Transport characterisation of a PIM system used for the extraction of Pb(II) using D2EHPA as carrier

• The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, his(2-ethylhexyl)-phosphoric acid (D2EHPA) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (TBEP), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5 x 10(-6) mol m(-2) s(-1), which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship Ph R(2)2HR and the extraction equilibrium constant value of 6.2 x 10(-4) determined independently by solid-liquid extraction. An activation energy of I I kJ mol(-1) was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was per-formed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis.

Nyckelord

facilitated transport

lead

D2EHPA

polymeric inclusion membrane

transport modelling

polymer inclusion membranes

supported liquid-membrane

facilitated transport

mobile carrier

acid

ion

lead(ii)

permeability

equilibrium

separations

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