Selective extraction of Ga(III) with p-t-butylcalix[4]arene tetrahydroxamic acid

Abstract

Solvent extraction behavior of p-tert-butylcalix[4]arene tetrahydroxamic acid towards some trivalent as well as divalent cations was studied. The extraction selectivity of some cations followed the order Ga(III) < In(III) < Fe(III) < Cu(II) < Zn(II), Ni(II). Since the extraction reagent exhibited high selectivity for Ga(III) and In(III), the detailed extraction behavior for Ga(III) and In(III) was investigated by slope analysis, the continuous variation method, and by loading tests. It was confirmed that both metals formed 1:1 complexes with the extraction reagent. Since the pKa values for hydroxamic acids are 8-9, there was 6-7 units of pH shift in the metal extraction caused by the complexation of Ga(III) indicating that this ligand served as an excellent reagent for selective extraction of Ga(III). The coordination site of the ligand for both metals was qualitatively investigated by IR spectra before and after metal loading on the ligand. The loaded Ga(III) was quantitatively stripped by using dilute acidic solutions and the ligand was regenerated.