Cellulose Triacetate Membrane Research Articles

Photoresponsive membranes : V. Amplification of photo-induced potential across an entrapped-retinal membrane by incorporation of a protein

The chromophore of a visual pigment, 11- cis retinal, was conjugated with proteins, such as bovine serum albumin, alcohol dehydrogenase, α-chymotrypsin, α-amylase, and lysozyme. These retinal-protein conjugates were incorporated in a cellulose triacetate membrane together with phosphatidyl choline. The entrapped-retinal membranes responded to visible light in their transmembrane potential. The photo-induced potential was triggered by the photoisomerization of the membrane-bound retinal. The incorporation of a protein, especially of a hydrophobic protein such as bovine serum albumin, was found to markedly enhance the extent of the photo-induced potential. The mechanism of potential generation is discussed.

Uphill transport of uranium across a liquid membrane

A liquid membrane was prepared by entrapping tributyl phosphate (TBP) in a cellulose triacetate (TAC) membrane matrix. The membrane was used to separate two aqueous solutions, one acidic and the other alkaline, which were saturated with TBP to prevent its loss from the membrane. Uphill transport of uranium was achieved with the TBP liquid membrane. Both solutions containing TBP were stirred magnetically. When the initial concentration of uranium in the two solutions was 3.5 m M, more than 50% of the uranium contained in the acidic solution was transported to the alkaline solution across the liquid membrane within 5 h. A transport mechanism is described in which the membrane-bound TBP acts as a mobile carrier for uranium.

Permeation of water vapor through cellulose triacetate membranes in hollow fiber form

AbstractA modification of the carrier gas method for measuring permeability of a hollow fiber to a vapor is described with particular application to water vapor permeation through asymmetric cellulose triacetate in hollow fiber from. Conventional methods are inadequate because the high flux of permeation vapor combined with its low pressure on the permeate side and the small diameter of the fiber lead to an excessive buildup of pressure in the permeate stream—in some cases so great as to render much of the fiber length ineffective. The method described in this paper involves the permeation from the outside to the inside of the fiber of a binary mixture consisting of the water vapor and a fairly highly permeable carrier (helium). There is a significant pressure drop along the fiber, but a theoretical treatment is presented to take this into account and to permit a determination of the vapor permeability. Experiments at 35°C over a range of water vapor pressures up to 1.7 cm Hg gave a water flux of 9 × 10−3 cc(S.T.P.)/cm2‐sec‐cm Hg, with an apparent slight decrease with increasing pressure. Over the same range of water vapor pressure the helium flux decreased from 2.3 × 10−4 to 1.85 × 10−4 cc(S.T.P.)/cm2‐sec‐cm Hg.

The use of filtration techniques for the lysis and study of red blood cells.

A filtration technique for the gentle lysis of erythrocytes has been developed using cellulose triacetate membranes. When cell suspensions are filtered under nitrogen pressure, lysis occurs at the surface of the filter in such a way that the cell ghosts are retained on the filter. The contents of the cell are extruded through the pores of the filter without mixing with the cell suspension. Cell ghosts and intact erythrocytes have been collected on membranes and examined by electron microscopy. These preparations have the advantage of being free of the structural artifacts that result from centrifugation. In addition, the filter facilitates preparation for electron microscopy by providing a support for the sample during fixation and then dissolving during the dehydration of the sample.

The Oxygen Gas Permselectivity of Dried Cellulose Acetate Membranes

Abstract The oxygen gas permselectivity of annealed cellulose di- and triacetate membranes were investigated. We have suggested that the permeation ratios of oxygen to nitrogen gases of these membranes attain 7–8 by annealing in air at 180 °C.

Permeability of water and water vapor through cellulosic membranes

To elucidate the water transport mechanism through homogeneous membranes, water and water vapor permeation through crosslinked cellulose membranes, cellulose diacetate, and cellulose triacetate membranes are studied. It is found that the water flux increases with the degree of hydration; and as for cellulose membranes, the degree of hydration is an increasing function of the degree of crosslinking. Activation energy of hydraulic permeability (Kw) is not equal to that of purely viscous flow, and is smaller than that of the water vapor diffusion coefficient (D) for all membranes. The free-volume concept relating the molar frictional coefficient to temperature and to degree of hydration explains reasonably the temperature dependence of hydraulic permeability and of water vapor diffusion coefficient and gives adequate values for the fractional free volume of the system. The critical volume V*, appearing in the Cohen-Turnbull expression between friction coefficient and free volume fraction, may be considered as the size of the cluster of water molecules. The value of V* in the case of hydraulic permeability is larger than that for water vapor diffusion by several times. Furthermore, the value V* increases with increase of degree of hydration for water permeation and water vapor diffusion.

