Experimental and modeling studies of lead (II) sorption onto a polyvinyl-chloride inclusion membrane

• Sorption of Pb(II) ions onto PVC/D2EHPA PIMs without added plasticizers. • PIM's characterization which also reveals the plasticizing role of D2EHPA. • Kinetic and equilibrium modeling of the sorption process. • Improved sorption and reuse properties comparing with other sorbents. • High potential to reduce the price comparing to the plasticized PIMs. In the present paper, a polymer inclusion membrane (PIM) containing 50% polyvinyl chloride (PVC), and 50% bis-(2-ethylhexyl) phosphate (D2EHPA) as extracting agent is used for the removal of Pb(II) ions from aqueous acid solution, by using the batch extraction technique. The optimal PIM composition was discussed both in correlations with the PIM's morphology, and also with the sorption mechanism. The characterization of PIM, realized by atomic force microscopy (AFM), and differential scanning calorimetry (DSC), highlighted the membrane morphology and the plasticizing role of the sorption agent D2EHPA, respectively. The sorption kinetics was well described by the pseudo-second order model, and the adsorption isotherm was best fitted by the Redlich–Peterson equation. The kinetic experiments confirm that the sorption process of Pb(II) into the optimal 50%D2EHPA/50%PVC PIM is a chemisorption. The Pb(II) sorption into the PIM occurs by a “relay mechanism”. The experimentally determined maximum sorption capacity of PIM for Pb(II) ions was found to be 60.785mg/g, and it is among the highest values reported in literature. Moreover, the desorption of Pb(II) ions, as well as the regeneration of PIM can be achieved at least five times by using 0.5M HNO3. We consider that this membrane (50%D2EHPA/50%PVC) is a good candidate to be used as solid sorbent, due its lower price comparing to the plasticized PIMs, high sorption capacity, and good regeneration properties, with the regeneration process simultaneous with the metal recovery.