Detoxification of acetonitrile-water wastes from liquid chromatography
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Acetonitrile is one of the most frequently used solvents in column liquid chromatography. Because of its toxicity, safe disposal of the waste solvent is essential. Combustion in a hazardous waste plant, if available, is recommended. Otherwise the waste can be degraded in the laboratory to acetic acid and ammonia by treatment with sodium hydroxide. The addition of hydrogen peroxide is not necessary. The waste needs to be diluted to 10% acetonitrile in water in order to prevent the formation of a two-phase system on addition of concentrated sodium hydroxide. This reagent must be added in excess; 2.5 mols of sodium hydroxide per mol of acetonitrile are recommended.
It was found that the kinetics are of second order, with an activation energy of 89 kJ mol−1 and a frequency factor of 9×109. Therefore even at room temperature degradation is possible, although a hydrolysis time of approximately 15 days is needed under these conditions. At 80°C, where refluxing is not necessary, hydrolysis is complete after, e.g., 2 h, depending on the amount of sodium hydroxide added.
Key WordsColumn liquid chromatography Acetonitrile disposal Acetonitrile hydrolysis Degradation kinetics Waste solvent management
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