Volume 18 Issue 1

A comparison of pyrolysis characteristics and gas product evolution of biochar with different packing arrangements was investigated. Pyrolysis properties and released gas products of rice husk char were obtained by particles in two different modes of packing. The results of the combustion characteristics of rice husk/char showed that the maximum pyrolysis rate of the rice husk decreased and the pyrolysis curve shifted to higher temperatures when the biomass was covered by Al₂O₃. The volatilization analysis of char from the covered biomass had a larger characteristic index and a lower activation energy. The 2D Fourier transform infrared (FTIR) results showed that layering hindered gaseous products from being released during rice husk pyrolysis, and there was no obvious release peak of C=O-containing organic matter. The 3D FTIR results showed that gaseous product absorption peak of solid product char pyrolysis gradually decreased while the rice husk conversion rate increased. The amount of H₂O, CO₂, CO, CH₄, and C=O-containing organic components released during combustion of pyrolyzed char when blended with Al₂O₃ decreased gradually. However, the pyrolysis gaseous product release was increased by the layering procedure.

Granular activated carbon (GAC) and powdered activated carbon (PAC) are the two most common forms of activated carbon with varying particle size range. The goal of this study was to analyze the key factors (particle size and activation temperature) affecting the surface characteristics of GAC and PAC derived from palm kernel shell (PKS). The surface morphology suggested that the pore network in PKS-PAC is more developed than that in PKS-GAC owing to the presence of a micropore structure when prepared at lower activation temperatures. This study also demonstrated that activation performed on different PKS particle size range influenced the mesopore domain of the activated carbon produced. The PKS-GAC was found to have more mesopores than PKS-PAC, which made it more reliable for dye adsorption in water treatment. Overall, this study demonstrated that applying different particle size range of PKS during the activation process can have a significant influence on the surface characteristics, thus having a direct impact on the application of activated carbon. An accurate particle size range will ensure that the most cost-effective activated carbon is selected to achieve the desired performance objectives.

Hydrogen peroxide (H₂O₂) bleaching in ethanol-water media was used to improve the bleaching efficiency of the chemi-thermomechanical pulp (CTMP). The brightness of CTMP increased and the yellowness decreased when the ethanol ratio was increased to 50%. However, when more than 50% ethanol was added, the brightness decreased, and the yellowness increased. In general, H₂O₂ bleaching in ethanol-water media, except for 100% ethanol, improved the optical properties of CTMP compared to conventional H₂O₂ bleaching. Moreover, the chemical composition of CTMP did not alter significantly. The best bleaching condition for CTMP was observed in 50% ethanol at a bleaching temperature and time of 80 °C and 120 min, respectively. The brightness of CTMP under this condition increased by approximately 22% compared with conventional H₂O₂ bleached CTMP. Principal component analysis (PCA) revealed that the optical properties of bleached CTMP were affected by the structural changes of the aromatic ring and carbonyl group in lignin and carbonyl group in hemicellulose. Consequently, the specific optimal ratio of ethanol that could improve the optical properties of CTMP was determined. The results can serve as a reference for fabricating improved CTMP for its practical application in high-grade papermaking.

The residual of perennials in landscape trimming and agricultural interval planting are produced massively, and they can provide an innovative way to increase anaerobic digestion efficiency via co-digestion process. In this study, the bio-methane potential (BMP) of different perennial crops (grass, alfalfa, and red clover) in various feedstock concentrations based on volatile solid (VS) and the kinetic analysis of the co-digestion process were investigated. The results showed that grass and legumes reached the highest methane yield at 5 VS/L and 20 VS/L, respectively. Co-digestion of grass and perennials had better methane production of 338 mL/g VS, which is 9.1% higher than mono-digestion. Further analysis demonstrated that VS removal efficiency of mono-legumes digestion was below 60%, while co-digestion of grass and legumes can improve VS removal efficiency dramatically. Volatile fatty acids (VFAs) and ammonia in the digestate accumulated at 40 VS_added/L. Additionally, kinetic analysis was employed to predict and evaluate the performance of anaerobic digestion, with the Cone model showing the best fitting curve.

The internal quality of the wood is one of the main factors affecting the stability of trees, and it has always been of great interest to science and practice. For this reason, the present study aims to compare the results obtained by wood tomograms with those of resistance to drilling and the visual appearance after cutting a slice with a chain-saw, both to evaluate the presence and dimensions of the inside defects, and also to evaluate the irregularities of the wood structure. Round pieces of lime wood harvested from public areas were used for comparison by taking sound tomograms, followed by taking resistograms on two perpendicular directions at the same level. The results showed that internal wood defects are not always the ones that lead to reduced speeds of sound propagation through the wood. In addition, there were instances in which changes in the internal structure of the wood led to improperly colored tomograms, namely the sections characterizing the point of insertion of a thick branch in the trunk, where the tomograms indicated low speeds of sound transfer through the wood in the stem and high speeds in the wood of the branch.

