Recovery of tantalum, niobium and titanium from low grade sources

摘要

Ta, Nb and Ti may be recovered from sources containing less than 10% Ta and Nb materials and up to 90% of Si, Ca, Fe, Al and Ti compounds by reacting with CaF2 in an amount at least stoichiometrically equivalent to the silicon and sufficient H2SO4, of at least 65% concentration, to generate the required amount of HF to remove the silica, heating at between 300 DEG and 500 DEG C. until dryness and continuing the heating until the acid content of the product is less than 9% calculated as H2SO4. Steam may be injected during the heating stage. The product may be leached with water to dissolve Al and Fe salts. During the leaching 10-20% of the liquor may be withdrawn, neutralized to precipitate Ta, Nb and Ti, and returned to the liquor as a seed. The liquor is further boiled to precipitate more Ta, Nb and Ti. The solids recovered may be reacted with HF solution to dissolve Ta, Nb and Ti, the solution filtered, and extracted with an organic solvent. Most of the fluoride used may be recovered.