Carboxyl Cellulose Research Articles

Study on various properties and behaviour of lime with hemp, metakolin and carboxyl cellulose

Study on various properties and behaviour of lime with hemp, metakolin and carboxyl cellulose

Temperature-Tolerant Versatile Conductive Zwitterionic Nanocomposite Organohydrogel toward Multisensory Applications.

Conductive hydrogels (CHs) are emerging materials for next generation sensing systems in flexible electronics. However, the fabrication of competent CHs with excellent stretchability, adhesion, self-healing, photothermal conversion, multisensing, and environmental stability remains a huge challenge. Herein, a nanocomposite organohydrogel with the above features is constructed by in situ copolymerization of zwitterionic monomer and acrylamide in the existence of carboxylic cellulose nanofiber-carrying reduced graphene oxide (rGO) plus a solvent displacement strategy. The synergy of abundant dipole-dipole interactions and intermolecular hydrogen bonds enables the organohydrogel to exhibit high stretchability, strong adhesion, and good self-healing. The presence of glycerol weakens the formation of hydrogen bonds between water molecules, endowing the organohydrogel with excellent environmental stability (-40 to 60 °C) to adapt to different application scenarios. Importantly, the multimodal organohydrogel presents excellent sensing behavior, including a high gauge factor of 16.3 at strains of 400-1440% and a reliable thermal coefficient of resistance (-4.2 °C-1) over a wide temperature widow (-40 to 60 °C). Moreover, the organohydrogel displays a highly efficient and reliable photothermal conversion ability due to the favorable optical absorbing behavior of rGO. Notably, the organohydrogel can detect accurate human activities at ambient temperature, demonstrating potential applications in flexible intelligent electronics.

Mesenchymal stem cell therapy using Pal-KTTKS-enriched carboxylated cellulose improves burn wound in rat model.

Despite the great progress in developing wound dressings, delayed wound closure still remains a global challenge. Thus, developing novel wound dressings and employing advanced strategies, including tissue engineering, are urgently desired. The carboxylated cellulose was developed through the in situ synthesis method and further reinforced by incorporating pal-KTTKS to stimulate collagen synthesis and improve wound healing. The developed composites supported cell adhesion and proliferation and showed good biocompatibility. To boost wound-healing performance, adipose-derived mesenchymal stem cells (MSC) were seeded on the pal-KTTKS-enriched composites to be implanted in a rat model of burn wound healing. Healthy male rats were randomly divided into four groups and wound-healing performance of Vaseline gauze (control), carboxylated cellulose (CBC), pal-KTTKS-enriched CBC (KTTKS-CBC), and MSCs seeded on the KTTKS-CBC composites (MSC-KTTKS-CBC) were evaluated on days 3, 7, and 14 post-implantation. In each group, the designed therapeutic dressings were renewed every 5days to increase wound-healing performance. We found that KTTKS-CBC and MSC-KTTKS-CBC composites exhibited significantly better wound healing capability, as evidenced by significantly alleviated inflammation, increased collagen deposition, improved angiogenesis, and considerably accelerated wound closure. Nevertheless, the best wound-healing performance was observed in the MSC-KTTKS-CBC groups among all four groups. This research suggests that the MSC-KTTKS-CBC composite offers a great deal of promise as a wound dressing to enhance wound regeneration and expedite wound closure in the clinic.

Improved enantioselective permeation in cellulose membrane-supported metal–organic framework via polyvinylpyrrolidone as the pore-forming agent

Chiral membranes have limited permeability and selective trade-off, which has been a major problem in chiral membrane separations. To address this issue, the carboxylated cellulose (CC) membranes were prepared with small pore size and low resistance substrate by regulating the amount of polyvinylpyrrolidone (PVP) and casting solution, and the CC@CuLBH composite membrane with chiral separation capability was fabricated by in situ formation of well-dispersed [Cu(L-mal)(Bipy)]·H2O (CuLBH) with the carboxyl group on the surface of CC membrane as the metal anchor points. Under the optimal conditions, the CC@CuLBH membrane showed good chiral separation ability with an ee value of 60% for R-1-(1-naphthyl)ethanol (R-NE). Compared with the CC/CuLBH membrane formed by physical blend, the CC@CuLBH membrane exhibited improved enantioselective permeation for R-NE enantiomer. Both the unique chiral microenvironment of CuLBH and the regular pore structure of CC membrane, in addition to their synergistic effects resulted in the highly permeable and enantioselectivity for the CC@CuLBH composite membrane, which broadened the preparation method of chiral membrane.

