After crushing and grinding tantalum ore is usually prepared by two steps. Wet process, through the jig, screw machine, washing tank, shaking table with the help of gravity separation of coarse concentrate. Enrichment coefficient is generally 400 to 500. In the dry process, the final concentrate can contain 10-50% Ta2O5 by magnetic separation or electrostatic method.
In the process of preparing tin ore containing tantalum, tantalum is enriched in tin concentrate during gravity separation by gravity separation technique. On rare occasions tantalum minerals are separated from tin concentrates by dry process, and most tantalum is smelted together with tin concentrates and concentrated in smelting furnace slag. The tantalum recovery varies from 40% to 85% depending on the type of ore.
The high tantalum slag containing 8%Ta2O5 is processed into tantalum concentrate by the same method. Because the processing cost of tantalum is mainly determined by the productivity, the slag with lower tantalum content should undergo the pre-enrichment process. For this reason, tin slag is smelted by adding iron, ferric oxide or scrap iron under reduction condition in electric arc furnace, and tantalum is enriched in ferro-alloy in the form of carbide. There are then three ways in which it can be further processed into concentrate.
(1) Iron is leached by inorganic acid (possibly followed by alkaline leaching) and then the carbide of tantalum is converted to an acid-soluble oxide by oxidative roasting.
(2) The ferroalloy is chlorinated in molten NaFeCl, and the mixed chlorides are separated by fractionation.
(3) ferroalloy is remelted with oxidizer added.
30%Ta2O5 was produced by leaching and remelting. Various tantalum concentrates are mainly leached by hydrofluoric acid. The addition of sulfuric acid can increase the recovery of niobium, which is usually present. After leaching, dilute the solution with water and separate the leaching residue. If the leaching slag still contains Nb and Ta, 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 accomplished by solvent extraction with methyl isobutanone. Tantalum and niobium enter the organic phase, and dissolved impurities such as titanium, silicon, iron, and phosphorus remain in the aqueous solution. After phase separation, niobium was extracted by water. After stripping tantalum from the charged tantalum phase with more water, pure tantalum hydroxide can be crystallized by ammonia. Then tantalum hydroxide is forged and burned, or potassium salt is added to crystallize a fluoride complex basin.
Natural and artificial concentrates can also be processed by chlorination of raw materials
