Adsorption最新文献

Total neutron scattering (TNS) has emerged as a powerful experimental method for characterising structural properties of liquids confined at nanoscale in porous materials, yet its application to studying room-temperature gas adsorption remains relatively unexplored. This work investigates the feasibility and sensitivity of TNS in detecting subtle structural responses for adsorption of gases including N₂, O₂, simulated Air, and CO₂ in zeolite 13X, under conditions typical of pressure swing adsorption (1 and 5 bar) utilised in medical oxygen concentrators (MOCs). Experimental results illustrate the capability of TNS to detect minor structural alterations induced by gas adsorption, thereby validating its potential as an insightful analytical method. Although the observed changes confirm known molecular interactions and adsorption behaviours, the precise molecular-level interpretation and mechanistic insights will predominantly derive from subsequent advanced molecular simulations. Future research will prioritise the development of quantitative TNS approaches through refined modelling protocols, aiming to accurately describe the spatial distribution of adsorbed gas molecules within zeolite frameworks. Thus, this work positions TNS not merely as a supportive technique but as a critical approach for deepening our fundamental understanding of molecular interactions of fluids confined in porous systems.

Findings tailored towards adsorption and corrosion inhibition of metal addressed limitations in describing the interaction between the inhibitor and metal surface, utilising kinetics, thermodynamics, and isotherm models through a central composite design-response surface methodology (CCD-RSM). Expired clindamycin (ECLI) was employed as an anti-corrosion agent to stampede the corrosion of mild steel in the oil and gas industries in optimised HCl concentration using the weight loss method. From the analysis of variance (ANOVA), the significance of process parameters was ascertained. The regression coefficients (R²) of the developed models and validation experiment conducted at optimum conditions insinuate that the predicted values are in excellent agreement with the experimental values. The change in enthalpy was positive and less than the 100 kJ/mol threshold, which indicates an endothermic reaction. The experimental data fit the Langmuir, Freundlich, Temkin, El-Awady, Frumkin, and Flory-Huggins isotherms, but the Langmuir isotherm best expresses the adsorption mechanism. The corrosion rate constant was evaluated using zero-order, first-order, and second-order kinetics; hence, the corrosion process followed zero-order kinetics. The adsorption of ECLI on mild steel in varying HCl media is plausible, spontaneous, and exhibits both physisorption and chemisorption according to Gibbs’ free energy threshold.

The pequi (Caryocar brasiliense) stands out for having significant economic value through its fruits in cooking. However, despite the numerous applications of the pequi, few studies are available on the socioeconomic importance of using the peel, fruit, and almond. Therefore, finding applications for its residues is essential; to this end, developing research that uses bioadsorbents– adsorbent materials of natural origin– becomes relevant for the scientific community. In this perspective, this study aimed to evaluate the adsorption properties and characterize the peel and mesocarp of the pequi as a potential application for the treatment of effluents from the textile industry. The fruit was separated into peel and fruit, placed in an oven, and ground in a mill after drying. After the grinding process, the material obtained had its particles classified into different particle sizes. The particle size of the peel chosen for the study was 45 mesh. After selecting the particle size, part of the material was calcined in a muffle furnace at 400 °C for 4 h. Subsequently, the bioadsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), surface area by the BET method, and scanning electron microscopy (SEM). The XRD analysis showed that the bioadsorbents presented predominantly amorphous structures. In the textural properties, the bioadsorbents were presented as a porous material, and it was also possible to observe that in the thermally calcined mesocarp material, this offered a larger surface area. Meanwhile, the morphological analysis showed that a more significant and deeper number of cracks and pores appeared in the thermally calcined bioadsorbents compared to the in natura bioadsorbents. Thermally calcined bioadsorbents achieved excellent adsorption capacity, which provided 90% dye removal efficiency in just 5 min, for both the bark bioadsorbent and the mesocarp bioadsorbent, proving to be a good system for dye removal in aqueous media. Therefore, replacing biomass as an adsorbent is feasible, since, compared to other synthetic materials, they have a reduced cost and are abundant.

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The current work presents a robust, generalizable, fully predictive computational fluid dynamics model of a complete pressure swing adsorption (PSA) system. Using an axisymmetric representation, the model accurately mimics all the key components of a gas separation plant, including adsorbent columns, air reservoir, product buffer tank, pressure regulator, solenoidal valves, and mesh filters. The cyclic operation of the PSA plants, typically controlled by solenoid valves, is emulated by dynamically modifying the boundary conditions of different subdomains. The integrated approach closely replicates the purity and pressure transients of an in-house PSA pilot setup, producing high-purity oxygen from the air. The advantage of the model lies in its ability not only to simulate column-level phenomena but also to integrate the dynamics of the entire plant in a fully predictive manner. The ability of the model to optimize the system-level performance to produce high-purity oxygen is also demonstrated.

Carbon dioxide (CO₂) adsorption at high pressures by alkali-impregnated activated carbons was studied in this paper. Four types of activated carbon, prepared by the two-step activation method and the activation combined with oxidation method, were impregnated in different concentrations of NaOH solution of 1, 4, 7 and 10% by weight. The results of CO₂ adsorption at 0 °C up to the saturation pressure showed that the maximum adsorption capacity was obtained from the activated carbon prepared by the activation combined with oxidation method under conditions of 180 min of total activation time, two cycles of carbon oxidation and 1 weight% NaOH impregnation. An increase of the concentration of NaOH impregnation solution decreased the adsorbed amount of CO₂ for the four types of carbons used in this investigation. A Grand Canonical Monte Carlo (GCMC) simulation was used to investigate the adsorption mechanism of CO₂ in the finite-length slit pore model in the absence and presence of NaOH. An early onset in the adsorption isotherms can be observed in the heterogeneous pores. The alkali can enhance the adsorbed amount at low pressures, when pressures increase, it may cause difficult diffusion to the pore. The allocation of NaOH on carbon surfaces also affects the adsorption behavior. The adsorption isotherm for the fixed and random topologies with 1%weight NaOH can enhance the adsorption of CO₂ in the larger pore at high pressures too. While in the case of smaller pore at high pressures, the fixed topology showed the domination adsorption isotherm than the homogeneous and the random topology pores.

Potentially toxic elements (PTE) pose environmental concerns due to their persistence, toxicity, and accumulation in living organisms. Their effective removal from waters and effluents is crucial for preserving aquatic ecosystems, human health, and biodiversity. Conventional treatment methods face challenges like waste generation and harmful substances. In this context, adsorption using agro-industrial residues emerges as a sustainable, low-cost, and environmentally friendly alternative. This is especially relevant in countries like Brazil, the United States, India, China, Argentina, and Thailand, where sugarcane and corn residues are abundantly available. This systematic literature review aims to provide a comprehensive overview of the adsorption of PTE from aquatic systems using sugarcane and corn residues, contributing to the identification of trends, gaps, and future directions in this field. Sugarcane bagasse and corncobs are highlighted as the most commonly used residues. The most frequently reported experimental conditions include grinding as treatment, batch mode adsorption, adsorbate concentration of 50 mg L⁻¹, adsorbent concentration of 10 mg L⁻¹, temperature of 25 °C, and a contact time of 60 min. Specific details such as particle size (0.25 mm for sugarcane, 0.15 mm for corn), main PTE (Pb for sugarcane, Cd for corn), and optimal pH (5 for sugarcane, 6 for corn) were also identified. However, research gaps remain, such as the use of sugarcane and corn leaves, the biological modification of residues, and the study of less-explored PTEs like Fe and Mn. These gaps provide opportunities for future investigations and advances in water treatment technologies.

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The efficacy of an Al₈P₈ double nanoring as a sensor for sulfur hexafluoride (SF₆) decomposition gases (H₂S, HF, SO₂, SO₂F₂, and SOF₂) is investigated using density functional theory with the PBE0-D4 functional and def2-TZVP basis set. Additionally, highly accurate DLPNO-CCSD(T)/cc-pVTZ single-point energy calculations are employed to refine the interaction energies. Interaction energies ranging from − 43.31 to − 63.92 kJ mol^− 1 are reported, with H₂S exhibiting the strongest adsorption. SO₂ adsorption induces the most significant change in the HOMO-LUMO gap, narrowing it to 1.34 eV from 3.18 eV, which suggests a substantial enhancement in electrical conductivity upon interaction. Non-covalent Interactions (NCI) analysis reveals a diverse range of interaction types, including hydrogen bonding and van der Waals interactions, contributing to the adsorption behavior. Rapid recovery times are observed, indicating the reusability of the sensor. The findings demonstrate that the Al₈P₈ double nanoring shows promise as a sensitive, selective, and reusable sensor, particularly for SO₂, with potential applications in industrial gas leak detection and environmental safety monitoring.

Valid textural characterization is crucial for many applications such as catalysis, separation as well as energy storage/conversion. In that regard, textural characterization in the gas/dry state using gas physisorption and mercury porosimetry is well established, but these methods might not be sufficient for the characterization of wet materials used in liquid-phase processes. Within this context, the applicability of nuclear magnetic resonance (NMR) relaxometry for surface area assessment of nonporous silica/carbon materials has been demonstrated [Schlumberger et al. (2023). https://doi.org/10.1021/acs.langmuir.2c03337]. However, a comprehensive and rigorous assessment of the applicability of NMR relaxometry for surface area and pore size assessment of nanoporous materials coupled with a systematic investigation of how the confinement affects the NMR relaxation behavior is missing so far. Hence, we present here a systematic study based on a series of ordered mesoporous silica model materials exhibiting well-defined pore sizes between approx. 2.5 and 10 nm saturated with a bulk liquid water as well as a bulk water vapor phase. The study suggests that an adaption of the two-fraction-fast-exchange model to account for the pore geometry is necessary for valid surface area assessment as well as pore size analysis of nanoporous silica material particularly for pores smaller than approx. 10 nm.

We report a molecular simulation study on the adsorption-based trapping of different gaseous contaminants using nanoporous materials. In more detail, in the context of gas decontamination for space applications, we focus on adsorption from low pressures up to larger pressures of specific molecules ranging from water, hydrocarbons, and siloxanes. As far as the nanoporous adsorbents are concerned, we restrict the present study to a set of prototypical materials: an active carbon, a zeolite and a metal-organic framework. In addition to discussing the ability of each material type to adsorb specific gas molecules, we illustrate how simple descriptors such as Henry’s constant in the low-pressure range (K_text {H}) and the pressure (alpha) at which half the nanoporosity gets filled can be used to rationalize and design molecular “getters” for space decontamination. Finally, by considering a specific yet representative binary gas mixture, we show that the adsorption of hydrophilic molecules– water– and hydrophobic molecules– siloxane– occurs without competitive/collective adsorption effect (provided adsorption occurs at low to moderate pressures).

The Redlich-Peterson isotherm is widely used in liquid phase adsorption studies but the combination with the Ideal Adsorbed Solution Theory is hampered by the fact that an analytical expression for the reduced grand potential does not exist in the range of low pressures or concentrations. In this contribution we demonstrate an efficient approach to approximate the reduced grand potential using a Padé approximant allowing to perform the calculations with the Fast-IAS algorithm leading to execution times that are slightly slower but comparable to a dual site Langmuir/Fast-IAS combination. While the non-autonomous initial value approach remains a simpler method for this isotherm, the proposed method is recommended when execution times have to be minimized.