College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong Province, China.
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, Shandong Province, China.
Int J Environ Res Public Health. 2019 Aug 2;16(15):2771. doi: 10.3390/ijerph16152771.
Soil leaching is an effective remediation technique using agents to leach the target pollutants from the soil. However, the dynamics and mechanisms for leaching of Cr and other non-pollutant metals from Cr-contaminated soils are not yet well understood. Here, column leaching experiments were conducted to determine the effect of hydrochloric acid (HCl), citric acid (CA), and oxalic acid (OX) on the leaching of Cr, as well as of Ca, Mg, Fe, and Mn, from a soil contaminated by a Cr slag heap. Acid leaching decreased soil pH and enhanced the mobility of all the surveyed metals. Leaching dynamics varied with both metals and acids. OX had the highest removal rates for Cr, Fe, Mn, and Mg, but had the poorest ability to leach Ca. HCl leached the largest amount of Ca, while CA leached similar amounts of Mg and Mn to OX, and similar amounts of Fe and Cr to HCl. Cr in the leachates was correlated with Ca, Mg, Fe, and Mn. Cr mainly interacted with soil mineral components and showed a punctate distribution in soil particles. The X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) analyses showed soil mineralogical and morphological properties were differently altered after leaching by different acids. Complexation of Cr(III), competitive desorption, and reduction of Cr(VI) make significant contribution to Cr leaching by organic acids. In conclusion, OX can be applied in leaching remediation of Cr-contaminated soil, but the concomitant removal of other non-targeted metals should be taken into account because of the loss of soil minerals and fertility.
土壤淋洗是一种利用淋洗剂从土壤中淋洗目标污染物的有效修复技术。然而，铬污染土壤中铬和其他非污染物金属淋洗的动力学和机制尚不清楚。本研究采用柱淋洗实验，考察了盐酸（HCl）、柠檬酸（CA）和草酸（OX）对铬渣污染土壤中铬以及钙（Ca）、镁（Mg）、铁（Fe）和锰（Mn）淋洗的影响。酸淋洗降低了土壤 pH 值，增强了所有调查金属的迁移性。淋洗动力学随金属和酸的不同而变化。OX 对 Cr、Fe、Mn 和 Mg 的去除率最高，但对 Ca 的淋洗能力最差。HCl 淋洗出的 Ca 量最大，而 CA 淋洗出的 Mg 和 Mn 量与 OX 相似，Fe 和 Cr 量与 HCl 相似。淋出液中的 Cr 与 Ca、Mg、Fe 和 Mn 呈正相关。Cr 主要与土壤矿物成分相互作用，在土壤颗粒中呈点状分布。X 射线衍射（XRD）、扫描电子显微镜与能谱分析（SEM-EDS）和 X 射线光电子能谱（XPS）分析表明，不同酸淋洗后土壤矿物学和形态特性发生了不同的变化。Cr(III)的络合作用、竞争解吸和 Cr(VI)的还原对有机酸淋洗 Cr 有重要贡献。总之，OX 可应用于铬污染土壤的淋洗修复，但由于土壤矿物和肥力的损失，应考虑其他非目标金属的同时去除。
