Search Results (42)

Hydrothermal treatment of wood, particularly steaming with saturated water steam, is often used to achieve a more intensive and homogenous wood color or to vary its hue. However, information on pear wood (Pyrus communis L.) steaming is limited in the available literature. This paper investigates the influence of steaming on the color of pear wood. Green, water-saturated samples of pear wood heartwood and sapwood were steamed with saturated water steam for 24 h at 98 °C. The color of the heartwood and sapwood was assessed both visually and with a standard three-stimulus colorimeter using the CIEL*a*b* system, and compared to the natural color of pear-wood. Additionally, FT-IR spectrometry was employed to analyze chemical changes in the wood samples. The results showed that both heartwood and sapwood experienced a decrease in lightening (L*), an increase in redness (a*), and a decrease in yellowness (b*) during steaming. Furthermore, a trend toward the equalization of L*, a*, and b* parameters between heartwood and sapwood over time was observed. FT-IR spectroscopy revealed that the chemical changes during steaming were primarily related to extractives and hemicelluloses, with no significant changes in cellulose and lignin. The obtained results suggest that pear wood color can be equalized to some extent by steaming and that the extent of the color change to darker tones is dependent on steaming time. Full article

This study explores the hydrothermal carbonization (HTC) process applied to the exhausted chestnut produced by the tannin extraction industry, utilizing process water recirculation to enhance the efficiency and sustainability of the conversion process. Tannin extraction from wood typically involves hot water treatment, leaving behind residual wood biomass known as exhausted wood. These by-products maintain their renewable properties because they have only been exposed to hot water under a high pressure, which is unlikely to cause major alterations in their structural components. Hydrothermal treatment was carried out at temperatures of 220 °C and 270 °C for 1 h, with process water being recirculated four times. This investigation focused on analyzing the effects of recirculation on the yield and fuel properties of hydrochar, as well as characterizing the combustion behavior of the obtained hydrochar. The results indicated that recirculation of process water led to improvements in both the mass and energy yields of hydrochar. The mass yield of the hydrochar samples increased by 5–6%, and the ERE of the hydrochar samples increased by 5–8% compared to the HTC reference sample. However, alterations in the combustion characteristics were observed, including decreases in ignition temperature and combustion reactivity. The results indicate that, with PW recirculations, the combustion index decreased by about 14% and 18% for 220 °C and 270 °C, respectively. Overall, this research demonstrates the potential of utilizing HTC on chestnut tannin residue with process water recirculation to produce stable solid fuel and provides insights into the combustion behavior of the resulting hydrochar. Full article

CQDs are a type of fluorescent nanocarbon material that possess excellent optical properties. They have a wide range of raw material sources, making them a versatile option for various applications. The use of fluorescent materials to enhance the solar energy capture capacity of chloroplasts has the potential to significantly improve natural photosynthesis. CQDs and N-CQDs were prepared from natural Salix wood powder using a simple, green, and environmentally friendly hydrothermal method. These materials can effectively capture ultraviolet (UV) light and were used for photosynthesis to enable chloroplasts to utilize UV light that cannot be absorbed by them. The chlorophyll content of leaves treated with CQDs and N-CQDs increased, with the N-CQDs 25 mg/L treated group showing a 35.6% increase compared to the untreated group. Additionally, the treatment of CQDs and N-CQDs positively affected the transfer of electrons from photosystem II, further enhancing photosynthetic activity. This study presents ideas for expanding the use of solar energy, optimizing the photosynthesis charge transfer pathway, and improving solar energy conversion efficiency. Full article

Biofibres’ wide application in mortar enhancement has thus far been restricted by factors related to their chemical composition and hygroscopic nature. Their hydrophilic behaviour increases the water demand of mortar mixtures and diminishes their affinity to the matrix, while further moisture-related fibre degradation issues may arise. Additionally, natural fibres seem to be susceptible to degradation caused by exposure to alkaline environmental conditions such as those experienced by cement mortars, restricting their utilisation in the construction industry. Therefore, the current study investigates the potential of fibre modification through treatments that would permanently alter their structure and chemical composition to improve their performance. In this study, wood fibres of black pine and beech species were exposed to mild thermal treatment (140 °C 2 h, under a steam atmosphere), characterised in terms of the physical and chemical properties and incorporated in cement mortars, applying the proportion of 1.5% v/v in the mortar, in order to assess their performance as reinforcement material. The mortars’ workability (at a fresh state) was examined, as well as other physical, hygroscopic, thermal, and mechanical characteristics of the mortars at the ages of 28, 90 and 365 days and weathering performance, by subjecting them to different artificial ageing environments (freeze–thaw cycles or outdoor exposure). The results revealed the beneficial role of the treated fibres in dimensional stability, flexural strength, thermal insulation properties and capillary absorption of the mortar specimens, especially during the ageing process, with the black pine fibres showing the greatest improvement. The hydrothermally treated wood fibres seem to help maintain the integrity of cement mortars under all ageing conditions, proving that they could provide low-cost and eco-friendly mortar enhancement pathways. Full article

