Research on water purification has recently revolved around nanomaterials because of their large specific surface area. However, there are still some problems associated with the preparation, application, and recovery of nanomaterials. Herein, we report for the first time a novel approach for one-step synthesis of porous hybrid fibers (PHFs), which can be used as an effective adsorbent for dye removal from polluted water. A low-cost biopolymer cellulose was chosen as the matrix of the fibers, whereas a NaOH solution was applied as the coagulation bath for the cellulose spinning dope that contained a certain amount of FeCl3. The obtained Fe(OH)3@Cellulose PHFs exhibited a multiscaled pore structure, with the in situ generated Fe(OH)3 nanoparticles uniformly distributed on the regenerated cellulose nanofibrous network of the fibers. These structural attributes are quite advantageous for an efficient adsorbent. The maximum Congo red removal capacity of the Fe(OH)3@Cellulose PHFs reached 689.65 mg/g, which was much higher than many early reported values. Importantly, the Fe(OH)3@Cellulose PHFs could favorably remove the dye at natural pH through filtration adsorption with excellent reusability. This approach, with the desired characteristics of simplicity, high efficiency, low cost, and being environmentally friendly, demonstrated a great potential for industrial applications.Keywords: Cellulose; Fe(OH)3 nanoparticles; Filtration adsorption; Porous fibers; Water purification;

•Superhydrophilic GO@CNF membrane was fabricated for the first time.•The micro/nanoscale hierarchical roughness surface was created through a facile method.•The membrane exhibited high water flux and superior antifouling performance.•The membrane was capable to separate oil/water mixtures in harsh environment.Inspired from fishscales, membranes with special surface wettability have been applied widely for the treatment of oily waste water. Herein, a novel superhydrophilic graphene oxide (GO)@electrospun cellulose nanofiber (CNF) membrane was successfully fabricated. This membrane exhibited a high separation efficiency, excellent antifouling properties, as well as a high flux for the gravity-driven oil/water separation. Moreover, the GO@CNF membrane was capable to effectively separate oil/water mixtures in a broad pH range or with a high concentration of salt, suggesting that this membrane was quite promising for future real-world practice in oil spill cleanup and oily wastewater treatment.

Cellulose nanofibers (CNFs)/poly(N-isopropylacrylamide) (PNIPAm) composite aerogels were successfully fabricated from a CNF aqueous suspension containing PNIPAm solute via lyophilization. PNIPAm was synthesized through free radical polymerization, and CNFs were individualized from filter paper cellulose fibers using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation pretreatment followed by mechanical nanofibrillation. It was discovered that the incorporation of CNFs could remarkably improve the structural integrity of composite aerogels by preventing them from shrinking during lyophilization. The structure and properties of the obtained aerogels were comprehensively analyzed with various techniques, including infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption analysis, compression testing, and water contact angle (CA) measurements. Due to the synergistic effects from the two components, the composite aerogels exhibited attractive thermoresponsive properties with exceptionally high compressive strength. The ultimate compressive strength for the composite aerogel (A4) at 70% strain reached 0.227 MPa, more than 12 times higher than that of the neat CNF aerogel. The CA measurements demonstrated that the hydrophilicity/hydrophobicity of CNF/PNIPAm composite aerogels could be switched at a certain temperature. The CA sharply increased from 0 to 97° when the temperature was increased from 20 to 35 °C, exhibiting strong temperature-dependent water absorption behaviors.Keywords: Aerogel; Cellulose nanofibers (CNFs); Compressive strength; Poly(N-isopropylacrylamide) (PNIPAm); Thermoresponsive properties

•The Fe(OH)3@CNFs were used in the removal of phosphate for the first time.•The maximum sorption capacity of Fe(OH)3@CNFs for phosphate was 142.86 mg/g.•It achieved a superior adsorption capacity over a wide range of pH conditions.•An increased solution ionic strength would remarkably enhance the adsorption.Ferric hydroxide-coated cellulose nanofibers (Fe(OH)3@CNFs) were synthesized for the removal of phosphate from wastewater. The maximum sorption capacity of Fe(OH)3@CNFs for phosphate was estimated to be 142.86 mg/g, demonstrating a superior adsorption capacity compared with many adsorbents reported in the literature. Batch experiments were performed to investigate various adsorption conditions on the adsorption performance. It was discovered that an increased solution ionic strength would remarkably enhance the adsorption. Additionally, Fe(OH)3@CNFs achieved a favorable adsorption performance over a wide range of pH conditions, which could result in operation cost savings. The adsorption of phosphate can be described by both the Langmuir isotherm and pseudo-second-order models. The phosphate adsorbed by Fe(OH)3@CNFs was characterized using XPS, SEM, SBET and EDS. The data obtained revealed that the electrostatic attraction and ligand exchange constituted the major forces in phosphate adsorption. This work suggested that Fe(OH)3@CNFs are a promising adsorbent for phosphate removal.

