Download or read book Tailoring Morphology of Polyamide Thin Film Composite Membranes with Nanobubble Chemistry for Enhanced Separation Performance in Desalination and Water Reuse written by 彭露 and published by . This book was released on 2021 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Efficient Polyamide Thin Film Nanocomposite Membranes written by Mohamed M. A. Elleithy and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The availability of fresh water is directly associated with accessible natural resources. However, 2.5 billion of the world's population (around 40%) does not have access to proper sanitation systems, with 6 to 8 million annual deaths related to inadequate water supply, sanitation and hygiene in 2013. Currently, sea water desalination offers a feasible strategy to face global water challenge. Different water desalination techniques were developed and membrane desalination is currently the highest cost effective technique. Reverse osmosis (RO) system is by far considered the least expensive membrane process. Typically, RO system uses the thin film composite (TFC) membranes. A typical TFC membrane consists of two layers: a top dense polyamide (PA) skin layer (responsible for salt rejection) applied on an underlying support layer (responsible for mechanical support of the thin PA layer). Recently, a new category of membranes has emerged known as thin film nanocomposite membranes (TFNC) where nanoparticles (NPs) are incorporated into the support layer to enhance its properties. The support layer surface pore diameters are quite crucial in supporting and preserving the integrity of the PA layer. Thus, the ideal support layer shall comprise a non-porous to slightly porous top surface. However, a support layer with non-porous surface would resist the water flow. Consequently, the main target of the work represented was to fabricate a highly porous membrane that could still support a PA layer on top of it. Membranes with symmetric cross section have high permeability due to the highly interconnected porous structure. Yet, the surface of the symmetric membranes is also highly porous; and hence, serving as a TFNC support is challenging. Thus, this study focuses on tailoring symmetric TFNC support membranes to effectively support the PA layer. Firstly, we investigated the influence of different fabrication parameters on the support membrane properties. This entailed the understanding of the thermodynamic behavior of the cast solution during fabrication till the final precipitation of the support membrane. TFNC support membranes were prepared using cast solution of Polyethersulfone (PES) polymer in N-methyl-2-pyrrolidone (NMP) as a solvent. Afterwards, the effect of non-solvent addition was investigated using Triethylene Glycol (TEG). Furthermore, Pluronic® (Plu) and Titanium dioxide (TiO2) NPs were incorporated in two different sets of experiments to compare the enhancement of support membrane hydrophilicity and mechanical stability. Support membranes were fabricated using two consecutive phase separation processes, namely: Vapor-Induced Phase Separation (VIPS) followed by Liquid-Induced Phase Separation (LIPS). Various conditions were tested during the VIPS process, including relative humidity degree (RH) at exposure, exposure time and the effect of air convection during the exposure period. The cast solutions were prepared under 30% and 80% RH for exposure time ranging from 1 to 5 minutes. Forced convection condition was applied to the cast solutions whereas compressed dry air was introduced to the cast solution during the exposure period. On the other hand, free convection condition was defined in terms of the absence of compressed dry air introduction during VIPS process. Solution composition was systematically changed to further understand its influence on the thermodynamic behavior under VIPS process. This entailed studying the change in PES content ranging from 10 to 15 wt%, as well as the TEG (0 to 60 wt%), Plu (0 to 5 wt%) and TiO2 (0 to 1 wt%). This variability in cast solution composition clarified the influences of the solution viscosity and hygroscopicity on the thermodynamic behavior of the cast solution, which in turns, reflected on the support membrane final morphology. Afterwards, support membranes were characterized for their cross-sectional morphology using scanning electron microscopy, pore size distribution using the capillary flow porometer, hydrophilicity using contact angle method, surface charge using surface charge analyzer and chemical composition using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Also, membranes hydraulic permeability and wettability were tested. Membranes fabricated under different conditions showed various structures including asymmetric and symmetric cross section morphologies. The effect of air convection was significantly important and in some cases even switched the cross section structure from asymmetric to completely symmetric. Interestingly, at low RH value (30%) and under free convection condition, membranes with semi-symmetric structure were successfully produced. This novel structure holds the privileges of both symmetric and asymmetric membranes. It showed high water permeability and mechanical stability due to the highly interconnected pores structure, as well as, having a very thin skin surface to support the PA layer on top of it. Furthermore, the semi-symmetric membrane showed higher compaction resistance (91.3%) and recovery (94%) as compared to the asymmetric membrane. As a consequence, the semi-symmetric morphology was considered as the structure of our interest as a TFNC support membrane. Support membrane hydrophilicity, water permeability, mechanical stability and morphology are known to have high contribution to the overall TFNC membrane performance. Thus, the developed semi-symmetric structure was then reproduced using cast solutions containing the hydrophilic additives Plu and TiO2. Results showed that the addition of TiO2 had increased both the membrane hydrophilicity and compaction resistance. However, semi-symmetric supports were only achievable with 0.05 and 0.1 wt% TiO2 concentrations. As a concluding step, polyamide (PA) top skin layer was fabricated on semi-symmetric support membranes of different compositions. The final TFNC showed the higher permeability values when semi-symmetric supports were compared to asymmetric support of same composition. Furthermore, the highest TFC permeability was for support membrane containing 1 wt% Plu and that containing 0.1 wt% TiO2.

