In this paper the mass transfer behaviors of Fe(Ⅲ)

Co(Ⅱ) and Ni(Ⅱ) with Cyanex302(bis(2

4

4- trimethylpentyl)monothiophosphinic acid) from sulfate medium by using hollow fiber membrane in counter-currently circulating operation were studied. The effect of acidity in aqueous solution and the extractant concentration on the mass transfer coefficient (Kw) was discussed. The reaction mechanism of membrane extraction was considered as a false one series reaCtion and the rate controlling step was membrane resistance. When the value of Kw arrived at 1.0 × 10-6 m/s

△pH:CoFe equaled tO 6.225

and △pH:NiFe was bigger than △p HCoFe.