GB785723A - Process of electrolysis of aqueous electrolytes for producing bromine and iodine - Google Patents

Abstract

785,723. Electrolytic production of bromine and iodine. MAKHTSAVEI ISRAEL. April 20, 1955, No. 11450/55. Class 41. Aqueous bromide and iodide solutions are continuously electrolysed without anodic evolution of gas in a cell without a diaphragm between anolyte and catholyte while feeding fresh electrolyte into the electrochemically neutral zone between the anolyte and catholyte. Preferably, the aqueous electrolyte contains magnesium halide as well as an alkali metal bromide or iodide so that part of the cathodic product is magnesium hydroxide. If the electrolyte contains chloride also, the feed of fresh electrolyte and the electrolysis is regulated so as to produce an aqueous solution of bromine or iodine and, if magnesium ions are present, so as to convert the major part of the cathodically formed alkali hydroxide into alkali halide with simultaneous formation of magnesium hydroxide. In the absence of insoluble hydroxide, the current efficiency falls, calcium hydroxide giving a lower efficiency than magnesium hydroxide. The electrolysis may be carried out in a U-tube with electrodes and catholyte and anolyte overflows in the side limbs and an electrolyte supply in the bend, the supply and overflow tubes being provided with cocks. The iodine and bromine produced are recovered by solvent extraction. In the practical embodiment shown, the cell comprises an upright cylindrical vessel 17, a coaxial inner cylindrical chamber 24, a sleeve-shaped cathode 37 between them and an anode 32 within the chamber, a receptacle 22 beneath the anode chamber 24 and an annular passage between them through which the anode chamber communicates with the cathode chamber, anolyte and catholyte drains 42, 43 at substantially the same upper level in the cell and a sediment drain 44 at the bottom of the cell, and an electrolyte feed pipe 40 opening into the receptacle. The anode may be a graphite rod carried by a cap 34 insulated from a tube 31 on the lid 26 of the chamber 24 which is axially displaceable by a rod and nut connection to the cell cover 29. The cell is surrounded by a cooling water jacket having an inlet 19 and an outlet 20.