Magnesite (MgCO3) and dolomite (Mg,Ca)(CO3)2 are the main minerals involved in the production of magnesium metal, which is considered as a critical raw material in the EU and USA. In this study, we ...investigated the hydration mechanisms of (101̅4) magnesite and dolomite surface by static density functional theory relaxations and ab initio molecular dynamics simulations. For both minerals, the dissociative adsorption of water was unfavored compared to the molecular adsorption, which displayed an adsorption energy of −101.2 kJ mol−1 and −94.2 kJ mol−1 for magnesite and dolomite, respectively. In the case of dolomite, the adsorption of water was slightly favored on the surface calcium ions compared to magnesium ions, which was attributed to stronger interactions between the hydrogen atoms of water and the oxygen atoms of the surface. Then, the coverage was gradually increased to reach a monolayer: the adsorption energies for magnesite displayed a slight increase with increasing coverage, whereas dolomite exhibited no sensitivity to water coverage. Using ab initio molecular dynamics simulations conducted at 300 K, we showed that, beyond the first layer, water displayed a clustering behavior induced by the intermolecular interactions, while the isosteric enthalpies of adsorption continuously decreased with increasing coverage, due to the screening effect of deeper water layers. When more water molecules were added, until reaching the complete hydration of magnesite and dolomite surfaces, a refined water structuration emerged: a significant layering effect was exhibited, due to highly-organized layers, until 8–10 Å from the surface, which therefore corresponded to the distance at which the surface had no more effect on water layers. Overall, magnesite exhibited a larger affinity for water than dolomite, including adsorption energies and structuration of water, which provides new insights in the understanding of the fine surface mechanisms involved in the subsequent flotation process.
Display omitted
•Water adsorbs under molecular form on magnesite and dolomite surfaces.•ΔEads of a water molecule is − 101.2 on magnesite and − 94.2 kJ·mol−1 on dolomite.•Higher coverage studies confirm that magnesite is more hydrophilic than dolomite.•Better structuration of water above magnesite compared to dolomite.•Reverse flotation recommended for the dolomite/magnesite separation.
Display omitted
•Radial distribution function can evaluate interaction behavior of rubber asphalt.•Agglomeration of rubber-asphalt is more obvious than inter-components of asphalt.•Adsorption of ...rubber to asphalt follows this order: BR > SBR > NR.•Agglomeration of rubber asphalt is more clustered for more light fractions asphalt.
In order to clear the interaction mechanism between rubber and asphalt binder in rubber asphalt, radial distribution function was selected to investigate the variation of the agglomeration of rubber asphalt with rubber and asphalt binder types, where molecular models of rubber asphalt were built firstly, molecular dynamics simulations were performed afterwards and the variation of agglomeration behavior and adsorption effect were analyzed finally based on Materials Studio 8.0. The results show that the agglomeration of asphalt binder is changed significantly with the addition of rubber. The agglomerations of rubber-naphthene aromatic and rubber-saturate is more clustered than that of asphaltene-naphthene aromatic and asphaltene-saturate, and the agglomeration of rubber-naphthene aromatic is more clustered than that of rubber-saturate. The adsorption of different rubber types to light fractions of asphalt binder follows this order: cis-polybutadiene rubber (BR) > styrene butadiene rubber (SBR) > natural rubber (NR). In addition, the more clustered agglomeration structure of rubber-asphalt will be formed with the higher proportion of naphthene aromatic and saturate in asphalt binder.
