Water Flux Of Composite Membrane Research Articles

Multifunctional fly ash-based GO/geopolymer composite membrane for efficient oil-water separation and dye degradation

Membrane fouling and separation materials with low cost and high efficiency are challenges for membrane separation technology in wastewater treatment. Superhydrophilic and underwater superoleophobic membranes show broad application prospects in oily wastewater treatment because of their high permeability, selectivity, and antifouling performance; however, they are generally ineffective for organic pollutant molecules. In this study, a novel graphene oxide (GO)/geopolymer composite membrane with superhydrophilic and underwater superoleophobic characteristics was prepared by dipping a mixed slurry of GO and fly ash-based geopolymer onto a stainless steel mesh via a facile self-assembly process. The results show that GO could adjust the hydrophilicity and water flux of composite membranes. The composite membrane containing 0.4 wt% GO (4GO/GCM) had the best hydrophilic, water flux of 1363 kg/(m2·h), and high separation efficiencies (≥98.2%) for oil-water mixtures and oil-in-water emulsions under gravity-driven. In addition, the 4GO/GCM sample exhibited excellent stability under harsh conditions, including hot water and strong acid, alkali, and salt solutions. Importantly, the sample derived from fly ash exhibited unique photocatalytic degradation performance for organic dye molecules under simulated solar-light irradiation. Thus, it is believed to this strategy has substantial potential for high-value utilization of fly ash and the sustainable treatment of oily and dye wastewater.

Performance improvement of polyethersulfone ultrafiltration membrane containing variform inorganic nano-additives

Lamellar graphene oxide (GO) and hollow halloysite nanotubes (HNTs) have aroused increasing interest with their unique structure and performance, deriving a new research direction for materials science. In this work, polyethersulfone (PES) ultrafiltration (UF) composite membrane incorporated with lamellar GO and hollow HNTs were prepared via non-solvent induced phase separation (NIPS) process, respectively. The prepared membranes were characterized by using various techniques, including Fourier Transform Infrared (FTIR), Raman spectra, Scanning Electron Microscopy (SEM), Confocal Scanning Microscopy (CSM), etc. Remarkably, the pure water flux of composite membranes with 0.05 wt% GO and 0.01 wt% HNTs loading reached maximum values of 327 and 346 L m−2 h−1, respectively. Moreover, the permeability of PES/HNTs composite membranes were more stable than PES/GO composite membranes. The rejection of the prepared composite membranes for bovine serum albumin (BSA) almost reached 98.5%, while it exhibits quite different flux recovery ratio in the anti-fouling test, which indicates that the variform inorganic nano-additives could produce widely divergent influences on the performance of membrane.

Preparation and Characterization of AgNp/PVDF Cmposite Ultrafiltration Membrane

In this study, polymeric ultrafiltration (UF) membranes were prepared by phase inversion method to obtain both antibacterial and organic antifouling properties. The membranes were cast from a solution of polyvinylidene fluoride (PVDF) and formative silver (Ag) nanoparticles were successfully immobilized on a polymer. This was done using a solvent N, N-dimethylformamide (DMF) which is a solvent for the PVDF polymer meanwhile it is a reducing agent for silver ion. The effect of silver nanoparticles additives on the performance of polymeric ultrafiltration membrane was verified. Chemical composition and morphology of the surfaces of the membranes were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The antibacterial property of modified membrane and the influence of silver nanoparticles on pure water flux of composite membrane at 0.2 Mpa were also verified. The experimental results obtained concluded that the composite membrane properties have been improved by the integration of Ag nanoparticles. The grafted membrane with silver nanoparticles has shown a clear ability to inhibit the growth of E. coli, Pseudomonas Aeruginosa, and Bacillus Cereus. While the clean PVDF membrane (without any additives) did not show any effect of preventing the growth of these species of bacteria referred to above. The pure water flux, porosity and the mean pore size of composite membrane can reach 261.8 L/m2 h, 85.4%, and 0.0206 µm, respectively, and it was much more than that of pure PVDF membrane.

