Volume 16 Issue 2

Physico-chemical properties and the environmental impacts were studied relative to the leaching of rubber fly ash and bottom ash. The pozzolanic properties of fly ash and bottom ash were confirmed by the chemical composition, including silicon oxides, calcium oxides, and aluminum oxides. The geo-technical characteristics of rubber wood fly ash and bottom ash, i.e., modified compaction, plasticity, and the soaked California Bearing Ratio, were evaluated to assess the feasibility of fly ash or bottom ash mixed with lateritic soil as aggregate materials for the subbase in road construction in order to optimize the replacement of lateritic soil by fly ash or bottom ash. The leachates from rubber fly ash and bottom ash did not exceed standard thresholds. The measured characteristics of fly ash or bottom ash mixed with lateritic soil were in good alignment with the effective engineering thresholds. Recommendations were developed for safe reuse of byproducts from rubber renewable power plant in subbase road construction.

Excessive fertilizer applications in oil palm plantations are conventionally done to increase the oil yield, but they result in high production cost and environmental pollution. There have been only separate reports on the effects of fertilizer application on soil physical, chemical characteristics, and microbial biodiversity. Therefore, this study was conducted to determine the correlation between soil characteristics and soil microbial biodiversity in oil palm plantation after long-term frequent chemical fertilizer application compared with secondary soil, using molecular methods of polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and MiSeq. Secondary forest soil was chosen as the control. The results showed that after 25 years of fertilizer application, the total nitrogen and organic carbon contents decreased from low to very low scale, indicating soil infertility condition. Reduction of Firmicutes was related to suppression of soil borne diseases, and Bacteroidetes which is an indicator of soil health were both almost eliminated after 25 years of fertilizer application. In conclusion, long-term inorganic fertilizer application reduced the soil nitrogen, and organic carbon, altered beneficial microbes in the soil.

Using reed (Phragmites australis (Cav.) Trin. ex Steud) as raw material, straw pulp was prepared by low alkali (less than 6%) pretreatment combined with mechanical grinding. The effects of pretreatment times and alkali dosages on pulp properties and pretreatment solution were investigated. The results demonstrated that alkali pretreatment affected FPI beating efficiency, and the beating energy consumption was lowest when pretreated with alkali dosage of 4%. With 5% NaOH pretreatment, the produced handsheets showed excellent properties that exceeded the requirements of food packaging paper and C-class corrugated paper. Moreover, low silicon content (≤1.12 g/L) in the pretreatment liquor had an almost negligible effect relative to alkali recovery. Therefore, this study is important for researchers and industrial representatives seeking to use reed straw as material for pulping.

To mitigate global warming and the serious problems incurred by the disposal of petroleum-based plastics, it is important to develop derivatives of biomass materials that can be used as substitutes. To overcome the lack of thermoplasticity of wood, a wet extrusion molding process for wood powder using a cellulose derivative, hydroxypropylmethyl cellulose (HPMC), had been developed. However, this material quickly reabsorbed water, swelled, and disintegrated in liquid. In the present study, a natural organic acid, citric acid, was added and kneaded together with the wood powder, the HPMC, and water. The resultant clay-like material was extruded into a tube-shaped material. The tube was air-dried and heated at 180 °C for 5 min to 30 min to allow crosslinking. By heating 1% citric acid for 30 min, the material avoided disintegrating in water for 60 min. The addition of 3% citric acid with 30 min crosslinking gave the material water resistance in water for 12 h. The degradability in the water was found to be controllable by changing the amount of citric acid and the heating time. This is a novel result because wood can be molded into a practical three-dimensional (3D) biomass composite material using this technology with natural substances without relying on petroleum-based plastics.

The paper sludge conditioning effects of waste polyester textile fibers as skeleton builders combined with ferric chloride (FeCl3) were evaluated and the sludge dewatering mechanism was explored. The catalytic effect of Fe-rich sludge biochar (Fe-SB) on enhancing sludge dewaterability was evaluated. Results showed the combined fiber-FeCl3 conditioning significantly promoted the sludge dewaterability compared with conditioner alone, leading to a 77.5% decrease in specific filtration resistance and a 68.9% increase in net yield. The decrease of extracellular polymeric substances (EPS) contents showed that the EPS were difficult to extract and sludge floc strength was enhanced as a result of chemical reactions such as complexation processes and charge neutralization. Hence, the enhancement of sludge dewaterability was primarily due to the sludge cake with a porous and incompressible structure formed by fiber and FeCl3, and the rigidity structure of fiber. Moreover, the Fe-SB prepared by fiber-FeCl3 conditioning sludge could effectively activate persulfate to enhance the sludge dewaterability, with water content of dewatered sludge decreasing by 14.6%. The Fe-SB had dual functions of the heterogeneous catalyst of persulfate and skeleton builder. This study presents a sludge recycling method that combined physicochemical conditioning and sludge biochar materials prepared by pyrolysis.

