Surface Of Microfiltration Membrane Research Articles

Surface Modification of a Zeolite Microfiltration Membrane: Characterization and Application to the Treatment of Colored and oily Wastewaters

Membrane-based technologies used for water treatment can be an excellent alternative to handle wastewater including both conventional and emerging pollutants as they can provide technological (e.g., high quality of treated water) and economic (e.g., small footprint and low unit cost of production) advantages over other water treatment processes. Recently, low cost ceramic membranes fabricated from natural resources like kaolinitic clay, bentonite clay, phosphate are increasingly used owing to their low-cost starting materials, low sintering temperature and their excellent additional properties. Moreover, the modification of the surface by grafting process provides membranes appropriate for low UF process (dp < 10 nm) and suitable for micropollutants removal at relatively high permeate flux value which can be maintained during filtration due to antifouling characteristics of the UF active layer. In this work, the surface of microfiltration membranes made from natural zeolite was chemically modified by grafting with 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane molecule named PFAS. Various characterization methods and techniques, including scanning electron microscopy (SEM), mercury porosimetry, FTIR, TGA, and contact angle, were used to check the properties of the membranes surface before and after grafting. The grafted membranes pore size and porosity were reduced, as proved by SEM images. The determination of the water permeability shows a reduction from 1218 L.h−1.m−2.bar −1 to 204 L.h−1.m−2.bar −1 which confirm the surface densification. The application of the grafted membrane to the treatment of Indigo Blue (IB) colored solution and oily wastewater was investigated to evaluate the performances of this membrane in terms of permeate flux and pollutants retention. The filtration results revealed a good retention of color and oil, exceeding 95% for both parameters. Therefore, it is interesting to recommend this new low-cost membrane for the treatment of industrial wastewater containing recalcitrant pollutants such as color. The study of the effect of the treated colored solution on plant growth, shows that the presence of some residual nutrients required for crops growth, might make the IB treated water beneficial for irrigation purposes.

Comparative study of graphene oxide and copper oxide nanoparticle as surface modifiers in microfiltration membranes and adsorbents for efficient removal of textile dyes from contaminated water

Despite technological development, the textile industry still generates effluents with a high content of emerging contaminants, which are harmful to the environment. Conventional wastewater treatment methods struggle to remove emerging contaminants, necessitating advanced techniques. One promising solution is the modification of membranes and adsorption methods. The same modifying agents were used to modify the surface of microfiltration membranes and to create an adsorbent, allowing a comparison of the two processes in water treatment contaminated with dyes. Copper oxide nanoparticles were produced through green synthesis, and polyethersulfone microfiltration membranes were surface-modified using graphene oxide and copper oxide nanoparticles via a pressure-assisted method. Among the tested membranes, MF_GO1.0 + CuO3.0 showed the best performance, demonstrating a synergistic effect between the modifying agents, efficiently removing 97.69 % of Levafix Blue CA dye and recovering 84.88 % of the flux. It also exhibited outstanding removal rates (>99 %) for other textile dyes, such as Solophenyl Blue and Reactive Black 5. Membrane characterization revealed a decrease in contact angle for membranes modified with CuO and GO-CuO, rendering them more hydrophilic and improving permeability. Scanning Electron Microscopy depicted a compacted membrane, characteristic of graphene oxide, with nanoparticles on the surface. Chemical stability tests, conducted at neutral pH for 7 days, demonstrated no significant variation in permeability and contaminant removal. Although adsorption had limited effectiveness in removing the Levafix Blue CA dye, it provided valuable insights into the underlying mechanisms. Comparing membrane modification with adsorption, membranes displayed more efficiency in dye removal and showed enhanced antifouling properties. These results indicate the potential of modified membranes in treating dye-containing wastewater. As dye production increases, these innovative technologies offer promising solutions to reduce the environmental impact of textile industry effluents. By employing such advanced methods, we can work towards safeguarding our water resources and ecosystems from the harmful effects of textile wastewater pollution.

