US3406108A - Regeneration of spent ammonium persulfate etching solutions - Google Patents

Regeneration of spent ammonium persulfate etching solutions Download PDF

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US3406108A
US3406108A US495374A US49537465A US3406108A US 3406108 A US3406108 A US 3406108A US 495374 A US495374 A US 495374A US 49537465 A US49537465 A US 49537465A US 3406108 A US3406108 A US 3406108A
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persulfate
anolyte
catholyte
sulfate
copper
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Kenneth J Radimer
Frank E Caropreso
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FMC Corp
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FMC Corp
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Priority to GB4296766A priority patent/GB1141407A/en
Priority to BE687500D priority patent/BE687500A/xx
Priority to NL6613705A priority patent/NL6613705A/xx
Priority claimed from US61679267 external-priority patent/US3400027A/en
Priority to FR1570970D priority patent/FR1570970A/fr
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02Electrodes; Connections thereof
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D9/00Crystallisation
    • B01D9/0004Crystallisation cooling by heat exchange
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B15/00Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
    • C01B15/055Peroxyhydrates; Peroxyacids or salts thereof
    • C01B15/06Peroxyhydrates; Peroxyacids or salts thereof containing sulfur
    • C01B15/08Peroxysulfates
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01CAMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00Ammonia; Compounds thereof
    • C01C1/24Sulfates of ammonium
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G3/00Compounds of copper
    • C01G3/10Sulfates
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23FNON-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
    • C23F1/00Etching metallic material by chemical means
    • C23F1/46Regeneration of etching compositions
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00Electrolytic production, recovery or refining of metals by electrolysis of solutions

