Lignin-containing Cellulose Nanocrystals Research Articles

Simultaneous preparation of lignin-containing cellulose nanocrystals and lignin nanoparticles from wood sawdust by mixed organic acid hydrolysis

In the global search for sustainable and environmentally friendly materials, the efficient utilization of biomass resources has become a hot research topic. Due to the high specific surface area, nanocellulose crystals (CNCs) have attracted considerable attention. However, CNC preparation often requires the separation of lignin and hemicellulose, which wastes resources. In this study, lignin-containing cellulose nanocrystals (LCNCs) and lignin nanoparticles (LNPs) were prepared from p-toluenesulfonic acid (p-TsOH)/formic acid (FA) pretreated poplar wood in one-step. The process was performed in a mixed acid system with a mass ratio of p-TsOH, FA, and deionized water (DI) of 3:5:2, and mechanical stirring at 80 ºC for 3 h. Under these conditions, the lignin removal rate was about 70 %, and the LCNCs yield was more than 40 %. The p-TsOH is regained by vacuum distillation and recrystallization, and the recovery rate can reach 60 %. The prepared LCNCs were then carbonized and used as an electrode for electrochemical testing. The electrode obtained by carbonizing LCNC exhibits an areal capacitance of 156.4 F g−1 (0.5 A g−1). The study provided a new prospect for the efficient utilization of lignocellulosic nanomaterials.

Lignin-containing cellulose nanocrystals enhanced electrospun polylactic acid-based nanofibrous mats: Strengthen and toughen

Biodegradable polylactic acid (PLA) nanofibrous mats prepared by electrospinning serve as suitable packaging materials. However, their practical applications are limited by their weak mechanical properties, poor thermal stability, and high cost. In this study, green and low-cost lignin-containing cellulose nanocrystals (LCNCs) with different lignin contents were developed and employed as reinforced materials to synergistically enhance the thermal, mechanical, and hydrophobic properties of PLA electrospun nanofibrous mats. The presence of moderate lignin improved the interfacial compatibility between the LCNCs and PLA, resulting in excellent mechanical properties of the nanofibrous mats. Compared to pure PLA mats, the tensile strength of the composites reached up to 21.0 MPa, representing a 6.6-fold increase. Its toughness was synchronously enhanced by 16 times, reaching a maximum of 3.6 MJ/m3. The maximum decomposition temperature of PLA/LCNCs electrospun nanofibrous mats increased from 339 °C to 365 °C. Furthermore, the increase in lignin in the LCNCs positively contributed to improving the hydrophobicity of the PLA/LCNCs electrospun nanofibrous mats. This bio-based strategy of LCNCs employed in the enhancement of fully bio-based PLA nanofibrous mats offers a viable approach for the advancement of packaging films.

Correction to: A facile, low-thermal, and environmentally friendly method to improve the properties of lignin-containing cellulose nanocrystals (LCNCs) and cellulose nanofibrils (LCNFs) from bagasse unbleached soda pulp

Correction to: A facile, low-thermal, and environmentally friendly method to improve the properties of lignin-containing cellulose nanocrystals (LCNCs) and cellulose nanofibrils (LCNFs) from bagasse unbleached soda pulp

Nano Boron Oxide and Zinc Oxide Doped Lignin Containing Cellulose Nanocrystals Improve the Thermal, Mechanical and Flammability Properties of High-Density Poly(ethylene).

The widely used high-density polyethylene (HDPE) polymer has inadequate mechanical and thermal properties for structural applications. To overcome this challenge, nano zinc oxide (ZnO) and nano boron oxide (B2O3) doped lignin-containing cellulose nanocrystals (L-CNC) were blended in the polymer matrix. The working hypothesis is that lignin will prevent CNC aggregation, and metal oxides will reduce the flammability of polymers by modifying their degradation pathways. This research prepared and incorporated safe, effective, and eco-friendly hybrid systems of nano ZnO/L-CNC and nano B2O3/L-CNC into the HDPE matrix to improve their physio-mechanical and fire-retardant properties. The composites were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, thermo-gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, horizontal burning test, and microcalorimetry test. The results demonstrated a substantial increase in mechanical properties and a reduction in flammability. The scanning electron microscope (SEM) images showed some agglomeration and irregular distribution of the inorganic oxides.