Over the past decades, heavy metal ions, especially hexavalent chromium [Cr(VI)], have substantially ravaged the aquatic environment and human health. Thus, the development of new, more efficient, and environmentally friendly methods to tackle this problem becomes very urgent. In this study, a novel dendrimer poly(amidoamine)-grafted cellulose nanofibril (PAMAM-g-CNF) aerogel was synthesized for Cr(VI) removal. The morphology, structure and adsorption properties of the PAMAM-g-CNF aerogel were investigated in detail. The results indicated that the aerogel bore abundant functional groups with a bimodal pore structure and a high specific surface area, all of which are essential for an efficient adsorbent. The maximum Cr(VI) removal capacity of the aerogel reached 377.36 mg g−1, the highest one ever reported for biosorbents. It was interesting to note that part of Cr(VI) ions had been reduced to Cr(III) during the adsorption process, which meant that PAMAM-g-CNFs could detoxify Cr(VI).

Aerogels from polyethylenimine-grafted cellulose nanofibrils (CNFs-PEI) were developed for the first time as a novel drug delivery system. The morphology and structure of the CNFs before and after chemical modification were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Water-soluble sodium salicylate (NaSA) was used as a model drug for the investigation of drug loading and release performance. The CNFs-PEI aerogels exhibited a high drug loading capability (287.39 mg/g), and the drug adsorption process could be well described by Langmuir isotherm and pseudo-second-order kinetics models. Drug release experiments demonstrated a sustained and controlled release behavior of the aerogels highly dependent on pH and temperature. This process followed quite well the pseudo-second-order release kinetics. Owing to the unique pH- and temperature-responsiveness together with their excellent biodegradability and biocompatibility, the CNFs-PEI aerogels were very promising as a new generation of controlled drug delivery carriers, offering simple and safe alternatives to the conventional systems from synthetic polymers.Keywords: aerogel; cellulose nanofibrils (CNFs); controlled release; drug delivery; polyethylenimine (PEI)

•A waterproof Ag/Ag2O@cellulose membrane was fabricated to mimic water striders.•The nanoparticles of Ag/Ag2O provide the membrane a water contact angle of 140°.•The hybrid membrane exhibited oil/water separation capacity.•The hybrid membrane could effectively kill E. coli.Water striders can walk on water. To mimic this function, a porous membrane consisted of bamboo cellulose fiber was hybridized with Ag/Ag2O nanoparticles through a facile in situ method to produce water repellent and well-ventilated materials. Herein, we report the sole surface roughness created by Ag/Ag2O nanoparticles could render the membrane a water contact angle (CA) of 140 ± 3.0°. When floating on water, the hybrid membrane was able to support a heavy load more than 10 times the weight of the membrane itself. Additionally, this membrane demonstrated capabilities for oil sampling under water or oil/water separation and strong antibacterial activity against Escherichia coli. Thus we foresee that this novel hybrid membrane can be potentially utilized as drag-reducing, gas permeable and antibiotic substrates for constructing miniature aquatic devices.

•Nonwovens of cellulose nanofibers were electrospun from cotton.•Fast tangential velocity of the collector promoted nanofiber alignment.•Tensile strength was largely improved for the nonwovens with aligned nanofibers.•The nonwovens were assessed as potential tissue engineering scaffolds.•Cells proliferated rapidly not only on the surface but also in the entire scaffold.Nonwovens of cellulose nanofibers were fabricated by electrospinning of cotton cellulose in its LiCl/DMAc solution. The key factors associated with the electrospinning process, including the intrinsic properties of cellulose solutions, the rotating speed of collector and the applied voltage, were systematically investigated. XRD data indicated the electrospun nanofibers were almost amorphous. When increasing the rotating speed of the collector, preferential alignment of fibers along the drawing direction and improved molecular orientation were revealed by scanning electron microscope and polarized FTIR, respectively. Tensile tests indicated the strength of the nonwovens along the orientation direction could be largely improved when collected at a higher speed. In light of the excellent biocompatibility and biodegradability as well as their unique porous structure, the nonwovens were further assessed as potential tissue engineering scaffolds. Cell culture experiments demonstrated human dental follicle cells could proliferate rapidly not only on the surface but also in the entire scaffold.

