Potentiometric study of copper(II) and nickel(II) complexation by a cross-linked poly(acrylic acid) gel Original Research Article

Copper(II) or nickel(II) complex formation with an insolubilized cross-linked poly(acrylic acid) was investigated in dilute aqueous solution (0.1 mol l−1 NaNO3; 25°C). Potentiometric titrations were carried out, first to precisely measure the acid–base properties of the polymer, and secondly to determine the stability constants of the MA and MA2 complex species formed. Bjerrum’s method, modified by Gregor et al. (1955) for the study of polymeric acids was used. The results obtained showed that copper(II) was more readily bound to the polymer than nickel(II). For the operative conditions considered here, CuA2 was the predominant observed species; the global stability constant log β102 was found to be 6.6. With nickel(II), neither of the complex species MA or MA2 becomes predominant (log β102 = 5.4). Finally, the results were compared to those obtained previously under the same conditions with two hydrosoluble poly(acrylic acids) (HPAAs) of high molecular weight; it appeared that linear and cross-linked polymers present identical binding properties.