Repulsive Energy Research Articles

Comigration Behavior of Cr(VI) and Microplastics and Remediation of Microplastics-Facilitated Cr(VI) Transportation in Saturated Porous Media

The study of the co-transport of Cr(VI) and microplastics (MPs) in porous media is important for predicting migration behavior and for achieving pollution removal in natural soils and groundwater. In this work, the effect of MPs on Cr(VI) migration in saturated porous media was investigated at different ionic strengths (ISs) and pHs. The results showed that pH 7 and low IS (5 mM), respectively, promoted the movement of Cr(VI), which was further promoted by the presence of MPs. The Derjaguin–Landau–Verwey–Overbeek (DLVO) results showed that the repulsive energy barrier between MPs and quartz sand decreased with increasing IS and decreasing pH, respectively, which promoted the retention of MPs in quartz sand and constrained the competition of Cr(VI) for adsorption sites on the surface of the quartz sand, thus facilitating the enhanced migration of Cr(VI), while Cr(VI) behaved conversely. Sodium alginate/nano zero-valent iron-reduced graphene oxide (SA/NZVI-rGO) gel beads could achieve the removal of MPs through a π-π interaction, hydrogen bonding, and electrostatic attraction, but the MPs removal would be reduced by 40% due to the competitive adsorption of Cr(VI). Notably, 97% Cr(VI) removal could still be achieved by the gel beads in the presence of MPs. Therefore, the gel beads can be used as a permeation reaction barrier to inhibit the MP-induced high migration of Cr(VI). The Cr(VI) breakthrough curves in reactive migration were well-fitted with the two-site chemical nonequilibrium model. Overall, the findings of this work contribute to the understanding of the migration behavior of Cr(VI) and MPs in saturated porous media and provide a theoretical basis for the remediation of soils and groundwater contaminated with Cr(VI) and MPs.

What is the exchange-repulsion energy? Insight by partitioning into physically meaningful contributions.

It is shown that the exchange repulsion energy, Exr, can be rationalized by partitioning the respective energy expression for two systems with Hartree-Fock orbitals into physically meaningful contributions. A division of Exr into a positive kinetic and a negative potential part is possible, but these contributions correlate only poorly with the actual exchange repulsion energy. A more meaningful partitioning is derived, where all kinetic energy contributions are collected in a term that vanishes for exact Hartree-Fock orbitals due to their stationarity conditions. The remaining terms can be distinguished into an exchange integral contribution as well as contributions to the repulsion energy with two, three and four orbital indices. The forms, relationships and absolute sizes of these terms suggest an intuitive partitioning of the exchange repulsion energy into Molecular Orbital Pair Contributions to the Exchange repulsion energy (MOPCE). Insight into the analytic form and quantitative size of these contributions is provided by considering the 3Σ+u (1σg1σu) state of the H2 molecule, the water dimer, as well as an argon atom interacting with Cl2 and N2.

Recent advances in solid‐state nuclear magnetic resonance studies on membrane fusion proteins

Membrane fusion is an essential biological process that merges two separate lipid bilayers into a whole one. Membrane fusion proteins facilitate this process by bringing lipid bilayers in close proximity to reduce the repulsive energy between membranes. Along with their interactions with membranes, the structures and dynamics of membrane fusion proteins are key to elucidating the mechanisms of membrane fusion. Solid‐state NMR (SSNMR) spectroscopy has unique advantages in determining the structures and dynamics of membrane fusion proteins in their membrane‐bound states. It has been extensively applied to reveal conformational changes in intermediate states of viral membrane fusion proteins and to characterize the critical lipid–membrane interactions that drive the fusion process. In this review, we summarize recent advancements in SSNMR techniques for studying membrane fusion proteins and their applications in elucidating the mechanisms of membrane fusion.

