U.S. Water News Online
SAN FRANCISCO -- Leftovers processed from farm crops could be used clean drinking water and industrial wastewater, a U.S. Department of Agriculture (USDA) scientist says.
Chemist Jacob Lehrfeld of USDA's Agricultural Research Service has chemically converted low-value agricultural residues, such as corn bran, into resins to bind up lead, other metals, and some pesticides that contaminate water. He reported his research at the national meeting of the American Chemical Society here.
In experiments at the National Center for Agricultural Utilization research at Peoria, Ill., Lehrfeld produced phytic acid resin by heating crop residues or newsprint shreddings with phytic acid in a slight vacuum.
"Phytic acid resin is a natural for cleaning wastewater in chromium and copper plating industries," said Lehrfeld. "It binds nearly three times more heavy metal than a similar volume of the petroleum-based sulfonated styrene-divinylbenzene resin, now widely used in wastewater cleanup."
Phytic acid resin currently would be more expensive to make than the petroleum-based product, Lehrfeld noted. The greatest expense is the phytic acid, which now sells for about $12 per kilogram in a 50 percent liquid solution. It is used for treating metals to prevent rust, and in some countries tiny amounts are added to food oils to inhibit development of rancid flavors.
Phytic acid can be chemically extracted from corn steep liquor, a byproduct of starch production. Corn steep liquor is the same dark brown, syrup-like liquid in which USDA scientists at Peoria mass-produced penicillin more than 50 years ago, launching the antibiotics industry. About 100,000 metric tons of phytic acid could be processed from corn steep liquor produced in the United States.
Today as in the past, corn steep liquor is mixed with corn bran and dried into a livestock feed. Removing the phytic acid from the corn steep liquor could result in a more valuable and nutritious feed. That's because phytic acid binds up calcium, zinc, and other trace minerals in the feed and makes them indigestible for animals with a single stomach, such hogs, chickens, and fish.
Besides corn bran, agricultural residues that might be combined with phytic acid to form resins include ground corncobs, oat hulls, soy hulls, and sugarbeet pulp, Lehrfeld said.
In his research, Lehrfeld found that phytic acid resins also removed some organic chemicals such as the herbicide atrazine from watery solutions. He is continuing research to pinpoint the conditions in which the resins quickly and selectively bind to lead, cadmium, and other heavy metals.
Lehrfeld has applied for a patent on the production of resins made with phytic acid and is seeking industrial cooperators to help transfer the technology to the marketplace.
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