Adsorption Of Molecules Research Articles

Transition from Internal to External Oxidation in Binary Fe–Cr Alloys Around 900 °C

The transition from external to internal oxidation of a binary Fe-10Cr alloy has been investigated in Fe/FeO Rhines pack (RP) and H2/H2O between 850 and 900 °C. Internal oxidation is facilitated by increasing temperature and presence of water vapor. A classical Wagnerian diffusion analysis predicts external oxidation for ferritic (BCC) Fe-10Cr and internal oxidation for austenitic (FCC) Fe-10Cr. The α-to-γ transformation is demonstrated to be the primary factor promoting internal oxidation in Fe–Cr around 900 °C. Water vapor is believed to promote internal oxidation due to a higher reactivity of H2O compared to O2 and higher preferential adsorption of the H2O molecule.

Machine learned interatomic potentials for gas-metal interactions

Abstract Developing interatomic potentials for gas-metal systems is difficult due to the wide range of chemical compositions that the potential must be able to reproduce. There is a need for these types of potentials for studying plasma-material interactions in fusion reactors where gaseous plasma species will implant in metallic reactor components. The challenges presented by these material systems make them suitable candidates for treatment by a machine learning approach, such as that of the spectral neighbor analysis potential (SNAP). However, constraining the dynamics with these more flexible potentials is difficult. In this work, we have developed a SNAP potential for W-N and W-H in order to study the material degradation due to ion implantation in tungsten. We have developed a large set of density functional theory training data spanning multiple chemical environments including gas phase, surface, bulk, and gas-metal configurations. Additional methodologies for developing training data and optimizing the potential for accurately describing fast diffusing impurity species are detailed. The SNAP potential well-reproduces key material properties relevant for modeling plasma-material interactions including defect formation energies, surface adsorption energies, dimer binding energies, and tungsten nitride formation energies. In addition to testing on static energetic properties, the SNAP potential was also used to simulate thermal and dynamic gas-metal interactions, including bulk diffusion, molecular gas adsorption isotherms, and ion implantation. The SNAP potentials are demonstrated to well-reproduce behavior in the wide range of chemical environments investigated, demonstrating the suitability of these machine learned interatomic potentials for future studies of plasma material interactions.

Interface Electron Transfer Direction-Tuned Urea Electrooxidation Over Multi-Interface Nickel Sulfide Heterojunctions.

Hydrogen can be produced by electrolyzing urea aqueous solution under smaller overpotentials, owing to the lower thermodynamic potential of urea oxidation reaction (UOR) at anode than oxygen evolution reaction (OER). The efficient and selective electrocatalysts for UOR are crucial to achieve this. Herein, two NiS-based NiS/Ni3S2 and NiS/NiS2 heterojunctions with Ni cores embedding in nitrogen-doped carbon nanotubes (NiS/Ni3S2- and NiS/NiS2-Ni@NCNT) are demonstrated as efficient UOR electrocatalysts. The electrocatalytic UOR performance over heterojunctions is efficiently tuned by altering the electron transfer direction on their interfaces. NiS/Ni3S2-Ni@NCNT with interface electrons transferring from Ni3S2 to NiS, delivers a 10 mA cm-2 UOR current density in 1.0 m KOH with 0.5 m urea at 1.37 V, superior to NiS/NiS2-Ni@NCNT with the electron transfer direction from NiS to NiS2. Experimental and theoretical calculation results reveal that NiS/Ni3S2 Mott-Schottky heterojunctions facilitate the rapid in situ formation of NiOOH active species by removing electrons of Ni3S2, and also accelerate the adsorption and conversion of urea molecules and key intermediates of *CON2 at its interfaces. This work demonstrates an interface electron transfer direction tuning strategy on heterojunctions for harvesting high-performance UOR electrocatalysts.

