Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
  • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms

Definitions

• the present invention relates to an electrolytic cell for the electrolytic treatment of process solutions and waste water.
• Preferred applications are cathodic reductions and anodic oxidations of inorganic and organic compounds as well as the cathodic deposition of metals with low residual contents.
• the new electrolytic cell has a large specific electrode surface, which is optimally flowed on to achieve good mass transfer. It is therefore particularly suitable for the effective implementation of such cathodic and / or anodic electrochemical processes, which are controlled in terms of mass transfer, and for the high specific
• Electrode surfaces and good mass transfer conditions are important prerequisites for high electricity yields with low specific electrical energy consumption.
• EP 0 436 1 46 A1 discloses a process for the electrochemical regeneration of chromosulphuric acid which is carried out in an electrolysis cell which is formed from two trough-shaped metal half-shells with an ion exchange membrane arranged in between.
• EP 0 573 743 A2 describes a process for the electrolytic detoxification or regeneration of an aqueous solution containing cyanide, and a device for carrying out this process.
• the electrolytic cell used for this purpose according to Example 1 has electrodes arranged in parallel in a plate-like manner with spacing, the anode made of coated titanium acting on both sides and the terminally arranged cathodes made of expanded metal mesh made of copper-plated titanium.
• An electrode arrangement for gas-forming electrolytic processes in membrane cells can be found in WO94 / 20649. This consists of lamellar expanded metal elements arranged one above the other, the upper edges of which extend to the l Facilitating the gas discharge are angled backwards and bear against the ion exchange membrane at the front.
• an unfavorable potential distribution in three-dimensional electrodes is usually responsible for the fact that the available electrode surface can only be partially used electrochemically. Often there is already such a drop in current density in a thin surface layer facing the counterelectrode that the more distant surface areas can no longer participate in the electrolysis process.
• WO 00/341 84 describes an electrolysis cell with a so-called "open configuration", in which the electrodes can be made from several layers of expanded metal that are in contact with one another. The contacting eliminates any influence on the current density distribution between the individual layers By far the greatest current input in the electrolytes takes place via the expanded metal layer closest to the counterelectrode and drops sharply to the neighboring layers.
• DE 36 40 020 has divided Electrolysis cells with an anode and a plurality of planar, liquid-permeable and electrically insulated cathodes are proposed, the increasing ohmic resistances with increasing distance from the anode being compensated by higher applied cell voltages so that the current is evenly distributed over the individual cathodes.
• the same operating principle is proposed in DE 40 07 297, but with a cathode and a plurality of liquid-permeable anode plates with separate power supply.
• the cathodes or anodes which are designed as liquid-permeable multiple electrodes, flow through them perpendicular to their longitudinal extent.
• the electrolysis cells are also quite complex in terms of equipment.
• the individual or grouped electrodes preferably consisting of metal wire nets, are to be arranged electrically insulated from one another and provided with separate power connections.
• the present invention relates to an electrolytic cell comprising flat anodes and cathodes which are separated from one another by means of separators and which are arranged in a cell trough or in a plurality of electrode frames which are clamped to one another and are electrically connected in a monopolar or bipolar manner, characterized in that the cathodes and / or anodes are in the form of multilayers Expanded metal electrodes are made which consist of at least two expanded metal layers which are in contact with one another via internal resistance paths and through which the electrolyte solutions flow in the longitudinal direction.
• 4 to 1 2 expanded metal layers become a multilayer expanded metal electrode via internal resistance paths with one another and with one Electrode base plate contacted.
• Intermediate layers made of a porous electrode material can also be arranged between at least two expanded metal layers.
• Electrode gaps occur. The electrical resistance and thus the cell voltage increase only minimally.
• porous intermediate layers preferably consisting of metal foams, metal wire knits or carbon fiber nonwovens, already have a relatively large inner surface with a thickness of preferably 1 to 2 mm and a desired high gap volume of at least 70%.
• the surface factor (OF) as the ratio of the geometric
• the surface area of the respective expanded metal or intermediate layers is between 1, 5 and 4 for the expanded metal layers and between 10 and 20 for the porous intermediate layers.
• the surface factor achievable by the multi-layer expanded metal electrode should preferably be in the range between 5 and 100.
• the surface factors in the upper area can practically only be achieved by using porous intermediate layers.
