GB661946A - Improvements in or relating to the separation and/or recovery of vanadium and aluminium compounds - Google Patents

Abstract

Vanadium and aluminium are removed from solutions containing alkali metal chromates and aluminates and a minor proportion of alkali metal vanadates by adding a lead compound, e.g. the oxide, hydroxide, sulphate, basic sulphate, nitrate, chloride, or acetate, and simultaneously or subsequently bringing the pH to 8-9, to co-precipitate the alumina, and substantially all the vanadate ion and a little of the chromate ion as their lead salts, and removing the precipitate from the solution. The process finds application in the extraction of chrome ores as disclosed in Specification 661,945, the "raw liquor" being treated as above described. The alumina-lead chromate-vanadate precipitate may be discarded, or treated with sulphuric acid to produce lead sulphate and an impure aluminium sulphate solution. Alternatively, it may be dissolved in 50 per cent caustic soda solution, and treated with sodium, calcium, barium, &c. or hydrogen sulphide to reduce the chromate and to precipitate lead sulphide. The vanadium-containing sodium aluminate solution is purified by treatment with barium halide (chloride) or sulphate or hydroxide to precipitate a barium vanadium complex. The chromic hydroxide-lead sulphide precipitate from the previous operation is treated with sulphuric acid to produce lead sulphate and hydrogen sulphide for reuse, and chromic sulphate solution.