The ubiquitous presence of poly- and perfluoroalkyl substances (PFAS) in different natural settings poses a serious threat to environmental human health. Soils sediments represent one the important exposure pathways PFAS for humans animals. With increasing bioaccumulation mobility, it is extremely understand interactions molecules with dominant constituents soils such as clay minerals. This study reports first time fundamental molecular-level insights into adsorption, interfacial structure,...

Classical molecular dynamics simulations were performed for the smectite clay hectorite with charge-balancing Cs+ cations using a newly developed structural model disordered distribution of Li/Mg substitutions in octahedral sheet and fully flexible CLAYFF force field. Calculations systems interlayer galleries containing 0–19 H2O/Cs+ suggest that monolayer hydrate is only stable state at all relative humidities ambient pressure temperature, agreement experimental results previous...

The incorporation of Ca2+ into smectite minerals is well-known to have a significant effect on the swelling behavior and mechanical properties this environmentally technologically important group materials. Relative common alkali cations such as Na+, K+, Cs+, has larger charge/ionic radius ratio thus interacts very differently with interlayer water molecules oxygens clay basal surface. Recent 2H 43Ca NMR studies mineral, hectorite, show that molecular scale dynamics quite different than...

In situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) experiments combined with molecular dynamics simulations using the grand canonical ensemble [grand (GCMD)] show that cation size, charge, solvation energy play critical roles in determining interlayer expansion of smectite clay minerals when exposed to dry supercritical scCO2 (scCO2) under conditions relevant petroleum reservoirs geological CO2 sequestration conditions. The GCMD results mineral, hectorite, containing alkali...

Adsorption and mobility of radioactive Cs+ isotopes in soil are among the most important factors affecting long-term environmental footprint nuclear accidents such as Chernobyl (1986) Fukushima Daiichi (2011). In particular, ions can be retained through their exchange with K+ naturally present muscovite mica, one common mineral components. The ClayFF force field allowed us to realistically represent local inhomogeneities structure, composition, charge on (001) surface identify three...

Grand Canonical Molecular Dynamics (GCMD) simulations were performed to investigate the intercalation of CO2 and H2O molecules in interlayers smectite clay, Na-hectorite, at temperatures pressures relevant petroleum reservoir geological carbon sequestration conditions equilibrium with H2O-saturated CO2. The computed adsorption isotherms indicate that enter interlayer space Na-hectorite only when it is hydrated approximately three per unit cell. immersion energies show bilayer hydrate...

Layered aluminosilicates play a dominant role in the mechanical and gas storage properties of subsurface, are used diverse industrial applications, serve as model materials for understanding solvent-ion-support systems. Although expansion presence H2O is well-known to be systematically correlated with hydration free energy interlayer cation, particularly environments dominated by nonpolar solvents (i.e., CO2), uptake into not well-understood. Using novel high-pressure capabilities, we...

Variable-temperature X-ray diffraction and 2H NMR spectroscopy of the smectite mineral, hectorite, containing interlayer Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, Pb2+ equilibrated at 43% relative humidity (RH) mixed with 2H2O to form a paste provide comprehensive picture structural environments dynamics relationships these properties hydration state, energy polarizability cation, temperature, formation ice-1h in interparticle pores. The variation basal spacing shown by XRD data correlates well...

The results from novel in situ high-pressure nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) and X-ray diffraction (XRD) investigation of the interaction smectite hectorite with variably wet supercritical methane (scCH4) at 90 bar 323 K (hydrostatic conditions equivalent to ∼1 km depth) show that CH4 occurs clay interlayers, pores external individual particles, as bulk fluid. occupancy each environment depends on relative humidity (RH) CH4-rich fluid hydration energy size...

CRC-MD simulations show that nanopores in shales bounded by clay minerals have a strong preference for CO₂ relative to CH₄.

Soil minerals and organic matter play critical roles in nutrient cycling other life-essential biogeochemical processes, yet the structural dynamical details of natural (NOM) film formation on smectites are not fully understood molecular scale. XRD Suwannee River NOM-hectorite (a smectite clay) complexes shows that humic fulvic components NOM bind predominantly at external surfaces packets platelets rather than interlayer slit pores, suggesting key behavior governing smectite-NOM interactions...

We performed constant reservoir composition molecular dynamics (CRC-MD) simulations at 323 K and 124 bar to quantitatively study the partitioning of fluid species between nano- mesopores clay a bulk containing an equimolar mixture CO2 CH4. The results show that basal (001) protonated edge (010) surfaces illite both demonstrate strong preference for over CH4 adsorption; stronger than surfaces, especially with K+ as exchangeable cation; structuring near-surface by is Na+. have somewhat greater...

