US3682701A - Integrated waste water treatment for reusage after cyanide type plating - Google Patents

Integrated waste water treatment for reusage after cyanide type plating Download PDF

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Publication number
US3682701A
US3682701A US11004A US3682701DA US3682701A US 3682701 A US3682701 A US 3682701A US 11004 A US11004 A US 11004A US 3682701D A US3682701D A US 3682701DA US 3682701 A US3682701 A US 3682701A
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United States
Prior art keywords
metal
solution
plating
wash
cyanide
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US11004A
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Leslie E Lancy
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LANCY LAB
LANCY LAB Inc
Lancy International Inc
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LANCY LAB
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Assigned to DOLLAR BANK FEDERAL SAVINGS BANK reassignment DOLLAR BANK FEDERAL SAVINGS BANK SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LANCY INTERNATIONAL, INC.
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/16—Regeneration of process solutions
    • C25D21/20—Regeneration of process solutions of rinse-solutions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C02F2101/18—Cyanides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes

Definitions

  • This invention relates to the reconditioning of wash waters that have been used for removing cyanide plating bath drag-out from a metal plated surface of one metal and as reconditioned are to be used for removing dragout from a plated surface of a workpiece having a plating thereon of a different, less noble metal.
  • An important phase of the invention deals with making a used wash water treatment solution fully innocuous for subsequent reuse, irrespective of whether or not the plated surface in the first usage is of different metal than or of a different nobility condition of the same metal used for the plated surface of the second usage.
  • a Waste treatment system for workpieces that has a toxic cyanide carryover or drag-out is dislcosed in US Pat. No. 2,725,314. It makes use of chlorine and a caustic for neutralizing an after-treatment wash water solution for the workpieces, such that a subsequent fresh water rinse will be innocuous for sewer or stream discharge and the treatment wash solution may be reused as neutralized.
  • cyanide compounds are oxidized to cyanate (NaCNO) and, ultimately, to the gases, carbon dioxide and nitrogen.
  • This treatment process has been highly successful, but a problem has arisen where more than one or a group of cyanide type plating lines for different metal coatings are being used in one plant.
  • the same finishing facility or plant may have a process line for Zinc plating using a zinc-cyanide plating system, a process line for cadmium plating using a cadmium-cyanide system, a line for copper plating using a copper-cyanide system, or a line for brass plating using a copper-zinc-cyanide system.
  • Typical agents are ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid, ethyleneglycol-bis, and N,N-tetraacetic acid.
  • the presence of such an agent causes a complexing of the metal content of the solution and prevents such content from being precipitated out from the solution.
  • Plating metal is thus retained in soluble form in the solution, where otherwise, under the pH conditions of about 10 to 14, the metal salt or salts used in the plating operation in view of such pH and presence of no other solubilizing agent would be insoluble and precipitate.
  • the chelating agent has the characteristic of holding plating metals in solution as a chelate thereof.
  • wash water contains active chlorine as an oxidizing agent, it tends to accelerate an adverse reaction that has been found to occur between the chelated metal and the plated surface.
  • the chelated metal content of the wash solution is represented by a metal that is more noble than the plated metal.
  • the reaction involves an electrochemical exchange of metals. This causes corrosion or tarnishing of the less noble metal and a plating out of the more noble metal. For example, cadmium in the Wash solution, being more noble than a zinc plating or coating, would react in such a manner.
  • the invention as devised is carried out in such a manner as to satisfy the chelating compounds hunger for holding a before-used plating metal in solution, where otherwise such metal, under the solution conditions involved, would precipitate as an inert material.
  • This hunger is satisfied by providing or adding one of a class of metals of low nobility that will serve as an exchange medium with the plating metal that is chelated or held by the chelating agent, whether it is copper, cadmium, tin, zinc, nickel, silver or other more noble plating metal.
  • Such exchange agent is provided in the used Wash solution in excess or over a stoichiometric amount to reduce the soluble more noble metal content to not greater than 4 to 5 mg./l. which represents the optimum maximum that is permissible without resultant adverse reaction with the plated surfaces of a workpiece.
  • the chelate-held metal or metal present in the actual plating solution are earlier soluble, since the cyanide content has held them in a complex, whereas Without the cyanide they would be insoluble.
  • the metals are complexed by the relatively small quantity of the chelating agent present, holding a sufiicient proportion or percentage of the plating metal or metals in solution as to give rise to the difli'culty.
  • each of the metal salts of the class consisting of calcium, magnesium, barium, lithium and aluminum is suitable to satisfy a chelating agent
