Separation study of seven heavy metal cations through a bulk liquid membrane containing N,N’,N -Tri-(4-ethyl benzene) phosphoric triamide

The competitive seven metal ion transport of: Co2+, Cd2+, Ag+, Pb2+, Ni2+, Cu2+ and Zn2+ from an aqueous phase contained equimolar concentrations of metal ions (at pH=4/9) into an aqueous receiving phase (at pH=3) through an organic phase facilitated by N, N’, N -Tri-(4-ethyl benzene) phosphoric triamide as a carrier was used in organic membrane phase. The following solvents were examined as membrane phase: chloroform (CHCl3), nitrobenzene (NB), 1, 2-dichloroethane (1, 2-DCE), dichloromethane (DCM). The obtained results show that the selectivity and efficiency of transport for these heavy metal ions change with the nature of the organic solvents which were used as liquid membrane in these experiments [1, 2]. A good selectivity was observed for Cu2+ cation by this ligand in most solvent systems, but in the case of 1, 2-DCE that was selective to Zn2+. Moreover, the selectivity of metal cations in DCM is higher than the other solvents. The percent of total Cu2+ metal cations in the receiving phase (%Receiving), percent of total metal cations in the membrane phase (%Membrane) and rate of the Cu2+ ion transport (J (mol per 24 h) ) were 0/47, 1/03 and 0/59×10-7 respectively after 24 h in DCM solvent. The influence of several factors such as the nature of carboxylic acids: stearic acid (S.A), palmitic acid (P.A), therphetalic acid (T.A) and fumaric acid (F.A) as surfactant in the membrane phase and the time of transport of Cu2+ cation were investigated. According to obtained results, the %Membrane of Cu2+ ion transport increases in presence of these fatty acids (no acid:1/68, S.A: 21/15, P.A: 3/28, T.A: 15.57 and F.A: 12/41). The maximum transport rate for Cu2+ cation from the source phase into the receiving phase concludes, over a period 24 h.