The main process of tantalum smelting is to decompose concentrate, purify and separate tantalum and niobium to make the pure compounds of tantalum and niobium, and finally make the metal.
Hydrofluoric acid decomposition, sodium hydroxide melting and chlorination can be used to decompose the ore. The separation of tantalum and niobium can be achieved by solvent extraction (common extractant is methyl isobutyl copper (MIBK), tributyl phosphate (TBP), sec-octanol and acetamide), step crystallization and ion exchange.
Separation: firstly, hydrofluoric acid and sulfuric acid are used to decompose tantalum and niobium in the concentrate of tantalum niobium iron ore by using hydrofluoric acid and sulfuric acid. At the same time, associated elements such as iron, manganese, titanium, tungsten and silicon are also dissolved in the leaching solution, forming a strong acidic solution with very complex composition. Tantalum niobium leaching solution was extracted with methyl isobutyl ketone and extracted into the organic phase at the same time. The impurities in the organic phase were washed with sulfuric acid solution, and the pure tantalum-niobium containing organic phase wash solution and extractum were obtained. The pure tantalum-niobium organic phase was extracted by dilute sulfuric acid solution. Niobium and a small amount of tantalum enter the aqueous phase and then extract the tantalum with methyl isobutyl ketone to obtain the pure niobium containing solution. The pure tantalum containing solution can be obtained by reverse extraction with water. The organic phase return after backextraction of tantalum was used for recycling. Pure flutantalate solution or pure fluniobium acid solution reacted with potassium fluoride or potassium chloride to form potassium flutantalate (K2TaF7) and potassium fluniobate (K2NbF7) crystals, respectively, and can also react with ammonium hydroxide to form tantalum hydroxide or niobium hydroxide precipitate. Tantalum and niobium hydroxide under 900 ~ 1000 ℃ calcination of tantalum and niobium oxide.
Metal tantalum powder can be prepared by metal hot reduction (sodium hot reduction) method. Under inert atmosphere with reduced metal sodium fluoride tantalum acid potassium: K2TaF7 + 5 na ─ and Ta + 5 + 2 kf naf. Reaction was carried out in stainless steel tank, when heated to a temperature of 900 ℃, reduction reaction quickly completed. The tantalum powder produced by this method is irregular in shape and fine in grain size, which is suitable for making tantalum capacitors. Metal tantalum powder can also be by molten salt electrolysis legal system: with tantalum acid potassium fluoride, potassium fluoride and potassium chloride mixture of molten salt electrolyte the tantalum pentoxide (Ta2O5) dissolved, electrolysis under 750 ℃ and 99.8 ~ 99.9% purity tantalum powder can be obtained.
