Methods for purifying biuret

摘要

Methods are provided for recovering purified biuret from aqueous solutions containing biuret and higher molecular weight urea condensation products by contacting such solutions with the hydroxide ion form of an anion exchanger and extracting biuret from the ion exchanger with an aqueous extractant. The useful biuret-containing solutions also may contain urea. These methods are capable of recovering biuret of 99.9 percent plus purity from solutions containing higher molecular weight urea condensations products such as triuret, melamine, ammelide, and others. Elevated temperatures increase biuret recovery rate and concentration, and the extractant can be recycled into contact with additional biuret-containing anion exchangers to increase biuret concentration even further. The biuret-containing extract can be employed as is, concentrated by evaporation or otherwise, or treated to crystallize biuret. An integrated process is provided which involves pyrolyzing urea to form biuret and higher molecular weight condensation products and selectively recovering biuret from an aqueous solution of the resulting pyrolyzed urea as described.