Potentiometric study of Cd(II) and Pb(II) complexation with two high molecular weight poly(acrylic acids); comparison with Cu(II) and Ni(II).

The cadmium (II) or lead (II) complex formation with two poly(acrylic acids) of high molecular weight (Mw=2.5 x 10(5) and 3 x 10(6)) was investigated in dilute aqueous solution (NaNO(3) 0.1 mol l(-1); 25 degrees C). Potentiometric titrations were carried out to determine the stability constants of the MA and MA(2) complex species formed. Bjerrum's method, modified by Gregor et al. (J. Phys. Chem. 59 (1955) 34-39), for the study of polymeric acids was used. The results were compared to those previously obtained in the same conditions with copper (II) and nickel (II) [1]. It appeared that the two polymers under study present similar binding properties and that the stability constants of the complex species formed increased in the following order, depending on the metal ion: Ni(II)