Oxalic Acid Adsorption on Rutile: Experiments and Surface Complexation Modeling to 150 °C

Machesky, Michael L.; Ridley, Moira K.; Biriukov, Denys; Kroutil, Ondřej; Předota, Milan

doi:10.1021/acs.langmuir.8b03982

Cited by 8 publications

(15 citation statements)

References 52 publications

(92 reference statements)

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“…In between these barriers, there are local minima in the free energy profiles corresponding to outer-sphere complexes. These have also been observed in previous MD simulations of oxalic acid adsorption on rutile from water 91 and napthenic acid adsorption on calcite from water. 92 For SA, the headgroup was defined as the carboxyl group −COOH.…”

Section: Adsorptionsupporting

confidence: 85%

Molecular Simulations of Surfactant Adsorption on Iron Oxide from Hydrocarbon Solvents

Acero

Mohr

Bernabei

et al. 2021

Preprint

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The performance of lubricant additives, such as organic friction modifiers (OFMs), depends critically on their ability to adsorb onto the surfaces of moving components and form protective self-assembled layers (SAMs). Therefore, understanding the relationship between the concentration of the additive in the base oil and the resulting surface coverage is extremely important for lubricant formulations, as well as many other surfactant applications. Here, we use molecular dynamics (MD) simulations to study the adsorption isotherms of three different OFMs, stearic acid (SA), glycerol monoostearate (GMS), and glycerol monooleate (GMO), onto a hematite surface from hydrocarbon solvents, n-hexadecane and poly-α-olefin (PAO). First, we calculate the potential of mean force (PMF) of the adsorption process using MD simulations with the adaptive biasing force (ABF) algorithm. Our MD simulations show that SA has the weakest adsorption energy on hematite, followed by GMS, and finally GMO, due to the increasing number of functional groups available to bind to the surface. We also estimate the area occupied by each OFM molecule on the surface in the high-coverage limit using MD simulations of the annealing of OFM films with different initial surface coverages. We obtain a similar hard-disk area for GMS and GMO, but a lower value for SA, which is due to its smaller headgroup size. Based on the adsorption energy and surface area, we determine the corresponding adsorption isotherms using the molecular thermodynamic theory (MTT), which agree well with one available experimental data-set for SA. Two other experimental data-sets for SA require lateral interactions between surfactant molecules to be accounted for. SA forms monolayers with lower surface coverage than GMO and GMS at low concentrations (due to a smaller adsorption energy), but also has the highest plateau coverage (due to a smaller hard-disk area). We validate the adsorption energies from the MD simulations using high frequency reciprocating rig (HFRR) friction experiments with different concentrations of the OFMs in PAO. We use the Jahanmir and Beltzer model to estimate the surface coverage at each concentration and the adsorption energy of each OFM from the HFRR friction data. For OFMs with saturated tailgroups (SA and GMS), we obtain good agreement between the predictions made by the simulations and the experiments. The MD simulation and experimental results deviate for OFMs containing Z-unsaturated tailgroups (GMO), with the former suggesting stronger adsorption for GMO than GMS, while the latter predicts the opposite trend. We suggest that this is can be attributed to the higher steric barrier of adsorption of the OFMs with kinked Z-unsaturated tailgroup through a partially formed monolayer, an aspect which was not captured in the current simulations. This study demonstrates that MD simulations with the ABF algorithm, alongside MTT, are an accurate and efficient tool to predict adsorption isotherms at solid-liquid interfaces.

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Section: Adsorptionsupporting

confidence: 85%

Molecular Simulations of Surfactant Adsorption on Iron Oxide from Hydrocarbon Solvents

Acero

Mohr

Bernabei

et al. 2021

Preprint

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“…Importantly, for the surface charge densities explored, there are no adjacent bridging hydroxyls at nonhydroxylated surfaces, so OS5 and OS6 complexes are unfavorable at these surfaces. Since real surfaces are in between the extreme scenarios of surface hydroxylation studied here, that is, nonhydroxylated and hydroxylated surfaces, , OS1 and OS2 are considered to be predominant outer-sphere complexes for a wide range of pH and temperature . This is also true for hydrogenoxalate, which favors the OS1 and OS2 structures at both nonhydroxylated and hydroxylated surfaces.…”

Section: Resultsmentioning

confidence: 96%

“…Adsorption pH edges for 0.001 m oxalic acid in NaCl electrolyte (0.3 m and 0.03 m ) from experiment, charge-distribution multisite ion complexation (CD-MUSIC) surface complexation modeling (using OS1 and OS2 outer-sphere complexes; see ref for details), and CMD simulations ( nh and h surfaces, and average data from those).…”

