Study on the mechanism of deoxidization and purification for Li2BeF4 molten salt via graphite nanoparticles

Graphite nanoparticles originated from high purity graphite crucible were used for deoxidization and purification of Li2BeF4 molten salt containing a bit of (NH4)2BeF4 under high temperature vacuum condition. And the mechanism of deoxidization and purification via graphite nanoparticles was put forward based on analysis of sample characterization and chemical reaction Gibbs free energy calculation. The morphology, particle size, chemical composition and crystal structure of graphite nanoparticles in Li2BeF4 molten salt were characterized by High Resolution Transmission Electron Microscopy (HRTEM, SAED and EDS). Phase analysis, total oxygen content, full elemental and anion concentration for as-prepared Li2BeF4 products were studied by X-Ray Diffraction (XRD), LECO nitrogen-oxygen analyzer, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Ion Chromatography (IC), respectively. The results of sample characterization showed that graphite nanoparticles in Li2BeF4 molten salt were the poly-crystal round sheet shape with an average diameter of <100 nm. The concentration of total oxygen, sulfur and nickel in as-prepared Li2BeF4 molten salt after treatment were 548 ppm, <0.6 ppm and <0.4 ppm, respectively. Experiment and calculation all showed that SO42− and NO3− could react with carbon at 700 °C. And vacuum degassing play an excellent role in deoxidization and purification for Li2BeF4 molten salt via graphite nanoparticles.