Extensive investigation on extraction behaviour of organo-phosphrous based bi-functional ionic liquids for separation of molybdenum (Mo) from spent Co-Mo/Al2O3 leach liquor

Abstract

The sulphate mediated spent catalyst Co-Mo/Al2O3 leached liquor bearing ∼ 6.05 g/L of Mo, 1.75 g/L of Al and 1.44 g/L of Co was subjected to the solvent extraction separation of Mo using noble bi-functional ionic liquids (BILs). Comparative extraction behaviour of Mo with two BILs such as quaternary ammonium D2EHPA(R4ND) and quaternary ammonium Cyanex 272 (R4NCY) synthesized from Aliquat 336 in combination with D2EHPA and Cyanex 272 was systematically investigated. The purity of synthesized ILs was ascertained from NMR analysis. The role of both BILs concentrations appears to be critical on extraction of Mo at acidic pH ranges of the solution with an association of 1 mol each as evident from slope analysis equilibrium study. The Extraction of Mo as H2MO4 at optimum solution pH of 2.0 gives rise to achieve a selective separation of Mo in presence of Co and Al as ensured from separation factor (S.F.) value; βMo/Co = 5388.8 and 1642.5 for R4ND and R4NCY and βMo/Al = 1309.2 and 13522.1 for R4ND and R4NCY respectively. The extraction yield of Mo with ILs was enhanced while increasing the temperature of the solution as indicated from the positive ΔH (+40.26 KJ/mol & 73.27 βMo/Co = 5388.8 and 1642.5 for R4ND and R4NCY and βMo/Al = 1309.2 and 13522.1 for R4ND and R4NCY) values. The diluents effect on Mo extraction was consistent with either of the ILs and they follows the order as n-Hexane > Tolune > Kerosene > Benzene > Xylene. The Mc-Cabe Thiele plot constructed at A: O = 5:1 has predicted 2 stages using 0.6 M each of R4ND and/or R4NCY and later it was validated from CCS leading to attain>99.9 % Mo extraction. The extraction behaviour of R4NCY was efficient and effective on clean separation of Mo over R4ND at the studied experimental condition. Stripping of Mo-loaded-R4NCY by NH4OH was promising with the Mo enrichment up to 3 times with generation of purified stripped bearing 90.71 g/L of Mo. FTIR characteristic peak of R4ND and R4NCY before and after extraction confirms in support of the Mo extraction with ILs. The purity of synthesized ILs was ascertained from NMR analysis.