Download or read book Nanocomposite Membranes for Water and Gas Separation written by Mohtada Sadrzadeh and published by Elsevier. This book was released on 2019-11-13 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocomposite Membranes for Water and Gas Separation presents an introduction to the application of nanocomposite membranes in both water and gas separation processes. This in-depth literature review and discussion focuses on state-of-the-art nanocomposite membranes, current challenges and future progress, including helpful guidelines for the further improvement of these materials for water and gas separation processes. Chapters address material development, synthesis protocols, and the numerical simulation of nanocomposite membranes, along with current challenges and future trends in the areas of water and gas separation. - Explains the development of nanocomposite membranes through bio-mimicking nanomaterials - Discusses the surface modification of nanomaterials to fabricate robust nanocomposite membranes - Outlines the environmental and operational challenges for the application of nanocomposite membranes

Download or read book Nanofiltration Membranes written by Lau Woei Jye and published by CRC Press. This book was released on 2016-12-19 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covering fabrication, characterization, and applications nanofiltration (NF) membranes, this book provides a comprehensive overview of the development of NF membrane technology over the past decade. It uniquely covers a variety of fabrication techniques, comparing the procedures of each technique to produce polymeric membranes of different morphologies. The book also discusses advances in the materials used in thin film composite (TFC) polyamide membrane fabrication and their influences on properties with respect to structural and separation characteristics. A comprehensive review on NF characterization methods and techniques is provided, assessing physical and chemical properties and separation characteristics and stability. Technical challenges in fabricating a new generation of NF membranes are also reviewed and the possible approaches to overcome the challenges are provided. The book concludes with relevant case studies on the use of NF membranes in industrial implementation of both aqueous and nonaqueous media. Details the latest progress on the fabrication techniques of asymmetric and composite NF membranes. Discusses characterization methods used in assessing membrane physical/chemical properties, separation characteristics, and performance stability. Describes the potential of advanced materials in improving properties of polyamide selective layer as well as microporous substrate. Reviews the technical challenges in fabricating a new generation of composite membrane—thin film nanocomposite (TFN) membrane—possible approaches to overcome challenges. Offers case studies on the applications of NF membranes for both aqueous and nonaqueous media.

