Besides formic acid and formaldehyde several organic reagents are used to decompose nitric acid. Denitration by use of sugar was first carried out at HANFORD, USA. More than 12 moles nitric acid can be decomposed per mole sucrose. The decomposition is linerarly dependent on the concentration of sugar and the presence of iron increases the reaction rate. On account of the slow reaction, which does not give rise to foaming, a simple uncomplicated design of reaction vessels is possible. Moreover the reagent is very cheap. At the Karlsruhe Nuclear Research Centre the denitration by use of ethanol was investigated. The nitric acid waste solution can be mixed at room temperature and after heating up to about 80°C the decomposition reaction starts without induction time. In a simulated medium level liquid waste solutiom more than 90% of the initial nitric acid are decomposed within 2 h. The reaction rate depends on the concentration of nitric acid and nitrate salts. The molar ratio of alcohol to nitric acid is between 0.5 and 1. The off gas contains mainly of CO2 and N2O. A selective precipitation of transuranium elements during denitration is possible by use of diethyl oxalate. In acid medium this reagent hydrolyzes to give ethanol and oxalic acid, which serve as denitration and precipitation reagents, respectively.
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- Alternative Organic Reductants for Denitration
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