Liquid-liquid extraction of cadmium and cobalt with mixtures of 1-phenyl-3-methyl-4-stearoyl-5-hydroxypyrazole (HPMSP) and n-dodecylamine (DDA) in toluene

The synergistic extraction of cobalt and cadmium (M2+) from sulfate and perchlorate media with mixtures of 1-phenyl-3-methyl-4-stearoyl-5-hydroxypyrazole (HPMSP, PMSP- after deprotonation) and n-dodecylamine (DDA, DDAH(+) after protonation) has been studied in toluene. In sulfate medium, an easy phase separation is observed. The synergistically extracted species is DDAH . M(PMSP)(3), which results from the addition of the predominating DDAH . PMSP ion pair on M(PMSP)(2) with logK(syn) = 4.05 (Co) and 4.7 (Cd). In perchlorate medium, in the presence of an excess of DDAH . ClO4, which is the predominating DDA species, a stable emulsion appears in the aqueous phase in contact with a clear organic phase. Due to the interfacial character of the extraction process and to aggregation phenomena, a stronger synergistic effect is achieved with Co than with Cd, leading to an increase of the Co/Cd separation coefficient. The synergistic extraction performed from perchlorate medium is slower than that from sulfate medium.