氨基三乙酸对污染土壤中镉活化迁移的影响

Effect of Aminotriacetic Acid on Cadmium Activation and Migration in Contaminated Soil

为了探究氨基三乙酸(NTA)对污染土壤中镉活化迁移的影响,采用批实验研究了淋洗前后镉形态的变化、土壤有机质含量的变化以及镉的活化量与NTA浓度和pH值的关系。通过傅立叶红外光谱仪(FTIR)分析了淋洗前后土壤颗粒官能团的组成,并采用SEM对淋洗前后土壤颗粒表面进行了表征。结果表明镉的活化量主要受到NTA浓度和淋洗液pH值的影响。一方面镉的活化量随着NTA的输入浓度增大而增大,且与土壤实际结合NTA量变化趋势一致,土壤颗粒由淋洗前的羟基官能团变为淋洗后的酯基官能团,进而降低了土壤颗粒对镉的固定;另一方面淋洗过程中通过H^+与镉之间的交换反应,导致镉的活化,同时交换反应消耗质子会使得淋洗液pH值升高,在较高的pH值条件下镉会形成Cd(OH)_2沉淀而被部分固定。

Batch leaching experiments were conducted to understand the leaching behavior of cadmium from using Cd-contaminated soil using aminotriacetic acid(NTA). The variation of cadmium speciation and organic matter content in soil were studied before and after the leaching experiment. The relationship between the amount of leached Cd and the concentration of NTA and the pH values of the leachate were also analyzed. Then the FTIR and SEM analysis were conducted to study the variation of the functional groups combined with the soil particles before and after leaching. The experiment results indicate that the leached Cd from the soil is closely associated with the concentration of NTA and the pH value of leachate. The total amount of leached Cd increased with the increase of the concentration of NTA and changed with the amount of NTA combined onto the soil particles. The change from hydroxy functional groups to the ester based functional groups combined with the soil particles after leaching results in the mobilization of Cd from contaminated soil. During the leaching experiment, the exchange reaction between H+ and Cd promoted the mobilization of Cd and increases the pH value of eluent as well. Under the high pH condition, some amount of Cd precipitated as Cd(OH)2 and re-immobilized in soil particles.