Research Articles

Heavy metal contaminated biomass is a severe environmental problem. Presently, the disposal of heavy metal contaminated biomass tends to seek the recovery of both heavy metals and bioenergy. In this study, pyrolysis technology was employed to pyrolyze contaminated biomass to elucidate the influence and fate of the heavy metals and the potential for recovering bioenergy. The results showed that heavy metals in biomass reduced the reaction energy in the main decomposition stage by approximately 10%, while 25% of the biomass decomposed to solid products. Moreover, 63.2% to 68.2% of the Cd and 69.0% to 77.9% of the Cu were retained in the solid, and the metals in the residues existed as metal elements that can be recovered by general smelting. The majority of the biomass (75%) generated volatile products and was only slightly influenced by heavy metals. Compared with the uncontaminated biomass, the component of bioenergy was reduced only slightly, which suggests strong potential for recovering bioenergy. The finding of this paper can be a theoretical foundation to support the responsible disposal, through pyrolysis, of biomass contaminated by heavy metals.

Thermoplastic mengkuang composites are an alternative material to solve environmental pollution issues associated with synthetic polymers. Mengkuang, or Pandanus atrocarpus, raw fiber was cut, dried, ground, and sieved to the required size. The fiber was filled into the matrix of natural rubber (NR) and high-density polyethylene (HDPE) by melt blending via internal mixer. The blend of HDPE/NR at 60/40 ratio with fiber sizes of 125 µm, 250 µm, and 500 µm were prepared at fiber contents of 10%, 20%, and 30%. The effects of fiber size and fiber content on the thermoplastic composite were investigated using tensile test, impact test, water absorption, and field emission scanning electron microscopy (FESEM). The maximum tensile strength and tensile modulus were obtained at 20% fiber content of 250 µm fiber size. Impact strength gradually decreased with the increased percentage of fiber content at fiber size, 125 µm and 250 µm. The highest tensile strain at break and lowest water absorption was observed at 10% fiber content for all sizes being studied. The effects of fiber size on water absorption, and percentage of fiber content on impact strength and tensile strain at break were statistically significant (p < 0.05).

Cationic xylan derivatives were prepared by etherification using 3-chloro-2-hydroxypropyltrimethylammonium chloride as the cationic reagent under an alkaline condition. These derivatives were utilized as strengthening agents to enhance the mechanical strength properties of paper. Cationic xylan derivatives with different degree of substitution (DS) values (0.11 to 0.35) that corresponded to different cationic charge densities (0.51 mmol/g to 0.85 mmol/g) were successfully synthesized, and the reaction parameters were optimized based on the DS and charge density. The cationic xylan derivatives were characterized by means of elemental analysis, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectrometry. The xylan derivatives had a good performance in strengthening the physical properties of the paper, such as the tensile, tear, and burst strengths. When the DS of the cationic xylan derivative was higher, the strengthening effectiveness was better. At a 2.4-wt.% (based on dried pulp) dosage with the xylan derivative that had a DS of 0.32, the tensile, tear, and burst indices of the pulp increased by 63%, 58%, and 42%, respectively. For the pulps with different beating degrees, the cationic xylan derivative was more beneficial to the pulps with a lower beating degree.

Cellulases and β-glucosidases (βGSD) are enzymes commonly used in the biofuel industry. In this study, smaller-sized variants were generated with aminopeptidase such that high catalytic capabilities were retained. Under the defined experimental conditions, the degree of hydrolysis was greater using cellulase substrates, compared to βGSD, based on ortho phthaldialdehyde (OPA) assay data (44% versus 15%). Proteolysis of cellulases was also evident based on sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE) protein banding patterns seen after peptidase treatment. Residual cellulase activity was retained after peptidase hydrolysis (67% to 73%) based on standard filter paper assays. Peptidase treated cellulases and βGSD were then utilized for hydrolysis of alkaline-pretreated switchgrass (Panicum virgatum). Interestingly, the efficiency of the reaction, defined as milligrams of sugar produced per filter paper unit, was higher using truncated cellulases for bioprocessing reactions (~14%), especially in the absence of sodium azide. Conversely, incubation of βGSD with peptidase revealed minimal proteolysis with low impact on the efficiency of hydrolysis.

The potential for using the enzyme pectinase as a pre-treatment to improve the properties of eucalyptus particle-based panels was investigated at different pre-treatment times, temperatures, and particle-to-enzyme ratios. As the pre-treatment time was increased from 10 min to 30 min, the free formaldehyde emission content was reduced (P < 0.0001). The pectinase enzyme pre-treatment reduced the pectin content and increased the permeability of treated wood, allowing more free formaldehyde to be released from the panels. The free formaldehyde emission content of all panels was lower than 3.0 mg per 100 g, due to the kind of urea-formaldehyde (UF) resin used. When the pre-treatment time was 30 min and the temperature was 45 °C, the mechanical properties, including modulus of elasticity (MOE), modulus of rupture (MOR), and internal bonding strength (IB), of the resulting panels were the best among all the selected treatment times and temperatures. As the ratio of particles to solution was reduced from 1:100 to 1:80 or 1:60, the mechanical properties of the particle board panels were improved (P < 0.0001). This was attributed to the pectinase enzyme pretreatment changing the surface of the particles, resulting in a better interface between UF resin and particles.