Definitions

  • This invention relates to the recovery of unused persulfate values in spent etching solutions, and further, to the regeneration of spent ammonium persulfate etching solutions.
  • Solutions of peroxygen chemicals such as ammonium persulfate are commonly used to dissolve metals such as copper, cobalt, iron, nickel and zinc. This is desirable, for example, in place of ordinary machining in order to remove specified amounts of these metals from surfaces of fragile or peculiarly shaped objects.
  • a more widespread application of this technique is the production of printed electrical circuits.
  • a resist or mask in the form of the desired circuit is placed over the surface of a copper iilm laminated to a base, and the partially masked copper film is treated with the etchant. The copper area not covered by the resist is dissolved, while the copper covered by the resist remains to form the desired circuit.
  • Ammonium persulfate solutions are desirable in such applications because they do not generate obnoxious fumes, are easy to work with, and are relatively noncorrosive to certain common materials of construction such as stainless steels.
  • the metal e.g., copper is dissolved in the nonmasked areas by the persulfate solution until the dissolution rate is below commercially acceptable rates.
  • the resulting spent etchant must be treated to remove the dissolved metal, e.g., copper before it is sewered.
  • a second problem is that the treatment of spent persulfate solutions to remove metal values, e.g., copper, entails an additional process step 'which adds to the expense of disposing of these solutions. Copper must be removed from the persulfate solutions before they are sewered because of the toxicity of the copper values.
  • metal values e.g., copper
  • spent persulfate etching solutions to remove the metal values, e.g., copper, ⁇ present in the etching solution and to regenerate the persulfate values in said etching solution so as to obtain etchants yielding consistent, commercially acceptable etching rates.
  • a spent aqueous ammonium persulfate etching solution which has been used to dissolve a metal such as copper, cobalt, iron, nickel and zinc, and which contains the corresponding metal sulfate, arnmonium sulfate and residual ammonium persulfate values can be regenerated by treating said solution to remove a substantially persulfate-free mixture containing ammonium sulfate and the corresponding metal sulfate, using the persulfate-free mixture as the catholyte of an electrolytic cell, using the remainder of said ⁇ spent solution containing sulfate values and residual persulfate values ⁇ as the anolyte of said electrolytic cell, the cathode and anode sections of the electrolytic cell being contained in a manner (preferably separated by a diaphragm) which permits at least hydrogen ions to pass freely between the anolyte and catholyte but which prevents any substantial amounts of persul
  • a fresh aqueous 0,75 to 1.25 molar (M) ammonium persulfate etching solution (containing from about 171 g. to 285 lg. of ammonium persulfate per liter of water) can be heated to temperatures of from about 35 to 46 C. and used to etch unmasked portions of copper.
  • the etching can take place either by conventional immersion etching or spray etching.
  • immersion etching process the masked copper workpiece is immersed in the solution for the amount of time required to etch the exposed copper surface.
  • the persulfate solution is discharged from a spray nozzle under pressure and the spray impinges on the masked copper workpiece.
  • the spray etching technique is preferred because it permits shorter etching times and results in a better quality etch. This is due in large measure to the constant replacement of the copper-rich layer of etchant in immediate contact with the workpiece with fresh etchant.
  • Etching can be continued until the solution has been depleted of persulfate values-to va concentration of about 0.4 to 0.6 M ammonium persulfate. At this point, the ⁇ solution is capable of further etching, but the etch rate and quality of etch diminishes and such solutions are normally discarded as spent solutions.
  • this spent Vsolution is passed to a crystallizer, preferably a vacuum crystallizer, which is maintained ata temperature of to 20 C., whereupon copper sulfate and arnmonium sulfate crystallize leaving substantially all the persulfate values in the remaining mother liquor.
  • a crystallizer preferably a vacuum crystallizer
  • the exact temperature of cooling is not critical but it should be 'suiciently low to crystallize substantial amounts of copper sulfate and ammonium sulfate, normally in the form of a hydrated double salt, but not ammonium persulfate values.
  • a temperature of about 0 to l0" C. is optimum. In many cases vacuum crystallizers are desired in order to remove some of the water in the remaining solution.
  • The'resulting crystals are separated from the solution by filtering or by centrifugal separators. During the separation care must be taken to remove adhered mother liquor from the precipitate in order to prevent loss of ammonium persulfate values.
  • the precipitated crystals are then dissolved in water and passed into the cathode section of an electrolytic cell for use as a catholyte. It is critical that the catholyte be free of any substantial amounts of persulfate since the presence of persulfate interferes with the proper functioning of the electrolytic cell.
