Abstract A process for the destruction of cyanide anions in aqueous solutions is provided using hydrogen peroxide and a soluble metal compound catalyst such as a soluble copper compound to increase the reaction rate. An aqueous composition containing hydrogen peroxide and the catalyst is also provided which can be added directly to the cyanide solution. The pH of the cyanide solution to be treated is adjusted with acid or base to a pH of about 8.3 to 11, the soluble metal compound catalyst is added at a level to give about 5 to 1,000 p.p.m. of catalyst, the hydrogen peroxide is added to give a molar ratio of hydrogen peroxide to cyanide anions of at least about 0.8 and the temperature of the solution is maintained within the range of about 20* to 75* C.
The process of claim 1 wherein the cyanide anions are introduced into the solution of the catalyst and hydrogen peroxide by a cyanide-contaminated metal workpiece zinc coated in an aqueous, alkaline, cyanide zinc electroplating bath.
Claim 2
Dependent Claim
18 words
The process of claim 2 wherein hydrogen peroxide is added incrementally to the solution to maintain its concentration.
Claim 3
Dependent Claim
115 words
A process for the destruction of cyanide anions in an aqueous solution comprising: (a) adjusting the pH of the solution within the range of about 8.3 to 11; (b) adding to the solution a metal compound catalyst soluble therein so that the solution contains from about 5 to 1,000 p.p.m. of catalyst selected from the group consisting of silver, tungsten and vanadium compounds and copper; (c) adding hydrogen peroxide to the solution to give a molar ratio of hydrogen peroxide to cyanide anions within the range of about 0.8 to 1.4; and (d) maintaining the solution at a temperature within the range of about 45* to 66* C. to effect destruction of the cyanide anions.
Claim 4
Dependent Claim
96 words
A process for the destruction of cyanide anions in an aqueous alkaline cyanide solution comprising: adjusting the pH of the solution within the range of about 8.5 to 10.5; adding to the solution cupric salt so that the solution contains from about 5 to 40 p.p.m. of copper; adding hydrogen peroxide to the solution to give a consumed molar ratio of hydrogen peroxide to cyanide within the range of about 0.8 to 1.4 and maintaining the solution at a temperature within the range of about 45* to 66* C. to effect destruction of the cyanide anions.
Claim 5
Dependent Claim
56 words
The process of claim 5 wherein the aqueous, alkaline solution is the effluent from an aqueous, alkaline, cyanide Zinc electroplating bath and the solution, after the cyanide anions are destroyed, is neutralized to a pH within the range of about 7.2 to 7.8 to precipitate zinc solids and the zinc solids are separated from the solution.