SELECTIVE EXTRACTION OF CESIUM AT TRACER LEVEL CONCENTRATION FROM A SODIUM-NITRATE SOLUTION WITH CALIX-CROWNS - MOLECULAR MODELING STUDY OFTHE CS+ NA+ SELECTIVITY/

Calix[4]arene mono- and bis-crown6 in the 1,3 alternate conformation a re highly selective extractants for cesium towards sodium in an acidic liquid waste. Extraction and selectivity are related to complexation properties which can be studied by Molecular Dynamics techniques. In t his paper, we describe the results of Molecular Dynamics simulations i n an explicit water phase for four complexes of 1,3-alternate mono- an d bis-crown-calix[4]arenes. The structural features obtained are inter preted on the basis of cation/ligand complementarity and can explain t he relative performances in Na+ and Cs+ extraction for the compounds s imulated. The relative free energy of binding can be computed and is i n a semi-quantitative agreement with complexation data in an homogeneo us medium.