Volume 12 Issue 2

The ultrasonic wave velocities in wood impregnated with a fire-retardant chemical were measured via a non-contact method. An air-coupled ultrasonic wave was made to propagate along the radial direction of the wood. The wave velocities in the wood samples after chemical impregnation were larger than those before impregnation. With increased chemical concentration, the relative changes in the velocities increased to a maximum of 16.3%, and these velocity changes exhibited a strong correlation with the chemical retention. These findings suggest that it is possible to evaluate the uniformity distributions of chemicals in fire-retardant-treated wood via a non-contact and nondestructive method based on air-coupled ultrasonics.

Mechanical properties related to wooden dowel welding were studied using five different moisture content (MC) values. Birch wooden dowels and Chinese larch substrates were used in this study. A 2% MC for the wooden dowels and a 12% MC for the substrates resulted in the highest pullout resistance. A fitting analysis showed that there was a linear relationship between the pullout resistance and the different values of MC. The errors between the calculated values and the test values were less than 10%. The pullout resistance of the wooden dowel welding fit a Weibull distribution. No accurate linear relation existed between the 95% reliability pullout resistance and the different MC values. Chemical analyses were performed separately on the wooden dowel and the welding interface of a wooden dowel sample with 2% MC and a substrate with 12% MC. X-ray diffraction (XRD) analysis revealed that the degree of crystallinity of the welding interface was 75% higher than that of the wooden dowel. Finally, thermogravimetric analysis (TG) illustrated that pyrolysis of the wood components occurred during the wooden dowel welding process.

The removal of cationic methylene blue (MB) and anionic acid red 1 (AR1) dyes from aqueous solution was studied using cellulose-g-p(AA-co-AM) bio-adsorbent (CP bio-adsorbent). The CP bio-adsorbent with surface multiple functional groups and macroporous network structure was synthesized via grafting the acrylic acid (AA) and acrylamide (AM) onto cellulose molecules. The adsorption behavior of the bio-adsorbent to dyes in the aqueous solution was studied. The effects of solution pH, temperature, initial dye concentration, and contact time on the adsorption capacity of the bio-adsorbent were investigated. Due to the abundant functional groups and macroporous network structure, the CP bio-adsorbent exhibited remarkable adsorption performance for the removal of type dyes with an equilibrium adsorption capacity of 998 mg·g-1 for MB and 523 mg·g-1 for AR1. The kinetic studies revealed that the adsorption of dyes was exactly described by a pseudo-second-order kinetic model. Comparison with other bio-adsorbents confirmed that the eco-friendly CP bio-adsorbent possessed excellent potential for water purification.

To improve prospects for high-value utilization of biomass, torrefaction pretreatments were conducted at 210, 230, 250, 270, and 300 °C with a reaction time of 30 min. The pyrolysis of torrefied biomass was also performed on a fixed-bed reactor system at 450 °C. The effect of torrefaction temperature on the yield, energy yield, structure, physical-chemical characteristics, and production composition of bio-oil was studied. The torrefaction pretreatment improved the fuel characteristics of pyrolysis products. When the torrefaction temperature was increased, the -OH and C=O contents decreased, the C=C contents increased, the pyrolysis peak temperature decreased, the residual carbon contents noticeably increased, and the Ea value remained in the range of 69 to 129 kJmol-1. The pore volume increased and the crystallinity index decreased due to degradation and recrystallization. The solid yield of pyrolysis biomass decreased sharply in contrast to the liquid yield. When the torrefaction temperature increased, the bio-oil yield decreased from 36.82 wt.% to 20.13 wt.%. The phenol content in the bio-oil markedly increased; however, oxygen-containing compounds such as acids, sugars, and furans, significantly decreased, which indicated that torrefaction pretreatment efficiently improved the quality of the fuel.

Phenolic-based sugar palm fibres (SPFs) were used as a filler for composites that were fabricated by hot pressing. The composites were prepared using various volume loadings of SPFs. Dynamic mechanical analysis (DMA) was carried out to evaluate the storage modulus (Eʹ), loss modulus (Eʺ), and tan delta as a function of temperature. The SPFs were treated by seawater for 30 days and a 0.5 alkaline solution for 4 days. The phenolic composites with 30% volume loading of SPFs were used to determine the effect of treatments on the DMA properties of the composites. The obtained results indicate that incorporating a SPF filler notably increased the Eʹ and Eʺ properties and decreased the damping factor of the phenolic composites. Both treatments affected the DMA results. However, the alkaline-treated composites showed higher DMA properties compared with the seawater-treated and untreated fibre composites.

The hydrothermal treatment of bamboo was carried out to investigate the effects of different temperatures (230 °C, 260 °C) and residence times (30 min, 60 min) on the combustion behaviors and properties of hydrochar. The higher heating value (HHV) increased gradually with increasing hydrothermal temperature and residence time, while the energy yield decreased. It was found that 260 °C and 30 min with a HHV of 22.8 MJ/kg and an energy yield of 57.8% were appropriate parameters for the production of hydrochar. The atomic oxygen/carbon ratio indicated that the upgrading process converted the bamboo into fuel that was similar to clean solid fuel with a high energy density. The thermal gravimetric analysis showed that the temperature and the residence time had noticeable impacts on the combustion behavior and the activation energy of hydrochar. The combustion reaction ability and rate were greatly improved when the hydrochar was prepared at temperatures greater than 200 °C. The activated energy value was determined by the model-free methods, of which Kissinger-Akahira- Sunose (KAS), Flynn-Wall-Ozawa (FWO) were the most appropriate for this purpose and resulted in similar values.