Sorption of Strontium and Lead by Impregnated Sorbents Based on Di(tert-butylcyclohexano)-18-crown-6 and an Ionic Liquid

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Sorption of Sr(II) and Pb(II) onto impregnated sorbents based on di(tert-butylcyclohexano)-18-crown-6 and an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C₄mim⁺Tf₂N⁻), was studied. The influence of the crown ether concentration in the sorbent, kind and pretreatment of the support, and kind of the solvent used for impregnation on the sorption of Sr and Pb onto sorbents based on di(tert-butylcyclohexano)-18-crown-6 and C₄mim⁺Tf₂N⁻ was analyzed. Sr(II) is taken up most efficiently from neutral and weakyl acidic (up to 0.01 M HNO₃) media with the degree of sorption R > 90% and distribution coefficients K_d from 1410 to 706 cm³ g⁻¹, respectively. The efficiency of the Sr(II) sorption is not affected by Na+ ions in the solution up to their concentration of 1 M. In the presence of calcium ions, as the Ca(II) concentration in the solution is increased from 0.02 to 0.16 M, K_d of Sr(II) decreases by a factor of 4. In sorption of ⁹⁰Sr from seawater, K_d is 193 cm³ g⁻¹; it increases by a factor of 1.05 and 1.25 upon dilution of seawater by a factor of 2 and 10, respectively. Lead(II) is quantitatively taken up from neutral media (R > 98%) and from 0.01–1.0 M HCl and 0.01–3.0 M HNO₃ solutions (R > 87%). The sorbents prepared show promise for radioanalytical determination of Sr and Pb radionuclides in natural objects.