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
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/21—Manganese oxides
• • 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
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
• • 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
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/056—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of textile or non-woven fabric
• • 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
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/061—Metal or alloy
  • C25B11/063—Valve metal, e.g. titanium
• • 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
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
  • C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F1/00—Etching metallic material by chemical means
  • C23F1/46—Regeneration of etching compositions

Definitions

• the present invention relates to a method for oxidizing manganese species in a treatment device, the method comprising the steps
• Metallizing non-metallic substrates such as plastic substrates has a long history in modern technology. Typical applications are found in automotive industry as well as for sanitary articles.
• etching a surface modification of the substrate's surface
• compositions comprising environmentally questionable chromium species, such as hexavalent chromium species (e.g. chromic acid). Although these compositions usually provide very strong and acceptable etching results, environmentally friendly alternatives are more and more demanded and to a certain extent already provided in the art. In many cases manganese-based etching compositions are utilized instead.
• environmentally questionable chromium species such as hexavalent chromium species (e.g. chromic acid).
• manganese-based etching compositions are either acidic or alkaline.
• acidic manganese-based etching compositions are inherently more susceptible to degradation, in particular permanganate-based etching compositions.
• etching compositions require a constant and comparatively high level of replenishment of active manganese species.
• etching compositions are continually recycled to maintain a comparatively constant level of active manganese species. This is typically either achieved by chemical oxidation or by applying an electrical current. Respective regeneration methods and devices are known in the art.
• CN 109628948 A refers to a regeneration device comprising a ceramic diaphragm for recycling a permanganate ion solution.
• CN 1498291 A refers to an electrolytic regeneration treatment device for regenerating an etching treatment solution.
• WO 2013/030098 A1 refers to a device for an at least partial regeneration of a treatment solution comprising permanganate, which is used for treatment and/or etching of plastic parts.
• WO 01/90442 A1 refers to a cathode for an electrochemical arrangement for regeneration of permanganate etching solutions and a device for electrolytically regenerating permanganate etching solutions.
• the efficiency of regeneration typically depends on the current invested into a respective treatment device and how this current is interacting with the respective manganese species.
• the method of the present invention allows a very effective oxidation (preferably regeneration) of manganese species because it particularly utilizes at least one anode with specifically a surface density of 6 m 2 /L or more, based on the total volume of said at least one anode.
• at least one anode provides an exceptionally large effective surface area in already at least one single anode.
• a large effective surface area per litre provides a correspondingly large area for contacting the manganese species having the first oxidation number.
• this manganese species is efficiently oxidized at said anode to provide a manganese species with said second oxidation number.
• a method of the present invention is preferred, wherein the one or more than one anode is a single anode and is at the same time the at least one anode having a surface density of 6 m 2 /L or more.
• a method of the present invention is preferred, wherein more than one anode is provided in step (B), wherein at least one thereof has a surface density of 6 m 2 /L or more, preferably all thereof have a surface density of 6 m 2 /L or more.
• the method of the present invention anodically oxidizes a manganese species having a first oxidation number to a manganese species having a second oxidation number, wherein the second oxidation number is higher than the first oxidation number.
• Preferred is a method of the present invention, wherein the first oxidation number is +4 or below.
• the first oxidation number comprises +4, +3, and/or +2.
• the manganese species having the first oxidation number comprises Mn 2+ ions and/or Mn 3+ ions.
• the manganese species having the first oxidation number comprises manganese particles (preferably oxides thereof), preferably colloidal manganese particles (preferably oxides thereof), most preferably colloidal MnO 2 particles. This preferably includes optional agglomerates thereof.
• the second oxidation number is above +4, preferably is +7 (preferably comprises +7).
• this does not necessarily exclude manganese species having an oxidation number of +5 or +6.
• the manganese species having the second oxidation number comprises permanganate ions.
• the method of the present invention is most preferably effective in treating such an acidic liquid.
• the liquid is a treatment composition for treating, preferably etching, non-metallic substrates in an etching compartment, preferably plastic substrates.
• the liquid was in contact with a plastic substrate.
