Volume 12 Issue 1

This paper reports on the preparation and mechanical properties of hybrid polymer composites involving areca fine fibers (AFFs), sisal fibers (SFs), and roselle fibers (RFs) as reinforcing agents in a phenol formaldehyde (PF) resin-based polymer matrix. For comparative study, an AFF/glass fiber-reinforced PF hybrid composite and AFF/PF composite were also prepared. Hybrid composites were fabricated using a hand lay-up technique, where the weight fraction of fibers was kept at 40 wt% at a ratio of 1:1. Tensile and flexural properties of randomly oriented intimately mixed hybrid polymer composites were evaluated. The results revealed that the mechanical properties of the AFF/PF composite increased by a considerable amount when hybridized with the sisal fibers. Scanning electron microscopy (SEM) was used to analyze the fractured surface of the composite specimens after mechanical testing.

The acid-catalyzed liquefaction of rape straw in methanol using microwave energy was examined. Conversion yield and energy consumption were evaluated to profile the microwave-assisted liquefaction process. Chemical components of the bio-oils from various liquefaction conditions were identified. A higher reaction temperature was found to be beneficial to obtain higher energy consumption efficiency as heated by microwaves. Fourier transform infrared spectroscopy of the bio-oils indicated that hydroxyl groups underwent oxidation with increasing liquefaction temperature and/or prolonged reaction time; methanol esterification of oxidation products was also observed during the liquefaction process. The GC-MS chromatograms indicated that the further decomposition of C5 and C6 sugars resulted in a remarkable reduction of hydroxyl group products and an apparent increase in levulinic ester; furan derivatives and succinic acid derivatives were increased as well. The chemical reactions in liquefaction for the production of bio-oils mainly included decomposition of hemicelluloses, cellulose, and lignin; the oxidation reactions of the hydroxyl groups and methanol esterification were also presented. Comprehensively, a high content of hydroxyl group products was obtained at a moderate liquefaction condition (140 °C/15 min), and a high yield of levulinic ester products was acquired in severe reaction conditions (180 °C/15 min), regardless of energy consumption efficiency.

Cellulose, an abundant natural polysaccharide, can be applied to immobilize particles on the surface due to the presence of ample hydroxyl groups. A series of different sizes and contents of gold nanoparticles (AuNP) were prepared on cellulose nanocrystal (CNC). The obtained AuNP/CNC nanocomposites were then blended with shape-memory polyurethane (SMP) to prepare light-triggered AuNP/CNC/SMP nanocomposites through solvent conversion and a solution casting method. The nanocomposite films were endowed with higher mechanical properties and striking remote-control light-triggered shape-memory properties. Moreover, the CNC in the composites also enhanced the photothermal effect of AuNPs by preventing the aggregation of AuNPs. At the same time, the content of AuNPs with existing CNC had a stronger effect on the elevated temperature (∆T) and the shape-memory properties of films in comparison to the size of the AuNPs.

This study modeled and optimized the operational parameters for biohydrogen production from waste sugarcane leaves and assessed hydrogen production on a semi-pilot scale. A Box-Behnken design with input variables of substrate concentration (8 to 24 g/L), inoculum concentration (10% to 50% v/v), and hydraulic retention time (HRT, 24 to 96 h) was used. A coefficient of determination (R2) of 0.90 and the predicted optimum operational set-points of 14.2 g/L substrate concentration, 32.7% inoculum concentration, and 62.8 h HRT were obtained. Experimental validation produced a biohydrogen yield of 12.8 mL H2/g fermentable sugar (FS). A semi-pilot scale process in a 13-L Infors reactor under optimized conditions gave a cumulative hydrogen volume and yield of 3740 mL and 321 mL H2 g-1 FS, respectively, with a peak hydrogen fraction of 37%. Microbial analysis from the process effluent conducted by Polymerase Chain Reaction cloning indicated the presence of hydrogen-producing bacteria belonging to Clostridium sp., Klebsiella sp., and Enterobacter sp. These findings highlight the feasibility of biohydrogen production from sugarcane waste and provide preliminary knowledge on process scale up.

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.

Agro- and forest-industrial wastes are abundant and low cost sources of carbohydrates and phenolic compounds, which can be converted into biofuels, biomaterials, and high added-value compounds by different pathways in small and large biorefineries. The development of technologies based on hydrothermal treatments could improve the utilization of lignocellulosic wastes through the separation of its components (cellulose, hemicellulose, lignin, and extractives) in sequential processes. The adopted technologies for the separation and conversion of these lignocellulosic wastes into synthesis intermediates or products of high added value represent an important part of the total production cost. Low liquid to solid ratios and mild temperatures in the pre-treatment are interesting ways of reducing energy costs, subsequently economizing both steam and electricity. This work focuses on the advantages of using low liquid to solid ratios in the hydrothermal treatment of different agro- and forest-industrial wastes, paying particular attention to the performance of separation, purification, and conversion of hemicelluloses.