Classifications

• • 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

Definitions

• the invention relates to a method for electrolytic detoxification or regeneration of an aqueous solution containing cyanide, wherein cyanide is converted into carbon dioxide and / or nitrogen and / or ammonia by means of anodic oxidation, and to an apparatus for carrying out the method.
• the concentration of the cyanide being greatly reduced by anodic oxidation to ammonia and, at the same time, the silver in spongy form deposited on the cathode, periodically stripped from there and collected in a funnel arranged at the bottom of the regeneration cell and filtered.
• the anode has a titanium-platinum plating, while the cathode contains a pure silver plating, so that here too the problem of the high removal rates of platinum-plated titanium electrodes arises with the consequently high consequential costs.
• the invention is based on the object of treating the high loads of cyanide wastewater occurring in the metal industry, in particular in electroplating plants, at low cost by electrochemical means, high power yields being possible even at low concentrations and further detoxification processes being unnecessary; Furthermore, a device for electrolytic detoxification or regeneration of an aqueous solution containing cyanide is to be specified; the service life of the anodes is also to be increased.
• a major advantage of the method is that, due to the high efficiency, a rapid reaction sequence is achieved, whereby both the electricity costs and the electrode costs (coating costs) can be kept relatively low.
• Another advantage is achieved by reusing the cathodically deposited metallic part from the cyanide compound.
• the invention is achieved according to the device by the characterizing features of claim 8.
• a major advantage of the device is that the anode enables a long service life due to its dimensionally stable structure and high durability of its coating. Furthermore, the size of the device and thus the system costs can be kept relatively low due to the high efficiency.
• an electrochemical cell with a solution container which has an attached cell housing in which there is an electrode packet with elongated plate-shaped electrodes arranged in parallel and spaced apart, whereby the anodes are in the middle and the cathodes are arranged at the ends.
• the cathode consists of an expanded metal grid made of copper-plated titanium (copper surface), while the anode is designed as a dimensionally stable anode based on titanium, the electrocatalytic coating of which consists of oxides of platinum group metals and / or titanium and of platinum group metals.
• the basic structure of such anodes is known for example from DE-PS 20 41 250.
• the volume of the Solution tank is in the range of 50-1000 l; the anodic current density is in the range of 100-2500 A / m2.
• the electrode spacing is in the range of 0.5-5 cm.
• the reaction takes place at a temperature in the range of 20-50 ° C.
• the electrolytic detoxification is carried out until a final concentration of cyanide of 0.2 mg / l and copper of 0.1 mg / l is reached.
• Example 1 When treating a solution corresponding to Example 1 with added copper in the range of 10-500 mg / l copper ions, it is also possible to carry out the first treatment phase (1st trip) with a cathode made of expanded titanium without a copper-coated surface or copper coating.
• the copper additive is added either in the form of copper sulfate (solid or dissolved) or in the form of a wastewater solution containing copper ions.
• the other process parameters of Example 1 and the known structure of the dimensionally stable anode and electrode spacing are retained.
• an electrochemical device with a dimensionally stable anode according to Examples 1 and 2 which has a cathode made of expanded copper foil.
• the electrochemical treatment is carried out until a silver ion concentration is reached which is below 0.1 mg / l; the residual cyanide concentration after the demetallization is 8.6 g / l of free cyanide ions.
• the other process parameters, such as anodic and cathodic current density, electrode spacing and temperature correspond to those of Example 1.
• the demetallized solution thus obtained can be detoxified either by the process according to Example 1 or by the process given below as Example 4.
• a silver cyanide solution with elaborated silver (silver ion concentration below 0.1 mg / l) and 8.6 g / l free cyanide is fed to a correspondingly constructed electrochemical cell, the cathode of which is made of copper-plated expanded titanium. Current density and electrode spacing as well as operating temperature are maintained in accordance with the aforementioned examples.
• the electrolytic detoxification (anodic oxidation) is carried out until a cyanide content of 0.1 mg / l can be measured.
• solution is supplied to the cell housing in the region of its housing base by means of a circulating device and, after passing through the electrode pack, is fed to a cascade-like drain container with its own overflow for degassing by means of an overflow over the side walls of the cell housing; After passing through a second overflow, the now largely degassed solution is returned to the solution tank and recirculated and subjected to an electrochemical treatment until the desired or legally prescribed residual concentration is reached.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrolytic Production Of Metals (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6460670

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (2)

Family Cites Families (4)

• 1992
  • 1992-06-10 DE DE19924218916 patent/DE4218916C2/de not_active Expired - Fee Related
• 1993
  • 1993-03-16 EP EP93104209A patent/EP0573743A3/fr not_active Withdrawn
  • 1993-06-07 CA CA 2097869 patent/CA2097869A1/fr not_active Abandoned
  • 1993-06-10 JP JP5138711A patent/JPH06101081A/ja active Pending

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