Functionalization of Flat Sheet and Hollow Fiber Microfiltration Membranes for Water Applications (original) (raw)
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Porous polyvinylidene fluoride (PVDF) polymeric membranes with inclusion of Fe 2 O 3 nanoparticles and multi-walled carbon nanotubes (MWCNTs) were developed for the Fenton-like catalytic degradation of organic contaminants at neutral pH. The PVDF was modified by in situ polymerization with methyl methacrylate to improve its hydrophilicity, and a range of membranes with different Fe 2 O 3 and MWCNTs loadings were casted. The effect of these compositions on membrane morphology, surface functionality and hydrophilicity was investigated by microscopic, spectroscopic and surface characterization techniques. Contact angle measurements showed that MWCNTs did not change the membrane hydrophilicity, while the Fe 2 O 3 was effective in increasing hydrophilicity. The optimum combination of 0.2% MWCNTs and 1% Fe 2 O 3 induced pore formation and improved membrane permeability. The removal efficiency of cyclohexanoic acid (CHA) and humic acids (HAs) were evaluated. Batch studies revealed that 48% of CHA was degraded after 24 h of membrane exposure with H 2 O 2 . For HAs, removal with H 2 O 2 addition was significantly higher than without at 53.1 7 4.4% and 28.1 7 4.1%, respectively. These membranes also showed a significant reduction in membrane fouling. Overall, the permeate flux achieved with H 2 O 2 was four times higher as compared to without H 2 O 2 addition which is ascribed to the catalytic oxidation of organic molecules which accumulated at the membrane surface.
Polymers, 2016
Membranes are finding wide applications in various fields spanning biological, water, and energy areas. Synthesis of membranes to provide tunable flux, metal sorption, and catalysis has been done through pore functionalization of microfiltration (MF) type membranes with responsive behavior. This methodology provides an opportunity to improve synthetic membrane performance via polymer fabrication and surface modification. By optimizing the polymer coagulation conditions in phase inversion fabrication, spongy polyvinylidene fluoride (PVDF) membranes with high porosity and large internal pore volume were created in lab and full scale. This robust membrane shows a promising mechanical strength as well as high capacity for loading of adsorptive and catalytic materials. By applying surface modification techniques, synthetic membranes with different functionality (carboxyl, amine, and nanoparticle-based) were obtained. These functionalities provide an opportunity to fine-tune the membrane surface properties such as charge and reactivity. The incorporation of stimuli-responsive acrylic polymers (polyacrylic acid or sodium polyacrylate) in membrane pores also results in tunable pore size and ion-exchange capacity. This provides the added benefits of adjustable membrane permeability and metal capture efficiency. The equilibrium and dynamic binding capacity of these functionalized spongy membranes were studied via calcium ion-exchange. Iron/palladium catalytic nanoparticles were immobilized in the polymer matrix in order to perform the challenging degradation of the environmental pollutant trichloroethylene (TCE).
Journal of Water Process Engineering, 2019
Vermiculite nanoparticles (Verm NPs) incorporated polyvinylidene fluoride (PVDF) flat sheet membrane was prepared using phase inversion method and compared with aluminum oxide (Al 2 O 3), silicon dioxide (SiO 2), and copper oxide (CuO) NPs incorporated PVDF. The nanocomposites PVDF membranes were modified via an ultrathin coating surface layer of a dilute poly(vinyl alcohol) (PVA) aqueous solution in order to provide sufficient hydrophilicity, rejection, and a reduced surface roughness. The characterizations of pure PVDF, PVA/PVDF, PVA/PVDF/Al 2 O 3 (M1), PVA/PVDF/SiO 2 (M2), PVA/PVDF/CuO (M3) and PVA/PVDF/Verm (M4) membranes were performed using FTIR, Contact angle, and SEM. The membrane performances were evaluated and antifouling properties of the synthesized membranes were examined via numerous fouling/washing series using feed solutions of bovine serum albumin (BSA) such as a potential foulant. The highest permeate flux obtained with a modified ultrafiltration technique was in the order of Verm (628.7) > Al 2 O 3 (598) < SiO 2 (590) > CuO (585 L/ m 2 •h) and the humic acid (HA) rejection was in order of Verm (94.56) > Al 2 O 3 (91.7) > SiO 2 (89) > CuO (88.3%) based on an optimum concentration of 0.2, 0.3, 0.1, 0.2 wt.%. The results clearly showed that the incorporation of Verm NPs was favorable to the enhancement of antifouling properties, membrane performances and the mechanical properties compared to other membranes at the identical condition. The synthesized PVA/ PVDF membrane and the nanocomposite membranes were used for the removal of four different types of dyes, i.e. Malachite green (MG), Methylene blue (MB), Congo red (CR) and Safranin O (SO) from aqueous solution as examples for organic wastewater treatment.
