Carboxymethylated Lignin Reinforcement of SPI Adhesive: Enhancing Strength, Antimicrobial, and Flame-Retardant Properties without Excessive Alkali Introduction.

To address the challenges associated with formaldehyde emissions in engineered wood adhesives and simultaneously enhance adhesive properties related to water resistance, fire resistance, and mold resistance, a novel environmentally sustainable biomass-based adhesive was formulated. In this work, kraft lignin was carboxymethylated and then blended with the soy protein isolate (SPI)-based adhesive, the dry and wet shear strength of the plywood bonded by the resultant adhesive was enhanced from 1.10 and 0.63 MPa to 1.73 and 1.23 MPa, respectively, resulting in improvements of 157% and 195%. Carboxymethylated lignin (CML) significantly improved the mold resistance and flame-resistance residual rate of the adhesive and decreased the water absorption rate from 190% to 108%. Furthermore, the adhesive exhibits outstanding flame-retardancy, with self-extinguishing capability rendering it suitable for industrial production. In addition, we also evaluated the performances of resulting adhesives cured with different diepoxides and triepoxides, and the comparisons of the adhesive in this work to commercial urea glue and soy protein-based adhesives were conducted. To our delight, the SPI-10CML adhesive presented comparable or even improved performances, showing its promising practical applications such as for fire doors.

Fabrication of versatile lignocellulose nanofibril/polymerizable deep eutectic solvent hydrogels with anti-swelling, adhesive and low-temperature resistant properties via a one-pot strategy.

Lignocellulosic nanofibril (LCNF) is indispensable in numerous potential applications because of its unsurpassed quintessential characteristics. While it still remains a challenge to assemble LCNF in a facile and environmental economy-first manner. In this work, a simple and green one-step synthetic approach was reported to prepare a series of LCNF-containing versatile hydrogels using deep eutectic solvent (DES). In particular, the LCNF5% hydrogel (namely LCNF5%-gel) in this work perfectly integrated superior stretchability (∼643 %), and displayed a dramatically improved anti-swelling ability (25 %) compared to the control sample (neat DES hydrogel, 2252 %). Simultaneously, the LCNF5% hydrogel presented underwater adhesiveness and outstanding long-term low-temperature resistance (stable at -25 °C for a month). This novel multifunctional hydrogel, prepared by a facile and eco-friendly strategy, is potentially useful in wet adhesion or underwater applications.

A general large-scale synthesis approach for crystalline porous materials.

Crystalline porous materials such as covalent organic frameworks (COFs), metal-organic frameworks (MOFs) and porous organic cages (POCs) have been widely applied in various fields with outstanding performances. However, the lack of general and effective methodology for large-scale production limits their further industrial applications. In this work, we developed a general approach comprising high pressure homogenization (HPH), which can realize large-scale synthesis of crystalline porous materials including COFs, MOFs, and POCs under benign conditions. This universal strategy, as illustrated in the proof of principle studies, has prepared 4 COFs, 4 MOFs, and 2 POCs. It can circumvent some drawbacks of existing approaches including low yield, high energy consumption, low efficiency, weak mass/thermal transfer, tedious procedures, poor reproducibility, and high cost. On the basis of this approach, an industrial homogenizer can produce 0.96 ~ 580.48 ton of high-performance COFs, MOFs, and POCs per day, which is unachievable via other methods.

Comparison of cellulose derivatives for Ca2+ and Zn2+ adsorption: Binding behavior and in vivo bioavailability.

