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1.
In the present work we blended cellulose acetate (taken from sugar cane bagasse) (CA) with polystyrene (taken from postconsumer plastic cups) (PS). The blends were produced in the following ratios (w/w) of the polymers: CA 50%/PS 50%, CA 90%/PS 10%, and CA 10%/PS 90%, using dichloromethane as solvent. The blends were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. The results show that the presence of polystyrene hinders the organization of regions responsible for the crystallinity originally existing in pure cellulose acetate. We also made measurements of water flux through blends, using the Payne cup technique. The flux properties were compared with those obtained for commercial membranes by Osmonix: nanofiltration (SG) and reverse osmosis (CG). The results show that the blend CA 90%/PS 10% presents water vapor flux comparable with that of commercial membranes for nanofiltration (SG). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 516–522, 2005  相似文献   

2.
《分离科学与技术》2012,47(13):2895-2912
Abstract

Flat sheet ultrafiltration membranes from cellulose acetate (CA)/low cyclic dimer polysulfone (LCD PSf) were prepared by a phase inversion method. N, N′‐Dimethyl formamide and different molecular weight of polyethylene glycol (PEG 200, PEG 400, and PEG 600) were used as solvent and pore‐forming additive, respectively. The membranes were characterized in terms of pure water flux, water content, porosity, membrane hydraulic resistance, and morphology. The pure water flux was found to reach the highest value of 181.82 Lm?2h?1 at 5 wt.% PEG of 600 molecular weight and 10 wt.% LCD PSf content in the blended solution for membrane preparation. SEM micrographs indicated that the addition of PEG into the CA/LCD PSf solution changes the inner structure of the membrane. The influence of filtration time and applied pressure on membrane permeability was examined by copper/polyethylenimine complex rejection studies. With increase in filtration time, the rejection of the copper/polyethylenimine complex decreased and the results were discussed.  相似文献   

3.
《分离科学与技术》2012,47(2):398-421
Abstract

Ultrafiltration membranes are largely being applied for heavy metal ion separations from aqueous streams. Cellulose acetate (CA) and aminated polysulfone (APSf) based membranes are prepared in the absence and presence of the polymeric additive, polyethylene glycol, PEG 600, in various compositions. The effects of polymer blend composition and additive concentration on compaction, pure water flux, membrane hydraulic resistance, water uptake, and contact angle has been investigated to evaluate the performance of the membranes and the results are discussed. Surface and cross-sectional morphologies of membranes were also analyzed using scanning electron microscopy. Toxic heavy metal ions such as Cu2+, Ni2+, Cd2+, and Zn2+ were separated by the blend membranes using polyethyleneimine (PEI) as polymeric ligand. The rejection and permeate flux efficiencies of the blend membranes are compared with pure cellulose acetate membranes.  相似文献   

4.
Asymmetric micro porous membranes have been prepared successfully from blending of cellulose acetate (CA) and polyethersulfone (PES) by the phase inversion method with N, N-dimethylformamide (DMF) as solvent. Two additives were selected in this study, including polyethylene glycol 600 (PEG 600) and polyvinylpyrrolidone (PVP). The effects of concentration of additives on CA/PES blend membrane performance and cross-section morphology were investigated in detail. CA/PES membranes were compared with CA/PES/PEG and CA/PES/PVP membranes in the performance such as pure water flux, membrane resistance, porosity and cross-section morphology. The resulting blend membranes were also carried out the rejection and permeate flux of Egg Albumin (EA) proteins with molecular weight of 45 Da. The membranes thus obtained with an additive concentration of 5 wt% of both PEG and PVP exhibited superior properties than the 80/20% blend composition of CA and PES membranes. The permeate flux of protein was increased from 44 to 134 lm2 h with increase in concentrations of both PVP and PEG in 80/20% blend composition of CA and PES membranes. Cross-sectional images from scanning electron microscopy showed larger macropores in the bottom layer of the membranes with increasing additives content. Observations from scanning electron microscopy provided qualitative evidence for the trends obtained for permeability and porosity results.  相似文献   

