Blend Membranes Research Articles

A step-by-step assessment of the backwashing process impact on the fouling mitigation of blended PVC/PC and nanocomposite PVC/PC/MAg membranes in a membrane bioreactor (MBR) treating pharmaceutical wastewater

Membrane bioreactors are widely used for industrial wastewater treatment. However, membrane fouling is one of the critical problems in applying these systems. fouling mitigation is an essential issue since membrane fouling results in decreased permeability, increased energy consumption, and reduced membrane lifespan which should be addressed in industrial designs. In this study, our objective was to evaluate the filtration performance and fouling behavior of the blended polyvinyl chloride/polycarbonate (PVC/PC) and nanocomposite PVC/PC/modified silver nanoparticles (PVC/PC/MAg) hollow fiber membranes in continuous and intermittent (filtration with backwashing) filtration experiments at constant pressure. Additionally, an experimental module was designed for the backwashing process so that the fouling phenomenon could be investigated step-by-step for both membranes. The performance of the nanocomposite membrane was compared with that of the blended membrane after each backwashing step in terms of flux recovery and fouling resistances. Permeate flux of the blended and nanocomposite membranes at the end of the continuous filtration experiments compared with the initial flux declined by 61% and 48%, respectively. During the intermittent filtration experiments, the average flux of the blended and nanocomposite membranes in the last step decreased by about 16% and 7% in comparison with the first step, respectively. Flux recovery for the nanocomposite membrane at the end of each backwashing step in the intermittent filtration experiment was over 95% resulting in lower permeability decline over the filtration process. Moreover, the present study reveals that incorporating silver nanoparticles into the structure of the PVC/PC membrane results in an increase in permeability and enhancement of antifouling properties, as well as it increases the flux recovery during the backwashing process in MAg-filled nanocomposite membranes.

Efficient dye rejection using a mixed matrix polyphenylsulfone/polysulfone membrane containing basil seed mucilage hydrogel

In this work, basil seed mucilage (BSM) hydrogel was first extracted using a facile approach. Then, a mixed matrix blend membrane containing polyphenylsulfone/polysulfone incorporated with basil seed mucilage hydrogel was fabricated using the VIPS-NIPS strategy, in which 1,4-dioxane was utilized as the co-solvent. BSM was utilized in this research work because of its significant hydrophilicity and outstanding water stability. Accordingly, different membrane compositions with a variety of BSM contents were fabricated in order to obtain an optimized membrane with extraordinary dye rejection and flux performance. Different dyes rejection performance, including Direct Yellow (DY), Methyl Green (MG), Methylene Blue (MB), and Crystal Violet (CV), was evaluated by the fabricated membranes, based on which an excellent rejection performance (dye rejections of 99.5, 99.2, 98.5 and 97 for DY, MG, CV, and MB, respectively) was achieved. Furthermore, it was observed that after the incorporation of BSM, water flux was significantly enhanced (0.8, 2.5, 3.18 and 4.9 L.m-2.h-1.bar-1 for the neat membrane and the membranes incorporated with 0.1, 0.2, and 0.5 wt% BSM). It is also noteworthy that long-term stability of the optimum membrane, i.e., PSf/PPSU@BSM 0.2, was evaluated, by which it was demonstrated that after ten days, dye rejection and flux performance showed negligible changes because of dilution and fouling effect.

Effect graphene oxide nanostructure/tannic acid on mixed polymeric substrate‐surface modified RO membranes

