Multimodal Characterization of Hierarchically Porous Nanocomposite Materials: The Case Study of the PEARL Membrane (original) (raw)
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On the nanostructure of micrometer-sized cellulose beads
Analytical and Bioanalytical Chemistry, 2011
The analysis of the porosity of materials is an important and challenging field in analytical chemistry. The gas adsorption and mercury intrusion methods are the most established techniques for quantification of specific surface areas, but unfortunately, dry materials are mandatory for their applicability. All porous materials that contain water and other solvents in their functional state must be dried before analysis. In this process, care has to be taken since the removal of solvent bears the risk of an incalculable alteration of the pore structure, especially for soft materials. In the present paper, we report on the use of small-angle Xray scattering (SAXS) as an alternative analysis method for the investigation of the micro and mesopores within cellulose beads in their native, i.e., water-swollen state; in this context, they represent a typical soft material. We show that even gentle removal of the bound water reduces the specific surface area dramatically from 161 to 109 m 2 g −1 in cellulose bead sample type MT50 and from 417 to 220 m 2 g −1 in MT100. Simulation of the SAXS curves with a bimodal pore size distribution model reveals that the smallest pores with radii up to 10 nm are greatly affected by drying, whereas pores with sizes in the range of 10 to 70 nm are barely affected. The SAXS results were compared with Brunauer-Emmett-Teller results from nitrogen sorption measurements and with mercury intrusion experiments.
Carbohydrate Polymers, 2016
In this study, cellulose based scaffolds were produced by electrospinning of cellulose acetate (CA) solution followed by its saponification with NaOH/ethanol system for 24 h. The resulting nonwoven cellulose mat was treated with sodium borohydride (SB) solution. In situ hydrolysis of SB solution into the pores of the membrane produced hydrogen gas resulting a three-dimensional (3D) cellulose sponge. SEM images demonstrated an open porous and loosely packed fibrous mesh compared to the tightly packed singlelayered structure of the conventional electrospun membrane. 3D cellulose sponge showed admirable ability to nucleate bioactive calcium phosphate (Ca-P) crystals in simulated body fluid (SBF) solution. SEM-EDX and X-ray diffraction studies revealed that the minerals deposited on the nanofibers have the nonstoichiometric composition similar to that of hydroxyapatite, the mineralized component of the bone. 3D cellulose sponge exhibited the better cell infiltration, spreading and proliferation compared to 2D cellulose mat. Therefore, a facile fabrication of 3D cellulose sponge with improved mineralization represents an innovative strategy for the bone tissue engineering applications.
Porous and non-porous cellulose acetate (CA) – cellulose nanocrystal (CNC) electrospun nanocomposite fibers and electrosprayed-electrospun composite membranes were fabricated using two different binary solvent systems. To evaluate the expression of CNC as the active entity in the membrane, dye adsorption studies were carried out using Victoria Blue. To overcome the low surface area of thick porous fibers, a porous electrosprayed-electrospun composite has developed which exhibited 98% dye removal compared to non-porous counterparts (67.9%). The porous membrane with CNC showed an increase of 38 mV in surface zeta potential compared to 9 mV increases in the case of the nonporous membrane and after the dye adsorption, it maintained the negative charge, indicating that further adsorption is feasible. Moreover, the mechanical properties of porous fibers were found to be tenfold better than that of nonporous fibers. Creating porous CA-CNC composites is demonstrated as a tool for ensuring better exposure of active materials during the adsorption reaction.
Nanomaterials, 2019
Thin-film nanocomposite membranes (TFNs) are a recent class of materials that use nanoparticles to provide improvements over traditional thin-film composite (TFC) reverse osmosis membranes by addressing various design challenges, e.g., low flux for brackish water sources, biofouling, etc. In this study, TFNs were produced using as-received cellulose nanocrystals (CNCs) and 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNs) as nanoparticle additives. Cellulose nanocrystals are broadly interesting due to their high aspect ratios, low cost, sustainability, and potential for surface modification. Two methods of membrane fabrication were used in order to study the effects of nanoparticle dispersion on membrane flux and salt rejection: a vacuum filtration method and a monomer dispersion method. In both cases, various quantities of CNCs and TOCNs were incorporated into a polyamide TFC membrane via in-situ interfacial polymerization. The flux and rejection performance of the resulting membranes was evaluated, and the membranes were characterized via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The vacuum filtration method resulted in inconsistent TFN formation with poor nanocrystal dispersion in the polymer. In contrast, the dispersion method resulted in more consistent TFN formation with improvements in both water flux and salt rejection observed. The best improvement was obtained via the monomer dispersion method at 0.5 wt% TOCN loading resulting in a 260% increase in water flux and an increase in salt rejection to 98.98 ± 0.41% compared to 97.53 ± 0.31% for the plain polyamide membrane. The increased flux is attributed to the formation of nanochannels at the interface between the high aspect ratio nanocrystals and the polyamide matrix. These nanochannels serve as rapid transport pathways through the membrane, and can be used to tune selectivity via control of particle/polymer interactions.
