Adsorption Structure Research Articles

Competition & UV254 projection in odorants vs natural organic matter adsorption onto activated carbon surfaces: Is the chemistry right?

Powdered activated carbon (PAC) adsorption remains an indispensable method for addressing odor problems in drinking water. While natural organic matter (NOM) is ubiquitous and competes strongly in deteriorating odorant adsorption capacity, it can also serve as a promising indicator for predicting odorant adsorption through online measurement. However, the impact of PAC surface chemistry on NOM competition and feasibility of prediction across various adsorbents are not well understood. Here, we examined the role of PAC properties (pore structure and surface chemistry) in the competitive adsorption between odorants and NOM components, aligned with the applicability assessment of using NOM optical properties for odorant adsorption projection across various PAC samples. Chemical oxidation and thermal treatment achieved considerable changes in surface functional group composition, alongside minimal changes in pore structure, of two typical PAC products with microporous/mesoporous pore characteristics. The effect of NOM interference on the reduction of odorant adsorption exhibited a similar level regardless of the PACs with different pore structure (average pore size of 1.7 nm vs. 4.2 nm). Surface modification increased the equilibrium adsorption capacity (qe50) of odorants by 15.1% to 146.4% (thermal treatment) or decreased by -81.3% to -34.1% (chemical oxidation), respectively, but minimal changes in odorant-NOM selectivity. For various odorants, hydrophobicity (log D) influenced the adsorption capacity while the structural flexibility (reflected by the rotatable bonds) affected the vulnerability of odorant adsorption to NOM competition. It was found for the first time that four-parameter Richards model (RMSE = 2.6%) is superior to the linear model (RMSE = 12.5%) or logarithmic model (RMSE = 77.6%) to describe the S-shape UV254 projection curves associated with odorant adsorption on PAC. Moreover, the feasibility was confirmed to use UV254 projection curves of pristine PAC fitted with the Richard model to predict the odorant adsorption on surface-modified PAC in two different surface waters (RMSE 9.2% and 7.4%, respectively). This study provides insight into the role of PAC surface chemistry and pore characteristics in odorant adsorption in NOM-containing waters and enhances the feasibility of the NOM surrogate model for odorant monitor and control during PAC adsorption.

Magnetic injection of α-CP nanoribbons and investigation of spintronic device applications of magnetic α-CP nanoribbons based on first principles calculations

Since the successful synthesis of α-phosphorus carbide (α-CP) using carbon doping technology, α-CP has exhibited excellent carrier mobility and anisotropy at room temperature, underscoring its potential for spintronic applications. The application of CP in spintronic devices is limited due to its lack of magnetism. Effective magnetic injection in non-magnetic semiconductors can typically be achieved by doping with magnetic atoms. In this study, we calculated the electromagnetic properties of transition metal (TM) atoms adsorbed at different positions on α-CP using first principles. Notably, we found that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metallicity. We discovered that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metal properties and design magnetic tunnel junctions with half-metallic Fe_H12 and Mn_H12 adsorption structures. The results show that Mn_H12 and Fe_H12 devices exhibit a highly efficient spin filtering effect, with a TMR as high as 5521%. These findings provide theoretical guidance for the application of CP-based spintronic devices.

Mechanism of action of the novel reagent dodecyl trimethyl ammonium chloride on magnesite and quartz surfaces

Silica impurities are one of the key factors that reduce the quality of magnesite. In this experiment, dodecyl trimethylammonium chloride (KDMP) was used as a quartz collector for silica-magnesium separation, and mineral flotation tests demonstrated that KDMP can effectively desiliconize and purify magnesite under the conditions of 20 mg/L and pH 5.0. Contact angle and Zeta potential measurements show that KDMP alters quartz’s characteristics more than magnesite. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) tests show that KDMP works on quartz and adsorbs solely on its surface, not on magnesite. Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) images revealed that the KDMP collector adsorbed exclusively on the quartz surface, forming a layer of adsorption structure, but was weak on the magnesite surface. As a result, the KDMP collector is a highly intriguing flotation collector that can efficiently separate magnesite from quartz while also introducing a new form of collector for the separation and purification of low-grade magnesite.

