Testing carbon structures for metal-free catalytic/photocatalytic ozonation to remove disinfection by-product formation potential

Abstract

Different graphitic carbon structures were prepared and tested for catalytic and photocatalytic ozonation of the precursors of chlorination disinfection by-products to remove their disinfection formation potential (DBPFP). Commercial graphite was submitted to ball milling and two chemical treatments with ammonium nitrate or potassium oxalate to increase its surface area. Additionally, ozonation in gas phase and liquid phase were used to generate surface oxygen groups in these materials and in commercial graphene. All the carbon samples were tested and compared with commercial graphene oxide in the removal of humic acid solutions. The highest catalytic activity during the catalytic/photocatalytic ozonation of humic acid was observed for commercial graphene, ozonated graphene and for graphene oxide; however, this did not result in high DBPFP removal and the instability of the materials was demonstrated. With a moderate catalytic activity but better stability, ball-milled graphite ozonated in liquid phase, was selected for photocatalytic ozonation of real surface water leading to a high DBPFP removal at the conditions tested (88 % 5-HAAs (haloacetic acids), 70 % 4-THMs (trihalomethanes), 70 % AOX (adsorbable organic halides); conditions: semi-batch experiments; 0.5 L volume; 5 mg L−1 O3; Qg = 10 L h−1; DOC0 = 5 mg L−1; pH = 7.8; 180 min under simulated solar radiation with average irradiance 580 W m−2).