Download or read book Preparation of Thin film composite Polyamide Membranes for Desalination Using Novel Hydrophilic Surface Modifying Macromolecules written by Belal Abu Tarboush and published by . This book was released on 2008 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thin Film Composite Membranes Via Layer by layer Assembly for Pervaporation Separation written by Elnaz Halakoo and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this study was to develop LbL membranes based on polyethyleneimine and graphene oxide (PEI/GO) and to investigate them for three different applications, namely the pervaporative desalination of high-salinity water, dehydration of ethylene glycol (EG) and dehydration of ethanol (EtOH) and isopropanol (IPA). Salts are non-volatile, EG has a high boiling point, and EtOH and IPA can form an azeotrope with water. To prepare LbL membranes in this work, a chlorine-treated thin film composite (TFC) polyamide membrane was used as a substrate, and PEI and GO were used as polycation and polyanion, respectively. To the best of our knowledge, it is for the first time the aforementioned LbL membranes were prepared and investigated in pervaporation applications. Chlorine-treatment of TFC polyamide was initially studied to determine the suitable chlorination conditions. It was found that pure water flux was more than doubled after chlorination with sodium hypochlorite at 6000 ppm for 2h at room temperature. The as-chlorinated membrane showed that the water permeation flux was almost tripled (i.e., 1.3 kg/m2h ) while the salt rejection decreased by 2% (i.e., 95.8%) for pervaporative desalination of 20 wt% feed salt concentration. The chlorine-treated TFC polyamide membranes with improved flux were used as substrates throughout this study. First, attempts were made to improve the pervaporative desalination performance. PEI/GO LbL membrane formed on the surface of chlorine-treated TFC polyamide membrane for pervaporation desalination of high-salinity water was investigated for the first time, and for this reason, concentrations of PEI and GO were 0.02 monomol/L and 100 ppm, respectively. It was shown that the incorporating PEI and GO to the chlorine-treated TFC polyamide membranes improved the salt rejection. The PEI/GO LbL membrane was tested for the desalination of aqueous solutions containing NaCl, Na_2 SO_4, MgSO_4, and MgCl_2 salts, and a water flux as high as 8 kg/m^2h with a high salt rejection (>99.9%) was obtained for all the tested salts at various temperatures and feed concentrations. In order to assess the temperature dependence of the permeation flux through the membrane, the apparent activation energy for permeation of water was determined. The water permeation flux increased with an increase in temperature due to the augmented driving force and diffusivity in the membrane. The properties of the membranes surface were studied using Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle measurements. Based on the experimental data and stability of the PEI/GO LbL membrane, the formation of the membranes through the LbL self-assembly with PEI and GO showed potential for applications in the treatment of high-salinity water such as industrial wastewater and concentrated reverse osmosis (RO) brine. EG is one of the important substances in gas and chemical industries. Therefore, after the efficiency of PEI/GO LbL membrane with one bilayer was found and analysed for pervaporative desalination of salts, the PEI/GO membrane was further modified by increasing the number of bilayers for uses in the dehydration of ethylene glycol (EG) with and without the presence of salts in the feed. The effects of operating temperature and feed concentration on the membrane performance were studied. The nano self-assembly of GO and PEI with three bilayers showed a satisfactory performance; a permeation flux of 114 g/(m2 h) and a separation factor of 213 were achieved at 35 C for a feed water concentration of 2 wt%. The impact of inorganic salt in the feed on the pervaporation properties were tested by using NaCl as a model salt. The permeation flux decreased with feed salt concentrations while permeate water content increased. The effects of the number of PEI/GO bilayers on membrane performance were also investigated. Increasing number of bilayers from 1 to 15 caused separation factor to increase by 148% while the total permeation flux decreased by 38%. It was for the first time in the literature that the resistance per bilayer and substrate resistance in LbL membranes were evaluated based on the resistance-in-series approach. FTIR and AFM were used to study the chemistry and morphology of the surface of the PEI/GO LbL membranes with different bilayers, respectively. Water contact angle measurements showed that the surface of the PEI/GO LbL membranes was hydrophilic (lower than 54°), which is advantageous for dehydration of EG. Following dehydration of EG, the PEI/GO LbL membranes were crosslinked with glutaraldehyde (GA) to further improve the performance of membranes for pervaporation dehydration of EtOH and IPA. A two-level factorial design was used to determine the effects of three main factors in the membrane preparation (i.e., GA concentration, crosslinking time and temperature) on the permeation flux and separation factor. It was found that the GA concentration and crosslinking time were the most significant factors on the performance of the membranes for alcohol dehydration. The effects of operating temperature and feed concentration on the separation performance of the crosslinked LbL membrane were studied. For the crosslinked LbL membrane, total flux increased sharply with operating temperature, while separation factor showed little dependence on temperature. At 60 oC, the crosslinked (PEI/GO) LbL membrane with seven bilayers had fluxes of 1.8 kg/m2h and 1.5 kg/m2h at 2 wt% water in feed, and the corresponding separation factors were 77 and 197 (respectively for EtOH/water and IPA/water mixtures). It was also showed that the membrane performance can be efficiently adjusted by altering the number of bilayers. The permeance ratio increased to 250 and 620 for water/EtOH and water/IPA systems, respectively, demonstrating that the membrane became much more permselective after deposition of the bilayers on the substrate. FTIR, AFM and contact angle measurements were used to study the surface chemistry, morphology and hydrophilicity of the (PEI/GO) LbL membranes with different bilayers, respectively. The separation performance of the XL(PEI/GO)7 membrane was monitored over an operation time of 210 h at 50 oC to verify the membrane stability. The long-term data showed there were no significant variations in pervaporation performance, implying the feasibility of the crosslinked membrane for pervaporation processes. For all target applications, the activation energies for permeation of each penetrant based on permeation flux (E_J) and membrane permeance (E_P) were calculated and discussed in detail. The activation energies of the different penetrants were compared as they were affected by the types of PEI/GO LbL membranes and the composition of the feed solutions to be separated. Finally, suggestions for future work include optimization or modification of the PEI/GO LbL membrane preparation to further improve membrane performances for pervaporation applications. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) can be used to look at the PEI/GO LbL membranes with and without crosslinking in more detail in future studies.