The gas-sensing mechanism of Nb2C monolayer for SF6 decomposition based on the DFT study

Abstract In addressing malfunctions in gas-insulated switchgear (GIS) systems, it is imperative to have a real-time tracking system for SF6 decomposition products to guarantee the safety and reliability of the equipment's operation. Although a variety of gas detection technologies are currently available on the market, low-power gas detection devices for SF6 decomposition products are still in the development stage, and technological advances in this area are of great significance for improving the reliability of GIS systems. Based on the density functional theory (DFT), the Nb2C crystal surface structure was established and six adsorption structures of SO2, H2S, SOF2, SO2F2, HF and CO gas molecules on Nb2C crystal surface were constructed by geometrical optimization in this paper. The gas-sensitive properties of each adsorption system were explored in terms of adsorption energy, charge transfer, electron density, density of states and recovery time. The results showed that the Nb2C crystal surface was unfit HF and CO gases detection, both of which showed weak physical adsorption; the adsorption energies of SO2, H2S, SOF2, and SO2F2 on the Nb2C crystal surface were -1.846 eV, -1.081 eV, -5.270 eV, and -10.582 eV, respectively, and all of them were strong chemical adsorption. It was further shown by theoretical recovery time calculations that the Nb2C crystal surface can act as SOF2 and SO2F2 gas scavengers, and are able to desorb H2S (4.69 s) and SO2 (2.26 s) gases by appropriately increasing the temperature, but the Nb2C crystal surface is more suitable for use as a low-power gas-sensitive material for H2S gas detection. Therefore, Nb2C is anticipated to be a promising material for high response, low-power consumption and fast recovery for H2S gas detection in SF6 decomposition gas.

Adsorption and sensing performances of transition metal doped ZnO monolayer for CO and NO: A DFT study

In this study, theoretically, density functional theory was employed to explore the adsorption behavior of CO and NO prevalent hazardouss gases, on transition metal (TM = Fe, Co, Ni, and Cu) doped ZnO monolayer. The multifaceted analysis encompasses an array of critical aspects, including the adsorption structure, adsorption energy, density of states (DOS) and electron transfer to unravel the adsorption behavior. Our calculations show that TM atom doped ZnO monolayer exhibit high stability. TM doped can significantly enhance the interaction between the gas molecules (CO and NO) and the ZnO monolayer. Analysis of the recovery time and electrical conductivity of the adsorbed systems suggests that the Co-ZnO could be a suitable material for CO sensing,while the Cu-ZnO and Ni-ZnO can be used for NO sensing. These results suggest that transition metal doped can be a promising sensor candidate for toxic gas molecules adsorption and detection.

Multilayer Adsorption Characteristics of CO2 in Organic Nanopores with Different Pore Sizes: Molecular Simulation and Ono-Kondo Lattice Model.

Shale contains numerous organic micropores with significant potential for CO2 storage. To precisely evaluate the CO2 storage potential of shale reservoirs, it is essential to accurately quantify the adsorption of CO2 within these pores. This study used Grand Canonical Monte Carlo (GCMC) molecular simulations to analyze the CO2 adsorption behavior in organic micropores of varying sizes. The study clarified the number and width of the CO2 adsorption layers in micropores of various sizes and proposed a method for segmenting the multilayer adsorption structure. Additionally, the classic Ono-Kondo lattice (OK) model was extended to characterize pore-filling adsorption, incorporating solid-gas and gas-gas interactions. Accurate characterization of CO2 multilayer adsorption and precise calculation of CO2 absolute adsorption in micropores were achieved. Results indicate that CO2 exhibits pore-filling adsorption behavior in organic micropores, forming a multilayer adsorption structure governed by the pore size. Following symmetry principles, the adsorption layer structure in organic micropores can be simplified to a maximum of three layers. When only one adsorption layer forms, its width equals the gas-accessible pore size. For two or more layers, the width of the original layer stabilizes as additional layers form. The stable adsorption layer widths, from nearest to farthest from the pore wall, are 0.33, 0.45, and 0.39 nm. The improved OK model accurately describes CO2 excess and absolute adsorption isotherms across different pore sizes and calculates the CO2 density in each adsorption layer, showing high consistency with GCMC simulation results. These findings highlight the importance of understanding the CO2 multilayer adsorption structure for accurately estimating CO2 adsorption in organic micropores.

