Hydrophilic Cellulose Acetate Membrane Research Articles

A sandwich-like silk fibroin/polysaccharide composite dressing with continual biofluid draining for wound exudate management

Optimal wound healing requires a wet microenvironment without over-hydration. Inspired by capillarity and transpiration, we have developed a sandwich-like fibers/sponge dressing with continuous exudate drainage to maintain appropriate wound moisture. This dressing is prepared by integrating a three-layer structure using the freeze-drying method. Layer I, as the side that contacts with the skin directly, consists of a hydrophobic silk fibroin membrane; Layer II, providing the pumping action, is made of superabsorbent chitosan-konjac glucomannan sponge; Layer III, accelerating evaporation sixfold compared to natural evaporation, is constructed with a graphene oxide soaked hydrophilic cellulose acetate membrane. Animal experiments showed that the composite dressing had superior wound-healing characteristics, with wounds decreasing to 24.8% of their original size compared to 28.5% for the commercial dressing and 43.2% for the control. The enhanced wound healing can be ascribed to the hierarchical porous structure serves as the fluid-driving factor in this effort; the hydrophilicity of a membrane composed of silk fibroin nanofibers is adjustable to regulate fluid-transporting capacity; and the photothermal effect of graphene oxide guarantees exudates that have migrated to the top layer to evaporate continuously. These findings indicate the unidirectional wicking dressing has the potential to become the next generation of clinical dressings.

Modeling of fouling and foulant attachments on heterogeneous membranes in ultrafiltration of latex solution

The aim of the present study was to obtain the predictive models that would allow for the accurate estimation of the depositional and coagulation attachments, at different operational conditions and using heterogeneous membranes with non-uniform pore size. The fouling attachments predicted by the model can in turn be applied in estimation of the added mass due to fouling and the increase in transmembrane pressure using the developed fouling model applicable in the case of non-uniform pore size membranes. The fouling model and the correlations found in the present study form a comprehensive set of predictive models, generalized for the applications of hydrophilic membranes to a variety of materials with different molecular weight cut off (MWCO) values. The effects of the operating conditions on the fouling attachments, mass of fouling, cake layer, and permeate flux in ultrafiltration of latex solution using heterogeneous membranes was also investigated. Polysulfone flat membrane with MWCO of 60,000 was used under a constant flow rate and cross-flow mode in ultrafiltration of the latex paint solution. Response Surface Methodology (RSM) was implemented in the experimental design. Furthermore, hydrophilic Ultrafilic membranes and hydrophobic Polyvinylidene Difluoride membranes, with a MWCO of 100,000, and hydrophilic cellulose acetate membranes, with a MWCO of 20,000, were used to test the accuracy of the correlations for applications with non-uniform pore size membranes. The model well predicted the deposition attachment of diverse hydrophilic membranes with different MWCO values.

A simple cellulose acetate membrane-based small lanes technique for protein electrophoresis

Combining electrophoresis with a cellulose acetate membrane-based technique, we developed a simple and low-cost method, named cellulose acetate membrane-based small lanes (CASL), for protein electrophoresis. A home-made capillary plotter controlled by a 3D moving stage was used to create milli-to-micro channels by printing poly(dimethylsiloxane) on to a hydrophilic cellulose acetate membrane. In the hydrophilic channels, 5 nL protein mixture was separated on the basis of electro-migration under an electric field. Compared with polyacrylamide gel electrophoresis (PAGE), CASL resulted in higher protein signal intensity for separation of mixtures containing the same mass of protein. The platform was easily fabricated at low cost (approx. $0.005 for each 1-mm-wide channel), and separation of three protein mixtures was completed in 15 min. Both electrophoresis time and potential affected the separation. Rather than chromatographic separation, this method accomplished application of microchannel techniques for cellulose acetate membrane-based protein electrophoresis. It has potential in proteomic analysis, especially for rapid, low-cost, and low-volume sample analysis in clinical diagnosis.

Mechanisms and factors influencing the removal of microcystin-LR by ultrafiltration membranes

In this study, we investigate the application of ultrafiltration (UF) for the removal of the cyanotoxin, microcystin-LR, and determine the dominant removal mechanisms. System variables examined included membrane characteristics, feed concentration, water recovery and operating pressure. While adsorption dominated rejection for most UF membranes, at least at early filtration times, both size exclusion and adsorption were important in removing microcystin-LR by the tight thin-film (TF) membranes. Adsorption was primarily attributed to hydrophobic interactions, although hydrogen bonding and physical surface properties such as surface roughness, thickness, and porosity may also play a role. Polysulfone membranes, the most hydrophobic membrane examined, significantly adsorbed microcystin-LR (∼91%), whereas the more hydrophilic cellulose acetate membranes adsorbed little or no microcystin-LR. The initial feed concentration had a significant influence on the adsorption capacity of TF membranes for microcystin-LR, which could be described based on a linear adsorption isotherm. An increase in water recovery and/or operating pressure led to an increase in the adsorption of microcystin-LR, probably due to increased convective transport. On the other hand, microcystin-LR rejection through size exclusion was reduced for higher water recovery and/or applied pressure.

