Dead-end Filtration Experiments Research Articles

Nanocomposite membranes prepared from cellulose acetate or polysulfone with Ag0 nanoparticles and nitron reagent for nitrate ion removal

This paper presents the preparation route for new cellulose acetate and polysulfone membranes with silver nanoparticles (Ag0 NPs) incorporated and functionalized with a nitrate-selective reagent, nitron (C20H16N4): M1 (CA 20%), M2 (CA 20% + Ag0 NPs), M3 (CA 20% + Ag0 NPs, nitron-impregnated), M4 (CA 20% + Ag+: nitron complex, 1:1 molar ratio), M5 (Psf 15%), M6 (Psf 15% + Ag0 NPs), M7 (Psf 15% + Ag0 NPs, nitron-impregnated), and M8 (Psf 15% + Ag+: nitron complex, 1:1 molar ratio), that were morphologically and structurally characterized by ATR-FTIR and 2D FTIR imaging, UV-Vis, XPS and TG-DSC techniques and scanning electron microscopy coupled with energy dispersive spectroscopy. Dead-end filtration experiments were carried out to characterize the hydrodynamic performance of the prepared membranes. The best nitrate retention values were obtained for nitron-functionalized membranes M3 - 94.4% and M4 - 87.82%, comparable to those of commercially available nanofiltration membranes.

Modification of PVDF membrane by post-modified NH2-MIL-88B(Fe) showing improved permeability and oil/water separation performance

Metal organic frameworks (MOFs) possess excellent post-modification characteristics, high specific surface area, diversity of skeleton composition and pore tunability, have been increasingly applied in membrane modifications. In this work, NH2-MIL-88B(Fe) (NM88B) was first fixed onto polyvinylidene fluoride (PVDF) membrane by polyethyleneimine (PEI) through a vacuum-assisted self-assembly process, and the deposited NM88B was subsequently grafted with perfluoroalkyl polyethoxyacetic acid (FPEOAA) via a condensation reaction to realize the surface modifications. The modified membranes (named as N1Fx) showed improved hydrophilicity and underwater-oleophobicity. In addition, very high pure water flux (up to 9403 L‧m−2‧h−1) was obtained for the N1Fx membranes due to the high porosity of introduced NM88B. In the dead-end filtration experiments of n-hexadecane-water emulsion, the optimum membrane N1F20 showed a good oil rejection rate (98.3%) and high permeation flux (667 L‧m−2‧h−1) which is approximately seven times of the pure PVDF membrane, indicating that the surface-modified membranes had excellent permeability and good separation performance. Even after four filtration cycles of oil-water emulsion, the rejection rate maintained higher than 97%, showing good reusability. Furthermore, the study found that N1F20 had certain acid and alkaline resistance and great potential for engineering applications.

A Novel Anaerobic Gravity-Driven Dynamic Membrane Bioreactor (AnGDMBR): Performance and Fouling Characterization.

Despite numerous studies undertaken to define the development and significance of the dynamic membrane (DM) formed on some coarse materials, the optimization of reactor configuration and the control of the membrane fouling of anaerobic dynamic membrane bioreactor (AnDMBR) need to be further investigated. The aim of this study was to design a novel anaerobic gravity-driven dynamic membrane bioreactor (AnGDMBR) for the effective and low-cost treatment of municipal wastewater. An 800 mesh nylon net was determined as the optimal support material based on its less irreversible fouling and higher effluent quality by the dead-end filtration experiments. During the continuous operation period of 44 days, the reactor performance, DM filtration behavior and microbial characteristics were studied and compared with the results of recent studies. AnGDMBR had a higher removal rate of chemical oxygen demand (COD) of 85.45 ± 7.06%. Photometric analysis integrating with three-dimensional excitation–emission matrix fluorescence spectra showed that the DM effectively intercepted organics (46.34 ± 16.50%, 75.24 ± 17.35%, and 66.39 ± 17.66% for COD, polysaccharides, and proteins). The addition of suspended carriers effectively removed the DM layer by mechanical scouring, and the growth rate of transmembrane pressure (TMP) and the decreasing rate of flux were reduced from 18.7 to 4.7 Pa/h and 0.07 to 0.01 L/(m2·h2), respectively. However, a dense and thin morphological structure of the DM layer was still observed in the end of reactor operation and plenty of filamentous microorganisms (i.e., SJA-15 and Anaerolineaceae) and the acidogens (i.e., Aeromonadaceae) predominated in the DM layer, which was also embedded in the membrane pore and led to severe irreversible fouling. In summary, the novel AnGDMBR has a superior performance (higher organic removal and lower fouling rates), which provides useful information on the configuration and operation of AnDMBRs for municipal wastewater treatment.