Fabrication of a tough, long-lasting adhesive hydrogel patch via the synergy of interfacial entanglement and adhesion group densification.

Adhesive hydrogels (AHs) are considered ideal materials for flexible sensors. However, the lack of effective energy dissipation networks and sparse surface polar groups in AHs lead to poor mechanical properties and interfacial adhesion, which limit their practical application. Herein, a tough, long-lasting adhesive and highly conductive nanocomposite hydrogel (PACPH) was fabricated via the synergy of interfacial entanglement and adhesion group densification. PACPH was obtained by the in situ polymerization of highly carboxylated cellulose nanocrystals (SCNCPA, surface pre-grafted polyacrylic acid chains, C-COOH = 11.5 mmol g-1) with the acrylic acid precursor. The unique tacticity of SCNCPA provides strong interface entanglement and multiple hydrogen bonds with the PACPH network, which further increases the energy dissipated during SCNCPA displacements, and enhances the mechanical properties of PACPH (tensile strength = 1.45 MPa, modulus = 332 kPa, and fracture toughness = 13.2 MJ m-3). Meanwhile, SCNCPA increases the density of surface polar groups in PAPCH and also acts as an anchor point to improve the adhesion strength (>2-3 times) of PACPH on various substrates. The combination of excellent mechanical, adhesive, and conductive properties of the PAPCH-integrated patches enables long-term monitoring of human daily activities and electrocardiogram (ECG) signals, verifying that PAPCH is a promising material platform for the further development of flexible sensors and other health management devices.

Highly stretchable, environmentally stable, self-healing and adhesive conductive nanocomposite organohydrogel for efficient multimodal sensing

Conductive hydrogel (CH) has drawn widespread interest in flexible electronics, human–computer interaction, and electronic skins (e-skins). However, it is challenging to integrate satisfactory self-adhesion, self-healing, environmental stability, and multi-stimulus response into a single CH system. Herein, a conductive nanocomposite organohydrogel with the above characteristics is well-designed and developed via incorporating carboxylic cellulose nanofibers-carrying carboxylic carbon nanotubes (C-CNTs) and phytic acid (PA) into polyacrylamide network through free-radical polymerization plus glycerol solvent displacement strategy, aiming for a high-performance multimodal sensing platform. Here, the coupling of C-CNTs and ionization of PA contributes a favorable conductivity, and the coexistence of glycerol and PA is beneficial for the formation of amounts of hydrogen bonds that endow the organohydrogel with outstanding stretchability, self-healing, and favorable adhesion in a wide temperature range of −30 to 60 °C. Besides, the resultant organohydrogel can effectively detect multiple external stimuli, manifesting high strain sensitivity over a broad strain range (0–1566 %), good humidity detectability at 0–85 % RH, and reliable thermosensation capability over a wide temperature window (−30 to 60 °C). Significantly, the application of the organohydrogel as e-skins are conducted to detect full-range human activity movements even in the extreme environments, identify hand gestures, and recognize the spatial distribution of humidity in noncontact sensing. All these indicate the preponderance of our organohydrogel in the fields of flexible smart electronics.

Temperature-Sensitive Aerogel Using Bagasse Carboxylated Cellulose Nanocrystals/N-Isopropyl Acrylamide for Controlled Release of Pesticides.