A novel Al-based MOF with straight channel and pocket pore structure for trace benzene adsorption and benzene/cyclohexane separation

Benzene (Bz) vapor poses significant health risks to humans, even at trace concentrations. Additionally, the separation and recycling of Bz and cyclohexane (Cy) is challenging due to their similar kinetic diameters and boiling points. Developing an adsorption-separation material with stronger interactions with Bz than with Cy could serve as a viable strategy for trace Bz adsorption and Bz/Cy separation. In this study, we present a novel aluminum-based metal–organic framework, ZJU-521(Al), composed of tetrakis (4-carboxyphenyl)methane and a helical chain [Al5(OH)7(−COO)8]∞, featuring a simple network of one-way rods and tetrahedra. This framework exhibited a uniform micropore size of 7.23 Å and a specific surface area of 1,248 m2 g−1, demonstrating excellent trace Bz adsorption (4.18 mmol g−1) at P/P0 = 0.01, attributed to its straight channel and orthogonal-array pocket pore structure. The ideal adsorbed solution theory selectivity and separation factor values of ZJU-521(Al) for Bz/Cy were 22.50 and 6.20, respectively, indicating its potential as a material for Bz/Cy separation. Multicomponent simulations showed that Bz molecules were preferentially adsorbed in the pocket due to stronger interactions, such as Al–π interactions. Thus, ZJU-521(Al) exhibits stronger interactions with Bz than with Cy, facilitating effective Bz/Cy separation.

Enhancement of interaction between Shenhua coal and GON-based dispersant with “surface-to-surface” adsorption by regulating the oxidation degree of GON: Experiments and simulations

The present study focuses on the synthesis of several graphene oxide nanosheet (GON)-based dispersants with an adsorption mode of “surface-to-surface” for the preparation of Shenhua coal (SC) water slurry (SCWS), achieved by grafting allyl polyoxyethylene ether (APEG) onto GON edges with varying degrees of oxidation using emulsion polymerization and esterification techniques. The impacts of the oxidation degree of GON on its structural characteristics and the performance of GON-based dispersants in SCWS were comprehensively assessed through a range of experimental techniques, alongside molecular dynamics (MD) simulations. Results demonstrated that with the increase in oxidation degree, there was an elevation of oxygen-containing groups, in which the content of COH decreased while the content of COC increased. Among all dispersants, GA-2, which was synthesized using GON-2 as the raw material with a graphite-to-KMnO4 mass ratio of 1:2.5, exhibited superior viscosity-reducing and stabilizing abilities compared to other dispersants. All SCWSs demonstrated pseudoplastic fluid behavior and showed good agreement with the Herschel-Bulkley model. After the adsorption of dispersants in SC, both the Zeta potential and surface wettability of SC significantly improved, especially with GA-2. The interaction mechanism between the dispersant and SC was analyzed by establishing and employing three adsorption models (M-1, M-2, and M-3). The interfacial adsorption structure confirmed that the dispersant exhibited “surface-to-surface” mode on coal through hydrophobic interaction, hydrogen bonding, and π–π interaction. Energy studies revealed that M-2 with the highest Eads (−105.31 kcal/mol) demonstrated superior adsorption strength compared to M-1 and M-3. Investigations into water molecule mobility revealed that the interaction between the GON-based dispersant and SC resulted in a reduction of water molecule mobility, thereby promoting water molecule aggregation to facilitate the formation of hydration films and enhance SCWS stability. In summary, an optimal oxidation degree of GON was found to be crucial for enhancing the performance of GON-based dispersants; higher oxidation levels may hinder dispersant adsorption on coal surfaces by converting hydroxyl and carboxyl groups into epoxide groups, thus impairing the conjugated structure.

