Academic literature on the topic 'Cellulose acetate negatives'

Biofouling, due to the existence of bacteria in water, becomes one of the barriers in cellulose acetate (CA) membrane applications. Although chitosan has been incorporated into CA membranes, its antimicrobial activity has not been improved significantly yet. In this study, cellulose acetate-chitosan membranes were prepared by modification using ZnO and Al2O3 nanoparticles during phase separation method. The membranes were then characterized in term of water permeability, and surface morphology. The anti-bacteria property was examined by using gram-negative bacteria. Modification of cellulose acetate-chitosan membranes with ZnO and Al2O3 nanoparticles have not shown optimal results where no clear zones around the membrane are visible.

Cellulose acetate (CA) is one of the most important esters of cellulose and it was analyzed by means of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and EDX spectra. The FT-IR spectrum presented both the C=O and C�O stretching bands for acetyl groups. The EDX spectrum confirms the presence of C and O elements. The SEM image presented a spongy structure that is important for many applications. The antimicrobial properties of cellulose acetate solutions in acetic acid were determined in tests on two gram-negative species (Pseudomonas aeruginosa - ATCC 27853 and Escherichia coli - ATCC 25822), two gram-positive species (Staphylococus aureus - ATCC 29213 and Streptococcus pyogenes - ATCC 19615) and yeast species (Candida albicans - ATCC 10231). We have shown that samples of cellulose acetate solutions in acetic acid can be used to fight microbial and fungal infections. Of the gram-positive species tested, the strongest antimicrobial effect was observed against S. aureus. The diameter of inhibition zones of cellulose acetate solutions in acetic acid (P1 and P2) for S. aureus far exceeded inhibition zone both of reference substance (gentamicin) and of acetic acid solutions (M1 and M2), given values between 3.15 cm (P1) and 3.55 cm (P2). Also, the results suggested that the studied solutions (P1 and P2) had an antimicrobial effect pronounced for gram-negative species as P. aeruginosa, in which the P1 sample gave an inhibition zone of 2.95 cm, and the P2 sample achieved an inhibition of 3.15 cm. So, the antimicrobial activity of cellulose acetate solutions tested in vitro had a good antimicrobial effect, proportional to the concentration of the active substance.

Supercritical CO2 was used as a green solvent and impregnation medium for loading cellulose acetate beads with carvacrol in order to obtain a biomaterial with antibacterial properties. Supercritical solvent impregnation was performed in a high-pressure view cell at temperature of 50°C and pressures of 10, 21, and 30 MPa with the processing time ranging from 2 to 18 h. The rate of impregnation increased with the pressure increase. However, maximum impregnation yield (round 60%) was not affected by the pressure applied. Selected samples of the impregnated cellulose acetate containing 6–60% of carvacrol were proven to have considerable antibacterial effect against Gram-positive and Gram-negative bacterial strains including methicillin-resistant Staphylococcus aureus which causes severe infections in humans and animals. In addition, cellulose acetate beads containing 6.0–33.6% of carvacrol were shown to have a porous structure with submicron pores which is of interest for the controlled delivery applications.

In this study, the removal of Pb(II), Cu(II), Cd(II), and Zn(II) ions from aqueous solutions was investigated using succinic anhydride modified cellulose monoacetate. In the first part, the cellulose acetate was successfully succinylated in a homogenous medium of DMF using 4-dimethylaminopyridine (DMAP) as a catalyst. The obtained material (AcS) was analyzed by FTIR and CP/MAS 13C NMR Spectroscopy, thermogravimetry analysis and DRX patterns. The titration method was used to determinate the degree of hydroxyl group substituted by carboxyl group (DS) and was found to be 1.36. In the second part, the Bach technique was used to study the effects of pH, contact time, concentration of metals, ionic selectivity and regeneration. Maximum sorption capacities of AcS for Pb(II), Cu(II), Cd(II), and Zn(II) were 241.81, 133.76, 156.61 and 73,58 mg.g-1, respectively. The Langmuir isotherm and the pseudo second order kinetic models provided best fit to the experimental data of metal ion sorption. The nature of the adsorption process was exothermic and spontaneous in nature with negative values of ΔG° and ΔH°. Regeneration of the modified cellulose acetate was accomplished using nitric solution and showed high stability and good recyclability.

