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Lammers, Laura Nielsen

Publications and source records attributed to Lammers, Laura Nielsen.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Electrophoretic and potentiometric signatures of multistage CaCO3 nucleation

HYPOTHESIS: Calcium carbonate nucleation is often a complex and multistep process that is difficult to follow in situ. The time-resolved electrochemical and electrophoretic methods can provide a new insight into the nucleation pathway. EXPERIMENTS: Here, we used a combination of speciation calculations with time-resolved electrophoretic and potentiometric methods to monitor calcium carbonate precipitation from a slightly supersaturated solution. FINDINGS: After an initial mixing period of three minutes in which metastable CaCO 3 phases may have nucleated and subsequently dissolved due to locally-high supersaturations, bulk solution pH and Ca 2+ concentrations stabilize before decreasing in tandem with the precipitation of a CaCO 3 phase. After an hour, the precipitate is dominated by calcite that grows at the expense of dissolving vaterite. The time-dependent electrokinetic potential shows analogous signatures of multistage nucleation process: initial rapid changes in ζ-potential are followed by much slower equilibration starting about one hour after reagents are mixed. The changes in ζ-potential, solution pH, saturation indexes, and particle morphology are consistent with vaterite to calcite transformation via dissolution of the former and recrystallization of the latter. These findings highlight the potential use of ζ-potential measurements for monitoring polymorphic transformations of carbonate phases in-situ.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnesian calcite solid solution thermodynamics inferred from authigenic deep-sea carbonate

Magnesian calcite is perhaps the most well studied solid solution in the geosciences due to the widespread use of marine carbonates to reconstruct paleoenvironment. Despite decades of research, the low temperature thermodynamic properties of magnesian calcite in seawater are poorly constrained, largely because very slow reaction kinetics prevent the direct measurement of equilibrium distribution coefficients ($K_d^{Mg}$) for anhydrous Mg-bearing minerals. In this study, we use the Mg content of authigenic calcite formed in deep-sea marine carbonate sediments to determine the dependence of $K_d^{Mg}$ on temperature and aqueous Mg/Ca between ~2 and 25 °C. We find that the solid activity coefficient of magnesite in Mg-calcite is strongly temperature dependent in this range, leading to predicted exsolution of Mg at low temperatures. At the temperatures typical of ocean bottom water, equilibrium Mg distribution coefficients are at least an order of magnitude lower than values inferred from inorganic calcite growth experiments. Moreover, the equilibrium temperature dependence of $K_d^{Mg}$ agrees well with field-based paleotemperature calibrations determined for low-Mg benthic and planktonic foraminifera at temperatures <20 °C. Partitioning of Mg in foraminiferal tests is expected to be highly dependent on the Mg/Ca ratio in the calcifying fluid, so ignoring secular variations in seawater Mg/Ca can lead to significant underestimation of paleotemperatures.

58 GEOSCIENCES↗
DOE OSTI2018

Greenhouse Gas Production and Transport in Desert Soils of the Southwestern United States

Deserts comprise a large portion of the Earth's land area, yet their role in the fluxes and cycles of greenhouse gases is poorly known and their likely response to climate change largely unexplored. We report here a reconnaissance investigation of the concentrations and fluxes of CO 2 , CH 4 , and N 2 O along two elevation (climate) gradients in the southwestern United States. In-soil concentrations of CO 2 increased with elevation (up to 5,000 ppm). Concentrations of CH 4 declined with depth in all soils (to less than 1 ppm), but the rates of decrease with depth increased with elevation. In contrast, concentrations and depth trends of N 2 O varied erratically. Soils were net CO 2 sources (0 to >1,500 kg CO 2 ·ha -1 ·year -1 ), and net CH 4 sinks (0.2 to >3 kg CH 4 ·ha -1 ·year -1 ). The small and variable N 2 O fluxes were inconsistent with the trends in soil N δ 15 N values, which decreased by 5‰ to 6‰ over about 1,000 m of elevation. The high soil N δ 15 N values (up to nearly 17‰ at the lowest elevation) indicate that there is a soil N loss mechanism that is highly depleted in 15 N, and gaseous losses—either NH 3 or N 2 O/N 2 —are suspected of driving these values. In summary, there appears to be a strong climate control on both soil CO 2 and CH 4 concentrations and to a lesser degree on calculated fluxes. The soil N trace gas concentrations indicate that deserts can be either small sources or sinks of N 2 O and that there may be significant consumption of arid soil N 2 O.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

A structural coarse-grained model for clays using simple iterative Boltzmann inversion

