Extraction of radionuclides 137Cs, 90Sr, 90Y and UO22+ from aqueous solutions using solid-Phase extractants impregnated with calix[4]arene phosphine oxides

The extraction of radionuclides 137Cs, 90Sr, 90Y, and UO22+ was studied using solid-phase extractants SPE-TBP, SPE-C45 and SPE-CIP67 depending on the acidity of the aqueous solution. SPE-C45 and SPE-CIP67 are porous styrene-divinylbenzene copolymer pellets impregnated with calix[4]arene tetraphosphine oxide C45 (5,11,17,23-tetrakis-diethylphosphinoylmethyl-25,26,27,28-tetrapropoxycalix[4]arene) and CIP67 (5,11,17,23-tetrakis-dipropylphosphinoylmethyl-25,26,27,28-tetrapropoxycalix[4]arene). Commercial solid-phase extractant SPE-TBP based on tributylphosphate was used for comparison. The influence of the radionuclides contact time with extractant on the establishment of extraction equilibrium was analyzed. It was shown that the equilibria in the systems using SPE are established in 3-4 hours. A significant influence of the acidity of the aqueous solution on the extraction efficiency of the radionuclides was found: an increase in acidity leads to an increase in the distribution coefficients. The influence of the nature of cations on the extraction efficiency is shown. The extraction of the radionuclides increases in the following series: UO22+ > 90Y > 90Sr > 137Cs. It was revealed that the extraction of the radionuclides depends on the length of the alkyl radical at the phosphorus atom of the macrocyclic skeleton of calix[4]arene phosphine oxide. Cations are extracted more efficiently with calix[4]arene of shorter alkyl radical length at phosphorus atom. The ability of SPE-calixarenes towards the studied radionuclides exceeds the extraction ability of SPE-TBP and varies in the following order: SPE-TBP< SPE-CIP67< SPE-C45. The conducted studies have shown the possibility of using the studied solid-phase-liquid extraction systems in the organization of radiation control of natural waters. In this case, the method of solid-phase extraction is convenient for radionuclide extraction, as it is simple and allows minimizing waste.