Electrocapillary activity and adsorptive accumulation of U(VI)-cupferron and U(VI)-chloranilic acid complexes on mercury electrode

Interfacial activity of uranium (VI)-cupferron and uranium(VI)-chloranilic acid (CAA) complexes (in 0.1 M acetate buffer pH 4.6 or 0.1 M NaClO4 respectively) on polarized mercury electrode at 110 mV, 10 mV or - 240 mV respectively vs. saturated calomel electrode (SCE), and under conditions of the application of adsorptive stripping voltammetric techniques was studied. It revealed a competitive effect of interfacial activity of the mentioned complexes consisting in a nonmonotonous effect of the bulk concentration of U(VI) on the adsorption of the mentioned complexing reagents at their constant concentrations. At concentrations lower than 5 x 10(-5) mol L-1 the complexes U(VI)-cupferron or U(VI)-CAA exhibited a relatively strong electrosorption providing the adsorption coefficients beta of the order 10(4) L mol(-1), the maximum surface excess Gamma(m) approximate to 5 to 10 mumol m(-2) and average Frumkin interaction coefficients reaching their absolute values 2 to 2.6.