AbstractIn this work, polyamide (PA) layer of (TFC) thin‐film composite in reverse osmosis (RO) membranes are compared to facile cost‐effective lower rejection RO‐ blend membranes using graphene oxide. Polyvinyl alcohol (PVA) is cross‐linked with glutaraldehyde hydrogel and thereby showing the effect of a fixed concentration of graphene oxide (GO) at different surface modification stages. Surface grafting using methacrylic acid is performed to govern the role of the protective layer on the efficiency of the covered TFC layer as membranes performance regarding salt rejection and permeability. GO concentration of 0.25 wt% in PVA solution shows a maximum % rejection reaching 70 for 3PG and the highest permeate flux for 1PG is 45.52 LMH. While the TFC membranes T and TG have shown higher rejection percentages to reach 88.31% for 3TG of and the highest permeate flux is 30.7 LMH for 1TG and decreases to reach 24.56 LMH for 3TG. Different membrane characterizations are fulfilled through surface morphology, wettability, BET area, and adsorptive fouling. Optimized ratios for tannic acid, ZnO‐nanostructure, and graphene oxide with the mixed polymeric substrate are reached. The effect of graphene oxide in the surface grafting layer over blend and TFC membranes are presented.

A novel PES-C/(GO-COOH/Ce) blended membrane for treating heavy-metal-ion wastewater

A GO-COOH/Ce complex was introduced into a phenolphthalide polythersulfone (PES-C) matrix to prepare a PES-C/(GO-COOH/Ce) blended membrane by nonsolvent-induced phase transformation (NIPS). FT-IR and EDS analysis confirmed that the GO-COOH/Ce complex was successfully incorporated into the PES-C matrix. SEM showed that the blended membrane possessed an asymmetric structure with finger-like pores. The best comprehensive performance was obtained for a PES-C/(GO-COOH/Ce) blended membrane prepared using 0.1 wt.% of the GO-COOH/Ce complex in the casting liquid. The specific results for the blended membrane were as follows: the fluxes of pure water and 0.1 g/L lead nitrate solution were 272 L/m2·h and 214 L/m2·h, respectively; the rejection of bovine serum albumin (BSA) was 99.4%; the rejection of lead ions was 96.2%; the moisture content was 10.9%; the contact angle was 67.1°; the Young's modulus was 35.7 MPa; and the flux recovery ratio was 1.5 times higher than that of the pure PES-C membrane. The antibacterial-zone diameters of the PES-C/(GO-COOH/Ce) blended membrane used against Escherichia coli and Staphylococcus aureus were 2.50 cm and 2.88 cm, respectively. A catalytic cleaning test showed a flux recovery ratio of 63% after washing the PES-C/(GO-COOH/Ce) blended membrane with a 0.2 g/L acetic acid solution for 0.5 h.

(Invited) Novel Ionomers and Ionomer Membranes for Fuel Cells and Redox-Flow Batteries

In this contribution the development of new nonfluorinated and partially fluorinated polymeric platsforms containing perfluoroaromatic building blocks, and their modification with phosphonic and/or sulfonic acid groups and/or anion-exchange groups and/or flexible alkane side chains by nucleophilic aromatic substitution of F or via other synthesis routes is described. The prepared polymers were, where appropriate, blended among each other or with basic high-performance commercial polymers such as polybenzimidazoles or self-synthesized novel basic aromatic polymers to further improve their membrane properties by ionic cross-linking. Moreover, composite membranes consisting of ion-conductive or non-conductive electrospun fiber mats which were filled with PFSA dispersions were synthesized and optimized. The synthesized ionomers and ionomer (blend) membranes were characterized in terms of composition via NMR and FTIR, molecular weight by size exclusion chromatography (SEC), thermal stability via TGA-FTIR-GC-MS coupling and via DSC, and mechanical properties via stress-strain tests and DMA, morphology via electron microscopy, and conductivity via impedance spectroscopy. The (blend) membranes were then applied in fuel cells (low-T and high-T, H2 and direct alcohol fuel cells), and in redox-flow batteries, yielding good performance in these applications.

