Liquid—liquid extraction of metal ions with sulfonamide chelating agents

Abstract

The liquid—liquid extraction of divalent metal ions (Co, Cu, Zn, Cd, Pb, Hg) with 8-octanesulfonamidoquinoline (I; HL), 1,2-bis(octanesulfonamido)benzene (II; H 2L), 1,8-bis(octanesulfonamido)naphthalene (III; H 2L), 2-octanesulfonamidophenol (IV; H 2L), and some other related sulfonamide chelating agents was studied between aqueous and aromatic solvents. Compound I extracted divalent metals by forming ML 2-type complexes; copper(II) was extracted at by far the lowest pH region except for mercury(II). Compounds II–IV formed ML complexes with divalent metals, which were extracted in the organic solution in the presence of lipophilic uncharged ligands (A) such as 4-benzylpyridine and 1,2-bis(alkyltihio)ethane through the formation of MLA m -type complexes. Copper(II) was again the most readily extracted, but the extraction selectivity among the metals was less than that with compound I. Compounds II and III extracted divalent metals in the presence of lipophilic quaternary ammonium salt (trioctylmethylammonium chloride, Aliquat-336S, Q +Cl −); a mechanism including the formation of an anionic complex of the type ML 2− 2 or MLCl n− n followed by an ion-pair extraction with Q + is suggested. The sulfonamides I–IV showed by far the highest extraction ability for mercury among the divalent metal ions. An especially strong affinity was shown by compound I, with which mercury was extracted completely even at pH 1. Several other sulfonamide homologues of I–IV were also synthesized and the metal complexes which relate to those formed in the extraction were isolated.