Research Articles

Graphene oxide (GO) was used as a catalyst support and for regeneration of a homogeneous catalyst in the catalytic conversion of glucose to lactic acid (LA). First, a solid base catalyst was prepared through the adsorption of Pb²⁺ ions by GO through ionic interaction with oxygenated groups of GO. The collected GO-Pb catalyst was characterized, demonstrating the successful loading of Pb²⁺ onto GO sheets using FTIR and XPS. The GO-Pb catalyst was subsequently used for the conversion of glucose into LA. A maximum LA yield of approximately 30% was achieved in 30 min. The catalyst demonstrated the ability to be used for at least five cycles. In contrast, the leached Pb²⁺ ions during the hydrothermal process were regenerated through adsorption with fresh GO. The regenerated catalyst demonstrated the possibility of the regenerated Pb²⁺ ions for further catalytic conversions of lactic acid. This study could be essential to produce valuable chemicals through the use of heterogeneous catalysts that are produced via a simple and environmental benign process.

The hybrid composite was prepared from cassava bagasse (CB) and sugar palm fiber (SPF) by casting technique using cassava starch (CS) as a matrix and fructose as a plasticizer. The chemical composition and physical properties of SPF and CB were studied in this work. SPF was added at different loadings of 2, 4, 6, and 8% dry starch to the CS/CB composite films with 6% CB. The addition of SPF influenced the hybrid properties. It was observed that the addition of 6% SPF to the composite film increased the tensile strength and modulus up to 20.7 and 1114.6 MPa, respectively. Also, dynamic-mechanical properties of the hybrid composites were investigated using a DMA test. The incorporation of SPF increased the storage modulus (E’) value from 0.457 GPa of CS to 1.490 GPa of CS-CB/SPF8 hybrid composite film. Moreover, the incorporation of SPF slightly decreased the water vapor permeability (WVP) compared to the CS/CB composites film. It can be concluded that the incorporation of SPF led to changes in cassava starch composite film properties, potentially improving the bio-degradability, WVP, and mechanical properties of the film. Based on its excellent properties, CB/SPF-CS hybrid composite films are suitable for various purposes such as packaging, automotive, and agro-industrial applications, at lower cost.

The decay resistance of zinc borate-reinforced wood-plastic composites (WPCs) was studied against two types of brown-rot fungi (Rhodonia placenta and Coniophora puteana). The WPCs with 70% wood fibers (Pinus sylvestris L.) were reinforced with 1% and 2% zinc borate. The reinforced WPCs were exposed to a decay test according to the EN 113 (1996) standard. The composite samples were characterized by their weight losses and water absorption capacity (WAC) as well as by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The weight losses and WAC results showed that zinc borate improved the decay resistance of the WPCs to a certain degree against brown rot fungi. The FTIR and SEM results showed that the brown rot fungi attacked the WPCs. It was concluded that the use of 1-2% zinc borate provided resistance to fungal attack on WPCs to a certain degree.

In this publication, the ultrasonic-assisted deep-drawing of fiber-based materials, whose implementation was presented in Löwe et al. (2016), was studied in detail. Methods were developed for measuring the properties of deep-drawn cups, including cup stability, shape deviation, and surface quality. The relationship between these properties and the process parameters were determined with a design of experiment, which allows the user to adjust the cup properties in order to optimize them.

The properties and capacities of the ligninolytic enzymes of Daedaleopsis spp. are still unknown. This is the first study on the effect of plant residues and period of cultivation on the properties of Mn-oxidizing peroxidases and laccases of D. confragosa and D. tricolor, as well as their ligninolytic potentials. Wheat straw was the optimal carbon source for synthesis of highly active Mn-dependent peroxidases (4126.9 U/L in D. confragosa and 2037.9 U/L in D. tricolor). However, laccases were the predominant enzymes, and the best inducer of their activity (up 16000.0 U/L) was cherry sawdust. Wheat straw was the most susceptible plant residue to the effect of the enzymes, and extent of lignin degradation was 43.3% after 14 days of fermentation with D. tricolor. However, D. confragosa was a more effective lignin degrader, as it converted even 21.3% wheat straw lignin on the 6th day of cultivation. The results of the study clearly showed that delignification extent depends on mushroom species and on the type of plant residue, which is extremely important for potential use in biotechnological processes.