In this study, short-term accelerated creep tests were conducted using the stepped isostress method (SSM) to investigate the impact of hydrothermal treatment on the long-term creep behaviour of Japanese cedar wood and to determine optimal hydrothermal treatment conditions. The results showed that SSM can effectively predict the creep behaviour of hydrothermally treated wood. Among the treatment conditions tested, Japanese cedar wood treated hydrothermally at 180 °C for 4 h exhibited higher flexural strength retention (91%) and moisture excluding efficiency (MEE) (44%) and demonstrated superior creep resistance compared to untreated wood. When subjected to a 30% average breaking load (ABL) over 20 years, the specimen’s creep compliance, instantaneous creep compliance, b value, activation volume, and improvement in creep resistance (ICR) were 0.17 GPa⁻¹, 0.139 GPa⁻¹, 0.15, 1.619 nm³, and 4%, respectively. The results indicate that subjecting Japanese cedar wood to hydrothermal treatment at 180 °C for 4 h has a negligible effect on its flexural properties but results in significant improvements in both dimensional stability and creep resistance. Full article

Palladium (Pd) nanoparticle catalysis has attracted increasing attention due to its efficient catalytic activity and its wide application in environmental protection and chemical synthesis. In this work, Pd nanoparticles (about 71 nm) were synthesized in aqueous solution by microwave-assisted thermal synthesis and immobilized in beech wood blocks as Pd@wood catalysts. The wood blocks were first hydrothermally treated with 10% NaOH solution to improve the internal structure and increase their porosity, thereby providing favorable attachment sites for the formed Pd nanoparticles. The stable deposition of Pd nanoparticle clusters on the internal channels of the wood blocks can be clearly observed. In addition, the catalytic performance of the prepared Pd@wood was investigated through two model reactions: the reduction of 4-nitrophenol and Cr(VI). The Pd@wood catalyst showed 95.4 g⁻¹ s⁻¹ M⁻¹ of normalized rate constant k_norm and 2.03 min⁻¹ of the TOF, respectively. Furthermore, Pd nanoparticles are integrated into the internal structure of wood blocks by microwave-assisted thermal synthesis, which is an effective method for wood functionalization. It benefits metal nanoparticle catalysis in the synthesis of fine chemicals as well as in industrial wastewater treatment. Full article

Nitrogen-doped activated carbons with controlled micro- and mesoporosity were obtained from wood and wastes via chemical processing using pre-treatment (pyrolysis at 500 °C and hydrothermally carbonization at 250 °C) and evaluated as oxygen reduction catalysts for further application in fuel cells. The elemental and chemical composition, structure and porosity, and types of nitrogen bonds of obtained catalyst materials were studied. The catalytic activity was evaluated in an alkaline medium using the rotating disk electrode method. It was shown that an increase in the volume of mesopores in the porous structure of a carbon catalyst promotes the diffusion of reagents and the reactions proceed more efficiently. The competitiveness of the obtained carbon materials compared to Pt/C for the reaction of catalytic oxygen reduction is shown. Full article

Lignocellulosic biomasses have a very important role as raw materials to produce biobased chemicals. However, a sustainable, efficient, and economically competitive way to convert lignocellulosic biomass into these chemicals has still not been achieved. This study is related to the selective separation and conversion of birch wood C5 carbohydrates into furfural during the H₃PO₄–NaH₂PO₄-catalyzed hydrothermal pretreatment simultaneously preserving cellulose in the lignocellulosic leftover for glucose production by the enzymatic hydrolysis. The ratio of H₃PO₄–NaH₂PO₄ in the catalyst solution was changed (3:0, 2:1, 1:1, and 1:2). Results show that around 64.1 to 75.9% of available C5 carbohydrates were converted into furfural. The results of birch wood lignocellulosic leftover chemical composition analysis show that cellulose losses during the pretreatment stage did not reach more than 10% of the initial amount. Based on the enzymatic hydrolysis screening experiments, a suitable catalyst for pretreatment was selected and an in-depth study was carried out. Enzymatic hydrolysis experiments were organized based on the three-factor central composite face-centered design. The variable parameters were treatment time (24–72 h), enzyme load (10–20 U/g cellulose), and substrate amount in reaction media (10–20%). At optimal conditions, 49.9 ± 0.5% of available cellulose in lignocellulosic leftover was converted into glucose. Full article

