Abstract
Hydrogel-facilitated phase separation (HFPS) has recently been applied to make microstructured porous membranes by modified phase separation processes. In HFPS, a soft lithographically patterned hydrogel mold is used as a water content source that initiates the phase separation process in membrane fabrication. However, after each membrane casting, the hydrogel content changes due to the diffusion of organic solvent into the hydrogel from the original membrane solution. The absorption of solvent into the hydrogel mold limits the continuous use of the mold in repeated membrane casts. In this study, we investigated a simple treatment process for hydrogel mold recovery, consisting of warm and cold treatment steps to provide solvent extraction without changing the hydrogel mold integrity. The best recovery result was 96%, which was obtained by placing the hydrogel in a warm water bath (50 °C) for 10 min followed by immersing in a cold bath (23 °C) for 4 min and finally 4 min drying in air. This recovery was attributed to nearly complete solvent extraction without any deformation of the hydrogel structure. The reusability of hydrogel can assist in the development of a continuous membrane fabrication process using HFPS.
Highlights
Membrane technology is a well-established method for highly selective separation of a wide variety of contaminants from water [1,2,3,4]
For the first time, a simple treatment process that allows repeated usage of the same hydrogel mold in micropatterned phase separation membrane castings
The formation of hydrogel-facilitated phase separation (HFPS) membranes relies on the demixing process between solvent from the polymer solution and water contained within the hydrogel mold
Summary
Membrane technology is a well-established method for highly selective separation of a wide variety of contaminants from water [1,2,3,4]. To improve membrane performance and lower the membrane fouling, chemical treatments [11,12] or physical modifications [13,14] have commonly been attempted by either coating the membrane surface with hydrophilic/hydrophobic layers or modifying the membrane matrix by blending with additives (such as nanofillers, surfactants, and polymeric additives). These approaches suffer from many disadvantages which restrict their extended applications in practice. Leaching of additives out of the polymer matrix and detachment of surface-coated materials even in mild filtration conditions have been widely reported in the literature [15,16,17]
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