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Altered milk protein cleans up pollution: amyloid fibers can snatch heavy metal contaminants from water.

Tenacious proteins similar to those implicated in Alzheimer's disease could help purify polluted water.

A newly designed membrane uses thin amyloid protein fibers to pull heavy metals and radioactive wastes out of water. The membranes can capture more than their own weight in some contaminants, scientists in Switzerland report online January 25 in Nature Nanotechnology.

"What's really interesting in this study is that it actually used a protein material, which is novel," says Qilin Li, an environmental engineer at Rice University in Houston. The team converted milk proteins into fibers of durable amyloid protein. Other amyloids are infamous for building up in the brains of Alzheimer's patients, but the team put its amyloids' sticky tendrils to different use.

When paired with strong, porous carbon in a membrane, the lab-made amyloids successfully filtered over 99 percent of toxic materials out of solutions that mimicked severely polluted waters, the scientists report. The amyloids trapped particles of lead and mercury at a molecular site that is involved in turning the original milk protein into amyloid fibers. Radioactive waste particles also got tangled in the membranes. And the membranes snagged gold contaminants, which the team found could later be recovered and purified. A membrane with less than 6 milligrams of amyloids could trap 100 milligrams of gold.

It's exciting to see that the amyloids can hold more than their own mass in heavy metal particles, Li says. More typical membrane materials, she says, would grab only a fraction of their weight.

The membranes could be developed for small- or large-scale water purification units, says study coauthor Raffaele Mezzenga of ETH Zurich. He estimates the technology would cost roughly $1 per every thousand liters of water filtered. And a membrane can recover hundreds of times its own value in precious metals, Mezzenga says. The simple, flexible membrane design could be adjusted to optimize cleanup or metal recovery, he says.

Li says the membranes need to be tested in real polluted waters, which may have chemical complications such as high or low acidities. But the amyloids' performance is encouraging, she says.

Caption: Cleanup crew A new amyloid-carbon membrane filtered over 99.9 percent of lead pollutants out of a contaminated solution, bringing the overall concentration of lead to below a measurable threshold of 0.02 parts per million. SOURCE: S. BOUSETTY AND R. MEZZENGA/ NATURE NANOTECHNOLOGY 2016


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Title Annotation:EARTH & ENVIRONMENT
Author:Schwartz, Sarah
Publication:Science News
Geographic Code:1USA
Date:Feb 20, 2016
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