Adsorption最新文献

Adsorption Heat Pumps (AHPs) promise to play a leading role in achieving targets for decarbonization and reducing worldwide energy consumption. Metal-organic frameworks (MOFs) have been extensively explored in recent years as the medium for AHP due to their outstanding tunability, large surface area, and pore volume. In this work, we computationally design a series of Zr-MOFs with a csq topology using organic linkers of varying lengths to investigate the improvement of the coefficient of performance for heating (COP_H) and cooling (COP_C). Employing DFT methods, we assess the mechanical stability of these csq-Zr-MOFs by analyzing bulk modulus, shear modulus, and Young’s modulus. We set criteria for mechanical stability, requiring hypothetical csq-Zr-MOFs to have superior or at least equal mechanical properties compared to the experimentally obtained reference MOFs: DUT-6, DUT-60, and MOF-399. It is encouraging to observe that mechanically stable, in silico designed csq-Zr-MOF-5T demonstrates superior cooling performance with a COP_C = 0.88. Furthermore, 5T approaches the theoretical COP_H limit with a COP_H = 1.91. This highlights the importance of pore engineering in optimizing MOF properties. In addition to creating new types of MOFs, we advocate for fine-tuning the existing MOFs using molecular simulations as a guidance.

Gamma-Hydroxybutyric acid (HBA) has been banned by the Food and Drug Administration (FDA) due to its extensive use in sexual assaults. HBA must be detected in biological media through effective methodologies. This paper evaluated the feasibility of exploiting pristine and Pt-decorated BC2N nanosheets in HBA detection using density functional theory (DFT). HBA molecules were found to be adsorbed onto BC2N, with an adsorption energy of -52.1 kJ/mol. The space around N atoms on the adsorbent and drug is a major determinant of the interaction (particularly the steric hindrance effect). The pristine BC2N nanosheets showed a poor tendency to adsorb HBA, with a negligible response of 5.3 at 298 K. The Pt atom, on the other hand, strongly adsorbed the HBA through its C head, releasing − 151.2 kJ/mol of adsorption energy and inducing a sufficiently long distance from the N atom on account of smaller crowding. The BC2N nanosheet facilitated the adsorption of HBA onto Pt through the O head of HBA molecules, with an adsorption energy of -151.2 kJ/mol. Therefore, the adsorption mechanism was concluded to be chemisorption. The decoration of BC2N with Pt remarkably enhanced its HBA sensitivity and provided a reactivity of 340.7, which would be explained by the major charge transfer from the adsorbate to the adsorbent. A recovery time of 4.9 s was predicted for the desorption of HBA from Pt@BC2N. Thus, Pt decoration enabled BC2N nanosheets to be a promising HBA nanosensor.

The intention of this study is to develop an effective material for CO₂ adsorption by synthesizing a zinc glutamate (ZnG) crystal at room temperature via the gel diffusion method. The crystal’s structure was investigated using X-ray diffraction (XRD), and information about its optical and thermal characteristics was obtained using diverse spectroscopic methods, photoluminescence, and thermogravimetric analysis (TGA). Molecular geometry optimization was done using density functional theory (DFT), and hydrogen interactions inside the crystal were evaluated using Hirshfeld fingerprint mapping. With a high CO₂/N₂ selectivity of 19.62, a heat of adsorption (Qst) of 19.67 kJ/mol, and a CO₂ adsorption capacity of 18.022 weight% at 273 K, the ZnG crystal showed promise as a material for CO₂ capture.