Membranes were used in many aqueous applications, including in food processing, e.g., clarification of fruit juices. Typical drawbacks of membrane processes are membrane fouling, which promotes deterioration of processed products. During application of membranes for fruit juice clarification, biofouling occurred as the process deals with food substances. Biofouling is commonly dominated by bacterial attachment and growth on membrane surface, following the deposition of organic molecules from food substances. Natural antibiotics such as Olea europaea leaves extract might be used to improve the antibiofouling properties of membranes due to its phenolic contents. In this work, Olea europaea substances were obtained by extraction to get the green active solid nanoparticles. Phenolic green nanoparticles then filled into cellulose acetate as membrane matrix. The mixed matrix membrane, therefore, has a safe antibiofouling properties and is suitable for food application. The anti-biofoulant effect has been proven by decreasing bacterial attachment down to 23% from initial condition, especially for Gram-negative bacteria such as Eschericia coli.

Abstract This study presents the successful development of cellulose fiber based membranes embedded with silver nanoparticles. These fine fiber membranes were developed utilizing the Forcespinning (FS) technique followed by alkaline hydrolysis treatment. The fiber morphology, homogeneity and yield were optimized by varying spinning parameters such as polymer concentration and angular velocity of the spinnerets. The structure, thermal and mechanical properties, and water absorption capability of the developed membranes were investigated. The cellulose acetate (CA) present in the membrane was converted to cellulose in the presence of embedded silver nanoparticles by alkaline hydrolysis. The silver nanoparticles embedded cellulose membrane exhibits outstanding water absorption capacity with fast uptake rate. Its high porosity, three-dimensional network structure with well-interconnected pores, as well as the intrinsically highly hydrophilic nature of cellulose material greatly favor its potential application as wound dressings. The antimicrobial activity was evaluated by the disk diffusion method. The composite membranes exhibit excellent antimicrobial activity against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus, owing to the slow and sustained release of embedded silver nanoparticles.

The demand for substitution of fossil-based materials by renewable bio-based materials is increasing with the fossil resources reduction and its negative impacts on the environment. In this study, environmentally friendly regenerated cellulose films were successfully prepared using 1-allyl-3-methylimidazolium chloride (AmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl), 1-ethyl-3-methylimidazolium chloride (EmimCl), and 1-ethyl-3-methylimidazolium acetate (EmimAc) as solvents, respectively. The results of morphology from scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that all the cellulose films possessed smooth, highly uniform, and dense surface. The solid-state cross-polarization/magic angle spinning (CP/MAS)13C NMR spectra and X-ray diffraction (XRD) corroborated that the transition from cellulose I to II had occurred after preparation. Moreover, it was shown that the ionic liquid EmimAc possessed much stronger dissolubility for cellulose as compared with other ionic liquids and the cellulose film regenerated from EmimCl exhibited the most excellent tensile strength (119 Mpa). The notable properties of regenerated cellulose films are promising for applications in transparent biodegradable packaging and agricultural purpose as a substitute for PP and PE.

