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Reactive Transport Modeling of Hydrogen Production from Serpentinization of Olivine
Hydrogen production from serpentinization of ultramafic rocks represents a promising natural pathway for generating carbon-free energy, yet its kinetics and controlling factors remain incompletely understood. A key challenge in advancing serpentinization research lies in the heterogeneity of porosity and permeability in rocks, which leads to nonuniform fluid velocity fields, as well as uncertainties in estimating reactive surface area and identifying appropriate mineral reaction equilibria. Additional complexities arise from the role of dissolved SiO 2 , Fe 2+ /Fe 3+ partitioning, and the limited effect of pH variations within the strongly alkaline regime on hydrogen yields. These challenges hinder straightforward extrapolation from laboratory tests to practical applications of hydrogen production from natural rocks. Here, in this work, we address these questions using a simulation-based reactive transport modeling framework calibrated against controlled laboratory experiments reported elsewhere. The model couples geochemical kinetics, multiphase flow, and mineralogical feedbacks, enabling systematic evaluation of how surface area, dissolved silica concentration, Fe redox state, temperature, and pressure govern serpentinization and H2 generation. We find that surface area exerts the strongest control on reaction rates and hydrogen yields, while Fe 2+ /Fe 3+ ratios act as secondary modulators. Elevated dissolved silica concentrations suppress hydrogen production but accelerate serpentine precipitation, whereas increasing pH beyond 12 within the strongly alkaline regime produces only marginal gains. Finally, we demonstrate that integrating targeted experiments with calibrated simulations offers a powerful and efficient approach for predicting hydrogen yields and assessing parameter trade-offs in industrial-scale applications. This integration can substantially reduce the experimental burden while improving predictive capability, thereby enhancing both the mechanistic understanding and the practical feasibility of hydrogen production from serpentinization.
Observations from High-Velocity Recovery Experiments of the Crystallization Behavior of Olivine from Iron-Enriched Melts
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Vaporization of Major Mantle Silicates: Vapor Curves for Olivine and Bronzite
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Effect of Particle Size on Raman Signal Strength of Silicate Minerals
Understanding the effects of particle size is necessary for quantifying minerals in mixtures using Raman spectroscopy. Raman signal intensity is evaluated using six common silicate minerals (two olivines, two pyroxenes, and two feldspars) at 10 particle size ranges. For olivines and feldspars, the highest peak intensities are observed in samples with 38–63 and 63–106 μm particle sizes. There is no such consistent trend for the pyroxene samples, although the overall low signal strength complicates those measurements. In conclusion, Raman spectra of samples with varying particle sizes appear to be influenced by two competing effects: scattering from particle boundaries and effective sampling volume.
Comparative Dissolution of Iron-Bearing Minerals by Catecholate and Hydroxamate Siderophores under Oxic and Anoxic Conditions
Siderophores play a crucial role in biological iron (Fe) acquisition and mobilization by promoting Fe mineral and rock weathering. While the effects of the hydroxamate siderophore desferrioxamine B (DFOB) have been extensively studied, the role of catecholates in the dissolution of Fe mineral and rock under varying redox conditions remain limited. Moreover, despite Fe being one of the most redox-active metals, the siderophore-mediated redox transformations of solid-phase Fe and their impact on mineral dissolution are not well understood. Herein, this study systematically investigated dissolution behavior of both Fe(II) and Fe(III)-bearing minerals and rocks (Fe(II)- bearing basalt and olivine, and Fe(III)- bearing nontronite and goethite), by two structurally distinct biological siderophores, catecholate protochelin and hydroxamate DFOB, under both oxic and anoxic conditions. Batch experiments quantified Fe and transition metals (Mn, Ni, Zn, Mo) released from the tested minerals in the presence of siderophores. Throughout the dissolution experiments, siderophore concentrations and Fe-siderophore complexation in solutions were measured using UV-vis spectrometry. Fe redox changes under oxic and anoxic conditions by siderophores were determined, and mineral surface alterations following siderophore treatments were characterized through scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Results revealed distinct interplays of dissolution mechanisms, including ligand-exchange promoted dissolution and reductive dissolution, along with Fe(III) reduction and Fe(II) oxidation, contributing to the Fe(II)- and Fe(III)-rich mineral weathering under varying redox conditions. Under oxic conditions, both protochelin and DFOB enhanced Fe release from Fe(II)-rich basalt and olivine more effectively than from Fe(III)-rich minerals. DFOB induced greater Fe(II)-mineral dissolution than protochelin. This difference was attributed to a higher level of Fe(II) oxidation by DFOB in contrast to protochelin, as well as the protochelin oxidation with the loss of Fe binding groups (catechols). Under anoxic conditions, both siderophores significantly reduced Fe(III) in nontronite and goethite, with protochelin demonstrating substantially stronger Fe(III) reduction capacity than DFOB. However, Fe(III) reduction negatively impacted Fe release from Fe(III)-rich minerals. Instead, Fe release from Fe(II)-rich minerals was enhanced under anoxic conditions due to the absence of Fe(II) oxidation and labile Fe(II). Variations in siderophore adsorption also contributed to dissolution differences. Beyond iron, the release of transition metals from tested minerals was influenced by elemental contents, mineral compositions, and siderophore types, revealing distinct metal- and siderophore-dependent patterns. This systematic investigation highlights the roles of siderophores in Fe redox cycling and metal mobilization, enhancing our understanding of different siderophore behaviors in siderophore-mediated microbial metal acquisition within redox-dynamic environments, with implications for bioleaching industries and applications in agriculture and climate change mitigation.