Cellulose with distinct colloidal states exhibited different adsorption capability for ions and whether the intake of cellulose would bring positive or negative influence on the mineral bioavailability is inconclusive. This work investigated the binding behavior of carboxymethyl cellulose (CMC), TEMPO-oxidized nanofibrillated/nanocrystalline cellulose (TOCNF/TOCNC), and microcrystalline cellulose (MCC) with Ca2+and Zn2+ and compared their effects on mineral bioavailability in vitro and in vivo. The results suggested that CMC displayed a higher adsorption capability (36.6 mg g-1 for Ca2+ and 66.2 mg g-1 for Zn2+) than the other types of cellulose because of the strong interaction between carboxyl groups of cellulose and the ions. Although the cellulose derivatives had adverse effects on ion adsorption in vitro, the fermentability endowed by TOCNF/TOCNC counterbalanced the negative impacts in vivo. The findings suggested that the colloidal states of cellulose affected the bioavailability of minerals and could provide useful guidance for applications of specific cellulose.

Valuable aramid/cellulose nanofibers derived from recycled resources for reinforcing carbon fiber/phenolic composites.

The scale-up preparation of aramid nanofiber (ANF) and cellulose nanofiber (CNF), still faces serious challenges such as extreme production cost and lengthy preparation cycle. Herein, a feasible top-down strategy was proposed to achieve the efficient reclamation of waste resources, further realizing the large-scale production of high value-added nanofibers. The ANF/CNF as nanoscale building blocks and their reinforcement effects on the mechanical performances of carbon fiber/phenolic composites were investigated. Related strength and modulus of ANF/CNF-enhanced composites in the tensile, bending, shear and nano indentation tests, increased by 118.1% (tensile strength), 141.2% (tensile modulus), 142.2% (flexural strength), 354.4% (flexural modulus), 38.8% (shear strength) and 94.4% (elastic modulus), respectively. Our work offers a valuable reference in the fabrication of low-cost ANF/CNF derived from waste resources, which would facilitate the wide application of nanofibers in fabricating high-performance advanced functional materials.

Zwitterionic Cellulose Nanofibrils with High Salt Sensitivity and Tolerance.

To improve the salt tolerance/sensitivity of cellulose nanofibrils (CNFs), zwitterionic cellulose nanofibrils (ZCNFs) were prepared from softwood bleached kraft pulp fibers via a sequential process of anionic modification with 2,2,6,6-tetramethylepiperidin-1-oxyl (TEMPO)-mediated oxidation, cationic modification with (2,3-epoxypropyl) trimethylammonium chloride (EPTMAC), and high-pressure homogenization. To produce ZCNFs with different contents of cation group, EPTMAC loadings of 0.15 to 1.15 g/g fiber were explored during cationization. The obtained ZCNFs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and rheological measurements. The salt tolerance of the ZCNFs was investigated by adding mixed salts into the ZCNF dispersions. The results demonstrated that the ZCNFs with both anionic and cationic charges were produced. Compared with the TEMPO-mediated oxidized cellulose nanofibrils (TOCNFs), the ZCNFs exhibited an excellent "salt-thickening" behavior under the studied salt concentrations (2-24% w/w). Moreover, increasing the content of the cation group increased the salt tolerance/sensitivity of ZCNFs. This work demonstrated that introducing cationic charges to the anionic charged TOCNFs imparts the produced ZCNFs with excellent salt sensitivity and tolerance, which could expand the application of nanocellulose in oil recovery or wastewater treatment.

Cellulose nanofibril-polymer hybrids for protecting drilling fluid at high salinity and high temperature.

A copolymer (PADH) was first synthesized from 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-dimethylacrylamide (DMA), and 2-Hydroxyethyl acrylate (HEA) by UV-induced polymerization. Subsequently, cellulose nanofibrils (CNFs) were introduced into the copolymer through ironic cross-linking between ferric ions and carboxylate groups as well as sulfonic acid groups to produce a hybrid product (PADHC-Fe3+-3). The salt tolerance and thermal stability of the copolymers and the hybrid product were investigated. The results showed that the optimum HEA dosage was 5% (in relation to the total mass of AMPS and DMA). In addition, the fluid loss test showed that the hybrid product PADHC-Fe3+-3 had excellent salt tolerance (maximum tolerance: 26.5 wt% NaCl and 32 wt% combined salts) and thermal stability (maximum tolerance: 200 °C). The SEM images indicated that the filter cakes became denser after the addition of PADHC-Fe3+-3. The results demonstrated that the cross-linked hybrid product was very promising for industrial application in drilling engineering.