Journal of Applied Polymer Science, 2019
Thin-film nanocomposite (TFN) membranes were fabricated by interfacial polymerization of a polyamide (PA) layer on the shell side of hollow fiber membrane supports. TiO 2 nanoparticle loadings in the thin-film layer were 0.01, 0.05, and 0.20 wt %. Nanoparticle-free PA thin-film composite (TFC) membranes served as the comparative basis. The TFN membranes were characterized in terms of the chemical composition, structure, and surface properties of the separation layer. Incorporating nanoTiO 2 improved membrane permeability up to 12.6-fold. During preliminary laboratory-scale evaluation, TFN membranes showed lower salt rejection but higher TOC rejection in comparisons with the corresponding values for TFC controls. Based on the performance in lab-scale tests, TFN membranes with 0.01 wt % nanoTiO 2 loading were selected for an evaluation at the pilot scale with synthetic surface water as the feed. While the permeate flux during long-term pilot-scale operation gradually decreased for TFC membranes, TFN membranes had a higher initial permeate flux that gradually increased with time. The TOC rejection by TFN and TFC membranes was comparable. We conclude that TFN membranes show promise for full-scale surface water treatment applications.
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Chemical pollutants, such as methyl orange (MO), constitute the main ingredients in the textile industry wastewater, and specifically, the dyeing process. The use of such chemicals leads to huge quantities of unfixed dyes to make their way to the water effluent and consequently escalates the water pollution problem. This work investigates the incorporation of hydrophobic carbon nanospheres (CNS) prepared from the pyrolysis of acetylene using the chemical vapor deposition technique with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) in order to enhance its hydrophobicity. Moreover, a deep eutectic solvent (DES) was used to enhance the membrane’s porosity. The former was based on the quaternary ammonium salt (N,N-diethyl-ethanol-ammonium chloride) as a chemical addition throughout the membrane synthesis. Direct contact membrane distillation (DCMD) was employed to assess the performance of the modified membrane for treatment of MO contaminated water. The phase inversion me...
Journal of Membrane Science, 2017
Functionalized PVDF membrane platforms were developed for environmentally benign in-situ nanostructured Fe/Pd synthesis and remediation of chlorinated organic compounds. To prevent leaching and aggregation, nanoparticle catalysts were integrated into membrane domains functionalized with poly (acrylic acid). Nanoparticles of 16-19 nm were observed inside the membrane pores by using focused ion beam (FIB). This technique prevents mechanical deformation of the membrane, compared to the normal SEM preparation methods, thus providing a clean, smooth surface for nanoparticles characterization. This allowed quantification of nanoparticle properties (size and distribution) versus depth underneath the membrane surface (0-20 µm). The results showed that nanoparticles were uniformly sized and evenly distributed inside the membrane pores. However, the size of nanoparticles inside the membrane pores was 13.9% smaller than those nanoparticles located on the membrane surface. Investigating nanoparticles inside membrane pores increases the accuracy of kinetic analysis and modeling aspects. Furthermore, the Fe/Pd immobilized membranes showed excellent performance in the degradation of chlorinated organics: Over 96% degradation of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) was achieved in less than 15 s residence time in convective flow mode. The regeneration and reuse of this catalytic membrane system were also studied. Particles were examined in XRD upon formation, after deliberate oxidation, and after regeneration. The regenerated sample showed the same crystalline pattern as the original sample. Repeated degradation experiments demonstrated successful PCB 126 dechlorination with nanoparticles regenerated for four cycles with only a small loss in reactivity. It demonstrated that Fe/Pd immobilized membranes have the potential for large-scale remediation applications.
