Mechanistic insights into the co-recovery of nickel and iron via integrated carbon mineralization of serpentinized peridotite by harnessing organic ligands.

The rising need to produce a decarbonized supply chain of energy critical metals with inherent carbon mineralization motivates advances in accelerating novel chemical pathways in a mechanistically-informed manner. In this study, the mechanisms underlying co-recovery of energy critical metals and carbon mineralization by harnessing organic ligands are uncovered by investigating the influence of chemical and mineral heterogeneity, along with the morphological transformations of minerals during carbon mineralization. Serpentinized peridotite is selected as the feedstock, and disodium EDTA dihydrate (Na2H2EDTA·2H2O) is used as the organic ligand for metal recovery. Nickel extraction efficiency of ∼80% and carbon mineralization efficiency of ∼73% is achieved at a partial pressure of CO2 of 50 bars, reaction temperature of 185 °C, and 10 hours of reaction time in 2 M NaHCO3 and 0.1 M Na2H2EDTA·2H2O. Extensive magnesite formation is evidence of the carbon mineralization of serpentine and olivine. An in-depth investigation of the chemo-morphological evolution of the CO2-fluid-mineral system during carbon mineralization reveals several critical stages. These stages encompass the initial incongruent dissolution of serpentine resulting in a Si-rich amorphous layer acting as a diffusion barrier for Mg2+ ions, subsequent exfoliation of the silica layer to expose unreacted olivine, and the concurrent formation of magnesite. Organic ligands such as Na2H2EDTA·2H2O aid the dissolution and formation of magnesite crystals. The organic ligand exhibits higher stability for Ni-complex ions than the corresponding divalent metal carbonate. The buffered environment also facilitates concurrent mineral dissolution and carbonate formation. These two factors contribute to the efficient co-recovery of nickel with inherent carbon mineralization to produce magnesium carbonate. These studies provide fundamental insights into the mechanisms underlying the co-recovery of energy critical metals with inherent carbon mineralization which unlocks the value of earth abundant silicate resources for the sustainable recovery of energy critical metals and carbon management.

Structure of ice confined in silica nanopores.

Observed anomalous thermodynamic properties of confined water such as deviations in the melting point and freezing point motivate the determination of the structure of confined water as a function of pore size and temperature. In this study, we investigate the dynamic evolution of the structure of confined ice in SBA-15 porous materials with pore diameters of 4 nm, 6 nm, and 8 nm at temperatures ranging from 183 K to 300 K using in operando Wide-Angle X-Ray Scattering (WAXS) measurements, X-Ray Partial Distribution Function (PDF) measurements, and classical Molecular Dynamics (MD) simulations. Formation of hexagonal ice structures is noted in all the three pore sizes. In silica nanopores with diameters of 4 nm, cubic ice formation is noted in addition to hexagonal ice. Longer lasting hydrogen bonds and longer residence times of the water molecules in the first coordination shell contribute to observed crystalline organization of ice in confinement. Self-diffusion coefficients of confined liquid water, predicted from classical MD simulations, are four orders of magnitude higher compared to ice formed in confinement. These experimental and simulation results provide comprehensive insights underlying the organization of confined water and ice in silica nanopores and the underlying physico-chemical interactions that contribute to the observed structures.

Confinement induces stable calcium carbonate formation in silica nanopores.

Scalable efforts to remove anthropogenic CO2via the formation of durable carbonates require us to harness siliceous nanoporous geologic materials for carbon storage. While calcium carbonate formation has been extensively reported in bulk fluids, there is a limited understanding of the influence of nanoconfined fluids on the formation of specific stable and metastable polymorphs of calcium carbonates in siliceous materials that are abundant in subsurface environments. To address this challenge, silica nanochannels with diameters of 3.7 nm are architected and the formation of specific calcium carbonate phases is investigated using X-ray diffraction (XRD), and molecular dynamics (MD) simulations. The formation of stable calcium carbonate (or calcite) is noted in silica nanochannels. The presence of fewer water molecules in the first hydration shell of calcium ions in confinement compared to in bulk fluids contributes to stable calcium carbonate formation. These studies show that nanoporous siliceous environments favor the formation of stable calcium carbonate formation.

Porous Colloidal Nanoparticles as Injectable Multimodal Contrast Agents for Enhanced Geophysical Sensing.

