Abstract
Column-leaching and pilot-scale experiments were conducted to evaluate the use of biosolids (sewage sludges) to control the mobilization of metals from contaminated soils with smelting slags. The pilot-scale experiments using amended soils showed that Cu, Pb and Sb were retained, decreasing their concentrations from 250 mg/L, 80 mg/L and 6 mg/L, respectively in the leachates of contaminated soils, to <20 mg/L, 40 mg/L and 4 mg/L, respectively, in the amended material. Hydrogeochemical modeling of the leachates using Minteq revealed that the degree of complexation of Cu rose 56.3% and 57.6% in leachates of amended soils. Moreover, Cu may be immobilized by biosolids, possibly via adsorption by oxyhydroxides of Fe or sorption by organic matter. The partial retention of Pb coincides with the possible precipitation of chloropyromorphite, which is the most stable mineral phase in the pH-Eh conditions of the leachates from the amended material. The retention of Sb may be associated with the precipitation of Sb2O3, which is the most stable mineral phase in the experimental conditions. The organic amendments used in this study increased some metal and metalloid concentrations in the leachates (Fe, Mn, Ni, As and Se), which suggests that the organic amendments could be used with caution to remediate metal contaminated areas.
Highlights
Soils contaminated with smelting wastes have traditionally been considered poor reactive materials because the potential contaminants are encapsulated in low-solubility compounds such as silicates, Minerals 2012, 2 oxides and glassy forms [1,2]
The organic amendments used in this study increased some metal and metalloid concentrations in the leachates (Fe, Mn, Ni, As and Se), which suggests that the organic amendments could be used with caution to remediate metal contaminated areas
The results showed low leaching of metals, except Ni, possibly because of the content of this metal in the sewage sludge (Table 2)
Summary
Soils contaminated with smelting wastes have traditionally been considered poor reactive materials because the potential contaminants are encapsulated in low-solubility compounds such as silicates, Minerals 2012, 2 oxides and glassy forms [1,2]. Smelter slags are reactive and may be the source of metals such as Ag, As, Ba, Cd, Cu, Pb, Sb and Zn in stream, soil and groundwater contamination [3,4,5,6,7,8,9,10,11,12]. The use of organic amendments as reactive materials may control metal mobilization [14,15] and aid the reclamation of contaminated soils at smelting sites, since such areas typically lack natural vegetation and have other deficiencies [16]. Sugar foam waste has been applied to red soils [19] in a semiarid environment similar to the study area conditions
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