This study presents the synthesis, structure and characterization of a novel two-dimensional coordination polymer (CP) constructed from Pb(II) ions and m-sulfanilic acid. The CP was characterized using various techniques, including element analysis, FTIR-, UV-Visible spectrometry, TG- DTA analysis, powder and single-crystal X-ray diffraction. The crystal structure of the catena-(bis(µ3-3-aminobenzenesulfonato)lead(II)) complex shows that each lead(II) ion is surrounded by two nitrogen atoms and six oxygen atoms from the amino and sulfonate groups of the 3-aminobenzenesulfonate ligands. Importantly, the lead(II) ions have a stereochemically active lone pair of electrons, which results in a distorted coordination geometry. This distortion, known as hemidirected coordination, arises from the uneven distribution of ligands around the lead ion due to the influence of the lone pair. Its electrical conductivity was measured, revealing its potential for electronic applications. Adsorption properties were evaluated for gas N₂. The BET surface area was calculated to be 383.108 m²/g, with a monolayer capacity of 4.2 mmol/g and a C value of 120. The molecular cross-sectional area for nitrogen was taken as 0.162 nm²/molecule. The porosity (ε) of the sample was determined to be 0.65, considering both open and closed pores. Additionally, Hirshfeld surface analysis provided insights into intermolecular interactions within the CP, primarily O—H/H—O interactions (32.1%), H—H interactions (24.8%), and C—H/H—C interactions (16.7%). Pb—O/O—Pb interactions contribute 10.1%, and O—C/C—O interactions contribute 7.3%. Other interactions, such as Pb—N/N—Pb, O—O, O—N/N—O, Pb—H/H—Pb, and Pb—C/C—Pb, contribute smaller percentages. The Continuous Symmetry Measure (CSM) analysis of the lead complex indicates a nearly symmetric structure with slight distortions, as evidenced by its coordination number of 7.7369 and a distortion index of 0.02089. Bond Valence Sum (BVS) analysis confirms that the lead ion is in an oxidation state close to + 2, with a total BVS of 1.87.

Electronic waste poses a huge threat to the environment and health due to the release of toxic metals and coated resins occurred during improper recycling. In this context, a facile approach was employed for the preparation of surface modified hydrogels involving polyvinyl alcohol (PVA) and chitosan (CS) with conducting polymers viz. polyaniline (PANI) and polypyrrole (PPy) to remove the selective Pb(II) and Cd(II) ions from synthetic solution and real-time waste computer printed circuit boards (wPCBs). FTIR spectroscopy clearly revealed the crosslinking effectiveness, identification of functional groups and coating efficiency. The prepared hydrogels were thermally stable up to 500 ºC as determined from thermogravimetric analysis. The surface of PVA-CS hydrogel modified by PANI and PPy showed large amount of active sites to entrap the metal ions as revealed by scanning electron microscopy. Surface area determined by BET analysis for PVA-CS hydrogel coated by PANI and PPy with 299.7 and 264.05 m²/g, respectively exhibits an opportunity to recover huge amount of metal ions. At varied parameters such as surface coating efficiency, contact time and hydrogel dosage, the recovery of toxic metal ions was widely investigated. At an optimized condition, the hydrogels were employed for the successful recovery of selective Pb(II) and Cd(II) ions from the waste PCBs. Kinetic and isothermal models study revealed best fit results for Pseudo second-order and multilayer adsorption by Freundlich isotherm. Hence, the prepared surface modified hydrogels could act as promising adsorbents for the successful recovery of toxic and other precious metals from e-waste.

Heterosubstitution is widely used to control the surface properties of graphene materials. The knowledge of the mechanism of organic solvent vapour sorption on doped graphene materials is necessary for development of air purification technologies, volatile organic compounds sensors, metal-free catalysis and for many other applications. The effect of N, S and Si doping and oxidative functionalization of few-layer graphene nanoflakes on the adsorption of organic solvent vapours was measured. The nanoflakes were also analyzed by TEM, XPS, Raman spectroscopy and low-temperature nitrogen physisorption. Special attention was paid to the dependence of the isosteric heat of adsorption on the surface coverage for various adsorbate-adsorbent pairs, which carry information about the energy inhomogeneity of the surface, the hierarchy of adsorbate-adsorbate, adsorbate-basal plane and adsorbate-functional groups interactions, and the mechanism of adsorption. This dependence for the hexane sorption can be used to detect hydrophilic groups on the surface, and to compare the degree of curvature of graphene layers in different heterosubstituted graphene materials.

