Cladophora Cellulose Research Articles

Efek Variasi Konsentrasi NaOH pada Pembentukan Struktur Selulosa Cladophora sp.

The effect of NaOH concentration values was observed on the cellulose structure of Cladophora. Cladophora cellulose is synthesized from Cladophora sp., a green alga that lives in aquatic environments (seawater and freshwater) and soil surfaces (rocks and wetlands). Cellulose synthesis is carried out through the processes of bleaching, alkali hydrolysis, and acid hydrolysis. Bleaching uses NaClO 2 , alkaline hydrolysis uses NaOH with varying concentrations (0.4; 0.5; 0.6; 0.7; 0.8 M), while acid hydrolysis uses 5% HCl. The physical properties of cellulose were analyzed using Fourier Transformation Infra-Red (FTIR) to determine functional groups, X-Ray Diffraction (XRD) to determine crystal structure, and scanning electron microscopy (SEM) to determine the morphology of cellulose structure. FTIR pattern analysis showed peaks with OH group stretching at 3331, 3347, 3360 cm -1 , CH group stretching at around 2929 cm -1 , C = O stretching at 1640-1650 cm -1 , and CH 2 flexural stretching at 1420-1430 cm -1 in all samples. XRD pattern analysis confirmed the recovery of Cladophora cellulose from a highly crystalline of sample c (NaOH 0.5 M) with a crystallinity index of 94.0 % and a particle size of 31.54 nm. SEM image analysis showed the surface morphology of Cladophora rod-shaped raw material with an average diameter of 21.30 µm. At the same time, Cladophora cellulose refers to the formation of a web-like nanofibril network with an average diameter of 30.63 nm. These results indicate that the synthesis has successfully removed lignin, hemicellulose, and amorphous group in Cladophora and formed crystalline cellulose confirmed by nano-sized cellulose .

Characterization of the supramolecular structures of cellulose nanocrystals of different origins

Properties of cellulose nanocrystals (CNCs) depend upon their supramolecular structures, which are important to understand in order to optimize their applications. In this investigation, the structures of CNCs produced upon 48–64% H2SO4 hydrolysis of hydrothermally-treated poplar, bleached kraft pulp, cotton microcrystalline cellulose, bacterial cellulose, tunicin, and cladophora cellulose were comparatively analyzed. TEM provided information on the morphological aspects. Raman, MAS-NMR, and XRD provided information on one aspect of the supramolecular organization, namely, crystallinity (CrI). Other characteristics of supramolecular structure were analyzed by various Raman methods, namely, accessibility to water, exocyclic CH2OH conformation ratio, and chain conformation disorder (CCONDIS)—the last method was developed in the present study. In general, CNCs retained the crystallinity of the starting material irrespective of the measurement method of CrI. Additionally, it was found that crystallite size and supramolecular organization influenced CrI as well. These analyses further indicated that poplar- and pulp-CNCs had significantly higher water accessibility as compared with CNCs from cladophora, bacterial, tunicin, and cotton MCC CNCs, implying higher molecular disorder, which was also reflected in measurements of CH2OH conformation ratio and CCONDIS. The findings indicate that significant differences among the CNCs seem to arise largely from differences between the starting materials. Additionally, considering that CNCs can have very different morphologies and structural properties depending upon how they are produced, the analyses carried out here can characterize such CNCs and estimate their applications.

