Separation study of some heavy metal cations through a bulk liquid membrane containing 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane

Abstract

Competitive permeation of seven metal cations from an aqueous source phase containing equimolar concentrations of Co2+, Fe3+, Cd2+, Cu2+, Zn2+, Ag+ and Pb2+ metal ions at pH 5 into an aqueous receiving phase at pH 3 through an organic phase facilitated by 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix5) as a carrier was studied as bulk liquid membrane transport. The obtained results show that the carrier is highly selective for Ag+ cation and under the employed experimental conditions, it transports only this metal cation among the seven studied metal cations. The effects of various organic solvents on cation transport rates have been demonstrated. Among the organic solvents involving nitrobenzene (NB), chloroform (CHCl3), dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE) which were used as liquid membrane, the most transport rate was obtained for silver (I) cation in DCM. The sequence of transport rate for this cation in organic solvents was: DCM>CHCl3>1,2-DCE>NB. The competitive transport of these seven metal cations was also studied in CHCl3–NB and CHCl3–DCM binary solvents as membrane phase. The results show that the transport rate of Ag+ cation is sensitive to the solvent composition and a non-linear relationship was observed between the transport rate of Ag+ and the composition of these binary mixed non-aqueous solvents. The influence of the stearic acid, palmitic acid and oleic acid as surfactant in the membrane phase on the transport of the metal cations was also investigated.