Studies on hydrophilic polysulfone ultrafiltration membranes

Ultrafiltration membranes were produced from carboxylated polysulfone polymers having different degrees of substitution (DS). Solute separation was found to increase with increasing DS. The techniques of single solute permeation and permoporometry were used to determine the pore size of these membranes. Permoporometry measurements indicated that pore size decreased with increasing DS. Solute separation was predicted by inserting the distribution of pore sizes obtained from permoporometry into a restricted transport model. Similar results were obtained from a nonlinear least squares fit of the restricted transport model to the experimental data. Both techniques produced similar sieving curves. It was concluded that pore size decreases were not due to the increasing repulsion of solute molecules by hydrophilic polysulfone but to changes in polymer solution properties as the DS increased.     

Studies on ion-exchange membranes. XXXII. Heterogeneity in ion-exchange membranes

Twelve kinds of cation-exchange membranes were treated with hydrogen peroxide. Some of them (Selemion CMV, Nepton CR-61, Scrion C-100, SAM-1) were completely destroyed. Heterogeneity is believed to be present in that part of their chemical structures that is decomposable by the treatment. The other membranes were converted into porous membranes by the decomposition of the resinous part. Water permeabilities and electric resistances of the porous membranes were examined to evaluate the pore radius. It was concluded that the “paste method” membranes have a heterogeneity or localized distribution of the resinous part under 50 mμ. The “paste method” membranes seemed to resemble the “graft method” membranes in chemical structure and to be much different from the mosaic-type membranes such as Permaplex and MC-3142. These results were also supported by extraction of the membranes with appropriate solvents and observation by electron microscopy.     

Studies on effect of irradiation on semipermeable membranes

The effect of γ irradiation on reverse osmosis (RO) semipermeable membranes has been studied in order to evaluate their performance under the radiation environment arising in the processing of various streams in nuclear industry by reverse osmosis process. Both cellulosic and noncellulosic membranes in dry as well as wet conditions were used. A Co⁶⁰ source was used for γ doses from kilorads to megarads. The transport properties, namely, salt retention and water flux of membranes determined before and after irradiation, suggested deterioration in the membrane properties due to irradiation. The tensile strength and viscosity of membrane polymer also suggested membrane degradation. Differential scanning calorimetry was taken to look into any structural changes in the membrane polymer as a result of irradiation. IR spectra and X-ray of membrane polymer was also undertaken to understand the changes on the molecular level.     

Studies on ultrafiltration membranes. I. Development of cellulose nitrate membranes

Ultrafiltration membranes were prepared from cellulose nitrate under different conditions and were characterized using a solution of 1.0% dextran-150 having a salinity of 1500 ppm. The role of various parameters such as polymer concentration, ratio of ether to alcohol, methanol as the solvent, and other additives is systematically studied and presented. Similarly, the effect of operational and hydraulic parameters on the membrane performance is evaluated and the minimum activation energy for the solvent permeability is experimentally deduced.     

Studies on syntheses and permeabilities of special polymer membranes

Summary An ion exchange membrane containing carboxyl groups, insoluble in acidic and alkaline aqueous solutions, was prepared from poly(isobutylene-alternating co-maleic anhydride) and poly(vinyl alcohol). Using the membrane in a diaphragm cell, one side being adjusted to be acidic and the other alkaline, it was possible to transport actively and selectively alkali metal ions through the membrane from the alkaline side to the acidic side.     

Studies on syntheses and permeabilities of special polymer membranes

Summary An active transport of alkali metal ion through cation exchange membranes was studied under various conditions. This active transport was facilitated by using a greater anion species on an acidic side in a diaphragm cell, in which one side of the solution was adjusted to be acidic and the other side alkaline across the membrane. An active transport fraction of alkali metal ion was in order poly(styrenesulfonate)>benzenesulfonate>Cl^– >I^–>Br^– of anion species on the acidic side. A rate, fraction and period of the active transport of metal ion were significantly influenced by an electric potential gradient in the membrane.     

