Patent GB-1119059-A (GB)
Title: Method of obtaining metallic gallium from combustion gases
IPC: B01J27/192
Filed: 1965-07-12
Abstract: In obtaining metallic gallium by electrolysis the solution electrolysed contains sodium gallate or gallium oxide and is obtained by preparing a coal mixture in which, the weight ratio of gallium content in organic gallium compounds to the total gallium content is at least 1:3, the organically combined iron content is at least 50 times by weight the total gallium content, and the moisture content is at least 5% by weight, burning the said coal mixture, dedusting the furnace gases so produced, washing the said gases in an aqueous washing solution or suspension containing an oxidising agent, separating the precipitated solids from the aqueous washing solution or suspension and roasting the said solids with an alkali metal carbonate or bicarbonate in an atmosphere containing free oxygen, ozone, or a mixture of free oxygen and ozone; the roasted solids being then leached with an alkaline solution to which, after removal of insoluble deposits, ammonium sulphate is added to give the desired electrolysis solution. The coal mixture used is preferably provided by a mixture of a coal containing gallium present as organic compounds and a coal containing gallium present as inorganic compounds. Lime water may be added to the solution during leaching and electrolysis to prevent any precipitation of the gallium content by atmospheric CO2.  Electrolysis may be effected using a current density between 80 and 120 amps/sq decimetre and a voltage between 15 and 17 volts.  The preferred roasting temperature is about 400 DEG C.  After separating the precipitated solids, the aqueous washing solution may be distilled, and the fraction distilling below a 100 DEG  C. may be oxidised in alkaline solution and the gallium and iron salt deposit so obtained be leached with an alkaline solution and the gallium content obtained therefrom by known methods.  Gallium oxide may be precipitated from the solution after electrolysis by adding thereto gaseous CO2 or ammonium carbonate the gallium oxide being filtered off and dissolved in an alkaline solution which can then be submitted to electrolysis to produce gallium.  After this electrolysis further gaseous CO2 may be added to the residual electrolyte to precipitate the remaining gallium residues from this electrolyte. These residues together with those insoluble residues left after leaching the roasted solids may be dissolved in sulphuric or hydrochloric acid and a metal which gives positive ions in solution or a salt of such a metal is then added to the solution which is then electrolysed forming a cathodic deposit containing gallium.  Alternatively the deposit which remains after the roasted solids have been leached is dissolved in an alkaline solution to which metallic zinc or a zinc salt is added, the solution is then electrolysed at a current density of 40 to 80 amps/sq decimetre forming a zinc-gallium alloy at the cathode, which alloy may be distilled to obtain gallium.ALSO:In obtaining metallic gallium by electrolysis the solution electrolysed contains sodium gallate or gallium oxide and is obtained by preparing a coal mixture in which, the weight ratio of gallium content in organic gallium compounds to the total gallium content is at least 1:3, the organically combined iron content is at least 50 times by weight the total gallium content, and the moisture content is at least 5% by weight, burning the said coal mixture, dedusting the furnace gases so produced, washing the said gases in an aqueous washing solution or suspension containing an oxidizing agent, separating the precipitated solids from the aqueous washing solution or suspension and roasting the said solids with an alkali metal carbonate or bicarbonate in an atmosphere containing free oxygen, ozone, or a mixture of free oxygen and ozone; the roasted solids being then leached with an alkaline solution to which, after removal of insoluble deposits, ammonium sulphate is added to give the desired electrolysis solution. The coal mixture used is preferably provided by a mixture of a coal containing gallium present as organic compounds and a coal containing gallium present as inorganic compounds.  Lime water may be added to the solution duringl each ing and electrolysis to prevent any precipitation of the gallium content by atmospheric CO2. Electrolysis may be effected using a current density between 80 and 120 amps/sq. decimetre and a voltage between 15 and 17 volts.  The preferred roasting temperature is about 400 DEG  C. After separating the precipitated solids, the aqueous washing solution may be distilled, and the fraction distilling below 100 DEG  C. may be oxidized in alkaline solution and the gallium and iron salt deposit so obtained be leached with an alkaline solution and the gallium content obtained therefrom by known methods. Gallium oxide may be precipitated from the solution after electrolysis by adding thereto gaseous CO2 or ammonium carbonate the gallium oxide being filtered off and dissolved in an alkaline solution which can then be submitted to electrolysis to produce gallium. After this electrolysis further gaseous CO2 may be added to the residual electrolyte to precipitate the remaining gallium residues from this electrolyte.  These residues together with those insoluble residues left after leaching the roasted solids may be dissolved in sulphuric or hydrochloric acid and a metal which gives positive ions in solution or a salt of such a metal is then added to the solution which is then electrolysed forming a cathodic deposit containing gallium.  Alternatively the deposit which remains after the roasted solids have been leached is dissolved in an alkaline solution to which metallic zinc or a zinc salt is added, the solution is then electrolysed at a current density of 40 to 80 amps/sq. decimetre forming a zinc-gallium alloy at the cathode, which alloy may be distilled to obtain gallium.