Hydraulic Resistance and Macromolecular Structure of Aerobic and Anaerobic Mixed-Culture Extracellular Polymeric Substances Gel Layers: Opportunities and Challenges

Soluble Extracellular Polymeric Substances (sEPS) are a mixture of microbial soluble polymers produced during aerobic or anaerobic treatment of wastewater. Gel layers mainly consisting of sEPS are usually present in the fouling layers of membrane bioreactors (MBRs) and in the dynamic membranes (DMs) of dynamic membrane bioreactors (DMBRs), and their properties have not been thoroughly investigated over the years. In this study, sEPS fractions recovered from aerobic and anaerobic reactors were analyzed and tested to build-up EPS gel layers on a 0.2 µm pore size polycarbonate carrier. Dead-end filtration experiments showed that anaerobic sEPS layers, which have a low polysaccharide:protein (PS:PN) ratio, had a lower hydraulic resistance than the aerobic sEPS gel layers, which show a high PS:PN ratio. Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM) analyses highlighted that both layers had similar thicknesses and 3D structural organizations. Fluorescent staining of organics and biovolume analysis revealed that for the anaerobic sEPS (low PS:PN), the abundance of proteins appears to destabilize the polysaccharide network increasing the water permeability through the layer. Additionally, the polysaccharides present in the anaerobic sEPS were mainly of the α-linked type, contributing to a more open crosslinked network within the layer, resulting in the low filtration resistance measured. The filtration characteristics observed in this study for the sEPS layers from anaerobic mixed cultures are of interest for possible future application of those layers as dynamic membranes within anaerobic reactors.

Effective Removal of Methyl blue and Crystal Violet Dyes Using Improved Polysulfone / ZIF-8 Nanocomposite Ultrafiltration Membrane

Zeolitic Imidazole framework 8 (ZIF-8) was successfully prepared in an aqueous medium and then dissolved with concentrations ranging from 0.5% to 5% in polysulfone (PSF) to prepare an ultrafiltration membrane. ZIF-8 nanosized material uniformly distributed in the PSF membrane ultrafiltration membrane was prepared in a polar solvent of N,N'-dimethyl formamide (DMF) by phase inversion procedure. Significantly, ZIF-8 enhanced the membrane flux from 50.42 L/m2.h (PSF) to 83.65 L/m2.h at 100 Kpa, and the rejection of methyl blue and crystal violet dyes up to 95.1% and 89.65 %, respectively compared to the PSF membrane without ZIF-8, 41.08%, 46.32%. Wavelength dispersive X-ray fluorescence (WD-XRF), X-ray Diffraction (XRD), scanning electron microscopy (SEM), contact angle, and dead-end filtration experiment were carried out to characterize the morphology and performance of the prepared ZIF-8 and membranes. The hydrophilicity of the membrane was determined by a contact angle test between water and membrane. SEM was used to study the surface and the cross-sectional morphologies.