(Invited) Anion Exchange Membrane Fuel Cells in LIME Laboratory: From Commercial Polymers Towards Biomass Based Materials

Anion exchange membrane fuel cells (AEMFCs) are clean energy conversion devices that are an attractive alternative to the more common proton exchange membrane fuel cells, because they present the advantage of not using noble metals as catalysts for the oxygen reduction reaction (ORR). Unfortunately the low durability of anion exchange membranes (AEMs) in basic conditions limits their use on a large scale. The International Laboratory "Ionomer Materials for Energy" (LIME) group has extensively worked on synthesis of ionomers applying different strategies to mitigate the damaging effect of alkaline media on anion exchange membranes: the delocalization of the positive charge, the introduction of a long chain to separate the charge and the backbone [1], the introduction of a second phase, backbone without ether groups, and recently the use of biomass to prepare more sustainable materials for fuel cells. In this presentation, after a short overview on the progress made on anionic membranes based on commercial polymers, such as polysulfone (PSU) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) [2], I will focalize on the synthesis of the new ionomer poly(alkylene biphenyl butyltrimethyl ammonium) (ABBA) with a backbone devoid of alkaline-labile C-O-C bonds and with quaternary ammonium groups grafted on long side chains [3]. The ionomer was achieved by metalation reaction on 2-bromobiphenyl, followed by the introduction of the long chain with 1,4-dibromobutane. The precursor was polycondensed and then quaternized using trimethylamine (TMA). The reaction is efficient, well controllable and easy to modulate. The ability to form stable solutions over several months, combined with the spacing of the positive charge from the backbone, the flexibility due to the quaternary carbon in the matrix and the high IEC values such as 2.5 meq/g, allows us to consider this ionomer a good candidate as an electrode binder and AEM. Other synthesis of backbones without ether linkage was explored e.g. a crosslinked poly(vinylbenzylchloride-co-hexene) copolymer grafted with N,N-dimethylhexylammonium groups [4]. The copolymerization was achieved by the Ziegler–Natta method, employing the complex ZrCl4 (THF)2 as a catalyst. The resulting aliphatic ionomer showed good alkaline stability, after 72 h of treatment in 2M KOH at 80 °C the remaining IEC of 76% confirmed that ionomers without ether bonds are less sensitive to a SN2 attack. The ionic conductivity of blended membrane with polyvinyl alcohol (PVA) at 25 °C in the OH− form was 29.5 mS/cm. The last part of presentation will be focus on a more sustainable fuel cell, based on heterocycle building blocks exploiting biomass resources.

Structure-Property-Transport Relationships of Miscible Ionomer Blend Systems

Systematically designing the spatial arrangement is a key to understanding the structure and property relationships of proton-exchange membranes (PEM)/ionomers. Miscible polymer blends provide a cost-effective method for developing new materials in polymer science industries instead of synthesizing new polymers. In this study, commercially available Pentablock Copolymer (PBC(1.0)) ionomers were blended with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) in varying blend ratios. The FTIR studies showed composition-dependent interaction between the methyl group of PPO and phenyl rings of Polystyrene blocks in PBC(1.0). However, the sulfonate peaks at PBC(1.0): PPO (50:50) blend ratios were significantly reduced . The reduction in the peak intensity at this blend ratio may be attributed to specific interactions within this blend composition. The miscibility of the blends was confirmed by the single glass transition temperature from the DSC studies. And the application of the Fox rule to the experimental glass transition confirmed the conformational rearrangements of the blends. At the same time, applying the Kwei equation to the glass transition temperature confirmed the presence of specific interactions in the PBC(1.0): PPO (50:50) blend ratio observed in FTIR studies. The thermal stability studies demonstrated morphology dependence behavior with the rule of mixtures with the highest stability of 454oC at PBC(1.0): PPO (50:50) blend ratio. Higher stability at the PBC(1.0): PPO (50:50) blend ratio may be attributed to the specific interactions within this composition. High water uptake correlated with enhanced conductivity for the blend membranes, which strongly depended upon the PBC composition in the blend. Gas permeation studies exhibited that the blending can significantly reduce the permeability of H2 without altering its selectivity compared to pure membranes and Nafion, indicating the desired low fuel cross-over during the fuel cell operation. In conclusion, the gas transport and physical properties of the miscible blends showed strong dependence on composition. The morphological transitions that occur due to the compositional changes will be investigated in future studies.

