Voltammetric methods for distinguishing between dissolved and particulate metal ion concentrations in the presence of hydrous oxides. A case study on lead(II)

Abstract

Voltammetric techniques (differential pulse polarography, DPP, anodic stripping voltammetry, ASV, and differential pulse anodic stripping voltammetry, DPASV) were evaluated for their capability to distinguish between dissolved and particulate Pb(II) concentrations. Colloids of FeOOH, MnO<sub>2</sub>, and SiO<sub>2</sub> were found to have no effect on the electrochemical reversibility (peak width, peak potential, and pseudopolarographic half-wave potential) of the Pb(II) reduction system. Soluble Pb(II) concentrations measured in the presence of colloids were consistent and independent of the voltammetric method used and the different time scales employed in these techniques. Equilibrium constants for the specific adsorption of Pb<sup>2+</sup> on FeOOH, MnO<sub>2</sub>, and SiO<sub>2</sub> surfaces were determined. Applicability of voltammetric techniques to other metals and in the presence of other colloids and in natural waters is discussed.