Continuous extraction of vanadium(V) and iron(III) with acetylacetone under high-speed stirring with Teflon phase separator.

Abstract

A continuous extraction system consisting of a distillation flask, an extraction flask (Morton flask) containing a high speed stirrer and a Teflon phase separator was investigated. The utility of the system was examined by the separation and concentration of V(V) and Fe(III) with acetylacetone(AA).m-Xylene was selected as the extraction solvent because distillation took place at about 140°C. Fe(III) was easily extracted into the organic solvent with AA. On the other hand, V(V) was not extracted with AA without adding pentyl alcohol. Therefore, V(V) was extracted by the synergism between AA and pentyl alcohol. The effect of stirring speed was examined on the extractions of V(V) and Fe(III). The recommended procedure for the stepwise determination of V(V) and Fe(III) was as follows: A solvent mixture ofm-xylene (15 cm3)and AA(1 cm3) was added to the sample solution (50 cm3, pH 4) containing Fe(III) and V(V) in the Morton flask (200cm3) containing a stirring rod and a Teflon phase separator. The stirring speed was kept at 1800 rpm. The rate of solvent-transport by the Peristaltic pump was regulated at 1.6 cm3/min. The extraction was stopped after 30 min and the distillation flask containing the concentrate for Fe(III) analysis was removed. The distillation flask in the extraction-apparatus was then exchanged and 1 cm3 of pentyl alcohol and 0.5 cm3 of AA were added to the extraction solvent in the Morton flask. Subsequently, 1 cm3 of 8 mol dm-3 HCl solution was added in order to adjust the pH to 2.5. The extraction was then performed again. After 60 min, the absorbance of the concentrated extract was measured at 449 nm after dilution to 10 cm3 with m-xylene. Similarly, the amount of Fe(III) in the previous flask was determined at 437 nm. The metal ions were quantitatively extracted by the proposed method. The extractability of V(V) by this batch method was 63%. The determination ranges of V(V) and Fe(III) were 20100 μg and 1080 μg, respectively.