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Achieving highly selective separation of organic mixtures is crucial to modern fine chemicals and pharmaceutical industries. The membrane-based organic solvent reverse osmosis (OSRO) technology is expected to break through this barrier. The key to achieving the separation of organic mixed liquids is to design the OSRO membrane as needed based on the physical and chemical properties of the target separation solvent. However, this poses a huge challenge to traditional OSRO membranes. In this work, we report composite polyamide (PA) OSRO membranes with ultrahigh polar/non-polar organic mixture selectivity. The surface polarity of the composite PA membrane is increased by coating a layer of Fe3+/tannic acid (Fe3+/TA) layer on the surface of the PA membrane. The enhanced surface polarity increases the interaction difference between polar and non-polar solvents and the membrane. And a polarization layer is formed on the membrane surface, which weakens the concentration polarization effect on the membrane surface. Under high-concentration feed liquid (the mass ratio of methanol/hexane is 7:3), the separation factor of the prepared membrane reaches 218, which is the highest value of all OSRO membranes reported so far. For the first time, we establish a partial flux analysis for the OSRO process. This analysis unravels the pressure, concentration dependence, and sensitivity of separation performance. It provides novel insights into the design of high-performance OSRO membranes. [Display omitted] • High-performance OSRO PA membrane prepared by Fe3+/TA surface modification. • Fe3+/TA coating enhances the surface polarity of PA membrane. • Enhanced surface polarity affects membrane-solvent interactions. • PA-Fe3+/TA membranes show ultrahigh separation factor for methanol/hexane mixture. • Established partial flux analysis to gain in-depth understanding of OSRO process. [ABSTRACT FROM AUTHOR]

• The stability of graphene oxide/methylene blue (GO/MB) membrane was enhanced obviously. • An effective strategy to prepare GO/MB membrane with outstanding separation performance. • The effect of various factors on dyes rejection was summarized, which had far-reaching significance in wastewater treatment. • Molecular dynamics simulations were utilized to trace nanoscale events occurring over interfacial behaviors. To improve the stability and rejection for dyes of graphene oxide (GO) membrane, we employed methylene blue (MB) as a modifier to prepare GO/MB composite membrane through vacuum filtration. The rejection of GO/MB membrane for different dyes (methyl orange, disperse black 9 and rhodamine B) reached 93.32%, 99.85% and 82.56%, respectively, and the pure water flux was 7.67 L⋅m−2⋅h−1, indicating that GO/MB composite membranes have good application prospects. The interaction mechanism between GO and MB was described in detail. Moreover, the united-atomic models for molecular dynamics (MD) simulation was performed, through which we can trace the nanoscale events occurring over the interfacial behaviors and provided molecular information at nanoscale interfaces for our study. The effects of the interaction between dye molecules and composite membrane, charges of the dyes, molecular weight and molecular structure of dyes on nanofiltration performance were also discussed, which laid foundation of the research in field of water treatment. [ABSTRACT FROM AUTHOR]

The development of membranes for protein purification has stringent requirement of disinfection resistance, low protein adsorption and anti-fouling, without changing protein structure. In this study, hydrophilic titanium dioxide (TiO 2)/calcium alginate (TiO 2 /CaAlg) hydrogel membranes were prepared by a simple ionic cross-linking method. The effects of the porogenic agent polyethylene glycol (PEG) concentration, the molecular weight of PEG, and the concentration of TiO 2 on the filtration properties were systematically investigated. The TiO 2 /CaAlg membrane exhibited excellent bovine serum albumin (BSA) rejection and anti-fouling properties. The mechanical properties and