Electronic waste, such as discarded mobile phones, computers, and tablets, contains a large number of precious metals including copper, zinc, gold, silver, etc.
Electronic waste has been considered as one of the most important resources of urban mining. However, recovering valuable metals from waste requires lots of efforts and time.
A typical industrial process to recycle metal from waste includes high-temperature burning, smelting of metal, chemical leaching, and further electrochemical treatment.
A drawback of this process is that it only focuses on “clean” waste like batteries and mobile phones after disassembly. How to recover precious metal from mixtures of all kinds of end-of-life electronic waste is unknown.
Now researchers from Netherlands and China solve the problem. In a study newly published in Waste Management, they report an effective method that can extract copper from complex electronic waste.
In their research, copper was selectively recovered using an ammonia-based process. Ammonia is a compound of nitrogen and hydrogen with the formula NH3.
Researchers focused on the role of different ammonium salts during the whole process of copper recovery. The recovery process has two stages: selective extraction of copper from waste and copper electrowinning from the solution.
Researchers compared the reactivity of the leaching solution with different ammonium salts, their physiochemical behavior, and the leaching efficiency.
They found that the copper recovery rate could reach 95% with ammonium carbonate as the leaching salt. When copper was recovered from the solution, electrodeposition (the deposition of a substance on an electrode by the action of electricity) was introduced.
Researchers found that when the electrodeposition was carefully controlled, the recovery efficiency could be improved to 80 – 90%, depending on the ammonia salts and high purity copper (99.9 wt.%).
This research provides a new way to extract and recycle copper from waste, and it may improve electronic waste management. Future work will examine the recovery of other precious metals.
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