Kinetically controlled separation of cadmium(II) from zinc(II) with dithizone in the presence of nitrilotriacetic acid

The extraction rates of cadmium(II) and zinc(II) with dithizone (H(2)dz) in the presence of nitrilotriacetic acid (NTA) were measured, and the possibl e kinetic separation of cadmium(II) from zinc(II) was investigated. Upon th e addition of NTA, the difference in the extraction rate between cadmium(II ) and zinc(II) became large. Based on the observed rate constant under the condition [NTA] = 1 x 10(-2) mol dm(-3), [H(2)dz](org) = 1 x 10(-3) mol dm( -3), and pH = 7.0, the shaking time required for the quantitative separatio n of cadmium(II) from zinc(II) was calculated to be between 326 and 995 s. The experimental results agreed with the prediction, and the quantitative s eparation of cadmium(II) from zinc(II) was performed within the above-menti oned range of shaking times.