Reservoir-scale model of geologic hydrogen production from serpentinization: Cyclic injection in a dual-permeability fracture-matrix system
Geologic hydrogen (GeoH 2 ) from serpentinization is a promising low-carbon resource, but its reservoir-scale behavior remains poorly understood. We develop a dual-permeability reactive transport model for an injector–producer well pair in ultramafic rock that couples multiphase flow, heat transfer, geochemistry, and porosity–permeability evolution. Here, the model is calibrated to olivine flow-through experiments and upscaled to two-year long simulations with continuous injection and cyclic injection with shut-in-to-injection ratios (SIR = 1, 0.5, 0.1). Olivine reacts along high-flux pathways to form lizardite and magnetite, increasing pH; H 2 (aq) and H 2 (g) peak early and then decline as exsolution and advective export outpace local generation. Continuous injection yields the highest cumulative H 2 but the lowest water-use efficiency (1.138 x 10 –6 mol/kgw). Cyclic injection increases this ratio to 1.35 x 10 –6 , 1.377 x 10 –6 , and 1.182 x 10 –6 mol/kgw for SIR = 1, 0.5, and 0.1, respectively; SIR = 0.5 provides a ~20% improvement over continuous injection and the best compromise for pilot design.
The Role of Dislocations in the Anelasticity of the Upper Mantle
Dislocation‐based dissipation mechanisms potentially control the viscoelastic response of Earth's upper mantle across a variety of geodynamic contexts, including glacial isostatic adjustment, postseismic creep, and seismic‐wave attenuation. However, there is no consensus on which dislocation‐based, microphysical process controls the viscoelastic behavior of the upper mantle. Although both intergranular (plastic anisotropy) and intragranular (backstress) mechanisms have been proposed, there is currently insufficient laboratory data to discriminate between those mechanisms. Here, we present the results of forced‐oscillation experiments in a deformation‐DIA apparatus at confining pressures of 3–7 GPa and temperatures of 298–1370 K. Our experiments tested the viscoelastic response of polycrystalline olivine—the main constituent of the upper mantle—at stress amplitudes from 70 to 2,800 MPa. Mechanical data are complemented by microstructural analyses of grain size, crystallographic preferred orientation, and dislocation density. We observe amplitude‐ and frequency‐dependent attenuation and modulus relaxation and find that numerical solutions of the backstress model match our results well. Therefore, we argue that interactions among dislocations, rather than intergranular processes (e.g., plastic anisotropy or grain boundary sliding), control the viscoelastic behavior of polycrystalline olivine in our experiments. In addition, we present a linearized version of the constitutive equations of the backstress model and extrapolate it to conditions typical of seismic‐wave propagation in the upper mantle. Our extrapolation demonstrates that the backstress model can explain the magnitude of seismic‐wave attenuation in the upper mantle, although some modification is required to explain the weak frequency dependence of attenuation observed in nature and in previous experimental work.
