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PVDF membranes were prepared with nonsolvent-induced phase separation, using solvents with various dipole moments, including HMPA, NMP, DMAc and TEP. Both the fraction of the polar crystalline phase and the water permeability of the prepared membrane increased monotonously with an increasing solvent dipole moment. FTIR/ATR analyses were conducted at the surfaces of the cast films during membrane formation to provide information on if the solvents were present as the PVDF crystallized. The results reveal that, with HMPA, NMP or DMAc being used to dissolve PVDF, a solvent with a higher dipole moment resulted in a lower solvent removal rate from the cast film, because the viscosity of the casting solution was higher. The lower solvent removal rate allowed a higher solvent concentration on the surface of the cast film, leading to a more porous surface and longer solvent-governed crystallization. Because of its low polarity, TEP induced non-polar crystals and had a low affinity for water, accounting for the low water permeability and the low fraction of polar crystals with TEP as the solvent. The results provide insight into how the membrane structure on a molecular scale (related to the crystalline phase) and nanoscale (related to water permeability) was related to and influenced by solvent polarity and its removal rate during membrane formation.

This paper reports on a novel membrane adsorber comprising metal–organic frameworks (MOFs) for water treatment. Two types of MOF (ZIF-8 and ZIF-L) were grown within a porous α-alumina support to form a membrane for the adsorption of a dye molecule, rose bengal, in aqueous phase. The external surface of ZIF-L was shown to exhibit strong affinity for rose bengal. We also observed that small crystals (with a large external surface area) are beneficial to adsorption. The surfactant CTAB was used in the synthesis of ZIF-L-based membrane adsorbers in order to reduce the size of ZIF-L particles and increase the loading of ZIF-L within the membrane. The membrane adsorber synthesized with the highest concentration of CTAB achieved the highest dynamic adsorption capacity. The ZIF-L-based membrane adsorbers exhibited water permeance (approximately 2 × 104 L m−2 bar−1 h−1) far exceeding that of most existing membrane adsorbers.

The synthesis of single-walled aluminosilicate nanotubes (AlSiNTs) generally requires conductive heating over a period of 4 days. This paper outlines a novel microwave-assisted method for the synthesis of AlSiNTs, which achieves yields on par with conventional methods in just 12 hours. The AlSiNTs obtained using the proposed method are much shorter (average length of 140 nm) than those synthesized in a reactor subjected to conductive heating in an oil bath (average length of 480 nm). The proposed synthesis method produces a product with highly monodispersed length distribution (100 – 200 nm), compared to those obtained from a conductively-heated reactor (50 – 950 nm). We applied suspensions of the resulting AlSiNTs to produce thin films via spin coating. The thin films cast from microwaved AlSiNTs yielded a far smoother top surface with uniform surface morphology. This can be attributed to the shorter average length and the narrower length distribution of the AlSiNTs in the casting solution.

The present work investigated the permeation of indium ions through a polymer inclusion membrane (PIM), prepared with cellulose triacetate (CTA) as the base polymer, tris(2-butoxyethyl) phosphate (TBEP) as the plasticizer and di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant. With 5 M HCl aqueous solution as the strip solution, we observed an initial indium permeability of 2.4 × 10−4 m/min. However, the permeability decreases with time, dropping to about 3.4 × 10−5 m/min after 200 min of operation. Evidence was obtained showing that hydrolysis of CTA occurred, causing a dramatic decrease in the feed pH (protons transported from strip to feed solutions) and a loss of extractant and plasticizer from the membrane, and then leading to the loss of indium permeability. To alleviate the problem of hydrolysis, we proposed an operation scheme called polymer inclusion membranes with strip dispersion: dispersing the strip solution in extractant-containing oil and then bringing the dispersion to contact with the polymer membrane. Since the strong acid was dispersed in oil, the membrane did not directly contact the strong acid at all times, and membrane hydrolysis was thus alleviated and the loss of indium permeability was effectively prevented. With the proposed scheme, a stable indium permeability of 2.5 × 10−4 m/min was obtained during the whole time period of the permeation experiment.