Emerging pervaporation technology is very promising to realize clean and renewable bioethanol recovery from biomass fermentation broth. The huge challenge of this technology is the need for a pervaporation membrane with high separation performance. Based on the solution-diffusion mechanism, pervaporation membrane for ethanol recovery should possess hydrophobic selective layer to improve sorption ability toward ethanol molecules, thereby enhancing the separation performance. In this study, a superhydrophobic zeolitic imidazolate framework-8 (ZIF-8) layer with a nano-level bud-like surface morphology was grown on polydimethylsiloxane (PDMS) composite membrane via ZIF-8 particle dip-casting, secondary seeded growth, and hydrophobic modification by n-octadecylphosphonic acid for highly efficient ethanol/water separation. The mole ratio of 2-methylimidazole and zinc nitrate (Hmim/Zn 2+ ) in the process of ZIF-8 secondary growth was systematically studied to construct appropriate micro-nano structure on PDMS composite membrane. The resultant optimal composite membrane exhibited a water contact angle of about 163° and an ethanol contact angle of 0°. In addition, it also displayed an outstanding separation factor of 17.4 corresponding to a total flux of 0.64 kg/m 2 h with 5 wt% ethanol aqueous solution at 30 ℃, and thus the superior pervaporation performance to most other reported PDMS-based mixed matrix membranes. The strategy of constructing superhydrophobic layer on PDMS composite membrane may provide a meaningful guidance for preparing high-performance pervaporation membrane for organic recovery from aqueous solution.
In recent years, with the rapid development of new energy vehicles, the demand for lithium resources has been increasing sharply. Positively charged nanofiltration (NF) membranes can accurately separate magnesium ions (Mg 2+ ) and lithium ions (Li + ), which have become an important technology for extracting lithium resources from salt lakes. The introduction of intermediate layer in thin-film composite (TFC) NF membranes could improve the permeability and selectivity for Mg 2+ /Li + separation. However, there is a problem of poor bonding between the intermediate layer and the supporting membranes through the simple physical combination on the membrane surface. Inspired by the controlled growth of succulent plants, the positively charged PA/ZIF-8/PSF composite NF membranes with “multilayer interlocking” structure were prepared successfully based on ZIF-8 layer anchored constrained growth and further interfacial polymerization. The zinc ion ligands of ZIF-8 were pre-anchored on the PSFsolution to provide reaction sites, and the grown ZIF-8 nanoparticles were embedded in the PSFsupporting membrane surface layer. The embedded ZIF-8 nanoparticles can enhance the interface bonding between the PSFsupporting membranes and the ZIF-8 layer. Additionally, the confined growth method can solve the problems of ZIF-8 particle aggregation and poor dispersion. Compared with membranes without ZIF-8 layer, the prepared PA/M − 6 membrane had a high flux of 47.2 L m −2 h −1 , which was 1.82 times that of PA/M-0. Meanwhile, the Mg 2+ /Li + separation factor of the PA/ZIF-8/PSF composite NF membranes could reach 47.6. In particular, the prepared NF membranes exhibited good long-term stability for Mg 2+ /Li + separation.
Hexiang Sun,Zachary Magnuson,Wenwen He,Weijie Zhang,Harsh Vardhan,Xiaolong Han,Gaohong He,Shengqian Ma
The desulfurization property of conventional mixed matrix membranes (MMMs) cannot meet the necessary demand due to particles aggregation and interface defects. Here, we put forward a layer-by-layer (LBL) approach to make a novel PEG@ZIF-8/poly(vinylidene difluoride)(PVDF) composite membrane for pervaporation desulfurization. In this way, a ZIF-8 layer is covered on the surface of the PVDF porous membrane via an in situ growth method. Then, a PEG layer is covered on the ZIF-8 layer by a casting method. Compared with pristine PEG membranes, the separation performance of the ZIF-8@PEG/PVDF nanocomposite membrane increased significantly. This can be attributed to the homogeneous ZIF-8 particle layer and better compatibility between the poly(ethylene glycol) (PEG) matrix and ZIF-8 particles. The membrane achieves a maximum total flux of 3.08 kg·m–2·h–1 at the third in situ growth cycles of ZIF-8 particles and a maximum sulfur enrichment factor of 7.6 at the sixth in situ growth cycles of ZIF-8 particles.
危险品化学品经营许可证（带存储）