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Abstract A novel smart membrane with ion-recognizable nanogels as gates on interconnected pores is developed for simple and rapid detection of trace lead(II) ions in water. The membrane is prepared via one-step vapor-induced phase separation (VIPS) method, and featured with interconnected porous structure and Pb2+-responsive poly(N -isopropylacrylamide- co -benzo-18-crown-6-acrylamide) (PNB) nanogels on polyethersulfone (PES) membrane pore surfaces as gates. Afforded by such a unique architecture, both high flux and significant responsive characteristics are achieved. With the proposed strategy, the nanogels are fixed onto the membrane pore surfaces during the formation of interconnected porous structure; thus, the immobilization of nanogels onto the membrane pore surfaces does not result in the decrease of pore sizes. The water fluxes of fabricated membranes could be even higher than 6000 kg m−2 h−1 driven by the static pressure of 20 cm water column under gravity at 34 °C, because of the three-dimensionally interconnected porous structures. Due to high sensitivity and selectivity of PNB nanogels on the membrane pore surfaces in response to Pb2+ ions, the fabricated membranes can efficiently detect Pb2+ ions with a limit of detection as low as 10−9 mol/L. With the proposed novel membrane, rapid detection of trace lead(II) ions in water can be easily achieved by simply monitoring the trans-membrane flux change in a gravity-driven membrane module device, which is highly potential and promising in real-time and easy-to-popularize monitoring of drinking water safety and may expand the scope of applications of facile detection techniques. Graphical abstract fx1 Highlights • A novel membrane is fabricated with ion-recognizable nanogels as gates on interconnected pores. • The membrane is featured with both high flux and significant responsive characteristics. • The membrane can be used to detect trace lead(II) ions in water with a gravity-driven device. • The membrane can efficiently detect Pb2+ ions with a limit of detection as low as 10−9 mol/L. [ABSTRACT FROM AUTHOR]

Abstract A novel composite catalytic membrane is developed by blending silicon oxide coated ferroferric oxide (Fe 3 O 4 @SiO 2) nanoparticles in polyether sulfone (PES) membrane as Fenton-like catalysts via liquid-induced phase separation (LIPS) method. By introducing Fe 3 O 4 @SiO 2 nanoparticles in PES membrane matrix, the surface hydrophilicity, porosity and mean pore diameter of as-prepared composite catalytic membranes are improved due to the hydrophilic nature of the SiO 2 coating layer on the Fe 3 O 4 @SiO 2 nanoparticles. The as-fabricated catalytic membrane can filter large particles above ~100 nm and shows a high water flux of 2084 kg m−2 h−1 under 0.1 MPa. Importantly, the composite catalytic membrane shows efficient catalytic performance and satisfactory stability in the degradation of organic pollutants based on the Fenton-like reaction mechanism. The proposed strategy for membrane fabrication and the experimental results in this study provide valuable guidance for developing high-flux catalytic membranes with efficient catalytic performances for treatment of industrial and municipal wastewater. Graphical abstract fx1 Highlights • High-flux efficient catalytic membranes are developed for degradation of organic pollutants. • The membranes are fabricated by blending Fe 3 O 4 @SiO 2 nanoparticles in PES via LIPS. • Porous microstructures are formed between nanoparticles and membrane matrix during LIPS. • The membranes exhibit high flux, efficient catalytic performance and satisfactory stability. [ABSTRACT FROM AUTHOR]

In this study, a universal model is developed for describing the responsive performances of both positively and negatively responsive smart gating membranes with structural and responsive parameters. The model is derived by assigning the membrane pore size change ratio before and after immobilizing responsive gates and the volume change coefficient as well as the stacking effect coefficient of responsive gates as independent dimensionless variables. The reliability and fitting precision of the proposed model have been validated by the experimental results of positively thermo-responsive and negatively Pb2+-responsive gating performances of smart gating membranes, which are prepared by immobilizing poly(N -isopropylmethacrylamide- co -4-acrylamidobenzo-18-crown-6) (PNMB) microgels in porous poly(ether sulfone) (PES) membranes as functional gates that exhibit both thermo-induced shrinking and Pb2+-induced swelling responsive characteristics. All the experimental data of both positively and negatively responsive gating performances of smart gating membranes fit well with the developed model. The proposed model provides new insights for describing and explaining the responsive gating performances of both positively and negatively responsive smart gating membranes, and offers rational guidelines for designing and fabricating smart gating membranes with desired responsive gating performances by predetermining the structural and responsive parameters of smart gates for various applications. [Display omitted] • A universal model is developed for describing responsive performances of smart gating membranes. • The model is derived by assigning structural and responsive parameters of smart membranes as variables. • Both positively and negatively responsive performances of smart membranes can be priecisely described. • Smart membranes are prepared by immobilizing dual responsive microgels in porous substrates. • Reliability and fitting precision of the model are validated by experimental data of smart membranes. [ABSTRACT FROM AUTHOR]

