Effect of lignin content and magnesium-to-manganese ratio on the
selectivity of oxygen delignification in softwood kraft pulp*
Lucian A. Lucia and Rachel S. Smereck
Institute of Paper Science and Technology, Georgia
Institute of Technology, 500 10th St., NW, Atlanta, Georgia 30318-5794,
Abstract: A series of oxygen delignification experiments were
performed on two softwood kraft pulps that had differing starting lignin
contents. One had an initial kappa of 40 and the other 25, corresponding
to lignin contents of 6% and 3.75% by dry mass, respectively. Several
chemical process modifications were examined to determine their influence
over the delignification selectivity and final pulp viscosity. A 2k
factorial format was used to assess the significance of varying the
temperature, time, and Mg/Mn ratio during the oxygen delignification
of the pulps. It was found that the lower lignin content pulp displayed
greater delignification selectivity than the higher lignin content pulp.
Kappa numbers, viscosity values, and ICP metals contents were determined
and are the basis of discussion for the results obtained.
* An issue of reviews and research papers based on
presentations made at the IUPAC/ICSU Workshop on
Electrochemistry and Interfacial Chemistry in Environmental Clean-up
and Green Chemical Processes, Coimbra, Portugal, 6-7 April, 2001.
** Corresponding author.
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