紫色土对3种邻苯二甲酸酯吸附特性的研究

Adsorption Characteristics of Three Precedence-Controlled Phthalate Esters on Purple Soil

以三峡库区典型土壤—紫色土为供试土壤,采用固相萃取-高效液相色谱法研究了紫色土对3种优先控制有机污染物邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)和邻苯二甲酸二丁酯(DBP)的吸附动力学、吸附热力学特征及其影响因素.研究结果表明,紫色土对DMP,DEP和DBP的吸附动力学过程可分为最初的表面快速吸附与向土壤颗粒内部慢速扩散的两个阶段,假二级动力学方程可以很好地描述紫色土对三者的吸附动力学特征,吸附速率常数由大到小顺序为DMP,DEP,DBP;Langmuir方程可以较好地拟合紫色土对DMP,DEP和DBP的等温吸附特征,平衡吸附量由大到小顺序为DBP,DEP,DMP;DMP,DEP和DBP在紫色土表面存在竞争吸附,竞争力由大到小顺序为DBP,DEP,DMP;热力学试验表明温度对紫色土吸附DMP,DEP和DBP有明显影响,随着温度的升高,紫色土对三者的吸附量逐渐减少;热力学参数ΔG,ΔH和ΔS表明紫色土对3种邻苯二甲酸酯的吸附反应是自发、放热的过程;反应体系pH和离子强度对紫色土吸附DMP,DEP和DBP的影响较大,随着pH值的增加吸附量减少;随离子强度的增大吸附量增大.

The characteristics of adsorption kinetics and adsorption thermodynamics of three kinds of precedence-controlled organic pollutants[DMP（dimethyl phthalate）,DEP（diethyl phthalate）and DBP（dibutyl phthalate）]on purple soil the typical soil in the Three Gorges Reservoir Area and the influencing factors in the process were studied with the solid phase extraction-HPLC method.The results showed that the adsorption kinetics of DMP,DEP and DBP by purple soil could be divided into two stages：the initial surface fast adsorption and the slow diffusion of soil particles,which could be well explained by the pseudo-second-order kinetic equation,and the adsorption rate constants could be arranged in the order of DMP〉DEP〉DBP.The isothermal adsorption characteristics of the three kinds of phthalate esters（PAEs）could be well fitted by the Langmuir equation,and the equilibrium adsorption capacity could be arranged in the order of DBP〉DEP〉DMP.Competitive adsorption of the three kinds of mixed PAEs on the purple soil was detected,and the order of competitive ability was DBP〉DEP〉DMP.Thermodynamic experiments showed that temperature had a significant effect on the adsorption of the three PAEs on purple soil.The adsorption capacity of PAEs decreased gradually with increasing temperature.The thermodynamic parameters of ΔG,ΔH andΔS suggested that the adsorption reaction was a spontaneous and exothermic process.In the reaction system,pH and ionic strength made a difference in adsorption.The adsorption capacity decreased with increasing pH and increased with increasing ionic strength.