The answer to tomorrows 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
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
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
The material that theyve 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 theyre 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 thats already known for making molecules
stick. In the textile industry, its the compound that helps
dye cling to cotton and wool fibers.
is the U.S.
Department of Agricultures chief scientific research