As global energy demand increases, natural gas recovery from source rocks is attracting considerable attention since recent development in shale extraction techniques has made the process economically viable. Kerogens are thought to play an important role recovery; however, interactions between trapped and kerogens remain poorly understood due complex, heterogeneous microporous structure of kerogens. This study examines diffusive behavior methane molecules kerogen matrices different types...

The intercalation of H2O, CO2, and other fluid species in expandable clay minerals (smectites) may play a significant role controlling the behavior these geological carbon sequestration enhanced petroleum production has been subject intensive study recent years. This paper reports results computational effects properties charge-balancing, exchangeable cations on H2O CO2 smectite mineral, hectorite, equilibrium with an H2O-saturated supercritical under reservoir conditions using grand...

In recent years, there have been increasing initiatives undertaken worldwide to employ alternative per- and polyfluoroalkyl substances (PFAS) molecules in order minimize the environmental health effects associated with legacy PFAS molecules. Hexafluoropropylene oxide dimer acid (HFPO-DA), commonly known as GenX, is one of important replacements currently used for PFOA. However, growing investigations suggest that GenX identified natural settings, including soils groundwater, thus emphasizing...

Molecular dynamics (MD) computer simulations were performed for an aqueous film of 3 nm thickness adsorbed at the (001) surface ammonium-substituted muscovite mica. The results provide a detailed picture near-surface structure and topological characteristics interfacial hydrogen bonding network. effects deuterium=hydrogen isotopic substitution in N(H=D) 4 + on consequently convergence structural properties have also been explored. Unlike many earlier simulations, much larger area...

The intercalation of nonaqueous fluids in the nanopores organic and inorganic materials is significant interest, particularly energy science community. Recently, X-ray powder diffraction computational modeling results have shown that structural F– for OH– substitution layered silicates makes them more hydrophobic. Here, we use grand canonical molecular dynamics calculations to investigate how increasing F–/(F– + OH–) ratio a prototypical silicate (the smectite Na-hectorite) impacts behavior...

²³Na MAS NMR spectroscopy of the smectite mineral hectorite acquired at temperature from −120 °C to 40 shows presence complex dynamical processes in interlayer galleries that depend significantly on their hydration state.

The Callovo-Oxfordian clay formation (COx) is the potential host rock for long term nuclear waste repository in France. clayey component of COx consists mostly illite, smectite and interstratified illite/smectite (I/S) minerals. We performed a series molecular dynamics (MD) computer simulations order to quantify scale mechanisms responsible adsorption transport ions at hydrated surfaces smectite, I/S clays. New structural models allowed us identify several structurally different sites basal...

Abstract Proteoglycans (PGs), consisting of glycosaminoglycans (GAGs) linked with the core protein through a tetrasaccharide linkage region, play roles in many important biological events. The chemical synthesis PG glycopeptides is extremely challenging. In this work, enzymes required for chondroitin sulfate (CS) (CSPG) have been expressed and suitable sequence enzymatic reactions has established. To expedite CSPG synthesis, peptide acceptor was immobilized on solid phase glycan units were...

The determination of gas phase thermochemical properties per- and polyfluoroalkyl substances (PFAS) is central to understanding the long-range transport behavior PFAS in atmosphere. Prior gas-phase studies have reported perfluorinated sulfonic acid (PFOS) octanoic (PFOA). Here, this study reports enthalpies formation short- long-chain their precursor molecules determined using density functional theory (DFT) ab initio approaches. Two functionals, two methods an empirical method were used...

ConspectusIn the mid 2010s, high-pressure diffraction and spectroscopic tools opened a window into molecular-scale behavior of fluids under conditions many CO2 sequestration shale/tight gas reservoirs, where CH4 are present as variably wet supercritical fluids. Integrating spectroscopy with molecular modeling has revealed much about ways that behave in reservoir components, particularly slit-shaped micro- mesopores layered silicates (phyllosilicates) abundant caprocks shales. This Account...

Proteoglycans (PGs), consisting of glycosaminoglycans (GAGs) linked with the core protein through a tetrasaccharide linkage region, play roles in many important biological events. The chemical synthesis PG glycopeptides is extremely challenging. In this work, enzymes required for chondroitin sulfate (CS) (CSPG) have been expressed and suitable sequence enzymatic reactions has established. To expedite CSPG synthesis, peptide acceptor was immobilized on solid phase glycan units were directly...

Following the global regulation of legacy PFAS molecules, fluorotelomer molecules have been widely employed as replacements to PFOS in aqueous film-forming foam (AFFF) and PFOA other products. Recent field...