Sorption of Cesium and Strontium Radionuclides by Synthetic Ivanyukite from Model and Process Solutions

The sorption of 137 Cs and 90 Sr radionuclides from model and real solutions of various salt compositions has been studied on a synthetic powder and pelletized titanosilicate represented by ivanyukite (SIV), the technology of which was developed at the Kola Science Center, Russian Academy of Sciences. Titanosilicate sorbents successfully recover Cs and Sr from mixed multicomponent solutions in a broad pH range (from 4 to 11) at a salt content of up to 10 g/L with a purification coefficient of more than 200 in the case of powder materials. In the case of a pelletized sorbent, the distribution coefficient K d decreases due to the partial dissolution (peptization) of silicate binder, which results in a decrease in the effective specific surface of sorbent. When there is no salt background, the sorption of radionuclides by SIV significantly decreases. This fact is caused by the protonation of the sorbent and, consequently, competition between hydrogen ions and radionuclides. The extraction ability of SIV towards 137 Cs and 90 Sr, as well as 51 Cr, 54 Mn, and 60 Co, in the presence of the salts of other elements in the form of unfiltered suspension allows one to carry out sorption without a preliminary water preparation stage, which is represented by precipitation with iron or aluminum salts. The sorption characteristics of SIV have been compared to the Termoksid-35 ferrocyanide sorbent employed in industry for the recovery of 137 Cs. The possibility of using one type of sorbent, SIV, for deactivating liquid radioactive waste (LRW) instead of the conventional purification scheme employed at an enterprise would remarkably facilitate the sorption scheme of processing of LRW. Considering this feature of SIV, one can expect a decrease in the volume of secondary radioactive waste in the form of spent sorbents for subsequent utilization. Verifying the process in dynamic mode has confirmed the effectiveness of SIV for processing LRW. The possibility of utilizing the spent sorbent in the form of ceramic material of SYNROC type possessing high radiation and chemical stability is an important potential advantage of SIV.