A rigid body dynamics model to predict the combined effects of particle size and shape on pressure filtration

• Developed a novel computational workflow for simulating pressure filtration. • Rigid body dynamics used to simulate cake formation with various particle shapes. • A “local” Ergun equation developed to capture spatial variations in cake structure. • Platelet-shaped particles predicted to generate low porosity and poor filterability. • Large and small particle mixtures predicted to generate spatial heterogeneities. Many theoretical studies have focused on the effects of spherical particle size on pressure filtration, a solid-liquid separation method commonly used in pharmaceutical manufacturing and other industries. While experimental studies have demonstrated the importance of particle shape as well as size on the filterability of non-spherical particles commonly produced from pharmaceutical crystallization, process models that mechanistically capture how particle morphology affects the microscopic properties of the particle cake are lacking. The objective of this study was to investigate the combined effects of particle shape and size on pressure filtration performance using rigid body dynamics simulation, a powerful method for predicting porous cake structure based on the properties of the constituent particles. Once a detailed cake structure was generated, the Ergun equation was used to predict the macroscopic flow behavior of the filtration process. This workflow was validated by comparing model predictions with filtrate flow measurements from a series of dead-end filtration experiments using spherical particles with heterogeneous size. By simulating cylindrical particles over a wide range of aspect ratios, we showed that particle shape can have a dramatic effect on cake porosity and filtrate flow with disk-shaped particles predicted to be particularly difficult to filter. Rigid body simulation allowed the prediction of local as well as average cake properties. We predicted that heterogeneously sized particles with small or large aspect ratios such as disks or needles could produce highly asymmetric cake structures characterized by densely packed and low porosities near the filter medium. A modified Ergun equation based on local particle size and porosity was developed and shown to predict substantially different filtrate flows than the standard Ergun equation based on spatially-averaged properties, especially for cylindrical particles with high aspect ratio.

Incorporation of lanthanum particles to polyethersulfone ultrafiltration membrane for specific phosphorus uptake: Method comparison and performance assessment

It is known that phosphorus is a major contributor to the occurrence of eutrophication. As such, it is of importance to remove it from water. Nanofiltration (NF) has low phosphorus selectivity and requires a relatively high pressure to achieve the separation, though it is capable of removing phosphorus. In this paper, we report our findings of method development on fabrication and application of a lanthanum (La)-incorporated polyethersulfone (PES)/sulfonated polyphenylenesulfone membrane for phosphorus treatment. The performances of membranes fabricated by the in situ and ex situ methods were examined in a series of batch adsorption and dead-end filtration experiments. The membrane fabricated by the in situ method demonstrated higher adsorption capacity (48.0 mg/g), faster kinetics (equilibrium in 6 h) and higher water permeance (>100 LMH/bar), which outperformed that by the ex situ method. Furthermore, the PES/La (in situ) membrane showed a comparable phosphate removal with a much higher permeance (about 20 times) than the NF90 (a nanofiltration commercial membrane). Moreover, the multiple cycles of filtration study showed that the membrane was reused satisfactorily in treating low-phosphate contaminated water and meeting the stringent phosphate standard limit of 0.15 mg/L. The removal of phosphate by the membranes was attributed to the mechanisms of ion exchange and electrostatic attraction/complexation. The study reported here provides a better approach in fabrication of functionalized membrane for water treatment, such as phosphate removal in either batch adsorption or membrane filtration process.

Polyzwitterionic hydrogel coating for reverse osmosis membranes by concentration polarization-enhanced in situ “click” reaction that is applicable in modules

