Scientists have been able to extract useful metals from ash

During waste incineration, flue gases are purified and fine particles are separated, resulting in the formation

fly ash.It contains toxic substances, dioxins, and is therefore usually classified as hazardous waste and disposed of in landfills. But it also contains valuable metals, such as zinc, which are lost during disposal.

But the new method of the University of TechnologyChalmers, tested and detailed over several years of research, involves treating this waste with acid to separate the zinc from the fly ash. The zinc can then be extracted, washed and processed into raw materials.

“In our pilot study, we found that70% of the zinc present in fly ash can be recycled. Zinc is recovered not as a pure metal, but as a zinc-rich product that is useful in the metallurgical industry, ”explains Karin Karlfeldt Fedier, associate professor at Chalmers University of Technology and researcher at recycling and disposal company Renova AB.

By further improving the method, the researchers were able to significantly reduce the toxicity of the waste.

“After metal extraction, we burn againresidual ash to break down dioxins. 90% of this ash is then converted to bottom ash, which, for example, can be used as a building material, ”explains Karin Karlfeldt Fedier.

"Technology for extracting zinc from fly ashcould have several positive effects, such as reduced need for primary zinc mining, reduced ash toxicity levels and a significant reduction in landfill volumes,” concludes Sven Andersson, Associate Professor at Chalmers University of Technology and R&D Manager at Babcock & Wilcox Vølund AB, which deals with flue gas purification.

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