Influence of injection conditions on EDDS-flushing of metal-contaminated soil

Irene M C Lo, Daniel C.W. Tsang, Theo C M Yip, Fei Wang, Weihua Zhang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

37 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)667-675
Number of pages9
JournalJournal of Hazardous Materials
Issue number2
Publication statusPublished - 30 Aug 2011
Externally publishedYes


  • Chelating agent
  • Multi-pulse
  • Pore-water velocity
  • Single-pulse
  • Step-gradient

ASJC Scopus subject areas

  • Health, Toxicology and Mutagenesis
  • Pollution
  • Waste Management and Disposal
  • Environmental Chemistry
  • Environmental Engineering


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