Synthesis, spectroscopic characterization, crystallographic studies, Hirshfeld surface analysis, DFT, and molecular docking studies of (4-phenylthiazol-2-yl)(thiophen-2-yl)methanone

In the present research article, we have synthesized a novel (4-phenylthiazol-2-yl)(thiophen-2-yl)methanone molecule. The structure of this compound was confirmed using 1H and 13C NMR spectroscopic techniques. Additionally, the crystal structure was determined through single crystal X-ray diffraction, revealing stabilization by various intra and intermolecular interactions, along with π⋅⋅⋅π interaction. These interactions lead to the formation of R_2^2(4) S(6) and S(5) synthons, which play a crucial role in enhancing the stability of the crystal structure. Moreover, the interactions were verified using Hershfield surface analysis and 2D fingerprint plot evaluations. Energy framework analysis was employed to determine the extent to which the interactions existed and the 3D arrangement of the packing economy within the crystal. The outcomes showed that dispersion energy is higher than repulsion and coulomb energies in the crystal structures' interaction energies and chemical pairs. The electronic properties, such as MEP and HOMO-LUMO energy levels have been investigated using DFT. A substantial HOMO-LUMO energy gap of 3.760 eV suggests that the synthesized molecule exhibits high kinetic stability. Also, molecular docking studies were conducted on the target protein (PDB ID: 3S7S) to explore the binding modes and interactions between the proteins and the ligand.

Understanding the Enhanced Separation Mechanism of C2H4/C2H6 at Low Pressure by HKUST−1

The production of ethylene (C2H4) is typically accompanied by the formation of impurities like ethane (C2H6), making the separation of C2H4 and C2H6 crucial in industrial processes. Here, we investigated the S-shaped adsorption phenomenon of C2H6 on the metal–organic framework HKUST−1. The virial equation is used to fit the C2H6 and C2H4 adsorption isotherms under low coverage. The results showed that the repulsion energy between neighboring C2H6 molecules was significantly higher than that between neighboring C2H4 molecules, which was an important reason for the lower adsorption of C2H6 by HKUST−1 at low coverage. As more molecules are adsorbed, gas molecules aggregate within pores, leading to more hydrogen bonds formed between HKUST−1 and larger-sized C2H6 under high coverage conditions. This phenomenon plays a crucial role in the S-shaped adsorption behavior of HKUST−1 on C2H6. Additionally, this unique adsorption behavior allows for the efficient separation of C2H4/C2H6 mixtures at low pressures. The ideal adsorbed solution theory (IAST) selectivity of HKUST−1 for C2H4/C2H6 mixtures was 3.78 at 283 K and 1 bar, but increased significantly to 7.53 under low pressure. This unique mechanism provides a theoretical basis for the low-pressure separation of C2H4/C2H6 by HKUST−1 and establishes a solid foundation for future practical research applications.

4+2]‐Cycloaddition Reactions to Corannulene Accelerated by η6‐Coordination of Ruthenium Complexes

AbstractThe influence of different (LRu)nII (L=Cp– (n=1, 2); C6H6) moieties η6‐coordinated to corannulene ((CpRu)+, (Benzene)Ru2+ and (CpRu)22+) has been explored by using the Activation Strain Model (ASM) of reactivity together with the Energy Decomposition Analysis (EDA) scheme. The results obtained have been compared with those obtained for the non‐coordinated corannulene counterpart. It has been observed that the presence of the ruthenium moiety favors both kinetically and thermodynamically the [4+2]‐cycloaddition reaction with cyclopentadiene. The factors governing these differences depend on the nature of the [Ru] complex. Whereas the interaction energy is solely responsible for the lower activation energy for the monocationic system (CpRu)+, not only the higher interaction but also the lower strain energy explain the much higher reactivity observed for the dicationic systems ((C6H6)Ru2+ and (CpRu)22+). In this latter case, the Pauli repulsion energy term is the factor controlling the differences in the interaction energies, following the so‐called Pauli repulsion‐lowering concept. Finally, when η6‐coordinating mono‐ or dicationic ruthenium complexes, although the [4+2]‐cycloaddition reaction in the external rim bonds remains the thermodynamically and kinetically more favourable, the cycloaddition becomes also thermodynamically feasible in some internal bonds.

