Effect of preozonation on the adsorption behaviors of NOM on alumina

In order to understand the mechanisms of 'ozone-induced particle destabilization', the effect of preozonation on the adsorption behaviors of natural organic matters (NOM) on alumina (α-Al₂O₃) was investigated. Besides, the characteristic transformation of NOM after ozonation was also evaluated. The results revealed that ozone will destroy the aromatic structures of NOM and increase the content of the acidic functional groups. The SUVA value decreased 25%~35% and the total organic acidity increased 0.3~1.4 mmol · g^-1. The transformation of molecular weight and polarity after ozonation was affected by the characteristics of NOM. The solubility of NOM increased after ozonation at a low organic carbon concentration, which counteracted the enhanced adsorption caused by the increased acidic functional groups. At a high organic carbon concentration, the adsorption capacity of NOM on alumina was enhanced after ozonation. Taking CHA as an example, the adsorbed CHA displayed a well-proportioned spheric aggregates structure. After CHA was oxidized by ozone at a dosage of 2.5 mg · L^-1, the microtopography transformation of CHA was observed. The adsorption height of CHA was decreased prominently, while the coupling among CHA molecules and the surface coverage of mica was increased slightly. The integral microtopography presented a network structure.