Co-pyrolysis of spent radioactive ion exchange resin and manganese dioxide: Decrease the decomposition temperatures of functional groups

With the development of the nuclear industry and clean energy, spent radioactive ion exchange resin has become a major concern that needs to be solved urgently. In this study, the mixed resin (sulfonic aid and quaternary ammonium polystyrene beads, 1:2, v/v) is co-pyrolyzed with manganese dioxide in a tube furnace, selecting argon as the reaction atmosphere. Manganese dioxide exhibits unique catalytic and oxidative activity, and a low mass remaining efficiency of 34.14% is obtained under low heating temperature of 300 ℃. The required decomposition temperatures of functional groups and benzene are decreased by approximately 100 ℃, and that of polymer chain is decreased by 130 ℃. The TGA analysis shows the decomposition temperature rule of functional groups and base polymer. The FT-IR spectra and XPS analysis reveal the bridging effects of manganese sulfonate and sulfide group. The SEM diagrams prove that the two processes including depolymerization and reunion could be found in co-pyrolysis. The XRD analysis indicates manganese dioxide undergoes the reduction path of MnO₂→Mn₃O₄→MnO, and MnS is formed with the decomposition of manganese sulfonate. The possible mechanism of solid-phase reaction is proposed to explain the promotion of manganese dioxide on co-pyrolysis.