Asymmetric Cellulose Acetate Membranes Research Articles

アルコール溶媒置換法による非対称型乾燥酢酸セルロース膜の気体透過特性

アルコール溶媒置換法による非対称型乾燥酢酸セルロース膜の気体透過特性

Transport properties of Toray's asymmetric cellulose acetate membranes

Using several asymmetric cellulose acetate membranes (CA), transport parameters such as the hydrodynamic (ℓ p) and osmotic (ℓ π) permeability and the asymptotic solute rejection (r ∞) were determined from hyperfiltration experiments at 25° C with different brine solutions (0.1 M and 0.5 M NaCl, 0.1 M NaNO 3, 0.05 M Na 2SO 4). All membranes used exhibit a quite constant performance.

Selective behaviour of hyperfiltration cellulose acetate membranes: Part I. selectivity to cations and electroosmotic flow

Concentration potentials and electroosmotic flow through five asymmetric cellulose acetate membranes cured at 55, 65, 75, 85 and 95°C are measured in solutions in NaCl, CsCl HCl, CaCl 2 and LaCl 3. The influence of external concentration, counterion valency and curing temperature of membranes on their apparent transport numbers, permselectivity and electroosmotic permeability are determined. Hyperfiltration membranes exhibited the behaviour of loose, weakly charged cationic membranes. Selective behaviour is stronger the higher the curing temperature and the cation charge and the lower the external concentration. Counterions of high membrane affinity cause selectivity reversal. Results are correlated with the expected potential profile through asymmetric membranes. Electroosmotic permeability rises with the decrease in solution concentration up to a limiting value. Water transport measured in the presence of alkali and alkaline earth cations increases with hydrated size and/or charge of cations parallel to the cation-water friction coefficient. The electrokinetic cross coefficient obtained from electroosmotic measurements is found to vary with current density

The effect of solute—membrane affinity on cyclic hydrocarbon—water transport in pressure-driven membrane separation processes

Experimental results for the pressure-driven membrane separation of cyclic hydrocarbons (1,3-cyclohexadiene, cyclohexene, and cyclohexane) from dilute binary aqueous solution using asymmetric cellulose acetate membranes are reported here. In these experiments, total solution fluxes are significantly lower than pure water fluxes at the same applied pressure; this flux reduction is attributed to strong solute—membrane affinity rather than to the osmotic pressure of either the bulk retentate or the boundary layer. An empirical parameter, Z, is used to describe flux reduction. A theoretically based friction parameter, B, is derived assuming the membrane can be represented as an ideal, finely porous membrane; this parameter indicates the influence of solute—membrane affinity on flow through the pores of the membrane. Both the empirical parameter Z and the theoretically based parameter B relate flux reduction to concentrations in the system. Both Z and B increase as solute—membrane affinity increases and decrease as membrane pore size increases. It is concluded that both the empirical flux reduction parameter, Z, and the theoretically based friction parameter, B, indicate the same system properties: solute—membrane affinity and membrane pore size.

Physicochemical interactions in pressure-driven membrane separation of glucose, ascorbic acid, citric acid, and mannitol from single solute aqueous solution

The pressure-driven membrane separation of dilute single-solute aqueous solutions of glucose, ascorbic acid, citric acid, and mannitol was studied at low pressure using an asymmetric cellulose acetate membrane in a batch stirred cell. Results were analyzed based on a mass transfer analysis which included both convective and diffusive effects. Rejection followed the trend glucose mannitol⪢ascorbic acid⪢citric acid. Transport parameters followed the trend glucose≈mannitol<ascorbic acid<citric acid. The observed results are explained on the basis of significant physicochemical interactions between solute, solvent, and membrane.

Permanent-use haemofilter based on porous glass capillaries

Modules of surface-modified porous glass capillaries with a hydraulic conductivity of 0.25-0.70 ml min -1 mmHg -1 m -2 were tested for suitability for clinical haemofiltration by ex vivo dog experiments and by in vitro perfusion. The results show that (1) the construction of reusable haemofilters based on porous glass capillaries is possible; (2) operational data of testmodules are comparable with hollow-fiber high-flux haemofilters based on asymmetric cellulose acetate membranes; and (3) blood-surface interaction of porous glass capillaries is characterized by protein deposition which entails very low protein cutoff.