Hydrogels prepared from cellulose nanofibrils via ferric ion-mediated crosslinking reaction for protecting drilling fluid.

Ionic-covalent cross-linked poly-2-acrylamido-2-methylpropane sulfonic acid (AMPS)-N,N-Dimethylacrylamide (DMA)-cellulose nanofibril (CNF)-Fe3+ (PADC-Fe3+) hydrogels were synthesized by immersing CNFs reinforced covalent poly-AMPS-DMA (PAD) composite hydrogels into ferric chloride aqueous solution. To produce PADC-Fe3+ polymer with different CNF contents, CNF loadings of 5-20% were explored. The UV-spectroscopy analysis demonstrated the occurrence of CNF coalescence and optimized that 10% CNF loading resulted in the production of PADC-0.1-Fe3+ with the highest absorbance. Compared to copolymers (PAD or PADC-0.1) prepared without CNF or Fe3+, the synthesized PADC-0.1-Fe3+ showed much better tolerance to salt, high temperature, and shear. After adding synthesized PADC-0.1-Fe3+ as a filtrate reducer into the drilling fluids prepared with fresh water and 4% sodium chloride (NaCl), the filtrate loss was significantly reduced even at an elevated temperature of 200 ℃. Additionally, the addition of PADC-0.1-Fe3+ also increased the portion of fine cement particles in the drilling fluid.

Improving salt tolerance and thermal stability of cellulose nanofibrils by grafting modification.

Poor colloid stability of cellulose nanofibril (CNF) hydrogels at high temperature and high salinity can severely limit their industrial applications. This paper aims to prepare cellulose nanofibril hydrogels with improved salt tolerance and thermal stability. This was attained by simultaneous grafting of N,N-Dimethylacrylamide (DMA) and Butyl Acrylate (BA) onto the CNF surface based on the ceric ammonium nitrate-induced radical polymerization. The modified and original CNF samples were characterized by FT-IR, FBRM and rheological measurements. The FBRM results showed that the maximum salinity (NaCl) the CNF hydrogels can withstand increased from 1 wt% to 8 wt% after the simultaneous grafting of DMA (2 g/L) and BA (3 g/L). Moreover, rheological analysis results showed that the modified CNF hydrogels exhibited a much improved long-term thermal stability and a "salt-thickening" effect. As nano-cellulose based materials, the modified CNF hydrogels may have great potential as a promising petrochemical alternative for enhanced oil recovery applications.

Cationic cellulose nanofibers as sustainable flocculant and retention aid for reconstituted tobacco sheet with high performance.

The study that cationic cellulose nanofibers (CCNF) acts as sustainable flocculant and retention aid of precipitated calcium carbonate (PCC) for the preparation of reconstituted tobacco sheet (RTS) was carried out, thanks to the properties of CCNF. In this work, the enhanced flocculation, reflocculation and size properties of PCC flocs induced by CCNF were investigated via a focused beam reflectance measurement (FBRM) system. The physical properties of RTS such as bulk and air permeability etc. were also studied. The results indicated that CCNF could distinctly improve the flocculation and reflocculation properties of PCC with a desirable chord length in the tobacco slurry, and that the PCC retention was also increased with CCNF addition along with a slight decrease of tensile strength of RTS. The mechanisms of flocculation and reflocculation, as well as the reasons of enhanced bulk and air permeability properties ascribed to CCNF were also demonstrated.

Poly dimethyl diallyl ammonium chloride assisted cellulase pretreatment for pulp refining efficiency enhancement.

