Research Articles

Levulinic acid (LA), a renewable and valuable platform chemical from lignocellulosic biomass, has exhibited major potential in the production of biomaterials and biofuels. This study reports the production of LA from lignocellulose using a recyclable aromatic acid, toluene sulfonic acid (p-TsOH), and its reaction kinetics were investigated. The adoption of p-TsOH, which has a special hydrophobic and hydrophilic structure, dramatically improved the yield of LA to a competitive level (57.9±4.1%) at the optimum conditions (reaction temperature = 162 °C, catalyst concentration = 0.95 mol/L, and reaction time = 64 min). Meanwhile, the kinetics involving the simultaneous conversion of both glucan (the cellulose component) and mannan (the hemicellulose component) to LA were examined. The results indicated that the activation energy values in the reaction kinetics were lower than those in previous studies that used H₂SO₄ as a catalyst. Consequently, the maximum yield of LA was easily obtained at a lower temperature (170 °C). The results of this study are important for process modelling applications and the production of LA from lignocellulosic materials.

This work focused on the addition of different pore formation-controlling agent to a polysulfone/cellulose acetate blend membrane via immersion precipitation using phase inversion technique to improve the fouling resistance and selective polyphenol removal of apple juice. The membranes were prepared by blending hydrophilic polyvinylpyrrolidone (PVP) and amphiphilic Pluronic F127 (Plu) with polysulfone/cellulose acetate matrix in N-methyl-2-pyrrolidone. The morphology, mechanical strength, flux permeation, flux recovery ratio, and polyphenol separation of these membranes were characterized. It was found that the fabricated membranes with addition of PVP and Plu were more effective than the membrane without a pore formation-controlling agent. The flux recovery of the membranes with combined pore formers after ultrafiltration of bovine serum albumin increased from 12.4% to 66.9%. The selectivity of polyphenols increased from 6% to 79% with an improved flux recovery of 79%, which shows the reduction of yellowish-brown pigment in apple juice.

Regression trees, random forests, and generalized additive models (GAM) are statistical techniques often used in several disciplines, but rarely in wood technology. This study presented a novel approach to predicting the modulus of elasticity of Uruguayan pine timber by applying three statistical techniques and using visual parameters and non-destructive testing. For this purpose, two sample groups of beams (50 mm × 150 mm × 2800 mm) were selected from two commercial plantations, one comprised of 122 specimens from 14-year-old loblolly pine (Pinus taeda) and the second comprised of 111 specimens from 27-year-old slash pine (P. elliottii). The visual parameters and dynamic modulus of elasticity for each specimen were obtained and associated with their experimental static bending stiffness. The number of annual rings per centimeter, twist, crook, and knot size were the most relevant visual variables for the modulus of elasticity prediction. The inclusion of the dynamic modulus of elasticity in the modeling improved the stiffness prediction by reducing the prediction error by 46% on average. The GAM had the best prediction, with a 10% prediction error, and explained 88% of the variability. These results suggested that GAM is a useful tool for stiffness prediction of Uruguayan pine timber.

To analyze the influence of the milling parameters, including the spindle speed, feed rate, axial cutting depth, and radial cutting depth, on the milling force during high-speed milling of wood-plastic composites, an orthogonal test was performed with carbide cutting tools. The results showed that the tangential (F_x) and radial forces (F_y) decreased with an increase in the spindle speed, increased with an increase in the feed rate, and increased with an increase in the axial milling depth. Also, both were influenced by a relatively small amount of change in the axial milling depth. Mathematical models of F_x and F_y during the high-speed milling of wood-plastic composites were established with a multiple linear regression method. The variance analysis showed that the two mathematical models of the milling forces were significant overall.

Softness, as a subjective perception, is difficult to define and quantify. For decades, panel tests have been used to judge differences in the softness of hygiene tissue samples. Panel tests can be a time-consuming and expensive process. A number of protocols have been developed to quantify the physical properties of tissues associated with softness. The Tissue Softness Analyzer (TSA) by Emtec has gained popularity in characterizing the physical properties of tissues associated with softness. The instrument was designed with softness in mind and attempts to simulate the touch of the human hand. There is currently no comprehensive study that compares the results from a TSA and human panel. In this work, panel tests were used to validate the performance of the TSA with bath tissue. It was determined that one component of the TSA measurements (TS7) linearly correlated with the panel results. Among all of the algorithms available for use with the TSA, the TP2 algorithm most accurately predicted the panel scores. The TSA performed better in predicting the softness of the samples that were dried with a conventional wet press or creped-through air-dryer.