A facile, low-thermal, and environmentally friendly method to improve the properties of lignin-containing cellulose nanocrystals (LCNCs) and cellulose nanofibrils (LCNFs) from bagasse unbleached soda pulp

A facile, low-thermal, and environmentally friendly method to improve the properties of lignin-containing cellulose nanocrystals (LCNCs) and cellulose nanofibrils (LCNFs) from bagasse unbleached soda pulp

Preparation and characterization of lignin-containing cellulose nanocrystals from peanut shells using a deep eutectic solvent containing lignin-derived phenol

In this work, a method of preparing lignin-containing cellulose nanocrystals (LCNC) from agricultural waste peanut shells by ultrasonic-assisted deep eutectic solvents (DES) was studied. The peanut shells were pretreated with binary DES ChCl-GG (choline chloride: guaiacol, 1:1 molar ratio) and ternary DES ChCl-GG-AlCl3·6 H2O (choline chloride: guaiacol: aluminum trichloride hexahydrate, 1:1:0.01, 1:1:0.03, 1:1:0.05, and 1:1:0.07 molar ratios) at 120 ℃ for 3 h, and then subjected to mild mechanical decomposition. Under the optimal DES pretreatment conditions (the molar ratio of ternary DES is 1:1:0.07), the cellulose content of peanut shell reached the highest of 59.49% (36.39% without treatment), and the removal rates of lignin and hemicellulose were 73.22% and 93.05%, respectively. At the same time, LCNC obtained by this process shows good thermal stability (Tmax = 337 ℃) and has the potential for further applications. When the conditions were optimal, the length of LCNC was about 188.94 nm, the width was about 2.60 nm, and the crystallinity of cellulose I was 69.97%. The results showed that the green and economical DES could effectively pretreat lignocellulosic materials, providing a prospect for future utilization and the separation of LCNC.

Development of pH-responsive active film materials based on purple corncob and its application in meat freshness monitoring

The use of petroleum-based food packaging materials is causing environmental damage and increasing greenhouse gas production. Consequently, there is a great interest in developing smart and sustainable alternative materials. In this study, an agricultural waste product (purple corncob extract, PCCE) was used as a raw material to prepare environmentally friendly pH-sensitive packaging materials. Natural pH-sensitive pigments (anthocyanins) and lignin-containing cellulose nanocrystals (LCNC) were extracted from the purple corncobs. A cationic biopolymer (chitosan) was used as a scaffolding material to assemble the film matrix. Composite film (LCNC-PCCE-chitosan) was produced using a simple solvent casting method. Fourier transform infrared spectroscopy and scanning electron microscopy analyses showed that the PCCE and LCNC were well dispersed within the chitosan matrix and they interacted with the matrix through hydrogen bonding and electrostatic interactions. The addition of LCNC improved the hydrophobicity and mechanical properties of the film and imparted antioxidant activity and UV-blocking properties. The presence of anthocyanins in the PCCE endowed the film with a sensitive and reversible pH response, which could be well used to monitor changes in the freshness of pork and shrimp products.

Lignin-rich cellulose nanocrystals from coir fiber treated with ionic liquids: Preparation and evaluation as pickering emulsifier

Lignocellulosic materials are promising sources of energy and biomaterials. In this context, the biomass from the mesocarp of the green coconut can be used to produce nanocellulose. For this purpose, this work proposed approaches for pretreatment of coconut biomass using protic ionic liquids (PILs), which are solvents that have specific characteristics and less environmental impact, followed by acid hydrolysis to obtain lignin-containing nanocellulose. Thus, three PILs were produced, and two pretreatment methodologies were evaluated. The results showed that, when using the ionic liquid 2-HEAA and Methodology B, there was a delignification of 17.4 %, a reduction of 14 % of hemicelluloses and a gain of 50.8 % of cellulose. Furthermore, acid hydrolysis provided a stable suspension of lignin-containing cellulose nanocrystals (zeta potential of −34.6 mV) with particles in the nanometer scale and more thermally resistant. When testing these lignin-containing cellulose nanocrystals as a stabilizer for oil-in-water emulsions, satisfactory results were obtained at a concentration of 0.50 %, which generated a stable emulsion for 14 days (−47.5 mV of zeta potential and mean diameter of 6.23 µm).

