Volume 14 Issue 3

A novel porous xylan-based hydrogel was prepared using methacrylated xylan and acrylic acid via free radical polymerization. The structure, morphology, and thermal stability of the hydrogel were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The pH value had an important effect on the swelling and dye-adsorption properties of the hydrogel. When methylene blue was used as a dye model, the dye adsorption of the hydrogel followed the Langmuir isotherm model and pseudo-second order kinetic model. The calculated maximum adsorption capacity reached 4720 mg/g. Besides, the hydrogel retained about 90% of its adsorptive capacity even after 4 cycles of usage. Therefore, the xylan-based hydrogel presented excellent dye adsorption performance and could be a promising superabsorbent for wastewater treatment.

Preliminary research on supercritical ammonia pulping of bamboo was completed using a differential thermal analyzer, scanning electron microscope, X-ray diffractometer, and an energy spectrometer. The results showed that ammonia can be recovered from bamboo raw materials under the supercritical condition of 185 to 190 °C. Compared with conventional kraft bamboo pulp, the separated bamboo pulp met the pulp quality requirements of industrial paper, achieving high efficiency and a multi-level utilization of biomass resources. Ammonia in the system can be recycled.

The development of biobased-plastic through natural filler addition into polymers has been the best method to resolve numerous environmental problems caused by overconsumption and the increasing waste disposal of non-degradable plastic films. This article produced biodegradable polyvinyl alcohol (PVOH) films by adding Mimusops elengi seed shell powder (MESSP) as a filler. The membrane casting method was used to develop the films instead of using the commercially studied solution casting method to avoid inconsistency in the thickness of the casted films. Increasing the MESSP loading enhanced the tensile modulus, resistance towards water absorption, and biodegradability of the PVOH/MESSP films. However, the tensile strength and elongation at break were reduced compared with the unfilled PVOH film. Fourier transform infrared (FTIR) analysis confirmed the reduction of intermolecular bonding between the MESSP and PVOH with increasing the MESSP loading, which is responsible for the reduction in tensile strength, deformability and water absorption of the films. After soil burial exposure, unfilled PVOH films experienced swelling due to water absorption, and there was no evidence of bio-degradation after 9 weeks of exposure. Meanwhile, the PVOH/ MESSP films were prone to microorganism activity and biodegradation can be seen as early as 3 weeks after exposure to soil.

Lignin was separated from wheat straw by NaOH cooking and enzymatic hydrolysis, obtaining yields of 86.2% and 78.6%, respectively. Fourier transform infrared spectrometry (FT-IR) and two-dimensional nuclear magnetic resonance (2D-HSQC) analyses indicated that the H units (p-hydroxyphenyl units) of the Enzymatic Hydrolysis Lignin (EHL) did not suffer much damage. The number-average molecular weight (Mn) of the EHL measured by gel permeation chromatography (GPC) was 3348 g/mol, which was higher than that (3047 g/mol) of Alkali Lignin (AL). The Cr(VI) adsorption experiments demonstrated that the maximum removal percentages and maximum adsorption amount of the EHL and AL were 31.5%, 88.9%, 135.1 mg/g, and 271.7 mg/g, respectively. In addition, the adsorption kinetics, adsorption isotherm and thermodynamics of Cr(VI) on these two lignins were reported in detail.

Typha fibers were chemically retted in 5% sodium hydroxide solution for 1 h, 2 h, 4 h, and 8 h. Changes in chemical compositions of the untreated and treated fibers were monitored with Fourier transmission infrared spectroscopy, while changes in the crystallinity index were studied via X-ray diffraction. The FTIR spectra and scanning electron microscope images corroborated the successful removal of amorphous portions from the Typha leaf fibers during alkali treatment, which resulted in an enhanced crystallinity index for alkali-treated fibers. The alkali-treated Typha fiber for 1 h showed the highest water contact angle of 87.5°, while the untreated composite showed the lowest contact angle. Typha fiber treated for 4 h had high tensile strength, Young’s modulus, and elongation at break of 158 MPa, 1600 MPa, and 7%, respectively. The results showed that there was a general increase in the interfacial shear strength of Typha fiber with epoxy resin and polyester resin with increased time. Both the mechanical properties and crystallinity index of the Typha leaf fibers increased with increased time of retting until 4 h, after which further alkaline retting resulted in decreased values. The overall results showed that alkaline-extracted Typha leaf fibers are suitable for biodegradable film composites.

