Membrane Antifouling Properties Research Articles

Different combined systems with Fenton-like oxidation and ultrafiltration for industrial wastewater treatment

Combining Fenton-like oxidation with ultrafiltration by membranes seems promising for wastewater treatment, while it still has defects in comprehensive comparison of different combinations for industrial wastewater treatment. To fill in these gaps, mixed matrix Fe3O4/polyvinylidene fluoride membranes were used for setting up three combined systems, i.e., sequential oxidation and filtration (Seq-O&F), simultaneous oxidation and filtration (Sim-O&F), and sequential filtration and oxidation (Seq-F&O) systems. Performance on industrial wastewater decontamination was evaluated, and anti-fouling property of membranes was measured by flux decline and recovery efficiency. Characterizations of membranes and change of molecular weight distribution were also investigated for auxiliary analysis. Furthermore, the stability of membrane matrix and catalyst was investigated for time-equivalent of 10,000 L/m2 wastewater treatment. The results indicate that Seq-O&F system shows the best decontamination and anti-fouling performance, but with multi-units and low stability of the catalyst. Sim-O&F system shows acceptable decontamination and anti-fouling performance, yet the stability for long-term operation needs to be further improved. Seq-F&O can effectively save the oxidant and prolong operational life, but performs worse in decontamination and anti-fouling. We believe this study gives a new understanding of Fenton-like oxidation and ultrafiltration combined systems for industrial wastewater treatment, and provides guidance for further application.

Synergetic effects of dodecylamine-functionalized graphene oxide nanoparticles on antifouling and antibacterial properties of polysulfone ultrafiltration membranes

The potential use of dodecylamine-functionalized graphene oxide (rGO-DDA) nanoparticles as an antifoulant and antibacterial nanofiller was investigated. GO and rGO-DDA were analyzed using Raman spectroscopy, FTIR, SEM, TEM, and TGA that all confirmed the successful functionalization of GO structure. Polysulfone (PSF) ultrafiltration membranes incorporating varied loadings of GO and rGO-DDA were then fabricated via phase inversion approach. All membranes were characterized in terms of chemical structure, morphology, hydrophilicity, porosity and mean pore size. Cross-section SEM images showed the distribution of GO and rGO-DDA between the pores and on the polymer walls. AFM results demonstrated that GO addition increased the roughness of membrane; while with rGO-DDA addition the surface became smoother. Pristine PSF and rGO-DDA based membranes exhibited similar hydrophilicity, while GO-based membranes exhibited higher hydrophilicity as revealed by contact angle measurements. Permeability, separation and antifouling experiments were performed in a cross-flow membrane setup and showed that flux decreases with the increase in GO and rGO-DDA concentration. rGO-DDA membranes showed higher antifouling and antibacterial performance compared to the pristine PSF and GO membranes. Neat PSF exhibited 65.4 % flux recovery ratio (FRR) against BSA that was increased to 86.9 % and 89.1 % with GO-0.1 and rGO-DDA-0.1, respectively. Against HA, FRR was improved from 87.8 % for neat PSF to 95.6 % and 99.3 % with GO-0.1 and rGO-DDA-0.1, respectively. Additionally, rGO-DDA membrane exhibited higher bacteriostatis rate (83.6 %) against H. aquamarina than GO membrane (62.9 %). Moreover, rGO-DDA nanoparticles exhibited excellent dispersibility in several solvents making them promising nanofillers for various membranes with high antifouling and antibacterial performance.