Interaction between Molnupiravir and noble metal substrates in SERS detection: A DFT method and Raman characteristic study

Molnupiravir, a nucleoside analogue (EIDD-2801), is an RNA polymerase inhibitor that effectively treats infections caused by novel coronaviruses and can be administered orally. Therefore, it is necessary to monitor the distribution of Molnupiravir in vivo after oral administration. Surface-enhanced Raman spectroscopy (SERS) is a suitable detection method, so it is necessary to understand the interaction between Molnupiravir and noble metal nanoparticles in the SERS effect. Therefore, we used density functional theory combined with surface-enhanced Raman spectroscopy to investigate the interaction between Molnupiravir and noble metal/composite nanoparticles in the SERS effect. To study the interaction sites of Molnupiravir and the substrate in the SERS effect, the molecular electrostatic potential (MEP) of Molnupiravir was calculated. Considering the significant role of binding energy in studying molecular docking, the binding energy between Molnupiravir and Metal6 (Au6, Ag6, Au3Ag3) atomic clusters was calculated. The calculated results of the frontier orbitals and relevant molecular parameters of Molnupiravir and Molnupiravir-Metal6 complexes reveal the changes in the molecular properties of Molnupiravir in the SERS effect. Finally, the theoretical Raman spectra differences between Molnupiravir and complexes were compared and analyzed, and the adsorption structure of Molnupiravir on the substrate surface was determined based on the surface selection rules of SERS. The research results will provide insights into the interaction between Molnupiravir and the substrate in the SERS effect, and also offer theoretical support for the application of SERS methods in biomedical detection.

Investigation of the double layer structure of 1-butyl-3-methylimidazolium thiocyanate at the air-water interface using sum-frequency generation vibrational spectroscopy.

The interfacial structure and adsorption behavior of 1-butyl-3-methylimidazolium thiocyanate ionic liquids (ILs) aqueous solutions were investigated using sum-frequency generation vibrational spectroscopy (SFG-VS) and surface tension measurements. Polarization-dependent measurements revealed a dramatic increase in the SFG signal for both CH and CN stretching modes with increasing ILs concentration, reaching a maximum at a mole fraction of 0.01. This concentration dependence was accompanied by a dramatic drop in surface tension. Upon further increasing the concentration, surface tension varied slightly and reached a constant value, while the SFG signal decreased significantly. Quantitative polarization analysis showed that as the bulk concentration increased, the apparent molecular orientation of the SCN- transition dipole at the interface changed from 51° to 46°, and the tilt angle of CH3 group of the butyl chain attached to the imidazole cationic ring changed from 18° to 32°. The decrease in the SFG signal can be explained by the formation of a double layer adsorption structure at the air/water interface. It was also demonstrated that the anions were adsorbed at the interface simultaneously with the cationic group, rather than by successive adsorption as proposed in a previous study. Using the Shereshefsky model, the thermodynamic Gibbs free energy of adsorption deduced from surface tension data was compared with SFG results.

