Removing heavy metal pollutants from water could soon be easier than ever, thanks to an experimental new sponge. With just one treatment, the device brought contaminated water down to safely drinkable levels.
Building upon two previous studies, the technology is being developed by scientists at Illinois' Northwestern University.
The researchers started out with a cheap commercially available cellulose sponge, and placed it in a slurry of manganese-doped goethite nanoparticles. They then removed it, let it dry, and rinsed it with water to flush out any loose particles.
The result was a sponge with a high-surface-area nanoparticle coating that was just tens of nanometers thick. Manganese-doped goethite particles were chosen not only because they adsorb lead ions, but also because they're inexpensive and non-toxic to humans.
When the sponge was immersed in tap water containing more than one part per million of lead, it sequestered lead ions to the point that they were no longer detectable in the water … this made the water safe to drink.
What's more, the lead could subsequently be removed from the sponge by rinsing the latter in mildly acidic water. That reclaimed lead could then conceivably be utilized in products such as batteries, while the rinsed-out sponge was reused to treat more tainted water – it wasn't quite as effective in later cycles, although it was still able to remove over 90% of lead ions from samples.
The scientists have now developed a platform known as Nanomaterial Sponge Coatings for Heavy Metals (Nano-SCHeMe), to guide other teams in selecting different types of nanoparticles for sequestering different types of heavy metals.
"The presence of heavy metals in the water supply is an enormous public health challenge for the entire globe," said Prof. Vinayak Dravid, senior author of a paper on the study. "It is a gigaton problem that requires solutions that can be deployed easily, effectively and inexpensively. That’s where our sponge comes in. It can remove the pollution and then be used again and again."
The paper was recently published in the journal ACS ES&T Water.
Source: Northwestern University
