Thermal and Alkali Stability of Sodium Dithionite Studied Using ATR-FTIR Spectroscopy

Vijaya Lakshmi Vegunta, Jasna S. Stevanic, Mikael Lindström, Lennart Salmen


Sodium dithionite (Na2S2O4) may have the potential to be used as a reducing agent for the stabilization of glucomannan in kraft cooking for increased pulp yield. However, due to the fact that dithionite decomposes under the conditions of kraft pulping, studies of the effects of dithionite in kraft pulping are non-conclusive; sometimes clearly showing an increased yield, and in other studies no effect at all. The specific conditions influencing dithionite degradation are also unclear. For that reason, this study was conducted to determine the thermal and chemical stability of sodium dithionite with respect to specific factors, such as the pH, temperature, heating time, and the concentration of sodium dithionite solution. The study was performed under anaerobic conditions using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The thermal and alkali stability of the sodium dithionite solution was shown to decrease with increasing temperature, heating time, and concentration of the solution at the alkaline conditions studied. The thermal stability decreased rapidly at weak alkalinity (pH 9) as well as in high alkalinity (pH 14), whereas the sodium dithionite was rather stable at moderate alkalinity (pH 11.5 to pH 13).


Alkalinity; Concentration; Dithionite; ATR-FTIR; Stability; Temperature

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