Comparison of Gas-sensitive response of three metal-doped GaNNT with Pb, Pd and Pt after adsorption of hazardous gases

In this paper, we comparatively analyze the gas-sensing ability of Pb, Pd and Pt metal-doped GaNNT (M-GaNNT) materials for the hazardous H2S, SO2, NH3 and Cl2 gases. The adsorption structure, adsorption energy (Eads), density of states (DOS), differential charge density and frontier molecular orbital of the M-GaNNT adsorbed hazardous gas have been studied based on the density functional theory (DFT) calculations. The results show that the energy gap of Pb-GaNNT performs the largest change with an increasing percentage change of 358 % after the Cl2 adsorption compared with that before the Cl2 adsorption, while the energy gap of Pt-GaNNT has the least change with an average value of 20.8 %. The doping of metal atoms can effectively improve the gas-sensitivity of M-GaNNT, and the gas-sensitivity follows the order of Pb-GaNNT> Pd-GaNNT> Pt-GaNNT. The potential applications of M-GaNNT in gas sensor and adsorbent are then predicted through the analysis of the adsorption energy, sensitive response (SR) and recovery time (τ). Pb-GaNNT performs the best Cl2 gas removal since the largest Eads (-5.883 eV), largest SR (4.4 × 1015) and largest τ (2.9 × 1087s) can be determined for Cl2 adsorption on Pb-GaNNT. Furthermore, Pb-GaNNT is a good NH3 gas sensor since the related τ is only 2.9 s at 498 K, and a small Eads (-1.232 eV) with large SR (9.7 × 105) can be determined as well. The research findings in this paper provide a new sensor material option for both the detection and the removal of harmful gases, and the systematically theoretical method can spread to other systems.

Efficient adsorption and selective separation of high value-added chemicals from simulated expired energy drinks by metal-organic frameworks

Expired energy drinks contain a certain amount of high-value chemicals, such as caffeine, that possess biological activity. The recovery and recycling of these valuable chemicals plays a crucial role in promoting the achievement of carbon emission reduction goals. In this work, 11 kinds of water-stable MOFs with different pore channel structure were synthesized and used for the first time to adsorb caffeine, nicotinic acid, or taurine from water. It has been found that the size effect of the topological structure of MOF adsorbents is the fundamental factor governing their adsorption performance. The optimized adsorbent UiO-67 exhibits excellent adsorption performance for caffeine and nicotinic acid, with respective adsorption capacities of 830 mg/g and 583 mg/g. The investigated MOF has a very low adsorption capacity for taurine (48 mg/g); therefore, selective separation of caffeine/taurine and nicotinic acid/taurine was achieved. The adsorption process can be accurately described by both the Langmuir model and pseudo-second-order model. Adsorption mechanism reveals that the main driving forces of the adsorption process are π-π interaction between UiO-67 and CN in caffeine, as well as hydrogen bonding interactions between the N atom of caffeine’s two CO groups and μ-OH of UiO-67.

In-situ Assembly of Polyoxometalate-Based Metal-Organic Framework for High-Efficiency Recovery of Uranium

Extracting uranium from water is crucial for environmental protection and the sustainable nuclear power industry. However, high-efficiency extraction and mild desorption condition still poses significant challenges. Herein, a polyoxometalate-based metal-organic framework (POMOF) for high-performance uranium extraction is prepared by in situ confined encapsulating H3[PW12O40] (PW12) into MIL-101(Cr). The highly dispersed PW12 enables adsorption sites to be sufficiently exposed, supports the pore structure of MIL-101(Cr), while being protected by spatial confinement. Furthermore, its abundant oxygen groups form high-affinity coordination with uranium and provide the pH-dependent conformation switch to achieve selective adsorption and instantaneous structural transformation. The assembly of structure and function makes POMOF exhibit substantial synergistic stability and adsorption capacity. Consequently, the constructed MIL-101(Cr)@PW12 exhibits excellent uranium adsorption ability of 461.88mg/g, as well as superior selectivity towards a wide variety of metal ions. Remarkably, instantaneous desorption can be achieved in 2s under mild desorption conditions of 0.005mol/L HCl, and the adsorption capacity remained at 94.30% after 8 adsorption cycles. POMOF demonstrates the vast potential for uranium capture from water and offers new insight into designing structure and functional synergistic materials for the selective adsorption and instantaneous desorption of uranium.

