Influence factors: workability and metal material chemical composition, hardness, toughness, thermal conductivity, metallographic structure and work hardening ability and other factors. Because of its good chemical, physical and mechanical properties, tantalum has become an important engineering material in chemical industry, electronics and high temperature engineering. After crushing and grinding, tantalum ore is usually prepared through two processes. In wet process, crude concentrate is obtained by gravity separation through jig, screw machine, washing tank and shaking table. The enrichment factor is usually 400 to 500. In the dry process, the final concentrate containing 10-50% Ta2O5 can be obtained by magnetic separation or electrostatic method.
In the process of preparation of tin ore containing tantalum, tantalum is enriched in tin concentrate by gravity separation technology. In rare cases, tantalum is separated from tin concentrate by dry process, but most tantalum is smelted together with tin concentrate to concentrate in smelting slag. The recovery rate of tantalum varies between 40% and 85% depending on the type of ore.
(1) Leaching of iron with an inorganic acid (possibly followed by alkaline leaching) and conversion of tantalum carbides into acid-soluble oxides by oxidative roasting.
(2) The ferroalloy was chlorinated in molten NaFeCl and the mixed chlorides were separated by fractionation.
(3) Remelting the ferroalloy with oxidant.
An artificial concentrate of up to 30%Ta2O5 was produced through the leaching and remelting processes. Various tantalum concentrates are mainly treated by hydrofluoric acid leaching. The recovery of niobium (which is usually present) can be improved by the addition of sulfuric acid. After leaching, the solution is diluted with water and the leaching residue is separated. If the leached slag still contains tantalum and niobium, it can be returned to the tin smelting slag treatment process for smelting again. The separation of tantalum and niobium from aqueous solution is usually achieved by methyl isobutanone solvent extraction. Tantalum and niobium enter the organic phase, while dissolved impurities such as titanium, silicon, iron, and phosphorus remain in the aqueous solution. After phase separation, niobium was extracted with water. After extracting tantalum from the charged phase with more water, pure tantalum hydroxide can be crystallized by ammonia. The tantalum hydroxide is then calcined or potassium salt is added to crystallize the fluoride compound basin (K2TaF7).