Cesium-137 is a crucial byproduct of nuclear energy generation and is environmentally threatening due to its long half-life and affinity for naturally occurring micaceous clays. Current experimental observations of illite and phlogopite mica indicate that Cs+ is capable of exchanging with K+ bound in the anhydrous interlayers of layered silicates, forming sharp exchange fronts, leading to interstratification of Cs- and K-illite. We introduce here a coarse-grained (CG) model of the anhydrous illite interlayer developed using iterative Boltzmann inversion that qualitatively and quantitatively reproduces features of a previously proposed feedback mechanism of ion exchange. The CG model represents a 70-fold speedup over all-atom models of clay systems and predicts interlayer expansion for K-illite near ion exchange fronts. Contrary to the longstanding theory that ion exchange in a neighboring layer increases the binding of K in lattice counterion sites leading to interstratification, we find that the presence of neighboring exchanged layers leads to short-range structural relaxations that increase basal spacing and decrease cohesion of the neighboring K-illite layers. We also provide evidence that the formation of alternating Cs- and K-illite interlayers (i.e., ordered interstratification) is both thermodynamically and mechanically favorable compared to exchange in adjacent interlayers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Techno-economic Assessment for Integrating Biosorption into Rare Earth Recovery Process

The current uncertainty in the global supply of rare earth elements (REEs) necessitates the development of novel extraction technologies that utilize a variety of REE source materials. Herein, we examined the techno-economic performance of integrating a biosorption approach into a large-scale process for producing salable total rare earth oxides (TREOs) from various feedstocks. An airlift bioractor is proposed to carry out a biosorption process mediated by bioengineered rare earth-adsorbing bacterium. Techno-econmic asssements were compared for three distinctive categories of REE feedstocks that require different pre-processing steps. Key parameters identified that affect profitability include REE concentration, composition of the feedstock, and costs on feedstock pretreatment and waste management. Among the 11 specific feedstocks investigated, coal ash from the Appalachian Basin was projected to be the most profitable, largely due to its high-value REE content. Its cost breakdown includes leaching (80.7%), biosorption (16.0%), and oxalic acid precipitation and TREO roasting (3.3%). Surprisingly, biosorption from the high-grade Bull Hill REE ore is less profitable due to the high material cost and low production revenue. Altogether, our results confirmed that the economic potential of applying biosorption to low-grade feedstocks is viable.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Recovery of Rare Earth Elements from Low-Grade Feedstock Leachates Using Engineered Bacteria

The use of biomass for sorption of rare earth elements (REEs) for bioremediation and biomining applications has been the subject of many recent investigations. However, REE adsorption by bioengineered systems has been scarcely documented, and rarely tested with complex natural feedstocks. In this study, we engineered E. coli cells for enhanced cell surface-mediated extraction of REEs. Using Lpp-OmpA as an anchor, up to 16 copies of a Lanthanide binding tag (LBT) per OmpA protein were displayed on the E. coli cell surface, resulting in a 2-fold increase in Tb adsorption capacity compared to control cells. To test the efficacy of engineered E. coli cells to extract REEs from complex source materials, biosorption was performed with leachates from two mine tailings and two rare earth deposits. Although control E. coli cells exhibited preferential adsorption of REEs over most metals, functionalization of the cell surface with LBT yielded several notable advantages. First, the efficiency of REE adsorption from all tested leachates was enhanced with distribution coefficients for individual REEs increased by 2-10 fold. Second, although, Cu, Al, Ga and Pb were found to be the best competitors for REE binding to the E. coli cell surface, LBT-display enhanced the cell surface affinity for REEs over all non-REEs except Cu. Third, LBT-display systematically enhanced the affinity of the cell surface for REEs as a function of decreasing atomic radii, providing a means to separate high value HREEs such as Dy and Tb from more common LREEs such as La. Altogether, our results demonstrate that REE biosorption of high efficiency and selectivity can be achieved by engineering the native bacterial surface.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Direct Exchange Mechanism for Interlayer Ions in Non-Swelling Clays

The mobility of radiocesium in the environment is largely mediated by cation exchange in micaceous clays, in particular Illite—a non-swelling clay mineral that naturally contains interlayer K + and has high affinity for Cs + . Although exchange of interlayer K + for Cs + is nearly thermodynamically nonselective, recent experiments show that direct, anhydrous Cs + -K + exchange is kinetically viable and leads to the formation of phase-separated interlayers through a mechanism that remains unclear. Here, using classical atomistic simulations and density functional theory calculations, we identify a molecular-scale positive feedback mechanism in which exchange of the larger Cs + for the smaller K + significantly lowers the migration barrier of neighboring K + , allowing exchange to propagate rapidly once initiated at the clay edge. Barrier lowering upon slight increase in layer spacing (~0.7 Å) during Cs + exchange is an example of “chemical-mechanical coupling” that likely explains the observed sharp exchange fronts leading to interstratification. Interestingly, we find that these features are thermodynamically favored even in the absence of a heterogeneous layer charge distribution.

Ruiz Pestana, Luis↗