Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 351, Issue -, Pages 138-146Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jhazmat.2018.03.005
Keywords
Zerovalent iron; Metal speciation; Sequential extraction; Lead species
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Funding
- National Natural Science Foundation of China [51708307]
- Applied Basic Research Program of Sichuan Province, China [2014JY0241]
- Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences [CAAS-ASTIP-2015-BIOMA-2]
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Zerovalent iron (ZVI) is an environmental-friendly reactive reagent for recovering heavy metals. However, the detailed recovery mechanism remains unclear due to a lack of quantitative analysis of recovery products. Herein, microscale ZVI, nanoscale ZVI and Ni/Fe nanoparticles were used to recover Pb(II) in aqueous solution and a sequential extraction procedure (SEP) was applied to determine the formed lead species quantitatively. At high initial Pb(II) concentration (500 mg L-1), more than 99.5% of Pb(II) was immobilized by Ni/Fe and n-ZVI, whereas m-ZVI caused inferior recovery efficiency (< 25%). XRD and XPS results revealed that Pb(II) was reduced to Pb prior to the formation of metal hydroxides as the external shell of ZVI. SEP results showed that the fraction bound to carbonates (PbO), fraction bound to iron oxides and exchangeable fraction were the main lead species conducted by Ni/Fe, n-ZVI and m-ZVI, respectively. Consequently, (co-)precipitation and specific adsorption dominated Pb(II) recovery by Ni/Fe and n-ZVI, whereas m-ZVI conducted Pb(II) recovery mainly via weak adsorption. The reactivity of ZVI toward Pb(II) followed the increasing order of m-ZVI < < n-ZVI <= Ni/Fe. The detailed mechanisms of Pb(II) recovery conducted by different ZVI were proposed.
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