Tailored pseudopotentials for magnesium surface core level shift calculations

In x-ray photoelectron spectroscopy (XPS), identifying the origin of peaks in the spectrum can be guided by theory calculations. With density functional theory (DFT), using pseudopotentials, one can obtain the difference in photoelectron energy for electrons originating from atoms of different environments, for example surface and bulk atoms, and thus model the surface core level shift (SCLS) energies. The focus in this work is to prepare for calculations of magnesium (Mg) 2p SCLSs in material systems where dispersion interactions play a role, primarily in Mg surface degradation and adsorption of molecules as relevant, for example, in degradable bioimplants. For SCLS DFT calculations in metallic surfaces, the state of the photoelectron must be treated as a core state. In the case of Mg, standard pseudopotentials treat the 2p state as a valence state, not a core state. We therefore need Mg pseudopotentials with the 2p electrons in the core, leaving only two electrons for the valence region (the 3s electron); Two-valence electron pseudopotentials are not common, because DFT calculations of Mg-containing materials usually are better or more easily described using 10 valence electrons. In this work, new two-electron Mg pseudopotentials are therefore created for use in dispersion-inclusive DFT calculations. To our knowledge, no such two-electron Mg pseudopotentials exist, proven to work well with the nonlocal, dispersion-inclusive, exchange-correlation functional vdW-DF-cx or similar functionals. We create a number of two-electron Mg pseudopotentials and their 2p-hole partners, and for four of the most promising we assess their performance in vdW-DF-cx. We provide results for Mg and MgO bulk phases and for the Mg(0001) surface energy, structure, and SCLS, and where possible we compare with results that we obtain by using conventional 10-electron Mg pseudopotentials, all-electron calculations, and with experiments. This work not only reports and tests the specific conditions for creating 2p Mg results, it will also, we believe, be of help in creating other similar pseudopotentials to aid the analysis of XPS spectra in other materials. Published by the American Physical Society 2024

Enhanced electrochemical oxygen reduction reaction on “C–O–Si” bonds in Si-doped graphene-like carbon

The use of heteroatom-doped carbon materials as non-precious metal catalysts for oxygen reduction reactions has attracted much attention from researchers. This paper presents the synthesis of two-dimensional Si-doped graphene-like materials (Si-GLC) featuring “C–O–Si” bonds through an in-situ doping method. Since the electronegativity of the Si (1.90) is much smaller than that of C (2.55) and O (3.44), the formation of the “C–O–Si” bond causes Si to lose a large number of electrons and become positively charged. This increases the adsorption of electronegative oxygen, thereby improving the activity of oxygen reduction reactions. The adsorption energy of oxygen molecules on Si-GLC was calculated to be −3.57 eV using density functional theory, much lower than on GLC (−2.18 eV). This suggests that Si doping enhances the adsorption of oxygen molecules by graphene-like materials, which is crucial for improving the performance of oxygen reduction reaction. Si-GLC displayed a half-wave potential of 0.80 V (vs. RHE) and a diffusion-limited current density of 5.81 mA cm−2 in 0.1 M KOH solution, demonstrating excellent catalytic activity for oxygen reduction reaction. It also exhibits good stability and tolerance to methanol crossover effect. In-situ doping creates “C–O–Si” bonds, modulating charge density and providing a strategy for high-performance oxygen reduction catalysts.

Sensing-performance improvement of 2D MoSH based gas sensors for detecting NO, NO2, and NH3 gas molecules

Nitrogen group oxide is one of the major pollutants in the air, and its accurate and rapid detection is essential for environmental protection and human health. Therefore, it is of great significance to develop high-performance new line sensor for Nitrogen group oxide. Here, we investigate the potential of monolayer 2D MoSH materials as candidates for NO gas sensing using a combination of density functional theory and non-equilibrium functions to construct nanodevices based on MoSH monolayer, and theoretically study the adsorption behavior of MoSH monolayer to NO, NO2, and NH3 gas molecules. The results indicate that MoSH monolayer exhibit metallicity, and nanodevices based on 2D MoSH monolayer exhibit anisotropic transport properties and significant negative differential resistance effects(NDR). More interestingly, gas sensors based on MoSH monolayers exhibit typical chemical adsorption of NO, NO2, and NH3 gas molecules, and the anisotropic transport properties still maintain, but significant differences of sensitivity appear for these three gas molecules. Specifically, the MoSH based gas sensor has the highest sensitivity to NO, reaching 93.1% and 76.3% along the armchair and zigzag directions, respectively. These results show that 2D MoSH monolayer is an excellent gas-sensing material with excellent application prospects for NO gas detection.

