Volume 13 Issue 2

Waste rice straw and iron-containing sludge were converted into catalytic particle electrodes (CPEs). The CPEs were tested for their ability to strengthen electro-Fenton (EF) oxidation of real paper mill wastewater. The prepared CPEs were characterized by different techniques including scanning electron microscopy, X-ray diffraction, BET surface area, and X-ray fluorescence. The CPEs exhibited excellent electro-catalytic activity and appreciably reduced the levels of pollutant parameters during EF process at near neutral pH conditions. Additionally, the treated wastewater was more biodegradable and had lower toxicity, which met Chinese effluent discharge criteria. Optimized treatment conditions used were a current density of 10 mA/cm2, a CPEs dosage of 1.0 g/L, and an aeration rate of 5 L/min. Based on the measurements of H2O2 and hydroxyl radicals (•OH), the enhancement of catalytic activity was attributed to more in situ •OH being produced from the H2O2 which was generated from dissolved oxygen (DO). Moreover, the CPEs showed superior stability, and successive recycle runs were completed with efficient and economical application advantages.

This study investigated how various hemicellulosic fractions extracted from corncob, which have different chemical structures, affect paper strength properties when derivatized and used as paper strengthening agents. Four hemicellulosic fractions with different molecular weights and heteropolymer branching were extracted from corncob via a selective precipitation process; afterwards, the fractions were then chemically modified to obtain cationic hemicelluloses, which were used as strengthening agents for recycled pulp papermaking. These cationic hemicellulosic fractions improved the mechanical strengths of handsheets composed of recycled fibers and paper machine white water fines; however, the level of improvement was different among the fractions. Cationic hemicellulosic fractions showed a better improvement on the strength of handsheets without fines than that of the handsheets with fines. Especially, cationic hemicellulosic fraction obtained from 30% ethanol aqueous medium had the highest molecular weight and the highest substitution degree and thus showed the best enhancement in the mechanical strength of handsheets. Hence, this work demonstrates how to utilize hemicelluloses efficiently as strength agents for recycled pulp papermaking.

As a bamboo processing residue, bamboo green (B) was evaluated as an additive to wood fiber (W) for developing composite panels. According to a Box-Behnken design, urea-formaldehyde resin-glued panels were fabricated from blends of B and W, with three preparation variables: B weight percentage in fibrous material (20%, 40%, and 60%), hot-pressing temperature (160 °C, 180 °C, and 200 °C), and hot-pressing duration (60, 120, and 180 s). The panels were tested for water uptake, thickness expansion, bending strength, and bending modulus. The results showed that the physical-mechanical properties of panels satisfied the strictest requirements of GB/T 11718 (2009). Four quadratic models were established to predict the four properties using the three variables. All models were statistically significant, with coefficients of variation below 5% and coefficients of determination beyond 0.96. An analysis of variance revealed that all variables significantly influenced panel properties. Their effect mechanisms were discussed. A response surface analysis demonstrated that, for different properties, the optimum B percentage, hot-pressing temperature, and hot-pressing duration ranged from 35% to 49%, 173 °C to 198 °C, and 111 s to 134 s, respectively. When all four properties were simultaneously optimized, the optimum preparation conditions were 42%, 179 °C, and 119 s, respectively.

The influence of certain adjustable parameters (sample property, temperature, and solvent type) on the advanced fexIKA extraction outputs was determined. Extracts were obtained from black locust (Robinia pseudoacacia L.) heartwood and analysed by high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). The amount of extract yield remained similar, regardless of the wood particle size, whereas the total amount of phenolic compounds gradually decreased when the particle size increased. The highest amounts of extractives were obtained at higher temperatures, and at 170 and 200 °C, a significant influence from the temperature on the chemical composition was noticed. Namely, the phenol and robinetin yields increased, while the rest of the main phenolic compounds were degraded. Additionally, at higher temperatures (170 and 200 °C), two newly formed furfural compounds were detected.

Fire-resistance and thermal degradation were evaluated for particleboards incorporated with colemanite and common boron-based fire retardants (zinc borate and boric acid:borax mixture). The main purpose of this study was to suggest an alternative fire retardant to be used in particleboards with low cost and considerably lower environmental impact compared to common boron-based fire retardants. For this purpose, the colemanite mineral was chosen as a raw boron mineral because of its good fire performance demonstrated previously in wood-plastic composites. The test compounds were incorporated into the furnish during the particleboard manufacturing process. Fire performance tests and thermal degradation analysis were then performed in the treated particleboard specimens. Mass loss calorimeter tests were applied to determine the oxidative thermal degradation properties of the produced particleboards, whilst thermogravimetric analyses were used to evaluate the non-oxidative thermal behavior of the particleboards. The lowest peak heat release rate and the highest activation energy values were recorded for the boric acid:borax mixture-incorporated particleboards at a loading level of 10%. Overall the results showed that colemanite had a lower fire-retardant property in the particleboards compared to the common boron-based compounds tested in the study.

Red false heartwood is a defect that largely influences the quality of beech wood and is formed by air penetration into mature wood. The air in the mature zone accelerates the process of parenchyma dying and initiates the formation of red false heartwood substances and tyloses. For this study, the selections of suitable logs were made immediately after logging the trees on the same day. The first log was chosen without any type of red false heartwood, and the second log was chosen with healthy red false heartwood. The drying schedule was divided into two phases. After these measurements it was concluded that red false heartwood had a remarkably lower initial moisture content (MC) than the mature wood. The measured difference was almost 20%. The moisture gradient before drying was higher in the red false heartwood samples than in the mature wood samples. The red false heartwood had no effect on the intensity of casehardening. For both groups of samples, the drying quality was good without damaging the dried samples.

Synthetic fibers have characteristics that plant fibers do not have, such as water resistance, chemical resistance, heat resistance, and thermal stability. If mixed with plant fibers and applied to make air filter paper, then the required properties of paper could be obtained. Two kinds of synthetic fiber, polypropylene (PP) and polyester (PET), were mixed with softwood pulp to make air filter base paper. The effects of the mixing ratio, the beating degree of softwood pulp, the variety and addition amount of reinforcing agents, and the process of pressing and drying on the properties of base paper were explored. Samples were found to meet the requirements of the physical properties and porosity of the filter paper base paper at the same time when the mixing ratio of synthetic fiber and plant fiber was 20/80, the beating degree of softwood pulp was 22 °SR, and the added amount of cationic polyacrylamide (CPAM) was 0.06%. The PP fiber fell off easily from the page, but PET fiber did not. The addition of PET fiber increased the porosity, tear index, and folding endurance of the paper. In sum, PET fiber was more suitable for making air filter paper than PP fiber.