On the Capacities of Freestanding Vanadium Pentoxide–Carbon Nanotube–Nanocellulose Paper Electrodes for Charge Storage Applications

Herein, a one‐step protocol for synthesizing freestanding 20 μm thick cellulose paper electrodes composed of V2O5 ⋅ H2O nanosheets (VOx), carbon nanotubes (CNTs), and Cladophora cellulose (CC) is reported. In 1.0 m Na2SO4, the VOx–CNT–CC electrodes deliver capacities of about 200 and 50 C g−1 at scan rates of 20 and 500 mV s−1, respectively. The obtained capacities are compared with the theoretical capacities and are discussed based on the electrochemical reactions and the mass loadings of the electrodes. It is shown that the capacities are diffusion rate limited and, consequently, depend on the distribution and thickness of the V2O5 ⋅ H2O nanosheets, whereas the long‐term cycling stabilities depend on vanadium species dissolving in the electrolyte. The electrodes feature high mass loadings (2 mg cm−2), good rate performances (25% capacity retention at 500 mV s−1), and capacity retentions of 85% after 8000 cycles. A symmetric VOx–CNT–CC energy storage device with a potential window of about 1 V exhibits a capacity of 40 C g−1 at a scan rate of 2 mV s−1.

Redox active covalent organic framework-based conductive nanofibers for flexible energy storage device

Covalent organic frameworks (COFs) constitute a family of crystalline porous polymers that are being studied for electrochemical energy storage. However, their low electrical conductivity and poor processability have largely limited their electrochemical performances and practical applications. Here, we develop an interfacial synthesis method to grow few-layered 2D redox-active COFs (DAAQ-TFP COF) on the surface of carboxylated carbon nanotubes (c-CNTs) in order to fabricate core-shell c-CNT@COF nanofibers, for which the thickness and the morphology of the COF nanolayers can be finely controlled. When using the c-CNT@COFs as electrode material, the tailored nanostructure with high electrical conductivity allows efficient electron transfer, while the few-layered structure of the COF promotes fast electrolyte ion diffusion in the near-surface region, which results in an efficient utilization of the redox active sites in COF. More significantly, c-CNT@COFs with nanofibrous structure show good processability and can be assembled into freestanding and flexible nanopapers with the assistance of Cladophora cellulose. Given the good electrochemical performance and excellent flexibility, the nanopaper electrodes are assembled into flexible hybrid capacitors, showing high areal capacitance and extremely long lifetime. This study provides a new pathway for the development of next generation sustainable and flexible energy storage devices based on COFs and cellulose materials.

Dissolution Behavior of Flufenamic Acid in Heated Mixtures with Nanocellulose

Flufenamic acid (FFA) is a problem drug that has up to eight different polymorphs and shows poor solubility. Variability in bioavailability has been reported in the past resulting in limited use of FFA in the oral solid dosage form. The goal of this article was to investigate the polymorphism and amorphization behavior of FFA in non-heated and heated mixtures with high surface area nanocellulose, i.e., Cladophora cellulose (CLAD). As a benchmark, low surface area microcrystalline cellulose (MCC) was used. The solid-state properties of mixtures were characterized with X-ray diffraction, Fourier-transform infrared spectroscopy, and differential scanning calorimetry. The dissolution behavior of mixtures was studied in three biorelevant media, i.e., fasted state simulated gastric fluid, fasted state simulated intestinal fluid, and fed state simulated intestinal fluid. Additional thermal analysis and dissolution tests were carried out following 4 months of storage at 75% RH and room temperature. Heated mixtures of FFA with CLAD resulted in complete amorphization of the drug, whereas that with MCC produced a mixture of up to four different polymorphs. The amorphous FFA mixture with CLAD exhibited rapid and invariable fasted/fed state dissolution in simulated intestinal fluids, whereas that of MCC mixtures was highly dependent on the biorelevant medium. The storage of the heated FFA-CLAD mixture did not result in recrystallization or changes in dissolution profile, whereas heated FFA-MCC mixture showed polymorphic changes. The straightforward dry powder formulation strategy presented here bears great promise for reformulating a number of problem drugs to enhance their dissolution properties and reduce the fasted/fed state variability.

