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Separating low/high-valent ions with sub-nanometer sizes is a crucial yet challenging task in various areas (e.g., within environmental, healthcare, chemical, and energy engineering). Satisfying high separation precision requires membranes with exceptionally high selectivity. One way to realize this is constructing well-designed ion-selective nanochannels in pressure-driven membranes where the separation mechanism relies on combined steric, dielectric exclusion, and Donnan effects. To this aim, charged nanochannels in polyamide (PA) membranes are created by incorporating ionic polyamidoamine (PAMAM) dendrimers viainterfacial polymerization. Both sub-10 nm sizes of the ionic PAMAM dendrimer molecules and their gradient distributions in the PA nanofilms contribute to the successful formation of defect-free PA nanofilms, containing both internal (intramolecular voids) and external (interfacial voids between the ionic PAMAM dendrimers and the PA matrix) nanochannels for fast transport of water molecules. The external nanochannels with tunable ionizable groups endow the PA membranes with both high low/high-valent co-ion selectivity and chemical cleaning tolerance, while the ion sieving/transport mechanism was analyzed by employing the Donnan steric pore model with dielectric exclusion.

This paper reports a modeling and experimental study of the mass transfer enhancement of water deoxygenation by using a helical hollow fiber membrane (HHFM) to enable Dean vortices. Experiments demonstrated that the HHFM deoxygenating rate was doubled compared with straight hollow fiber deoxygenation. A new model to describe the HHFM deoxygenation mass transfer was derived combining the helical coordinate system mass continuity equation on the lumen side and a modified dusty gas model for the mutual gaseous diffusion in the porous membrane. The model simulation showed that Dean vortices induce transverse fluid disturbance in the fiber, which significantly promotes lumen side mass transfer. The key parameters influencing the strength of Dean vortices are the Reynolds number of the lumen side and the curvature of HHFM. Operating and membrane structure parameters were optimized for HHFM deoxygenation design. The new model could be employed to describe quantitatively the mass transfer behavior of all types of HHFM gas-phase separation processes.

To investigate the effect of the surface properties and the coating layer properties on surface modification via electrostatic adsorption, the electrostatic adsorption behavior of zwitterionic copolymers on negatively charged surfaces was studied. A series of positively charged zwitterionic copolymers and a series of negatively charged surfaces, including porous substrates and dense films, were fabricated. The electrostatic adsorption behavior of the zwitterionic copolymers on the negatively charged porous substrates was confirmed using the contact angles and fluorescently labeled protein adsorption experiments. The adsorption behavior of the zwitterionic copolymers on the negatively charged dense films was confirmed using quartz crystal microbalance determination and a fluorescently labeled protein adsorption experiment. The results indicated that a lower charge density on the zwitterionic copolymer brings about a higher adsorption mass on the charged surface, whereas an extremely low charge density on the coating layer results in a lower adsorption mass on the charged surface, due to weak interaction. A high density of the film surface charge is beneficial for surface adsorption, whereas an extremely high density of the film surface charge leads to low surface adsorption due to steric hindrance of the negatively charged sites. This work provides an insight into the best strategy for surface modification via electrostatic adsorption.

Pressure retarded osmosis (PRO) process is hindered by severe fouling occurring within the porous support of the forward osmosis (FO) membranes. We designed a novel double-skinned FO membrane containing a polyamide salt-rejecting layer and a zwitterionic brush-decorated, multiwalled carbon nanotube (MWCNT/PSBMA) foulant-resisting layer on the back side. Our results demonstrated that the coating of the MWCNT/PSBMA layer on the porous polyketone (PK) support imparted enhanced hydrophilicity and smaller membrane pore size, thereby providing excellent resistance toward both protein adhesion and bacterial adsorption. We also further evaluated this resultant double-skinned membrane (i.e., TFC-MWCNT/PSBMA) in dynamic PRO fouling experiments using protein and alginate as model organic foulants. Compared to the pristine TFC-PK and hydrophobic TFC-MWCNT membranes, the TFC-MWCNT/PSBMA membrane exhibited not only the lowest water flux decline but also the highest water flux recovery after simple physical flushing. These results shed light on fabrication of antifouling PRO membranes for water purification purposes.

The cost-effective treatment of emulsified oily wastewater discharged by many industries and human societies is a great challenge. Herein, based on an aliphatic polyketone (PK) polymer with a good membrane formation ability and an intrinsic intermediate hydrophilicity, a new class of reduced PK (rPK) membranes combining an all hydrophilic and electrically neutral surface chemistry comprising ketone and hydroxyl groups, and a fibril-like morphology featuring re-entrant structure, was facilely prepared by phase separation and following fast surface reduction. The synergetic cooperation of surface chemistry and surface geometry endowed the prepared membranes with excellent superhydrophilicity, underwater superoleophobicity, and underoil superhydrophilicity, in addition to antiprotein-adhesion property. Thus, fouling-resistant and self-cleaning filtrations of challenging oil-in-water emulsions containing adhesive oil, surfactant, high salinity, and proteins were effortlessly realized with high flux (up to ∼50 000 L m–2h–1bar–1), slow and reversible flux decline, and low oil permeate (<20 ppm). In contrast, a commercial superhydrophilic microporous membrane made of mixed cellulose ester suffered severe fouling gradually or immediately when carrying out the emulsion filtrations due to its less than ideal surface properties. It is believed that this class of membranes with desirable superwettability, high flux, and preparation simplicity can be a potential new benchmark for high performance and large-scale oil–water separation in complex environments.

Efficient treatment of difficult emulsified oil–water wastes is a global challenge. Membranes exhibiting unusual dual superlyophobicity (combined underwater superoleophobicity and underoil superhydrophobicity) are intriguing to realize high-efficiency separation of both oil-in-water and water-in-oil emulsions. For the first time, a robust polymeric membrane demonstrating dual superlyophobicity to common apolar oils was facilely fabricated via a simple one-step phase separation process using an aliphatic polyketone (PK) polymer, thanks to a conjunction of intermediate hydrophilicity and re-entrant fibril-like texture upon the prepared PK membrane. Further chemical modification to improve surface hydrophilicity slightly can enable dual superlyophobicity to both apolar and polar oils. It is found that a nonwetting composite state of oil against water or water against oil was obtainable on the membrane surfaces only when the probe liquids possess an equilibrium contact angle (θowor θwo) larger than the critical re-entrant angle of the textured surfaces (73°), which can explain the existences of dual superlyophobicity and also the nonwetting to fully wetting transitions. A simple design chart was developed to map out the operational windows of material hydrophilicity and re-entrant geometry, that is, a possible zone, to help in the rational design of similar interfacial systems from various materials. Switchable filtrations of oil-in-water and water-in-oil nanoemulsions were achieved readily with both high flux and high rejection. The simplicity and scalability of the membrane preparation process and the well-elucidated underlying mechanisms illuminate the great application potential of the PK-based superwetting membranes.

Based on POC set theory and SOC unit, a 1T3R parallel stable platform is proposed. The Single cylinder force analysis is studied. Then uses Newton-Euler method, gives full consideration to these various factors: without neglecting the ball screw rotation, friction between the spherical joint, the mass and the moment of inertia of electric cylinders, based above the dynamic theoretical Analysis of the stable platform is researched. The paper makes the guide sense for the follow-up research and the application of the 1T3R mechanism.