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首页> 外文期刊>Separation and Purification Technology >Niobium and tantalum processing in oxalic-nitric media: Nb2O5 center dot nH(2)O and Ta2O5 center dot nH(2)O precipitation with oxalates and nitrates recycling
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Niobium and tantalum processing in oxalic-nitric media: Nb2O5 center dot nH(2)O and Ta2O5 center dot nH(2)O precipitation with oxalates and nitrates recycling

机译：草脂培养基中的铌和钽加工：Nb2O5中心点NH（2）o和Ta2O5中心点NH（2）o沉淀与草酸盐和硝酸盐回收

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摘要

Oxalate-based aqueous media represent one of the rare options for solubilizing weighable amounts of niobium (Nb) and tantalum (Ta) without using toxic fluoride-based mixtures. Recent progress in the hydrometallurgy of Nb and Ta also highlighted the potential of oxalate-nitrate media for the separation of Nb and Ta. Nonetheless, the resulting purified aqueous solutions, containing Nb or Ta in HNO3-H2C2O4 mixtures, need to be further processed in order to yield Nb and Ta solid products that can be commercialized. Furthermore, oxalic acid is relatively expensive in the frame of the hydrometallurgy of Nb and its recycling can significantly increase the process economy. In this study, the precipitation behavior of Nb, Ta, and their usual minor impurities (Ti and Fe), from oxalic-nitric acid solutions has been investigated for the first time. Neutralization of Nb-HNO3-H2C2O4 mixtures to pH 7-8 by concentrated NaOH or NH4OH was found to be effective in decomposing the oxalate complexes ([NbO(C2O4)(3)](3-) and [NbO(C2O4)(2)(H2O)(2)](-)) and precipitating Nb in the form of amorphous Nb2O5 center dot nH(2)O((S)) while leaving the oxalate and nitrate ions in the filtrates. The same phenomena take place with the Ta-HNO3-H2C2O4 solutions with precipitation of Ta2O5 center dot nH(2)O((s)). Taking advantage of the solubility difference between nitrate and oxalate salts, the subsequent concentration of the nitrate-oxalate filtrates by evaporation yields to the quantitative and selective recovery of the oxalates as crystalline Na2C2O4(s) or (NH4)(2)C2O4 center dot H2O(s) (purity > 95%) and a concentrated solution of sodium or ammonium nitrate. The developed method exhibits high precipitation yields (> 99.9%) for Nb and Ta and high recovery yields (> 99%) for the nitrates and oxalates. The process was optimized at the laboratory scale and then validated on industrial Nb (similar to 10 g/L) and Ta (similar to 400 ppm) solutions with successful production of purified Nb2O5 center dot nH(2)O((s)) (purity of 99.5 wt%) and a Ta2O5 center dot H2O(s) concentrate (> 20 wt% Ta), followed by the recovery and separation of the oxalates and nitrates. Taken together, the proposed precipitation method and the fluoride-free liquid-liquid Nb-Ta separation recently reported pave the way for more sustainable hydrometallurgical processes for Nb and Ta.
机译：基于草酸盐的含水介质代表了在不使用含有毒性氟化物的混合物的情况下溶解可溶解可氧化铌（Nb）和钽（Ta）的罕见选择之一。 Nb和Ta氢晶粒的最新进展也强调了草酸硝酸盐培养基的潜力，用于分离Nb和Ta。尽管如此，需要进一步加工含有Nb或Ta的所得纯化的水溶液，以产生可以商业化的Nb和Ta固体产物。此外，在Nb的氢管框架中，草酸相对昂贵，其再循环可以显着增加工艺经济性。在该研究中，首次研究了来自硝酸溶液的Nb，Ta和通常的少量杂质（Ti和Fe）的沉淀行为。发现通过浓缩的NaOH或NOH4OH的Nb-HNO3-H 2 C 2 O 4混合物与pH 7-8的混合物有效地分解草酸盐络合物（[NbO（C2O4）（3）]（3-）和[NBO（C2O4）（2 ）（H 2 O）（2）]（ - ）），以无定形NB2O5中心点NH（2）O（（S））的形式沉淀Nb，同时将草酸盐和硝酸盐离子留在滤液中。通过TA-HNO3-H2C2O4溶液进行同样的现象，具有TA2O5中心点NH（2）O（（S））的沉淀。利用硝酸盐和草酸盐之间的溶解度差异，通过蒸发的硝酸盐 - 草酸酯滤液的随后浓缩浓缩，得到了草酸盐的定量和选择性恢复，作为结晶Na 2 -O 4或（NH4）（2）C2O4中心点H2O （S）（纯度> 95％）和浓缩钠或硝酸铵溶液。开发的方法表现出Nb的高沉淀产率（> 99.9％），硝酸盐和草酸盐的Nb和Ta和高回收率（> 99％）。该方法在实验室规模进行了优化，然后在工业NB（类似于10g / L）和TA（类似于400ppm）的溶液上进行验证，具有成功生产纯化的Nb2O5中心点NH（2）O（（S））（纯度为99.5wt％）和Ta2O5中心点H2O（S）浓缩物（> 20wt％Ta），然后回收和分离草酸盐和硝酸盐。连同，提出的沉淀方法和无氟液 - 液Nb-Ta分离最近报道了铺平了Nb和Ta的更可持续的液压冶金方法。

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