Polyols, which are important compounds of polyurethane adhesives (PU), were prepared in this work from renewable sources. Beech wood sawdust was liquefied using ethylene carbonate as a new solvent and sulfuric acid as a catalyst in the two phases. The first phase of the liquefaction process was carried out at temperatures 110 to 160 °C, and the catalyst content was studied in the second phase. The biopolyol was used for two types of polyurethane adhesive by blending two types of isocyanate, poly4,4′- diphenyl methane diisocyanate (PMDI) and toluene diisocyanate (TDI), in different NCO/OH ratios for the preparation of polyurethane adhesives. Liquefaction temperature had a great influence on the characteristics of polyol such as acid and hydroxyl numbers and yield. Moreover, the polyol obtained at 130°C and 120 min with yield 85% was found to be a suitable polyol for preparing polyurethane adhesives. By increasing the molar ratio (NCO/OH) to 1.7, the lap shear strength was increased. The optimal lap shear strengths in PU PMDI and PU TDI were 1.64MPa and 1.46MPa, respectively. FTIR results showed that due to the presence of hydroxyl groups (OH), beechwood sawdust can be a source of polyol. Urethane bonds can form between the polyol and isocyanate in polyurethane adhesives.

The direct conversion of hemicellulose in corn stover to xylose while avoiding further degradation in water by using maleic acid as a catalyst was studied. When 0.06 M maleic acid was added, a 96.8 wt.% hemicellulose conversion was achieved, with relatively low conversion of cellulose (24.1 wt.%) and lignin (20.7 wt.%) at 140 °C for 2 h, and a relatively high yield of 22.5 wt.% (95.5 mol%) to xylose was achieved. Maleic acid interacted with the open form of xylose via hydrogen bonding to stabilize xylose, whereas its further degradation pathway was blocked, which led to improved yield and selectivity. The conversion of hemicellulose in bamboo, apple tree, straw, and mulberry to produce xylose (at 140 °C, for 2 h) catalyzed by maleic acid was also effective (Y^a = 17.8 wt.%, Y^b = 127.1 mol% xylose yield for hardwood and Y^a = 25.1 wt.%, Y^b = 109.6 mol% yield for grass) under the same conditions.

Heavy metal removal from aqueous matrices may help reduce disease and cancer incidences. In this study, reed biochar (RBC) and RBC modified by ferrous ammonium sulfate addition (1 mol Fe L-1) were compared for potential Cd and Pb removal from varying pH aqueous solutions. Surface functional groups were identified using Fourier transform infrared (FTIR) analysis, and their surface physicochemical structure was observed using scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). Batch experiments showed that the modified-reed biochar (MRBC) had greater Cd and Pb removal capacities over a wide pH range (1 to 8), as well as greater metal sorption capacities compared to RBC. Metal reaction kinetics occurred relatively quickly (i.e., within 60 min), and Langmuir modeling suggested that Cd and Pb removal by MRBC was maximized at 2.97 mg g−1 and 17.5 mg g−1 at 45 °C, respectively. The MRBC effectively sorbed Cd and Pb likely due to associations with functional groups modified by the Fe addition. In the future, MRBC may be used as an efficient and eco-friendly adsorbent for Cd and Pb removal from aqueous solutions and may help reduce water-borne issues associated with metal contamination.

The essential oil was extracted from the wood of Phoebe bournei (Hemsl.) Yang by a hydrothermal method and then analyzed by gas chromatography-mass spectrometry. The wood oil was comprised mainly of α-copaene (5.44%), α-muurolene (7.32%), δ-cadinene (11.44%), and 1s-calamenene (5.18%). P. bournei wood essential oil exhibited significant antifungal properties against Candida albicans, Trichophyton rubrum, Epidermophyton floccosum, and Microsporum gypseum, and it showed good potential antitumor activity against leukemia cell lines. Although P. bournei (Hemsl.) Yang wood essential oil exhibited weaker activity against the four tested bacteria, it had some effect on promoting glucose uptake by adipocytes.

The brightness of bleached bamboo chemo-mechanical pulp (CMP) is often too low to be used as a furnish in value-added paper products. In this study, preliminary optimization of various parameters of a modified hydrogen peroxide (H2O2) bleaching procedure for bamboo CMP pulps was performed using the inclusion of ethanol in the bleaching medium (IEBM). Compared with a conventional bleaching method, this modified process is aimed at improving bleaching efficiency and brightness ceiling of bamboo CMP with the proper usage of chemicals. The CMP was bleached to a brightness of 74.2% ISO at the usage level of 12% H2O2, which shows it increased by 7.4% ISO compared with the conventional method. For a brightness target of 72.0% ISO, bleaching with the IEBM method reduced the H2O2 consumption by approximately 60%. In addition, a higher activation energy of H2O2 for the IEBM method was calculated to be 23.3 kJ/mol, which was increased by 3.3 kJ/mol compared with the conventional method.