• the manganese species having the first oxidation number were in contact with a non-metallic substrate, preferably a plastic substrate, prior to step (A).
• the liquid comprises an acid, preferably an inorganic acid, most preferably phosphoric acid.
• the method of the present invention is a recycling method for manganese species.
• recycling refers to a re-oxidation of (preferably already utilized) manganese species with subsequent re-utilization thereof.
• a method of the present invention is preferred, wherein the method is carried out continually or at least semi-continually.
• Continually preferably denotes that at least steps (A) and (C) of the method of the present invention are carried out continually, i.e. without interruptions.
• semi-continually preferably denotes that step (A) and/or step (C) is interrupted from time to time for at least a little while. Such an interruption might be necessary for maintenance or to stabilize a concentration of one of the species present during the method of the present invention.
• a continual utilization is preferred.
• etching a plastic substrate with e.g. permanganate chemically reduces permanganate to manganese species with lower oxidation numbers while the material of the plastic is at least partly oxidized.
• a method of the present invention is preferred, wherein the treatment device utilized in the method of the present invention is external relative to the etching compartment. This means that the treatment device is outside the etching compartment. This is typically preferred. However, in other cases a method of the present invention is preferred, wherein the treatment device utilized in the method of the present invention is at least partly integrated into the etching compartment. This preferably means that the treatment device is internal relative to the etching compartment.
• the non-metallic substrate preferably the plastic substrate
• the non-metallic substrate comprises acrylonitrile butadiene styrene (ABS), acrylonitrile butadiene styrene - polycarbonate (ABS-PC), polypropylene (PP), polyamide (PA), polyurethane (PU), polyepoxide (PE), polyacrylate, polyetherimide (PEI), a polyetherketone (PEK), mixtures thereof, and/or composites thereof; preferably acrylonitrile butadiene styrene (ABS), acrylonitrile butadiene styrene - polycarbonate (ABS-PC), polyamide (PA), polyurethane (PU), polyepoxides (PE), polyacrylate, mixtures thereof, and/or composites thereof.
• plastic substrates are often used in decorative applications such as automotive parts, in particular ABS and ABS-PC.
• the one or more than one anode and the at least one cathode preferably have a comparatively low distance to each other.
• a method of the present invention is preferred, wherein the one or more than one anode and the at least one cathode have a distance to each other ranging from 9 mm to 70 mm, preferably from 10 mm to 60 mm, more preferably from 11 mm to 50 mm, even more preferably from 12 mm to 30 mm, most preferably from 13 mm to 20 mm. This most preferably applies to the at least one anode having a surface density of 6 m 2 /L or more.
• the distance is defined as the shortest distance between the one or more than one anode and the closest (preferably corresponding) at least one cathode.
• the distance is preferably the shortest outer distance between the one or more than one anode and the closest (preferably corresponding) at least one cathode.
• the term "outer” preferably refers to the outermost of the one or more than one anode directly facing towards the outermost of the closest at least one cathode.
• the at least one cathode is (at least mainly) built around (in a sense of surrounding) the one or more than one anode, in particular around the at least one anode having the surface density of 6 m 2 /L or more.
• the at least one cathode at least mainly encircles or circulates the one or more than one anode, preferably the at least one anode having the surface density of 6 m 2 /L or more, wherein this wording does not limit the ensemble to a circular shape.
• this anode/cathode arrangement is not necessarily mandatory in the context of the present invention.
• a method of the present invention is preferred, wherein the one or more than one anode and the at least one cathode are separated from each other by a permeable barrier, preferably a permeable membrane.
• a permeable barrier preferably a permeable membrane.
• an anolyte and a catholyte is preferably formed.
• the anolyte comprises the manganese species having the first oxidation number.
• the anolyte is said liquid as described above.
• the catholyte preferably comprises an inorganic acid, more preferably sulfuric acid and/or phosphoric acid, most preferably (preferably only) phosphoric acid.
• the current applied in step (C) can flow such that at least a portion of the manganese species having the first oxidation number is anodically oxidized to the manganese species having said second oxidation number.
• the permeable barrier is basically not permeable for negatively charged or neutral manganese species.
