Removal or modification of pollutants in industrial or mineral-processing wastewaters by electrosorption at high specific-area carbon materials (felts or powders) has been envisaged in previous work. Electrodes based on high-area substrates behave as quasi-three-dimensional interfaces, thus minimizing diffusion limitation in removal of trace impurities in waters. In the present paper, processes of open-circuit adsorption and electrosorption at electrochemically polarized, high-area C-felt electrode modules are quantitatively examined by means of in situ electrical resistance and optical absorbance measurements made in appropriately designed cells. The effectiveness of the procedures is examined by application to the adsorption and electrosorption of a series of related S-containing anions and the kinetics of their adsorption at the C-felt electrodes have also been evaluated in two cases. The adsorbability of such impurity ions is related to their hydration properties in water.