Long-term stability of dithionite in alkaline anaerobic aqueous solution

摘要

Closed-system experiments were conducted to investigate the decomposition of sodium dithionite in aqueous solutions under varying pH and starting concentrations to simulate the deployment of dithionite as an in-situ redox barrier. Co-determination of dithionite and its degradation products was conducted using UV-Vis spectrometry, iodometric titration, and ion chromatography. In unbuffered solutions, dithionite reacted rapidly, whereas in near-neutral solutions (pH similar to 7), it persisted for similar to 50 days and in alkaline solution (pH similar to 9.5) for > 100 days. These are the longest lifetimes reported to date, which we attribute to not only excluding oxygen but also preventing outgassing of H2S. Thoroughly constraining the reaction products has led to the following hypothesized reaction: