Research Articles

Hydrotropic pretreatment is an environmentally friendly technology that can be applied for lignin isolation from lignocellulosic biomass to enhance enzymatic hydrolysis. In this study, conventional hydrotropic pretreatment was modified with additional alkali and acid to investigate the lignin removal mechanism. Lignin recovered from the hydrotropic solution was analyzed by Heteronuclear Single Quantum Coherence-Nuclear Magnetic Resonance (HSQC-NMR). It was found that the amounts of β-O-4 linkages in the different types of hydrotropic lignin were more than 50%. Alkali-hydrotropic lignin particularly contained 74.9% of β-O-4 linkages. Also, the cleavage of α-O-4 formed more phenolic groups in alkali-hydrotropic lignin. The addition of acid in the hydrotropic treatment could reinforce the broken β-O-4 bond. Modified hydrotropic pretreatments more easily displaced the lignin from the fiber surface and improved the enzymatic accessibility of the pretreated substrates. Considering other impact factors including the fiber structure and total lignin content, enzymatic hydrolysis was heavily influenced and facilitated by the acid-hydrotropic method.

Pot experiments were conducted to study the effects of rice straw (RS), rice straw ash (RSA), and bone charcoal (BC) on the bioavailability of 15 rare earth elements (REEs) in soil and the absorption and accumulation of REES by rice. Adding RSA and BC to REE-contaminated soil remarkably increased the biomass and yield of rice, and the addition of RS remarkably inhibited the growth of rice. Compared with the control check (CK), the total REE concentration in the soil solution at the tillering stage, heading stage, and maturity stage was significantly increased by adding RS, and the total REE concentration in the soil solution was remarkably decreased by adding RSA and BC. The concentration of 15 REEs in the roots, shoots of rice, and brown rice were remarkably decreased via RSA addition. The concentration of total REEs in rice roots, shoots, and grains decreased 79.1%, 76%, and 18.3%, respectively, and the concentration of total REEs in the roots and shoots of rice decreased 19.9% and 67.2%, respectively via RSA addition. However, there was no noticeable effect on the concentration of total REEs in brown rice. So BC and RSA are suitable to be added to REE-contaminated soil, but RS is not.

Due to their biocompatible and eco-friendly properties, natural polymers have attracted significant attention as controlled drug delivery carriers. In this paper, a facile method is presented for preparing pH-sensitive microspheres via acidic esterification between sodium alginate (SA) and hydroxypropyl methylcellulose (HPMC). The resulting microspheres were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). To evaluate the potential applications of microspheres as a drug carrier, the controlled release of a model drug—diclofenac—was examined. The SEM analysis revealed that the microbeads were spherical with a relatively smooth outer surface and porous inner network structure. The drug release experiments indicated that the cumulative release of diclofenac was less than 1% in an acidic medium, whereas it was close to 100% within 3 h in a pH 6.8 phosphate buffer saline solution. These results demonstrated that the SA/HPMC microspheres are promising candidates as pH-sensitive drug delivery system.

The potential of fast-growing poplar species was evaluated for bioethanol production. The yields of glucose and xylose from acid and enzymatic hydrolysis were compared. The hydrolysis processes were performed on raw and extracted wood. The extracted wood was obtained by action of a chloroform and 96% ethanol (93:7 w/w) mixture. Additionally, to enhance the enzymatic hydrolysis efficiency, a liquid hot water (LHW) pretreatment was used. The acid hydrolysis turned out to be a good method to verify the biomass potential for bioethanol production. After acid hydrolysis of raw and extracted biomass, high total sugars yields were obtained (between 626.2 to 808.5 mg/g raw or extracted biomass), while in the case of enzymatic hydrolysis the total sugars yields were very low (between 45.5 to 68.9 mg/g raw or extracted biomass). The LHW pretreatment greatly enhanced the enzymatic digestibility of the studied wood. The average glucose yield from enzymatic hydrolysis was up to 602.0 mg/g pretreated biomass and was higher than that from acid hydrolysis (the maximum yield was 566.9 mg/g extracted biomass). As a result of the LHW pretreatment, up to 91.3% of the hemicelluloses were removed from the solid fraction. From the obtained glucose and xylose results, it was concluded that Populus trichocarpa wood had a higher potential for bioethanol production than P. deltoides x maximowiczii wood. The presence of extractives (low molecular substances) in raw poplar wood (up to 2.8%) had a low impact on the yield from acid and enzymatic hydrolysis.

Water-soluble polyuronic acid was prepared via Acetobacter xylinum in this study. The structural features of the two polyuronic acid samples were characterized by gel permeation chromatography, Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. It was found that when using glucuronic or galacturonic acid as a substrate, with samples incubated at 20 °C to 30 °C in the fermentation medium for 3 weeks to 6 weeks, water-soluble polyuronic acid products could be collected from the colloids that formed on the surface of the medium. The yield of polyuronic acid was approximately 25 wt.%. The weight-average molecular weight of the product was 150,000 to 390,000, and the polydispersity was approximately 1.01 to 1.35. These results indicated that polyuronic acid can be easily prepared by a polymerization method using Acetobacter xylinum. The product polymers possessed high water solubility. The FTIR and ¹H-NMR spectra indicated glycosidic linkages were successfully formed.