• the permeable barrier is an ion-selective permeable barrier, preferably an ion-selective permeable membrane.
• the permeable barrier is a cation-selective permeable barrier, preferably a cation-selective permeable membrane.
• the permeable barrier is a cation-selective permeable barrier, preferably a cation-selective permeable membrane.
• the permeable barrier is not mineral.
• the permeable barrier is mineral, preferably comprises a ceramic.
• the permeable barrier is organic. More preferred is a method of the present invention, wherein the permeable barrier is organic and comprises fluorine (preferably is fluorinated), most preferably is organic and perfluorinated. Most preferably, the at least one permeable barrier is a Nafion-type-membrane, although the membrane is not particularly limited to this particular brand. Membranes, preferably said organic membranes, are very thin and therefore positively contribute to a comparatively short distance, and, thus, to a compact design. In contrast, a method of the present invention is also preferred, wherein the one or more than one anode and the at least one cathode are not separated from each other by a permeable membrane, preferably a permeable barrier.
• the at least one anode has a surface density of 6 m 2 /L or more.
• the surface density denotes a parameter defining the total effective surface area per geometric volume.
• a plate geometrically of 1 m 2 and having a thickness of 1 mm typically has a total effective surface are of 2.004 m 2 including front and rear side as well as the area of the cutting edges.
• the surface density of this plate is 2.004 m 2 /L, i.e. roughly 2 m 2 /L.
• surface factor total effective surface area per geometric area
• a surface density above 2 is obtained if e.g. a plate has holes and a mesh has openings, respectively, in a defined number and with defined dimensions.
• the surface factor of commercially available meshes today is typically not exceeding 2.5.
• the surface factor does not sufficiently define electrodes having a significant third dimension.
• the surface density in the context of the present invention is defined as m 2 per liter of the respective anode.
• the at least one anode having a surface density of 6 m 2 /L or more comprises, most preferably in the inside of said anode, a random structural pattern, a uniform structural pattern, or a regularly recurring structural pattern.
• a uniform structural pattern and/or a regularly recurring structural pattern most preferably in 3D-printed anodes, woven fabric anodes, permanently fixed stacked single-layer anodes (preferably permanently fixed by welding, gluing, and/or riveting), separatable stacked single-layer anodes (preferably separatable by unscrewing and/or unclamping), and packed bed anodes with a defined package.
• a random i.e.
• a chaotic and without long-range order, structural pattern is slightly less preferred but typical e.g. for so called packed bed anodes with loosely filled materials, knot anodes, foam anodes, and 3D-printed anodes with a random structural pattern.
• a uniform and regularly recurring structural pattern ensures a homogeneous penetration depth of the electrical field into the interior of said anode, which is assumed to be an advantage over a random structural pattern.
• a structural pattern comprises caverns and/or holes inside said anode, which are materially accessible from the outer surface and preferably cause the comparatively large total effective surface area.
• random structural patterns are easy to obtain and, as for packed bed anodes, comparatively low in price.
• preferred single-layer anodes comprise meshes and/or plates, preferably expanded metals (i.e. expanded laths).
• the at least one anode having a surface density of 6 m 2 /L or more comprises (preferably is) a single-segment anode or a separable multi-segment anode.
• single segment anode denotes an anode which consists of one piece and can be separated/dismantled only by destruction. In other words, such kind of anode is not designed for dismantling.
• Preferred single-segment anodes comprise 3D-printed anodes, woven fabric anodes, permanently fixed stacked single-layer anodes (preferably permanently fixed by welding, gluing, and/or riveting), knot anodes, packed bed anodes with a sintered, welded, and/or compressed anode material, and/or foam anodes.
• a separable multi-segment anode consists of at least two, preferably multiple, individual joint segments which are designed for non-destructive dismantling.
• a preferred separable multi-segment anode comprises separatable stacked single-layer anodes (preferably separatable by unscrewing and/or unclamping), packed bed anodes with a defined package, and/or packed bed anodes with loosely filled materials.
