湖库底泥对环丙沙星吸附特性的研究

The Adsorption Characteristic of Reservior Sediment to Ciprofloxacin

为探明环丙沙星在湖库底泥中的吸附特性,以长春市新立城水库底泥为供试样品,利用OECD guideline 106批平衡吸附试验方法,研究环丙沙星在底泥中的吸附行为,并探讨pH和Ca^(2+)强度对环丙沙星吸附过程的影响。结果表明:环丙沙星的等温吸附能较好的拟合Herry-Freundlich和Herry-Langmuir复合吸附等温方程,其中Herry-Langmuir方程的拟合效果更好,相关系数r=0.995 3,达到差异极显著水平。环丙沙星在底泥中的整个吸附过程符合准二级反应动力学方程,吸附参数k=8.76×10^(-3)kg/(min·mg)。研究发现,pH值在3~11的条件下,环丙沙星的吸附量随pH的增加呈先升高后降低的趋势。当pH=5时,吸附效果最好,可吸附环丙沙星总量的99.75%,强酸性和强碱性条件均不利于底泥对环丙沙星的吸附。随电解质中CaCl_2浓度的增加,底泥对环丙沙星的吸附能力降低,吸附量减少。当Ca^(2+)浓度增加到1.5mol/L时,Ca^(2+)和环丙沙星二者间的竞争性吸附逐渐达到平衡,底泥对环丙沙星的吸附量不会再随Ca^(2+)浓度的增加而变化,此时吸附量为总量的62.34%,由此可推断阳离子交换是环丙沙星在底泥中吸附过程的重要机制之一。

In order to understand the adsorption characteristics of sediment to ciprofloxacin,sediment in Xinlicheng Reservoir of Changhcun,chosen as the test sample,was used to study the adsorption behavior of sediment for ciprofloxacin,and to explore the influence of pH and Ca^2＋ intensity on the absorbed process of the ciprofloxacin by means of the OECD guideline 106 batch of equilibrium adsorption test method.The results showed that the isothermal adsorption behavior of the sediment to ciprofloxacin could better fit with HerryFreundlich and Herry-Langmuir complex adsorption isotherm.The Herry-Langmuir equation had the best fitting effect,and its correlation coefficient reached significant difference level（r=0.9953）.The adsorbed process of ciprofloxacin in sediment accorded with the secondary reaction kinetics equation,with the adsorption parameter k=8.76×10^（-3） kg/min·mg.The results also showed that,when pH value was under the condition of 3~11,adsorption quantity of ciprofloxacin increased with the increase of pH,and then decreased.When pH=5,the adsorption effect was the best,and 99.75% of the total amount of ciprofloxacin could be absorbed,but under strong acid and strong alkali conditions,it was not conducive to the adsorption of sediment to ciprofloxacin.With the increase of CaCl2 concentration in electrolyte,the adsorption capacity of sediment and its adsorption amount to ciprofloxacin were reduced respectively.When Ca^（2＋）concentration was increased to 1.5mol/L,the competitive adsorption of Ca^（2＋）and ciprofloxacin gradually achieved a balance.The adsorption capacity of the sediment to ciprofloxacin would not change with the increase of Ca^（2＋）concentration,and it was 62.34% of the total adsorption amount of sediment to ciprofloxacin at this time.Therefore,it can be concluded that cation exchange was one of the important mechanisms for the adsorbed process of ciprofloxacin in the sediment.