Carboxyl Cellulose Research Articles

Salt sorption on regenerated cellulosic fibers: electrokinetic measurements

Streaming potential measurements were conducted on lyocell and viscose fibers, to determine the relative order in sorption extents of salt cations and anions. The sorption of K+ was greater than Na+ ions, and the sorption extents of the anions, Cl− and Br−, were similar. Previously, we had examined accessibility of the same ions in the fibers, and found them to follow the order: K+ < Na+ and Cl− < Br−. From these two contrasting results, we find that the mode of salt interaction with cellulose, from aqueous solutions, changes with the salt concentration. At low concentrations, the interaction is governed by ion-exchange processes with the cellulose carboxyl groups and the Donnan equilibrium; but at higher concentrations, the interaction is a function of the mobility (or diffusivity) of the ions. Thus, sorption and accessibility of cellulose fibers as measured with salts may not apply for other solutes, and conversely, similar studies with other probe molecules may not be relevant for salts.

Sol–gel Entrapped Nitroxyl Radicals: Catalysts of Broad Scope

AbstractSol–gel entrapped TEMPO‐like radicals are excellent supported molecular catalysts for the selective and clean alcohol oxidation, including the primary hydroxyl functions of cellulose. Could these materials reach widespread utilization for the synthesis of fine chemicals, bio‐based building blocks and even carboxyl cellulose nanofibrils? This study offers a critical perspective.

Using carboxylated cellulose nanofibers to enhance mechanical and barrier properties of collagen fiber film by electrostatic interaction.

Collagen-based films including casings with a promising application in meat industry are still needed to improve its inferior performance. In the present study, the reinforcement of carboxylated cellulose nanofibers (CNF) for collagen film, based on inter-/intra- molecular electrostatic interaction between cationic acid-swollen collagen fiber and anionic carboxylated CNF, was investigated. Adding CNF decreased the zeta-potential but increased particle size of collagen fiber suspension, with little effect on pH. Furthermore, CNF addition led to a higher tensile strength but a lower elongation, and the water vapor and oxygen barrier properties were improved remarkably. Because the CNF content was 50 g kg-1 or lower, the films had a homogeneous interwoven network, and CNF homogeneously embedded into collagen fiber matrix according to the scanning electron microscopy and atomic force microscopy analysis. Additionally, CNF addition increased film thickness and opacity, as well as swelling rate. The incorporation of CNF endows collagen fiber films good mechanical and barrier properties over a proper concentration range (≤ 50 g kg-1 collagen fiber), which is closely associated with electrostatic reaction of collagen fiber and CNF and, subsequently, the form of the homogenous, compatible spatial network, indicating a potential applications of CNF in collagenous protein films, such as edible casings. © 2017 Society of Chemical Industry.

Carboxyl cellulose nanocrystal extracted from hybrid poplar residue

Ammonium persulfate (APS) oxidation was employed to isolate carboxyl cellulose nanocrystals (CNCs) from hybrid poplar residue. Structure changes resulting from APS oxidation were investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The further oxidation of the ensuring CNCs with sodium periodate manifested selective oxidation of hydroxyl groups at the C6 position of cellulose into carboxyl groups during APS oxidation. The introduction of active carboxyl groups resulted in lower thermal stability. Transmission electron microscopy (TEM) and width distribution showed that the produced CNCs ranged from 10 nm to 24 nm. Carboxyl CNCs with a yield of 63.2% were isolated via APS oxidation, and they were suitable for large-scale CNCs production.

Production of cellulose nanofibers using phenolic enhanced surface oxidation

In this study we demonstrate that lignin monomers formed as byproducts of pulping or bioprocessing of lignocellulosic biomass is an effective enhancer to oxidize cellulose surfaces with ozone for the production of cellulose nanofibers (CNF). Never dried softwood pulp with minimum mercerization was enzymatically treated leading to a homogeneous pulp slurry with a higher reactivity. The slurry was oxidized by ozone gas in the presence of syringic acid, a lignin degradation model compound, as an oxidation enhancer at room temperature and pH 11. Transmission electron microscopy (TEM) observations showed that stable CNF bundles with 3–10nm widths and lengths >100nm were obtained after ultrasonication of the oxidized product in water. Extensive characterization of the new CNF films revealed the nanofibers had carboxylate content similar to conventional carboxylated cellulose prepared by TEMPO-mediated oxidation. Based on NMR spectra, chemical conversion of the syringic acid during oxidation is proposed.

