GB548853A - Improvements in the manufacture of aluminium hydroxide - Google Patents

Abstract

548,853. Aluminium hydroxide. ROGERS, F. H. (Antonoff, G.). Jan. 20, 1942, No. 827. [Class 41] Aluminium hydroxide is electrolytically prepared from clays, kaolin, or like silicates in a cell having the anode chamber or chambers separated from the cathode chamber by a permeable diaphragm of perforated india rubber or the like. The finely ground silicates are introduced as a slurry into the anode chamber of the cell which contains water made conducting by sulphuric acid or sodium sulphate and are maintained as a suspension by agitation, a small quantity of sodium fluoride being introduced into this chamber. As the result of the electrolysis sodium and aluminium hydroxides are produced in the cathode chamber and silica, which it is necessary to remove continuously, as a precipitate in the anode chamber. The cell shown in Fig. 1 comprises an anode chamber 1 formed of inert material with permeable (e.g. perforated india rubber) diaphragms 2 and surrounded by the cathode chamber 3, the carbon, lead, or other anodes 4 and cathodes 5 being disposed in parallel relationship. Circulation of the anolyte is maintained by a pump 6 fed through a conduit 7, the liquid passing through one or other of the filters or separators 8 and returning by conduit 9, separated silica &c. being removed through pipes 12. Similar circulating means and separators are provided for the catholyte, to remove precipitated aluminium hydroxide after treatment with CO2 in one of the vessels 18 ; in this instance, however, the filtrate is returned to the anode chamber through pipe 17. Fig. 2 shows a modified form of cell provided with two anode chambers and a single cathode compartment.