Electrochemical Delignification Mediated with Violuric Acid and Subsequent Bleaching of Poplar Kraft Pulp

摘要

The electrochemically mediated delignification (E_M) is one of new methods for pulp delignification and bleaching. In this paper, the electrochemical delignification mediated with violuric acid (VIO) of the kraft pulps were carried out. The results showed that VIO was suitable mediator for the electrochemical delignification of poplar kraf pulp. At the optimum conditions, the Kappa number was reduced from 17.4 to 11.7 and viscosity was decreased from 1144cm/g to 1059cm/g. The alkali treatment after E_M could further reduce Kappa number and increase brightness of electrochemical-VIO treated pulp. The Kappa number of pulp treated with E_ME could be reduced to 8.9 with the delignification rate of 48.8% and viscosity only decreased to 1065 cm/g. The brightness of E_ME treated pulp increased from original 39.2% ISO to 50.7%. The E_M treated pulps could be bleached to 80% ISO with the subsequent QP or EQP sequences at 2.0% of H_2O_2 charge.