• porous intermediate layers The influence of the porous intermediate layers will be explained using the example of a multilayer expanded metal electrode consisting of 9 expanded metal layers with a surface factor of 2 each. For the 9 layers there is a
• the internal resistance sections to be provided according to the invention for compensation or buffering of the current density decrease can be formed by the contact resistances between the individual expanded metal or porous intermediate layers.
• the individual layers are only by pressure means, for. B. made of plastic webs or plastic screws against each other and pressed against the electrode base plate.
• the measured contact resistances build up internal resistance paths which can lead to voltage differences of 0.1 to 0.5 V.
• the contact resistance is usually lower between two expanded metal layers.
• the contact resistance can be reduced by reducing the contact area by partially covering with non-conductive materials, e.g. B. thin fabric inserts, can be increased according to the requirements.
• Resistance paths are formed in that individual or more expanded metal and / or intermediate layers are separated from one another by spacers made of electrically non-conductive material.
• the current is transported from layer to layer via contact surfaces which are preferably arranged laterally or above and below.
• Internal resistance sections are built up in that the electrolysis current has to pass through the individual expanded metal layers in their longitudinal or transverse direction.
• the electrolysis current thus flows through the multilayer expanded metal electrode in a meandering manner, the current intensity decreasing from layer to layer in accordance with the effective surface and the real current density.
• the relevant expanded metal layers can be welded to one another at the contact points in order to achieve good and long-term contact.
• a current density gradient present within the multilayer expanded metal cathode can even be used in a targeted manner to achieve high current and conversion yields.
• several expanded metal segments with different current densities separated by porous intermediate layers are equipped within an electrolysis cell by separate feed and discharge lines for the electrolyte solutions.
• the hydrodynamic switching is carried out in such a way that the segment with the higher current density closest to the counter electrode flows through first and the segment with the lower current density further away from the counter electrode subsequently flows through the electrolyte solution.
• the main reaction in which the starting materials are still present in a higher concentration, is carried out in the expanded metal segment with the higher current density.
• the reaction in the expanded metal segment with the low current density is brought to an end.
• This has the same effect as with a cascade of several electrolysis cells with different current density, in which the main reaction takes place in the electrolysis cell with a high current density, while the after-reaction is carried out in the electrolysis cell with a lower current density.
• the only major advantage in carrying out the invention is that no second electrolysis cell is required for the after-reaction.
• the achievable space-time yield is therefore also much higher.
• the hydrodynamic coupling of the two electrolyte streams can take place by that the electrolyte solution can be transferred from the segment of high current density through the porous intermediate layer into the segment of low current density by an adjustable pressure difference. As a result, the flow through the porous intermediate layer is simultaneously further improved.
• the expanded metal layers to be used according to the invention preferably consist of stainless steel, nickel, copper or valve metals coated by means of noble metals, noble metal oxides or doped diamond.
• the expanded metals made of coated valve metals are mainly used for anodic oxidation processes. So on expanded metals made of niobium, coated on both sides with doped diamond, very high anode potentials can be achieved, even at the relatively low current densities that are aimed for, such as, for. B. needed for an effective oxidative degradation of pollutants.
• Metal wire mesh can be used. Expanded metals are preferred, however, because they generally have a more favorable opening ratio for the flow in the longitudinal direction and also have greater mechanical stability.
• Bipolar cells with multi-layer expanded metal cathodes should be used with particular preference when large current capacities are required in the kA range.
• An advantageous embodiment of such a bipolar cell construction is shown schematically in FIG. 1.
• 1 a shows three bipolar cell units with a section through the electrochemically active areas.
• 1 b shows a cross section through these three bipolar single cells, also in the electrochemically active range.
• the anode plates 1 and the cathode base plates 2 are arranged on both sides of the bipolar electrode base body 3 made of plastic.
• the cooling channels 5 and the inlets and outlets for anolyte 6, 7, catholyte 8, 9 and the cooling medium 1 0, 1 1 are integrated in the electrode base body.
• the cooling channel is located on the anode side, whereby the anode plate lying there is cooled directly. In principle, cooling on the cathode side and cooling on both sides are also possible.
• the multilayer expanded metal cathodes are connected to it and connected to it in an electrically conductive manner.
• Four expanded metal layers 1 2 and one porous intermediate layer with a large inner surface 1 3 are shown as examples.
