Cellulose Acetate Type Research Articles

Hydrophobic Cellulose Acetate Aerogels for Thermal Insulation.

As naturally derived material, cellulose aerogels have excellent thermal insulation properties due to their unique high porosity and three-dimensional mesoporous structure. However, its hydrophilic properties limit its application in the field of building insulation. Here, we propose a method to prepare high hydrophobicity by adopting the sol-gel method and chemical vapor reaction strategy using cellulose acetate type II as raw material and 2,4-toluene diisocyanate as the cross-linking agent. Thermal properties of cellulose acetate aerogels (CAAs) were measured, where pyridine was the catalyst, acetone was the solvent, and perfluorodecyltriethoxysilane (PFDS), hexamethyldisilazane (HMDS), and methyltriethoxysilane (MTES) were used as hydrophobic agents (by process hydrophobic test). Compared with MTES-modified cellulose acetate aerogels (M-CAAs) and HMDS (H-CAAs)-modified cellulose acetate aerogels, PFDS-modified (P-CAAs) cellulose acetate aerogels are the most hydrophobic. By implementing hydrophobic modification of PFDS both inside and outside the structure of cellulose acetate aerogels, the water contact angle can reach up to 136°, strongly demonstrating the potential of PFDS as a hydrophobic agent. The results show that the thermal conductivity and compressive strength of cellulose acetate aerogel with the best hydrophobic properties are 0.035 W m−1 K−1 at normal pressure and 0.39 MPa at 3% strain, respectively. This work shows that the highly hydrophobic cellulose acetate aerogel has potential as a waterproof material in the field of building thermal-insulation materials.

Neoteric approach for efficient eco-friendly dye removal and recovery using algal-polymer biosorbent sheets: Characterization, factorial design, equilibrium and kinetics

A new approach of algal-polymer -sheets was performed by the embedding of two algal seaweeds (Ulva fasciata and Sargassum dentifolium) into cellulose acetate (CA) polymer forming two types of cellulose acetate; Ulva (CA-U) and Sargassum (CA-S) sheets. Afterward, the two sheets were characterized then subjected to 3-Rs evaluation (Removal, Recovery, and Reuse) of methylene blue dye (MB). Characterization data exhibited good properties for biosorption process. Algal biosorbents achieved more than twice biosorption capacity (Qmax) after the embedding into the polymer sheet. Additionally, according to factorial design data, the contact time and the dose of biosorbents had positive effects on the biosorption in the two sheets. Freundlich, Langmuir, and pseudo-second order models displayed good represented data in the two sheets. Furthermore, the two sheets (CA-U, followed by CA-S sheet) were successfully given more than 98% adsorption of 273 mg/l MB concentration. Moreover, the recovery and reuse data proved that the two sheets can be performed in good behavior for more than three cycles.

Ultra-Trace Determination of Lead(II) in Water Using Electrothermal Atomic Absorption Spectrometry after Preconcentration by Solid-Phase Extraction to a Small Piece of Cellulose Acetate Type Membrane Filter

A simple and inexpensive preconcentration technique has been developed for the ultra-trace determination of lead(II) using electrothermal atomic absorption spectrometry (ETAAS). The lead(II) complex with dicyclohexano-18-crown 6-ether (DC18C6) was extracted to a small piece of cellulose acetate-type membrane filter (2 × 5 mm) merely by vigorously eccentric stirring for 120 min under the coexistence of sodium dodecyl sulfate (SDS) at around pH 7. The extraction medium was inserted into a graphite cuvette for the determination of lead(II) by ETAAS. A linear relation was obtained for the range of 0.1-5.0 ng in 10 ml of lead(II) standard solution (r = 0.998). The detection limit was found to be 0.03 ng of lead(II) in 10 ml (0.003 µg l(-1)) of water sample. The proposed method was applied to the ultra-trace determination of lead(II) in river water, underground water, tap water, and snow fall samples.

