sulfuric acid and sodium sulfate was found to be 4.4 mol / l.
• the amount of sodium peroxodisulfate was 6,740 g, corresponding to a current yield of 71.4%. Copper was deposited 1,187 g. The cell voltage averaged 6.2 V. Based on the peroxodisulfate formation alone, this resulted in a specific electrolysis direct current consumption of 1.95 kWh / kg. With this procedure, the entire amount of peroxosulfate consumed in the pickling process was regenerated (complete regeneration).
• the entire available cathodic current capacity was used for copper recovery.
• the anodic current capacity is not sufficient to reoxidize the entire amount of persulfate used in the pickling process.
• the difference had to be compensated for by adding sodium peroxodisulfate (partial regeneration).
• the procedure for this was as follows using the electrolytic cell according to Example 6.
• the exhausted pickling solution with the same composition as in Example 8 was continuously metered into the cathode and subsequently also continuously passed through the anode compartments connected downstream.
• the metering rate was adjusted in such a way that the copper concentration in the cathode compartment did not drop below 1 g / l in order to avoid spongy copper deposition.
• An average of 15.8 l / h of the pickling solution was dosed (anolyte outlet).
• the regenerated pickling solution contained 101 g / l Na persulfate and a residual copper content of 1.1 g / l. 371 g of copper were deposited per hour and 1 ⁇ 96 g of sodium peroxodisulfate was regenerated (71.9% current yield). In fact, around 2 ⁇ 00 g / l Na peroxodisulfate was used in the pickling process (utilization rate based on the amount of copper recovered, approx. ⁇ %). The difference of 904 g / h was metered in in the form of a concentrate containing 400 g / l NaPS (approx. 2.3 l / h). At the same time, the drag-out losses of pickling solution from the pickling bath became approximately balanced.
• the used sulfate demetallization solution contained ⁇ 2.7 g / l copper sulfate (approx. 21 g / l Cu) 199 g / l nickel sulfate and 4 ⁇ g / l nickel peroxosulfates, calculated as NiS 2 Os (total 86 g / l nickel).
• the nickel does not deposit metallic in the strongly acidic catholyte and nickel is constantly being redissolved, a part of the decoupled catholyte solution must be removed periodically.
• the nickel can be recovered from it in an undivided electrolysis cell according to example 1.
• Diamond coating (12 anode pockets, each with two anode strips 600 x 13 mm).
• the composition of the starting solution and the test conditions were comparable to those in Example 6 (500 A, catholyte in the circuit, anode spaces in the flow).
• ⁇ l / h of the cathodically treated solution were metered in on average.
• the anodic current density was 27 A / dm 2
• the cell voltage was 6.0 V.
• a regenerate with a NaPS content of 98 g / l was obtained, corresponding to a current efficiency of 68.4% (specific electrical energy consumption approx 2.0 kWh / kg).
• An exhausted sulfuric acid-hydrogen peroxide pickling solution for copper contained 33 g / l copper, 115 g / l free sulfuric acid, 7.5 g / l excess hydrogen peroxide as well as organic stabilizers and complexing agents (1, ⁇ g / l COD).
• organic stabilizers and complexing agents (1, ⁇ g / l COD).
• a chemical nickel waste solution contained ⁇ , 9 g / l nickel, as well as large amounts of unmounted hypophoshite, phosphite and organic complexing agents.
• the total of the oxidizable substances was shown as a COD value (COD content approx. 62 g / l).
• 50 l of the solution were first treated anodically and then cathodically. Electrolysis was carried out anodically in the circuit over 24 h. The COD value was up to 2.1 g / l be reduced. The majority of the organic complexing agents were thus oxidatively broken down and the hypophosphite or phosphite was oxidized to the phosphate.
• the electricity yield was approx. 84%.
• the solution obtained was metered into a catholyte circuit in such an amount that the pH was kept in the range of pH 4 to ⁇ favorable for the nickel deposition.
• the residual nickel content was ⁇ 0.1 g / l.
• the divided electrolytic cell according to Example 6 was equipped with 12 new strip anodes 600 x 60 x 1, 5 mm made of titanium, coated with iridium-tantalum mixed oxide.
• the anode pockets were thus used in the entire available width, the anodic current density was thereby reduced to 11.6 A / dm 2 at a maximum current load of 500 A.
