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

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Spent radioactive ion exchange resin poses a significant challenge for the nuclear industry and clean energy sectors.
• Effective management strategies are urgently needed to address radioactive waste disposal.

Purpose of the Study:

• To investigate the co-pyrolysis of mixed ion exchange resin and manganese dioxide.
• To evaluate the catalytic effect of manganese dioxide on the decomposition of radioactive resin.
• To understand the reaction mechanism and optimize the process for waste management.

Main Methods:

• Co-pyrolysis of mixed resin (sulfonic acid and quaternary ammonium polystyrene beads) with manganese dioxide in an argon atmosphere using a tube furnace.
• Thermogravimetric Analysis (TGA) to study decomposition behavior.
• Fourier-Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) for chemical analysis.
• Scanning Electron Microscopy (SEM) for morphological analysis.
• X-ray Diffraction (XRD) to identify phase transformations.

Main Results:

• A low mass remaining efficiency of 34.14% was achieved at 300°C.
• Manganese dioxide lowered decomposition temperatures by approximately 100°C for functional groups and benzene, and 130°C for the polymer chain.
• FT-IR and XPS revealed bridging effects of manganese sulfonate and sulfide groups.
• SEM indicated depolymerization and reunion processes during co-pyrolysis.
• XRD confirmed the reduction of manganese dioxide (MnO₂→Mn₃O₄→MnO) and formation of manganese sulfide (MnS).

Conclusions:

• Manganese dioxide effectively catalyzes the co-pyrolysis of radioactive ion exchange resin at low temperatures.
• The process significantly reduces the decomposition temperature of the resin.
• A solid-phase reaction mechanism is proposed to explain the catalytic promotion by manganese dioxide.
• This method offers a promising approach for the treatment and management of spent radioactive ion exchange resin.