Research Articles

Outdoor bamboo-fiber-reinforced composites (OBFRCs) with four different densities were prepared, and the microstructure and physicomechanical properties of pristine samples were evaluated. In addition, the surface color, glossiness, roughness, water absorption, and wettability of the samples were tested to investigate the effects of panel density on the extent of surface weathering due to ultraviolet radiation. The results showed that the OBFRCs exhibited excellent physical and mechanical properties, which improved with increasing density. However, increases in the density led to decreases in the hygroscopicity and dimensional stability of the OBFRCs. After weathering, the surface contact angle and surface roughness increased, and the dimensional stability improved. The surface glossiness, water absorption, and surface free energy decreased. A higher density resulted in improved color stability, which suggested that density played an important role in determining surface photodegradation properties. Thus, density-increasing treatments had positive effects on the physical and mechanical properties as well as the color stability and wettability of the OBFRCs, but they may negatively affect the roughness and dimensional stability. Based on service-performance and cost-minimization considerations, 1.1 g/cm³ was determined as the most appropriate density for general applications.

Endoglucanase and lipase showed good deinking efficiency for waste papers. The performances could be greatly improved further by the combined use of the two enzymes. To reduce the enzyme production cost and enhance synergistic action of endoglucanase and lipase on laser-printed paper and newspaper, a chimeric enzyme with endoglucanase and lipase activity was constructed and expressed in Pichia pastoris. The data indicated that the chimera Lip-EG1CD improved the ink removal efficiencies and sheet brightness better than a single enzyme or a mixture of two enzymes. The chimera Lip-EG1CD demonstrated an 89% removal of toner on both papers and 91% ISO and 60% ISO sheet brightness for laser-printed paper and newspaper, respectively. Handsheet strength was also clearly improved. It revealed that the combined deinking of endoglucanase and lipase on waste papers could be strengthened by constructing proper chimera due to intramolecular synergistic action. This would be useful for developing an economical process for waste paper recycling.

A combined process consisting of an enzymatic pretreatment of small poplar wood chips, followed by an ultrasonic treatment was proposed and performed. Under the ultrasonic action of cavitation, thermal, and mechanical effects, the two processes of pulping and bleaching can be completed in one procedure. Before the ultrasonic treatment assisted pulping, an enzyme pretreatment was used to destroy the bonds between the cellulose, hemicellulose, and lignin to make the subsequent ultrasonic treatment exhibit higher selectivity and efficiency. This provided a poplar ultrasonic assisted pulp (PUP) with a 75% yield. A further analysis of the pulp, utilizing a scanning electron microscope (SEM), showed the fine fibrillation degree of the fiber surface of PUP was comparable to the traditional poplar chemimechanical pulp (PMP) and poplar chemical pulp (PCP). Thermogravimetric analysis and Raman analysis showed that the final residue obtained from the PUP was 20%. In addition, a decorative base paper was successfully made using the poplar ultrasonic pulp, and the physical properties reached or exceeded the industry standard of decorative base paper.

Effects of different acid hydrolysis conditions were studied relative to the chemical transformations of lignin in eucalyptus, sugarcane bagasse, and sugarcane straw, and on the transformations of multiple polysaccharides in eucalyptus. The acid hydrolysis using 12 mol/L sulfuric acid followed by acid hydrolysis using approximately 0.41 mol/L sulfuric acid was used as the reference for the lignin and sugar analysis. During acid hydrolysis, the relative amount of lignin increased with longer reaction times and/or greater acid concentrations for all biomasses. The overestimation of lignin in harsher acidic conditions resulted from the summation of lignocellulosic-derivatives (pseudo-lignin) together with lignin itself. Lignin reactions (dissolution/deposition) for bagasse and straw occurred in a greater extent than for eucalyptus, considering similar conditions of acid hydrolysis. The sugar transformation during acid hydrolysis was also investigated for eucalyptus. The sugar content quantified in eucalyptus decreased as the acid concentration and/or reaction time in the second hydrolysis increased. Glucose, galactose, and mannose were more resistant to harsher acidic conditions than xylose and arabinose. However, the most severe conditions (121 ºC, 90 min, and 6.15 mol/L H2SO4) caused complete sugar degradation.

Obtaining cellulose from recyclable waste paper contributes to the sustainability of forest resources, water and energy savings, and the reduction of environmental pollution. However, waste paper collected under inappropriate conditions for recycling can be degraded in a short time, thus becoming economically useless. This study examined the factors affecting source-separated collection processes of waste paper in Istanbul hotels, as well as the correlation among these factors. The economic value of the assumed benefits of source-separated waste paper was also calculated. To achieve these objectives, various inputs and methods were used, including the percent tabulation technique and the chi-square independence test. As a result, it was determined that 70% of managers and employees of Istanbul hotels were sensitive to recycling waste paper, but they were not aware of the entire benefits of waste paper recycling. It was also determined that because of waste paper recycling, 18 thousand trees, 5 million kWh of electricity, 3 thousand tons of water, and 1.3 thousand tons of fuel oil were saved, and the generation of 27 thousand tons of CO2 was prevented annually. Hotels in Istanbul provide the economy with an annual average of 752 tons of waste paper, which corresponds to 78% of the foreign trade deficit of Turkey’s paper and paper products sector in the last five years.