Rapid, high-yield production of lignin-containing cellulose nanocrystals using recyclable oxalic acid dihydrate

Nanocellulose is of growing interest due to its great potential in many value-added applications and its unique characteristics. However, conventional methods for nanocellulose isolation are challenged by various economic and environmental concerns. With the use of recyclable oxalic acid dihydrate (OAD), this study demonstrated the rapid, high-yield production of lignin-containing cellulose nanocrystals (LCNCs) from thermomechanical pulp (TMP). Serving as the sole solvent and reactant, molten OAD effectively hydrolyzed TMP within 30 min at 110 °C, leading to complete removal of hemicellulose (97 %) but retaining most of the cellulose (93 %) and lignin (97 %). This modified TMP can be converted into LCNCs with a high overall yield of >70 % via microfluidization. The LCNCs possessed satisfactory thermal stability and exhibited a nanoscale morphology of highly uniform cellulose nanocrystals (7.0 nm in width, 3.9 nm in height, 200–300 nm in length, and 72 % in crystallinity), randomly implanted by lignin aggregates. The unreacted OAD could also be readily recycled via crystallization from the post-hydrolysis mixture. The recycled OAD showed good performance retention for at least 4 cycles, indicating its suitability for continuous TMP hydrolysis. Further life cycle assessment suggested that the recycling potential could reduce the global warming potential and energy use by 48 % and 47 %, respectively. Overall, it was apparent that recycling molten OAD provided a promising approach to rapidly make clean, high-yield LCNCs with low energy use and improved reagent utilization.

Cauliflower Waste Derived Lignin-Containing Cellulose Film: Synthesis, Characterization and Study of Thermal and Electrical Conductivity Properties

Cauliflower has the highest ratio of non-edible to edible portion and hence generates a huge amount of waste biomass which may comprise of proximately 17.32% cellulose, 9.12% hemicellulose, and 5.94% lignin. This study focused on the successful synthesis of lignin- containing cellulose nanocrystals (LCCN) from the non-edible portion of cauliflower using a combination of alkali treatment and mild acid hydrolysis. The highly dispersed nanophase of the synthesized nanocellulose in LCCN was confirmed by X-ray diffraction (XRD) and had a crystallite size of 7.26 nm and a crystallinity index of 53.5%. The chemical, mechanical and conductive properties of LCCN were examined by standard methods such as Fourier- transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and four-probe instrument. Uniform and flexible thin films of the synthesized LCCN using 40% acid fraction were found to be suitable and were successfully prepared on a glass plate at ambient temperature by solvent casting method. The thickness of this 40% fraction LCCN film was measured to be 55μm by the interference method and it also showed the lowest thermal expansion and highest thermal stability. Conductivity studies indicated the lowest resistivity of 0.755 Ohm. cm in 40% LCCN. Therefore the synthesized LCCN film can be a useful low-cost, environment-friendly biopolymer material for a number of next-generation composite preparations, conductive substances, and packaging applications.

Isolation of lignin‐containing cellulose nanocrystals: life‐cycle environmental impacts and opportunities for improvement