Cellulose Nanostructure-Based Membranes: Structure, Synthesis, and Applications
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Cellulose nanostructures and composite membranes incorporating nanoscale cellulose have gained attention due to their promising utility in various applications. Cellulose nanocomposites in the forms of aerogels, thin films, and nanopapers have been studied extensively. This review focuses on nanocomposite membranes of cellulose which find uses in desalination, sensing, electrical, and biomedical applications. The presence of abundant hydrogen bonds and easily functionalizable surfaces makes cellulose an appropriate material for the fabrication of membranes that can be leveraged for their adsorptive capabilities applicable to water treatment. Membranes of nanocellulose, their modifications by various reinforcements, augmentation of thermal stabilities, selectivity as sensors etc., are discussed in detail here along with pertinent physicochemical aspects. Regenerated cellulose which has different characteristics compared to natural cellulose, is also being discussed.
Journal of Membrane and Separation Technology, 2015
Ultrafiltration (UF) membranes have been widely used for many separation processes in which high performance is required. Commercial regenerated cellulose UF membranes with variable molecular weight cutoffs were characterized by high performance atomic force microscopy (AFM) using the novel quantitative nanomechanical mapping mode and the versatility of its signal channels towards nanoscale features elucidation of the materials surface. In addition, Raman spectroscopy was applied in order to investigate some possible chemical behavior changes associated with the UF membranes' cutoffs. Overall, the results showed that the proposed AFM method was reliable to gain qualitative and quantitative data at unprecedented nanoscale resolution and such information can be used to distinguish UF membranes according to their specific molecular weight cutoffs and properties even on situations in which the molecular behavior were not influenced by the UF membrane' cutoff. This approach can be useful on quality control procedures of researchers and manufacturers producing or modifying these polymeric materials.
2021
1 Mapua University, School of Chemical, Biological and Materials Engineering and Sciences, 658 Muralla St., Intramuros, Manila, Philippines 1002 2 KTH Royal Institute of Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Fibre and Polymer Technology, Wallenberg Wood Science Center, Teknikringen 56-58, SE-100 44, Stockholm, Sweden 3 Mapúa University, Resiliency and Sustainable Development Center and School of Civil, Environmental and Geological Engineering, Philippines
Macromolecules, 1994
The structure of ultrathin cellulose acetate membranes, known as active layer membranes, has been investigated using small-angle neutron scattering. These membranes are known to have structural and functional similarity to the surface or "skin" layer in commercial reverse-osmosis (RO) membranes and hence are useful model systems for understanding the structure of the RO membrane skin layer. Active layer membranes were studied after swelling them with either DzO or CD30D. The results in both cases clearly indicated the presence of very small (10-20 A) porous structures in the membrane. The presence of such pores has been a subject of long-standing controversy in this area. The data was analyzed using a modified Debye-Bueche analysis and the resultant membrane structure was seen to agree well with structural information from electron microscopic studies. Finally, a possible explanation for the differences in scattering observed between the DzO swollen membranes and the CD30D swollen membranes has been presented.
FTIR Identification of cellulose extracted from wheat straw Biomaterials and Nanomaterials
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Silica has a wide range of industrial uses and its nontoxic and highly biocompatible characteristics lend well to applications in scaffolds for tissues, drug-delivery system, biosensors and imaging. Conventional methods for silica synthesis typically require a combination of high temperatures and extreme pH and are limited by structure controlling. However, the discovery of the principle molecules involved in biosilicification both in diatoms (silaffins and polyamines) and sponges (silicateins) brings out understandings about biosilicification and has created a new paradigm for silica synthesis under ambient or mild conditions. The prerequisite for the utilization of biosilicification machinery is the availability of enzymatically active recombinant proteins involved in silica formation. Recombinant silicatein α, however was expressed both in eukaryotic (e.g. Pichia pastoris) and prokaryotic systems (e.g. E. coli), yielding limited quantities of the protein in the former, and formi...
Insight into cellulose-based-nanomaterials - A pursuit of environmental remedies
International Journal of Biological Macromolecules, 2020
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