Volume 13 Issue 3

Green and biodegradable cellulose filters with controlled designer pore structures were prepared using organic solvent-based freeze casting. In this paper, the relationship between the different freeze media, including ethanol, isopropanol, and tertiary-butyl alcohol, and the microstructure of the porous filters was investigated. The results of the pore size distribution indicated that the pore channel size decreased remarkably when organic solvents were used as the freezing media. Moreover, the filters showed high filtration efficiencies, up to 99.70% and 99.66% for 0.5 µm and 0.3 µm particles, respectively, under a pressure drop of 180 Pa and at 32 L·min^-1 flow rate. The fabrication of cellulosic filters would not only make it a promising candidate for capturing fine particulate matter, but also provide a versatile approach to regulate and design a porous structure for materials applied in various fields.

Gelatin (GEL) obtained from animals is famous for its biocompatibility and biodegradability. However, its poor mechanical properties limits possible applications as bio-inks to fabricate tissue scaffolds through three-dimensional (3D) printing. In this work, a high strength hydrogel based on cellulose nanofibers and GEL (CNF/GEL) was designed for 3D printing. Scanning electron microscopy and breaking strength results indicated that a CNF filling content of 10% was the best content in the CNF/GEL hydrogels. The rheological properties of the samples with different solid contents were investigated, and the 10%-CNF/GEL-5 hydrogel was proposed for 3D printing. Then, a printing strategy with optimal conditions, including a crosslinking procedure for obtaining a 3D scaffold, was proposed. The biocompatibility of G-10%-CNF/GEL-5 was also investigated using CCK-8 and Hoechst 33342/PI double-staining assays. These results confirmed that the 10%-CNF/GEL-5 composite hydrogel has potential to be used as a 3D bio-ink for application in tissue repair.

A series of bimetal-doped beta zeolites were prepared via a simple post-synthesis strategy including dealumination and metal ion incorporation. The incorporation of ferromagnetic metals into lattice sites of Sn-beta was evidenced by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The high reduction temperature (1094 K) of cobalt in Co-Sn-beta zeolite, as determined by temperature programmed reduction (TPR), confirms that Co interacts strongly with the zeolite support, consistent with lattice tetrahedral (Td) coordination. Co-doped Sn-beta zeolite was found to be a promising Lewis acid catalyst together with a carbon solid acid for the conversion of furfural to isopropyl 4-oxovalerate (i-PL) and γ-valerolactone (GVL). The highest total yield of 92.02% was obtained after reaction for 16 h at 160 °C, including 48.3% i-PL, 37.7% GVL, and 6.0% levulinic acid (LA). The catalysts could also be applied as robust catalysts in glucose conversion to 5-hydromethylfurfural. Zeolite catalysts designed and prepared by this strategy contain multiple metals, enhancing their flexibility and adjustability of function via changing the species and ratio of metals to derive optimized catalysts for specific reactions.

This study demonstrated the strength of a theoretical model founded on the Box-Behnken experimental design method to determine the surface roughness (Ra parameter) of solid Oriental beech (Fagus orientalis Lipsky) wood. The working parameters (sanding belt grit size of 60 to 100, feeding speed of 4 m/min to 10 m/min, and sanding cutting depth of 0.1 mm to 0.3 mm) of a wide belt sanding machine were determined. The Ra of the samples was experimentally described so that the experimental results were also remodeled with the Box-Behnken method to find the optimum parameters for the lowest Ra. An adjusted correlation factor of 93.6% for the Ra confirmed the compatibility between the experimental and theoretical findings. The high correlation (strength) allowed for a more detailed discussion of the effect of the working parameters on the Ra. The theoretical approach showed that the grit size factor had the largest effect on the Ra compared with the other factors. The optimum parameters were found to be a grit size of 100, feed speed of 4 m/min, and sanding depth of 0.1 mm for a minimum Ra for Oriental beech wood. The experimental data supported these parameters.

Wood collapse-shrinkage is a severe defect that occurs in Eucalyptus timber during drying. To solve this problem and provide the technical support for the Eucalyptus application as high value-added wood products, Eucalyptus urophylla × E. grandis samples were pre-treated by ultrasound at 400 W power for 1, 3, or 6 h and then dried in the kiln. The effects of ultrasound pre-treatment on drying rates, residual stress, and total shrinkage after kiln drying were investigated. The results indicated that ultrasound pre-treatment increased drying rates, which was increased by 5%, 13%, and 11% when moisture content (MC) was above 24%MC according to the treating duration, and below 24%MC, which were increased by 25%, 28%, and 23%. Drying rate increased below 24% MC. The residual stress decreased during the later drying stage, especially for the condition of 3 h of ultrasound pre-treatment compared with the untreated samples, while it increased in the early stage of the drying process. The total shrinkage decreased after ultrasound pre-treatment, and it decreased 14.9% after 3 h pre-treatment. Ultrasound pre-treatment broke the pit membranes and modified the microstructures of the wood. The microstructure changes not only affect the drying rate, but also affect the developing of stress and strain, collapse, and its recovery.