• the multilayer expanded metal cathodes are laterally delimited by a cathode frame 4 made of plastic, which is also used for lateral pressure of the expanded metal layers to the cathode base plates.
• Arranged on the anode plates are the anode sealing frames 1 4, which limit and seal the anode spaces to the outside.
• the ion exchange membranes 15, which separate the anode spaces from the cathode spaces, are clamped between the anode sealing frames and the cathode frames of the adjacent bipolar units.
• the anode spacers 1 6 and cathode spacers 1 7 made of plastic serve to center and hold the ion exchange membranes.
• contact is made between the cathode base plate and the anode plate of a bipolar unit by means of contact rails 18 arranged on both sides outside the electrode base body.
• FIGS. 2 to 5 show several variants for the bipolar electrode plates, again in section through the electrochemically active areas.
• Figures 2 and 3 schematically show the sectional views of two bipolar units with multilayer expanded metal cathodes for a catholyte circuit.
• the variant shown in FIG. 2 basically corresponds to the cell variant shown in FIG. 1 except for the arrangement of the inlet and outlet connections and an additional cooling channel on the cathode side.
• the same bipolar units are shown in FIGS. 4 and 5, but with separate expanded metal cathode segments for two separate catholyte circuits.
• the multilayer expanded metal cathode consists of two segments each with two expanded metal layers and an intermediate layer made of a porous electrode material with a large inner surface.
• the intermediate layer simultaneously forms the separating layer between the expanded metal segment near the anode with a high current density and the segment away from the electrode with a lower current density.
• the cathode base plate like the anode plate, is solid, only broken through with the passage openings for the supply and discharge of the electrolyte solutions. This means that both electrodes can also use the rear electrodes for the arrangement of cooling channels for internal heat dissipation.
• the cathode base plate provided with the current supply is already equipped with an expanded metal layer, the cathode rear space is filled with the catholyte here. Therefore, only the anode rear space can be used for the arrangement of a cooling channel.
• FIG. 6 shows the process diagram of an electrolysis plant with a
• Electrolysis cell analogous to FIG. 4 with two expanded metal cathode segments, which have a separate flow. Both cathode segments, separated by a porous intermediate layer with low permeability, are integrated in separate catholyte circuits with integrated gas separation.
• the 1st Circuit B consisting of a circulation pump and a circulation vessel with gas separator
• the reaction is completed with a lower current density.
• Both circulatory systems are hydrodynamically coupled in such a way that the metering into the higher current density circuit (dosing station D) and the electrolyte is removed from the lower current density circuit E.
• the passage through the porous intermediate layer is controlled by the pressure difference between the two circuits.
• the anolyte is conveyed through the anode compartments by means of the metering station G.
• the gas exiting at J is separated off in the gas separator H and the anolyte exits at I.
• a monopolar electrical circuit of the multilayer expanded metal electrodes is preferably considered for the electrolytic cell according to the invention, the expanded metal layers or the porous intermediate layers being arranged in a planar or cylindrical manner.
• a continuous expanded metal layer is spirally wound up and the beginning of the spiral is connected in an electrically conductive manner to the outer or inner tube of the cylindrical cell provided with the power supply.
• An internal resistance path can be constructed in a simple manner in that a layer of insulating spacer material is also spirally wound up together with the expanded metal layer, as a result of which the individual expanded metal layers are electrically insulated from one another. This forces the electrolysis current to take the longer path along the spiral, so that voltage differences form between the different expanded metal layers.
• the electrodes and separation systems can be arranged either in a cell trough or in a plurality of electrode frames which are clamped together.
• FIG. 7 shows an example of a preferred embodiment of such a monopolar electrolytic cell with planar electrodes which are arranged in electrode frames which are clamped together. It shows the cross-section through the electrochemically active area of a monopolar electrolytic cell, each with two multilayer expanded metal cathodes connected in parallel and two plate anodes separated by cation exchange membranes, which are arranged in three plastic frames clamped together (the clamping frame is not in the picture) ) Shown.
• the two anode plates 1 and the two cathode base plates 2 are provided with power supplies and electrically connected in parallel.
• the anode plates are made of titanium and are provided with an active layer in the electrochemically active area, e.g. B. with Ir-Ti mixed oxide.
