Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopic Study of Bleaching and Yellowing of Eucalypt Cold Soda Pulp

Abstract

E. regnans cold soda pulp has been bleached to a high brightness (about 87) in a single-stage treatment with alkaline hydrogen peroxide, and also in 2- and 3-stage sequences which used sodium borohydride in the second stage. The sequences did not provide further appreciable increases in the brightness level, but the borohydride-treated pulp showed greater brightness stability when irradiated with UV light, even when the pulp had been subjected to a third stage hydrogen peroxide bleach. Chemical changes in the pulps resulting from the bleaching treatments and from their exposure to UV light have been followed by studying the DRIFT spectra (1400–1800 cm⁻¹) of the wire side of handsheets. Variations in band intensity have been related to changes in pulp brightness and to oxidation of the pulps. Some features of the observed variations are not readily explicable.