QQ-PAC core-shell structured quorum quenching beads for potential membrane antifouling properties

Quorum quenching (QQ) has been proven to be an effective method to reduce MBR membrane biological contamination. In this paper, a novel and efficient QQ-PAC core-shell beads were prepared for mitigating the membrane contamination. The bead was composed of two parts: QQ bacteria embedded in the core and PAC in the shell. The microstructure of the bead was observed by scanning electron microscopy (SEM) and the functional groups were revealed by Fourier transform infrared spectroscopy (FTIR). Meanwhile, the mechanical strength, swelling property, penetration property and QQ activity of the core bead, the core shell-without PAC bead and the core shell-with PAC bead were compared. The core shell-with PAC structure improved the adsorption capacity under good mass transfer conditions. Besides, the combined effect of QQ bacteria and PAC enhanced the QQ effect and alleviated the process of MBR membrane biological contamination consequently. Therefore, the QQ-PAC core-shell beads have a potential possibility in MBR membrane fouling control as the immobilization technology of QQ bacteria.

Towards to better permeability and antifouling sulfonated poly (aryl ether ketone sulfone) with carboxyl group ultrafiltration membrane blending with amine functionalization of SBA-15

A series of sulfonated poly (aryl ether ketone sulfone) with carboxyl groups (C-SPAEKS) blending with amine functionalization of SBA-15 particles were fabricated by the phase inversion method applied in ultrafiltration (UF) field. The 4-carboxyphenyl hydroquinone (4C-PH) and sulfonated poly (aryl ether ketone sulfone) with carboxyl groups (C-SPAEKS) were demonstrated by 1H NMR spectra and the FT-IR. The scanning electron microscope (SEM) showed that the nanoparticles were evenly distributed and finger-like channels were formed in the film. The task results showed that the amine functionalization of SBA-15 particles greatly increased the hydrophilicity, water fluxes and antifouling properties of membranes. The pure water flux of C-SPAEKS membrane and hybrid membrane were 259 (L/m2h) and 564 (L/m2h), respectively, which were much higher than those of conventional UF membrane. The pure water flux of hybrid membrane with the concentration of 0.1% nanoparticles was 419 (L/m2h) and at the same time the membrane maintained highly rejection (96%) with higher FRR (93%). In short, all the results indicated that sulfonated poly (aryl ether ketone sulfone) with carboxyl groups (C-SPAEKS) and hybrid membrane blending with amine functionalization of SBA-15 nanoparticles have the great prospect in ultrafiltration.

Investigation of Anti-fouling and UV-Cleaning Properties of PVDF/TiO2 Mixed-Matrix Membrane for Humic Acid Removal.

Natural organic matters (NOMs) have been found to be the major foulant in the application of ultrafiltration (UF) for treating surface water. Against this background, although hydrophilicity has been demonstrated to aid fouling mitigation, other parameters such as membrane surface morphology may contribute equally to improved fouling resistance. In this work, with humic acid solution as the model substance, the effects of titanium dioxides (TiO2) types (PC-20, P25, and X500) on membrane anti-fouling and defouling properties were comparatively analysed. The aims are (1) to determine the correlation between membrane surface morphology and membrane fouling and (2) to investigate the anti-fouling and UV-cleaning abilities of PVDF/TiO2 mixed-matrix membranes with different membrane topographies and surface energy conditions. The mixed-matrix membrane with P25 TiO2 exhibited the most significant UV-defouling ability, with a high irreversible flux recovery ratio (IFRR(UV)) of 16.56 after 6 h of UV irradiation, whereas that with X500 TiO2 exhibited both superior anti-fouling and defouling properties due to its smoother surface and its highly reactive surface layer.

Rapid Surface Modification of Ultrafiltration Membranes for Enhanced Antifouling Properties.

