Tantalum Carbide Recovering Ammonium Paratungstate,Tantalum

Tantalum, an inactive metal element, symbiosis with niobium, is mainly existed in tantalite, with moderate hardness and full scalability, low coefficient of expansion. Since the tantalum surface will produce stable protective film of Ta₂O₅, thus blocking the continually reaction, and makes that tantalum has a very good corrosion resistance.

Tantalum carbide is based on tungsten carbide alloy composed of cobalt and titanium, its composition is of complexity. Tungsten can be easily recovered in the form of ammonium paratungstate because of the large amount; however, niobium and tantalum with the low levels, therefore only recovered as a general enrichment, so there are a variety of recycling processes have been developed. Zinc Treatment and Molten Sodium Nitrate Enrichment are two of the common methods, the steps seen as following.

Zinc Treatment Method
1. The sintered carbide is decomposed with liquid zinc at 800℃, to break down the bonds of carbide particles and bonds between titanium and cobalt;
2. The decomposition products are carried out vacuum distillation to separate the zinc out which can be recycled;
3. The products after removal of zinc are oxidation and finely grounded, and then go on with alkali treatment and flooding, etc., to make tungsten leaching into the fluid in the form of NaWO₃, thereby ammonium paratungstate is prepared to recycle tungsten;
4. Use sulfuric acid to leach cobalt and titanium, the leaching residue obtained is the tantalum and niobium concentrate, then further separation to recover cobalt and. tantalum.

Molten Sodium Nitrate Enrichment Method
1. The waste carbide together with sodium nitrate are melt processed at the temperature of 700~800℃ to make the carbide decomposition and oxidation;
2. Add water into the melting for leaching out tungsten, thereby preparing ammonium paratungstate to recover tungsten;
3. Filtration, separation the Tungsten-containing solution and residue, and then add hydrochloric acid to leaching out cobalt to recover cobalt;
4. Finally, recover tantalum and niobium concentrate in hydrochloric acid leaching residue thus to recovery of tantalum and niobium.

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