A study of crystallinity changes in oxidised celluloses

Isolation and characterization of cellulose nanocrystals from Chinese medicine residues

Nanocellulose has become a vital material with excellent and crucial properties in the field of nanotechnology and advanced materials science. Plant-based traditional Chinese medicines are mostly plant rhizomes, which contain a large amount of cellulose, hemicellulose, and lignin. In this study, carboxylated cellulose nanocrystals (CNCs) were prepared from traditional Chinese medicine residues (CMR) by sequential periodate-chlorite oxidation without mechanical treatment. The obtained nanocelluloses were analyzed by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray diffractometry (XRD); the carboxyl content and specific surface area were also measured, simultaneously. XRD results revealed that the crystallinity index decreased after sequential oxidation; however, the cellulose I structure was maintained. From the morphology analysis, the average length and width of CNCs were 139.3 and 10 nm, respectively. From the FTIR analysis, with the particle size decreasing, hydrogen bonds were broken and recombined. TGA results showed that the thermal property was decreased with a reduction of nanocellulose particle size and crystallinity index. This study is the first to refine utilization of traditional Chinese medicine residues as a potential source of cellulose, that is, to prepare nanocellulose efficiently with high carboxyl content which finds its application in nanomaterials.

Preparation and characterization of cellulose nanocrystals from spent edible fungus substrate

BACKGROUND

Spent edible fungus substrates were identified as potential sources to produce cellulose derivatives, namely purified cellulose and dicarboxyl cellulose nanocrystal (DCNC). Purified celluloses were obtained via chemical treatments and then oxidized by sequential periodate-chlorite without mechanical process. The structural properties of the DCNCs were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermal gravimetric analysis (TGA).

RESULTS

XRD results showed that the cellulose I structure was maintained, however, the crystallinity index decreased after oxidation process. The initial pyrolysis temperature of DCNCs ranged from 242 to 344 °C. TEM results revealed that DCNC was rod-shaped with an average length and width of 130.88 nm and 7.3 nm, respectively. The average specific surface area (SSA) was 366.67 m²  g^-1 . The carboxyl content was around 3.485 mmol g^-1 . Finally, the adsorption capacity for contaminations was 76.98, 126.22, 64.44 and 9.63 mg g^-1 for copper ion (Cu²⁺ ), lead ion (Pb²⁺ ), chromium (Cr³⁺ ) and amoxicillin (AMX), respectively.

CONCLUSION

This work showed a sequentially chemical oxidation for preparing nanocellulose from secondary agricultural waste with many functional applications. © 2021 Society of Chemical Industry.

Insights into efficient adsorption of the typical pharmaceutical pollutant with an amphiphilic cellulose aerogel

An amphiphilic cellulose aerogel (HCNC-TPB/TMC) was fabricated by grafting 1,3,5-Tris (4-aminophenyl)benzene (TPB) and trimesoyl chloride (TMC) onto the aldehyde nanocellulose through Schiff alkali and substitution reaction. The obtained HCNC-TPB/TMC exhibited good morphology with cellulose fiber and owned abundant hydrophilic amino and carboxyl groups and hydrophobic aromatic groups. The batch adsorption experiments demonstrated that HCNC-TPB/TMC showed excellent adsorption performance (Q_max = 526.32 mg g^-1) for sodium diclofenac (DCF), wide pH applicability (4-10) and outstanding stability and reusability. The DCF adsorption obeyed the pseudo-second-order kinetic model and the Langmuir isotherm, and underwent a spontaneous exothermic process. The main adsorption mechanisms involved electrostatic interaction, hydrogen bonds, π-π stacking interaction and hydrophobic effect. Importantly, the introduced carboxyl aromatic groups on TMC could effectively strengthen the hydrogen bonds and the π-π stacking between HCNC-TPB/TMC and DCF.

Biosorption of nickel ions Ni2+ by natural and modified Pinus caribaea Morelet sawdust

The potential of Pinus caribaea Morelet sawdust for the removal of nickel ions (Ni²⁺) and other metallic trace ions (Co²⁺, Cr³⁺, Mn²⁺) from aqueous solutions was investigated under batch conditions. Several parameters such as size of particles, contact time, pH, initial metal and biomass concentrations, desorption conditions and reusability were evaluated on natural biomass. Biosorption was fast, effective (73%) and biomaterial can be reused after five cycles. To enhance the removal capacity of nickel, pine sawdust was modified by acidic and oxidative treatments. Cellulosic residues from sawdust sequential extraction showed great biosorption capacity (96%). In the presence of a metal mixture, oxidized sawdust had better selectivity for Cr³⁺ ions than for Ni²⁺. Pinus caribaea biomass could be an environmental, inexpensive and renewable material for the depollution of water laden with metallic trace elements.

