Volume 11 Issue 3

To improve the thermal properties of softwood soda lignin, we studied a method of lignin modification using black liquor powder and polyethylene glycol (PEG). In this process, the black liquor powder was directly treated with PEG under alkaline conditions to produce a thermal melting material (alkaline PEG treatment). A model experiment was performed to determine the reaction of the lignin. The lignin in the black liquor powder consisted of 62.16% acid-insoluble lignin (purified lignin) and 37.84% acid-soluble lignin. After alkaline PEG treatment using purified lignin, the samples exhibited weak thermal melting during softening point analysis but did not exhibit appropriate thermal melting during thermal mechanical analysis (TMA). Nuclear magnetic resonance (NMR) data suggest that there was no linkage between lignin and PEG in the alkaline PEG-treated lignin prepared from the purified lignin. On the other hand, when using acid-soluble lignin, NMR data suggest that PEG was introduced to the lignin at its α-carbon position. Acid-soluble lignin PEG derivatives could work as plasticizers to induce the thermal melting of the alkaline PEG-treated lignin prepared from black liquor powder.

A novel cationic lignin-amine emulsifier with high surface activity was prepared from kraft lignin (KL) via the phenolation of KL to obtain phenolated kraft lignin (PKL) and improve reaction sites. The introduction of dehydroabietyl groups as hydrophobic groups and diethylenetriamino groups as hydrophilic groups in PKL, by Mannich reactions, enhanced the performance of the emulsifier. The results showed that the number of the hydroxyphenyl groups in PKL was 0.27/C9 unit when 1 mol lignin was treated with 10 mol phenol at 60 °C for 6 h under 60 wt% sulfuric acid. The numbers of dehydroabietyl groups and diethylenetriamino groups in PKL were 0.18/C9 and 0.13/C9 unit, respectively. The surface tension of the emulsifier was 30.03 mN·m-1 at a concentration of 0.03 M hydrochloric acid aqueous solution with a pH 2.0, which is close to the commercial surfactant cetyltrimethylammonium bromide (CTAB). The zeta potential of the emulsifier was 45.1 mV, and its emulsifiability was 72 min. In contrast, the surface tension of the emulsifier prepared by non-phenolated lignin at the same condition was 38.67 mN·m-1, where the maximum zeta potential was 40.03 mV and its emulsifiability was 53 min. As expected, the performance of the emulsifier was reinforced by the phenolation reaction.

Most plant fibers are good sorbents of oil; however, synthetic sorbents have a much higher sorption capacity (SC) than plant fibers. This study evaluated the effect of fiber treatments, specifically hot-water treatment and mercerization, on the absorption characteristics of selected plant fibers. Five common plant fibers—corn residues, soybean residues, cotton burr and stem (CBS), cattail, and oak—were evaluated for their absorption characteristics in crude oil, motor oil, deionized (DO) water, and a 80:20 mix of DO water. The fiber treatments included ground fiber (control), hot-water treatment at 80 °C for 4 h and 125 °C for 4 h, mercerization at room temp for 48 h, and mercerization at 300 °C for 1 h. The absorption capacity (AC) varied with fiber type, absorption medium, and fiber treatment. Mercerization at 300 °C increased the water absorption of soybean residue up to 8 g/g. Mercerization at room temperature and the hot-water treatment at 125 °C increased the crude oil absorption capacity. After certain treatments, the crude oil absorption capacity of CBS and corn fibers increased over 5 g/g, and the motor oil absorption capacity of cattail, corn, and soybean also increased to 4 to 5 g/g.

The influence of the burning temperature was evaluated for the non-volatile combustible content of wood and bark of plantation-grown trees, at temperature intervals ranging from 500 °C to 1000 °C relative to ash production and the concentration of Ca, Mg, K, Mn, Zn, and Fe in ash, thermal properties, and ash fusibility. Production of ash from combustion of juvenile wood at t = 500 °C was Ad = 0.74% and juvenile bark Ad = 6.88%. Ash production decreased with increasing burning temperature. This was attributed to the chemical diversity of minerals contained in the wood and bark and their slow decomposition. Analyses of the presence of inorganic substances in ash from wood and bark revealed the highest presence of Ca. The concentration of calcium in ash from wood was Ca = 189 ± 46 g.kg-1 and in bark Ca = 278 ± 25g.kg-1. The ratio of processed calcium, potassium, magnesium, zinc, manganese, and iron in ash from wood at a burning temperature of t = 500 °C was Ca:K:Mg:Zn:Mn:Fe = 1:0.58:0.13:0.04:0.03:0.02 and from bark Ca:K:Mg:Zn:Mn:Fe = 1:0.41:0.07:0.01:0.01:0.003, respectively. The influence of the burning temperature non-volatile combustible was reflected in the concentration of each elements in ash and was contradictory. While concentration of Ca, Mg, Mn, and Fe in ash from wood and bark increased, concentration K and Zn in ash decreased. The decrease in concentration K, had a positive influence upon the thermal characteristics of the ash and the creation of ash in the form of loose matter.

