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Turning rice farming waste to useful silica compounds

The researcher who developed the process says it could save approximately six tons of carbon emissions per ton of silica compounds produced. He estimates the cost of the technique to be 90 percent less than the current process, with virtually no carbon footprint. Developed by Richard Laine, a professor of materials science and engineering, the new technique is believed to be the first simple, inexpensive chemical method for producing high-purity silica compounds from agricultural waste, according to press release in EurekAlert!

Much of the world's agricultural waste contains silica, and the search for a practical way to extract it stretches back 80 years. While the new process could be used to produce silica and silicon-containing chemicals from many types of agricultural waste, Laine focused on using the hulls left over from processing rice. The hull is the outermost layer of the rice grain. It's removed when rice is processed. Hundreds of millions of tons of the hulls are produced around the world every year. Many are burned to produce electricity, and the ash that's left over contains high levels of silica. Some of this ash is used in construction or as insulation, but much of it is dumped in landfills.

But while the world is awash in silica-rich rice hull ash, getting that silica out has proven to be a major challenge. The difficulty stems mostly from the incredibly strong chemical bond between silicon and oxygen, one of the strongest that exists in nature. Laine found two easy and inexpensive ways to break that bond: ethylene glycol, or antifreeze, and ethanol, or grain alcohol. The antifreeze combined with a small amount of sodium hydroxide weakens the chemical bonds between the silica and the rice hull ash at the beginning of the process, dissolving the silica into a liquid solution.

Read the entire press release from December 17 on EurekAlert's website: http://www.eurekalert.org/pub_releases/2015-12/uom-trf121715.php



 

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