Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing single metal
Reexamination Certificate
2000-08-25
2002-04-09
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing single metal
Reexamination Certificate
active
06368489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to copper electrowinning, which is a low current density, oxygen evolving application. The copper can be electrowon utilizing a modified lead electrode. The modified electrode is suitable for use as an oxygen anode in copper electrowinning.
2. Description of the Related Art
Lead or lead alloy anodes have been widely employed in processes for the electrowinning of metals, such as copper, from sulphate electrolytes. These lead anodes, nevertheless, have important limitations such as undesirable power consumption and anode erosion. This anode erosion can lead to sludge production and resulting contamination of electrolyte, as well as contamination of the plated product, e.g., lead contamination of a copper plated product.
Therefore, it was proposed to make a composite anode from a sintered article of one metal, e.g., titanium, which article is infiltrated with the other metal, e.g, lead. These anodes have been proposed, for example, in U.S. Pat. No. 4,260,470. The titanium can be ground, compressed and sintered to prepare a titanium sponge as a porous matrix. This matrix is then infiltrated with molten lead or lead alloy. The object is first to provide planar anodes in the form of strips. The strips are then joined together in a parallel, co-planar array to provide a large sheet anode. The patent teaches employing these anodes particularly for use in electrowinning zinc or copper from sulfate electrolytes.
It has also been proposed to prepare catalytic particles of a metal such as titanium, which particles are activated with a platinum group metal. These particles are then uniformly distributed over, and partly embedded within, the surface of an anode base of lead or lead alloy. The lead plate is thus covered with a layer of these particles, such as of activated titanium sponge particles. Such an anode has been disclosed in U.S. Pat. No. 4,425,217.
It has also been proposed to use a lead substrate as a support structure. This support structure provides a surface that may engage another member, e.g., a valve metal expanded metal mesh. As disclosed in U.S. patent application Ser. No. 09/273,981, the mesh member has a front and back surface with the back surface facing the lead support structure. At least the front surface of the mesh member is an active surface. Securing of the mesh member to the lead support structure in electrical connection permits the lead support structure to serve as a current distributor for the mesh member. The mesh member may engage the surface of the lead support structure as by pressing or rolling the mesh onto the lead.
It would, however, be desirable to provide an electrode for such service having improved lifetimes and provide voltage savings without this being offset by a prohibitive cost due either to a high cost of the electrode materials or a high production cost or a combination of these.
SUMMARY OF THE INVENTION
There has now been found an electrode, which provides improved lifetimes and voltage savings, both of which may be coupled with enhanced current efficiency during cell operation, while remaining cost effective. The electrode is especially beneficial to the electrowinning industry by providing significant voltage savings compared with conventional lead anodes, substantial elimination of sludge formation resulting in less downtime for cleaning of cells and fewer environmental disposal problems. Additionally, the purity of the plated product is improved.
In one aspect, the invention is directed to a process for electrowinning of copper from a solution in an electrolytic cell comprising at least one anode, with there being oxygen evolution and cell voltage savings during said electrowinning, which process comprises:
providing an unseparated electrolytic cell;
establishing in the cell a sulfate electrolyte containing the copper metal in solution;
providing an anode in the cell in contact with the electrolyte which anode has a lead base and a metal mesh surface member, which metal mesh surface member has a broad, coated front face and a broad back face that faces the lead base, with the coated front face having an electrocatalytic coating consisting of palladium oxide and ruthenium oxide constituents in a proportion of from at least about 50 mole percent up to about 99 mole percent ruthenium and at least about 1 mole percent palladium up to about 50 mole percent palladium basis 100 mole percent of these metals present in the coating;
impressing an electric current on the anode; and
conducting the electrowinning at an applied current density of below about 1 kA/m
2
.
In another aspect, the invention is directed to a process for electrowinning copper from a solution in an electrolytic cell comprising at least one anode, with there being oxygen evolution and cell voltage savings during said electrowinning, which process comprises:
providing an unseparated electrolytic cell;
establishing in the cell a sulfate electrolyte containing the copper metal in solution;
providing an anode in the cell in contact with the electrolyte which anode has a lead base and a metal mesh surface member, which metal mesh surface member has a broad, coated front face and a broad back face that faces the lead base, with the coated front face having an electrocatalytic coating consisting of rhodium oxide and ruthenium oxide constituents in a proportion providing from at least about 0.5 mole percent up to about 50 mole percent rhodium and at least about 50 mole percent up to about 99.5 mole percent ruthenium basis 100 mole percent of these metals present in the coating;
impressing an electric current on the anode; and
conducting the electrowinning at an applied current density of below about 1 kA/m
2
.
In yet another aspect, the invention is directed to a process for electrowinning a metal from a solution in an electrolytic cell comprising at least one anode, with there being oxygen evolution and cell voltage savings during said electrowinning, which process comprises:
providing an unseparated electrolytic cell;
establishing in the cell an electrolyte containing the metal in solution;
providing an anode in cell in contact with said electrolyte which anode has a lead base and a metal mesh surface member, which metal mesh surface member has a broad, coated front face and a broad back face that faces the lead base, with the coated front face having an electrocatalytic coating consisting of palladium oxide and ruthenium oxide constituents in a proportion of from at least about 50 mole percent up to about 99 mole percent ruthenium and at least about 1 mole percent palladium up to about 50 mole percent palladium, basis 100 mole percent of these metals present in the coating;
impressing an electric current on the anode; and
conducting the electrowinning at an applied current density of below about 1 kA/m
2
.
In a still further aspect, the invention is directed to a process for electrowinning a metal from a solution in an electrolytic cell comprising at least one anode, with there being oxygen evolution and cell voltage savings during the electrowinning, which process comprises:
providing an unseparated electrolytic cell
establishing in the cell an electrolyte containing the metal in solution;
providing an anode in the cell in contact with the electrolyte which anode has a lead base and a metal mesh surface member, which metal mesh surface member has a broad, coated front face and a broad back face that faces the lead base, with the coated front face having an electrocatalytic coating consisting of rhodium oxide and ruthenium oxide constituents in a proportion providing from at least about 50 mole percent up to about 99.5 mole percent ruthenium and at least about 0.5 mole percent rhodium up to about 50 mole percent rhodium, basis 100 mole percent of these metals present in the coating;
impressing an electric current on the anode; and
conducting the electrowinning at an applied current density of below about 1 kA/m
2
.
In a still further aspect, the invention is directed to an electrode for use in a lo
Brown, Jr. Carl W.
Ernes Lynne M.
Hardee Kenneth L.
Bell Bruce F.
Eltech Systems Corporation
Hudak & Shunk Co. L.P.A.
Tyrpak Michele M.
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