Reversible Electrosorption of Bentazone on Activated Carbon Cloth

An electrochemical technique has been applied to enhance the removal of a common herbicide (bentazone) from aqueous solutions using an activated carbon cloth as electrode. In open-circuit (OC) conditions, a pH increase reduces the uptake and rate of bentazone adsorption. Also, increasing the oxygen content (i.e., acidic nature) of the carbon cloth causes a decrease in the loading capacity at all pH values. This indicates that adsorption is governed by both dispersive and electrostatic interactions, the extent of which is controlled by the solution pH and the surface functionalization of the adsorbent. Anodic polarization of the carbon cloth noticeably enhances the adsorption of bentazone, the extent depending on the applied current. The electrosorption is promoted via π-π dispersive interactions with the aromatic ring approaching to the carbon surface, although attractive electrostatic interactions between the anionic form of bentazone and the positively charged carbon surface might also occur. Bentazone is desorbed by reversing the polarization to the cathodic side. Hence, the electrochemical technique allows to perfectly control the level of water pollution by pesticides and to regenerate the activated carbon.