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Pinus caribaea sawdust is an effective biosorbent of metallic trace elements.

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High Ni²⁺ removal efficiency was observed at pH 8 with 5 g/L of biosorbent.

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Equilibrium adsorption was described by Freundlich and Langmuir isotherms.

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Pine sawdust is a reusable biosorbent with good desorption capacity.

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Efficiency of acidified and oxidized adsorbents.

Enhancing Removal of Cr(VI), Pb2+, and Cu2+ from Aqueous Solutions Using Amino-Functionalized Cellulose Nanocrystal

In this work, the amino-functionalized cellulose nanocrystal (ACNC) was prepared using a green route and applied as a biosorbent for adsorption of Cr(VI), Pb²⁺, and Cu²⁺ from aqueous solutions. CNC was firstly oxidized by sodium periodate to yield the dialdehyde nanocellulose (DACNC). Then, DACNC reacted with diethylenetriamine (DETA) to obtain amino-functionalized nanocellulose (ACNC) through a Schiff base reaction. The properties of DACNC and ACNC were characterized by using elemental analysis, Fourier transform infrared spectroscopy (FT-IR), Kaiser test, atomic force microscopy (AFM), X-ray diffraction (XRD), and zeta potential measurement. The presence of free amino groups was evidenced by the FT-IR results and Kaiser test. ACNCs exhibited an amphoteric nature with isoelectric points between pH 8 and 9. After the chemical modification, the cellulose I polymorph of nanocellulose remained, while the crystallinity decreased. The adsorption behavior of ACNC was investigated for the removal of Cr(VI), Pb²⁺, and Cu²⁺ in aqueous solutions. The maximum adsorption capacities were obtained at pH 2 for Cr(VI) and pH 6 for Cu²⁺ and Pb²⁺, respectively. The adsorption all followed pseudo second-order kinetics and Sips adsorption isotherms. The estimated adsorption capacities for Cr(VI), Pb²⁺, and Cu²⁺ were 70.503, 54.115, and 49.600 mg/g, respectively.

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m-2·atm-1·day-1 to 27.97 g·mm·m-2·atm-1·day-1 and oxygen permeability (OP) value decreasing from 0.14 cm3·mm·m-2·day-1·atm-1 to 0.026 cm3·mm·m-2·day-1·atm-1. Meanwhile, the maximum decomposition temperature (Tdmax) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.

Partially Oxidized Cellulose grafted with Polyethylene Glycol mono-Methyl Ether (m-PEG) as Electrolyte Material for Lithium Polymer Battery

Herein, a novel cellulose derivative has been synthesized and investigated as a nature-derived solid polymer electrolyte for lithium batteries. Cellulose is oxidized in a two-step process to dicarboxylic acid cellulose to allow for grafting low molecular weight poly(ethylene glycol) monomethyl ether (550 g mol^-1) via Fischer-Speier esterification at the thus obtained carboxyl groups. The chemical structure of the synthesized materials is confirmed by Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy as well as X-ray diffraction. Incorporating lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI) as conducting salt and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr₁₄TFSI) ionic liquid as plasticizer results in the realization of an amorphous and solvent-free solid polymer electrolyte. These electrolyte membranes are characterized by high thermal and electrochemical stability and ionic conductivities of about 1×10^-5 S cm^-1 at 20 °C and 2.5×10^-4 S cm^-1 at 80 °C, which enables very stable lithium stripping and plating for more than 800 h.