A facile and efficient double co-axial microfluidic device has been developed for fabricating polyethersulfone (PES) hollow fiber membranes via phase separation. The co-axial microchannels with easy center alignment consist of a cylindrical tube for bore fluid, a cylindrical tube for dope fluid and a rectangular tube for coagulation fluid. In such a double co-axial microfluidic device, three phase core-annular flows are formed for continuously fabricating hollow fibers via phase separations at the interfaces. The nascent PES hollow fibers can be extruded from the outlet of microfluidic device continuously without clogging. Typical PES hollow fiber membranes have two dense skin layers on both outer and inner surfaces, due to the phase separation at both interfaces between the dope fluid and the bore fluid as well as the coagulation fluid. The effects of fabrication conditions including microfluidic flowrates, PES concentration in dope fluid and operation temperature on the structures of microfluidic-fabricated PES hollow fiber membranes are investigated systematically. Ternary fluid-flow diagrams are created for fabricating PES hollow fiber membranes with different PES concentrations and operation temperatures. The results in this study provide valuable guidance for fabricating hollow fiber membranes with controllable microstructures and dimensions via microfluidic approach. [ABSTRACT FROM AUTHOR]

A novel three-dimensional (3D) helical membrane is developed for process intensification via generation of Dean vortices in helical membrane channel. 3D helical porous polyethersulfone membrane is fabricated by casting the membrane forming solution on the surface of 3D-printed porous substrate with a 3D helical channel structure by high-speed rotation method, and then curing by vapor-induced phase separation. The optimal helical radius and internal channel height are both 19 mm for the prepared 3D helical membranes. When the feed flowrate is higher than the minimum critical flowrate, Dean vortices can be easily generated in the 3D helical membrane channel, and thus the membrane fouling can be effectively mitigated. The ratio of average transmembrane flux of 3D helical membrane to that of conventional cylindrical membrane increases from 1.0 to ∼2.0 when the feed flowrate increases from 2.1 to 106.1 mm s−1, and from 1.0 to ∼1.9 when the feed particle concentration increases from 0 to 20 g L−1. No matter how the microstructures of particles in feed solutions vary, Dean vortices generated in 3D helical membrane channels are always efficient to diminish the particle deposition on membrane surface. The proposed strategy is highly promising for developing efficient membranes with different materials for various applications. [Display omitted] • 3D helical porous polyethersulfone membranes are developed for process intensification. • The process intensification in 3D helical membranes is achieved by generation of Dean vortices. • There exists the minimum critical flowrate for generation of Dean vortices in 3D helical membranes. • The Dean vortices are efficient to diminish the particle deposition and membrane fouling. • Membrane process intensification can be acheived by Dean vortices for treating various particles. [ABSTRACT FROM AUTHOR]