Graphical Abstract

Adsorption is the process of enriching or depleting components at the interface of phases, and isothermal adsorption experiments are key to studying the adsorption capacity of coal-rock porous media. These experiments reveal that coal-rock samples require significant time to reach adsorption equilibrium, often lasting several tens of days, and the efficiency of various adsorption modes remains unclear. This paper introduces a mathematical model for gas isothermal adsorption at constant volume and varying pressure. It establishes numerical models based on three common adsorption modes and validates them against experimental results. Methane is initially adsorbed on the coal surface until uniform pressure is reached, after which it gradually penetrates the coal. Achieving uniform adsorption can take over 1000 h. By comparison, the time required for different adsorption modes to reach equilibrium for gas in coal under certain conditions was determined as follows: keeping the connecting valve open reduces time by 41.47% compared to keeping it closed at the same initial pressure, while closing the valve at the same equilibrium pressure shortens the time by 41.56% compared to keeping it open, and by 58.84% compared to constant pressure adsorption. Additionally, the paper discusses an equilibrium determination method based on pressure accuracy (Δp) and determination duration (Δt), emphasizing the need to avoid lower accuracy equipment and shorter durations in long adsorption processes. This research aids in selecting optimal experimental methods for time-consuming isothermal adsorption experiments and establishes criteria for determining adsorption equilibrium.

With the growing global population and rapid industrial expansion, the demand for clean water has significantly surged. Major pollutants, such as textile dyes, heavy metals, sewage, and industrial effluents, are increasingly contaminating the aqueous sources, posing significant threat to the public health and to the entire eco-system. Traditional water treatment methods are struggling to meet this demand due to rising operational costs. To safeguard natural water bodies, efficient strategies are required to control and mitigate pollution. The groundbreaking discovery of nanomaterials, as one of the most versatile materials, and their broad applications across various industries have spurred researchers to explore further modifications to enhance their performance. Among these, carbon-based and metal-oxide based nanomaterials have emerged as highly efficient due to their abundant availability, efficiency, and cost-effectiveness compared to other types of nanomaterials. This review focuses on the increasing prevalence of contaminants, advancements in treatment technologies, and the role of adsorption as a key approach for the removal of contaminants. It highlights the various synthetic strategies and potential of nanomaterials, particularly carbon-based and metal oxide-based nano-adsorbents, in effectively treating dye-contaminated wastewater, offering advanced and cost-effective solutions for water purification. Additionally, this article provides a comprehensive discussion on multitude of aspects encompassing the adsorption kinetics and isotherms, while emphasizing on the different operating parameters associated with the adsorption process and the regenerability of the fabricated adsorbents. Dedicated sections focused on the real-world applications, environmental fate and toxicity, and economic feasibility of these nanomaterials have been extensively presented. Finally, the challenges associated with the practical implementation of these nano-adsorbents, as revealed in the literature, have been addressed, proposing ways for future advancements for addressing these challenges.

In this project, we have studied the possibility of using the C2N Monolayer (ML) for sensing and adsorption of several chlorofluorocarbon (CFC) derivatives from the gaseous environment. The density functional theory (DFT) approach was applied to optimize the geometrical structures of the isolated C2N ML and its complexes with of CH₃F, CH₂F₂, CHF₃, CH₃Cl, CH₂Cl₂, CHCl₃, and CF₂Cl₂ air pollutants gases. The results of the thermodynamics of adsorption indicated that C2N ML could adsorb all of the considered CFCs except CF₂Cl₂. Also, the recovery time calculations showed that in all cases (from CHF₃ with the recovery time of 3.45(10^− 4) s to CF₂Cl₂ with the recovery time of 9.47(10^− 12) s) the C2N ML is a good recoverable sorbent. The results of the conductivity calculations indicate that the presence of CH₃F, and CH₃Cl increase the σ value for the isolated C2N ML from 1.94(10^− 29) S m^− 1 to 3.16(10^− 29) S m^− 1, and 3.07(10^− 29) S m^− 1, respectively. Thus, C2N ML is able to sence the presence of the mentioned CFCs.

In this work, we searched for the exclusive electronic and adsorption properties of Ag₄ cluster modified BSe based nanomaterials for the purpose of sensing glycine, hystidine and phenylalanine amino acids. Adsorption distances, band structures, difference in electron densities and interaction energies were calculated to understand the impact of amino acids adsorptions on the chemical reactivity of Ag cluster modified BSe nanostructures. Diverse configurations were inspected for the adsorption of amino acids to survey the effective bio interface through the interaction with diverse sites existing on the organic amino acid molecules. The interaction of all amino acids via O site was found to be critical for energetically favorable adsorption modes. The PDOS analysis also revealed the large interactions of the amino acids with the Ag cluster modified BSe nanosheets. Our theoretical DFT results suggested that Ag₄ cluster modified BSe nanostructures held great potential for practical applications in biomolecular sensing of amino acids.