Full Adsorption Research Articles

Coverage-dependent adsorption of n-hexane and isopropanol on silica: A density-functional study

This study delves into the adsorption behavior of both polar and non-polar molecules on silica surfaces, spanning a range from low coverage to full adsorption scenarios. Our results reveal that isopropanol exhibits a self-competitive adsorption mechanism on the surface. However, due to its thermodynamic stability, we anticipate fully covered pores under experimental conditions. In contrast, n-hexane demonstrates a substantial interaction with the hydrophilic substrate, displaying an enhanced adsorption effect whereby the adsorption gets stronger with an increasing number of molecules adhering to the pore’s surface. As a consequence, we predict a complete coverage of the pores under experimental conditions, accompanied by a discernible reduction in the mobility of these attached molecules. This observation carries significance, as alkanes are typically employed as probing molecules for measuring the geometric tortuosity of silica pores, assuming a reflective surface. Caution is advised, particularly for pores with thin diameters, in the order of a few molecular sizes.

Optimizing MOF properties for seasonal heat storage: a machine learning approach

In the quest to enhance thermochemical energy storage using promising sorbents, this work presents a study on the optimization of Metal Organic Frameworks (MOFs) properties for gas sorption, with a focus on CO2 and H2O adsorption. Through the analysis of crystallographic descriptors, the study aims to streamline the selection of MOFs that could potentially exceed the performance of existing water sorbent pairs. A comprehensive comparison of sequential learning (SL) algorithms reveals a method for identifying the minimal set of descriptors that influence adsorption properties of MOFs. The protocol involves constructing and training machine learning (ML) models to determine the number of influential descriptors and utilizing SHAP analysis to evaluate their importance. Findings suggest that including only these critical descriptors in the exploration space reduces computational load. Notably, the COMBO and the FUELS algorithms consistently outshine random guessing, validating their efficacy in materials optimization. The challenge of accessing full adsorption properties across the entire coverage range is addressed by a computational screening procedure requiring minimal input data. This method suggests that some vanadium based MOFs, originally designed for different purposes, could surpass the current leading compounds for thermal energy storage, primarily due to their optimal Henry coefficient values for water adsorption.

Improved ion adsorption capacities and diffusion dynamics in surface anchored MoS2⊥Mo4/3B2 and MoS2⊥Mo4/3B2O2 heterostructures as anodes for alkaline metal-ion batteries.

First-principles calculations were performed to analyze the atomic structures and electrochemical energy storage properties of novel MoS2⊥boridene heterostructures by anchoring MoS2 nanoflakes on Mo4/3B2 and Mo4/3B2O2 monolayers. Both thermodynamic and thermal stabilities of each heterostructure were thoroughly evaluated from the obtained binding energies and through first-principles molecular dynamics simulations at room temperature, confirming the high formability of the heterostructures. The electrochemical properties of MoS2⊥Mo4/3B2 and MoS2⊥Mo4/3B2O2 heterostructures were investigated for their potential use as anodes for alkaline metal ion batteries (Li+, Na+ and K+). It was revealed that Li+ and Na+ can form multiple stable full adsorption layers on both heterostructures, while K+ forms only a single full adsorption layer. The presence of a negative electron cloud (NEC) contributes to the stabilization of a multi-layer adsorption mechanism. For all investigated alkaline metal ions, the predicted ion diffusion dynamics are relatively sluggish for the adsorbates in the first full adsorption layer on MoS2⊥boridene heterostructures due the relatively large migration energies (>0.50 eV), compared to those of second or third full adsorption layers (<0.30 eV). MoS2⊥Mo4/3B2O2 exhibited higher onset and mean open circuit voltages as anodes for alkaline metal-ion batteries than MoS2⊥Mo4/3B2 hybrids because of enhanced interactions between the adsorbate and the Mo4/3B2O2 monolayer with the presence of O-terminations. Tailoring the size and horizontal spacing between two neighboring MoS2 nano-flakes in heterostructures led to high theoretical capacities for LIBs (531 mA h g-1), SIBs (300 mA h g-1) and PIBs (131 mA h g-1) in the current study.