Dichloromethane -methanol fraction of Mahonia nepalensis containing Berberine, Jatrorrhizine, and tetrahydroberberine as corrosion inhibitor for mild steel

A potentially superior alternative source of environmentally acceptable corrosion inhibitors for metallic materials is plant extracts. This study reports on the use of compounds separated from Mahonia nepalensis (MN) bark extract as an environmentally friendly corrosion inhibitor for mild steel (MS) in 1 M H2SO4. The organic layer was separated from MN bark extracts and then Berberine, Jatrorrhizine, and Tetrahydroberberine were identified and quantified by Liquid column mass spectroscopy (LC-MS) in dichloromethane (DCM) −Methanol fraction of Mahonia nepalensis. The DCM − Methanol fraction of extract was characterized by Ultra violet − visible spectroscopy (UV–Vis) and Fourier Transform Infrared (FTIR). The DCM-Methanol fractions in 1 M H2SO4 were applied to study corrosion inhibition of MS by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed above 91 % inhibition efficiency (IE) for DCM-Methanol fraction containing 2.12 ppm berberine, jatrorrhizine, and tetrahydroberberine at room temperature indicating that it is an effective and cheap candidate for the corrosion prevention of MS in industry. The potentiodynamic polarization demonstrated a reduction in current density without affecting the reaction mechanism but reduced the hydrogen reduction indicated by suppression in cathodic current. Based on polarization curves and open circuit potential, it exhibited mixed inhibitory behavior. Similarly, EIS analysis revealed a drop in double-layer capacitance accompanied by an increase in charge transfer resistance. EIS and a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) ascertain the adsorption of inhibitor molecules forming a protective layer on the MS surface.

Exploring Zeolite Potential for Hydrofluorocarbon Capture and Recycling: Insights from Molecular Simulations

The need for efficient separation of hydrofluorocarbons for recycling and environmental protection is critical due to their substantial impact on global warming. However, conventional methods such as cryogenic distillation face significant limitations due to the azeotropic behavior of many of these hydrofluorocarbons. This study evaluates the adsorption behavior of various hydrofluorocarbons in zeolite structures, specifically Linde Type A (3A, 4A, and 5A) and Faujasite Type X (13X), using molecular dynamics and grand canonical Monte Carlo simulations. The simulations were validated against experimental data, confirming the reliability of the computational models. Adsorption isotherms were fitted using the Langmuir-Freundlich model to describe the adsorption behavior across different pressures. Focusing on fluoromethane derivatives, the study highlighted key interactions and adsorption capacities in various zeolites. The isotherms of various hydrofluorocarbons in zeolite 13X were explored, revealing differential adsorption based on molecular structure. The potential for using zeolite 13X and 5A to separate refrigerant mixtures was also studied, showing distinct selectivity patterns. Additionally, the temperature dependence of adsorption isotherms and isosteric heat was studied to gain insights into the thermodynamics of the adsorption processes. Key results indicate that zeolite 13X demonstrates strong cation-fluorine interactions, particularly effective for the adsorption of large hydrofluorocarbon molecules, which preferentially occupy 12-membered ring windows. In contrast, zeolite 5A exhibited predominant hydrogen bonding interactions at low pressures, with hydrofluorocarbon molecules occupying the smaller 8-membered ring windows. These findings underscore the selective adsorption capabilities of these zeolites, highlighting their potential application in hydrofluorocarbon separation and recycling processes.

Enhancing NH3-SCR denitrification performance through synergistic A- and B-site effects via CeFe modification of LaMnO3

