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This study reports highly permeable ultrathin film composite (uTFC) membranes whose rejection layer was reinforced by polymer chains during the interfacial polymerization of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) to achieve enhanced salt rejection. A rejection layer of approximately 20 nm was formed at an MPD concentration of 0.01 wt%. This reinforced membrane had a water permeability of about 16.7 L/(m2 h bar), while exhibiting an improved divalent salt (Na 2 SO 4) to monovalent salt (NaCl) selectivity compared with the control TFC membrane without reinforcement (3.44 vs. 1.06). The role of the reactable polymer chains in interfacial polymerization was discussed as MPD adsorbent and reactant, according to the measurements by quartz crystal microbalance and X-ray photoelectron spectroscopy. This work provides a new pathway for the design and construction of uniform ultrathin layers as well as the preparation of high performance separation membranes. [ABSTRACT FROM AUTHOR]

Four tertiary amine based amphiphilic copolymers with similar composition but different sequence structures in terms of diblock (Poly(dimethylamino-2-ethyl methacrylate- b -methyl methacrylate) (P(MMA- b -DMAEMA))), triblock (P(DMAEMA- b -MMA- b -DMAEMA)), four-armed diblock (P(MMA- b -DMAEMA) 4 ) and random (P(MMA- r -DMAEMA)) were synthesized and used for fabricating functional porous membranes by blending method. The retention ratios and surface enrichment ratios of the copolymers in blend membranes were determined by hydrogen nuclear magnetic resonance ( 1 H-NMR) and X-ray photoelectron spectroscopy (XPS). The composition of the formed membranes was investigated and the durability was experimentally tested. The hydrophilicity of the membranes was evaluated by water contact angle measurement. The performance of membranes under different conditions including water fluxes at different pH and various ionic strength, the adsorption capabilities for Cr(VI) and negatively charged dye sunset yellow at different pH was studied. The results show that tertiary amine based amphiphilic copolymers with block and multi-armed sequence structures enable the blend membranes with higher copolymer retention ratios, more surface tertiary amine groups contents and better composition stability as well as more sensitive to the variation of pH, ionic strength, higher equilibrium anions, and negatively charged dyes uptakes. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Thin film composite (TFC) polyamide membranes set the golden standard for reverse osmosis technology, but tuning their permeability and selectivity remains a major challenge because of the inherent permeability-selectivity trade-off. Creating nano-sized voids within the polyamide rejection layer can tune the membrane roughness and increase its effective filtration area to improve the water permeability. Here we prepare nano-foamed polyamide rejection layers by adding sodium bicarbonate into the aqueous solution of amine monomers. We show a systematic evolution of the roughness structure of polyamide membranes, with increasingly leaf-like and belt-like features appearing under enhanced nano-foaming conditions. These nano-foamed features can result in remarkable improvements in both water permeability and salt rejection and reduce membrane fouling propensity at the same time. Our study paves a new research direction for designing future generation of desalination membranes, which holds vast potential to reduce the cost and energy consumption of desalination while achieving improved product water quality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crosslinking the copolymer enhanced its migration resistance and membrane stability. • The membrane exhibited pH-dependent adsorption and easy recovery properties. • The membrane removal/regeneration process resulted in the concentration of purified target pollutants. In this study, a blend membrane consisting of polyvinylidene fluoride (PVDF) and tertiary amine containing random copolymer poly(methyl methacrylate-r-dimethylamino-2-ethyl methacrylate) (P(MMA- r -DMAEMA)) was fabricated and utilized as an adsorptive membrane for micropollutants (anionic dye and heavy metal ions) removal from aqueous solutions. Cross-linking the random copolymer by p-xylylene dichloride (XDC) produced the membrane with improved copolymer retention ratio and stability, while slightly variated physicochemical properties. Besides, the fluxes of crosslinked blend membranes dramatically increased from 0.7 ± 0.1 L/(m2h) to 118.6 ± 5.9 L/(m2h). Then the present blend membrane was carried out adsorption and filtration experiments to investigate the influence of various of operation parameters including initial solution pH value, contacting time, initial solution concentration, and recycling efficiency on micropollutants removal. The experimental results showed that the removal of the anionic dyes and heavy metal ions on this tertiary amine containing blend membrane was a pH-dependent process with the maximum adsorption capacity at the initial solution pH of 3.5 for anionic dyes and 6.0 for metal ions, respectively. The membrane