Catalytic Ozonation of Emerging Pollutants in Water in the Presence of MCM-41 and Fe-MCM-41

Abstract

The possibility that the modification of Mobil Composition of Matter No. 41 (MCM-41) by the incorporation of iron in its molecular structure and the loading of the support (iron substituted MCM-41; Fe-MCM-41) with active metals of manganese and cerium improve the removal of the representative organic pollutants (ibuprofen (IBU) and oxalic acid (OA)) in water in a catalytic ozonation process was investigated in this thesis. This study particularly addresses the preparation of modified catalysts, the role of pH and water matrices on the performance and stability of the catalysts, reaction pathways, and kinetics of the catalytic ozonation processes. As for preparation of modified catalysts, Fe-MCM-41 catalysts were effective for the ozonation of OA in water. The molecular framework of the prepared Fe-MCM-41 catalysts were stable up to 1wt% iron content and did not leach iron to the reaction solution during catalytic ozonation processes. High (94%) removal of OA was achieved in the presence of Fe-MCM-41 loaded with manganese and cerium oxides. However, the deposited metals on the Fe-MCM-41 support leached significantly (13-38% of initial concentration) during the processes. Regarding the reaction pathways, it was found out that the degradation of OA predominantly occurred by the reaction with hydroxyl radicals while IBU is mainly degraded by ozone molecule. The pH of reaction solution affected the activity and stability of catalysts for the removal of OA and IBU differently. For degradation of OA, Fe-MCM-41 presented similar catalytic activity in acidic pH conditions (55% removal of OA) with enhanced catalytic activity (14% additional OA removal) in basic pH conditions due to the generation of hydroxyl radicals. For degradation of IBU, the catalyst was very active (74-94% IBU removal) at the pH levels below the pHpzc of the catalyst. However, the catalyst was inactive at pH levels above pHpzc due to the permanent damage in its morphological structure. A modified kinetic model was derived basically by the mass balance of the consumed ozone and degraded total organic carbon. The results of the model were in good agreement with the literature, and it also confirmed the experimental observations.