The purpose of this study was to determine the best laminated veneer lumber (LVL) in terms of the density, modulus of rupture (MOR), and elasticity (MOE). This study was planned as a laboratory work for non-structural purpose. LVL were formed with five different layer arrangements (APPPPPA, APPAPPA, APAPAPA, AAPPPAA, and AAPAPAA) using 3-mm thick ash (A) (Fraxinus angustifolia Vahl) and Turkish red pine (P) (Pinus burita Ten.) veneers. Accordingly, the LVL materials (12% ± 0.5 moisture level) were made and polyvinyl acetate was preferred for bonding the veneers because it was very easy to apply in laboratory applications. The test specimens were conditioned at a relative humidity of 65% ± 2% and temperature of 20 °C ± 2 °C, until attaining a constant mass, at every stage of wood sheets production and before testing. The density, MOR, and MOE tests were conducted according to the conditions specified in different standards. The results confirmed that, as the amount of the solid ash material increased in the LVL, the material had values closer to those of solid ash sample. Additionally, as a result of the experimental measurement results, the best results in terms of the density, MOR, and MOE were achieved with the AAPAPAA-layered LVL.

Non-woody fiber is a sustainable resource for composite products. In this study, salacca frond was used as a raw material, and the effects of citric acid-maltodextrin composition ratio, pressing temperature, and pressing method were investigated. The boards were manufactured under the conditions as follows: single-step press method, adhesive contents 20 wt%, pressing temperature (180 to 200 °C), and adhesive composition of citric acid/ maltodextrin (100/0; 87.5/12.5; 75/25; 62.5/37.5; 50/50 wt%).   A three-step press cycle method was also applied to reduce the pre-   drying time before hot pressing. The total pressing time was 10 min, and the breathing stage was applied at various times after the starting time. The results showed that salacca frond is a potential material for   composite board. The addition of maltodextrin in certain ratios improved the mechanical properties. The mechanical properties of board prepared using citric acid/maltodextrin satisfied the requirement of the JIS A 5908 type 13 (2003) standard. Infrared analyses indicated that carboxyl        groups of citric acid react with the hydroxyl groups of the maltodextrin and salacca frond. Furthermore, the three-step press cycle method was more effective than the single-step press method. Adding a breathing stage improved the quality of citric acid/maltodextrin bonded composite board.

Electron beam irradiation at certain absorption doses can affect the chain scission and crosslinking of poly(butylene succinate) (PBS) molecules, as well as their thermal properties. In this study, slow release fertilizer composites were produced by compounding neat PBS with NPK fertilizer and oil palm empty fruit bunch using a twin-screw extrusion method. It was found that granular PBS irradiated with up to 50 kGy remarkably improved the bonding and dispersion of the PBS matrix. The subsequent experiment also showed that the biodegradation of slow release fertilizer composites in soil could be improved via electron beam irradiation.

To investigate the potential application of vacuum-pressure methods for dyeing low-quality hardwood veneers produced from young, small-diameter logs, Eucalyptus globulus veneers were dyed with a 2% solution of the reactive dye Procion Brown PX-2R at a vacuum of -100 kPa for 15 min prior to pressure being applied. The effects of various pressures and pressure times on dye uptake, dye penetration, and colour change were evaluated. Veneers with varying moisture content (MC) were used and were labeled as green veneer (80% ± 5% MC) or dried veneer (12% MC). The dyeing method was based on the results of the preliminary experiments. The vacuum-pressure method had remarkable influence on the dye uptake, dye penetration, and colour change, particularly when the samples were dyed at a pressure of 1000 kPa and pressure time of 120 min. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy results indicated that the reactive dye was able to react with the wood compounds, and scanning electron microscopy (SEM) analysis showed that the ray parenchyma cells provided an effective radial path for dye penetration.

Eucalyptus bleached chemical pulp was fibrillated using a PFI pulp beater and ball mill method and was modified by acryloyl chloride. A novel porous cellulose-based hydrogel was prepared from the modified cellulose and acrylic acid for the removal of methylene blue (MB) from aqueous solution. The structure and morphology of the hydrogel were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), respectively. The influence of various parameters, such as pH value, hydrogel dosage, initial MB concentration, and contact time on the dye adsorption, were investigated. The equilibrium experimental data fitted well to the Langmuir isotherm model, and the maximum adsorption capacity of the hydrogel reached 3003 mg/g. In addition, the reusability study suggested that the hydrogel showed great adsorption capacity and a high removal ratio, even after the 5th adsorption-desorption cycle. Thus, the modified cellulose-based hydrogel is a potential superabsorbent for the removal of MB from wastewater.