• the multilayer expanded metal cathodes which are each arranged in a cathode frame 4, are contacted with the stainless steel cathode base plates.
• the multi-layer expanded metal cathodes each consist of 1 0 expanded metal layers 1 2, which are combined individually or in groups and separated from one another by plastic cathode spacers 1 7.
• the various expanded metal layers separated by spacers are laterally contacted with one another in such a way that the electrolysis current flows through the multilayer expanded metal cathode in a meandering manner.
• the resistance of the interconnected expanded metal layers towards the anode increases four times (the number of interconnected expanded metal layers decreases from four to one).
• the cathode frames contain the inlets and outlets for the catholyte 8, 9.
• the expanded metal and spacer layers are flowed through from the bottom upwards in the longitudinal direction by the catholyte.
• the centrally arranged electrode base body 3 contains the inlets and outlets for the anolyte 6, 7.
• the anolyte enters through the overflow openings through the sealing frames and the anode sheets into the anode compartments at the bottom and out again together with the anode gases formed. These anode spaces are formed by the anode sealing frame 1 4.
• Anode spacers 1 6 made of plastic are inserted, on which the ion exchange membranes 1 5 are positioned.
• Such monopolar cell units can have several within one
• the electrolytic cell according to the invention is particularly suitable for the following application processes.
• the electrolysis cell according to the invention is preferably used with a multilayer expanded metal cathode for the complete or partial cathodic reduction of organic or inorganic compounds.
• electrolytic and potentiostatic electrolysis can be carried out.
• Organic compounds that are functional groups can be reduced, CC double and triple bonds, aromatic CC linkages, carbonyl groups, heterocarbonyl groups, aromatic CN linkages, nitro and nitroso groups, C-halogen single bonds, SS bonds, NN single and Contain multiple bonds and other heteroatom-hero atom bonds.
• Such reactions can take place both in protic solvents, such as. B. water, alcohols, amines, carboxylic acids, as well as in a mixture with aprotic polar solvents, for. B.
• the electrolysis according to the invention is carried out in the presence of an auxiliary electrolyte, as described, for example, in EP 0808 920 B1.
• an auxiliary electrolyte as described, for example, in EP 0808 920 B1.
• the electrolytic cells according to the invention with multilayer expanded metal cathodes are particularly suitable for the complete or partial reduction of natural and synthetic dyes such as, for example, carotenoids, quinone dyes, for example Carminic acid and 1,8-dihydroxyanthraquinone, madder dyes, indigo dyes, e.g. B. indigo, indigotine and 6,6-dibromoindigo, vat dyes and sulfur dyes and to reduce the nitro functionalities.
• the new cells are also suitable for decoloring dyeing process solutions and waste water.
• indigoids and vat dyes can be carried out both as indirect electrolysis, as described in the documents DE 1 95 1 3 839 A1 and DE 100 1 0 060 A1, and without the addition of a mediator.
• sulfur dyes such.
• B. C.l. Sulfur Black 1 for the corresponding Leuko-Sulfur Black 1 connection can be both completely and partially reduced, as described in EP 1 01 2 21 0 A1.
• the cathodic reduction is preferably carried out in an alkaline environment (pH 9 to 14).
• the new electrolytic cells can also be used for the complete or partial anodic oxidation of organic and / or inorganic compounds. They are particularly suitable for the oxidative degradation of pollutants in process solutions and waste water.
• Multi-layer expanded metal anodes consisting of niobium expanded metals coated on both sides with doped diamond, can be used particularly advantageously.
• oxidizing agents such as e.g. Peroxodisulfate, hypochloride or radical anions, which complete the desired breakdown of pollutants in a post-reaction.
• platinum-coated expanded metals made of titanium the high anode potentials required for the decomposition process can often be achieved in such oxidation reactions.
• Metal deposition can be used particularly advantageously from very dilute solutions. Electrodes made of the metal to be recovered can be used, which are replaced after appropriate metal loading. In this case the use of a trough cell with attached, easily replaceable multilayer expanded metal cathodes is an advantage. To small amounts of metals such. B. to remove from waste water, can also be worked with inert cathode materials, from which the deposited metals are periodically dissolved with a suitable solvent. Porous intermediate layers with a large inner surface are particularly suitable for this purpose, with which very low residual metal contents can be achieved.
