Comparison of different solid adsorbents for the removal of mobile pesticides from aqueous solutions

The intensive use of mobile plant protection products, such as bentazon, clopyralid and isoproturon, in agriculture has led to an increasing contamination of groundwater and surface water. In this study, the sorption capacity of various activated carbon samples, metal–organic frameworks (MOFs) and resins were compared. After an initial screening the activated carbon samples and the activated carbon related resin Lewatit AF 5 were selected to characterize the total sorption dynamics. Based on the Freundlich isotherms, the zeolites and MOFs performed well because of their more rapid adsorption of a large amount of pesticides and the lower affinity for the pesticides in view of regeneration. On the other hand, the Temkin model showed physisorption for all adsorbents. Finally, the unstable structure of MOF-235, of which FeCl_4^ - -ions were split off when it comes into contact with a liquid, excluded regeneration of this material.