Study of ultrafiltration of a single and binary protein solution in a thin spiral channel module

The aim of this paper is to demonstrate the factors influencing a protein filtration process. Therefore single and mixed solutions of lysozyme and myoglobin were ultrafiltered through a hydrophilic membrane (cellulose acetate type) with a molecular weight cutoff (MWCO) of 30 kDa. The proteins are of similar molar mass and size. Filtration was done using a thin spiral channel module (TCF10). The change in transmission and flux was evaluated and the data of the single protein solutions compared with the binary protein mixture. Further, the effects of Dean vortex formation, was evaluated. From the collected data the effects of the parameters dominating the filtration process were assessed. By comparing the experimentally obtained mass transfer coefficients with literature data, it can be seen that the curved channel led to an increased mass transfer as compared with classical modules. For both proteins, a Sherwood correlation was derived and based on these data a separation process was modeled. Results obtained from separation experiments correlated well with the developed model. It could be shown that the separation of proteins by ultrafiltration is possible, but for proteins bearing similar molar masses it is a difficult task. Separation factors up to 2.5 were achieved. As expected the selectivity increases with the crossflow velocity and decreasing transmembrane pressure (TMP). The separation process requires careful choice of the pH value and the ionic strength. Further, attention has to be paid to the membrane stability and protein solubility while varying the pH value.

Studies on protein transmission in thin channel flow module: the role of dean vortices for improving mass transfer

This study is mainly comprised of evaluating mass transfer coefficient from the volumetric flux and protein transmission data in a thin channel flow module. Dilute solutions of lysozyme were ultrafiltered through hydrophilic membrane (cellulose acetate type) with molecular weight cut off (MWCO) of 30,000. Experiments were performed in thin channel flow (TCF10) configuration and data for transmission and volumetric flux obtained as a function of pressure and cross flow velocity. The results were analysed keeping into account the formation of Dean vortices and it was seen that the presence of Dean vortices gave better performance in terms of mass transfer. The mass transfer coefficient obtained with Dean vortices was comparable with the other commercial cross flow system involving secondary flow like Taylor vortices. A new mass transfer correlation has also been presented and compared with the reported correlations in literature.

Membrane Concentration and Separation of L-Aspartic Acid and L-Phenylalanine Derivatives in Organic Solvents

Abstract The concentration and separation of the amino acids N-benzyloxycarbonyl L-aspartic acid and L-phenylalanine methyl ester hydrochloride in organic solvents have been investigated using reverse osmosis membranes of two types of cellulose acetate, a nanofiltration membrane of polyamide-polyphenylene sulfone (PA-PPSO) composite and a gas separation membrane of polyimide composite in a stirred batch cell. The organic solvents used included primary, secondary, and tertiary alcohols, an ester, and a ketone. There were significant variations in permeate flux, solute rejection, and membrane stability. Usually the rejection of both amino acids was similar; however, certain membrane-solvent combinations gave significantly different levels of rejection. The highest rejection of amino acids (∼0.94) at the lowest pressure of 0.5 MPa was obtained with the PA-PPSO membrane using methanol as a solvent. The cellulose acetate membranes gave reasonable rejection and fluxes but the membrane stability was very poor. The performance of the polyimide composite membrane was good with ethanol but poor with other solvents. The PA-PPSO membrane with methanol as solvent appeared the most promising combination, and the separation performance according to concentration polarization was discussed.

Performance of a cellulose acetate permeator with permeability‐influenced feed

We study the effect of variable permeabilities on the performance of a permeator employing a cellulose acetate type of membrane. The experiments were conducted using a CO 2 -N 2 mixture. The variation in the permeabilities of CO 2 and N 2 with the pressure and the feed composition has been measured experimentally, and statitical models have been fitted to the data. The experimental data have been compared with theoretical results obtained using a perfect mixing model which incorporated variable permeabilities.