Particle oscillation at corrugated membrane-water interface: An in-situ direct observation and implication to membrane fouling control

Membrane surface patterning is an emerging technique for membrane fouling control. However, the underlying mechanism for this technique has not been well understood due to the lack of direct evidence on the flow field and the associated contaminant transport at the membrane-water interface. Therefore, an in-situ real-time observation system was constructed in this study with the assistance of computational fluid dynamics (CFD) simulation, and used to determine the transport and deposition behaviors of particle tracers on a corrugated microfiltration membrane surface (sawtooth shape, height ≈ 197 ± 14.7 μm, width ≈ 805.5 ± 44.5 μm). It was observed that most particles traveled wavily along the membrane surface pattern. Meanwhile, The particles entering the pattern valley were (i) trapped stagnantly at Ul = 0.05 m/s (Re = 228), while oscillated (ii) spirally in the direction of the pattern valley at Ul = 0.08 m/s (Re = 364), and (iii) irregularly at Ul = 0.1 m/s (Re = 445). During oscillation, some particles were able to escape the valley and return to the bulk flow. Complementary numerical simulation results indicated that the surface pattern induced local turbulence (wake) and boundary layer separation were the major mechanisms underlying the observed particle behaviors. These intriguing results gave rise to an intuitive understanding of the dynamics of particle transportation associated with patterned membrane filtration. Accordingly, a self-cleaning membrane may be prepared by optimizing the patterns as well as the superficial liquid velocities to invoke strong wake flow capable of mitigating particle deposition on membrane surfaces.

Pre‐deposited dynamic membrane adsorber formed of microscale conventional iron oxide‐based adsorbents to remove arsenic from water: application study and mathematical modeling

AbstractBACKGROUNDThis study reports the development of a dynamic membrane (DM) adsorber by pre‐depositing powdered‐sizedfraction of iron oxide‐based adsorptive material on the surface of a microfiltration(MF) membrane. The aim is to use the developed DM adsorber for arsenate (As(V)) remediation from water by a combined mechanism of adsorptive and membrane filtration. The two applied iron oxide‐based adsorptive materials are micro‐sized granular ferric hydroxide and micro‐sized tetravalent manganese feroxyhyte, and are available at affordable price.RESULTSThe results show that As(V) removal efficiency strongly depends on the physicochemical properties of the depositing material such as specific surface area, isoelectric point and particle size of the pre‐depositing material. The experimentally determined As(V) removal rates were mathematically modeled using a homogeneous surface diffusion model, which incorporates the equilibrium parameters and mass transport coefficients of the adsorption process. The simulations showed that the mathematical model could describe the As(V) removal rates accurately over a broad range of operating conditions. The results further showed that the longer filtration times with very low normalized As(V) permeate concentration (C/Cf = 0.1, for example) can be prolonged by operating the DM adsorber at the lowermost membrane water flux of 31 L m−2 h−1 and a large amount of pre‐depositing material on the MF membrane surface (Ma = 14 mg cm−2).CONCLUSIONThe results presented in this study confirm that use of these inexpensive materials (side‐product of granular iron oxide‐based adsorbents) in treating As(V)‐polluted water would enhance the sustainability of the industrial production process of conventional granular adsorbents by utilizing the wastes created during the process of adsorbent production. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).

Enhancing hydrophilicity and comprehensive antifouling properties of microfiltration membrane by novel hyperbranched poly(N-acryoyl morpholine) coating for oil-in-water emulsion separation

Hydrophilic polymers with low affinity for foulants were broadly utilized as functional membrane surface modifiers to mitigate fouling owing to superior hydration capability. Herein, novel hydrophilic hyperbranched poly(N-acryoyl morpholine) (HPA) synthesized through one-step RAFT polymerization was immobilized onto commercial PVDF microfiltration membrane surface using biomimetic adhesion polydopamine as an intermediate reaction platform. The surface composition and morphology of HPA decorated membranes (M-PD/HPA) were examined, demonstrating that the nano-sized HPA was facilely anchored on the membrane surface without obviously changing membrane pore size and distribution. In comparision with hydrophobic pure membrane (M-PVDF), hydrophilic and underwater superoleophobic M-PD/HPA exhibited excellent multiple defense capability toward oil, protein and bacteria due to the presence of a steric repulsive barrier of hydrated HPA layer. For model hexane-in-water emulsion separation at 0.02 MPa, permeation flux of M-PD/HPA up to 149.8 L m−2 h−1 was improved by three times and the rejection was up to 99.5%. Importantly, for the separation of complex artificial oily wastewater, relevant flux reduction of M-PD/HPA was decreased from 60.9% of M-PVDF to 36.8% and flux recovery ratio of M-PD/HPA was increased from 34.8% to 82.6%. Therefore, M-PD/HPA has a promising prospect for emulsified oil separation and water purification.