In this paper, we investigate the effects of geometric shape of various roughnesses on the fluid flow passing through a nanochannel by using of molecular dynamics simulation. The results of ...simulations are presented for the modeled structures (the five models defined) as number density, velocity, and system temperature profiles for various conditions. By applying roughness to the inner surface of the ideal nano-channel at a thrust force of 0.002 eV/Å, the amplitude of number density of the fluid particles near the walls decreased, while the mean and maximum velocities increased by 6.5% and 2.5% in the presence of square cuboid and hemispheroid roughness, respectively. Furthermore, the dimensionless slip velocity and slip length were, respectively, increased by a maximum of 41.1% and 21.5% in the presence of square cuboid roughness and by a minimum of 0.9% and 0.5% in the presence of hemispheroid roughness. The temperature of the particles at the center of the nano-channel was increased by a maximum of 9.1% and a minimum of 2.8% in the presence of square cuboid and hemispheroid roughness, respectively. Calculation of the Argon-Argon radial distribution function indicated that the maximum of this function decreased by a maximum of 11.8% and a minimum of 8.5% in the presence of rectangular cuboid and ellipsoid roughness, respectively, compared to the ideal nano-channel.
•Effects of geometric shape of various roughnesses were investigated.•The results are presented for the five models.•Molecular dynamics simulation method was employed.•The open-source software, LAMMPS was used for simulation
Display omitted
•The micropore and mesopore models of bituminous coal were established.•Simulation of unary CH4, CO2 and N2 adsorbed into micro- and meso-pores of coal by Monte Carlo simulation.•Pore ...size had a great influence on gas adsorption and diffusion.•In micro- and meso-pores, the effective distance and radius of action between coal molecules and gas molecules were different.
The characteristics of gas loading, diffusion and adsorption in pore models of coal molecules within variety pore sizes were different. The Grand canonical Monte Carlo and Molecular Dynamic were conducted in this paper to investigate the loading, adsorption and diffusion characteristics of CH4, CO2, and N2 in micropores and mesopores. Three micropore models (0.5, 1 and 2 nm) and two mesopore models (5 and 8 nm) were established to study the microscopic mechanism of three gases loading, adsorption and diffusion. The results shown that the loading amounts in pore models increased with increasing pore size. However, the tight adsorption amounts and adsorption heats decreased with increasing pore size. The tight adsorption amounts, loading amounts and adsorption heats all followed CO2 > CH4 > N2. There were exponential changes between isometric heats and loading amounts. The diffusion characteristic of three gases in the pores was CH4 > N2 > CO2, and the larger pores were more conducive to gas diffusion. Radial Distribution Function was implemented to study the action radius between gases and C atoms of coal molecules. There was the smallest effective distance and the largest effective radius between CO2 and C atoms. The action distance between N2 and C atoms was the largest, and the action scope between them was the smallest.
Key roles of the sulfonamide antibiotics adsorption on graphene and graphyne.
Display omitted
•A new strategy for clarifying the adsorption mechanisms was proposed.•Antibiotics were adsorbed at a ...distance of 4–5 Å from the adsorbent surfaces.•Orthogonal configuration is hard to be adsorbed due to easy molecular aggregation.•Increasing the π electron density of adsorption system enhance the interactions.•Electron cloud density and configuration play the key roles in the adsorption.
Electron transfer often drives the adsorption, but its role is difficult to determine by traditional experimental methods. In this work, two typical carbonaceous materials, graphene (GPE) and graphyne (GPY) were selected as adsorbents, and three sulfonamide antibiotics, sulfamethazine (SMT), sulfamethoxazole (SMX), and sulfamethizole (SMZ) were used as the model adsorbates. Molecular dynamics simulations and quantum chemical calculations were combined to explore the adsorption behavior and mechanisms. Molecular dynamics results showed that the antibiotic molecules were most likely to be adsorbed at a distance of 4–5 Å from the GPE and GPY surfaces. Subsequently, the energies and electronic information were analyzed based on quantum chemical calculations. The N-atom in the pyrimidine ring of SMT exhibited a stronger electron-donating ability than the O- and S-atoms in the heterocycles of SMX and SMZ, thereby enhancing its interaction with GPE and promoting its adsorption. GPE has a stronger π electron system and conjugation effect compared with GPY, and its triangular electron cloud configuration gives it a stronger adsorption ability. The electron cloud density and configuration played key roles in the adsorption. These results provide fundamental theoretical support for the structural design and optimization of carbonaceous materials and the efficient removal of sulfonamide antibiotics.
