Synthesis of phosphonic acid extractants and selective extraction of In(III) and Ga(III) from acidic media containing Zn(II)

Abstract

Two types of bis-alkylaminophosphonic acid, [bis(2-ethylhexyl)amino]methyl phosphonic acid monobutyl ester (BEAMP) and [bis(2-ethylhexyl)amino]methyl phosphonic acid (BEAAP) as novel extraction reagents were synthesized to develop selective extractants for In(III) and Ga(III) in acidic media containing Zn(II). These newly synthesized extractants were successful in the selective separation of In(III), Ga(III) and Zn(II), a separation that the commercial phosphorus acid extractants such as D2EHPA and PC-88A could not achieve. Their extraction selectivity for the metal ions in aqueous ammonium nitrate solution was in the following order: In(III) > Ga(III) > Zn(II). The extraction equilibria for In(III), Ga(III), and Zn(II) with BEAMP were quantitatively investigated by a batchwise method at 303 K. In(III), Ga(III) and Zn(II) were extracted with BEAMP (HR) according to the following reactions, respectively: In3++ 1.5(HR)2→INR3 + 3H-, Ga3++ 2.5(HR)2 + NO3→-GaR 2(HR)3(NO3) + 2H+, and Zn 2+ + 1.5(HR)2 + NO3→- ZnR(HR) 2(NO3) + H+ The extraction equilibrium constants of In(III), Ga(III) and Zn(II) with BEAMP were determined to be K ex,M= 3.16×103 (mol dm3) 15,44.67 [mol dm-3]1.5 and 0.14 [mol dm -3]1.5, respectively.