Investigation of the flotation behavior and interaction characteristics of micro-fine quartz and magnesite in a dodecylamine system under ultrasonic treatment

Ultrasonic treatment, as an important surface modification method, profoundly affects the flotation behavior of minerals. This study examined the impact of ultrasonic treatment on the surface properties and flotation performance of magnesite and quartz in a dodecylamine (DDA) flotation system. Atomic force microscope detection results revealed that the surface roughness and roughness size of both magnesite and quartz increased after ultrasonic treatment. Flotation tests indicated that the recovery rates of magnesite and quartz were lower after ultrasonic treatment. At pH of 10 and DDA of 75 mg/L, ultrasonic treatment led to a 0.66%, 3.46%, and 0.33% decrease in the flotation recovery rates for three different magnesite particle sizes. Following ultrasonic processing, the flotation recovery rates for three different quartz particle sizes decreased by 8.48%, 30.76%, and 43.69%, in that order. X-ray photoelectron spectroscopy detection results showed an increased presence of characteristic Mg and Si sites on the surfaces of magnesite and quartz following ultrasonic treatment. DDA acted on the surfaces of the two minerals through electrostatic adsorption and hydrogen bonding adsorption and repelled the flotation of minerals owing to the same charge as characteristic sites, thereby reducing flotation recovery. Adsorption capacity tests and contact angle measurements demonstrated a decrease in DDA adsorption and contact angle on the surfaces of magnesite and quartz after ultrasonic treatment, explaining the reduced floatability. Extended Derjaguin–Landau–Verwey–Overbeek theoretical calculations indicated that before ultrasonic treatment, there was a repulsive energy between magnesite and fine-grained quartz particles. After ultrasonic treatment, the interaction energy between magnesite and fine quartz particles is mutual attraction.

A Variational Model of Charged Drops in Dielectrically Matched Binary Fluids: The Effect of Charge Discreteness

This paper addresses the ill-posedness of the classical Rayleigh variational model of conducting charged liquid drops by incorporating the discreteness of the elementary charges. Introducing the model that describes two immiscible fluids with the same dielectric constant, with a drop of one fluid containing a fixed number of elementary charges together with their solvation spheres, we interpret the equilibrium shape of the drop as a global minimizer of the sum of its surface energy and the electrostatic repulsive energy between the charges under fixed drop volume. For all model parameters, we establish the existence of generalized minimizers that consist of at most a finite number of components “at infinity”. We also give several existence and non-existence results for classical minimizers consisting of only a single component. In particular, we identify an asymptotically sharp threshold for the number of charges to yield existence of minimizers in a regime corresponding to macroscopically large drops containing a large number of charges. The obtained non-trivial threshold is significantly below the corresponding threshold for the Rayleigh model, consistently with the ill-posedness of the latter and demonstrating a particular regularizing effect of the charge discreteness. However, when a minimizer does exist in this regime, it approaches a ball with the charge uniformly distributed on the surface as the number of charges goes to infinity, just as in the Rayleigh model. Finally, we provide an explicit solution for the problem with two charges and a macroscopically large drop.

Mott interactions driven insulating behaviour in ruthenium based double perovskites: A2SmRuO6 (A = Ba & Sr)

Double perovskites (DP’s) are important for understanding the diverse physical properties arising from strongly correlated interactions. According to experimental observations, the DP’s A2SmRuO6 (A = Ba & Sr) are insulators; however, first-principles calculations using GGA approximations show that they are metallic. We observed a band gap (Eg) opening of 1.3 eV for Ba2SmRuO6 (BSRO) and 1.4 eV for Sr2SmRuO6 (SSRO) upon the insertion of Hubbard parameter (U) in the theoretical computations for accounting the electron-electron interactions. Further investigations using core-level spectroscopy reveal Eg of 1.05 eV for BSRO and 0.85 eV for SSRO. Furthermore, the calculations for Δ (charge transfer energy), U (coulomb repulsion energy), and W (bandwidth) from the combined spectra show U < Δ and U/W > 1.15, which confirms these compounds be classified as Mott-Hubbard insulators. These results expand our understanding of the strongly correlated compounds around the Fermi level, which might have applications in optoelectronics.

