Liquid-Liquid Extraction of Transition Metal Ions with N-Phenyl-N′-(2-butylthiophenyl)thiourea

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N-Phenyl-N′-(2-butylthiophenyl)thiourea (PBT, HL) was synthesized by the reaction of 2-butylthioaniline with phenylisothiocyanate and was studied for extracting Cu(II), Zn(II), Co(II), Cd(II), Ni(II), Hg(II) and Pd(II) from aqueous solution. Pd(II), Hg(II) and Cu(II) were readily extracted into chlorobenzene at low pH. Though the extraction of Co(II) and Zn(II) from an acidic solution was not complete, extraction from an alkaline aqueous solution
containing potassium oxalate was quantitative. The composition of the complexes, Cu(II)-PBT and Cd(II)-PBT, formed in the organic phase, was found to be ML₂ by studying the pH dependence and the metal-PBT mole ratio dependence of metal extraction. The synergistic effect of 4-benzylpyridine and trioctylphosphine oxide in the metal extraction was small. PBT is suited for separating Cu(II) from a mixture of conventional metal ions other than Pd(II)
and Hg(II).