Sorption Kinetics Of Ofloxacin In Particles With Different Properties

The environmental behavior of antibiotics is not well known and thus the accurate rise assessment is not practical. The prediction and control of their potential environmental and health risks require fundamental understanding of their environmental behavior, especially their interaction with environmental matrixes. For ionic organic contaminants, the sorption mechanisms were believed to be diverse and various mechanisms contribute simultaneously. However, the environmental behavior of antibiotics is not well known and the precise environmental risk assessment is not practical. At present, single component is used as the medium of antibiotic sorption, and experimental conditions have a gap with natural soil environment. Components of the natural soil rarely exist alone and interact frequently with other coexistence components, which immobile contaminants. Therefore, it is necessary to investigate systematically the sorption mechanisms of antibiotics in natural soil.Some studies have shown that the sorption process of organic pollutants in natural soil is not instantaneous equilibrium. Some of pollutants sorption require actually days, even months to reach equilibrium. sorption may in fact require weeks to months to reach equilibrium. Ignoring slow sorption kinetics can lead to an underestimation of the true extent of sorption, false predictions about the mobility and bioavailability of contaminants, and perhaps the wrong choice of cleanup technology. The mechanisms governing sorption kinetics are not fully established yet, and need for further research. The sorption dynamics researches of antibiotics on natural soil particles were rarely reported. Therefore, it is necessary to investigate relevant mechanisms and to see how it works.In the study, through the results of sorption kinetics, the effects of the physical and chemical properties of the natural soil and carbonaceous sorbents were revealed. The mechanism of adsorption kinetics of antibiotic in natural soil was discussed. The main innovative conclusions of this study are as follows:1. OFL sorption kinetics on natural soil showed obvious two phase characteristics, which named the fast adsorption in initial stage and slow adsorption with subsequent stage;2. The apparent sorption kinetics could be mathematically recognized as two sorption compartments, with the sorption rate constants differed1-2orders of magnitude;3. The apparent sorption rates and the contributions of fast compartment decreased with the organic carbon contents of solid particles, also decreased with OFL concentrations. These results may suggest that the slow sorption is not a diffusion-controlled process;4. OFL sorption on high-energy sorption sites (for example, the exposed hydroxyl and carboxyl groups) occurs very fast and reaches its saturation with the increased OFL loading. OFL sorption in inner sites (for example, the sites located in organo-mineral complex and the inner pores of mineral aggregates) is relatively slow. Because of the interactions between the passing-through OFL molecules and the adsorbed OFL molecules, or the surface functional groups, the slow sorption is not a diffusion-controlled process. The nonlinear sorption antibiotics on natural soil is contributed to slow sorption.5. Through comparative simulation study of the dynamic adsorption process between SMX and OFL on peat soil and combining with other findings, this study concluded that quinolone sorption in the natural soil is mainly physical sorption, such as in the form sorption behavior of electrostatic forces with the soil organic matter, and partition with organic matter, etc.