Scientists already know that powder made from spent coffee grounds can be used to rid water of harmful heavy metal ions … that's all well and good, but the powder then needs to be filtered out of the water. A group of Italian scientists has developed a step-saving alternative, in the form of a filter made of coffee-impregnated foam.

Led by Despina Fragouli of Genoa's Istituto Italiano di Tecnologia, the researchers created a foam filter made from 60 percent spent coffee powder (by weight) and 40 percent silicone elastomer.

Sitting in still, contaminated water, the material removed up to 99 percent of lead and mercury ions from the water over a period of 30 hours. In a setup where tainted water flowed through the filter, the foam took out up to 67 percent of the lead ions. And, unlike the case with loose coffee powder, the filter could just be pulled out and discarded after use.

The research is described in a paper that was recently published in the journal ACS Sustainable Chemistry & Engineering.

If other projects are anything to go by, one could almost be surprised that coffee grounds are still simply disposed of at all. Among other things, they've been shown to be an effective carbon capture medium, sustainable road material, biofuel, sewer gas filter, and a source of useful succinic acid.