In this work, several ultrafiltration (UF) membranes with enhanced antifouling properties were fabricated using a rapid and green surface modification method that was based on the plasma-enhanced chemical vapor deposition (PECVD). Two types of hydrophilic monomers—acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) were, respectively, deposited on the surface of a commercial UF membrane and the effects of plasma deposition time (i.e., 15 s, 30 s, 60 s, and 90 s) on the surface properties of the membrane were investigated. The modified membranes were then subjected to filtration using 2000 mg/L pepsin and bovine serum albumin (BSA) solutions as feed. Microscopic and spectroscopic analyses confirmed the successful deposition of AA and HEMA on the membrane surface and the decrease in water contact angle with increasing plasma deposition time strongly indicated the increase in surface hydrophilicity due to the considerable enrichment of the hydrophilic segment of AA and HEMA on the membrane surface. However, a prolonged plasma deposition time (>15 s) should be avoided as it led to the formation of a thicker coating layer that significantly reduced the membrane pure water flux with no significant change in the solute rejection rate. Upon 15-s plasma deposition, the AA-modified membrane recorded the pepsin and BSA rejections of 83.9% and 97.5%, respectively, while the HEMA-modified membrane rejected at least 98.5% for both pepsin and BSA. Compared to the control membrane, the AA-modified and HEMA-modified membranes also showed a lower degree of flux decline and better flux recovery rate (>90%), suggesting that the membrane antifouling properties were improved and most of the fouling was reversible and could be removed via simple water cleaning process. We demonstrated in this work that the PECVD technique is a promising surface modification method that could be employed to rapidly improve membrane surface hydrophilicity (15 s) for the enhanced protein purification process without using any organic solvent during the plasma modification process.

Mixed-Matrix Membranes Comprising of Polysulfone and Porous UiO-66, Zeolite 4A, and Their Combination: Preparation, Removal of Humic Acid, and Antifouling Properties.

High-performance Mixed-Matrix Membranes (MMMs) comprising of two kinds of porous fillers UiO-66 and Zeolite 4Aand their combination were fabricated with polysulfone (PSf) polymer matrix. For the very first time, UiO-66 and Zeolite 4A were jointly used as nanofillers in MMMs with the objective of complimenting synergistic effects. The individual and complimentary effects of nanofillers were investigated on membrane morphology and performance, pure water flux, humic acid rejection, static humic acid adsorption, and antifouling properties of membranes. Scanning Electron Microscopy (SEM) analysis of membranes confirmed that all MMMs possessed wider macrovoids with higher nanofiller loadings than neat PSf membranes and the MMMs (PSf/UiO-66 and PSf/Zeolite 4A-UiO-66) showed tendency of agglomeration with high nanofiller loadings (1 wt% and 2 wt%). All MMMs exhibited better hydrophilicity and lower static humic acid adsorption than neat PSf membranes. Pure water flux of MMMs was higher than neat PSf membranes but the tradeoff between permeability and selectivity was witnessed in the MMMs with single nanofiller. However, MMMs with combined nanofillers (PSf/Zeolite 4A-UiO-66) showed no such tradeoff, and an increase in both permeability and selectivity was achieved. All MMMs with lower nanofiller loadings (0.5 wt% and 1 wt%) showed improved flux recovery. PSf/Zeolite 4A-UiO-66 (0.5 wt%) membranes showed the superior antifouling properties without sacrificing permeability and selectivity.

Preparation of Hydrophilic UHMWPE Hollow Fiber Membranes by Chemically Bounding Silica Nanoparticles

In this work, ultra-high molecular weight polyethylene (UHMWPE) microfiltration hollow fiber membranes prepared via the thermally induced phase separation (TIPS) method were modified by chemically bounding hydrophilic silica (SiO2) nanoparticles onto the surface to improve anti-fouling performance. A range of testing techniques including attenuated total reflection Flourier transformed infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), water contact angle, mechanical test, filtration and anti-fouling performance were carried out to discuss the influence of different modification conditions on the properties of the membranes. The prepared hollow fiber membranes display the significantly excellent performance when the vinyl trimethoxy silane (VTMS) concentration was 13%, the pH value of the hydrolyzate was 4 and the hydrolysis reaction time was 6 h. In particular, the hydrophilicity of modified membranes was improved effectively, resulting in the enhancement of membrane anti-fouling properties. The results of this work can be consulted for improving the anti-fouling performance of the UHMWPE microfiltration hollow fiber membrane applied in the field of water purification.