Display omitted
•The process of LiCoO2 Leaching was analyzed by molecular dynamics simulation.•There is a strong spatial correlation between H2O2 and the LiCoO2 surface at 1.125 Å.•The non-bonding ...interaction energies are mainly contributed by the electrostatic force.•H2O2 dosage has the strongest effect on the interaction energy.
The mechanism of interaction between H2SO4 + H2O2 solution and LiCoO2 surface were studied by molecular dynamics (MD) simulation. The impact of H2SO4 concentration, H2O2 dosage, and temperature on the alterations in the molecular distribution characteristics in the leaching solution was revealed by analyzing the diffusion coefficients, radial distribution function (RDF), and interaction energies from a molecular perspective. The simulation results show that the diffusion coefficients of H2O, H2O2, and SO42- increase and subsequently decrease with increasing H2SO4 concentration and H2O2 dosage, and they increase with increasing temperature. The radial distribution function shows a strong spatial correlation between the H2O2 molecules and the LiCoO2 surface at 1.125 Å, and the highest peak value is 31.21 with 3 M H2SO4, 12 vol% H2O2, and temperature of 363 K. The non-bonding interaction energy between leaching solution and LiCoO2 surface consists of electrostatic force, and the order of the influencing strength of these three factors on the interaction energy is as follows: H2O2 dosage > temperature > H2SO4 concentration. Additionally, the simulation results were validated through single factor leaching experiments. This study provided a molecular-level understanding of the leaching mechanisms of spent LiCoO2 batteries.
Hybrid lithium-air batteries (HLABs) effectively solve the bottleneck problem of discharge product Li2O2 blocking non-aqueous lithium-air batteries' electrode pores, attracting extensive attention. ...This paper analyzes the battery's cycle performance, deep discharge performance, and main failure reasons in an ambient environment using the LiOH and KOH aqueous solutions as cathode electrolytes. Meanwhile, the authors intensely study the internal mechanism of mass transfer by molecular dynamics simulation method based on these two cases of electrolytes. The KOH aqueous solution as cathode electrolytes of HLABs has superior deep discharge performance due to the better diffusion ability of K+, and the hydration of cations weakened. However, because the KOH is more alkaline than LiOH, the corrosion on LAGP plates will be severe, affecting the battery's cycle performance. So, the cycle discharge performance of the LiOH aqueous solution as cathode electrolytes of HLABs is significantly better than that of the KOH solution. Under the external electric field, the hydration of cations weakened, which is more favorable to the mass transfer of batteries. Therefore, the HLABs with KOH perform better in deep discharge, and the HLABs with LiOH perform better in long cycles. The research results provide a particular reference for subsequent research and application.
Display omitted
•Benzothiazole based Schiff bases showed excellent anticorrosive property in 1 M HCl.•Electrochemical study unveiled corrosion inhibition efficiency of the studied ...inhibitors.•Heteroatoms and molecular structure effecting corrosion inhibition has been explained.•FESEM, AFM and contact angle confirmed inhibitors’ adsorption on mild steel surface.•DFT, Fukui indices, NCI-RDG, MD simulation and RDF analysis validated experimental findings.
