Solvent extraction and separation of AI (III) and Ni (II) from aqueous medium by cyanex-272 (Bis-(2,4,4-trimethylpentyl) phosphinic acid) in kerosene

The solvent extraction and separation of AI (III) and Ni(II) from aqueous medium using Cyanex-272 (bis- (2,4,4-trimethylpentyl) phosphinic acid) in kerosene has been investigated as functions of contact time, aqueous phase acidity (pH), concentration of extractant-in the organic phase, temperature, and loading capacity of the extractant. The equilibrium was reached within 9 min for AI(III) and 2 min for Ni(II). It was observed that the amount of AI(III) extraction was about 65% with 0.1 mol/l Cyanex-272 in kerosene at (26 +-) degree c and pH 4.2, whereas at the same time the amount of Ni(ll) extraction was about 8.5% with the same condition. In both cases, the metal ion (AI(III) and Ni(II)) concentration in the organic phase gradually increased with the time of extraction until the curves levelled off. The extraction of AI(III) increased with increasing concentration of the extractant, aqueous phase acidity (pH), and the temperature. However, the amount of Ni(ll) extraction at all temperatures was negligible and decreased with increasing extractant concentration. The temperature dependence data gave delta H = 15.23 kJ/mol up to 60 degree c, suggesting endothermic extraction. The loading capacity of AI(III) and Ni(ll) was about 25.75 g and 0.5 g, respectively per mole of Cyan ex- 272, with 0.2 M Cyanex-272 at pH 4.1. Loading data indicates AI : Cyanex-272 ratio varied from 0.95 : 1 to 1.6 : 1 for Al(lll) extraction indicating almost 1 : 1 complex formation in the organic phase. (author)