Adsorption behavior of enrofloxacin in soil and sediment and its response mechanism to environmental factors

As an important part of lake and reservoir ecosystem, sediment is an important “source” and “sink” of pollutants. Antibiotics, as a kind of important emerging organic pollutants, have attracted global attention. In order to understand the adsorption behavior and mechanism of antibiotics in sediment, enrofloxacin (ENR) was used as the target pollutant to evaluate its adsorption behavior in sediment and soil and the response mechanism of environmental factors by using the intermittent equilibrium method. The results showed that the adsorption equilibrium time of ENR in sediment and soil was 6 h, and the adsorption kinetics was in line with the quasi-second-order kinetics. The two-compartment model Herry-Langmuir can better describe the adsorption of ENR by sediment and soil. There is a lag phenomenon in desorption process.The average lag coefficient HI of sediment and soil was 1.08 × 10−3 and 0.43 × 10−3, respectively, indicating that ENR was difficult to be released. When pH = 5, the adsorption capacity is the highest, indicating that the adsorption mechanism of ENR in the sample is mainly cation exchange; the higher the cationic valence state of the background liquid is, the stronger the competitive adsorption capacity is, which leads to the gradual decrease of ENR adsorption capacity in the sample. Because ENR contains -F group, resulting in complex reaction with Al3+ in the solution, thus reducing the activity of Al3+, reducing the competitive adsorption of Al3+ and ENR, then ENR adsorption capacity increased. The change of ENR adsorption capacity of sediment and soil is Q(Al3+)>Q(Na+)>Q(K+)>Q(Ca2+)>Q(Mg2+)>Q(Fe3+). The adsorption capacity of ENR on sediment was higher than that on soil under all conditions.