Adsorptive and electrosorptive removal of aniline and bipyridyls from waste-waters

Removal of aniline, 2,2′-bipyridyl, 4,4′-bipyridyl and their protonated cations from dilute aqueous solutions, simulating polluted waste-waters, by adsorption and electrosorption at high-area carbon cloth (C-cloth) electrodes is described. The adsorption behaviour and kinetic parameters for rates of adsorption of these solutes at high-area porous-C electrodes were followed and evaluated in situ by means of UV spectrophotometry. The results obtained show that the above neutral adsorbates have stronger affinity over their protonated cations for the surface of C-cloth electrodes. Polarization of the C-substrate electrodes leads to a great increase in both rates and extents of adsorption for each of the adsorbates investigated but complete adsorptive removal of aniline and 2,2′-bipyridyl was attained only under certain conditions. The extents of adsorptive removal of the adsorbates and the rate-constants for such processes are summarized quantitatively. Polarization electrosorption under slow alternating positive/negative conditions or combination of open-circuit adsorption with polarizing electrosorption procedures dramatically enhanced the extents of adsorption in most cases, leading to complete removal of the adsorbate from solution in each of the cases of aniline, 2,2′-bipyridyl, 4,4′-bipyridyl and their singly protonated cations under various conditions. The latter observation is valuable for the development of methodologies for purification of industrial waste-waters.