5.
The effects of two different hydrophilic additives and two solvents on the membrane morphological structure,permeability property and anti-fouling performances of cellulose acetate (CA) ultrafiltration membranes were investigated.During the phase-inversion process,cellulose acetate was selected as a membrane forming polymer;polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) were used as additives;acetone (Ac):N,N-Dimethylacetamide (DMAc) andN,N-Dimethylformamide (DMF) were used as solvents;and deionized (DI) water was used in the coagulation bath.All the prepared membranes were characterized in terms of hydraulic permeability (Pm),membrane resistance,average pore radius,and hydrophilicity.The top surface and crosssectional view of the prepared membranes were also observed by using field emission scanning electron microscopy.Membrane fouling and rejection experimentations were done using a stirred batch-cell filtration set-up.The experimental studies of fouling/rinsing cycles,rejection,and permeate fluxes were used to investigate the effect of PEG and PVP additives and effect of the two solvents on the fabricated membranes using bovine serum albumin (BSA) as a model protein.  相似文献   

6.
《分离科学与技术》2012,47(8):1933-1954
Abstract

Ultrafiltration techniques have particular advantages for simultaneous purification, concentration, and fractionation of macromolecules. A comparative study is presented on novel ultrafiltration polymeric blend membranes based on cellulose acetate (CA) prepared in the absence and presence of polymeric additives such as polyethylene Glycol 200 (PEG) and polyvinylpyrrolidone (PVP) by phase inversion technique using N,N′-dimethylformamide (DMF) as solvent. Polymer blend composition, additive concentration and casting, and gelation conditions were standardized for the preparation of asymmetric membranes by pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 h. The pure water flux was measured at 345 kPa pressure. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressures and found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut-offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20 to 69 kDa depending on the PEG 200 and PVP content in the blend in the casting solution. Skin surface porosity of the membranes was analyzed by scanning the samples at various magnifications. The characterized CA, CA/PEG200 and CA/PVP membranes were used for cadmium ion rejection studies at 345 kPa.  相似文献   

7.
A process for purifying aqueous solutions containing macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin, and trypsin has been investigated. Protein removal from food and biorelated industrial waste streams are gaining increased visibility due to environmental concern and saving precious materials. Ultrafiltration (UF) processes are largely being applied for protein separation from aqueous streams. In this work, an attempt has been made to separate the valuable proteins using cellulose acetate (CA)/sulfonated poly(ether imide) (SPEI) blend UF membranes prepared in the absence and presence of the additive, polyethyleneglycol (PEG600) in various compositions. The blend membranes were subjected to the determination of pore statistics and molecular weight cut‐off (MWCO). Porosity and pore size of the membranes increased with increasing concentrations of SPEI and PEG600 in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to greater than 69 kDa, depending on the various polymer blend compositions. Surface morphology of the blend membranes were analyzed using scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of proteins. On increasing the concentration of SPEI and PEG600, the rejection of proteins is decreasing, whereas the permeate flux has an increasing trend. The effect of hydrophilicity of SPEI on fouling of protein for CA/SPEI blend membranes was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

8.
《分离科学与技术》2012,47(5):963-978
Abstract

The permeate flux and retention of aqueous solutions of poly(ethylene glycols) (PEG) with different molecular weights ranging from 4000 to 35,000 Da have been investigated using various compositions such as 100/0, 90/10, 80/20, and 70/30 wt% of cellulose acetate (CA)/sulfonated poly(etheretherketone) (SPEEK) ultrafiltration blend membranes. The factors affecting the rejection rate and permeate flux such as molecular weight of PEGs, concentration of the solute, composition of the membranes, and transmembrane pressures have been studied. It is seen that the increase in the concentration of PEG results in the decreased permeate flux and increased rejection for increasing CA content in the membranes. A similar observation in the flux and rejection was made for increasing the molecular weight of PEGs. Further, the mass transfer, diffusion, and true retention coefficients of the solute have been studied with different operating variables like molecular weight and concentration of PEGs. An increase in the molecular weight of PEGs results in the decrease of mass transfer and diffusion coefficients and increase of the true retention coefficient. A reverse trend is observed with increasing concentrations of PEG.  相似文献   