Purification and Concentration of Betalaines by Ultrafiltration and Reverse Osmosis

ABSTRACTBeet juices prepared by solid‐liquid extractions were processed by ultrafiltration (UF) and reverse osmosis (RO) to 30°Brix at 20°C. De Danske Sukkerfabrikker (DDS) UF/RO Lab Module‐20 plate‐and‐frame system was used having a 0.72‐m2 effective membrane area and pressures from 50‐40 bar. After prefiltering, pectinase treated juices were sequentially processed through 20,000 and 6,000 (UF) molecular weight (MW) cut‐off membranes. The UF purified products were then concentrated by RO processes on several types of cellulose acetate (CA) membranes, one with a 500 MW cut‐off and 70% NaCl permeability provided colorants that were separated from a majority of soluble solids. Addition of invertase to pectinase‐treated juices decreased flux but yielded a three‐fold increase in betalaine concentration on a dry weight basis. Betalaine concentration by UF and RO processes also halved nitrate level and greatly reduced flavor.

Study of overlapping transitions in polymers by combined differential scanning calorimetry and thermal optical analysis methods

In some polymers, thermal transitions and molecular relaxation processes may be situated closely together on the temperature scale or may actually overlap. In such cases, observations by differential scanning calorimetry. (DSC) may lead to ambiguous results or to erroneous conclusions. In many instances, the ambiguity can be removed by making additional measurements at the same scanning rate on polymer samples of similar past history by thermal optical analysis (TOA). The combined use of these two types of measurements, DSC and TOA, is here applied to a study of transitions and structural changes in several types of cellulose acetate. From the results obtained, it is possible to resolve and identify various overlapping thermal processes such as the glass transition of the polymer chains, subsequent crystallization, melting of ordered phases and thermal degradation.

Hyperfiltration studies XVIII. The optimization of two-stage plants for desalination of brackish waters

A computer program was developed for parametric analysis of hyperfiltration with one- and two-stage plants where each stage could be divided into sections Provisions are made in the code to permit repressurization between sections through booster pumps and to allow for recirculation of solution within each section with a separate pump. With the code optimum costs can be obtained (optimum pressures and cross-flow velocities) at fixed water recoveries. The code was applied to cost analyses of hyperfiltration of salt solutions with 1,000 to 5,000 ppm of salt and with membranes of assumed permeabilities of 0.3 to 15 gal/day·ft 2·atm.Most calculations were for an ion exchange membrane for which rejection decreases with salt concentration from 92% for 1,000 ppm solution to 81% for 5,000 ppm solution. Some calculations were also carried out for a membrane with characteristics representative of cellulose acetate (rejection 95% and permeability 0.5 gal/day·ft 2·atm). As conditions were changed which caused a transition between one- and two-stage plants, costs changed smoothly. Conditions were found where two-stage plants produced cheaper water than one-stage plants. Two-stage plants can use more highly permeable membranes than one-stage plants. For feed concentrations up to 4,000 ppm, lower costs were obtained with the moderately rejecting high flux membranes than with the cellulose acetate type, if plant costs per unit membrane area are equal. Under some conditions, plants combining the two membrane types may be more economical than plants using either type exclusively.

Electrophoretic separation of soluble rat liver cell proteins on gelatinized cellulose acetate

Soluble rat liver cell proteins have been separated by electrophoresis on filter paper (1, 2) cellulose acetate (3), and starch gel (4) and by the Tiselius method (5). Although each of these approaches has its disadvantages, the main problem with cellulose acetate is drying of the strips during sample application and electrophoresis at higher voltages. Recently, a new type of gelatinized cellulose acetate, Cellogel, became available (Colab Laboratories, Chicago Heights, Illinois). This product is not prone to drying, and gives superior separations of liver cell proteins when compared with four other types of cellulose acetate.

Separation of Hydrocarbon Liquids by Flow Under Pressure Through Porous Membranes

Abstract : Three different types of porous films were used in the experiments. Two types of cellulose acetate and one type of polyethylene were used. The feed solution systems tested were xylene-ethyl alcohol, xylene-n-heptane, and n-heptane-ethyl alcohol. The operating cell consists of a stainless steel pressure chamber of two detachable parts. The film is mounted on a stainless steel porous plate embedded in the lower part of the cell through which the membrane permeated liquid leaves the system at atmospheric pressure. The upper part of the cell contains the feed solution under pressure in contact with the membrane. The separation technique was successful in all the cases tested.