EDTA和柠檬酸淋洗去除污染粉土柱中Pb的研究

以场地重金属污染的修复治理为背景,通过室内压实制备Pb污染土柱以模拟现场污染土,采用乙二胺四乙酸二钠二水合物(EDTA)和柠檬酸对Pb污染粉土柱进行淋洗,考察淋洗剂类型、淋洗剂浓度、淋洗时间和污染土中Pb的负载量等各个因素对污染土中Pb的释放特性的影响。研究表明:相较于柠檬酸,EDTA对Pb的去除效果明显更优。随淋洗时间延长,不同浓度的EDTA对Pb的淋洗效率趋于一致。污染土中Pb负载量越小,EDTA对Pb的去除率越高,64.5%～83.6%的Pb可以从污染土中解吸出来;柠檬酸浓度越高,对Pb的去除效果越好。由于柠檬酸浓度较低时易吸附于土体表面,并且抑制Pb的解吸,低浓度柠檬酸淋洗总体效果偏差,最高去除率仅为11.4%。因此,现场修复Pb污染土若采用EDTA可采用较低浓度(0.005 mol/L)淋洗,而若选择柠檬酸需要提高其浓度。

Study on removal of Pb from contaminated silty soil column by washing with EDTA and Citric acid

By taking the remediation of the heavy metal contaminated site as the study background，the washing of the Pb contaminated silty soil column with Disodium dihydrogen ethylenediamine tetraacetic dihydrate ( EDTA) and Citric acid is carried out by simulating the in situ contaminated soil through the indoor compacted and prepared Pb contaminated silty soil column，and then the impacts from all the factors，such as type of eluting agent，concentration of chelating agent，concentration of chelating agent，washing time，concentration of Pb in soil，etc．，on the releasing characteristics of Pb in the contaminated soil are investigated． The study result shows that compared with Citric acid，the removal effect on Pb from EDTA is significantly much better． Along with the extension of time，the washing efficiencies of different EDTA concentrations tend to the same． The smaller the Pb load in contaminated soil is，the higher the removal rate of EDTA for Pb is to be，from which Pb of 64. 5% ～ 83. 6% can be desorbed from the contaminated soil，while the higher the concentration of Citric acid is，the better the removal effect on Pb is to be． However，the general effect of the washing made by Citric acid with lower concentration is relatively poorer with the maximum removal rate of only 11. 4% due to the fact that Citric acid is prone to be adsorbed on soil surface and then restrains the desorption of Pb． Therefore，if the in situ remediation of the Pb contaminated soil is made by EDTA，the lower concentration ( 0. 005 mol /L) can be adopted，but if Citric acid is selected for the washing，the concentration of it is necessary to be increased．