PFSA Membrane Thickness Impact on Chemical Degradation Rates

As the large-scale commercialization of proton exchange membrane fuel cells (PEMFC) for numerous applications, including heavy-duty trucks draws nearer, there is increasing interest in optimizing fuel cell membranes for both improved efficiency and durability. One of the major membrane attributes being considered for optimization is thickness. The current range of (perfluorosulfonic acid) PFSA membrane thicknesses employed for commercial applications range from 8 -25 µm. As with most adjustable materials parameters, there are a host of properties (cost, gas permeability, proton conductivity, etc.) that require co-optimization to provide the overall preferred position. For example, thin membranes will minimize proton resistance, facilitating high power densities, but will simultaneously allow increased gas crossover fluxes that can contribute to both reduced fuel efficiency and increased oxidative stress. On the other end of the spectrum, thick membranes will decrease gas crossover fluxes, offering improved fuel efficiency while simultaneously decreasing power density. A major question surrounding the tradeoffs of membrane thickness involves the chemical durability impact. Here, we report our investigations of PFSA membrane chemical durability as a function of thickness. For the studies reported here, a thickness series (8, 12 and 20 µm) of ePTFE reinforced Nafion®-like PFSA standalone membranes (SAMs) were prepared.A two-pronged approach was taken for this study. The first involves investigation of intrinsic chemical stability of the ionomer as a function of membrane thickness using an ex-situ H2O2 vapor test. The second investigative mode, which targets the oxidative stress generated by crossover gas flux, employs OCV durability tests of full MEAs. In addition to membrane thickness, gas crossover rates are known to be functions of membrane hydration and gas pressures.1,2 Accordingly, a 3(4-1) fractional factorial experimental design was executed to probe the role of membrane thickness as well as the other factors known to affect gas crossover. The fractional factorial design allows all main effects to be determined and further allows estimation of two factor interactions, if present.References T. Sakai, H. Tanenaka, E, Torikai, “Gas Diffusion in Dried and Hydrated Nations” J. Electrochem. Soc., 1986, 133, 88-92R. Jiang, T. Fuller, S. Brawn, C. Gittleman, “Perfluorocyclobutane and poly(vinylidene fluoride) blend membranes for fuel cells” Electrochimica, Acta, 2013, 110, 306-315

Morphology and Surface Characteristics of PVDF/Poly(2-methoxyethyl acrylate) Blend Membranes Prepared via NIPS and Their pH-Independent Low-Fouling Properties

Morphology and Surface Characteristics of PVDF/Poly(2-methoxyethyl acrylate) Blend Membranes Prepared via NIPS and Their pH-Independent Low-Fouling Properties

Preparation and Performance of PU/Cpsf Blend Ultrafiltration Membranes for Removal of Heavy Metal Ion Rejection Studies

The performance of membranes for a specific application can be determined with the help of structural properties such as molecular weight cut-off (MWCO), morphology, and pore statistics. Heavy metal ions from aqueous streams can be separated with the help of ultrafiltration membranes. In the presence and absence of the various components of the additive poly (ethylene glycol) 600, MWCOs and pore statistics of polyurethane (PU) and carboxylated polysulfone (CPSf) blend ultrafiltration (Total Polymer Concentration = 17.5 wt %) were studied with the help of dextran of different molecular weights ranging from 19 kDa to 150 kDa. The derived pore size, porosity, and the number of pores have a remarkable relationship with the MWCO, morphology, and the flux performance of the membranes. The blend membranes rejected certain toxic divalent heavy metal ions such as copper, cadmium, nickel, and zinc by complexing them into a polymeric ligand, poly(ethyleneimine) (PEI). The effect of polymer blend compositions and additive concentrations on metal ions' rejection and permeate flux are discussed

Synthesis of Anion Exchange Membranes Containing PVDF/PES and Either PEI or Fumion®.

