Lipophilic, Mono-ionizable, Calix[4]arene-bis(benzocrown-6) Compounds for Solvent Extraction of Cesium from Nuclear Wastes: Synthesis and Evaluation

As potential radiocesium extractants from nuclear waste solutions, a series of lipophilic, proton-ionizable calix[4]arene-bis(benzocrown-6) compounds with their calixarene units locked in the 1,3-alternate conformation was prepared. In these ligands, the acidic side arm is positioned over one crown ether cavity to enhance metal ion extraction. Upon ionization of the acidic group, the ligand provides the requisite anion for electroneutral extraction complex formation. To enhance the lipophilicity of the extractants, a 2-ethylhexyl group was attached to the benzo group of each crown ether fragment. Using radiotracer techniques and ICAP spectrometry, the ligands were evaluated in terms of the efficiency and selectivity with which they extract Cs+ from aqueous solutions into chloroform.