Fig. 3. Free energy of formation of selected fluorides as a function of temperature. Figure 1 shows a schematic flow diagram of the proposed process for extracting desirable metals from lunar ores; it also produces oxygen for life support and for use as propellants. 6. BIPOLAR ELECTROLYTIC CELLS In the proposed system, either unbeneficiated or mechanically beneficiated lunar dust would be used as ore. The fine particle size of the dust makes magnetic and electrostatic separation attractive. No grinding is necessary. All use of water would be avoided. The ore would be fed into a bipolar cell having a cryolite (Na3AlF(i) base electrolyte. Lunar ore should dissolve easily in molten cryolite. The solubility in cryolite and the decomposition potentials of the various oxides in lunar ores are shown in Table 1. The proposed biopolar cell would be similar to that used in the Alcoa Smelting Process for electrolysis of aluminum from-aluminum chloride in molten chloroaluminate melts (Figure 2). Electric current would enter the cell through a terminal anode, flow through numerous bipolar plates between the terminal electrodes and exit through a terminal cathode. The top surface of each bipolar plate would act as a
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