In this work, the preparation of dense blended membranes, from blends of poly(vinylidene fluoride) (PVDF), poly(ether sulfone) (PES) and polyethyleneimine (PEI) or Fumion®, with possible applications in alkaline fuel cell (AEMFC) is reported. The blended PEI/Fumion® membranes were prepared under a controlled air atmosphere by a solvent evaporation method, and were characterized regarding water uptake, swelling ratio, thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), ion exchange capacity (IEC), OH− conductivity and novel hydroxide ion exchange rate (HIER), which is related to the mass transport capacity of the OH− ions through the membrane. The effect of the chemical composition on its morphological and anion exchange properties was evaluated. It was expected that the usage of a commercial ionomer Fumion®, in the blended membranes would result in better features in the electrical/ionic conductivity behaviour. However, two of the membranes containing PEI exhibited a higher HIER and OH− conductivity than Fumion® membranes, and were excellent option for potential applications in AEMFC, considering their performance and the cost of Fumion®-based membranes.

Gas separation improvement of PES/PSF/PVP blend mixed matrix membranes inclusive of amorphous MOFs by O2 plasma treatment

AbstractIn this study, crystalline UiO‐66 and NH2‐UiO‐66 metal organic frameworks (MOFs) were prepared by typical solvothermal method and then were transformed into amorphous phase by using ball milling process. The prepared MOFs were incorporated into tertiary polymer blend matrix including polyethersulfone/polysulfone/polyvinylpyrrollidone (PES/PSF/PVP:40/40/20 wt%) to examine gas separation performance of constructed mixed matrix membranes (MMMs). The synthesized MMMs were analyzed by FT‐IR, SEM, TGA, XRD, AFM, and DSC methods and also by pure gas permeation test for CO2 and CH4 gases. Afterwards, the surface of amorphous MOF‐contained MMMs was influenced by O2 plasma to thrive polar groups of membranes surface. The best gas separation result owned to amorphous NH2‐UiO‐66 comprised MMM treated by O2 plasma for 3 min at 600 W with CO2 permeability and CO2/CH4 selectivity of 10.96 Barrer and 97.91, respectively. The mentioned MMM showed CO2 permeability and CO2/CH4 selectivity of 8.69 Barrer and 75.56 before plasma treatment which were 170 and 50% higher than those of pristine PES/PSF/PVP blend membrane.

Polyamidoamine dendrimers-Mil-125(Ti) MOF embedded polyethersulfone membrane for enhanced removal of heavy metal, antibiotic and dye from water

In the current study, the solvo-thermal method was used to synthesize Mil-125(Ti). Then, polyamidoamine dendrimer G.02 (PAMAM) was produced by Michael’s addition reaction and then loaded on the surface of Mil-125(Ti) to produce Mil-Den nanocomposite. The FESEM images, XRD pattern and FTIR analyses were used to investigate the physicochemical and structural features of synthesized Mil-Den. Next, the prepared Mil-Den nanocomposite was used for the fabrication of mixed matrix polyethersulfone (PES) membranes. The morphology, water flux, anti-fouling properties, hydrophilicity, and rejection of the Na2SO4 salt, Lead (II) nitrates as heavy metal, cefixime antibiotic, and six different reactive dyes were assessed. The incorporation of Mil-Den nanocomposite into PES membrane led to porosity enhancement from 66.8% for the bare membrane to 87.2% for the blended ones containing 1 wt% of Mil-Den. Also, the water contact angle of membrane was reduced from 59.2° to 31.2° by use of Mil-Den. The water flux of the membrane was remarkably increased from 17.9 to 287.6 (L/m2/h) by the addition of Mil-Den. The dye rejection for the blended membrane containing 0.2 wt% of Mil-Den nanocomposite measured 99.33%, 85.18%, 98.20%, 94.67%, 82.49% and 79.05% for RG19, RB50, RB21, RY145, RY160 and RY39, respectively. In addition, the rejection of cefixime antibiotic, lead ion, and sodium sulfate solutions were measured 80.04%, 97.36%, and 65.21%, respectively. The flux recovery ratio determined > 68% for the bare PES membrane whereas that was > 90% for the modified membrane with 0.1 wt% Mil-Den nanocomposite. Consequently, this study indicated the high potential of blended Mil-Den/PES-based membranes in water treatment.