Enhanced sorption of hyper-cross-linked polymers for enrofloxacin via polystyrene adhesion: Exploring the feasibility of a collaborative treatment approach for emerging contaminants

The conventional treatment processes adopted by wastewater treatment plants (WWTPs) are unable to completely remove antibiotics and microplastics (MPs), resulting in the discharge of residual antibiotics and MPs into the environment, which poses threats to both ecological and human health. Therefore, targeted removal of residual antibiotics and MPs in effluent from WWTPs is crucial. Moreover, the presence of MPs in the wastewater system is likely to affect the removal of antibiotics. Here, the impact of polystyrene (PS) on the sorption characteristics and mechanisms of enrofloxacin (ENR) by hyper-cross-linked polymers (HCPs) was studied. The possibility of collaborative treatment of antibiotics and MPs was also discussed. The results showed that PS could affect the sorption of ENR by interacting with HCPs. The addition of PS increased dispersibility of HCPs and the number of sorption sites, thereby enhancing the sorption of ENR. However, as the concentration of PS increased, the repulsive energy between HCPs and PS decreased from 600 to 280 kT, leading to further heterogeneous aggregation between HCPs and PS. It prevented some of the sorption sites from being exposed to ENR, thereby reducing the promotion effect from 57% to 13%. Additionally, PS facilitated the sorption of ENR through promoting electrostatic attraction, π−π, and n−π interactions. The presence of PS also enhanced the removal of ENR in actual water samples with the efficiency of 98.2%. While removing antibiotics, MPs can also be separated from sewage by forming aggregates with HCPs. This study contributes to a deeper understanding of the role of MPs in the treatment of antibiotics within wastewater systems and offers new insights for the collaborative treatment of emerging contaminants in wastewater systems.

Computation of rate coefficients in solutions based on transition state theory combined with a heuristically corrected polarizable continuum model: intermolecular Diels-Alder reactions as case studies.

Transition state theory (TST) based on activation parameters computed using quantum mechanics calculations combined with the polarizable continuum model (QM/PCM) is a fundamental tool for investigating reaction rates in the liquid phase. In conventional QM/PCM methods, thermodynamic data and partition functions for a solute are often derived from a quasi-ideal gas treatment (IGT) widely implemented in commercially available computation packages. This approach tends to overestimate entropy because calculations of thermodynamic parameters in the liquid phase ignore hindered translational and rotational modes in real solutions. The present work formulated partition functions for more realistic solutes hindered by surrounding solvent molecules in conjunction with the basic QM/PCM concept. In addition, a configuration partition function for solute molecules at a standard concentration of 1 mol dm-3 was incorporated using a simple lattice model. The canonical partition function and thermodynamic functions were derived based on statistical thermodynamics for localized systems. Expressions for rate coefficients within TST were also derived with a consistent formalism based on the standard state selected in partition function calculations. The performance of the proposed method was assessed by predicting rate coefficients for three different Diels-Alder reactions and comparing these with experimental results. QM/PCM calculations at the G4//ωB97X-D/6-311++G(d,p)/IEF-PCM level of theory with corrections for the dispersion and repulsion energies were performed to obtain the electronic structures of stationary points on potential energy surfaces as a means of finding activation enthalpy, entropy and Gibbs energy values based on revised partition functions as well as predicting rate coefficients. The activation Gibbs energies obtained from our proposed method were lower than those obtained from the IGT method due to reasonable entropy computations. The proposed method overestimated the rate coefficients by one to two orders of magnitude compared to the experimental values, whereas the IGT method underestimated them by the same amount. This discrepancy arises because the proposed method calculates the partition function from the viewpoint of a localized system, whereas the IGT method calculates it from the viewpoint of a non-localized system. Given that actual liquids exist in a state between non-localized and localized systems, it is essential to formulate the partition function in a way that more accurately represents the liquid state.

