Research Articles

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.

The objective of this study was to investigate the mechanical and physical properties of bamboo-based fiber reinforced composites (BFRC) that were formed by using loose bamboo bundles (LBB) and phenol formaldehyde (PF) adhesive. Three resin content levels (10%, 14%, and 18%) and seven different assembly patterns were selected when the bundles were glued together. Board performance testing showed that the bond quality was improved by increasing the resin content. The board face layers impregnated with 18% resin content and core layers impregnated with 14% resin content had the best mechanical properties, and the boards impregnated with 18% resin content had the best dimensional stability properties. The mechanical and physical properties increased with increasing resin content and were affected by the assembly pattern. Various performance indices of the BFRC met the requirements of the China national standard GB/T 20241 (2006).

The effects of substrate Ca²⁺ concentration were studied relative to the anaerobic digestion and microbial community structure of anaerobic granular sludge. In the treatment of papermaking wastewater by anaerobic granular sludge, the cumulative gas production was maximum at a Ca²⁺ concentration in the substrate of 120 mg/L, whereas it was the lowest at a concentration of Ca²⁺ in the substrate of 4000 mg/L. A high Ca²⁺ concentration in the substrate (≥1200 mg/L) will cause the pH of the fermentation broth to decrease during the fermentation process, which is not conducive to the anaerobic fermentation of the methanogenic process, resulting in unsatisfactory anaerobic digestion of the granular sludge. In addition, when the Ca²⁺ concentration was below 200 mg/L, the abundance of the important bacterial family Ruminococcaceae (rumen bacteria) in the anaerobic fermentation hydrolysis stage was drastically reduced and methane gas production increased. When the Ca²⁺ concentration was above 200 mg/L, the abundance of Anaerolineaceae (Anaerobic Streptomyces), which supplies organic acids, was substantially reduced. The methane gas production decreased as the Ca²⁺ concentration increased. Thus, the results showed that when the concentration of Ca²⁺ was above 200 mg/L, the methanogenic activity of granular sludge decreased.

Carboxymethyl cellulose (CMC) was prepared from Gliricidia sepium and Cola gigantea cellulose with yields of 1.59 g/g and 1.76 g/g, respectively. The pH of the products were weakly acidic (6.47 and 6.54, respectively). The sodium chloride content was 0.22 for C. gigantea CMC and 0.27 for G. sepium CMC, while the degree of substitution was 0.46 and 0.51, respectively. The swelling capacity of G. sepium CMC was 802%, which was higher than the 519% of C gigantea CMC. Fourier transform infrared (FTIR) spectroscopy confirmed that the products were CMC, and a thermogravimetric analysis (TGA) confirmed that C. gigantea CMC was more stable than G. sepium CMC. Detergent fortified with G. sepium CMC had better performance than C. gigantea CMC in terms of cleaning action and emulsion index, and it competed favorably with a detergent fortified with commercial grade CMC.

The laser processing method was applied to wood processing, and the water-jet-guided laser processing was adopted to design a numerical control nanosecond water-jet-guided laser processing test bench, which will provide a new theory and method for laser-processing wood. The numerical control nanosecond water-jet-guided laser processing test bench was built. Pinus sylvestris was used as the test subject. Laser energy, cutting speed, and defocus amount were used as the experimental factors. The aspect ratio was used as a response indicator. A three-factor, three-level Box-Behnken design was studied. A regression model of the three factors and aspect ratio was established. The test results showed that laser energy and cutting speed were the significant effects (p < 0.001) and that defocus amount was the notable effect (p < 0.05). The interaction of laser energy × cutting speed and laser energy × defocus amount had a significant effect on the aspect ratio. The optimal processing parameters were as follows: laser energy of 195.24 mJ, cutting speed of 1.03 mm/s, and defocus amount of -0.69 mm. The authors compared the surface of nanosecond water-jet-guided laser processing with the surface of laser processing. The former had little slag, and the cutting processing was stable. Therefore, nanosecond water-jet-guided laser processing showed better processing quality.