Lancy flush

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A lancy rinse , also known as a reduction rinse , is a detoxification rinse used in electroplating . Toxic buildup on workpieces, especially cyanide or chromate (VI) , is not simply rinsed off with water, but converted into less toxic substances through chemical reactions.

functionality

After chrome plating in a chromium (VI) electrolyte , which is almost exclusively used for chrome plating , detoxification takes place in the Lancy rinse with dithionite or bisulfite, which is built up as a level rinse or immersion rinse . It is reduced to the less toxic chromium (III). The successful detoxification is easy to control because the color change from the toxic chromium (VI) to the less toxic green chromium (III) is clearly visible.

After coating in an electrolyte containing cyanide , for example copper (I) cyanide or zinc cyanide , it can be oxidized with sodium hypochlorite in the detoxification rinse . Whether the complete cyanide oxidation has taken place via the intermediate stage of the cyanate can be seen from the evolution of gas ( carbon dioxide ).

Possible disadvantages

The oxidation of cyanides with sodium hypochlorite can create problematic organic halogens (AOX) as a by-product.

Historical

The name "Lancy flush" goes back to the inventor Leslie Emery Lancy, who received a patent in 1955 for a detoxification treatment system that was described under the name "integrated process". The corresponding company Lancy Laboratories Inc. in Zelienople, Pennsylvania , then also obtained a patent for rendering toxic waste water intact, e.g. B. 1964 a patent for the removal of chromate from cooling water. It received further patents for the detoxification of electroplating waste water and products, e.g. B. for the detoxification of solutions with cyanide (1969) or workpieces contaminated with chromate (1970).

The Lancy flush was used e.g. B. implemented in the 1960s in several US electroplating plants (1961–1962 in a plant in Columbia (South Carolina) , 1964–1965 in Fayetteville (Arkansas) and 1964–1966 in Kalamazoo ) and was then distributed internationally.

Individual evidence

  1. ^ Günter Dietrich: Hartinger Handbook Abwasser- und Recyclingtechnik . Carl-Hanser-Verlag, 2017, page 375; limited preview in Google Book search.
  2. ↑ Chemical rinses. In: European Commission: Integrated Pollution Prevention and Control Reference, Document on Best Available Techniques for the Surface Treatment of Metals and Plastics. European Comission, August 2006, accessed October 1, 2019 .
  3. ↑ Patent US2725314 : In Line Treatment of Toxic Carry-Over of Work Pieces. Registered January 29, 1955 , published November 29, 1955 , inventor: Leslie Emery Lancy. ‌
  4. ↑ Patent US3294680 : Treatment of Spent Cooling Waters. Applied on November 18, 1964 , published December 27, 1966 , Applicant: Lancy Laboratories, Inc., Inventor: Leslie Emery Lancy. ‌
  5. ↑ Patent DE1517682 : Process for the detoxification of wastewater containing cyanide and iron cyanide complex salts. Filed June 20, 1963 , published August 28, 1969 , applicant: Lancy (originally misspelled "Lany") Laboratories, Inc., inventor: Leslie Emery Lancy. ‌
  6. ↑ Patent US3475219 : Bright Treatment for Workpieces Having Toxic Carryover. Filed July 12, 1966 , published October 28, 1969 , applicant: Lancy Laboratories, Inc., inventor: Leslie Emery Lancy. ‌
  7. ↑ Patent US3537896 : Beneficial after-treatment of work pieces. Applied on September 23, 1968 , published November 3, 1970 , applicant: Lancy Laboratories, Inc., inventor: Walter Nohse, Gunter Fischer. ‌
  8. ↑ Neal Schreur: Lancy Integrated System for treatment of cyanide and chromium wastes at electroplating plants . In: Purdue University (Ed.): Engineering bulletin . Engineering extension series no. 129, Proceedings of the 22nd Industrial Waste Conference May 1967. Volume 52 , no. 3 . Lafayette July 1968, p. 310-316 ( online at Purdue University Libraries [accessed October 1, 2019]): "This method is the simplest and most foolprof to operate."