Temperature-sensitive carboxylated cellulose nanocrystals/N-isopropyl acrylamide aerogels (CCNC-NIPAMs) were developed as novel pesticide-controlled release formulas. Ammonium persulfate (APS) one-step oxidation was used to prepare bagasse-based CCNCs, and then the monomer N-isopropyl acrylamide (NIPAM) was successfully introduced and constructed into the temperature-sensitive CCNC-NIPAMs through polymerization. The results of the zeta potential measurement and Fourier infrared transform spectrum (FTIR) show that the average particle size of the CCNCs was 120.9 nm, the average surface potential of the CCNCs was -34.8 mV, and the crystallinity was 62.8%. The primary hydroxyl group on the surface of the CCNCs was replaced by the carboxyl group during oxidation. The morphology and structure of CCNC-NIPAMs were characterized via electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), compression performance, porosity analysis, and thermogravimetric (TG) analysis. The results demonstrate that CCNC-NIPAM has a high porosity and low density, as well as good thermal stability, which is conducive to loading and releasing pesticides. In the swelling, drug loading, and controlled release process, the CCNC-NIPAM exhibited significant temperature sensitivity. Under the same NIPAM reaction amount, the equilibrium swelling rate of the CCNC-NIPAM first increased and then decreased with increasing temperature, and the cumulative drug release ratio of the CCNC-NIPAM at 39 °C was significantly higher than that at 25 °C. The loading efficiency of the CCNC-NIPAM on the model drug thiamethoxam (TXM) was up to 23 wt%, and the first-order model and Korsmyer-Peppas model could be well-fitted in the drug release curves. The study provides a new method for the effective utilization of biomass and pesticides.

Reuse of used paper egg carton boxes as a source to produce hybrid AgNPs- carboxyl nanocellulose through bio-synthesis and its application in active food packaging

The proper disposal of disposable synthetic plastic food packaging materials presents a significant challenge for both the environment and the solid waste management community. To address this issue, an antibacterial-based high-strength bio-composite serves as the optimal alternative to conventional packaging materials. This study aims to produce a hybrid material of AgNPs-carboxyl cellulose nanocrystals (AgNPs-CCNCs), obtained from used egg carton boxes (UECBs), through bio acid hydrolysis and an in-situ generation process. Furthermore, AgNPs- carboxyl cellulose nanofibers (AgNPs-CCNFs) will be synthesized through a combination of bio acid hydrolysis and ball milling, followed by an additional in-situ generation step. The AgNPs-carboxyl nanocellulose (AgNPs-CCNCs, and AgNPs-CCNFs) exhibited excellent crystallinity index, morphology, thermal, and antibacterial properties. The morphological analysis was performed by electron microscopy, and the results showed the uniform distribution and spherical form of AgNPs appearing over the carboxyl nanocellulose through the in-situ generation process, which was confirmed through XRD analysis. The study further explores the impact of AgNPs-carboxyl nanocellulose on the mechanical, chemical, antibacterial, and thermal properties of the PVA matrix. The results demonstrate that the bio-nanocomposite film offers opportunities for utilization in active packaging applications.

Chemical composition of underutilized nipa (Nypa fruticans) frond and its valorization for one-pot fabrication of carboxyl cellulose nanocrystals

This study analyzed the chemical composition of nipa frond (NF) and proved that it consisted of 24.6 ± 0.2 wt% cellulose, 22.4 ± 0.4 wt% hemicellulose, 35.0 ± 0.2 wt% Klason lignin, 2.0 ± 0.1 wt% acid-soluble lignin, 5.4 ± 0.2 wt% soluble organic compounds, and 9.5 ± 0.1 wt% ash. To valorize the lignocellulosic biomass resource, NF was used for one-pot synthesis of carboxyl cellulose nanocrystals (CCNC) using an HNO3–NaNO2 mixture. TEM images revealed that nanocrystals were successfully extracted from NF with a mean diameter of 20 ± 4 nm. In addition, EDX spectroscopy, FTIR spectroscopy, and acid-base titration revealed that carboxylic (-COOH) groups were generated from the oxidation of hydroxylmethyl (-CH2OH) groups on cellulose structures. The discovery of a high carboxyl content of 3.38–5.62 mmol/g (15–25 wt%) in CCNC paves the way for its use as an ion-exchange material.

