Process For Recovering Alkali Metals and Sulfur From Alkali Metal Sulfides and Polysulfides

摘要

Alkali metals and sulfur may be recovered from alkali polysulfides in an electrolytic process that utilizes an electrolytic cell having an alkali ion conductive membrane. An anolyte solution includes an alkali polysulfide and a solvent that dissolves elemental sulfur. A catholyte solution includes alkali metal ions and a catholyte solvent. Applying an electric current oxidizes sulfur in the anolyte compartment, causes alkali metal ions to pass through the alkali ion conductive membrane to the catholyte compartment, and reduces the alkali metal ions in the catholyte compartment. Sulfur is recovered by removing and cooling a portion of the anolyte solution to precipitate solid phase sulfur. Operating the cell at low temperature causes elemental alkali metal to plate onto the cathode. The cathode may be removed to recover the alkali metal in batch mode or configured as a flexible band to continuously loop outside the catholyte compartment to remove the alkali metal.