Eric Heinen De Carlo

Sorption of rare-earth elements from seawater onto synthetic mineral particles: An experimental approach☆☆☆

Abstract The sorptive properties of the rare-earth elements (REE) in seawater-pure synthetic mineral phase systems were investigated through standard batch equilibration experiments. Mineral phases associated with marine ferromanganese deposits such as vernadite, goethite and apatite were synthesized at low temperature and pressure and used in single solid-phase batch experiments. Results from our adsorption studies are in agreement with features of REE patterns in natural deposits including the Ce anomaly found in deep-sea marine ferromanganese minerals and a general trend of preferential uptake of light (LREE) relative to heavy (HREE) rare-earth elements. Although fractionation trends lead to a general LREE enrichment for all phases investigated, significant differences exist in the adsorptive properties of iron oxyhydroxides (α-FeOOH) and vernadite (δ-MnO 2 ). These include a positive Ce anomaly on vernadite and a difference in the extent of REE fractionation between the two phases. In addition to the fractionation of LREE from HREE which was observed on vernadite and goethite, the REE sorption patterns on hydroxylapatite lead us to suggest that incorporation of the light to intermediate REE may also occur by crystal lattice substitution for Ca 2+ .

The Influence of Redox Reactions on the Uptake of Dissolved Ce by Suspended Fe and Mn Oxide Particles

AbstractLaboratory experiments were conducted to evaluate the partitioning ofrare earth elements (REE) between solution and suspended particles. Becauseof their strong tendency to complex, the REE can be used to study a varietyof marine processes and in particular particle scavenging. In this study, anemphasis was placed on examining abiotic redox processes that influence theuptake of dissolved Ce by particles. Batch sorption experiments wereconducted with REE and synthetic mineral phases over the range of pH4–9. The solutions varied in ionic strength between 0 and 0.7 M andconsisted of individual solutes (NaNO3, NaCl, andNa2SO4), ionic mixtures that duplicate theseawater composition, and natural seawater. The uptake of REE from solutionwas also studied at a Pt electrode coated with

Geochemistry of hydrothermal deposits from Loihi submarine volcano, Hawaii

\delta {\text{ - MnO}}_{\text{2}}

Rare earth elements in the water column of Lake Vanda, McMurdo dry valleys, Antarctica

using cyclic voltametry.Experimental results are consistent with uptake of dissolved Ce onto

Autonomous in situ measurements of seawater alkalinity.

\delta {\text{ - MnO}}_{\text{2}}

Micromorphological characteristics of a marine ferromanganese crust

occurring by a combination of oxidativescavenging and surface complexation. The contribution of oxidativescavenging to the removal of Ce from solution is most pronounced at acidicpH, where the strictly trivalent REE exhibit little propensity for sorptiononto