HYDROLYSIS OF PRODUCTS OF UREA DENITRATION OF NITRIC ACID RAFFINATE OF EXTRACTION URANIUM REFINING

Abstract

The paper deals with the nitric acid extraction of uranium that has one significant drawback – the lack of technology for the utilization of nitric acid from raffinate. In the overwhelming majority of the cases, spent nitric acid is neutralized by an alkaline agent, and the nitrates of alkaline or alkaline-earth metals are discharged to the tailings pond. One of the possible ways of handling raffinates is their carbamide denitration which minimizes the unproductive loss of nitric acid. However, until now, the issue of effective treatment of urea nitrate precipitate (CO(NH2)2·HNO3) has not been solved. The paper contains the results of research aimed at solving the problem of utilization of urea nitrate. Urea nitrate can be processed into ammonium nitrate through acid hydrolysis of urea. The subject of the study is a solution containing 200 g/l urea nitrate and a solution containing 200 g/l urea nitrate and 100 g/l nitric acid. The process is studied in the temperature range 70–150 ºC at atmospheric and elevated pressures using an autoclave. IR spectra of the urea nitrate hydrolysis products confirmed the completeness of the process for 4 hours at 150 ºC and a pressure of 30 atm. The introduction of an equimolar amount of nitric acid into the reaction volume increases the rate of hydrolysis of urea nitrate by a factor of 2 and does not impede the completeness of its transformation into ammonium nitrate. The activation energy of the urea nitrate hydrolysis is 28,9 kJ/mol that is comparable to the activation energy of urea enzymatic (urease) hydrolysis. Urea nitrate hydrolyzate (ammonium nitrate) can be used as a desorption solution in the process of uranium sorption refining of the technology of underground uranium leaching.