Plasma modification of substrate with poly(methylhydrosiloxane) for enhancing the interfacial stability of PDMS/PAN composite membrane

Organosiloxane membranes for heavy aromatic oil fractionation

The industrial separation of hydrocarbons relies on distillation. Organic solvent nanofiltration can provide an energy-efficient alternative. We prepared high performance organosiloxane membranes for fractionation of heavy aromatics. They achieved a high permeance up to 0.13 L m-2 h-1 bar-1, with a rejection rate of 88.7% for hydrocarbons with five aromatic rings.

A Comprehensive Review of Performance of Polyacrylonitrile-Based Membranes for Forward Osmosis Water Separation and Purification Process

Polyacrylonitrile (PAN), with its unique chemical, electrical, mechanical, and thermal properties, has become a crucial acrylic polymer for the industry. This polymer has been widely used to fabricate ultrafiltration, nanofiltration, and reverse osmosis membranes for water treatment applications. However, it recently started to be used to fabricate thin-film composite (TFC) and fiber-based forward osmosis (FO) membranes at a lab scale. Phase inversion and electrospinning methods were the most utilized techniques to fabricate PAN-based FO membranes. The PAN substrate layer could function as a good support layer to create TFC and fiber membranes with excellent performance under FO process conditions by selecting the proper modification techniques. The various modification techniques used to enhance PAN-based FO performance include interfacial polymerization, layer-by-layer assembly, simple coating, and incorporating nanofillers. Thus, the fabrication and modification techniques of PAN-based porous FO membranes have been highlighted in this work. Also, the performance of these FO membranes was investigated. Finally, perspectives and potential directions for further study on PAN-based FO membranes are presented in light of the developments in this area. This review is expected to aid the scientific community in creating novel effective porous FO polymeric membranes based on PAN polymer for various water and wastewater treatment applications.

Interlocking-interface-enabled thermally deformable liquid metal/polymer membrane with high bonding strength

HYPOTHESIS

The high surface tension of liquid metal (LM) causes interface incompatibility and poor bonding strength with many substrates. Fine adjustment towards the properties of the surface area is sufficient to introduce strong bonding. Hence, we hypothesize that the interlocking structure using hydrophilic polyvinyl alcohol (PVA) as a "bridge" should be helpful for tight interfacial bonding of LM with polymeric substrates, thus achieving high-performance LM/polymer membranes, which have wide applications in the field of soft sensors and robotics.

EXPERIMENTS

The bulk EGaIn was fabricated into LM nanoparticles (LMNPs@PVA) solution. Then, PVA molecules were "doped" into the surface crosslink of the plasma treated polymer substrate by an interfacial penetrating method. Afterward, the solution was evenly dropped on the surface of the treated substrate to obtain the LMNP/polymer membrane after the water evaporated. Photothermal actuators were fabricated based on the membranes.

FINDINGS

During the interlocking structure, PVA macromolecules could be doped and trapped onto the top surfaces of various polymer substrates as binding "bridges" between the LMNPs and the matrix materials. The achieved LMNP membrane exhibites satisfactory bonding strength, durability and water-assisted erase-reprint, which can be used as soft photothermal actuators with remote laser control.

Fabrication of ZnO/y-FeOOH nanoparticles embedded on the polyethylene terephthalate membrane: Evaluation of antifouling behavior and COD removal

Nanofiltration contributes to the development of advanced treatment of wastewater. An antifouling mixed matrix recycled polyethylene terephthalate (rPET) membrane modified by the hydrophilic ZnO/y-FeOOH nanoparticles (NPs) was fabricated via the electrospinning method. The effect of ZnO/y-FeOOH NP_S embedded in rPET as a modifier on the fabrication of nanocomposite membranes was investigated regarding water flux, membrane morphology, permeability, fouling resistance, and COD removal. The surface morphology of the rPET-ZnO/y-FeOOH membrane was evaluated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), water contact angle (WCA), and porosity and pore structure.Due to the embedding of NPs, the resulting rPET-ZnO/y-FeOOH membrane, with a low WCA of 53.404° angle, conforms significantly improved hydrophilicity and water permeation flux. The FESEM image displayed the distribution of cuboidal and needle-like ZnO and FeOOH NPs on the rPET membrane. The performance of the nanofiltration system related to the removal efficiency of COD was studied. It was deduced that the rPET-ZnO/y-FeOOH membrane had a superior COD removal capability (95.7%) at a pressure of 2 bar. Protein rejection tests were performed on antifouling behavior. The nanocomposite membrane with a high antifouling capability was related to 0.5 wt·% ZnO/y-FeOOH NPs (flux recovery ratio [FRR] = 96.2%, R_r = 90.21%, and R_ir = 3.001%). The modification procedure in this study (as a great improving technique) was proposed to fabricate the antifouling nanofiltration membrane.