Directly Compressed Tablets of Free Acid Ibuprofen with Nanocellulose Featuring Enhanced Dissolution: A Side-by-Side Comparison with Commercial Oral Dosage Forms

We have previously reported that heated powder mixtures of ibuprofen (IBU) and high surface area nanocellulose exhibit an enhanced dissolution and solubility of the drug due to IBU amorphization. The goal of the present work was to further elaborate the concept and conduct side-by-side in vitro drug release comparisons with commercial formulations, including film-coated tablets, soft gel liquid capsules, and IBU-lysine conjugate tablets, in biorelevant media. Directly compressed tablets were produced from heated mixtures of 20% w/w IBU and high surface area Cladophora cellulose (CLAD), with 5% w/w sodium croscarmelose (AcDiSol) as superdisintegrant. The side-by side studies in simulated gastric fluid, fasted-state simulated intestinal fluid, and fed-state simulated intestinal fluid corroborate that the IBU-CLAD tablets show more rapid and less variable release in various media compared to three commercial IBU formulations. On the sidelines of the main work, a possibility of the presence of a new meta-crystalline form of IBU in mixture with nanocellulose is discussed.

Flexible Freestanding MoO3-x -Carbon Nanotubes-Nanocellulose Paper Electrodes for Charge-Storage Applications.

Herein, a one-step synthesis protocol was developed for synthesizing freestanding/flexible paper electrodes composed of nanostructured molybdenum oxide (MoO3-x ) embedded in a carbon nanotube (CNT) and Cladophora cellulose (CC) matrix. The preparation method involved sonication of the precursors, nanostructured MoO3-x , CNTs, and CC with weight ratios of 7:2:1, in a water/ethanol mixture, followed by vacuum filtration. The electrodes were straightforward to handle and possessed a thickness of approximately 12 μm and a mass loading of MoO3-x -CNTs of approximately 0.9 mg cm-2 . The elemental mapping showed that the nanostructured MoO3-x was uniformly embedded inside the CNTs-CC matrix. The MoO3-x -CNTs-CC paper electrodes featured a capacity of 30 C g-1 , normalized to the mass of MoO3-x -CNTs, at a current density of 78 A g-1 (corresponding to a rate of approximately 210 C based on the MoO3 content, assuming a theoretical capacity of 1339 C g-1 ), and exhibited a capacity retention of 91 % over 30 000 cycles. This study paves the way for the manufacturing of flexible/freestanding nanostructured MoO3-x -based electrodes for use in charge-storage devices at high charge/discharge rates.

Cladophora Cellulose: Unique Biopolymer Nanofibrils for Emerging Energy, Environmental, and Life Science Applications.

Because of its natural abundance, hierarchical fibrous structure, mechanical flexibility, potential for chemical modification, biocompatibility, renewability, and abundance, cellulose is one of the most promising green materials for a bio-based future and sustainable economy. Cellulose derived from wood or bacteria has dominated the industrial cellulose market and has been developed to produce a number of advanced materials for applications in energy storage, environmental, and biotechnology areas. However, Cladophora cellulose (CC) extracted from green algae has unprecedented advantages over those celluloses because of its high crystallinity (>95%), low moisture adsorption capacity, excellent solution processability, high porosity in the mesoporous range, and associated high specific surface area. The unique physical and chemical properties of CC can add new features to and enhance the performance of nanocellulose-based materials, and these attributes have attracted a great deal of research interest over the past decade. This Account summarizes our recent research on the preparation, characterization, functionalization, and versatile applications of CC. Our aim is to provide a comprehensive overview of the uniqueness of CC with respect to material structure, properties, and emerging applications. We discuss the potential of CC in energy storage, environmental science, and life science, with emphasis on applications in which its properties are superior to those of other nanocellulose forms. Specifically, we discuss the production of the first-ever paper battery based on CC. This battery has initiated a rising interest in the development of sustainable paper-based energy storage devices, where cellulose is used as a combined building block and binder for paper electrodes of various types in combination with carbon, conducting polymers, and other electroactive materials. High-active-mass and high-mass-loading paper electrodes can be made in which the CC acts as a high-surface-area and porous substrate while a thin layer of electroactive material is coated on individual nanofibrils. We have shown that CC membranes can be used directly as battery separators because of their low moisture content, high mesoporosity, high thermal stability, and good electrolyte wettability. The safety, stability, and capacity of lithium-ion batteries can be enhanced simply by using CC-based separators. Moreover, the high chemical modifiability and adjustable porosity of dried CC papers allow them to be used as advanced membranes for environmental science (water and air purification, pollutant adsorption) and life science (virus isolation, protein recovery, hemodialysis, DNA extraction, bioactive substrates). Finally, we outline some concluding perspectives on the challenges and future directions of CC research with the aim to open up yet unexplored fields of use for this interesting material.

