Pure Water Flux Recovery Ratio Research Articles

TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membrane: Improvement in flux and anti-fouling properties

Based on the previous study, the properties, separation efficiencies, and anti-fouling performances of TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membrane made via non-solvent-induced phase separation were investigated. SEM, contact angle measurement, ATR-FTIR, and other methods were used to characterize the membranes, and then the pure water flux (PWF) and dye rejection were measured. The TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes were prepared by stepwise solution blending method. Compared to the pristine PEEKWC/PEI cross-linked ultrafiltration membrane, the anti-fouling and pure water flux performances were enhanced as the addition of TiO2 nanoparticles. The pure water flux of TiO2 nanoparticle embedded membranes was significantly increased and could even reach 3368.2 LMH at 5 bar much greater than that of the pristine PEEKWC/PEI ultrafiltration membrane (1423.8 LMH), remaining a retention rate for BBR higher than 98.5%. And the TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes exhibited a certain degree of increase of FRR (higher than 80%) after UV illumination. After a series of characterisation, the dye wastewater treatment property of membranes was assessed through filtration of Coomassie brilliant blue and Congo red solutions and researches were conducted on the anti-fouling capabilities of membranes. The TiO2 nanoparticle embedded PEEKWC/PEI cross-linked ultrafiltration membranes exhibited self-cleaning efficiency with lower irreversible fouling ratio. The pure water flux recovery ratio following dye fouling was higher after being exposed to UV irradiation, which could be attributed to the TiO2 nanoparticles' photocatalytic destruction of organic pollutants.

Anti-fouling nanofiltration membranes based on macromolecule crosslinked polyvinyl alcohol

Nanofiltration membranes with excellent anti-fouling properties were fabricated through a green surface crosslink method. Poly (styrene-maleic anhydride) (SMA) blended polyethersulfone (PES) membrane was used as a support. The SMA in the PES support served as a macromolecular crosslinker. After coating of polyvinyl alcohol (PVA) on the surface of the SMA-PES support, a PVA selective layer with gradient cross-linked structure was formed, through the esterification between the anhydride groups in SMA and the hydroxyl groups in PVA. This process adopts a full-water fabrication strategy without secondary pollution. The gradiently cross-linked PVA/SMA-PES membrane, with molecular weight cut-off (MWCO) about 600 Da and permeance around 10-12 L/(m2·h·bar), exhibited good dye/salts separation performance. In the filtration of a mixed solution of Congo Red (CR) and calcium chloride (CaCl2), the membrane rejected 98% CR and only had 10% rejection of CaCl2. In addition, this membrane processed an excellent anti-fouling property. In the BSA fouling test, the pure water flux recovery ratio (FRR) was 99%. It is expected that the PVA/SMA-PES membrane can be used in organic desalination.

A double anti-fouling mechanism established by self-assembly of TiO2 on F127 chains for improving the hydrophilicity of PES membrane based on RTIPS method

Novel polyethersulfone (PES) membranes with porous top surface and sponge-like structure based on reverse thermally induced phase separation (RTIPS) method modified by titania sol (TiO2 sol) and triblock copolymer (F127) were developed. The highlight of this work was that the self-assembly of TiO2 on F127 was obtained during the RTIPS membrane formation process. Properties of PES/TiO2/F127 membranes, which varied with TiO2 sol, F127 and coagulation water bath temperature, were investigated by cloud point, SEM, EDX, AFM, TGA, XPS, FRR, contact angle and so on. SEM morphologies revealed that homogeneous porous top surface as well as sponge-like structure appeared in the membrane prepared by RTIPS process, while dense skin surface and finger-like cross-section obtained from the membranes by NIPS method. As a result, the pure water flux, rm and porosity of the membranes by RTIPS method were higher than that by NIPS method. EDX results indicated that the agglomeration of titanium dioxide was avoided by sol gel process. The XPS data revealed that the self assembly of TiO2 on PEO segments in F127 alleviated the leakage of TiO2 from the modified membrane and then improved the hydrophilic stability of the membrane. The water contact angle illustrated that the addition of TiO2 and F127 improved the hydrophilicity of the membrane. Furthermore, the pure water flux recovery ratio of the modified membranes were higher (>79%) than that of pure PES membrane (61%). In a word, the permeability and anti-pollution performance of the PES/TiO2/F127 membrane could be improved by the addition of TiO2 sol and F127, moreover, RTIPS method was a superior method for membrane preparation.