ABSTRACTThe lack of consumable water in urban and industrial-dense areas encourages research on clean water treatment methods. Some current treatment methods, such as precipitation, adsorption, and UV light irradiation are ineffective for water with high levels of suspended solids, organic matter, and turbidity. Therefore, alternative approaches are required to support the availability of clean and consumable water. The membrane technology is an alternative filtration method proposed in the East Surabaya's municipal waterworks area. The membrane filtration method is quite simple and easy to operate. This study aimed to determine the performance of cellulose acetate-based porous plate membranes synthesized by phase inversion for E. coli bacteria's ultrafiltration. As a raw material, cellulose acetate is preferred because of its high hydrophilicity and good biocompatibility. Membrane synthesis was carried out through the phase inversion method with acetone solvents and non-solvent water in the coagulation bath. The positive test for E. coli bacteria was carried out through the MPN (Most Probable Number) method on the municipal waterworks water samples before and after filtering with membranes. The results showed that the synthesis of cellulose acetate membrane had good homogeneity. This result was supported by the results of ANOVA single factor statistical data analysis. Also, cellulose acetate membrane had good permeability and flux performance as ultrafiltration of E. coli bacteria with a flux of 37.25 L/m2.hour.bar at a sufficient pressure of 5 bar. Test results for the presence of E. coli bacteria in PDAM water samples using the MPN method gave an initial indication that the water sample after filtration with cellulose acetate membrane was negative. Keywords: membrane, cellulose acetate, permeability, water fluxABSTRAKMinimnya air bersih yang layak konsumsi di daerah perkotaan dan padat industri mendorong penelitian tentang metode pengolahan air bersih. Kurangnya efektivitas metode pengolahan sebelumnya seperti pengendapan, adsorbsi, dan penyinaran dengan sinar UV untuk air dengan kadar suspended solids, zat organik, dan kekeruhan yang tinggi, diperlukan metode alternatif untuk mendukung ketersediaan air bersih layak konsumsi. Metode filtrasi alternatif yang ditawarkan di PDAM di kawasan Surabaya Timur. Metode filtrasi dengan membran sangat sederhana dan mudah dalam operasionalnya. Penelitian ini bertujuan untuk mengetahui kinerja membran plat berpori berbasis selulosa asetat yang disintesis secara inversi fasa untuk ultrafiltrasi bakteri E.coli. Selulosa asetat dipilih sebagai bahan baku membran karena selulosa asetat merupakan bahan polimer yang memiliki hidrofilitas tinggi dan biokompatibilitas yang baik. Sintesis membran dilakukan melalui metode inversi fasa dengan pelarut aseton dan nonpelarut air dalam bak koagulasi. Uji positif bakteri E.coli dilakukan melalui metode MPN (Most Probable Number) pada sampel air PDAM sebelum dan sesudah difiltrasi dengan membran. Hasil penelitian menunjukkan bahwa sintesis membran selulosa asetat memiliki homogenitas baik yang ditunjukkan oleh hasil analisis data statistika ANOVA single factor. Selain itu, membran selulosa asetat memiliki kinerja permeabilitas dan fluks yang baik sebagai ultrafiltrasi bakteri E.coli dengan ketercapaian fluks sebesar 37,25 L/m2.jam.bar pada tekanan efektif sebesar 5 bar. Hasil uji keberadaan bakteri E.coli pada sampel air PDAM dengan metode MPN memberikan indikasi awal bahwa sampel air setelah filtrasi dengan membran selulosa asetat adalah negatif.Kata kunci: membran, selulosa asetat, permeabilitas, fluks air

Cellulose-based membrane materials allow for separations in both aqueous solutions and organic solvents. The addition of nanocomposites into cellulose structure is facilitated through steric interaction and strong hydrogen bonding with the hydroxy groups present within cellulose. An ionic liquid, 1-ethyl-3-methylimidazolium acetate, was used as a solvent for microcrystalline cellulose to incorporate graphene oxide quantum dots into cellulose membranes. In this work, other composite materials such as, iron oxide nanoparticles, polyacrylic acid, and lignin sulfonate have all been uniformly incorporated into cellulose membranes utilizing ionic liquid cosolvents. Integration of iron into cellulose membranes resulted in high selectivity (>99%) of neutral red and methylene blue model dyes separation over salts with a high permeability of 17 LMH/bar. With non-aqueous (alcohol) solvent, iron–cellulose composite membranes become less selective and more permeable, suggesting the interaction of iron ions cellulose OH groups plays a major role in pore structure. Polyacrylic acid was integrated into cellulose membranes to add pH responsive behavior and capacity for metal ion capture. Calcium capture of 55 mg Ca2+/g membrane was observed for PAA-cellulose membranes. Lignin sulfonate was also incorporated into cellulose membranes to add strong negative charge and a steric barrier to enhance antifouling behavior. Lignin sulfonate was also functionalized on the commercial DOW NF270 nanofiltration membranes via esterification of hydroxy groups with carboxyl group present on the membrane surface. Antifouling behavior was observed for both lignin-cellulose composite and commercial membranes functionalized with lignin. Up to 90% recovery of water flux after repeated cycles of fouling was observed for both types of lignin functionalized membranes while flux recovery of up to 60% was observed for unmodified membranes.

