Fe(III)-loaded activated carbon as catalyst to improve omethoate degradation by ozone in water

Omethoate (OMT), a typical organophosphorus pesticide and also an oxidation byproduct of dimethoate, is very difficult to remove from water due to its hydrophilic nature and relatively low reactivity towards ozone. In this work, Fe(III)-loaded activated carbon (Fe@AC) was prepared and used as catalyst to promote OMT degradation by ozone. The catalytic activity of Fe@AC was investigated under various experiment conditions. Results indicate that the OMT removal was significantly enhanced in O₃/Fe@AC through effective generation of hydroxyl radicals (·OH), as compared to ozonation alone and O₃/AC. The Fe(III) deposited on AC mainly existed in the form of ferrihydrite (FHD) particles which provided the main active sites promoting ozone decomposition. The optimal pH ranged from 7.0 to 8.0 for catalytic ozonation, which corresponded to a nearly neutral surface charge of the catalyst. The apparent rate constant of OMT degradation was almost linearly correlated with the aqueous ozone concentration. The acute toxicity of the reaction solution was substantially reduced by catalytic ozonation with Fe@AC.