Physical and Chemical Foundations of the Extraction Refining of Natural Uranium

Abstract

The paper presents the results of studies of the physicochemical processes of the extraction and nitric acid purification of uranium salts obtained by the method of precipitation of ammonium uranyl carbonate (AUC) from ore solutions of leaching of uranium and polymetallic ores with their subsequent dissolution in nitric acid. It is shown that the process of extraction on a mixture of tributyl phosphate (TBP) in kerosene makes it possible to obtain high-purity uranium oxide. For the selective extraction of impurities, the process of uranium extraction from the nitric acid medium was carried out with a mixture of TBP and di(2-ethylhexyl) phosphoric acid (DEHPA) in kerosene. The first uranium concentration 40…50 g/L simulated the process of uranium desorption, the second ≤ 100 g/L simulated the process of dissolution of uranium oxide. The study of the uranium extraction made it possible to determine the required number of extraction stages to achieve the minimum uranium content in the raffinate and the maximum extractant capacity, which ensured the specified coefficients of uranium purification from metal impurities (V, Mo, etc.). After extraction, the nitric acid raffinate served as a raw material for the production of a mineral fertilizer – sodium nitrate.

Physical and Chemical Foundations of the Technology for Obtaining Uranium Oxides

“…Along with the advantages, low cost, and availability of sulfuric acid, produced at uranium plants, this method has a drawback lime which is used for neutralization, forms gypsum dumps. This significantly increases the volume of waste pulp and the area of their storage [1,3].…”

“…This technology has not found wide application due to the higher than sulfuric acid cost, and the need to create an associated production line for the utilization of nitrate ions. Associated production of fertilizer from reagents used for the processing of uranium and rare metals was more profitable than the direct production of saltpeter from Na 2 CO 3 and HNO 3 [2,3].…”

“…The use of nitric acid in the uranium technology was developed in Ukraine only at the Prydniprovsky chemical plant (PChP) [3]. At the same time, nitric acid was utilized in the production of ammonium or sodium nitrates.…”

“…This also made it possible to extract such valuable elements as molybdenum, vanadium, iron, scandium, etc. The process of extracting uranium from nitric acid media was first studied at the PChP, some results are presented in [3].…”

“…The purpose of industrial testing was to optimize the parameters of the processes of extraction, re-extraction, drying and calcination, reduction of U(VI) to U(IV). To do this, it was necessary to study the processes of selective extraction of uranium from its various compounds with purification from impurities to a purity of 99.9%, obtaining uranium dioxide with a bulk density of 2.7…2.9 g/cm 3 . For the processing of ore solutions of various chemical compositions, it was necessary to optimize the technological scheme to ensure a high extraction of uranium and its purification from thorium, molybdenum, and vanadium.…”