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Sweet Solution for Chromium Pollution
29 March 2007 (All day)
Researchers may have found a sugar-coated answer to a toxic waste problem. At a presentation yesterday at the semiannual meeting of the American Chemical Society in Chicago, Illinois, a team of chemists reported that a sugar-based solution effectively reduced the threat of the heavy metal chromium, without creating new pollution headaches in the process.
Chromium, like some of its chemical cousins, can be either beneficial or harmful to living things, depending on its form, concentration, and method of absorption. Chromium III, for example, the metal's natural state, is stable and an essential nutrient. On the other hand, hexavalent chromium--or Cr(VI)--is highly reactive and a potential carcinogen if inhaled or consumed in contaminated fish or polluted water. Used in the manufacturing of videotapes, dyes, paints, and other industrial applications, Cr(VI) achieved notoriety several years ago as the subject of a well-publicized class-action lawsuit in California, which was depicted in the movie Erin Brockovich. Up to now, removing Cr(VI) from the environment has been difficult and messy, requiring treatment with acid, which itself can degrade local water quality.
The new approach involves solutions of two common sugars, fructose and sucrose. Chemist and lead researcher Bryan Bilyeu of Xavier University of Louisiana in New Orleans reported that the fructose mix removed 94% of Cr(VI) from contaminated wastewater (sucrose achieved a 93% removal) and soil samples in the lab. Based on these "very preliminary" results, he says chromium-using industries might eventually treat their wastewater with sugar solutions to convert enough Cr(VI) into Cr(III)--which is about 1000 times less toxic--to meet or exceed environmental requirements. And instead of the acid-disposal problems that exist with current chromium treatment methods, he notes, the waste sugars would pose no hazard.
Bilyeu says he and his colleagues at the Universidad Autónoma del Estado de México in Toluca are also studying how to filter wastewater through processed orange peels, cactus, and other natural fibers. He says this method would remove chromium entirely from the effluent, instead of discharging it in a less toxic form. Sugar solutions might even be able to treat contamination by other heavy metals, such as cadmium or copper, Bilyeu adds, but his team hasn't yet investigated those possibilities.
The chromium-contaminated water treatment strategy makes sense, says soil chemist Paul Schwab of Purdue University in West Lafayette, Indiana. But it might find only limited success in treating contaminated soils, he notes, because the sugar solutions would tend to wash the chromium away, instead of retaining it and converting it to Cr(III).