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This study delves into the potential of vermiculite-based adsorbents for phosphate removal from aqueous solutions. CTAB and zirconium-modified natural vermiculite slices (CZV) were employed, with XRF analysis confirming successful zirconium loading. The Langmuir model indicated monolayer adsorption behavior, suggesting a preferential adsorption characteristic. The presence of coexisting ions showed varied effects on phosphate removal, with increasing CO32− concentrations slightly inhibiting phosphate removal by CZV, while increasing NO3−, SO42−, and Cl− concentrations improved phosphate removal by all adsorbents. Notably, the vermiculite adsorbents, despite their larger particle size, demonstrated a competitive adsorption capacity when compared to other adsorbents. The practicality of these adsorbents is further emphasized by their potential direct application in artificial wetlands and lakes without posing ecological risks. Moreover, the reutilization of used vermiculite adsorbents is highlighted as a sustainable approach, considering their beneficial effects on the growth of submerged macrophytes and sediment microecological environments. The adsorption mechanism is attributed to surface complexation and ligand exchange. This research underscores the efficacy of modified natural vermiculite slices in phosphate adsorption, paving the way for broader environmental applications and offering a promising solution to water purification challenges. [ABSTRACT FROM AUTHOR]

The grand canonical ensemble Monte Carlo simulation and density-functional theory are applied to calculate the structures, local mole fractions, and adsorption isotherms of binary hard-core Yukawa mixtures in a slitlike pore as well as the radial distribution functions of bulk mixtures. The excess Helmholtz energy functional is a combination of the modified fundamental measure theory of Yu and Wu [J. Chem. Phys. 117, 10156 (2002)] for the hard-core contribution and a corrected mean-field theory for the attractive contribution. A comparison of the theoretical results with the results from the Monte Carlo simulations shows that the corrected theory improves the density profiles of binary hard-core Yukawa mixtures in the vicinity of contact over the original mean-field theory. Both the present corrected theory and the simulations suggest that depletion and desorption occur at low temperature, and the local segregation can be observed in most cases. For binary mixtures in the hard slitlike pore, the present corrected theory predicts more accurate surface excesses than the original one does, while in the case of the attractive pore, no improvement is found in the prediction of a surface excess of the smaller molecule. [ABSTRACT FROM AUTHOR]

Density functional theory method has been employed to investigate the adsorption of H2 molecule and H atom on α-U(001) surface. There exist four initial sites [top (A), triangle-center (B), long-bridge (C), and short-bridge (D)] for H2 and H atom adsorptions on α-U(001) surface. The Eads (adsorption energy) values on the top sites of H2-U(001) configurations are around −0.666 eV, and H2 molecule has been elongated but not broken into H atoms. For the other three sites, the Eads values are around −1.521 eV. The long-bridge site is the most reactive site for H2 decomposing. For the H-U(001) configurations, the Eads are around −2.904 eV. Top site and short-bridge site are the most reactive sites for the H atom react on the α-U(001) surface. Our work reveals that the different reactive sites play discrepant effects on hydrogenation process. Geometric deformations, diffusion paths, and partial density of states of H2-U(001) and H-U(001) configurations have also been analyzed. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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The generalized gradient approximation of density functional theory was used to investigate the adsorption and dissociation of a single isopropyl nitrate molecule on an Al(111) surface. The isopropyl nitrate tends to adsorb in a parallel mode with respect to the Al(111) surface. A total of 10 dissociation modes were investigated including both the vertical and parallel dissociations. The analysis of transition states, density of states, and the Hirshfeld populations have been carried out. In general, the dissociations on the same site would produce similar products. The surface aluminum atoms would attract the oxygen or nitrogen atoms dissociated from the nitro group, leading to the formation of three Al-O or Al-N bonds on the surface. Our study presented a deep insight into the dissociation behaviors as well as the mechanisms of isopropyl nitrate on the aluminum surface. Moreover, the smallest activation barrier energy for the isopropyl nitrate dissociation on the aluminum surface is 58.51 kJ/mol, which is much lower than that of 158 kJ/mol for the direct decomposition. [ABSTRACT FROM AUTHOR]

