Process for making a calcium/sodium ferrate adduct by the

Abstract

Described is a process for making a calcium/sodium ferrate adduct with sodium ferrate in a divided-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 during operation. 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 material 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 calcium compound to produce a calcium/sodium ferrate adduct. Alternatively the sodium ferrate may be first recovered in a solid form and then reacted with a calcium compound to produce said adduct.