Volume 6 Issue 2

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.

Flammability properties of plasma pretreated cotton fabrics subjected to flame-retardant treatment were studied. Plasma pretreatment, using an atmospheric pressure plasma jet (APPJ), was applied to cotton fabrics to enhance material properties, while retaining inherent advantages of the substrates. An organic phosphorus compound (flame-retardant agent, FR) together with a melamine resin (crosslinking agent, CL) and phosphoric acid (catalyst, PA) were used. Titanium dioxide (TiO2) or nano-TiO2 was used as a co-catalyst for cotton fabrics to improve treatment effectiveness and minimize side effects. Surface morphology of plasma pretreated cotton specimens subjected to flame-retardant treatment showed a roughened and wrinkled fabric surface with high deposition of the finishing agent, caused by an etching effect of plasma and attack of acidic FR. Combustibility of FR-CL-PA-TiO2 and FR-CL-PA-Nano-TiO2 treated fabrics was evaluated by a 45° flammability test. FR-CL-PA-treated specimens showed superior flame-retardancy, which was further improved by plasma pretreatment and addition of metal oxide as a co-catalyst. However, in comparison with the control sample, flame-retardant-treated cotton specimens had lower breaking load and tearing strength, resulting from side effects of the crosslinking agent used, while plasma pretreatment might compensate for the reduction in tensile strength caused by flame-retardant agents. In addition, both plasma pretreatment and metal oxide co-catalyst added in the flame-retardant finishing improved the crosslinking process between FR and cotton fabric, minimizing formation of free formaldehyde and allowing the use of FR in industry.

The objective of the study is to develop a new filler for the production of natural filler thermoplastic composites using the waste rapeseed stalks. The long-term water absorption and thickness swelling behaviors and flexural properties of rapeseed filled polypropylene (PP) composites were investigated. Three different contents of filler were tested: 30, 45, and 60 wt%. Results of long-term hygroscopic tests indicated that by the increase in filler content from 30% to 60%, water diffusion absorption and thickness swelling rate parameter increased. A swelling model developed by Shi and Gardner can be used to quantify the swelling rate. The increasing of filler content reduced the flexural strength of the rapeseed/PP composites significantly. In contrast to the flexural strength, the flexural modulus improved with increasing the filler content. The flexural properties of these composites were decreased after the water uptake, due to the effect of the water molecules.

The compositions of alkaline extractives in bamboo sulfonated chemi-mechanical pulps (SCMP) were analyzed by UV spectroscopy and gas chromatography-mass spectrometry (GC-MS), and their effects on peroxide bleaching were studied. The extractives were composed of short-chain aliphatic compounds, phenols, and fatty acids, of which phenols were the major components. The amount of extractives was increased with the dosage of NaOH, and correspondingly, the bleachability of the extracted pulp was improved. When 3.5% NaOH was used, the brightness gain was 5.83%ISO, and the post-color (PC) number was decreased by 55.7%. The phenol compounds, which might easily generate conjugated structures, may play an important role in bleachability of bamboo SCMP and brightness stability of pulp.

Barrier paper, which is made of bleached absorbent kraft pulp, is a significant layer of decorative laminates, since it controls the see-through of brown color of saturating kraft paper and its opacifying effect usually is achieved by a heavy loading of TiO2. The TiO2, due to its very small particle size, passes between the cellulosic fibers and drains into the white water. To overcome this problem, papermakers try to use various retention aids for improving overall retention of TiO2, but agglomeration of TiO2 causes a decrease in light scattering efficiency of TiO2. During the subsequent saturation operation, the air in the voids is replaced by melamine formaldehyde, which has a refractive index close to that of cellulose. As a result, the sheet becomes translucent and poses ‘see through’ problem. Keeping this in view, anhydrous magnesium silicate is used as an extender with TiO2 because it effectively increases the overall filler retention, sheet brightness, opacity. The dispersed aqueous slurry of anhydrous magnesium silicate forms fine gel that entraps TiO2 in the wet web and prevents removal of fines and fillers. The addition of 25% TiO2, 7% micronized soapstone powder, 8% anhydrous magnesium silicate, 1% melamine formaldehyde, and 0.1% sodium hexameta-phosphate was found to improve the overall retention by 65.25% and to cut the manufacturing cost by US$ 546.00 per tonne of pulp without affecting the product quality.

