Hongyan Sun, Huasen Lin, Jianmin Shi, Zhiqing Kuang
The efficient removal of natural organic matter (NOM) through a coagulation process is crucial for improving the quality of drinking water. Recent studies have focused on the interaction between NOM and coagulants during the floc formation and aging process. Therefore, based on the relevant literature from the past few decades, this review focuses on changes in floc activity during floc formation and aging at a molecular level. It systematically clarifies the mechanisms and factors influencing floc formation and aging and summarizes the characterization techniques for NOM and flocs. Notably, the interaction between NOM and coagulant flocs is determined by the presence of carboxyl groups and hydroxyl groups on NOM and hydroxyl groups (η-OH) and water molecules (η-OH2) on coagulant flocs. Aging involves the transformation of coagulant species and an increase in floc crystallinity, which leads to the absorption or release of organic matter. Although numerous analytical techniques currently offer new insights into the interaction between coagulants and NOM, in situ characterization techniques remain limited. This review provides a theoretical foundation for the full life cycle assessment of NOM in coagulation processes, which is of great significance for advancing drinking water technologies and achieving carbon neutrality goals.