Stripping of Zn(II), Cu(II), Co(II), and Cd(II) from DEHPA using EDTA in ahollow-fiber membrane module

The equilibrium behavior of liquid-liquid extraction of Zn(II), Cu(II), Co( II), and Cd(II) from DEHPA (di(2-ethylhexyl)phosphoric acid) with EDTA (eth ylenediamine-tetraacetic acid) was studied. A concentration of 0.003M EDTA was able to extract simultaneously 83, 70, 88 and 54% of the cadmium, cobal t, copper and zinc, respectively at a pH between 1.6 and 1.8. The non-equilibrium liquid-liquid extraction behavior was studied using a p olysulfonic hollow fiber membrane module with 1 mm ID and 5,000 molecular w eight cut-off. The aqueous feed solution and EDTA was passed through the tu beside of the two membrane modules, and the organic DEHPA solution was circ ulated through the shellside. The optimum flow rate for the organic solutio n was 77ml/min and that of the aqueous feed and strip solutions were 78ml/m in. The shellside pressure was maintained at 1.0-1.2 psig and that of the t ubeside was kept at atmospheric pressure so that a stable organic interface was achieved. Under these conditions, 77, 63, 93, and 56% of cadmium, coba lt, copper and zinc were extracted from DEHPA, respectively.