Volume 13 Issue 2

Biochar, a carbon-rich product, can be obtained from crop residues via pyrolysis. Its properties may vary widely depending upon the pyrolysis conditions and feedstock type. Physicochemical properties were studied for biochars produced from rice straw, wheat straw, corn stover, rape stalk, and cotton stalk pyrolyzed at 300 °C to 700 °C. At higher pyrolysis temperatures, the carbon content, pH, and electrical conductivity of the biochars slightly increased, while the O/C and H/C ratios decreased. The pH values had a strong negative linear correlation with the H/C ratio. Higher carbonization temperatures resulted in larger pores and increased the aromatic/aliphatic carbon ratio in the biochars. The oxygen functional groups in the biochars, such as -COOH and -OH, decreased with an increasing carbonization temperature. The combustion performance of the biochars varied with the carbonization temperature because of the differences in the physicochemical compositions of the biochars. Additionally, the crop residue types also influenced the physicochemical properties. The cotton stalk biochar had the highest fixed carbon content and lowest H/C ratio, and thus can be used as a solid biofuel. The rice straw biochar, which had the highest N and O contents, may be a potential soil amendment.

Rice straw fibers are potential raw materials that can be used to produce biogas and reinforcing fibers for composites. In order to ascertain the effects of anaerobic digestion on the structural properties of the fibers, the structure of fibrous residuals with different digestion time, including 0, 10, 20, and 30 days, were investigated. The normalized biogas production volume was 224 mL/g volatile solid of substrate, of which the methane content was about 50%. Fiber detergent analyses of the straw before and after 10 days digestion indicated that the cellulose levels increased from 34.3% to 41.3%, and cellulose crystallinity index ranged from 44.9% to 49.9%, respectively. After the rice straw had been digested for 30 days, the cellulose and hemicelluloses of the rice straw were partially degraded; the crystallinity index of the cellulose decreased from 44.9% to 40.1% based on XRD analyses, and the amount of hydroxyl groups were observed to decrease based on FT-IR analyses. Consequently, the polarity and hygroscopicity of the rice straw fibers were speculated to be lowered based on these observed changes. Furthermore, the relative amount of lignin in the straw residuals increased as digestion time increased, which increased the thermal stability of the resulting fibers. As a result of anaerobic digestion, the properties of the rice straw fibers for their use in plastic composites were enhanced.

Different agents were used to control the crystalline morphology of calcium carbonate on the surface of fly ash, which was then used as a papermaking filler in an attempt to improve the utilization rate of fly ash and reduce the dust pollution problem. A mixed solution of calcium hydroxide and fly ash was used as the raw materials, and then three crystal form control agents were tested: (NaPO₃)₆, ZnCl₂, and Na₂B₄O₇·10H₂O. A certain amount of carbon dioxide was bubbled into the mixture to form a precipitated calcium carbonate deposit on the surface of fly ash. The calcium carbonate on the fly ash surface was altered by changing the amount of crystal form control agent to determine the best coating effect. The results showed that at the 0.35% ZnCl₂ dosage (relative to the theoretical quantity of the calcium carbonate), the surface of the fly ash was uniformly coated with a layer of spherical calcium carbonate crystals and there was a good coating effect. The highest fly ash brightness obtained was 65.3% ISO, and when this fly ash was used as a paper filler, the paper brightness was 75.6% ISO. More importantly, this study demonstrated the potential of fly ash in papermaking.

Norway spruce is one of the most important wood species in Central Europe. Unfortunately, bark beetles have prominently attacked spruce trees. Bark beetles colonize wood in symbiosis with ophiostomatoid fungi, which is visible in prominent blue staining. This reduces the commercial value of the infested wood. The relevant properties of blue stained wood were therefore determined: bending and compression strength, sorption properties, DVS analysis, water uptake, and durability against wood decay fungi. This information was applied in the Meyer-Veltrup model for assessment of material resistance. Scanning electron microscopy analysis confirmed severe infestation of blue stained wood, which was also evident from the color of the specimens. The mechanical properties were almost unaffected, as were the sorption properties. However, the durability and water exclusion efficacy of blue stained wood were considerably decreased, which indicates that decay can be expected to appear faster on blue stained wood than on control-untreated wood specimens.

Decorative bamboo filament is a new material made with bamboo filament by weaving or adhesive. When it is used in indoor wall and ceiling decorations, the fire resistance of the decorative bamboo filament is very important. Guanylurea phosphate (GUP) flame retardants were used in this study to treat decorative bamboo filament. The microstructures before and after the flame retardant treatment were observed by environmental scanning electron microscopy. The effects on the heat release and smoke release were also evaluated with cone calorimetry. The resistance to mildew was tested before and after the modification. The results showed that the GUP fire retardants had good deposition in parenchyma cells. The treated samples containing 25% GUP effectively reduced the heat and smoke release. The peak value of heat release rate (PK_HRR) and the total heat release (THR) in 115 s was respectively reduced by 44.9% and 42.2%; the peak value of smoke release rate (PK_SPR), the total smoke production (TSP), and the specific extinction area (SEA) of treated decorative bamboo filament was respectively reduced 67.4%, 95%, and 94.4%. The prevention of mildew was slightly enhanced. The prevention rate of Trichoderma viride even reached 100%.