The objective of this study was to evaluate the energy potential of Astronium fraxinifolium and Enterolobium gummiferum wood species that grow in the Savannah of Minas Gerais, Brazil, focusing on the production of charcoal. Two discs were removed at 1.30 m from the ground of three trees of each species, and these were later sampled into wedges that were applied in the analysis of wood characteristics and charcoal production in a muffle furnace. The extractives content and basic density of the wood species were determined, and apparent density of charcoal, ash content, heating value, and energy density of both materials were also determined. The woods under study have potential for application in energy production. Emphasis was placed on A. fraxinifolium, which presented wood and charcoal that was denser, had higher energy density, and achieved greater gravimetric yield.

Cellulose-derived materials are an emergent opportunity for reducing the environmental impact of polymers. Microcrystalline cellulose (MCC) has increasing relevance in many sectors, including pharmacy, food, and reinforcement of polymers, but its application is limited by the low coupling between it and nonpolar polymers and the polar behavior of cellulose derivates. There is not a well-defined model for the isolation of MCC and the factors involved in the length and width, which are elements of high influence on the reinforcement effect of MCC. This study proposes a mechanism for the size reduction of cellulose fibrils isolated through acid hydrolysis and a post-plasma surface modification (PSM) to enhance coupling of the MCC with hydrophobic polymer matrixes. MCC was characterized by FTIR, XRD, and SEM before and after the plasma surface treatment with caprolactone, a biodegradable polymer. There were no changes in the FTIR spectra; however, in XRD the sample exhibited a decrease in intensity. These results suggest that PSM did not change the structure of MCC or chemical composition. However, an increase in the peak temperature of degradation confirmed the surface modification of MCC.

Wood plastic composites (WPCs) were prepared by extrusion molding with eucalyptus powder, polyvinyl chloride (PVC), and silica as additives. The mechanical properties, creep behavior, thermal properties, and cross-section microstructure of the composites were analyzed by universal testing machine, thermogravimetric analyzer, and scanning electron microscope. The results show that with the increase of silica content, the tensile strength, bending strength, and impact strength of the WPCs first increased and then decreased. When the silica content was 3.0%, the tensile strength, bending strength, and impact strength of WPC reached the maximum values of 27.5 MPa, 48.8 MPa, and 4.18 KJ·m^-2, respectively, which represented increases of 12.6%, 9.4%, and 20.1%, respectively, compared with those without silica. When the stress was 13.4 MPa, the strain value of 3.0% SiO₂-eucalyptus/PVC wood plastic composite was 3.3 times that of 4.46 MPa and 1.7 times that of 8.92 MPa. The pyrolysis process of eucalyptus/PVC WPCs showed a similar trend with different silica content.

Eucalyptus/polyvinyl chloride (PVC) composites were prepared by extrusion molding with eucalyptus as filler, PVC as matrix, and different contents of acrylonitrile styrene acrylate copolymer (ASA). The effects of different ASA content on the mechanical properties, water absorption properties, and thermal stability of eucalyptus/PVC composites were studied. The morphology of the tensile section of the composites was observed by scanning electron microscopy (SEM). The results showed that the addition of ASA could improve the mechanical properties, heat resistance, and interfacial compatibility of eucalyptus/PVC composites. It also could reduce the water absorption of the composites. When ASA content was 10 wt%, the mechanical properties and heat resistance of eucalyptus/PVC composite were the best, and the water absorption in 24 h was the lowest.

The material constants of wood required for finite element analysis (FEA) are usually calculated using small clear specimens. However, defects, such as knots and slope of grain affect the strength reduction in the full-size specimens. Consequently, an error occurs if only the material constant calculated from the small clear specimens is used to predict modulus of rupture (MOR). Therefore, in this study, the MOR reduction coefficient according to defect was obtained through the bending test of the full-size specimens and applied to the FEA, in addition to the material constant from the small clear specimens. The maximum bending moment section was measured for a 3-section four-point load, and defects in the outermost tension layer were measured for laminated timber and glulam. The result of the bending test confirmed that MOR also decreased as the size of the defect increased. Therefore, when predicting MOR, a strength reduction ratio according to visual grade was applied. The MOR predicted FEA was twice as large as the actual MOR before defect correction, but the prediction error after defect correction was greatly reduced to 8%, thus increasing the prediction accuracy.