Fate of chelating agents used in the pulp and paper industry

The use of chelating agents in the Scandinavian pulp and paper industry has drastically increased during the 1990s due to the elimination of the use of elemental chlorine in pulp bleaching and the implementation of bleaching sequences utilizing oxygen-based chemicals and chlorine dioxide. The decomposition of hydrogen peroxide, oxygen, and ozone is accelerated by transition metal ions such as manganese, iron, and copper. Thus, the optimized control of metal ions in pulp through chelating agents has become an important issue. Recent developments in analytical techniques have enabled the accurate determination of chelating agents such as diethylenetriaminepentaacetic acid (DTPA) and ethylenediaminetetraacetic acid (EDTA) both in bleach liquors and in pulps. This paper reports results on the total mass balances of chelating agents during modern ozone and hydrogen peroxide bleaching processes. World consumption of chelating agents and their behavior in a mill's effluent treatment system and in recipients are also briefly discussed.