Oxidized Renewable Materials for the Removal of Cobalt(II) and Copper(II) from Aqueous Solution Using in Batch and Fixed-Bed Column Adsorption

Batch and continuous adsorption of Co2+and Cu2+from aqueous solutions by oxidized sugarcane bagasse (SBox) and oxidized cellulose (Cox) were investigated. The oxidation reaction of sugarcane bagasse and cellulose was made with a mixture of H3PO4‒NaNO2to obtain SBox and Cox, with the introduction of high number of carboxylic acid functions, 4.5 and 4.8 mmol/g, respectively. The adsorption kinetics of Co2+and Cu2+on SBox and Cox were modeled using two models (pseudo-first-order and pseudo-second-order) and the rate-limiting step controlling the adsorption was evaluated by Boyd and intraparticle diffusion models. The Sips and Langmuir models better fitted the isotherms with values of maximum adsorption capacityQmaxof 0.68 and 0.37 mmol/g for Co2+and 1.20 and 0.57 mmol/g for Cu2+adsorption on Cox and SBox, respectively. The reuse of both spent adsorbents was evaluated. Adsorption of Cu2+and Co2+on SBox in continuous was evaluated using a 22factorial design with spatial time and initial metal concentration as independent variables andQmaxand effective use of the bed as responses. The breakthrough curves were very well described by the Bohart–Adams original model and theQmaxvalues for Co2+and Cu2+were 0.22 and 0.55 mmol/g. SBox confirmed to be a promising biomaterial for application on a large scale.

Bioactive bacterial cellulose membrane with prolonged release of chlorhexidine for dental medical application

Bioabsorbable barrier membrane is desired in dental medicine for treatment of periodontal diseases caused by different types of bacteria. Bioactive and bioabsorbable bacterial cellulose (BC) is a promising material for such application. However, a key challenge to implement this approach is produce BC membranes selectively oxidized and loaded with a bactericide, in order to modulate bioabsortion time and bactericide effect, respectively. In the present study, the drug model chlorhexidine (CHX) was chosen and NaIO₄ was used as oxidizing agent. To modulate CHX release and efficacy, inclusion complexes of CHX with β-cyclodextrin (CHX:βCD) were synthesized. A linear dependence between degree of oxidation (DO) and oxidant concentration was found (DO = 2.07 + 45 [NaIO₄]). CHX has strong chemical interaction with cellulose structure, contributing for its significant retention. The association of membrane oxidation and formation of the inclusion complex with βCD causes a 10-fold increase in CHX release rate compared to unmodified cellulose. Thus, validating the concept that CHX release can be modulated using these two strategies. All membranes loaded with CHX inhibited S. aureus, E. coli and C. albicans growth, but DABC+CHX:βCD showed greater inhibition zone (p < 0.05). That, associated with other results, indicates potential application as bioactive and bioabsorbable membrane.

The Preparation of Nano-SiO₂/Dialdehyde Cellulose Hybrid Materials as a Novel Cross-Linking Agent for Collagen Solutions

Nano-SiO₂ was immobilized onto dialdehyde cellulose (DAC) to prepare SiO₂/DAC hybrid materials. Fourier transform infrared spectra (FTIR), thermogravimetric analysis and field emission scanning electron microscopy of SiO₂/DAC indicated that nano-SiO₂ had been successfully hybridized with DAC. X-ray diffraction suggested that the structure of DAC was influenced by the nano-SiO₂. SiO₂/DAC was then used as the cross-linker of collagen solutions. Gel electrophoresis patterns and FTIR reflected that cross-linking occurred between DAC and collagen, but that collagen retained the native triple-helix, respectively. Differential scanning calorimetry indicated that the thermal stability of collagen could be effectively improved by SiO₂/DAC. Dynamic rheology tests revealed that the flowability of collagens cross-linked by SiO₂/DAC was superior to that of those cross-linked by DAC; meanwhile, collagens cross-linked by SiO₂/DAC possessed a more homogeneous morphology compared to those cross-linked by DAC. The hybridization of SiO₂/DAC as a cross-linker for collagen could effectively prevent the gelation caused by excessive cross-linking, and significantly improve the thermostability of collagen, which could be helpful for collagen being applied in fields including biomaterials, cosmetics, etc.

