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COMBINED USE OF ZERO VALENT IRON AND MAGNETIC SEPARATION FOR EX-SITU REMOVAL OF BIOAVAILABLE METALS FROM CONTAMINATED SEDIMENTS
Feng, N., H. Ghoveisi, A. Boularbah, G. Bitton, and J.-C.J. Bonzongo.
Soil and Sediment Contamination: An International Journal 27(2):131-146(2018)

Sandy and organic sediments characterized by different heavy metal binding capacities (HMBC), and contaminated with Cu, Hg, or Zn were treated ex situ using a remediation approach consisting of (i) sorption onto oxidized zero-valent iron (ZVI) surfaces and (ii) retrieval of formed metal-ZVI complexes from sediment matrices by magnetic separation. The research focused on the reduction/elimination of the bioavailable fractions of metals. The efficiency of the method was assessed by a combination of a bacterial (MetPLATE™) and invertebrate-based (48-h Ceriodaphnia dubia) bioassays. In sandy sediments, characterized by low HMBC (20.8, 23.5, and 39.6 for Hg, Cu, and Zn, respectively), the determined toxicity units (TU) prior to sediment treatment increased in the order Hg < Cu < Zn, regardless of the bioassay used. Using ZVI and magnetic separation in the sandy sediments achieved up to 97% TU reduction. In organic-rich sediments, the affinity of the studied metals for organic matter resulted in much higher HMBC values (83.9, 108.3, and 136.2 for Cu, Zn, and Hg, respectively) and much lower TU values before sediment treatment with ZVI. The use of MetPLATE on non-treated sediments resulted in TU values increasing in the order Hg < Cu < Zn, with TU removal efficiencies ranging from 83-97% after treatment. The TU values measured with the 48-h C. dubia assay were higher than those obtained with MetPLATE, and in this case, sediments contaminated with Zn exhibited the lowest percentage of TU removal, with only 81.7% and 80.5% TU removal for sediments with contamination levels of 400 and 800 mg/kg, respectively. For organic sediments contaminated with Cu and Hg, TU removal exceeded 95%.



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