Preliminary study of the electrolysis of aluminum sulfide in molten salts
A preliminary laboratory-scale study of the electrolysis of aluminum sulfide in molten salts investigated the (1) solubility of Al/sub 2/S/sub 3/ in molten salts, (2) electrochemical behavior of Al/sub 2/S/sub 3/, and (3) electrolysis of Al/sub 2/S/sub 3/ with the determination of current efficiency as a function of current density. The solubility measurements show that MgCl/sub 2/-NaCl-KCl eutectic electrolyte at 1023 K can dissolve up to 3.3 mol % sulfide. The molar ratio of sulfur to aluminum in the eutectic is about one, which suggests that some sulfur remains undissolved, probably in the form of MgS. The experimental data and thermodynamic calculations suggest that Al/sub 2/S/sub 3/ dissolves in the eutectic to form AlS/sup +/ species in solution. Addition of AlCl/sub 3/ to the eutectic enhances the solubility of Al/sub 2/S/sub 3/; the solubility increases with increasing AlCl/sub 3/ concentration. The electrode reaction mechanism for the electrolysis of Al/sub 2/S/sub 3/ was elucidated by using linear sweep voltammetry. The cathodic reduction of aluminum-ion-containing species to aluminum proceeds by a reversible, diffusion-controlled, three-electron reaction. The anodic reaction involves the two-electron discharge of sulfide-ion-containing species, followed by the fast dimerization of sulfur atoms to S/sub 2/. Electrolysis experiments show that Al/sub 2/S/sub 3/ dissolved in molten MgCl/sub 2/-NaCl-KCl eutectic or in eutectic containing AlCl/sub 3/ can be electrolyzed to produce aluminum and sulfur. In the eutectic at 1023 K, the electrolysis can be conducted up to about 300 mA/cm/sup 2/ for the saturation solubility of Al/sub 2/S/sub 3/. Although these preliminary results are promising, additional studies are needed to elucidate many critical operating parameters before the technical potential of the electrolysis can be accurately assessed. 20 figures, 18 tables.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5933436
- Report Number(s):
- ANL/OEPM-83-3; ON: DE83014552
- Country of Publication:
- United States
- Language:
- English
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ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM SULFIDES
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
DATA
DEPOSITION
ELECTRODEPOSITION
ELECTROLYSIS
ELEMENTS
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
INFORMATION
LYSIS
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
METALS
MOLTEN SALTS
NUMERICAL DATA
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
SALTS
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUBILITY
SULFIDES
SULFUR COMPOUNDS
SURFACE COATING
THERMODYNAMICS
VERY HIGH TEMPERATURE
VOLTAMETRY