Adsorption of bentazone herbicide onto mesoporous silica: application to environmental water purification

Within the last few years, the presence of bentazone herbicide has been observed in many water resources. For the first time, removal of bentazone using mesoporous silica was investigated revealing reversible adsorption. The adsorption isotherm was well described using the Freundlich model. The affinity towards bentazone is strongly affected by pH in the range of 2-7, decreasing with the increase of the pH, becoming negligible at the neutrality. Regeneration of the adsorbent was possible, and a recovery as high as 70 % was obtained using CH3OH-NaOH solution. Furthermore, appreciable recovery (47 %) was also obtained using water. Applications on the purification of lake water and wastewaters, both characterized by a significant organic carbon load, spiked with 2 mg L(-1) bentazone were tested, observing removal yields in the range of 61-73 %. Taking advantage of the fast adsorption kinetics observed, an in-flow purification treatment was set-up, with quantitative removal of bentazone from polluted water.