Volume 20 Issue 4

Thinned Chinese fir (Cunninghamia lanceolata) and waste stems of Uncaria were used as raw wood materials with melamine–urea–formaldehyde as a co-condensation resin adhesive to produce particleboard. The effects of Uncaria stem incorporation on the composite’s nail-holding capacity, antibacterial activity, decay resistance, insect resistance, and fire retardancy were investigated. GC-MS analysis identified 19 bioactive compounds in Uncaria stems, including esters, terpenes, carboxylic acids, and indole alkaloids. At 50% Uncaria stem mass fraction, nail-holding strength peaked at 170.8 N/mm, a 10.3% increase over pure fir boards. Anti-mold, decay, termite resistance, and fire-retardancy tests demonstrated that Uncaria’s active components significantly mitigated fir’s inherent vulnerabilities via a dual “chemical inhibition + physical barrier” mechanism. A 50% substitution reduced mold coverage from 100% to 3%, while 75% substitution decreased white-rot fungal mass loss from 35.8% to 25.7% and linearly lowered termite-induced mass loss from 18.2% to 7.5%. Cone calorimetry revealed that 75% Uncaria-substituted composites exhibited a 4.6% reduction in peak heat release rate, a 4-second ignition delay, and increased char residue from <5% to 11%, achieving GB/T 8624 Class B1 fire-retardant rating. Uncaria waste stems thus serve as a functional filler for fir particleboard, endowing it with multi-bio-durability and flame-retardant properties. This offers theoretical and technical support for the high-value utilization of agro-forestry waste and development of green wood-based composites.

Biomass energy is the largest source of renewable energy, accounting for approximately 55% of global renewable energy consumption. Therefore, it holds great importance for the efficient utilization of biomass. Hydrothermal liquefaction (HTL) has been demonstrated to convert biomass into liquid biofuels, with physicochemical properties comparable to conventional crude oil. Because moisture content is a key factor in choosing the best conversion method, HTL is especially well-suited for fresh biomass, which usually contains a substantial amount of moisture. This comprehensive review examines the research progress in biomass hydrothermal liquefaction, focusing on biomass types, liquefaction parameters, reactor configurations, and catalyst types, with particular emphasis on a comparative analysis of catalytic mechanisms. This study provides a structured framework for selecting optimal conversion processes by linking biomass types, parameters, reactors, and catalysts. Future research should prioritize the development of cost-efficient bifunctional catalysts and optimization of continuous reaction systems with respect to heat and mass transfer efficiency, and integration design of catalysts, while also aiming to minimize byproduct handling costs.

Bayberry tannin and acacia tannin were selected as raw materials to prepare tannin-sucrose adhesives, and their properties were investigated. Fourier transform infrared spectroscopy (FT-IR) analysis results indicated that both bayberry tannin and acacia tannin were condensed tannins, composed of polymerized flavonoid monomer units, with their repeating units often closely connected to the A and B rings of carbohydrates, with bayberry tannin containing relatively more trisubstituted benzene structural units. Hot-pressing temperature was found to have a significant impact on the adhesive performance. When the hot-pressing temperature was set at 215 °C, the bayberry tannin-sucrose adhesive exhibited excellent bonding performance, meeting the strength requirements of Class II plywood in GB/T 17657 (2022) (≥0.70 MPa). Thermogravimetric (TG) test results revealed that the cured product of the bayberry tannin-sucrose adhesive had superior thermal stability. Scanning electron microscopy (SEM) observations showed that the cured product of the acacia tannin-sucrose adhesive had cracking and porosity on the cross-section, while the cured product of the bayberry tannin-sucrose adhesive presented a unique complex wrinkled structure on the cross-section, which endowed it with higher toughness and better environmental resistance.

New adhesives were developed using sustainable bayberry tannin and sucrose as raw materials. Through introducing three catalysts—citric acid, p-toluenesulfonic acid, and phytic acid—a comprehensive analysis of their differential impact mechanisms on catalyzing sucrose conversion, promoting cross-linking reactions, and shaping the microstructure of the adhesive was conducted. The results showed that under the phytic acid catalytic system, the yield of 5-hydroxymethylfurfural (5-HMF) reached 17.5 μg/mL, which was higher than that of p-toluenesulfonic acid (14.1 μg/mL) and citric acid (12.9 μg/mL). The introduction of catalysts led to a stepwise improvement in the mechanical properties of the adhesive. The adhesive catalyzed by phytic acid exhibited excellent bonding strength and water resistance, reflecting its advantage in promoting deep cross-linking between 5-HMF and tannin. Scanning electron microscopy results intuitively demonstrated the reshaping of the adhesive layer morphology by the catalysts, evolving from the loose and porous structure of the blank group to a dense, wrinkled morphology after the action of the catalysts. The results of thermogravimetric analysis further quantified the enhancement effect of the catalysts on the thermal stability of the network structure, with the three-dimensional network structure built by the phytic acid system exhibiting superior thermal protection capabilities.

A reinforced composite aerogel composed of carboxymethyl chitosan (CMCS) and cellulose nanofibers (CNFs) was synthesized via chemical crosslinking with epichlorohydrin (EH) for the efficient removal of Pb(II) ions from aqueous solutions. The CMCS, a chitosan derivative, was successfully prepared through a simple chemical reaction with a degree of substitution of 1.96. The incorporation of CNFs imparted enhanced mechanical stability to the aerogel matrix and increased the surface area, whereas carboxymethyl cellulose contributed functional carboxyl groups that facilitated efficient metal ion adsorption. In addition, crosslinking with EH significantly improved the structural integrity and water stability of the aerogels, rendering them suitable for application in aqueous environments. The composite aerogels exhibited a porous structure and good adsorption of lead ions (Pb²⁺) in water with a removal percentage of 98%. Upon the addition of 1 wt% CNF loading, the compression strength of the composite aerogels was enhanced 42% compared with the samples without CNF loading. The adsorption kinetics showed a high correlation with the pseudo-second-order model (R² = 0.99). The good structural stability and water absorption of the prepared CMCS aerogels make them an ideal candidate for eco-friendly heavy metal-ion treatment.

A direct comparison was made between raw banana peel waste (RBPW) and acid-treated banana peel waste (ABPW), under identical conditions, for adsorption of crystal violet (CV). Sorption kinetics, isotherms, and thermodynamics were considered to reveal the underlying mechanisms. The effects of contact time, pH, initial CV concentration, temperature, and adsorbent dosage were evaluated. The sorption process obeyed a pseudo-second-order kinetic model, while the Langmuir isotherm model best explained the equilibrium data with maximum adsorption capacities. The Dubinin–Radushkevich model supported the potential of ion-exchange mechanisms for the acidified sample. Adsorption was spontaneous and endothermic, as revealed by negative Gibbs free energy, positive enthalpy (+16.4 kJ/mol for RBPW and +53.5 kJ/mol for ABPW) and positive entropy (RBPW = 6.79 J/mol·K and ABPW = 14.65 J/mol·K) values. The lower ΔH for the raw peel is more consistent with physisorption, while higher ΔH of the acid-treated peel suggests stronger interactions consistent with chemisorption/ion-exchange. The FT-IR analysis confirmed that functional groups such as –OH, –COOH, C=O, C-O, and possibly aromatic moieties on banana peel waste are involved in the sorption of CV. The enhanced performance of ABPW is attributed to acid-induced surface modifications that increased porosity, making the functional groups available for sorption process.