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

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.