Novel assessment of molten salt oxidation for cation exchange resin treatment: Effective neutralization of sulfurous gas with Li2CO3-Na2CO3-K2CO3 system

The conventional thermal treatment of cation exchange resin substantially releases sulfurous gases, causing significant equipment corrosion and air pollution. In contrast, the Li₂CO₃-Na₂CO₃-K₂CO₃ as an alkaline molten system effectively neutralizes sulfur gas and mitigates waste gas production inherent in thermal oxidation methods. In the molten salt oxidation process, the volume concentration of SO₂ was reduced by 81.7 % compared to that in the traditional thermal oxidation process, and this method reduces the generation of hazardous gases such as CO, CH₄, and C₂H₆. The integration of online gas mass spectrometry and phase stability diagrams for carbonate and sulfur interception products demonstrate excellent thermodynamic stability during the molten salt oxidation (MSO) process. Moreover, a more accurate assessment of the acid gas neutralization capacity of the molten salt system is provided, and the acid gas neutralization capacity of the Li₂CO₃-Na₂CO₃-K₂CO₃ carbonate system can reach 82.58 % at 800 °C. The predominant contributors to acid gas neutralization are Na₂CO₃ and K₂CO₃, as evidenced by waste salt composition and ternary phase diagrams. The stable presence of Li₂CO₃ throughout the MSO process contributes to the lowering of the melting point of the carbonate system to 393 °C.