  • the mother liquor from the crystallization step which contains the remaining copper, ammonium and sulfate values as well as the residual persulfate values, is passed into the anode section of the above electrolytic cell and 4used as an anolyte.
  • sulfate values as used in the specification and claims refers to both sulfate and bisulfate water-soluble compounds.
  • the anolyte and catholyte solutions must be contained in a manner to prevent any substantial amounts of persulfate values in the anolyte from mixing with the catholyte, but without preventing the ow of an electric current between these solutions. Separation of the solutions by differences in specific gravity is workable but best results are achieved by placing a diaphragm between the two solutions. The diaphragm permits the ow of an electric current between the anolyte and catholyte, but prevents substantial amounts of persulfate in the anolyte from diffusing into the catholyte.
  • the flow of current between the anolyte and catholyte takes place by passing certain ions, principally hydrogen ions, through the diaphragm and is a necessary part of the electric circuit of the cell.
  • the diaphragm in the electrolytic cell can be any porous membrane such as a porous porcelain sheet, asbestos membrane, plastic membranes, etc.
  • Au electrode then is immersed in each catholyte and anolyte solution.
  • These electrodes can be any material which can conduct an electric current and which does not react with the solutions of the cell during the electrolysis.
  • noble metals such as platinum or gold are preferred as anodes
  • 4and copper is preferred as the cathode, since copper plates out on the cathode in the ensuing reaction.
  • An electric potential is placed across the electrodes (the anode and cathode) by means of a battery, rectifier or other source of direct current to complete the electrolytic cell.
  • the electric potential which is applied across the electrodes must be suicient to cause a positive electrical current to flow outside the cell from cathode to anode to plate out copper at the cathode and convert sulfate valuesV to persulfate iat the anode.
  • an EMF of at least about 2.5 volts has been found operable with from about 5 to 7 volts being preferred.
  • the electrolytic regeneration is conducted at a temperature of from about 2 to 30 C. with temperatures from about 5 to 20 C. being pre- (NHiCNS) is present in the anolyte in concentrations of up to about 0.2%.
  • urea or NH4CNS in vamounts of about 0.005% has been found most effective in increasing anode eiliciency forithe production of persulfate from sulfate by to 100%.
  • the presence of urea or NH.,CNS in the catholyte does not interfere in any manner with the regeneration or operation of the electrolytic cell.
  • a cathode having a large surface area is used to facilitate copper deposition while the anode can have a much smaller surface area.
  • current densities from 25 to 30 amps per square foot at the cathode and 1100 amps/sq. ft. at the anode have been used with good effect.
  • the desired half-reactions for each of the half cells are as follows:
  • Ammonium bisulfate is preferred as a source of supplementary sulfate values because it does not introduce foreign ions into the anolyte solution.
  • Other soluble compounds which increase the anolytes sulfate concentration can also be used providing that they do not interfere with the electrolytic regeneration or with the subsequent etching.
  • Sulfate values might be increased by introducing materials such as ammonium sulfate, sodium sulfate, or sulfuric acid.
  • the supplementary sulfate values are preferably introduced into the spent etchant before crystallization of copper and ammonium sulfate from it, as set forth above, in order to increase the extent of crystallization of copper values from the aqueous solution; this solution after being electrolyzed has therefore a lower copper concentration which leads to better etching.
  • the added sulfate values can be introduced directly into the mother liquor subsequent to crystallization. In either case the sulfate values in the mother liquor, which pass into the anolyte, are increased.
  • the electrolysis can be conducted batchwise or continuously.
  • electrolytic cells should be used in which the electrolytes are introduced at one end of the cell and flow along the membranes until they are removed from the cell at the opposite end. During this ow reduction of the copper concentration in the catholyte and an increase in the persulfate concentration in the anolyte occur.
  • the solutions can be introduced into other such cells in cascade if desired.
  • the persulfaterich anolyte is passed to the etching machine and the eXit catholyte is passed to an evaporator.
  • the persulfate concentration of the anolyte can be raised to any extent desired up to about 0.8 to 1.0 M; such solutions have been found to be acceptable etchants.
  • water is stripped from the exit catholyte.
  • the resulting -concentrated catholyte contains sulfate values, principally as ammonium bisulfate, and is useful for supplying supplementary sulfate values required in subsequent anolytes as described above.
  • the nal catholyte contains virtually no copper and therefore can be sewered if the ammonium bisulfate values are not desired.
  • a crystallization procedure was used in order to prepare a persulfatefree catholyte.
  • a portion of the etchant intended for use as catholyte may be treated to decompose persulfate values. This may be done for example by merely heating that portion of the etchant to a temperature between about 50 C. and 100 C. at which temperature the persulfate decomposes.
