Electrochemical reactor for copper removal from barren solutions

A method for treating a barren solution from a precious metal mill to free complexed cyanide and remove heavy metal contaminant and recover the heavy metal in sheet form comprising:

• passing a barren solution containing cyanide ions complexed with heavy metal, said barren solution being recovered from a precious metal mill, through a porous cathode and across the surface of an anode of a first electrochemical cell, said cathode comprising a porous material having a high electrochemically active surface area per unit volume and stable in acid and alkaline media when used cathodically and anodically, and said anode being impermeable to said barren solution,
• maintaining a potential difference between said cathode and said anode to effect electrochemical deposition of said heavy metal in said porous cathode to form a heavy metal loaded cathode and a treated solution rich in free cyanide and poor in heavy metal,
• recovering said solution rich in free cyanide,
• removing the heavy metal loaded cathode from said cell and disposing said loaded cathode in a second electrochemical cell containing an aqueous electrolyte, as an anode of said second cell, said second cell having a sheet metal cathode,
• establishing a potential difference between said anode and cathode of said second cell effective to dissolve the heavy metal from the anodic loaded cathode in the electrolyte and redeposit the dissolved heavy metal as a sheet on said sheet metal cathode, and
• removing the sheet of heavy metal from said sheet metal cathode.

An apparatus for treating a barren solution from a precious metal mill to remove heavy metal contamination and free complexed cyanide comprising:

• an electrochemical cell having an anode and a porous cathode therein, said anode being impermeable to the barren solution,
• an inlet for flow of barren solution contaminated with heavy metal and containing complexed cyanide into said cell, and an outlet for discharge of treated solution rich in free cyanide and poor in heavy metal from said cell,
• a flow path in said cell extending from said inlet to said outlet,
• said porous cathode being disposed in said flow path for flow of solution therethrough and said anode defining a wall of said flow path for flow of solution thereagainst.