Dissolving pulp from Pinus caribaea was oxidized by means of the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxide radical)/NaBr/NaClO system. Effects of the conditions including pH, NaClO dosage, and time on the carboxyl group content, degree of polymerization (DP), and solid recovery of oxidized cellulose were determined. A pH of 10 to 10.5 was found to be optimum for selectively oxidizing cellulose, and carboxyl groups were up to 0.75 mmol/g. However, increasing pH from 9 to 12 facilitated cellulose depolymerization by consistently indicating a gradual drop in DP, thus resulting in cellulose loss. In addition, oxidation was accelerated by the addition of 1 mmol/g to 6 mmol/g NaClO; however, further addition did not enhance the carboxyl groups. The maximum value of carboxyl groups was more dependent on NaClO dosage and governed by the crystal structure of the raw material. To obtain oxidized cellulose with a higher yield and DP, NaClO dosage could be controlled at 4 mmol/g to 6 mmol/g, while the reaction time was limited to 6 h to 8 h.

Activated carbons (AC) serve as adsorbents in various applications requiring specific functionalities. In this study, the effects of biomass type, pre-carbonization process, and activation method on the properties of ACs were investigated. Chemical (KOH and H3PO4) and physical (CO2) activations were performed on slow pyrolyzed and hydrothermally carbonized (HTC) biochars produced from two feedstocks, willow and Scots pine bark (SPB). In addition, the adsorption capacities of the ACs were tested with two dyes and zinc metal. Distinct differences were found between the biochars and ACs regarding pore size distributions, surface area (238 – 3505 m2 g-1), and surface chemistry. KOH activation produced highly microporous ACs from all biochars, whereas with H3PO4 and CO2 there was also increase in the meso- and macroporosity with the HTC biochars. Adsorption capacity for dyes was dependent on the surface area, while for zinc it depended on AC’s pH. The results provide interesting insights into tailoring ACs for specific applications.

Fast-changing market conditions of consumer goods, influenced by customer needs, impact forest enterprises. Thus, management of forest enterprises requires customer-oriented marketing. This paper explores the preliminary issues of customer behavior in the roundwood segment of the selected oligopoly state forest enterprise in Central Europe, Slovakia. This research was carried out by the qualitative approach using standardized interview by means of structured questionnaire. According to research requirements, significant roundwood customers were identified by portfolio analysis of the chosen forest enterprise. Regarding the small rate of significant respondents (customers), non-parametric statistical methods like Spearman’s correlation coefficient and Wilcoxon test were used for the evaluation of customer behavior, or to identify significant correlation among qualitative signs of customer conduct. This paper gives further instructions for the assessment of the results regarding the wood trade manners on the Slovakian market. Additionally, this research presents a special contribution to the achievement of substantial results based on the small rate of respondents, which supports short-term marketing decision-making in trading with wood assortments on the regional trade level in practice.

The use of lightweight concrete in timber-concrete composite structures for the purposes of reconstruction, upgrading, and strengthening has increasing application potential. The correct combination of mechanical properties of both materials can preserve the beneficial aspects of timber in tension and concrete in compression, while reducing the weight of the structure. This paper experimentally evaluated the slip modulus of screw connectors as one of the key issues in the structural design of these types of composite structures. The results of four groups of push-out tests, which were performed on composite samples, are presented. All of the samples had identical cross sections, but each group was made with a different lightweight concrete density class according to Eurocode 2. The obtained results were compared with the values recommended by Eurocode 5. The analysis showed that the code recommendations yielded slip modulus values that were considerably higher than the ones obtained experimentally, which could lead to unsafe timber and lightweight concrete structures.

Basic dyes, which are widely used in industry, can cause serious damage to the environment if they are discharged to waterways. If directly discharged into water, they can cause serious damage to the environment due to their deep color and low degradation rate. The results showed that the average chemical oxygen demand removal rate from the wastewater was greater than 60%, while the methylene blue removal rate was greater than 90%. Anaerobic granular sludge can remove methylene blue and organic matter simultaneously. Candidatus Cloacimonetes was not detected when the methylene blue concentration was 0 mg/L, 2 mg/L, or 4 mg/L. When the methylene blue concentration was 6 mg/L, 8 mg/L,  and 10 mg/L, more Candidatus Cloacimonetes was detected in the sludge as the concentration of methylene blue increased. The Candidatus Cloacimonetes content was found to be 1.02%, 1.08%, and 2.11% in these samples, respectively.