Alkaline peroxide mechanical pulp (APMP) is a newly emerging high yield pulp (HYP) with numerous advantages. However, the drawback of the alkaline peroxide mechanical pulp from untreated plant biomass is its poor network strength. In this work, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) modification was proposed to enhance pulp network strength by fiber surface modification that could enhance fiber bonding. Three factors were analyzed by response surface methodology (RSM) to optimize treatment conditions based on factorial designs. The results showed that the optimal conditions were CHPTAC dosage of 0.8% (oven-dry pulp), NaOH dosage of 0.1% (oven-dry pulp), and pulp concentration of 8%. The modified pulp fibers were characterized by elemental analysis, charge density analysis, Fourier transform infrared spectroscopy (FTIR), thermal gravity analysis (TGA), and internal bond strength analysis, as well as zero span tensile analysis. The physical strength of the modified APMP pulp was increased in terms of tensile index, tear index, and burst index. After modification, the tensile index, tear index, and burst index increased by 35.3%, 29.2%, and 16.7% respectively. The internal bonding strength increased by 144.4%; however, the increase of zero span tensile index of modified pulp fibers was insignificant.

Synergic effects of different fire retardant compounds and zinc borate on wood-plastic composites filled with polypropylene (PP) and medium-density fiberboard (MDF) waste fibers were investigated. For this purpose, zinc borate, synergic compounds (antimony trioxide, ammonium phosphate, and magnesium hydroxide), and a coupling agent, i.e., maleic anhydride-grafted polypropylene (MAPP), were used in the production of wood-plastic composites (WPCs). The composite samples were characterized in terms of the burning rate and limiting oxygen index (LOI) analyses, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) along with mechanical tests, i.e., flexural properties, tensile properties, elasticity modulus, and impact strength. It was found that the synergic influence of the combination of zinc borate, antimony trioxide, and magnesium oxide on WPCs increased the heat resistance according to the burning rate, LOI, TGA, and DSC tests. Also, the mechanical properties of the WPCs decreased slightly, but their elasticity modulus increased.

The influence of residual black liquor in pulp on wastewater pollution after the bleaching process was studied. The results show that the CODCr in bleaching effluent has a remarkable linearity with bleaching loss of pulps without residual black liquor. For pulps with some residual black liquor, more than 34% of the overall CODCr is produced by the residual black liquor. It follows that more effective washing to reduce the residual black liquor is an appropriate way to control the pollutant discharges from pulp and paper mill industry.

The effects of the pyrolysis conditions in terms of temperature (400 to 600 °C), residence time (0.5 to 3.5 h), nitrogen flux (0 to 1 L/min), and temperature increase rate (1.5 to 3 °C/min) on the physicochemical properties of biochar were studied. The physicochemical properties evaluated in the biochar were specific surface area, pore volume, average pore size, total carbon content, pH, total acidity, elemental composition, and polycyclic aromatic hydrocarbons (PAHs) content. A higher specific surface area of 108.28 m2/g and a mean pore size diameter of about 2.24 nm were found when the pyrolysis was conducted at 600 °C. In general, the pH and total acidity increased with the increased pyrolysis temperature. The total PAH concentration in all of the combinations studied varied from 0.16 to 8.73 μg/kg, and only phenanthrene, pyrene, and chrysene were detected. The increased temperature seemed to decrease the PAH concentration in the biochar. Nevertheless, there was no correlation found between the PAH content and the combined evaluated parameters.

A laboratory study was undertaken to extract nano-fibrillated cellulose (NFC) from the pseudostem (a waste from the fruit harvest) of two commercial banana cultivars (‘Grand Naine’ and ‘Poovan’) in Tamil Nadu using a novel approach: a one-step method with a bleaching agent and alkali-free acid hydrolysis coupled with ultrasonication. The acid hydrolysis was performed using nitric acid and acetic acid (1:10 ratio). The treatment was effective in the depolymerization and defibrillation of banana pseudostem fiber and in the formation of NFC, which was confirmed by several physico-chemical techniques. The average diameters of the nanofibrils were 6 to 8 nm and 4 to 6 nm for ‘Grand Naine’ and ‘Poovan’, respectively. The XRD analysis revealed an increased cellulose crystallinity of almost 20% in the NFC compared with the respective raw banana fibers. The Fourier transform infrared (FT-IR) spectroscopy and thermal gravimetric analysis (TGA) confirmed the absence of lignin, hemicelluloses, and pectin in the nano-fibrillated samples. The thermal analysis showed the increased thermal stability of the NFC.