The methodology for a polyzwitterionic anti-fouling hydrogel coating for reverse osmosis polyamide (PA) thin-film composite (TFC) membranes by concentration polarization-enhanced in situ thiol-ene “click” reaction has been developed. A copolymer with zwitterionic sulfobetain and reactive methacrylate side groups as well as a bis-thiol crosslinker in water were used as reactive system. By means of rheology, best suited solution composition parameters for efficient cross-linking at ambient temperature toward stable hydrogels were established first. Thereafter, factors that influence hydrogel coating of PA TFC membranes were investigated in dead-end filtrations, such as copolymer concentration, flux and stirring speed. It was found that hydrogel formation will occur within the first few minutes if the critical reactant concentration required for cross-linking is reached at the membrane surface and further filtration/reaction time will increase hydrogel layer thickness. Specific parameters, selected based on results of dead-end filtration experiments yielding thick hydrogel coatings (1–2 μm, in dry state), lead to only very thin hydrogel layers under cross-flow conditions in a spacer-filled channel. However, such thin hydrogel-coated membranes had also very good antifouling properties compared to the unmodified membrane. The extent of coating can be adjusted toward thicker hydrogels by increasing flux also under cross-flow conditions in a spacer-filled channel. Finally, the feasibility of the hydrogel coating of PA TFC membranes in industrial spiral-wound modules and the use of such modules for treatment of cooling water in a steel manufacturing plant were demonstrated. Overall, suited materials and methods as well as partial fundamental understanding of the influence of parameters that can be used for a scalable antifouling hydrogel coating of membranes in spiral-would modules have been established in this work.

Polyimide ultrafiltration membrane embedded with reline-functionalized nanosilica for the remediation of pharmaceuticals in water

This study introduces the use of choline chloride-urea (ChCl-U) deep eutectic solvent (DES) in polyimide (PI) ultrafiltration (UF) membranes to enhance the filtration removal of aqueous pharmaceuticals such as ibuprofen and paracetamol. The DES is immobilized over silica nanofiller particles by impregnation, and the composite ChCl-U@SiO2 is embedded at different loadings in the preparation of the PI UF membrane case solutions. The effects of ChCl-U@SiO2 loading on the resulting surface roughness, porosity, average pore size, hydrophilicity, and mechanical properties of the membranes were evaluated and correlated with the UF performance. The modified membrane was assessed using dead-end vacuum filtration experiments to measure the water permeate flux, solution permeate flux, and removal efficiency for 50 ppm paracetamol and 50 ppm ibuprofen from synthetic aqueous mixtures. The results showed that a 2 wt% ChCl-U@SiO2 nanofiller loading was necessary to produce membranes with the optimal aforementioned performance characteristics. The ChCl-U@SiO2 (2 wt%) PI UF membrane showed a significant increase in the water flux (250 L/m2 h) compared to the pristine membrane (30 L/m2 h), due to the enhancement of the hydrophilic character of the membrane. The large water flux was accompanied by an outstanding removal efficiency of up to 99.9% for paracetamol, exceeding that of the bare PI membrane (15%) by ~ 6 folds. The rejection removal of ibuprofen (87%) was roughly 7.9 times greater than that for the pristine membrane. This study provided substantial insights for the potential application of DES as a green modifier in the membrane-based removal of pharmaceutical pollutants from water.

Designing nanofibrous membrane with biomimetic caterpillar-like structured for highly-efficient and simultaneous removal of insoluble emulsified oils and soluble dyes towards sewage remediation

Purification of insoluble emulsified oils and soluble organic pollutants from sewage has attracted tremendous attention in today's society. Herein, a stable and environmentally friendly nanofibrous membrane with hierarchical caterpillar-like structure was fabricated via in-situ hydrothermal growing the nickel-cobalt layered double hydroxides (NiCo-LDHs) on tche polyacrylonitrile (PAN) electrospun nanofibers. The wrapped hydrophilic NiCo-LDHs constructed the hierarchical structure and endowed the membrane attractive superhydrophilicity (≈ 0°)/underwater superoleophobicity (≈ 161°) and enhanced oil-repellency performance. Meanwhile, the NiCo-LDH@PANI/oPAN NFMs can display the ultra-fast flux of SSEs (xylene/water emulsion, 4175 L m−2 h−1) and satisfactory separation efficiency (99.07%). Moreover, the introduction of positively charged NiCo-LDHs increased plentiful adsorption active sites for membranes, which is beneficial to demulsify ionic SSEs and adsorb organic pollutants. Finally, for simultaneous purification of complex sewage by the dead-end and cross-flow filtration experiment, the composite membrane both displayed splendid removal rate of oil (> 99.0%) and dyes (> 99.0%), robust regeneration recycle-ability and no secondary pollution. Hence, it is expected that such strategy of combining electrospun and chelating-assisted in-situ hydrothermal can provide a low energy consumption and high decontamination technology for severe environmental crisis.

