Patent GB-458679-A (GB)
Title: Improvements relating to the treatment of metals or alloys for the separation or recovery of metallic impurities or constituents
IPC: C22B13/06
Filed: 1935-06-18
Abstract: Tellurium is recovered from lead and lead alloys by treating the molten metal with molten caustic soda, with or without sodium chloride, in the presence of air and/or suitable oxidizer such as sodium nitrate and then treating the caustic reagent containing the tellurium with water or weak caustic soda solution and finally removing the tellurium from the solution.  The tellurium may be precipitated by adding a reducing agent such as finely powdered tin or stannous chloride which reduces the sodium tellurite present. When treating lead alloys containing arsenic and/or tin, the arsenic &c. is converted into sodium arsenate and/or sodium stannate which reduces the sodium tellurite to sodium telluride which in turn in reduced to tellurium by treatment with the water &c.  If the alloy also contains antimonate, the precipitate of sodium antimonate and tellurium is filtered off, dried and roasted in air, tellurium oxide being produced.  The mixture as then lixiviated with caustic soda, sodium tellurite being produced.  The insoluble sodium antimonate is filtered off and the tellurium precipitated from the filtrate by a reducing agent as stated above.  Specifications 142,398, 184,639, and 189,013, [all in Class 82 (i)] are referred to.ALSO:Tellurium is recovered from lead and lead alloys containing antimony, arsenic, or tin, by treating the molten lead &c. with molten caustic soda, with or without sodium chloride, in the presence of air and/or suitable oxidizer such as sodium nitrate, and then treating the caustic reagent containing the tellurium as sodium-tellurium compound with water or weak caustic soda solution, and finally removing the tellurium from the solution. The molten lead is preferably treated by circulating it through a bath of the caustic reagent.  The tellurium may be precipitated from the solution by adding a reducing agent such as finely powdered tin or stannous chloride, which reduces the sodium tellurite present.  When treating lead alloys containing also arsenic and/or tin, the arsenic and/or tin are converted into sodium arsenate and/or stannate which reduce the sodium tellurite to sodium telluride which in turn is reduced to tellurium by the treatment with water &c. If the alloy also contains antimony, the sodium antimonate is produced and this acts as an oxidizing agent, but as it is insoluble it is mixed with tellurium.  To separate the tellurium, the precipitate is filtered off, dried and roasted in air, tellurium oxide being produced.  The mixture is then lixiviated with caustic soda, the tellurium oxide being dissolved in the form of sodium tellurite.  The insoluble sodium antimonate is removed by filtration or other means and the tellurium precipitated from the filtrate, with finely divided tin or stannous chloride.  Any antimony still remaining in the lead may be extracted by circulating the lead in the caustic reagent, using sodium nitrate as the oxidizing agent. Specifications 142,398, 184,639, and 189,013, [all in Class 82], are referred to.