Volume 6 Issue 2

Variation in the pore structure of eucalyptus fibre during recycling was investigated using low-temperature nitrogen adsorption, atomic force microscopy (AFM), and fractal geometry. The Brunauer- Emmett-Teller (BET) surface area of the fibre fell to 55.1% of the original value after the first cycle, and to 49.0% after the second cycle, ultimately declining to 35.0% after the fourth. The Barret-Joyner- Halenda (BJH) adsorption cumulative pore volume fell to 38.4% of the original by the fourth. After four cycles, the average pore diameter fell to 82% of the original. AFM tests showed that the pore structure in fibre expressed high self-similarity in statistics, and the pore structure in the fibre could be regarded as a fractal. Fractal geometry analysis of the results showed that the fractal dimension of eucalyptus virgin fibre is 2.954. With the number of process cycles increasing, the fractal dimension fell to a minimum of 2.886 after four cycles. The water retention value (WRV) of the fibre was proportional to the fractal dimension and the crystallinity of fibre.

The aim of this work was to study the effect of ozone, either alone or combined with an activated sludge system, on the reduction of the recalcitrant COD in the effluent of a chemimechanical pulping (NaOH -Na2SO3) integrated mill. Several alternative schemes involving ozonation were tested on liquors and effluents of the pulp mill, and on two kinds of effluents were taken at different points of an activated sludge pilot plant. The largest decrease in COD was 33%, whereas that in aromatic compounds (absorbance at 232.5 nm) was of 73%. The most obvious result of the ozone treatment was effluent decolorization. It was not possible to use ozonation as tertiary treatment, as ozone was necessary to treat the BOD generated, and therefore the effluent must necessarily pass through a biological treatment. With a scheme including an intermediate ozonation between two secondary treatments (post-activated sludge and pre-aeration lagoon), the maximum reductions achieved were of 70% in COD, of 93% in aromatics, and of 96% in color. The limits of COD allowed by the environmental regulations (<250 mg/L) could be achieved with the following stages: 1) primary clarifier, 2) activated sludge system, 3) ozonation, 4) aeration lagoon, and 5) stabilization lagoon.

Dilute sulfuric acid hydrolysis was performed before the isolation of cellulose from Eulaliopsis binata. And then, the effects of dilute acid hydrolysis on composition and structure of the cellulose was studied in detail. The results indicated that hemicellulose was dissolved mostly and that the lignin-hemicellulose-cellulose interactions were also partially disrupted during the dilute acid hydrolysis. Cellulose in Eulaliopsis binata was identified as the cellulose I allomorph with low crystallinity. What’s more, hydrolysis with dilute acid at high temperature increased the degree of cellulose crystallinity and relatively reduced the proportions of less ordered cellulose allomorphs. This was attributed to a preferential degradation of amorphous cellulose and less ordered crystalline forms during the hydrolysis. The cellulose preparation from Eulaliopsis binata after dilute acid hydrolysis had a higher thermal stability than the cellulose preparation from untreated Eulaliopsis binata.

Hydroxyphenyl (H-type) and guaiacyl (G-type) lignin model polymers composed of the β–O–4 structure without g–hydroxymethyl groups were synthesized. The chemical structures of the H- and G-type lignin models were characterized by 1H- and 13C-NMR, as well as MALDI-TOF/MS. The pyrolysis response was analyzed by means of TG-DTG, Py-GC/MS, and a tube furnace technique. 1H-, 13C-NMR, and MALDI-TOF/MS showed that the lignin models were linear polymers. The polymers included the β–O–4 linkage, as in natural lignin. Pyrolytic products from H-type lignin model only possessed p-hydroxyphenyl structure without methoxyl groups, and the pyrolytic products from G-type lignin model only possessed guaiacyl structure with methoxyl groups. Pyrolysis products from H- and G- type lignin models were classified into char, gas, and liquid (bio-oil), and the gaseous products of two model compounds mainly consisted of H2, CO, CH4, CO2, and C2H4.

The aim of this study was to evaluate the potential of a new, straw-based fibre manufacturing technology integrated to bioenergy and biofuels production. The process is based on a novel hot water treatment and subsequent mechanical refining, both of which are performed at a high temperature. Soda process, ethanol production, and chemical defibration based on hot water treatment and subsequent alkaline peroxide bleaching were selected as references. The idea is to utilise the fibre fraction for packaging and the dissolved solids and the formed fines for energy. The investment costs of this process are significantly lower than those of a soda process. Additionally, a chemicals recovery process is unnecessary. Furthermore, the process offers an attractive alternative for biogas production. However, the assessment showed that the process could only be economical in some terms. Subsidies for investment would probably be needed to promote the acceptance of this environmentally safe process.