• the surface density is in a range from 6 m 2 /L to 100 m 2 /L, preferably from 8 m 2 /L to 70 m 2 /L, more preferably from 10 m 2 /L to 50 m 2 /L, even more preferably from 12 m 2 /L to 40 m 2 /L, yet even more preferably from 14 m 2 /L to 30 m 2 /L, most preferably from 16 m 2 /L to 22 m 2 /L.
• the method of the present invention includes a manufacturing of a respective anode or whether the anode is simply provided but manufactured at a different place and subsequently relocated to be utilized in the method of the present invention.
• the woven fabric anodes comprise woven metallic wires and/or woven metallized filaments.
• the thickness of such wires and filaments define the maximum surface density.
• the maximum surface density is preferably ranging from 18 m 2 /L to 22 m 2 /L, based on the total volume of said anode, preferably about 20 m 2 /L.
• the maximum surface density is preferably ranging from 30 m 2 /L to 42 m 2 /L, based on the total volume of said anode, preferably from 35 m 2 /L to 40 m 2 /L.
• the woven fabric anodes comprise flat woven fabric anodes and/or pile fabric anodes.
• the 3D-printed anodes comprise 3D-printed lattice anodes and/or 3D-printed lamella anodes.
• the printing resolution in 3D-printing defines the maximum surface density.
• 3D-printed spots with a minimum dimension of about 50 ⁇ m preferably result in a 3D-printed anode having a surface density ranging from at least 60 m 2 /L up to 100 m 2 /L, based on the total volume of said anode, preferably from 70 m 2 /L to 90 m 2 /L.
• the foam anodes comprise a solid and/or flexible foam anode.
• the packed bed anodes comprise a package compartment selected from the group consisting of raschig ring, lessing ring, pall ring, bialecki ring, dixon ring, net balls, and Hex-X compartments.
• the at least one anode having a surface density of 6 m 2 /L or more comprises 3D-printed anodes and/or woven fabric anodes.
• 3D-printed anodes for example, as already mentioned above, can theoretically manufactured with a potentially very high surface density.
• the surface density is 100 m 2 /L or below for such kind of anodes, based on the total volume of said anode, preferably ranging from 30 m 2 /L to 80 m 2 /L, preferably from 40 m 2 /L to 50 m 2 /L.
• woven fabric anodes have a surface density ranging from 10 m 2 /L to 40 m 2 /L, based on the total volume of said anode, preferably from 15 m 2 /L to 30 m 2 /L.
• a method of the present invention is preferred, wherein the one or more than one anode does not comprise stacked single-layer anode layers (preferably as defined above as being preferred) having an individual surface density of 3 m 2 /L or below. Most preferably, the one or more than one anode does not comprise stacked single-layer anodes having an individual surface factor of 3 or below. In some cases, a method of the present invention is even preferred, wherein the one or more than one anode, preferably the at least one anode having the surface density of 6 m 2 /L or more, does not comprise stacked single-layer anodes at all.
• stacked single-layer anodes are basically possible and desired to be used in the context of the present invention, they typically need to be assembled compared to other preferred anodes which are manufactured in basically automated manufacturing methods.
• the at least one anode having a surface density of 6 m 2 /L or more comprises a material selected from the group consisting of platinum, titanium, niobium, lead, gold, alloys comprising at least one thereof, oxides thereof, and mixtures thereof.
• the one or more than one anode comprises a material selected from the group consisting of platinum, titanium, niobium, lead, gold, alloys comprising at least one thereof, oxides thereof, and mixtures thereof. This preferably means that it applies to all anodes.
• the manganese species having the first oxidation number is preferably provided/comprised in a liquid. Since the liquid is preferably highly acidic and because of the strong oxidizing character of certain manganese species, the material of the one or more than one anode is preferably carefully selected. A preferred minimum requirement is that a respective material is (electro-)chemically inert towards the liquid. Typically, the aforementioned materials are resistant, at least for a certain time. Very preferred is a method of the present invention, wherein the one or more than one anode comprises a platinized anode and/or a platinum anode, preferably a platinized titanium anode, and/or a platinized niobium anode. Such anode material is highly resistant, even over longer times. This most preferably applies to the at least one anode having a surface density of 6 m 2 /L or more.