Cellulose Oxidation and the Use of Carboxyl Cellulose Metal Complexes in Heterogeneous Catalytic Systems to Promote Suzuki-Miyaura Coupling and C−O Bond Formation Reaction

This work shows the modification of microcrystalline cellulose by the selective oxidation of primary hydroxyl groups to carboxylate groups by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated system and its application as a heterogeneous ligand by ionic exchange with catalytic metals ions such as palladium, nickel and copper. Afterwards is described the application of the synthesized material as catalyst in coupling reactions such as Suzuki-Miyaura coupling and C−O bond formation reaction in different conditions, which are of great importance for the synthesis of drugs, natural products and new materials such as dendrimers, liquid crystals and polymers with magnetic and optical properties. The carboxyl cellulose matrix shows to have superior catalytic results as a ligand for all coupling reactions. Can be also highlighted the affinity of the carboxyl cellulose ligand in polar solvents such as water and alcohols and its application in mild conditions.

Highly Carboxylated Cellulose Nanofibers via Succinic Anhydride Esterification of Wheat Fibers and Facile Mechanical Disintegration.

We report herein the preparation of 4-6 nm wide carboxyl-functionalized cellulose nanofibers (CNF) via the esterification of wheat fibers with cyclic anhydrides (maleic, phtalic, and succinic) followed by an energy-efficient mechanical disintegration process. Remarkable results were achieved via succinic anhydride esterification that enabled CNF isolation by a single pass through the microfluidizer yielding a transparent and thick gel. These CNF carry the highest content of carboxyl groups ever reported for native cellulose nanofibers (3.8 mmol g-1). Compared to conventional carboxylated cellulose nanofibers prepared via Tempo-mediated oxidation of wheat fibers, the present esterified CNF display a higher molar-mass and a better thermal stability. Moreover, highly carboxylated CNF from succinic anhydride esterification were effectively integrated into paper filters for the removal of lead from aqueous solution and are potentially of interest as carrier of active molecules or as transparent films for packaging, biomedical or electronic applications.

Fabrication of pH-Controlled-Release Ferrous Foliar Fertilizer with High Adhesion Capacity Based on Nanobiomaterial

Iron deficiency is a worldwide problem in modern agriculture, which causes leaf chlorosis and severe declines in crop yield. Therefore, improving the utilization efficiency (UE) of ferrous fertilizer is an urgent need. This study developed a pH-controlled-release ferrous foliar fertilizer (PCRFFF) composed of ferrous sulfate (FeSO4·7H2O), microcrystalline cellulose (MC), and attapulgite (ATP). Therein, MC was oxidized to form carboxyl cellulose (CC) that possessed plenty of carboxyl groups (-COOH) on the surface and could effectively chelate Fe2+ [Fe(II)] to form CC–Fe(II) microfibers. Then the CC–Fe(II) microfibers were tightly coated by abundant ATP nanorods through hydrogen bonds to produce PCRFFF. Under acidic conditions, the chelated Fe(II) became isolated and the ATP coating became loose, which facilitated the release of Fe(II) from PCRFFF. Thus, the release of Fe(II) could be efficiently controlled by pH. In addition, PCRFFF displayed high adhesion capacity on a crop leaf surface. This technology c...

