A NEW METHOD TO DESCRIBE 2-PHASE SOLVENT-EXTRACTION BASED ON NET TRANSPORT POTENTIAL DERIVED AS LINEAR-COMBINATIONS OF FORWARD AND REVERSE CONSTITUENTS

With the levels to avoiding the difficulties encountered in estimating thermodynamic activities of the multiple chemical species in two-phas e liquid system, a set of forward, reverse, net and total transport po tentials are defined to represent the chemical state of a transferring solute during transient using bulk concentrations. The net transport potential corresponds to that in the conventional two-film model of di ffusion-controlled processes. The overall driving forces of mass trans port are redefined as the derivatives of the relevant transport potent ials differentiated with respect to a state variable newly defined in terms of the bulk concentrations of the solute contained in both phase s. Net and total quantities. i.e. transport potentials, overall drivin g forces and the molar fluxes are obtained as linear combinations of t hose for forward and reverse directions. The topical features presente d by these quantities and their mutual relations are discussed in deta il. The experimental new overall transport coefficient for U(VI) varie d in accord with the changes in the theoretical net transport potentia l and overall driving force. The present method permits describing the extractive mass transport consistently both to forward and reverse di rections of transport.