It has been reported that natural cellulose （cellulose I） can not be oxidized by TEMPO - NaOCI - NaBr system, one of TEMPO-mediated selective oxidant systems, but regenerated cellulose （cellulose Ⅱ ） can be compl...It has been reported that natural cellulose （cellulose I） can not be oxidized by TEMPO - NaOCI - NaBr system, one of TEMPO-mediated selective oxidant systems, but regenerated cellulose （cellulose Ⅱ ） can be completely selectively oxidized. In the present work, natural cellulose pulp was treated with NaOH solution, which concentration is lower than 20 wt%. The alkaline celluloses obtained were oxidized by TEMPO - NaOCI - NaBr system and the factors which influence the selective oxidation reaction rate have been investigated. The structure of the oxidized products has been characterized by Fourier transform-infrared （FTIR）, nuclear magenatic resonace （NMR） and wide angle X-ray diffraction （WAXD） methods, and their adsorption properties for Cu^2＋ and Cd^2＋ in aqueous solutions have been preliminarily examined. The results show that after the alkaline treatment, the primary hydroxyl at C6 position of natural cellulose can be selectively oxidized to carboxyl group in the reaction medium at pH 10.8, the oxidation rate becomes greater with the NaOH concentration and alkaline treatment time increasing. The alkaline treatment has a great effect on the crystal structure of natural cellulose, but the crystal structure of alkaline cellulose keeps almost unchanged after oxidation. The adsorption capacity is enhanced by introducing carboxyl groups into the cellulose macromolecular chains.展开更多
Hardwoods are important raw material for making pulp and paper products. Eucalyptus camaldulensis is a fast-growing hardwood species with a wide distribution in Iran and can be introduced as appropriatematerial to com...Hardwoods are important raw material for making pulp and paper products. Eucalyptus camaldulensis is a fast-growing hardwood species with a wide distribution in Iran and can be introduced as appropriatematerial to compensate the wood shortages of the natural forest. Kraft pulping was performed under different cooking conditions and, based on the relations of pulp yield and kappa number, bleachable kraft pulp at screened yield of 43.3% and kappa number of 31.3 was selected for DED （Chlorine Dioxide-Alkaline Extraction-Chlorine Dioxide） bleaching and its bleachability was studied at different kappa factor in D~ stage. The results indicated that the bleachable kraft pulp from this species has high kappa number at acceptable screened yield and to complete the delignification in the bleaching process, higher kappa factor may be needed in DED bleaching sequence. The main reduction in final kappa number and yield loss were observed at kappa factor level of 0.2 but by further increase in kappa factor up to 0.4, more development were observed in optical properties but at lower opacity.展开更多
Poplar alkaline peroxide mechanical pulp （APMP） was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested. The raw poplar APMP fibers are stiff...Poplar alkaline peroxide mechanical pulp （APMP） was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested. The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process. During the refining process, the APMP fibers did not swell and fibrillate; they were easily broken and formed into fragments. The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces. The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR. The maximum tear strength was achieved at 61 ~SR of the beating degree. These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length. Along with the increase of the beating degree, the sheet density increased while the opacity decreased.展开更多
文摘It has been reported that natural cellulose （cellulose I） can not be oxidized by TEMPO - NaOCI - NaBr system, one of TEMPO-mediated selective oxidant systems, but regenerated cellulose （cellulose Ⅱ ） can be completely selectively oxidized. In the present work, natural cellulose pulp was treated with NaOH solution, which concentration is lower than 20 wt%. The alkaline celluloses obtained were oxidized by TEMPO - NaOCI - NaBr system and the factors which influence the selective oxidation reaction rate have been investigated. The structure of the oxidized products has been characterized by Fourier transform-infrared （FTIR）, nuclear magenatic resonace （NMR） and wide angle X-ray diffraction （WAXD） methods, and their adsorption properties for Cu^2＋ and Cd^2＋ in aqueous solutions have been preliminarily examined. The results show that after the alkaline treatment, the primary hydroxyl at C6 position of natural cellulose can be selectively oxidized to carboxyl group in the reaction medium at pH 10.8, the oxidation rate becomes greater with the NaOH concentration and alkaline treatment time increasing. The alkaline treatment has a great effect on the crystal structure of natural cellulose, but the crystal structure of alkaline cellulose keeps almost unchanged after oxidation. The adsorption capacity is enhanced by introducing carboxyl groups into the cellulose macromolecular chains.
文摘Hardwoods are important raw material for making pulp and paper products. Eucalyptus camaldulensis is a fast-growing hardwood species with a wide distribution in Iran and can be introduced as appropriatematerial to compensate the wood shortages of the natural forest. Kraft pulping was performed under different cooking conditions and, based on the relations of pulp yield and kappa number, bleachable kraft pulp at screened yield of 43.3% and kappa number of 31.3 was selected for DED （Chlorine Dioxide-Alkaline Extraction-Chlorine Dioxide） bleaching and its bleachability was studied at different kappa factor in D~ stage. The results indicated that the bleachable kraft pulp from this species has high kappa number at acceptable screened yield and to complete the delignification in the bleaching process, higher kappa factor may be needed in DED bleaching sequence. The main reduction in final kappa number and yield loss were observed at kappa factor level of 0.2 but by further increase in kappa factor up to 0.4, more development were observed in optical properties but at lower opacity.
文摘Poplar alkaline peroxide mechanical pulp （APMP） was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested. The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process. During the refining process, the APMP fibers did not swell and fibrillate; they were easily broken and formed into fragments. The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces. The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR. The maximum tear strength was achieved at 61 ~SR of the beating degree. These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length. Along with the increase of the beating degree, the sheet density increased while the opacity decreased.