Antifouling thin-film composite membranes with multi-defense properties by controllably constructing amphiphilic diblock copolymer brush layer

We developed a novel amphiphilic copolymer architecture for thin-film composite (TFC) membranes to integrate “resistant” and “release” strategies against membrane fouling. Two materials were sequentially grafted on TFC reverse osmosis membrane surfaces via dual surface-initiated atom transfer radical polymerization (SI-ATRP): zwitterionic polymer, poly[2-(methacryloyloxy)ethyl-dimethyl-(3-sulfopropyl) ammonium hydroxide] (pMEDSAH) with strong hydrophilicity and poly(2,2,2-trifluoroethyl methacrylate) (pTFEMA) with low surface energy. According to MD simulation and theoretical quantification, the p(MEDSAH-b-TFEMA)-grafted membranes (i.e. amphiphilic TFC membranes) possess not only strong hydration, but also lower surface energy, which yield the features of both fouling resistant and fouling release properties. The superiority of possessing multi-defense properties was further confirmed by the long-term, multi-cycle membrane fouling and cleaning filtration. Compared with pristine TFC and hydrophilic TFC membranes, the amphiphilic TFC membranes showed not only less water flux decline during the fouling filtration, but also higher water flux recovery after cleaning by water. Both theoretical and experimental results strongly suggest that the amphiphilic TFC membrane is a novel candidate for improving membrane antifouling properties.

Development of Hydrophilic PVDF Membrane Using Vapour Induced Phase Separation Method for Produced Water Treatment.

During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable properties of high hydraulic performance combined with high membrane fouling resistance. This project employs the vapor induced phase separation (VIPS) technique to develop a hydrophilic polyvinylidene fluoride (PVDF) membrane with polyethylene glycol (PEG) as an additive for produced water treatment. Results show that thanks to its slow nonsolvent intake, the VIPS method hinders additive leaching during the cast film immersion. The results also reveal that the exposure of the film to the open air before immersion greatly influences the structure of the developed membranes. By extending the exposure time from 0 to 30 min, the membrane morphology change from typical asymmetric with large macrovoids to the macrovoid-free porous symmetric membrane with a granular structure, which corresponds to 35% increment of steady-state permeability to 189 L·m−2h−1bar−1, while maintaining >90% of oil rejection. It was also found that more PEG content resides in the membrane matrix when the exposure time is extended, contributes to the elevation of surface hydrophilicity, which improves the membrane antifouling properties. Overall results demonstrate the potential of VIPS method for the fabrication of hydrophilic PVDF membrane by helping to preserve hydrophilic additive in the membrane matrices.

Surface modification of thin-film composite forward osmosis membranes with polyvinyl alcohol–graphene oxide composite hydrogels for antifouling properties

In this study, the polyamide (PA) layers of commercial thin-film composite (TFC) forward osmosis (FO) membranes were coated with glutaraldehyde cross-linked polyvinyl alcohol (PVA) hydrogel comprising of graphene oxide (GO) at various loadings to enhance their fouling resistance. The optimal GO concentration of 0.02 wt% in hydrogel solution was confirmed from the FO membrane performance, and its influence on membrane antifouling properties was studied. The properties of the modified membranes, such as surface morphology, surface charge and wettability, were also investigated. PVA/GO coating was observed to increase the smoothness and hydrophilicity of the membrane surface. The foulant resistances of the pristine, PVA-coated and PVA/GO-coated membranes were also reported. PVA hydrogel-coated TFC membrane with a GO loading of 0.02 wt% showed a 55% reduction in specific reverse solute flux, only a marginal reduction in the water flux, and the best antifouling property with a 58% higher flux recovery than the pristine TFC membrane. The significant improvement in the selectivity of the modified membranes meant that the hydrogel coating could be used to seal PA defects. The biocidal GO flakes in PVA hydrogel coating also improved the biofouling resistance of the modified membranes, which could be attributed to their morphologies and superior surface properties.

