Volume 15 Issue 2

Poplar wood flour wood-plastic composites (WPCs) prepared with high-density polyethylene and modified with different amounts of ethylene vinyl acetate (EVA) were created. The influence of EVA content on the surface properties and weathering characteristics after ultraviolet (UV) treatment was investigated. The results showed that WPCs treated with EVA had improved thermal stability, and the surface polarity was reduced. The addition of EVA slowed the fading of the WPCs, and the color difference was the smallest when the EVA content was 5%. Both the bending strength and the modulus of elasticity (MOE) of the WPCs decreased after the UV treatment. However, when the EVA content was 5%, the bending strength retention ratio and MOE retention ratio were greatest. Scanning electron microscopy showed that the addition of EVA reduced the amount of pores and gaps on the fractured surfaces of the WPCs. The comprehensive performance of the WPC anti-weathering properties was greatest when the EVA level was 5%.

This study aimed to evaluate the influence of white liquor sulfidity on the efficiency of the kraft pulping process. For this study, Eucalyptus spp. chips were used. Laboratory cooking with variable sulfidity levels (0 to 40% at 5% intervals) was conducted under previously optimized conditions, aiming to obtain pulp with a Kappa number of 18 ± 0.9 and residual effective alkali between 9 and 12 gL-1. At the end of each cook, Kappa number, solids generation, specific wood, and alkali consumption were evaluated. The sulfidity variation in white liquor influenced all analyzed parameters, and concerning the specific wood consumption, a distinct behavior was observed for the low sulfidity (S ≤ 19.52%) and high sulfidity regions (S ˃ 19.52%). Based on the obtained results, the production of eucalyptus kraft pulp with white liquor sulfidity of approximately 20% is recommended.

Fermentative valeric acid production is a promising way to recycle valuable resources from waste activated sludge (WAS). This study investigated the feasibility of using riboflavin (RF) to enhance volatile fatty acids (VFAs) production, especially valeric acid production from WAS coupled with solid reduction. The results indicated that RF (0.5 mM) promoted the VFAs production by up to 41.0%. Valeric acid accounted for the most abundance within the VFAs components. When RF dosages were 0.05 to 5.0 mM in the WAS fermentation systems, the chemical oxygen demand fractions of valeric acid to the total VFAs were 41.0% to 62.8%, which were much higher than those using other chemical supplements. Moreover, RF enhanced the reduction of mixed liquor volatile suspended solids (MLVSS). When RF dosage was 0.2 mM, MLVSS reduction achieved a maximum at 47.4%, compared to that in the RF-free control (33.9% reduction). Riboflavin in this study was considered as a feasible chemical to enhance the fermentative valeric acid generation coupled to MLVSS reduction, realizing the reduction of solids and the reutilization of valuable resources from WAS.

The conversion of lignin into valuable products has attracted the interest of researchers. A series of modified polyurethane adhesives were prepared by blending corn straw enzymatic hydrolyzed lignin with polyester polyol and tolylene-2,4-diisocyanate. Mechanical properties, chemical structures, and thermal stability of the adhesives were characterized by mechanical properties tests, Fourier transform infrared spectrometry (FTIR), and thermogravimetric analysis (TGA). The results of shear strength test under room temperature and high temperature showed that the shear strength for modified polyurethane adhesives was improved by introduction of lignin. The introduction of lignin also improved the heat resistance of polyurethane adhesive. The TGA analysis results showed there were two stages in the thermal decomposition of the lignin blend modified polyurethane adhesive, and the maximum decomposition temperature of the first stage increased with the increase of lignin content, while the maximum decomposition temperature of the second stage decreased with the increase of lignin content. The TGA-FTIR combination analysis studied the main gas generated in the two decomposition stage’s peak times, of which CO2 was produced in the first stage, and CH4 was created in the second stage, indicating that the molecular chain fracture process of the two kinds of adhesives was similar in the whole decomposition process.

Banana pseudostems (BP) are a promising cellulose source that remains underutilized despite its potential to be formed as biodegradable food packaging material. This work was directed towards utilizing BP waste in a powder form to produce potential food packaging material that is environmentally friendly. A solvent casting method was used to produce starch/BP films at different BP percentage compositions (0, 10, 20, 30, and 40 wt% on the dry basis of starch). The effects of different percentage compositions of BP in starch on the morphology, optical, mechanical, and barrier properties of the films were investigated. The optical and mechanical properties of the starch films decreased with the addition of BP. However, the mechanical and barrier properties of the films improved with the increase in BP composition. An optimum percentage composition of 40 wt% BP powder can be utilized to produce starch/BP films for potential food packaging application.

