Research Articles

A turbidimetric method for the determination of total sulfur content in green liquors was developed. The proposed method involves the quantitative conversion of reduced sulfur with hydrogen peroxide to form sulfate at room temperature for 2 min. After barium chloride is added, sulfate instantly reacts with barium chloride to form precipitated barium sulfate that is measured with a UV-Vis spectrophotometer. The interference from carbonate can be eliminated by adding hydrochloric acid. Proper analytical conditions were determined as follows: detection wavelength of 420 nm, the stabilizer of polyvinyl alcohol (PVA), and an analysis time of 10 min. The results showed that the method has an excellent measurement precision (RSD < 1.30%) and accuracy (recovery = 100.1 ± 1.7%) for the quantification of total sulfur content in green liquors. The present method is simple, rapid, and accurate, and can be used for the efficient determination of total sulfur in green liquors.

A model for syngas production from pyrolysis oil gasification was developed, validated, and used in this work to predict the effect of operating conditions on syngas properties. The model consists of a process line that includes units for pyrolysis-oil drying, decomposition, combustion, and gasification processes. The model was validated using experimental data from the literature, showing a good agreement between the results and the reference method. Syngas potential applications were assumed, e.g., for direct use in fuel cells and fuel production. Sensitivity analysis was carried out to evaluate the impacts of gasifying agent, temperature, and the oil moisture content on syngas composition, lower heating value (LHV), and H2:CO molar ratio. For fuel cells applications, gasifying with O2 and air lead to a substantial decrease in syngas LHV. The syngas should be produced at a high temperature. The moisture content in pyrolysis-oil also should be minimized. For fuel production applications, partial O2 can be used to adjust the H2:CO molar ratio. The syngas should be produced at an appropriate temperature around 1000°C. The moisture content in pyrolysis oil should also be selected at 40%.

The quality of milled surface medium-density fibreboards (MDF) and the effect of the wrong milling direction during the process of automatic milling in real conditions in practice (production machine, production tool, and material) are presented in the paper. Moreover, the effect of the double vs. single bladed milling cutter on the final surface quality with the simultaneous changes in individual parameters of feed rate, thickness of the removed layer, and cutting direction was investigated. The MDF was separated using the strategy “one per pass“ with required cutting direction (climb or conventional) and the required thick strips cutting off (4 mm to 16+ mm) at a constant operation speed of the milling cutter (n = 20000 min−1) and a changing feed rate from vf = 1 m/min−1 to vf = 5 m/min−1. The use of a multi-bladed milling cutter resulted in the higher quality of the milled surface in all cases (change in feed rate, thickness of removed layer, and cutting direction). The effect of the wrong milling direction during automatic milling was observed only for a single-bladed milling cutter used. An increase in surface roughness (Ra) occurred; therefore, using the double-bladed milling cutter, which was not associated with an increase in surface roughness, is recommended.

Metal pollution in soil is an increasing concern. Cadmium poses significant risks to ecosystems, and methodologies for its removal, including adsorption, have been researched. There are several environmentally friendly adsorbing materials (such as Biochar) for Cd removal. In this study, to improve the adsorptive capacity of Cd, coconut and peanut shells were used as raw materials to prepare Biochar at 300 °C and 600 °C. The effects of the pyrolysis temperature and material type on the physicochemical properties of the adsorbents were investigated by elemental analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Magnesium-loaded BC was synthesized to determine its Cd2+ absorptivity. The adsorption characteristics and mechanisms of Cd2+ in an aqueous phase were studied through batch adsorption experiments. The results demonstrated that the pseudo-second-order kinetics model accurately described the adsorption kinetics of adsorbents of Cd2+. The adsorption behavior of the Cd2+ adsorbent conforms to the single layer adsorption described by the Langmuir model. Adsorption of Cd2+ involves a spontaneous endothermic process. The initial pH of the solution greatly influenced the adsorption of Cd2+ and showed a trend of rapid growth and then slow growth. Thus, magnesium-modified biomass carbon has good potential for applications in pollutant remediation.

In the construction sector, wood products are gaining interest. Methods are necessary to quantify material use and evaluate their potential effects. When quantifying the building material consumption, many studies are limited to residential buildings due to the lack of data for non-residential buildings. This research aimed at investigating a methodology to account for non-residential building material consumption. A method to estimate the volume of wood products in the structures of the new non-residential buildings was presented. Then, projections of the estimation were suggested according to three scenarios (minimum, average, and maximum). Sensitivity analyses highlighted the parameters that present the greatest contribution to the scenarios. The relative importance of the estimation to the total harvesting of all wood markets was also assessed. Despite the high uncertainty in wood consumption for non-residential building structures, the estimation had a small weight on the total harvesting of the Quebec province. The results showed how and when the resource availability could be constrained depending on the assumptions. This method can serve for life cycle inventory for an environmental assessment or wood flow analysis, but more research on the material composition of the non-residential building archetypes is necessary.

