Migration And Simulation Of Ciprofloxacin In Porous Media

In recent years, with the rapid development of chemical industry, chemicals have been closely linked with human life. Among them, the influence of widely used antibiotics(aquaculture, poultry farming, food processing) on the environment has drawn increasing attention. Antibiotics may go into the soil environment and river in the ultimate animal excretion or many other ways. And they also endanger groundwater with the downward movement of soil water and groundwater migration through leaching, percolation or other ways. Soil antibiotic pollution directly affects the safety of agricultural and threat human health. Therefore, in order to reveal the adsorbed migration mechanism of ciprofloxacin in the soil, evaluate the ecological risks in the environment, and provide a scientific basis for managing ciprofloxacin pollution in soil, it is necessary to explore the different adsorption and transport conditions of antibiotics in soil and predict the negative effects that may be caused. In this paper, some batch equilibrium adsorption experiments and soil column experiments were conducted to investigate to the sorption and transport characteristics of ciprofloxacin in quartz sand under different physical(quartz sand particle size) and chemical factors(pH and ionic strength). The experimental data were fitted by Langmuir and Freundlich empirical formulas. And the migration progress of ciprofloxacin in quartz sand. The main conclusions are as follows:(1) In the static adsorption isotherm experiments, the adsorption of ciprofloxacin in quartz sand increase with the increase of ciprofloxacin concentration in balanced solution. It was found that with the increase of pH value or ionic strength, adsorption capacity of ciprofloxacin decreased. On the contrary, adsorption capacity of ciprofloxacin was increased with the decrease of particle size. The certainty coefficient of Freundlich model was more than 0.886, the certainty coefficient of Langmuir model was 0.806. So Freundlich equation had a better efficacy.(2) The transport experiments in quartz sand at different pH and ionic strength were conducted to investigate the transport characteristics of ciprofloxacin. The higher pH was, the higher ionic strength was, the sooner flow time was, the sooner to reach peak(C/C0) and the smaller time span throughout the process was. That was to say, the higher pH and higher ionic strength were in favor of ciprofloxacin transport in quartz sand. The greater the particle size of quartz sand, the sooner flow time was, the higher peak value was. But in the high ionic strength or low pH, the flow characteristics have little difference. This result illustrates, in this case, different particle size have little effect on breakthrough curve.(3) The transport of Ciprofloxacin in iron oxide coated sand have obviously different transport phenomenon at different pH and ionic strength. The adsorption of ciprofloxacin in quartz was much better than the adsorption in iron oxide coated sand.And the breakthrough curve has serious trailing phenomenon. The flow time was sooner,the time to reach peak(C/C0)was sooner, the particle size was lower, while the time of span throughout the process was bigger.(4) The pH of flowing solution decline after rising as the pore volume of solution increased, eventually leveling off. The pH of the stream increased with the decrease of initial ionic strength. As the pore volume of solution increased, the EC of flow liquid first rose then fall, and gradually increased, finally leveling off. Also, the whole EC of flow liquid increased with initial pH increasing.(5) Freundlich equation was used to fit the data of static adsorption experiment.And the retardation factor Rd was obtained, and bigger than the Rd obtained by HYDRUS-1D. That was to say, the Rd obtained by static adsorption experiment had some limitations, and it should be selected appropriately.(6) The nonequilibrium single-point adsorption model(OSM) in HYDRUS-1D can better describe the migration behavior of ciprofloxacin in quartz sand, and in the three quartz sands, silt can best fit the results. ? is small, indicating that a certain non-uniformity was in the quartz sand surface, but the difference was small.Differences in adsorption sites showed that the presence of chemical non-equilibrium phenomena. ω value is much less than 100, which indicated that the non-equilibrium caused by the adsorption sites differences played a leading role in the migration progress of ciprofloxacin in silt,and non-transient absorption existed in the progress.