Highly Selective Transport of a Uranyl Ion through a Liquid Membrane Containing a Lipophilic Ion-Associate of Methyltrioctylammonium and Hydroxycalix[n]arene-p-sulfonates (n = 6, 8) as Metal Carriers

Abstract

Uranyl ion, UO₂²⁺, in an aqueous sodium hydrogen carbonate solution of pH 4 - 8 (source phase) was simultaneously and selectively transported into a dilute sulfuric acid solution (receiving phase) through a membrane (chloroform, bulk) containing a lipophilic ion-associate of methyltrioctylammonium ion and hydroxycalix[n]arene-p-sulfonate ion, 2_n (n = 6, 8), MTA⁺-2_n, as a metal carrier. The rate of transport increased in proportion to the concentrations of UO₂²⁺ in the source phase and carrier in the membrane and along with an increase in the temperature of the system. The rate was also increased along with an increase in the pH of the source phase. None of the other metal ions were transported, or obstructed the transport of UO₂²⁺, while the presence of large amounts of sodium hydrogencarbonate and sodium chloride in the source phase interfered with the transport by causing a delay in the start of transport.