Extraction of Sr²⁺ with thiacalix [4]arene-biscrowns 4 in HNO₃ solution

In the high-level radioactive waste liquid separation process of spent fuel reprocessing, new separation materials are of great significance for the efficient extraction of strontium. In the paper, 1,2-alternate thiacalix[4]biscrowns 4 (TCACE) was synthesized by using calix[4]arene and triethylene glycol di(p-toluenesulfonate). TCACE was characterized by FT-IR, ¹H NMR and MS. The influence of different diluents on extraction rate was studied, and CH₂Cl₂ was chosen as diluent by optimization. Extraction rate of Sr²⁺ was excellent and average mass transfer coefficient was 1.36×10^-5 m·s^-1 under the conditions of CH₂Cl₂ as organic solvent, nitrate acid concentration was 3 mol·L^-1, TCACE concentration was 1×10^-3 mol·L^-1, Sr²⁺ concentration was 5×10^-4 mol·L^-1, extraction was conducted for 80 min and at 25℃. Different technological conditions on extraction for Sr²⁺ were studied. Furthermore, the extraction measurement equation was also studied. The extraction complex was {Sr(NO₃)₂}·{TCACE} as shown by experiment. The extraction effects for other metal ions Mo⁶⁺, Ni²⁺, Ag⁺, Sn⁴⁺ with TCACE were also studied. It was found that TCACE showed excellent selectivity for Sr²⁺ .