Title
Understanding of HEDP used as a chelator in pulp bleaching
Authors
LANFENG HUI FAYE WANG JINJIANG PANG and ZHONG LIU

Received March 25, 2015
Published Volume 51 Issue 3-4 March-April
Keywords 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), pulp bleaching, chelator, Fenton reaction, hydroxyl radicals

Abstract
This study investigated the use of a water treatment agent, 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), as chelator in the OPQP bleaching sequence of Acacia mangium kraft pulp. The results showed that the effect of HEDP in bleaching is better than that of EDTA with respect to pulp viscosity, and HEDP is similar to EDTA and DTPA as regards other properties under the same chelating conditions. The optimum Fenton reaction conditions were as follows: temperature of 60 °C, hold time of 30 min, Fe2+ to H2O2 concentration ratio of 1:30, and H2O2 concentration of 10 mM. Under these conditions, it was found that the chelating ability of HEDP was between those of EDTA and DTPA. In addition, HEDP has the ability to scavenge hydroxyl radicals, whereas DTPA does not have this ability in the UV/H2O2 irradiation system.