To verify the effect of softening treatment on the cutting force during slicing of veneers, an experiment was performed using a veneer slicer with steam injection heating function. Several conditions were set to soften the experimental materials of poplar (Populus L.), eucalyptus (Eucalyptus robusta Smith), pine (Pinus massoniana Lamb.), and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.). The cutting force was detected by the YE7600 signal analysis system. The results showed that the cutting force increased with increased slicing thickness. The cutting force was observed to follow the order, from high to low for the conditions of being soaked in cold water, then steam heated, water-poached, and steam heated again. Compared to the case of non-steam heating, the effect of steam heating on reducing the cutting force was satisfactory, and the maximum decrease percentage reached 83.1%. The cutting force was positively related to the wood density and hardness, and the cutting stroke had a great influence on the cutting force. After being softened, the four kinds of fast-growing wood were sliced into veneers with ≤ 6 mm thickness, and the cutting force was generally no more than 6850 N.

The biggest threats to the longevity of a timber bridge are rot and decay. Wood protection by design, inspections, and monitoring of the bridge for elevated moisture content will ensure that the full service life of the structure can be achieved. Today’s sensors for moisture content measurements are limited in their functionality and range. This paper presents a sensor that can be both factory installed and retrofitted, which can measure the moisture content through the cross-section of the member in a timber bridge. The sensor has been mounted on Sundbron bridge during manufacturing and retrofitted on Gislaved bridge. The ensuing measurements helped to adjust a design flaw on Gislaved bridge. Monitoring of Sundbron showed that the bridge deck dried up after the bridge had been exposed to sleet and snow during the on-site assembly of the stress laminated bridge deck.

The potential of using sorghum brewers spent grain (BSG) was examined for the production of bioelectricity. A local brewery company, with a production capacity of 24 tons per day of sorghum brewers spent grain as biomass waste, was used as a source of boiler fuel. After a full proximate analysis, the sorghum brewers spent grain had an average calorific value of 12.6 MJ/kg whilst coal had 19.9 MJ/kg. In addition, the BSG had a fixed carbon content of 41.6%. This indicated that it was feasible to generate electricity using sorghum brewers spent grain as a source of fuel just like coal; however the moisture content of the BSG must be controlled at minimum levels to attain high calorific values. An assumed feed rate of 1100 kg/h BSG being fed, operation at 86% efficiency, maximum pressure of 9 bars, and a steam output of 1689 kg/h were designed to supply a one megawatt (MW) turbine generator. An economic analysis was done with a total investment cost of USD$ 3.4 million, a payback period of 3.7 years, and a return on investment of 27.4%. Sorghum BSG can be provided as an alternative source of bioelectricity for the brewery industry.

For the value-added utilization of industrial lignin both from pulping black liquor and acid hydrolysis residues, the eucalyptus alkali lignin (AL) and enzymatic mild acidolysis corncob-to-xylitol residue lignin (EMARL) were isolated. Their pyrolysis behaviors were investigated by thermogravimetric analysis (TGA), in situ Fourier transform infrared spectroscopy (FTIR), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The chemical bonds of EMARL were easier to break than AL at relatively lower temperatures, which was confirmed by the relationship between temperature and the differential absorbance of functional groups (such as carbonyl and hydroxyl). Based on the analysis of pyrolysis products, the value-added monomers were the main products. At 400 °C, AL mainly contained guaiacyl-type and syringyl-type compounds and the yields were 28.95% and 62.54%, respectively, while EMARL contained more guaiacyl-type products (62.96%). When the temperature was increased to 600 °C, the contents of phenol-type increased, suggesting that the demethoxylation reaction occurred during lignin pyrolysis. Study of the characteristics of pyrolysis could be significant for understanding the thermochemical depolymerization of AL and EMARL for value-added products.

Lamination is one of the most widely used techniques for the surface treatment of wood-based composites such as particleboards, fiberboards, etc. It is usually carried out using décor papers impregnated with amino thermosetting resins, mostly melamine-formaldehyde, urea-formaldehyde, or their mixture. Conventional laminates with non-bioactive surfaces are not able to reduce or stop microbial growth when contaminated with organic substances. In this work, zinc oxide (ZnO) nanoparticles were applied into their surface structure to improve their anti-bacterial and anti-mold properties. Melamine-formaldehyde (MF) resin, for the white décor paper impregnation, was modified with ZnO in amounts of 0.1 wt.%, 0.3 wt.%, 0.6 wt.%, and 1 wt.% and pressed onto particleboards. The presence of ZnO in the melamine-laminated surfaces somewhat improved their resistance to the Gram-positive bacteria Staphylococcus aureus (by 20.7% or 9.5%). However, the improvement was considerable (~65% or 46.8%) against the Gram-negative bacteria Escherichia coli. The presence of ZnO in MF resins increased the anti-mold resistance of the intentionally contaminated laminated surfaces against the microscopic fungi Aspergillus niger and Penicillium brevicompactum at most by approximately 50%. ZnO nanoparticles had none or only a small negative effect on the resistance of the laminated surfaces towards aggressive chemicals and dry heat 180 °C, and their abrasion resistance decreased at most by approximately 17%.