• a method of the present invention is preferred, wherein the material comprises lead and/or lead alloys.
• Preferred lead alloys comprise tin and/or silver as alloying elements.
• the material comprise platinum, most preferably is platinized.
• lead is more and more an undesired material in terms of human and environmental hazards.
• step (B) at least one cathode is provided.
• the at least one cathode comprises a material selected from the group consisting of titanium, platinum, niobium, lead, alloys comprising at least one thereof, oxides thereof, stainless steel, and mixtures thereof.
• the at least one cathode preferably is of a wide variety of materials as long as a respective material is sufficiently acid resistant, sufficiently stable against hydrogen embrittlement, and/or chemically resistant to the liquid (if in contact with the liquid).
• a method of the present invention is preferred, wherein the material of the at least one cathode is identical to the material of the at least one anode having a surface density of 6 m 2 /L or more, preferably to the material of the one or more than one anode.
• the material of the at least one cathode is different from the material of the at least one anode having a surface density of 6 m 2 /L or more, preferably from the material of the one or more than one anode.
• the cathodic current protects the at least one cathode such that even less resistant materials can be utilized, preferably stainless steel.
• a permeable barrier preferably a permeable membrane is utilized in the method of the present invention, such that a catholyte is formed, preferably a catholyte comprising phosphoric acid, more preferably comprising as only mineral acid phosphoric acid, most preferably comprising as only acid phosphoric acid.
• the at least one cathode comprises a sheet cathode, a mesh cathode, a woven web cathode, an expanded metal cathode, a 3D-printed cathode, a woven fabric cathode, a foam cathode, and/or a packed bed cathode.
• the at least one cathode comprises a sheet cathode, a mesh cathode, a woven web cathode, an expanded metal cathode, a 3D-printed cathode, a woven fabric cathode, a foam cathode, and/or a packed bed cathode.
• Preferred is a sheet cathode and/or a mesh cathode.
• the at least one anode having the surface density of 6 m 2 /L or more.
• total effective surface area refers to the area available for participation in electrochemical redox-reactions. This is also used/included in the definition of the surface density.
• a 1 are from the at least one anode having the surface density of 6 m 2 /L or more, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, yet even more preferably 90% or more, most preferably 95% or more, yet even most preferably 99% or more.
• a 1 : A 2 is ranging from 5:1 to 100:1, preferably from 10:1 to 85:1, more preferably from 15:1 to 70:1, even more preferably from 20:1 to 60:1, most preferably from 30:1 to 50:1.
• a 1 : A 2 is ranging from 5:1 to 30:1, preferably from 6:1 to 25:1, more preferably from 7:1 to 20:1.
• a 1 : A 2 is at least 10:1, preferably at least 20:1, more preferably at least 30:1, most preferably at least 40:1. More preferred is a method of the present invention, wherein A 1 : A 2 is ranging from 10:1 to 100:1, preferably from 20:1 to 70:1, more preferably from 30:1 to 50:1, most preferably from 35:1 to 45:1. This is in some cases most preferred, if no permeable barrier is utilized.
• a 1 is ranging from 10 dm 2 /dm 3 to 200 dm 2 / dm 3 , based on a total free inner volume in the treatment device, preferably from 15 dm 2 / dm 3 to 175 dm 2 / dm 3 , more preferably from 20 dm 2 / dm 3 to 150 dm 2 / dm 3 , even more preferably from 25 dm 2 / dm 3 to 125 dm 2 / dm 3 , yet even more preferably from 30 dm 2 / dm 3 to 100 dm 2 / dm 3 , most preferably from 35 dm 2 / dm 3 to 75 dm 2 / dm 3 , yet even most preferably from 40 dm 2 / dm 3 to 50 dm 2 / dm 3 .
• the total free inner volume corresponds to the total inner volume in the treatment device subtracted by at least the volume (i.e. the tare volume) of the one or more than one anode including e.g. its parts for installation and preferably all other installations inside the treatment device such as pipes, etc.
• the total free inner volume is more preferably the volume that the liquid can maximally occupy within the treatment device.