Studies on the radiolytic degradation of cellulose acetate membranes

The effect of γ-irradiation on the performance of wet cellulose acetate membranes in the dose range of 2.5–10 Mrads was investigated using a ⁶⁰Co source. Changes in transport properties and inherent viscosity of the membranes suggested continued degradation as a result of irradiation. Solubility and specific gravity changes accompanying irradiation indicated some sort of structural aggregation occuring at higher doses. Consumption of dissolved oxygen during irradiation and the extent of deacetylation of the membrane polymer were determined to study the kinetics of the degradative process. Analysis of the end products of irradiation was attempted by UV spectroscopy. ESR spectra of membrane polymer after irradiation were analyzed to identify the free radicals generated. A tentative mechanism of radiolytic degradation causing the observed performance failure is proposed.     

Studies on the radiation stability of ion exchange membranes

This article deals with some aspects of γ-radiation stability of (phenolsulfonic acid, PSA) cation exchange membranes synthesized in the laboratory. The changes in cation exchange capacity, moisture content, coion sorption, concentration potential, area resistance, counterion transference number, and solute flux of the membranes were evaluated before and after irradiation. The membrane samples were irradiated under wet conditions using a ⁶⁰Co source up to a total dose of 18.65 Mrads. The experimental data point out the possibility of degradation of PSA membranes beyond a dose of 9.78 Mrads, resulting in the loss of functional groups from membrane matrix.     

Studies on syntheses and permeabilities of special polymer membranes

Summary The permeabilities of various cellulose ester membranes and cellulose membranes were investigated using pure water and aqueous solution of glycerol as feed. In all membranes, the permeation rate for aqueous solution of glycerol was greater than for pure water. The permeation rates of cellulose ester membranes increased with an increase in number of carbon atoms of the substituent group in cellulose ester.     

Studies on syntheses and permeabilities of special polymer membranes

Summary The permeation and separation characteristics of methanol/n-pentanol systems and n-propanol/n-heptane systems through nylon 12 membranes were studied by changing the feed composition of the binary organic mixtures. These characteristics were discussed from the viewpoints of physical and chemical nature of the permeating molecules and the membrane.     

Studies on synthesis and permeability of special polymer membranes

Summary The permeation characteristics of polymer blend membranes from poly(vinylidene fluoride) and poly-(ethylene glycol) to aqueous polymer solution were investigated under carefully controlled conditions. The permeation characteristics were influenced significantly by the blend ratio, the temperature and time of heat treatment, which changed the structure of the resulting membranes.     

Studies on the hydrogen belts of membranes: III. Glycerol permeability of dihydrosphingomyelin-cholesterol membranes

The permeability of an N-oleoyldihydrosphingomyelin bilayer against glycerol was similar to that of a bilayer of phosphatidylcholine with identical effective hydrophobic chain length. Cholesterol at 1∶1 molar ratio reduced the permeability, and also reduced the energy of activation of glycerol penetration, an effect not found for diesterphosphatidylcholine with cholesterol. The higher level of the ground state of the entropy of activation for permeability can be interpreted in terms of a hydrogen belt model which postulates lipid-lipid hydrogen bonding in membranes and explains the effect found as a disturbance of the hydrogen belt structure. Dihydrosphingomyelin can be considered to function as an “extender” in the hydrogen belt network.     

Studies on syntheses and permeabilities of special polymer membranes. VI. Permeation characteristics of cellulose nitrate membranes and cellulose membranes

The permeation characteristics of cellulose nitrate membranes and cellulose membranes were investigated using aqueous solutions of poly(ethylene glycol) as feed. To gain cellulose membranes the nitro groups in cellulose nitrate were converted to hydroxyl groups. It was found that cellulose nitrate membranes separate poly(ethylene glycol) 6000 but not any cellulose membrane did separate poly(ethylene glycol) 20 000.     