  • the particular salt that is an optimum for use will depend on thetype of chelating agent and particularly, on the type of metal that is being removed or deleted from the chelating complex. For example, it has been determined that copper in a complex can be exchanged better with magnesium; calcium is better for precipitating cadmium, although lithium and barium are also useful in this connection. However, calcium has been found to be an optimum ingredient for precipitating all the various plating metals.
  • the exchange agent will be provided in excess in the used wash solution to provide a full or maximized exchange reaction with the chelated metal. Any excess does not interfere with the process but may be lost in settling out in the form of sludge.
  • the optimum maximized permissible level of the chelated metal is about 4 to 5 m-g./l.
  • this tolerance level tends to vary with the type of plating metal.
  • the upper limit which at least minimizes the trouble caused by chelated metal is about to mg./l.
  • the tolerance limit is not more than about 5 mg./l., while with cadmium the tolerance limit is in the 10 to 15 mg./l. range.
  • Trouble from chelated copper may appear as low as about 3.56 mg./l. and will fully disappear below this level, while trouble with cadmium will fully disappear at or below about the 7 mg./l. level.
  • the reference to noble and less noble metals is a designation based on the order of the metals in the electromotive series, an electrochemical tabulation that ranges metals in order of their tendency to react with water and acids, wherein a given metal has the property of displacing from solution those below it (or less nobility) in the series and is, in turn, displaced by those above it (of greater nobility) in the series.
  • the exchange metals are preferably added to the wash solution in soluble form, although they may also be added as a suspension of their insoluble salts. For simplicity of operation, the soluble form can be metered more easily. Also, it is advantageous to use the chloride of the salt, since the drag-out containing wash water has been chlorinated and consists mainly of chlorides in view of the chlorine reaction with cyanide.
  • a separate treatment tank for each of a group of plating system or lines may be provided for collecting the wash solution or recovery dip which is used to remove the drag-out plating solution from surfaces of the workpieces, it is desired to combine the treatment solutions in a single reservoir for pumping back to the individual treating wash or recovery dip baths or zones in the individual process lines. Initial separation is needed due to the presence of unprecipitated metals. Using an individual treatment wash station and providing a sufficiently large reservoir solution combining tank, it is possible to precipitate the various metals and settle them out before a solution is returned to each of the lines for reuse.
  • suflicient residual metal ions remain in a used treatment wash solution, as produced and reconditioned in the manner shown in FIG. 1 of US. Patent No. 2,725,314, even after the retention time provided by a final mixing reservoir tank, such as to interfere with trouble-free use of the reconstituted solution in washing the drag-out from surfaces of workpieces being processed in individual systems or lines, thus causing staining and discoloration of freshly plated metal surfaces.
  • a final mixing reservoir tank such as to interfere with trouble-free use of the reconstituted solution in washing the drag-out from surfaces of workpieces being processed in individual systems or lines, thus causing staining and discoloration of freshly plated metal surfaces.
  • relatively small quantities of dissolved or soluble cadmium or copper in the aqueous washing solution will cause a corrosive action on such plated surface, since both cadmium and copper are more noble than zinc.
  • a first treatment solution maintained at a pH of about 13.1 and containing 1800 mg./l. of free chlorine and a dissolved copper concentration of about 3.56 mg./l. will produce an appreciable staining of the surfaces of workpieces that have been, for example, plated with zinc, aluminum or other less noble metal.
  • Another or second solution which on analysis had a pH of 13, a free chlorine concentration of 2800 mg./l. and a dissolved cadmium concentration of 570 mg./l. caused objectionable results on, for example, a zinc-plated surface. Such contaminants are representative of the dissolved metal contents of typical operating lines.
  • the first example represents a situation that occurs when both a zinc plating and a copper plating line or system are being used and the wash solution of such lines has been reconditioned and combined in a reservoir for individual reuse.
  • the second example is illustrative of a situation where a plant employs a zinc plating line and a cadium plating line.
  • Another object has been to develop a treatment of Washing solutions used in cyanide plating systems or lines that will enable contaminated or used wash treatment solutions to be taken off, reconditioned and combined or combined and reconditioned, and reused indiscriminately as aqueous wash treatment solutions in any or all of the lines, without producing an adverse reaction on or staining previously plated surfaces of workpieces.
  • a further object of the invention has been to reconstitute or recondition metal cyanide containing used aqueous waste treatment solutions in such a manner that they can be most effectively reused for washing-off and removing drag-out on surfaces of workpieces in individual plating lines without damaging previously plated surfaces.
