Separation of Tantalum and Columbium by Liquid- Liquid Extraction

This study investigates the effectiveness of four solvent extraction systems for the separation of tantalum and columbium. The objective is to determine the efficiency of various acids in conjunction with different solvents in extracting and purifying these two metals from aqueous feed solutions. Utilizing cyclohexanone, 3-methyl-2-butanone, and 2-pentanone as organic phases, the experiments involved contacting solutions with diverse HF-HCl and HF-H2SO4 concentrations. A notable multistage continuous test was performed using a polyethylene pulse column with cyclohexanone. The results indicated that columbium and tantalum purities exceeded 95% in single-stage tests, particularly under low acidity conditions. Remarkably, separation factors between 1700 and 2400 were achieved using HF-HCl mixtures, while an impressive separation factor over 6000 was recorded with a 2 N HF and 2 N H2SO4 mixture when 2-pentanone was employed. High efficiency was confirmed as 99.9% of tantalum and 98.2% of columbium were recovered in the organic phase at elevated acid concentrations. This solvent extraction approach substantially compares favorably to existing industrial methods, highlighting its potential for practical application in the extraction and separation of these metals.