surface energy of the TiO 2 /CaAlg membrane were significantly improved. The chemical bonding mechanism of TiO 2 and NaAlg was investigated by molecular dynamic simulation. The TiO 2 /CaAlg membrane had good chlorine resistance and could be disinfected or cleaned with sodium hypochlorite. The TiO 2 /CaAlg hydrogel membrane loaded with polyhydroxybutyrate (PHB) nanofibers maintained high flux (136.7 L/m2h) and high BSA rejection (98.0 %) at 0.1 MPa. The results of circular dichroism and synchronous fluorescence indicated that the secondary structure of BSA was maintained after membrane separation. This study provides one method for the preparation of green and environmentally friendly membrane for protein purification. [Display omitted] • TiO 2 /CaAlg membrane exhibited good anti-fouling property and chlorine resistance. • Interaction mechanism of TiO 2 and NaAlg was investigated by MD simulation. • Surface energy of TiO 2 /CaAlg was 23 times higher than that of CaAlg, which reduced protein adsorption. • TiO 2 /CaAlg-PHB was used for BSA purification and the flux was 136.7 L·m−2·h−1 at 0.1 MPa. • Structure of BSA could be maintained after membrane separation. [ABSTRACT FROM AUTHOR]

The development of membranes for protein purification has stringent requirement of disinfection resistance, low protein adsorption and anti-fouling, without changing protein structure. In this study, hydrophilic titanium dioxide (TiO 2)/calcium alginate (TiO 2 /CaAlg) hydrogel membranes were prepared by a simple ionic cross-linking method. The effects of the porogenic agent polyethylene glycol (PEG) concentration, the molecular weight of PEG, and the concentration of TiO 2 on the filtration properties were systematically investigated. The TiO 2 /CaAlg membrane exhibited excellent bovine serum albumin (BSA) rejection and anti-fouling properties. The mechanical properties and surface energy of the TiO 2 /CaAlg membrane were significantly improved. The chemical bonding mechanism of TiO 2 and NaAlg was investigated by molecular dynamic simulation. The TiO 2 /CaAlg membrane had good chlorine resistance and could be disinfected or cleaned with sodium hypochlorite. The TiO 2 /CaAlg hydrogel membrane loaded with polyhydroxybutyrate (PHB) nanofibers maintained high flux (136.7 L/m2h) and high BSA rejection (98.0 %) at 0.1 MPa. The results of circular dichroism and synchronous fluorescence indicated that the secondary structure of BSA was maintained after membrane separation. This study provides one method for the preparation of green and environmentally friendly membrane for protein purification. [Display omitted] • TiO 2 /CaAlg membrane exhibited good anti-fouling property and chlorine resistance. • Interaction mechanism of TiO 2 and NaAlg was investigated by MD simulation. • Surface energy of TiO 2 /CaAlg was 23 times higher than that of CaAlg, which reduced protein adsorption. • TiO 2 /CaAlg-PHB was used for BSA purification and the flux was 136.7 L·m−2·h−1 at 0.1 MPa. • Structure of BSA could be maintained after membrane separation. [ABSTRACT FROM AUTHOR]

Highly efficient hydrogen separation membrane is critical in the future hydrogen powered zero carbon society. However, challenges left in searching for hydrogen separation membranes with high permeability, selectivity and easy accessibility. Here, this target was partially achieved by a series of membranes made from in-situ ozone oxidized intrinsic mciroporous polymer membranes (O 3 -PIMs) within minutes. The FT-IR spectra and XPS results suggested that C O and OH groups were formed after the oxidation reaction. The TGA and EDS mapping results indicated that the oxidation reaction happened only on the skin surface of PIM-1 membrane within 10 μm in depth. After O 3 oxidation, the O 3 -PIMs showed a large drop in gas permeability whereas huge increases in gas pair selectivity, resulting in large improved overall performance for H 2 /N 2 , H 2 /CH 4 and H 2 /CO 2 that beat the latest trade-off lines. The O 3 -PIM-60 showed a H 2 permeability of 1294 Barrer and H 2 /N 2 , H 2 /CH 4 and H 2 /CO 2 selectivity of 93.7, 121, and 2.92, respectively. The