showed highly efficient capture of sunset yellow (above 99%). Meanwhile, the captured sunset yellow was recovered and concentrated with a small volume of alkaline solutions at pH 10.0, which simultaneously regenerated the membrane for its reuse. In a 3-cycle capture-recovery test, the membrane demonstrated a high sunset yellow recovery ratio and a volumetric concentration ratio as high as 400%. Our study provides an alternative strategy for functionalized membrane fabrication, micropollutants removal and recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • COFs (Covalent organic frameworks) was chosen as the shell material in heterogeneous catalyst. • A yolk-shell (Pd/C)@TpPa COFs catalyst was synthesized via a template method. • The catalytic performance was tested in Suzuki reaction. • The heterogeneous catalyst showed a high conversion with only 0.05 mol% Pd loading. • Catalytic selectivity by size exclusion due to COFs was observed, amounting to 100%. • The heterogeneous catalyst also showed good recyclability. • Environment-friendly, stable, and robust nano catalyst for cross-coupling reactions. A novel catalyst with a yolk-shell structure was designed to overcome the leaching of noble metals in heterogeneous catalysis. Through a template method, palladium (Pd) nanoparticles were encapsulated by hollow spherical covalent organic frameworks (COFs) consisting of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) and p-phenylenediamine (Pa). The final catalyst with a yolk-shell structure was denoted as (Pd/C)@TpPa COFs. The unique morphology and chemical structure of this novel composite (Pd/C)@TpPa COFs were confirmed by a transmission electron microscope (TEM), a laser particle analyzer, X-ray diffraction (XRD), and N 2 adsorption and desorption. Subsequently, to demonstrate its catalytic performance brought by structural design, this novel catalyst was applied to catalyze the Suzuki reaction. Interestingly, this catalyst exhibited a brilliant size cutoff efficiency for aryl benzene amounting to 100% and achieved a high conversion with only 0.05 mol% Pd loading. Besides, this catalyst could be readily recovered via filtration and reused for at least five consecutive cycles without any significant loss in its activity. [ABSTRACT FROM AUTHOR]

Superhydrophobic polyvinylidene fluoride (PVDF) membrane is a promising material for membrane distillation. Existing approaches for preparing superhydrophobic PVDF membrane often involve separate manipulation of surface roughness and surface chemistry. Here we report a one-step approach to simultaneously manipulate both the surface roughness and surface chemistry of PVDF nanofibrous membranes for enhanced direct-contact membrane distillation (DCMD) performances. The manipulation was realized in a unique solvent-thermal treatment process, during which a treatment solution containing alcohols was involved. We demonstrate that by using different chain-length alcohols in the treatment solvent, surface roughness can be promoted by creating nanofin structures on the PVDF nanofibers using an alcohol which has moderate affinity with PVDF. Meanwhile, surface chemistry can be tuned by adjusting the fraction distribution of crystal phases (nonpolar α phase and polar β phase) in the membrane using different alcohols. PVDF membranes with different surface wettabilities were used to evaluate the effects of surface roughness and surface energy on the DCMD performances. Combining both low surface energy and multi-scale surface roughness, pentanol-treated PVDF membrane achieved best anti-water property (water contact angle of 164.1° and sliding angle of 8.1°), and exhibited superior water flux and enhanced anti-wetting ability to low-surface-tension feed in the DCMD application. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract We report a novel membrane surface modification method using a fast polydopamine coating (fPDAc) strategy. Specifically, NaIO 4 was introduced in the coating process to accelerate the polydopamine deposition rate. Surface properties and separation performances of fPDAc-coated reverse osmosis membranes were characterized and compared to those obtained using the conventional slow polydopamine coating (sPDAc) strategy. Quartz crystal microbalance measurements showed greatly increased polydopamine deposition rate using the fPDAc method, resulting in a reduction of 97% coating time to reach an areal mass of 2000 ng/cm2. Both fPDAc and sPDAc enhanced the surface hydrophilicity and reduced the membrane surface charge. At relatively low areal mass deposition (<1000 ng/cm2), fPDAc-coated membranes showed improved NaCl rejection together with only mild loss of pure water flux. Nevertheless, this rejection enhancement effect was not noticeable when extensive polydopamine coating was applied due to the undesirable cake-enhanced concentration polarization effect. The extensive polydopamine coating was further accompanied with severe loss of membrane permeability, suggesting that shorter coating time (e.g., 4 min) is preferred using the fPDAc method. Our study provides a more rapid and effective membrane surface coating method compared to the conventional sPDAc method. [ABSTRACT FROM AUTHOR]