Technology to detoxify cyanogen/cyanide

Cyanogen/cyanide is fatally poisonous material but it is widely used because of its superior chemical characteristics. Cyanogen is a simple compound of carbon and nitrogen. So it happens to generate in manufacturing process even without using it intentionally. We must change the way we tackle cyanogen/cyanide according to its form of existence, volume of waste water treated, density and co-existing materials.

Solution to treat cyanogen/cyanide in waste water

There are following methods to treat cyanogen/cyanide in waste water.

  1. Oxidation decomposition (Alkaline chlorination・Ozoneoxidation・Electrolysic)
    Waste water with cyanogen/cyanide is mostly treated by alkaline chlorination method. Cyanogen is transformed to cyanic acid by feeding sodium hypochlorite according to ORP meter’s instruction when pH is over 10 (first stage). Then cyanic acid is decomposed into nitrogen and carbon dioxide at around neutral pH under ORP meter’s instruction, thus cyanogen/cyanide is detoxified. This system is suited to the treatment of waste water with cyanogen/cyanide of concentration density around 100 mg/L. It can decompose cyanogen complex bonded to metals except the ones of iron and nickel. It is impossible to decompose cyanogen complex [Fe(CN)64-, [Fe(CN)63-)
  2. Table of equipment to treat cyanogen/cyanide by alkaline chlorination method

    Type Model Capacity of reaction tank(L)Treatment capacity (m3/batch)(m3)
    Batch typeAQB-CN-CL-100010000.8
    Continuous typeAQC-CN-CL-1000
    Continuous typeAQC-CN-CL-2000
    Batch typeAQB-CN-CL-500050004.0
    Continuous typeAQC-CN-CL-5000
    Batch typeAQB-CN-CL-10000100008.0
    Continuous typeAQC-CN-CL-10000
    Batch type AQB-CN-Custom-made Custom-made
    Continuous typeAQC-CN-Custom-made Custom-made
  3. Insoluble complex method (Prussian blue method, Zinc white method, Reduced copper method)
    It is impossible to treat waste water containing iron cyanogen complex ([Fe(CN)6]4-) by the method 1 described above.
    So by using the nature that Fe2[Fe(CN)6] is a poorly-soluble compound, cyanogen/cyanide is precipitated as insoluble compound by feeding ferrous ion and removed from waste water. While Prussian blue method has a disadvantage that it generates sludge containing cyanogen/cyanide, the method has also an advantage that ferrous sulphate is inexpensive and iron cyanogen complex can be removed.
    Recently Prussian blue attracts an attention as a material able to immobilize radioactive cesium (Cs). Waste water with cyanogen/cyanide contains ammonia because cyanogen is easily hydrolyzed to form ammonia, Zinc chloride used for zinc white method is expensive. Besides the process has difficulty in controlling zinc content under 2mg/L of regulatory value because residual zinc generates complex with ammonia. So the process is suited to treatment of waste water with low concentration cyanogen/cyanide.
    Product:We would like to deal with only custom made product in this categiry.Though we have various experiences with Insoluble Complex Method,products supplied shall be of custom-made.
  4. Hydrothermal reaction(Thermal hydrolysis method・Wet oxidation method))
    This method is suited to treatment of waste water of high concentration cyanogen/cyanide (5000mg/L〜2000mg/L). When the waste water with cyanogen/cyanide is kept in autoclave at high temperature (170〜260℃), hydrolysis reaction occurs, as formulas (1) and (2).and cyanogen/cyanide decomoses. Most coexistihg metals precipitate as simple substances (Au,Pt,etc) or oxide (Fe3O4 etc).Some metals form ammonia complex and dissolve in water. (Fe3O4

    NaCN + 2H2O = HCOONa + NH3 (1)
    Na4Fe(CN)6 + 2NaOH + 11・H2O + 1/6・O2 = 6NH3 + 6HCOONa +1/3・Fe3O4 (2)
    Advantages of this method
    @No chemicals are required to decompose cyanogen/cyanide because it is a reaction with water
     APrecious metals can be recovered as simple substances.
    (3)This method is unexpectedly energy-saving and the running cost is low because latent heat of vaporization is low and thermal recycled heat recovered since the reactiom is carried out inside the pressure vessel.
    (4)Possible to easily decompose iron cyanogen complex which alkaline chloride method cannot deal with.
    (5)Possible to efficiently treat waste water with high concentration cyanogen/cyanide.
    (1)Necessary to treat ammonia and formate of organic sludge generated as by-products.
    (2)High equipment cost
    (3)Difficult to treat ammonia complex formed from generated anmonia and copper,nickel,zinc and such by conventional method(hydroxide method)

  5. Table of equipment for waste water treatment with cyanogen by thermal hydrolysis method (Batch type)

    Type of processModel Capacity of reaction vessel(L)Treatment Capacity(m3/batch)
    Batch typeAQB-CN-TH-100010000.7
    AQB-CN-  Custom-made Custom-made

    Table of equipment for waste water treatment with cyanogen/gyanide by thermal hydrolysis method (continuous type)

    Type of processModel Capacity of reaction vessel(L) Treatment capacity(m3/Hr)
    Continuous typeAQC-CN-TH-100010000.25
    AQC-CN-  Custom-madeCustom-made

  6. Microorganism treatment
    Suited to waste water treatment with low concentratio cyanogen/cyanide
  7. . Others
    Phase consult us about treatement measures or analyzing technologies for hydrogen cyanide gas and sludge containing cyanogen/cyanide.

    Plant in operation to detoxify cyanogen/cyanide       Equipment to detoxify cyanogen/cyanide

Peripheral technologies for treatment of cyanogen/cyanide

When cyanogen/cyanide is decomposed by thermal hydrolisis,ammonia and formic acid are formed. Aquatech has high-level know-how and experiences on peripheral technologies for treatment of cyanogen/cyanide and can provide appropriate and safe operation methods.

  1. Technology to remove metal ion coexisting with cyanogen
  2. Measures to treat anmonia generated from cyanogen/cyanide
    • Ammonia stripping and catalytic decomposition
    • Nitrification and denitrification with microorganism
  3. Measures to treat hydrogen cyanide gas
    • Gas absorption with scrubber
    • Catalyfic decomposition technology

Recovery of precious metals by treatment technology of cyanogen/cyanide

In detoxification of cyanogen/cyanide,it is necessary to recover sludge remaining in reaction vessel. Aquatech provides technologie to decompose high concentration cyanogen/cyanide with pipe-type thermal hydrolysis reactor and recover precious metajs efficiently.

Experiments and research on cyanogen/cyanide, design and manufacturing of treatment equipment

We conduct treatment experiments and contracted research on cyanogen/cyanide,including small size autoclave experiments possible to carry out and experiments on oxidative decomposition and insoluble complex method. Besides, we design and manufacture treatment equipment, so please feel free to contact us whenever you have any requests.