ADSORPTION STUDIES OF OCTADECYLTRIMETHYL AMMONIUM BROMIDE BY ELECTROCHEMICAL METHODS

The adsorption of octadecyltrimethyl ammonium bromide (ODTABr) at the mercury electrode surface and the influence of the adsorbed layer upon the electrode reduction of cadmium were studied by electrochemical methods. The adsorption processes have been investigated in the presence of electrolytes of different surface activities, namely NaCl and NaClO4. The adsorbed layer of ODTABr on a NaClO4 subphase showed a simple blocking effect by inhibiting the electrode reduction of cadmium. However, accumulation of cadmium in the adsorbed layer of ODTABr has been observed in NaCl solutions and attributed to the adsorption of its uncharged complex species CdCl2 at the electrode surface modified by adsorbed ODTA+Cl- ionic pairs. In comparison with the model, the stability constant of the surface complex (ODTA+Cl--CdCl2)degrees(ads) was estimated to be lambda2 = 1.9 x 10(4) dm3 mol-1.