First principles modeling of WO3 transport in molten Na2WO4 via a grotthuss-like mechanism and the kinetic characterization involved

Between the inherent difficulties associated with high temperature experiments and the inherent complexity of multi-component liquid phase systems, a Grotthuss-like transport mechanism for WO3 in molten Na2WO4 has been discovered and investigated in order to deepen the understanding of the properties of the Na2WO4-WO3 molten salt and to broaden its applications in areas such as electroplating, catalysis and energy. The research on the Grotthuss-like transport mechanism of WO3 in molten Na2WO4 shows that the mass transfer rate of this mechanism is about 1.5 times faster than the self-diffusion of tungsten ions. The bridging oxygen bond of W2O72- is longer, the Mayer bond level is lower and has a smaller ELF than that of the non-bridging oxygen bond, which makes the bridging oxygen bond more susceptible to breakage. The total energy, Pauli mutual repulsion energy and orbital interaction energy of the non-bridging oxygen bond are larger than those of the bridging oxygen bond. The transition state of the W2O72- dissociation process is the torsion of the bridging oxygen bond with a potential barrier of 42.903 kJ/mol.

Influence of the alkyl chain-length on the luminescent properties of 6‑hydroxy-2-naphthoate moieties: Preparation, crystal structure and Hirshfeld surface analysis

To further explore the luminescent materials, a set of 6‑hydroxyl-naphthoate derivatives have been obtained through the esterification reaction of 6‑hydroxy-2-naphthoic acid with a series of organic alcohols (methanol, ethanol, n-propanol and n-butanol, respectively) in the presence of phenyl sulfonic acid. The title compounds were characterized by FT-IR, elemental analysis (EA), UV–vis spectra, NMR and single-crystal X-ray diffraction. Compounds 1–5 are 6‑hydroxy-2-naphthoic acid, methyl 6‑hydroxy-2-naphthoate, ethyl 6‑hydroxy-2-naphthooate, n-propyl 6‑hydroxy-2-naphthoate and n‑butyl 6‑hydroxy-2-naphthoate, respectively. Compounds 1–5 crystallizes in the space group P21/c, Pna21, P21/n, P21/c and P-1, respectively. The C/OH···O hydrogen bonds can be observed. The luminescent emission maxima of compounds 1–5 can be found at 386, 393, 405, 407 and 420 nm in the solid state, respectively, indicating that the photoluminescent peaks occur the bathochromic-shift with the growth of the alkyl chain-lengths. Additionally, there exists the same order for the quantum yields. Meanwhile, the Hirshfeld surface analysis proves that the H···H interactions can be responsible for the emission maxima of these target compounds. The trend of the melting point decreases with the reduction of O···H interactions, and with the increment of the alkyl chain-lengths. The repulsion energy of the target compounds also shows the same tendency, which can be confirmed by the energy framework analysis.

A novel solution for the in-situ Microcystis aeruginosa capture and flotation removal using fly ash derived buoyant cenospheres