Thin‐Film Nanocomposite Nanofiltration Membranes Incorporated with Graphene Oxide for Phosphorus Removal

AbstractFor the first time, thin‐film nanocomposite (TFN) nanofiltration membranes incorporated with graphene oxide (GO) were synthesized and used to separate phosphorus from water sources of varying properties. Prior to phosphorus removal tests, two different TFN membranes and one control thin‐film composite (TFC) membrane were subject to standard characterization in order to determine pure water flux, salt rejection, surface hydrophilicity, pore size, and porosity. By incorporation of GO, the water flux of composite membranes could be significantly improved with minimum decrease in salt rejection, mainly due to improved surface hydrophilicity coupled with enlarged pore size and overall structural porosity. Especially the TFN‐1 membrane was found to perform better owing to its good combination of water flux and solute rejection, higher water flux, and comparable phosphorus rejection in comparison to the TFC membrane.

Composite ultrafiltration membrane tailored by MOF@GO with highly improved water purification performance

Developing advanced filtration membrane with high flux, good solute rejection and excellent antifouling performance is highly demanded. Hydrophilic graphene oxide (GO) nanosheets are attractive fillers for the preparation of composite membranes for water purification. However, strategies that can fully exploit the advantages and remedy the drawbacks of GO nanosheets are still needed. In this work, UiO-66 was specifically anchored to the GO layers as a porous modifier. The incorporated UiO-66 can effectively prevent the GO layers from stacking and introduce unique properties into the composite (UiO-66@GO). A series of novel composite membranes were prepared with the obtained UiO-66@GO composite and polyethersulfone (PES). As a result, the prepared composite membranes (UiO-66@GO/PES) exhibit high hydrophilicity and water purification performance. Especially, the water flux of composite membrane with 3.0wt% UiO-66@GO loading shows an increase of 351% and 78% respectively in comparison with that of the PES and GO/PES membranes. Moreover, the UiO-66@GO/PES membranes exhibit good solute rejection and impressive antifouling performance, which is appealing for the application of industrial water purification.

The preparation and application of a low-cost multi-channel tubular inorganic–organic composite microfiltration membrane

Low-cost multi-channel tubular inorganic–organic composite microfiltration membranes were prepared by a convenient compression coating approach employing 19-channel ceramic support (pore sizes ranging from 5 to 20μm) as substrate, and PVDF/CA blend as separation layer. The membranes were characterized in terms of water permeability, selectivity, as well as the performance of purifying rice bran fermentation. Obtained results show that the pure water flux of composite membranes with PVDF/CA skin layer increases from 200 to 2000L/m2h as the PVDF/CA concentration in coating solution decreases from 18 to 8wt%, and the retention rate to polyethylene oxide (Mw=1,000,000) is much higher than that of ceramic membrane with an average pore diameter of 50nm, and the ratio of turbidity removal is up to 99% when the composite membranes were applied to treat rice bran fermentation broth. More significantly, the composite membranes showed a high recovery rate of pure water flux after a simple physical cleaning process. It is found that the concentration of PVDF/CA coating solution appeared to be the key factor on the separation performance of composite membrane, and higher concentration would result in a higher rejection rate. To understand the relationship between the preparation condition and membrane performance, the viscosity of coating solution and morphology of composite membranes were characterized by arotational viscometer and scanning electron microscope (SEM), respectively. Finally, the result of cost analysis shows that the composite membranes have an advantage over the commercial ceramic membranes and could be recognized as a promising a candidate for industrial applications.

Permeability and morphology study of polysulfone composite membrane blended with nanocrystalline cellulose

Polysulfone (PS) composite membranes blended with nanocrystalline cellulose (NCC) for ultrafiltration were prepared by a Loeb–Sourirajan phase inversion process. The effect of NCC content, PS content, and additive content on both permeability and morphology of composite membranes were studied. The surface and cross-section morphologies of the composite membranes were investigated using scanning electron microscopy with both the porosity and mean pore size of composite membranes being compared. The experimental result showed that the morphology of composite membranes changed significantly with the aforementioned factors. Through the experimental work, the proper composite membrane preparation condition was obtained as follows. The NCC content was 0.3 wt% and the PS content was 18 wt%. The solvent was N,N-dimethylacetamide. PS glycol 1000 was used as the additive with a concentration of 3 wt%. The coagulation bath was deionized water and its temperature was maintained at 30°C. Due to the addition of NCC the pure water flux of composite membrane increased from 175.6 L/(m2 h) in the pure PS to 343.2 L/(m2 h), the porosity and mean pore size of composite membrane increased from 40.5% and 33.6nm in the pure PS membrane to 67.6%, 47.1 nm, respectively.