increased selectivity of O 3 -PIMs is due to their remarkably enhanced size sieving effect induced enhanced diffusion selectivity. Theoretical simulation showed that this is caused by the O 3 reaction induced pore blocking effect that shifted the mciropore of PIM-1 to the ultra-micropore region, and thus, significantly improved the hydrogen sieving efficiency. In all, this facile and highly efficient ozone oxidation method provides a great perspective in searching for high performance hydrogen separation membranes. [Display omitted] • O 3 -PIMs was obtained by in-situ ozone oxidation of PIM-1 for the first time. • This method is simple, controllable and highly efficient. • The O 3 oxidation happened at the surface within 10 μm in depth. • The performance improvement originated from the enhanced diffusion selectivity. • O 3 -PIM-60 membrane exceed the 2015 Robeson upper bounds for H 2 /N 2 and H 2 /CH 4. [ABSTRACT FROM AUTHOR]

To improve the mechanical strength, antimicrobial and anti-swelling ability of calcium alginate hydrogel membrane, the graphene oxide/calcium alginate hybrid (GCA-H) hydrogel filtration membrane was prepared by ion cross-linking without organic solvent in this study. Meanwhile, the morphology, structure, and chemical bonding mechanism of membranes were characterized. Furthermore, we also investigated the mechanical strength, swelling behaviors, anti-bacterial, and anti-fouling properties of the GCA-H membrane. Since the excellent hydrophilicity, the GCA-H membrane showed high flux recovery rate (>97 %) based on the alternating filtration tests without cleaning the membrane. It was mentioned that the maximum stress-strain of the GCA-H membrane could reach 1.53 MPa, which was 2.34-fold more than that of the unmodified membrane. Due to the enhanced structure, it was beneficial to design the thinner membrane for further application. Moreover, we evaluated the impact of the operating parameters on dye/salt separation performance in this work. Generally, the rejections of Coomassie brilliant blue (CBB) and NaCl of GCA-H membrane were approximately 99 % and 8 %, respectively. Finally, we summarized the separation factor and nominalized flux for the dye/salt separation. The GCA-H membrane still maintained a good separation efficiency after being placed for 45 days. So the GCA-H membrane has a great potential in the selectivity separation process, which may provide a sustainable strategy for dye recycle. Graphene oxide/calcium alginate hybrid hydrogel (GCA-H) membrane was prepared by ion-crosslinking and applied for the separation of dye/salt. The GCA-H membrane exhibited high selectivity for salt and dye and the selectivity coefficient was 230.5. The GCA-H membrane showed high antimicrobial property. [Display omitted] • A graphene oxide/calcium alginate hybrid (GCA-H) hydrogel filtration membrane was fabricated in water. • The chemical bonding mechanism of GO and NaAlg was investigated. • The GCA-H membrane has excellent antimicrobial and anti-fouling properties. • The selectivity coefficient of GCA-H membrane for dye/salt was 230.5. [ABSTRACT FROM AUTHOR]

(a) MD simulation of pore structure (red: alginate matrix, white: membrane pore structure, blue: interface pore structure) and (b) pore size distribution of BaAlg hydrogel, (c) schematic diagrams of the molecule/ion separation process of BaAlg-PET membrane and (d) the selectivity for the separation of dye/NaCl of the membranes in this work and compared with other reported membranes. [Display omitted] • PET non-woven resisted the deformation of CaAlg hydrogel than PHB nanofibers and PP non-woven. • BaAlg-PET exhibited higher strength, flux and better separation performance than CaAlg-PET. • Membrane pore structure and pore size distribution of BaAlg hydrogel were generated via MD simulations. Calcium alginate (CaAlg) hydrogel has good anti-pollution performance. However, the self-supporting CaAlg hydrogel filtration membrane is difficult to be batch prepared due to its poor mechanical properties. In this paper, polyester (PET) non-woven fabric, polypropylene (PP) non-woven fabric and