Tertiary amine block copolymer containing ultrafiltration membrane with pH-dependent macromolecule sieving and Cr(VI) removal properties

To obtain ultrafiltration (UF) membranes with multi-functions in permeation, macromolecule sieving and specific heavy metal removal by adsorption, tertiary amine groups containing amphiphilic block copolymers (poly(methyl methacrylate-b-dimethylamino-2-ethyl methacrylate) (P(MMA-b-DMAEMA))) were designed and synthesized. Then the block copolymers were used to fabricate the tertiary amine block copolymer containing blend membranes with poly(vinylidene fluoride) (PVDF) via a non-solvent induced phase separation (NIPS) process. Hydrogen nuclear magnetic resonance (H-1 NMR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the bulk and the surface layer compositions of the prepared membranes. It was found that P(MMA-b-DMAEMA) stably retained in the blend membranes and greatly enriched onto the surface layers. The pH-dependent performances of the membranes were investigated in details. With the change of pH values, the surface hydrophilicity, water permeation, dextran sieving behaviors and hexavalent chromium (Cr(VI)) adsorption properties varied greatly. And the membrane performed obviously reversible pH-dependent property. From the results, a feasible method could be inferred for fabricating UF membranes with tunable filtration, macromolecule sieving and anion adsorption properties under different pH conditions. (C) 2014 Elsevier B.V. All rights reserved.