A novel dual-responsive bio-derived magnetic nanocomposite: An excellent catalyst for efficient photodegradation of contaminants and detection of food additive in wastewater

Industrial development has been a global issue due to massive disposal of pollutants in water bodies. Considering this, many researchers adopt photocatalysis as an efficient technology for coordinated abatement of pollutants from wastewater. However, designing of materials that grant dual applicability in removal as well as detection of pollutant is still a challenge. Thus, demonstrated herein were bio-derived bi-functional hybrid magnetic nanocomposites that presented high photocatalytic degradation and electrochemical detection of noxious contaminants in wastewater. Magnetic nickel ferrite (NF) nanoparticles were organized on bio-derived template constructed from carboxylated cellulose (CCL) and carboxylated graphene oxide (CGO) via facile hydrothermal treatment to fabricate CCL-CGO-NF nanocomposites which were validated through various characterization techniques such as FT-IR, Powder XRD, FE-SEM, HR-TEM, EDX, XPS and VSM studies. The photocatalytic activity was investigated for degradation of three virulent model contaminants: Fast green (FG), Levofloxacin (LV) and p-Nitrophenol (PNP). Results displayed higher degradation efficiency of CCL-CGO-NFx nanocomposites than pure NF with highest degradation of 98%, 75% and 94% for FG, LV and PNP, respectively using CCL-CGO-NF70. Moreover, CCL-CGO-NF70 was employed for electrochemical sensing of FG that exhibited low detection limit of 1 μM in concentration range of 5–1200 μM. The nanocomposite established good stability, repeatability, reproducibility and sensitivity in real samples that certifies its dual practical applicability in environment detoxification as a photocatalyst and an electrochemical sensor. Finally, social implications and future perspectives concerning this proposed method was discussed.

On the mechanism of enhanced foam stability by combining carboxylated cellulose nanofiber with hydrocarbon and fluorocarbon surfactants

The effect of carboxylated cellulose nanofiber (CCNF) on the firefighting foam stability and stabilization mechanism is investigated. The results show that equilibrium surface tension of CTAB/FC1157 solution decreases when CCNF concentration increases to 0.5 wt%, while CCNF has little effect on that of SDS/FC1157 solution. Besides, when CCNF concentration increases to 1.0 wt%, the foam initial drainage of SDS/FC1157 solution is delayed for about 3 min. Increasing CCNF concentration can slow down foam coarsening process and liquid drainage process of SDS/FC1157 and CTAB/FC1157 solutions, improving the foam stability. The foam stability enhancement of CTAB/FC1157-CCNF solution is due to the formation of bulk aggregates and the increase of viscosity. However, the foam stability enhancement of SDS/FC1157-CCNF solution may be caused by the increase of viscosity. CCNF significantly reduces the foaming ability of CTAB/FC1157 solution when CCNF concentration is >0.5 wt%. Nevertheless, the foaming ability of SDS/FC1157 solution decreases significantly when CCNF concentration reaches 3.0 wt%, and its foaming ability remains higher than CTAB/FC1157 solution. The foaming ability of SDS/FC1157-CCNF solution is mainly dominated by viscosity, while that of CTAB/FC1157-CCNF solution is dominated by viscosity and adsorption kinetics. Adding CCNF is expected to enhance the stability of firefighting foam and increase the efficiency of extinguishing fire.

