Polymeric catalytic membrane for ozone treatment of DEET in water

The ozone treatment of N,N-diethyl-meta-toluamide (DEET) in water was carried out in a membrane reactor that uses ozone-resistant polymer membranes for ozone distribution, catalytic contactor and water separation. Iron oxide (ferrihydrite) nanoparticles supported on powdered activated carbon (CAT1) were used as catalyst, and were coated on the surface of the membrane contactor/distributor. Ferrihydrites promote ozone dissolution and transformation to reactive hydroxyl radicals, and accelerate the conversion and mineralization of DEET. The powdered activated carbon helped retain the organic pollutants in the reaction zone leading to greater conversion and deeper mineralization. Consistently, the catalytic membrane contactor/distributor displayed the highest DEET conversion and TOC reduction over the entire studied range of ozone dosage and reaction residence time. The selective removal water by the membrane separator had the desired effect of concentrating the organic pollutants resulting in their improved treatment. The compact membrane reactor unit equipped with catalytic membrane contactor/distributor and membrane water separator outperformed a semi-batch ozone reactor with 60% DEET conversion compared to 20%, and 30% TOC reduction versus 5%.