Increased E. coli bio-adsorption resistance of microfiltration membranes, using a bio-inspired approach

Cells have inherent anti-fouling properties. The mechanisms underpinning these natural properties inform the design of an anti-biosorption coating for a polyethersulfone microfiltration membrane, which includes polydopamine and chitosan layers. This tri-layered membrane is created using quick and easy synthesis method. Its ability to resist bio-adsorption and membrane extracellular polymeric substances (EPS) formation is investigated using the bacterium E. coli (ATCC 11775, 1.5 × 107 CFU/mL). In addition, the proliferative bio-adsorption process is explored on the microfiltration membrane surface, using natural water under static and shaken conditions, while monitoring the bio-adsorption kinetics and EPS dynamic changes. The characterization results show that the modification by polydopamine and chitosan change the membrane surface morphology and increase its hydrophilicity. After 10 min dipping in 5 g/L chitosan solution, the pure water flux of the modified membrane is 5469 ± 30 L/(m2·h) (0.2 bar) and the contact angle decreases to 36.7 ± 1.0°, compared with 9889 ± 23 L/(m2·h) (0.2 bar) and 60.3 ± 1.5° for the unmodified polyethersulfone membrane, respectively. In proliferative bio-adsorption tests, the modified membrane is shown to decrease bio-adsorption by 0.4–2.3 orders of magnitude. However, no antimicrobial function is observed, probably due to the alkaline environment and insufficient functional amino groups. A series of linear and non-linear kinetic models is applied to fit the proliferative bio-adsorption process. The pseudo-second-order model is found to describe the proliferative bio-adsorption process best. Neither total organic carbon (TOC) nor protein is detected on the modified membrane surface. In contrast, on the unmodified PES membrane the ratios of protein/TOC (%), TOC/abundance ((μg/cm2)/CFU (log)) and protein/abundance ((μg/cm2)/CFU(log)) are 10%–16%, 0.17–0.28 and 0.02–0.04, respectively. No significant difference (p > 0.05) is found between static and shaken conditions. All these results point to improved anti-biosorption properties for water treatment applications, encouraging further studies on this membrane.

Improved permeability and biofouling resistance of microfiltration membranes via quaternary ammonium and zwitterion dual-functionalized diblock copolymers

In order to improve permeability and biofouling resistance of microfiltration (MF) membranes, quaternary ammonium and zwitterion dual-functionalized diblock polyelectrolyte copolymers, poly(dimethylaminoethyl methacrylate-butylammonium bromide)-b-poly(sulfobetaine methacrylate) (PDB-b-PSB) prepared via RAFT polymerization, were immobilized on commercial poly(vinylidene fluoride) (PVDF) MF membrane surface via using a versatile and facile mussel-inspired method to fabricate hierarchical copolymer brushes. Hierarchical PDB-b-PSB brushes contained bottom passive anti-adhesive zwitterionic PSB layer and upper active biocidal quaternary ammonium PDB layer. The surface chemical composition and morphology characterizations of pure and modified membranes demonstrated that PDB-b-PSB copolymers were successfully grafted to the dopamine-modified membrane surface via thiol mediated Michael addition reaction, which did not significantly change the membrane pore structure. However, the initial contact angle of PDB-b-PSB modified membrane (M/PDB-b-PSB) was changed from 128° for pure membrane (M/pure) to 43.2° and became 0° within 10 s, indicating the enhanced hydrophilicity. More importantly, the M/PDB-b-PSB membrane exhibited active biocidal effects against E. coli and S. aureus with inhibition rates over 98% and the E. coli and S. aureus suspension fluxes of M/PDB-b-PSB membranes were 1.61 times and 1.35 times higher than those of M/pure membranes. The M/PDB-b-PSB membrane had excellent anti-biofouling property with a better water flux recovery rate of 72%, which was 30% higher than that of the M/pure membrane. Moreover, PDB-b-PSB brushes showed a good immobilization stability. Therefore, the approach of poly(dopamine)-assisted fabrication of anti-biofouling MF membranes with quaternary ammonium and zwitterion dual-functionalized diblock copolymers had a prospect application in membrane-based separation technology and water purification.

