Application of hemicelluloses precipitated via ethanol treatment of pre-hydrolysis liquor in high-yield pulp

Enhancing Liquefaction Efficiency: Exploring the Impact of Pre-Hydrolysis on Hazelnut Shell (Corylus avellana L.)

Hazelnut shells (HS), scientifically known as Corylus avellana L. shells, are waste produced by companies that process nuts. The main objective of this study was to find an efficient way to maximize the chemical potential of HS by solubilizing the hemicelluloses, which could then be used to recover sugars and, at the same time, increase the lignin content of this material to produce adhesives or high-strength foams. In order to optimize the pre-hydrolysis process, two different temperatures (160 and 170 °C) and times varying from 15 to 180 min were tested. All the remaining solid materials were then liquefied using polyalcohols with acid catalysis. The chemical composition of hazelnut shells was determined before and after the pre-hydrolysis. All of the process was monitored using Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) by determining the spectra of solids and liquids after the pre-hydrolysis and liquefaction steps. The highest solubilization of hazelnut shells was found for 170 °C and 180 min, resulting in a 25.8% solubilization. Chemical analysis after the hydrolysis process showed a gradual increase in the solubilization of hemicelluloses as both the temperature and time of the reactor were increased. Simultaneously, the percentages of α-cellulose and lignin in the material also increased with rises in temperature and duration. FTIR-ATR allowed for the detection of significant spectral changes in the hazelnut shells from their initial state to the solid residue and further into the liquefied phase. This confirmed that pre-hydrolysis was effective in enhancing the chemical composition of the material, making it more suitable for the production of adhesives, polyurethane foams, or in the production of bioplastics and composite materials, combined with other biopolymers or synthetic polymers to enhance the mechanical properties and biodegradability of the resulting materials.

Preparation and shape change of silver nanoparticles (AgNPs) loaded on the dialdehyde cellulose by in-situ synthesis method

With the improvement of medical and health care level in our society, the demand for antibacterial materials is increasing. In this work, we prepared the antibacterial materials by loading silver nanoparticles (AgNPs) on the dialdehyde cellulose (DAC) with in-situ synthesis method. DAC was prepared by pretreating cellulose fiber with sodium metaperiodate (NaIO₄) to convert the hydroxyl group into aldehyde group, and then reacted with silver nitrate (AgNO₃) to obtain AgNPs loaded on DAC. UV-Vis results show that the characteristic absorption peak of AgNPs at 428 nm appeared in the AgNPs-loaded-DAC. It was observed by SEM that the spherical AgNPs were distributed uniformly on the DAC surface without obvious flocculation. The color of DAC was not changed significantly, indicating that a small amount of AgNPs was loaded. In addition, sodium citrate (Na₃C₆H₅O₇) was added in the reaction of DAC and AgNO₃ and its effect on the formation of AgNPs was studied. The results demonstrated that the color of DAC turned deeper and finally dark yellow with reaction time extended. When the reaction time was 60 h, the spherical AgNPs were gradually grown and transformed into triangular prism on the DAC surface. The antibacterial properties of AgNPs showed inhibition zones of 4.90 mm and 7.35 mm (60 h) against Gram-negative (E. coli) and Gram-positive (S. aureus), respectively, which increased by 40.00% and 14.85% compared with spherical AgNPs (2.5 h) obtained without Na₃C₆H₅O₇. The research of AgNPs-loaded cellulose-based materials promotes the development prospect of new nano-antibacterial materials.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10570-022-04692-6.

Scalable Preparation of Cellulose Nanofibers from Office Waste Paper by an Environment-Friendly Method

Waste paper is often underutilized as a low-value recyclable resource and can be a potential source of cellulose nanofibers (CNFs) due to its rich cellulose content. Three different processes, low acid treatment, alkali treatment and bleaching treatment, were used to pretreat the waste paper in order to investigate the effect of different pretreatments on the prepared CNFs, and CNFs obtained from bleached pulp boards were used as control. All sample fibers were successfully prepared into CNFs by 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) oxidation. It was quite obvious that the bleached CNFs samples showed dense fibrous structures on a scanning electron microscopy (SEM), while needle-like fibers with width less than 20 nm were observed on a transmission electron microscopy (TEM). Meanwhile, the bleaching treatment resulted in a 13.5% increase in crystallinity and a higher TEMPO yield (e.g., BCNF, 60.88%), but a decrease in thermal stability. All pretreated CNFs samples showed narrow particle size distribution, good dispersion stability (zeta potential less than −29.58 mV), good light transmission (higher than 86.5%) and low haze parameters (lower than 3.92%). This provides a good process option and pathway for scalable production of CNFs from waste papers.

Pretreatment of Lignocellulosic Materials as Substrates for Fermentation Processes

Lignocellulosic biomass is an abundant and renewable resource that potentially contains large amounts of energy. It is an interesting alternative for fossil fuels, allowing the production of biofuels and other organic compounds. In this paper, a review devoted to the processing of lignocellulosic materials as substrates for fermentation processes is presented. The review focuses on physical, chemical, physicochemical, enzymatic, and microbiologic methods of biomass pretreatment. In addition to the evaluation of the mentioned methods, the aim of the paper is to understand the possibilities of the biomass pretreatment and their influence on the efficiency of biofuels and organic compounds production. The effects of different pretreatment methods on the lignocellulosic biomass structure are described along with a discussion of the benefits and drawbacks of each method, including the potential generation of inhibitory compounds for enzymatic hydrolysis, the effect on cellulose digestibility, the generation of compounds that are toxic for the environment, and energy and economic demand. The results of the investigations imply that only the stepwise pretreatment procedure may ensure effective fermentation of the lignocellulosic biomass. Pretreatment step is still a challenge for obtaining cost-effective and competitive technology for large-scale conversion of lignocellulosic biomass into fermentable sugars with low inhibitory concentration.