Amorphisation of Free Acid Ibuprofen and Other Profens in Mixtures with Nanocellulose: Dry Powder Formulation Strategy for Enhanced Solubility.

The formulation of arylpropionic acid derivatives (profens), which are poorly soluble Biopharmaceutical Classification System (BCS) Type II drugs, has a strong impact on their therapeutic action. This article shows that heat-treated powder mixtures of free acid profens with high surface area Cladophora cellulose induces drug amorphization and results in enhanced solubility and bioavailability. Similar mixtures produced using conventional low surface area cellulose, i.e., microcrystalline cellulose, does not produce the same effect. The concept is thoroughly described and links the solid-state characterization data, such as differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infra-red spectroscopy, with in vitro dissolution in biorelevant media and in vivo pharmacokinetic analysis in rats. The concept is demonstrated for several substances from the profens group, including ibuprofen (main model drug), ketoprofen, flurbiprofen, and naproxen. The presented approach opens new ways to produce solid dosage forms of profen drugs in their free acidic form as alternatives to existing analogues, e.g., drug-salt conjugates or soft gel liquid capsules.

(Plenary) Separators As a Tool for Enhanced Battery Performance

Separators have the critical function of preventing electronic conduction (short circuiting) while permitting ionic conduction through the electrolyte which is soaked into the porous structure. Conventional separators of microporous polyolefins, used in lithium-ion batteries, have good mechanical strength and chemical stability, but poor thermal stability and low electrolyte wettability. The development of entirely new classes of inexpensive insulating materials that optimize both thermal stability and electrolyte wettability are therefore needed and separators where a functionality is included can even enhance the cycling stability of a battery. In this presentation a survey of different strategies to develop modified or new cellulose-based separators or to utilize conducting polymers with the goal to tailor structural and mechanical properties such as porosity, surface wettability, thermal stability, and at the same time make separators possible to produce. We will show the following examples: How mesoporous Cladophora cellulose (CC) separators constitute very promising alternatives to existing ones based on their high crystallinity, good thermal stability and straightforward manufacturing. [1]How overoxidized polypyrrole, with high thermal and ionic conductivity, is deposited as a layer on a traditional separator, will enhance the rate capability of Li-ion batteries. [2]How a low-cost, renewable, mechanical flexible nanocellulose can be used as both, anode and cathode host, as well as a mesoporous separator in a lithium metal battery design. Nanocellulose with flexible building blocks can produce a 3D porous conducting cellulose paper (CCP) current collector in combination with carbon nanofibers. After electrochemically plating Li into the interconnected nanocellulose/carbon fibers architectures a stable Li metal anode can be obtained. [3]A bilayered cellulose‐based separator design will be presented that can enhance the electrochemical performance of Li‐ion batteries via the inclusion of a porous redox‐active layer. The proposed flexible redox‐active separator consists of a mesoporous, insulating nanocellulose fiber layer that provides the necessary insulation between the electrodes and a porous, conductive, and redox‐active polypyrrole‐nanocellulose layer. The latter layer provides mechanical support to the nanocellulose layer and adds extra capacity to the Li-ion batteries s. [4] The advantes and disadvantages of the different systems will be discussed based on careful electrochemical and material science characterisation of the materials as such and their function in a battery.