  • a still further object of the invention has been to provide means for making the metal content of a used wash water innocuous for subsequent washing utilization, particularly as applied to the washing of a surface that is coated with a dilferent metal.
  • the drawing is an illustrative schematic of a treating line or system that may be employed in accordance with principles of the invention.
  • chelating agents or compounds are currently being used as addition agents to metal plating solutions, including those employed in zinc, cadmium, copper, brass and other plating processes and employed at a high pH level at which an in-line-cyanide chlorination system such as set forth in the above-mentioned patent can be used.
  • Chelating compounds or agents such as those previously specifically mentioned by way of example, have a preferential bonding action with lower nobility metals and especially with calcium. Such agents appear to have a tighter bond with the calcium ion, thus allowing precipitation of the cadmium, copper, nickel and other metal salts.
  • a factor existing in the desired reaction is the presence of relatively high concentrations of sodium carbonate such that calcium salts are added would normally be insoluble unless the chelating agents or compounds would solubilize them. It appears that the exchange reaction takes place either with precipitated calcium or other metal carbonate or with the soluble calcium or other metal salt before it is precipitated from the wash water or solution. It has been found that sodium of potassium carbonates are always present in such waste treatment solutions in view of the fact that a cyanide type plating bath are operated at a high pH, as attained by use of caustic soda or caustic potash. Both the latter chemicals undergo some decomposition to carbonates taking carbon dioxide from the air. Also, the cyanide chemicals are continuously partially oxidized to carbonates as one of the final breakdown products of a cyanide compound.
  • a metal displacing salt of the class consisting of calcium, barium, lithium, magnesium and aluminum is applied in an excess quantity to a used aqueous treatment wash or waste solution of a typical content that contains a chelating agent to exchange dissolved salts of metals, such as those of copper, cad mium, nickel, silver and lead.
  • the exchange is accomplished by precipitating, making inert or dissolving-out such more noble metal contaminants by using the calcium or other less noble metals as an innocuous exchange substitute therefore in the solution.
  • the treatment processing of the invention may be applied either to individually taken-off and collected washing solutions from different plating systems or lines before such solutions are combined in a reservoir, but preferably at the time they are combined, so that the exchange may be all inclusive as to the mixed wash Waters to make them fully reconditioned for reuse in any or all of the plating lines or systems, indiscriminately without danger of corroding, damaging or discoloring plated surfaces of workpieces moving along such systems or lines.
  • the specific requirements as to the quantity or amount of exchange chemical can be more easily calculated from the standpoint of its application to an individual wash solution that contains a specific type of metal contaminant, no adverse results are encountered in adding an excess of exchange salt to a mixed wash solution containing several types of metal contaminants. In other words, for example, if calcium chloride is being used, suflicient of it will be provided in the treatment solution reservoir or tank -E (see the drawing) to avoid going below the stoichiometric requirements of a desired exchange operation.
  • a used wash treatment solution containing alkali metal hydroxides and alkali metal carbonates and cyanide treatment carryover residue of a cyanide plating bath having a pH within a range of about 10.5 to 14 which has been treated with free chlorine results in the presence of an alkaline metal hypochlorite in the amount of at least 50 mg./l.
  • the calcium or other exchange salt may be added either continually or periodically to the taken-off used solution to effect transition of the dissolved metal compounds into insoluble metal compounds. This results in the precipitation of such metal salts from the solution.
  • A illustrates the last treating tank in a work process line where, for example, a cyanide solution is employed.
  • the work line 10 may be a continuous strip denoting the travel path of the work process line, with tank B serving as a recovery dip for the cyanide solution which is returned to the tank A through line 11.
  • tank C the work line or piece 10 is shown as being given a toxic carryover treatment wash and, in tank D, as being given a fresh water rinse.
  • Overflow 14 controls the level of solution in tank C and has a branch line 15 returning the solution to the reservoir B through a header 35 and main line 15a.
  • a liquid chlorine container F is provided to, with the solution of container G, renew the solution in container or reservoir E.
  • Water may be continuously supplied to the rinse tank D from a source 16 and discharged to a sewer through line 17. Overflow 18 maintains the level of solution in the tank and may also discharge into the sewer through line 19.
  • main return flow line 21a is connected to an overflow return 20 of the reservoir E and that the solution moves along the main return line 21a as aided by pump 34 into a common header 36 and from thence into at least one branch return line, such as line 21.