Fabrication of a lithium chloride solution based composite supported liquid membrane and its moisture permeation analysis

A novel composite supported liquid membrane has been prepared for ventilation air moisture recovery. The membrane is composed of three layers: two hydrophobic protective layers and a sandwiched hydrophilic support layer in which LiCl solution is immobilized to facilitate water vapor transfer. A test is conducted to measure the moisture permeation rate through the composite membrane. Various resistances in the cell and in the composite membrane are clarified. Linear equilibrium relations between humidity, temperature, and LiCl concentration in the liquid solution layer are obtained to aid in the model set-up. It has been found that the mean moisture permeation rate through the composite membrane is around 1.14 × 10 −4 kg m −2 s −1, almost two times higher than that through a solid hydrophilic cellulose acetate membrane with comparative thickness. Further, the supported liquid layer only accounts for 12% of the total moisture transfer resistance in the cell, indicating that there is much potential for further performance improvement.

Anti-Fouling Effect of Bentonite Suspension in Ultrafiltration of Oil/Water Emulsion

The effect on membrane fouling resistance during ultrafilration of oil/water emulsion with the presence of bentonite suspension is experimentally evaluated. The fouling resistance was analyzed as a function of different membrane types and bentonite concentration. The total membrane fouling was categorized into reversible and irreversible, by adopting an appropriate chemical cleaning technique. The results revealed a 40 % flux augmentation with the increase of bentonite concentration up to an optimum value of 300 mg l−1 for cellulose acetate membrane. Further increase of bentonite concentration led to particle deposition on the membrane surface and reduced the flux. The polysulfone membrane did not show a similar flux improvement. This could be due to its high hydrophobicity. The absorption of oil/water emulsion on bentonite increased TOC removal rate from 65% to 80%, and this effect was the major cause of reduction in gel layer formation on the membrane surface. The extent of irreversible fouling of the hydrophilic cellulose acetate membrane was much smaller than that of the polysulfone membrane. These experiments demonstrated that, presence of bentonite could induce transformation of irreversible fouling caused by oil emulsion to reversible fouling, which could be periodically chemically cleaned.

The behavior of membrane fouling initiation on the crossflow membrane bioreactor system

A membrane bioreactor (MBR) system (i.e. an activated sludge system where the clarifier has been replaced with membrane filtration) has many advantages compared with the conventional activated sludge process. However a serious problems that has prevented this technology from reaching its potential is membrane fouling. In this study, the biomass was cultivated under three conditions: normal (high dissolved oxygen, DO); bulking; and normal conditions with low DO concentration. Membrane filtration tests were performed with cellulose acetate (CA), sulfonated polyethersulfone (SPES) and polyethersulfone (PES) membranes, respectively. Relatively hydrophobic PES membranes fouled more seriously than hydrophilic CA membranes. This phenomenon was especially significant under bulking conditions. Ultimate flux was almost equal for all three membrane types however, since the PES and SPES started with higher initial fluxes. Effluent quality was not affected by membrane fouling/flux but did deteriorate at low DOs.

Triacylglycerol hydrolysis by lipase in a flat membrane bioreactor

Hydrolysis of olive oil into fatty acids by lipase in a flat membrane module is reported. Lipase was immobilized by adsorption onto a hydrophilic cellulose acetate membrane. Hydrolysis was carried out by circulating pure olive on the enzyme side of the membrane and water phase on the other side. Conversion reached 85 % after 50 hours reaction time.

Selective concentration of metal ions through a hydrophobic membrane with a chelating agent

Selective concentration of metal ions was attempted with the expectation that the solvent phase in the solvent extraction method may be replaced by a membrane. Metal ions in aqueous solutions containing acetylacetone as a chelating agent permeated through a membrane under a pressure gradient. In the case of a hydrophobic polystyrene membrane, cupric ions were selectively concentrated, while in the case of a hydrophilic cellulose acetate membrane, ions were rejected. The maximum enrichment of Cu 2+ ions by the polystyrene membrane was about 1.7-fold. Co 2+ and Zn 2+ were also concentrated, but Cd 2+ and Fe 3+ were rejected in this membrane system.