Process development for the separation of niobium and tantalum from fluoride medium using trioctyl amine and application of Taguchi's method to optimize solvent extraction parameters

Abstract

Niobium and tantalum have a wide range of application in various industries such as steel and electronic industry. The conventional tributyl phosphate based solvent extraction process for producing pure niobium and tantalum generates solid waste which is a mixture of fluoride with other anions like sulphate, chloride and acetate. This waste has no industrial application and requires effective disposal. The aim of this study is to develop a trioctyl amine (TOA) based solvent extraction process, which eliminates the generation of mixed fluoride waste. Batch experiments were carried out to determine the suitable extraction conditions and effective stripping agents. The developed process involves single stage co-extraction of niobium and tantalum followed by selective stripping of pure niobium. The tantalum rich organic phase is then stripped to obtain pure tantalum. The process parameters were optimized (for obtaining the highest purity of niobium) using Taguchi's method and the significance of each parameter was determined using Analysis of Variance (ANOVA). The optimum organic to aqueous phase volume (O/A) ratio for extraction is 2, TOA concentration in the organic phase is 25% (v/v), and the O/A ratio for stripping is 3. The most important parameter in determining the purity of niobium in the strip solution is TOA concentration in the organic phase (contribution 49.85%), followed by O/A ratio of stripping (contribution 47.20%). The developed process resulted in 98.88% pure niobium and tantalum of 98.08% purity.