Preparation and characterization of poly(vinylidene fluoride) composite membranes blended with nano-crystalline cellulose

Poly(vinylidene fluoride) (PVDF) composite membranes blended with nano-crystalline cellulose (NCC) for ultrafiltration were prepared by a Loeb–Sourirajan (L–S) phase inversion process. The effects of NCC concentration on the membrane performances were investigated. Surface chemical compositions, surface and cross-section morphologies, degree of crystallinity and the thermal stability of the membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA) respectively. The mechanical properties of the membranes were also investigated. All the experimental results indicated that the properties of the composite membranes were improved due to the addition of NCC. The pure water flux of composite membranes can reach 230.8L/(m2h) and increase up to 47.5% compared with pure PVDF membranes. At the same time, the rejection ratio of a bovine serum albumin solution (1g/L) was up to 92.5%. The porosity and the mean pore size of the composite membranes were 65% and 49nm, respectively. Due to the addition of NCC, the degree of crystallinity was increased to 52.1% resulting in the enhanced mechanical properties. A typical asymmetric structure, which was composed of sponge-like dense layer and finger-like microporous support layer, was observed in SEM images of composite membranes.

Preparation and characterization of alkyl ketene dimer (AKD) modified cellulose composite membrane

Abstract Cellulose was dissolved in 8 wt.% lithium chloride/N,N-dimethylacetamide. Under the homogeneous conditions, alkyl ketene dimer (AKD) was added to react with the dissolved cellulose. The mixed solvent was utilized to form composite membrane by phase transfer technique. The supermolecular structure, morphology, thermal and physical properties of the membrane were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), scanning electron microscope (SEM), wide-angle X-ray diffraction (WAXD), etc. The results showed that AKD reacted with cellulose under the homogeneous conditions. Moreover, the water absorption and water flux of composite membrane noticeably decreased compared with unmodified cellulose membrane.

Study on a novel polyester composite nanofiltration membrane by interfacial polymerization. II. The role of lithium bromide in the performance and formation of composite membrane

Composite membranes were prepared by interfacial polymerization of trimesoyl chloride (TMC) with (i) triethanolamine (TEOA), and (ii) N-methyl-diethanolamine (MDEOA) on addition of various contents of LiBr in aqueous phase. The influence of LiBr in aqueous phase on the composite membrane performance and surface morphologies was investigated. For monomer TEOA, the pure water flux of composite membrane enhanced as the LiBr content increased and it reached a maximum at 3% of LiBr, then decreased. However, the extreme value of the salt rejection functioned with the content of LiBr changed to 1% (a turning point), at which the membrane displayed a lowest salt rejection. The change in performance of the composite membrane with the content of LiBr was due to the competition of two factors. One was the interaction of Li + ion with the hydroxyl oxygen atom of alcohol amine, which could induce an increase in the density and reactivity of OH groups in the aqueous phase, forming a dense skin layer of the composite membrane as a result. The other factor was the complexation of Li + ion with the carbonyl in TMC, causing the acid chloride group of TMC preferring to hydrolyze which could induce to construct a hydrophilic and loose surface layer. The role of LiBr in the formation of the composite membrane was further testified by investigating another monomer MDEOA. The analysis of the composite membrane formation in the presence of LiBr was validated by reaction coefficient, contact angle, streaming potential, SEM, and AFM.

Water transport behavior of chitosan porous membranes containing multi-walled carbon nanotubes (MWNTs)

In this work, the effects of MWNTs content on water transport behaviors and tensile properties of prepared chitosan porous membranes were investigated. In the case of chitosan membrane using low molecular weight PEG6000 as a porogen, a percolation-like behavior of water transport rate was observed for the first time in composite membranes with a critical MWNTs content (5 wt%). The water flux of composite membrane with 10 wt% MWNTs (128.1 L/m 2 h) is 4.6 times that of neat one (27.6 L/m 2 h). This could be understood as due to the formation of MWNTs network located among the pore network of chitosan membrane at high MWNTs content, where the hollow nanochannel of MWNTs and their interspaces could provide a new transport channel for water. In contrary, when high molecular weight PEG10000 is used as the porogen, a decreased water flux of the prepared composite membrane is found with increase of MWNTs content. In this case, a strong compatibilizing effect of MWNTs on chitosan/PEG10000 blends is observed, resulting in a decreased pore size and poor water flux of the membranes. Furthermore, a greatly improved tensile strength of chitosan porous membranes has been achieved by adding MWNTs, no matter which molecular weight PEG is used as porogen. Our work provides a novel way to improve water flux and/or control the pore size of polymer porous membranes by using MWNTs.