Synergistic extraction of cobalt(II) from cesium containing aqueous solutions with mixtures of 4-acyl-pyrazol-5-ols and crown ethers

Abstract The synergistic extraction of cobalt(II) from aqueous solutions loaded with cesium chloride or nitrate, with mixtures of 1-phenyl-3-methyl-4-acyl-pyrazol-5-ols (HL) [acyl = benzoyl (HPMBP), para- tert. -butyl-benzoyl (HPMB′P), stearoyl (HPMSP)] and crown ethers E = B15C5, 18C6, DC18C6, DB18C6 and DB24C8 (DC = dicyclohexano, B = benzo, DB = dibenzo), in CHCl 3 , CH 2 Cl 2 and ClCH 2 CH 2 Cl, has been studied. The experimental data agree with the extracted species E 2 CsCoL 3 (E = B15C5), ECsCoL 3 , (E = DB18C6) and CoL 2 E (E = DB24C8). The extraction yields follow the orders: 18C6 ⩾ DC18C6 > DB18C6 > B15C5 > DB24C8, HPMBP > HPMB′P > HPMSP, and ClCH 2 CH 2 Cl > CH 2 Cl 2 > CHCl 3 . In spite of the better complexation of potassium than cesium with “18C6” type crown ethers, the extraction of ECsCo (PMBP) 3 is generally higher than the EKCo(PMBP) 3 one. Except in the case of DB24C8, loading the aqueous phase with Cs + , K + , Sr 2+ or Ba 2+ improves the synergistic extraction of cobalt.