Research Articles

Changes in chemical constituents and some physical properties such as swelling and water absorption of hornbeam (Carpinus betulus L) and uludag fir (Abies bornmulleriana Mattf.) wood were investigated after heat treatment at three different temperatures (170 oC, 190 oC, and 210 oC) for three different durations (4, 8, and 12 hours) by using thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectrometry. The results of TGA show that there was less weight loss in the main degradation region (300-500 oC) for the heat-treated samples as compared to untreated (control) samples. In addition, there was greater weight loss of hornbeam wood than of uludag fir wood in a similar degradation region. This difference could be due to the chemical constituents of softwoods and hardwoods. The results of FTIR spectrometry show that the chemical constituents of the hornbeam wood samples were more affected by heat treatment. All heat-treated samples exhibited lower water absorption and swelling compared to control samples. It was found that the relative decrease in swelling and water absorption for uludag fir was higher than for hornbeam. The maximum decrease in water absorption and swelling was found for both species that were heat-treated at 210 oC for 12 hours.

Kraft lignin, a by-product of the pulp and paper industry, was explored as an adsorbent for six dietary oils and was compared to chitosan, which is widely used in the pharmaceutical market. The dissolution and adsorption efficiency of kraft lignin were tested at an acidic pH corresponding to the stomach, as well as at a basic pH corresponding to the intestine. Results showed that kraft lignin is a powerful adsorbent that can take up dietary oils at up to about 6 times its own weight. Kraft lignin exhibits higher stability and insolubility at the pH of the stomach in comparison to chitosan. The adsorption isotherm of dietary oils fits well with the Freundlich model, and the adsorption kinetics follows a pseudo-second order relationship.

The emergence of novel high-speed inkjet printing technology has been hindered because of claims of poor deinkability of the printed product. Based on our results the decolorization of inkjet inks with the laccase-mediator system is a possible approach to improve the deinkability of inkjet-printed paper. The commercial Myceliophtora thermophila and Trametes versicolor laccases (1 U/mL) and a mediator compound acetosyringone (0.1 mM) decolorized water-soluble textile and inkjet ink dyes by up to 94% and aqueous dye-based inkjet inks by 40 to 98%. M. thermophila laccase decolorized magenta and black inks effectively even at pH 9.0. Acetosyringone was a better mediator compared to ABTS and violuric acid because of its high efficiency and low inherent color. The enzymatic decolorization of inkjet ink was also achieved in deinking experiments with inkjet-printed paper. A treatment with M. thermophila laccase (2 U/g of paper) and acetosyringone (0.02% of paper weight) improved ISO-brightness of the pulp by 5%.

Polymer nanocomposites reinforced with lower volume fractions of nanofiller have recently attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. In this study, composites based on high density polyethylene and rice husk flour with different loading of nanoclay were fabricated in an internal mixer. The influence of nanofiller at four levels (0, 2, 4, and 6 per hundred compounds (phc)) on the thermal and rheological behavior was studied. The morphology of nanoclay was determined by X-ray diffraction (XRD), and the effect of morphology on the thermal and dynamic mechanical properties were considered. Results indicated that the crystallization temperature, crystallization enthalpy, and crystallinity level increased with increase of nanoclay up to 2 phc and then decreased. Also, the dynamic mechanical behavior of composites was improved by the addition of nanofiller. X-ray diffraction patterns (XRD) revealed that the nanocomposites formed were intercalated. Morphological findings showed that samples containing 2 phc of nanoclay had higher order of intercalation and better dispersion. It seems that the thermal and dynamic mechanical properties of the HDPE/rice husk flour composites were improved by increasing addition of coupling agent.

Rice straw (RS) and sawdust (SD) were evaluated for the manufacturing of fiber-cement bricks. The utilization of these bio-wastes will contribute to the reduction of the environmental impact of waste disposal. Pre-treating the fiber wastes, mechanically and/or chemically, was carried out before mixing them with cement and the appropriate amount of water. This approach was done for trials to reduce the tendency of fibers to absorb water, and consequently overcome the side effects of exposing the fiber-bricks to humidity. Different chemical treating agents, based on organic and inorganic materials, were used, e.g., gelatin-hexamine mixture, sodium silicate, and linseed oil. The results obtained show that the investigated organic treatments, especially linseed oil, were effective to reduce the water retention value (WRV) of RS and SD by 60% and 65%, respectively. The treatment provided bricks with compressive strengths of 4.9 MPa and 5.4 MPa, respectively. According to the Engineering Encyclopedia of Building standards, these values are suitable for construction purposes. The bricks manufactured from linseed oil-treated fibers with cement and Nitobond AR may be suited for load-bearing walls, since the compressive strength reached is 7.8 to 8.6 MPa.