A wide variety of waste bioresources are available on our planet for conversion into bioproducts. In the biological systems, microorganisms are used to utilize waste as an energy source for the synthesis of valuable products such as biomass proteins and enzymes. The large quantities of byproducts generated during the processing of plant food involve an economic and environmental problem due to their high volumes and elimination costs. After isolation of the main constituent, there are abundant remains which represent an inexpensive material that has been undervalued until now. Pea peel waste is one of the undervalued, unused sources of energy that can serve as a potential source for cellulase production. Batch experiments have been performed, using pea peel waste as a carbon source for cellulase production under solid state cultivation by Trichoderma reesei. It was observed that 30 oC temperature and pH 5.0 are the most favorable conditions for cellulase production by T. reesei. FPase activity significantly increases by incorporation of whey as well as wheat starch hydrolysate in the basal salt media used in the production study. The present study describes the utility of pea peel waste, whey as well as wheat starch hydrolysate in cellulase production by T. reesei. The utilization of economically cheap, pea peel waste for cellulase production could be a novel, cost effective, and valuable approach in cellulase production as well as in solid waste management.

The pyrolysis of two types of tobacco residue was carried out at different pyrolysis temperatures between 300 and 600 °C and a residence time of 1 h in a nitrogen atmosphere. The effect of pyrolysis temperature on the product distributions was investigated and the composition of the bio-oils identified. The variation in product distribution depended on both the temperature and the type of tobacco residues. The maximum liquid yields were obtained at 400°C for one sample and at 500°C for the other. The compositions of bio-oils from the pyrolysis of the two samples were found to be very similar. N-containing compounds were found to be the major compounds identified in ether extracts for both samples.

Enzymatic hydrolysis (EH) lignin was modified with formaldehyde. TG-DSC and PY-GC-MS analysis methods were adopted to characterize the differences between EH lignin and the modified lignin. The modified lignin was then mixed with wood sawdust and made into a lignin-based composite under the following conditions: pressure of 2 to 5 MPa, temperature of 175 to 190 oC, and the modified lignin dosage of 20% to 70%. The effects of pressure, temperature, and the modified lignin dosage on the properties of the composites were also evaluated. The pressure of 2 MPa was not enough to make a strong composite, and the composite with low dosage of modified lignin could not resist water, which signifies pressure and the ratio of modified lignin to sawdust are vital factors. Temperatures of 175 oC and 190 oC did not make much difference to change the mechanical properties of the composites. The composites which were made under 3 MPa, 180 oC, and the ratio of 1:1 modified lignin to wood sawdust was of fair quality. The samples made with the modified lignin dosage of 70% under 2MPa at 180 oC for 10min showed a low thickness swelling and low rates of water absorption from humid air and liquid water. Their free formaldehyde contents were also low and met Grade 2 in the national standard of China.

The aim of this study was to investigate the effects of tannin and thermal treatment on physical properties such as dimensional stability and moisture content (%), as well as mechanical properties such as bending strength, modulus of elasticity, and compression strength of laminated chestnut wood composites, which are used commonly for shipboard construction in Turkey. The chestnut wood used in boat construction is usually exposed to several treatments in order to achieve better bonding performance and to remove excessive tannins. According to the results obtained, physical properties of laminated chestnut wood without tannin were better compared to samples with tannin. Oven-dry density and air-dry density were found to be higher in samples containing tannins and not exposed to thermal treatment. Moreover, the lowest value of density was observed in samples containing no tannin and exposed to thermal treatment. In terms of mechanical properties, the highest bending strength and modulus of elasticity were obtained from samples containing tannins and not exposed to heat treatment. The lowest values were found in samples without tannin exposed to heat treatment. Regarding compression strength, the maximum and minimum values were found in samples containing tannins and not exposed to heat treatment and samples without tannin and exposed to heat treatment, respectively.