Fouling-resistant microfiltration membrane modified with magnetite nanoparticles by reversible conjunction

Abstract We developed a stimuli-responsive poly(tetrafluoroethylene) (PTFE) microfiltration (MF) membrane by reversible conjunction of magnetite nanoparticles. We modified the magnetic particles with maleimide functional groups and attached them to a furan-modified PTFE membrane via a Diels–Alder (DA) cycloaddition reaction to prepare an anti-fouling membrane that responds to magnetism and temperature. The combined results of Fourier-transform infrared spectroscopy, X-ray diffractometry, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy investigations clearly showed that the maleimide-modified magnetic nanoparticles were successfully synthesized and coupled with the furan-modified PTFE MF membrane by the DA reaction. The modified membrane produced a micro-vortex under a rotating magnetic field, and showed a high resistance to fouling with a water flux higher than 50% of initial flux even after 30 min in the fouling test, whereas the neat membrane had a water flux falling below 20% of initial flux in 30 min. Moreover, the magnetite nanoparticles were readily and repeatedly regenerated on the MF membrane surface using a thermally driven peel-and-stick process; 75% of the water flux was recovered, even after three fouling cycles.

Split injection of coagulant to enhance the water permeability of a cake layer in a coagulation–microfiltration process

A split injection of an aluminum coagulant at the initial stage of rapid mixing was investigated to improve the water permeability of a cake layer composed of chemical flocs on a microfiltration membrane surface. The split ratio of the first to second injections was changed to find an optimized injection condition. With an increase in the split ratio, the cake compressibility index decreased because compact chemical flocs were produced with reduced dosage of the second injection, but the specific cake resistance increased due to small size of chemical flocs with the insufficient amount of coagulant at the second injection. At a small split ratio, the particle size distribution of the split injection was similar to that of normal single injection, and the compressibility index was small, leading to better water permeability of the cake layer at higher pressure.

Microfiltration (MF) membrane fouling potential evaluation of protein with different ion strengths and divalent cations based on extended DLVO theory

Membrane fouling is a major obstacle to the wide application of microfiltration membrane bioreactor (MF MBR). Protein-like substances have been known to contribute significantly to membrane fouling in MF MBRs. In this study, the effects of ionic strength and divalent cations on MF membrane fouling by protein were investigated. Fouling experiments showed that MF membrane fouling by protein was enhanced with increasing ionic strength and calcium ion addition. Measured interaction energies among protein molecules and between protein molecules and clean MF membrane confirmed the fouling trends of MF membrane. It was consistently shown that solution chemistries that induced higher fouling rates of MF membrane were associated with greater attractive and lower repulsive interaction energies among protein molecules and between protein molecules and clean MF membrane. Analysis of fouled MF membrane surface roughness further indicated that MF membrane fouled by protein with higher ion strength and calcium addition made attachment of foulant onto MF membrane surface easier.

Study on the in Situ Enzymatic Self-Cleansing of Microfiltration Membrane for Valorization of Olive Mill Wastewater

In this study intensified removal of pectins was integrated with microfiltration step to develop in situ self-cleansing biocatalytically active membranes. This method was developed to reduce the severe fouling that occurred during microfiltration (MF) of olive mill wastewater (OMWW) for the recovery of bioactive compounds using integrated membrane processes. As a proof-of-concept, pectinase has been immobilized on the MF membrane surface and flux performances as a function of time has been monitored and compared with inert membrane. For the experiments real OMWW has been used. The steady-state flux through the enzyme immobilized on the membrane surface solo was 50% higher than inert membrane. The mechanism for the better performance of the biocatalytically active on the surface has been explained as based on both degradation of deposited pectins (in situ self-cleansing) and overcome of product inhibition as it is continuously removed from the reaction site. The inhibitory effect has been clearly identifie...

