Thermodynamics and Kinetics of Sulfuric Acid Leaching Transformation of Rare Earth Fluoride Molten Salt Electrolysis Slag

In the realm of rare earth element recovery through molten salt electrolysis, the loss of approximately 8% in waste molten salt slag poses significant challenges. Despite the pressing need for effective recycling technologies for rare earth molten salt slag, scant research has addressed this concern, necessitating a novel approach for its treatment. This study investigates the recovery of rare earth elements from fluoride molten salt electrolytic slag utilizing methodologies such as weak magnetic iron separation, sulfuric acid leaching transformation, water leaching, hydrogen fluoride water absorption, and cycle precipitation. The research emphasizes the thermodynamic and kinetic processes involved in sulfuric acid leaching, revealing a strong temperature dependency where increased temperatures elevate the equilibrium constant of the reaction, beneficially impacting the leaching process. The activation energy for the Nd transformation was determined to be 41.57 kJ/mol, indicating that the leaching is primarily controlled by interfacial chemical reactions. Additionally, a correlation was established between particle size and reaction rate, with finer particles enhancing the kinetic process. The study further highlights that increasing sulfuric acid concentration enhances the reaction kinetics, illustrating the potential for optimized rare earth recovery from industrial waste. This work underscores the importance of advancing recycling techniques in the rare earth sector.