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)<Cd(II)<Cu(II)<Pb(II). Lead (II) ions seemed to be particularly well bound to PAAs (the global stability constant log beta(102) was found to be close to 7.0) and allowed the formation of the predominant PbA(2) species in a quite large pH domain. Finally, the greater stability of PAA complexes compared to those of their monomeric analogs, glutaric and acetic acids, was confirmed.
Morlay
C
C
Laboratoire d'Electrochimie Analytique-LICAS, Université Claude Bernard Lyon 1, CPE, 43 Bvd. du 11 novembre 1918, Villeurbanne Cedex, France. morlay@univ-lyon1.fr
Cromer
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M
Mouginot
Y
Y
Vittori
O
O