Immediate-Release Nifedipine Binary Dry Powder Mixtures with Nanocellulose Featuring Enhanced Solubility and Dissolution Rate.

Nifedipine (NIF) is a 1,4-dihydropyridine-based calcium channel blocker with poor solubility, whose bioavailability is highly dependent on the type of formulation. Dry powder mixtures of 20% w/w NIF with microcrystalline cellulose (MCC) and its high surface area nanocellulose analogue, which is namely Cladophora (CLAD) cellulose, were produced by heating at the melting temperature of the drug for 1 h. Non-heated samples were used as a reference. The solid-state properties of the mixtures were characterized by scanning electron microscopy, differential scanning calorimetry and X-ray diffraction. The drug release was studied in biorelevant media, including simulated gastric fluid (SGF), fasted-state simulated intestinal fluid (FaSIF) and fed-state simulated intestinal fluid (FeSIF). An enhanced apparent solubility and faster dissolution rate of NIF were observed in the heated mixture of NIF with CLAD-H in all tested biorelevant media (i.e., SGF, FaSIF and FeSIF), which was due to NIF amorphization in the high surface area nanocellulose powder. Ordinary MCC, which is essentially non-porous, did not produce an enhancement of a similar magnitude. The results of the study suggest that dry powder formulation using high surface area nanocellulose is a facile new strategy for formulating calcium channel blocker drugs, which could potentially be a viable alternative to currently used soft gel liquid capsules.

High‐Performance Activated Carbons Synthesized from Nanocellulose for CO2 Capture and Extremely Selective Removal of Volatile Organic Compounds

AbstractA series of sustainable activated carbons (ACs) with large surface areas and tunable pore sizes is synthesized from Cladophora cellulose and its chemically modified derivatives in a one‐step physical carbonization/activation process. The molecular structure of the cellulose precursors and the carbonization/activation atmosphere (N2 or CO2) significantly influence the pore structure of the ACs. When using oxidized cellulose and its further cross‐linkages as the precursor, the ACs have a large volume of ultramicropores (pore diameter < 0.8 nm). Activation in CO2 results in ACs with surface areas up to 1241 m2 g−1. These ACs have a high CO2 uptake capacity (2.29 mmol g−1 at 0.15 bar, 5.52 mmol g−1 at 1 bar; 273 K) and a high CO2–over–N2 selectivity (42 at 273 K). In addition, the capacity of the ACs to adsorb vapors of volatile organic compounds (VOCs) is remarkable, with values up to 0.97 mmol g−1 at very low VOC concentrations (200 ppmv). The ACs have ultrahigh VOCs–over–N2 selectivity up to 9.35 × 103 at 293 K for 0.02 vol%/99.8 vol% of benzene/N2 mixture. It is anticipated that these ACs will be useful as sorbents for the postcombustion capture of CO2 and for indoor removal and direct air capture of various VOCs.

On importance of impurities, potential leachables and extractables in algal nanocellulose for biomedical use

Nanocellulose-based biomaterials for biomedical and pharmaceutical applications have been extensively explored. However, studies on different levels of impurities in the nanocellulose and their potential risks are lacking. This article is the most comprehensive to date survey of the importance and characterization of possible leachables and extractables in nanocellulose for biomedical use. In particular, the (1,3)-β-d-glucan interference in endotoxin detection in algal nanocellulose was addressed. Potential lipophilic and hydrophilic leachables, toxic heavy metals, and microbial contaminants are also monitored. As a model system, nanocellulose from Cladophora sp. algae is investigated. The leachable (1,3)-β-d-glucan and endotoxin, which possess strong immunogenic potential, from the cellulose were minimized to clinically insignificant levels of 4.7μg/g and 2.5EU/g, respectively. The levels of various impurities in the Cladophora cellulose are acceptable for future biomedical applications. The presented approach could be considered as a guideline for other types of nanocellulose.

