Preparation of poly(etherimide) based ultrafiltration membrane with low fouling property by surface modification with poly(ethylene glycol)

Preparation of Ultrafiltration Membrane by Polyethylene Glycol Non-Covalent Functionalized Multi-Walled Carbon Nanotubes: Application for HA Removal and Fouling Control

Polyethylene glycol (PEG) non-covalent-functionalized multi-walled carbon nanotubes (MWCNT) membrane were prepared by vacuum filtration. The dispersion and stability of MWCNT non-covalent functionalized with PEG were all improved. TEM characterization and XPS quantitative analysis proved that the use of PEG to non-covalent functionalize MWCNT was successful. SEM image analysis confirmed that the pore size of PEG–MWCNT membrane was more concentrated and distributed in a narrower range of diameter. Contact angle measurement demonstrated that PEG non-covalent functionalization greatly enhanced the hydrophilicity of MWCNT membranes. The results of pure water flux showed that the PEG–MWCNT membranes could be categorized into low pressure membrane. PEG-MWCNT membrane had a better effect on the removal of humic acid (HA) and a lower TMP growth rate compared with a commercial 0.01-μm PVDF ultrafiltration membrane. During the filtration of bovine serum albumin (BSA), the antifouling ability of PEG-MWCNT membranes were obviously better than the raw MWCNT membranes. The TMP recovery rate of PEG–MWCNT membrane after cross flushing was 79.4%, while that of raw MWCNT–_COOH and MWCNT membrane were only 14.9% and 28.3%, respectively. PEG non-covalent functionalization improved the antifouling ability of the raw MWCNT membranes and reduced the irreversible fouling, which effectively prolonged the service life of MWCNT membrane.

Deposition of graphene nanoparticles associated with tannic acid in microfiltration membrane for removal of food colouring

A modified microfiltration (MF) membrane was prepared by flow-through coating method. First the sulfuric acid solution was vacuum filtered on the polyethersulfone (PES) MF membrane, providing the introduction of a sulfonic acid group to the backbone of PES. Sequentially, the polyethyleneimine solution was vacuum filtered to provide amine groups on the membrane surface. Finally, the graphene oxide solution, functionalized with different masses of tannic acid, was vacuum filtered on the membrane surface, producing the cross-linked modified membranes. These were efficient in the removal of anionic food colouring, achieving high removal rates and low fouling, compared to unmodified membrane. The best membrane in terms of bright blue dye removal was the MF PEI₅GO₁TA₄, capable of removing all the feed solution, and demonstrating its possibility of reuse in five cycles of operation.

Fouling behaviour of membranes with different characteristics by urban wastewater secondary effluent

Fouling behaviours and antifouling properties of polyvinylidene fluoride (PVDF) ultrafiltration membranes blending with polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and polymethyl methacrylate (PMMA) had been investigated using the secondary effluent as the filtration medium. The results demonstrated that the antifouling properties of membranes using PVA and PVP as the additives were generally stronger than those using PMMA. Additives PVA and PVP could effectively improve the structural property and hydrophilicity of the membrane and result in an outstanding antifouling property. A dense membrane surface could prevent low molecular foulants from entering into the membrane pores, depositing on the membrane with a loose spongy layer and penetrating into the internal macropore structure. The not fully generated internal macropores on the membrane surface were trend to be plugged, which resulted in serious flux decay and the membrane fouling was irreversible. Filtration cake formed on the membrane due to concentration polarization, which caused membrane flux decline and high flux recovery after cleaning.

A Scalable Method toward Superhydrophilic and Underwater Superoleophobic PVDF Membranes for Effective Oil/Water Emulsion Separation

A superhydrophilic and underwater superoleophobic PVDF membrane (PVDFAH) has been prepared by surface-coating of a hydrogel onto the membrane surface, and its superior performance for oil/water emulsion separation has been demonstrated. The coated hydrogel was constructed by an interfacial polymerization based on the thiol-epoxy reaction of pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) with diethylene glycol diglycidyl ether (PEGDGE) and simultaneously tethered on an alkaline-treated commercial PVDF membrane surface via the thio-ene reaction. The PVDFAH membranes can be fabricated in a few minutes under mild conditions and show superhydrophilic and underwater superoleophobic properties for a series of organic solvents. Energy dispersive X-ray (EDX) analysis shows that the hydrogel coating was efficient throughout the pore lumen. The membrane shows superior oil/water emulsion separation performance, including high water permeation, quantitative oil rejection, and robust antifouling performance in a series oil/water emulsions, including that prepared from crude oil. In addition, a 24 h Soxhlet-extraction experiment with ethanol/water solution (50:50, v/v) was conducted to test the tethered hydrogel stability. We see that the membrane maintained the water contact angle below 5°, indicating the covalent tethering stability. This technique shows great promise for scalable fabrication of membrane materials for handling practical oil emulsion purification.

Probing the morphology and anti-organic fouling behaviour of a polyetherimide membrane modified with hydrophilic organic acids as additives

A polyetherimide based membrane was modified with various hydrophilic organic acids as additives. The results showed that the additives exhibited a remarkable improvement in the antifouling properties (FRR of 72%).

Preparation of antifouling polyetherimide/hydrolysed PIAM blend nanofiltration membranes for salt rejection applications

Polyetherimide/hydrolysed PIAM blend NF membranes have been prepared and characterized. The PEI/hydrolysed PIAM composition of 80 : 20 showed very good salt rejection (sodium sulphate) up to 76% with a pure water flux of 11.8 L m⁻² h⁻¹. This study provides a simple and effective approach to produce negatively charged NF membranes for water desalination applications with low energy consumption.

Characterization of oligo(ethylene glycol) and oligoglycerol functionalized poly(ether imide) by angle-dependent X-ray photoelectron spectroscopy

PURPOSE

Previous investigations have shown that poly(ether imide) (PEI) membranes can be functionalized with aminated macromolecules. In this study we explored whether the characterization of PEI functionalized with oligo(ethylene glycol) (OEG) or linear, side chain methylated oligoglycerols (OGMe), by angle-dependent X-ray induced photoelectron spectroscopy (XPS) can be used to prove the functionalization, give insight into the reaction mechanism and reveal the spatial distribution of the grafts.

METHODS

PEI membranes were functionalized under alkaline conditions using an aqueous solution with 2 wt% of α-amino-ω-methoxy oligo(ethylene glycol) (Mn = 1,320 g·mol(-1)) or linear, side chain methylated monoamine oligoglycerols (Mn = 1,120, 1,800 or 2,270 g·mol(-1)), respectively. The functionalized membranes were investigated using XPS measurements at different detector angles to enable comparison between the signals related to the bulk and surface volume and were compared with untreated and alkaline-treated PEI membranes.

RESULTS

While at a perpendicular detector angle the bulk signals of the PEI were prominent, at larger surface volume-related detector angles, the signals for OGMe and OEG were determinable.

CONCLUSION

The surface functionalization of PEI with OEG and OGMe could be verified by the angle-dependent XPS. The observations proved the functionalization at the PEI surface, as the polyethers were detected at angles providing signals of the surface volume. Furthermore, the chemical functions determined verified a covalent binding via the nucleophilic addition of the amine functionalized OGMe and OEG to the PEI imide function.