Composite membranes with an integrated skin layer: preparation, structural characteristics and pervaporation performance

Composite membranes with an integrated skin layer were prepared using a “fusion” technique, where the skin layer of the composite membrane was prefabricated, and a polymer solution, prepared by dissolving the polymer in a mixture of solvent containing 0.2 wt.% of 1-methyl-2-pyrrolidone (a good solvent for the skin material), was then applied to the skin (sulfonated poly(ether ether ketone) (SPEEK)) to form the porous substrate by the wet phase inversion process. The SPEEK skin layer was found to be partially dissolved, and perfectly integrated into the substrate due to the formation of the SPEEK/the substrate material (a binary blend) ternary blends. The structural stability of the composite membrane was analyzed in terms of the features of the ternary blend layer, which also acts as a barrier layer for permeation. The superior pervaporation separation performance of the composite membrane demonstrated in ethylene glycol dehydration is attributed to the suppressed swelling of the skin layer by the effective reinforcement of the substrate. The stability of the membrane was also tested with a long-term dehydration of ethylene glycol in batch operation.