• the procedure for regenerating an iron-III-chloride etching solution for copper materials was as follows:
• the catholyte was circulated from a circulation vessel over the cathode compartment of the cell.
• another partial stream of the exhausted etching solution was metered directly into the anode compartments.
• concentration and quantity ratios were set or measured: 5.7 l / h pickling solution were metered into the catholyte circuit, 34.3 l / h pickling solution directly into the anode compartments, and 6.4 l / h overflow from the Catholyte circulation (approx. 0.7 l / h water transfer through the membrane). Approx. 40 l / h of regenerated etching solution emerged from the anode compartments.
• concentrations occurred in the stationary operating state: exhausted etching solution catholyte leak regenerated etching solution g / ⁇ mol / I g / l mol / I g / l mol / I
• Example 13 A spent chloride nickel bath (Watts bath) with a nickel content of 6 ⁇ g / l and a total chloride content of 37 g / l CI " was batch-operated via the cathode compartment of the electrolytic cell from Example 12 with Ir-Ta- Mixed oxide-coated anodes were pumped in a circuit. The pH was buffered to 4-5 by adding sodium hydroxide solution. A sulfuric acid sodium sulfate waste solution with approx. 200 g / l sodium sulfate, also conveyed in batch mode via the anode compartments, served as the anolyte. At the cathode, the nickel was depleted to a residual content of approximately 0.1 g / l.
• Example 14 A spent sulfuric acid-iron-III-sulfate pickling solution for copper materials was regenerated by means of the electrolytic cell equipped according to example 12. For this purpose, a partial flow of the exhausted pickling solution of 22 l / h was first fed via the cathode compartment and after cathodic copper deposition to the anode compartments of the cell. Another larger partial flow of the exhausted pickling solution of 158 l / h was the
• the procedure for recovering platinum from platinum-containing materials was as follows: 1000 l of an extraction solution containing 200 g / l sulfuric acid and approx. 30 g / l hydrochloric acid were passed through the Anode spaces of the electrolysis cell (equipment according to Example 12) and conveyed in a circuit with 100 kg of the starting material to be extracted.
• the current strength was set in such a way that the free chlorine content in solution did not exceed approx. 2 g / l (from the initial ⁇ OO A, the current strength was gradually reduced to 100 A).
• Platinum dissolved as hexachloroplatinate was set in such a way that the free chlorine content in solution did not exceed approx. 2 g / l (from the initial ⁇ OO A, the current strength was gradually reduced to 100 A).
• the platinum content was monitored and the electrolysis ended after about 1 ⁇ h after no further increase was detectable.
• the final concentration was 1.6 g / l platinum.
• the platinum-containing solution was used as the catholyte in the subsequent cycle and was circulated through the cathode space of the cell.
• the platinum predominantly separated out in a compact form.
• the platinum, which only powders at the end of the cycle, was first dissolved again when filling with the extraction solution still containing free chlorine in the subsequent cycle and then separated again (in compact form) after the electrolysis current was switched on. 1 ⁇ 30 g of platinum with a content of 96% were recovered.
• Example 16 To regenerate a stainless steel pickle based on iron III sulfate hydrofluoric acid, the electrolysis cell according to Example 12 was equipped with anion exchange membranes of the Neosepta ACS type. A used pickling solution had the following stationary composition (for free Acids metals are counted as sulfates, although in part as
• Nickel as Ni 2+ 0.28 mol / I (approx. 16 g / l)
• the electrolytic cell was charged with a total of 11.9 l / h of the pickling solution. Of these, 9 ⁇ l / h were fed directly to the anode compartments, and 2.4 l / h were metered into a stationary catholyte circuit.
• the free acids released by the cathodic reduction of the iron III ions or by the cathodic metal deposition were depleted via the anion exchange membranes and converted into the anolytes.
• a pH of 3-4 required for the deposition of an iron-nickel-chromium alloy was established in the catholyte circuit.
• the heavily depleted metal was also passed through the anode compartments.
• Approx. 271 g / h of a stainless steel alloy separated out approximately in the composition present in the pickling bath (approx. 70% electricity yield).
• the consumed and cathodically reduced iron was anodically reoxidized to the iron III sulfate.
• the regenerated pickling solution had the following composition: iron as Fe 3+ 1.80 mol / l (approx. 49 g / l)

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