To reuse biorefinery waste, cellulose ethanol lignin was treated with a laccase system and used as an adhesive for plywood panel preparation. The effects of the amount of laccase, the pH of the reaction system, the reaction temperature, and the reaction time on the bonding strength were studied. The reaction characteristics of the lignin were analyzed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). The results showed that the amount of laccase and the pH value of the reaction system had a significant effect on the bonding strength, and the addition of Tween-80 and polymeric diphenylmethane diisocyanate (PMDI) could improve the wet strength of the cemented system. FT-IR indicated that the lignin had been etherified and NMR analysis showed the partial ether bond in the β-O-4 structure was cleaved so that the lignin fragment was involved in the gluing of the small molecules. Microscopically speaking, the SEM analysis did not observe the activation of lignin adhesives infiltrating the wood substrate, indicating a weak mechanical gluing.

This study aimed to improve the sintering quality of biomass composite powder by using walnut shell and copolyester hot melt adhesive (Co-PES) powders as the main raw materials to prepare the walnut shell/Co-PES composite (WSPC) powder for selective laser sintering (SLS). An orthogonal experimental design of five factors and four levels was adopted to optimize the process parameters for the SLS experiment. Moreover, through range analysis, the influences of laser power, preheating temperature, scanning speed, layer thickness, and scan spacing on the quality of WSPC were also studied. In addition, the synthesis weighted scoring method was used to determine the optimum process parameters. The results showed that the WSPC part quality was optimum when the laser power was 12 W, the scanning speed was 2000 mm/s, layer thickness was 0.15 mm, scan spacing was 0.2 mm, and preheating temperature was 80 °C.

The aim of this work was to demonstrate the production potential of a combination of the two materials cellulose nanofibrils (CNF) and chitin nanowhisker (CNW) using wheat straw and chitin. CNF and CNW were prepared from TEMPO-oxidation and acid hydrolysis prior to high-pressure homogenization. The zeta potential results indicated the differences in the suspended mechanism for the CNF and CNW dispersions. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) revealed that the chemical composition and crystal unit changes during the chemical separation process. Hybrid CNF/CNW films were prepared via casting and evaporation. The films had better mechanical properties, which were ascribed to multivalent physical interactions between CNF and CNW. However, increasing the CNW content up to 50% negatively affected the mechanical properties of the hybrid films. In addition, all films showed high transparency and excellent flexibility. These results indicated that the interaction between CNF and CNW effectively enhanced the mechanical performance of films.

This paper presents the effects of a low velocity impact test on the hybrid composites of kenaf and Kevlar. In recent years, there has been a trend to replace the synthetic fibers, used as reinforcement in epoxy composites formation, with natural fibers due to their low cost, high flexibility, biodegradability, and recyclability. In order to surpass the low mechanical strength of natural fibres in comparison to the conventional composites, hybrid composites combining both types of fibres was introduced. This combination will lead to improvement in the mechanical strength and biodegradability of epoxy composites, which is important for waste reduction and protection of the environment. The materials were fabricated in a seven-layer laminate configuration utilizing a ratio of 3:1:3 (Kevlar:kenaf:Kevlar) for a hybrid composite. This combination earlier had been found to give the best tensile test performance. An original composite with seven layers of kenaf (full kenaf) and one with seven layers of Kevlar (full Kevlar) were also prepared for comparison. The selected specimens underwent a low velocity impact test with variations in energy. The failure mode was observed. The results showed that a seven layer laminate only withstood an impact energy below 30 Joules, and it failed when the impact energy approached 40 Joules. The hybrid composites approached the quality performance of full Kevlar and exhibited better mechanical properties than full kenaf composites. Therefore, the novel hybrid composites can be used for product development in environmentally friendly technologies.

To remove methylene blue (MB) from water, rhamnolipid-modified biochar (BC-RL) was synthesized via a facile method. The surface structures and properties of the biochar (BC) and BC-RL were characterized by scanning electron microscopy, Fourier transform infrared spectra, X-ray diffraction spectra, X-ray photoelectron spectra, N2 adsorption-desorption isotherms, and Raman spectra. The results showed that modification with rhamnolipid remarkably increased the functional groups on the BC-RL, but reduced the surface area. The MB removal efficiency of the BC-RL increased with an increase in the adsorbent loading and temperature. Moreover, the adsorption performance of the BC-RL was obviously higher than that of the BC, which was mainly attributed to the increased number of functional groups. The adsorption kinetic data was fitted well to the pseudo-second-order model with a coefficient of determination greater than 0.999. The coefficients of determination of the adsorption isotherm fitted by different models decreased in the following order: BET > Freundlich > Langmuir. This indicated that the adsorption of MB onto the BC-RL involves a multilayer formation process. These results suggested that the BC-RL could be an environmentally benign and cost-effective adsorbent for the removal of MB from aqueous solutions.