Flocculation kinetics of precipitated calcium carbonate induced by electrosterically stabilized nanocrystalline cellulose

Abstract The interactions between precipitated calcium carbonate (PCC) and electrosterically stabilized nanocrystalline cellulose (ENCC), dissolved carboxylated cellulose (DCC), and a mixture of DCC and ENCC have been studied. ENCC can be produced by periodate, chlorite and TEMPO oxidations of cellulose fibers. It has a large surface area, a high carboxylated content and can be used as a high-performance reinforcement material. It is likely to effectively bind and flocculate with PCC to improve the properties of filled paper. Dissolved carboxylated cellulose (DCC) is produced together with ENCC in the oxidation reactions, and also has a high charge density. The flocculation of PCC induced by ENCC/DCC was measured by photometric dispersion analysis (PDA). It was demonstrated that ENCC or DCC adsorbed first on PCC particle surfaces due to electrostatic attractions, and subsequently ENCC or DCC induces flocculation between PCC. The repulsive electrostatic force reduces to zero when the isoelectric point of PCC particles is reached, allowing attractive van de Waals forces to dominate, resulting in maximum PCC flocculation. After the charge neutralization point was reached, more dissolved carboxylated cellulose adsorbed on the PCC particles, resulting in net negative charges on PCC surfaces, and dispersion of flocs due to electrostatic repulsion. For mixtures of dissolved carboxylated cellulose (DCC) and ENCC, DCC adsorbed faster on PCC than ENCC. Excess ENCC resulted in the exchange of DCC with ENCC, with ENCC particles able to bridge PCC. This mechanism was proved by photometric dispersion analysis and dynamic light scattering experiments.

Preparation of nanospheres from oxidised cellulose nanofibrils via polyelectrolyte complexation

Cellulose consists of both crystalline and amorphous region. The amorphous regions are cut down when disturbed, with only the remaining crystalline regions consisting of nanometer size. The TEMPO specific oxidation of cellulose fibre provides carboxylated cellulose nano-crystals. The surface carboxylated cellulose was prepared by TEMPO-mediated specific oxidation method. Supernatant of the reaction mass contains oxidised cellulose nanofibrils that were isolated. The anionic cellulose nanocrystals were enabled to undergo polyelectrolyte complexation with cationic polymers. The nano-spheres were prepared from oxidised cellulose through polyelectrolyte complexation with chitosan in different concentrations. The shape of the nanosphere was identified by SEM. The nano-spheres were agglomerate on excess chitosan. To overcome that, the surface was hydrophobically modified with alkyl tail. The hydrophobic modification was given individual nano-spheres and they were distinctly identified. This communication will derive a new nanomaterial of CNF, which will act as a nano carrier for delivery applications.

Aqueous synthesis and biostabilization of CdS@ZnS quantum dots for bioimaging applications

Bionanohybrids, combining biocompatible natural polymers with inorganic materials, have aroused interest because of their structural, functional, and environmental advantages. In this work, we report on the stabilization of CdS@ZnS core–shell quantum dots (QDs) using carboxylated cellulose nanocrytals (CNCs) as nanocarrieers in aqueous phase. The high colloidal stability was achieved with sufficient negative charge on CNC surface and the coordination of Cd2+ to carboxylate groups. This coordination allows the in-situ nucleation and growth of QDs on CNC surface. The influences of QD to CNC ratio, pH and ZnS coating on colloidal stability and photoluminescence property of CNC/QD nanohybirds were also studied. The results showed that products obtained at pH 8 with a CdS to CNC weight ratio of 0.19 and a ZnS/CdS molar ratio of 1.5 possessed excellent colloidal stability and highest photoluminescence intensity. By anchoring QDs on rigid bionanotemplates, CNC/CdS@ZnS exhibited long-term colloidal and optical stability. Using biocompatible CNC as nanocarriers, the products have been demonstrated to exhibit low cytotoxicity towards HeLa cells and can serve as promising red-emitting fluorescent bioimaging probes.

Superparamagnetic iron oxide coated on the surface of cellulose nanospheres for the rapid removal of textile dye under mild condition

Magnetic composite nanoparticles (MNPs) were prepared by anchoring iron oxide (Fe3O4) on the surface of carboxyl cellulose nanospheres through a facile chemical co-precipitation method. The as-prepared MNPs were characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, wide-angle X-ray diffraction measurement, thermal gravity analysis and vibrating sample magnetometry. These MNPs were of a generally spherical shape with a narrow size distribution, and exhibited superparamagnetic behaviors with high saturation magnetization. High efficient removal of Navy blue in aqueous solution was demonstrated at room temperature in a Fenton-like system containing the MNPs and H2O2, which benefited from small particle size, large surface area, high chemical activity, and good dispersibility of the MNPs. The removal efficiency of Navy blue induced by the MNPs prepared at a weight ratio of cellulose to iron of 1:2 were 90.6% at the first minute of the degradation reaction, and 98.0% for 5min. Furthermore, these MNPs could be efficiently recycled and reused by using an external magnetic field. The approach presented in this paper promotes the use of renewable natural resources as templates for the preparation and stabilization of various inorganic nanomaterials for the purpose of catalysis, magnetic resonance imaging, biomedical and other potential applications.

