The effect of surfactants on the structure and performance of PES membrane for separation of carbon dioxide from methane

Improving Hemocompatibility of Polysulfone Membrane by UV-Assisted Grafting of Sulfonated Chitosan

The most prevalent type of hemodialysis membrane is polysulfone (PSf). However, due to inadequate biocompatibility, it significantly compromises the safety of dialysis for patients. In this study, we modify the surface of the PSf membrane with 2,4-dihydroxybenzophenone (DBPh) groups to serve as anchoring sites during UV irradiation. Subsequently, a tailored sulfonated dihydroxy propyl chitosan (SDHPCS) is grafted onto the modified PSf membrane to compensate for the deficiencies in hydrophilic additives. The modified PSf membrane exhibits outstanding hydrophilicity and stability, as demonstrated by its characterization and evaluation. This paper focuses on investigating the interaction between platelet membrane formation, protein adsorption, and anticoagulant activity. The results show that the modified PSf membrane exhibits remarkable enhancement in surface hydrophilicity, leading to a significant reduction in protein and platelet adsorption as well as adhesion.

Drug Release from Surfactant-Containing Amorphous Solid Dispersions: Mechanism and Role of Surfactant in Release Enhancement

PURPOSE

To understand how surfactants affect drug release from ternary amorphous solid dispersions (ASDs), and to investigate different mechanisms of release enhancement.

METHODS

Ternary ASDs containing ritonavir (RTV), polyvinylpyrrolidone/vinyl acetate (PVPVA) and a surfactant (sodium dodecyl sulfate (SDS), Tween 80, Span 20 or Span 85) were prepared with rotary evaporation. Release profiles of ternary ASDs were measured with surface normalized dissolution. Phase separation morphologies of ASD compacts during hydration/dissolution were examined in real-time with a newly developed confocal fluorescence microscopy method. The water ingress rate of different formulations was measured with dynamic vapor sorption. Microscopy was employed to check for matrix crystallization during release studies.

RESULTS

All surfactants improved drug release at 30% DL, while only SDS and Tween 80 improved drug release at higher DLs, although SDS promoted matrix crystallization. The dissolution rate of neat polymer increased when SDS and Tween 80 were present. The water ingress rate also increased in the presence of all surfactants. Surfactant-incorporation affected both the kinetic and thermodynamics factors governing phase separation of RTV-PVPVA-water system, modifying the phase morphology during ASD dissolution. Importantly, SDS increased the miscibility of RTV-PVPVA-water system, whereas other surfactants mainly affected the phase separation kinetics/drug-rich barrier persistence.

CONCLUSION

Incorporation of surfactants enhanced drug release from RTV-PVPVA ASDs compared to the binary system. Increased drug-polymer-water miscibility and disruption of the drug-rich barrier at the gel-solvent interface via plasticization are highlighted as two key mechanisms underlying surfactant impacts based on direct visualization of the phase separation process upon hydration and release.

Chemical Cleaning Process of Polymeric Nanofibrous Membranes

Membrane fouling is one of the most significant issues to overcome in membrane-based technologies as it causes a decrease in the membrane flux and increases operational costs. This study investigates the effect of common chemical cleaning agents on polymeric nanofibrous membranes (PNM) prepared by polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polyamide 6 (PA6) nanofibers. Common alkaline and acid membrane cleaners were selected as the chemical cleaning agents. Membrane surface morphology was investigated. The PAN PNM were selected and fouled by engine oil and then cleaned by the different chemical cleaning agents at various ratios. The SEM results indicated that the use of chemical agents had some effects on the surface of the nanofibrous membranes. Moreover, alkaline cleaning of the fouled membrane using the Triton X 100 surfactant showed a two to five times higher flux recovery than without using a surfactant. Among the tested chemical agents, the highest flux recovery rate was obtained by a binary solution of 5% sodium hydroxide + Triton for alkaline cleaning, and an individual solution of 1% citric acid for acidic cleaning. The results presented here provide one of the first investigations into the chemical cleaning of nanofiber membranes.

Structure-Properties Relationship of Electrospun PVDF Fibers

Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers’ morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- and micro-sized fiber diameters were prepared by a controlled and reliable electrospinning process. The fibers with diameters from 276 nm to 1392 nm were spun at a voltage of 25 kV–50 kV from the pure PVDF solutions or in the presence of a surfactant—Hexadecyltrimethylammonium bromide (CTAB). Although the presence of the CTAB decreased the fibers’ diameter and increased the electroactive phase content, the piezoelectric performance of the PVDF material was evidently deteriorated. The maximum piezoelectric activity was achieved in the fibrous PVDF material without the use of the surfactant, when a piezoelectric charge of 33 pC N⁻¹ was measured in the transversal direction on a mean fiber diameter of 649 nm. In this direction, the material showed a higher piezoelectric activity than in the longitudinal direction.