AbstractDeep eutectic solvent (DES) has recently been attracting great interest for its role in isolating nanocellulose owing to its distinct advantages of biodegradability, low toxicity, and recyclability. Lignin‐containing cellulose nanocrystals (LCNCs) obtained using DES pretreatment has led to an improvement in the production of nanomaterials. Understanding the potential environmental impacts of this novel technology at the laboratory scale provides important insights to improve its sustainability at full scale in the future. This study evaluates the environmental impacts of the production of LCNCs from thermomechanical pulp (TMP) following acidic DES pretreatment (using a binary system of ‘choline chloride – oxalic acid dihydrate’ or a ternary system of ‘choline chloride – oxalic acid dihydrate – p‐toluenesulfonic acid’) based on various laboratory trials. The evaluation was conducted through a cradle‐to‐gate life‐cycle assessment for global warming potential (GWP), acidification potential (AP) and the cumulative energy demand (MJ). The average GWP, AP, and energy use were 39 kg CO2‐eq, 0.17 kg SO2‐eq, and 995 MJ per kg LCNCs, respectively. The sensitivity analysis showed that different degrees of reduction in environmental impact could be achieved by varying the input volume and/or reuse frequency of DES solutions. The largest reductions in GWP, AP, and energy use were achieved by reducing the input volume of DES solutions to 20% of its default value. The results of this LCA study illustrate the direction for future research and development (R&D) to further improve the sustainability of this DES‐mediated LCNC production technology. Through comparisons with the existing literature, this study also confirms the predominant contribution of chemical manufacturing to the overall environmental impacts of nanocellulose isolation technologies in general. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Sustainable and cost-effective approach for the synthesis of lignin-containing cellulose nanocrystals from oil palm empty fruit bunch

Cellulose nanocrystals (CNC) have received great research attention since the last few decades due to their extraordinary properties and wide range of applications. In this study, a sustainable and cost-effective method for the synthesis of lignin-containing cellulose nanocrystals (LCNC) from oil palm empty fruit bunch (EFB) is presented. This method is able to retain the lignin in EFB and manifest the properties of lignin. The proposed synthesis process is simpler than the conventional method of producing lignin-coated CNC by first removing the lignin to synthesize CNC followed by the re-coating of lignin on the structure. The samples of LCNC were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and water contact angle analysis. In addition, by altering the acid concentration during acid hydrolysis process (53% - 60% H2SO4), both surface hydrophobicity (66.0° - 75.1°) and length of LCNC (467 nm–177 nm) can be altered wherein a higher concentration of acid resulted in a greater contact angle and a shorter length of LCNC. Cost and energy analysis deduced that the proposed synthesis method saved about 62% of the total material cost and 80% less energy as compared to the synthesis of lignin-coated CNC.

Performance of polyvinyl alcohol hydrogel reinforced with lignin-containing cellulose nanocrystals

Lignin-containing cellulose nanocrystals (LCNCs) were produced from old newspapers using the sulfuric acid hydrolysis process, and the product was used in reinforcing polyvinyl alcohol (PVA) based hydrogel. The lignin content of LCNCs was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS), and LCNCs had 8–19 wt% lignin located on their surfaces. The transmission electron microscopy (TEM) confirmed the presence of lignin on LCNCs as small globular-like particles/patches. The increase in the lignin content of LCNCs increased the thermal stability and hydrophobicity while decreasing the crystallinity of LCNCs. Moreover, the effect of LCNC loading (0.1–1 wt%) on the mechanical strength, rheological properties, swelling behavior, morphology, and thermal stability of PVA-based hydrogel was further elucidated. The incorporation of LCNCs in hydrogel at a low dosage improved the swelling behavior of hydrogel. The lignin present on the surface of LCNCs led to enhanced viscoelasticity, increased compressive strength, and improved thermal stability of hydrogel. In addition, the pore size of the hydrogel dropped more significantly (4.26–1.52 μm) with the use of LCNCs containing more lignin. At a low dosage of 0.1 wt%, all studied properties of hydrogels were improved using the LCNC with high lignin content. This study provides a new prospect for the use of lignin-containing CNCs for the production of a high-performance hydrogel.