Optimization of cellulose and sugarcane bagasse oxidation: Application for adsorptive removal of crystal violet and auramine-O from aqueous solution

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H₃PO₄-NaNO₂ mixture to obtain adsorbent materials with high contents of carboxylic groups. The oxidation reactions of Cel and SB were optimized using design of experiments (DOE) and response surface methodology (RSM). The optimized synthesis conditions yielded Cox and SBox with 4.8mmol/g and 4.5mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state ¹³C NMR. The adsorption of the model cationic dyes crystal violet (CV) and auramine-O (AO) on Cox and SBox in aqueous solution was investigated as a function of the solution pH, the contact time and the initial dye concentration. The adsorption of CV and AO on Cox was described by the Elovich equation and the pseudo-first-order kinetic model respectively, while the adsorption of CV and AO on SBox was described by the pseudo-second-order kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities (Q_max) of 1117.8mg/g of CV and 1223.3mg/g of AO on Cox and 1018.2mg/g of CV and 682.8mg/g of AO on SBox. Desorption efficiencies were in the range of 50-52% and re-adsorption capacities varied from 65 to 81%, showing the possibility of reuse of both adsorbent materials.

Synthesis and Characterization of Periodate-Oxidized Polysaccharides: Dialdehyde Xylan (DAX)

The cleavage of the C2-C3 bond in the building units of 1 → 4-linked polysaccharides by periodate formally results in two aldehyde units, which are present in several masked forms. The structural elucidation of such polysaccharide dialdehydes remains a big challenge. Since polysaccharide derivatives are increasingly applied in materials technology, unveiling the exact structure is of utmost importance. To address this issue for xylan, dialdehyde xylan (DAX, oxidation degree of 91.5%) has been synthesized as water-soluble polymer. The ATR-FTIR spectrum of DAX showed free aldehyde to be absent and exhibited a characteristic absorption at 858 cm(-1) related to hemiacetal groups. By a combination of 1D and 2D NMR techniques, it was confirmed that oxidized xylan is present as poly(2,6-dihydroxy-3-methoxy-5-methyl-3,5-diyl-1,4-dioxane). Based on GPC analysis, the DAX polymer shows a slightly lower molar mass (6.6 kDa) compared to the starting material (7.7 kDa) right after oxidation, and degraded further after one month of storage in 0.1 M NaCl solution (4.3 kDa). The oxidized xylan demonstrated lower thermal stability upon TGA analysis and a greater amount of residual char (20.6%) compared to the unmodified xylan (13.7%).

Thermoreversible laminin-functionalized hydrogel for neural tissue engineering

Traumatic injury to the central nervous system (CNS) triggers cell death and deafferentation, which may activate a cascade of cellular and network disturbances. These events often result in the formation of irregularly shaped lesions comprised of necrotic tissue and/or a fluid-filled cavity. Tissue engineering represents a promising treatment strategy for the injured neural tissue. To facilitate minimally invasive delivery of a tissue engineered system, a thermoreversible polymer is an attractive scaffold candidate. We have developed a bioactive scaffold for neural tissue engineering by tethering laminin-1 (LN) to methylcellulose (MC), a thermoresponsive hydrogel. The base MC chain was oxidized via sodium m-periodate to increase MC tethering capacity. Protein immobilization was facilitated by a Schiff base reaction between primary amine groups on LN and the carbonyl groups of the oxidized MC chain. Immunoassays demonstrated tethering of LN at 1.6 +/- 0.5 ng of LN per milligram of MC. Rheological measurements for different MC-LN constructs indicated MC composition- and MC treatment-dependent effects on solution-gelation transition temperature. Cellular assays with primary rat cortical neurons demonstrated enhanced cell adhesion and viability on LN-functionalized MC when compared with base and oxidized MC. This bioadhesive thermoresponsive scaffold may provide a robust delivery vehicle to injured CNS tissue for neural cell transplantation strategies.

Preparation of Ultrafine Oxidized Cellulose Mats via Electrospinning

Ultrafine oxidized cellulose (OC) mats were prepared by oxidation of ultrafine cellulose mats produced by electrospinning and subsequent deacetylation of cellulose acetate for potential applications in nonwoven adhesion barriers. When ultrafine cellulose mats were oxidized with a mixture of HNO3/H3PO4 - NaNO2 (2/1/1.4 v/v/wt %), their ultrafine mat structure remained unchanged. The yield and carboxyl content of OC mats were 86.7% and 16.8%, respectively. OC showed lower crystallinity than cellulose because the oxidation of cellulose proceeded via disruption of hydrogen bonds between cellulose chains. The swelling behaviors of ultrafine OC mats were dependent on the type of swelling solution. In a physiological salt solution, their degree of swelling was approximately 230%.