  • Chlorine from liquid container F may be supplied by line 26 where it is fed to control valve 27 of a chlorinator 27a as a gas and out through a recorder 27b, connector 28 to connector 24 to discharge through lines 25 and 29 into the reservoir E.
  • main outflow line 22 which removes used solution from the tank C through the agency of the pump 23, is shown as applied only to one representative treatment wash tank C, it will be apparent that it, like the outflow line 15, may be connected by a header (not shown) with branch lines from other treatment wash tanks C of other processing lines (not shown).
  • the present application fully incorporates the disclosure of the Lancy U.S. Pat. No. 2,725,314, including the showing of the FIG. 1 diagrammatic layout.
  • the only change in such a layout needed (see the drawing of the present application) to carry out the present invention is to use a solution container corresponding to G for a less noble metal salt, such as for a calcium, lithium, barium, magnesium or aluminum chloride, and to employ a pump 30 in a line, such as 31, for introducing the salt in solution form into treatment solution reservoir E. If the container G for such salt is, however, located above the reservoir E, gravity flow may be employed.
  • used treatment wash solution such as from a tank or bath C of each of a group of lines for applying different plating metals
  • used treatment wash solution may be taken-off, as by lines 15, 15" and 22 leading from the treatment wash tank (corresponding to C) of each line, and introduced into a treatment reservoir E.
  • a single reservoir E as a treatment reservoir for a mixture of the washing solutions taken from the group of workpiece treating lines.
  • the overflow return shown may be connected to a common header 36 of line 21a for a group of return lines 21, 21 and 21", one for the treatment washbath or tank C of each individual line of the group of lines for plating different metals.
  • a suitable return flow pump corresponding to the pump or a suitable centrifugal pump 34 may be utilized in the common outflow header for the main return line 21a or an individual pump may be used in each branch line 21, 21' and 21".
  • the treating or reconditioning of used wash treatment solutions from one or a group of treatment wash baths, zones or tanks, such as C may be continuously effected in accordance with the procedure, with a continuous return flow of reconstituted or reconditioned solution being supplied to each tank.
  • a metal salt of low nobility such as calcium metal
  • the salt may be employed fully for all of the used solutions, irrespective of the more noble metal that is being plated in a particular electroplating line.
  • the second plating line may have a separate treat ment reservoir similar to E for therein reacting its replacement salt with the chelated metal and for providing a full reconditioning treatment using the chlorine and caustic reactants.
  • the base metal salts that are employed as exchange ingredients for chelated plating metal may be employed in the used treating solution either singularly or as a mixture of one or more of the specified class of less noble metals. ⁇ Whether one or more metal salts are used, the criterion is that all of them should be of a less noble metal than the plating metal that is to be removed from a dissolved condition in the used solution.
  • the exchange ingredient introduced into the wash water solution comprises a salt of a metal of the class consisting of calcium, lithium, barium, aluminum and magnesium.
  • aqueous waste treatment solution is collected, recondi tioned, and reused; the reconditioning being effected by employing neutralizing chemicals in the solution for neutralizing the drag-out taken from the surfaces of the workpiece, and by adding the exchange metal salt to the solution after the solution has been collected and before it is reused.
  • the pH of the solution taken-ofit' in used condition is within the range of about 10 to 15 and chlorine and an alkaline metal are added thereto to enrich it for reuse
  • the less noble exchange metal salt is of the classconsisting of calcium, lithium, barium, aluminum and magnesium
  • the plated surface of the workpiece is of the class consisting of tin, copper, brass, cadmium, silver and nickel.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Removal Of Specific Substances (AREA)
  • Chemically Coating (AREA)
US11004A 1970-02-12 1970-02-12 Integrated waste water treatment for reusage after cyanide type plating Expired - Lifetime US3682701A (en)

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US (1) US3682701A (enExample)
JP (1) JPS5015733B1 (enExample)
BR (1) BR7100945D0 (enExample)
CA (1) CA929839A (enExample)
GB (1) GB1323750A (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3956121A (en) * 1973-11-15 1976-05-11 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler Process for the precipitation of heavy metal ion-polycarboxylate complexes

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5460919U (enExample) * 1977-10-05 1979-04-27
DE3169600D1 (en) * 1980-12-12 1985-05-02 Interox Chemicals Ltd Process for detoxification
JPS6153445U (enExample) * 1984-09-13 1986-04-10

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3956121A (en) * 1973-11-15 1976-05-11 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler Process for the precipitation of heavy metal ion-polycarboxylate complexes

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JPS5015733B1 (enExample) 1975-06-07
GB1323750A (en) 1973-07-18
BR7100945D0 (pt) 1973-04-19
DE2049369B2 (de) 1975-05-15
CA929839A (en) 1973-07-10
DE2049369A1 (de) 1971-09-02

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Owner name: LANCY INTERNATIONAL, INC., 525 WEST NEW CASTLE ST.

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