Preparation and antifouling performance of PVDF-DCOIT composite hollow fiber membranes

Membrane fouling is the main bottleneck that hinders the applications of membrane bioreactors (MBRs). 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), as an environmentally-acceptable antifouling biocide, was mixed with Polyvinylidene fluoride (PVDF) to fabricate hollow fiber membrane via non-solvent induced phase separation (NIPS), which was able to effectively improve the antifouling performance of the membranes in this work. Overall research of the prepared membrane revealed that membranes with 3 wt% DCOIT exhibited the optimum antifouling performance. With the addition of DCOIT, hydrophilicity and pure water flux of 3 wt% DCOIT membranes maintained remarkable improvement by 22.9% and 64.6% than that of membranes without DCOIT. Meanwhile, the surface morphologies of 3 wt% DCOIT membranes were smoother than the control group in terms of SEM and AFM images, which was beneficial to alleviate membrane fouling. In antifouling experiments, the flux variation rate of membranes with 3wt% DCOIT filtrated in bull serum albumin, sodium alginate and humic acid solution were 81.42%, 54.25%, 50.5%, while membrane without DCOIT were 64.6%, 24.72% and 29%, respectively. Similar results were obtained by filtrating anaerobic sludge for 24 h. The flux variations of 3 wt% DCOIT membranes were 59.4%, 47.8% and 46.0%, respectively in three stages. However, the flux variations of membranes without DCOIT were 44.8%, 36.7% and 19.8%, respectively, which showed better antifouling ability and higher flux recovery efficiency The novel membranes would provide some theoretical basis and technical support for the rational combinations in elevating the overall antifouling properties of membranes.

High water permeable PEI nanofiltration membrane modified by L-cysteine functionalized POSS nanoparticles with promoted antifouling/separation performance

In this research L-cysteine as an amino acid was applied to modification of octa glycidyloxypropyl-silsesquioxane (glycidyl POSS) and construction of L-cysteine modified-POSS nanoparticles. The synthesized nanoparticles were introduced into PEI-based nanofiltration membranes for tuning of membrane permeability, antifouling ability and separation efficiency. Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-Ray diffraction analysis (XRD) and atomic force microscopy (AFM) analysis were used for characterization of synthesized nanoparticles and prepared membranes. The membranes porosity, mean pore size, contact angle, water content, pure water flux, Na2SO4 and CrSO4 rejection and antifouling properties of membranes also studied. The results showed that pure water flux (PWF) enhanced from 17.63 L/m2 h for neat membrane to 95 L/m2 h for the blended 1 wt% [L-cysteine-co-POSS/PEI] membrane. The Na+ and Cr+2 rejection measured 69% and 52% for pristine PEI membrane whereas they were 80% and 79% for the modified membrane containing of 1 wt% nanoparticles. The highest FRR% was also obtained 95% for the blended [1 wt% NPs-PEI] membrane.

Graphene-based electro-conductive anti-fouling membranes for the treatment of oil sands produced water

In this study, a thin layer of polyaniline (PANI)-reduced graphene oxide (rGO) was laminated on polyethersulfone (PES) support by pressure-assisted technique. Organic fouling on the resulting robust and electro-conductive membranes reduced significantly by applying an external electric field. The electrical conductivity of pristine PANI film was 0.46 S/m while it was increased up to 84.53 S/m by adding appropriate amount of rGO. Both anodic and cathodic potentials in a wide range were applied to the prepared membranes using synthetic sodium alginate and real oil sands boiler feed water (BFW) waste of Alberta, Canada. Filtration tests showed that fouling resistance of electro-oxidative membranes towards sodium alginate improved, and 31.9% flux decline recovered when 2 V anodic cell potential was applied. By increasing the applied voltage from 3 V to 9 V, the antifouling property of membrane, as well as flux recovery ratio (FRR), improved dramatically and reached to 97.47% in the anodic setting. Such a significant improvement was attributed to electrostatic repulsive force between foulant and membrane surface, massive gas bubble generation, and electro-oxidation reactions. The cathodic electro-reduction configuration was also tested for BFW, where water flux decline and rejection performance were both improved by elevating electric potential.

