Leaching process and kinetics of niobium-tantalum concentrate by HF-H2SO4 mixed acid
As rare precious metals,niobium and tantalum are widely used in the fields of high-precision instruments and military equipment due to their excellent physical and stable chemical properties.China is rich in niobium and tantalum resources,most of which are associated deposits that coexist with various metal minerals and have high comprehensive utilization value.In response to the separation and recovery of uranium,thorium,and rare earth resources in niobium and tantalum concentrates,the HF-H2SO4 mixed acid method is used to preferentially extract niobium and tantalum,while enriching uranium,thorium,and rare earth in the slag.In this research,the one-factor experimental design is applied to study the leaching behavior of niobium and tantalum,meanwhile,the process mechanism and kinetics are discussed.The results show that using high concentration hydrofluoric acid,increasing the amount of hydrofluoric acid and sulfuric acid is beneficial for the leaching rate of niobium and tantalum.Reducing the ore particle size,increasing temperature,and extending leaching time all has favorable effect on the leaching rate of niobium and tantalum.The optimal leaching conditions obtained are as follows:40wt％HF 1120 g/kg,H2SO4 392 g/kg,average particle size-25 μm(75％),leaching temperature 80 ℃,and leaching time 4 h.In which the leaching rate of niobium is greater than 98％,and that of tantalum is greater than 97％.Uranium,thorium,and rare earth are retained in the slag,and the enrichment rate in the slag reaches 3.0 to 4.2.The kinetic research has shown that the leaching process of tantalum and niobium conforms to the shrinkage core model and belongs to the chemistry and diffusion mixed control.The apparent activation energy of Nb obtained from the experiment is 34.00 kJ/mol,and that of Ta is 36.26 kJ/mol.This method effectively extracted niobium-tantalum and enriched the other valuable elements,which build the foundation for the design of the separation and purification process.
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