Volume 9 Issue 4

Anaerobic digestion is considered to be a priority disposal technology for rice straw and sewage sludge. In this study, the synergistic and alkali-treat effect on co-digestion of rice straw and sewage sludge was investigated. The results indicated that the co-digestion of alkali-treated rice straw and sewage sludge had the best biogas yield of 338.9 mL/gVS, which was 1.06 and 1.75 times that of either alkali-treated rice straw or sewage sludge alone, respectively. The actual biogas and methane yields of a co-digestion group with raw rice straw and sewage sludge (G4) increased 26.39% and 24.79% relative to the theoretical calculation based on raw rice straw digestion (group G2) and sewage sludge digestion (group G5), suggesting that a synergistic effect occurred during the co-digestion process. The maximum concentration of volatile fatty acids (VFA) was 4860 mg/L on the 4th day in the sewage sludge group. Xylanase activity reached a maximum of 10.55 U/mL on the 6th day in the alkali-treated rice straw group, while the concentration of protease enzyme was relatively higher in the sewage sludge group than in others. The removal rates of cellulose and hemicellulose in groups with alkali treatment were 32.25% and 36.96% (G1) and 40.86% and 41.61% (G3), higher than that of groups without treatment.

Ground calcium carbonate (GCC) was modified with starch/sodium stearate complexes and used to prepare modified GCC of different size by use of a BSJ-200 oscillating sieving machine. Modified GCC was characterized by scanning electron microscopy (SEM) and particle size analysis. Eight kinds of modified GCC of different size and a kind of modified GCC without screening were used in papermaking and the paper strength properties, especially in tensile, tear, and burst index, were investigated. It was found that the size of modified GCC played an important role in the physical properties of the paper. The best size of modified GCC was within the range 35 to 54 µm.

Torrefaction refers to thermal treatment of biomass at 200 to 300 °C in an inert atmosphere, which may increase the heating value while reducing the oxygen content and improving the storability. In this study, the effects of torrefaction temperatures on the properties of rice husk were analyzed. Torrefaction experiments were performed using a lab-scale device designed to reduce heat and mass transfer transient effects. A new method is described for clarifying torrefaction time and minimizing experimental error. Results from analysis of torrefaction temperatures (200, 230, 260, and 290 °C) support the supposition that the fiber structure is damaged and disrupted, the atomic oxygen ratio is reduced, the atomic carbon ratio and energy density are increased, the equilibrium moisture content is reduced, and the hydrophobic properties of rice husk are enhanced. The data presented in this paper indicate that torrefaction is an effective method of pretreatment for improving rice husk. Torrefaction at 230 to 260 °C for 30 min was found to optimize fuel properties of the torrefied rice husk.

The effects of alkali treatment and polyisocyanate crosslinking on the mechanical properties of kraft fiber-reinforced UPE composites were investigated by means of tensile evaluation, SEM analysis, and XRD analysis. The results indicated that the alkali treatment decreased the tensile strength of the prepared composite before aging from 121 MPa to 97 MPa due to the decreased degree of crystallinity of the alkali-treated kraft fiber. Polyisocyanate crosslinking could apparently improve the mechanical properties and stability in terms of a 43% increase of non-aged tensile strength and 52% increase of hydrothermal-aged tensile strength compared with the controlled composite without crosslinking modification, which was attributable to the formation of strong chemical bonding between the interfaces of kraft fiber and polyester.

To improve the performance of precipitated calcium carbonate (PCC) as a papermaking filler, the combination of cationically derivatized chitosan and carboxymethyl chitosan was employed as modification agents for PCC. When the dosage ratio of cationic chitosan to carboxymethyl chitosan was 1:2, the two polymers were efficiently deposited onto precipitated calcium carbonate, which showed better retention than the control PCC at the same dosage. The brightness and opacity of handsheets filled with modified precipitated calcium carbonate were markedly improved in comparison to the control. Furthermore, handsheets filled with modified precipitated calcium carbonate reduced the loss of tensile strength compared to the control at the same precipitated calcium carbonate content.