Targeted construction of porous biochar with well-developed pore structure for high-performance CO2 adsorption

Targeted construction of porous biochar is vital for the development of carbon capture. In this paper, we use the KOH chemical activation with walnut shell as raw material, to investigate the effects of the preparation process on the targeted construction of CO2 adsorbents. We have revealed the vital factors influencing CO2 adsorption and developed the design strategy for porous biochar under different application conditions. The specific surface area can up to 2115 m2 g−1, and the microporosity can up to 95.5 %. The CO2 adsorption capacities are 6.75 mmol g−1 and 17.59 mmol g−1 at 0°C, 1 bar and 10 bar. Meanwhile, the heat of adsorption ranges from 18 to 30 kJ mol−1. In addition, the sample exhibits outstanding adsorption kinetics, good adsorption selectivity, and its CO2 adsorption capacity fluctuates within 5 % after 10 adsorption-desorption cycles. Therefore, the strategy developed in this paper can be applied to the high-performance adsorption of CO2 under different conditions.

Investigation into geometric configurations and electronic properties of CeO2-supported gold clusters

A detailed understanding of the geometric structure and electronic properties of gold nanoparticles on the ceria surface is crucial for comprehending their unique catalytic activity. Using the first-principles method based on density functional theory, the adsorption of Aux (x = 1–4) clusters on the CeO2(111) surface was studied. It was discovered that the standing configurations of Au2 and Au3, as well as the tetrahedral structure of Au4, are the most stable adsorption structures. The stability of these configurations is jointly determined by the number and strength of Au-Au bonds, the Au-O bonding energy, and the interaction dynamics between the clusters and the substrate. The analysis of Bader charge, difference charge density and density of states suggested that lattice relaxation and electronic localization occur in the reduced Ce3+. The reduced amount and location of Ce3+ are significantly influenced by the position and charge transfer amount of Aux cluster. The adsorption of CO on Au4/CeO2(111) indicated that stronger Au-C bonding energy due to the hybridization of Au-5d and C-2p, thereby enhancing the catalytic activity for CO oxidation reactions.

Coadsorption of ZnTPP and 2HMCTPP on Rutile TiO2(110).

Pure zinc tetraphenylporphyrin (ZnTPP) adsorbs on rutile TiO2(110) as flat-lying molecules, mostly interacting with the surface through weak van-der-Waals interactions. Pure monocarboxyphenyl triphenylporphyrin (2HMCTPP) forms a covalent bond to the rutile TiO2(110) surface through the carboxylic acid group, yielding densely-packed layers of upright-standing molecules. If given the chance, 2HMCTPP could therefore be expected to displace the weaker-bonding ZnTPP molecules. However, if 2HMCTPP is deposited on top of a ZnTPP layer, a coadsorption structure instead forms, with the carboxylic-acid groups of the 2HCMTPP molecules bonding to titanium atoms of the surface exposed by gaps between the molecules in the flat-lying ZnTPP adsorption structure.

Water orientation on platinum surfaces controlled by step sites.

In this work, the adsorption structure of deuterated water on the stepped platinum surface is studied under an ultra-high vacuum by using heterodyne-detected sum-frequency generation spectroscopy. On a pristine Pt(553), D2O molecules adsorbed at the step sites act as hydrogen bond (H-bond) donors to the adjacent terrace sites. This ensures the net D-down orientation at the terrace sites away from the steps. In particular, the pre-adsorption of oxygen atoms at the step sites significantly alters the D-down configuration. The oxygen pre-adsorption leads to a spontaneous dissociation of the post-adsorbed water molecules at the step to form hydroxyl (OD) species. Since the hydroxyl at the step acts as a strong H-bond acceptor, D2O at the terrace no longer maintains the D-down configuration and adopts flat-lying configurations, significantly reducing the number of D-down molecules at the terrace. Density-functional theoretical calculations support these pictures. This work demonstrates the critical role of steps in controlling the net orientation of the interfacial water and provides an important reference for future considerations of the reactions at electrochemical interfaces.