The use of poly (diallyldimethylammonium chloride) (PDADMAC) as an additive in the cellulase pretreatment process (the PDADMAC-assisted cellulase pretreatment process) prior to pulp refining, was investigated, with the objective of decreasing the energy consumption and/or cellulase dosage in the pulp refining process. Results showed that PDADMAC significantly improved the cellulase adsorption onto pulp fibers, which is responsible for enhancement in the cellulase treatment efficiency. The low molecular weight PDADMAC is more effective than the high molecular weight counterpart, because it is capable of infiltrating into the fiber pores to attack the fiber internal structure, while the high molecular weight PDADMAC just stays on the fiber surfaces. The developed pretreatment process facilitates the subsequent pulp refining process. The addition of PDADMAC has negligible effect on the strength properties of pulp while reducing the energy consumption with less cellulase dosage. One version of this process concept is proposed.

Enhancing the Fock reactivity of dissolving pulp by the combined prerefining and poly dimethyl diallyl ammonium chloride-assisted cellulase treatment.

Dissolving pulp is an important source of cellulose raw material, and its key quality parameter is the Fock reactivity for viscose rayon application. Cellulase treatment is an effective method for improving the Fock reactivity of kraft-based dissolving pulp. In this study, a novel process concept of improving the cellulase treatment for this purpose was developed, and it consists of mechanical pre-refining and PDADMAC-assisted cellulase treatment. The hypothesis is based on: 1) opening up the fiber structures to improve the cellulase accessibility by pulp prerefining, 2) the addition of cationic poly DADMAC to the subsequent cellulase stage enhances the cellulase adsorption onto anionic fibers due to favorable electrostatic interactions. The results showed that the Fock reactivity of the resultant pulp from the combined treatment is much higher than that of the control, yet, achieved at a much lower cellulase dosage.

Production of bioethanol and value added compounds from wheat straw through combined alkaline/alkaline-peroxide pretreatment.

An efficient scheme was developed for the conversion of wheat straw (WS) into bioethanol, silica and lignin. WS was pre-extracted with 0.2 mol/L sodium hydroxide at 30 °C for 5 h to remove about 91% of initial silica. Subsequently, the alkaline-pretreated solids were subjected to alkaline hydrogen peroxide (AHP) pretreatment with 40 mg hydrogen peroxide (H2O2)/g biomass at 50 °C for 7 h to prepare highly digestible substrate. The results of enzymatic hydrolysis demonstrated that the sequential alkaline-AHP pretreated WS was efficiently hydrolyzed at 10% (w/v) solids loading using an enzyme dosage of 10 mg protein/g glucan. The total sugar conversion of 92.4% was achieved. Simultaneous saccharification and co-fermentation (SSCF) was applied to produce ethanol from the two-stage pretreated substrate using Saccharomyces cerevisiae SR8u strain. Ethanol with concentration of 31.1 g/L was produced. Through the proposed process, about 86.4% and 54.1% of the initial silica and lignin were recovered, respectively.

Ethanol production from bamboo using mild alkaline pre-extraction followed by alkaline hydrogen peroxide pretreatment.

A sequential two-stage pretreatment process comprising alkaline pre-extraction and alkaline hydrogen peroxide pretreatment (AHP) was investigated to convert bamboo carbohydrates into bioethanol. The results showed that mild alkaline pre-extraction using 8% (w/w) sodium hydroxide (NaOH) at 100°C for 180min followed by AHP pretreatment with 4% (w/w) hydrogen peroxide (H2O2) was sufficient to generate a substrate that could be efficiently digested with low enzyme loadings. Moreover, alkali pre-extraction enabled the use of lower H2O2 charges in AHP treatment. Two-stage pretreatment followed by enzymatic hydrolysis with only 9FPU/g cellulose led to the recovery of 87% of the original sugars in the raw feedstock. The use of the pentose-hexose fermenting Saccharomyces cerevisiae SR8u strain enabled the utilization of 95.7% sugars in the hydrolysate to reach 4.6%w/v ethanol titer. The overall process also enabled the recovery of 62.9% lignin and 93.8% silica at high levels of purity.

