GB814852A - Improvements in or relating to the separation of tellurium from selenium - Google Patents

Abstract

Metal selenide- and telluride-containing material, e.g. copper refinery anode slime, is leached with an aqueous solution of alkali metal hydroxide, in the presence of oxygen at elevated pressure, and at a temperature above the normal b.p. of the solution. Selenium thereby passes into solution leaving a residue of tellurium-containing material. An oxygen pressure of at least 20 p.s.i.g., preferably 60-120 p.s.i.g., a temperature of 150-400 DEG C., preferably 200-250 DEG C., an alkali metal hydroxide concentration of 5-50 per cent, preferably 10-40 per cent, and a leaching time of at least 5 hours, preferably 10-24 hours, may be employed. Hydroxides of lithium, sodium, potassium, rubidium and caesium are specified. Selenium may be recovered from the leach liquor as described in Specification 808,637, or by acidifying e.g. with sulphuric or hydrochloric acid, and treating with sulphur dioxide in the presence of chloride. Tellurium may be recovered from the solid residue in known manner by fusing with alkali and leaching. The residue may first be aerated in dilute sulphuric acid to remove copper. Selenium- and tellurium-containing materials other than copper refinery anode slimes may be treated provided that the selenium and tellurium is first converted to selenide and telluride if it does not already exist as such. Other materials specified are sulphuric acid plant flue dust and lead chamber sludge, and selenium- and tellurium-containing vegetation.