Culture conditions of a newly isolated basidiomycetous strain were optimized for the enhanced production of extracellular alkali-thermo-tolerant cellulase-poor xylanase using wheat bran as the sole carbon source under solid state fermentation (SSF). SEM and ITS sequencing confirmed it as Coprinopsis cinerea HK-1 NFCCI-2032. Among various inexpensive agro-residues, wheat bran (carbon source) came up as the most potent enzyme inducer under SSF, and resulted in 54% higher xylanase activity compared to that in submerged fermentation mode. The strain grew well even at 47 ºC. The highest xylanase (695.8 IU/mL) titer was recorded at a substrate:moisture ratio of 1:3 after 7 days of incubation at 37 oC at pH 6.4 along with 0.541 IU/mL of poorly associated cellulase activity. The xylanase exhibited remarkable stability and retained 50% of its activity at pH 8.0 on incubation at 55 ºC for 15 min and 78, 43, and 23% of its activity at temperatures 65, 75 and 85 oC, respectively, demonstrating an approximately 50% alkali-thermo-tolerant nature, which is suitable for biobleaching.

A series of cellulose/soy protein membranes (CSM) was coated with chitosan to improve the mechanical properties, cytocompatibility, and hemocompatibility. The original CSM and chitosan-coated CSM (CH/CSM) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, water contact angle testing, and tensile testing. CH/CSM had a smoother surface microstructure and enhanced mechanical properties as compared to the corresponding CSM. The cytocompatibility and hemocompatibility of CSM and CH/CSM were evaluated by cell culture, MTT assay, in vitro platelet adhesion testing, plasma recalcification time (PRT) measurement, and hemolysis assay. The higher cell adherence and improved cytocompatibility of CH/CSM were mainly ascribed to the coated composition and the altered surface microstructure of CSM. CH/CSM also showed lower platelet adhesion, longer PRT, and a lower hemolysis rate, all resulting from the good hemocompatibility of chitosan and the smoother membrane surface after chitosan coating. Undoubtedly, surface coating with chitosan improved the microstructure, mechanical properties, cytocompatibility, and hemocompatibility, thus widening the possible range of applications for cellulose/soy protein-based biomaterials.

Prehydrolysis was used as the first treatment of bamboo materials for producing high dissolving pulp for textile applications. In this paper, green bamboo (Dendrocalamopsis oldhami)was hydrolyzed in water, and the hydrolysis process was optimized. The morphology and super-molecular structures of the raw material and prehydrolyzed material were studied by SEM and XRD, respectively. Based on the optimum conditions, a study of the kinetics and mechanism showed that pentosan dissolution during the hydrolysis process was a first order reaction. When cooking temperature was 150 oC, 160 oC, 170 oC, and 180 oC, the corresponding reaction rate constants were 0.00411h-1, 0.00495h-1, 0.00730h-1, and 0.00925h-1, respectively. The activation energy was 44.94 kJ/mol based on the Arrhenius empirical equation. SEM results revealed that after the pre-hydrolysis process, the bamboo structure became loose because of hemicellulose dissolution, which created a favorable environment for chemical penetration in the subsequent treatment. Furthermore, the degree of crystallinity was increased from 45.43% to 57.06% during the prehydrolysis. Both the treated and the untreated fibers were assumed to be cellulose I.

An orthogonal designed experiment was used to investigate the effects of sulfite pretreatment on the components separation and saccharification of wheat straw. The process involved sulfite pretreatment of wheat straw under acidic conditions followed by mechanical size reduction using a high consistency refiner. Reaction temperature, retention time, and charges of sodium bisulfite and sulphuric acid were considered as key factors. The results showed the four factors had impact on saccharification of wheat straw. Raising the temperature, increasing the charge of sodium bisulfite or sulphuric acid, or extending the retention time would improve the dissolution of pentosan, lignin, and saccharification efficiency, while causing further conversion of pentose. The separation of lignin and pentosan from wheat straw was the main cause of improvements in saccharification. With an enzyme loading of 5 FPU cellulase plus 4 CBU β-glucosidase per gram of o.d. substrate, a glucose yield 72.45% was achieved using the substrate pretreated under the conditions of temperature 180 oC, sodium bisulfite charge 3%, sulfuric acid charge 1.48%, and retention time 20 min.

The present work deals with the use of multiple-step procedures to obtain valuable sub-products, including nanocellulose, from rice husk. Each sub-product was characterized after every step by analyzing the chemical composition (mainly based on thermogravimetric analysis, Fourier transformed infrared spectra, and X-ray diffraction) and morphology (using visual observations and scanning electron microscopy). The results clearly showed that the selected procedure gave the possibility to separate silica in the first step and then to purify the resultant material, leading to nanocellulose production. All acquired sub-products can be used as additives and fillers in a very wide range of applications. The obtained results will be useful both from technological and academic points of view, mainly for people working in the field of biocomposites. The final material could give added value to a raw biomass material source such as rice husk.