Extraction of heavy metal ions with 3-[(dioctylamino)methyl]alizarin

3-[(Dioctylamino)methyl]alizarin (C₈AL), which is endowed with high solubility in nonpolar organic solvents through introduction of dioctylaminomethyl group into the alizarin nucleus was studied for extracting heavy metal ions such as Cu(II), Zn(II), Cd(II), Co(II), MnII), and Ni(II), from aqueous solution. Cu(II) was most readily extracted into chlorobenzene at low pH and thus was separated from other metal ions. The metal ions stabilized in alkaline solution in the presence of water-soluble chelating agents were found to be extracted by this, alizarin-type extraction agent into chlorobenzene with the assistance by lipophilic quaternary ammonium salt, Capriquat^TM (methyltrioctylammonium chloride, Q⁺C1^-). The proton dissociation process of C₈AL was studied, and the mechanism of these metal extractions was discussed. The separation of Cu(II) and Ni(II) from the mixture with other divalent metal ions was also studied.