9.
Highly productive cellulose acetate membranes were cast under conditions of very short air exposure periods from cellulose acetate–acetone–formamide casting solutions having a high cellulose acetate (CA) content and lying close to the phase boundary. Air exposure periods as short as 0.05 sec were used with CA content up to 32 wt-%. Membranes from a casting solution containing 30 wt-% cellulose acetate (E-398-3), 45 wt-% acetone, and 25 wt-% formamide perform as well as membranes from other compositions at all salt rejection levels for a 0.5 wt-% NaCl feed at 600 psig. Partial replacement of acetone by dioxane in the casting solution substantially increases the water flux from membranes cast with short air exposure periods at any given salt rejection level below 96% salt rejection. Addition of small amounts of ZnCl2 to nondioxane casting solutions with 32 wt-% CA improves membrane performances remarkably for lower salt rejection levels, while the improvement in performance of membranes from 30 wt-% CA casting solutions with dioxane due to ZnCl2 addition is marginal. Variation in air exposure from 0.05 to 2 sec results in minor performance variations in the membranes having any of these compositions. With air exposure periods beyond 2–3 sec, membrane fluxes drop drastically. The concept of a thinner skin satisfactorily explains the improvement in mixed solvent systems, whereas ZnCl2 acts as a swelling salt. A Kimura-Sourirajan-type membrane performance plot indicates that for a 0.5 wt-% NaCl feed at 600 psig, membranes of the present work perform as well as the best performing membranes reported in the literature for conversion of brackish water.  相似文献   

10.
In this work, various cellulose acetate (CA) membranes for pervaporation were prepared by the incorporation of different additives, i.e. polyethylene glycol-600 (PEG-600), propylene glycol (PG), and ethylene glycol (EG) to enhance the separation of isopropanol (IPA)/water mixtures. These membranes were characterized by FTIR, DSC, TGA, SEM and UTM. Each additive was responsible for its characteristic effect on the membrane morphology, mechanical strength, permeation flux and separation factor. The SEM micrograph showed that the additives were evenly dispersed in the membrane matrix with the formation of dense membranes. The UTM tests for the membrane reveled that both the Young's Modulus and tensile strength increased with the increase in additive contents. TGA studies for the CA/PEG blend membrane exhibited the highest thermal stability as compared to the CA/PG and CA/EG blends. For each of these synthesized membranes, the separation factor decreased while the permeation flux increased with the increase in additive contents, while the CA/PG membrane with 20 wt.% additive content showed highest permeation flux of 452.27 g/m2h.  相似文献   

11.
Surface functionalization and modification including the grafting process are effective approaches to improve and enhance the reverse osmosis (RO) membrane performance. This work is aimed to synthesize grafted/crosslinked cellulose acetate (CA)/cellulose triacetate (CTA) blend RO membranes using N-isopropylacrylamide (N-IPAAm) as a monomer and N,N-methylene bisacrylamide (MBAAm) as a crosslinker. The morphology of these membranes was analyzed by scanning electron microscopy and their surface roughness was characterized by atomic force microscopy. The performance of these membranes was evaluated through measuring two major parameters of salt rejection and water flux using RO unit at variable operating pressures. It was noted that the surface average roughness obviously decreased from 148 nm for the pure CA/CTA blend membrane with 2.5% CTA to 110 nm and 87 nm for the grafted N-IPAAm and grafted/crosslinked N-IPAAM/MBAAm/CA/CTA-RO membranes, respectively. Moreover, the contact angle decreased from 51.98° to 47.6° and 43.8° after the grafting and crosslinking process. The salt rejection of the grafted CA/CTA-RO membrane by 0.1% N-IPAAm produced the highest value of 98.12% and the water flux was 3.29 L/m2h at 10 bar.  相似文献   

