三种邻苯二甲酸酯在不同黏土矿物上的吸附

Adsorption of Three Phthalic Acid Esters on Different Clay Minerals

邻苯二甲酸酯类(PAEs)作为一类常见的增塑剂可以通过多种途径进入土壤,并在土壤中富集。黏土矿物是土壤的一个重要组分,对有机污染物的迁移有重要的作用。通过考察三种PAEs,即邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)和邻苯二甲酸正丁酯(Dn BP)在改性之后的K+饱和黏土矿物(K-FZ-10,K-SMF和K-Kao)上的吸附行为,分析了黏土矿物类型、PAEs种类以及温度对吸附的影响。试验结果能较好地用Freundlich方程进行拟合,结果表明:PAEs的疏水性越强,固相-水分配系数(Kd)越大,PAEs越容易被黏土矿物吸附;三种PAEs在黏土矿物上的吸附量均呈现DMP<DEP<Dn BP的顺序,与PAEs的疏水性呈正相关;三种K+饱和黏土矿物对PAEs的吸附能力均是K-FZ-10>K-SMF>K-Kao,其与黏土矿物的表面积呈正相关。不同温度(4、10、20℃和30℃)的试验结果表明,黏土矿物对三种PAEs的吸附量随温度升高而减少。黏土矿物的类型、PAEs的疏水性和温度对PAEs在黏土矿物上的吸附均有显著影响,即黏土矿物表面积越大,PAEs的疏水性越强,环境温度越低,PAEs的吸附量越大,表明这三种因素对PAEs在土壤中的迁移起重要作用。

Phthalic acid esters(PAEs)are widely used as plasticizers and are easily released into the environment, posing potential harms to human. Clay minerals are an important component of soil. After PAEs enter soils, the clay minerals would inevitably affect the transformation and fates of PAEs. Here we examined PAEs adsorption on clay minerals using two montmorillonite clays(FZ-10, SMF)and one kaolinite clay(Kao)as adsorbents that were saturated with K ions(K-FZ-10,K-SMF and K-Kao). Results showed that the adsorption of PAEs by clay minerals were in the following order: dimethyl phthalate(DMP)<diethyl phthalate ester(DEP)<di-n-butyl phthalate(Dn BP). Their adsorption coefficients(Kd)were positively related to their hydrophobicities(DMP<DEP<Dn BP)and their adsorption capacity by clay minerals was increasing with increasing hydrophobicities of PAEs. The adsorption of DEP on three clay minerals was K-FZ-10 >K-SMF >K-Kao.Both type and surface area of clay minerals contributed to the adsorption ability. Temperature rise reduced the adsorptions of three PAEs on K-FZ-10, K-SMF and K-Kao, indicating that the adsorption was exothermic and spontaneous. This study revealed that the type of clays,hydrophobicityof PAEs and temperature were three important factors affecting the adsorption of PAEs on clay minerals. The adsorption of PAEs onto soil could be used to predict the transportation in soil to some extent.