Integrated microwave and alkaline treatment for the separation between hemicelluloses and cellulose from cellulosic fibers

In this study, the microwave was employed during the alkaline treatment process, in order to separate the hemicelluloses and cellulose from a delignified hardwood kraft pulp. In relation to hemicelluloses yield, the integrated microwave and alkaline treatment resulted in 9.25% and 12.05% at 50°C and 80°C, respectively. Correspondingly, the resultant pulp fibers presented the increased cellulose content, which was desirable for manufacturing dissolving pulp. Additionally, the effect from mechanical refining pretreatment followed microwave and alkaline treatment, on the separation of hemicelluloses and cellulose, was also investigated.

Preparation and Application of Cationic Modified Cellulose Fibrils as a Papermaking Additive

This paper deals with cationic modified cellulose fibrils obtained by reacting the cellulose fibrils with 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). The physical and chemical properties of unmodified cellulose fibrils (UMCF) and cationic modified cellulose fibrils (CMCF) were characterized by SEM, FTIR, degree of substitution, colloid titration, zeta potential, and thermogravimetric analysis. The experimental results showed that, after cationization, surface charge density and zeta potential reversed, thermal stability decreased, and new functional groups appeared, while the surface morphology did not show much difference from the UMCF. With the addition of three kinds of additives (UMCF, CMCF, and cationic starch (CS)) to BCTMP, the addition of UMCF and CMCF had little effect on zeta potential, while the addition of CS changed zeta potential obviously. With the increasing of additive amount, the bulk of paper sheets added CMCF did not change obviously, while the bulk of paper sheets added UMCF and CS decreased rapidly. With regard to physical strength, all the three kinds of additives could improve the tensile index and tear index; the tensile index of paper sheets added CS was higher than that of added UMCF and CMCF, while the tear index of paper sheets added CMCF was the highest among the three additives.

Degradation and dissolution of hemicelluloses during bamboo hydrothermal pretreatment

To elucidate the hemicelluloses degradation and dissolution during hydrothermal pretreatment, hemicelluloses separated from both hydrolysate and pretreated substrate were investigated. Along with the pretreatment proceeding, some hemicelluloses fractions dissolved and diffused into the bulk liquor; MW (molecular weight) of these hemicelluloses fractions increased first and then decreased as well as amount of the fractions. Based on the definition of MW of the soluble hemicellulose, it has been concluded that some insoluble hemicellulose fractions appeared in the hydrolysate. In contrast, the hemicellulose degradation occurred continually and had been observed by the gradual decrease of MW of the hemicellulose isolated from pretreated substrate. Lingering dissolution at the later stage might attribute to the facts that some soluble fractions were still entrapped in the substrate. 5-15% hemicellulose fractions remained in the pretreated substrate at the later stage were composed of soluble species.

Recovery of acetic acid from pre-hydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine

Acetic acid was one of the main compositions of the pre-hydrolysis liquor (PHL), which was recovered by reactive extraction with triisooctylamine (TIOA) diluted with decanol. Dilution of TIOA played an important role in extracting acetic acid from the PHL. The recovery of acetic acid from the PHL by TIOA was increased from 10.34% to 66.60% with the dilution of TIOA to 20% by decanol at the HAc to TIOA molar ratio of 1, consequently, the equilibrium distribution coefficient KD increased. The effects of time, temperature and pH on the extraction process were also studied. The extraction process was very fast. The acetic acid extraction decreased from 65.13% to 57.34% with the rise of temperature to 50°C from 20°C. A higher pH increased the dissociation of acetic acid, as a result, decreased acetic acid extraction. The hemicelluloses in the PHL were unaffected on the extraction process of acetic acid.

Comparison of different alkali-based pretreatments of corn stover for improving enzymatic saccharification

Corn stover was treated with NaOH, NaOH+anthraquinone (AQ), NaOH+Na(2)SO(3) (alkaline), NaOH+Na(2)SO(3) (neutral), and NaOH+Na(2)S, respectively. The treated corn stover was subjected to hydrolysis with cellulase (20 FPU/g dry biomass) and β-glucosidase (10I U/g dry biomass). Compared with other pretreatment methods, alkaline sodium sulfite pretreatment (ASSP) at a relatively low temperature of 140°C provided for the best lignin removal of about 92%. After ASSP with 10 wt.% of the total alkali charge (Na(2)SO(3):NaOH=1:1) at 140°C for 30 min and subsequent enzymatic hydrolysis, a total sugar yield of 78.2% was obtained on the basis of the amount of glucose and xylose released from raw corn stover. This yield was 24.0% higher than that achieved with NaOH only under the same conditions. Therefore, the supplement of Na(2)SO(3) in alkali pretreatment can facilitate delignification and significantly improve the enzymatic saccharification.