Synthesis of advanced multifunctional biopolymeric membrane via emulsion templating method

A cost effective and reproducible method for preparing free standing porous hydrophilic biopolymeric membranes is reported in this study. Silver nanoparticles (AgNp) impregnated micropourous alginate-chitosan crosslinked biopolymeric membranes were prepared by the emulsion templating method. The instantaneous gelation of sodium alginate in the presence of Ca+2 ions enabled the liquid paraffin droplets in the initial emulsion to be settled quickly and thus aided in the pore generating process. Prisitne Alginate membrane, Alginate-Chitosan blended membrane (Alg-Ch), nanopraticle incorporated Alginate membrane (Alg-AgNp) and silver nanoparticle impregnated alginate-chitosan membrane (Alg-Ch-AgNp) were synthesized with as well as without templates, so as to compare their feasibility. On extraction of the templates, pore size corresponding to the original emulsion droplet sizes was obtained. All the variety of membranes synthesized was characterized by SEM, TGA/DTA and swelling studies. The emulsion templating method introduced micropores in the membrane morphology within the range of 100 nm–2 μm as compared to the non template alginate membranes. The decomposition of Alg-Ch-AgNp starts from 225 °C and terminates at around 328 °C with a weight loss of about 27.09 %. Alg-Ch membrane which lost about 34.385 % of its weight, showed less thermal stability than Alg-AgNp and Alg-Ch-Ag Np membranes. The swelling of Alg-Ch-AgNp membrane was about 52 % in acidic environment, 160 % in neutral environment and around 180 % in acidic environment. The results prove that Alg-Ch-AgNp is thermally the most stable and also having the best swelling characteristics among all.

Acid-triggered polyether sulfone - Polyvinyl pyrrolidone blend anion exchange membranes for the recovery of titania waste acid via diffusion dialysis

Dense PES (polyether sulfone) - PVP (polyvinyl pyrrolidone) blend membranes are proposed to recover titania waste acid by diffusion dialysis. These dense membranes can simply be prepared by the solution casting method, and the spontaneous quaternization of the N and O atoms in pyrrolidone with H+ in sulfuric acid solution turns them into effective anion exchange membranes very suitable for the fractionation of sulfuric acid/sulfate. In this work, the influence of the PVP molecular weight (K30 and K90), the composition of the casting solution and the concentration of sulfuric acid in the post-treatment step on the physicochemical properties and mass transfer performance of the membranes are systematically investigated. It is found that the content of absorbed sulfuric acid in the dense membranes increases with the increasing PVP content (20–60 wt%) in the membranes, after the equilibration in 2.68 M H2SO4. The content of H+ in blend membranes with PVP K30 (K30 series) is 0–5.73 mmol/(g dry membrane), while that in the membranes with PVP K90 (K90 series) is 0–5.34 mmol/(g dry membrane). The permeability coefficients of H2SO4 and FeSO4 in the K30 and the K90 series membranes also increase gradually, ranging from 0–200 × 10−9 m2/h and 0–8.81 × 10−9 m2/h, respectively. The largest selectivity coefficient of H2SO4/FeSO4 can reach 1800. The permeability coefficients of H2SO4 and FeSO4 also increase gradually with the increase of the solution acid concentration, and the selectivity remains excellent. These PES-PVP dense membranes show very good chemical stability, the permeability coefficients of H2SO4 and FeSO4 for a blend membrane with 55 wt% PVP K30 remain unchanged in a 2.68 M H2SO4 solution for 337 days. This study would provide valuable guidance for the application of these PES-PVP blend anion exchange membranes in the recovery of titania waste acid by diffusion dialysis.

