环丙沙星在亚高山草甸土和沼泽土中的吸附特性

Adsorption Characteristics of Ciprofloxacin on Subalpine Meadow Soils and Marsh Soils

为了研究环丙沙星(Ciprfloxacin,CIP)在土壤中的吸附过程及主要影响因素,以川西北高原亚高山草甸土和沼泽土为研究对象,采用OECD guideline 106批平衡方法,分析了亚高山草甸土和沼泽土对CIP的吸附动力学特征、吸附热力学特征以及pH、温度、CIP初始浓度等对其吸附过程的影响.结果表明:①不同初始浓度CIP在两种土壤中的吸附过程均符合准二级吸附动力学模型,R 2为0.9202~0.9886.②Freundlich等温吸附模型能够较好地拟合两种土壤对CIP的吸附热力学过程,吸附等温线符合“L”型.③在15~35℃范围内,吸附热力学参数ΔHθ(吉布斯自由能)和ΔGθ(焓变)均小于0,ΔSθ(熵变)大于0,表明两种土壤对CIP的吸附过程以物理吸附为主,属于吸附体系混乱度增加的自发进行的放热反应.④吸附容量lg K f满足沼泽土大于亚高山草甸土,说明沼泽土对CIP的吸附能力强于亚高山草甸土,且两种土壤的吸附能力与CIP的初始浓度呈正相关.⑤在pH为3~9条件下,吸附量均随pH的增加呈现先增后减的趋势,当pH为5时,两种土壤对CIP的吸附效果均最好,表明强酸和碱性环境均不利于土壤对CIP的吸附.研究显示,CIP在两种土壤中的吸附容量、吸附强度以及吸附速率均存在较大差异,温度、CIP的初始浓度和pH对两种土壤吸附CIP存在一定影响.

In order to understand the adsorption characteristics of antibiotics on soil,the equilibrium oscillation method was used to study the sorption kinetics and thermodynamics of ciprofloxacin on subalpine meadow soil and marsh soil.Here,soil samples were collected in the northwest of Sichuan Plateau.The relationships between ciprofloxacin adsorption and soil physicochemical properties and environmental factors(temperature,solution pH and initial concentration)were quantified.The results showed that the adsorption kinetics of ciprofloxacin was best described by the pseudo-second-order model,and the correlation constant R 2 was 0.9202-0.9886.The adsorption thermodynamic process was in accordance with the Freundlich model,and the isotherm adsorption belonged to the L-type.At 15-35℃,the thermodynamic parameter analysis showed that Gibbs free energy(ΔGθ)and Entropy(ΔHθ)were less than zero,and Enthalpy(ΔSθ)was greater than zero,indicating that the adsorption was a spontaneous exothermic reaction with an increase of chaotic degree accompanied mainly by physical adsorption to the surface.The adsorption capacity followed the order:marsh soil>subalpine meadow soil,and the adsorption capacity of the two soils was positively correlated with the initial concentration of ciprofloxacin.Moreover,in the pH range of 3-9,the adsorption of ciprofloxacin increased and then decreased with the increase of pH,the maximum adsorption on the two soils was obtained at pH 5.Thus,strong acid and alkali conditions were unfavorable to ciprofloxacin adsorption.The results had important implications that the adsorption capacity of different soils for ciprofloxacin was different,and ciprofloxacin adsorption on the two soils was strongly related to temperature,initial concentration of ciprofloxacin and pH.