垃圾填埋场衬垫土壤材料对Cr(Ⅵ)的吸附特性研究

Adsorption of Cr( Ⅵ ) onto landfill liner-soil materials

通过静态平衡吸附试验对采用颗粒活性炭及酸活化膨润土改良的垃圾填埋场衬垫土壤材料吸附重金属的特性进行了观察。试验结果表明:研究中的所有土壤样本对Cr(Ⅵ)的吸附属于非线性的Langmuir模式。经颗粒活性炭及酸活化膨润土改良的衬垫土壤材料与天然黏土材料相比,对Cr(Ⅵ)的吸附强度有了很大的提高,说明颗粒活性炭和酸活化膨润土可以作为改良衬垫土壤的材料去吸附重金属。所有土壤样本对Cr(Ⅵ)的吸附量均随着温度的升高而增大,随着土壤固体颗粒浓度的增大而减小。Langmuir等温参数(qm,b)随着土壤固体颗粒浓度的增大而呈对数性减小,但随着土壤固体颗粒浓度进一步增大到某一临界值(例如200 g/L),其值基本稳定了,另外等温参数也随着温度的升高呈线性增大的趋势。由试验结果可以得出,采用较低的土壤固体颗粒浓度所确定的吸附参数值不适合模拟实际工程条件,其值将引起对垃圾填埋场衬垫的迟滞因子作出过高估计。因此,为了获得与实际工程条件比较接近的吸附参数值,静态平衡吸附试验必须在一个充分大的固体颗粒浓度条件下进行。

The adsorption capacity of landfill liners containing granular activated carbon （GAC）, or bentonite activated by acid, for Cr（Ⅵ） is investigated by the batch tests. The results show that the Cr（Ⅵ） sorption to all soil samples is nonlinear and characterized by a Langmuir isotherm model. Both the GAC and activated bentonite can be used as sorptive amendments for trapping Cr（Ⅵ） in landfill liners. The adsorption capacity of Cr（Ⅵ） onto all the soils increases with increasing temperature, and decreases with an increase of soil-solid concentration. As the soil-solid concentration increases, the Langmuir isotherm parameters（qm, b） first decreases logarithmically, but then stabilizes when the soil-solid concentration exceeds a critical value （e.g., 200 g/L）. The isotherm parameters also increase linearly with increasing temperature. It is concluded that the values of the isotherm parameters measured under low soil-solid concentration may not properly simulate the real engineering situation. The isotherm parameters obtained with low soil-solid concentration can result in an overestimation of the retardation factor of landfill liner. Consequently, the batch tests should be conducted using a sufficiently high soil-solid concentration in order to obtain isotherm parameters close to the field situation.