Correction to: Desalination characteristics of new blend membranes based on sulfonated polybenzimidazole and sulfonated poly(arylene ether sulfone)

Correction to: Desalination characteristics of new blend membranes based on sulfonated polybenzimidazole and sulfonated poly(arylene ether sulfone)

Norbornene-based acid–base blended polymer membranes with low ion exchange capacity for proton exchange membrane fuel cell

Norbornene-based acid–base blended polymer membranes with low ion exchange capacity for proton exchange membrane fuel cell

Fabrication of PVDF/EVOH blend hollow fiber membranes with hydrophilic property via thermally induced phase process

In this study, thermally induced phase separation (TIPS) technology was used to fabricate the PVDF/EVOH blend hollow fiber membranes using water-soluble mixed diluents. An interconnected bulk structure was formed by L-L phase separation for both the pristine membrane and blend membrane. The surface enrichment for EVOH during the cooling process enhanced the hydrophilicity of prepared hollow fiber membranes. It was found that the tensile strength of the blend membrane significantly increased from 2.6 MPa to 8.8 MPa. The variation of the membrane structure made the water permeability increase from 60 L m−2 h−1 bar−1 to 287 L m−2 h−1 bar−1 for the optimized blend membrane. Compared with the pristine membrane, EVOH blend membrane exhibited higher antifouling properties for BSA, HA, and oil-in-water emulsion filtrations.

Co3O4@Fe3O4/cellulose blend membranes for efficient degradation of perfluorooctanoic acid in the visible light-driven photo-Fenton system

Co3O4@Fe3O4/cellulose membrane was synthesized by coating rod-like MOF-derived Fe3O4 with Co3O4 nanoparticles and blending with cellulose solution, further applied in the visible light-driven photo-Fenton system for perfluorooctanoic acid (PFOA) degradation. In the H2O2/membrane/visible light system, the Electron paramagnetic resonance (EPR) analysis and scavenger experiment results suggested that PFOA degradation was a co-dependent mechanism via photogenerated electrons, photogenerated holes (h+) and various radical species, rather than a single active constituent. Co3O4@Fe3O4/cellulose membrane showed outstanding degradation performance, stability and recyclability under optimal conditions. Compared with pure Fe3O4 or Co3O4 nanoparticles, the Co3O4@Fe3O4/cellulose membrane can degrade around 94.5% PFOA within 180 min in reaction system, and the leached Fe and Co was only 0.05 and 0.49 ppm, respectively. Moreover, Co3O4@Fe3O4/cellulose was reused by rinsing with ultra-pure water and the degradation capacity was still 80.4% after five cycles. The degradation pathway of PFOA also was proposed based on UHPLC-MS analysis.

Antibacterial Activity of Silver Nanoflake (SNF)-Blended Polysulfone Ultrafiltration Membrane

The aim of this research was to study the possibility of using silver nanoflakes (SNFs) as an antibacterial agent in polysulfone (PSF) membranes. SNFs at different concentrations (0.1, 0.2, 0.3 and 0.4 wt.%) were added to a PSF membrane dope solution. To investigate the effect of SNFs on membrane performance and properties, the water contact angle, protein separation, average pore size and molecular weight cutoffs were measured, and water flux and antibacterial tests were conducted. The antimicrobial activities of the SNFs were investigated using Escherichia coli taken from river water. The results showed that PSF membranes blended with 0.1 wt.% SNFs have contact angles of 55°, which is less than that of the pristine PSF membrane (81°), exhibiting the highest pure water flux. Molecular weight cutoff values of the blended membranes indicated that the presence of SNFs does not lead to enlargement of the membrane pore size. The rejection of protein (egg albumin) was improved with the addition of 0.1 wt.% SNFs. The SNFs showed antimicrobial activity against Escherichia coli, where the killing rate was dependent on the SNF concentration in the membranes. The identified bacterial colonies that appeared on the membranes decreased with increasing SNF concentration. PSF membranes blended with SNF, to a great degree, possess quality performance across several indicators, showing great potential to be employed as water filtration membranes.