Extraction of Lanthanum and Gadolinium(III) at the Cloud Point Using p -Sulfonatocalyx[ n ]arenes as Chelating Agents

摘要

The extraction of gadolinium(III) and lanthanum(III) ions at the cloud point is studied in Triton X100 micellar solutions in a wide range of pH. In the absence of chelating agents, lanthanum(III) and gadolinium( III) ions are unselectively extracted at pH > 6. It is shown that the use of p -sulfonatothiacalyx[6(8)]arenes as chelating agents noticeably enhances the degree of extraction at pH 2–6. The composition and stability of lanthanum– p -sulfonatothiacalyx[ n ]arene complexes ( n = 4, 6, 8) are estimated in a wide range of pH by pHpotentiometry. The degree of Gd 3+ and La 3+ ions extraction, which is performed at the cloud points employing calyxarene macrocycles of different sizes, is depended on the acidity of a medium.