LaCl_(3)-KCl熔盐体系物化性质研究

Study on the physicochemical properties of the LaCl_(3)-KCl molten salt system

合理选择熔盐体系在电解法制备稀土金属工业生产过程中至关重要。文中采用阿基米德法、拉筒法和连续变电导池常数法(CVCC)测定了不同配比的LaCl_(3)-KCl熔盐在1073~1223 K下的密度、界面张力和电导率。结果表明,随着温度升高,相同成分的LaCl_(3)-KCl熔盐的密度(ρ)和界面张力(σ)均呈降低趋势,而电导率(κ)逐渐增大;在相同温度下,随着LaCl_(3)含量增加,LaCl_(3)-KCl熔盐的密度和界面张力均逐渐增大,而电导率逐渐减小。通过拟合获得密度、界面张力以及电导率的经验公式分别为ρ=a-b×T×10^(-3)、σ=a-b×T×10^(-3)、κ=A+B×T×10^(-3)+C×T^(2)×10^(-6),明晰了熔盐的物化性质随温度及组分的变化规律,为熔盐电解法制备镧及其镧合金提供科学依据。

Reasonable selection of molten salt systems is crucial in the industrial production process of the rare earth metal industry prepared by electrolysis.The density,surface tension and conductivity of LaCl_(3)-KCl molten salt of different ratios at 1073—1223 K were determined by the Archimedes method,tube pulling method and continuous variable conductivity cell constant method(CVCC).The results show that as the temperature increases,the density(ρ)and interface tension(σ)of the LaCl_(3)-KCl molten salt of the same component decrease,while the conductivity(κ)gradually increases.At the same temperature,with increasing LaCl_(3) content in the molten salt,the density and interfacial tention increase,while the conductivity gradually decreases.The empirical formulas for density,interface tension and conductivity are,ρ=a-b×T×10^(-3),σ=a-b×T×10^(-3),κ=A+B×T×10^(-3)+C×T2×10^(-6),respectively.The change law of the physicochemical properties of molten salt with temperature and components is clarified,which provides a scientific basis for the preparation of lanthanum and its alloys by molten salt electrolysis.