Abstract: 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.

Abstract: A highly reliable detoxifying method of the cyano matters is provided. The waste-liquor (1), which contains at least one of free cyano matters, 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 boiling point, and which includes a high temperature range of 80° C. or more, followed by holding the temperature (7); oxidation-reduction potential of the waste liquor is measured from the room temperature; and, hypochlorite (2) is intermittently or continuously added to the waste liquor from the room temperature, until the oxidation-reduction of the the hypochlorite is detected.