Process for making potassium ferrate Fe(VI)! by the electrochemical formation of sodium ferrate

摘要

Described is a process for making potassium ferrate by the formation of sodium ferrate in a membrane-type electrolysis cell. The anolyte chamber of the cell is charged with an aqueous solution of sodium hydroxide and a sodium ferrate-stabilizing proportion of at least one sodium halide salt. The anolyte chamber additionally contains ferric ions Fe(III)!. The catholyte chamber contains an aqueous sodium hydroxide solution. The source of ferric ion in the anolyte may be either an iron- containing anode or at least one iron-containing compound present in the anolyte solution or both. The preferred membrane material for separating the anolyte chamber from the catholyte chamber is comprised of a gas- and hydraulic-impermeable, ionically-conductive, chemically-stable ionomeric film (e.g., a cation-exchange membrane) with carboxylic, sulfonic or other inorganic exchange sites. Sodium ferrate is prepared in the anolyte chamber by passing an electric current and impressing a voltage between the anode and cathode of the cell. During electrolysis, sodium ferrate forms in the aqueous sodium hydroxide anolyte. This anolyte is reacted with a potassium compound to product potassium ferrate Fe(VI)!. Alternatively, the sodium ferrate may be first recovered in a solid form and then reacted with a potassium compound to produce potassium ferrate.