polyhydroxybutyrate (PHB) nanofibers were used as support layer to prepare CaAlg composite membranes. A series of studies proved that CaAlg-PET membrane showed higher stability and flux, which revealed that PET non-woven fabric was the best carrier among the three fiber carriers to enhance the various properties of hydrogel. Methyl blue (MB) and sodium chloride (NaCl) were used as the representatives of molecules and ions, respectively. The effects of concentration, operating pressure and temperature on the separation performance of MB/NaCl by CaAlg-PET membrane were investigated. The flux of CaAlg-PET membrane was 19.3 L·m−2·h−1·bar−1, and the membrane showed a high selectivity of 183.4 to MB/NaCl mixture (99.5% rejection of MB and 8.3% rejection of NaCl). Moreover, Barium ion was used to cross-link sodium alginate to prepare barium alginate (BaAlg) hydrogel coated composite membrane (BaAlg-PET) using PET fiber as the carrier. The BaAlg-PET membrane exhibited higher strength, stability, flux and better separation performance than CaAlg-PET membrane. BaAlg-PET membrane exhibited a high flux of above 35.5 L·m−2·h−1·bar−1, and the molecular ion selectivity was 306.3 (99.7% rejection of MB and 8.1% rejection of NaCl). Membrane pore structure and pore size distribution of BaAlg hydrogel membrane were generated by molecular dynamic (MD) simulations. In sum, this work provided a green, economical and expandable new idea and membrane material for the separation of molecules and ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • PES/SPSf membrane was prepared via NIPS method using adipic acid as additive. • A sponge-like structure was formed due to the H-bonding between adipic acid & SPSf. • Hydration radius was estimated by MD simulations to reveal the rejection of dyes. • The membrane exhibited a higher dye rejection at low ionic strength. • High rejection of membrane for dyes was a synergy of size sieving and charge effect. Polyethersulphone (PES)/sulfonated polysulphone (SPSf) tight ultrafiltration (TUF) membrane was tailored for dye/salt selective separation via non-solvent induced phase separation (NIPS) method using adipic acid (AA) as a pore forming agent. Sucrose and PEG (200–1000 Da) as neutral model molecules and eight kinds of charged dye model molecules (269.3–960.8 Da) were employed to explore the roles of size sieving and charge effect during the membrane separation process. Results showed that the membrane obtained from the casting solution with the mass ratio of PES/SPSf = 84/16 and 11 wt% AA possessed a fully sponge-like structure with an average pore size of 1.8 nm and the molecular weight cut off (MWCO) of 7250 Da. The pure water permeance of the membrane was up to 72.2 L/m2 h bar and displayed a reasonable retention for the neutral molecules including PEG 1000 (46.0%), PEG 400 (19.7%) and sucrose (17.2%). Simultaneously, the membrane exhibited a higher rejection for dyes with the similar molecular weight (M w) such as methyl orange (MO) (69.4%), acid blue 25 (AB25) (92.6%) and Evans blue (EB) (100%). The high rejection for these dyes was mainly attributed to the synergy between the size sieving and charge effect. Furthermore, the rejection of membrane for methyl red (MR), MO and AB25 was 50.1%, 69.4% and 92.6%, respectively. Molecular dynamics (MD) simulations revealed that the hydration radius of AB25 (1.04 nm) was bigger than that of MR (0.94 nm) and MO (0.99 nm), leading to higher rejection illustrating that size sieving played an important role in the rejection of dyes (M w less than 696.7 Da) with the same charge. Specifically, the contribution rate of steric hindrance and charge effect to the dye rejection gradually decayed as an increase on the molecular weight of dyes (over 416.0 Da). In addition, the rejection of MR, MO, indigo carmine (IC) and acid fuchsin (AF) decreased with an increase in the ionic strength of feed solutions due to the shielding effect of space charge. In summary, our work provides a profound understanding of the membrane selective separation mechanism for dye wastewater treatment and reuse. [ABSTRACT FROM AUTHOR]