Effects of the pretreatment of wheat straw by steam explosion and ethanol were evaluated relative to the structural changes of lignin from the pretreated pulp. The lignin from steam explosion pulp (LS), lignin from steam blasting residual liquid (LL), lignin from ethanol pretreatment pulp (LE), lignin from black liquor (LB), and lignin from wheat straw (LW) were separated, and the structural characteristics of the lignin fractions were compared based on analyses of Fourier transform-infrared, ultraviolet, thermogravimetric, and 1H and 13C nuclear magnetic resonance spectra. The proportions of the three structural units in all lignin fractions clearly changed during the pretreatment process because of inter-conversion reactions. The conjugated structure of lignin was destroyed in the pretreatment process and was also affected by the alkali extraction process. The alcoholic hydroxyl links on the aliphatic side chain were partly transformed into carbonyl groups during ethanol pretreatment. Demethoxylation occurred in all lignin fractions during the ethanol pretreatment and steam explosion process. The thermal stability of the LB fraction was relatively high because of the condensation reaction.

There is a need to understand the effect of wood particle size, as it affects the characteristics of wood-based composites. This study considers the effect of wood particle size relative to the dynamic behavior of wood composites. The compression Split Hopkinson Pressure Bar (SHPB) was introduced to execute dynamic compression testing at the strain rate of 650 s-1, 900 s-1, and 1100 s-1, whereas a conventional universal testing machine (UTM) was used to perform static compression testing at the strain rate of 0.1 s-1, 0.01 s-1, and 0.001 s-1 for four different particle sizes (63 µm, 125 µm, 250 µm, and 500 µm). The results showed that mechanical properties of composites were positively affected by the particle sizes, where the smallest particle size gave the highest values compared to the others. Moreover, the particle size also affected the rate sensitivity and the thermal activation volume of sawdust/HDPE, where smaller particles resulted in lower rate sensitivity. For the post-damage analysis, the applied strain rates influenced deformation behavior differently for all particle sizes of the specimens. In a fractographic analysis under dynamic loading, the composites with large particles experienced severe catastrophic deformation and damages compared to the smaller particles.

Old corrugated container fiber foam material (OCCM) was prepared using a liquid frothing approach. The effect of the content of Al/Si compounds, the molar ratio of Al3+/SiO2, and different addition form on the limited oxygen index (LOI) and residue percentage of OCCM was optimized using an orthogonal design. The fire resistance of OCCM was best when the content of Al/Si compounds was 900 mL, the molar ratio of Al3+/SiO2 was 1:1, and the aluminum sulfate solution was added first, followed by the separately added sodium silicate solution. Under these conditions, the LOI and residue percentage of OCCM reached 32.3 and 53.51%, respectively. Thermogravimetric analysis indicated that Al/Si compounds promoted char formation and reduced the heat release of the optimized OCCMs during depolymerisation. Compared with the control group, the residue percentage of optimized OCCM was increased from 12.49% to 37.98%. Fourier transform infrared spectroscopy identified the functional groups of Al/Si compounds in the optimized OCCMs, confirming that pyrolysis of the optimized OCCMs was affected by Al/Si compounds.

The effectiveness of microwave-assisted sodium hydroxide pretreatments to enhance the saccharification performance of pineapple waste was evaluated. Microwave alkali pretreatments for short exposure times (up to 60 s) significantly improved the yield of the enzymatic hydrolysis compared with non-pretreated waste. The greatest increase of fermentable (35.7%) and total sugars (33.5%) was obtained at 6.375 W/g for 5 s. However, longer exposure times resulted in sugar degradation and released fermentation inhibitors, such as phenols or hydroxymethylfurfural (HMF), as a consequence of thermal degradation. Nevertheless, the obtained phenols values were not sufficient to inhibit subsequent fermentation. Scanning electron microscope (SEM) images confirmed that applying microwaves for short exposure times promoted structural changes that improved enzymatic hydrolysis. By contrast, an increase in the severity of the treatment led to a compacted structure, which hindered access to enzymes and consequently reduced the release of sugars into the medium.

Novel lignin solvents were developed by adding H2O to diethylene glycol (DEG). The solubility of lignin in the DEG/H2O solvents was determined at 25 °C, and the effect of mass ratio of H2O to DEG on lignin solubility was investigated. The DEG/H2O solvents exhibited highly efficient capacity for lignin dissolution, even at room temperature. The possible dissolution mechanism is proposed to be the interaction between the DEG and lignin. In addition, the DEG/H2O solvents hardly disrupt the structure of lignin.

Pulp concentration was increased, during preparation of microfibrillated cellulose (MFC), in an effort to improve the efficiency of cellulase pretreatment. It was hypothesized that increased pulp concentration could possibly increase the interactions between cellulase and cellulose, therefore improving the cellulase pretreatment efficiency and benefiting MFC and its film properties. Results showed that higher pulp concentration enhanced the cellulase adsorption ratio from 70% to 90% for pulp concentrations of 2% and 10%, during the pretreatment process. While pulp concentration was changed from 2% to 10% during cellulase pretreatment, the specific area rose from 30.1 m2/g to 35.5 m2/g. Compared with the original eucalyptus pulp, the crystallinity degree of different pulp concentration was increased, presumably due to the enzymatic breakdown of amorphous cellulose. In addition, the aspect ratio of MFC rose from 19.1 to 35.5. Concurrently, MFC film properties showed better performance, as the elongation at break increased from 0.75% to 1.95%, tensile strength increased from 15.3 MPa to 33.5 MPa, and oxygen permeability coefficient decreased from 111×10-14 cm3·cm/cm2·s·Pa to 89.7×10-14 cm3·cm/cm2·s·Pa, reflecting the oxygen barrier properties of MFC film.