Gas-solid reaction-based selective lithium leaching strategy for efficient LiFePO 4 recycling
As the electric-vehicle market continues to expand, LiFePO 4 (LFP) batteries, valued for their intrinsic safety and cost-effectiveness, are being increasingly utilized. However, this widespread adoption highlights the urgent need for innovative and environmentally friendly recycling methods for spent LFP batteries due to their relatively low material value and the environmental challenges associated with traditional recycling processes. Here, in this study, we present a novel selective lithium leaching technique that involves a gas–solid reaction with chlorine gas. This method achieves a remarkable leaching efficiency of 99.8 % and a selectivity of 98.8 % at 200 °C within just 10 min, without generating acidic wastewater. The resulting LiCl solution was successfully converted into Li 2 CO 3 with an excellent purity of 99.5 %, while producing NaCl solution as the only byproduct. Notably, the olivine structure of the LFP was preserved as FePO 4 after lithium leaching. The regenerated LFP demonstrated excellent performance, retaining 94.1 % of its capacity after 150 cycles, while the lithium-leached FePO 4 delivered a reversible capacity exceeding 150 mAh/g. This approach not only enhances the efficiency of LFP recycling but also paves the way for more sustainable battery technologies.
Geologic hydrogen as an emerging fuel: experimental insights, thermodynamics, kinetics, and reactive transport modeling
Geologic hydrogen (GeoH 2 ) is emerging as a viable clean energy source. It is largely produced through serpentinization, a geological process in which ultramafic rocks react with water under suitable temperature and pressure. Here, this review synthesizes the current understanding of H 2 generation by serpentinization, with an emphasis on reaction mechanisms, kinetics, and thermodynamics, as well as on modeling flow and transport of reacting fluids in geological formations. We describe the role of mineral assemblages, such as olivine and pyroxene, fluid-rock interactions, and catalytic surfaces, in influencing GeoH 2 yield and reaction rates. By integrating models of reaction kinetics, subsurface reactive flow and transport, and the serpentinization process, and by accounting for the thermodynamic state of the system, this review aims to guide future GeoH 2 research and to evaluate the potential of natural hydrogen as a sustainable clean energy source.
Chronology of ungrouped achondrites Northwest Africa 11119 and 7325/8486: implications for early evolution of a heterogeneous crust on a differentiated planetesimal
The chronology of ungrouped achondrites provides key insights into the timeline of igneous activity in the early Solar System. Two ungrouped achondrites – Northwest Africa (NWA) 11119 (andesite-dacite) and NWA 8486 and its pair NWA 7325 (olivine gabbro) – are the focus of this study, where their chronologies are investigated using multiple high-resolution techniques. Here we report the lead-lead (207Pb-206Pb) and manganese-chromium (53Mn-53Cr) systematics of NWA 11119, as well as the 207Pb-206Pb systematics of NWA 8486 alongside aluminum-magnesium (26Al-26Mg) systematics for NWA 7325. The U-corrected 207Pb-206Pb ages of NWA 11119 and the combined ages of NWA 7325/8486 are 4566.4 ± 0.8 Ma and 4563.8 ± 1.9 Ma, respectively. Additionally, we report the 53Mn-53Cr age of NWA 11119 to be 4564.4 ± 2.5 Ma and the 26Al-26Mg age of NWA 7325/8486 to be 4563.1 ± 0.3 Ma. The formation of NWA 11119 requires partial melting of a (likely chondritic) source reservoir leading to eruption of Si rich, alkali depleted magmas, while NWA 7325/8486 likely formed from a chemically fractionated reservoir with superchondritic Al/Mg. The clear geochemical and isotopic similarities of these achondrites, combined with the chronology reported here, is suggestive of formation of these two ungrouped achondrites on a common parent body which likely formed in the inner Solar System and experienced early differentiation under reducing conditions. If these achondrites did share a parent body, it would suggest that primary asteroids in the early Solar System commonly produced mineralogically and geochemically heterogeneous crusts. While mineralogical and geochemical heterogeneity is known to exist in the (mostly mafic) crust of asteroid Vesta, our findings show that even more significant crustal heterogeneity (representing felsic and mafic compositions) may exist on other asteroids.