  • the residual persulfate in this portion of the etchant may be destroyed by reacting it with a chemical reducing agent such as sulfur dioxide.
  • the resulting etching solution, free of residual persulfate can then be used as the catholyte.
  • Untreated spent etchant which still contains residual persulfate, may be used as the anolyte.
  • the electrolytic regeneration is carried out using these solutions as catholyte and anolyte, respectively, in the same manner as set forth previously.
  • supplementary sulfate values preferably in the form of ammonium bisulfate can be supplied from any available source including the exit catholyte, once cyclic regeneration has commenced.
  • supplementary sulfate values can be obtained in the form of copper ammonium sulfate crystals. These can be obtained by cooling some spent etchant to 0 to 20 C. to precipitate these crystals, and adding the crystals to the anode chamber during electrolysis.
  • An alternate method is to manufacture ammonium bisulfate for use in start up.
  • One method is to cool spent etchant to obtain crystals, redissolve these crystals in water for use as a catholyte, and use the mother liquor as the anolyte.
  • ammonium bisulfate is formed in the catholyte which can be used as a source of supplementary sulfate values.
  • One embodiment of the invention that is contemplated to enable an ammonium persulfate solution to be used indefinitely for etching is carried out by continuously removing a portion of the etching solution, continuously add-ing concentrated exit catholyte thereto, cooling the resulting solution to precipitate sulfate insolubles and continuously removing sulfate insolubles from the supernatant solution.
  • the sulfate insolubles (free of persulfate) are dissolved in water continuously and this solution continuously fed to the cathode compartment of an operating electrolytic cell; the remaining supernatant solut-ion in similar fashion is fed continuously in the anode compartment of the electrolytic cell.
  • the resulting electrolytic regeneration increases the persulfate values in the anode compartment of the electrolytic cell while converting copper ions to copper metal in the cathode compartment.
  • the regenerated anolyte enriched in persulfate values, is removed from the cell and recycled back to the main body of etching solution continuously.
  • the exit catholyte substantially free of copper, is passed continuously into an evaporator to remove some of its water.
  • the resulting concentrated exit catholyte is removed and continuously added to the stream of spent etchant prior to the cooling and crystallizing step as described above.
  • the resulting etching solution in such a process thus can be used continuously with this cyclic crystallization and regeneration procedure unless or until foreign impurities which may be introduced inadvertently or build up in the solution to a point where the quality of etch is affected.
  • Such a process obviates the need for replacing etch-ing solution and for disposing of the spent solutions or other Waste materials.
  • the quality of etch obtained by using regenerated persulfate solution is about the same as that obtained with fresh ammonium persulfate solution.
  • the electrolytic regeneration technique described above does not entail any reduction in the high quality of etch obtained when using ammonium persulfate etchants.
  • an ammonium persulfate etching solution is heated in an etching machine 2 and used to etch photo-resisted, copper laminated printed circuit panels un. til the rate and quality of etch are no longer commercially acceptable.
  • the spent solution is then withdrawn from the etching machine 2 and transferred to a vacuum crystallizer 4 in which the contents are cooled to a temperature of 0 to 10 C.
  • a vacuum crystallizer 4 In the vacuum crystallizer 4 some Water is vaporized during cooling and sent to condenser 24; during cooling crystals of copper ammonium sulfate are precipitated. These crystals, which contain substantially no ammonium persulfate, are separated from the mother liquor in centrifuge 6.
  • the mother liquor which contains copper sulfate, ammonium sulfate, ammonium bisulfate and residual ammonium persulfate is then discharged into the anode compartment 8 of an electrolytic diaphragm cell 10 for use as the anolyte.
  • the copper ammonium sulfate crystals are dissolved in water obtained from water storage tank 26 and discharged into the cathode compartment 12 of the diaphragm cell 10.
  • the diaphragm cell 10 is made up of an anode compartment 8 and a cathode compartment 12 separated by a diaphragm 14 through which hydrogen ions can pass, but which prevents any substantial diffusion of other ions from one side of the diaphragm to the other.-The diaphragm must prevent substantial amounts of persulfate ions from diffusing from the anode to the cathode compartment. Where desired, the free surface of the catholyte in the cathode compartment 12 can be maintained slightly higher than that of the anolyte in the anode compartment 8 to diminish such diffus-ion.
  • the anolyte and catholyte are electrolyzed by passing a direct current through the anode 16 immersed in the anolyte and through the cathode 18 immersed in the catholyte.
  • the direct current is supplied by battery 20 or other equivalent source of direct current.
  • Within the cell electrical current is carried between the 7 anode and cathode by the ions which diffuse through the diaphragm.
