Polymeric and mixed matrix polyimide membranes

• Three different polyimide polymers were used to prepared porous asymmetric membranes.
• The effect of the casting solvent on membrane properties was investigated.
• Mixed matrix membranes containing multiwalled carbon nanotubes were prepared.
• The MWCNTs improved the membrane performance in dyes solutions filtration.

Three different polyimide type polymers were used to prepare porous asymmetric membranes by non-solvent induced phase separation (NIPS): a homopolymer (Matrimid) and two co-polymers (P84 and Torlon). The effect of the casting solvent on membrane morphology and transport properties was studied. Moreover, the co-polyimide P84 was selected for further investigations in the form of mixed matrix membranes (MMMs) containing functionalized multiwalled carbon nanotubes (oxidized or aminated MWCNTs). The introduction of polar functional groups was found to be fundamental in order to have a good dispersion of the MWCNTs in the casting solution before, and in the formed membrane, after NIPS, thanks to the formation of hydrogen bonds between the solvents, the MWCNTs and the polymer. The presence of the MWCNTs in the membrane matrix improved the performance in the filtration of dyes solutions in water or ethanol (enhanced permeance and reduced fouling, with similar or higher rejection), with respect to reference polymeric membranes (without MWCNTs). The separation properties of the membranes produced were also compared with literature data obtained with commercial and other laboratory made mixed matrix membranes.

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