SEM study of the morphology of asymmetric cellulose acetate membranes produced from recycled agro-industrial residues: sugarcane bagasse and mango seeds (original) (raw)

Characterization of asymmetric membranes of cellulose acetate from biomass: Newspaper and mango seed

Carbohydrate …, 2010

Asymmetric membranes may be used in a broad range of applications such as reverse osmosis, hemodialysis and separation of organic mixtures. In this paper, asymmetric membranes were produced using cellulose acetate (CA) from biomass: newspaper and mango seed. The degree of substitution of CA was 2.65 ± 0.07. Different formulations were used to prepare the CA membranes: CA/dichloromethane/water with and without magnesium perchlorate. The asymmetry of the membranes was characterized by scanning electron microscopy (SEM). Membranes produced with magnesium perchlorate presented higher water vapor flux than those produced without this salt. This difference is due to pore formation in the membrane skin when using magnesium perchlorate. Membrane substructure showed to be a determining factor in ion diffusion experiments. The coefficient of ion diffusion for the membrane of cellulose acetate from mango seed was 1.82 Â 10 À8 cm 2 s À1 while for the membrane of cellulose acetate from newspaper was 7.43 Â 10 À8 cm 2 s À1 which similar to the value reported in the literature for commercial CA (8.46 Â 10 À8 cm 2 s À1 ).

Preparation of an Asymmetric Membrane from Sugarcane Bagasse Using DMSO as Green Solvent

Applied Sciences, 2019

Asymmetric cellulose acetate membranes have been successfully fabricated by phase inversion, using sugarcane bagasse (SB) as the starting material. SB is a raw material with high potential to produce cellulose derivatives due to its structure and morphology. Cellulose was extracted from SB by pretreatment with solutions of 5 wt% NaOH, 0.5 wt% EDTA; then bleached with 2 wt% H2O2. Cellulose acetate (CA) was prepared by the reaction between extracted cellulose with acetic anhydride, and H2SO4 as a catalyst. The obtained CA exhibited a high degree of substitution (2.81), determined with 1H-NMR spectroscopy and titration. The functional groups and thermal analysis of the extracted cellulose and the synthesized CA have been investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The change in the crystallinity of the extracted cellulose and CA was evaluated by X-ray diffraction (XRD) spectroscopy. Asym...

Characterization of cellulose triacetate membranes, produced from sugarcane bagasse, using PEG 600 as additive

Polymer Bulletin, 2008

Cellulose Acetate (CA) produced from sugarcane bagasse cellulose was used to produce membranes, using poly(ethylene glycol) (PEG 600) as additive. Results showed that PEG 600 was washed out the membranes during the preparation step. Thermal Analysis showed that the temperature of degradation of the membranes increased in 10 °C when PEG 600 was added to the composition, but did not change as more PEG 600 was added in the composition. On the other hand, the crystalline content (%C) of the membranes increased as PEG 600 was added. The addition of PEG 600 also increased the resistance of the membranes to pressure and the pure water flux rate, but membranes produced with PEG 600 content lower than 5% did not present water flux. PEG 600 also increased the coefficient of ion diffusion of the membranes.

Water flux, DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse, using PEG 600

Polymer Bulletin, 2007

In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water flux measurements (Payne's cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated that the studied membranes present a nontoxic behavior.

Coconut water as a potential resource for cellulose acetate membrane preparation

Polymer International, 2008

BACKGROUND: Cellulose acetate membranes are frequently used for pressure-driven membrane processes. The aim of this work was to prepare cellulose acetate membranes from nata-de-coco using coconut water as starting material. The use of this lignin-free material will certainly minimize the use of chemicals usually needed in the traditional pulps and substitute for the use of wood, which helps prevent global warming and preserves nature as well.