Eucalyptus alkaline peroxide mechanical pulp (APMP) fibers were modified by a low-temperature plasma (LTP) treatment within an air and oxygen mixture. An atomic force microscope (AFM) and electronic spectroscopy chemical analysis (ESCA) were used to analyze the morphological and chemical information of eucalyptus APMP fibers. According to the AFM results, LTP treatment etched the fibers’ surface, allowing for the removal of hydrophobic substances from the surface. According to the ESCA, the oxygen to carbon ratio of the APMP fiber surface increased from 50.08% to 55.47%, and the C1 peak area decreased from 8.89% to 8.45% after a LTP treatment. All of these results indicate that a LTP treatment can modify the APMP fibers and reduce the contents of lignin and extractives, thus exposing more carbohydrate.

Anaerobic biological technology has been widely used in the treatment of high-concentration organic wastewater such as old newspaper (ONP) pulping wastewater and bagasse spray washing wastewater before pulping. However, due to the high calcium content and complex chemical properties of the ONP pulping wastewater, granular sludge calcification occurs during the anaerobic treatment, which has negative effects. In contrast, calcification does not occur in the bagasse spray washing wastewater. Therefore, a comparative analysis of the biological flora and structure of the granular sludge for these two types of wastewater can provide theoretical and data support for revealing the cause of calcification of granular sludge. The results indicate a considerable difference between the anaerobic granular sludge for the treatment of bagasse spraying wastewater (B-GS) and the treatment of ONP pulping wastewater (P-GS). The microorganisms in the B-GS were mainly Bactericides (25.4%), Proteobacteria (20.2%), Hyd24－12 (14.4%), Chloroflexi (10.6%), and Firmicutes (8.9%). The microorganisms in the P-GS were mainly Bacteroidetes (20.4%), Chloroflexi (19.5%), Proteobacteria (19.3%), Firmicutes (6.2%), Spirochaetae (4.8%), Actinobacteria (4.4%), and Lentisphaerae (4.3%). Methanomassiliicoccus were detected only in the P-GS. The methanogens had a higher relative abundance in the P-GS (50%), and only a small fraction (10%) of methanogens was detected in the B-GS.

The bioelectric activity of two lab scale microbial fuel cell (MFC) designs, MFCI (1,500 cm3) and MFCII (12,000 cm3) were examined using old corrugated containerboard (OCC) discharge for simultaneous effective treatment with greater power production. The decrease of MFC internal resistance (MFC-Rin) resulted in increased generated power output. The different parameters used in MFC included electrode conducting area (ECA), cathodic redox solution (CRS), MFC volume capacity, and MFCs connections. The generated current densities (CD) and power densities output (PD) at variables of external resistances (Rex) that ranged from 10 Ω to 20,000 Ω were calculated to estimate the MFC-Rin. In MFCI, using potassium ferri-cyanide as CRS, the change of ECA from 16 cm2 to 64 cm2 decreased the MFCI-Rin from 130 Ω to 110 Ω, and it was further decreased to 65 Ω when manganese dioxide was used as the CRS. Using Rex 100 Ω, MFCII exhibited lower Rin 18.46%, enhanced voltage 37.5%, and greater chemical oxygen demand removal 4.77% compared with MFCI. Series and parallel connections between four MFCI increased the generated PD by 286% and 258%, respectively, compared with that obtained by single MFCI.

Silica/cationic polyacrylamide (SiO2/CPAM) composites with a dendritic structure were prepared via in situ polymerization based on silica containing vinyl groups and acrylamide monomers. The structure and surface properties of the composites were revealed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The adsorption behavior and properties of aqueous Ca(II) on the SiO2/CPAM composites were also investigated. The effect of the pH value, the initial Ca(II) concentration, adsorption time, and temperature on adsorption properties were examined. The results showed that the SiO2/CPAM composites displayed a high adsorption performance for aqueous Ca(II). The maximum adsorption capacity of the SiO2/CPAM composites for Ca(II) was 123.4 mg•g-1 at room temperature and pH 9. The adsorption behavior was in agreement with the Langmuir isotherm model. The adsorption was an endothermic and spontaneous process. Adsorption kinetics fitted well with the pseudo-second-order model. The adsorption of Ca(II) on the SiO2/CPAM composites was mainly attributed to chemical interaction, and chelation was more significant than electrostatic interaction.