Fabrication of a Novel Antifouling Polysulfone Membrane with in Situ Embedment of Mxene Nanosheets.

Membrane fouling is still a critical issue for the application of ultrafiltration, which has been widely used in water treatment due to its efficiency and simplicity. In order to improve the antifouling property, a new 2D material MXene was used to fabricate composite ultrafiltration membrane with the approach of in situ embedment during the phase inversion process in this study. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), water contact angle, bovine serum albumin rejection and porosity measurements were utilized to characterize the prepared membranes. Due to the hydrophilicity of the MXene, the composite membranes obtained higher hydrophilicity, confirmed by the decreased water contact angle. All the modified membranes had a high bovine serum albumin rejection above 90% while that of the pristine polysulfone membrane was 77.48%. The flux recovery ratio and the reversible fouling ratio of the membranes were also improved along with the increasing content of the MXene. Furthermore, the highest flux recovery ratio could also reach 76.1%. These indicated the good antifouling properties of MXene composite membranes. The enhanced water permeability and protein rejection and excellent antifouling properties make MXene a promising material for antifouling membrane modification.

Crosslinkable polyaryletherketone ultrafiltration membranes with solvent-resistant improvement

We demonstrate the successful synthesis of a novel crosslinkable polyaryletherketone, SCBI-PAEK-6F, which has pendant benzimidazole groups as a tunable content. With the strategic incorporation of benzimidazole groups, the SCBI-PAEK-6F membranes prepared by non-solvent induced phase separation (NIPS) method became cross-linkable. Then the solvent-resistance of ultrafiltration membranes was improved through cross-linking. The structures and performances of the membranes, along with the effects of the post cross-linking, had been systematically investigated. The solvent-resistance test confirmed that the membrane stability in representative polar aprotic solvents had been pronouncedly enhanced after cross-linking. Cross-linked membranes had high gel contents of about 80% after soaking in the solvents for 7 days. Pore size and porosity analysis had shown that the mean pore size and porosity of SCBI-PAEK-6F membranes became larger after the cross-linking process. Meanwhile, the cross-linked membranes showed the improved ultrafiltration performance, the cross-linked membranes had pure water flux which is 50% bigger than the pristine membranes. In addition, all membranes showed superior bovine serum albumin rejection (over 98%), but the antifouling property of membranes became a little worse after the cross-linking process.

Preparation of an Asymmetric Membrane from Sugarcane Bagasse Using DMSO as Green Solvent

Asymmetric cellulose acetate membranes have been successfully fabricated by phase inversion, using sugarcane bagasse (SB) as the starting material. SB is a raw material with high potential to produce cellulose derivatives due to its structure and morphology. Cellulose was extracted from SB by pretreatment with solutions of 5 wt% NaOH, 0.5 wt% EDTA; then bleached with 2 wt% H2O2. Cellulose acetate (CA) was prepared by the reaction between extracted cellulose with acetic anhydride, and H2SO4 as a catalyst. The obtained CA exhibited a high degree of substitution (2.81), determined with 1H-NMR spectroscopy and titration. The functional groups and thermal analysis of the extracted cellulose and the synthesized CA have been investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The change in the crystallinity of the extracted cellulose and CA was evaluated by X-ray diffraction (XRD) spectroscopy. Asymmetric membranes were fabricated using dimethyl sulfoxide (DMSO) as the solvent, with a casting thickness of 250 µm. The obtained membranes were studied by scanning electron microscopy (SEM), DSC and atomic force microscopy (AFM). The hydrophilicity of the membranes was evaluated, as demonstrated by the measurement of water contact angle (WCA) and water content. Furthermore, the antifouling properties of membranes were also investigated.

