Research Articles

Fruit nursery paper is a protective technical paper that is used in agriculture to improve the percentage of the fruit that meets quality standards and the fruit’s exterior qualities, such as the smooth surface finish and fruit color. In this work, a more efficient and environmentally friendly method, i.e., the printing method, was proposed in order to minimize environmental pollution, reduce the loss of carbon black, and lower the high production cost caused by the traditional method of directly adding carbon black. The effects of printing pressure and inking amount on the properties of the fruit nursery paper were investigated. The durability and safety of the fruit nursery paper produced by the printing method were also studied. The optimal inking amount and printing pressure under laboratory conditions were 1 mL and 350 N, respectively. The amount of ink transferred to the paper surface increased with increasing printing pressure, which led to better opacity but slightly decreased porosity and softness. A more important finding was that the fruit nursery paper produced by the printing method had excellent durability, and the properties can satisfy the requirements of the end use and safety standards of 94/62/EC stipulated by the Europeon Parliament and Councile directive. Based on these low-cost, environmentally friendly characteristics, the development of this new fruit nursery paper could be beneficial.

The research aimed at optimizing the conditions of pretreatment of wheat straw and of enzymatic hydrolysis of the cellulose (ethanol pulp). The ethanol pretreatment process involving acid-catalytic and enzymatic hydrolysis were evaluated for bioconversion of wheat straw to glucose. The influence of the independent process variables on cellulose yields, cellulose contents, lignin contents, and the rate of lignin removed were analyzed over a broad range by the response surface methodology (RSM). The results of the factorial experiment showed that the significant external factors affecting acid-catalytic ethanol pretreatment of wheat straw were ethanol concentration, maximum temperature, acid dosage, and time at maximum temperature. By analyzing the response surface plots, the optimum process parameters for pretreatment were obtained as follows: ethanol concentration 65%, maximum temperature 180 ºC, acid dosage 1.2%, and time at maximum temperature 60 min. Pulps with residual klason lignin ranging from 9.27% to 13.56% (w/w) were prepared from wheat straw using the acid-catalytic ethanol pretreatment process and were evaluated for bioconversion using enzymatic hydrolysis of the cellulose fraction to glucose. The effects of temperature, pH value, time of enzymolysis, and cellulase dosage on the hydrolysis yield of cellulose were separately examined.

The differences in the physical and mechanical properties and chemical composition of Bambusa rigida bamboo before and after accelerated aging tests were comparatively investigated. The results revealed that the aged specimens had lower physical and mechanical properties than the controls. The differences in chemical composition provided evidence that the reduction in physical and mechanical properties was related to the loss of low-molecular weight substances, such as extracts and inorganic matter, and the depolymerization of the carbohydrates cellulose and hemicellulose. Lignin caused the main resistance to the accelerated aging test because the aged specimens had relatively high Klason lignin content. Significant differences (p<0.05) in surface color between the control and aged specimens were observed, and variations in bamboo properties among culm heights were also evaluated in this study. The results showed that basic density and mechanical properties for both the control and aged specimens increased with increasing culm height, while the volume shrinkage showed an inverse trend.

Recently, more and more attention has been centered on developing cheaper, highly efficient, environmentally friendly adsorbents for the removal of metal ions from industrial effluents. The present work deals with the removal of metal ions from an aqueous solution using a highly efficient, biodegradable adsorbent from hydrogel prepared by the free radical graft polymerization of sugarcane bagasse with acrylic acid and acrylamide using N, N-methylene-bis-acrylamide as a crosslinker. FTIR and SEM/EDX spectroscopies were used to characterize the structure and the morphology of adsorbent before and after the metal ions adsorption. The effects of pH, contact time, and initial concentration of metal ion on the adsorption capacity were studied. The adsorption equilibrium time of Pb2+, Cd2+, and Cu2+ were 60, 90, and 180 min, respectively. The maximum adsorption capacities of Cu2+, Pb2+, and Cd2+ were 268, 700, and 320 mg/g, respectively. The adsorption data were fit to often-used models for adsorption kinetics and isotherms. It was determined that the experimental results were well fitted to the pseudo-second-order equation and Langmuir adsorption isotherms.

This study aimed to determine glucose and xylose content by acid hydrolysis of wood samples, both unmodified and thermally modified (modification time was 2, 6, 10 hours), using high performance liquid chromatography. Optimization of the hydrolysis process on the native ash wood samples showed that 3 h was the best time in the hydrolysis process. After that time, 58.8% of glucose and 20.8% of xylose were obtained. In turn, chromatographic analysis showed incomplete hydrolysis of ash wood samples, which were modified in a nitrogen atmosphere, especially at shorter times (2 and 6 h) of modification. With longer modification times (10 h), the hydrolysis of ash wood samples was completed. The above mentioned problem was caused mainly by the increase of cellulose crystallinity degree. The decrease of this parameter was observed only after 10 h of thermal modification, which would facilitate the process of acidic hydrolysis. Additionally, it was observed that the thermal modification of ash wood at 190 °C in a nitrogen atmosphere for 10 h caused a drastic decrease in the xylose content (from 20.8% to 8.0%) and only a slight decrease in the glucose content (from 58.8% to 54.9%).

