Current state and future possibilities for niobium extraction via hydrometallurgy
As one of critical materials in modern industry,niobium(Nb)has exceptional properties like resistance to high temperature and corrosion as well as superconductivity.Hydrometallurgical treatments are the mainly adopted technique to produce niobium product with purity of above 99.5%.Being able to dissolve approximately 90%Nb ores,however,HF only suits the high-grade.In industry,HF-H2SO4 binary system is widely adopted.When leaching Nb ores using H2SO4,careful controls of H2SO4concentration and gangues bearing silicium and calcium are essential.Despite the decreased use of HF in the presence of carboxylic acid,its effect in dissolving Nb ores directly is unsatisfactory.Alkaline dissolution using potassium and sodium salts as leachants or fluxes is capable to treat low grade Nb ores.However,its application is limited by the large consumption of alkaline agent and severe equipment corrosion.Sub-molten salt leaching could overcome these drawbacks thus exhibiting promising potential to tackle low grade Nb ores.For extracting Nb from leaching solution,MIBK,TBP,CHO and 2-OCL are four types of commercialized extractants,while they have several disadvantages,referring to dependence on HF,great mass loss and low adoptability to impurities.Though modest concentration having attracted in Nb recovery,ion exchange is a promising technique to extract Nb from leaching solution.Precipitation along with calcination are commonly employed to treat Nb-enriched solution,nevertheless,the quality of final production is low due to the poor selectivity during this procedure.From future perspectives,worthy efforts should be devoted to developing combined treatments consisting of separation-smelting as well as pyrometallurgy-hydrometallurgy.It is also recommended to study the kinetics and ascertain the controlling steps during dissolution and leaching procedures.For low grade Nb leaching solutions,extraction strategies with high efficiency,low energy consumption and high selectivity are expected.
Nb oreslow gradehydrometallurgyextractioncombined process
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