Abstract
A liquid-liquid extraction system consisting of a benzene solution of 5-(4-pyridyl)nonane N-oxide (P
y
NO
x
) and mineral acid solutions has been studied for the extraction of chromium(VI). The optimal conditions for the extraction have been carefully selected from a critical study of the various factors involved, such as the effects of the concentration of the mineral acids, chromium, and the solvent; and the salting and complexing agents. Common anions have little effect on extraction in concentrations up to 0.5 M. Backextraction of the metal can be accomplished by a number of solutions and by water. Extraction of several metals was investigated under optimal conditions for the extraction of chromium. Common base metal ions like iron, aluminum, magnesium, calcium, etc. are not extracted. The mechanism of extraction has been studied by using slope analyses and saturation experiments. The predominant mode of extraction appears to be ionic association with the probable composition of the extracted species being P
y
NO
x
H
+
.HCr
2
O
7
−
, with some additional contribution by benzene. Extraction at a high aqueous to organic ratio has been studied by using an extraction plant with a pulsation column.