Volume 5 Issue 3

A new method was developed for production of low molecular weight chitosan, in which high molecular weight chitosan was treated with dilute sulfuric acid at 120°C. Chitosan was dissolved in the acid solution in a few minutes, and as depolymerized to low molecular weight chitosan by longer times. Low molecular weight chitosan was recovered from the acid by cooling down the solution and increasing the pH to 8-10. A low molecular weight chitosan with Mv (viscosity average molecular weight) of 174×103 was prepared from a high molecular weight chitosan (Mv = 1,388×103) with 82% recovery by using 72 mM sulfuric acid solution for 30 min. Increasing the time to 240 min reduced the Mv to 24×103, though the recovery of chitosan was reduced to 54%. Higher concentrations of acid (216 and 360 mM) resulted in higher depolymerization degrees and lower recoveries of chitosan in identical treatment times. Analysis of glucosamine and N-acetyl glucosamine showed that the prepared low molecular weight chitosan had more than 80% purity.

Sugarcane bagasse was delignified with alkali and peracetic acid in a two-stage process to obtain pulps with high yield and low kappa number. The experimental results indicated that alkali pretreatment prior to peracetic acid (PAA) delignification could significantly reduce PAA loading by partially removing lignin and swelling the fibers. An optimum condition for the two-stage delignification was obtained for pulping of sugarcane bagasse. The pulps were further characterized by chemical composition analysis, strength property tests, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), and Thermal Gravimetric Analysis (TGA). It was found that the alkali-PAA process could be conducted under milder conditions with resulting higher pulping selectivity, higher degree of polymerization (DP), and superior mechanical properties of pulps, compared to the kraft pulping process. Both kraft pulps and alkali-PAA pulp had similar FTIR spectra, XRD spectra, and TGA (DTG) curves. However, further analysis indicated that the alkali-PAA pulp had higher infrared crystallization index and cellulose crystallinity.

Statistically based experimental designs were used to construct a mixed-culture community for maximizing the chemical oxygen demand (COD) degradation of pulping effluents by the use of six different strains, i.e., Agrobacterium sp., Bacillus sp., Enterobacter cloacae, Gordonia, Pseudomonas stutzeri, and Pseudomonas putida. Significant effects of single and mixed strains on COD degradation were quantified first by applying a fractional factorial design (FFD) of experiments, and four strains were selected as the main driving factors in the process of biodegradation of effluents. Then the Steepest Ascent method was employed to approach the experimental design space, followed by an application of response surface methodology to further optimize the proportion of cell concentration for different strains in pulping effluent. A quadratic model was found to fit COD removal efficiency. Response surface analysis revealed that the optimum levels of the tested variables for the degradation of COD, and optimized cells concentrations (OD600) of four strains in mixed-culture community were 0.35 Agrobacterium sp., 0.38 Bacillus sp., 0.43 Gordonia sp., and 0.38 P. putid., respectively. In a confirmatory experiment, three test runs were performed by using the optimized conditions, and a COD removal efficiency of (65.3 ± 0.5)% was observed, which was in agreement with the prediction.

Malaysian cultivated kenaf has been identified as a suitable raw material for linerboard production. This study examines the soda-antraquinone (soda-AQ) pulp of kenaf fibers versus old corrugated container (OCC) and unbleached softwood kraft pulps as the main sources for linerboard production. The results showed significant differences among the pulp properties. The unbleached kraft pulp with very high freeness required high beating to reach an optimized freeness and produced paper with the highest strength properties, except for tear resistance. The OCC gave paper with the lowest strength properties. In the case of kenaf fractions, bast pulp with high freeness needed less beating than softwood and produced paper with high tear resistance. Core fiber, which had the lowest freeness and highest drainage time, led to paper with high strength but very low tear resistance. Kenaf whole stem pulp showed intermediate properties between core and bast and close to those of unbleached softwood pulp, but with very lower beating requirement. Finally, kenaf whole stem, due to its strength properties, moderate separation cost, and simple pulping process, was judged to be more suitable for commercialization for linerboard production in Malaysia.

Bagasse is a renewable resource characterized by its low cost and environmental friendliness. In this work a novel technological process was proposed to make flame retarding composites (BFRCs) by using bagasse fiber. The bagasse was disintegrated by twisting it up and applying high consistency refining, and then it was used to prepare BFRCs via hot pressure. Chemical groups and thermal properties of bagasse fiber were studied through the use of FTIR spectroscopy, a universal mechanical testing machine, and TGA, while properties of BFRCs were also analyzed by SEM, and the surface water resistance and burning characteristics were measured. Results showed the pyrolysis temperature of bagasse fibers to be about 273oC. Chemical groups were not changed, while the content of groups was reduced a little during the manufacturing process. The BFRCs showed good performance for water resistance, and the optimum value was 1.7 g. They also had good flame retardant performance. The index of flame spread was 13.6 and the smoke index was 108, which reaches Class A by the ASTM E84-08 Standard.