•An efficient heavy metal adsorbent from functionalized CNFs aerogel is developed.•The robust aerogel has a large specific surface area with unique porous structure.•Separation of aerogel after use from water is simple and easy.•The aerogel exhibits excellent reusability.An efficient heavy metal adsorbent from quaternary ammonium-functionalized cellulose nanofiber aerogels was successfully developed. The highly porous aerogel could well retain its large specific surface area, which allowed rapid and effective removal of Cr(VI) from contaminated water. The aerogel adsorbent became mechanically robust after chemical crosslinking. It could be easily separated from water after adsorption without complicated centrifugation or filtration process. With only 1 g of aerogel, more than 99% of Cr(VI) in 1 L of 1 mg/L solution could be removed in 50 min. Besides, the aerogel also exhibited excellent reusability.

•An environmentally friendly approach for preparing cellulose hydrogels.•Dialysis and ultrasonication are the key processes for cellulose gelation.•Cellulose hydrogels are mainly composed of micron-sized short fibers.•The electrostatic repulsion between cellulose governs the gelation behaviors.•pH and salt strongly influence the formation of cellulose hydrogels.We demonstrated for the first time that dimensionally stable hydrogels could be obtained from bamboo pulp fibers through dialysis against distilled water followed by a short time of ultrasonic treatment. Micron-sized short fibers rather than cellulose nanofibrils constituted the majority of fibers in the hydrogels. During the pulping process with HNO3 and KClO3, carboxylic groups could be introduced to cellulose due to the mild oxidation of hydroxyl groups. When presented in aqueous NaOH, the carboxylic groups could be converted into their sodium salt form. The subsequent dialysis treatment against water made the negatively charged COO− groups extensively exposed. The negatively charged cellulose fibers could induce considerable electrostatic repulsion between them, which was discovered to govern the formation of hydrogels. In addition, it was revealed that homogeneous hydrogels could be formed when the pH was at 7, 9 and 11. However, when salt was added, no dimensionally stable hydrogel was obtained.

•All-cellulose nanocomposites were fabricated using CNFs as the reinforcement.•CNFs greatly enhanced mechanical properties of the nanocomposite films.•An optimal CNFs concentration of 10 wt% in the composites was found.•The nanocomposite films exhibited excellent optical transparency.•The nanocomposite films exhibited enhanced thermal stability.All-cellulose nanocomposite films were prepared using native cellulose nanofibrils (CNFs) as fillers and lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) dissolved regenerated cellulose as the matrix. The CNFs, with diameters in the range of 15–40 nm were obtained by combined physical methods of ultrasonic treatment and high shear homogenization. The morphology, structure, and properties of the nanocomposite films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), optical transmittance, thermal gravimetric analysis (TGA), and mechanical testing. The nanocomposite films exhibited good optical transparency, thermal stability, and remarkably enhanced mechanical properties compared to the regenerated cellulose matrix. By varying the CNFs content, the tensile strength of the nanocomposite films increased from 61.56 MPa to 99.92 MPa and the Young's modulus increased from 0.76 GPa to 4.16 GPa. This work provided a promising pathway for manufacturing high performance and environmental-friendly all-cellulose nanocomposites.