12.
Hollow‐fiber ultrafiltration (UF) membranes were prepared from blends of poly(vinyl chloride) (PVC) and polystyrene (PS) with a dry/wet phase inversion method. Poly(ethylene glycol) (PEG) and N,N‐dimethylacetamide were used as the additive and solvent, respectively. The effects of the PEG concentration in the dope solution as an additive on the cross sections and inner and outer surface morphologies, permeability, and separation performance of the hollow fibers were examined. The mean pore size, pore size distribution, and mean roughness of both the inner and outer surfaces of the produced hollow fibers were determined by atomic force microscopy. Also, the mechanical properties of the hollow‐fiber membranes were investigated. UF experiments were conducted with aqueous solutions of poly(vinyl pyrrolidone) (PVP; K‐90, Mw = 360 kDa). From the results, we found that the PVC/PS hollow‐fiber membranes had two layers with a fingerlike structure. These two layers were changed from a wide and long to a thin and short morphology with increasing PEG concentration. A novel and until now undescribed shape of the nodules in the outer surfaces, which was denoted as a sea‐waves shape, was observed. The outer and inner pore sizes both increased with increasing PEG concentration. The water permeation flux of the hollow fibers increased from 104 to 367 L m?2 h?1 bar?1) at higher PEG concentrations. The PVP rejection reached the highest value at a PEG concentration of 4 wt %, whereas at higher values (from 4 to 9 wt %), the rejection decreased. The same trend was found also for the tensile stress at break, Young's modulus, and elongation at break of the hollow fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 989‐1004, 2013  相似文献   

13.
Polyethylene glycol-grafted nanodiamond (ND-PEG) was synthesized from pristine detonation NDs and utilized to prepare novel cellulose acetate/polyethylene glycol-grafted nanodiamond(CA/ND-PEG)nanocomposite membranes. Due to unique thermal, mechanical, and antibacterial properties and very easy cleaning of fouled ND-embedded CA nanocomposite membranes, we tried to investigate the performance of CA/ND-PEG membrane for humic acid (HA) removal from contaminated water. Surface functionalization was confirmed by Fourier transform infrared spectroscopy and thermogravimetry analysis. Pristine and functionalized ND with different concentration was added in the casting solution containing CA. The prepared membranes were characterized using contact angle, mechanical strength, scanning electron microscopy (SEM), transmission electron microscopy, and permeation tests. SEM micrographs of the surface of the membranes depicted the increase in the number of pores by the addition of ND and especially ND-PEG into polymer matrix. The results indicated that the nanocomposite membrane with 0.5 wt% ND-PEG exhibited excellent hydrophilicity, mechanical properties, permeability, high rejection, high abrasion resistance, and good anti-fouling performance. The HA adsorption on the membrane surface decreased from 2.85 to 2.15 mg cm?2 when the ND-PEG content increased from 0 to 0.5 wt%. Most importantly, the HA filtration experiments revealed that the incorporation of ND and especially ND-PEG particles reduced membrane irreversible fouling, dramatically. Meanwhile, the analysis of the fouling mechanism based on Hermia’s model revealed that cake formation is a prevailing mechanism for all membranes.  相似文献   

14.
Enhancement of the hydrophilicity in polymeric membrane materials results in membranes with higher flux and better membrane characteristics. Hence, polysulfone was carboxylated and ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones having various degrees of carboxylation with a total polymer concentration of 20 wt % in casting solution and at different blend polymer compositions. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, and membrane hydraulic resistance (Rm) have been investigated. The influence of the polymer concentration in the blend solution on the performance of blend membranes at various blend polymer compositions has also been investigated and compared with that of blend membranes prepared from blends of cellulose acetate and polysulfone or carboxylated polysulfone with a total polymer concentration of 17.5 wt %. Further, the solute rejection performance of the membranes has also been investigated by subjecting the membranes to metal ion permeation studies using polyelectrolyte‐enhanced ultrafiltration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 976–988, 2005  相似文献   

