Tungsten recovery from tungsten ore concentrates by caustic digestion

摘要

Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than about 200 mesh, dispersing the comminuted ore to separate agglomerated particles, adding the dispersed ore to aqueous sodium hydroxide at a concentration of at least 10 molar and digesting at a temperature of from about 75 DEG C. to 150 DEG C. for a sufficient period of time to convert substantially all of the tungsten values to soluble sodium tungstate, and diluting the mixture to reduce the sodium hydroxide concentration to between about 4.5 and 5.5 molar at a temperature below about 90 degrees centigrade to substantially dissolve all of the sodium tungstate.