Bamboo cellulose nanofibers-graft-poly (acrylic acid) (BCN-g-PAA) and bamboo cellulose nanofibers-graft-poly (acrylic acid)/sodium humate (BCN-g-PAA/SH) were synthesized for the first time and sequentially utilized as biosorbents for removal of Cu2+ from aqueous solutions. The chemical structure and morphology of both modified nanofibers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Batch adsorption experiments were conducted to elucidate their adsorption behaviors on Cu2+. The influencing factors, such as pH, contact time and initial Cu2+ concentration, on Cu2+ adsorption were investigated in detail. It was discovered that pH strongly influenced the Cu2+ adsorption. When pH increased from 2.0 to 4.5, the adsorption capacities of both modified nanofibers were improved significantly. Adsorption isotherm studies indicated that the Cu2+ adsorption could be described well by the Freundlich equation. Meanwhile, their adsorption kinetics was more likely to follow the pseudo-second-order model. These nanocellulose-based adsorbents exhibited very fast adsorption rates. The calculated adsorption capacities at equilibrium (qcale) for BCN-g-PAA and BCN-g-PAA/SH were 0.727 and 0.709 mmol g−1, significantly higher than that of BCN (0.286 mmol g−1). Adsorption/desorption cycling tests suggested that the introduced SH segments allowed for improved reusability of BCN-g-PAA/SH.

Uniaxially aligned cellulose nanofibers with well oriented cellulose nanocrystals (CNCs) embedded were fabricated via electrospinning using a rotating drum as the collector. Scanning electron microscope (SEM) images indicated that most cellulose nanofibers were uniaxially aligned. The incorporation of CNCs into the spinning dope resulted in more uniform morphology of the electrospun cellulose/CNCs nanocomposite nanofibers (ECCNN). Polarized light microscope (PLM) and transmission electron microscope (TEM) showed that CNCs dispersed well in ECCNN nonwovens and achieved considerable orientation along the long axis direction. This unique hierarchical microstructure of ECCNN nonwovens gave rise to remarkable enhancement of their physical properties. By incorporating 20% loading (in weight) of CNCs, the tensile strength and elastic modulus of ECCNN along the fiber alignment direction were increased by 101.7 and 171.6%, respectively. Their thermal stability was significantly improved as well. In addition, the ECCNN nonwovens were assessed as potential scaffold materials for tissue engineering. It was elucidated from MTT tests that the ECCNN were essentially nontoxic to human cells. Cell culture experiments demonstrated that cells could proliferate rapidly not only on the surface but also deep inside the ECCNN. More importantly, the aligned nanofibers of ECCNN exhibited a strong effect on directing cellular organization. This feature made the scaffold particularly useful for various artificial tissues or organs, such as blood vessel, tendon, nerve, and so on, in which cell orientation was crucial for their performance.

•A chemical-free method for extracting CNFs from dry softwood pulp.•Refining facilitates high shear homogenization for CNFs extraction.•Diameters of CNFs prepared are mainly between 16 and 28 nm.•Crystallinity of CNFs is increased compared with that of raw fibers.•Thermal stability of CNFs is decreased compared with that of raw fibers.The objective of this study was to extract cellulose nanofibrils (CNFs) from dry softwood pulp through a simple and environmentally friendly physical method of refining pretreatment coupled with high shear homogenization. An optical microscopy (OM) clearly showed the morphological development from the cellulose fibers to CNFs under repeated shear forces. The morphology, structure and properties of the obtained CNFs were comprehensively investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectra, X-ray diffraction (XRD) and thermogravimetric (TG) analysis. The results indicated that the CNFs had diameters mainly ranged from 16 to 28 nm. Compared with the pulp fibers, the CNFs exhibited a slightly higher crystallinity and a lower thermal stability. Moreover, a novel nanopaper with high optical transparency was prepared from the obtained CNFs, and a possible mechanism for the high optical transparency was discussed.

Over the past decades, heavy metal ions, especially hexavalent chromium [Cr(VI)], have substantially ravaged the aquatic environment and human health. Thus, the development of new, more efficient, and environmentally friendly methods to tackle this problem becomes very urgent. In this study, a novel dendrimer poly(amidoamine)-grafted cellulose nanofibril (PAMAM-g-CNF) aerogel was synthesized for Cr(VI) removal. The morphology, structure and adsorption properties of the PAMAM-g-CNF aerogel were investigated in detail. The results indicated that the aerogel bore abundant functional groups with a bimodal pore structure and a high specific surface area, all of which are essential for an efficient adsorbent. The maximum Cr(VI) removal capacity of the aerogel reached 377.36 mg g−1, the highest one ever reported for biosorbents. It was interesting to note that part of Cr(VI) ions had been reduced to Cr(III) during the adsorption process, which meant that PAMAM-g-CNFs could detoxify Cr(VI).