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Results for “Zeta potential”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Design of PGM-free cathodic catalyst layers for advanced PEM fuel cells

Here, the design of cathodic catalysts layer (CCL) consisted of Platinum Group Metal-free (PGM-free) electrocatalysts was done by catalyst coated membrane approach. Three different Fe-Mn-N-C compounds were synthesized with Fe:Mn ratio of 1:1, 2:1 and 2:1 with modified heat treatment profile. The catalysts were characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, pore and particle size distribution, zeta potential and transmission electron microscopy. Electrocatalysts were integrated into membrane electrode assembly and evaluated by electrochemical methods. Electrochemical impedance spectroscopy in combination with modeling were used for estimation of proton conductivity of CCL and its oxygen diffusivity. It was found that all CCLs possess extremely high proton conductivity, which was demonstrated for the first time for these types of PGM-free catalysts. The observed ORR mechanism was predominantly 4e- due to peroxide/radicals scavenging effect of Mn.

impedance↗
DOE OSTI2021

Mechanisms dominating thixotropy in limestone calcined clay cement (LC3)

Limestone calcined clay cement (LC3) is a green binder with great practical importance for the cement industry. Growing application has increased the need to understand the mechanisms governing its thixotropy for better control of workability. While formation of C-S-H bridges is understood to dominate the thixotropy of ordinary Portland cement, LC3 paste displayed unique thixotropy properties. In this study, focused beam reflectance measurement, zeta potential, 1H nuclear magnetic resonance relaxometry and micro X-ray computed tomography were used to track the colloidal interaction and hydration extent within LC3 paste. Results showed that flocculation due to the negative surface charge and water affinity of calcined clay appears to be the dominating factor. This leads to a reduction of water available to contribute to fluidity of the paste and, in turn, governing the development of thixotropy over time. In addition, the dilution effect due to high clinker substitution diminishes thixotropy growth with time.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effectiveness of PCE superplasticizers in calcined clay blended cements

Highlights: • Cements containing 0–40 wt% of a calcined clay rich in meta kaolin were studied. • The calcined clay decreases fluidity of the blended cements considerably. • In cement, the calcined clay adsorbs a large amount of Ca{sup 2+} ions. • A common HPEG polycarboxylate superplasticizer fluidizes OPC/CC blends best. • A zwitterionic PCE also fluidizes well and adsorbs in similar amounts as HPEG. The impact of a calcined clay (CC) rich in meta kaolin (~50 wt%) present in composite cements at 0–40% substitution rate for the clinker was studied relative to the dispersing force of different PCE superplasticizers. It was found that CC increases the water demand of the blended cements considerably (+85% for the 60:40 blend vs. neat OPC). Furthermore, PCEs which fluidize OPC best also provide optimal performance in CC blended cements, but require much higher dosages (in OPC/CC 60:40, 4–6 times as compared to neat OPC). In all systems, HPEG-PCE produced superior dispersing performance over anionic MPEG-PCEs. A mechanistic study involving zeta potential measurements revealed that the initially negatively charged calcined clay surface adsorbs huge amounts of Ca{sup 2+} ions from the pore solution, thus facilitating adsorption of anionic PCE superplasticizers. The results signify that commercially available PCE products can effectively fluidize OPC/CC blended cements.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of PCEs with different structures on hydration and properties of cementitious materials with low water-to-binder ratio

Polycarboxylate ethers (PCEs) with different structures and densities of anchor groups in the backbone were synthesized and characterized. The surface tension of their solutions, their adsorption on cementitious particles and zeta potential of cement-silica fume pastes with PCEs were measured. Their effects on hydration and properties of cement-silica fume paste with low water-to-binder ratio were examined. Results indicated that the adsorption kinetics of theses PCEs on cementitious particles are fitted the pseudo-second-order model. The introduction of long silane chain on PCE decreased its electrostatic adsorption, while PCE was adsorbed onto the surface of particles via both chemical and electrostatic adsorption, when silicon hydroxyl is directly connected to its backbone. In the presence of PCE with higher adsorbed amount, pastes exhibited lower yield stress and higher flowability, and higher strength at 7 d and 28 d. The low plastic viscosity, autogenous and drying shrinkage were related to the low surface tension of PCE solution.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Polymer intercalation synthesis of glycoboehmite nanosheets