The hydrophilicity of smart additives thermodynamically and kinetically affects the degree and velocity of the phase separation of casting solution, together with their distribution on the membranes, which ultimately affects the microstructure and properties of smart membrane. However, the reasonable design and successful preparation of additives with different hydrophilicity, as well as the observation of their migration during membrane formation process and final distribution on/in the membranes remain challenges. The three kinds of thermo-responsive submicrogels with similar chemical structures and different hydrophilicity were successfully fabricated and blended into poly(ether sulfone) (PES) as functional gates to prepare smart membranes via vapor-induced phase separation (VIPS). The hydrophilicity of poly(N - n -propylacrylamide) (PNN), poly(N -isopropylacrylamide) (PNI) and poly(N -isopropylmethacrylamide) (PNM) submicrogels were quantitively measured; their diameters and thermo-responsive factors in water were similar. Moreover, the effects of the hydrophilicity of submicrogels on the microstructures and properties of as-prepared smart membranes were systematically investigated and the results were elucidated in principle. The results showed the velocity of phase separation of casting solution, the pore size of membranes and the number of submicrogels distributed on membranes increased whereas the stability of submicrogels on membranes decreased with the enhancement of hydrophilicity of submicrogels. The membrane blended with PNI submicrogels with optimal hydrophilicity, which was provided with both a large number of submicrogels stably distributed on the membrane pores as smart gates and appropriate pore size, exhibited excellent permeability and thermo-responsiveness. The maximum water flux through this membrane was 26271 kg m−2 h−1 bar−1, and its maximum normalized thermo-responsive coefficient N value reached to 28.7. The results will provide valuable guidance for understanding the mechanism of phase separation and further development of smart membranes with satisfactory performances. Image 1 • Smart membranes blending different hydrophilic submicrogels are prepared via VIPS. • The hydrophilicity of different submicrogels are quantitively measured. • The velocity of phase separation speeds up by enhancing the hydrophilicity. • The pore size of membrane is enlarged as the submicrogels hydrophilicity increasing. • The membrane blended with PNI submicrogels exhibits the optimal properties. [ABSTRACT FROM AUTHOR]

Abstract: pH-responsive poly(ether sulfone) (PES) composite membranes blended with amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) diblock copolymers are fabricated through simple phase inversion in water. The anchor block PS has a lower surface tension than that of PES, which is beneficial to anchor the PS block near the membrane pore surfaces. Modification of membrane matrix surface including membrane surface and pore surface by PAA chains is achieved by surface-segregation of PS-b-PAA copolymers, and confirmed by water contact angle measurement on membrane surface and confocal laser scanning microscopy characterization of membrane cross-section. The effects of the blended PS-b-PAA copolymers on the microstructures and pH-responsive characteristics of the PES composite membranes are investigated systematically. The hydraulic permeation results show that the pH-responsive characteristics of composite membranes blended with PS-b-PAA copolymers are proven to be significant, fast, reversible and durable with pH switching between 3 and 8. FITC-dextran sieving experiments of a PS-b-PAA blended composite membrane at ambient pH values of 3 and 8 show 28% and 90% rejection of 70kDa solute, respectively. At pH=3 (pK a ), the membrane pores are in “closed” state due to the swollen conformation of the PAA chains. The results provide valuable guidance for fabricating stimuli-responsive membranes by blending amphiphilic block copolymers. [Copyright &y& Elsevier]

Antifouling poly(ether sulfone) (PES) composite membranes with novel bi-continuous porous structures, high fluxes and hydrophilic surfaces are successfully prepared by simultaneously manipulating the migration of amphiphilic three-block polymer poly(ethylene glycol)- block -poly(propylene glycol)- block -poly(ethylene glycol) (Pluronic® F127) to the membrane surfaces and the microstructures of membranes by vapor-induced phase separation (VIPS) method. Effects of the additive mass ratios of Pluronic® F127 to PES and VIPS process parameters, including the dissolution and vapor temperature (T), the relative humidity of vapor (RH) and the exposure time to vapor (t), on microstructures of membranes and the surface hydrophilicity of membranes are systematically investigated. When the additive mass ratio of Pluronic® F127 to PES is 100%, PES/Pluronic® F127 composite membranes with bi-continuous porous structure across the full cross-section can be easily fabricated. For the composite membranes with additive mass ratio of 100%, when t = 1 min, the water contact angles of membranes decrease remarkably when the temperature increases from T = 25 °C to T = 40 °C. For the PES/Pluronic® F127 composite membranes prepared via VIPS method with T = 25 °C, RH = 70% and t = 20 min, the water contact angle is as low as 34.5°, the water flux is as high as 236512 L m−2 h−1 bar−1 and the static adsorption amount of bovine serum albumin (BSA) is only 4.6 μg cm−2. Valuable guidance is presented in this study about the design and fabrication of antifouling membranes with high flux and hydrophilic surfaces. Image 1 • Composite membranes with bi-continuous porous structures and hydrophilic surfaces are fabricated. • The membranes are featured with both high fluxes and antifouling properties. • The membranes are prepared via VIPS by blending Pluronic F127 into PES matrix. • Microstructures of membranes can be controlled effectively by adjusting VIPS conditions. [ABSTRACT FROM AUTHOR]