Winning gold by recycling PCBs
A new process of recovering metals from PCBs is more environmentally friendly than existing techniques – and is very simple.
Professor Derek Fray, of the Department of Materials Science and Metallurgy at Cambridge, says the UK currently generates 50,000 tonnes per annum of PCB scrap, of which only 15% is recycled. Under the EU’s WEEE regulations, now in force, all manufacturers and importers of such equipment will become responsible for the cost of collection, treatment and recycling of such waste generated in the UK from July 1 2007.
Sending the waste to the Far East or Africa is not only socially undesirable but ignores the value of what is being thrown away – especially the copper, tin (in the solder), palladium and gold. There may not be much palladium or gold but because they are so valuable, they equate to £3.13 per kg for the gold and £2.70 per kg for the palladium.
Prof Fray has developed a process that involves dissolving the solder with fluoroboric acid (HBF4), shredding the bared boards, leaching the copper and then burning the remainder in such a way as to catch the bromine. The copper, tin, lead and precious metals are recovered by electrowinning. While HBF4 is a very harsh chemical, the whole process has been progressed to pilot scale and been shown it can be safely operated in a clean environment.
So far, he says, the only serious business interest has come from South Africa.
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