Evaluation of phosphate thermodynamic properties for spent electrolyte recycle

Kofuji, Hirohide  ; Amamoto, Ippei; Yasumoto, Masaru*; Sasaki, Kazuya*; Myochin, Munetaka; Terai, Takayuki*

Adaptation of the phosphate conversion technique was undertaken and evaluated for application to the recycle process of the spent electrolyte generated from metal electrorefining process which is a kind of pyrochemical reprocessing technologies. The conceptual flow sheet has been discussed based on the thermodynamic properties of constituent. However few data have been published relating to the phosphate, therefore, the thermodynamic data were attempted to be obtained by the calorimetry and vapor pressure measurements. The measurements have been started with pure substance such as lithium phosphate. Through the measurements of HTMS and TG-DTA, it was clarified that decomposition or phase transition of LiPO occurred at specific temperatures below the melting point of LiPO. To avoid the influence of fragment substances which have high vapour pressures, improved method of the HTMS measurement was examined.