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-ben zoyl (HPMB'P), stearoyl (HPMSP)] and crown ethers E = B15C5, 18C6, DC1 8C6, DB18C6 and DB24C8 (DC = dicyclohexano, B = benzo, DB = dibenzo), in CHCl3, CH2Cl2 and ClCH2CH2Cl, has been studied. The experimental da ta agree with the extracted species E2CsCoL3 (E = B15C5), ECsCoL3 (E = DB18C6) and CoL2E (E = DB24C8). The extraction yields follow the orde rs: 18C6 greater-than-or-equal-to DC18C6 > DB18C6 > B15C5 > DB24C8, HP MBP > HPMB'P > HPMSP, and ClCH2CH2Cl > CH2Cl2 > CHCl3. 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 ph ase with Cs+, K+, Sr2+ or Ba2+ improves the synergistic extraction of cobalt.