ABO3 type perovskite catalysts are widely used in NH3-SCR to remove NOx due to excellent low-temperature reduction performance. To study the synergistic effect of A and B sites on the structure, morphology and redox performance of modified perovskite catalysts (La1-xCexMn1-yFeyO3), LaMnO3 perovskite catalysts were co-doped with CeFe by sol-gel method, and the crystal structure, surface chemical environment, optimal metal co-doping ratio and surface adsorption of the modified perovskite catalysts were clarified through various characterizations. In addition, through first-principles calculations, the differential charge density and binding energy of each doping system were analyzed, the relationship between the difficulty of Ce doping and the electronic population of Mn atoms and the redox ability of the catalyst was discussed, and the key bond types and their changing rules in perovskite catalytic reduction were clarified. The results showed that co-doping Ce and Fe could improve the denitrification efficiency and sulfur resistance of the catalyst. When the Fe doping ratio is 0.1, the denitrification activity is the highest. Among them, the La0.9Ce0.1Mn0.9Fe0.1O3 catalyst showed the most favorable active acid site distribution and the best reduction performance, which was conducive to the adsorption and redox of gas molecules on the catalyst surface. At the same time, when the A and B sites were co-doped, the electron transferred mainly occurs between Ce ions and Fe ions, forming a synergistic effect and changing the covalent components between Mn-O and Fe-O bonds. This made the valence states of Mn and Fe ions more, enhanced the catalytic activity of perovskite, and promoted the redox of NO on the catalyst surface, thus providing a new idea for the redox reaction pathway of modified perovskite catalysts.

Enhancing CO2 Foam Stability with Hexane Vapours: Mitigating Coarsening and Drainage Rates

CO2 foams often suffer from poor stability due to high coarsening and coalescence rates, limiting their effectiveness in various applications. While it is well-established that small amounts of insoluble vapours such as alkane or fluorocarbon vapours can impede coarsening and recent studies have demonstrated their impact on coalescence, their specific effect on the CO2 foams has not been studied. This research provides a comprehensive examination of stabilising effect of hexane on CO2 foams in the presence of sodium dodecylbenzenesulfonate (SDBS). We investigated the foam stability of CO2 foams, benchmarking them against N2 foams by analysing foam lifetime, liquid drainage rate, and the evolution of bubble size. Additionally, we quantified the stabilising impact of hexane by calculating the coarsening rate. To gain insights into the adsorption mechanism of surfactants in the presence of hexane, we conducted surface tension and interfacial dilational rheology measurements, which demonstrated an increased adsorption of surfactant molecules at the interface and increased dilational viscoelasticity of interface when n-hexane was present. The introduction of hexane significantly improved foam stability, reducing coarsening rates by more than an order of magnitude. This improvement in foam stability is attributed to inhibited CO2 diffusion from the bubbles, as well as enhanced surfactant adsorption and surface elasticity, resulting in an approximate 3.6-fold increase in foam half-life.

Fabrication and characterization of acidic high internal phase emulsion gels stabilized solely by wheat gluten for plant-based mayonnaise

Plant-based diets are currently gaining more popularity as a means of reducing the environmental footprint and promoting human health. Herein, plant protein-based acidic high internal phase emulsion gels (HIPE gels) were fabricated via a facile one-pot approach using wheat gluten (WG) solely. Pre-dissolving WG in edible vinegar-water solution was contributed to the fabrication of stable emulsion gels. Factors that affect the structure and performance of plant proteins as HIPE gels stabilizers were investigated. The results indicated that the stable HIPE gels could be formed with a vinegar concentration between 5 % and 20 % and a WG concentration of 1.0 %–7.5 % only. Microscopy images reveal that a collaboration of the soluble protein molecules adsorption and protein aggregate Pickering stabilization at oil-water interface, which was turned to form stable HIPE gels. In addition, the resulted HIPE gels exhibited shear thinning behavior, viscoelastic features, and good thixotropic recovery, which provide a similar perceived texture and sensory property for formulating egg-free mayonnaise. These findings provide a useful approach to construct HIPE-based softs from low-cost wheat gluten for preparing plant-based mayonnaise.

DFT investigation of Co/Ni decorated borophene for efficient removal of methylene blue from wastewater effluent

