System For Recycling Printed Circuit Boards
A process for recycling printed circuit boards includes pyrolyzing a number printed circuit boards to from an ash. Metals form the circuit boards are separated from the ash by density separation techniques. The metals are formed into a slurry electrode. The slurry electrode and a deposition electrode are placed in an electrolyte bath and the metals are electrorefined to form bars of metal. The slurry electrode is made by combining powderized metals with carbon powder and an ionic liquid to form an electrode paste. The electrode paste is placed inside a container with a screen to form the slurry electrode.
The present invention claims priority on provisional patent application, Ser. No. 61/128561, filed on May 22, 2008, entitled “Printed circuit board Recycling Process” and is hereby incorporated by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCHThis invention was made in the performance of a Cooperative Research and Development Agreement with the Department of the Air Force. The Government of the United States has certain rights to use the invention
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENTNot Applicable
REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGNot Applicable
BACKGROUND OF THE INVENTIONThe fast pace of product life cycles in the electronics and computer industry results in large amounts of obsolete electronic products. These electronic products represent a landfill problem. These products often have heavy metals that can seep into ground water and contaminate water supplies. Recent legislation in Europe, China and several US states now mandate that in the near future electronics' manufactures must to take back their products at the end of the products life. In addition, the stringent rules of many landfills no longer allow these products to be thrown away. One of the main problems in recycling electrical and electronics products is the circuit boards. The circuit boards and their components have most of the heavy metals and may contain lead, mercury, cadmium and chromium. All of which are being strictly regulated. Presently, the only way to separate and extract these metals is to expose the circuit board to high temperatures until the metals vaporize and then the specific heavy metal can be separated and recovered. Unfortunately, this process is expensive, requires a tremendous amount of energy and introduces toxic off gasses into the atmosphere.
Thus there exists a need for a process for recycling circuit boards.
BRIEF SUMMARY OF INVENTIONA process for recycling printed circuit boards includes pyrolyzing a number printed circuit boards to from an ash. Metals from the circuit boards are separated from the ash by density separation techniques. The metals are formed into a slurry electrode. The slurry electrode and a deposition electrode are placed in an electrolyte bath and the metals are electrorefined to form bars of metal.
A process for recycling printed circuit boards includes pyrolyzing a number printed circuit boards to from an ash. Metals form the circuit boards are separated from the ash by density separation techniques. The metals are formed into a slurry electrode. The slurry electrode and a deposition electrode are placed in an electrolyte bath and the metals are electrorefined to form bars of metal.
In operation, the slurry electrode will contain many metals, such as copper, zinc and silver. The deposition electrode will be formed of the metal that has the lowest oxidation reduction potential, for example copper. The voltage will be increased until a current starts to flow. This results in the copper in the slurry electrode 52 being plated onto the deposition electrode 58. Once all the copper in the slurry electrode 52 is removed, the copper deposition electrode will be removed. Next a zinc electrode will be used as the deposition electrode. This is because the oxidation reduction potential of zinc is less than that of silver. The voltage is increased until current starts to flow. This results in the zinc in the slurry electrode being plated onto the deposition electrode 58. Once all the zinc is removed, the process is repeated for the silver using a silver electrode.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.
Claims
1. A process for recycling printed circuit boards, comprising the steps of:
- pyrolyzing a plurality of printed circuit boards to form an ash;
- separating a plurality of metals from the ash; and
- electrorefining the plurality of metals, to form a plurality of pure metal bars.
2. The process of claim 1, wherein the step of electrorefining includes the step of creating a slurry electrode.
3. The process of claim 2, wherein the step of creating a slurry electrode includes mixing the plurality of metal with a carbon powder to form a electrode powder.
4. The process of claim 3, further including the steps of mixing the electrode powder with an ionic liquid to form an electrode paste.
5. The process of claim 4, further including the steps of placing the electrode paste in an electrode container having a screen.
6. The process of claim 1, wherein the step of electrorefining includes the steps of creating an ionic liquid of choline chloride ethylene glycol.
7. The process of claim 1, wherein an anode and a cathode of the electrorefining step are stacked vertically.
8. A process for electrorefining a plurality of metals comprising the steps of:
- combining a plurality of metals in powder form with a carbon powder to form an electrode powder;
- mixing the electrode powder with an ionic liquid to form an electrode paste;
- placing the electrode paste in a holder to form a slurry electrode;
- placing a deposition electron next to the slurry electrode in an electrolyte bath; and
- applying a voltage between the slurry electrode and the deposition electrode.
9. The process of claim 8, wherein the step of combining the plurality of metals in powder form includes the step of grinding the plurality of metals.
10. The process of claim 8, wherein the step of applying the voltage includes the step of increasing the voltage until a current exceeds a predetermined threshold.
Type: Application
Filed: May 20, 2009
Publication Date: Nov 26, 2009
Inventors: James Carl Dills (Monument, CO), Dale B. Halling (Colorado Springs, CO), John S. Wilkes (Larkspur, CO), Sandra Trott (Colorado Springs, CO)
Application Number: 12/469,015
International Classification: C25C 1/00 (20060101); C25C 7/02 (20060101);