Adsorption-Desorption Characteristics Research Of Ciprofloxacin And Enrofloxacin In Sediment And Soil

In recent years,antibiotics have been used extensively in the treatment of human and animal diseases for a long time,and also as a feed additive used in animal husbandry and aquaculture.Most antibiotics can not be completely absorbed by the body, the vast majority of them(75% to 90%)are excreted as original formation or their metabolites together with wastes and they finally through different path ways get into soils and waters to pollute the environment.Nowadays, antibiotics are one of the important new pollutants in the environment.Quinolone antibiotic is shared livestock antibiotics,and it is the second largest antibacterial drugs in our country.The research use sediments and surrounding soil in Changhcun Xinlicheng Reservoir as the research samples, select two kinds of Quinolones: Ciprofloxacin(CIP) and Enrofloxacin(ENR), use the OECD guideline 106 of batch equilibrium adsorption desorption test method, study the adsorption desorption behavior of CIP and ENR in sediment and soil, and explore different environmental factors on the absorption desorption behavior of the CIP and ENR, so that provide theoretical basis for ecological risk assessment and water quality management in water environment. The results are summarized as follows:The isothermal adsorption processes of CIP and ENR are more in line with the Freundlich model, and the correlation coefficient r reached a very significant level. The adsorption capacity(lg Kf) of sediments are greater than soil, and in the same sample, the lg Kf of ENR is greater than CIP. In addition, CIP and ENR have significant desorption hysteresis in the sample, more obvious in the soil.The adsorption / desorption characteristics of CIP and ENR in samples are basically the same. The adsorption / desorption process can be divided into fast and slow two stages, reach adsorption equilibrium after 6 hours and reach desorption equilibrium after 5 hours. The adsorption / desorption processes are in accordance with the Quasi Two stage kinetic model, and the correlation coefficient r is 0.8915~0.9728, which showed significant difference; The adsorption rate constant(k1) decreases with the increase of the initial concentration of CIP and ENR, under the same conditions, the sediment> soil, indicating that the adsorption rate of sediment samples is faster than in soil.With the increase of temperature, the adsorption capacity of the two samples on the CIP showed a trend of first increasing and then decreased, and the adsorption effect at 25℃ was the best, which accounted for 99.65% and 99.43% of the total amount respectively. However, with the temperature was increased, the adsorption capacity of sediment on ENR is gradually decreased, but it was gradually increased in the soil. The adsorption of ENR was stable at about 30℃, and the adsorption effect at 15℃ was the best, which accounted for 99.92% and 99.65% of the total amount respectively. In addition,with increasing temperature, the desorption of CIP in samples increased. In the sediment, the desorption of ENR increases with increasing temperature,decreasing in the soil.With the increase of p H, the adsorption capacity of the two samples on CIP and ENR showed a trend of first increasing and then falling, while the adsorption effect was best at p H=5. While the desorption increased with the increase of p H, indicating that the drug under alkaline conditions favor the desorption process in the sample.With increasing Ca Cl2 concentration in the electrolyte solution, the adsorption of ENR and CIP in samples have different degrees of reduction, and the adsorption capacity was stable when the concentration of Ca Cl2 was 2 mol/L, the decline is 14.95%- 39.11%; When the Ca Cl2 concentration is 1 mol/L, the desorption is maximum, which the rising rate was 69.95% ~ 99.95%. In addition to Al3+, the higher valence cations that prepared for electrolyte solution, the lower the adsorption capacity of the ENR and CIP in sample, but the higher the amount of desorption. The Al3+ reaction with F- of CIP and ENR, resulting in adsorption/desorption process anomalies.With the increase of N and P content in solution, the adsorption/desorption processes of CIP and ENR in the samples have different effects. The increase of P content is beneficial to the adsorption of CIP and ENR in two samples. The increase of N content could inhibit the adsorption of CIP in the soil, but in the case of N and P, the adsorption could be promoted. For the desorption process, N and P addition will inhibit the desorption behavior of ENR in the sample. But with the increasing of N and P contents, the inhibitory effect decreased, so desorption increased.