Cleaning Water with Soybean Scraps
AEN News
Washington - The answer to tomorrow's water pollution
problems could come from soybeans, according to Agricultural
Research Service (ARS) scientists. Not from the tender
legumes themselves, but from the overly abundant hulls
that typically end up as a livestock feed.
ARS chemists Wayne Marshall and Lynda Wartelle have
discovered that these undervalued hulls--as well as
leftover stalks and stems from already-plucked corn
and sugarcane plants--make the ideal foundation for
a potent filtering agent that can adsorb harmful
levels of lead, chromium, copper and cadmium from
contaminated waters.
Marshall and Wartelle--who work at the ARS Southern
Regional Research Center (SRRC) in New Orleans,
La.--have found that it takes just two simple steps
to convert these cheap and abundant crop residues
into a powerful magnet capable of snagging both
positively- and negatively-charged particles of heavy
metals in water.
The material that they've succeeded in creating is known
as a dual-functioning ion exchange resin. These
resins--which are commonly used for treating industrial
and municipal waste waters and for recycling heavy
metals from solutions--are typically effective in
capturing only one kind of particle with either a
positive or negative charge.
But the SRRC researchers' resins can grab both. And
Marshall has found that they're more cost-effective
than two synthetically-made resins currently in use.
Ion exchange resins work by swapping, or exchanging,
the undesirable ions in a water supply with benign
ones. In a classic example of this interplay, water
softeners work by drawing out and replacing unwanted
"hard water" particles, like calcium and magnesium,
with ions from sodium.
Marshall and Wartelle give their plant residues a negative
charge by adding citric acid, a common food industry
additive. The positive charge comes from choline
chloride, which the researchers bind to plant fibers
by adding DMDHEU (or dimethyloldihydroxyethylene urea)
--a chemical that's already known for making molecules
stick. In the textile industry, it's the compound that
helps dye cling to cotton and wool fibers
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