In this work, novel materials based on the aluminum oxyhydroxide boehmite phase were prepared using a glycothermal reaction in 1,4-butanediol. Under the synthesis conditions, the atomic structure of the boehmite phase is altered by the glycol solvent in place of the interlayer hydroxyl groups, creating glycoboehmite. The structure of glycoboehmite was examined in detail to determine that glycol molecules are intercalated in a bilayer structure, which would suggest that there is twice the expansion identified previously in the literature. This precursor phase enables synthesis of two new phases that incorporate either polyvinylpyrrolidone or hydroxylpropyl cellulose nonionic polymers. These new materials exhibit changes in morphology, thermal properties, and surface chemistry. All the intercalated phases were investigated using PXRD, HRSTEM, SEM, FT-IR, TGA/DSC, zeta potential titrations, and specific surface area measurement. These intercalation polymers are non-ionic and interact through wetting interactions and hydrogen bonding, rather than by chemisorption or chelation with the aluminum ions in the structure.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Superhydrophobic composite asymmetric electrospun membrane for sustainable vacuum assisted air gap membrane distillation

Membrane distillation (MD) relies on superhydrophobic membranes that must achieve the competing goals of high liquid entry pressure (LEP) and high permeability. Here, in this study, we developed the first superhydrophobic composite electrospun asymmetric membrane using fluorinated graphite (FG). We also provided among the first comparisons of the relative benefits of membrane asymmetry and composite coatings via 3D electrospinning and spraying. FG particles increased the roughness and reduced the zeta potential of the membranes. Superhydrophobic composite membranes had a contact angle of 157° (sliding angle of 7°) and an LEP of 327 kPa. Long-term MD testing revealed that FG particles could increase MD's sustainability while decreasing membrane wetting. Vacuum-assisted air gap membrane distillation (V-AGMD) showed that the composite asymmetric membrane outperformed the non-asymmetric version (composite nanofiber) membrane by 21 % in average water flux and 25 % in average thermal efficiency because of the asymmetric structure of the membrane. The numerical model developed for the V-AGMD system also successfully predicted the water flux generated experimentally from the composite nanofiber and composite asymmetric membranes. Our results confirmed that electrospun asymmetric FG membranes with high contact angle, low sliding angle, high permeability, and high gained output ratio (GOR) would be promising candidates for sustainable MD.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Enabling aqueous processing for LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA)-based lithium-ion battery cathodes using polyacrylic acid

Replacing N-methyl-2-pyrrolidone (NMP) with water in the production of lithium-ion battery cathodes is critical to realizing process cost savings and improved worker safety. LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) is a poor fit for aqueous processing due to destructive Al current collector corrosion resulting from highly basic slurries and detrimental surface reconstruction reactions that occur in water. In this study, polyacrylic acid (PAA, MW = 450,000 g·mol -1 ) is examined as a corrosion-mitigating and surface-stabilizing agent. Adding PAA to an aqueous NCA slurry can provide a stable pH (4.0–8.5) for at least 4 h, since the carboxyl groups from PAA dissociate and increase the proton concentration in the slurry. Further, these groups can also adsorb to the surface of NCA particles and provide electrostatic stability from active material particle agglomeration, as revealed by zeta potential measurements. Minor cracking does occur at the electrode surface; this cracking likely caused poorer adhesion to the Al current collector in the aqueous-processed film when compared to the NMP-processed baseline. Electrochemically, the leached Li does cause a lower initial capacity for the aqueous-processed cathode, though the capacity retention of the aqueous-processed cathode is better than the baseline. The cracks in the coating led to a rise in charge transfer resistance that hindered rate capability above 1C.

