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Nathalie Marlin, Dominique Lachenal, Laurence Magnin, Marie-Christine Brochier-Salon

Study of the oxygen effect on mechanical pulp lignin using an improved lignin isolation method

Keywords: kraft lignin, lignin isolation, oxygen treatment, phenolic hydroxyl groups, quinone groups, TMP lignin

Lignins from kraft and mechanical pulps were isolated before and after oxygen treatment with conventional methods (acidolysis and enzymatic isolation) and with a novel two-step method combining an enzymatic treatment and acidolysis. Results showed that the combined enzymatic hydrolysis-acidolysis made it possible to extract lignin from pulp with a better yield than acidolysis alone and with a higher degree of purity than after enzymatic hydrolysis alone. The lignin samples isolated with the two-step method were analysed by ¹³C NMR, ¹⁹F NMR and by gel permeation chromatography. It was shown that the behaviour of mechanical pulp lignin during oxygen treatment was different from that of kraft pulp lignin. Most of these differences could be explained by the lower phenolic content and larger molecular size of the mechanical pulp lignin. As a consequence, oxygen had a poor delignifying effect. Finally, ¹⁹F NMR spectroscopy showed that oxygen could destroy some quinones induced by the alkaline conditions of the O stage.

Holzforschung, Walter de Gruyter

Print ISSN: 0018-3830
Volume: 59, 02/2005
Pages: 116 - 123

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