Preparation and Characterization of Nanofiltration Membrane for Water Treatment
2012
Thin-film composite (TFC) nanofiltration (NF) membranes were developed by terephthaloyl chloride (TPC) crosslinked the hydroxyl ended groups of hyperbranched polyester (HPE) on polyacrylonitrile (PAN) support. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated that a thin layer of crosslinked HPE molecules were deposited on PAN porous membrane surface successfully. The preparation conditions were also optimized. The separation performance of PAN-HPE-TPC NF membranes are mainly related with the concentration of monomer in the aqueous phase rather than that in the organic phase. Water permeability and salts rejections of the membranes were measured. The flux and rejection of these NF membranes for Na 2 SO 4 (1 g/L) reached 11.43 L/m 2 h and 96.5% under 0.6 MPa, respectively. At the same time, the nanofiltration properties were compared with other membranes prepared with hyperbranched polymers. All NF membranes prepared with hyperbranched polymers showed relative high permeate flux.
Environmental Science & Technology, 2018
We demonstrate the fabrication of a loose, negatively charged nanofiltration (NF) membrane with tailored selectivity for the removal of perfluoroalkyl substances with reduced scaling potential. A selective polyamide layer was fabricated on top of a poly(ether sulfone) support via interfacial polymerization of trimesoyl chloride and a mixture of piperazine and bipiperidine. Incorporating high molecular weight bipiperidine during the interfacial polymerization enables the formation of a loose, nanoporous selective layer structure. The fabricated NF membrane possessed a negative surface charge and had a pore diameter of ∼1.2 nm, much larger than a widely used commercial NF membrane (i.e., NF270 with pore diameter of ∼0.8 nm). We evaluated the performance of the fabricated NF membrane for the rejection of different salts (i.e., NaCl, CaCl 2 , and Na 2 SO 4) and perfluorooctanoic acid (PFOA). The fabricated NF membrane exhibited a high retention of PFOA (∼90%) while allowing high passage of scale-forming cations (i.e., calcium). We further performed gypsum scaling experiments to demonstrate lower scaling potential of the fabricated loose porous NF membrane compared to NF membranes having a dense selective layer under solution conditions simulating high water recovery. Our results demonstrate that properly designed NF membranes are a critical component of a high recovery NF system, which provide an efficient and sustainable solution for remediation of groundwater contaminated with perfluoroalkyl substances.
Journal of Membrane Science, 2011
Membranes containing reactive nanoparticles (Fe and Fe/Pd) immobilized in a polymer film (polyacrylic acid, PAA-coated polyvinylidene fluoride, PVDF membrane) are prepared by a new method. In the present work a biodegradable, non-toxic -"green" reducing agent, green tea extract was used for nanoparticle (NP) synthesis, instead of the well-known sodium borohydride. Green tea extract contains a number of polyphenols that can act as both chelating/reducing and capping agents for the nanoparticles. Therefore, the particles are protected from oxidation and aggregation, which increases their stability and longevity. The membrane supported NPs were successfully used for the degradation of a common and highly important pollutant, trichloroethylene (TCE). The rate of TCE degradation was found to increase linearly with the amount of Fe immobilized on the membrane, the surface normalized rate constant (k(SA)) being 0.005 L/m(2)h. The addition of a second catalytic metal, Pd, to form bimetallic Fe/Pd increased the k(SA) value to 0.008 L/m(2)h. For comparison purposes, Fe and Fe/Pd nanoparticles were synthesized in membranes using sodium borohydride as a reducing agent. Although the initial k(SA) values for this case (for Fe) are one order of magnitude higher than the tea extract synthesized NPs, the rapid oxidation reduced their reactivity to less than 20 % within 4 cycles. For the green tea extract NPs, the initial reactivity in the membrane domain was preserved even after 3 months of repeated use. The reactivity of TCE was verified with "real" water system.