Structure of swollen carboxylated cellulose fibers

Structural changes in cellulose fibers were elucidated for carboxymethylated fibers and fibers that are oxidized by periodate and chlorite. Non-fibrillated and partially fibrillated softwood, kraft fibers (SKF, m-SKF) were carboxymethylated to investigate the contribution of the S1 layer to the swollen fiber structures. Carboxymethylated non-fibrillated fibers (CMF) form balloon-like structures as they swell heterogeneously. When partially fibrillated SKF is carboxymethylated (m-CMF), the fibers do not exhibit this ballooning phenomenon due to the degradation of the S1 layer. Carboxymethylation disrupts the native cellulose crystalline structure without breaking the fibers apart. Periodate–chlorite oxidized fibers, on the other hand, swell homogeneously without disrupting the native cellulose I crystalline form. Periodate–chlorite oxidation damages all three secondary layers to the extent that any microfibril confinement caused by the swelling is removed. Each chemistry and mechanical treatment affects the cellulose fibers differently to yield various swollen structures.

Synthesis of carboxyl cellulose sulfates with regioselective sulfation and regiospecific oxidation using cellulose trifluoroacetate as intermediates

Synthesis of cellulose sulfates (CSs) and carboxyl cellulose sulfates (COCSs) with regioselectively or regiospecifically distributed functional groups within anhydroglucose units was reported. CS with regioselectively distributed sulfate groups at 2,3-O- or 2,6-O-position were homogeneously synthesized and cellulose trifluoroacetate (CTFA) was used as intermediates. The trifluoroacetyl groups were detected primarily at 6-O-position and their distributions could be altered by changing the amount of trifluoroacetyl anhydride (TFAA). Various sulfating agents were used for further homogeneous sulfation of CTFA. The total degree of sulfation (DSS) and the distribution of sulfate groups within the repeating units were affected by the amount of TFAA, the type and amount of sulfating agents. Subsequent homogenous 4-acetamide-TEMPO or TEMPO-mediated oxidation of CS led to COCS with carboxyl groups regiospecifically distributed at C6 position, which may be interesting structural mimics for natural occurring heparin.

Preparation for Humidity Control Composite Paperboard and their Humidity Control Properties

The humidity control composite paperboard with excellent humidity control performance was prepared, comprising sodium chloride, anhydrous potassium carbonate, diatomite, pyrrolidone carboxylic acid-Na, carboxymethyl cellulose and self-made humidity control material. The moisture absorption and desorption rate of the sample are about 0.6231 (g/7h•g-1) and 0.5852 (g/7h•g-1), respectively. The equilibrium humidity fluctuates from 52% to 56% and moisture capacity is 31 %. Moreover, it can reach to the equilibrium levels within 60 minutes. Above all, it shows outstanding humidity control properties, meeting the requirement of micro-environment particularly for something sensitive to humidity such as cultural relic.

Granulation Technology Experiments of Novel Mesoporous Composite Water Purification Material

A novel mesoporous composite water purification material was synthesized from natural zeolite to possess certain water purification properties as well as in proper particle size range for optimal fluid flow, particle retention and mass transfer in fixed bed applications. The meerschaum was used as the framework material in the experimental manufacturing procedure, polyethylene alcohol with carboxylic methylic cellulose was used as cohesive reagent, and H2O2 as bubble-forming agent. And the resulted granular product has good abrasion resistance ability with the measured impact breaking time reaching 12 hours. In addition, its decoloring rate is only 4.4% lower and its CODcr removing is only 13.2% lower than those of the original powder product, respectively. As a whole, the granulation potential and significantly expands the zeolite wastewater treatment application range with (only is not necessary) minor reduction of its treatment efficiency.