Improved separation and antifouling properties of PVDF gravity-driven membranes by blending with amphiphilic multi-arms polymer PPG-Si-PEG

Fabricating high-flux, low-fouling gravity-driven membranes (GDM) has proved to be an extremely challenging work. In this study, a novel tailored amphiphilic multi-arms polymer poly(propylene glycol)-silane-poly(ethylene glycol) (PPG-Si-PEG) was synthesized and blended into Polyvinylidene Fluoride (PVDF) matrix to fabricate GDM via nonsolvent induced phase separation method. The incorporation of multi-arms polymers affected phase separation and surface segregation behaviors, resulting in the formation of more porous structure, which were demonstrated by scanning electron microscopy (SEM). Moreover, the hydrophilic PEG arms in polymers were enriched onto membrane surface through surface segregation and utilized to improve the hydrophilicity of membranes, which were confirmed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The separation and antifouling properties of the membranes were evaluated by using gravity as the driving force, employing bovine serum albumin (BSA) as the model foulant. The water flux of membranes increased from 4.6 L m−2 h−1 for the control membrane to 12.1 L m−2 h−1 for PVDF/PPG-Si-PEG∼5% membrane. The antifouling properties of modified membranes were effectively improved in comparison with that of control membrane. The flux recovery ratio, especially for PVDF/PPG-Si-PEG∼5% membrane, was up to 99.4%. This study provided a new method for antifouling modification of GDM.

Evaluation of self-cleaning performance of the modified g-C3N4 and GO based PVDF membrane toward oil-in-water separation under visible-light

Photocatalytic membranes (PMs), coupling of membrane filtration and photocatalysis, have exhibited the potential for application in the wastewater treatment. In this study, we firstly adopted the supramolecular aggregates of melamine (M), cyanuric acid (C), and urea (U) in specific dimethyl sulfoxide (DMSO) as precursors to prepare carbon nitride MCU-C3N4 with high photocatalytic performance, and a kind of novel-designed photocatalytic membrane was prepared via filtrating the mixture of graphene oxide (GO) nanosheets and MCU-C3N4 on PVDF membrane supports, and then crosslinked using glutaraldehyde (GA) to construct a steady coating on the GO/MCU-C3N4/PVDF membrane. GO/MCU-C3N4/PVDF composite membrane exhibited higher permeation flux than that of GO/PVDF membrane and exhibited excellent separation performance for oil-in-water emulsion. A visible light-driven self-cleaning four-stage filtration by a self-built dead-end filtration system was carried out to evaluate membrane antifouling property, and GO/MCU-C3N4/PVDF membrane (M2) possessed higher flux recovery ratio (FRR) (∼92.36%) and lower irreversible fouling resistance (Rir) ratio (∼8%) under 30min visible-light irradiation, maintaining relatively higher FRR (>72%) during 4 cycling of four-stage filtrating experiments. GO/MCU-C3N4/PVDF PMs are equipped with high permeation flux, separation performance, anti-fouling property and stability, indicating potential application in water treatment.

Zwitterion-Ag Complexes That Simultaneously Enhance Biofouling Resistance and Silver Binding Capability of Thin Film Composite Membranes.

Biofouling can be overcome with zwitterion grafts and antimicrobial, metallic nanoparticles. However, the mechanism underpinning this effective approach remains unclear. To elucidate the role of each component in this system while maximizing membrane antifouling and antimicrobial properties, here we performed a comparative study to investigate the impact of zwitterion type and their interactions with Ag of various states. Two different zwitterions (SO3--based and COO--based) were employed to modify polyamide (PA) thin film composite (TFC) membranes, and the metallized and mineralized membranes were developed via in situ formation of silver (Ag) nanoparticles and deposition of silver chloride (AgCl) particles on the zwitterion-modified TFC membranes. The presence of zwitterions was key to enhance Ag content, resulting in significantly improved antimicrobial and antifouling properties without compromising the nanofiltration separation performance. COO--based zwitterions were found more favorable toward Ag metallization and mineralization compared to SO3--based zwitterions. The underlying mechanisms underpinning this discovery were further revealed using density functional theory (DFT) to reveal Gibbs free energy of the binding between zwitterions and Ag+ ions. This fundamental knowledge is crucial for designing next-generation antibiofouling strategies.