Preparation of low‐phytate rapeseed protein by ultrafiltration: II. Membrane development and testing

AbstractThe feasibility of using ultrafiltration (UF) to eliminate phytate from aqueous sodium chloride extracts of rapeseed was studied. With a proper choice of casting solution composition and casting conditions, high flux asymmetric cellulose acetate membranes of different surface porosity capable of giving different levels of phytate‐protein separation were effectively created. The efficiency of the cast cellulose acetate membranes on phytate‐protein separation was greatly influenced by the solution pH. The presence of sodium chloride in the processed solution was important to obtain a low retention of phytate. Complete removal of phytate from rapeseed extract with little or no loss of proteins was achieved using continuous diafiltrarion.

Formation of asymmetric cellulose acetate membranes

Cellulose acetate membranes were prepared from casting solutions containing dioxane as a solvent and varying concentrations (up to 6%) of maleic acid as an additive. Coagulation took place in water at different temperatures. The effect of these variables on membrane structure and membrane properties is related to two phenomena of phase separation in the system cellulose acetate/dioxane/water, viz. gelation in the toplayer and liquid-liquid phase separation in the sublayer of the membrane. We adopted a solution transport model which correlates membrane flux with the skin thickness and membrane salt rejection with the compactness (microstructure) in the skin. Effects of variables such as maleic acid concentration and coagulation temperature on the position of curves in the phase diagram and on membrane properties are discussed. It is concluded that more work should follow on the kinetics of the phase changes mentioned.

Irreversible fouling caused by plasticization of asymmetric reverse osmosis membranes

Bench-scale reverse osmosis measurements have been performed on aqueous solutions of phenol, p-nitrophenol, aniline, coumarin, sodium lauryl sulfate and sodium naphtalene sulfonate. Asymmetric cellulose acetate membranes were used. Low concentrations of dissolved organics produce modest reversible reductions of permeate flux. Higher concentrations of aniline dissolve the membrane, while high phenol concentrations effectively plasticize the membrane removing its asymmetric structure. Electron micrographs of plasticized and unplasticized membranes are shown.

Water transport mechanisms through asymmetric membranes

AbstractPermeability coefficients and activation energy values for the transport of water through asymmetric cellulose acetate membranes were determined in order to establish the mechanism of the process when different driving forces are applied. A stirred Lucite cell with controlled temperature was used to measure the membrane transport properties under hydraulic and osmotic pressure differences and also in the presence of a tracer concentration gradient across the membrane. The experimental results based on the temperature dependence of water flow show that the controlling step for water transport is diffusion with net flux in the dense zone of the membrane under hydraulic or osmotic pressure gradients. When a tracer concentration gradient is used, equimolar diffusion of water in the thicker, porous zone of the membrane is the controlling mechanism. A mass transport model based on the composed structure of the membrane is presented to provide a general framework for treating the particular cases. Finally, the difference in the controlling barriers, in agreement with a previous work by Hays,18 is shown to account for the much higher absolute values of osmotic than tracer water permeabilities determined here and frequently reported in the literature.

