Remediation of hexavalent chromium contaminated soil by stabilized nanoscale zero-valent iron prepared from steel pickling waste liquor

• Steel pickling waste liquor is used as iron precursor to prepare nZVI.
• Removal capacity of soil-bound Cr(VI) by CMC-nZVI is studied.
• The removal mechanism of Cr(VI) in contaminated soil by CMC-nZVI is proposed.
• Feasibility of CMC-nZVI in Cr(VI)-contaminated soil remediation is tested by TCLP.

The removal of Cr(VI) from contaminated soil using sodium carboxymethyl cellulose (CMC)-stabilized nanoscale zero-valent iron prepared from steel pickling waste liquor was systematically investigated. Laboratory batch experiments indicated that 0.09 g L−1 of Fe0 nanoparticles at a soil to solution ratio of 1 g: 10 mL completely reduced the aqueous-bound Cr(VI), which contributed about 46% of the pre-sorbed Cr(VI) in the soil (Cr(VI) = 102 mg kg−1). Furthermore, the addition of Fe0 nanoparticles only removed a portion of the soil-bound Cr(VI). When the soil was treated with 0.3 g L−1 of Fe0 nanoparticles for 72 h, 80% of the loaded Cr(VI) was reduced to Cr(III), which resulted in a residual Cr(VI) concentration of 20 mg kg−1. Based on the studies of elemental distributions and XPS analysis, it is proposed that reduction and immobilization may be equally important removal mechanisms for Cr(VI) by CMC-nZVI. Following the treatment by CMC-nZVI, the TCLP leachability of the Cr(VI) and Crtotal was significantly reduced by 100% and 82%, respectively. This study sheds new light on the remediation of Cr(VI)-contaminated soil by CMC-nZVI.

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