河道底泥中重金属的EDTA淋洗研究

以城市河道底泥为研究对象,用EDTA淋洗进行底泥无害化处理研究。分别探讨了EDTA浓度、淋洗时间、液固比等因素对底泥淋洗效果的影响。目的是为了给底泥中重金属的淋洗实际应用提供技术参数。实验结果表明:淋洗条件如EDTA浓度、淋洗时间和液固比都对淋洗效果有显著影响。本实验中所用底泥0.1 mol/L的EDTA在液固比10∶1的条件下,淋洗效果最好,淋洗30 min就能去除掉70%~80%的Cu和Cd。研究中还比较了淋洗前后底泥中重金属形态分布的变化,详细探讨了底泥与重金属的结合方式对淋洗效果的影响。从形态分析可以得出,原底泥中重金属的分布形态可以用来预测淋洗效果。EDTA淋洗主要针对的是离子态和碳酸盐结合态的重金属,对结合力较强的铁锰氧化物、有机物结合态和残渣态重金属效果较差。因此,可预先进行重金属形态分析来确定底泥是否可用EDTA进行淋洗。

Study on EDTA washing of heavy metal in river sediment

The paper took sediment from city river as the target and used EDTA washing to study the decontamination of sediment.It probed the influence of the factors such as EDTA concentration, washing time and liquid/solid ratio on washing efficiency for the purpose of providing parameters for real application.The result indicated that washing conditions such as EDTA concentration, washing time and liquid/solid ratio all have significant impact on washing effect.EDTA of 0.1 mol/L, liquid/solid ratio of 10:1 can achieve the best result.70%-80% of Cu and Cd could be removed after 30 min of washing. In addition,the form distribution of heavy metal in sediment before and after washing was compared. It investigated the combination way of sediment and heavy metal to affect washing efficiency.Washing by EDTA was more effective to heavy metal in exchangeable and carbonate-bound forms while relatively ineffective to Fe-Mn oxides, organics-bound species and residuals. Therefore, it is advisable to conduct the form analysis of heavy metal so as to decide whether EDTA is used for washing.