• the aforementioned parameter denotes an anode density (i.e. total effective anode surface area per dm 3 of said total free inner volume).
• anode density i.e. total effective anode surface area per dm 3 of said total free inner volume.
• the aforementioned anode densities are typically considered as high. It is a parameter to characterize the compact and dense packing of the treatment device.
• the treatment device has at least one inner surface comprising or consisting of a fluorinated plastic, preferably polyvinylidene fluoride (PVDF) and/or polytetrafluoroethylene (PTFE). Own experiments have shown that such materials have the needed chemical resistance to prevent harm and damage (e.g. by means of dissolution and/or etching) to the treatment device.
• PVDF polyvinylidene fluoride
• PTFE polytetrafluoroethylene
• step (C) of the method of the present invention a current is applied, preferably an electrical current.
• step (C) the current has a current density ranging from 0.1 A/dm 2 to 10 A/dm 2 , preferably from 0.2 A/dm 2 to 8 A/dm 2 , more preferably from 0.3 A/dm 2 to 6 A/dm 2 , even more preferably from 0.4 A/dm 2 to 4 A/dm 2 , yet even more preferably from 0.5 A/dm 2 to 2.8 A/dm 2 , most preferably from 0.6 A/dm 2 to 1.5 A/dm 2 .
• This is the anodic current density preferably based on the effective anode surface area.
• the anodic current density is comparatively low in order to reduce undesired anodic oxygen gas production, which in turn reduces the current efficiency.
• step (C) the at least one cathode has a cathodic current density ranging from 2 A/dm 2 to 70 A/dm 2 , preferably from 3 A/dm 2 to 60 A/dm 2 , more preferably from 4 A/dm 2 to 50 A/dm 2 , even more preferably from 5 A/dm 2 to 40 A/dm 2 , yet even more preferably from 6 A/dm 2 to 30 A/dm 2 , most preferably from 7 A/dm 2 to 20 A/dm 2 .
• This is the cathodic current density.
• a comparatively low anodic current density it is desired to have a comparatively high cathodic current density. This typically leads to hydrogen gas production. Although this is generally not desired, in the context of the present invention, it may suppress undesired cathodic decomposition reactions of desired manganese species.
• a method of the present invention is preferred, wherein in step (C) the at least one cathode has a cathodic current density ranging from 2 A/dm 2 to 30 A/dm 2 , preferably from 3 A/dm 2 to 25 A/dm 2 , more preferably from 4 A/dm 2 to 20 A/dm 2 , even more preferably from 5 A/dm 2 to 15 A/dm 2 , most preferably from 6 A/dm 2 to 12 A/dm 2 .
• a method of the present invention is preferred, wherein in step (C) the at least one cathode has a cathodic current density ranging from 10 A/dm 2 to 70 A/dm 2 , preferably from 12 A/dm 2 to 65 A/dm 2 , more preferably from 14 A/dm 2 to 60 A/dm 2 , even more preferably from 16 A/dm 2 to 50 A/dm 2 , most preferably from 18 A/dm 2 to 35 A/dm 2 .
• the manganese species having the first oxidation number are comprised in a liquid.
• step (A) in the liquid all manganese species together (i.e. including the manganese species having the first oxidation number) have a total concentration ranging from 0.02 mol/L to 0.3 mol/L, based on the total volume of the liquid, preferably from 0.03 mol/L to 0.25 mol/L, most preferably from 0.035 mol/L to 0.2 mol/L.
• step (C) in the liquid all manganese species together (i.e. including the manganese species having the first oxidation number) have a total concentration ranging from 0.02 mol/L to 0.3 mol/L, based on the total volume of the liquid, preferably from 0.03 mol/L to 0.25 mol/L, most preferably from 0.035 mol/L to 0.2 mol/L.
• the liquid comprises acids in a total concentration ranging from 5 mol/L to 13 mol/L, based on the total volume of the liquid, preferably from 6 mol/L to 12 mol/L, more preferably from 7 mol/L to 11.5 mol/L, most preferably from 8 mol/L to 11 mol/L. Most preferably this applies to inorganic acids.
