Extracting precious zinc from waste ash

But this ash often contains significant amounts of precious metals, such as zinc. A unique method developed by researchers at Chalmers University of Technology, Sweden, can now help extract these precious metals, potentially leading to reductions in environmental pollution, landfill and transport.

During waste incineration, the released flue gases are purified and the small particles present are separated, leading to the formation of fly ash. This fly ash contains toxic substances, such as dioxins, and so is normally classified as hazardous waste and landfilled. But it also contains valuable metals, such as zinc, which are thereby lost.

But a new method from Chalmers University of Technology, tested at pilot scale and detailed over several years of research, involves treating this waste with an acid wash, also separated from the flue gases, to separate the zinc from the fly ash. The zinc can then be extracted, washed and processed into raw material.

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