Evaluation of molecularly imprinted polymer blend filtration membranes under solid phase extraction conditions

Abstract

Molecularly imprinted polymer (MIP) blend membranes from cellulose acetate (CA) and sulfonated polysulfone (SPS) with 100/0, 95/5, 90/10 and 85/15 compositions and using Rhodamine B (Rh B) as template molecule were prepared by the phase inversion technique. Blank membranes for structural and functional evaluation were prepared under the same conditions without addition of Rh B. Step by step template removal was performed using water and methanol as extracting solvents under controlled conditions. Pure water permeability studies were performed at 3 bar, and contact angle measurements revealed that the MIP blends with a higher SPS content were somewhat more hydrophobic than CA. Then, all membranes were characterized as membrane adsorbers: Rh B uptake from dilute aqueous solutions was measured in filtration experiments (membrane solid phase extraction). The MIP CA/SPS blend membrane with 95/5 composition had the highest binding capacity. Rh B binding to all MIP membranes was significantly higher than binding to the respective blank samples. Washing with water and sodium chloride and subsequent elution with methanol were carried out in order to identify and differentiate the weak and strong binding to the membrane surface. The obtained data reveal that molecular imprinting via phase inversion yields not only a higher number of Rh B binding sites than preparation without template but also a larger fraction of sites binding strongly under aqueous conditions. Considering the impact of SPS content onto MIP surface hydrophobicity, an unexpected contribution of the polysulfone backbone to molecular recognition was postulated. Full recovery of the bound template and reusability of the membrane adsorbers were also demonstrated.