Coupling catalytic ozonation and membrane separation: A review

Abstract

Ozonation is an efficient process for oxidation of organic pollutants. This process is effective but it can sometimes generate by-products more toxic than the initial micropollutants. For a better oxidation, an enhanced production of hydroxyl radicals can be obtained through to the use of ozonation catalysts. In order to improve the removal of organic compounds in water, a promising solution relies on the coupling of membrane filtration with catalytic ozonation. Indeed, it allows combining advantages of filtration (possible rejection of colloids, molecules and ions) and advantages of catalytic ozonation (degradation of molecules).Various process configurations were investigated for the ozonation membrane filtration (OMF) and the catalytic ozonation membrane filtration (COMF). Three main types of processes can be defined, with water ozonation occurring before, during or after the membrane filtration, respectively. In the case of simultaneous ozonation and membrane separation, catalysts can be dispersed in the feed or supported on the membrane.The literature about such coupling is not very abundant but some studies were performed, involving mainly organic or ceramic ultrafiltration membranes. Removal of micropollutants and mitigation of membrane fouling have been evidenced.Coupling catalytic ozonation and nanofiltration appears as very promising with both organic and ceramic membranes. Nanofiltration would enable a better selectivity and retention of very small molecules as well as a higher efficiency as contactor for catalytic ozonation.