CO₂ Solubility In LiF-Li₂CO₃-Based Molten Salts System And Physicochemical Properties

Electrolysis of CO2 using LiF-Li2CO3 molten salt system is a important method for comprehensive utilization of CO2.The physicochemical property of LiF-Li2CO3 molten salt system and CO2 solubility in the system has an important effect on the electrolytic process.Therefore,the physicochemical property of LiF-Li2CO3 molten salt system and CO2 solubility in the system were studied.In this paper,the physicochemical properties such as liquidus temperature,density,and conductivity of LiF-Li2CO3 molten salt system was studied,of which the mole fraction of LiF is from 30 to 60%,moreover,the solubility of carbon dioxide in LiF-Li2CO3 molten salt system was also studied.The effects of LiF,temperature and additives on the physicochemical property were discussed.The additives used in the experiments were NaF,KF,NaCI,and KCI,of which the mole fraction were 5-25%.The liquidus temperature of LiF-Li2CO3 molten salt system was measured using cooling curve method.The results indicate that the liquidus temperature of LiF-Li2CO3 system decreases with the content of additives increasing,and the effect of KF on liquidus temperature is greater than that of NaF,whereas the effect of NaCl on liquidus temperature is greater than that of KCl.The eutectic composition of LiF-Li2CO3-NaCl melt is 37.5%:37.5%:25%(molar ratio),and the eutectic temperature of this system is 558.5?.In addition,the eutectic temperature of LiF-Li2CO3-KCl system is 580 0C.The density of LiF-Li2CO3 melts system was measured using the Archimedean method.The results show that density of LiF-Li2CO3 melts decreases with both the content of LiF and temperature increasing,and a linear relation exists between the density and temperature.Increasing of NaF and KF make an increase of the melt density,whereas rising the contents of NaCI and KCl results in an initial increase and subsequent decrease of the melt density.The density is maximum at the mole fraction of NaCl approximately 15%and KCI approximately 10%.The solubility of carbon dioxide in LiF-Li2CO3 molten salt system was studied using pressure differential method.The results show that the solubility of carbon dioxide in LiF-Li2CO3 melt decreases with both the content of LiF and temperature increasing.The carbon dioxide solubility reaches maximum,of which the value is 1.9×10-2 mol/L at 640? when the mole fraction of LiF is 50%.Moreover,the conductivity of the molten system increases with both the mole fraction of LiF and temperature,while decreases with the mole fraction of NaF and KF increasing.