Method for industrial copper electrorefining

Abstract

A method of copper electrorefining is disclosed. The method includes arranging at least one anode of copper material to be refined in contact with an electrolyte solution and arranging at least one cathode in contact with the electrolyte solution. The anode and cathode are connected electrically to an electrical source, and the source is operated under potential controlled conditions. The electrical potential at the cathode is −0.30 V to −0.55 V with respect to the copper material at the anode, thereby causing the deposition of electrorefined copper at the cathode. The method also includes potentiostatic pulse electrolysis (PPE) and periodic potential reversal (PPR) in order to produce a copper deposit having a controllable structure, for example in terms of roughness or porosity. An apparatus for performing potential controlled electrolysis is also disclosed.

1 . A method of industrial copper electrorefining comprising, arranging at least one anode of copper material to be refined in contact with an electrolyte solution; arranging at least one cathode in contact with the electrolyte solution; electrically connecting the anode and cathode to an electrical source, and operating the electrical source under electrical potential controlled conditions such that during at least part of the application of the said conditions, the electrical potential at the cathode is −0.30 V to −0.55 V with respect to the copper material at the anode, thereby causing the deposition of electrorefined copper at the cathode. 
     
     
         2 . A method according to  claim 1 , wherein the electrical potential controlled conditions include the application of complex form potential. 
     
     
         3 . A method according to  claim 2 , wherein, during the said conditions, one or more of the magnitude and polarity of the electrical potential are modulated. 
     
     
         4 . A method according to  claim 3 , wherein the electrical potential is modulated as a rectangular waveform having a magnitude of the electrical potential at the cathode of between −0.30 V and −0.55 V. 
     
     
         5 . A method according to any of  claims 1  to  3 , wherein the said conditions include potentiostatic pulse electrolysis (PPE) conditions in which a number of cathodic pulses in the range 3 to 300 are applied, each having a substantially constant potential in the range −0.30V to −0.55V with reference to the copper material at the anode, and each having a duration of between 5 and 18000 seconds, wherein the pulses are separated in time by open circuit breaks, each having a duration in the range 0.1 to 100 seconds. 
     
     
         6 . A method according to any of  claims 1  to  3 , wherein the said conditions include periodic potential reversal (PPR) conditions in which a cathodic pulse having a potential in the range −0.30 V to −0.55 V, with reference to copper material anode is applied for a duration in the range 5 to 18 000 seconds, the cathodic pulse being followed by an anodic pulse in the range of +0.05 V to +0.60 V, with reference to the copper material anode, whereby the duration of the anodic pulse is shorter than the cathodic pulse by at least 50% and wherein the sequence formed from the cathodic pulse and anodic pulse is repeated from 3 to 30 times. 
     
     
         7 . A method according to any of  claims 1  to  3 , wherein the said conditions include periodic potential reversal (PPR) conditions in which a cathodic pulse having a potential in the range −0.30 V to −0.55 V, with reference to copper material anode is applied for a duration in the range 5 to 18 000 seconds, the cathodic pulse being followed by an anodic pulse in the range of +0.05 V to +0.60 V, with reference to the copper material anode, whereby the duration of the anodic pulse is shorter than the cathodic pulse and wherein open circuit conditions are applied for a period between the cathodic and anodic pulses and the sequence formed from the cathodic pulse and anodic pulse is repeated from 3 to 30 times. 
     
     
         8 . A method according to  claim 7 , wherein the said open circuit conditions are applied twice during the sequence as the potential is reversed. 
     
     
         9 . A method according to any of the preceding claims, wherein the said at least one anode and at least one cathode are arranged as at least one pair and wherein the distance between the cathode and anode in a pair is 5 cm or less. 
     
     
         10 . A method according to any of the preceding claims, wherein the current efficiency of the process is 95% or more. 
     
     
         11 . A method according to any of the preceding claims, wherein an electrolyte comprising 90 g/dm 3  to 200 g/dm 3  H 2 SO 4  and 1 g/dm 3  to 50 g/dm 3  Cu is used. 
     
     
         12 . A method according to any of the preceding claims, wherein the method is carried out at the temperature of 18° C. to 65° C. 
     
     
         13 . A method according to  claim 12 , wherein the method is carried out at a temperature of 18° C. to 30° C. 
     
     
         14 . A method according to any of the preceding claims, further comprising, initially forming the said at least one anode from a fire-refined, scrap or recycled copper material. 
     
     
         15 . A method according to any of the preceding claims, wherein the method is performed using a cathode made of stainless steel or copper. 
     
     
         16 . A method according to any of the preceding claims, further comprising causing the electrolyte to be in motion with respect to the anode and cathode during the electrorefining. 
     
     
         17 . A method according to any of the preceding claims, wherein the electrolyte is substantially free of any organic additive. 
     
     
         18 . A method according to any of the preceding claims, wherein the refined copper has a purity in excess of 99.95%. 
     
     
         19 . An industrial copper electrorefining system comprising:
 a container for retaining an industrial electrolyte;   at least one first electrode formed from copper material to be refined and being positioned within use in contact with the industrial electrolyte within the container;   at least one second electrode positioned within use in contact with the industrial electrolyte within the container; and,   a power supply operable under electrical potential controlled conditions and connected electrically when in use to each of the said at least one first and at least one second electrodes, such that during at least part of the application of the said conditions, the electrical potential at the at least one second electrode is −0.30 V to −0.55 V with respect to the copper material at the at least one first electrode, thereby causing the deposition of electrorefined copper at the at least one second electrode.   
     
     
         20 . A system according to  claim 19 , further comprising an electrolyte management system arranged to control the movement of the electrolyte within the tank and to modulate the composition of the electrolyte during the electrorefining process. 
     
     
         21 . Apparatus according to  claim 19  or  claim 20 , further adapted in use to perform the method according to any of  claims 1  to  18 .