Study of Activation Methods of the Bleached Hardwood Kraft Pulp to Increase its Reactivity

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661.728; 577.152.37

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Abstract

A low content of hemicelluloses and low-polymeric fraction of cellulose in dissolving pulp is required for effective chemical processing and achieving of high quality. Dissolving pulp is produced using special pulping and bleaching conditions. It was proposed to obtain dissolving pulp from conventional hardwood kraft pulp by alkali and enzyme treatment. The advantage of the new technology is the higher yield of the final product.  The aim of this paper was to estimate the effect of various activation methods on bleached hardwood kraft paper-grade fibers, to characterize properties of treated pulp and to assess its suitability for chemical processing.  The commercial bleached hardwood kraft pulp produced from the mixture of birch and aspen was used. The improvement of kraft pulp reactivity requires deep development of fiber cell wall. Acidic, enzymatic and hot alkali treatments were used for pulp activation. Acid treatment was carried out at 95°C or 100°C; alkali treatment was carried out at 95°C or 110°C. The Cellulases (endoglucanases) Novozym 476 and the Faber Care D by the Novozymes and the xylanase Banzyme ATX2 by the Banmark were used for enzymatic treatment.  Pulp yield, ?-cellulose and pentosan content, viscosity of cellulose cuprammonium solutions and pulp reactivity for the viscose process were determined after various treatments. It was shown that xylanase pretreatment had a mild effect on the cell wall, improving the swelling ability, while the fiber structure was retained. Xylanase treatment has no effect on the viscosity of the pulp, so cellulase was used for reducing pulp viscosity at the final stage of the treatment.  As the acid treatment preceded the xylanase treatment, the swelling extent of pulp fibers in NaOH solution was slightly higher than in the case of the reverse stage order. Degradation in the hot alkaline conditions after acid treatment led to a considerable destruction of fiber cell wall. Intense swelling, local breaks and dissolution of the fibers were observed. The alkali degradation was more intensive when acidic hydrolysis was followed by xylanase treatment.  Application of xylanase and cellulase mixture on the pretreatment stage of pulp was suggested. Combined action of these enzymes for reactivity activation of bleached hardwood kraft pulp in the process of conversion to dissolving pulp allows improving xylan removal, enhancing fiber swelling and controlling the viscosity of the pulp at an acceptable cost of enzymes.

Authors

D.N. Poshina1, Chemist Expert P.V. Porotova2, Postgraduate Student K.Y. Terentyev2, Postgraduate Student D.G. Chukhchin2, Candidate of Engineering, Associate Professor L.A. Milovidova2, Candidate of Engineering, Associate Professor, Leading Researcher E.V. Novozhilov2 , Doctor of Engineering, Professor 1Sanitary-hygiene laboratory Federal State-Funded Healthcare Institution «Centre of hygiene and epidemiology», 2Northern (Arctic) Federal University named after M.V. Lomonosov,  1pr. Troitskiy,164/1, Arkhangelsk, 163001, Russia E-mail: poschin@yandex.ru 2Naberezhnaya Severnoy Dviny, 17, Arkhangelsk, 163002, Russia E-mail: e.novozhilov@narfu.ru

Affiliation

1Sanitary-hygiene laboratory Federal State-Funded Healthcare Institution «Centre of hygiene and epidemiology», 2Northern (Arctic) Federal University named after M.V. Lomonosov,

Keywords

hardwood kraft pulp, hot alkaline treatment, acid treatment, xylanase, cellulase, swelling, reactivity

References

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