Research Articles

This study investigated the effect of oxygen plasma treatment on the glass transition temperature of enzymatic hydrolysis lignin (EHL) derived from the production of bio-ethanol. Differential scanning calorimetry (DSC) was used to obtain the glass transition temperature (Tg) of EHL. The results showed that the Tg value of EHL under different heating rates ranged from 160 to 200 °C, and there was a strong linear correlation between heating rate and Tg. The Tg value of oxygen plasma treated EHL decreased when compared with the untreated samples. The apparent Tg of the untreated sample was 168.2 °C, while the value of the treated sample was 161.5 °C. Distinct chain scission and introduction of oxygen-based functional groups on the surface of EHL were detected by XPS analysis. These changes may occur mainly on the bulky side chain and thus enhance molecular mobility of EHL. This indicates that oxygen plasma treatment can modify the structure and improve the reactivity of EHL efficiently.

Changes in the lignocellulosic structure of oil palm empty fruit bunches (OPEFB) during composting treatment using an in-vessel composter was investigated in this work. The composting process was completed within 40 days of treatment, and the final C/N ratio achieved was 13.85. Scanning electron microscopy (SEM) revealed that the structure of OPEFB material was severely degraded, especially during the thermophilic phase where the biodegradation process was most active. Close examination of the physicochemical and thermal analysis using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermogravimetric and differential thermal analysis (TG/DTA) showed that the crystallinity size of the OPEFB structure decreased. This result was attributed to the removal of silica bodies from OPEFB materials. Also, the functional groups of cellulose, hemicelluloses, and lignin structures had changed throughout the composting period, and the most extensive degradation of cellulose was detected in the thermophilic phase. It was also found that the exothermic peak of the matured compost reduced most significantly compared to the raw OPEFB. In conclusion, the in-vessel composting system was able to enhance the degradation process of OPEFB materials for producing compost.

The objective of this study was to investigate the effect of uniaxial and biaxial compression loadings on the circumferential-radial mechanical properties of bamboo. A novel biaxial testing device, called the 3D composite material analysis system, was developed to conduct biaxial compression tests. Strain field analysis was characterized with the help of the digital speckle correlation method (DSCM). The effects of four different environmental treatments (I. air-drying, II. constant temperature and relative humidity, III. relatively low temperature, and IV. ultra-low temperature) on the circumferential performance of bamboo were examined in the experiment. The results of this study indicated that the diametric strength of bamboo evaluated by biaxial load was as 2.4 to 2.5 times the uniaxial compression. Under biaxial load, the strength of the bamboo node was about 2.38 times higher than the internode. Failure first occurred at the outside surface of bamboo at about the 45° position between X and Y axial when conducting a biaxial compression test. The distribution of X-strain field expressed itself more uniformly than the Y-strain field. The diametric mechanical properties of bamboo ring were σIV>σIII>σII>σI for both the uniaixal and biaxial compression tests.

There is increasing interest in replacing coal with woody biomass in co-firing plants for electrical power. A variety of pre-treatments can be used to make biomass more suitable for co-firing. This research presents a model that evaluates the delivered costs of various pre-treated biomass sources, electricity production costs, and constraints, and calculates a least cost mix. Results of the scenario presented indicate that wood chips are the most economical co-firing option for delivering biomass to direct-fired boilers. Apart from potential feeding and processing issues, the wood-chips options of forest residues present the lowest cost of electricity production for small-scale co-firing applications. From the options that will ensure minimum processing issues in the co-firing cycle, wood pellets from southern yellow pine represent the most economical choice. Based on coal displacement from the facility, torrefied wood pellets from southern yellow pine is a preferred option as compared to other choices evaluated. An alternative to torrefied wood pellets from southern yellow pine is dark torrefied Eucalyptus benthamii, providing similar electricity production costs while reducing coal utilization.

Chromium (VI) removal and its reduction to chromium (III) from aqueous solution by untreated and heat-treated Quercus cerris and heat-treated Quercus suber black agglomerate cork granules was investigated. Initial screening studies revealed that among the sorbents tested, untreated Q. cerris and Q. suber black agglomerate are the most efficient in the removal of Cr(VI) ions and were selected for adsorption essays. Heat treatment adversely affected chromium adsorption and chromium (VI) reduction in Q. cerris cork. The highest metal uptake was found at pH 3.0 for Q. cerris and pH 2.0 for black agglomerate. The experimental data fitted the Langmuir model and the calculated qmax was 22.98 mg/g in black agglomerate and 21.69 mg/g in untreated Q. cerris cork. The FTIR results indicated that while in black agglomerate, lignin is the sole component responsible for Cr(VI) sorption, and in untreated Q. cerris cork, suberin and polysaccharides also play a significant role on the sorption. The SEM-EDX results imply that chromium has a homogenous distribution within both cork granules. Also, phloemic residues in Q. cerris granules showed higher chromium concentration. The results obtained in this study show that untreated Q. cerris and black agglomerate cork granules can be an effective and economical alternative to more costly materials for the treatment of liquid wastes containing chromium.

