Determination of cadmium in Bentonite clay mineral using a carbon paste electrode

Sodium activated Bentonite, a sodium modified Montmorillonite, was submitted to cadmium sorption from nitrate solutions in order to simulate a cadmium polluted clay mineral. The remaining cadmium concentration in solution was analyzed at equilibrium by means of Differential Pulse Polarography (DPP) in order to calculate the cadmium concentration sorbed by the clay. The cadmium distribution between clay mineral and solution was observed for different concentrations, showing a Freundlich sorption profile. The clay mineral, previously submitted to the cadmium sorption procedure, was included in a carbon paste in order to investigate the cadmium content by voltammetric determination. For cadmium detection in Bentonite, a linear response of the carbon paste electrode (CPE) was observed in the 5 · 10^–5– 1.8 · 10^–4 mol/g range with good reproducibility. Received: 23 July 1998 / Revised: 19 November 1998 / Accepted: 26 November 1998