Membrane electrodes for studying the interaction of humic acids with heavymetals: Cu(II), Pb(II), Cd(II), and U(VI)

A new strategy for studying the incorporation process of metal cations in h umic acids, based on the use of membrane-carbon electrodes is described. Hu mic acids (HA) are entrapped between the membrane and the carbon surface, w hile freely diffusing cations are present in the electrochemical cell. In a first part, the response of the membrane electrode is characterized in the case of Ru(NH3)(6)(3+) as a cation model. Voltammetric responses are evalu ated with respect to several experimental factors such as HA concentration and pH. The efficiency of membrane HA-modified electrode is then evaluated by studying the accumulation of UO22+ at pH 5.1. The effect of clay within the HA-filling on the incorporation of UO22+ is also examined. The extend o f the incorporation of Tl+, Pb2+, Cd2+, Cu2+, Cu(NH3)(4)(2+), and of methyl viologen, an organic cation of environment involvement is investigated. The interest of the membrane HA-modified electrode to get insights into the in teraction of humic substances with metal cations is demonstrated.