Synthesis of Carboxyl Cellulose Nanocrystals/Copper Nanohybrids to Endow Waterborne Polyurethane Film with Improved Mechanical and Antibacterial Properties

The multifunctional nanohybrid fillers have attracted widespread attention in the field of polymer nanocomposites. In this study, carboxyl cellulose nanocrystals/copper nanoparticles (TCNC/Cu NP) nanohybrids were prepared by in situ growth of copper ions on the modified carboxyl CNC, and further doped into waterborne polyurethane (WPU) via solution blending. TEM, FTIR, XRD, and UV–vis analysis were used to characterize the morphology, composition, crystallization and structure of the as-prepared nanohybrid. TCNC/Cu NP nanohybrids exhibited good dispersion and interface compatibility in WPU matrix. The nanocomposite film obtained significantly enhanced mechanical, thermal stability and scratch resistance properties, which was attributed to a hydrogen bond network structure formed in the WPU matrix. Additionally, colony count method was performed to test antibacterial properties of various films. Compared to the pure WPU film, all of nanocomposite films showed better antibacterial properties against Escherichia coli and Staphylococcus aureus. The antibacterial ratio of the WPU nanocomposite film with the addition of TCNC/Cu NP (1:1) reach 99%. Furthermore, the results of a copper ion sustained release experiment showed that the nanocomposite film had a long-term release effect, which was ascribed to the strong bonding between TCNC/Cu NP nanohybrids and WPU matrix. Thus, Cu NP was firmly embedded in the hydrogen bonding network structure formed. This work gives a new approach to prepare the antibacterial WPU film with well mechanical properties.

Valorized soybean hulls as TEMPO-oxidized cellulose nanofibril and polyethylenimine composite hydrogels and their potential removal of water pollutants

Cellulose nanomaterial (CNM) and polyethylenimine (PEI) composites have attracted growing attention due to their multifunctional characteristics, which have been applied in different fields. In this work, soybean hulls were valorized into carboxyl cellulose nanofibrils (COOH-CNFs), and composited into hydrogels with PEI by combining them with cationic chelating and physical adsorption strategies. Cellulose nanofibrils (CNFs) were produced from soybean hulls prior to oxidation by a TEMPO mediated reaction to obtain COOH–CNFs; then drops of zinc chloride were added to 1.5% aqueous COOH–CNF dispersions, which were left for 24 h to form COOH-CNF hydrogels. Finally, the hydrogels were functionalized using different concentration of PEI solutions over a range of pH values. Elemental analysis results showed that 20% aq. PEI at pH 11.6 is the optimum condition to synthesize the COOH–CNF/PEI hydrogels. Additionally, the adsorption efficiency for the removal of anionic methyl blue dyes and Cu(II) ions from water was tested, reaching 82.6% and 69.8%, respectively, after 24 h. These results demonstrate the great potential of COOH–CNF/PEI hydrogels as adsorbent materials for water remediation.Graphical abstract

Fabrication of untreated and silane-treated carboxylated cellulose nanocrystals and their reinforcement in natural rubber biocomposites

In this study, cellulose nanocrystal (CNC) was extracted from Napier grass stems and subsequently functionalized to carboxylated cellulose nanocrystal (XCNC) by using an environmentally friendly method, namely, the KMnO4/oxalic acid redox reaction. The XCNC was subsequently modified with triethoxyvinylsilane (TEVS), called VCNC, by using ultrasound irradiation. The characterization of the prepared XCNC and VCNC was performed. The needle-like shape of XCNC was observed with an average diameter and length of 11.5 and 156 nm, respectively. XCNC had a carboxyl content of about 1.21 mmol g−1. The silane treatment showed no significant effects on the diameter and length of XCNC. When incorporated into natural rubber (NR), both XCNC and VCNC showed very high reinforcement, as evidenced by the substantial increases in modulus and hardness of the biocomposites, even at very low filler loadings. However, due to the high polarity of XCNC, tensile strength was not significantly improved with increasing XCNC loading up to 2 phr, above which it decreased rapidly due to the filler agglomeration. For VCNC, the silane treatment reduced hydrophilicity and improved compatibility with NR. The highly reactive vinyl group on the VCNC’s surface also takes part in sulfur vulcanization, leading to the strong covalent linkages between rubber and VCNC. Consequently, VCNC showed better reinforcement than XCNC, as evidenced by the markedly higher tensile strength and modulus, when compared at an equal filler loading. This study demonstrates the achievement in the preparation of a highly reinforcing bio-filler (VCNC) for NR from Napier grass using an environmentally friendly method and followed by a quick and simple sonochemical method.

