Evaluation of the capacity of copper(II) adsorption on surface functional groups of natural materials using carbon paste electrodes

A methodology was developed to evaluate the capacity of heavy metal ions adsorption on particulate samples using carbon paste electrodes. These were prepared by mixing spectroscopic grade graphite powder, the sample and using silicon oil as a binder. Diatomite and compost samples were used as a model of inorganic and organic natural product, respectively. In order to probe the methodology, copper(II) was used as cation model. The protocol involves the in situ monitoring of copper(II) adsorption using temporary open-circuit potential measurements. Copper(II) adsorbed on each sample dispersed in carbon paste was determined in 0.1mol L^-1 Na₂SO₄ by cyclic voltammetry. Functional groups of diatomite and compost responsible of adsorption were determined by Fourier-transform infrared spectroscopy. Besides, adsorption capacity of diatomite was exploited to electrochemical determination of copper(II) by differential pulse anodic stripping voltammetry.