Membrane bioreactors troubleshooting through the preparation of a high antifouling PVDF ultrafiltration mixed-matrix membrane blended with O-carboxymethyl chitosan-Fe3O4 nanoparticles

ABSTRACTPolymeric ultrafiltration (UF) membranes often used in membrane bioreactor (MBR) prone to be fouled by fouling agents. Therefore, in this paper, the antifouling characteristics of polyvinylidene fluoride (PVDF) UF membranes for wastewater treatment are improved through modifying membranes by O-carboxymethyl chitosan (OCMCS)-functionalized Fe3O4 nanoparticles (OCMCSFe3O4). The modifier agent was manufactured by the adsorption of OCMCS on Fe3O4 nanoparticles, which were synthesized via co-precipitating method. Antifouling performance of membranes was assessed by permeation tests done using activated sludge suspension as a biological foulant, then the calculation of the pure water flux recovery ratio (FRR) and fouling resistance parameters. Also, to investigate the protein rejection of membranes, permeation tests were conducted by the bovine serum albumin (BSA) solution. According to the obtained results, surface hydrophilicity of the embedded membranes was improved in the low concentrations of the modified nanoparticles. However, the high quantity of the OCMCS-Fe3O4 nanoparticles (>0.1 wt. %) in the casting solution lessened membrane performance owing to the agglomeration of the nanoparticles in the polymer matrix. Although, the 1 wt. % OCMCS-Fe3O4 membrane revealed considerably higher PWF and permeation than that of the other membranes. It was because of defects and cracks in the membranes. The 0.05 wt. % OCMCS-Fe3O4/PVDF membrane exhibited the highest FRR (95.7%) and protein rejection value (48%) and the lowest irreversible fouling resistance (Rir) value (4.2%). It is concluded that the blended membranes with modified nanoparticles resulted in a high-flux ultrafiltration membrane comparable with microfiltration membrane, while its separation properties remained similar to UF membrane.

Fabrication and characterization of amphiphilic PVDF copolymer ultrafiltration membrane with high anti-fouling property

Novel anti-fouling poly(vinylidene fluoride) (PVDF) membranes were fabricated via phase inversion method, directly using amphiphilic copolymers, which were synthesized from PVDFs with three different molecular weight grafted poly(ethylene glycol) methyl ether methacrylate (POEM) (PVDF-g-POEM), as membrane materials. Atom transfer radical polymerization (ATRP) method was employed to synthesize the amphiphilic PVDF copolymers. The membranes were characterized by scanning electron microscopy (SEM), pure water flux, contact angle measurement and BSA solution filtration experiments, etc. The permeability of the PVDF copolymer membrane reached to 567.8Lm−2h−1bar−1 with molecular weight cut off (MWCO) of about 40.0kDa. In addition, the stable state flux of the PVDF copolymer membranes was much higher than that of PVDF homopolymer membranes when BSA solution was filtrated, and after cleaning, the pure water flux recovery ratio of the copolymer membrane reached to 98.1%. These results indicate that the prepared PVDF membrane possesses good performance and anti-fouling property.

Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes

Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm−2h−1 to 95.36Lm−2h−1 upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application.

Novel high flux antifouling nanofiltration membranes for dye removal containing carboxymethyl chitosan coated Fe3O4 nanoparticles

In this study, polyethersulfone (PES) nanofiltration membranes were synthesized by blending of O-carboxymethyl chitosan/Fe3O4 nanoparticles via the phase inversion method. O-carboxymethyl chitosan bound Fe3O4 magnetic nanoparticles (CC–Fe3O4 NPs) were synthesized by the binding of carboxymethyl chitosan (CC) onto the surface of Fe3O4 magnetic nanoparticles via co-precipitating method. The modified membranes had considerably higher pure water flux and permeation compared to the unfilled PES membrane. Surface hydrophilicity of the modified membranes was improved due to water affinity improvement of the membrane surface. However, high content of CC–Fe3O4 NPs (>0.5%) in the casting solution diminished membrane performance due to agglomeration of the nanoparticles in the polymer matrix. The antifouling properties of the membranes were evaluated by powder milk solution and measuring the pure water flux recovery ratio (FRR). The 0.5wt.% CC–Fe3O4 NPs–PES membrane exhibited the highest FRR value (91.7%) and the lowest irreversible fouling resistance (Rir) value (8.33%). Nanofiltration performance was also examined by retention of Direct Red 16 dye. As a conclusion, the addition of CC–Fe3O4 NPs at lower concentration could result in membranes with superior pure water flux, higher rejection and good fouling resistance compared to the unfilled PES membrane.

Remediation of simazine from water through low-pressure thin film composite membrane using surfactants

The investigation was carried out to remediate simazine from water by the pressure driven filtration techniques (viz. nanofiltration, reverse osmosis). The separation of simazine through the membranes showed similar trend as glucose (organic marker) and salt. Surfactant-mediated filtration showed better performance of the membranes, though it depends on the nature of membranes and surfactants. The membranes having more porous (in terms of glucose and water permeability) structure showed improvement in the separation of simazine. The Sodium Dodecyl Sulphate (SDS) added water contaminated with simazine shows better separation with respect to Cetyl Trimethyl Ammonium Bromide (CTAB). Pure water Flux Recovery Ratio (FRR) is higher for the membranes dealt with SDS with respect to CTAB.