School of Environmental Science and Engineering, Sun Yat-Sen University, 135 Xin Gang Xi Road, Guangzhou 510275, China.
Chemosphere. 2012 Jul;88(6):730-5. doi: 10.1016/j.chemosphere.2012.04.003. Epub 2012 May 1.
Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid and its salts (EDTA) is very effective at removing cationic metals and has been utilized globally. However it is ineffective for anionic metal contaminants or metals bound to soil organic matter. The simultaneous removal of cationic and anionic metal contaminants by soil washing is difficult due to differences in their properties. The present study evaluated the potential of a washing process using two synthesized EDTA-derivatives, C(6)HEDTA (2,2'-((2-((carboxymethyl)(2-(hexanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid) and C(12)HEDTA (2,2'-((2-((carboxymethyl) (2-(dodecanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid), which consist of a hydrophilic polycarboxylic moiety and a hydrophobic moiety with a monoalkyl ester group. A series of equilibrium batch experiments at room temperature were conducted to investigate the efficacy of C(6)HEDTA and C(12)HEDTA as extractants for both oxyanion Cr(VI) and cationic Cu(II). Results showed that either C(6)HEDTA or C(12)HEDTA can extract both Cr(VI) and Cu(II) from humic acid simultaneously. However, C(6)HEDTA was less effective for Cr(VI) probably because it has no surface activities to increase solubility of humic acid, like C(12)HEDTA. Extraction of Cr(VI) was mainly attributed to the decreased surface tension and enhanced solubility of organic matter. Extraction of Cu(II) was attributed to both the Cu(II) chelation and enhanced solubility of humic acid. It was demonstrated that the hydrophilic polycarboxylic moiety of C(12)HEDTA chelates cations while the monoalkyl ester group produces surface active properties that enhance the solubility of humic acid.
土壤洗脱是去除金属污染物的少数几种永久性处理方法之一。乙二胺四乙酸（EDTA）及其盐类非常有效地去除阳离子金属，并已在全球范围内得到应用。然而，对于阴离子金属污染物或与土壤有机质结合的金属，它是无效的。由于性质的差异，同时去除土壤洗脱中的阳离子和阴离子金属污染物是困难的。本研究评估了使用两种合成 EDTA 衍生物，C（6）HEDTA（2,2'-（2-（羧甲基）（2-（己烷酰氧基）乙基）氨基）乙二酰二乙酸）和 C（12）HEDTA（2,2'-（2-（羧甲基）（2-（十二烷酰氧基）乙基）氨基）乙二酰二乙酸），进行洗涤过程的潜力，它们由亲水性多羧酸部分和带有单烷基酯基团的疏水性部分组成。在室温下进行了一系列平衡批实验，以研究 C（6）HEDTA 和 C（12）HEDTA 作为提取剂对氧阴离子 Cr（VI）和阳离子 Cu（II）的效果。结果表明，C（6）HEDTA 或 C（12）HEDTA 都可以同时从腐殖酸中提取 Cr（VI）和 Cu（II）。然而，C（6）HEDTA 对 Cr（VI）的效果较差，可能是因为它没有表面活性来增加腐殖酸的溶解度，而 C（12）HEDTA 则有。Cr（VI）的提取主要归因于表面张力的降低和有机物溶解度的提高。Cu（II）的提取归因于 Cu（II）的螯合和腐殖酸溶解度的提高。结果表明，C（12）HEDTA 的亲水性多羧酸部分螯合阳离子，而单烷基酯基团产生表面活性，提高腐殖酸的溶解度。
