Soybean Scraps Used To Develop Filtering Agent For Contaminated Water

Scientists have discovered that soybean hulls -- as well as leftover stalks and stems from already-plucked corn and sugarcane plants -- could be used to develop a filtering agent that can adsorb harmful levels of lead, chromium, copper and cadmium from contaminated water, Agricultural Research Service (ARS) officials stated on June 21.

ARS chemists Wayne Marshall and Lynda Wartelle -- who work at the ARS Southern Regional Research Center (SRRC) in New Orleans, La. -- have found that it takes just two steps to convert these 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 wastewaters 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. Additionally, 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.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

Wayne Marshall: http://www.ars.usda.gov/pandp/people/people.htm?personid=3588

Lynda Wartelle: http://www.ars.usda.gov/pandp/people/people.htm?personid=5922

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