A team of Italian scientists has used old coffee grounds to create a foam that can get rid of lead and mercury from water.
Despite the fact that coffee grounds can be a helpful addition to compost or gardening mixes, a large amount of the leftovers from one of the world’s favourite beverages still ends up in landfill. Once there, the grounds decompose, producing the greenhouse gas methane.
Given that our thirst for coffee isn’t likely to die down anytime soon, ideas for sustainable methods of recycling and upcycling old coffee grounds (and the takeaway cups that coffee is sometimes served in) are taking shape. Scientists have been analysing its effectiveness in water remediation and have had some success in using it to remove heavy metal ions from water. Researchers from the University of Genoa and the Italian Institute of Technology recently took this research a step further, looking to simplify the process and develop a way to remove the coffee powder from water once it had done its job. The result is a foam (or sponge) made out of old espresso coffee grounds, silicone and sugar that could act as a filter.
When dipped in still water, the foam removed 99 per cent of lead and mercury after 30 hours, which sounds great on paper but of far more interest (and potential greater impact) is the test they performed with flowing, lead-contaminated water, where the team found that the foam could remove 67 per cent of lead.
This is not the first time waste has been used to remove heavy metals from water. In 2015, a team of Australian scientists developed a polymer made using waste from the citrus and petroleum industries that could remove mercury from water. These “two-birds-with-one-stone” approaches could provide a solution to certain waste management issues while simultaneously making clean drinking water more widely available.