The adsorption and decomposition of trimethylene oxide (C3H6O) molecule on the Al(111) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell (6 x 6 x 3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between C3H6O molecule and Al atoms induce the C-O bond breaking of the ring C3H6O molecule. Subsequently, the dissociated radical fragments of C2H6O molecule oxidize the Al surface. The largest adsorption energy is about -260.0 kJ/mol in V3, V4 and P2, resulting a ring break at the C-O bond. We also investigated the decomposition mechanism of C3H6O molecules on the Al(111) surface. The activation energies (Ea) for the dissociations V3, V4 and P2 are 133.3, 166.8 and 174.0 kJ/mol, respectively. The hcp site is the most reactive position for C3H6O decomposing. [ABSTRACT FROM AUTHOR]

The adsorption and decomposition of the CH3OH molecule on Al13 clusters were investigated by generalized gradient approximation of the density functional theory. The strong attractive forces between the CH3OH molecule and aluminum atoms induce the breaking of the H-O and C-O bonds of CH3OH. Subsequently, the dissociated CH3O and OH radical fragments oxidize the aluminum clusters. The largest adsorption energy is -205.4 kJ/mol. We also investigated five reaction pathways of the CH3OH molecule on the Al13 clusters. The activation energies are in the range of 10.3−113.1 kJ/mol. Compared with the bond dissociation energies of the C-O and O-H bonds in the isolated methanol, Al13 performs very well in decreasing the bond break barrier of CH3OH. In addition, although the C-O bond is slightly weaker than the O−H bond, the O−H bond is even easier to decompose on the Al13 surface. The rate constants of five adsorption paths over the temperature range 300−700 K are presented. [ABSTRACT FROM AUTHOR]

The adsorption and dissociation mechanism of NHNO on the Mg surface have been investigated by the generalized gradient approximation of density functional theory. Calculations employ a supercell (3 × 3 × 3) slab model and three-dimensional periodic boundary conditions. The strong attractive force between oxygen and Mg atoms induces the N-O bond of the NHNO to decompose. The dissociated oxygen atoms and radical fragment of NHNO oxidize readily Mg atoms. The largest adsorption energy is −860.5 kJ/mol. The largest charge transfer is 3.76 e from surface Mg atoms to fragments of NHNO. The energy barriers of N-O bond dissociation are in a range of 11.6-36.5 kJ/mol. The adsorption energy of NHNO on the Mg surface compensates the energy needed for the N-O bond dissociation. [ABSTRACT FROM AUTHOR]

The adsorption and decomposition of the FOX-7 molecule on Al13 clusters were investigated by generalized gradient approximation of the density functional theory. The strong attractive forces between the FOX-7 molecule and aluminum atoms induce the N−O bond breaking of FOX-7. Subsequently, the dissociated oxygen atoms and radical fragment of FOX-7 oxidize the aluminum clusters. The largest adsorption energy is −1020.4 kJ/mol. We also investigated three adsorption reaction paths of the FOX-7 molecule on the Al13 clusters in the A configuration. The activation energy for the adsorption steps are 0.2, 11.4, and 10.2 kJ/mol, respectively, and Al13 is more active than the Al(111) surface and the Al13 cluster performs better in decreasing the adsorption barrier of FOX-7 on the aluminum surface as well. The rate constants of three adsorption paths increase as temperature increases over the temperature range 275-500 K. [ABSTRACT FROM AUTHOR]

The adsorption of hexogen (RDX) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and aluminum atoms induce the N−O and N−N bond breaking of the RDX. Subsequently, the dissociated oxygen atoms, NO group and radical fragment of RDX oxidize the Al surface. The largest adsorption energy is −835.7 kJ mol. We also investigated the adsorption and decomposition mechanism of RDX molecule on the Al(111) surface. The activation energy for the dissociation steps of V4 configuration is as large as 353.1 kJ mol, while activation energies of other configurations are much smaller, in the range of 70.5-202.9 kJ mol. The N−O is even easier than the N−NO bond to decompose on the Al(111) surface. [ABSTRACT FROM AUTHOR]

Density functional theory method with full geometry optimization was used to study the adsorption of nitroamine (NHNO) on Al cluster. Both dissociative and nondissociative adsorption structures were predicted with different NHNO molecule orientations on Al cluster surfaces. In dissociative chemisorption, the main decomposition products of NHNO are O atom(s) and NHNO or NHN species. The O atoms being ruptured from the N-O bond form strong Al-O bonds with the neighboring Al around the adsorbed sites. In addition, the species obtained as a result of O atom elimination remains bonded to the surface. The largest adsorption energy is −737.66 kJ/mol when the NHNO molecule decomposes into two O atoms and a NHN fragment. For nondissociative adsorption, the seriously deformed nitroamine forms various N-O-Al bonding configurations with Al. The significant charge transfer occurs for all adsorption configurations. The most charge transfer is 2.068 e from the Al cluster surface to the fragments of the decomposed NHNO. The change of the electronic structures is obvious due to the adsorption or dissociation of NHNO molecule. Nitroamine readily oxidizes the aluminum surface of the Al cluster. [ABSTRACT FROM AUTHOR]