Neural network potential calculations for melamine adsorption onto Pt (111) compared with density functional theory

Abstract The investigation of Pt-adsorbed melamine is important in elucidating the effect of molecular decoration on the enhancement of catalytic performance for fuel cells, and is an interesting system in which covalent stabilization between the surface and the molecule competes with resonance destabilization by the coordination. The present work discusses whether graph neural network potentials can predict the adsorption structure with the competition. The most stable structure predicted by preferred potential was consistent with that by density functional theory but underestimated resonance destabilization.

Molecular dynamics study of shale oil adsorption and diffusion behavior in reservoir nanopores: Impact of hydrocarbon composition and surface type

Understanding shale oil adsorption in reservoir nanopores is essential for efficient extraction. This study used MD simulations to analyze the adsorption and diffusion of two- and multi-component hydrocarbons (Aromatics, Alkanes, Resin) on various shale surfaces (Calcite, Montmorillonite, Quartzite, Organic) at 353 K and 25 MPa. Hydrocarbons formed a bilayer adsorption structure comprising a high-concentration adsorption layer (L1, 0.35–0.90 g/cm3) and a low concentration weak adsorption layer (L2), with adsorption density ranked as Resin > Aromatics > Alkanes. Reservoir surfaces were classified as ionic (e.g., calcite, montmorillonite) and non-ionic (e.g., quartz, graphite), and polar hydrocarbons exhibited higher adsorption densities and energies on ionic surfaces due to combined electrostatic and van der Waals interactions, while non-ionic surfaces showed smaller adsorption differences. For multicomponent hydrocarbons, adsorption layer densities followed the order: graphite > MMT-SiO > quartz > calcite > MMT-Na, with competitive adsorption observed. The polar component exhibited a greater adsorption advantage on the calcite, MMT-SiO side and graphite surfaces due to electrostatic interactions and π-π interactions, and a lesser advantage on the MMT-Na side and quartz surfaces. Hydrocarbon diffusivity was influenced by molecular mass and polarity and ordered as Alkanes > Aromatics ≫ Resin. Polar molecules had a weaker diffusion than nonpolar molecules at similar molecular masses. Among the multicomponent hydrocarbons, the self-diffusion coefficient (Self-D) of Resin increased, while that of lighter components decreased compared to two-component systems. These findings offer strategies for improving shale oil recovery by tailoring injection fluids to reservoir types, anionic surfactants or chelating agents may be used to reduce electrostatic interactions in carbonate and clay reservoirs, while nonionic surfactants may be more effective in quartz reservoirs.

Characterization of mineral composition using PIXE and EXAFS analyses to elucidate the Barium adsorption mechanism

Ningyo-toge is a uranium (U) mine that was operative in Japan. Currently, the mining area retains a dump of mill tailings. Groundwater is contaminated with U ore, and mill tailings might contain radioactive elements, such as U and radium (Ra), which can negatively impact the human body. This study determined the soil composition at the tailings dumping site using particle-induced X-ray emission, scanning electron microscopy, and X-ray diffraction and observed the adsorption structure of barium (Ba), an analog of Ra, using X-ray absorption fine structure analysis. The results revealed the existence of silicate minerals, such as quartz and mica, and metal oxides, such as Fe and Mn, in the soil. Ningyo-toge soil is similar to montmorillonite and bentonite. In particular, it was proposed that the adsorption of Ba on Mn oxide is an inner-sphere complex that immobilizes Ba. These findings will provide valuable information for estimating the behavior of Ra in the environment. The results of this study will be helpful for safety assessment and evaluating the impacts on the surrounding environment.