Grafted Glycopolymer-Based Receptor Mimics on Polymer Support for Selective Adhesion of Bacteria

A sugar-containing monomer (2-lactobionamidoethyl methacrylate, LAMA) was grafted on a polypropylene (PP) microfiltration membrane surface by UV-induced graft copolymerization. The degree of grafting can be controlled by variation of monomer concentration, UV irradiation time, and photoinitiator concentration. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to confirm the surface modification on the membranes. The water contact angle was used to evaluate the hydrophilicity change of the membrane surface before and after modification. Bacteria capture experiments showed that the membrane could selectively bind E. faecalis while adhesion of S. maltophilia was not influenced by the functionalization of PP with grafted poly(LAMA). The adhesion of E. faecalis onto poly(LAMA) grafted membrane could be inhibited by 200 mM galactose solution; however, glucose solution showed no inhibition effect. Moreover, occupying sugar residues on the membrane surface primarily by a galactose targeting lectin, peanut agglutinin, could significantly suppress the following adhesion of E. faecalis. All these results clearly demonstrate that this poly(LAMA) grafted PP membrane can selectively capture E. faecalis and that this selection is based on the interaction between galactose side groups on grafted flexible functional polymer chains on the membrane surface and galactose binding protein on the E. faecalis cell membrane.

The effects of (macro)molecular structure on hydrophilic surface modification of polypropylene membranes via entrapment

Entrapment of a variety of ethyleneoxide-containing substances from nonpolar solutions into polypropylene (PP) microfiltration membrane surface for hydrophilic modification was studied. The results from gravimetric weight gain, surface characterization by contact angle measurements and ATR-IR spectroscopy, water flux measurements and protein adsorption revealed that poly(ethylene glycol)s (PEGs) were ineffective, while many nonionic amphiphilic substances, especially some tri-block copolymers of poly(ethyleneoxide) (PEO) and poly(propylene oxide) (PPO) were very effective for PP surface modification. The relationship between modifier structure and architecture and entrapment behavior was investigated by studying the micellization of the amphiphilic modifiers in nonpolar solutions via pyrene-probe fluorescence and 1H NMR spectroscopy. We observed that the balanced structure of nonionic tri-block (macro)molecules tended to promote the formation of reverse micelles. For the most efficient polymeric modifiers, the lowest reverse critical micelle concentration (RCMC) had been observed. We conclude that a block copolymer structure and architecture promoting the self-association in the nonpolar solvent is the basis for a high modification efficiency, and that reverse micelles are involved in the entrapment modification performed at concentrations above RCMC. A different mechanism has been deduced for amphiphilic modifiers with low molar mass. This work provides more comprehensive insights in surface entrapment as a easy to perform physical surface modification method for polymeric materials.

Investigation of cake deposition on various parts of the surface of microfiltration membrane due to fouling

The accumulation of deposited layer on membrane surface in cross-flow microfiltration was investigated. This study provides a basis for elucidation of the membrane segments with superior tendency for cake deposition due to fouling. A commercially available GVWP membrane was fouled with a colored (blue indigo suspension in water) feed. The deposition pattern or fouling tendency was obtained using a digital camera, scanning electron microscope (SEM) and image analysis. The effects of feed concentration, transmembrane pressure and cross-flow velocity on cake deposition were investigated. In the early stages of the filtration trials, cake deposition was increased from the commencement portion (feed inlet) towards the furthermost part (concentrate outlet) of the membrane surface. However, at the completion of filtration, no pronounced difference was realized between cake deposition in the median and end parts of the membrane. Computational fluid dynamics (CFD) modeling of the membrane was carried out to predict the fouling behavior in various segments of the membrane at different operating conditions. The results of CFD modeling are in acceptable agreement with the experimental data. Accomplishment of the membrane sections with higher tendency for accumulation of foulants may provide a basis for manipulation of conditions to diminish the buildup of fouling deposition in the proposed segments. This results in lower cake deposition on vital parts to minimize the overall fouling.