Transparent, intrinsically stretchable cellulose nanofiber-mediated conductive hydrogel for strain and humidity sensing

Conductive hydrogels (CHs) have attracted considerable attentions in the fields of wearable electronics, disease diagnosis, and artificial intelligence. However, it is still a great challenge to prepare a single CH system with integrated characteristics of high stretchability, good transparency, and multisensory function through a simple fabrication process. Herein, carboxylic cellulose nanofibers (CCNF) were used to assist the homogeneous distribution of opaque conductive poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) into the crosslinked polyacrylamide network for the fabrication of stretchable and transparent interpenetrating network CH, aiming for a high-performance multisensory system. As expected, the ready formation of hydrogen bonds between the water molecules and a great deal of hydrophilic groups in the hydrogel endow the obtained CH with excellent humidity response behavior in a wide range (0–85%), and the introduction of CCNF and PEDOT: PSS is proved to be an effective strategy to enhance the humidity sensitivity, exhibiting great potential for the noncontact sensing of human respiration and finger movement. Meanwhile, it also displays excellent strain sensing behavior with favorable sensitivity in a broad range (0–837 %), fast response and reliable stability and reproducibility. Importantly, our prepared CH can also detect and discriminate complicated human activities and physiological signals. All these demonstrate the superiority of our prepared CH for the new generation of flexible wearable electronics.

Nanocellulose-intercalated MXene NF membrane with enhanced swelling resistance for highly efficient antibiotics separation

Two-dimensional (2D) nanomaterial-based membranes display attractive properties in molecular separation and transport, which holds their great promise for a host of applications. However, notorious swelling problem of 2D membranes result in unsatisfactory molecular/ions sieving performance, and the enhancement of structural stability for 2D membranes in aqueous solution is still challenging. Herein, we demonstrate how to efficiently stabilize the Ti3C2Tx MXene laminar architecture by the insertion of flexible and hydrophilic carboxylated cellulose nanofibers (CNFs). The importing of CNFs not only acted as a bridge to combine the adjacent 2D Ti3C2Tx sheets and enhance mechanical strength, but also assumed the role of pillar to fix the interlayer distance effectively and improve the anti-swelling properties of Ti3C2Tx membrane. Moreover, the intercalation of nanocelluloses into the interlayer of delaminated Ti3C2Tx is able to distinctly increase the interlayer spacing and create more open gaps for fast and selective molecular transport. When applied in antibiotics separative filtration process, the resultant membrane exhibits outperformed anti-swelling properties in water environment up to 76 h and simultaneously possesses satisfactorily high selectivity of antibiotics (∼99.0 % for azithromycin) with unprecedentedly high pure water permeance (∼26.0 L m−2h−1bar−1). Such 2D membranes can be easily fabricated by a facile and patternable vacuum-assisted filtration and nanocellulose induced self-assembly strategy, which holds great potential for their scalability that are applicable to many applications such as seawater desalination, industrial wastewater treatment and remediation of aquatic environment.

Cement-and-pebble nanofluidic membranes with stable acid resistance as osmotic energy generators

Osmotic energy between river water and seawater has attracted interest as a new source of sustainable energy. Nanofluidic membranes in a reverse electrodialysis configuration can capture energy from salinity gradients. However, current membrane materials suffer from high resistances, low stabilities, and low charge densities, which limit their further application. Here, we designed a high-performance nanofluidic membrane using carboxylic cellulose nanofibers functionalized with graphene oxide nanolamellas with cement-and-pebble microstructures and stable skeletons for enhanced ion transmembrane transport. By mixing artificial river water and seawater, the composite membrane achieved a high output power density up to 5.26 W m−2. Additionally, the membrane had an excellent acid resistance, which enabled long-term use with over 67 W m−2 of power density. The performance of this composite membrane benefited from the mechanically strong cellulose fibers and the bonding between nanofibers and nanolamellas. In this work, we highlight promising directions in industrial waste treatment using energy extracted from chemical potential gradients.