Utilization of adsorbing materials for uremic blood purification.

An apparatus that uses a charcoal-aluminum oxide cartridge for simplifying haemodialysis by reducing the dialysis solution has been studied. Some adsorbing materials coated with a deacetylated cellulose triacetate membrane were also studied. The coating improves the material biocompatibility and allows its use, through hemoperfusion, for the detossi-fication of uremic blood.

Effect of geometrical and chemical constraints on water flux across artificial membranes.

Studies have been made on the temperature dependence of both the hydraulic conductivity, L(p), and the THO diffusion coefficient, omega, for a series of cellulose acetate membranes (CA) of varying porosity. A similar study was also made of a much less polar cellulose triacetate membrane (CTA). The apparent activation energies, E(a), for diffusion across CA membranes vary with porosity, being 7.8 kcal/mole for the nonporous membrane and 5.5 kcal/mole for the most porous one. E(a) for diffusion across the less polar CTA membrane is smaller than E(a) for the CA membrane of equivalent porosity. Classical viscous flow, in which the hydraulic conductivity is inversely related to bulk water viscosity, has been demonstrated across membranes with very small equivalent pores. Water-membrane interactions, which depend upon both chemical and geometrical factors are of particular importance in diffusion. The implication of these findings for the interpretation of water permeability experiments across biological membranes is discussed.

Stages in phage R17 infection: II. Ionic requirements for phage R17 attachment to F-pili

A simple filtration assay procedure has been utilized to measure the effect of metal ions on the binding of RNA bacteriophage to F-pili. The assay involves the use of cellulose triacetate membrane filters for retention of phage-pili complexes, and is particularly suited for studies on phage-pili interactions in a simple, defined salts medium. Phage R17 attachment to F-pili was found to be independent of ion specificity, requiring only an adequate ionic strength (about 0.10 or greater) for maximum adsorption. Moreover, at optimal levels of any monovalent salt, the addition of a divalent salt causes no further stimulation of phage-pili complex formation.

Boron rejection by cellulose acetate reverse osmosis membranes

The rejection of boric acid by different types of reverse osmosis membranes has been measured. At 102-atm applied pressure, the rejection was about 56% with modified cellulose acetate membranes of the Loeb-Sourirajan type and about 67% with cellulose triacetate membranes. Boric acid permeability measurements carried out with dense cellulose acetate membranes show that the transport properties of these membranes are somewhat different from those of the thin solute-rejection layer on the modified membranes, and that solvent-solute flow coupling is observable in this system. Certain additions to the feed solution were found to enhance boric acid rejection by complex formation, and results obtained with mannitol additions are consistent with the known complex-formation equilibria.

Biological degradation of cellulose acetate reverse‐osmosis membranes

AbstractAn investigation has been carried out with the objective of relating losses in semipermeability of cellulose acetate (DS 2.5) reverse‐osmosis membranes to microbiological degradation (enzymic hydrolysis). Three sources of potentially destructive organisms were selected for study. One source was a set of degraded cellulose acetate reverse‐osmosis membranes; the other two sources were a surface soil sample and a lake bottom mud. From these, a total of 23 microbial isolates were obtained by culturing and enrichment. The isolates were characterized by staining and microscopic examination. Sterilized membranes were shaken continuously with sterile broths containing each isolate. In addition, membranes were placed on sterile agar and streaked with each isolate. Reverse‐osmosis testing of the membranes shaken in broth revealed losses in salt rejection of certain samples after 2 months. Visual observation of agar‐plated membranes showed complete degradation of several samples from each of the three sources of microorganisms. Infrared examination of degraded membranes showed up to 50% loss of acetyl content from the desalinating surface. No salt‐rejecting capability remained in these membranes. Cellulose triacetate membranes were resistant to degradation under conditions identical to those causing degradation of membranes having acetate DS of 2.3–2.5.