Cellulosic Nanomaterials in Food and Nutraceutical Applications: A Review.

Cellulosic nanomaterials (CNMs) are organic, green nanomaterials that are obtained from renewable sources and possess exceptional mechanical strength and biocompatibility. The associated unique physical and chemical properties have made these nanomaterials an intriguing prospect for various applications including the food and nutraceutical industry. From the immobilization of various bioactive agents and enzymes, emulsion stabilization, direct food additives, to the development of intelligent packaging systems or pathogen or pH detectors, the potential food related applications for CNMs are endless. Over the past decade, there have been several reviews published covering different aspects of cellulosic nanomaterials, such as processing-structure-property relationship, physical and chemical properties, rheology, extraction, nanocomposites, etc. In this critical review, we have discussed and provided a summary of the recent developments in the utilization of cellulosic nanomaterials in applications related to food and nutraceuticals.

Stabilization of Foam Lamella Using Novel Surface-Grafted Nanocellulose-Based Nanofluids.

To solve the potential risk of present oilfield chemistries to subterranean environment, our group contributes to the development of "green" petroleum production processes. This proof-of-concept research studied the well-defined nanocellulose-based nanofluids, i.e., original (NC), AMPS grafted (NC-KY), and AMPS and hydrophobic chains grafted (NC-KYSS), in stabilizing foam lamella for potential use in enhanced oil recovery (EOR). The data showed that the collaboration of the surface-functional nanocellulose considerately improved the foam stability particularly in the presence of hydrocarbons due to the thickened foam film coupled with the molecular interactions at interior lamella. Since the grafted AMPS and alkyl chains, NC-KYSS noticeably enhanced foam quality compared against NC and NC-KY. With the increase in gas pressure, the lamella stabilizing effect of NC-KYSS became increasingly significant. The coflowing behaviors of foam with oleic phase in porous media were examined in a five-spot visualization micromodel (15 cm × 15 cm × 1 cm) and identified using a digital analysis method. The defoaming/destabilizing effect of hydrocarbons was fairly notable in porous media, causing the foam to finger through the formed "oil bank". However, a tough displacement front was constructed when the surfactant synergized with NC-KYSS due to the stabilized foam lamella and 12% of incremental oil recovery was produced.

Evaluation of an integrated process to fully utilize bamboo biomass during the production of bioethanol.

Aiming for the complete utilization of bamboo biomass, an integrated process which combines ethanol production with the recovery of silica and lignin was proposed. To reduce chemical charge required for the fractionation of silica and lignin from bamboo and improve the digestibility of the obtained substrate, a sequentially two-stage pretreatment process of autohydrolysis and alkaline extraction was carried out. From the view of enhancing enzymatic hydrolysis and recovery of silica and lignin, a two-stage treatment of autohydrolysis at 180°C for 90min followed by alkaline extraction at 100°C with 6% NaOH (based on pretreated chips) for 120min was optimized. About 93.7% of original silica and 75.7% of original lignin could be recovered from bamboo. Enzymatic hydrolysis and fermentation of carbohydrates showed that an overall sugar yield of 88.6% of original sugar content and an ethanol recovery of 0.467g/g sugar were achieved based on the proposed scheme.

A biorefinery scheme to fractionate bamboo into high-grade dissolving pulp and ethanol.

