Coffee Infused Sponge-Foam Removes Harmful Lead And Mercury From Water

Coffee, the perky morning beverage so many of us rely on daily isn’t only good for boosting our energy (and possibly saving us from creating archenemies in those wee hours of the morning), its ground form has actually been found to remove harmful chemicals from contaminated water.

Scientists, led by Despina Fragouli from the Italian Institute of Technology, found that incorporating used coffee grounds in a foam filter can be helpful in removing harmful lead and mercury from water.

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Millions of tons of used coffee grounds are produced by restaurants, beverage industry and common households worldwide each year. While much of the used ground coffee goes to landfills, some of them are used as a biodiesel source, applied as fertilizer or mixed into animal feed. Previous studies have shown that powder made from used coffee grounds can remove harmful heavy metal ions from water. However, these studies called for additional steps to separate the powder from the purified water.

The foam was able to absorb more than five times as much lead by weight as spent coffee powder.

Now, Fragouli and colleagues have come up with a practical way to use spent coffee grounds. The team made a rubbery foam using spent ground coffee and silicone that is able to pull mercury and lead ions from water. They say the spongelike material could be used on a large scale to clean heavy-metal-contaminated water.

The foam was made by mixing finely ground used coffee and a small amount of sugar into a solution of the elastomer acetoxy polysiloxane and a polydimethylsiloxane surfactant. Then the mixture was allowed to dry and polymerize overnight. Next, the researchers dipped the material into warm water to dissolve the sugar crystals, leaving behind pores and yielding a spongy foam that contains 60 to 70% coffee by weight.

To test the innovative foam’s ability to clean dirty water, the researchers immersed the foam in aqueous solutions of varying concentrations of mercury and lead ions for 30 hours. Each gram of the foam is capable of absorbing a maximum of about 13 mg of lead and up to 17 mg of mercury ions. The foam was able to absorb more than five times as much lead by weight as spent coffee powder.

“This makes it realistic to use spent coffee in a large scale application,” Fragouli says.

By using a sufficient amount of foam, it should be possible to remove enough metal ions to meet drinking water standards. We are exploring ways to remove metal ions from the foams without altering their functionality so they can be reused,” she adds.

The team is now planning to produce foams that are fully biodegradable in order to make disposal simpler and more cost effective.