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Fractionation of dyes and salts is a great challenge in high salinity wastewater from the textile industry. In this work, a high performance loose nanofiltration membrane (LNM) was fabricated to fractionate the dyes and salts in the solution via green rapid coating (GRC) process on polyethersulfone (PES) substrate. The organic solvent-free GRC process was achieved within 10 min based on the crosslinking between polyethylenimine (PEI) and tannic acid (TA). The resultant LNM performance was optimized by altering the coating parameters including the TA concentration and the coating time. The microstructure, surface properties and dye/salt separation performance of the LNM were demonstrated by characterizations and filtration experiments, respectively. With the co-existence of dye and salt, the optimized LNM exhibited desirable permeability (40.6 LMH·bar−1) and dye rejection (99.8% for 0.1 g/L Congo Red) as well as low salt rejection (6.1% for NaCl and 2.2% for Na2SO4). Furthermore, it was observed that even under 60 g/L of salt content, the satisfying rejection of CR (99.3% in Na2SO4 and 97.6% in NaCl) and high permeation of salts (98.9% for Na2SO4 and 97.9% for NaCl) can still be maintained. Moreover, the LNM showed incredible stability during the filtration process (10 h) towards dye/salt aqueous mixture. The PEI-TA/PES LNM exhibited promising application potential in dye/salt separation.

The performance of thin film nanocomposite (TFN) membranes is substantively determined by the structure, composition and size of the incorporated nanofillers. In this work, an asymmetric organic nanofiller, resorcinol-formaldehyde nanobowls (RFB), was firstly designed via a modified Stober approach and introduced into the polyamide selective layer of the TFN membrane via an interfacial polymerization process. Thanks to the asymmetric structure, concave cavity and chemical groups of the incorporated RFB, enhanced nanofiltration performance of the prepared TFN membrane was achieved. The optimized TFN membranes exhibited higher water fluxes and well maintained salt rejections. The water fluxes of the TFN-B0.12 membrane were 119.74 ± 4.28 for the Na2SO4 solution and 141.46 ± 5.92 L/(m2·h) for the MgCl2 solution, which are 1.5 times higher than that of the control thin film composite (TFC) membrane, with comparable rejection (95.76 ± 0.29%) for Na2SO4 and 4.63% higher (25.98 ± 0.45%) rejection for MgCl2, respectively. Meanwhile, the basic resistance of the RFB modified TFN membrane was reinforced simultaneously as compared with that of the control TFC membrane. The results demonstrate the incorporation of the RFB significantly strengthened the nanofiltration performance of the TFN membrane.

A novel method for preparation of polyethersulfone (PES) hybrid ultrafiltration (UF) membrane with sustainable antifouling property is developed. The highlight of this method is that the self-assembly of TiO 2 nanoparticles around the pores of PES membranes was achieved during the formation of PES UF membrane via non-solvent induced phase separation (NIPS) process. The precursor (tetrabutyl titanate (TBT)) of TiO 2 nanoparticles and triblock copolymer (Pluronic F127) were introduced to PES casting solution. The synchronous self-assembly of TiO 2 nanoparticles around membrane pores and formation of PES polymeric membranes occurred during the NIPS process by controlling the hydrolysis and condensation of TBT. F127 plays an essential role in that its hydrophilic and hydrophobic segments have different affinity to the TiO 2 nanoparticles and PES matrix respectively. TEM and SEM–EDX mapping confirm that TiO 2 nanoparticles self-assemble around the pores of PES membranes. Water permeability of the resultant hybrid PES membranes was 4 times higher than that of neat PES membranes with a slight change of bovine serum albumin (BSA) rejection. The organic antifouling experiment, using BSA and humic acid (HA) as model foulants, manifest that the organic antifouling property of the PES hybrid membrane can be conspicuously enhanced. Importantly, the leaching of self-assembly TiO 2 nanoparticles is restrained due to the interaction between the TiO 2 nanoparticles and F127, which ensures a stable and sustainable antifouling activity of the membrane.

A new method for the preparation of γ-alumina membranes from aluminium chloride was investigated in this paper. Boehmite sol was synthesized by an anionic exchange method, which could offer OH − -ion and simultaneously remove Cl − -ion. Boehmite sols were then deposited on the inner surface of the hollow fiber supports by a filtration technique. The thermal evolution, phase transformation, structure, morphology and pore size distribution of the γ-alumina membranes were characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen isothermal adsorption measurement. SEM images showed that the membranes were defect-free. Gas permeability tests suggested that the obtained membranes possessed gas selectivity, and its separation factor for H 2 /N 2 and H 2 /CH 4 were 3.31 and 2.25 at 0.1 MPa, respectively. The most concentrative pore diameter, pore volume and specific surface area of an unsupported membrane calcinated at 600 °C were 3.7 nm, 0.18 ml/g and 176.9 m 2 /g, respectively.