Metal(loid)s behaviour in soils amended with nano zero-valent iron as a function of pH and time.
Nano zero-valent iron (nZVI) is currently investigated as a stabilising amendment for contaminated soils. The effect of pH (4-8) and time (48 and 192 h) on the behaviour of nZVI-treated Pb-Zn and As-contaminated soil samples was assessed. Additionally, soil leachates were subsequently used to study the direct interaction between soil solution components and nZVI particles in terms of mineralogical changes and contaminant retention. A typical U-shaped leaching trend as a function of pH was observed for Cd, Pb and Zn, while As was released predominantly under alkaline conditions. Oxidising conditions prevailed, so pH was the key controlling parameter rather than redox conditions. Generally, longer contact time resulted in increased soluble concentrations of metal(loid)s. However, the stabilisation effect of nZVI was only observed after the direct soil leachate-nZVI interactions, showing enhanced redox and sorption processes for the studied metals. A significant decrease of dissolved As concentrations was observed for both experimental soils, but with different efficiencies depending on neutralisation capacity, organic matter content or solid fractionation of As related to the origin of the soils. Scorodite (FeAsO4·2H2O) was predicted as a potential solubility-controlling mineral phase for As. Sorption of metal(loid)s onto secondary Fe- and Al-(oxyhydr)oxides (predicted to precipitate at pH > 5) represents an important scavenger mechanism. Moreover, transmission electron microscopy confirmed the retention of Zn and Pb under near-neutral and alkaline conditions by newly formed Fe oxides or aluminosilicates. This study shows that the efficiency of nZVI application strongly depends not only on soil pH-Eh conditions and contaminant type, but also on the presence of organic matter and other compounds such as Al/Fe/Mn oxyhydroxides and clay minerals.
Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic.
Martina
M
Vítková
Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic.
Simona
S
Rákosová
Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic.
Zuzana
Z
Michálková
Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic. Electronic address: komarek@fzp.czu.cz.
Michael
M
Komárek
D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates; D001151:Arsenic / Q000032:analysis / Q000737:chemistry; D002104:Cadmium / Q000032:analysis / Q000737:chemistry; D000077215:Clay; D018153:Czech Republic; D004787:Environmental Pollution; D052918:Environmental Restoration and Remediation; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007854:Lead / Q000032:analysis / Q000737:chemistry; D017895:Manganese Compounds / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D013997:Time Factors; D015032:Zinc / Q000032:analysis / Q000737:chemistry
D000538:Aluminum Silicates; D017895:Manganese Compounds; D019216:Metals, Heavy; D008903:Minerals; D010087:Oxides; D012989:Soil Pollutants; D002104:Cadmium; D007854:Lead; C027424:manganese oxide; D007501:Iron; D015032:Zinc; D000537:Aluminum Oxide; D001151:Arsenic; D000077215:Clay
Arsenic; Metals; Nano iron; Soil stabilisation; pH-stat leaching