High-heat treatment after surface application of chitosan was used in an effort to improve physical and mechanical performances of particleboard. Particleboard is mainly used in the furniture industry and also used as a home decoration material; however, it has a poor dimensional stability. In this work, hardwood chips were obtained from a commercial plant; half of the chips were used for the control panels without chitosan treatment, and the other half were treated with chitosan acetate solutions (2% wt). Those chitosan-treated particles were also exposed to extra high-heat (140°C) treatment for 90 minutes to convert chitosan acetate back to chitin. Liquid phenol-formaldehyde resin was sprayed onto dry particles at a level of 6 and 7% (wt) based upon oven-dry weight. The mat was pressed (200°C) for 11 minutes to form 19 mm thickness and a target of 0.63 g cm^-3 density panels. Thickness swelling, linear expansion, and water gain of the treated panels were reduced over untreated panels during a 24-hour water-soak test. In addition, chitosan-treated panels showed better internal bond strength than control panels. Static bending test results showed a negative effect for the chitosan treated particleboard.

Selective logging in mature hardwood stands of Caspian forests often causes physical damage to residual trees through felling and skidding operations, resulting in a decline in bole quality and subsequent loss of tree value. This study evaluated the logging damage to residual trees following logging operations. A total density of 5.1 trees/ha and 17.3 m3/ha of wood were harvested. On average, 9.8 trees were damaged for every tree extracted, including 8 trees destroyed or severely damaged. The most common types of damage included uprooted stems, stem wounds to the cambial layer, and bark scrapes. Damage to trees sustained along skid trails was found to be significantly more than the damage that incurred within logging gaps and winching areas. The results of this study suggest that logging practices also need to be accompanied by close supervision of field personnel and post-logging site inspections to be implemented properly.

The objective of this study was to evaluate the discoloration of European beech (Fagus sylvatica) and Scots pine (Pinus sylvestris) specimens treated with different chemicals and surface coated with different UV absorbers before being subjected to artificial weathering. The results showed that the influence of coatings containing UV absorbers (UV screeners micronized TiO2 and UVA of hydroxyphenyl-s-triazine types) were similar to each other. The UV screener TiO2 led to the least discoloration of the coated wood surface, closely followed by the UVA of hydroxyphenyl-s-triazines (HPT). The color stability was determined to be better for pine wood treated with micronized copper preservative coated with UV absorber, in comparison to when it was only coated with UV absorbers and then subjected to weathering. Microscopic observation revealed that the clear-coats penetration behavior was different in wood preservative-treated and in untreated wood of Scots pine, which has various extractives. However, the color stability and coating penetration was nearly the same in beech wood treated with preservatives and in untreated beech wood. We provide an explanation for why these effects occurred and discuss the implications of our findings for the development of weather-resistant wood materials.

Tetra acetyl ethylene diamine (TAED) was used as an activator in H2O2 bleaching to improve bleaching efficiency. The present work was aimed at confirming different activations for various H2O2/TAED bleaching processes, including the addition of acetic anhydride and the step-addition of sodium hydroxide. The results showed that an acetic anhydride dosage of 1%, an acetic anhydride treatment time of 10 min, and an addition time of 45 min were the optimal treatment conditions. The optimum processes of NaOH step-addition treatment in H2O2 bleaching and in H2O2/TAED bleaching also were confirmed, respectively. The o-quinone contents of H2O2 bleached lignin and H2O2/TAED bleached lignin were determined. The results indicated that H2O2/TAED bleached lignin has a lower o-quinone content than H2O2 bleached lignin, which is one of the reasons for the H2O2/TAED bleaching process having better bleaching efficiency than H2O2 bleaching.

Biomass represents an abundant and relatively low cost carbon resource that can be utilized to produce platform chemicals such as levulinic acid. Novel oligomeric flame retardants, the poly(MDP-PDCP-MA)s (PMPMs), were designed and synthesized using diphenolic acid as one of the raw materials, which is derived from levulinic acid. To change the molar ratio of reactants, a series of PMPM samples with different nitrogen contents were obtained and characterized by FTIR and solid-state 13C NMR spectroscopy. The solubility test and thermogravimetric analysis (TGA) indicated a good solvent-resistant property and thermal stability. The flame retardancy and thermal behavior of ABS with 30% loading of different PMPM samples were investigated by limiting oxygen index test (LOI), TGA, and microscale combustion colorimeter (MCC). The results showed that PMPMs are effective charring agents that can increase the thermal stability and flame retardancy of ABS. Scanning electron microscopy (SEM) observations of the residue of ABS/PMPM blends indicated the compact charred layer formed was responsible for improving the thermal stability and char yield of ABS with low nitrogen content in PMPM-1 flame retardant.