Study on the thiophosphinic extractants. II. Thermodynamic functions and structural parameters of the w/o microemulsion of the saponified acid systems

Purified sodium salt of Cyanex302, di (2,4,4-trimethylpentyl) monothiophosphinic sodium, NaDTMPTP, and that of Cyanex301, di (2,4,4-trimethylpentyl) dithiophosphinic sodium, NaDTMPDTP, are prepared from the corresponding extractant respectively. The thermodynamic function ΔGo→i0 (standard Gibbs free energy change of transferring alcohol from oil phase to interface phase) and structural parameters of the sodium salt NaA (0.200 g)–alcohol–diluent–H2O microemulsion system are measured. The effects of substitution of oxygen by sulfur in the extractant molecule, the used diluent, alcohol, the temperature and water content VH2O on the thermodynamic function and structural parameters are discussed and compared with the corresponding sodium salt of phosphinic acid (purified Cyanex272) system, respectively. The replacement of oxygen atom(s) by sulfur in HA or NaA molecules makes their steric configurations and polarities changed.