Electric field as a useful tool to improve the poor adsorption affinity of pollutants on carbonaceous aerogel pellets

Abstract

The removal of ionisable drugs (fluoxetine, sulfamethizole and antipyrine) from aqueous solution was performed by conventional adsorption using carbonaceous aerogel pellets as adsorbents. Although >96 % elimination was achieved for sulfamethizole and antipyrine after 1440 min, only 2.5 % fluoxetine was removed. In a multicomponent system, the presence of these three drugs in the solution leads to a fivefold depletion of the adsorbed total mass. Thus, the authors proposed to influence the traditional adsorption process by an electric field to improve the low affinity of fluoxetine to the aerogel. Specifically, the electrosorptive removal of fluoxetine was investigated by applying different voltages between 0.8 and 1.3 V, with the maximum adsorption achieved at 1.2 V. The application of an electric field increases the affinity of the contaminants to aerogel pellets. After demonstrating the applicability of the electrosorption in the removal of fluoxetine, the effect of the water matrix on the process was analysed. For this purpose, the removal of these ionisable drugs was evaluated using real wastewater, specifically, raw wastewater and wastewater after primary and tertiary treatment from a municipal wastewater treatment plant. As expected, pollutant removal was somewhat lower due to the complexity of the water matrix. Total percent removal of all pollutants was achieved using only the effluent treated water as the matrix due to minimal competitive adsorption. Finally, the Microtox® test confirmed the excellent ability of this approach to remove these pharmaceuticals, resulting in luminescence inhibition that decreased by 60–80 % depending on the water matrix compared to the polluted influent.