Lignin-containing cellulose nanocrystals/sodium alginate beads as highly effective adsorbents for cationic organic dyes

Cellulose nanocrystals (CNCs) is an exciting class of sustainable and carbohydrate material, which has great potential applications in molecular adsorption. However, the complex preparation process and limited adsorption capacity of CNCs hinder its commercial application. In this study, we design a novel functional cellulose nanocrystals-based adsorbent by an ingenious mixing of lignin-containing cellulose nanocrystals (LCNCs), sodium alginate (SA), and calcium chloride solution. Benefiting from the sulfonate groups of lignin, carboxyl groups of SA, the maximum adsorptive capability of LCNCs/SA beads for methylene blue was found to be 1181 mg g−1, which was significantly higher than previously reported biomass-based adsorbents. More importantly, LCNCs/SA beads can be reused several times. This strategy can not only improve the adsorption performance of CNCs-based materials, but also simplify the production technology of CNCs, which greatly promote the commercial application of CNCs materials.

Performance of high lignin content cellulose nanocrystals in poly(lactic acid)

High lignin-containing cellulose nanocrystals (HLCNCs) were successfully isolated from hydrothermally treated aspen fibers and freeze-dried and compounded with poly (lactic acid) (PLA) by extrusion and injection molding. As a comparison, PLA composites containing commercial lignin-coated CNCs (BLCNCs) were also produced. HLCNCs showed higher crystallinity, larger surface area, lower degree of agglomeration, and more hydrophobic surfaces compared to BLCNCs, as characterized by electron microscopy, surface area measurements, thermal analysis, spectroscopy and water contact angle measurements. The effect of lignin and CNC morphology on the mechanical, thermal and viscoelastic properties and CNCs/polymer interfacial adhesion of nanocomposites was investigated with tensile test, DSC and DMA. Compared to neat PLA, the Young's modulus, elongation to break, and toughness of PLA/2%HLCNCs were improved by 14, 77, and 30%, respectively. HLCNCs and BLCNCs act as nucleating fillers, increasing the degree of crystallinity (χc) of PLA in nanocomposites. The presence of lignin nanoparticles in the HLCNC increased the compatibility/adhesion between CNCs and polymer matrix which increased the storage modulus.

Effect of fiber drying on properties of lignin containing cellulose nanocrystals and nanofibrils produced through maleic acid hydrolysis

The effect of fiber drying on the properties of lignin containing cellulose nanocrystals (LCNC) and nanofibrils (LCNF) produced using concentrated maleic acid hydrolysis of a never dried unbleached mixed hardwood kraft pulp was evaluated. Two drying conditions, i.e., air drying and heat drying at 105 °C were employed. It was found that drying (both air and heat) enhanced acid hydrolysis to result in slightly improved LCNC yields and less entangled LCNF. This is perhaps due to the fact that drying modified the cellulose supermolecular structure to become more susceptible to acid hydrolysis and the enhanced hydrolysis severity at the fiber surface when using dried fibers. Drying substantially improved LCNC crystallinity and LCNF suspension viscoelastic behavior. The present study quantitatively elucidated the effect of pulp drying (either air or heat) on producing cellulose nanomaterials and has practical importance because commercial market pulp (heat dried) is most likely to be used commercially.

Integrated production of lignin containing cellulose nanocrystals (LCNC) and nanofibrils (LCNF) using an easily recyclable di-carboxylic acid

Here we demonstrate di-carboxylic acid hydrolysis for the integrated production of lignin containing cellulose nanocrystals (LCNC) and nanofibrils (LCNF) using two unbleached mixed hardwood chemical pulps of lignin contents of 3.9 and 17.2%. Acid hydrolysis experiments used maleic acid solution of 60wt% concentration at 120°C for 120min under ambient pressure. Yields of LCNC were low of less than 6% under this set of conditions. The higher lignin content sample produced LCNC with greater height (diameter) of 25nm but similar length of approximately 230nm to that from the lower lignin content fibers (height of 20nm). Interestingly, the higher lignin content sample resulted in LCNF with smaller height (diameter) of 7nm but longer length of >1μm, or greater aspect ratio than the LCNF from the lower lignin fibers of height 10nm and length <1μm. Lignin protected cellulose from esterification which resulted in LCNC and LCNF that was less carboxylated compared to those lignin-free CNC and CNF and therefore had lower charges. However, lignin is more hydrophobic and thermally stable than carbohydrates therefore LCNC and LCNF are favorable for composite applications.