Raw jute fiber was treated with o-hydroxybenzenediazonium salt (o-HBDS) in alkaline media. Raw and modified jute fiber were used to prepare composites by mixing with polypropylene (PP) plastic in different weight fractions (20, 25, 30, and 35%) of jute fiber. The mechanical properties except elongation at break of o-HBDS-treated (in alkaline medium) jute fiber-PP composite were higher than those of PP alone, raw jute fiber-PP composites, and alkali-treated jute fiber-PP composites. The elongation at break of treated jute-PP composite decreased to a large extent as compared to that of PP. The increase of tensile strength, tensile modulus, flexural strength, flexural modulus, and Charpy impact strength were found to be exceptionally high (in some cases ~200%) as compared to those of literature values.

This paper estimates and discusses the specific belt sanding resistance K (N·cm-2) and specific belt sanding intensity SI (g·cm-2·min-1), for wood of Pinus sylvestris L., Picea abies L., Quercus robra L., Acer pseudoplatanus L., Alnus glutinosa Gaertn., and Populus Nigra L., by different sanding pressure pS, different sanding grit NG number, and different wood grain angles Phi(v).

Rice bran carbon (RBC) prepared from rice bran (an agricultural waste) was successfully utilized for the removal of hexavalent chromium from aqueous solution. The potentiality of RBC was tested and compared with commercial activated carbon (CAC), and it was found that RBC removed 95% of hexavalent chromium at pH 2, 1000 µM Cr(VI) concentration, temperature 30 oC, and adsorbent dose of 2 g/L. The maximum uptake of total chromium obtained by applying the Langmuir isotherm model was 138.88 mg/g for RBC, which was found comparable to that obtained by utilizing CAC (116.28 mg/g) at 40 oC. The removal of Cr(VI) was found maximum at a proton to chromium ratio of 10 and chromium to carbon ratio of 0.052, and these ratios were found to be applicable over a range of Cr(VI) concentrations. The removal of Cr(VI), at low pH (< 2.0), was not only due to sorption of Cr(VI) but also because of reduction of Cr(VI) into less toxic Cr(III), which was also adsorbed on the surface of the sorbent. The rate of reduction removal of Cr(VI) followed pseudo-first order kinetics, whereas the sorption of total chromium followed pseudo-second order kinetics for both the types of activated carbons.

Biocide programs have become necessary in most fine paper manufacturing circuits, as drastic reduction of fresh water consumption in the industry enhances microbial development. Depending on their chemical nature, biocides may interfere with typical wet-end chemistry additives and furnish. A reference wet-end chemistry was set (including fixing aid, dry strength aid, sizing agent, and retention system), then biocides were added to the furnish (bleached virgin fibres + mineral filler) prior to handsheet making. Four of the tested biocides (organo-sulfur, dibromonitrilopropionamide, isothiazoline, and glutaraldehyde) were not found to interact with wet-end chemistry. On the other hand, the tested quaternary ammonium salt biocide showed very detrimental effects: it reduced filler retention in the sheet, decreased sheet strength, and destroyed sizing (sheet hydrophobicity).

Bacillus sp. MG-33 was isolated from the desert of Rajasthan (India). The organism produced 500 and 200 Ug-1 of thermostable mannanase (after 96h) in solid state fermentation (SSF) of wheat bran and wheat straw rich-soda pulp at the moisture ratio of 1:1.5 and 1:3 at 30ºC, respectively. Two-step partially purified mannanase was optimally active at 65ºC and was 100% thermostable at 55 to 60ºC for 2h and also retained more than 50% residual activity at 65ºC for 2h. A pH of 6.5 was optimum for enzyme activity and 100% stability up to 4h at this pH. Mannanase activity was slightly enhanced by Ca2+, Fe3+, and Mg2+, while 100% activity was retained in the presence of Ba3+, Li+, and NiCl2 at 1.0-10mM. 1M NaCl and urea did not reduce the enzyme activity. The Km and Vmax of mannanase were 0.2mgml-1 and 60Umg-1ml-1, respectively. Hydrolysis of locust bean was rapid and linear between 5 and 20 min, and ~300µgml-1 mannose was obtained after 20 min of catalytic reaction by enzyme at 65ºC. TLC was used to confirm the mannose as an end product after hydrolysis of locust bean gum.