Because of the increasing interest in studying the phenomenon exhibited by charge-stabilized colloidal suspensions in confining geometry, we present a density functional theory (DFT) for a hard-core multi-Yukawa fluid. The excess Helmholtz free-energy functional is constructed by using the modified fundamental measure theory and Rosenfeld's perturbative method, in which the bulk direct correlation function is obtained from the first-order mean spherical approximation. To validate the established theory, grand canonical ensemble Monte Carlo (GCMC) simulations are carried out to determine the density profiles and surface excesses of multi-Yukawa fluid in a slitlike pore. Comparisons of the theoretical results with the GCMC data suggest that the present DFT gives very accurate density profiles and surface excesses of multi-Yukawa fluid in the slitlike pore as well as the radial distribution functions of the bulk fluid. Both the DFT and the GCMC simulations predict the depletion of the multi-Yukawa fluid near a nonattractive wall, while the mean-field theory fails to describe this depletion in some cases. Because the simple form of the direct correlation function is used, the present DFT is computationally as efficient as the mean-field theory, but reproduces the simulation data much better than the mean-field theory. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSCs) using anatase TiO2 nanocrystals exposing a specific lattice plane on the surface were studied. It was found that dye adsorption strongly depends on the lattice plane exposed on the TiO2 nanocrystal surface, which greatly affects DSC performance. TiO2 nanocrystals exposing mainly the (010) plane have a higher dye adsorption capacity and a higher Voc for DSC than normal spherical nanocrystals. TiO2 nanocrystals with a large adsorption constant Kad can yield a high Jsc. The highest Jsc (20.6 mA/cm2) was achieved by using TiO2 nanocrystals with the specific lattice plane on the surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized OPHS zwitterionic surfactant exhibits wetting reversal and competitive adsorption effects. • The wetting reversal mechanism of OPHS has a time-dependent effect. • OPHS can remove the adsorbed oil film on the shale surface and desorb methane. • Contact angle testing proved effective wettability alteration by OPHS zwitterionic surfactant. Shale reservoirs have the characteristics of low permeability and low porosity. In order to enhance the recovery of shale oil and gas, surfactant flooding is a mature reservoir oil recovery method. However, the adsorption of different surfactants on the reservoir rock surface is restricted, depending on the type of surfactant. Therefore, a zwitterionic surfactant (OPHS) was synthesized from oleic acid, 3-dimethylaminopropylamine and sodium 3-chloro-2hydroxypropanesulfonate, and characterized by FTIR, 1H NMR, and TGA, and the mechanism of the OPHS for enhancing oil and gas recovery on shale surfaces was investigated. The results showed that the critical micelle concentration (CMC) of OPHS surfactant solution is 7.9 × 10-4 mol/L and the γ CMC is 27.5 mN/m; the concentration of 0.1 % OPHS surfactant solution could reduce the contact angle of the cores from 127.2° to 38.8°, which resulted in spontaneous imbibition; The absolute Zeta potential of shale particles in the OPHS surfactant solution was measured at 39 mV, whereas in deionized water at 15.3 mV. This difference can be attributed to the formation of a stable hydration film on the surface of shale particles induced by the wetting reversal effect. Spontaneous imbibition experiments showed that a 0.1 % solution of OPHS surfactant was able to increase the recovery rate by more than four times compared to the imbibition solution without added surfactant; In high-pressure gas adsorption/desorption experiments, the OPHS surfactant solution demonstrated a higher affinity for adsorption onto the shale surface. It effectively occupied adsorption sites, ultimately facilitating methane gas desorption from the shale. In summary, OPHS zwitterionic surfactants exhibit the capability to desorb hydrocarbons from shale pores through mechanisms such as wetting reversal and competitive adsorption. This research holds significant potential for advancing the field of shale oil and gas recovery, providing valuable insights for enhancing recovery processes. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of NH2NO2 molecule on the Al2O3(001) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell model represented with 2×2 of periodic boundary conditions. The strong attractive forces between NH2NO2 molecule and Al2O3 induce obvious change of the NH2NO2 and Al2O3 structure. Although the NH2NO2 molecule does not decompose, Alartially decompose and some Oorm, whose bond lengths are intervenient between Obond length and Obond length. The largest adsorption energy is −453.8kcalmol−1. By the adsorption energy and the change with structure of NH2NO2 and Al2O3, it can be concluded that aluminized explosive of NH2NO2 keeps high reactivity even if the aluminum is oxidized to form a film of the alumina. This finding can make clear the activated aluminum as a stored energy source for propellants and the good performance of aluminized explosives. The energies of DOS for N and O atoms of the NH2NO2 molecule match with those of Al atoms, and Ale:glyph name="sbnd" />N bond forms easily at the corresponding energies range. The DOS projections on the N, O and Al atoms occur with obvious shift of peaks, which infers energy bands become broad and the interactions of chemical bonds are strengthened. [Copyright &y& Elsevier]