15.
In this article, a new modified poly(ether sulfone) flat‐sheet ultrafiltration membrane, which is expected to effectively handle coking sewage, was prepared by an immersion precipitation phase‐inversion technique to settle the wastewater treatment problem in coking plants. Nanometer TiO2 particle–poly(ethylene glycol) (PEG) blends were used as additives to modify the membranes by a blending method. The effects of different PEG mass concentrations on the membrane structure and properties were studied. The pure water flux and chemical oxygen demand (COD) rejection rate were analyzed as aggregative indicators by the comprehensive evaluation method, and then, the optimal PEG mass concentration was determined. The results show that the best modified effect was obtained at a PEG mass concentration of 0.25%. When coking sewage in a secondary settling tank was filtered with such membranes, the COD rejection rate reached 90.68%, and the water flux was 127.21 L m?2 h?1. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45149.  相似文献   

16.
《分离科学与技术》2012,47(3):490-501
Abstract

Acetic acid/sodium acetate and propionic acid/sodium propionate were separated by the diffusion dialysis technique using Neosepta AFN‐7 and Selemion DSV membranes. Accounting for molarities of carboxylic acids and salts in broths produced by the pH controlled bacterial fermentation (pH 4–6), the experiments were carried out with carboxylates in excess of acids. The sorption equilibria established for acetic acid, propionic acid, and the sodium salts of both acids (single solute experiments) revealed a high sorption of acids in both membranes and the rejection of carboxylates. The partition coefficients were found to be from unity up to 2 for the acids and 0.04–0.05 for the salts. Reflecting a high sorption, the fluxes for the acids amounted from 1.5 to 2.0 mol · m?2 · h?1 and only 0.07–0.08 mol · m?2 · h?1 for the salts (one molar solutions). The separation factors computed upon the experiments performed with the ternary solutions were found between 20 to 37 for the Neosepta AFN‐7 membrane and about 29 for the Selemion DSV membrane. Accounting additionally, for the results of the separation of lactic acid from sodium lactate reported in our earlier paper the results prove the diffusion dialysis to be applicable to the separation of mean strength and weak carboxylic acids from their salts.  相似文献   

17.
The blend polyethersulfone (PES)/cellulose acetate (CA) flat‐sheet microporous membranes were prepared by reverse thermally induced phase separation (RTIPS) process. The effects of CA content and coagulation bath temperature on membrane structures and properties were investigated in terms of membrane morphology, water contact angle, permeation performance, and mechanical properties. The cloud point results indicated that the cloud point decreased with the increasing content of CA. When the coagulation bath temperature was lower than the cloud point, the membrane formation process underwent nonsolvent induced phase separation (NIPS) process and dense skin layer and finger‐like structure were formed in membranes. These membranes had lower pure water flux and poor mechanical properties. But when the coagulation bath temperature was higher than the cloud point, the membrane formation process underwent RTIPS process. The porous top surface as well as porous cross‐section of the membranes were formed. Therefore, high pure water flux and good mechanical properties were obtained. The contact angles results indicated that the hydrophilicity of the prepared membranes improved obviously with the addition of CA. When the content of CA was 0.5 wt% and the membrane formation temperature was 323K, the PES/CA microporous membrane which was prepared via the RTIPS process displayed a optimal permeability of the pure water flux of 816 L m?2 h?1 and the BSA rejection rate of 49.5%, which showed an increase of 48.9% and 23.6% than that of pure PES membrane, respectively. Moreover, the mechanical strengths of the membranes obtained by RTIPS process were better than those membranes prepared by NIPS process. POLYM. ENG. SCI., 58:180–191, 2018. © 2017 Society of Plastics Engineers  相似文献   