Lignins are important biopolymers that can be converted into value-added materials by enzymatic treatments. However, the heterogeneity of the lignin polymer makes it a challenging material to modify. Thus, chemical fractionation was used to obtain lignins with high homogeneity in order to assess their biotechnological utilization. Commercial Alcell, birch organosolv lignins, and steam-exploded pine and eucalypt lignins were sequentially fractionated by ether, ether/acetone 4:1 (v:v), and acetone. All fractions were structurally characterized prior to treatments with Thielavia arenaria, Trametes hirsuta, and Melanocarpus albomyces laccases. The reactivities of the enzymes towards the lignins were determined by oxygen consumption measurements, and the degree of polymerization was confirmed by size exclusion chromatography. Field emission scanning electron microscopy revealed that the surfaces of the lignin nanoparticles were dispersed in the enzyme treatment, suggesting an increase in hydrophilicity of the surfaces detected as loosened morphology. Hence, it was concluded that enzyme-aided valorization is an attractive means for lignin modification, provided that optimum reaction conditions are employed.

Kenaf bast fiber was chemically modified by using propionic and succinic anhydrides. Five retention times were compared: 30, 60, 120, 180, and 240 minutes at 100°C. Confirmation of anhydride modification was established by the weight percent gain (WPG) and was further confirmed by Fourier Transform Infra-Red (FT-IR) spectroscopy. Based on WPG, succinylated fibers exhibited higher WPG than propionylated fibers. The results of WPG for both succinylated and propionylated fibers showed that 180 minutes was an optimum time for modification, yielding the highest WPG. The thermal stability of modified fibers was characterized with Thermal Gravimetric Analysis (TGA). Succinylated fibers showed better thermal stability than propionylated fibers. Anhydride modification also enhanced the fiber smoothness, as demonstrated by Scanning Electron Microscopy (SEM) analysis. Succinylated fibers showed a much smoother surface as compared to propionylated fibers and untreated fibers. Anhydride modification significantly decreased the contact angle of kenaf bast fibers, thus imparting good adhesion characteristics to the fibers.

Cotton linter pulp was oxidized in the TEMPO-NaBr-NaClO system with ultrasonic treatment, and cellulose nanocrystals having high carboxylate content were produced directly. Results showed that the C6 primary hydroxyl group of cellulose fiber was converted to the carboxylate group, whose amount could be up to 1.66 mmol/g. During the oxidizing reaction, some of the amorphous region in the cellulose fiber was modified and gradually hydrolyzed, but the crystalline region still remained. It was also shown by TEM (Transmission electron microscopy) that the widths of cellulose nanocrystals were approximately 5-10 nm, and the lengths were approximately 100-400 nm. The high carboxylate content cellulose nanocrystals could be produced in one step by this method, yielding a stable and well dispersed aqueous suspension.

Severe shortage of suitable wood for Medium Density Fiberboard (MDF) production makes it necessary to consider using uncommon and non-conventional raw materials such as agricultural residues. In order to demonstrate the suitability and the potential of two agricultural residues (cotton and corn stalks), laboratory MDF boards were produced. Three press temperatures (170, 180 and 190 ºC) were used. Test samples were prepared from the boards after conditioning at 65% RH and 21 ºC, and all tests were performed according to relevant EN standard methods. The results indicated that the MOR and MOE of boards produced from corn stalks were higher than those from cotton stalks, by almost 25%. However significant difference was not observed for internal bonds of boards. Thickness swelling of MDF boards from corn stalks was lower than cotton stalks. Comparing the results obtained with the strength of boards produced from hardwoods showed similarity between corn stalks and wood, but the strength of MDF boards from cotton stalks was lower. However, the results almost satisfied the EN 622-5;1997 requirement.

Organosolv lignins can replace petroleum chemicals such as phenol either partially or totally in various applications. Eight lignins, seven of which corresponded to the ethanol-water fractionation of bagasse and the other to a reference lignin (Alcell®) were analyzed with the aim to evaluate their chemical and physicochemical characteristics. The purity of the lignin fractions was determined by high pressure liquid chromatography (HPLC) and by ash content. Fourier Transform-Infrared Spectroscopy (FTIR) techniques and differential UV spectroscopy were applied to identify the chemical groups in the lignin samples. The molecular weight distribution was determined by size exclusion chromatography (HPSEC). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques were used to determine the mass loss due to the high temperature treatment. The lignins studied showed the presence of p-hydroxyphenyl (H unit) and a greater proportion of guaiacyl (G unit) moieties, lower purity, similar or greater amount of phenolic hydroxyl groups, and higher degradation temperatures, than the Alcell® lignin.