With the widespread use of electronic communication devices, ultra-thin, flexible, and high-performance electromagnetic interference (EMI) shielding materials are widely used to prevent radiation pollution. Moreover, graphene-reinforced polymer-based nanocomposites have received increasing attention in the field of EMI shielding because of their excellent electrical properties. In this work, ultrathin and flexible nickel/reduced graphene oxide/cellulose nanofiber (Ni/RGO/CNFs) composite paper was fabricated using a step-by-step vacuum-assisted filtration method. The prepared composite paper with Ni/RGO to CNF ratio of 3:1 and a thickness of 105 µm attained the electrical conductivity of 1664 S/m and 22.6 dB of excellent electromagnetic shielding effectiveness (SE). In addition, the composite paper (2:1) exhibited great mechanical properties, leading to a high tensile strength of 78.4 MPa, 10.3% fracture strain, and no obvious fractures or cracks when the composite paper was folded. Therefore, the Ni/RGO/CNFs composite paper prepared in this study is an effective lightweight shielding material, especially in flexible electronics and wearable devices.

The soluble lignin present in the pre-hydrolysis liquor (PHL) is detrimental for value-added utilization of the PHL from production of kraft-based dissolving pulp. In this paper, the soluble lignin was separated from PHL by activated carbon adsorption and subsequent desorption with methanol. The structural characteristics of the soluble and dioxane lignins (from bamboo-willow material) were analyzed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). The FTIR and proton-NMR results showed that cleavage of β-O-4 aryl-ether linkages and demethylation occurred in the lignin structure during the pre-hydrolysis. The main linkages between structural monomeric units of the soluble lignin were β-β, β-5, β-1, and β-O-4. Additionally, the TGA results showed that the residual char yield at 800 °C of the soluble and dioxane lignins were 33.4% and 35.3%, respectively. Therefore, the soluble lignin obtained from PHL possessed thermal stability comparable to that of dioxane lignin, and can be used as a renewable source for carbon fiber.

Removing xylan from the outer surface of cellulose could promote the accessibility of cellulase to cellulose. Under this premise, in order to develop an efficient pretreatment method to obtain fermentable reducing sugar from poplar fiber, a response surface methodology was created via the combination of the Plackett-Burman design and the Box-Behnken design and was utilized by the Design-Expert software. The optimum conditions were as follows: a liquid-solid ratio of 4.95 to 1 (mL/g), a pre-hydrolysis xylanase temperature of 70.3 °C, and a total hydrolysis time of cellulase of 52.9 h. Under these conditions, the maximum amount of reducing sugars converted from poplar fiber was 159.6 mg/g. The average amount from the validation results was 160.1 mg/g, which was in agreement with the predicted value. Meanwhile, the poplar fiber hydrolyzed via a xylanase-aided two-stage pretreatment was compared with the poplar fiber hydrolyzed via only a cellulase pretreatment, using scanning electron microscopy. The xylanase-aided treatment revealed a surface with a more damaged structure, indicating that the utilization of xylanase could further improve the effects of hydrolysis on poplar fibers.

The effects of extraction conditions on the yield of polysaccharides from the fruit of Chaenomeles sinensis (FCS) using a hot compressed water method were investigated. The results showed that an appropriately high temperature (150 °C) and a moderate extraction time (45 min) at a material to water ratio of 1 to 10 g/mL led to a high yield of alcohol precipitation polysaccharide (PA). The purified polysaccharides (CSP-1, CSP-2, and CSP-3) were successfully obtained using a DEAE-52 chromatographic column. Chemical analysis showed that CSP-2 and CSP-3 were homogenous and exhibited characteristics of esterified pectins, whereas CSP-2 mainly consisted of galacturonic acid (GalA), galactose (Gal), arabinose (Ara), rhamnose (Rha), and mannose (Man) with an average molecular weight of 59.1 kDa. Furthermore, CSP-1 possessed stronger antioxidant ability according to DPPH scavenging and reducing power compared with CSP-2 and CSP-3. However, it was weaker with respect to OH scavenging. The technical data presented in this study could help the industry make use of polysaccharides from FCS as a source of pectin for a range of pharmaceutical, culinary, and cosmetic products.

The contamination of agricultural soil with heavy metals is a complex phenomenon that causes negative consequences for various organisms. Poplars may have considerable phytoremediation potential, and this plant species can tolerate Cd, Cu, and Pb up to 15.6, 63.6, and 173.3 mg kg-1 soil, respectively, with 100% survival. The analyzed data revealed significant reduction in vegetative growth traits and leaf N, P, K, and carbohydrate (%) and leaf green color degree. However, a simultaneously significant increase in enzymatic activities and electrolyte leakage were recorded in comparison to control plants. A bioconcentration factor of plant organs was ˂ 1, and the translocation factors (TF) of Cd and Cu were ˂ 1 ( ˂100%) under various concentrations of each heavy metal, while TF of Pb was ˃ 1(>100%), except for the first level. More Cd, Cu, and Pb contents were localized in roots compared to leaves or stems. Thus, the risk of contamination through leaf can be minimized. Populus nigra has defense mechanisms against Cd, Cu, and Pb up to 7.8, 29.8, and 91.1 mg/kg soil, respectively because the tolerance index (TI) of either biomass or root was >0.8. Finally, it is a good candidate for research of phytoremediation and phytoextraction.