Wood is a biomass material that is easily eroded by wood-rotting fungi. Coptis chinensis is a natural green plant, which has an inhibitory effect on most microorganisms. Based on the highly toxic effects of the currently used wood chemical preservatives on humans, animals, and the environment, Coptis chinensis was selected to perform decay resistance experiments of wood in this paper. The active ingredients with bacteriostatic properties in Coptis chinensis were separated and screened via chemical treatment, and their structure was identified via nuclear magnetic resonance spectroscopy. The primary bacteriostatic components in Coptis chinensis were berberine hydrochloride, palmatine, and jatrorrhizine. The bacteriostatic zone experiment with a single component and different compounds for white-rot and brown-rot fungus were tested by the disc agar diffusion method. The bacteriostatic effect of berberine hydrochloride in a single active fraction was better. The three-fraction compound had the best bacteriostatic effect and was equivalent to alkaline copper quaternary. The natural active bacteriostatic fractions in Coptis chinensis had noticeable inhibitory effects on white-rot fungus (Trametes versicolor (L.) Lloyd) and brown-rot fungus (Gloeophyllum trabeum (Pers.) Murrill). The minimum bacteriostatic concentration was 0.01 g/mL. The results showed that Coptis extracts had potential as a wood protectant.

Tool wear conditions monitoring is an important mechanical processing system that can improve the processing quality of wood plastic composite furniture and reduce industrial energy consumption. An appropriate signal, feature extraction method, and model establishment method can effectively improve the accuracy of tool wear monitoring. In this work, an effective method based on discrete wavelet transformation (DWT) and genetic algorithm (GA) – back propagation (BP) neural network was proposed to monitor the tool wear conditions. The spindle power signals under different spindle speeds, depths of milling, and tool wear conditions were collected by power sensors connected to the machine tool control box. Based on the feature extraction method, the approximate coefficients of spindle power signal were extracted by DWT. Then, the extracted approximate coefficients, spindle speeds, depths of milling, and tool wear conditions were taken as samples to train the monitoring model. Threshold and weight of BP neural network were optimized by GA, and the accuracy of monitoring model established by the GA – BP neural network can reach 100%. Thus, the proposed monitoring method can accurately monitor tool wear conditions with different milling parameters, which can achieve the purpose of improving the processing quality of wood plastic composite furniture and reducing energy consumption.

Physical properties are one of the ‎drawbacks of oil palm wood ‎‎(OPW) and they need to ‎be ‎improved via an appropriate method. The ‎response surface methodology (RSM) based on central composite ‎design (CCD) was used to evaluate and optimize the parameters of a hydrothermal treatment ‎and to create an ‎empirical model of the mass loss (ML, %), equilibrium moisture ‎content ‎‎(EMC, %), and anti-swelling efficiency (ASE24h, %)‎‏ ‏responses‎. This ‎study focused on the ‎effect of ‎hydrothermal treatment (HTT) ‎in ‎buffer solutions to control the ‎destructive effects of ‎released ‎acids ‎caused by the degradation of ‎hemicellulose acetyl groups‏.‏‎ A CCD, as ‎the most common RSM design, was applied with three treatment factors including the ‎buffer solutions ‎‎(acidic, neutral, ‎and alkaline with pH of 5 to 8), temperature (80 to 140 ‎‎°С), ‎time (40 to ‎‎‎120 ‎min), and a total of 20 ‎experiments‎.‎‏ ‏‎The results ‎showed that the ‎effect of the treatment temperature ‎was more notable ‎than time. The medium acidity (pH) variations in HTT can lead ‎to ‎the removal of ‎extractives and starch, hemicelluloses ‎hydrolysis‎, ‎the ‎destruction of the parenchymal cells wall, and ‎weight loss. Based on the variance analysis, the ‎quadratic and linear models proved to be highly significant with ‎minimal probability values (< 0.0001). The optimum conditions ‎predicted for the HTT were a pH of 7.3, a temperature of ‎112.7 ‎°С, and ‎a‏ ‏time of ‎109.6 ‎min.

The effects of a three-layer structure and age on the mechanical properties of moso bamboo were investigated. The ages of 1-, 3-, and 5-year-old bamboo were chosen to make test samples, and specimens from each age of moso bamboo were divided into three groups (raw bamboo, bamboo removed from outer layer, and bamboo removed from inner layer) for evaluation of modulus of rupture and parallel-to-grain compressive strength. The regression analysis was completed to evaluate the relationship between mechanical properties and bamboo age. The results showed that the age of moso bamboo was positively correlated with the flexural and parallel-to-grain compressive strengths. The mechanical strength of moso bamboo increased with the increased age of moso bamboo. For the moso bamboo with same age, the flexural and parallel-to-grain compressive strengths decreased for the samples without bamboo outer layer. However, for the samples without bamboo inner layer, the parallel-to-grain compressive strength remained unchanged, but the flexural strength increased. The outer layer of bamboo with high toughness and flexibility played an important role during bending. However, the inner layer of bamboo is relatively brittle, which has negative effects on its flexural strength. These results provide an important basis for the bamboo used in engineering.

By structurally and practically analyzing the use of Nd: YAG laser for cutting black walnut veneer, this study considered practical and environmental concerns regarding the global warming protection measures. A numerical model of laser wood veneer cutting was based on the relation between process parameters and the material thickness. A pulsed Nd: YAG was used to cut black walnut veneer of 0.3 mm thickness under different machining conditions regarding laser power and cutting speed to study the cut kerf width. An analysis of variance was conducted to test the significance of machining parameters. The parameters studied were laser power, cutting speed, kerf width, cut surface, safety, and eco-friendliness. The results showed that the kerf width decreased significantly with increased cut speed and, inversely, by laser output power. An efficient cut with a narrow kerf, clean and smooth, with less burn, was possible at laser cutting speeds of 2.5, 5.0, and 5.5 mm/s with kerf widths of 0.544, 0.69, 0.62 mm, respectively. As multiple factors affect the micro-thin wood laser cutting process, finding the optimal process parameters is crucial for successful machining with no burn effect.