Recently, Ailanthus altissima wood has received increased attention in China. Although Ailanthus altissima has a number of advantages, such as fast-growing character and high density, the low dimensional stability is a restraining factor. Chemical modification could be a feasible way to overcome such drawbacks. The aim of this research was to study the physical and chemical properties of Ailanthus altissima veneers treated by urea-formaldehyde pre-polymer impregnation and compression drying. The results showed that this approach not only significantly increased the dimensional stability of wood, but also enhanced the bending strength and compressive strength parallel to the grain. The FT-IR analysis showed that the intensity of hydroxyl (-OH) and carbonyl (C=O) absorption peaks decreased, which indicated that the NH-CH2-OH of the pre-polymer reacted with the wood’s carboxyl and hydroxyl groups. The positions of the XRD peaks did not change, which indicated that the structure of cellulose crystallinity was not noticeably affected by the chemical modification. The TGA showed that the thermal stability of modified wood was improved , while FESEM showed that the wood cell wall and vessels were impregnated with chemicals.

Foam buffer package materials composed of plant fibers have been a focus of research in recent years because of their environmentally beneficial ability to become fully disintegrated. In this study, bleached bagasse pulp was micronized using a PFI mill, and foam buffer materials were prepared using the micronized fiber. The effects of the beating degree of micronized fibers on the dimensional stability, moisture absorption, static compression, and dynamic compression characteristics were discussed. Results showed that, in both the static and the dynamic compression experiments, the buffer properties improved with an increasing beating degree. The buffer materials made of highly micronized fiber were stronger under pressure and impact. Specifically, the highly micronized fiber’s ability to absorb energy curing impact was improved, demonstrating that it can support a higher compression and impacting load in a certain deformation scope. However, during the drying process, the dimensional stability of the samples also declined with an increasing beating degree. The moisture absorption of the samples improved when the beating degree was increased.

Microcrystalline cellulose (MCC) was functionalized with quaternary amine groups for use as an adsorbent to remove Congo Red dye (CR) from aqueous solution. The ultrasonic pretreatment of MCC was investigated during its functionalization. Characterization was conducted using infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The batch adsorption of the functionalized MCC was studied to evaluate the effects of dye concentration, pH of solution, temperature, and NaCl concentration on the adsorption CR. The adsorbent (FM-1) obtained using ultrasonic pretreatment of MCC under 10.8 kJ•g^-1 exhibited an adsorption capacity of 304 mg•g^-1 at initial pH under a dose of 0.1 g•L^-1 and initial concentration of 80 mg•L^-1. After functionalization, the FT-IR and XPS results indicated that the quaternary amine group was successfully grafted onto the cellulose, the surface was transformed to be coarse and porous, and the crystalline structure of the original cellulose was disrupted. FM-1 has been shown to be a promising and efficient adsorbent for the removal of CR from an aqueous solution.

This paper deals with nail withdrawal strength of spruce (Picea abies L.) with a focus on its dependence on thermal modification. Nail withdrawal strength is a feature of wood that is very important in the construction of wooden buildings. There are many studies dealing with the nail withdrawal strength of natural wood; however, this feature is much less explored with respect to thermally modified wood. Spruce wood was thermally modified at three different temperatures (140, 180, and 240 °C), and the nail withdrawal strength was evaluated for three types of nails driven into three anatomical directions. Values of nail withdrawal strength of thermally modified wood were compared with values of control spruce wood. The effect of thermal modification was clear: with increasing temperature, gradually decreasing values ​​of nail withdrawal strength were obtained. The highest values ​​were found in the tangential direction, and the lowest occurred in the axial direction. Annularly threaded nails had the highest values of nail withdrawal strength, while helically threaded nails had the lowest results.

Lime mud (LM), whose main component is calcium carbonate, is a by-product in the pulp and papermaking industry. For non-wood pulping processes, large amounts of LM are produced every year, and a portion of them has been used as a paper filler. However, LM significantly lowers alkyl ketene dimer (AKD) sizing efficiency when added to paper. In this study, LM slurry was first pre-flocculated using some commonly used wet-end additives; then, the pre-flocculated LM was added to the pulp for handsheet preparation. The effect of LM pre-flocculation on AKD sizing efficiency was investigated by means of Cobb60 value, contact angle, and sizing reversion. Finally, the AKD adsorption, particle size, BET surface area, BJH pore volume, and zeta potential of native and pre-flocculated LM were measured. It was found that handsheets filled with pre-flocculated LM had lower Cobb60 values and larger contact angles compared to handsheets filled with native LM. The sizing reversion was also alleviated to a certain extent. This was probably because the BET surface area and BJH pore volume of pre-flocculated LM were lower than native LM and the zeta potential was higher than native LM, which led to a much less adsorption of AKD. Thus, AKD sizing efficiency was significantly improved.