Removal of dyes is a significant aspect of environmental remediation to ensure clean water and atmosphere. In this study, we report metals decorated (M = Co, Ni) borophene (B36) for effective removal of cationic dye (methylene blue) using density functional theory calculations. The calculations shows that the metals are strongly anchored at the surface of B36 system with stronger binding energies and larger positive charge. The molecular dynamics simulations evince that the M@B36 are thermally stable and withstand to high temperature as 500 K. The application of M@B36 as adsorbent for the removal of MB dye shows that the dye could strongly adsorbed over the M@B36 surface involving the formation of a chemical bond and larger adsorption energies (−2.99 and −2.73 eV for MB@Co-B36 and −2.27 and −2.11 eV for MB@Ni-B36) compared to bare B36 system. The electron density difference, partial density of states and atom in molecule analysis gives evidences of the presence of stronger covalent bonds between the M@B36 and MB. This chemical bonding leads to the chemisorption of MB over the M@B36 surface. The solvation effect decreases the desorption time of the MB molecules from M@B36. This is further verified by explicit solvent effects, which shows that the addition of water molecules weaker the intermolecular forces and lower the adsorption energy value to −1.32 eV. The protonated dye molecule is strongly adsorbed over the metal-decorated B36 system, showing that the dye molecule adsorption in an acidic medium is feasible. The selectivity study shows that the MB dye is selectively adsorbed over the metal-decorated borophene compared to water molecules due to larger adsorption energy values. These results show that this study will help the experimentalists to explore M@B36 system as new metal doped adsorbent for removal of toxic pollutants from waste water.

In situ QXAFS study of CO and H2 adsorption on Pt in [PtAu8(PPh3)8]-H[PMo12O40] solid.

The adsorption behaviors of H2 and CO molecules in crown-motif [PtAu8(PPh3)8]-H[PMo12O40] (PtAu8-PMo12) solids were investigated by in situ quick-scan X-ray absorption fine structure (QXAFS) measurements with a time resolution of 0.1 s. The electronic state of Pt in PtAu8-PMo12 was drastically changed by the adsorption of H2 and CO molecules because of the formation of Pt-H2/Pt-CO interactions. H2 was adsorbed more rapidly (<0.5 s) on Pt than CO (∼2.5 s) and showed reversible adsorption/desorption behavior on Pt atoms in PtAu8-PMo12. The rapid adsorption of H2 is due to the fast diffusion of H2, which has a smaller kinetic diameter than CO, in the narrow channels between the closed voids in PtAu8-PMo12. Meanwhile, CO was irreversibly adsorbed on Pt, resulting in structural isomerization to the stable "chalice-motif" PtAu8, which was determined by XAFS analysis and density functional theory calculations. Structural isomerization was involved by pushing ligands aside to make space for CO adsorption as the void size near Pt in the crown-motif PtAu8-PMo12 was narrower than the kinetic diameter of CO.

Terminalia bellirica fruit shell extract by microwave assisted extraction as a green inhibitor for mild steel acid corrosion: insight from chemical, electrochemical and computational studies

In the current study, the corrosion protection role of ethanol extract of Terminalia bellirica fruit shell on Mild Steel (MS) in 0.5 M HCl solution was studied by using weight loss, Tafel plot, AC impedance and surface techniques. The existence of functional groups in the plant extract was confirmed with the aid of FT-IR spectroscopy technique. The presence of 31.12% of gallic acid in the Terminalia bellirica fruit shell extract was complemented with HPLC and LCMS results. The surface coverage and protection efficiency of Terminalia bellirica fruit shell extract were enhanced with its concentration and declined with solution temperature. The activation parameters such as activation enthalpy, entropy and change in Gibb’s free energy are related to adsorption process were calculated and discussed. The adsorption of Terminalia bellirica fruit shell extract was found to obey the Langmuir adsorption model. The process of adsorption of inhibitor molecules on the metal surface can be verified by using UV–Visible spectroscopy technique. The potentiodynamic polarization and impedance results suggest that, Terminalia bellirica fruit shell extract functioned by adsorption at metal (MS)-Corrodent (0.5 M HCl) interface, which blocks the both cathodic and anodic half reactions of the MS corrosion process. Theoretical approach by Monte Carlo (MC) simulations and quantum chemical study support the experimental findings and adsorption of extract of Terminalia bellirica fruit shell molecules on MS surface.

