Empirical Evaluation Of Chloride-oxide Melts Electrical Conductivity Via Molar Volume And Electrical Field Strength

Abstract:

Chloride-oxide melts are the possible electrolytes for electrochemical refining of crude lead. The physical-chemical properties are very important for technological process optimization. The specific conductivity of KCl-PbCl2-LiCl and KCl-PbCl2-PbO molten mixtures have been evaluated via molar volume and electrical field strength. The mixtures under investigation contained from 0 to 10 wt. % of PbO and LiCl. At the moment the approaches describing properties of halide melts from one hand and oxide melts from the other hand are very different. There is a need to find some common points for modeling physical properties of halide-oxide melts. The initial point can periodical table of elements. Bockris with co-workers found that influence of different component of molten glasses depends on the valence of cation[1]. They placed all cations into 3 groups. Group 1 contains alkali cations : Li, Na+, K+ . The second one is formed from divalent cations: Mg, 2+Ca2+, Sr2+, Ba2+, M2+n and Fe2+. The third group consists of A3+l and Ti4+ . The most conductive are cations of the first group and the less conductive are cations of third group. The same influence of valence on electrical conductivity of molten chlorides was found by Biltz and Klemm[2]. They divided all molten chlorides on good conductors and bad ones depending on the place of an element at periodic table. The best conductors are alkali and alkaline-earth chlorides. It was found recently that this classification can explained using ionic potential (charge/radius) of cations[3]. It allows dividing all individual molten chlorides into some groups according their ionic potential. Inside every group electrical conductivity can be described as a function of molar volume. For example, electrical conductivity of molten alkali chlorides is lnx = 4,9* exp[-(2747-33724/V)/T] *exp(53,7/V) [1]Where V-molar volume, cubic cm/mol, x -specific conductivity, Sm/cm, T - temperature, K This expression is valid as for pure salts and for some mixtures such as NaCl-KCl, LiCl-NaCl, KCl-CsCl. It is possible to use eq. 1 for alkali chloride mixtures with other salts such as PbCl2 with some additional coefficient. Electrical conductivity can be also evaluated via electrical field strength [4]

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