Molybdate ion partition in the aqueous two-phase system formed by CuSO4 + PEG 4000+H2O at different pH and temperatures

In this study, the aqueous two-phase system (ATPS) formed by CuSO4 + PEG 4000 + H2O, for the partition of the molybdate ion at different pH values (1.5, 2.0 and 2.5) and at five different temperatures, T= (298.15, 308.15, 318.15, 328.15 and 338.15) K was studied. Two different salts, Na2MoO4 and (NH4)(6)Mo7O24, were used for the experimental partition tests. The extraction percent for the molybdate ion in the ATPS was studied as a function of pH and temperature. The experimental results indicate that the extraction percent increases with increasing temperature. The maximum extraction reached was 93.07% at pH = 2.5 and T = 338.15 K, for the CuSO4 + PEG + H2O + Na2MoO4 system, and 92.66% in the CuSO4 + PEG + H2O + (NH4)(6)Mo7O24 system at pH = 2.5 and T= 318.15 K. In addition, the pH effect on the liquid-liquid equilibria of the ATPS CuSO4 + PEG + H2O at T= 308.15 K was studied, where no significant influence was observed in the working pH range (from 1.5 to 2.5). However, if it is compared with the literature data, it has a relevant importance. With decreasing pH, the two-phase area decreases, thus the tie-line slope also varied. Chen-NRTL and Wilson modified models were applied to correlate the liquid-liquid equilibrium. A good agreement between experimental data and correlated results was obtained. (C) 2017 Elsevier B.V. All rights reserved.