A highly reliable detoxifying method of the cyano matters is provided. The waste-liquor, which contains at least one of free cyano material, a cyano complex and a reducing compound exhibiting volatility in alkaline aqueous solution, is heated under an alkaline condition to a temperature range, which lies within a range of from room temperature to the boiling point, and which includes a high temperature range of 80° C. or more, followed by holding the temperature; oxidation-reduction potential of the waste liquor is measured from the room temperature; and, hypochlorite is intermittently or continuously added to the waste liquor from the room temperature, until the oxidation-reduction of the hypochlorite is detected.

Method for treating cyanide waste liquid

PURPOSE:To perfectly and inexpensively decompose cyan by subjecting a cyan compd., a nitrogen compd. or the like in waste water to wet oxidation treatment in the presence of oxygen and separating and removing sludge and/or metal components from the treated soln. and adding sulfuric acid, sulfur or the like to the treated soln. before applying wet oxidation treatment thereto. CONSTITUTION:The cyan-containing waste water from a waste water storage tank 1 is mixed with the oxygen-containing gas from a compressor 22 to be supplied to a primary reaction tower 5. The quantity of oxygen added to this waste water is set to below theoretical oxygen quantity necessary for decomposing a cyan compd., a nitrogen compd. or the like into harmless products. The treated soln. issued from the reaction tower 5 is sent to a gas-liquid separator 6 through a heat exchanger 3 and a cooling tower 7 and the separated liquid phase component 10 is separated into a primary treated soln. 12 and a solid 3 by a solid-liquid separator 11 and a part of the primary treated soln. 12 is allowed to meet with the treated soln. of the reaction tower 5 and the remainder thereof is sent to an intermediate storage tank 16 and mixed with sulfuric acid supplied from a sulfuric acid storage tank 14. The resulting soln. mixed with oxygen-containing gas is sent to a secondary reaction tower 20 packed with a catalyst and subjected to wet oxidation treatment.

Heihachi Takahashi

Papers

Treatment of waste water containing metal cyan complex ion