Thickness difference induced pore structure variations in cellulosic separators for lithium-ion batteries

The pore structure of the separator is crucial to the performance of a lithium-battery as it affects the cell resistance. Herein, a straightforward approach to vary the pore structure of Cladophora cellulose (CC) separators is presented. It is demonstrated that the pore size and porosity of the CC separator can be increased merely by decreasing the thickness of the CC separator by using less CC in the manufacturing of the separator. As the pore size and porosity of the CC separator are increased, the mass transport through the separator is increased which decreases the electrolyte resistance in the pores of the separator. This enhances the battery performance, particularly at higher cycling rates, as is demonstrated for LiFePO4/Li half-cells. A specific capacity of around 100 mAh g−1 was hence obtained at a cycling rate of 2 C with a 10 µm thick CC separator while specific capacities of 40 and close to 0 mAh g−1 were obtained for separators with thicknesses of 20 and 40 µm, respectively. As the results also showed that a higher ionic conductivity was obtained for the 10 µm thick CC separator than for the 20 and 40 µm thick CC separators, it is clear that the different pore structure of the separators was an important factor affecting the battery performance in addition to the separator thickness. The present straightforward, yet efficient, strategy for altering the pore structure hence holds significant promise for the manufacturing of separators with improved performance, as well as for fundamental studies of the influence of the properties of the separator on the performance of lithium-ion cells.

Mesoporous Cladophora cellulose separators for lithium-ion batteries

Much effort is currently made to develop inexpensive and renewable materials which can replace the polyolefin microporous separators conventionally used in contemporary lithium-ion batteries. In the present work, it is demonstrated that mesoporous Cladophora cellulose (CC) separators constitute very promising alternatives based on their high crystallinity, good thermal stability and straightforward manufacturing. The CC separators, which are fabricated using an undemanding paper-making like process involving vacuum filtration, have a typical thickness of about 35 μm, an average pore size of about 20 nm, a Young's modulus of 5.9 GPa and also exhibit an ionic conductivity of 0.4 mS cm−1 after soaking with 1 M LiPF6 EC: DEC (1/1, v/v) electrolyte. The CC separators are demonstrated to be thermally stable at 150 °C and electrochemically inert in the potential range between 0 and 5 V vs. Li+/Li. A LiFePO4/Li cell containing a CC separator showed good cycling stability with 99.5% discharge capacity retention after 50 cycles at a rate of 0.2 C. These results indicate that the renewable CC separators are well-suited for use in high-performance lithium-ion batteries.

Transition from Bioinert to Bioactive Material by Tailoring the Biological Cell Response to Carboxylated Nanocellulose.

This work presents an insight into the relationship between cell response and physicochemical properties of Cladophora cellulose (CC) by investigating the effect of CC functional group density on the response of model cell lines. CC was carboxylated by electrochemical TEMPO-mediated oxidation. By varying the amount of charge passed through the electrolysis setup, CC materials with different degrees of oxidation were obtained. The effect of carboxyl group density on the material's physicochemical properties was investigated together with the response of human dermal fibroblasts (hDF) and human osteoblastic cells (Saos-2) to the carboxylated CC films. The introduction of carboxyl groups resulted in CC films with decreased specific surface area and smaller total pore volume compared with the unmodified CC (u-CC). While u-CC films presented a porous network of randomly oriented fibers, a compact and aligned fiber pattern was depicted for the carboxylated-CC films. The decrease in surface area and total pore volume, and the orientation and aggregation of the fibers tended to augment parallel to the increase in the carboxyl group density. hDF and Saos-2 cells presented poor cell adhesion and spreading on u-CC, which gradually increased for the carboxylated CC as the degree of oxidation increased. It was found that a threshold value in carboxyl group density needs be reached to obtain a carboxylated-CC film with cytocompatibility comparable to commercial tissue culture material. Hence, this study demonstrates that a normally bioinert nanomaterial can be rendered bioactive by carefully tuning the density of charged groups on the material surface, a finding that not only may contribute to the fundamental understanding of biointerface phenomena, but also to the development of bioinert/bioactive materials.

