Interaction of metal oxyions and phosphate with carbonate green rust: Insights into Earth's modern and ancient environments
Description
Carbonate green rust is often found in suboxic and anoxic environments, and is known to be highly reactive towards dissolved metals and other aqueous compounds. Though the reactivity of carbonate green rust towards a variety of aqueous compounds has been determined in previous studies, its reactivity under conditions relevant to modern and ancient marine environments has not been systematically explored. Furthermore, the fate of the aqueous compounds upon aging of the carbonate green rust remains almost completely unknown. To inform the interaction of carbonate green rust with oxyion-forming metals during the mineral's precipitation and aging, we conducted a series of co-precipitation experiments of Cr(VI), Mo(VI), V(V), U(VI), and phosphate with carbonate green rust in seawater-analog solutions, at pH 8.0, 25˚C, and under anoxic conditions. The experimental results are provided as uptake precentages at different metal:Fe ratios and as a series of partition coefficients of the studied oxycation and oxyanions between aqueous solution and carbonate green rust. Additionally, aging experiments up to 13 months in duration were conducted at metal concentrations of 1µM and under the same experimental conditions, to quantify the retention or release of the metals associated with carbonate green rust transformation to themodynamically stable phases. We relate the uptake of the metals and phosphate to the chemical composition of the seawater-analog experimental solutions, and discuss the mechanisms of uptake and retention/release in the context of mineral transformations during aging. We identify a role for dissolved silica in both the uptake and the aged mineral assemblage, and discuss the implications of our findings for modern and ancient natural environments and for environmental remediation.
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- Israeli Science FoundationGrant ID: 1015/18
- Perlman Grant