ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Estimation of hydrogen peroxide effectivity during bleaching using the Kappa number

Giorgio Tofani, Iris Cornet, and Serge Tavernier

iPRACS – Intelligence in Processes, Advanced Catalysts and Solvents, Faculty of Applied Engineering, University of Antwerp, Antwerp, Belgium

E-mail: giorgio.tofani@df.unipi.it

Received: 24 April 2021  Accepted: 25 June 2021

Abstract:

The bleaching of wood fibres using hydrogen peroxide is the primary process to produce paper with suitable brightness. Several studies were made to define the hydrogen peroxide consumption and the brightness gain rate. However, the effectivity of the hydrogen peroxide towards the reaction with the chromophores in the fibres and not lost by decomposition reactions has not been studied in detail before. In the presented research, three of the most common wood fibre types used in the paper industry were bleached using a hydrogen peroxide sequence composed of five subsequent stages, each with the same amount of hydrogen peroxide. The total consumption of the bleaching agent was measured by applying an adaptation to the commercial procedure developed by Merck KGaA using the Reflectoquant® apparatus. The corresponding electron exchange was calculated using the Kappa number to estimate the amount of hydrogen peroxide effectively consumed by reaction with the chromophores present in the lignin. In this case, it was observed that the decomposition reactions are significant with respect to the bleaching reactions. In all cases, this approach allowed to differentiate between the amount of hydrogen peroxide consumed by bleaching and the amount lost by decomposition under the applied assumptions.

Graphical abstract

Keywords: Wood fibres; Hydrogen peroxide consumption; Kappa number; Bleaching effectivity; Brightness gain

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01756-y

Chemical Papers 75 (11) 5749–5758 (2021)