Research Articles

To obtain a functional composite paper with antibacterial activity, 2-hydroxypropyl trimethylammonium chloride chitosan (HACC) was prepared and sprayed onto the surface of paper made of bamboo fiber. HACC was synthesized from chitosan with 2,3-epoxypropyl trimethylammonium chloride (GTAMC), and the optimal preparation conditions were selected by single-factor tests. The highest degree of substitution (DS) of HACC reached 0.868, when the ratio of chitosan to GTAMC was 1:4, and the water solubility was noticeably improved. The structural characterization demonstrated the successful modification on the original chitosan with a decrease in heat stability and the peak correlated with hydroxypropyl trimethylammonium chloride groups in FTIR. The addition of HACC in the bamboo fiber paper greatly increased the antibacterial activity, and water absorption was higher as well. These results may serve as a basis for the modification and the preparation of chitosan antibacterial agents.

Nanocellulose (NC) is an attractive reinforcement agent that can be incorporated into protective coatings because it is a renewable, biodegradable, and biocompatible polymer resource. In this study, a series of epoxy resin-based nanocomposites were prepared in the form of coatings with various amounts of NC loadings, and the coatings were applied onto mild steel at room temperature. The characterizations of the NC and nanocomposites were performed via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR). The thermophysical properties of the nanocomposites were evaluated using differential scanning calorimetry (DSC) and thermogravimetry (TGA) analyses. The transparency of the nanocomposite specimens was examined by ultraviolet visible (UV-Vis) spectroscopy in the range of 300 to 800 nm. The corrosion protection properties of the coated mild steel substrates immersed in a 3.5% NaCl solution were studied comparatively by electrochemical impedance spectroscopy (EIS). The results showed that all of the nanocomposite coatings with NC noticeably influenced the epoxy-diamine liquid pre-polymer, both physically and chemically. Furthermore, the 1 wt.% NC nanocomposite coating system was found to have the most pronounced anti-corrosion properties, as confirmed by a 30-day EIS study.

The objective of this study was to understand the effect of different concentrations of xylose and glucose on butyric acid production by Clostridium tyrobutyricum. C. tyrobutyricum was cultured in a medium containing xylose, glucose, or mixtures of xylose and glucose as the main carbon source. The butyric acid concentration increased from 3.5 to 16.3 g/L in the xylose media, and from 2.6 to 27.0 g/L in the glucose media when the initial sugar concentration increased from 5 to 75 g/L. The yield from xylose to butyric acid started to decrease as the sugar concentration was above 35 g/L, while for glucose media higher glucose concentration resulted in higher yield. At low sugar concentrations (5 g/L or 15 g/L), xylose was more efficient than glucose for butyric acid generation, but at high concentrations (55 or 75 g/L), glucose was more efficient. In mixtures containing both sugars, glucose was the preferred sugar for bacteria growth and xylose was rapidly consumed only after the glucose was exhausted. The xylose to glucose ratio affected bacterial growth and butyric acid production. High xylose to glucose ratios (4:1 or 3:2) showed better butyric acid production than low ratios (1:1, 2:3, or 1:4) when the total initial sugar content in the media was kept at 30 g/L.

Inadequate rheological properties of gelatin methacrylamide (GelMA) were successfully improved by incorporating cellulose nanofibers (CNFs), such that the printed scaffolds could maintain their structural fidelity during the three-dimensional (3D) bio-printing process. The CNFs provided an outstanding shear thinning property, and the GelMA/CNF inks exhibited high zero shear viscosity and structural fidelity under a low dispensing pressure. After evaluating the printability, composite inks containing 2% w/v CNF were observed to have an optimal concentration of CNF to prepare 3D print stable constructs. Therefore, these inks were used to manufacture human nose and ear structures, producing highly porous structures in the printed composite hydrogels. Furthermore, the mechanical stability of the GelMA/CNF composite hydrogel was increased when CNFs were incorporated, which indicated that CNFs played an important role in enhancing the structural properties of the composite hydrogels. Additionally, the biocompatibility of CNF-reinforced hydrogels was evaluated using a fibroblast cell line.