• Example 1 Reduction of indigo
• the reduction of indigo to leuco indigo is carried out.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is converted into a two-circuit electrolysis Apparatus with pump circuit introduced.
• the flow rate in the cathode compartment should be 0.1 m / s.
• the catholyte was produced by pouring 100 g of a Cl Sulfur Black 1 press cake from DyStar Textilmaschine GmbH into a mixture consisting of 2000 g water and 1 2 g sodium hydroxide solution 50% and adding another 4350 g press cake in the course of the electrolysis.
• the electrolysis is carried out in accordance with EP 1 01 2 21 0 A1.
• a current of 1 0 A (current density: 9.5 * 1 0 "3 A / cm 2 ) and a cell voltage between 7.0 -4.3 V are applied.
• the reduction was made after introducing a charge of 238.3 Ah 4350 ml of a leucosulfur black-1 solution with a concentration of reductant equivalent of 438 Ah based on 1 kg of dry dye were obtained.
• a reduction of nitrobenzene to azobenzene is carried out in the cell according to the invention with a platinized titanium electrode and a cathode consisting of three expanded nickel metal grids with a total area of 1,050 cm 2 (visible area: 1,00 cm 2 ).
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow rate should be 0.1 m / s.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by pouring 48.5 g of indigo over 100% into the cathode circuit in a mixture consisting of 5000 g of water, 1 20 g of EC mediator VE PEDF 1 20 from DyStar Textilmaschine GmbH and 80 g of sodium hydroxide solution.
• For the electrolysis 2.2 to 2.0V cell voltage and 2A current are applied. The electrolysis was carried out at a temperature between 55-60 ° C
• Example 5 Reduction of Cl Vat Yellow 46
• a platinized titanium electrode and a sandwich cathode consisting of two stainless steel expanded metal layers and an intervening wire mesh intermediate layer with a total electrode area of 21 30 cm 2
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by mixing 48.6 g of commercial Cl Vat Yellow 46 over 100% in a mixture consisting of 5000 g of water, 1 71 g of EC mediator VE PEDF 1 20 from DyStar Textilmaschine GmbH and 80 g of 50% sodium hydroxide solution fills the cathode circuit.
• For the electrolysis 2.2 to 2.0V cell voltage and 2A current are applied. The electrolysis was carried out at a temperature between 55-60 ° C with a current density of 9.4 * 10 4 A / cm 2 . The reduction was ended after 4.61 F / mol with a current efficiency of 87%.
• Cl Vat Green 1 is reduced to its leuco connection.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by adding 50 g of commercially available Cl Vat Green over 100% in a mixture consisting of 5000 g of water, 1 71 g of EC mediator VE PEDF 1 20 from DyStar Textilmaschine GmbH and 80 g of sodium hydroxide 50% in the cathode circuit , For the electrolysis, 1.6 to 2.0 V cell voltage and 0.5 A current are applied. The electrolysis was carried out at a temperature between 55-60 ° C with a current density of 2.35 * 10 4 A / cm 2 . The reduction was ended after 2.08 F / mol with quantitative current efficiency.
• Example 7 Reduction of Cl Vat Red 10 in the cell according to the invention with a platinized titanium electrode and a sandwich cathode consisting of two stainless steel expanded metal layers and an intermediate wire mesh intermediate layer with a total electrode area
• the reduction of Cl Vat Red 10 to its Leuko connection is carried out from 2130 cm 2 .
• the anode and cathode compartments are through a cation exchange membrane
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s.
• indigo to leukoindigo is carried out in the cell according to the invention with a platinized titanium electrode and a cathode consisting of six expanded stainless steel meshes with a total electrode area of 1 1 20 cm 2 .
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s.
• the reduction of indigo to leuco indigo is carried out.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow velocity within the cell should be 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by pouring 48.5 g of indigo over 100% into a mixture consisting of 5000 g of water and 80 g of sodium hydroxide 50% into the cathode circuit. 1.8 V cell voltage and 1 A current are applied for the electrolysis. The electrolysis was carried out at a temperature between 55-60 ° C Current density of 0.442 * 1 0 ⁇ 4 A / cm 2 performed. The reduction was terminated after 2.5F / mol with a current efficiency of 80%.