Unlike the recycling of particleboards, the recycling of medium-density fiberboards (MDF) is not a widespread industrial practice, and currently, most waste MDF panels are landfilled or incinerated after the end of their life cycle. Therefore, it is of great importance to develop cost-effective methods for MDF recycling. The extraction of resins used for bonding the panels, mostly urea–formaldehyde (UF) resins, is carried out mainly with hydrolysis. Hydrothermal hydrolysis is a more environmentally friendly and cheaper recycling technique compared to acid hydrolysis and allows obtaining a high yield of recycled fibers. The aim of this research work was to investigate and evaluate the effect of hydrolysis regime applied on its efficiency and on the properties of the recycled MDF fibers. For this purpose, thermal hydrolysis was carried out in an autoclave with saturated steam as a heat carrier. The main novelty of the research is the preliminary preparation of the recyclable MDF in samples with dimensions close to those of pulp chips. The effect of hydrolysis regime characteristics, i.e., process time and temperature on the properties of recycled MDF wood fibers, was studied. The hydrolysis temperatures used were 121 °C (saturated steam pressure of 0.2 MPa) and 134 °C (saturated steam pressure of 0.3 MPa); for each temperature, three durations were applied—30, 45, and 60 min. After hydrolysis, the resulting fiber fraction was refined using a hammer mill. The fractional and elemental composition of the recycled fibers obtained were evaluated. The hemicellulose content after each hydrolysis treatment was also determined. The chemical oxygen demand (COD) was defined as an indicator of wastewater contamination and as an indirect indicator of the quantitative yield of the process. The results revealed no significant changes in the elemental composition of the recycled fibers, and the hydrolysis regimes used showed no decrease in pentosan content. The recycled MDF fibers exhibited similar fiber morphology and fractional composition, being shorter than fibers from industrial pulp. The increased temperature and time of hydrolysis resulted in a significant increase in COD values. Based on the obtained results, with a view to the slightest contamination of wastewater (as determined by COD), the most promising hydrolysis regime was at a temperature of 121 °C and a time of 30 min. It should be emphasized that for a confirmation of this statement, the properties of MDF panels fabricated with fibers recycled in different regimes should be subsequently investigated. Full article

Zeolites in powder form have the potential to agglomerate, lowering access to active sites. Furthermore, a suspension of fine zeolite powder in liquid media is difficult to separate. Such drawbacks could be improved by dispersing zeolite crystals on support materials. This work demonstrates the dispersion of zeolite NaY crystals on bamboo wood by mixing the wood with zeolite gel before hydrothermal treatment. The syntheses were performed with acid-refluxed and non–refluxed wood. The phase of zeolites, particle distribution and morphology, zeolite content in the wood, and zeolite–wood interaction were investigated using X-ray diffraction, X-ray tomography, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption analysis, and X-ray photoelectron spectroscopy. Higher zeolite content and better particle dispersion were obtained in the synthesis with the acid–refluxed wood. The composite of NaY on the acid-refluxed wood was demonstrated to be an effective adsorbent for Ni(II) ions in aqueous solutions, providing a higher adsorbed amount of Ni(II) per weight of NaY. Full article

The total amount of cellulose from paper, wood, food, and other human activity waste produced in the EU is in the order of 900 million tons per year. This resource represents a sizable opportunity to produce renewable chemicals and energy. This paper reports, unprecedently in the literature, the usage of four different urban wastes such as cigarette butts, sanitary pant diapers, newspapers, and soybean peels as cellulose fonts to produce valuable industrial intermediates such as levulinic acid (LA), 5-acetoxymethyl-2-furaldehyde (AMF), 5-(hydroxymethyl)furfural (HMF), and furfural. The process is accomplished by the hydrothermal treatment of cellulosic waste using both Brønsted and Lewis acid catalysts such as CH₃COOH (2.5–5.7 M), H₃PO₄ (15%), and Sc(OTf)₃ (20% w:w), thus obtaining HMF (22%), AMF (38%), LA (25–46%), and furfural (22%) with good selectivity and under relatively mild conditions (T = 200 °C, time = 2 h). These final products can be employed in several chemical sectors, for example, as solvents, fuels, and for new materials as a monomer precursor. The characterization of matrices was accomplished by FTIR and LCSM analyses, demonstrating the influence of morphology on reactivity. The low e-factor values and the easy scale up render this protocol suitable for industrial applications. Full article