Fabrication of high-flux asymmetric polyethersulfone (PES) ultrafiltration membranes by nonsolvent induced phase separation process: Effects of H2O contents in the dope

A series of asymmetric polyethersulfone (PES) membranes were fabricated using non-solvent induced phase separation (NIPS) process from the system of water/GBL/PVP/PES at 40 °C. Water, acting as the nonsolvent, was added in different amounts to the dope solution to modify the porous structure and enhance the permeability of the membranes. The fabricated membranes were tested systematically for their morphologies, physical properties, pure water fluxes, and rejection capacities against bovine serum albumin molecules (BSA). The SEM images indicated that the pore size and porosity of the top surface increased with increasing water content in the dope, and when 1.5 phr of water was incorporated, the macrovoids in the cross section disappeared and the pores interconnected to form numerous continuous channels within the PES matrix. This membrane exhibited a pure water flux of 642 L m−2h−1bar−1 and a tensile strength as high as 5.6 N/mm2. The dead-end filtration experiments indicated a very high BSA rejection of ~98% for membranes prepared from dopes containing ≤1.0 phr of water, and a moderately high (85%) rejection for that with a higher dope water content.

Preparation of a novel mixed non-covalent and semi-covalent molecularly imprinted membrane with hierarchical pores for separation of genistein in Radix Puerariae Lobatae

In this work, a novel mixed non-covalent and semi-covalent molecularly imprinted membrane (MIM) with hierarchical pores was prepared by cryopolymerization at −18 °C and using PEG2000 and dimethyl sulfoxide ice crystals as the pore templates. The free-standing MIM was characterized by scanning electron microscope and nitrogen adsorption-desorption isotherms, and the results confirmed the formation of the hierarchical pore structure. In the static adsorption, membrane permeation and dead-end filtration experiments, the results indicated that the mixed non-covalent and semi-covalent molecular imprinting was a good method to improve the performance of MIM which had a good adsorption selectivity toward genistein due to the presence of the imprinted sites in MIM and possessed strong imprinting efficiency toward genistein even in some similar compound mixture or extract of Radix Puerariae Lobatae.

Ultrafiltration Mixed Matrix Membranes Based on Mesoporous Silica (MCM-41, HMS)Embedded in Polysulfone

Three composite membranes (M1-M3), with mesoporous silica (MCM-41 or HMS-C12/C16-type) embedded in polysulfone (Psf) were obtained by phase-inversion method and their performances were tested for use in ultrafiltration membrane processes. The structures of M (Psf 12%, reference membrane), M1 (Psf 12% + MCM-41), M2 (Psf 12% + HMS-C12), M3 (Psf 12% + HMS-C16) have been assessed by FTIR, TG-DSC and SEM-EDAX and the morphology and their hydrodynamic performances have been evaluated by contact angle measurements, dead-end and cross-flow filtration experiments.

Self-cleaning Anti-fouling TiO2/Poly(aryl ether sulfone) Composite Ultrafiltration Membranes