Cellulose, a carbohydrate polymer of :ß-D-glucose, occurs in several different crystalline forms called allomorphs. “Cellulose II” is by far the most abundant allomorph found in nature, but a few organisms have been suggested to synthesize another crystalline form called “cellulose II” (summarized in). Some of these reports are now considered uncertain due to the presence of clay contaminants or because extractions requiring high concentrations of alkali can convert cellulose I to cellulose II. Because identification of organisms that synthesize native cellulose II could help further understanding of how cellulose crystallization occurs, we have reexamined several of the organisms suggested to produce this allomorph. Care was taken to minimize the atrifacts mentioned above. Included in this study were the algae HalicystisandEnteromorpha, and the slime mold Dictyostelium.In the course of our studies, we have also found that certain mutants of the bacterium Acetobacter xylinum synthesize cellulose II instead of the cellulose I allomorph produced by the wild type.Bacterial cellulose was purified from mutants of Acetobacter xylinum as previously described. After extraction in organic solvents, cellulose was purified from Halicystis (UTEX strain 1260) by brief treatment with 15-20% HCl at 100°C and extraction with 1N NaOH and 0.25M NaBH4 (2 x 30 minutes, 100°C). The ultrastructure of these samples were examined by negative staining with uranyl acetate. Cellulose from Enteromorpha (UTEX strain 739) was purified as described above or extracted by soaking overnight in 24% KOH at room temperature. X-ray diffraction powder patterns were recorded with a Debye-Scherrer camera and Cu k-alpha radiation. The crystalline form of cellulose from stalks of Dictyostelium discoidium was studied by electron diffraction. Individual stalks were harvested and cleaned in dilute HCl. Electron diffraction patterns produced at 120 kV were recorded on Kodak 35 mm Tri-X film.

This thesis aims to examine the issues involved in utilising digital images and assess whether image processing techniques can be used as a cost-effective method of reconstructing the image found in a deteriorated cellulose acetate negative. Negatives affected by the vinegar syndrome are found in large numbers within Australian institutions. This was confirmed by a survey (using a questionnaire) undertaken at the National Library of Australia in 2000. The survey also found that although these collections are large, and hence the level of deterioration variable, little could be done to restore any of the negatives once deterioration had begun. Storing negatives at low temperature and low relative humidity slows down the breakdown of cellulose acetate; however, it cannot reverse the process once it has commenced. Although removing the gelatine pellicular from the deteriorated cellulose acetate support (making the image easier to view) a possible method of restoration, this becomes unfeasible when dealing with a large collection. As a result, how to manage cellulose acetate negatives once they have deteriorated becomes problematic. Image-processing techniques used to digitally restore these negatives were examined via a series of case studies. These examinations were undertaken using two software packages-the Image Processing Tool kit (IPTK) and OPTIMAS. Deteriorated cellulose acetate negatives were scanned, then a number of program filters were applied to the digital image to determine whether disfiguring elements (referred to as channelling elements) resulting from the deteriorated support could be digitally removed. IPTK and OPTIMAS were not completely successful in removing the deteriorated elements from the digital version. The results highlighted that a number of issues relating to the use of digital technology needed to be addressed. These issues included knowledge of basic technical terms, an understanding of digital language, and how to include the use of digital technology into a long-term strategy for archiving a digitised collection. This thesis showed that issues relating to utilising digital systems could be addressed by implementing a preservation management plan. A preservation management plan can be used to incorporate the goals of digitising, the long-term issues of retaining digital files, ongoing access relating to the digital file, hardware and software, and the importance of having the relevant expertise when undertaking such a project. Due to the limitations of the printed hardcopy displaying features in a number of the images (figures) outlined in this thesis, a compact disk (CD) has been included with this submission and can be found at the end of this document.