Kinetics of hydrogen peroxide bleaching of ALCELL® derived pulp

In this study, a kinetic model of the final bleaching stage with hydrogen peroxide in a totally chlorine free (TCF) bleaching sequence for ALCELL® processed pulp was developed. The model was based on the rate of chromophore destruction characterized by the decrease in the light absorption coefficient of bleached pulp at 457 nm, C K . Based on the fact that the chromophore destruction proceeds rapidly in an initial phase followed by a much slower reaction during which a “floor‐level” chromophore concentration is approached asymptotically, we propose that the hydrogen peroxide stage of the ALCELL® derived pulp in the studied TCF sequence consists of two distinct phases. The initial phase is a very fast reaction. The rate equation of the second phase was determined as:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{- dC_K }}{{dt}} = 1.41 \times 10^{10} \exp \left({- 69610/RT} \right)\left[{HOO^ -} \right]^{0.5} \left[{C_K - C_{Kf}} \right]^2 $$\end{document}which is valid in a pH range of 10.5 to 11.5 and a temperature range of 60 to 92.5°C.