Room temperature sodium diffusion in sodium iron phosphate investigated with neutron scattering
Sodium iron phosphate, Na x FePO 4 , is currently one of the most promising cathode materials for sodium ion batteries. Here we employ a systematic approach using three neutron scattering techniques to investigate temperature dependent properties with a focus on the charge transfer processes. Two distinct Na + diffusive motions are observed with quasielastic neutron scattering, including room temperature motion. These processes correspond to rapid double jumps through extrinsic vacancy sites of ∼6 Å along with the more fundamental nearest neighbor jumps of 3.1 Å. Experimental observations of room temperature ionic diffusion are highly desirable, as the diffusion pathways are naturally well suited for efficient transport. Inelastic neutron scattering was used to probe the vibrational density of states that assist in the ionic and electronic (polaronic) transport processes, which are further supported with density functional theory. Neutron diffraction examines the disordering of the sodium sublattice upon transition to the solid-solution phase, which is believed to enhance the overall kinetics during sodium insertion/extraction. Finally, 57 Fe Mössbauer spectroscopy measurements probes polaron hopping and the local structural evolution that modifies the electron density surrounding the redox active iron sites. This study sheds light on the temperature induced atomic scale dynamics that occur in olivine Na x FePO 4 .
Chelation-Driven Chemistry Controls Dissolution Pathways for Facile Critical Mineral Recovery from Ultramafic Resources
The efficient recovery of critical minerals, such as nickel (Ni) and manganese (Mn) from the subsurface is of vital importance, given their role in modern technologies ranging from batteries to advanced alloys. This study explores an approach that employs chelation to enhance critical mineral recovery from ultramafic rocks using chelating ligands under ambient pressures and systematically evaluates the extraction process for the first time. Experimental results demonstrate the superior performance of EDTA and PrDTA in achieving high extraction efficiencies for both Ni and Mn. To further highlight the ability for optimization, the fluid exchange and variation of fluid-to-rock ratio experiments were conducted, revealing tunable controls for engineering recovery. We show that under optimized conditions, a Ni extraction efficiency of ?82% and a Mn extraction efficiency of ~60% is achieved at ambient pressures, which is equivalent to over 23 times the current global Ni production, and 2 million metric tonnes (MMT) greater than the current global Mn production. From both in-situ and ex-situ mining perspectives, the results highlight the potential of chelation to advance sustainable mineral processing. Overall, this work highlights the environmental benefits of innovative ligand-assisted recovery methods, addressing the critical need for the efficient utilization of olivine resources.
High Sodium Solubility in Magnesiowüstite in Iron‐Rich Deep Lower Mantle
Abstract (Mg,Fe)O ferropericlase‐magnesiowüstite has been proposed to host the majority of Earth's sodium, but the mechanism and capacity for incorporating the alkali cation remain unclear. In this work, experiments in the laser‐heated diamond anvil cell and first‐principles calculations determine the solubility of sodium and favorability of sodium incorporation in iron‐rich magnesiowüstite relative to (Mg,Fe)SiO 3 bridgmanite. Reaction of Mg/(Mg + Fe) (Mg#) 55 and 28 olivine with NaCl at 33–128 GPa and 1600–3000 K produces iron‐rich magnesiowüstite containing several percent sodium, while iron‐rich bridgmanite contains little to no detectable sodium. In sodium‐saturated magnesiowüstite, sodium number [Na/(Na + Mg + Fe)] is 2–5 atomic percent at pressures below 60 GPa and drastically increases to 10–20 atomic percent at deep lower mantle pressures. For these two compositions, there is no significant dependence of the results on Mg#. Our calculations not only show consistent results with experiments but further indicate that such an increase in solubility and partitioning of Na into magnesiowüstite is driven by the spin transition in iron. These results provide fundamental constraints on the crystal chemistry of sodium at lower‐mantle conditions. If the sodium capacity of (Mg,Fe)O is not strongly dependent on Mg#, (Mg,Fe)O in the lower mantle may have the capacity to store the entire sodium budget of the Earth.
Volatiles and Redox Along the East African Rift
Abstract The upper mantle under the Afar Depression in the East African Rift displays some of the slowest seismic wave speeds observed globally. Despite the extreme nature of the geophysical anomaly, lavas that erupted along the East African Rift record modest thermal anomalies. We present measurements of major elements, H 2 O, S, and CO 2 , and Fe 3+ /ΣFe and S 6+ /ΣS in submarine glasses from the Gulf of Aden seafloor spreading center and olivine‐, plagioclase‐, and pyroxene‐hosted melt inclusions from Erta Ale volcano in the Afar Depression. We combine these measurements with literature data to place constraints on the temperature, H 2 O, andfO 2 of the mantle sources of these lavas as well as the initial and final pressures of melting. The Afar mantle plume is C/FOZO/PHEM in isotopic composition, and we suggest that this mantle component is damp, with 852 ± 167 ppm H 2 O, not elevated infO 2 compared to the depleted MORB mantle, and has temperatures of ∼1401–1458°C. This is similar infO 2 and H 2 O to the estimates of C/FOZO/PHEM in other locations. Using the moderate H 2 O contents of the mantle together with the moderate thermal anomaly, we find that melting begins at around 93 km depth and ceases at around 63 km depth under the Afar Depression and at around 37 km depth under the Gulf of Aden, and that ∼1%–29% partial melts of the mantle can be generated under these conditions. We speculate that the presence of melt, and not elevated temperatures or high H 2 O contents, are the cause for the prominent geophysical anomaly observed in this region.