Orange peel (OP) was subjected to thermal hydrolysis at temperature (T) and pressure (P) values lower than 180 °C and 1000 kPa, respectively, to minimize the energy consumption and obtain a good ethanol yield. The process was conducted in an autoclave, a pressurized reactor for studying the effect of T (120 to 180 °C), P (500 to 1000 kPa), gas type (N2 or CO2), and OP loading (2.5 x10-2 and 5 x10-2 gmL-1) on the reducing sugars yield. The results were compared with those from acid hydrolysis. Hydrolysates were fermented using immobilized yeast on alginate beads, and the highest ethanol yield of 33.14 g/L was obtained from OP treated at 120 °C. Under these conditions, a minimum of 1,407 kWh energy consumption was achieved.

The wood drying rate was determined at five different relative humidities (RHs) using time domain nuclear magnetic resonance (TD-NMR). The objective of this study was to obtain the drying rate of bound water and free water, and to also build a relation between RH and drying rate. Two kinds of wood species, Qingpi poplar (Populus platyphylla var. glauca) and Pinus sylvestris var. mongolica Litv. were employed for the spin-spin relaxation time (T2) measurement. The mass of free water and bound water during drying were obtained at the same time. The results indicated that the poplar specimens had a higher fiber saturation point (FSP). For both wood species, free water decreases quickly, which contributes to the main drying, especially at the beginning of drying, and still exists even when the moisture content (MC) is below the FSP. Bound water decreases slowly, and its equilibrium content ranges from less than 10% to more than 20%, in the order from lower RH to higher RH. In addition, the drying rate decreases linearly with increasing RH.

The use of activated carbon (AC) from lignocellulosic wastes has gained a lot of research interest because of its great economic and environmental value. In this work, AC was prepared from mahogany fruit husk (MFH) via chemical activation with phosphoric acid and heat treatment. The relationships among the activation parameters H3PO4%, heating temperature, and holding time, and their effect on chromium (VI) removal, were investigated using the response surface method (RSM), following a central composite design (CCD). The optimized activation conditions resulted in a 92.3% Cr6+ removal efficiency for a 50 mg/L Cr6+ aqueous solution. The surface properties of the optimized MFHAC were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and nitrogen adsorption/desorption studies. The MFHAC prepared under the optimized conditions had a high surface area (SBET) of 1130 m2/g, with a well-developed porous structure. The equilibrium data of Cr6+ adsorption onto the MFHAC was best fit by the Langmuir isotherm model, while the adsorption kinetic data followed the pseudo-second order kinetic model. Hence, MFHAC proved to be an efficient technology for removing Cr6+ from simulated wastewater.

Changes of lignin’s structure were investigated resulting from an ionic liquid ([Bmim]Cl,1-butyl-3-methylimidazolium chloride salt) pretreatment. The purified lignin was pretreated by [Bmim]Cl under the following conditions: the ionic liquid to lignin mass ratio was 10:1, the temperature was 85 °C, and the processing time was 2 h and 4 h. The chemical structure of lignin was studied via Ultraviolet (UV) spectra, Fourier Transform infrared (FT-IR) spectra, Nuclear Magnetic Resonance Spectroscopy (13C-NMR), Gel Permeation Chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and Thermogravimetric Analysis (TG). The total content of phenolic hydroxyl increased with increased time. Moreover, the contents of [OHI] and [OHII] (types of phenolic hydroxyl groups) groups were disproportionately increased. The main structure of lignin still was present after the [Bmim]Cl pretreatment. The β-O-4 linkages were broken apart. The degree of lignin degeneration increased with increased time, after being pre-treated with [Bmim]Cl. Simultaneously, a condensation reaction also took place during the pretreatment. Understanding the chemical changes to wheat straw lignin during an ionic liquid pretreatment provides an important theoretical basis for its further industrial use.