Abstract
As a global environmental pollutant, mercury (Hg) threatens our water resources and presents a substantial risk to human health. The rate and extent of immobilization of Hg2+ (hereafter, Hg) on engineered sorbents (Thiol-SAMMS®, pine biochar, SediMite™, Organoclay™ PM-199, and quartz sand as a control) was evaluated using flow-through column experiments. The effectiveness of the sorbents was based on (1) the percentage of Hg removed in relation to the total amount of Hg passing the sorbent column, and (2) the rate of Hg uptake compared to the nonreactive tracer bromide (Br−). All sorbents removed Hg to a certain extent, but none of the sorbents removed all the Hg introduced to the columns. Thiol-SAMMS showed the highest mean percentage of Hg removed (87% ± 2.9%), followed by Organoclay PM-199 (71% ± 0.4%), pine biochar (57% ± 22.3%), SediMite (61% ± 0.8%), and the control quartz sand (11% ± 5.6%). Thiol-SAMMS was the only sorbent to exhibit retardation of Hg in comparison to the conservative tracer Br−. For the remaining sorbents, Br− along with low concentrations of Hg were eluted within the first 3 pore volumes, indicating limited retardation of Hg. Overall, removal of Hg by sorbents was substantial, suggesting that sorbents might be suitable for deployment in contaminated environments. High concentrations of DOM leaching from the soil columns likely influenced the speciation of Hg and inhibited sorption to the sorbents. Incomplete removal of Hg by any sorbent suggests that additional optimization is needed to increase efficiency.
Highlights
Mercury (Hg) is a global pollutant that threatens our water resources and poses a significant risk to human health
Organoclay PM-199 was highly reactive to Br− such that Br− did not elute from the columns
The goal of this study was to evaluate the immobilization of Hg by engineered sorbents to reduce ambient concentrations in water leaching from contaminated soils
Summary
Mercury (Hg) is a global pollutant that threatens our water resources and poses a significant risk to human health. Mercury is converted in terrestrial and aquatic ecosystems between various forms, which include elemental Hg0, inorganic mercuric Hg2+ (dissolved and particulate), and organomercurials (e.g., methylmercury). The conversion of Hg0 and Hg2+ to highly toxic MeHg in combination with bioaccumulation and biomagnification in aquatic environments leads to significant risks to environmental and human health (Clarkson 1998; Morel et al 1998). Engineered sorbents are used for the removal of heavy metals from industrial waste streams and in situ stabilization in contaminated subsurface environments. While remediation strategies using in situ sorbent amendments have been successfully demonstrated for many organic contaminants
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