Gambir is one of the most economically important natural products of Indonesia. Indonesia accounts for 80% of the global exports of this product. The product contains catechin, a phenolic compound of the flavonoid group, which has demonstrated bioactivity against horticulture-destroying fungi. However, its bioactivity in controlling wood-decaying fungi has not yet been reported. A laboratory study was conducted to examine the characteristics of the catechin of gambir and its bioactivity against the wood-decaying fungi Schizophylum commune Fr. Extraction of catechin from gambir was conducted via a gradual maceration process using hot water (70 °C, 3 h) followed by ethyl acetate (1:10 w/v, 4 h). The chemical components of catechin were analyzed by gas chromatography mass spectrometry (GCMS), while its bioactivity against S. commune was examined according to EN 113 (1986). The results showed that there were five chemical components in catechins, i.e., 1,2-benzenediol, catechol, 1,3,5-benzenetriol, dimethyl terephphtalate, and terephthalic acid. These compounds demonstrated the ability to remarkably inhibit the growth of S. commune.

Wood bark is a residue of forestry production that is used as a fuel source. The chemical composition of tree bark is similar to that of the harvested wood, and it contains a variety of useful compounds. To determine the chemical composition and antioxidant activities of different barks, fir (Abies nordmanniana), beech (Fagus orientalis), pine (Pinus sylvestris), poplar (Populus alba), and oak (Quercus robur) barks were selected because they are used for industrial purposes in Turkey. The dried bark powders were extracted using a 65:35 methanol-water mixture (v/v) to determine the total phenolic content, the flavonoid content, and the antioxidant properties (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), metal chelating, and H2O2 scavenging). The flavonoid components were analyzed by high performance liquid chromatography (HPLC) and extracted by hexane to analyze the volatile components by gas chromatography-mass spectrometry (GC-MS). The poplar bark extracts had the highest total phenolic content, highest total flavonoid content, and highest antioxidant content. The poplar bark extracts were rich in myricetin (87.761 mg/L), which is a flavonoid with rich antioxidant properties. The presence of valuable extracts suggests that barks may have uses as valuable raw materials for chemical applications such as cosmetics, perfumes, and food preservatives.

The microbial communities in ethanol-methane coupling fermentation reactors were studied. The community structure variation was monitored at the genus and phylum levels using PowerSoil® DNA Isolation Kit with 16S ribosomal RNA (16S rRNA). The distribution of microbial communities in the ethanol reactor was higher than the methane reactor at the phylum and genus level, indicating the influence of coupling fermentation. Clostridia (hydrogen producer) was the dominant species throughout the process at genus and phylum levels. This result indicates the efficient degradation of organic acids. In addition, Archaea methanogen species (aceticlastic methanogens) utilize both acetate and hydrogen to produce methane. The dominance of Methanosaeta rather than Methanosarsina in the anaerobic digestion reactor (R1) of coupling fermentation added further valuable information on food waste treatment. Moreover, lactic acid bacteria species (Lactococcus) was dominant in the ethanol reactor (R2), suggesting the efficient conversion of food waste to lactic acid, which could continue its conversion to ethanol. Interestingly, the high amount of ammonia, salts, and volatile fatty acids (VFAs) (including high acetate) could promote the SAO pathway in the coupling fermentation system.

The influence of a lignin additive at different loading levels on the surface properties, mechanical, and thermal performance of recycled polypropylene composites reinforced with wheat straw, before and after accelerated weathering, was studied. Eight groups of samples were exposed to an ultraviolet (UV) accelerated weathering tester for a total of 1200 h. The weathered surface morphology, chemical change, and color change were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and chroma meter analyses, respectively. Furthermore, the mechanical properties and oxidation induction time (OIT) were tested. It was shown that the use of lignin had a positive effect in improving mechanical properties and in reducing OIT values of filled composites due to the enhanced fiber/matrix interface bonding and its functions of anti-oxidation. Less fibers were falling off and shallower cracks occurred on the weathered surface of the lignin reinforced composites. The carbonyl index of wheat straw fibers reinforced recycled polypropylene composites (WSF/RPP) with 5 wt% lignin content showed a notable decrease of 4.9% when compared with the growth rate of the control groups. When the stabilizer was introduced to the blends, the mechanical properties and antioxidant capacity of the composites were improved during weathering.

The swelling and dissolution of cellulose are key parameters in the production of regenerated cellulose fibers. Since cotton is almost pure cellulose, it has been proposed that the recycling of cotton textiles may be accomplished through incorporating the cotton textiles into the production of regenerated cellulosic fibers. In this study, the supramolecular structure before and after pretreatment was characterized using solid-state carbon-13 nuclear magnetic resonance (13C NMR), and the findings related to the swelling of dissolving pulp and cotton were quantified with a fiber analyzer. The cotton and dissolving pulp samples were subjected to three different pretreatments: mild acid hydrolysis, acid hydrolysis in ethanol, and a hydrothermal treatment. The results showed that cotton was harder to swell than the dissolving pulp. This indicated that either waste cotton requires another type of activating pretreatment than those included in this study or very good solvents if it is to be included in the production of regenerated fibers.