DEP和DBP在黑土胶体微界面的动力学行为

Dynamic Behavior of DEP and DBP Developing on the Interface of Black Soil Colloid

邻苯二甲酸酯(phthalic acid esters,PAEs)可对生态环境、食品安全及人类健康构成威胁。东北黑土是中国主要的粮食产区之一。文章旨在探讨黑土胶体对PAEs的吸附动力学和热力学特征,研究PAEs在黑土胶体微界面的动力学行为,这对黑土PAEs污染风险控制具有重要的指导意义。以黑土胶体为试验材料,采用固相萃取-高效液相色谱法,对比研究邻苯二甲酸二乙酯(diethyl phthalate,DEP)和邻苯二甲酸二丁酯(dibutyl phthalate,DBP)两种有机污染物在黑土胶体上的吸附动力学和热力学行为。结果表明,准二级动力学方程可以很好地描述黑土胶体对DEP和DBP的吸附动力学特征,DEP的吸附速率常数大于DBP,DEP(COC,含有机质胶体)吸附速率常数为0.00134,DBP(COC)吸附速率常数为0.00123;颗粒内扩散模型表明,黑土胶体对DEP和DBP的吸附过程中土壤颗粒内扩散不是唯一的速率控制步骤;Langmuir和Freundlich方程可以较好地拟合黑土胶体对DEP和DBP的吸附,平衡吸附量DBP大于DEP,温度为308K时,DEP(COC)的吸附量为666.667mg·kg^-1,DBP(COC)的吸附量为813.01mg·kg^(-1);另外,COC的吸附能力优于去有机质胶体(CIC)。热力学试验表明,温度对黑土胶体吸附DEP和DBP有明显影响,随着温度升高,黑土胶体对DEP和DBP的吸附量减少;热力学参数?G°、?H°和?S°表明,黑土胶体对DEP和DBP的吸附反应是自发、放热的过程;反应体系pH对黑土胶体吸附DEP和DBP影响较大。综上所述,黑土胶体对DEP和DBP的吸附符合准二级动力学模型,吸附反应为放热过程,温度和p H在DEP和DBP的吸附和扩散过程中起着重要作用。

Phthalic acid esters(PAEs)are posing a serious threat to the ecological environment,food safety and human health,black soil is one of the main grain producing areas in Northeast China,in order to evaluate the risks,and control or repair the pollution,it is important to study dynamic behavior of PAEs on the interface of black soil colloid.In this paper,the adsorption kinetics and adsorption thermodynamics of diethyl phthalate(DEP)and dibutyl phthalate(DBP)on black soil colloid were studied using the solid phase extraction-HPLC method.The results showed that the adsorption kinetics of DEP and DBP could be well explained by the pseudo-second-order kinetic equation on the interface of black soil colloid,and adsorption rate constants of DEP was higher than the one of DBP.The adsorption rate constants of DEP(COC)and DBP(COC)were 0.001 34 and 0.001 23,respectively.The internal diffusion model showed that the intra-particle diffusion was not the sole controlling process.The isothermal adsorption characteristics of the two chemicals could be well explained by the Langmuir and Freundlich equation,and the equilibrium adsorption capacity of DBP was higher than that of DEP,the equilibrium adsorption capacity of DEP(COC)and DBP(COC)were 666.667 mg·kg-1 and 813.01 mg·kg-1 at 308 K,respectively.Furthermore,the adsorption capacity was better in coarse clay containing organic matter than that in coarse clay without organic matter.Thermodynamic experiments showed that temperature had a significant effect in the process,the adsorption capacity could be decreased gradually with increasing temperature.The thermodynamic changes onΔG°,ΔH°andΔS°suggested that the adsorption reaction was spontaneous and exothermic process.In addition,pH also had a significant effect in the process.In short,our results indicate that the adsorption behavior of DEP and DBP meets with the pseudo-second-order kinetics,and the process is exothermic.Meanwhile,temperature and pH play an important role in the process for the adsorption and diffusion.