Download or read book Polyamide Thin Film Composite Membranes for Water Applications written by Ying Siew Khoo and published by CRC Press. This book was released on 2024-08 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph presents the latest trends in characterization techniques for PA TFC (polyamide thin film composite) membranes and provides the most current and relevant information on these techniques tailored specifically for TFC nanofiltration and reverse osmosis membranes.

Download or read book Polyamide Membranes Enhanced by Interfacial Nanostructures written by 杨哲 and published by . This book was released on 2018 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis of Polysulfone polyamide Thin Film Nanocomposite Membranes for Forward Osmosis Applications written by Ahmed Omaia Abdelfattah Mohamed Rashed and published by . This book was released on 2018 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Forward osmosis (FO) has attracted significant interest as a promising alternative to reverse osmosis (RO) in membrane-based water desalination applications. FO water flux, salt rejection and reverse solute flux are three critical parameters affecting membrane performance. Thin film composite (TFC) membranes have been widely used in FO processes. A typical TFC membrane consists of a rejection polyamide (PA) layer on top of a highly porous support layer. In the current study, carboxyl functionalized multi-walled carbon nanotubes (F-MWCNTs) were used as nano-fillers in the membrane rejection layer to enhance the FO membrane performance. Polyamide (PA) thin film nano-composite (TFNC) membranes were synthesized on top of polysulfone (PSF) porous support layers by interfacial polymerization (IP) using m-phenylenediamine (MPD) in water and trimesoyl chloride (TMC) in hexane. The PSF support layer was synthesized by phase inversion in a water bath of a casting solution of PSF and polvinylpyrrolidone (PVP) (pore forming agent) dissolved in anhydrous dimethyl formamide (DMF). Multi-walled carbon nanotubes were functionalized by oxidation in strong acidic solutions, and then incorporated in the MPD aqueous solution during IP. For the support layer, PSF and PVP concentrations were varied while monomers (MPD, TMC) concentrations, contact time and curing temperature were varied for the rejection layer. Experimental designs for both the support and the rejection layers were carried out using Design-Expert software including statistical analysis to identify the most significant factors affecting the membrane performance. The support layer of 18 wt% PSF and 2 wt% PVP was selected as the membrane support with the highest possible FO water flux and minimum reverse solute flux while the PA rejection layer of 4 wt/vol% MPD and 0.2 wt/vol% TMC was selected as the membrane rejection layer with a salt rejection of 88.30±0.11%. Finally, the amount of F-MWCNTs was varied from 0.01 to 0.2 wt/vol% to study their effect on the membrane morphology and performance. The synthesized membranes were characterized using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectrophotometry (FTIR) and Brunauer-Emmett-Teller gas adsoprtion analysis (BET). FO performance was investigated using deionized water as the feed solution and 2 M NaCl as the draw solution. It was found that F-MWCNTs enhanced the membrane hydrophilicity and surface roughness that led to increased FO water flux. Most importantly, the salt rejection was also increased at low concentrations of F-MWCNTs (

Download or read book Fabrication and Characterization of Novel Environmentally Friendly Thin Film Nanocomposite Membranes for Water Desalination written by Farhad Asempour and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film Nanocomposite (TFN) membranes are a relatively new class of high-performance semipermeable membranes for Reverse Osmosis (RO) applications. Large scale applications of TFN membranes have not been achieved yet due to the high production cost of the nanoparticles, agglomeration of the nanoparticles in the thin polyamide matrix of the membrane, and leaching out of typically toxic inorganic nanoparticles into the downstream. In this work, these challenges are addressed by incorporation of two different nanofillers: Cellulose NanoCrystals (CNC), and surface functionalized Halloysite NanoTubes (HNT). Amine groups, carboxylic acid groups, and the first generation of poly(amidoamine) (PAMAM) dendrimers were used for functionalization of the HNT. CNC and HNT are environmentally friendly, low/non-toxic, abundant, and inexpensive nanoparticles with a unique size, and chemical properties. TFN membranes were synthesized via in situ interfacial polymerization of m-phenylenediamine (MPD) with trimesoyl chloride (TMC) and the nanoparticles. The control Thin Film Composite (TFC) membranes, and