Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Reexamination Certificate
2000-01-07
2001-09-25
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
C205S721000, C205S772000, C205S580000, C205S581000, C205S585000
Reexamination Certificate
active
06294071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods of dissolving copper into electrolytic solutions, and more particularly, to methods of accelerating copper dissolution into aqueous electrolytic solutions, such as those comprising nitrogen compounds. Specifically, this invention relates to methods of supplying an anodic current to copper or copper-containing metal that is in contact with an electrolytic solution comprising an amine (such as 2-aminoethanol or 2-hydroxyethylamine) and carbon dioxide, for example, by galvanic coupling with a material having a more positive reduction potential than copper (or the copper-containing metal) given the respective electrolyte conditions present at the copper (or copper-containing metal) and present at the galvanically coupled material. Copper-containing solutions thus formed may be useful, for example, as wood preservatives and for water treatment.
2. Description of Related Art
Copper-containing aqueous solutions are commonly used as biocidal fluids, for example, for pressure treating lumber and for water purification. Examples of such fluids and uses thereof may be found, for example, in U.S. Pat. No. 4,929,454. Such solutions may be formulated by dissolving copper into aqueous solutions containing alkyl amines or alkyl hydroxy amines, such as, 2-hydroxyethylamine. Relatively slow rate of copper dissolution may be a limiting feature in the production of copper-containing solutions. When in contact with aqueous alkanolamine solutions, copper is more active toward corrosion than it is in aqueous solutions which do not contain alkanolamines. However, copper is a poor catalyst for oxygen reduction. The presence of carbon dioxide may increase the solubility of copper in aqueous alkanolamine solutions, but the dissolution rate of copper may still be relatively slow.
In one conventional batch process for producing copper-containing amine solutions, approximately five days is required to achieve the target copper concentration (i.e., about 8%). Such a process may include, for example, placing copper metal into an aqueous solution containing 2-hydroxyethylamine and carbon dioxide at elevated temperature, while sparging with air.
SUMMARY OF THE INVENTION
Disclosed herein are methods and apparatus for forming copper-containing solutions, including methods and apparatus for accelerating the dissolution of copper into aqueous solutions and/or increasing the ultimate concentration of copper in such solutions. In one embodiment, disclosed is a method for increasing the rate of copper dissolution into an electrolytic solution containing one or more nitrogen compounds by supplying an anodic current to copper or copper-containing metal that is in contact with the electrolytic solution. An electrolytic solution may include at least one nitrogen compound (such as an aqueous solution containing alkanolamine), and an anodic current may be supplied by electrically coupling a metal comprising copper with a material acting as a cathode, i.e., capable of supplying an anodic current to the copper. Supplemental anodic current may be supplied to the copper metal by electrically coupling an optional power source to the copper metal, if so desired. Besides nitrogen compound/s, the aqueous solution may also include dissolved carbon dioxide and/or oxygen.
In one embodiment, the bulk of the cathodic reaction (e.g., oxygen reduction) may advantageously occur at the surface of a cathode material (e.g., a second cathode metal), instead of taking place on the surface of a first copper metal. To further enhance copper dissolution rate and reduce the solution formulation time, a material may be selected which functions catalytically as well as galvanically to accelerate copper dissolution. Combination of catalytic and galvanic enhancement may be used to result in vastly improved dissolution time and efficiency. For example, metals of relatively high oxygen reduction capacity compared to copper (e.g., such as silver) may be galvanically coupled to copper metal/s to cause an increase in copper dissolution rate. Besides silver, other metals having a reduction potential higher than the reduction potential of copper under the electrolytic conditions employed may be advantageously used, such as stainless steels.
Electrical coupling or contact between a copper containing metal and a cathode material (e.g., a second cathode metal) may be through any suitable electrical conductor through which electrical current is capable of flowing. Electrical contact may be advantageously used to form a galvanic couple between copper metal and a second cathode metal so that the anodic current density of the copper metal is increased, resulting in more rapid dissolution of copper as compared to dissolution rates realized using conventional copper dissolution systems and methods. Further advantageously, the disclosed process also may reduce the corrosion rate of a galvanically coupled second cathode metal, resulting in extension of its useful life.
As an example, in one embodiment, a doubling in copper dissolution rate in amine-containing solutions may be realized as compared to dissolution rates realized using conventional copper dissolution systems. In another embodiment, by increasing dissolved oxygen concentration in the presence of the second cathode metal, up to about thirty-fold increase in copper dissolution may be achieved. Surprisingly and significantly, solution formulation process time may be reduced from a conventional process time of about five days to a reduced process time of about one day, greatly facilitating and reducing the cost of preparing the copper-containing amine solutions. Maximum achievable concentration of dissolved copper in an electrolytic amine-containing solution may be greater than maximum achievable dissolved copper concentration using conventional copper dissolution methods due to greater thermodynamic driving force and shifted equilibrium. Thus, the disclosed method may be used to formulate a more concentrated copper-containing solution than would otherwise be achievable using conventional methods.
In another embodiment, an anodic current may be applied to a copper metal, either alone or in combination with galvanic coupling described elsewhere herein. Such an anodic current may be applied by electrically coupling a positive voltage of a power source to a copper metal and by coupling a negative voltage of the power source to a suitable counterelectrode. Advantageously, such an anodic current may be applied in addition to galvanic coupling to provide increased galvanic driving force for copper dissolution, in addition to catalytic enhancement of dissolution.
In another embodiment, a continuous flow process may be advantageously employed to produce copper-containing solutions without need for batch processing and reducing overall process time. In such an embodiment, a reaction vessel may be sized and dimensioned to optimize dissolution of copper ions into solution during a single pass through the reaction vessel to achieve the desired copper ion content.
In yet another embodiment, a second cathode material having a reduction potential that is greater than copper (given the respective electrolyte conditions present at the copper anode and the cathodic material cathode) may be electrically or galvanically coupled to a first copper metal while at the same time being located in a separate vessel and/or solution than the copper metal. The separate vessels or solutions may be in ionic communication by virtue of, for example, an electrolyte bridge which may or may not be sealed with an ion permeable membrane. Advantageously, by providing separate environments for a first copper metal and a second cathode metal, solution and operating conditions in the vessel containing the cathode metal may be optimized to increase, for example, oxygen reduction conditions, while allowing separate optimization of copper oxidation conditions in a separate vessel in which the copper metal is contained. Such optimization may be used alone or in combinat
McCoy David Ross
Miller David Lawrence
Huntsman Petrochemical Corporation
O'Keefe Egan & Peterman, LLP
Phasge Arun S,.
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