25 ENERGY STORAGE↗
DOE OSTI2020

Green synthesis and characterization of nontoxic L-methionine capped silver and gold nanoparticles

The simple green method for synthesis of stable L-Methionine (L-Met) capped silver (Ag@LM NPs) and gold (Au@LM NPs) nanoparticles (NPs) without adding any additional reduction agent or stabilizer was developed. Colloidal dispersions were characterized by UV–Vis spectrophotometry. The size and spherical shape of NPs were evaluated by transmission electron microscopy. Their surface covering was confirmed by atomic force microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential measurements. Density functional theory calculations pointed that the preferential adsorption mode of L-Met on both Ag and Au surfaces was a vertical binding geometry via –NH2 group, while horizontal binding mode via [sbnd]S[sbnd] and –NH2 groups is also possible. The genotoxicity (evaluated by the micronucleus assay) of NPs, as well as their effects on some oxidative stress parameters (catalase activity, malondialdehyde level), were assessed in vitro using human peripheral blood cells as a model system. The influence of NPs on the morphology of lymphocyte cells studied using atomic force microscopy revealed that the membrane of cells remained unaffected after the treatment with NPs. When considering the effects of NPs on catalase activity and malondialdehyde level, neither particle type promoted oxidative stress. However, the treatment of lymphocytes with Ag@LM NPs induced a concentration-dependent enhancement of the micronuclei incidence and suppression of the cell proliferation while Au@LM NPs promoted cell proliferation, with no significant effects on micronuclei formation. The Ag@LM NPs were more prone to induce DNA damage than Au@LM NPs, which makes the latter type more suitable for further studies in nano-medicine. © 2019.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Aging gracefully? Investigating iridium oxide ink's impact on microstructure, catalyst/ionomer interface, and PEMWE performance

Here, in this study, we conducted a thorough investigation of the impact of aging iridium oxide (IrO 2 ) perfluorosulfonic acid ionomer ink for up to 14 days on the properties of the ink and the resulting catalyst layers. We examined ink properties, such as zeta potential, dynamic light scattering (DLS), density, surface tension, and rheology, as functions of ink aging time. To evaluate the microstructure and catalyst/ionomer interface, we employed transmission electron microscopy (TEM), X-ray scattering, and X-ray photoelectron spectroscopy (XPS) techniques. Furthermore, we assessed the effect of ink aging on the performance of proton exchange membrane water electrolyzers (PEMWEs). Our findings reveal that most ink properties remain stable for 14 days. The variations in PEMWE cell performance are minimal, and no clear trend is observed in relation to ink aging time. This study demonstrates that the effects of aging the inks for 14 days on ink properties, catalyst layer structure, catalyst/ionomer interface, and PEMWE performance are negligible, indicating a substantial time window after ink preparation without any significant changes in its properties. These insights provide crucial guidance for the commercial production and coating processes of ink, which is necessary for scaling up PEM technologies to meet future demand.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Electro-osmo-dialysis through nanoporous layers physically conjugated to micro-perforated ion-exchange membranes: Highly selective accumulation of trace coions

This study explores theoretically and numerically the phenomenon of counter-flow accumulation of trace coions during electro-osmo-dialysis through composite membranes containing nanoporous and perforated ion-exchange layers. The combination of charged nanopores and perforations allows electroosmosis, and ion concentration polarization appears near the ion-exchange layer. Accumulation of trace coions occurs because their advective and electromigration flow velocity components have opposite signs and are locally compensating in depletion regions where electric fields are high. This local compensation of flow components can give rise to high accumulation factors (>1000 in some cases) for trace coions at some distance from the interface between the nanoporous and ion-exchange layers. Moreover, the extent of this accumulation depends on the trace-coion diffusion coefficient. The resulting selectivity between different coions might serve as a basis for environmentally friendly separation of ionic species such as synthetic peptides or rare-earth elements. For example, a periodic process might include accumulation followed by species release into smaller volumes of solution. For both rare-earth ions and peptide-like species, the accumulation selectivity between ions with small differences in mobilities depends on system parameters such as nanoporous-layer thickness, distance between the perforations, and the zeta potential of the nanopore surface. Here, the use of optimal values of these membrane parameters may enable tuning of the electro-osmo-dialysis system for separation of specific ions. Modelling reveals that despite inhomogeneous patterns of fluid and ion flows close to the nanoporous/perforated ion-exchange interface, at relatively short distances from this interface (less than half the distance between the perforations) all the flows become practically one-dimensional (1D). Similarly, the concentration profiles of trace coions also become 1D. The flow one-dimensionality at short distances from the current-polarized interface enables a simple 1D approximation that is useful for an approximate analysis of trends in this multi-parameter system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Engineering surface charges of nanofiltration membranes to maximize Li + /Mg 2+ separation properties

