Time dependent chlorination of CeO2, La2O3 and Nd2O3 by ZrCl4 dissolved in eutectic LiCl–KCl

• Published in: Journal of radioanalytical and nuclear chemistry Vol. 332; no. 6; pp. 1657 - 1665
• Main Authors: Chamberlain, Jarom, Taunque, Asmat, Simpson, Michael F.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-06-2023; Springer Nature B.V; Springer
• Subjects: Argon; Cerium oxides; Chemical reactions; Chemistry; Chemistry and Materials Science; Chlorination; Diagnostic Radiology; Diffusion layers; Diffusivity; Extreme values; Hadrons; Heavy Ions; Inorganic Chemistry; Lanthanum oxides; Lithium chloride; Molten salt; Molten salts; Nuclear Chemistry; NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Nuclear Physics; Nuclear waste; Physical Chemistry; Potassium chloride; Pyroprocessing; Rare earth oxides; Recycling; Shrinking core model; Solubility; Vapor pressure; Zirconium dioxide; Recycling; Pyroprocessing; Rare earth oxides; Nuclear waste; Molten salt
• ISSN: 0236-5731; 1588-2780
• DOI: 10.1007/s10967-023-08879-4

Partial chlorination of CeO
2
, La
2
O
3
, and Nd
2
O
3
was achieved using ZrCl
4
dissolved in molten LiCl–KCl at 450 °C over a period of 4–5 h. ZrCl
4
was pre-volatilized into an argon stream to maintain a constant vapor pressure for equilibration with the salt. This approach was effective at maintaining the ZrCl
4
concentration at the solubility limit of 1.3 mol% in the molten salt throughout the duration of two of the chlorination experiments and within about 60% of the solubility limit in the third experiment. Based on the analysis of salt samples, fractional conversion after four hours of reaction for CeO
2
, and five hours for La
2
O
3
, and Nd
2
O
3
were calculated to be 0.97, 0.28, and 0.65 respectively. Assuming a shrinking core diffusion-limited model, the diffusivity of ZrCl
4
through the hypothesized ZrO
2
layer was calculated for the chlorination of CeO
2
, La
2
O
3
, and Nd
2
O
3
were 1.76 × 10
–10
cm
2
/sec, 7.85 × 10
–12
cm
2
/sec, and 7.42 × 10
–12
cm
2
/sec, respectively. Given the extremely low values calculated for diffusivity, it was concluded that the process is chemical reaction rate limited and that a complete reaction of each rare earth oxide could be achieved. A chemically controlled shrinking core model was shown to also fit the experimental data closely.