AQUATECH Co.,Ltd.

Technology to detoxify cyanogen

Cyanogens are fatally poisonous material but it is widely used because of its superior chemical characteristics. Canogen chemical formula 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 according to its form of existence, volume of waste water treated, density and co-existing materials.

Solution to treat cyanogen in waste water

There are following methods to treat cyanogen in waste water.

  1. Oxidation analysis method (alkaline chlorination・ozone・electrolytic method)
    Waste water with cyanogen 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 dissolved into nitrogen and carbon dioxide around pH neutral by ORP meter’s instruction, thus to detoxify cyanogen. This system is suited to the treatment of waste water with cianogen density around 100 mg/L. It can dissolve cyanogen complex coordinate-bonded with metals except iron and nickel. It is impossible to dissolve iron cyanogen complex  [Fe(CN)64-, [Fe(CN)63-)
  2. Table of equipment to treat cyanogen 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
    AQB-CN-CL-200020001.6
    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 described in 1 above.
    So by using the nature that Fe2[Fe(CN)6] makes insoluble compound, we precipitate cyanogen as insoluble compound by feeding ferrous ion and remove cyanogen from waste water. While Prussian blue method has a disadvantage that it produces sludge containing cyanogen, the method has an advantage that ferrous sulphate is inexpensive and it can remove iron cyanogen complex.
    Recently Prussian blue attracts an attention as a material able to solidify radioactive cesium (Cs). Waste water with cyanogen contains ammonia because cyanogen is easily subject to hydrolysis reaction, partly transforming to ammonia, Price of zinc chloride used for zinc white method is expensive. Besides the process has difficulty in controlling zinc content under 2mg/L as regulated because residual zinc creates complex with ammonia. So the process is suited to treatment of waste water with low density cyanogen.
    Product: We would like to deal with only custom-made product in this category, though we have various business experiences.
  4. Hydrothermal reaction(thermal hydrolysis method・wet oxidation method))
    This method is suited to treatment of waste water with high density cyanogen (5000mg/L〜2000mg/L). If the waste water with cyanogen is kept in autoclave at high temperature (170〜260℃), hydrolysis reaction occurs, for instance, as formulas (1) and (2), dissolving to ammonia and formic acid. (Fe3O4

    NaCN + 2H2O = HCOONa + NH3 (1)
    Na4Fe(CN)6 + 2NaOH + 11・H2O + 1/6・O2 = 6NH3 + 6HCOONa +1/3・Fe3O4 (2)
    The advantage of this process
    @No chemicals are required to dissolve cyanogen because it is a reaction with water
     AWhen the quantity of originated precipitate is small and precious metals co-exist with canogen, it is possible to extract precious metal as simple substance.
    (3)The method is energy saving and its running cost is low because latent heat of evaporation is low and thermal recycle is possible since the reaction is originated inside pressure vessel.

    (4)Possible to easily dissolve iron cyanogen complex which alkaline chloride method cannot deal with
    (5)Possible to efficiently treat waste water with high density canogen
    Disadvantage
    (1)Necessary to treat ammonia and organic sludge namely formate generated as by-product (2)High equipment cost
    (3)Difficult to treat by conventional method (hydroxide precipitation method) because generated ammonia forms ammonia complex with copper, nickel and zinc.

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

    Type of processModel Capacity of reaction tank(L)Treatment Capacity(m3/batch)
    Batch typeAQB-CN-TH-100010000.7
    AQB-CN-TH-600060004.0
    AQB-CN-TH-12000120008.0
    AQB-CN-TH-240002400016.0
    AQB-CN-  Custom-made Custom-made

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

    Type of processModel Capacity of reaction tank(L) Treatment capacity(m3/Hr)
    Continuous typeAQC-CN-TH-100010000.25
    AQC-CN-TH-200020000.5
    AQC-CN-TH-600060001.5
    AQC-CN-TH-12000120003.0
    AQC-CN-  Custom-madeCustom-made

  6. Microorganism treatment
    Suited to waste water treatment with low density cyanogen
  7. . Others
    Ask us about means and ways or analyzing technology to treat cyan gas and sludge with cyanogen.

    Plant in operation to detoxify cyanogen       Equipment to detoxify cyanogen

Peripheral technologies for treatment of cyanogen

When cyanogen is dissolved by hydrothermal reaction, it produces ammonia and formic acid. Aquatech has high-level know-how and experience on peripheral technologies for treatment of cyanogen and can provide appropriate and safe operation method.

  1. Technology to remove metal ion coexisting with cyanogen
  2. Measures to treat ammonia generated from cyanogen
    • Ammonia stripping and catalyst degradation
    • Nitrification and de nitrification by microorganism
  3. Measures to treat cyan gas
    • Sucking of gas by scrubber
    • Catalyst degradation technology

Recovery of precious metals by treatment technology of cyanogen

During detoxifying cyanogen, it is necessary to recover sludge remaining in reaction tank. Aquatech dissolves high density cyanogen by pipe-typed hydrothermal reaction method and recovers efficiently precious metals.

Test・research of cyanogen, design・manufacturing of treatment equipment

We conduct treatment test and consigned research for cyanogen, including small sized autoclave test (wet-type oxidation test is possible) and oxidation analysis・insoluble complex method test. Besides, we design and manufacture treatment equipment, so please feel free to contact us whenever you have need.


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