| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method of high-purity urea water capable of lowering a biuret concentration by using urea produced inexpensively and by an inexpensive method.SOLUTION: A production method of high-purity urea water in which a biuret concentration is lowered by treating urea water stock solution having the biuret concentration of 2,500 ppm or higher by active carbon, comprises: a biuret adsorption removal step of treating urea water stock solution by active carbon; and a biuret desorption removal step of desorbing biuret from the active carbon adsorbing the biuret. First of all, the biuret adsorption removal step is performed, and thereafter the biuret desorption removal step is performed, when the biuret concentration in the urea water derived therefrom exceeds a regulation value of 2,400 ppm or lower. |