Deterioration of Asymmetric Cellulose Acetate Membranes with Sodium Hypochlorite

Deterioration of Asymmetric Cellulose Acetate Membranes with Sodium Hypochlorite

Deterioration of Asymmetric Cellulose Acetate Membranes with Sodium Hypochlorite

Deterioration of Asymmetric Cellulose Acetate Membranes with Sodium Hypochlorite

Ultrastructure of the surface of a polysulfone ultrafiltration membrane

Journal of Applied Polymer ScienceVolume 25, Issue 9 p. 2139-2142 NoteFree Access Ultrastructure of the surface of a polysulfone ultrafiltration membrane Uzi Merin, Uzi Merin Membrane Processing Laboratory, Department of Food Science, Dairy Manufactures Building, University of Illinois, Urbana, Illinois 61801Search for more papers by this authorMunir Cheryan, Munir Cheryan Membrane Processing Laboratory, Department of Food Science, Dairy Manufactures Building, University of Illinois, Urbana, Illinois 61801Search for more papers by this author Uzi Merin, Uzi Merin Membrane Processing Laboratory, Department of Food Science, Dairy Manufactures Building, University of Illinois, Urbana, Illinois 61801Search for more papers by this authorMunir Cheryan, Munir Cheryan Membrane Processing Laboratory, Department of Food Science, Dairy Manufactures Building, University of Illinois, Urbana, Illinois 61801Search for more papers by this author First published: September 1980 https://doi.org/10.1002/app.1980.070250928Citations: 37AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 R. L. Riley, J. O. Gardner, and U. Merten, Science, 143, 801 (1964). 2 R. L. Riley, U. Merten, and J. O. Gardner, Desalination, 1, 30 (1966). 3 R. E. Kesting, “ Asymmetric cellulose acetate membranes,” in Reverse Osmosis and Synthetic Membranes, S. Sourirajan, Ed., National Research Council Canada, Ottawa, Canada, 1977. 4 M. A. Frommer and D. Lancet, “ The Mechanism of membrane formation: Membrane structure and their relation to preparation conditions,” in Reverse Osmosis Membrane Research, H. K. Lonsdale and H. E. Podall, Eds., Plenum, New York, 1972. 5 R. F. Madsen, Hyperfiltration and Ultrafiltration in Plate-and-Frame Systems, Elsevier, Amsterdam, 1977. 6 G. J. Gittens, P. A. Hitchcock, and G. E. Wakley, Desalination, 12, 315 (1973). 7 I. Cabasso, E. Klein, and J. K. Smith, J. Appl. Polym. Sci., 21, 165 (1977). 8 F. S. Model and L. A. Lee, “ PBI reverse osmosis membranes: An initial survey,” in Reverse Osmosis Membrane Research, H. K. Lonsdale and H. E. Podall, Eds., Plenum, New York, 1972. 9 H. Strathmann, K. Kock, P. Amar, and R. W. Baker, Desalination, 16, 179 (1975). 10 H. Yasuda and J. T. Tsai, J. Appl. Polym. Sci., 18, 805 (1974). 11 Y. Ozari, G. Tanny, and J. Jagur-Grodzinski, J. Appl. Polym. Sci., 21, 555 (1977). 12 M. Cheryan and U. Merin, “ A study of the fouling phenomenon during ultrafiltration of cottage cheese whey,” in Ultrafiltration Membranes and Applications, A. C. Cooper, Ed., Plenum, New York, to appear. 13 A. R. Spurr, J. Ultrastruct. Res., 26, 31 (1969). Citing Literature Volume25, Issue9September 1980Pages 2139-2142 ReferencesRelatedInformation

Artificial particulate fouling of hyperfiltration membranes IV. Dynamic protection from fouling

Experimental results are presented and analyzed for an inexpensive method of membrane protection from colloidal fouling. An inexpensive dynamic precoat protective cover using diatomaceous earth is placed on the high pressure feed-water side of the asymmetric cellulose acetate membrane. Increased water and salt fluxes with the precoat as high as 2.3 times that without precoat were measured. The presence of submicron pin-holes in the membrane skin is used to explain the mechanism of protection against submicron colloids. This method of protection is most attractive for high-flux and medium-salt rejection applications for colloidal containing feed solutions. Such applications include the treatment of municipal, industrial, and agricultural waste-waters for reuse and as a possible pretreatment step for sea water reverse osmosis desalination.

Electrical and electroosmotic transport behavior of asymmetric cellulose acetate membranes. I. Transport behavior in dialysis-osmosis experiments

Using an asymmetric cellulose acetate (CA) membrane annealed at 82.5°C and the linear relationships of the thermodynamics of irreversible processes, the electrical and electroosmotic transport coefficients such as R e, l ep, and l pe as well as the hydrodynamic permeability, l p, have been determined as functions of the NaCl concentration, c s. The electroosmotic coefficient, l pe, and the so called “pressure-membrane potential” (pmp) coefficient, l ep, have been found to be strongly dependent on the external salt concentration. At larger NaCl concentrations both coefficients even change their sign being positive for c s < 0.07 mole/liter and negative for c s > 0.07 mole/liter. The positive values of l ep and l pe at concentrations c s < 0.07 mole/liter are in agreement with the cation exchange property of CA membranes. Furthermore, the hydrodynamic permeability, l p, and the electrical resistance, R e, of the asymmetric cellulose acetate membrane have been measured. The sign reversal of l ep and l pe is discussed by applying the finely porous membrane model to the two-layer membrane and taking into account the weak cation-exchange character of cellulose acetate membranes. The discussion indicates that both the weak cation-exchange character as well as the asymmetry of the cellulose acetate membrane are responsible for the significant sign reversal of the electrokinetic transport coefficients l ep and l pe at larger concentrations. Moreover, the value of the measured electrical resistance supports the idea of the two-layer model for the asymmetric cellulose acetate membrane.