In-situ growth of porous Cu3(BTC)2 on cellulose nanofibrils for ultra-low dielectric films with high flexibility

The design of flexible polymeric films with internal porous structures has received increasing attention in low dielectric applications. The highly porous metal-organic frameworks (MOFs) of [Cu3(BTC)2]n (BTC=benzene-1,3,5-tricarboxylate) were introduced into aramid nanofibers (ANF) matrix by using carboxylated cellulose nanofibrils (CNF) as carriers to obtain strong, flexible, and ultra-low dielectric films. The well-dispersed “flowers-branch” like [email protected] through in-situ growth of CuBTC on CNF surface endowed the ANF/[email protected] films with excellent thermal stability, mechanical integrity and low dielectric properties. Besides, the flexible dielectric films exhibited superior ultraviolet (UV) resistance, lower coefficient of thermal expansion (4.28×10−5 °C − 1) and increased water contact angle (83.81°). More interestingly, the removal of guest molecules from the ANF/[email protected] films according to the vacuum heat treatment (VHT) process significantly improved their dielectric response. The specific surface areas of the composite films after VHT increased obviously, and the dielectric constant and dielectric loss tangent decreased to the expected 1.8–2.2 and 0.001–0.03 at 100 MHz, respectively. Consequently, such designable ultra-low dielectric films with high flexibility play an incredible significance in applications of microelectronics under large deformation conditions, especially in flexible/wearable devices at the arrival of 5 G era.

Direct carboxylation of cellulose in deep eutectic solvent and its adsorption behavior of methylene blue

The surface of cellulose particles was carboxylated (2.44 mmol/g) in a deep eutectic solvent containing carboxylic acid. Based on the carboxyl content, the effects of key factors on cellulose carboxylation was systematically investigated. In addition, the reaction mechanism was studied by using liquid chromatography-mass spectrometry, and the influence of deep eutectic solvent containing carboxylic acid on the structure and physicochemical properties of cellulose during carboxylation was examined using different characterization techniques. The results showed that the type of carboxylic acid, cellulose particle size, and pretreatment methods significantly affect the carboxylation efficiency, degradation, and carbonization of cellulose. The internal crystal structure of cellulose did not change after the carboxylation reaction, while the surface crystal structure was destroyed by carboxylation, which greatly improved the dispersion and hydrophilicity properties of the product. The kinetics and thermodynamics of carboxyl cellulose adsorption were studied as well. Potential application of carboxyl cellulose in the adsorption of pollutants was demonstrated. This study provides a new method for the direct modification of cellulose in deep eutectic solvents, as well as a new sustainable strategy for modifying other materials.

Integration of g-C3N4 into cellulose/graphene oxide foams for efficient photocatalytic Cr(VI) reduction

Graphitic carbon nitride (g-C3N4) exhibits unique optical properties and it is regarded as an excellent photocatalyst. However, powdered g-C3N4 suffers from limited carrier mobility and poor recyclability. Here, g-C3N4 powders are integrated into cellulose/graphene oxide (GO) matrix to obtain a convenient and three-dimensional foam via a freeze-drying method. Owing to the formation of crosslinks between and g-C3N4 and carboxylic cellulose, the g-C3N4 particles attach tightly to the foam skeleton and are uniformly dispersed. As-prepared foams have good mechanical flexibility and superior water stability. Visible light driven reduction of Cr(VI) was utilized to evaluate the photocatalytic performance. The optimal sample (CG-3 with 60 wt% g-C3N4 loading) can reduce 98% of Cr(VI) within 3 h, even performs better than powdered g-C3N4 counterpart. The presence of GO facilitates the light absorption and promotes the stability of composite films. Moreover, the composite foams are facile to recycle without complex separation procedures. The CG-3 has no significant loss of its original reduction performance after 9 cycles, proving desirable reusability. This work provides a solution for powder catalyst recovery and inspires the materials design on g-C3N4.