Trenton R. Graham

Mixed aqueous electrolytes are increasingly important in industrial applications. Mixing NaNO ₃ and NaNO ₂ alters the aggregation free-energy landscape: it increases cluster growth and contraction rates while decreasing rearrangement rates among clusters of a fixed size.

Quantification of nitrate and nitrite concentrations is important for the management of radioactive tank waste chemistry, as these species influence solubility and corrosion. However, existing analytical methods are potentially hindered by turbidity, spectral interference, and delays from sample handling. We demonstrate quantitative ¹⁴N nuclear magnetic resonance (qNMR) spectroscopy as a direct, matrix-tolerant approach for nitrate and nitrite detection at natural abundance. Monte Carlo resampling was integrated into the workflow to quantify marginal uncertainty, establish precision–time trade-offs, and separate noise-limited uncertainty from systematic bias arising from shimming, transmitter offset, or excitation pulse conditions. Quantification of nitrate and nitrite was validated in controlled alkaline matrix challenges and in five multicomponent simulants of Hanford Waste. These results establish ¹⁴N qNMR as a practical, uncertainty-bounded tool for quantifying redox-active nitrogen species in chemically complex environments and provide an approach for quantitative analysis of solution-state quadrupolar nuclei.

In highly concentrated electrolyte solutions, where classical models often fail, specific ion–solvent interactions dictate bulk properties. Here, we combine small-angle X-ray scattering (SAXS) and Raman spectroscopy to link molecular coordination to mesoscale structure across alkali nitrate and nitrite solutions. Our results reveal a structural hierarchy driven by cation identity in that smaller cations (Li⁺, Na⁺) form discrete contact ion pairs, while larger cations (K⁺, Rb⁺) promote increasingly disordered local coordination and extended solute–solvent networks. Using nitrite salts as a structural control, we confirm this organizing principle across different anion geometries. Cs⁺ undergoes a concentration-induced transition to a uniquely ordered state, resulting in a highly structured solution. This work provides a direct, mechanistic explanation for how cation choice dictates the ‘rules’ of solution architecture, offering a predictive basis for understanding phase behavior in complex industrial and environmental systems.

Over the three-year CRADA, Pacific Northwest National Laboratory (PNNL) advanced a new class of Molecular Velcro™ self-healing wellbore cements designed to improve the long-term integrity of wells used for geothermal energy production and carbon storage. Conventional wellbore cement can crack due to repeated mechanical loading, temperature swings, and exposure to aggressive subsurface fluids. Once cracks form, they can create leakage pathways, drive expensive remediation (“workovers”), and in extreme cases shorten well life. This project addressed that problem by developing polymer-modified cement systems that can autonomously re-seal cracks and better tolerate the extreme conditions experienced in subsurface wells, while remaining compatible with practical cementing operations.

This study explores the hydration and transport properties of aqueous cesium hydroxide (CsOH) solution, with or without 1 molar (M) sodium nitrite (NaNO2). Historic studies of electrolyte solutions indicate that Cs+ ions decrease viscosity and increase diffusion rates, whereas OH− ions have the opposite effect. Here, the influence of OH− was dominant in CsOH solutions, leading to increased viscosity and reduced diffusion rates. There was a linear relationship between diffusion coefficients and water activity, emphasizing the significant role of ion–water interactions in determining transport properties. This may be because the interaction between Cs+ and the anions is weak even when they are in direct contact with each other. The weakness of the ion-pairing was established through thermodynamic analysis. The findings suggest that ion-pairing is not the only important interaction controlling transport properties when ion-pairing is weak. Nonetheless, ion-pairing or obstructions did result in more sluggish transport properties as electrolyte concentrations increased. Overall, the research enhances the understanding of the complexities underlying ion interactions in multicomponent solutions.

Gibbsite (α-Al(OH)₃, sometimes designated as γ-Al(OH)₃) plays a crucial role in the chemistry of aluminum in the environment and industry, yet its crystallization behavior under multianionic conditions is not well understood. In this study, we investigate how six common anions─fluoride (F^-), chloride (Cl^-), bromide (Br^-), nitrate (NO₃^-), sulfate (SO₄^2-), and phosphate (PO₄^3-)─influence the mineralization, structure, and morphology of gibbsite at room temperature. The results show that PO₄^3-, SO₄^2-, and F^- strongly inhibit gibbsite formation, stabilizing amorphous or alternative crystalline phases such as nordstrandite and cryolite. On the contrary, Cl^-, Br^-, and NO₃^- allow partial to complete crystallization of gibbsite without significant morphological changes. Solid-state ²⁷Al magic angle spinning nuclear magnetic resonance provides crucial insight into aluminum coordination environments in both crystalline and amorphous phases, distinguishing between octahedral, pentahedral, and tetrahedral Al species. The density functional theory calculations reveal a direct correlation between the Al-X bond strength and the inhibition of crystallization, following the order: PO₄^3- > SO₄^2- > F^- > NO₃^- > Cl^- > Br^-. These findings offer molecular-scale insights into anion-specific effects on aluminum hydroxide nucleation and transformation, improving the understanding of gibbsite formation and aluminum cycling in soils, phosphate retention, contaminant immobilization, and waste treatment strategies in nuclear and industrial settings. These insights can also guide the controlled synthesis of aluminum hydroxide materials with tailored crystallinity and morphology via liquid-assisted methods.

Nitrate impurities in gibbsite increase lattice disorder and suppress radiation-induced electron survival versus chloride analogues. Using ²⁷ Al MQMAS NMR with transverse-field µSR, we link impurity chemistry to structural disorder and electron fate.