CNC and HNT based TFN membranes were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared spectroscopy (FTIR) and contact angle measurements. The antifouling capacity of CNC based membranes was investigated with a solution of Bovine Serum Albumin (BSA) as the fouling agent. Also, the leachability of the HNT from the membranes was examined by shaking the membranes in a batch incubator for 48 h, and then tracing the leached out HNT using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Separation characteristics of the membranes were studied by desalination of synthetic brackish water with a cross flow RO filtration system. It was revealed that incorporation of functionalized HNT enhanced the permeate flux without sacrificing the salt rejection (99.1 % ± 0.1 %). Also, incorporation of 0.1% (w/v) CNC doubled the permeate flux (from 30 to 63 L/m2.h at 20 bar) without compromising the salt rejection (97.8%). At the same time, leaching out of HNT from the TFN membranes was decreased as a result of the HNT functionalization and formation of covalent bonds with the TMC. Also, antifouling properties of the CNC-TFN membranes were 11% improved in comparison with control TFC membrane.

Download or read book Fabrication and Modification of Nanocomposite Membranes for Enhanced Water Purification written by Jun Yin and published by . This book was released on 2014 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing cost-effective technologies to extend water resources and solve water pollution problems is critical to the sustainable development of human society. Membrane technology has been given much attention and already been widely used in many areas including drinking water treatment, brackish and seawater desalination, and wastewater treatment and reuse due to its simple operation, no involvement of phase change or chemical additives, and modular design for easy scale up. However, as the main type of membrane, polymeric membranes still have some challenges that need to be overcome, which include the trade-off between permeability and selectivity and fouling issues. In this work, novel nanocomposite membranes with enhanced separation performance were developed for water and wastewater treatment. First, both flat-sheet and hollow fiber membrane fabrication systems were set up to provide capabilities for nanocomposite membrane preparation. Then, to improve membrane performance, nanomaterials with different components (inorganic or organic), structures (porous or nonporous), and functionalities (inert, antimicrobial activity, or photocatalytic activity) were incorporated into polymeric membranes through phase inversion or interfacial polymerization process based on proposed applications. Novel nanomaterials, mesoporous silica, carbon nanotubes or graphene oxide, were applied to study their effects on membrane structure and other physicochemical properties. A biocidal nanomaterial, AgNPs, was used to improve membrane’s anti-biofouling capability. Finally, a photocatalytic nanomaterial, nitrogen doped TiO2 (N-TiO2) with good visible light activity, was applied to improve the membrane antifouling properties. The results showed that hydrophilic nanofillers could improve membrane surface hydrophilicity, leading to a membrane with enhanced water permeability and antifouling properties. Meanwhile, nanofillers containing internal pore structure could further improve water permeability by providing additional flow paths for facile water transport. To control membrane biofouling, silver nanoparticles (AgNPs) were chemically attached onto the thin-film composite (TFC) membrane surfaces with cysteamine as a bridging agent. The modified membranes showed good stability for the immobilized AgNPs and excellent antibacterial properties, while maintained a good water flux and salt rejection. Poly(vinylene fluoride) (PVDF)/N-TiO2 nanocomposite hollow fiber membranes (HFMs) possessing visible light activity were first developed, which demonstrated an improved water permeability and superior antifouling properties due to the photodegradation of foulants and photoinduced hydrophilicity enhancement. Based on these results, it was concluded that nanocomposite membranes were promising to mitigate or even overcome the intrinsic challenges of current polymeric membranes on the market. The incorporation of nanomaterials with conventional membrane polymers could not only tune structure and physicochemical properties (e.g. hydrophilicity, porosity, charge density, thermal, and mechanical stability) of membranes, but also introduce unique functionalities (e.g. antibacterial property and photocatalytic capability) into the membranes. Overall, nanocomposite provides polymeric membrane design a new dimension, which could lead to the next generation of high performance membranes.