Electrical and electroosmotic transport behavior of asymmetric cellulose acetate membranes. II. Transport behavior in hyperfiltration experiments

Using an asymmetric cellulose acetate (CA) membrane annealed at 82.5°C, the membrane potential has been determined as a function of the NaCl concentration, c′ s in hyperfiltration experiments at pressure differences, ΔP, of up to 10 atm. These membrane potential determinations have been repeated under dialysis conditions ( c′ s = c″ s). Both the membrane potential in dialysis, Δ Ψm , as well as in hyperfiltration, Δ ϕm , are strongly dependent upon the feed concentration, c′ s, and even change their sign at c′ s ∼- 0.07 mole/liter. The concentration dependence of the hyperfiltration membrane potential, Δ ϕm , is briefly discussed in terms of the finely porous membrane model applied to both layers of an asymmetric membrane. Furthermore, employing the same model, the difference of membrane potentials, ΔΨ m − Δ ϕm , is related to different concentration profiles within the porous sublayer of an asymmetric cellulose acetate membrane under the different boundary conditions. The small potential contributions of the porous sublayer to the entire membrane potential are due to larger diffusion coefficients and a smaller fixed charge concentration within the porous sublayer. Employing the integral of the Nernst-Planck equations and the Donnan potential relation, the membrane potential is calculated as a function of brine concentration in hyperfiltration at 10 atm as well as a function of the hydrostatic pressure difference, ΔP, for different brine concentrations.

Characterization of transport across cellulose acetate membranes in the presence of strong solute–membrane interactions

AbstractCertain organic solutes, including phenol, undergo anomalous enrichment when hyperfiltered through cellulose acetate membranes: the solute concentration is higher in the permeate than in the feed solution. A number of existing theoretical approaches describing hyperfiltration phenomena are presented and their merits and limitations upon application to the transport of phenol discussed. A new two‐parameter transport relationship is derived based on an extension of the solution–diffusion model. The enrichment, or negative solute rejection by the membrane, is predicted to occur whenever the pressure‐induced solute permeation velocity exceeds that of water. By acknowledging and incorporating the effect of pressure on the chemical potential of the solute, the present extended solution–diffusion model relationship successfully describes hyperfiltration data of phenol in homogeneous and asymmetric cellulose acetate membranes provided the contribution of convective flow to the overall solute transport is insignificant. In addition to the transport parameters of the extended solution–diffusion model, the transport parameters of the phenomenological, Kedem–Spiegler, and combined viscous flow–frictional relationship are evaluated from hyperfiltration data obtained with 0.05 and 0.1 wt % phenol feed solutions and homogeneous cellulose acetate membranes of different acetyl content.

Contaminants in Clinical Reverse Osmosis Water Purification Systems

To the Editor.— Reverse osmosis (RO) membrane separation processes have been successfully used by industry for several years to generate high purity water for injectables. More recently, miniature RO plants have been designed to produce injectables and dialysate solutions for hemodialysis and peritoneal dialysis in health care facilities. Existing commercial systems based on asymmetric cellulose acetate membranes have good separation properties for a number of solutes. 1 However, their behavior is such that certain compounds are not excluded; in fact, a few are transported preferentially and concentrated by the membrane. 2,3 This is in contrast with widely held views in engineering circles that regard RO membranes as sieves that filter largeand medium-sized molecules without regard to their chemistry. Poorly separated compounds include many common municipal water impurities such as pesticides, natural products, and industrial contaminants, which are found in high concentrations in some localities at certain times of the year.

Effect of alcohols on the mechanical and transport properties of asymmetric cellulose acetate membranes

The tensile properties and rejection performance of cellulose acetate membranes in the presence of alcohol-water solutions are reported. The analysis of experimental results indicates that cellulose acetate membranes can be used to recover alcohols from waste water via reverse osmosis. The analysis of stress-strain curves of both virgin membranes conditioned in alcohol solution can be used to assess the potentiality of this cellulose acetate membranes in alcohol recovery processes.

Characterization of water structure in cellulose acetate membranes by calorimetric measurements

AbstractThe heat capacities of homogeneous and asymmetric cellulose acetate membranes have been measured at different water contents within the temperature range of −40 to +20°C. The experimental heat capacity–temperature curves were verified by DTA measurements within a temperature range of −120 to +20°C. The results for the partial heat capacity of water within the membranes as well as for the heat of fusion were interpreted by assuming two different states of water—unfreezing bound water due to a sorption process and unbound water due to capillary phenomena, which freezes with a freezing point depression and a reduced heat of fusion.