BACKGROUND: Bamboo is a highly abundant source of biomass which is underutilized despite having a chemical composition and fiber structure similar as wood. The main challenge for the industrial processing of bamboo is the high level of silica, which forms water-insoluble precipitates negetively affecting the process systems. A cost-competitive and eco-friendly scheme for the production of high-purity dissolving grade pulp from bamboo not only requires a process for silica removal, but also needs to fully utilize all of the materials dissolved in the process which includes lignin, and cellulosic and hemicellulosic sugars as well as the silica. Many investigations have been carried out to resolve the silica issue, but none of them has led to a commercial process. In this work, alkaline pretreatment of bamboo was conducted to extract silica prior to pulping process. The silica-free substrate was used to produce high-grade dissolving pulp. The dissolved silica, lignin, hemicellulosic sugars, and degraded cellulose in the spent liquors obtained from alkaline pretreatment and pulping process were recovered for providing high-value bio-based chemicals and fuel. RESULTS: An integrated process which combines dissolving pulp production with the recovery of excellent sustainable biofuel and biochemical feedstocks is presented in this work. Pretreatment at 95 °C with 12% NaOH charge for 150 min extracted all the silica and about 30% of the hemicellulose from bamboo. After kraft pulping, xylanase treatment and cold caustic extraction, pulp with hemicellulose content of about 3.5% was obtained. This pulp, after bleaching, provided a cellulose acetate grade dissolving pulp with α-cellulose content higher than 97% and hemicellulose content less than 2%. The amount of silica and lignin that could be recovered from the process corresponded to 95 and 77.86% of the two components in the original chips, respectively. Enzymatic hydrolysis and fermentation of the concentrated and detoxified sugar mixture liquor showed that an ethanol recovery of 0.46 g/g sugar was achieved with 93.2% of hydrolyzed sugars being consumed. A mass balance of the overall process showed that 76.59 g of solids was recovered from 100 g (o.d.) of green bamboo. CONCLUSIONS: The present work proposes an integrated biorefinery process that contains alkaline pre-extraction, kraft pulping, enzyme treatment and cold caustic extraction for the production of high-grade dissolving pulp and recovery of silica, lignin, and hemicellulose from bamboo. This process could alleviate the silica-associated challenges and provide feedstocks for bio-based products, thereby allowing the improvement and expansion of bamboo utilization in industrial processes.

TEMPO-oxidized cellulose nanofibers (TOCNs) as a green reinforcement for waterborne polyurethane coating (WPU) on wood.

In this work, TEMPO-oxidized cellulose nanofibers (TOCNs) were investigated as a green additive to the waterborne polyurethane (WPU) based coating, for improving its mechanical properties. The structure, morphology, mechanical properties and performances of the WPU/TOCNs coating were determined. Results showed that TOCNs had good compatibility to the WPU coating, and significantly enhanced the mechanical properties of the coating. The Halpin-Tsai and Ouali models were used to fit for the Young's modulus of the resulting coating, and good agreements were found between the Ouali model and experimental results when the TOCNs content exceeded the critical percolation threshold (0.7vol% or 1.0wt%). It was also found that the pencil hardness of the coating was improved with the addition of TOCNs. However, AFM and pull-off test revealed the negative effects of the TOCNs addition on the surface roughness and adhesion strength of the coating to the wood surface.

Cationic amphiphilic microfibrillated cellulose (MFC) for potential use for bile acid sorption.

In this work, Micro-fibrillated Cellulose (MFC) was cationically modified by quaternary ammonium groups with different chemical structures aiming to improve the sorption capacity to bile acid. The in-vitro bile acid sorption was performed by investigating various factors, such as quaternary ammonium group content and length of its alkyl substituent of the modified cationic MFC (CMFC), ionic strength, initial concentration and hydrophobicity of bile acid. The results showed that the sorption behavior of the modified CMFC was strongly influenced by the quaternary ammonium group content and the lengths of its alkyl substituent, the sorption capacity for the modified CMFC with a C18 alkyl substituent, was approximately 50% of that of Cholestyramine. The experimental isotherm results were well fitted into the Temkin model. The effect of salts in the solution was smaller for the bile acid sorption onto the hydrophobic CMFC than the CMFC. It was also found that the binding capacity of CMFC was higher for more hydrophobic deoxycholate in comparison with cholate.