Analysis of carboxylate groups in oxidized never-dried cellulose II catalyzed by TEMPO and 4-acetamide-TEMPO.

In this report, never-dried regenerated celluloses, i.e. cellulose II, from their NaOH/urea/H2O solutions were subjected to TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) or 4-acetamide-TEMPO-mediated oxidation. Water-soluble and -insoluble fractions of carboxyl cellulose (COC) were obtained and their DO were determined to be between 0.08 and 0.85. Apart from conductometric titration, complexometric titration with EDTA was used to analyze the DO of COC. The conductometric titration can be used for lowly or highly oxidized celluloses, while the complexometric titration with EDTA is only adequate for COC with DO lower than 0.6. FT Raman spectroscopy represents characteristic bands of carboxyl and carboxylate groups. It demonstrates the feasibility of establishing novel analyzing methods for DO of COC with high correlation coefficients of up to 0.9867. Moreover, long oxidation duration, high temperature and high amounts of oxidizing agents are important for the synthesis of COC with high DO and yields.

Synthesis of carboxyl cellulose sulfate with various contents of regioselectively introduced sulfate and carboxyl groups

Both sulfate and carboxyl groups are found in many glycosaminoglycans exhibiting diverse biological activities, such as heparin. Present study reports on the preparation of cellulose derivatives containing both sulfate and carboxyl groups that were regioselectively introduced into anhydroglucose units (AGU) of cellulose. The products – carboxyl cellulose sulfates (COCS) – with various contents of both functional groups were obtained by two synthesis routes. One way started with sulfation of cellulose yielding cellulose sulfate (CS) and was followed by TEMPO-mediated oxidation of CS. In another way, cellulose at first underwent TEMPO-mediated oxidation yielding carboxyl cellulose (COC). Subsequently, acetosulfation of the COC was carried out. The products were characterized by diverse analysis methods, and the amounts of both functional groups in CS, COC and COCS were determined. Finally, the biological activity of COCS was examined.

Ultrasonic defouling of reverse osmosis membranes used to treat wastewater effluents

On-line ultrasonic cleaning was used to remove fouling from a commercially important polyamide based reverse osmosis membrane during cross-flow filtration of CaSO 4, Fe 3+ and carboxyl cellulose solutions. In each case, the permeate flux of the membrane increased significantly, with virtually no decrease in rejection in the presence of ultrasonication. Membrane surface characterization via scanning electron microscopy (SEM) confirmed the beneficial effect of ultrasonication on the membrane permeate flux. These studies suggest that ultrasonic defouling may be a very useful approach for the future development of reverse membranes, especially as far as fouling with organic materials is concerned.

Ion-exchange chromatography by dicarboxyl cellulose gel

A new column packing material for ion-exchange chromatography was prepared from cellulose gel by periodate oxidation followed by chlorite oxidation to form spatially paired carboxyl groups (dicarboxyl cellulose, DCC). The carboxyl group was quantitatively introduced to spherical cellulose gel by controlling the extent of oxidation. The DCC gels were examined for their ion-exchange activity for various amines at pH of 2.5–5.5. In this pH range, aromatic amines with acid dissociation constant (pKa) below 2.7 showed no interaction with DCC gels as expected from their lack of protonation. The amines with pKa greater than 3.3, both aromatic and aliphatic, showed strong interaction corresponding to the amount of carboxyl introduced to the gel. However, these amines showed anomalous dependence on pH of the mobile phase, showing a maximum in retention factor at around pH 4. This is in contrast with the nearly constant retention factor of these amines on conventional carboxylated cellulose packing at pH greater than 4.0. The maximum retention factor at pH 4 of DCC gel was 4–5-times greater than that of conventional gel having a similar amount of carboxyls. Since pKa of dicarboxyl groups ranges 3–5 as determined by acid–base titration, the pH giving maximum retention corresponds to the pH at which one of paired carboxyls is dissociated. Possible cause of this anomaly is presented in terms of dissociation state of dicarboxyl groups and its interaction with amines.