Injecting fluids into underground geologic structures is crucial for the development of long-term strategies for managing captured carbon and facilitating sustainable energy extraction operations. We have previously reported that the injection of metal-organic frameworks (MOFs) into the subsurface can enhance seismic monitoring tools to track fluids and map complex structures, reduce risk, and verify containment in carbon storage reservoirs because of their absorption capacity of low-frequency seismic waves. Here, we demonstrate that water-based Cr/Zn/Zr MOF colloidal suspensions (nanofluids) are multimodal geophysical contrast agents that enhance near-wellbore logging tools. Based on experimental fluid-only measurements, MIL-101(Cr), ZIF-8, and UiO-66 nanofluids have distinct complex conductivity and/or low-field nuclear magnetic resonance (NMR) signatures that are relevant to field-deployed technologies, implying the potential to enhance near-wellbore monitoring of CO2 injection and associated processes with downhole logging tools. Small- and wide-angle X-ray scattering characterization of ∼0.5 wt % MIL-101(Cr) suspensions confirmed phase stability and provided insight into the fractal nature of colloidal nanoparticles. Finally, low-field (2 MHz) NMR measurements of MIL-101(Cr) nanofluid injection into a prototypical Berea sandstone demonstrate how paramagnetic high-surface area MOFs may dominate the relaxation times of hydrogen-bearing fluids in porous geologic matrices, enhancing the mapping of near-surface and near-wellbore transport pathways and advancing sustainable subsurface energy technologies.

On the Structure and Lithium Adsorption Mechanism of Layered H2TiO3.

Layered H2TiO3 has been studied as an ionic sieve material for the selective concentration of lithium from solutions. The accepted mechanism of lithium adsorption on H2TiO3 ion sieves is that it occurs via Li+-H+ ion exchange with no chemical bond breakage. However, in this work, we demonstrate that lithium adsorption on H2TiO3 occurs via O-H bond breakage and the formation of O-Li bonds, contrary to previously proposed mechanisms. Thermogravimetric analysis results show that the weight loss due to dehydroxylation decreases from 2.96 wt % to 0.8 wt % after lithium adsorption, indicating that surface hydroxyl groups break during lithium adsorption. Raman and Fourier transform infrared spectroscopy studies indicate that H2TiO3 contains isolated OH groups and hydrogen-bonded OH groups. Among these two hydroxyl groups, isolated OH groups present in the HTi2 layers are more actively involved in lithium adsorption than hydrogen-bonded OH groups. As a result, the actual adsorption capacity is limited by the number of isolated OH groups, whereas hydrogen-bonded OH groups involved are for stabilizing the layered structure. We also show that H2TiO3 contains a high concentration of stacking faults and structural disorders which play a crucial role in controlling lithium adsorption properties.

Functionalized graphene oxide coating on Ti6Al4V alloy for improved biocompatibility and corrosion resistance.

The present study focused on the development of magnesium-functionalized graphene oxide (FGO) coating on titanium alloy (Ti6Al4V) by electrophoretic deposition. Graphene oxide (GO) was synthesized by modified Hummers' method and functionalized with magnesium ions. X-ray diffraction, infrared spectroscopy (IR) and Raman spectroscopy were employed to confirm the synthesis of GO and GO-coatings on Ti6Al4V. Functionalization of GO with Mg ions was confirmed by energy dispersive X-ray spectroscopy. The surface morphology of coated samples was examined through scanning electron microscopy. Reduction of FGO coating (labelled as rFGO) by heating at 200 °C was confirmed by IR. The rFGO coated Ti6Al4V was found to be hydrophilic in nature as determined by contact angle measurement which showed reduction in the contact angle of Ti6Al4V from 95.4° to 42.1°. The percent cell viability over the coated sample was appreciably improved compared to as-received Ti6Al4V sample owing to hydrophilicity of the former. The positive shift in open circuit potential and increase in polarization resistance was observed after coating Ti6Al4V samples with FGO. The significant decrease in the corrosion current density and negative polarization loop in the reverse scan of samples also confirmed the improved corrosion resistance of rFGO-coated Ti6Al4V over uncoated Ti6Al4V in the PBS solution. Furthermore, the impedance spectroscopy revealed that the preferential adsorption of ionic species (indicated by large Rads) at the surface improved the barrier characteristics of rFGO coated samples and exhibited an order of magnitude higher Rct compared to as-received samples.