Section: Resultsmentioning

confidence: 99%

Oxalic Acid Adsorption on Rutile: Molecular Dynamics and ab Initio Calculations

Biriukov¹,

Kroutil

Kabeláč³

et al. 2019

Langmuir

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Detailed analysis of the adsorption of oxalic acid ions, that is, oxalate and hydrogenoxalate, on the rutile (110) surface was carried out using molecular dynamics augmented by free energy calculations and supported by ab initio calculations. The predicted adsorption on perfect nonhydroxylated and hydroxylated surfaces with surface charge density from neutral to +0.208 C/m 2 corresponding to pH values of about 6 and 3.7, respectively, agrees with experimental adsorption data and charge-distribution multisite ion complexation model predictions obtained using the most favorable surface complexes identified in our simulations. We found that outer-sphere complexes are the most favorable, owing to strong hydrogen binding of oxalic acid ions with surface hydroxyls and physisorbed water. The monodentate complex, the most stable among inner-sphere complexes, was about 15 kJ/mol higher in energy, but separated by a large energy barrier. Other inner-sphere complexes, including some previously suggested in the literature as likely adsorption structures such as bidentate and chelate complexes, were found to be unstable both by classical and by ab initio modeling. Both the surfaces and (hydrogen)oxalate ions were modeled using charges scaled to 75% of the nominal values in accord with the electronic continuum theory and our earlier parameterization of (hydrogen)oxalate ions, which showed that nominal charges exaggerate ion−water interactions.

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“…Recently, the use of the electronic continuum correction (ECC) theory, which suggests some adjustment of point charges at Ti and O atoms to reproduce the adsorption phenomena occurring at the TiO 2 −liquid interface, has received significant attention [32][33][71][72][73][74][75]. MD simulations, augmented by free energy calculations and supported by ab initio calculations, were used to study the adsorption of oxalic acid ions (oxalate and hydrogen oxalate) on the rutile (110) surface [76][77]. The predicted adsorption on perfect non-hydroxylated and hydroxylated surfaces (Fig.…”

Section: Adsorption Of Small Additives Onto Tiomentioning

confidence: 99%

Recent advances in theoretical investigation of titanium dioxide nanomaterials. A review

et al. 2020

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Titanium dioxide (TiO2) is one of the most widely used nanomaterials in many emerging areas of material science, including solar energy harvesting and biomedical implanting. In this review, we present progress and recent achievements in the theory and computer simulations of the physicochemical properties of small TiO2 clusters, middle-size nanoparticles, as well as the liquid-solid interface. The historical overview and the development of empirical force fields for classical molecular dynamics (MD) of various TiO2 polymorphs, such as rutile, anatase, and brookite, are given. The adsorption behavior of solvent molecules, ions, small organic ligands, and biomacromolecules on TiO2 interfaces are examined with the aim of the understanding of driving forces and mechanisms, which govern binding and recognition between adsorbate and surfaces. The effects of crystal forms, crystallographic planes, surface defects, and solvent environments on the adsorption process are discussed. Structural details and dynamics of adsorption phenomena, occurring at liquid-solid interfaces, are overviewed starting from early empirical potential models up to recent reactive ReaxFF MD simulations, capable of capturing dissociative adsorption of water molecules. The performance of different theoretical methods, ranged from quantum mechanical (QM) calculations (ab initio and the density functional theory) up to classical force field and hybrid MM/QM simulations, is critically analyzed. In addition, the recent progress in computational chemistry of light-induced electronic processes, underlying the structure, dynamics, and functioning of molecular and hybrid materials is discussed with the focus on the solar energy applications in dye-sensitized solar cells (DSSC), which are currently under development. Besides, dye design principles, the role of anchoring moiety and dye aggregation in the DSSC performance are crucially analyzed. Finally, we outline the perspectives and challenges for further progress in research and promising directions in the development of accurate computational tools for modeling interactions between inorganic materials with not perfect structures and natural biomacromolecules at physiological conditions.

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Oxalic Acid Adsorption on Rutile: Experiments and Surface Complexation Modeling to 150 °C

Cited by 8 publications

References 52 publications

Molecular Simulations of Surfactant Adsorption on Iron Oxide from Hydrocarbon Solvents

Molecular Simulations of Surfactant Adsorption on Iron Oxide from Hydrocarbon Solvents

Oxalic Acid Adsorption on Rutile: Molecular Dynamics and ab Initio Calculations

Recent advances in theoretical investigation of titanium dioxide nanomaterials. A review

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