A Bibliometric Survey of Paraffin/Olefin Separation Using Membranes

Bibliometric studies allow to collect, organize and process information that can be used to guide the development of research and innovation and to provide basis for decision-making. Paraffin/olefin separations constitute an important industrial issue because cryogenic separation methods are frequently needed in industrial sites and are very expensive. As a consequence, the use of membrane separation processes has been extensively encouraged and has become an attractive alternative for commercial separation processes, as this may lead to reduction of production costs, equipment size, energy consumption and waste generation. For these reasons, a bibliometric survey of paraffin/olefin membrane separation processes is carried out in the present study in order to evaluate the maturity of the technology for this specific application. Although different studies have proposed the use of distinct alternatives for olefin/paraffin separations, the present work makes clear that consensus has yet to be reached among researchers and technicians regarding the specific membranes and operation conditions that will make these processes scalable for large-scale commercial applications.

Effect of functionalization of multiwalled carbon nanotubes with aminated poly(ether sulfone) on thermal and mechanical properties of poly(ether ether ketone) nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were functionalized with aminated poly(ether sulfone) (PES) through the amidation reaction. Characterizations by Fourier transform infrared spectroscopy and X-ray diffraction corroborated the success of grafting reaction. Raman spectra reveal that no further damage occurred after the anchoring of PES to the carboxylated MWCNTs. Transmission electron microscopy shows that PES functionalization resulted in better dispersion of MWCNTs than acid oxidation. Poly(ether ether ketone) (PEEK)/MWCNTs functionalized with PES (PES-MWCNTs) nanocomposites were fabricated by solution-mixing and compression-molding techniques. Thermogravimetric analysis indicates that PES-MWCNTs/PEEK nanocomposites have the highest degradation temperature and thermal stability. Furthermore, noticeable increases in the crystallization and melting temperature as well as in the degree of crystallinity were found from differential scanning calorimetry thermograms, attributed to the strong heterogeneous nucleating role of PES-MWCNTs. Tensile test presents that the attachment of PES to the surface of MWCNTs exceptionally improved the tensile strength and Young’s modulus, and obtained moderate elongation at break. Impact toughness test and dynamic mechanical analysis show that the addition of PES-MWCNTs greatly enhanced the toughness and storage modulus of PEEK, respectively. These results are attributed to improved dispersion of PES-MWCNTs and strong interfacial adhesion to matrix, which is evidenced by scanning electron microscopy.

Preparation of hydrophilic nanofiltration membranes for removal of pharmaceuticals from water

Asymmetric polyethersulfone (PES) nanofiltration membranes were prepared via phase inversion technique. PES polymer, Brij 58 as surfactant additive, polyvinylpyrrolidone (PVP) as pore former and 1-methyl-2-pyrrolidone (NMP) as solvent were used in preparation of the casting solutions. Distillated water was used as the gelation media. The scanning electron microscopy (SEM) images and measurements of contact angle (CA) and zeta potential were used to characterize the prepared membranes. Also performance of the membranes was examined by determining the pure water flux (PWF) and pharmaceuticals rejection. The addition of Brij 58 to the casting solution resulted in formation of the membranes with higher thickness and more porous structure in the sublayer in comparison with the net PES membrane. The surface hydrophilicity of the membranes was remarkably enhanced via the presence of Brij 58 in the casting solution, so that, the contact angel diminished from 74.7° to 28.3° with adding 6 wt. % of Brij 58 to the casting solution. The addition of Brij 58 to the casting solution resulted in formation of the membranes with superior PWF and higher rejection of amoxicillin and ceftriaxone in comparison with the pure PES membrane.

Facilitated transport of CO2 through novel imidazole-containing chitosan derivative/PES membranes

Here, a new imidazole alkyl derivative of chitosan (Im-CS) is synthesized and characterized by FT-IR and ¹H-NMR spectroscopy. This derivative was blended with polyethersulfone (PES) to fabricate newly integrally skinned PES membranes.

Novel polyoxadiazoles with non-coplanar ortho-linked structures as highly CO2 permselective membranes

A novel class of polyoxadiazole membranes containing non-coplanar 1,1′-thiobis(2-naphthoxy) groups was synthesized using versatile route and tested for CO₂ separation. Upon oxidation, the sulfone-containing membranes exhibited higher permeability and lower selectivity.