Delignification of wood and kraft pulp with peroxymonophosphoric acid

Selective delignification is important to ensure that lignin is removed from wood or pulp with minimal damage to cellulose and hemicellulloses, yielding strong pulps capable of repeated recycling. In this exploratory study, finely divided aspen wood and mixed northern pine kraft pulp were delignified with dilute aqueous solutions of peroxymonophosphoric acid. For aspen, peroxymonophosphoric acid was much more selective in delignification than were peroxymonosulphuric acid and pernitric acid. For pine, peroxymonophosphoric acid delignified more rapidly and more selectively than did peroxymonosulphuric acid. The results suggest that peroxymonophosphate treatment of alkaline-pretreated chips or fiberized wood could produce a highly delignified, bright pulp. Peroxymonophosphate might also be effective as a pretreatment to oxygen delignification.