Polyamide-based nanofiltration (NF) membranes are attractive for Li + /Mg 2+ separation for lithium recovery from salt brine (containing mainly Mg 2+ ). However, Li + and Mg 2+ have similar hydration radii, resulting in a low separation factor (SF Li/Mg ). Herein, we demonstrate that SF Li/Mg can be significantly enhanced by optimizing the membrane surface positive charges. This results in an unexpected maximum SF Li/Mg at a solution pH slightly below its isoelectric point (IEP). Specifically, NF270 membrane was surface-grafted with 2-(methacryloyloxy)ethyltrimethylammonium chloride (META) or polyethylenimine (PEI) using bio-adhesive dopamine, forming a thin, stable, charged layer (20–40 nm) on the surface. The effects of solution pH and surface modification on the surface zeta potential (ZP) and single- and mixed-salt Li + /Mg 2+ separation properties are thoroughly investigated. For example, the META grafting increases the ZP from 9.2 to 16 mV and SF Li/Mg by 130 % from 35 to 80 at pH 4, superior to the state-of-the-art commercial NF membranes. Furthermore, this surface modification occurs at ≈22 °C in aqueous solutions and can be utilized to enhance commercial modules for practical applications.

Li+/Mg2+ separation↗
DOE OSTI2022

Effect of a nanoparticle on wettability alteration and wettability retainment of carbonate reservoirs

The oil recovery in many carbonate reservoirs is low due to oil-wetness and heterogeneity. In this study, nanoparticles are evaluated for altering the wettability of oil-wet limestones and their properties are compared with those of an anionic surfactant. A surface-modified silica nanoparticle (SiNP) with a negative zeta potential was found to be aqueous stable in brines. Wettability studies showed that the SiNP cannot change the wettability of an initially oil-wet calcite plate, but SiNP treated calcite surface can remain water-wet after aging in oil. Spontaneous imbibition tests confirmed the observations of wettability tests and showed that a SiNP treated carbonate core retained its water-wettability during oil injection and aging. The imbibition into a SiNP treated and oil aged core was comparable to that in a water-wet core. However, SiNP was not able to remove the oil layers in initially oil-wet cores and imbibe water into these cores. In contrast, the anionic surfactant could alter the oil-wet carbonate rocks to a more water-wet condition, but failed to prevent the water-wet surface from getting oil-wet during oil-aging. The results suggest that the SiNP can be injected into wettability-altered (water-wet) reservoirs/regions to help retain the water-wettability during the long-term oil production. The 0.5 wt% SiNP dispersions transported through 18 mD limestone cores without any plugging. The SiNP retention was measured to be 2.5 mg/m 2 , much higher than that of the anionic surfactant.

02 PETROLEUM↗
DOE OSTI2025

Graphene Oxide Nanoribbons for High Early-Strength Cement Concrete

Longitudinal oxidative unzipping of the outer walls of multiwalled carbon nanotubes (MWCNTs) yields graphene oxide nanoribbons (GONRs), which exhibit greater open surface area and functional edge content than MWCNTs. This paper presents a study of the nano-amendment of Portland cement concrete with GONRs in concentrations between 0.05% (in weight of cement, wt%) and 0.0005 wt%, thus up to two orders of magnitude lower than that reported as lower-bound in the archival literature. The dispersibility in aqueous solution as a function of GONR concentration and oxygen weight content (O%) was assessed through dynamic light scattering (DLS) and zeta potential analysis. The results indicated that less effective suspensions were obtained for 0.05 wt% of GONRs and 22.7 O%. Therefore, GONR water suspensions with 30-40% O% were used to manufacture 50 mm × 100 mm cylindrical concrete specimens. After 7 days of curing, results from uniaxial compression tests using four specimens per configuration (MWCNT concentration and O%) showed that the incorporation of GONRs resulted in an average increase in compressive strength up to 45%. Consistent with the DLS and compression test results, SEM micrographs showed well-dispersed GONRs together with accelerated and preferential formation of calcium silicate hydrates (C-S-H) for all GONR concentrations. The results indicate, for the first time, that the incorporation of very small concentrations (as low as 0.0005 wt%) of well-dispersed GONR amendments can significantly enhance the early-age concrete strength. However, such enhancement became insignificant after 28 days of curing.

