Process for the production of alkali metal hydroxides and elemental sulfur from sulfur-containing alkali-metal salts

Abstract

A process for the production of alkali metal hydroxides, such as caustic soda, and elemental sulfur, characterized in that to an electrochemical cell an aqueous solution of an alkali metal sulfide, e.g., sodium sulfide, is fed in order to cause the following reactions to take place: at the anode Na.sub.2 S.fwdarw.2Na.sup.+ +S+2e.sup.- at the cathode 2H.sub.2 O+2e.sup.- .fwdarw.2OH.sup.- +H.sub.2 with the overall reaction being thus the following: Na.sub.2 S+2H.sub.2 O.fwdarw.2NaOH+S+H.sub.2. Elemental sulfur, which is insoluble, is recovered from the anodic solution by filtration. The NaOH solution is extracted from the cathodic compartment by the addition of water. The concentration of the solution of alkali metal hydroxide obtained is a function of the characteristics of the membrane used. The standard potential of the anodic reaction: S.sup.2- -2e=S.sup.0 is lower than of the corresponding processes which led to the development of gases (Cl.sub.2, O.sub.2), thereby an adavantageous decrease in cell voltage being made possible.

Dependencies are inferred from the claim text.