Download or read book Polymer Membranes written by Mahmoud Atef Abdulhamid and published by Walter de Gruyter GmbH & Co KG. This book was released on 2024-05-20 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore the comprehensive landscape of polymer membrane applications in this book, encompassing gas separation, organic solvent nanofiltration, water desalination, and fuel cells. The text delves into the subtle influence of polymer membranes on energy efficiency across diverse industries, spotlighting advanced variants such as bio-based, mixed matrix, and polyimides-based membranes. Offering an in-depth analysis, the book elucidates the discovery, development, and challenges associated with these state-of-the-art materials, underscoring their role in achieving enhanced performance and energy efficiency.

Download or read book Thin Film Composite Membranes Derived from Interfacial Polymerization for Nanofiltration and Pervaporation Applications written by Dihua Wu and published by . This book was released on 2015 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, thin film composite (TFC) membranes were prepared by interfacial polymerization on a microporous polyethersulfone (PES) substrate. These membranes were studied for salt separation by nanofiltration and ethylene glycol dehydration by pervaporation. The membranes with a layer-by-layer structure based on polyethylenimine (PEI) and trimesoylchloride (TMC) were prepared by sequential reactant depositions and reactions. The membrane properties can be tailored by controlling the number and sequence of the reactant depositions. In general, the PEI-TMC membranes were more permeable than the TMC-PEI membranes. The membrane formed by a single cycle of interfacial polymerization with 3.5 wt% PEI and 0.7 wt% TMC had a positively charged surface and showed a good nanofiltration performance; salt rejections of 95.1% for MgCl2, 94.4% for MgSO4, 80.5% for Na2SO4 and 85.1% for NaCl with a pure water permeation flux of 24.5 L/(m2.h) were obtained at a feed solute concentration of 500 ppm and transmembrane pressure of 0.8 MPa gauge. In another approach, monomeric amine piperazine (PIP) was embedded into the polymeric amine PEI as the amine reactant. Membranes with a single-ply polyamide layer were produced by reacting TMC with mixed amines of PEI and PIP. Incorporation of 10 wt% PIP in PEI resulted in a 6-fold increase in permeation flux while still maintaining a 91.6% MgCl2 rejection. In addition, 2-ply polyamide membranes were prepared by two cycles of PEI-TMC and PIP-TMC interfacial reactions, separately. It was demonstrated that by properly controlling the PIP/PEI concentration ratio, the 2-ply polyamide membranes with both a higher permeation flux and salt rejection than conventional single-ply polyamide membranes could be produced. The effects of chlorine exposure on the nanofiltration performance of the positively-charged polyamide membranes were studied. It was found that the PIP/TMC crosslinks on the outer sublayer improved the chlorine resistance of the membrane. Controlled exposure of the membrane to a low chlorine concentration could improve the nanofiltration performance. The effect of membrane chlorination was intensified at either an alkaline or acidic pH. The customarily used chlorination intensity (ppm.h), which is a composite parameter based on the product of chlorine concentration and chlorination time, was not adequate for use as a standalone parameter to characterize the chlorination conditions. The PEI/TMC nanofiltration membrane was further modified with self-polymerized polydopamine for use in dehydration of ethylene glycol by pervaporation. Deposition of polydopamine either as an outer layer (i.e., on top of the polyamide) or as a transition layer (i.e., between the polyamide and the substrate) would increase the total permeation flux and effectively improve the membrane selectivity. The modified membrane showed a total permeation flux of 81.03 g/(m2.h) and a separation factor of 388 for a feed containing 2.4 wt% water at 38 °C. The presence of inorganic salt NaCl in the feed mixture decreased the permeation fluxes of both water and ethylene glycol, but increased the water content in the permeate.