Tailored “Grafting‐From” Functionalization of Microfiltration Membrane Surface Photo‐Initiated by Immobilized Iniferter

AbstractSurface‐selective graft functionalization of hydrophilized poly(propylene) microfiltration membrane has been realized by two steps: (i) immobilization of dithiocarbamate group as iniferter and (ii) heterogeneous photo‐graft copolymerization controlled by this iniferter. Investigations regarding controllability of photo‐grafting were carried out with varied monomer concentration and UV‐irradiation time as well as cross‐linker monomer content by using ATR‐FTIR spectroscopy, scanning electron microscopy, water permeability, and measurements of pore size distribution. The developed grafting method exhibits high surface‐grafting selectivity and efficiency, uniform modification and high controllability over grafted layer thickness and (cross‐linked) architecture.magnified image

Accelerated Development Procedure for Molecularly Imprinted Polymers Using Membrane Filterplates

A novel technique for the synthesis and testing of large numbers of molecularly imprinted polymers is described requiring much less time than the commonly used miniMIP approach. Instead of vials, the polymers are synthesized on the surface of microfiltration membranes in multiwell filterplates. The thin polymeric films enable accelerated template removal. The MIP development procedure is thereby shortened to two days. Performance of the system was demonstrated by creating a combinatorial library of MIPs selective for cimetidine, an antiulcer drug. The polymer composition has been optimized. An experimental design combined with a multivariate analysis (i.e., response surface modeling) was used to minimize the number of experiments in the optimization process. The highest imprinting factor was obtained using a MAA/EDMA/template molar ratio of 3.5:19.5:1.

Track membrane with immobilized colloid silver particles

A method for modification of track membranes by immobilization of polymer complexes of colloid silver nanoparticles on the surface of microfiltration membranes was developed. The antimicrobial properties of track membranes modified with silver nanoparticles were tested on E. coli, Ps. aeruginosa, St. aureus, and B. cereus.

医薬品の除去に対する膜分離活性汚泥法分離膜の付加効果

The removal of pharmaceuticals in the membrane separation bioreactor process was examined. The deposition of activated sludge on the microfiltration membrane surface provided an additional barrier for the permeation of target substances, although the additional effect of the deposition on the removal was lower than 25% for hydrophilic compounds with log Kow between 2 and 3. The additional effect increased with time and log Kow, and reached 65% after 44 days of operation for a solute with a log Kow of 4.8.

Effective hydraulic resistance of the first cake layers at the membrane surface in microfiltration

The usual procedure for predicting the filtration flux in microfiltration processes is to assume that the total hydraulic resistance to filtration flow can be calculated as the mere addition of the membrane resistance and the intrinsic cake layer resistance. It is shown that this assumption is acceptable when the cake layer is sufficiently thick but questionable when the cake layer is thin, i.e. at the beginning of the microfiltration process when the filtration flux decreases drastically. In fact, the simple additive model underestimates the total hydraulic resistance in the early stages of the cake formation. This problem is studied using two dimensional boundary element methods to solve the coupled problem of Darcy flow in the cake layer and Stokes flow in the upper fluid region. For a given cake layer thickness, the numerical results show that the effective resistance of the cake layer increases as the membrane surface porosity decreases.

Stabilization of supported liquid membranes by interfacial polymerization top layers

In this paper, a new method of stabilizing supported liquid membranes is presented. The stabilization is based on the application of polymeric top layers to the surface of microfiltration membranes, preventing loss of the liquid membrane phase out of the support pores. The modified microfiltration membranes were used as supports for supported liquid membranes and tested on selective nitrate transport and stability. Screening experiments revealed that most applied top layers did not hinder the transport of nitrate ions. However, a few were able to improve the stability of the liquid membranes. Best results were obtained when piperazine (PIPA) and trimesoyl chloride (TMCl) were used as monomers. For Accurel polypropylene supports with PIPA/TMCl top layer, nitrate flux was constant at the initial 18 × 10 −10 mol cm −2 s −1 for 350 h of simulated operation. For uncoated supported liquid membranes (SLMs), the flux decreased within one day from 18 × 10 −10 to almost 0 mol cm −2 s −1. Scanning electron microscopy investigations revealed a particular, rippled surface texture of layers prepared with these monomers.