Precipitation of uranium from uranium liquid waste generated in yellow cake conversion using NaH2PO4 and NaOH

The operation of pilot conversion plant in Serpong Nuclear Area to produce nuclear grade uranium dioxide from yellow cake generated liquid waste containing uranium. This uranium liquid waste remains problematic because the existing treatment processes for radioactive waste in the radioactive waste processing installation is yet to accommodate liquid waste which contained uranium. Therefore, the study for treatment of this kind of waste is necessary to support the radioactive waste management and to maintain the sustainability of the operation of the pilot conversion plant. The objective of this work is to recover uranium in the liquid waste by precipitation, thus decreasing the concentration of uranium in the liquid waste. The study was carried out by simulation using PHREEQC code and direct precipitation experiment with NaH2PO4 and NaOH as precipitating agents. The aqueous uranium in the liquid waste was precipitated with the addition of each of precipitating agent in a beaker glass to produce uranium precipitates. After the precipitation, the precipitates and the supernatant were separated by centrifugation. The uranium precipitates obtained from the experiment were washed with deionized water and ethanol. Then, a small portion of the precipitates was taken and coated with sputtered gold prior to analysis using SEM-EDS. The supernatant, meanwhile, was filtered and the concentration of uranium in the filtrate was determined using ICP-OES. The results shows that uranium precipitates with NaH2PO4 were crystalline, whereas with NaOH were amorphous. The initial concentration of uranium in the liquid waste was 2878 mg/l, whereas after the precipitation the concentration became approximately 1 mg/l. These values correspond to 99.9% aqueous removal by precipitation with those precipitating agents which indicates that this method is promising to be further developed for uranium liquid waste treatment.