A variety of nanocomposites were prepared using lignin-cellulose nanofibers (L-CNF) and poly(lactic acid) (PLA) via a solvent casting process. Acid hydrolysis and high-pressure homogenization processes were used to produce L-CNF from unbleached kraft pulps. Tensile tests were conducted on thin films, and the nanocomposites containing 3 wt. % L-CNF showed a 32.4% increase in tensile strength compared to that of neat PLA. Dynamic mechanical analysis showed that the tensile storage modulus increased in the viscoelastic temperature region with increasing L-CNF content in the nanocomposites. Thermogravimetric analysis (TGA) showed that all the materials investigated were thermally stable from 25 to 310 ºC. Differential scanning calorimetry (DSC) showed a decrease in the cold crystallization temperature. A positive effect on the crystallization of PLA polymers in the nanocomposites with added L-CNF was observed using DSC and X-ray diffraction (XRD) analysis. The degradation profiles and swelling ratios of the nanocomposites improved.

Three polyamine fixing agents with increasing molecular weights (m.w.), PA-Lw, PA-Mw, and PA-Hw, were used to treat a deinked pulp at three different levels of chemical dosage. The objective was to elucidate whether the retention mechanism of colloidal substances (CS) onto fibers by a fixing agent is different when the dosage is different. The results show that, for the polyamine with the lowest molecular weight (PA-Lw), it performed in the colloidal fixation mode over a wide range of dosage, but re-dispersion of CS took place in the pulp when its dosage was increased to a level high enough but still beneath the charge reversal point. For the polyamine with the highest m.w. (PA-Hw), CS re-dispersion was not observed over the whole dosage range, but a small part of the colloidal agglomeration coexisted with colloidal fixation even when the dosage was very low. For the polyamine with the middle m.w. (PA-Mw), both CS re-dispersion and colloidal agglomeration were observed. This study showed that if one wants to determine the dosage of a fixing agent during CS control better, both CS removal ratio and CS agglomeration behavior should be considered.

Green liquor (Na2S + Na2CO3, GL) pretreatment is an effective pathway for improving the enzymatic digestibility of lignocellulosic biomass for the production of bioethanol. In this work, GL was employed as a pretreatment to enhance the enzymatic saccharification of poplar. During pretreatment, the increase of H-factor and TTA charge resulted in enhanced delignification and increased degradation of polysaccharides. The sugar yield of enzymatic hydrolysis increased rapidly with increasing TTA charge in GL pretreatment, while the effect of different H-factors (from 400 to 800) on sugar yield was unnoticeable. The pretreated solid recovery was 75.5% at a lignin removal rate of 29.2% under optimized conditions of total titratable alkali (TTA) charge 20%, sulfidity 25%, and H-factor 400. The sugar yield of glucan, xylan, and total sugar of GL-pretreated poplar in enzymatic hydrolysis reached up to 89.9%, 65.5%, and 82.8%, respectively, at a cellulase loading of 40 FPU/g-cellulose.

Stress wave velocity has been traditionally regarded as an indicator of the extent of damage inside wood. This paper aimed to detect internal decay of urban trees through reconstructing tomographic image of the cross section of a tree trunk. A grid model covering the cross section area of a tree trunk was defined with some assumptions. Stress wave data were processed beforehand to obtain the propagation velocity and the coordinate values. An image reconstruction algorithm for detecting internal decay was proposed based on an interpolation method, which estimated the velocity values of unknown grid points by utilizing the values of the surrounding points. To test the effectiveness of this method, Cinnamomum camphora tree samples were selected and tested using a stress wave tool. The area, positions, and extent of decay in the representative samples were displayed in tomographic images constructed by the interpolation method, and the results demonstrate the performance of the method.

SO3H-based acidic ionic liquids were used as Brønsted acid catalysts for synthesis of diphenolic acid (DPA) from the condensation of phenol and levulinic acid, a platform chemical from renewable materials. Evidence is presented that the product with p,p’– and o,p’-isomers was obtained. Under the optimal conditions, the 93.2 mol% yield of DPA and close to 100% selectivity to p,p’-DPA were achieved in a process promoted by [BSMim]HSO4. The favorable results can be attributed to the special structures of ionic liquids and thiol compound involvement. Furthermore, a mechanism of condensation promoted by acidic ionic liquid with ethanethiol is proposed.