In this work, a facile method was adopted to prepare TiO₂-WO₃ loaded onto a wood surface by a two-step hydrothermal method. The as-prepared wood composite material can be used as a photocatalyst under UV irradiation for the photodegradation of formaldehyde. Related tests showed that TiO₂-WO₃ nano-architectonic materials with spherical particles loaded onto the wood substratewere mainly caused by self-photodegradation of formaldehyde. The TiO₂-WO₃ nanostructured material firmly adheres to the wood substrate through electrostatic and hydrogen bonding interactions. Meanwhile, the appearance of the new chemical bond Ti-O-W indicates the successful loading of TiO₂-WO₃ onto the wood surface. The photodegradation rate was measured and it was confirmed that the highest photodegradation performance of the modified wood was achieved at a molar ratio of 5:1 of TiO₂ to WO₃. This work provides a new strategy for the preparing of novel photocatalysts based on wood substrate. Moreover, the wood loaded with TiO₂-WO₃ is a promising candidate for indoor formaldehyde treatment in practical applications. Full article

Based on Materials Studio software, a cellulose chain with a polymerization degree of 20 and several water molecules were constructed to form a cellulose amorphous region–water model. The effect of pressure on the wood properties during hydrothermal treatment was investigated to explain the changes in the macroscopic properties from a microscopic perspective, thus providing a theoretical basis for wood heat treatment research. In this study, we performed dynamic simulations at atmospheric pressure (0.1 MPa) and pressurized (0.2 MPa, 0.4 MPa, and 0.6 MPa) conditions under a combination of NPT. In addition, five aspects were analyzed in terms of energy change: cell parameters and density, cellulose mean square displacement, number of hydrogen bonds, and mechanical properties. The results showed that pressurized hydrothermal treatment increased the densification of the wood, decreased the volume, and increased the density. As the pressure increased, the difference between the average value of the nonbond energy and the total potential energy gradually decreased, the bond energy decreased, and the interatomic repulsive force within the molecule gradually weakened. The increase in the number of hydrogen bonds enhanced the restraining effect on the arrangement of cellulose molecular chains and slowed down the movement of the cellulose chains. Young’s modulus (E) and shear modulus (G) increased with increasing pressure, and Poisson’s ratio ($\gamma$) and K/G decreased with increasing pressure during the pressurized hydrothermal treatment of wood. The pressurized hydrothermal treatment increased the stiffness and decreased the toughness of the wood compared with those of the model with atmospheric pressure hydrothermal treatment. Full article

Hydrothermal treatment is an efficient and environmentally friendly method of enhancing the dimensional stability and durability of wood. The destructive effects of formic and acetic acids generated during thermal treatment, on the other hand, are known to have a negative impact on wood strength. As a result, hydrothermal treatment in different buffered media (acidic, neutral, and alkaline buffer) was performed in this study to mitigate the effects of the acids. As heating media, acidic buffer (pH 4 and 6), alkaline buffer (pH 8 and 10), and tap water (pH 7.43) were used to treat rubberwood at three different temperatures (160 °C, 180 °C, and 200 °C). The effects of different buffered media and treatment temperatures on the chemical components, crystallinity, and morphological changes in treated and untreated rubberwood were studied. The results of the experiments revealed that the chemical constituents of rubberwood changed along with the pH of the buffered media and treatment temperature. Rubberwood treated in alkaline media showed the least degradation, whereas water medium caused the most severe degradation. The crystallinity of wood increased initially (from 160 to 180 °C) and then decreased further at 200 °C. In addition, minimal damage to the wood cell was observed in an alkaline medium. Full article

Since the chemical composition of wood is closely related to its mechanical properties, chemical analysis techniques such as near-infrared (NIR) spectroscopy provide a reasonable non-destructive method for predicting wood strength. In this study, we used NIR spectra with principal component analysis (PCA) to reveal that vacuum hydrothermal (VH) treatment causes degradation of hemicellulose as well as the amorphous region of cellulose, resulting in lower hydroxyl and acetyl group content. These processes increase the crystallinity of the luanta fir wood (Cunninghamia konishii Hayata), which, in turn, effectively increases its compressive strength (σ_c,max), hardness, and modulus of elasticity (MOE). The PCA results also revealed that the primary factors affecting these properties are the hemicellulose content, hydroxyl groups in the cellulose amorphous region, the wood moisture content, and the relative lignin content. Moreover, the ratios of performance deviation (RPDs) for the σ_c,max, shear strength (σ_s,max), hardness, and modulus of rupture (MOR) models were 1.49, 1.24, 1.13, and 2.39, indicating that these models can be used for wood grading (1.0 < RPD < 2.5). Accordingly, NIR can serve as a useful tool for predicting the mechanical properties of VH-treated wood. Full article