Removal of cyanide from aqueous streams
AssigneeThe BOC Group, Inc.
InventorJohn Rakszawski
Life of this patent
Estimating the term…
Abstract
Cyanide present in aqueous streams, such as effluents from electroplating and gold mining operations is reduced or eliminated by contacting the cyanide-containing stream with oxygen and carbon dioxide in the presence of ferrous ions, nickelous ions or cobaltous ions. The oxygen may be provided by air or oxygen and the contacting is carried out until the pH of the aqueous stream is reduced to a value in the range of about 6 to 8 and preferably 6.5 to 7.5.
Claims20
A method of reducing the concentration of cyanide in a cyanide-containing aqueous stream comprising contacting the aqueous stream in a reaction zone with an oxygen-containing gas and carbon dioxide in the presence of a water-soluble catalyst comprising ferrous ions, nickelous ions, cobaltous ions or mixtures of these.
A method of reducing the concentration of cyanide in a cyanide-containing aqueous stream comprising contacting the aqueous stream in a contacting zone with an oxygen-containing gas and carbon dioxide in the presence of a water-soluble catalyst containing the Fe.sup.++ ion, the Ni.sup.++ ion, the Co.sup.++ ion or mixtures of these, the concentration of said oxygen-containing gas in the contacting zone being sufficient to provide an oxygen concentration in the range of about 0.02 to about 20 moles per mole of cyanide present in said aqueous stream, the amount of carbon dioxide added to the aqueous stream being sufficient to reduce the PH of the aqueous stream to a value in the range of about 6 to about 8, and the amount of water-soluble catalyst present in the contacting zone is at least about 0.2 mole per mole of cyanide ion present in the aqueous stream.
A method of treating aqueous gold mining tailings effluent to destroy residual cyanide contained in said effluent comprising contacting said effluent in a contact zone with an oxygen-containing gas and carbon dioxide in the presence of a water-soluble ferrous metal catalyst until the pH of the effluent reaches a value of about 8 or less.
Dependencies are inferred from the claim text.