Studies with chromium ferricyanide epoxy resin-based membranes

The solid membrane of chromium ferricyanide in epoxy resin has been used as a silver sensitive electrode. The electrode response to silver ions is non-Nernstian, but a linear plot has been obtained in the concentration range 10^?1-10^?3M with a slope of 46 mV per decade of activity. The response time of the electrode is a few seconds and potentials generated are reproducible. The electrode is not specific to silver ions but can nevertheless be used in presence of Hg²⁺, Zn²⁺ and Cd²⁺. Anions show no interference. Silver can be estimated even in the presence of interfering ions by potentiometric titration using the membrane as an end point indicator electrode.     

Studies on syntheses and permeabilities of special polymer membranes, 32. New preparation method of cellulose membranes

The preparation of cellulose membranes from mixtures of cellulose, nonprotonic polar organic solvents, paraformaldehyde, and basic catalyst was studied. When dimethyl sulfoxide was used as casting solvent, the resulting membrane was the densest. An increase of an additional amount of triethyl amine used as basic catalyst gave denser membranes.     

Studies on anhydrous proton conducting membranes based on imidazole derivatives and sulfonated polyimide

Anhydrous proton conducting membranes based on sulfonated polyimide (sPI) and imidazole derivatives were prepared. The acid-base composite membranes show a good chemical oxidation stability and high thermal stability. The addition of imidazole derivatives in sPIs can improve the chemical oxidation stability of the composite membranes enormously, and even much better than that of pure sPI. The proton conductivity of a typical sPI/xUI(2-undecylimidazole) composite membrane can reach 10⁻³ S cm⁻¹ at 180 °C under the anhydrous condition. The proton conductivity of the acid-base composite membranes increases significantly with increasing content of UI. Moreover, UI in sPI/xUI composite membrane is difficult to be brought out by the vapor due to the existence of long hydrophobic moiety, which will improve the stability and lifetime of the membranes in the fuel cells.     

Studies on PVA/AgI-based polymeric membranes for exploration of antibacterial activity

In the present communication, solid polymer electrolyte films have been prepared using solution cast technique based on polyvinyl alcohol (PVA) as host polymer and silver iodide (AgI) as salt. The objective of the study is to develop PVA electrolytic films with AgI and evaluate to protect against simulants of biological warfare agents. The antibacterial activities of the films are explored against Aeromonas hydrophila, Escherichia coli, Salmonella typhii, and Shigella boydii. The antibacterial effects of the PVA/Ag⁺ hybrids were assessed by the minimum inhibitory concentration method. Polymer electrolyte films show good antibacterial activity against A. hydrophilla, S. typhii, and S. boydii. Scanning electron microscopy is used to study the surface morphology of the polymeric membranes. Complex impedance spectroscopy is used for characterizing the electrical and dielectric properties of the electrolyte samples. Frequency-dependent various dielectric properties such as dielectric constant, dielectric loss, and loss tangent have been discussed. The variations of AC conductivity gives the explanation in understanding the mechanism of the ion transport and determine power exponent value n lying in the range 1 and 1.2 which represents the trapping of ions in the polymer matrix.     

Studies on syntheses and permeabilities of special polymer membranes. IV. Permeation characteristics of improved cellulose nitrate membranes

For the purpose of the application of cellulose nitrate membranes for artificial kidneys, the permeation characteristics and the bursting strength of three types of membranes, which were prepared from a system of cellulose nitrate/methyl alcohol/1,4-dioxane/barium perchlorate (CN-1), from a system of cellulose nitrate/methyl alcohol/formamide (CN-2), and a poly(ethylene terephthalate) cloth coated with the casting solution of CN-2 (CN-3), were investigated under various conditions. It was found that permeabilities of these membranes were influenced significantly by the preparation methods of the membranes and the permeation conditions, and they depended upon the structure of the resulting membranes and the interaction between the polymer in the membrane and the feed. In blood filtrations, the permeation rates of our three types of membranes had about four-fold values than a cuprophane membrane, and moreover no protein was found in the blood filtrate. The bursting strength of the membranes swollen with water was in the order CN-3 > cuprophane > CN-2 > CN-1, and this ratio was calculated to be about 5.9:1.0:0.5:0.3