Industrial Technology Research Institute

Hsia Hao-Chung

Tei-Chih Cheau

Shang-Lin Tsai

A method for separating aluminum, cobalt, and nickel ions contained in a sulfuric acid aqueous solution comprising the steps of (a) contacting a first water-immiscible organic solution containing a first extractant with the sulfuric acid aqueous solution for a period of time to selectively extract the Co ions into the first water-immiscible organic solution so as to obtain a Co-containing first organic phase and a first raffinate aqueous phase containing substantially no Co ions; (b) separating the Co-containing first organic phase from the first raffinate aqueous; (c) contacting a second water-immiscible organic solution containing the first extractant and a second extractant with the first raffinate aqueous solution for a period of time to selectively extract Ni ions into the second water-immiscible organic solution so as to obtain a Ni-containing second organic phase and a second raffinate aqueous phase containing substantially only Al ions; (d) separating the Ni-containing second organic phase from the second raffinate aqueous phase; (e) wherein the said first extractant is dialkyl dithiophosphinic acid or its salt is represented by the following formula: ##STR1## wherein R.sub.1 and R.sub.2 are C.sub.6 to C.sub.18 alkyl radicals; and X is H, NH.sub.4.sup.+, or alkali metal ions; and the second extractant is trialkyl phosphonate is represented by the following formula: ##STR2## wherein R.sub.3, R.sub.4, R.sub.5 are C.sub.3 to C.sub.18 alkyl radicals. The preferred first extractant is bis(2,4,4-trimethyl pentyl) dithiophosphinic acid and the preferred second extractant is dibutylbutyl phosphonate.

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Hsia Hao-Chung