PDMS with Tunable Side Group Mobility and Its Highly Permeable Membrane for Removal of Aromatic Compounds

Polydimethylsiloxane (PDMS), as the benchmark of organophilic membrane materials, still faces challenges for removal of aromatic compounds due to the undesirable transport channels. In this work, we propose to reconstruct the PDMS conformation with tunable side group mobility by introducing phenyl as rigid molecular spacer to relieve steric hindrance of large-sized aromatic molecules; meanwhile, polymer segments are loosely stacked to provide additional degrees of freedom as increasing the permeant size. Moreover, the reconstructed PDMS is engineered into the composite membrane with prevention of condensation of aromatic compounds in the substrate pores. The resulting thin-film composite membrane achieved one order of magnitude higher flux (11.8 kg m^-2  h^-1 ) with an equivalent separation factor (12.3) compared with the state-of-the-art membranes for aromatic removal. The permeant-customized membrane molecular and microstructure designing strategy opens a new avenue to develop membranes for specific separation targets.

A facile strategy to achieve monodispersity and stability of pigment TiO2 particles in low viscosity systems

Stable dispersion of TiO₂ particle is very desirable for its practical applications in various fields. It is a big challenge to stabilize pigment TiO₂ with relatively large size (200-300 nm) in low viscosity (~10 cP) systems. In the current work, we introduced a general strategy using a hydrophobic-hydrophilic structure to achieve single-dispersed TiO₂ particles with long storage stability in low viscosity systems. The modified TiO₂ particles (~250 nm) can be re-dispersed into water/glycol ethers mixture to form single dispersed suspension without any additives. Our study shows that the dispersion can be stable at least 60 days at room temperature and the rheological property is similar to the Newtonian fluids showing an extremely low yield stress at relatively high solid concentration. This work is expected to introduce a new strategy to improve the dispersion stability of the large size nanoparticles in low viscosity systems.

Compositions Based on PAN Solutions Containing Polydimethylsiloxane Additives: Morphology, Rheology, and Fiber Spinning

The effect of additives of polydimethylsiloxanes (PDMS) with various molecular weights on the morphology and rheological behavior of polyacrylonitrile (PAN) solutions in dimethyl sulfoxide has been analyzed. It was shown that only partial compatibility of the PDMS with the lowest molecular weight member of the homologous series studied—hexamethyldisiloxane—with PAN solution takes place. All other PDMS samples form emulsions with PAN solutions. The coalescence rate of PDMS drops depends on the viscosity ratio of the disperse phase and the continuous medium, which determines both the duration of dispersion preparation and the conditions for processing emulsions into fibers and films. An anomalous change in viscosity for a series of emulsions with different concentrations of additives, associated with the slippage, was detected. The relaxation properties of emulsions “feel” macro-phase separation. Modeling of the wet spinning process has shown that the morphology of the deposited solution drop reflects the movement of the diffusion front, leading to the gathering droplets in the center of the deposited formulation drop or to their localization in a certain arrangement. It was shown that the emulsion jets upon stretching undergo phase separation.

Acrylic acid-grafted pre-plasma nanofibers for efficient removal of oil pollution from aquatic environment

Oily wastewater is a worldwide problem threatening the environment and humans. High flux and low-energy consumption separation of oil and water is urgently required but still faces great challenges. In this study, nanofibrous membranes with superhydrophilic and underwater superoleophobic surfaces were fabricated by grafting acrylic acid onto plasma-treated electrospun polystyrene/polyacrylonitrile (PS/PAN) membranes. The morphologies, chemical compositions, mechanical and surface properties of the membranes were examined in detail. The water contact angles of the PS/PAN membranes were 137.4°, 130.1°, 119.5°, 88.1° and 80.2°, respectively, which decreased to 76.5°, 47.9°, 34.4°, 0° and 0° after grafting treatment, proving that the modification improved the surface hydrophilicity of the membranes due to the introduction of hydrophilic groups. In addition, a gravity-driven filtration device was utilized to investigate the oil/water separation potential of the membranes. The results indicated that the grafted PS/PAN membranes separated the layered oil/water mixtures with permeate flux up to 57509 L m^-2 h^-1, while high fluxes of 1390-6460 L m^-2 h^-1 for the separation of different oil-in-water emulsions. Importantly, the membranes still maintained high flux and efficiency even after several cycles of separation. Therefore, the reusable membranes can be expected to be potential cost-effective materials for oil/water treatment.

Fabrication of free-standing membranes with tunable pore structures based on the combination of electrospinning and self-assembly of block copolymers

Polydopamine could improve interface performance of composite membranes with tunable structures which were developed by combining electrospinning and BCP self-assembly.