ビス-2-エチルヘキシルアセトアミドによるNb, Taの抽出

Abstract

Extraction of Nb and Ta from acid solutions with bis-2-ethylhexyl acetamide and stripping of these metals with sulphuric acid solutions were investigated. The organic phase was a binary solution of bis-2-ethylhexyl acetamide and xylene, while the aqueous phase was composed of hydrofluoric acid solution or hydrofluoric-sulphuric acid solution containing 3.5-13 kg/m3Nb and 5-10 kg/m3Ta. Sulphuric acid, hydrochloric acid and nitric acid were used as salting out agents to understand the effect on the extraction.Both metals were not sufficiently extracted from hydrofluoric acid solutions, whereas the extraction of both metals remarkably increased with an addition of sulphuric acid to the aqueous phase. The separation factor decreased with an increase in the concentration of hydrofluoric acid at the constant sulphuric acid concentration of 5.8N, and both metals were completely coextracted in the aqueous condition of 6N hydrofluoric acid and 8N sulphuric acid.The stripping occurred for both metals with a high efficiency, when water or dilute sulphuric acid solution was used as a stripping agent. The increase in sulphuric acid concentration caused less stripping of Ta, while the stripping of Nb was maintained at 80% up to 7N sulphuric acid. The separation factor reached the maximum with the value of 116 in the use of 6.5N sulphurtc acid.The extraction behavior of Fe(II), Fe(III), Sn(IV) and Mn(II) was also examined with the results that these metals were not extracted even to the extent of the lowest limit of atomic absorption spectrophotometer. Moreover, the comparison of this extractant with MIBK and TBP, which were in common use, was carried out.