The color changes corresponding to chromophore structures in lignin caused by exposure of Eucalyptus (Eucalyptus grandis and E. urophylla) to heat were investigated. Eucalyptus wood powders were heat treated under saturated steam atmospheres for 10 h at 110 °C, 130 °C and 150 °C. The lignin was isolated before and after heat treatment. The physicochemical properties of the lignin and changes in chromophore structures during heat treatment was evaluated through wet chemical analysis, Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-Vis), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and ¹³C Cross polarization magic angle spinning nuclear magnetic resonance (¹³C CPMAS NMR). Wood color darkened and reddened with the increase in pressure and temperature. Depolymerization and dehydration reactions occurred via demethoxylation with heat treatment in saturated steam at 110 °C or 130 °C. Lignin condensed to form insoluble compounds after heat treatment in saturated steam at 150 °C. G units increased and S units decreased through demethylation during heat treatment, as revealed by FTIR and ¹³C-NMR analysis.

In this study, a novel and convenient bio-inspired modification strategy was used to create stable superhydrophobic structures on halloysite clay nanotubes (HNTs) surfaces. The polydopamine (PDA) nanoparticles can firmly adhere on HNTs surfaces in a mail environment of pH 8.5 via the oxidative self-polymerization of dopamine and synthesize a rough nano-layer assisted with vitamin M, which provides a catechol functional platform for the secondary reaction to graft hydrophobic long-chain alkylamine for preparation of hierarchical micro/nano structures with superhydrophobic properties. The micromorphology, crystal structure, and surface chemical composition of the resultant superhydrophobic HNTs were characterized by field emission scanning electron (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The as-formed surfaces exhibited outstanding superhydrophobicity with a water contact angle (CA) of 156.3 ± 2.3°, while having little effect on the crystal structures of HNTs. Meanwhile, the resultant HNTs also showed robust stability that can conquer various harsh conditions including strong acidic/alkaline solutions, organic solvents, water boiling, ultrasonic cleaning, and outdoor solar radiation. In addition, the novel HNTs exhibited excellent packaged capabilities of phase change materials (PCMs) for practical application in thermal energy storage, which improved the mass fractions by 22.94% for stearic acid and showed good recyclability. These HNTs also exhibited good oil/water separation ability. Consequently, due to the superior merits of high efficiency, easy operation, and non-toxicity, this bionic surface modification approach may make HNTs have great potentials for extensive applications.

Effects of Pre-Freezing Prior to Drying upon Some Physical and Mechanical Properties of Eucalyptus urophylla × Eucalyptus grandis Wood

Ordered mesoporous TiO2, loaded on walnut shell-based activated carbon, was prepared via sol-gel and ultrasonic-assisted technology. The obtained composites (M-TiO2/AC) were characterized via X-ray diffraction, N2 adsorption-desorption isotherms, and Fourier transform infrared spectroscopy. The adsorption–photocatalytic reduction capabilities were calculated using the removal rate of Acid Red 18 solution via UV spectrophotometry. The specific area of M-TiO2/AC increased from 563 m2·g-1 to 881 m2·g-1, compared to TiO2/AC. The removal rate was 92.3% when the Acid Red 18 with a concentration of 80 mg·L-1 was subjected to illumination for 2 h with 0.15 g of M-TiO2/AC. Under this condition the removal rate of Acid Red 18 solution by M-TiO2/AC was higher than that of TiO2/AC (83.7%), or AC (73.1%), which was attributed to the regular mesoporous structure, pore-pore synergistic amplification, and TiO2 photocatalysis. Acid Red 18 might be oxidized and decomposed into small molecular substances, such as CO2 and H2O, by strong oxidizing free hydroxyl radicals provided during the photocatalytic process by M-TiO2. The adsorption and photocatalytic processes followed the pseudo-second-order kinetic model. Internal diffusion and external diffusion processes influenced the adsorption rate.

To investigate the effect of bleach pretreatment on the surface photo-discoloration of dyed wood, two kinds of bleached and unbleached dyed wood veneers were irradiated in a xenon light source accelerated aging tester. The exposed surfaces’ color, spectral reflectivity, chemical functional groups, and microstructure were characterized. Bleach pretreatment improved the dyeing effect of the wood veneers. However, it decreased the light fastness of the samples, and as adsorption between the dyes and wood components was reduced, some chromophoric chemical structures of the wood lignin and dyes were degraded, and some extractives (which can function as antioxidants to protect wood surfaces from discoloration) were removed. After light irradiation, the reflectance curves of dyed wood veneers was shifted toward longer wavelengths and noticeable yellowing was observed. Some parenchyma tissue, such as pit membranes in wood cell walls, suffered serious deterioration, as indicated by SEM.