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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 preparation of poly(vinylidene fluoride) (PVDF) membranes with high mechanical strength via vapor-induced phase separation (VIPS) is still a great challenge. In this study, high strength PVDF membranes with cellular pore structure are successfully prepared by comprehensively regulating the process parameters such as the dissolution temperature ( T d ), vapor temperature ( T v ) and exposure time ( t ) during the VIPS process, as well as the membrane-forming parameter i.e. mass fraction of PVDF polymer. The effects of these parameters on microstructure and performances of the PVDF membranes are systematically investigated. In the investigated ranges of t from 0.67min to 20 min, the membranes with cellular structure are obtained at both elevated T d and T v of 65 °C, relative humidity of 70%RH and mass fraction of 15 wt% PVDF. All the PVDF membranes with cellular structure prepared at elevated T d and T v of 65 °C exhibit high mechanical properties, and the tensile stress at break ( σ * ) and tensile strain are higher than 2.5 MPa and 15%, respectively. The PVDF membrane prepared at t of 0.5 min has a critical structure and shows the maximum σ * of 4.0 MPa and tensile strain of 33%, respectively. It is expected that the results provide a valuable guidance for the design and fabrication of membranes from semi-crystalline polymer with desirable performances. [ABSTRACT FROM AUTHOR]

Ca-alginate/protamine/silica (APSi) hybrid capsule membranes with pH-responsive controlled release characteristics are successfully prepared by combining co-extrusion minifludics, adsorption and biosilicification under different pH conditions from 3 to 7. The microstructures of the prepared capsule membranes are characterized by optical photography, CLSM and SEM. The pH-responsive permeability of APSi hybrid capsule membranes is controlled by the electrostatic interactions between Ca-alginate networks and protamine molecules. Four kinds of solute molecules with different molecular weights including methylene blue, VB 12 , 4 kDa and 10 kDa FITC-dextran molecules are selected as solute molecules to comparatively study the diffusional permeability characteristics of solutes across APSi hybrid capsule membranes. The results show that, for the solutes with suitable molecule sizes such as VB 12 and 4 kDa FITC-dextran, the diffusional permeabilities across the capsule membranes at pH 4 are lower than those at pH 5; however, for the solutes with too small molecule size such as methylene blue or too large molecule size such as 10 kDa FITC-dextran, the diffusional permeabilities across the capsule membranes at pH 4 are very close to those at pH 5. The results in this study provide valuable guidance for fabrication and application of APSi capsule membranes in the various fields including controlled release of drugs and immobilization of enzymes and so on. [ABSTRACT FROM AUTHOR]