GB889295A - Improvements in and relating to the refinement of ores - Google Patents

Abstract

In a process for the recovery of molybdenum and tungsten from a molybdenum-contaminated solution containing tungsten and having a pH of at least 8, there is added to the solution at least 170% of the alkali metal sulphide stoichiometrically required to convert the molybdenum to the thiomolybdate complex ion, the solution is digested at at least 80 DEG C. to bring about the conversion, and the solution is acidified to a pH below 2,3 to form insoluble molybdenum trisulphide, which is separated. The alkali metal sulphide may be Na2S, NaHS, K2S or KHS. The starting solution may be one obtained by digesting a molybdenum-containing tungsten ore with an excess of sodium carbonate solution. After the addition of the alkali metal sulphide but prior to the acidification, the silica content of the solution may be lowered by adding alum to form an aluminium hydroxide precipitate which is removed together with silica. After acidification (e.g. with sulphuric acid) and removal of precipitated molybdenum trisulphide, the tungsten may be recovered by extraction with a p water-insoluble organic liquid (e.g. kerosene) containing an amine (e.g. bistridecylamine) which forms a tungstate-amine complex. The organic liquid is washed with water and then contacted with an aqueous ammonia solution to obtain an aqueous solution from which ammonium paratungstate (5[(NH4)20].12 WO3. 5H2O) is crystallized. A list of suitable amines and solvents, and examples of the process are given.