Characterization of dielectric properties of nanocellulose from wood and algae for electrical insulator applications.

Cellulose is one of the oldest electrically insulating materials used in oil-filled high-power transformers and cables. However, reports on the dielectric properties of nanocellulose for electrical insulator applications are scarce. The aim of this study was to characterize the dielectric properties of two nanocellulose types from wood, viz., nanofibrillated cellulose (NFC), and algae, viz., Cladophora cellulose, for electrical insulator applications. The cellulose materials were characterized with X-ray diffraction, nitrogen gas and moisture sorption isotherms, helium pycnometry, mechanical testing, and dielectric spectroscopy at various relative humidities. The algae nanocellulose sample was more crystalline and had a lower moisture sorption capacity at low and moderate relative humidities, compared to NFC. On the other hand, it was much more porous, which resulted in lower strength and higher dielectric loss than for NFC. It is concluded that the solid-state properties of nanocellulose may have a substantial impact on the dielectric properties of electrical insulator applications.

Susceptibility of Iα- and Iβ-Dominated Cellulose to TEMPO-Mediated Oxidation.

The susceptibility of Iα- and Iβ-dominated cellulose to TEMPO-mediated oxidation was studied in this work since the cellulose Iα-allomorph is generally considered to be thermodynamically less stable and therefore more reactive than the cellulose Iβ-allomorph. Highly crystalline Cladophora nanocellulose, which is dominated by the Iα-allomorph, was oxidized to various degrees with TEMPO oxidant via bulk electrolysis in the absence of co-oxidants. Further, the Cladophora nanocellulose was thermally annealed in glycerol to produce its Iβ-dominated form and then oxidized. The produced materials were subsequently studied using FTIR, CP/MAS (13)C NMR, XRD, and SEM. The solid-state analyses confirmed that the annealed Cladophora cellulose was successfully transformed from an Iα- to an Iβ-dominated form. The results of the analyses of pristine and annealed TEMPO-oxidized samples suggest that Iα- and Iβ-dominated cellulose do not differ in susceptibility to TEMPO-oxidation. This work hence suggests that cellulose from different sources are not expected to differ in susceptibility to the oxidation due to differences in allomorph composition.

Citric Acid Cross-Linked Nanocellulose-Based Paper for Size-Exclusion Nanofiltration.

This article explores the effect of cross-linking of nanocellulose with citric acid for the development of novel paper filters for potential application within nanofiltration, including sterile (virus) filtration. Cladophora cellulose paper sheets were cross-linked by first soaking in 16 wt % citric acid in the presence of 1 wt % sodium hypophosphate overnight and then curing at 160 °C for 10 min in a hot-press. The cross-linked paper filter samples were then characterized with FTIR, AFM, N2 gas adsorption, and tensile strength analysis (dry and wet strength). The particle retention properties were further studied with respect to filtering of 20 nm Au nanoparticles with SEM and comparing the UV absorbance intensity of the starting solution and the filtrate. The wet strength of the paper filter was greatly improved following the cross-linking, although in the dry state, the paper becomes brittle. The improved wet strength of the paper filter enables increasing the pressure gradient applied for filtration without compromising the integrity of the filter. This is the first report in which a fully nature-derived paper filter is capable of removing tracer particles as small as 20 nm. It is concluded that citric acid cross-linking of nanocellulose is beneficial for developing paper based sterile (virus) removal industrial filters.

A Size‐Exclusion Nanocellulose Filter Paper for Virus Removal

This is the first time a 100% natural, unmodified nanofibrous polymer-based membrane is demonstrated capable of removing viruses solely based on the size-exclusion principle, with a log10 reduction value (LRV) ≥ 6.3 as limited by the assay lower detection limit and the feed virus titre, thereby matching the performance of industrial synthetic polymer virus removal filters.