Asymmetric Cellulose Acetate Membranes Used in Separation Applications (original) (raw)
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In membrane-based water purification technology, control of the membrane pore structure is fundamental to defining its performance. The present study investigates the effect of the preparation conditions on the final pore size distribution and on the dye removal efficiency of cellulose acetate membranes. The membranes were fabricated by means of phase inversion (using different speeds of film casting and different thicknesses of the casted solution) and introducing modifications in the preparation conditions, such as the use of a coagulation bath instead of pure water and the addition of a surfactant as a solution additive. Both isotropic and anisotropic membranes could be fabricated, and the membranes’ pore size, porosity, and water permeability were found to be greatly influenced by the fabrication conditions. The removal capacity towards different types of water contaminants was investigated, considering, as model dyes, Azure A and Methyl Orange. Azure A was removed with higher e...
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In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L 9 orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 • C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).
Wastewater Treatment Using a Modified Cellulose Acetate Membrane
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The main objective of this work has been to study the performance of membranes developed for treating purified wastewater. Polymeric membranes have been developed from solutions containing cellulose acetate (AC) and polysulfone (PSF), using N,N-dimethylformamide (DMF) as solvent and polyethylene glycol (PEG) as additive. The phase inversion method was chosen as a technique for producing the membrane films. The incorporation of PEG allowed us to study the effect of the additive on the morphological structure, and to predict the performance of the membranes formed. Examining the flux, permeability and selectivity of the membranes allowed studying the efficiency and performance of each membrane. The application results achieved in wastewater treatment at Chenoua/TIPAZA station were very satisfactory and in accordance with the standards required by WHO. The optimal performance, in terms of permeability and selectivity, was obtained for the MC membrane with the composition: PSF/PEG/AC of...
Characterization of asymmetric membranes of cellulose acetate from biomass: Newspaper and mango seed
Carbohydrate …, 2010
Asymmetric membranes may be used in a broad range of applications such as reverse osmosis, hemodialysis and separation of organic mixtures. In this paper, asymmetric membranes were produced using cellulose acetate (CA) from biomass: newspaper and mango seed. The degree of substitution of CA was 2.65 ± 0.07. Different formulations were used to prepare the CA membranes: CA/dichloromethane/water with and without magnesium perchlorate. The asymmetry of the membranes was characterized by scanning electron microscopy (SEM). Membranes produced with magnesium perchlorate presented higher water vapor flux than those produced without this salt. This difference is due to pore formation in the membrane skin when using magnesium perchlorate. Membrane substructure showed to be a determining factor in ion diffusion experiments. The coefficient of ion diffusion for the membrane of cellulose acetate from mango seed was 1.82 Â 10 À8 cm 2 s À1 while for the membrane of cellulose acetate from newspaper was 7.43 Â 10 À8 cm 2 s À1 which similar to the value reported in the literature for commercial CA (8.46 Â 10 À8 cm 2 s À1 ).
Preparation and characterization of cellulose acetate propionate membrane
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Membrane technology is a technique in water and wastewater treatment that has many advantages. This study focuses on the manufacture and characterization of cellulose acetate propionate (CAP) membranes using the phase inversion method. The CAP is preferable since it is a biopolymer that is environmentally friendly and cheap. The production of CAP membrane was carried out using phase inversion method, and varied in 3 different concentrations of CAP i.e., 13, 14, and 15% wt., with additional material of polyethylene glycol (PEG). The characterization was conducted using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analysis to determine its morphology, pores, and functional groups. The results show that the membrane containing 13% wt. CAP exhibits higher porosity with more macropores than a membrane with 14 and 15% wt. CAP. However, membranes with higher concentrations of CAP show more uniform pores and fewer macropores. FTIR analysis confirmed the presence of functional groups in the membrane such as C-O, -CH3, C=O, C-H, and OH. It is also found that there is a shift in Wavenumber due to the increase in the concentration of CAP in each membrane.
Development of Acid Modified Cellulose Acetate Membranes for Salt Water Treatment
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The main objective of this work has been to study the performance of membranes developed for water treatment. Polymeric membranes (CTP and CTP-Acid) were developed from solutions containing cellulose acetate (CA), cellulose triacetate (CTA) and polysulfone (PSF), using maleic acid (MA) and acetic acid (AA) as additives and chloroform/dioxane as solvent. The NIPS-type phase inversion method was chosen as the membrane film manufacturing technique. The incorporation of 2.5% and 5% by weight of acids in the membrane mixture allowed us to study the additive effect on the morphological structure, and to predict the performance of the membranes formed. The characterization of the membranes was performed by SEM and FTIR analyses. Examining the flux, permeability and selectivity of the membranes also permitted to study the efficiency and performance of each membrane. The addition of AA and MA additives within the mixture increased the hydrophilic character and improved the flux rate by incre...
Formic acid crosslinked cellulose acetate defect-free asymmetric membrane for gas separation
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Cellulose acetate (CA) polymeric membrane has been used as gas separator; however, the modest selectivity and trade-off between permeability and selectivity have reduced the utilization of this polymer. Thus, the objectives of this study were to investigate the effect of polymer concentration and formic acid (FA) crosslinking agent loading on the formation of the membrane morphology and gas separation performance. The CA in tetrahydrofuran (THF) flat sheet asymmetric membrane was fabricated by dry/wet phase inversion process with two conditions of dope solution formulation: (1) varying the polymer concentration ranging from 13 to 16 wt.% and (2) manipulating FA:THF ratio between 0:100 to 10:90. The prepared membrane was analyzed by using viscometer, field emission scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, and tensile testing machine. The membrane gas permeation performance was tested using pure gases of hydrogen (H2), o...
Cellulose acetate reverse osmosis membranes: Optimization of preparation parameters
Journal of applied polymer …, 2007
Asymmetric cellulose acetate based membranes usually employed in reverse osmosis as well as in separations in aqueous systems can possibly be applied in the socalled salinity process of energy generation. For these applications, membranes with a relatively high water permeability (sometimes also called water flux) and low salt permeability (or high salt rejection) are required. In this study the authors present the optimization of such membranes, which concerns the preparation parameters. The membranes studied were prepared from a solution whose composition were previously optimized. The authors concluded that the optimum preparation parameters are as follows: thickness of the liquid film of 100 mm; 30 s allowed for evaporation of the solvent; and temperature of coagulation bath of 0-48C and 80-858C as annealing temperature.