Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.
J Hazard Mater. 2011 Aug 30;192(2):667-75. doi: 10.1016/j.jhazmat.2011.05.067. Epub 2011 May 27.
This study evaluated the design of step-gradient, single-pulse, multi-pulse, and continuous injection of biodegradable EDDS ([S,S]-ethylene-diamine-disuccinic acid, under the same total dosage) and the significance of pore-water velocities during in situ soil flushing. In view of the metal breakthrough and extraction efficiency of each injection mode, single-pulse injection was found to be the least effective for all metals. Multi-pulse injection was consistently more effective than single-pulse injection, although the efficiency of second and third pulse injections significantly diminished. Continuous injection offered a simple operation and the greatest Ni and Cu extraction, whereas step-gradient injection was the best option for Zn and Pb extraction because it mitigated the influence of metal exchange. Moreover, a rinsing step with a background solution following the initial injection of the multi-pulse injection removed newly formed metal-EDDS complexes from soil pores effectively before further EDDS-flushing. A decrease in pore-water velocity provided a longer residence time for greater Ni and Cu extraction, but also enhanced the rate-limited metal exchange of Zn-EDDS and Pb-EDDS complexes and thus hindered Zn and Pb extraction. These results suggest a slower and continuous injection for the best Ni or Cu removal, but a faster and step-gradient injection for Zn or Pb removal.
本研究评估了在原位土壤冲洗过程中，逐步梯度、单次脉冲、多次脉冲和连续注射可生物降解 EDDS([S,S]-乙二胺二琥珀酸，在相同总剂量下)的设计以及孔隙水速度的重要性。鉴于每种注射模式的金属突破和提取效率，单次脉冲注射对所有金属的效果最差。多脉冲注射始终比单次脉冲注射更有效，尽管第二和第三脉冲注射的效率显著降低。连续注射提供了简单的操作和最大的 Ni 和 Cu 提取，而分步梯度注射是 Zn 和 Pb 提取的最佳选择，因为它减轻了金属交换的影响。此外，在多脉冲注射的初始注射后用背景溶液进行冲洗步骤，可以在进一步的 EDDS 冲洗之前有效地从土壤孔隙中去除新形成的金属-EDDS 配合物。孔隙水速度的降低为更大的 Ni 和 Cu 提取提供了更长的停留时间，但也增强了 Zn-EDDS 和 Pb-EDDS 配合物的速率限制金属交换，从而阻碍了 Zn 和 Pb 的提取。这些结果表明，对于最佳的 Ni 或 Cu 去除，较慢和连续的注射是最佳的，但对于 Zn 或 Pb 去除，较快和逐步梯度的注射是最佳的。
