Source of waste tantalum recovery
Tantalum resources are few and expensive, so the utilization of secondary resources has special significance. The secondary resources of niobium and tantalum include two parts: one part is the waste generated in the smelting and processing of tantalum and niobium products, and the other part is the discarded components of tantalum and niobium products in the process of use. At present, the tantalum recovered from secondary resources accounts for about 15% to 20% of the tantalum raw materials.
According to the form of waste, tantalum niobium waste is mainly divided into pure metal, compound and alloy three categories. The pure metal waste is generally recovered by vacuum melting, electron beam melting and hydrogenation pulverization after chemical cleaning. Various recycling processes have been developed for the variety and complexity of compounds and alloys.
Tantalum containing carbide recovery
Tantalum-containing cemented carbide is an alloy composed of tungsten carbide as the basic composite carbide (WC-TiC-TaC-NbC) and titanium cobalt, with complex composition, tantalum niobium content is low, and is generally only recovered as enrichment.
1, zinc treatment
Sintered carbide is first decomposed with liquid zinc at 800℃ to break the bond between carbide particles and metal titanium and cobalt. The decomposition is then distilled by vacuum to separate zinc and recycled. The dezincized product is finely ground and oxidized, and then subjected to alkali treatment and water leaching, etc. Tungsten enters the leaching solution in the form of NaWO3 (from which ammonium paratungstate is prepared), and the detungsten slag is then used to leach cobalt and titanium with sulfuric acid (and then further separate and recover cobalt and titanium from the sulfuric acid solution), and the leaching slag is the tantalum niobium enrichment.
2, sodium nitrate melting enrichment method
The cemented carbide waste is first fused with sodium nitrate at 700 ~ 800 ° C to decompose and oxidize the cemented carbide. The resulting melt is first leached with water to extract tungsten (then extracted tungsten), the filtered slag is leached with hydrochloric acid to extract cobalt (then recovered cobalt), and tantalum and niobium are finally enriched in the hydrochloric acid leach slag. The concentration contains Ta2O5304%, WO31.26% and TiO238.6%.
Tantalum capacitor waste disposal
The recycling of waste tantalum capacitors is more complicated, especially the metal clad liquid tantalum capacitors must first remove the shell by chemical method (electrolysis method, regia acid pickling) or mechanized method, and then deoxidize by sodium reduction or carbon reduction method, and then carry out electron beam melting to obtain tantalum ingots. Resin clad solid tantalum capacitors are first treated with sulfuric acid to remove the plastic shell; For chip capacitors, the wire is not picked out by magnetic separator after grinding, and the plastic is separated by gravity separation method. The remaining anode block is leach tin with sodium hydroxide, dissolve silver with nitric acid, leach manganese with hydrochloric acid, deoxidize with sodium reduction, and then smelting with electron beam furnace to obtain tantalum ingots.