18.
A model for the adsorption of gold from I2/I? aqueous solutions onto a cellulose acetate (CA)‐polyaniline (PANI) porous membrane is presented. The adsorption of gold is represented by an ion‐exchange overall reaction in which AuI2? ions replace the Cl? ions at the active sites of the polyaniline matrix. The model incorporates the external mass transfer of AuI2? from the bulk solution to the membrane surface, followed by the pore diffusion of AuI2? to reach the active sites in the membrane. The overall ion‐exchange reaction was assumed to achieve local instantaneous equilibrium. Verification of the kinetic model with the experimental data showed that the effective diffusivity of AuI2? within the membrane is about 8.3 × 10?6 cm2/s. The potential applications of the present formulation are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

19.
A new cellulose acetate propionate (CAP) polymer has been synthesized and used to prepare high‐performance forward osmosis (FO) membranes. With an almost equal degree of substitution of acetyl and propionyl groups, the CAP‐based dense membranes show more balanced physicochemical properties than conventional cellulose acetate (CA)‐based membranes for FO applications. The former have a lower equilibrium water content (6.6 wt. %), a lower salt diffusivity (1.6×1014 m2 s?1) and a much lower salt partition coefficient (0.013) compared with the latter. The as‐prepared and annealed CAP‐based hollow fibers have a rough surface with an average pore radius of 0.31 nm and a molecular weight cut off of 226 Da. At a transmembrane pressure of 1 bar, the dual‐layer CAP‐CA hollow fibers show a pure water permeability of 0.80 L m?2 h?1 bar?1 (LMH/bar) and a rejection of 75.5% to NaCl. The CAP‐CA hollow fibers were first tested for their FO performance using 2.0 M NaCl draw solution and deionized water feed. An impressive water flux of 17.5 L m?2 h?1 (LMH) and a reverse salt flux of 2.5 g m?2 h?1 (gMH) were achieved with the draw solution running against the active CAP layer in the FO tests. The very low reverse salt flux is mainly resulting from the low salt diffusivity and salt partition coefficient of the CAP material. In a hybrid system combining FO and membrane distillation for wastewater reclamation, the newly developed hollow fibers show very encouraging results, that is, water production rate being 13–13.7 LMH, with a MgCl2 draw solution of only 0.5 M and an operating temperature of 343 K due to the incorporation of bulky propionyl groups with balanced physiochemical properties. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1245–1254, 2013  相似文献   

20.
Excessive amounts of copper ions in the water sources can be harmful to mammals and especially humans. In this study, a new RO composite membrane is fabricated via the interfacial polymerization (IP) reaction of trimesoyl chloride (TMC), piperazine (PZ) and 3,5-diaminobenzoicacid (DABA). The IP reaction was conducted on a polysulfone (PS) layer which acts as a mounting layer for the separation TMC-DABA-PZ layer. The IP reaction time, TMC concentration and transmembrane pressure were the selected study variables. For IP reaction times around 10 s the rejection and flux were equal to 79% and 21.3 L.m?2.h?1, respectively, while increasing the IP reaction time to 40 s elevates the rejection and flux to 92% and 27.7 L.m?2.h?1, respectively. TMC concentrations around 0.05% w/w demonstrated rejection and flux equal to 88% and 14.3 L.m?2.h?1, respectively, while its elevation to 0.2% w/w, increased the rejection and flux to 90% and 17.5 L.m?2.h?1, respectively. As with the transmembrane pressure, the optimum pressure was 20 bars, in which the rejection and flux were 95% and 24.07 L.m?2.h?1, respectively. Membrane morphology tests are also supporting evidence for these results. The mathematical modeling has also shown that the relation between the concentration, rejection and flux parameters match the resultant data from the conducted experiments. Since both the rejection and the flux of the fabricated membranes have shown great results, such membranes can be used for wastewater treatment at industrial scales.  相似文献   

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