The prediction of cellulose acetate membrane characteristics by recent phenomenological models

DESALINATION AND WATER TREATMENT, 2018

Membrane performance in separation processes is strongly dependent on the membrane structure which must be controlled during the formation step. In this study, a mixture of NMP and acetone with different ratios has been utilized as solvent to prepare cellulose acetate membranes with different morphologies. The membranes formed by 0-25% NMP in NMP/acetone mixture had a sponge-like structure with closed pores. By increasing the NMP concentration from 25 to 50%, the morphological structure of membranes changed from sponge-like to finger-like. Results showed that the common thermodynamic and kinetic parameters of membrane formation could not predict the proportion of solvents in which the primary structural change had occurred. Moreover, the analysis of some phenomenological models pertaining to the phase separation process such as Da, η 0 /X and η 0 /ΔP showed that the recent η 0 /Δp model offered a rather good description of the system morphology with changing mixed solvent composition. A significant finding was that the pure water permeability of membrane was correlated well with the trend predicted by both η 0 /Δp and η 0 /X data points.

Investigation of Porosity, Wettability and Morphology of the Chemically Pretreated Sugarcane Bagasse

Enzymatic hydrolysis is one of the major steps involved in the conversion from sugarcane bagasse to ethanol production. This process shows a higher potential on yields and selectivity, a lower energy costs and a milder operating conditions in comparison to conventional chemical processes. However, the presence of some factors limit the digestibility of the cellulose present in the lignocellulosic biomasses, such as lignin content, degree of crystallinity of cellulose and particle sizes. Pretreatment aims to improve the enzyme access to the substrate. Differences in BET and BJH surface area, pores diameter and volume, structural and morphological changes were investigated by SEM images, X-Ray, FTIR and Wettability for sugarcane bagasse in natura and submitted to two pretreatments: diluted sulfuric acid (1% H 2 SO 4) and alkaline-solution concentrations (1, 2, 3 and 4% NaOH). Results showed that it was possible to observe morphological changes occurred after pretreatments. Acid and alkaline treatments had an increase for both BET and BJH surface areas about 9.2%, diameter and volume of pores also increased. Crystallinity index also increased about 3.6% in the amorphous cellulose and lignin regions degradation. Other experimental techniques, such as FTIR (functional groups, bands and vibrations) and wettability (hydrophobicity and hydrophilicity), were also confirmed the increase in these structural changes. In summary, the pretreatments employed were effective in chemical degradation of lignocellulosic materials for the bioenergy generation.

Preparation of cellulose-rich membranes from wood: effect of wood pretreatment process on membrane performance

Cellulose

In this study cellulose-rich membranes were fabricated from untreated and treated hardwood biomass solutions in 1-ethyl-3-methylimidazolium acetate ([Emim][OAc])—dimetylsulfoxide (DMSO) system via wet phase separation. Wood treatment methods aimed to get purified cellulose fraction of wood. Treatment sequence was as followed: deep eutectic solvent pretreatment, sodium chlorite bleaching, and alkaline treatment. Resulted biomass after each treatment step was characterized by chemical composition and crystalline fraction content. Flat-sheet membranes were produced from biomass samples after each treatment step. Characterization of membranes included measurements of pure water permeability and (poly)ethyleneglycol 35 kDa retention, Fourier-transform infrared and Raman spectroscopy, X-ray diffraction measurements and thermogravimetric analysis. The study revealed that it was possible to fabricate membrane from untreated wood as well as from wood biomass after each of treatment steps. Th...

Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes

In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L 9 orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 • C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).

Structural changes in sugarcane bagasse cellulose caused by enzymatic hydrolysis

Journal of Wood Science

Cellulose I is not completely saccharified to glucose at a low cellulase concentration. In this study, sugarcane cellulose saccharification residues were investigated. Transmission electron microscopy images indicated that the cellulose microfibrils became shorter in the early stages of saccharification and gradually became narrower. The degree of polymerization also decreased in the early stages of saccharification. Cellulose saccharification residues were deuterated by immersing them in deuterium oxide. Infra-red spectra of the deuterated residues indicated that the deuterated hydroxyl group ratio decreased as saccharification progressed. This indicated that cellulose microfibrils were hydrolyzed in their hydrophobic planes by cellulase as if the surfaces were scraped. The increase of hydrophobic planes caused microfibril aggregation, poor accessibility of cellulase to the microfibrils, and a low saccharification rate.