Photoacoustic Fourier Transform Infrared Spectroscopic Study of Mechanical Pulp Brightening

Abstract

The technique of photoacoustic Fourier transform infrared spectroscopy (FTIR-PAS) was applied to the study of mechanical pulp brightening with hydrogen peroxide. Intensities relative to three internal standard peaks (3400, 1510 and 1056 cm⁻¹) were used since the absolute photoacoustic signal intensities were not reproducible. The internal standard method yielded a reproducibility of better than 5Z and made it possible to observe significant changes in the 1750–1600 cm⁻¹ region upon brightening with peroxide. The peak intensities were found to decrease due to alkaline deacetylation (1740 cm⁻¹), and to the net removal of conjugated carbonyl structures (1650 cm⁻¹).