cement↗
DOE OSTI2021

Polymer Coatings on Virus-like Particle Nanoreactors at Low Ionic Strength—Charge Reversal and Substrate Access

Virus-like particles (VLPs) are a class of biomaterials which serve as platforms for achieving the desired functionality through interior and exterior modifications. Through ionic strength-mediated electrostatic interactions, VLPs have been assembled into hierarchically ordered materials. This work builds on predictive models to prepare polymer-coated VLP dusters at very low ionic strength. Zeta potential measurements showed that the clusters carried a strongly positive charge, a complete charge reversal from the VLP building block. SAXS analysis confirmed polymer adsorption onto the VLP exterior. Furthermore, we then studied the activity of an encapsulated enzyme toward small molecular and macromolecular substrates to determine the effect of each component of the hierarchically assembled material. We found that while encapsulation and polymer coating did not have a large effect on access to the enzyme by its native, small molecular substrate, substrate modification with a macromolecule caused the polymer coating and encapsulation to affect the access to the enzyme.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Adsorption Mechanisms of Glyphosate on Ferrihydrite: Effects of Al Substitution and Aggregation State

Ferrihydrite is one of the most reactive iron (Fe) (oxyhydr)oxides in soils, but the adsorption mechanisms of glyphosate, the most widely used herbicide, on ferrihydrite remain unknown. Here, we determined the adsorption mechanisms of glyphosate on pristine and Al-substituted ferrihydrites with aggregated and dispersed states using macroscopic adsorption experiments, zeta potential, phosphorus K-edge X-ray absorption near-edge structure spectroscopy, in situ attenuated total reflectance Fourier transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy, and multivariate curve resolution analyses. Aggregation of ferrihydrite decreases the glyphosate adsorption capacity. The partial substitution of Al in ferrihydrite inhibits glyphosate adsorption on aggregated ferrihydrite due to the decrease of external specific surface area, while it promotes glyphosate adsorption on dispersed ferrihydrite, which is ascribed to the increase of surface positive charge. Glyphosate predominately forms protonated and deprotonated, depending on the sorption pH, monodentate-mononuclear complexes (MMH 1 /MMH 0 , 77-90%) on ferrihydrites, besides minor deprotonated bidentate-binuclear complexes (BBH 0 , 23-10%). Both Al incorporation and a low pH favor the formation of the BB complex. The adsorbed glyphosate preferentially forms the MM complex on ferrihydrite and preferentially bonds with the Al-OH sites on Al-substituted ferrihydrite. In conclusion, these new insights are expected to be useful in predicting the environmental fate of glyphosate in ferrihydrite-rich environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Developing and Demonstrating a Lab Method for Quantifying Hair Exposure to Environmental Tobacco Smoke with a Forensic Perspective

Forensic science and chemistry curricula often lack hands-on experimental designs that effectively simulate the impact of environmental tobacco smoke (ETS) or other common elements found at crime scenes, such as marijuana, on trace forensic evidence. Hair, a critical form of trace evidence, offers unique advantages for assessing long-term exposure to environmental pollutants, including ETS. This study presents a novel, noninvasive forensic laboratory module designed to evaluate ETS exposure on various human hair types (untreated, dyed, and bleached). The experimental procedure involved controlled cigarette smoke exposure, followed by analysis using UV−visible spectroscopy, FTIR spectroscopy, and zeta potential measurements. Thirteen students participated in the three-week lab module (three sessions per week). Pre- and postlab assessments were conducted to evaluate learning outcomes. The prelab assessment focused on baseline knowledge of forensic hair analysis, as well as student expectations and confidence. The postlab assessment evaluated knowledge gained, technical insights, application of techniques, self-reflection, conceptual understanding, and practical skill development. This design helped students comprehend the effects of chemical treatments that significantly influence hair’s capacity to adsorb ETS residues by altering its physical and chemical properties. Integration of this experiment into the forensic chemistry curriculum led to measurable gains in student understanding, technical competency, and appreciation for realworld forensic applications. This method offers a valuable teaching and investigative tool for assessing individual ETS exposure in forensic contexts.