Thermoelastic Properties of Iron-Rich Ringwoodite and the Deep Mantle Aerotherm of Mars
The Martian mantle is considered to have a higher Fe/Mg ratio than the Earth's mantle. Ringwoodite, γ-(Mg,Fe) 2 SiO 4 , is likely the dominant polymorph of olivine in the core-mantle boundary (CMB) region of Mars. We synthesized anhydrous iron-rich ringwoodite with molar Mg/(Mg + Fe) = 0.44 and determined its thermal equation of state up to 35 GPa and 750 K by synchrotron X-ray diffraction. Using a third order Birch-Murnaghan equation of state, we obtain K T0 = 182 (3) GPa, K' = 4.6 (2), and α 0 = 3.18 (6) × 10 -5 K -1 . Using these results and an updated mineralogical model with an iron-rich composition of Mg/(Mg + Fe) = 0.75 for the Martian mantle, we estimate ~1900 K for the temperature of the D1000 seismic discontinuity inside Mars. The resulting adiabat predicts a warm aerotherm, which could explain the presence of partial melt at the CMB of Mars recently detected with seismic data from the 2019 InSight mission.
Identifying critical features of iron phosphate particle for lithium preference
One-dimensional (1D) olivine iron phosphate (FePO 4 ) is widely proposed for electrochemical lithium (Li) extraction from dilute water sources, however, significant variations in Li selectivity were observed for particles with different physical attributes. Understanding how particle features influence Li and sodium (Na) co-intercalation is crucial for system design and enhancing Li selectivity. Here, we investigate a series of FePO 4 particles with various features and revealed the importance of harnessing kinetic and chemo-mechanical barrier difference between lithiation and sodiation to promote selectivity. The thermodynamic preference of FePO 4 provides baseline of selectivity while the particle features are critical to induce different kinetic pathways and barriers, resulting in different Li to Na selectivity from 6.2 × 10 2 to 2.3 × 10 4 . Importantly, we categorize the FePO 4 particles into two groups based on their distinctly paired phase evolutions upon lithiation and sodiation, and generate quantitative correlation maps among Li preference, morphological features, and electrochemical properties. By selecting FePO 4 particles with specific features, we demonstrate fast (636 mA/g) Li extraction from a high Li source (1: 100 Li to Na) with (96.6 ± 0.2)% purity, and high selectivity (2.3 × 10 4 ) from a low Li source (1: 1000 Li to Na) with (95.8 ± 0.3)% purity in a single step.
Carbon mineralization pathways in interfacial adsorbed water nanofilms
Carbon mineralization in humidified carbon dioxide offers a promising route to mitigate anthropogenic emissions in a world stressed by water security. Despite its technological importance, our understanding of carbonation in water-poor environments lags, as traditional dissolution-precipitation pathways struggle to explain the adsorbed water nanofilm-mediated reactivity. Here, we utilize in operando X-ray diffraction (XRD) and advanced molecular simulations to investigate nanoconfined reactions driving forsterite carbonation, the magnesium-rich olivine. By examining magnesium ion dissolution and transport in atomistic simulations of the forsterite-water-carbon dioxide interface and comparing these with the in operando XRD activation energies, we identify both processes as rate-limiting at saturation. Our simulations reveal a mechanistic view of interfacial carbonation, where dissolution and precipitation are mediated by anomalous quasi two-dimensional diffusion. The transport process involves intermittent diffusive hopping in the desorbed state, separated by crawling events that are spatially short but temporally long. This understanding transcends carbon mineralization, with implications for understanding the transport of contaminants in geosystems, the design of multifunctional materials, water desalination, and molecular recognition systems.