Classifications

• • 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
  • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
  • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
• • 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
  • C25D21/08—Rinsing
• • 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
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2101/00—Supply or distribution of decentralised, dispersed or local electric power generation
  • H02J2101/20—Dispersed power generation using renewable energy sources
  • H02J2101/28—Wind energy
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S210/00—Liquid purification or separation
  • Y10S210/902—Materials removed
  • Y10S210/903—Nitrogenous
  • Y10S210/904—-CN containing

Definitions

• This invention relates to the treatment or conditioning of aqueous solution carry-over, such as adheres to metal workpieces or articles, for removing or neutralizing its toxic material content.
• a phase of the invention deals with maintaining workpieces having easily tarnished or oxidized metal surfaces in a bright condition or inhibiting their oxidation while quickly and effectively conditioning the aqueous solution carry-over to make it non-toxic or innocuous.
• Another phase of the invention deals with an improved toxic carry-over conditioning solution.
• the difficulty has been to provide some approach to the problem that will meet all the factors involved; that will not adversely effect the removal or neutralizing procedure or cause surface staining of the workpieces, e.g., from the standpoint of adverse reaction with the chemicals or the reaction products of a neutralizing solution conditioning of the toxic carry-over, of making reconditioning-recirculation of the solution impractical, of limiting the concentration of the conditioning chemicals, of requiring an increased time period to complete the removal of the toxic material such as to make continuous in-line treatment impractical, and from the standpoint of surface-oxidizing difficulties during movement of the workpieces to a water washing or rinsing station or at such station.
• a treatment of copper, copper alloy (including brass) and silver surfaces of workpieces that have been subjected to a cyanide-type plating process is to rinse them in a solution containing an alkaline metal hydroxide, such as caustic soda, to provide a pH of about 8 to 14, with the introduction of chlorine to oxidize the cyanide.
• an alkaline metal hydroxide such as caustic soda
• Such rapid decomposition is important from the standpoint of safety of the operation, in that when the treated solution is to be recirculated from the treating tank it may be returned for use again in the treatment tank.
• the change must be rapid enough to avoid cyanide drag-out from the treatment tank and also insure faster flow through the treatment tank and to minimize any delay in flow from the reservoir tank. It is imperature that the cyanides be substantially completely destroyed or removed from the carry-over of the workpieces.
• a heretofore limiting or offsetting factor as to the concentration of the chlorine or other treating chemical used is that a freshly treated or plated copper, cuprous alloy or silver surface is prone to discoloration due to the oxidation as, for example, in a high chlorine concentration solution. It has thus been necessary to limit the chlorine solution concentration in the aqueous toxic removing or neutralizing solution for workpieces having such a type of surface to under 500 mg./l. and to under about mg./l. of chlorine for silver surfaces. Even under such limitations and with some alloys difficulty was encountered, in that a slight tarnishing or darkening of the surfaces resulted with uneven oxidation leading to streakiness, etc.
• Such a chemical is not only stable in a chlorinated solution, but also in an alkaline solution employed to neutralize work emerging from an acid pickling, brightening, or plating solution, where the workpieces are being subjected to a wash in a neutralizing treatment solution to which caustic soda and soda ash have been added and which solution may be operated at an elevated temperature.
• the inhibitor enables the full necessary concentrations of chlorine and other chemicals without adversely effecting their reactions or slowing down the processing.
• an inhibitor such as 1, 2, 3 benzotriazole, allows an increased range of treatment solution concentration, and limits or minimizes control requirements by widening the margin for safe operation. It minimizes controls while, at the same time, leads to faster oxidation of cuprous cyanide and silver cyanide solution complexes that are normally slow in their decomposition.
• cyanide compounds such as those of sodium, potassium, zinc or cadmium are decomposed in a matter of minutes, in comparison to those of copper, cuprous alloys and silver. It has been discovered that increasing the chlorine concentration in the treatment solution to hasten the oxidation reaction of the cyanide compounds will also effect the tendency to oxidize the metallic surface carrying the toxic chemical film solution that is to be broken down or neutralized.
• the oxidizing tendency of the chlorine in a chlorinated treatment solution or of the air when the metal surface is subjected to a neutralizing solution of high pH alkaline metal hydroxide, and especially at an elevated temperature, is overcome by the protection provided by the inhibitor and the invisible organo-metallic compound that is formed in view of the inhibiting action described.
