Study On The Sorption Behaviors Of Cefalexin On Marine Sediment

Cefalexin(CEX) is a kind of beta-lactam antibiotic and semi-synthetic penicillin antimicrobial agents. Because of its broad antibacterial spectrum, no cross-resistance, low-residue and drug side effects, it has been widely used in medicine, veterinary profession. It can achieve the goal of sterilization according to inhibiting of cell wall synthesis and making the contents of the cell expanded to rupture dissolved. It has antibacterial effects for both gram-positive bacteria and gram-negative bacteria, after the injection, absorbs quickly and completely with high biological efficiency. CEX is used in clinical medicine, it plays an important role controlling of a variety of serious infectious diseases for human. it can also used in offshore aquaculture to cure fish enteritis, gill, red skin and to prevent and treat of diseases such as hemorrhage. The phenomenon of abusing CEX appears recently because of without the right consciousness of using it. Recently, the overuse of antibiotics has aroused widespread concern and CEX as a large amount of antibiotics used, it has also become a residual concern. At present, environment behavior research work on CEX in domestic and overseas is relatively less and only a small amount of literature survey study the concentration of its residual in offshore seawater. Environmental behaviors of CEX is mainly caused by environmental microbial resistance and variation, faster replacement of antibiotics, other antibiotics can cause improper application of flora increased bacterial resistance. Especially applied to aquaculture, when aquatic bacteria sterilization effect is reduced the chance of being infected by resistant bacteria increases. In China, the estimated annual consumption of antibiotics is25,000tons, accounting for12.5%of global consumption around. In the long run, CEX will not be deprecated, systematic study of the adsorption/desorption behavior of CEX on marine sediments is very meaningful.A series laboratory simulation experiment had been done to research of the adsorption behaviour of CEX on marine sediments. Discussed influencing factors such as:sediment composition, salinity, temperature, pH and common pollutants and the adsorption mechanisms are also discussed. The conclusion is as follows:A. The adsorption behaviour of CEX could fit pseudo first order adsorption rate equation better. The adsorption isotherm could fit well with Henry adsorption isotherm model, Freundlich adsorption isotherm model and the Langmuir adsorption isotherm model, and fit the best with Freundlich adsorption isotherm model. Adsorption process could be divided into fast part and slow phase. The distribution coefficient had relationships with organic matter content of marine sediment.B. The adsorption ability of sediment using different treat method was discrepant. The order was:HCl treatment<H2O treatment<H2O2treatment. The adsorption ability of sediment in different position was also different. The order was negatively related to the carbon content in the sediment:No.2position> No.1position> No.3position.C. The adsorption behaviours of CEX were positively related to solution ionic strength. The equilibrium adsorption amount of CEX in different medium decreased following reduction of ionic strength.D. Under the different temperature, adsorption equilibrium time of CEX basically unchanged, but equilibrium adsorption amount was distinct. When the temperature rises, the adsorption quantity also increases. Thermodynamic parameters A Hθ>0process for heat absorption; A Gθ<0adsorption process is spontaneous.E. A set of pH value range in these experiment, there were relationships between the equilibrium adsorption amount and pH changes. When the pH value came close to7, the equilibrium adsorption was the largest, when was away from7, the equilibrium adsorption amount decreases. This was mainly because of CEX dissociation constant was different. When pH value was not the same, the forms of CEX in medium solution were different.F. The influences of different surfactants on the adsorption behavior of CEX were different. When added anionic surfactant SDBS, the promoting function to the equilibrium adsorption of CEX was the most obvious. When followed by cationic surfactant CTAB, the promoting function reduced. And nonionic surfactant Tween80added into the seawater, it showed negative effect when the concentrition was small, with the increasing of concentration, it showed inhibition.