Harmful algal blooms are increasingly prevalent globally, posing significant threats to water safety and ecological health. In this study, a novel positive charged buoyant cenosphere (FABC@CTS) was developed for capturing and floating algal cells using chitosan (CTS) and an easily available waste material—fly ash buoyant cenospheres (FABC). The prepared cell-capturing buoyant cenospheres were characterized by various analytical techniques and tested for the removal of Microcystosa aeruginosa. The results demonstrated that at a FABC-to-CTS mass ratio of 8:1 and an FABC@CTS dosage of 55.5 mg CTS/g algae, the removal efficiency of Microcystis aeruginosa exceeded 95%. XDLVO analysis indicated a significant reduction in the repulsive energy barrier after surface modification due to stronger electrostatic and van der Waals forces. Compared with 108 μm buoyant cenospheres, 50 μm FABC@CTS exhibited higher affinity to algal cells, significantly improved the compactness and floatability of aggregates, enabling the rapid flotation of microalgae in 1 min. The FTIR and XPS analysis results further revealed that the amino and hydroxyl functional groups on the surface of the FABC@CTS could effectively capture microalgae through hydrogen bonding and π–π bonding. Overall, the results of this study provide new insights into developing cost-effective and eco-friendly material for efficiently controlling cyanobacterial blooms and contribute to advancing the comprehensive utilization of fly ash solid waste.

Density functional theory from spherically symmetric densities: Ground and excited states of Coulomb systems.

Recently, Theophilou [J. Chem. Phys. 149, 074104 (2018)] proposed a peculiar version of the density functional theory by showing that the set of spherical averages of the density around the nuclei determines uniquely the external potential in atoms, molecules, and solids. Here, this novel theory is extended to individual excited states. The generalization is based on the method developed in the series of papers by Ayers, Levy, and Nagy [Phys. Rev. A 85, 042518 (2012)]. Generalized Hohenberg-Kohn theorems are proved to the set of spherically symmetric densities using constrained search. A universal variational functional for the sum of the kinetic and electron-electron repulsion energies is constructed. The functional is appropriate for the ground state and all bound excited states. Euler equations and Kohn-Sham equations for the set are derived. The Euler equations can be rewritten as Schrödinger-like equations for the square root of the radial densities, and the effective potentials in them can be expressed in terms of wave function expectation values. The Hartree plus exchange-correlation potentials can be given by the difference of the interacting and the non-interacting effective potentials.

Theoretical and Experimental Study on the Preparation of High-Viscosity Magnetic Nanofluid by Combined Surfactants.

In this study, the mechanism by which combined surfactants affect the dispersion stability of magnetic nanofluids (MNFs) was improved. Two stable lubricating oil-based magnetic nanofluids with high viscosity and one with low viscosity were prepared by chemical coprecipitation. Erucic acid and octanoic acid were used as the combined surfactants to modify the Fe3O4 nanoparticles (MNPs). The size and morphology of the particles were observed using TEM. The rheological properties were tested with a rotational rheometer. The magnetization of the lubricating oil-based magnetic nanofluids was characterized by VSM. The results indicated that the prepared magnetic nanofluids had high viscosity, high magnetism, and good stability. This study provided ideas for the preparation of a high-viscosity magnetic nanofluid. By using combined surfactants, sufficient steric repulsion energy can be provided to counteract the attraction energy of sterically protected nanoparticles, thus achieving a balance of the dispersion stability of MNF.

Insight into interaction of electrode particles from spent lithium-ion batteries assisted by pyrolysis

Pyrolysis-assisted dispersion for electrode particles from spent lithium-ion batteries (LiBs) is an extremely effective means to improve subsequent recovery efficiency. The relationship between interaction energy and surface properties of electrode particles has been constructed. The XRD results demonstrated that the mineral phases of both anode and cathode particles, mainly composed of graphite and LiCoO2 respectively, had little changes using a pyrolysis process at 550 ℃ for 30 min. Nevertheless, pyrolysis treatment could remove the organic film of electrode particles to alter the surface properties effectively. With the organic film removal by pyrolysis, the subtraction value on the contact angle of cathode and anode particles was increased from 9.3° to 35.44°, while the difference in charge ability was increased from 0.35 mV to 23.21 mV. The interaction energy calculations also illustrated that the electrostatic repulsion energy and hydrophilic repulsion energy both increased significantly, resulting in the total interaction energy of anode and cathode particles being 1.7 and 3.8 times that before pyrolysis. Furthermore, the total interaction energy, which determined the dispersing of electrode particles in suspension, mainly depended on the hydrophilic force. The findings might propose an alternative means for enhancing particle interaction to improve the recycling efficiency of electrode materials from spent LiBs by flotation.