Synthesis of challenging corrosion inhibitors is of prime importance to inhibit hydrogen-induced and localised metallic corrosion occur in the corrosive acidic solution. In this regard, the present research has been focused on the development of functionalised Schiff bases, namely, 1-(benzodthiazol-2-yl)-2-((furan-2-yl)methylene)hydrazine (BTFMH), 1-(benzodthiazol-2-yl)-2-((thiophen-2-yl)methylene)hydrazine (BTTMH), 1-(benzodthiazol-2-yl)-2-((5-methylthiophen-2-yl)methylene)hydrazine (BTMMH) with an aim of effectively curtailing the issues associated to hydrogen-induced cracking and subsequent inhibition of metallic corrosion taking place in the corrosive acidic solution. The corrosion inhibiting performances of the synthesized inhibitors have been assessed for mild steel surfaces exposed in 1 M HCl medium using gravimetric measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization study revealed that the synthesized inhibitor molecules retarded the cathodic hydrogen evolution reaction at cathodic site and subsequently minimized the oxidation of metals at anode; thereby, these Schiff bases acted as the mixed type inhibitors. The EIS study revealed that the corrosion inhibition phenomenon is being controlled through charge transfer processes. All of these three synthesized inhibitor molecules showed approximately 96–98 % corrosion inhibiting efficiency at exceedingly low concentration (0.5 mM). The inhibition efficacy obtained for these synthesized inhibitor molecules follows the order: BTMMH > BTTMH > BTFMH. The adsorption nature of these inhibitor molecules on mild steel surfaces have been revealed through surface morphology, topography and water contact angle studies. Thereafter, the insight of corrosion inhibition mechanism at atomic level have been explored by density functional theory (DFT). The optimized geometrical structure, electron density distribution of frontier molecular orbitals and their corresponding energy parameters obtained from DFT as well as Fukui indices analysis have been explored to unveil the plausible modes of adsorption or the reactive sites present within the inhibitor molecules which facilitate their interactions with surface atoms of metals. The non-covalent interaction based on reduced density gradient have been explored to study intrinsic feeble interaction acting with the molecules. Afterwards, molecular dynamics simulation has been employed to validate the spontaneity along with the nature of interaction at the metal inhibitor interface. Furthermore, the equilibrium adsorption configuration of the synthesized inhibitor molecules on the targeted metal surface atoms have been envisaged and the interfacial phenomenon has been explained.
•The diffusivity and intermolecular interaction strength of various amine blends are examined.•2EAE-TMPAD, 2EAE-DEAB, 2EAE-1DMA2P, 2MAE-2DMAE and 2EAE-2DMAE are selected.•The results show that the ...order of diffusion rate in the blended amines system is 2EAE-TMPAD > 2EAE-DEAB > 2EAE-1DMA2P > 2MAE-2DMAE > 2EAE-2DMAE.•The order of intermolecular strength of blended (PZ-2EAE) and pure amines (2EAE& DEA) is 30 %2EAE-10 %PZ˃30 %PZ-10 %2EAE and 2EAE˃DEA.•The intermolecular interaction intensity in single and mixed tertiary amines system is MDEA-PZ > 2DMAE-PZ > PZ-2DMAE > 2DMAE.
Based on the faster absorption kinetics of primary or secondary amines and the lower regenerating potential of tertiary amines, mixed amine solvents are being examined as a viable choice for CO2 capture. The critical parameters in the CO2 absorption process are the solubility of the solvent and the reaction kinetics of amine with CO2. Hence, the current work seeks to address these critical parameters by investigating the diffusivity and intermolecular interaction intensity of amines. In this regard, various secondary and tertiary amines (2EAE-TMPAD, 2EAE-DEAB, 2EAE-1DMA2P, 2MAE-2DMAE, 2EAE-2DMAE, and DMCA-MCA) are suggested as a mixed solvent. Molecular dynamic simulation is employed in the Material Studio program. The diffusivity and intermolecular interaction intensity results are interpreted by mean square displacement and radial distribution function analysis, respectively. The findings of current research demonstrate that 2EAE-TMPAD has the highest diffusion rate as compared to other blends. The order of diffusion rate in the blended amines system is 2EAE-TMPAD > 2EAE-DEAB > 2EAE-1DMA2P > 2MAE-2DMAE > 2EAE-2DMAE. The screening of the DMCA-MCA blended system shows that 10 %DMCA-20 %MCA has higher interaction strength than that of other concentrations. Furthermore, the diffusion coefficient of the DMCA-MCA blend is 0.61E-9 m2/s at 313 K, which agrees well with the experimental studies. The findings described in this paper are useful for evaluating the optimal hydrodynamics of fluid flow inside the absorption column and designing the column height, considering kinetics and mass transfer data.