• Example 1 1 Metal Recovery A monopolar split laboratory test cell constructed according to the invention contained a multilayer expanded metal cathode consisting of 4 stainless steel expanded metal layers with a base area of 70 cm 2 each and a stainless steel base cathode plate.
• the expanded metals had a mesh length of 16 mm and a mesh width of 8 mm with an expanded metal thickness of 1.5 mm.
• the electrolysis current was set to 7 A, corresponding to a current density of 0.1 A / cm 2 (based on the surface projection). The actual average current density was 1 1 mA / cm 2 .
• Electrolysis was carried out up to a final copper concentration of approx. 1 g / l.
• Example 1 2 Decolorization of a Dye Mixture
• the divided laboratory test cell according to Example 11 was equipped with a multilayer expanded metal anode consisting of a diamond-coated anode base plate made of niobium, four niobium expanded metal layers with a base area of 1 00 x 70, which were coated on both sides with diamond mm (surface projection 70 cm 2 ).
• the cathode was made of stainless steel, the cation exchange membrane of Nafion ® 450.
• a dye solution to be decolorized was used as the anolyte, which contained 1 g / l of a dye mixture and to which small amounts of sodium sulfate (about 8 g / l) were added to improve the conductivity.
• the dye mixture consisted of 1 part black (Cl Reactive Black 5), 1 part blue (Cl Reactive Blue 21), 1 part red (Cl Reactive Red 128) and 0.1 part yellow (Cl Reactive Orange 96).
• Electrolysis was carried out with a current of 7 A, a current density of 0.1 A / cm 2 , based on the cross-sectional area of the multi-layer expanded metal anode. The surface enlargement factor was approx.
• Example 13 Anodic Pollutant Degradation
• the divided laboratory test cell from Example 11 was equipped with a multilayer expanded metal anode, consisting of four titanium expanded metal electrodes, platinum-coated on both sides, measuring 100 x 70 mm, contacted with a platinum-coated titanium anode base plate.
• the cathode was made of stainless steel.
• the anolyte consisted of a 1 liter of a solution pumped in a circuit via the anode compartment, which contained 20 g / l sulfuric acid and 0.1 g / l dichlorophenol as an anodically degradable pollutant. A 20 g / l sulfuric acid was used as the catholyte.
• Electrolysis was carried out with a current of 35 A, corresponding to a current density based on the surface projection of 0.5 A / cm 2 .
• the magnification factor of the anode surface was 8.3, so that an average current density of 60 mA / cm 2 resulted.
• the cell voltage was 5.6 V.
• electrolysis was carried out in the divided laboratory test cell according to the invention with a platinized titanium electrode and a multilayer expanded metal cathode made of stainless steel. Anode and cathode compartments were separated by a cation exchange membrane (Nafion ® 424). Two different cathode designs were used.
• the surface enlargement factor was 21.3, so that an effective total cathode area of 21 30 cm 2 resulted.
• 6 expanded metal electrodes, each with a base area of 100 cm 2 were used, which were in contact with one another and with the cathode base plate.
• the surface enlargement factor was 1 1, 2, resulting in a total surface area of 1 1 20 cm 2 .
• a solution of 230 g 50% sodium hydroxide solution in 3000 g water was used as the anolyte.
• the catholyte was prepared by introducing 48.5 g of indigo (calculated as 100%) in a mixture consisting of 5000 g of water and 80 g of 50% sodium hydroxide solution and different amounts of the mediator VE PEDF 1 20 ® from DyStar.
• the divided cell was placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow rate of the catholyte inside the cell was adjusted to 0.1 m / s.
• the electrolysis was carried out at a temperature between 55 and 60 ° C.
• the reduction was ended after a current input of 2F / mol and the current efficiency of the indigo reduction was determined.
• the deviating test data and the results are summarized in the table below.
• Example 1 5 Reduction of Cl Sulfur Black 1
• a multilayer expanded metal cathode was used, consisting of a cathode baseplate made of nickel and three nickel expanded metal layers with an effective total area of 1,050 cm 2 (Surface enlargement factor 1 0.5).
• Nafion ® 424 was used again as the cation exchange membrane.
• Sulfur black 1 was reduced to leuco sulfur black 1.
• the cell was again placed in a two-circuit electrolysis apparatus with a pump circuit. The flow rate in the cathode chamber was 0.1 m / s.