A series of novel TiO2/poly(aryl ether sulfone) ultrafiltration membranes with anti-fouling and self-cleaning properties was designed and prepared. First, anti-photocatalytic degraded fluorine contained poly(aryl ether sulfone) matrix(PAES-F) was synthesized. Then the composite membranes were prepared via TiO2 nanoparticles and PAES-F polymer matrix by solution blending and non-solvent induced phase inversion methods. Further, separation efficiency, fouling behavior and self-cleaning property of the composite ultrafiltration(UF) membranes were investigated by dead-end filtration experiments using a polyacrylamide solution. The composite UF membranes exhibited outstanding self-cleaning efficiency and anti-photocatalytic degraded property after exposure to simulated sunlight irradiation. The water flux recovery ratios(FRR) of the optimal composite UF membranes could reach 74.24%, which was attributable to photocatalytic degradation of the organic contaminant by TiO2. And the retention rates of the composite UF membranes could maintain over 97%, which indicated the excellent photocatalytic degradation resistance of the fluorine contained PAES-F matrix. The novel high performance composite UF membranes have a broad application prospect in water treatment.

Efficient Removal of Polycyclic Aromatic Hydrocarbons and Heavy Metals from Water by Electrospun Nanofibrous Polycyclodextrin Membranes.

Here, a highly efficient membrane based on electrospun polycyclodextrin (poly-CD) nanofibers was prepared and exploited for the scavenging of various polycyclic aromatic hydrocarbons (PAHs) and heavy metals from water. The poly-CD nanofibers were produced by the electrospinning of CD molecules in the presence of a cross-linker (i.e., 1,2,3,4-butanetetracarboxylic acid), followed by heat treatment to obtain an insoluble poly-CD nanofibrous membrane. The membrane was used for the removal of several PAH compounds (i.e., acenaphthene, fluorene, fluoranthene, phenanthrene, and pyrene) and heavy metals (i.e., Pb2+, Ni2+, Mn2+, Cd2+, Zn2+, and Cu2+) from water over time. Experiments were made on the batch sorption of PAHs and heavy metals from contaminated water to explore the binding affinity of PAHs and heavy metals to the poly-CD membrane. The equilibrium sorption capacity (qe) of the poly-CD nanofibrous membrane was found to be 0.43 ± 0.045 mg/g for PAHs and 4.54 ± 0.063 mg/g for heavy metals, and the sorption kinetics fitted well with the pseudo-second-order model for both types of pollutants. The membrane could be recycled after treatment with acetonitrile or a 2% nitric acid solution and reused up to four times with similar performance. Further, dead-end filtration experiments showed that the PAH removal efficiencies were as high as 92.6 ± 1.6 and 89.9 ± 4.8% in 40 s for the solutions of 400 and 600 μg/L PAHs, respectively. On the other hand, the removal efficiencies for heavy metals during the filtration were 94.3 ± 5.3 and 72.4 ± 23.4% for 10 and 50 mg/L solutions, respectively, suggesting rapid and efficient filtration of heavy metals and PAHs by the nanofibrous poly-CD membrane.

Polyelectrolyte-Based Sacrificial Protective Layer for Fouling Control in Reverse Osmosis Desalination

Reverse osmosis (RO) membranes inevitably foul because of the accumulation of material on the membrane surface. Instead of trying to reduce membrane fouling by chemically modifying the membrane, we took a different approach based on adding a sacrificial coating of two polyelectrolytes to the membrane. After membrane fouling, this coating was removed by flushing with a highly saline brine solution, and a new coating was regenerated in situ to provide a fresh protective layer (PL) on the membrane surface. The utility of this approach was demonstrated by conducting four consecutive dead-end filtration experiments using a model foulant (alginate, 200 ppm) in a synthetic brackish water (2000 ppm of NaCl). Brine removal and regeneration of the PL coating restored the water flux to an average of 97 ± 3% of its initial flux, compared to only 83 ± 3% for the pristine membrane. The average water flux for the PL-coated membranes was 15.5 ± 0.6 L m–2 h–1 until the flux was decreased by 10% versus its initial flux, co...

