Kinetics of Adsorbable Organic Halogen Formation During the First Chlorine Dioxide Bleaching Stage of Eucalyptus Kraft Pulp

Huixia Zhu, Shuangquan Yao, Lei Jiang, Shuangfei Wang, Chengrong Qin

Abstract


The emission standard for adsorbable organic halogen (AOX) has been adjusted as a mandatory assessment indicator in the papermaking industrial pollutants emission standards of China. To provide a theoretical basis to reduce AOX formation, a kinetic model of the first chlorine dioxide bleaching stage (D0) is presented for elemental chlorine-free (ECF) bleaching of eucalyptus kraft pulp. The kinetics of the D0 stage can be expressed as dW/dt = 314.6e-20.53/RT[H+]0.21[ClO2]0.41K0.98, where the reaction series for lignin, chlorine dioxide dosage, and H+ concentration are 0.98, 0.41, and 0.21, respectively. The reaction activation energy was 20.53 kJ.mol-1. R2 was greater than 0.9, which means that the model was shown to have high prognostic ability and feasibility. In the D0 stage, mostly lignin was removed and the reaction was fast. Much AOX was formed at the beginning of bleaching, and the reaction rate was primarily determined by the lignin content and chlorine dioxide dosage. H+ existed primarily as a catalyst and had little influence on AOX formation. The AOX formation occurs easily, as the reaction activation energy is less than 30 kJ.mol-1.

Keywords


Eucalyptus Kraft pulp; ECF bleaching; Kinetic model; AOX; First chlorine dioxide bleaching stage

Full Text: PDF

Welcome to BioResources! This online, peer-reviewed journal is devoted to the science and engineering of biomaterials and chemicals from lignocellulosic sources for new end uses and new capabilities. The editors of BioResources would be very happy to assist you during the process of submitting or reviewing articles. Please note that logging in is required in order to submit or review articles. Martin A. Hubbe, (919) 513-3022, hubbe@ncsu.edu; Lucian A. Lucia, (919) 515-7707, lucian.lucia@gmail.com URLs: bioresourcesjournal.com; http://ncsu.edu/bioresources ISSN: 1930-2126