Thermal behavior investigation of bitumen embedding sodium nitrate: A non-isothermal study

• Thermal analysis of bitumen as a surrogate for radioactive waste embedding sodium nitrate. • Exothermic reactivity linked to bitumen oxidation by nitrate species was estimated. • Kinetic parameters determined using Kissinger, Friedman, and non-linear methods. • High agreement observed between different kinetic modeling approaches. • Energy of the reaction between bitumen and various NaNO 3 was estimated. This study investigates the thermal behavior of straight-run distillation bitumen embedding sodium nitrate through thermogravimetric analysis (TGA) coupled with differential thermal analysis (DTA). The examination explores various sodium nitrate concentrations and heating rates effects on the system. Non-isothermal characterization is conducted from 30 to 900°C under different heating rates (1, 2, 5, 10, and 25°C/min) in a nitrogen atmosphere. TGA and DTA results unveil an exothermic reactivity attributed to the oxidation of bitumen by nitrate species. The enthalpy associated with this oxidation process is quantified at 297 ± 13 kJ/mol of NaNO 3 . Kinetic parameters are determined utilizing Kissinger, Friedman, and advanced non-linear (NLN) methods to evaluate the effective activation energy for each event based on the non-isothermal experimental data. Remarkably, a high level of agreement is observed between the kinetic modeling approaches employed, providing valuable insights into the thermal behavior of the system.