  • diaphragm cell 10 is properly operating when the quantity of copper plated out at the cathode 18 is approximately equivalent chemically to the amount of persulfate produced in the anolyte. Electrolysis is continued until all the copper from the catholyte has been platedout on cathode 18 and the desired concentration of persulfate has been reached in the anolyte compartment S. The exit anolyte, rich in persulfate, is recycled back to the etching machine 2 for further etching. The exit catholtye from cathode compartment 12, which contains virtual- 1y no copper but which is rich in ammonium bisulf-ate, is transferred to evaporator 22 Where a substantial amount of its water is removed.
  • the water vapor is condensed in condenser 24 yand passed to a water storage tank 26.
  • the ammonium bisulfate concentrate from evaporator 22 may then 'be passed to the vacuum crystallizer 4 or directly to the anode compartment 8 of the diaphragm cell 10. ⁇ In either case, the-ammonium bisulfate hows to the anolyte as supplementary sulfate values; however, it is preferred to pass the concentrate' into the vacuum crystallizer 4 along with spent etchant in order to increase the eiiiciency of copper removal from the etchant during crystallization in vacuum crystallizer 4.
  • a process for regenerating anetching solution was carried out :as follows.
  • An etchant solution was prepared containing 1.1 moles of ammonia persulfate per liter and 5 p.p.m. of dissolved mercury as HgCl2 which is the etching catalyst. This was. used to etch photo-resisted, single-sided printed circuit test panels, -the copper foil of which weighed l oz. per sq. ft.
  • the etching was conducted 'by immersing the test panels in the air-agitated etchant at a temperature of 35-39 C. Etching rates and the quality of etch. were determined frequently during the run and were found to be satisfactory. When the etch rate dropped Ibelow about 0.2 mil of copper per minute, the etchant was considered to be spent. At this point one liter of it contained:
  • the mother liquor was added to the anode compartment of a diaphragm cell; urea w-as 'added to give a .02% solution.
  • the crystal solution was passed into the cathode compartment of the same diaphragm cell.
  • a platinum wire was suspended in the anode compartment to serve las an anode, while copper tu'bing was used as a cathode in contact with the crystal solution in the cathode compartment of the cell.
  • the anode and thode were connected to a rectifier and electrolysis was conducted for about 11 hours using a current of about 3 amperes.
  • the current density was about 1100 amps/sq. ft. at the anode and about 30 amps/sq. ft. at the cathode.
  • the temperature of the anolyte and catholyte was about Ztl-25 C. and 18-20o C., respectively, during electrolysis. After electrolysis the anolyte Iand catholyte were analyzed with the following results:
  • EXAMPLE 2 A series of runs was made, in which photo-resisted, single-sided, 1 oz./sq. ft., copper laminated printed circuit test panels wereretched. In these runs 500 ml. portions of a fresh aqueous etching solution, each having an ammonium persulfate concentration of about 1 M and 5 p.p.m. of HgCl2 (which is used as the etching catalyst), were used to etch the abovementioned circuit test panels until the solutions were about 50% depleted of their ⁇ ammonium persulfate. The etching was conducted by immersing the test panels in the air-agitated etchant maintained at a temperature of P18-39 C. The average etching rates were on the order of from about 0.25 to about 0.30 mils of copper per minute and the quality of etch obtained was good. -In general, an etch rate of about 0.2 mil of copper per minute is considered acceptable'for commercial use.
  • the spent etching solutions were cooled to a temperawas suspended in the cup and served as the anode while a copper tubing 0.25 in. in diameter was Wrapped in a helix around the porous cup and served as the cathode. Water was passed through the copper tubing for better temperature control.
  • the anolyte was continually agitated by means of a Teflon-coated magnetic stirring bar placed in the base of the porcelain cup.
  • the anode and cathode were connected to a rectifier which supplied direct current.
  • the electrolytic cell was operated 'by adjusting the voltage passing through the cell to give the desired current.
  • Each of the solutions in R-uns 1-4 was subjected to electrolysis for 60 minutes.
  • ammonium persulfate contents of the anolyte solutions both prior to and subsequent to regeneration were determined by addition of a known excess of stand-ard ferrous ammonium sulfate and 'back titration with standard potassium permanganate.
  • the compositions of the anolyte and catholyte prior to electrolysis are given in Table I along with the final persulfate contents of the anolytes.
  • the conditions under which electrolysis was carried out are also set forth in Table I. ⁇ In Run 3, sulfuric acid was ladded to the anolyte to supply additional sulfate values for conversion to persulfate. In Run 4, 0.02% by weight of urea was added to the anolyte and catholyte to increase the anode efficiency for production of persulfate.
  • the regenerated anolyte solution from Run 4 was used as a regenerated etchant to etch test panels identical to those etched by the initial etchant.
  • the rate of etch was found to be substantially above 0.2 mil of copper per minute and the quality of etch was good.
  • the electrolytic cell comprises a porous porcelain cup standing in a larger glass beaker.
  • the porous cup contained the anolyte and the area between the cup and the glass beaker contained the catholyte.
  • the porous cup served as the diaphragm to retard diffusion of persulfate from the anolyte (contained in the cup) to the catholyte (contained in an annular space between the cup and the vglass beaker).
  • a platinum wire 0.04 in. in diameter A series of runs were made in substantially the same manner as set forth in Example 2, Run 1, except that in place of copper the spent etchant contained either cobalt, iron, nickel or zinc dissolved in the etchant.
  • the spent etchant containing the ingredients and concentration level set forth in Table II were cooled to a temperature given in Table Il using a vacuum type crystallizer. Crystals were precipitated having the values set forth in Table II for each of the solutions. The crystals were filtered from the mother liquors and sufficient water was added to these crystals to dissolve them. The resulting solutions were then used as the catholytes in subsequent electrolytic regenerations. The mother liquors which remained after vacuum crystallization were used as the respective anolytes in the above electrolytic regenerations.
  • Zinc sulfate deposited. 4 Zinc -- 0. 5 0. 4 0.4 Zinc sulfatc 0 to 2 C Zinc su1fatc,-ammonium Zinc metal ⁇ 1)0.
  • a process for regenerating an ammonium persulfate etching solution which contains a dissolved metal selected from the group consisting of copper, cobalt, iron, nickel and zinc which comprises separating from said solution a persulfate-free mixture containing ammonium sulfate values and metal sulfate values corresponding to said dissolved metal land leaving a remaining solution containing sulfate values, adding said persulfate-free mixture into the cathode section of an electrolytic cell y.for use as a catholyte, adding said remaining solution containing sulfate values into the anode section of said electrolytic cell for use as an anolyte, said cathode and anode sections of said electrolytic cell being contained in a manner to prevent substantial amounts of persulfate values present in the anolyte from mixing with the catholyte, but permitting the free passage of at least hydrogen ions between said anolyte and said catholyte, passing an electric current through said cat
  • a process for lregenerating an ammonium persulfate etching solution which contains a dissolved metal selected from the lgroup consisting of copper, cobalt, iron, nickel and zinc which comprises cooling said solution to crystallize metal sulfate values corresponding to said dissolved metal and ammonium sulfate values from said solution without crystallizing substantial amounts of ammonium persulfate, separating the crystallized solids from the remaining mother liquor, adding said crystallized solids to an aqueous liquor to make up a substantially persulfatefree mixture, adding said persulfate-free mixture into the cathode section of an electrolytic cell for use as a catholyte, adding the -remaining mother liquor containing sul- ⁇ fate values into the anode section of the electrolytic cell for use as thev anolyte,lsaid cathode and anode sections of said electrolytic cell being contained in a 'manner to prevent substantial amounts of persulfate values present
  • a process for 'regenerating an ammonium persulfate etching solution which contains dissolved copper which comprises mixing said etching solution with an aqueous ammonium bisulfate solution, cooling the resulting Solution to crystallize copper sulfate and ammonium sulfate values from said resulting solution without crystallizing substantial amounts of ammonium persulfate, separating the crystallized soli-ds yfrom the remaining mother liquor, adding said crystallized solids to an aqueous liquor to make up a'substantially persulfate-free mixture, adding said persulfate-free mixture into the cathode section of an electrolytic cell for use as the catholyte, adding the remaining mother liquor containing sulfate values into the anode section of the electrolytic cell for use as the anolyte, said cathode and anode sections of said electrolytic cell being contained in a manner to prevent substantial amounts of persulfate values present in said anolyte from mixing
  • a process for regenerating an ammonium persulfate etching solution which contains dissolved copper which comprises cooling a first portion of said solution to obtain a rst crystal precipitate containing copper sulfate values and ammonium sulfate values substantially lfree of ammonium persulfate, separating said first crystal precipitate from the remaining first mother liquor, adding said iirst crystal precipitate to an aqueous liquor to Imake up a substantially persulfate-free first mixture, adding said persulfate-free first mixture into the cathode section of an electrolytic cell for use as a catholyte, adding said rst mother liquor containing sulfate values into the anode section of.
  • said electrolytic cell for use as the anolyte, said cathode and anode sections of said electrolytic cell being contained in a manner to prevent substantial amounts of persulfate values present in said anolyte from mixing with said catholyte but permitting the free passage of at least hydrogen ions between said anolyte and said catholyte, passing an electric current through said catholyte and said anolyte yby means of a cathodic electrode contacting said catholyte and an anodic electrode contacting said anolyte, converting copper ions to metallic copper :at said cathodic electrode and forming ammonium bisulfate in said catholyte, converting sulfate ions to persulfate ions at said anodic electrode, recovering a irst anolyte solution having an increased persulfate content, recovering a rst catholyte solution containing ammonium bisulfate and having a decreased copper content

