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The EPFL Valais “sponge” that extracts gold from water to become a start-up

Tuesday 25 January 2022

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The molecular sponge capable of recovering gold residues from wastewater will become a start-up launched on the Energypolis campus.

Although gold can be found in a number of different sources, such as electronic waste, seawater, freshwater, wastewater and sewage sludge, there is currently no material that can selectively extract gold from such complex environments.

In 2018, Professor Wendy L. Queen's lab at EPFL Valais developed a "sponge" that can extract gold from various complex liquids. The porous material, called Fe-BTC/PpPDA, consists of a "metal-organic framework" (MOF) and polymer building blocks and has a very large internal surface area, allowing it to adsorb up to one gram of gold per gram of material.

At present, research on this innovation is ongoing at the Energypolis campus in Sion (canton of Valais).

"Our goal is to bring this invention to the market, by finding industrial applications that promote the recycling and reutilization of gold," explains Olga Trukhina, a postdoctoral researcher at the Functional Inorganic Materials Laboratory at EPFL Valais. This compound is intended in particular for industries involved in the refining of precious metals. It should enable them to capture the gold contained in their liquid waste streams - particularly in their wastewater - in order to reintegrate it into their production cycle. "Global mining is one of the largest contributors to carbon emissions today. Facilitating the extraction of gold from complex waste streams will help reduce emissions from this sector."

A pilot demonstrator and a start-up

The various tests carried out with Swiss and foreign companies have highlighted the fact that during its use, the sponge can sometimes be subjected to very acidic liquid solutions. It must also be able to extract gold from huge quantities of iron, copper, nickel, lead and other heavy metals.

"Our objective is to adapt this compound to these different conditions," explains Olga Trukhina. "The next phase of the project will be to create a pilot demonstrator with industrial partners. We also hope to create a start-up company."

The recovery of metals contained in electronic waste such as smartphones and computers is also among the other potential sectors of application of this technology.

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