Adsorption behavior of antibiotics with different structures onto vivianite in the presence of dissolved organic matter during the phosphorus recovery process

Formation of vivianite is a promising strategy to recover phosphorus from urban sewage and livestock wastewater, in which both various antibiotics and dissolved organic matters are contained. In this study, the interaction relationship and mechanism between vivianite, antibiotics and DOM were analyzed through the variations of DOM and antibiotics concentrations in supernatant, combined with characterization analysis and theoretical calculation. It’s found that the adsorption of three kinds of antibiotics onto vivianite following the order: tetracycline (TC) (∼90%) > ciprofloxacin (CIP) (∼15%) > sulfamethoxazole (SMX) (∼5%). The presence of fulvic acid (FA) greatly enhanced the adsorption of CIP, SMX to about 90%, 17% respectively, while there was no significant change in the adsorption of TC probably due to its good adsorption in the absence of FA. Interestingly, further analysis demonstrated that the FA will enhance the adsorption of antibiotics to vivianite because of the non-bonding interaction between FA molecules adsorbed on the surface of vivianite and antibiotics, and make the vivianite form better crystal without significant influences on phosphorus recovery. In addition, this study found that the adsorption of different kinds of antibiotics by vivianite was significantly related to the molecular weight of dissolved organic matter (DOM) in the actual livestock wastewater. Interestingly, the promotion of SMX adsorption is more likely to occur in the presence of DOM with small molecular weight (<5 kDa), while the introduction of DOM with larger molecular weight has greater promotion effect on CIP adsorption. The results gained in this study will expand the knowledge about the fate of antibiotics and recovery of phosphorus from urban sewage and livestock wastewater in the formation of vivianite.