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US495374A 1965-04-28 1965-10-01 Regeneration of spent ammonium persulfate etching solutions Expired - Lifetime US3406108A (en)

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Application Number Priority Date Filing Date Title
US495374A US3406108A (en) 1965-04-28 1965-10-01 Regeneration of spent ammonium persulfate etching solutions
GB4296766A GB1141407A (en) 1965-10-01 1966-09-27 Electrolytic regeneration of ammonium persulphate
BE687500D BE687500A (no) 1965-10-01 1966-09-28
NL6613705A NL6613705A (no) 1965-04-28 1966-09-28
FR1570970D FR1570970A (no) 1965-04-28 1968-06-20

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US45163565A 1965-04-28 1965-04-28
US495374A US3406108A (en) 1965-04-28 1965-10-01 Regeneration of spent ammonium persulfate etching solutions
US61679267 US3400027A (en) 1965-04-28 1967-02-17 Crystallization recovery of spent hydrogen peroxide etchants
US65048467A 1967-06-30 1967-06-30

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891521A (en) * 1973-01-11 1975-06-24 Ppg Industries Inc Opening of molybdenite ores and the electrowinning of rhenium
US4073708A (en) * 1976-06-18 1978-02-14 The Boeing Company Apparatus and method for regeneration of chromosulfuric acid etchants
US4144144A (en) * 1976-12-23 1979-03-13 Fmc Corporation Electrolytic production of sodium persulfate
US4482440A (en) * 1983-10-06 1984-11-13 Olin Corporation Electrochemical cell and process for manufacturing temperature sensitive solutions
US4973380A (en) * 1983-10-06 1990-11-27 Olin Corporation Process for etching copper base materials
DE4430391A1 (de) * 1994-08-26 1996-02-29 Eilenburger Elektrolyse & Umwelttechnik Gmbh Verfahren zum oxidativen Abbau von Schadstoffen in Prozeßlösungen, Abwässern und Trinkwasser sowie Oxidations-, Entgiftungs- und Desodorierungsmittel
DE19506832A1 (de) * 1995-02-28 1996-08-29 Eilenburger Elektrolyse & Umwelttechnik Gmbh Kreislaufverfahren zum Beizen von Kupfer und Kupferlegierungen
DE19820001A1 (de) * 1998-05-06 1999-11-11 Andreas Moebius Verfahren zur Entfernung von Metallschichten auf Metall, Glas, Keramik und Kunststoffteilen

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4402788A1 (de) * 1994-01-31 1995-08-10 Emil Krechen Industrievertretu Verfahren zum Abtragen von Metallen

Citations (3)

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Publication number Priority date Publication date Assignee Title
US2435714A (en) * 1942-09-28 1948-02-10 Bendix Aviat Corp Electrochemical salvaging method
US2589982A (en) * 1947-05-12 1952-03-18 Porte Chemicals Ltd Electrolytic production of ammonium persulfate solutions
US3256165A (en) * 1961-06-19 1966-06-14 Anocut Eng Co Method and apparatus for use in electrolytic shaping

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2435714A (en) * 1942-09-28 1948-02-10 Bendix Aviat Corp Electrochemical salvaging method
US2589982A (en) * 1947-05-12 1952-03-18 Porte Chemicals Ltd Electrolytic production of ammonium persulfate solutions
US3256165A (en) * 1961-06-19 1966-06-14 Anocut Eng Co Method and apparatus for use in electrolytic shaping

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891521A (en) * 1973-01-11 1975-06-24 Ppg Industries Inc Opening of molybdenite ores and the electrowinning of rhenium
US4073708A (en) * 1976-06-18 1978-02-14 The Boeing Company Apparatus and method for regeneration of chromosulfuric acid etchants
US4144144A (en) * 1976-12-23 1979-03-13 Fmc Corporation Electrolytic production of sodium persulfate
US4482440A (en) * 1983-10-06 1984-11-13 Olin Corporation Electrochemical cell and process for manufacturing temperature sensitive solutions
US4973380A (en) * 1983-10-06 1990-11-27 Olin Corporation Process for etching copper base materials
DE4430391A1 (de) * 1994-08-26 1996-02-29 Eilenburger Elektrolyse & Umwelttechnik Gmbh Verfahren zum oxidativen Abbau von Schadstoffen in Prozeßlösungen, Abwässern und Trinkwasser sowie Oxidations-, Entgiftungs- und Desodorierungsmittel
DE19506832A1 (de) * 1995-02-28 1996-08-29 Eilenburger Elektrolyse & Umwelttechnik Gmbh Kreislaufverfahren zum Beizen von Kupfer und Kupferlegierungen
DE19820001A1 (de) * 1998-05-06 1999-11-11 Andreas Moebius Verfahren zur Entfernung von Metallschichten auf Metall, Glas, Keramik und Kunststoffteilen
DE19820001C2 (de) * 1998-05-06 2003-04-03 Andreas Moebius Verfahren zur Entfernung von Metallschichten auf Metall, Glas, Keramik und Kunststoffteilen

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NL6613705A (no) 1967-04-03
FR1570970A (no) 1969-06-13

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