Potentiometric enzymatic aptasensing of paralytic shellfish toxins using graphene-wrapped magnetic nanospheres and an all-solid-state cadmium-selective microelectrode

A highly sensitive potentiometric enzymatic aptasensing system for the detection of paralytic shellfish toxins (PSTs) is developed by integrating graphene-wrapped magnetic nanospheres (Fe3O4@SiO2@rGO) with an all-solid-state ion-selective microelectrode. The multilayered core-shell structure of Fe3O4@SiO2@rGO enhances the efficient adsorption of aptamer molecules tagged with cadmium sulfide (CdS) nanoparticles. These CdS-aptamer conjugates, when bound with PST molecules, can be desorbed from the Fe3O4@SiO2@rGO surface into the sample solution and subsequently digested by deoxyribonuclease I (DNase I). This digestion process releases the PST molecules for recirculation, significantly reducing the retention of CdS on the surface of Fe3O4@SiO2@rGO. After magnetic separation and acid dissolution, the released Cd2+ from the magnetic nanospheres are measured using an all-solid-state Cd2+-selective microelectrode, enabling sensitive potentiometric detection of PSTs. Using gonyautoxin 1/4 (GTX 1/4) as a model, the sensing system exhibits a linear concentration range from 5 to 150 pM and a low detection limit of 1.7 pM for GTX 1/4, and has been successfully applied in the analysis of seawater samples.

Zn2+ flux regulator to modulate the interface chemistry toward highly reversible Zn anode

The persistent challenges of diminished coulombic efficiency (CE) and the formation of Zn dendrites at the Zn anode interface substantially hinder the cycle life of aqueous Zn-ion batteries (AZIBs), thereby impeding their widespread deployment. To address these issues, multifunctional 2-amino-5-guanidino-pentanoic acid (AGPA) additive is introduced into the electrolyte, as a novel Zn2+ flux regulator (ZFR) to improve the reversibility and durability of Zn anodes. The distinctive zincophilicity of amino groups empowers such ZFR with a higher adsorption energy, enabling the construction of a multifunctional molecular adsorption layer on Zn electrode surface. Simultaneously, leveraging the exceptional nucleophilic characteristics of polar carboxyl groups, AGPA molecules tend to form chelating bonds with Zn2+ for manipulating the interface chemistry and solvation chemistry. The functional groups in ZFR work in synergy to attract zinc ions for homogenizing Zn2+ flux and suppress the interfacial side reactions, resulting in uniform dendrite-free Zn deposition. Consequently, the Zn//Zn symmetrical cell achieves an extended cycle life of 5500 h. Moreover, the ZFR enables stable operation of the full batteries with an ultra-long cycling lifespan of 6000 cycles at 5 A/g, showcasing the effectiveness of ZFR in advancing the commercialization of AZIBs.

Strategic defect engineering in TiO2 catalysts through electron beam irradiation: Unraveling enhanced photocatalytic pathways for multicomponent VOCs degradation

Defect engineering improves catalytic activity, electron transport efficiency, and stability by introducing defects such as oxygen vacancies, offering significant potential for applications in environmental remediation and energy conversion. Electron beam (EB) irradiation has emerged as a key technique in defect engineering, renowned for its mild reaction conditions and precise defect construction capabilities. This study synthesized defect-rich commercial TiO2 catalysts (P25) using high-energy EB irradiation to investigate the photodegradation efficiency of multicomponent VOCs. The EB irradiation technique promoted the formation of oxygen vacancies, which played a key role in the adsorption and activation of pollutant molecules. DFT calculations further confirmed the superior photocatalytic activity of the irradiated P25 catalyst. The photodegradation experiments showed that the 300P25 degraded pure ethyl acetate up to 99.05 % (40 min) and acetone up to 97.14 % (60 min), but toluene only up to 7.34 % (60 min). Interestingly, in acetone and toluene mixture, 300P25 achieved toluene removal as high as 68 % (60 min) with a rate constant (k) of 0.0181 min−1, a 12.1-fold than pure toluene (0.0015 min−1). In-situ infrared spectroscopy analysis revealed that during the simultaneous degradation of toluene and acetone, acetone significantly promoted the deep oxidation of toluene, leading to the rapid oxidation of intermediate products (benzyl alcohol and benzaldehyde) to benzoic acid and smaller molecules. This work provides important guidance for developing efficient and stable photocatalysts for degrading multicomponent VOCs.

Hydrogenation Reaction Mechanisms on Ni-Doped MoS2 Catalysts: A Density Functional Theory Study of Sulfur Edge Engineering and Coregulated Electronic Effects.

