Adsorption of Dissolved Organic Matter with Different Relative Molecular Masses on Inorganic Minerals and Its Influence on Carbamazepine Adsorption Behavior

: In this work, sorption experiments were conducted to understand the adsorption characteristics of dissolved organic matter (DOM) of different relative molecular masses on minerals and the effects of their interaction with PPCPs on the adsorption process. This study chose carbamazepine (CBZ) as the target pollutant, quartz sand as the inorganic mineral, and commercial humic acid (HA) as the DOM. We studied the structural characteristics of HA with different relative molecular masses and the impact of their interaction with CBZ on their adsorption based on dialysis experiments and infrared spectroscopy. It was found that large molecular weight fractions of HA, which contain more hydroxyl, aromatic hydrocarbons, and aliphatic hydrocarbons, were mainly hydrophobic substances, while the smaller fractions, containing more alcohols and carboxyl groups, were mainly hydrophilic substances. The combination of HA and CBZ had two major mechanisms, the combination of amino groups of CBZ and polar functional groups in small molecular weight fractions of HA and hydrophobic interactions between hydrophobic groups and aliphatic or/aromatic compounds in large molecular weight HA. The interaction between CBZ and HA resulted in obvious differences in the adsorption of HA or CBZ. When CBZ does not exist, hydrophobic combinations occurred between HA through the hydrophobic components and quartz sand, which also experienced the exchange coordination reaction with the hydroxyl or carboxyl group of HA. In addition, HA adsorbed the aliphatic and hydrophobic macromolecular components. Quartz sand was used to adsorb the large hydrophobic molecules. When CBZ existed, it adsorbed the small molecular weight fractions of HA. The maximum HA adsorption capacity of quartz sand decreased. CBZ could be adsorbed on quartz sand by hydrophobic interaction, van Edward forces, and polarity interactions in the absence of HA. When adding HA, the adsorption increment of carbamazepine on quartz sand was due to the co-adsorption or accumulation of HA and CBZ after their combination.