Abstract
Currently, production of porous polymeric membranes for filtration is predominated by the phase-separation process. However, this method has reached its technological limit, and there have been no significant breakthrough over the last decade. Here we show, using polyvinylidene fluoride as a sample polymer, a new concept of membrane manufacturing by combining oriented green solvent crystallization and polymer migration is able to obtain high performance membranes with pure water permeation flux substantially higher than those with similar pore size prepared by conventional phase-separation processes. The new manufacturing procedure is governed by fewer operating parameters and is, thus, easier to control with reproducible results. Apart from the high water permeation flux, the prepared membranes also show excellent stable flux after fouling and superior mechanical properties of high pressure load and better abrasion resistance. These findings demonstrate the promise of a new concept for green manufacturing nanostructured polymeric membranes with high performances.
Highlights
Production of porous polymeric membranes for filtration is predominated by the phase-separation process
polyvinylidene fluoride (PVDF) membranes as well as other microfiltration/ ultrafiltration polymeric membranes are produced via phaseseparation methods[3,4,5], predominately the non-solvent induced phase-separation (NIPS) method[2,5], some commercial membranes are produced by the thermal-induced phaseseparation (TIPS) method[6,7,8]
During the preparation process using the combined crystallization and diffusion (CCD) method, the membrane structure is closely related to the cooling rate
Summary
Production of porous polymeric membranes for filtration is predominated by the phase-separation process. We show, using polyvinylidene fluoride as a sample polymer, a new concept of membrane manufacturing by combining oriented green solvent crystallization and polymer migration is able to obtain high performance membranes with pure water permeation flux substantially higher than those with similar pore size prepared by conventional phase-separation processes. Apart from the high water permeation flux, the prepared membranes show excellent stable flux after fouling and superior mechanical properties of high pressure load and better abrasion resistance These findings demonstrate the promise of a new concept for green manufacturing nanostructured polymeric membranes with high performances. The growth of solvent crystallites can be sterically hindered if significant enrichment of polymer solute occurs at the time of solvent crystallization, provided a directed polymer concentration gradient can be built in the polymer solution Theoretically, this requirement can be fulfilled with a selected solvent whose melting point is only slightly lower than the room temperature. Enough polymer solute can diffuse to the cold end accompanying the nucleation/crystallization of the solvent, and fill into the space between solvent crystallites, sterically hindering the agglomeration of the crystallites to remain their small size
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