Precise modulation of local interatomic interactions affecting the electronic structure is an important method to control the catalytic activity and reaction pathways. In this study, we focused on the hydrogenation reaction of naphthalene and employed density functional theory calculations to investigate the specific influence of electronic effects triggered by the coregulation of Ni and sulfur edge engineering on the hydrogenation performance of Ni-doped MoS2 at different edge sulfur coverages (Ni-MoS2-X-θs). Our findings reveal that the interaction between Ni and S in the catalyst matrix material modifies the local electronic structure surrounding the sulfur atoms in the active site. Notably, Ni doping facilitates significant electron transfer, altering the charge and the electronic states at the catalyst edge. This, in turn, affects the adsorption capacity and reactivity of the catalyst, thereby reducing the energy barrier of the hydrogenation reaction. Furthermore, we paid particular attention to the modulation of catalytic activity and reaction pathways under the Eley-Rideal (E-R) mechanism. Interestingly, the sulfur coverage exhibited a nonlinear relationship with the adsorption and activation properties of the probe molecule. Typically, changes in the Mo edge sulfur coverage probability of Ni-MoS2-X-θs have a greater impact on the activation properties. Through comprehensive studies, we demonstrated that both compositional and structural factors must be considered when tailoring the catalytic performance. Importantly, adjusting the ratio of marginal sulfur atoms to metal atoms to 1:1 can effectively enhance the catalytic activity. This study provides valuable insights into the electronic effects regulating the hydrogenation reaction activity of MoS2-based catalysts. It also opens the way for the rational design of novel hydrogenation catalysts, offering a new strategy for optimizing the catalytic performance.

New insights into the significant drop of molybdenite flotation Recovery: The Overlooked oxidation of MoS2 basal facet

The oxidation of molybdenite in water-oxygen system adversely affects the flotation recovery. However, previous studies primarily focused on the oxidation of MoS2 edge surfaces, neglecting the oxidation of basal facets, which constitute a larger proportion of the overall surface area. In this work, we systematically investigated the oxidation behavior of the molybdenite base surface and explored the influence of base surface oxidation sites on flotation behavior. The results demonstrated that surface oxidation of molybdenite leaded to a negative surface potential, decreased hydrophobicity and reduced dodecane adsorption. Electrostatic potential (ESP) and density functional theory (DFT) calculations revealed that oxidation sites on the molybdenite surface exhibited a strong negative charge, enhancing the adsorption of water molecules while weakening kerosene adsorption. Molecular dynamics (MD) simulations indicated that the oxidized molybdenite surface formed a hydration layer with thickness of ∼ 6 nm, which impedes dodecane adsorption. Moreover, this study proposed an effective strategy to improve molybdenite flotation recovery, that is reducing the concentration of dissolved oxygen in the pulp to inhibit MoS2 oxidation. These findings provide new insights into the oxidation behavior of molybdenite, and contribute to a better understanding of its flotation behavior in pulp.

Desorption of Antibiotics from Granular Activated Carbon during Water Treatment by Adsorption

Although desorption of adsorbed pharmaceuticals from granular activated carbon (GAC) may inadvertently lead to their partial discharge with adverse effects on aquatic environments, there have only been a few reports of this phenomenon. This study has investigated desorption of antibiotics vancomycin and rifampicin from activated carbon in aqueous media regarding contact time and pH regime. Various characterizations of the three types of GAC were investigated. Then, antibiotics were loaded on them via adsorption. Subsequently desorption and re-adsorption of antibiotics were quantified for a range of contact times and ambient pH values. Within the first hour of a reversed concentration gradient at neutral pH, desorption released 2% to 54% of previously adsorbed antibiotics to water, which were subsequently re-adsorbed within 24 hours to four weeks with less than 1% antibiotics remaining in the liquid phase. Lower desorption was positively associated with higher GAC mesopore content and larger specific surface area. Effects of the ambient pH regime varied between studied adsorbents. The results are evidence that mesopore content and pore size in relation to the kinetic diameter of adsorbate molecules are important determinants of the extent of antibiotic desorption from GAC and the rates of subsequent re-adsorption. Physisorption was the dominant mechanism involved in both processes. Observed proportions and rates of antibiotic desorption suggest that selection of GAC properties should also consider their effects on unintended desorption and the re-adsorption during treatment processes in order to minimize potential pollution discharge or promotion of antibiotic resistance during treatment processes.