• Flow velocity in the cathode compartment was set back to 0.1 m / s. 1000 ml of 70% ethanol with 25 g of sodium acetate and 100 g of nitrobenzene were used as the catholyte. 2000 ml of a concentrated soda solution were used as the anolyte. Electrolysis was based on the Journal of Electrochemistry in 1898; 5; Pp. 108-1 13 with a current of 10 A (total current density 9.5 mA / cm 2 ). The reduction was terminated after a charge of 87.5 Ah. The resulting yellow alcoholic solution was removed from the cathode circuit, the excess ethanol was removed in vacuo, the residue was taken up in water and extracted several times with ethyl acetate. The combined organic phases were dried over sodium sulfate and the excess solvent was distilled off. 63 g of azobenzene (85% of theory) were obtained with a quantitative current efficiency.
• Example 17 Reduction of Cl Vat Yellow 46
• a platinized titanium electrode and a sandwich cathode consisting of two stainless steel expanded metal layers and an intermediate wire mesh intermediate layer with a total electrode area of 2130 cm 2
• the reduction of Cl Vat Yellow was 46 to his Leuko connection.
• the anode and cathode compartments are separated by a cation exchange membrane (Nafion ® 424).
• the divided cell is placed in a two-circuit electrolysis apparatus with a pump circuit.
• the flow rate within the cell was set at 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by mixing 48.6 g of Cl Vat Yellow 46, calculated as 100% (from the production of dried press cake) in a mixture consisting of 5000 g of water, 171 g of EC mediator VE PEDF 120 ® from DyStar and 80 g sodium hydroxide solution 50% entered and filled into the cathode circuit.
• the electrolysis current was set at 2 A, a cell voltage between 2.0 and 2.2 V being established.
• the electrolysis was carried out at a temperature between 55-60 ° C. with a current density of 0.94 mA / cm 2 and ended after a current input of 4.61 F / mol with a current efficiency of 87%.
• the flow velocity within the cell was 0.1 m / s. 3000 g of water with 230 g of 50% sodium hydroxide solution were used as the anolyte.
• the catholyte was prepared by dissolving 50 g of CI Vat Green, calculated as 100% (from the production incurred dried press cake) in a mixture consisting of 5000 g water, 171 g of EC mediator VE PEDF 120 ® from DyStar and 80 g of sodium hydroxide solution 50% filled in the cathode circuit.
• For electrolysis 1.6 to 2.0 V cell voltage and 0.5 A current are applied. The electrolysis was carried out at a temperature between 55-60 ° C with a current density of 0.23 mA / cm 2 . The reduction was ended after 2.08 F / mol with quantitative current efficiency.
• Example 2 In the same cell and circulation apparatus as in Example 1 8, the reduction of C.I. Vat Blue 6 performed on its Leuko connection.
• the flow rate within the cell was set at 0.1 m / s.
• the laboratory test cell of the invention with the platinized Ttananode and Nafion ® 424 cation exchange membrane was treated with a 1 2 expanded metal sheets made of stainless steel like 1 00 cm 2 existing multilayer -Streckmetallkathode equipped.
• the surface enlargement factor was 25, the total effective area was 2500 cm 2 .
• the cell was integrated into the two-circuit circulation apparatus.
• the catholyte consisted of 3 l of a solution with the following composition: 1 g / l Cl Vat Blue 6 1, 62 g / l FeCl 2 1 3.56 triethanolamine 1 2.48 NaOH A 0.1 N NaOH was used as the anolyte. Electrolysis was carried out at a temperature of 28 ° C.
• Example 21 In the electrolytic cell of Example 21 with 1 2 expanded metal layers made of stainless steel, a dye solution of 0.5 g / l Cl Reactive Red 4 was treated cathodically. 2 l of catholyte solution with a NaOH content of 0.6 mol / l were used. A sodium hydroxide solution with a content of 5 g / l served as the anolyte. Electrolysis was carried out with a current of 2 A, corresponding to an average current density of 0.8 mA / cm 2 . The cell voltage was 5.9 V, at an electrolysis temperature of approx. 30 ° C. After a specific current input of 4 Ah / I, the solution was 81% decolorized (based on weighted color code, see Example 1 2).
• FIGS. 1 to 7 1 anode plate
• Coolant inlet 1 Coolant outlet

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