Gui-E Chen

Fabrication and characterization of a novel nanofiltration membrane by the interfacial polymerization of 1,4-diaminocyclohexane (DCH) and trimesoyl chloride (TMC)

This study focuses on the preparation and nanofiltration properties of a novel thin-film composite polyamide membrane formed by the interfacial polymerization of 1,4-diaminocyclohexane (DCH) and trimesoyl chloride (TMC) on a porous polysulfone supporting membrane. At the same time, we found that the introduction of sodium N-cyclohexylsulfamate (SCHS) can improve to a degree the water flux and salt rejection. The active surface of the membrane was characterized by employing SEM and AFM. The performance of the nanofiltration membrane was optimized by considering the preparation conditions, including the monomer concentration, reaction time, curing conditions and SCHS concentration. The resulting NF membrane prepared under the optimum conditions exhibited a Na2SO4 rejection of 98.1% and a water flux of 44.6 L m−2 h−1 at 0.6 MPa. The pore size of the NF membrane was about 0.33–0.42 nm, which was calculated from the rejection of PEG and carbohydrates, respectively.

Hydrophilic Modification of PVDF Microfiltration Membrane with Poly (Ethylene Glycol) Dimethacrylate through Surface Polymerization

ABSTRACT The hydrophilic modification of poly (vinylidene fluoride) (PVDF) membrane with poly (ethylene glycol) dimethacrylate (PEGDMA) through grafting reaction for antifouling was reported. The influence of PEGDMA content, reaction temperature and time, on the structure, morphology, antifouling, and hydrophilicity of PVDF-g-PEGDMA membrane has been investigated. The PEGDMA monomers that were grafted on the surface of PVDF microfiltration membrane were confirmed by Attenuation total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and morphology study conducted by SEM revealed the changes before and after modification. The protein adsorption, filtration performance, water content, and dynamic contact angle were used to characterize the antifouling and hydrophilicity of the modified PVDF membranes. Compared with the pristine PVDF membrane, the bovine serum albumin (BSA) adsorption on the PVDF-g-PEGDMA membrane decreased about 80%, and the water contact angle of the membrane dropped to 0°. Besides, the experimental results revealed no significant differences between the membrane samples with respect to pore size. GRAPHICAL ABSTRACT

A PVDF/PVB composite UF membrane improved by F-127-wrapped fullerene for protein waste-water separation

A novel polyvinylidene fluoride (PVDF)/polyvinyl butyral (PVB) ultrafiltration (UF) membrane was prepared via a non-solvent induced phase inversion (NIPS) method and blended with F-127-wrapped fullerene at different fullerene contents (0.000 wt%, 0.025 wt%, 0.050 wt%, 0.075 wt% and 0.100 wt%, weight of casting solution). The composite membranes were analyzed using SEM, FT-IR, AFM, XPS and TG. The membranes had asymmetrical structures and widened channels, displayed –O–H vibrations at approximately 3700 cm−1, had smooth topographies, and had increased oxygen atom contents and excellent thermal resistances due to the incorporation of additives. The optimal ratios of PVDF, PVB, F-127 and fullerene determined by permeability studies were 16.2 wt%, 1.8 wt%, 1.0 wt% and 0.100 wt%, respectively. Under these ratios, the pure water flux (PWF) was increased, the flux recovery rate (FRR%) was doubled, the reversible fouling ratio (Rr%) was enhanced, and the irreversible fouling ratio (Rir%) was decreased. Furthermore, dynamic contact angle measurements testified that the surface was more hydrophilic. Besides, mechanical properties, porosity, molecular weight cut-off (MWCO) and pore size distribution were also investigated to evaluate the composite membranes. In protein separation applications, the membranes could provide selectable separation methods for bromelain (33 kDa), ovalbumin (OVA, 45 kDa) and bovine serum albumin (BSA, 68 kDa) up to 98.6%.

Synergy of graphene oxide–silver nanocomposite and amphiphilic co-polymer F127 on antibacterial properties and permeability of PVDF membrane

A graphene oxide–silver (GO–Ag) nanocomposite was formed by in situ reduction in the casting solution and was employed to decorate polyvinylidene fluoride (PVDF) membrane, together with amphiphilic co-polymer F127. The finger-like macro-voids morphology and surface roughness of modified membranes were presented by SEM and AFM microscopy. The FTIR spectrum and XPS analysis confirmed that the hydrophilic component contributed to the membrane wettability and permeability, while the graphene oxide–silver nanocomposite was conductive to membrane antimicrobial activity. Results indicated that under the comprehensive optimal conditions the prepared membranes possessed pure water flux of 269 L m−2 h−1 and BSA rejection ratio of 98.2%, the dynamic contact angles ranged from 60.5° to 10° within 80 s and the inhibition zone sizes against E. coli and S. aureus were 3 mm and 2 mm, respectively. Overall, the permeability, hydrophilicity and antibiofouling of modified membranes were regulated by the synergism between multifunctional modifier GO–Ag and F127 in a controllable blending-reaction modification process.

Novel β-CD@ZIF-8 Nanoparticles-Doped Poly(m-phenylene isophthalamide) (PMIA) Thin-Film Nanocomposite (TFN) Membrane for Organic Solvent Nanofiltration (OSN)

Organic solvent nanofiltration (OSN) membranes are always troubled by the “trade-off” effect between solvent flux and solute rejection. Hence, a rapid, convenient, and effective way to synthesize novel β-cyclodextrin-enhanced zeolite imidazole framework-8 (β-CD@ZIF-8) nanoparticles was first proposed and the nanoparticles were doped into both selective layer and poly(m-phenylene isophthalamide) support for fabricating thin-film nanocomposite membranes. Transmission/scanning electron microscopy images and X-ray photoelectron spectroscopy results demonstrate the successful synthesis of β-CD@ZIF-8. Atomic force microscopy images illustrate the more rougher surface compared to the pristine membrane, while the pure acetone flux reached 62.3 ± 2.3 L m–2 h–1, and Rose Bengal rejection achieved 96.6 ± 1.8 and 94.5 ± 0.5% in methanol (MeOH) and tetrahydrofuran at 0.6 MPa, respectively, when the dosage was 0.05% (w/v). The molecular weight cutoff around 574 Da of PPA2505 containing β-CD@ZIF-8 in both support and selective layers shows the optimum properties and outstanding OSN performances in erythromycin concentration and purification in MeOH and butyl acetate. Additionally, polyimide nanofiber and the formed net structure may offer a potential way to fabricate “ultrathin” film in the OSN industry.