FTIR↗
DOE OSTI2025

Coupling of Charge Regulation and Geometry in Soft Ionizable Molecular Assemblies

The size, shape, and charge of structures, such as proteins and amphiphile assemblies, respond in an interconnected manner to solution ionic conditions. Here, we analyze assemblies of an amphiphile (C 16 K 2 ), with two ionizable amino acids [lysine (K)] coupled to a 16-carbon alkyl tail, via small-angle X-ray scattering (SAXS), nonlinear Poisson–Boltzmann theory (nl-PB), and hybrid Monte Carlo-molecular dynamics (MC-MD) simulations. SAXS revealed structural transitions from spherical micelles to cylindrical micelles to bilayers with increasing pH. By combining SAXS-determined structural information and nl-PB, we derived the molecular degree of ionization as a function of pH. The back-calculated titration curves matched the experimental data over an extended pH range, without adjustable parameters. Similarly, the SAXS data on the evolution of spherical micelle structure with ionic strength were combined with nl-PB and MC-MD to derive the bare and effective charges. MC-MD, which considered finite ion sizes, showed that bare and effective charges saturate quickly with increasing salt concentration. Furthermore, the calculated effective charges closely matched results from Zeta-potential measurements. The presented approach has advantages over customary methods for charge regulation, such as the Henderson–Hasselbalch (HH) or Hill models, where molecular ionization/deionization in assemblies is described by effective pKs that are distinct from the pK for isolated molecules. However, these models lack a physical explanation for these pK shifts. By contrast, our approach of combining structural details with an electrostatic model and simulations provides a more intuitive understanding of structure-charge coupling and a framework for understanding charge regulation in many synthetic and biological systems.

ionization↗
DOE OSTI2026

Ion-Specific Effects on PuO 2 Nanoparticle Aggregation and Dissolution in Concentrated Electrolytes

Hydrolytic PuO 2 nanoparticles (NPs) are a dominant aqueous Pu-bearing phase in high ionic strength nuclear wastes, yet their reactivity in nonideal brines remains poorly constrained. We quantify how electrolyte identity and concentration control PuO 2 NP aggregation and ligand-assisted dissolution in acidic, high salinity solutions (NaCl, NaNO 3 , NaClO 4 , Na 2 SO 4 , Na 2 C 2 O 4 up to 5 M). A multitechnique workflow combining liquid scintillation counting (operationally defined aqueous [Pu]), scattering/electrokinetic measurements (aggregate size and zeta potential), and spectroscopy (UV–vis, XPS, Raman) resolves electrolyte-dependent partitioning between colloidal and molecular Pu species. Weakly coordinating anions (ClO 4 – , Cl – , NO 3 – ) largely preserve the (aggregated) nanoparticulate fraction but generate distinct dissolved species at high concentration, i.e., Pu(IV)–nitrato complexes in NaNO 3 and Pu(VI)–chloro complexes in NaCl. In contrast, stronger ligands substantially perturb PuO 2 NP stability: sulfate promotes partial dissolution to Pu(IV)–sulfate complexes at low concentration but reduces aqueous [Pu] at higher sulfate levels via secondary Pu(IV) sulfate formation, whereas oxalate drives strong dissolution to aqueous Pu–oxalate complexes. Aged NPs show similar trends with reduced aqueous fractions and more dominant aggregation mechanisms. In conclusion, these spectroscopically constrained speciation data provide a foundation for incorporating PuO 2 NP reactivity into thermodynamic and reactive transport models for high salinity waste and brine environments.

Aggregation↗