VOLTAMMETRIC STUDY OF CADMIUM(II) ION IN THE PRESENCE OF POLYSACCHARIDES

Complex formation of Cd(II) with alginic and polygalacturonic acids is studied by normal pulse (NPP), reverse pulse (RPP), and differential pulse polarography (DPP), as well as by cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Titrations of Cd(II) with partially neutralized alginic or polygalacturonic acids, at different ionic strengths, by DPP and DPASV allow the precise determination of the apparent formation constant K of both systems. The systems appear to be labile on the different time scales of the various techniques. Adsorption of both polysaccharides, and the further induced adsorption of Cd(II), is evidenced clearly by NPP. On the other hand, the induced adsorption of Cd(II) is minimized under the conditions of RPP. The reversibility of the redox couple Cd2+/Cd(Hg) is not strongly affected by the presence of polysaccharides. Dependence of the apparent formation constants on the total ionic strength is reported.