Needless to say, humans have a coffee obsession.
Last year, global coffee consumption weighed in at 10 million tons — or one and half Great Pyramids worth of beans ground into caffeinated oblivion. Now, a lab at the Italian Institute of Technology wants to put those discarded grounds to good use.
The team has engineered a coffee grounds-infused foam that removes hazardous metals, like lead, from water. Though still in its prototype phase, this foam might be able to clear the worst levels of lead contamination found in places like Flint, Michigan, within a few hours.
“The proposed method is cheaper [than current large-scale filtration systems], since it uses principally costless waste,” said IIT physicist Despina Fragouli who led the project. “and more sustainable compared to other systems, where synthetic materials are used.”
The idea isn’t entirely new. Scientists have known for years that coffee contains chemical groups — called carboxylates — that stick to metals. Early attempts at this water remediation concept tried smashing the coffee grounds into a fine powder, which was then mixed into lead-tainted water. The toxic metals bind the powder, and together, they are filtered out of the water. But this procedure is a bit redundant — you need a filter for a filter.
Fragouli and her colleagues simplified this process by chemically infusing the coffee powder onto a elastic foam. The final spongy foam is 60 to 70 percent coffee by weight.
“Both the coffee and the heavy metal ions are entrapped in the foam,” Fragouli said of her findings published in ACS Sustainable Chemistry and Engineering. “Therefore, no additional procedures are required for the removal of the [coffee] adsorbents and the pollutants from the water.”
So, a water official would simply pull the foam from the water to take out the metal toxins. The rate of removal depends on how much lead is in the water. If Fragouli’s team started with water containing nine parts per million of lead — 360 times higher than most common amount found during the Flint water crisis — the foam could remove a third of the contamination in 30 minutes.
Though promising, Fragouli said more research is needed to determine if the foam can obtain lead and mercury levels appropriate for drinking, especially with gunky water flowing through real-world pipes. So far, the sole field test occurred with wastewater from the IIT’s chemistry department, which contained a mixture of metal ions.
“The results show that the metal ions of interest can be effectively removed,” Fragouli said.
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