The adsorption and decomposition of HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane) molecule on the MgH 2 (1 1 0) crystal surface were investigated by employing the First Principles computation. With the N-NO 2 bond of HMX molecule as a reference, 12 possible adsorption configurations were considered that are either perpendicular (V1 ~ V6) or parallel (P 1 ~ P 6) to the MgH 2 (1 1 0) surface. The adsorption energy, density of states and charge transfer of MgH 2 (1 1 0)/HMX after adsorption were analyzed. The adsorption energies for all the 12 configurations are positive, suggesting exothermic and stable adsorption. The HMX molecules are chemically adsorbed on MgH 2 (1 1 0) surface in most cases. The charge analysis shows strong charge transfer between magnesium and oxygen, nitrogen atoms. 8 paths that HMX adsorbs and decomposes on MgH 2 (1 1 0) surface were determined. [ABSTRACT FROM AUTHOR]

Abstract: A novel core/shell structured TiO2/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO2 nanocrystal surface. The formation and nanostructure of the nanocomposite were investigated by FT-IR and UV–Vis spectra, TEM, FE-SEM, and TG–DTA analysis. Adsorption of aminobenzoate on the TiO2 surface is an effective method to obtain the uniform nanocomposite. The thickness of polyaniline layer coating on the TiO2 nanocrystal surface can be controlled in a range of 2–5nm by this method. A photoelectrochemical study was carried out on the TiO2/polyaniline nanocomposite, and found that polyaniline in the nanocomposite acted as a visible-light sensitizer in a photoelectrochemical reaction. The sensitization effect increased with increasing binding strength between polyaniline and TiO2. A dye-sensitized solar cell with a short circuit current density of 0.19mA/cm2 and an open circuit voltage of 0.35V was fabricated by using the TiO2/polyaniline nanocomposite film as a sensitized electrode. [Copyright &y& Elsevier]

Abstract: Poly-o-aminobenzoate (POA) was prepared by oxidizing o-aminobenzoic acid with (NH4)2S2O8 in an acidic solution. POA was adsorbed on TiO2 nanocrystal surface to obtain a POA–TiO2 nanocomposite. The polymerization reaction, structure, adsorption reaction on TiO2 surface, and visible light sensitization effect of the polymer adsorbed on TiO2 surface were studied by FT-IR and UV–visible spectra, cyclic voltammetry, and measurements of visible light photoelectrochemical and photocatalytic activities. Three kinds of POA with different long conjugate structures can be formed. These polymers have large absorbance in wide visible light region. POA molecules can be adsorbed on TiO2 surface by anchoring their carboxylate groups to the TiO2 surface with a multi-bridging chelating mode, which causes formation of the POA–TiO2 nanocomposite with a high stability. POA adsorbed on the TiO2 nanocrystal showed high visible light sensitization effect in the photocatalytic reaction. [Copyright &y& Elsevier]

Abstract: Adsorption of the organic sulfur compounds thiophene (TP) and 1-benzothiophene (1-BTP) in an organic model solution of hydrodesulfurizated gasoline (heptane with 1 wt% toluene and 0.156 mM (5 ppmw as sulfur) TP or 1-BTP) was studied by a batch method at 80 °C using metal-ion-exchanged Y-zeolites. Although NaY-zeolite or its acid-treated material rarely adsorbed the organic sulfur compounds, NaY-zeolites exchanged with Ag+, Cu2+, and Ce3+ ions and NH4Y-zeolites exchanged with Ce3+ ions showed markedly high adsorptive capacities for TP and 1-BTP. The sulfur uptake increased in the order CuY-zeolite(Na)