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Jahan M.S.,Pulp and Paper Research Division | He Z.,University of New Brunswick
Appita Journal | Year: 2010

An alkali source is needed to control the final pH of D1 and D2 stages in a conventional elemental chlorine free (ECF) chemical pulp bleaching sequence. This study evaluated the use of precipitated calcium carbonate (PCC) as an alternative alkali to caustic soda (NaOH) in the CIO 2 brightening of a hardwood kraft pulp. The PCC-based process showed improved brightening performance over the conventional NaOH-based process due to its lower initial pH and flat overall pH profile in the system. The pulp viscosity was also better than that of the control pulp. The PCC-based process can save up to 0.2% CIO2 in achieving the same target brightness as the control. PCC was also evaluated as the alkaline source for the alkaline extraction stage and the results showed that the final pulp brightness decreased but the COD in the effluent also decreased. However, at a 20% PCC substitution in the alkaline extraction stage, with the combination of the PCC-based D 1 and D2 stages, a fully bleached pulp with higher final brightness, less brightness reversion and better viscosity than the control can be produced. Source

Sarwar Jahan M.,Pulp and Paper Research Division | Shamsuzzaman M.,Pulp and Paper Research Division | Rahman M.M.,Pulp and Paper Research Division | Iqbal Moeiz S.M.,Dhaka College | Ni Y.,University of New Brunswick
Industrial Crops and Products | Year: 2012

The effect of hot-water and alkaline pre-extraction of rice straw on soda-anthraquinone pulping was carried out. The pre-extraction with hot water at 150 °C for 1. h dissolved 34.7% biomass and the pre-extracted liquor comprised of 16.6% sugars, 6.7% lignin, 6.6% acetic acid and other unknown products. But the pre-extraction with 1% NaOH at 100 °C for 1. h dissolved 10.2% sugars, 5.1% lignin and 10% acetic acid from rice straw. Pre-extracted rice straw was cooked by soda-anthraquinone process with varying alkali charges. The pulp from pre-extracted rice straw was low in kappa number with reduced pulp yield. The drainage resistance (°SR) improved obviously on pre-extraction of rice straw. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index was higher both with hot-water and alkaline pre-extraction. After bleaching, the gaps of the overall pulp yield and strength properties between pre-extracted and non-extracted rice straw became narrower. The alkaline pre-extraction showed improved yield and properties compared with hot-water pre-extracted rice straw. © 2011 Elsevier B.V. Source

Liu Z.,Tianjin University of Science and Technology | Liu Z.,University of New Brunswick | Fatehi P.,University of New Brunswick | Jahan M.S.,University of New Brunswick | And 2 more authors.
Bioresource Technology | Year: 2011

In this paper, we proposed a new modification for an ethanol-based pulping process, which would consist of the pre-hydrolysis (pre-extraction) of wood chips for removing hemicelluloses; the ethanol extraction of pre-hydrolyzed wood chips for removing lignin; and the post purification of cellulose, leading to the production of pure cellulose. We also experimentally evaluated the separation of hemicelluloses from the pre-hydrolysis liquor (PHL) obtained from a pulp mill. To remove lignin from the PHL, it was acidified to a pH of 2, which resulted in 47% lignin precipitation. The lignin separation from the acidified PHL was further improved via adding polyethylene oxide and poly aluminum chloride or adding ethyl acetate. To recover the hemicelluloses from the acidified PHL, ethanol was added to the acidified PHL with a volumetric ratio of 4 to 1. The isolated lignin and hemicelluloses were characterized by a Fourier transform infrared spectroscopy (FTIR) and a gas permeation chromatography (GPC). © 2010 Elsevier Ltd. Source

Jahan M.S.,University of New Brunswick | Jahan M.S.,Pulp and Paper Research Division | Saeed A.,University of New Brunswick | He Z.,University of New Brunswick | Ni Y.,University of New Brunswick
Cellulose | Year: 2011

Cellulose was extracted at a yield of 59.8% from jute fibres based on the formic acid/peroxyformic acid process at an atmospheric pressure. The amounts of dissolved lignin and hemicelluloses were determined in the spent liquor. The results showed that the spent liquor contained 10.6% total sugars and 10.9% lignin (based on jute). Microcrystalline cellulose (MCC) was further prepared from the jute cellulose based on the acid hydrolysis technique. A very high yield, 48-52.8% (based on the jute raw material) was obtained. The acid hydrolysate of cellulose contained 2.7% glucose and 0.2% xylose. The MCC samples obtained from two different conditions, one at a low acidity and the other at a high acidity, were characterized by means of Thermo Gravimetric Analysis, Fourier Transform Infrared, X-ray detraction, Scanning Electron Micrograph, and Transmission Electron Micrograph techniques. © 2010 Springer Science+Business Media B.V. Source

Li H.,University of New Brunswick | Saeed A.,University of New Brunswick | Jahan M.S.,University of New Brunswick | Jahan M.S.,Pulp and Paper Research Division | And 2 more authors.
Journal of Wood Chemistry and Technology | Year: 2010

A pre-hydrolysis step to remove hemicelluloses from mixed hardwood chips consisting of maple, aspen, and birch with a ratio of 7:2:1 has been carried out. The effects of parameters on the pre-hydrolysis such as time, temperature, acetic acid addition, and raw material species, were determined. Different sugars, acetic acid, and furfural formation in the pre-hydrolysis liquor were quantified. The results showed that the pre-hydrolysis is a dynamic process, in which the removal of hemicelluloses increased with time while the conversion of extracted hemicelluloses to monosaccharides due to acid hydrolysis increased and part of the xylose was converted to furfural. The maximum temperature was the most critical parameter for hemicelluloses extraction and conversion, and a temperature of 170°C was the optimum for hemicelluloses extraction with relatively low conversion of xylose to furfural. About 11% of the xylan (in both monomeric and oligomeric forms) was removed at 170°C. Due to the presence of a high amount of xylan, birch produced the highest amount of xylose, followed by maple, and then aspen. Source

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