Repulsive Shells

This paper develops a shape space framework for collision-aware geometric modeling, where basic geometric operations automatically avoid inter-penetration. Shape spaces are a powerful tool for surface modeling, shape analysis, nonrigid motion planning, and animation, but past formulations permit nonphysical intersections. Our framework augments an existing shape space using a repulsive energy such that collision avoidance becomes a first-class property, encoded in the Riemannian metric itself. In turn, tasks like intersection-free shape interpolation or motion extrapolation amount to simply computing geodesic paths via standard numerical algorithms. To make optimization practical, we develop an adaptive collision penalty that prevents mesh self-intersection, and converges to a meaningful limit energy under refinement. The final algorithms apply to any category of shape, and do not require a dataset of examples, training, rigging, nor any other prior information. For instance, to interpolate between two shapes we need only a single pair of meshes with the same connectivity. We evaluate our method on a variety of challenging examples from modeling and animation.

Dispersion-Driven Cooperativity in Alkyl Perylene Diimide Oligomers: Insights from Density Functional Theory.

The cooperative mechanism is of paramount importance in the synthesis of supramolecular polymers with desired characteristics, including molecular mass, polydispersity, and morphology. It is primarily driven by the presence of intermolecular interactions, which encompass strong hydrogen bonding, metal-ligand interactions, and dipole-dipole interactions. In this study, we utilize density functional theory and energy decomposition analysis to investigate the cooperative behavior of perylene diimide (PDI) oligomers with alkyl chains at their imide positions, which lack the previously mentioned interactions. Our systematic examination reveals that dispersion interactions originating from the alkyl side-chain substituents play an important role in promoting cooperativity within these PDIs. This influence becomes even more pronounced for alkyl chain lengths beyond hexyl groups. The energy decomposition analysis reveals that the delicate balance between dispersion energy and Pauli repulsion energy is the key driver of cooperative behavior in PDIs. Additionally, we have developed a mathematical model capable of predicting the saturated binding energies for PDI oligomers of varying sizes and alkyl chain lengths. Overall, our findings emphasize the previously undervalued significance of dispersion forces in cooperative supramolecular polymerization, enhancing our overall understanding of the cooperative mechanism.

Study on the adsorption mechanism of fluorescent nano-tracer in sandstone core

Chemical tracer testing technology has increasingly become the preferred method for reservoir monitoring in oil fields due to its low cost and high efficiency. Understanding the migration behavior and adsorption mechanisms of chemical tracers in porous media is crucial for designing tracer injection processes and enhancing the accuracy of tracer test interpretation. This study employs an enhanced Stöber sol-gel method to synthesize fluorescent silica nanoparticles. After surface modification with the silane coupling agent γ-(methacryloyloxy) propyltrimethoxysilane (KH570) and doping with two fluorescent dyes, a multicolor fluorescent nano-tracer (PMFN) was synthesized. This study conducted dynamic and equilibrium adsorption experiments to investigate the adsorption behavior of PMFN on sandstone surfaces. To elucidate the adsorption mechanism of PMFN, we fitted the adsorption equilibrium experimental data using the Langmuir, Freundlich, and Temkin isothermal adsorption models. The adsorption kinetics were studied using the Lagergren, Elovich, and pseudo-first-order kinetic models. Additionally, we assessed the influence of ionic strength and particle size on the adsorption of PMFN by calculating the DLVO interaction forces between PMFN and the sandstone surface. The results showed that PMFN adsorption on sandstone primarily occurs in the pre-contact stage and is characterized by monolayer adsorption. When the ionic strength of the solution is 0.001 mol/L, the maximum repulsive energy barrier between PMFN and the sandstone surface hinders adsorption.