Download or read book Polymeric Membranes for Water Purification and Gas Separation written by Rasel Das and published by Materials Research Forum LLC. This book was released on 2021-11-25 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various organic and synthetic polymers are important materials for the removal of organic and inorganic pollutants from wastewater and the separation of gases. The book discusses various types of membranes for microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis etc. A number of nanomaterials are available for the modification of polymeric membranes. Keywords: Polymeric Membrane, Water Purification, Water Softening, Water Desalination, Gas Separation, Osmosis Membranes, Microfiltration, Ultrafiltration, Nanofiltration, Carbon Nanotube, Nanosheets, MOFs, Porous Organic Cages, Titanium Dioxide, Zinc Oxide, Mesoporous Silica Nanoparticles, O2/N2 Separation, CO2/CH4 Separation, H2/N2 Separation.

Download or read book Preparation and Characterization of a Novel Thin Film Composite Polyamide Reverse Osmosis Membrane for Water Desalination written by Jacquana T. Diep and published by . This book was released on 2011 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel sequential hexafluoroalcohol (SHFA) membrane composed of a non-substituted aromatic polyamide under-layer and a hexafluoroalcohol-substituted aromatic polyamide top-layer, for the purpose of achieving improved performance in reverse osmosis (RO) desalination, is the major subject of this research study. At 2000 parts per million (ppm) salt solution, the SHFA membrane outperformed the reference (REF) membrane, which was formed by a conventional RO membrane process, in terms of salt rejection. A salt rejection of greater than 99.5% and a flux of greater than 50 liters/m2/h (LMH) were obtained at 400 psi and 25°C operating conditions. Either 2 or 3 min HFA-MDA reaction time could be used to process the SHFA membrane to achieve this performance. Results from the analyses of the REF membrane and SHFA membrane using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and a contact angle measurement tool were used to compare the two membranes' surface morphology. In addition to the SHFA membrane, works involving incorporation of nanocomposite particles onto the RO membranes for performance improvement are covered. The latest findings from this research led to the introduction of a porous nanoparticle (PNP) membrane whose low particle loadings (ranges from 0.01% to 0.05% weight-to-volume) were found to enhance water flux while retaining high salt rejection.

Download or read book Layer by layer Self assembly of Nanofilatration Membrane for Water and Wastewater Treatment written by Jingjing Sun and published by . This book was released on 2015 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preparation and Characterization of Disulfonated Polysulfone Films and Polyamide Thin Film Composite Membranes for Desalination written by Wei Xie and published by . This book was released on 2011 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current reverse osmosis desalination membrane market is dominated by aromatic polyamide thin film composite (TFC) membranes. However, these polyamide membranes suffer from poor resistance to continual exposure to oxidizing agents such as chlorine in desalination applications. To overcome these problems, we have synthesized and characterized a new generation of materials, disulfonated poly(arylene ether sulfone) (BPS) random copolymer, for desalination membranes. A key technical feature of these new materials is their high tolerance to chlorine in feed water and their excellent reproducibility in synthesis. In this study, water and sodium chloride solubility, diffusivity and permeability in BPS copolymers were measured for both acid and salt form samples at sulfonation levels from 20 to 40 mol percent. The hydrophilicity of these materials, based on water uptake, increased significantly as sulfonation level increased. The water and salt diffusivity and permeability were correlated with water uptake, consistent with expectations from free volume theory. In addition, a tradeoff was observed between water/salt solubility, diffusivity, and permeability selectivity and water solubility, diffusivity and permeability, respectively. The influence of cation form and degree of sulfonation on free volume, as probed via positron annihilation lifetime spectroscopy (PALS), was determined in BPS random copolymers in both the dry and hydrated states. PALS-based free volume data for hydrated polymers were correlated with water and salt transport properties. The influence of processing history on transport properties of BPS films was also studied. Potassium form BPS films having a 32 mol% sulfonation level were acidified using solid state and solution routes. Additionally, several films were subjected to various thermal treatments in the solid state. The influence of acidification, thermal treatment, and counter-ion form on transport properties was investigated. Finally, the influence of synthesis methods of polyamide TFC membranes from m-phenylenediamine (MPD) and trimesoyl chloride (TMC) via interfacial polymerization on transport properties is reported. Then, a disulfonated diamine monomer (S-BAPS) was used instead of MPD to prepare TFC membranes. The resulting membranes exhibited reduced chlorine tolerance than those prepared from MPD. However, introduction of S-BAPS to the MPD/TMC polymerization system increased the fouling resistance of the resulting polyamide TFC membranes.