EDTA与柠檬酸复配淋洗对土壤中重金属去除效果研究

Study on the Removal Effect of Heavy Metals From Soil by Compound Leaching With EDTA and Citric Acid

土壤重金属污染问题日趋严重,乙二胺四乙酸二钠(EDTA)和柠檬酸对土壤中重金属的淋洗去除效果明显。以某电镀厂的重金属污染土壤为研究对象,对比分析复配淋洗对重金属的去除效果。在25℃,p H=3.0,振荡淋洗时间为12 h,液固比为20的试验条件下,通过批量振荡淋洗试验,对比了不同浓度的EDTA和柠檬酸各自对重金属的去除效果,并将最佳浓度的EDTA和柠檬酸按照一定的体积比进行复配,探究其最佳复配比例,分析了在最佳洗涤条件下重金属形态变化。研究结果表明,采用0.1 mol/L的EDTA与0.3 mol/L的柠檬酸按1:3的体积比复配而成的淋洗剂对重金属的整体去除效果最好,且优于单一淋洗剂的去除效果,对Cu、Cr、Ni、Zn、Pb的去除率分别为79.1%、53.8%、53.9%、82.6%、78.7%。形态分析结果表明,复配淋洗对各形态的重金属均有较好的去除效果,对重金属全量去除贡献最大的为残渣态,并得出了淋洗后各形态的分布比例,为进行土壤环境风险评价提供依据。

The pollution of heavy metals becomes more and more serious in soil, and the effect of EDTA and citric acid on the leaching of heavy metals in soil is obvious. In this study, the heavy metal contaminated soil in an electroplating plant was taken as the research object, and the removal effect of heavy metal by compound leaching was compared and analyzed. When the temperature was 25 ℃, p H = 3.0, the oscillation leaching time was 12 h,and the liquid-solid ratio was 20, the removal effects of heavy metals by using different concentrations of EDTA and CA were compared to explore the optimal proportion by batch oscillating leaching tests, and the change of chemical forms of heavy metals under the best washing conditions was analyzed. The results showed that the eluent prepared from 0.1 mol/L EDTA and 0.3 mol/L CA（1：3） had the best effect on the overall removal of heavy metals, that was better than the single spray lotion, and the removal rates of Cu, Cr, Ni, Zn, Pb were 79.1%, 53.8%, 53.9%, 82.6%. 78.7%,respectively.Morphological analysis showed that compound leaching had the better effect for removing heavy metals, the largest contribution was residue state, and the proportion of speciation after leaching was obtained, which could provide the basis for soil environmental risk assessment.