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It is challenging to effectively purge wastewater containing heavy metal ions at low concentration. In order to remove trace Cr (VI) from wastewater efficiently, a positively charged microporous membrane was prepared by firstly non-solvent induced phase separation (NIPS) of amphiphilic polymer and secondly surface quaternization modification. The morphologies, surface roughness, surface charge, hydrophilicity, and pore size of membranes were characterized. Based on the dual action of micellar adsorption and charge repulsion, when surfactant is 4 mM and Cr (VI) is 60 ppm, the surface quaternization membrane (Q-MPVD) achieves 99.8 % Cr (VI) rejection simultaneously accompanied by a permeability of 100 LMH/bar. Meanwhile, the effects of STAC concentration, Cr (VI) concentration, pH as well as inorganic salt concentration on the composite micellar size, and Cr (VI) rejection performance were investigated, respectively. Moreover, the Q-MPVD membrane shows an excellent separation stability over a wide pH range, indicating its application perspective in engineering process. In summary, this work provided a positively charged membrane with high-efficiency performance for treating practical trace Cr (VI)-containing industrial wastewater. [ABSTRACT FROM AUTHOR]

Membranes with both high permeability and selectivity are desirable for practical separation. In this work, three hyperbranched polyesters (HPEs) with different numbers of hydroxyl-terminated groups and molecular structures were, respectively, incorporated into a polyamide film formed by the interfacial reaction between the mixtures of HPE/piperazine (PIP) and trimesoyl chloride (TMC) on PVC hollow fiber substrates to endow the corresponding thin film composite (TFC) membranes with different permselectivity performances. The successful incorporation of HPEs into the cross-linked polyamide matrix and their gradient distribution in the corresponding selective layer were confirmed by ATR-FTIR and XPS analyses. Moreover, the permeation experiments for the fabricated TFC membranes revealed that HPEs most likely existed within the network or/and aggregate pores of the polyamide matrix due to their nanometer sizes and flexible molecular structures. Both the changes in the pore structures and the increase in the hydrophilicity of the polyamide matrix with the introduction of abundant hydroxyl groups pending in the HPE molecules led to the permeate flux of the TFC membrane increasing significantly. Importantly, nearly spherical H40 HPEs with intramolecular cavities could act as a molecular sieve to endow the selective layer with a high rejection capability. Meanwhile, the H40/PIP selective layer with a more negatively charged surface exhibited a higher rejection for SO42− ions while maintaining a low rejection for Cl− ions. These findings encourage further exploration of a new alternative material with such structures like HPE by interfacial polymerization to construct an ultrathin barrier film with high permselectivity performance. [ABSTRACT FROM AUTHOR]

The separator, as one of the essential components for lithium‐ion batteries (LIBs), has garnered considerable attention because of its significant role in battery performance. Here, an in‐situ coating method to promote the wettability and thermal‐stability of polypropylene (PP) separators was reported. The separator was first dip‐coated with phenolic compound based on biologically inspired surface modification. Then silica layers were in‐situ formed on the separator via a sol–gel process of silicate solution, so that an inorganic–organic hybrid layer was coated on PP separators without the need of any polymer binders. Besides, this method hardly increases the film thickness or sacrifices microporous structure of the pristine separator. Due to the introduction of hybrid layers, the resulted separators showed excellent dimensional thermostability, as the thermal shrinkage was only 20% at 150 °C while that of the bare separator was about 80%. Meanwhile, electrochemical performances of cells with the modified separator were obviously improved, especially the rate performance. At the charge/discharge current density of 5 C, cells with PP separators nearly lost all the capacity, but the modified separator still held 45.7% of the discharge capacity at 0.2 C. This facile yet effective method has great application prospects in the preparation of ceramic‐coated separators. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47277. [ABSTRACT FROM AUTHOR]