• the liquid comprises phosphoric acid, preferably in a concentration ranging from 7.4 mol/L to 11.8 mol/L, based on the total volume of the liquid, preferably from 7.8 mol/L to 11.5 mol/L, more preferably from 8.2 mol/L to 11.2 mol/L, even more preferably from 8.5 mol/L to 11 mol/L, most preferably from 8.7 mol/L to 10.8 mol/L.
• phosphoric acid is the only (mineral) acid in the liquid.
• the liquid is substantially free of, preferably does not comprise, sulfuric acid.
• the liquid is substantially free of, preferably does not comprise, a methane sulfonic acid and salts thereof, preferably is substantially free of, preferably does not comprise, a C1 to C4 alkyl sulfonic acid and salts thereof, most preferably is substantially free of, preferably does not comprise, a C1 to C4 sulfonic acid and salts thereof.
• liquid is substantially free of, preferably does not comprise, bromide and iodide anions, preferably is substantially free of, preferably does not comprise, chloride, bromide, and iodide anions, most preferably is substantially free of, preferably does not comprise, halide anions.
• liquid comprises iodine-comprising compounds.
• liquid is substantially free of, preferably does not comprise, trivalent chromium ions and hexavalent chromium compounds, preferably is substantially free of, preferably does not comprise, any compounds and ions comprising chromium.
• the liquid comprises alkali metal ions, most preferably sodium ions, preferably in a total concentration ranging from 0.002 mol/L to 0.5 mol/L, based on the total volume of the liquid, preferably from 0.004 mol/L to 0.3 mol/L.
• step (C) Preferred is a method of the present invention, wherein during step (C) the liquid has a temperature ranging from 20°C to 65°C, preferably from 30°C to 50°C.
• step (A) and preferably additional after step (C) is acidic, preferably has a pH of 2 or below, more preferably of 1 or below, even more preferably of 0.5 or below.
• step (A) and preferably additional after step (C) the liquid has a density in a range from 1.2 g/cm 3 to 1.7 g/cm 3 , referenced to a temperature of 20°C, preferably from 1.3 g/cm 3 to 1.6 g/cm 3 , more preferably from 1.4 g/cm 3 to 1.6 g/cm 3 .
• the manganese species having the second oxidation number preferably the permanganate ions
• the manganese species having the second oxidation number preferably the permanganate ions
• a liquid comprising approximately 9 to 10 mol/L phosphoric acid, approximately 10 mmol/L permanganate ions, and approximately 2 mmol/L silver (I) ions was prepared as etching composition. Due to a high degree of self-decomposition, the amount of permanganate ions quickly decreased. The volume of the liquid was about 0.5 L.
• the etching composition was subjected to electrolytic re-oxidation as defined in the present invention in a treatment device for recycling.
• the treatment device the following different types of a single anode were tested:
• cathode As cathode, a lead alloy cathode was used. The anode and the cathode were separated by a ceramic permeable barrier such that an anolyte and a catholyte were formed.
• the treatment device was filled with a catholyte consisting of aqueous, concentrated phosphoric acid (70 wt.-%), wherein the liquid was the anolyte.
• the distance between the anode and the cathode was approximately 20 mm.
• the anodic current density was as mentioned above, wherein the cathodic current density was approximately 10 A/dm 2 .
• the manganese species having the first oxidation number While in contact with the anode, the manganese species having the first oxidation number was continually re-oxidized to permanganate ions (i.e. the manganese species having the second oxidation number).
• the manganese species having the first oxidation number comprised particulate manganese oxide.

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• 2021
  • 2021-06-16 EP EP21179861.6A patent/EP4105361A1/fr active Pending
• 2022
  • 2022-06-15 US US18/570,742 patent/US20250043435A1/en active Pending
  • 2022-06-15 JP JP2023577750A patent/JP2024522775A/ja active Pending
  • 2022-06-15 TW TW111122140A patent/TW202305184A/zh unknown
  • 2022-06-15 CN CN202280042790.2A patent/CN117500958A/zh active Pending
  • 2022-06-15 WO PCT/EP2022/066247 patent/WO2022263482A1/fr not_active Ceased

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