A Study on Anti – Fouling Behaviour and Mechanical Properties of PVA/Chitosan/TEOS Hybrid membrane in The Treatment of Copper Solution

In a wastewater treatment by using membrane filtration, fouling has been one of the major problems. In this study, the anti-fouling behaviour of the fabricated thin-film composite membrane were studied during the treatment of water containing copper ion. The membranes were prepared from a polymer blend of 2wt.% chitosan with 10 wt.% poly(vinyl alcohol) (PVA) and then it was cross – linked with tetraethylorthosilicate (TEOS) through sol-gel method. The membrane had been evaluated for its resistance against organic fouling where humic acid had been chosen as organic foulant model which represent the natural organic matter (NOM) in water or wastewater. The dead-end filtration experiments were carried out by using 50 ppm of copper solution with and without the presence of humic acid as feed solution, which was passed through two types of thin film composite membranes. The possible reversible fouling was evaluated by using relative flux decay (RFD) and relative flux recovery (RFR) calculations. The percentage of copper ion removal was evaluated by using Atomic Absorption Spectroscopy (AAS). Based on the results, with the presence of humic acid, the membrane incorporated with silica precursor (TEOS) showed lower flux decay (3%) and higher flux recovery (76%), which show that the formulated hybrid membrane possesses the anti fouling property. The same trend was observed in the mechanical properties of hybrid membrane, where the presence of TEOS has improved the tensile strength and flexibility of the membrane. Therefore, the fabricated thin film composite with the anti-fouling properties and good physical flexibility has potential to be used in the treatment of wastewater containing heavy metal as it could result in good saving in term of operational cost.

Selective concentration of uranium from bioleach liquor of low-grade uranium ore by nanofiltration process

Three commercially available nanofiltration membranes (PES-2, NF-1 and NF-2) were employed for selective concentration of uranium from a bioleach liquor of low-grade uranium ore. Performance of the membranes under a variety of operational conditions was evaluated by dead-end and cross-flow filtration experiments. Results showed that the NF-2 membrane had high uranium rejection (˃85%), appropriate permeate flux, and acceptable fouling propensity. Also, NF-2 was more selective than the two other membranes. In general, the nanofiltration process is recommended to be applied in practice for extraction of uranium from the bioleach liquor of low-grade uranium ore.

Mitigation of membrane biofouling by d-amino acids: Effect of bacterial cell-wall property and d-amino acid type.

Development of novel approaches for biofouling mitigation is of crucial importance for membrane-based technologies. d-amino acids (d-AAs) have been proposed as a potential strategy to mitigate biofouling. However, the effect of bacterial cell-wall properties and d-AAs type on biofouling mitigation remains unclear. This study assesses the effect of d-AAs type on membrane biofouling control, towards Gram positive (G+) and Gram negative (G-) bacteria. Three kinds of d-AAs were found to inhibit both G+ and G- bacterial attachment in short-term attachment and dead-end filtration experiments. The existence of d-AAs reduces extracellular polysaccharides and proteins on the membrane, which may decrease membrane biofouling. Cross-flow filtration tests further indicated that d-AAs could effectively reduce membrane biofouling. The permeate flux recovery post chemical cleaning, improved for both P. aeruginosa and B. subtilis treated with d-AAs. The results obtained from this study enable better understanding of the role of d-AAs species on bacterial adhesion and biofilm formation. This may provide a new way to regulate biofilm formation by manipulating the species of d-AAs membrane systems.

Preparation and Characterization of Ultrafiltration TiO2 Nanoparticles-Polysulfone Membranes

This paper presents the preparation route for new TiO2 nanoparticles-polysulfone membranes: M1 (Psf 12%), M2 (Psf 12% + TiO2 anatase), and M3 (Psf 12% + TiO2 76% anatase+ 24% rutile) that were structurally characterized by FTIR, TG-DSC and by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDAX). Contact angle measurements, dead-end and cross-flow filtration experiments were carried out to characterize the morphology and hydrodynamic performance of the prepared membranes. Improved mechanical properties, enhanced hydrophilicity and the relative large water flux measured for M2-M3 (721.83 L/m2�h and 305.4 L/m2�h, respectively) in cross-flow filtration experiments, make these membranes appropriate for ultrafiltration applications.