The spread of invasive alien plant species (IAPS) is a leading reason for worldwide environmental change due to their effects on biodiversity and humans. Some valued goods from IAPS have been produced, e.g. paper that consists of cellulose fibres from Japanese knotweed. Therefore, the aim of this study was to establish the usability of this paper grade as a printing substrate, since it does not have ideal optical properties as it is expected from commercial office paper. Because it is widely used, inkjet printing technology was employed. Print permanence is essential, especially when printing documents. However, typographic characteristics must be considered to make a text more legible. Two widely used typefaces (Arial and Times) were tested in three commonly used type sizes (8 pt, 10 pt, and 12 pt). The results showed that the paper made from Japanese knotweed could have valuable properties and suitable legibility, especially when using typefaces with a moderate counter size, high x-height, and minimal differences in the letter stroke width to obtain an appropriate typographic tonal density with an adequate type size. Even after exposure to light, the texts printed in a proper type size and stroke width remained visible.

White water treatment with combined predominant bacterial species and immobilized enzyme was investigated. The use of the single predominant bacteria of Brevundimonas diminuta or Virgibacillus pantothenticus resulted in poor treatment responses. With the combined bacterial species, the treatment effect was clearly improved. When the dosage ratio of Brevundimonas diminuta to Virgibacillus pantothenticus was 1:2, the chemical oxygen demand (CODCr) removal rate reached 70.5%, the cationic demand decreased 46.0%, and the electrical conductivity decreased 18.6% after 16 h of treatment. When mixed with the immobilized enzyme, the treatment efficiency increased with the immobilized pectinase dosage. When 8 g/L immobilized pectinase was added, the treatment time was shortened from 16 h to 4 h, the highest removal rate of CODCr was 74.1%, the cationic demand decreased 68.7%, and the electrical conductivity in the white water decreased 30.1%. The results indicated that the combination of predominant bacterial species and immobilized pectinase could greatly improve the treatment efficiency of white water.

Converting biomass into biochar is a smart recycling strategy. Biochar was produced from tobacco stems at temperatures of 400 °C, 500 °C, 600 °C, and 700 °C and holding times of 1.5 h, 2 h, 2.5 h, and 3 h. Its properties and adsorption capacities for Pb2+ and Cd2+ were evaluated. While the yield decreased, pH, phosphorus, potassium, ash, and surface area increased with increasing pyrolysis temperature and holding time. Nitrogen, volatile matter, and pore diameter decreased as the temperature increased, with an irregular effect of the holding time. A peak C content (652 g/kg) was recorded at 600 °C (2 h). The highest values obtained for the N, P, and K content were 25.6 g/kg (400 °C and 2 h), 7.82 g/kg and 168 g/kg (600 °C and 3 h), respectively. The heavy metal contents were within tolerable limits. The highest surface and micropore areas of 50.6 and 57.1 m2g-1, respectively, were obtained at 700 °C (3 h). The biochar had a wide range of aliphatic and aromatic C functional groups. The highest adsorption percentages of Pb2+ and Cd2+ (44.5 % and 38.3 %, respectively) by biochar produced at 700 °C (3 h) signified its suitability for heavy metal adsorption. These properties made the biochar a suitable soil amendment.

The possibility of using hemp flour as a filling material for melamine-urea-formaldehyde (MUF) adhesive was investigated for the process of manufacturing plywood. Adhesive mixtures were filled with various amounts of hemp flour and compared to rye flour as a reference mixture, and their properties were tested. The quantity of added filler had a significant effect on the resins viscosity. Moreover, the replacement of rye flour with the hemp flour resulted in acceleration of gel time and a slight increase in solid content. Due to the high proteins content, hemp flour led to a significant reduction of formaldehyde emission. Bonding quality of plywood made with hemp flour as a filling material for the adhesive mixture meet the requirements from the standard. Introducing it in an amount of 20 pbw and 25 pbw (parts by weight) allowed for the production of plywood characterized by equally good mechanical properties as that of reference plywood glued with an adhesive mixed with rye flour. In summary, the proper amounts of hemp flour can be applied as a filling material and formaldehyde scavenger for MUF adhesive without the deterioration of mechanical properties of manufactured plywood.

Starch is a natural polymer and eligible for short-term, single-use food packaging applications. Nevertheless, different starches have different features and properties determined by their botanical plant origins. This paper presents an approach that combines Shannon’s entropy and the Analytic Hierarchy Process method to aid the selection process of starch as matrix in green biocomposites for takeout food packaging design. The proposed selection system ranks alternative starches in terms of the key design elements, i.e. strength, barrier property, weight, and cost. Shannon’s entropy established corresponding weight values for the indicators selected. Six starches: wheat, maize, potato, cassava, sago, and rice were appraised using gathered data from the literature to determine their suitability as a more sustainable option. This study found that sago starch obtained the highest priority score of 26.8%, followed by rice starch (20.2%). Sensitivity analysis was then carried out to further verify the results; sago starch was at the top rank for five of six different scenarios tested. The results showed that sago starch is the starch that can best satisfy the design requirements. Despite the results attained, the selection framework used could be enhanced with a more comprehensive attributes assessment and extensive dataset.