Kinetics study of oxidation of the lignin model compounds by chlorine dioxide

Kinetics study of oxidation of 1-(3,4-Dimethoxyphenyl)ethanol (MVA), a lignin model compounds, with chlorine dioxide under simulated bleaching conditions were investigated. The UV-vis spectrophotometer was employed to characterize the reaction products of chlorine dioxide and 1-(3,4-Dimethoxyphenyl)ethanol. A possible reaction mechanism was proposed. The results showed the chlorination and oxidizing reaction of 1-(3,4-Dimethoxyphenyl)ethanol coexisted. The hypochlorous acid was the main reason to form adsorbable organic halides (AOX). An overall second-order rate equation was also established from UV-vis spectra results. It was shown as: -d[ClO2]/dt = k'[MVA][ClO2], where k' refers to observed second-order rate constants. The results showed the kinetics model correlated well with the experimental data, so the degree of 1-(3,4-Dimethoxyphenyl)ethanol oxidized by chlorine dioxide can be quantitative evaluated based on this model. AOX formation characteristic and practical implications of this work were investigated based on the kinetics and mechanism, which might bring a new door open for resolving the major problems of environmental pollution in elemental chlorine free (ECF) bleaching of pulp. (C) 2013 Elsevier B.V. All rights reserved.