The process of circuit board recycling
A circuit board recycling has high copper content. A great majority of printed circuit boards contain at least 1 ounce of copper per square foot but the PCB’s that handle higher power often have 2 to 3 ounces of copper. Circuit board recycling follows a process of recovery for copper and other valuable metals from the edge trim. The edge trim is initially treated with a stripping solution so that the precious metals will dissolve. Typically, the precious metals include gold, silver or platinum. Suitable reductants are added so that the ions of precious metals will be transformed into metal. Gold that is recovered through circuit board recycling can be further processed to that it can be commercially transformed into potassium gold cyanide. After the precious metals have been recovered, the edge trim is further processed in order to recover copper.
Wastewater sludge in the production of circuit boards also contains high amounts of copper which is recovered through circuit board recycling. The recovery process is generally simple and straightforward. The sludge is heated to 600 – 750oC so that excess amount of water can be removed and copper hydroxide can be converted to copper oxide. Recovered copper oxide is sold to smelters for the production of copper metal.
Copper can also be recovered from the etching process since the etching solution contains about 130 to 150 g/L of copper. In circuit board recycling, the spend solution is adjusted into a weak acidic condition so that most of the copper ions will be precipitated out as copper. The process is somewhat similar to the recovery of copper in wastewater sludge. The copper that remains in the filtrate is recovered through selective ion exchange resins.
Improvements in circuit board recycling
The commercial recycling process of wastes in the circuit board industry focuses on the recovery of copper and other valuable materials. While the recycling process is economically sustaining, various research activities are dedicated to the improvement of recycling technologies. The average price of copper has risen significantly due to the imbalance of supply and demand that is why improvements are being made in the recycling process to increase the supply of copper. As previously discussed, copper in wastewater is recycled in the form of copper oxide to be sold to smelters but there is another option where copper oxide particles are directly prepared from wastewater. This will lead to significant improvements in the quality of the recycled product. Copper oxide can be used in the preparation of high temperature semi-conductors including magnetic storage media, catalysts, pigments, gas sensors and cathode materials.