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THE EFFECT OF METAL-COMPLEXES IN THE ELECTROCHEMICALLY MEDIATED OXYGEN BLEACHING OF WOOD PULP

TitleTHE EFFECT OF METAL-COMPLEXES IN THE ELECTROCHEMICALLY MEDIATED OXYGEN BLEACHING OF WOOD PULP
Publication TypeJournal Article
Year of Publication1993
AuthorsPerng, YS, Oloman, CW, James, BR
JournalTappi Journal
Volume76
Pagination139-147
Date PublishedOct
Type of ArticleArticle
ISBN Number0734-1415
KeywordsAMPEROMETRY, BIBLIOGRAPHIES, bleaching, CATALYSTS, ELECTROCHEMISTRY, OXYGEN, REDOX POTENTIAL, transition metals
Abstract

The electrochemical behavior of transition-metal complexes is correlated with their effect in promoting electrochemically mediated oxygen bleaching of unbleached kraft softwood pulp. Ions of Fe, Mn, Co, Cr, Cu, and V with various ligands were examined in oxygen bleaching experiments at pH 9.4, 11.2, and 14. Only ferricyanide, iron/2,2’-dipyridyl, and ferrate exhibited significant synergistic effects with oxygen. Chemicals with reduction potential lower than that of the ferrocyanide couple at the pH of reaction, or those without reversible redox behavior, showed no synergistic effect. A mechanism is proposed in which the reaction of lignin with oxygen is initiated by oxidation of lignin with the higher valent species of the metal redox couple The metal redox couple may also catalyze peroxide decomposition via Fenton chemistry to generate the hydroxyl radical and thus promote degradation of cellulose.

URL<Go to ISI>://A1993MA71700024