• the chemical break-down of a cyanide solution is as follows:
• the conventional treatment has been to rinse the workpieces after acid pickling, brightening or plating in a neutralizing solution containing caustic soda and soda ash, using a reducing agent, such as sodium hydrosulfite (Na2S O to limit oxidation of the bright copper surface by air, by the caustic soda or by remaining oxidizing chemicals such as nitrates residual from a pickling process.
• a reducing agent such as sodium hydrosulfite (Na2S O to limit oxidation of the bright copper surface by air, by the caustic soda or by remaining oxidizing chemicals such as nitrates residual from a pickling process.
• sodium hydrosulfite sodium hydrosulfite at a concentration of about 500 mg./l. and to maintain the caustic soda and soda ash content to yield a pH of about 8 to 11.
• the copper salts dragged-in from the acid processing are then precipitated as cuprous oxide.
• Sodium hydrosulfite is a relatively expensive chemical, costing at the present time in the neighborhood of about twenty-five cents per pound, and it is readily consumed due to the quantity of copper processed, and also due to the fact that it is lost from oxidizing action of nitrate ions and, with air, itself, as the solution is aerated.
• Incorporating a chemical inhibitor in accordance with the present invention enables the complete elimination of sodium hydrosulfite in the make-up of the treating solution, to thereby greatly reduce the cost.
• An organic inhibitor chemical has been found to be relatively stable and to need only minimized replenishment, even in a continuous in-line process with treating solution recirculation, such as contemplated.
• caustic soda and soda ash may be made up to yield a pH of 8 to 14 which is a much wider and more desirable range than heretofore possible with sodium hydrosulfite and it is thus easier to control.
• Benzotriazole is incorporated in the aqueous solution in an effective working range of concentration of .10 to 1 g./ 1.
• An optimum range of this chemical in a treating solution after toxic cyanide or acid treating or processing has been found to be about .1 to .2 g./ 1. It produces a film on the workpieces that is invisible.
• the toxic compounds under consideration, dealing with copper and silver treating solutions, are the cyanides, such as alkali metal cyanides and metal complex cyanides, such as cuprous cyanide, silver cyanide, and cyanides of zinc or nickel when treating copper alloys containing these metals.
• the cyanide, itself, is oxidized by the chlorination reaction.
• the copper becomes insoluble in a cuprous hydroxide or cuprous carbonate form.
• a high chlorine concentration or a high pH, elevated temperature, caustic soda concentration accomplishes the same results.
• Cupric oxide is less soluble in water and is more inert when the solid waste is discarded, considering the possible toxic effect of precipitated sludges.
• cuprous cyanide by, itself, is insoluble as is silver cyanide.
• Such cyanide complexes are made soluble in a solution containing additional alkali metal cyanide compound. This means that for the dissolution of one mole of cuprous cyanide, an additional mole of sodium or potassium cyanide is needed.
• silver cyanide It has been determined that when oxidizing a chemical solution containing alkali metal cyanides and copper or silver cyanide complexes, the alkali metal cyanide may be decomposed with an insufficient concentration of chlorine; and, in view of the loss of alkali metal cyanide, cuprous cyanide will fall out as an insoluble compound in a precipitate.
• cuprous or silver cyanide would remain as an insoluble solid in the sludge.
• insoluble cuprous cyanide and silver cyanide the condition of insolubility is not an absolute one. Even though less than one mg./l. of cuprous or silver cyanide would be soluble in rain water or in the river where the sludges may be carried, this range of solubility is still suflicient to create a toxic condition.
• aqueous chemical neutralizing solution directly to the toxic carry-over on the workpieces under relatively high oxidizing conditions in the first treating zone during their movement therethrough and substantially completely neutralizing the toxic carryover of the workpieces in such zone, providing about .1 to 1 g./l. of benzotriazole in the aqueous chemical neutralizing solution and maintaining it in a stable condition with respect to the chemical content of the solution and to the content of the carry-over on the workpieces and to reaction through the second zone and while washing-01f their surfaces in the second zone.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Electrochemistry (AREA)
• Mechanical Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Inorganic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• ing And Chemical Polishing (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Chemically Coating (AREA)

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Citations (7)

• 0
  • NL NL137512D patent/NL137512C/xx active
• 1966
  • 1966-07-12 US US564550A patent/US3475219A/en not_active Expired - Lifetime
• 1967
  • 1967-01-31 GB GB4741/67A patent/GB1120675A/en not_active Expired
  • 1967-02-17 DE DE19671621613 patent/DE1621613A1/de active Pending
  • 1967-02-20 CH CH245167A patent/CH496101A/de not_active IP Right Cessation
  • 1967-03-17 AT AT260467A patent/AT272792B/de active
  • 1967-07-11 NL NL6709586A patent/NL6709586A/xx unknown

Patent Citations (7)

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