Tetragonal BN monolayer: A high-performance anode material for lithium-ion batteries

Searching for high-performance anode materials with fast charge-discharge rates, high specific capacity, low open circuit voltages, and good reversibility has attracted much attention over the past few decades. Herein, based on first-principles calculations, the performance of t-BN monolayer as an anode material for Li-ion batteries is investigated. The excellent stretchability of t-BN monolayer makes it good reversibility in the case of volume expansion caused by full adsorption. Additionally, t-BN monolayer with Li-adsorbed possesses metallic behavior, indicating excellent electrical conductivity. Furthermore, t-BN monolayer exhibits well-balanced performances with a low diffusion energy barrier (0.35 eV), a high specific capacity (1620 mA h g−1), an appropriate average open-circuit voltage (0.49 V), and small lattice constants change (2.5%). Finally, solvent effects are considered. The adsorption of Li-ions becomes more stable as dielectric constant of the solvent increases. Based on the above excellent properties, we speculate that t-BN monolayer can act as a promising anode material for LIBs.

Experimental and simulation study on the influence of pH on mono-molecular mechanical properties of benzene and graphene

In drug delivery systems, graphene materials are promising drug carriers. Drug molecules are loaded on graphene through π-π interaction between graphene and benzene ring structure, which is widely found in organic drug molecules. Then the drug molecules are released under different conditions, such as different environmental pH, at lesion site. In the application, the adsorption and desorption between benzene ring structure in drug molecules and graphene play a key role. Herein, an experimental method for measuring the adhesion force between a single phenyl and graphene is proposed, and the adsorption and desorption mechanical properties of a benzene ring structure on graphene surface at different environmental pH are firstly measured. The experimental results show that the adhesion force decreases with the increase of environmental pH. Moreover, molecular dynamics simulations show that the influence of pH on adhesion force is mainly realized by changing the electrostatic potential distribution on graphene surface, and the interaction force between a single benzene and graphene changes from attractive to repulsive with the increase of environmental alkalinity. In addition, a molecular dynamics model for the dynamic adsorption and desorption capacities of benzene molecules on graphene surface at different quantity of ions is established. Benzene molecules can achieve full adsorption on the surface of graphene when there are 10 and 20 hydrogen ions. And benzene molecules can achieve full desorption on the surface of graphene when there are 10 and 20 hydroxide ions.

Noncryogenic Air Separation Using Aluminum Formate Al(HCOO)3 (ALF)

Separating oxygen from air to create oxygen-enriched gas streams is a process that is significant in both industrial and medical fields. However, the prominent technologies for creating oxygen-enriched gas streams are both energy and infrastructure intensive as they use cryogenic temperatures or materials that adsorb N2 from air. The latter method is less efficient than the methods that adsorb O2 directly. Herein, we show, via a combination of gas adsorption isotherms, gas breakthrough experiments, neutron and synchrotron X-ray powder diffraction, Raman spectroscopy, and computational studies, that the metal-organic framework, Al(HCOO)3 (ALF), which is easily prepared at low cost from commodity chemicals, exhibits substantial O2 adsorption and excellent time-dependent O2/N2 selectivity in a range of 50-125 near dry ice/solvent (≈190 K) temperatures. The effective O2 adsorption with ALF at ≈190 K and ≈0.21 bar (the partial pressure of O2 in air) is ≈1.7 mmol/g, and at ice/salt temperatures (≈250 K), it is ≈0.3 mmol/g. Though the kinetics for full adsorption of O2 near 190 K are slower than at temperatures nearer 250 K, the kinetics for initial O2 adsorption are fast, suggesting that O2 separation using ALF with rapid temperature swings at ambient pressures is a potentially viable choice for low-cost air separation applications. We also present synthetic strategies for improving the kinetics of this family of compounds, namely, via Al/Fe solid solutions. To the best of our knowledge, ALF has the highest O2/N2 sorption selectivity among MOF adsorbents without open metal sites as verified by co-adsorption experiments..

Design and Screening of Metal-Organic Frameworks for Ethane/Ethylene Separation.

Separation of ethane and ethylene is considered to be industrially important for various chemical processes, but their similarities make the process expensive. In this study, we integrated computational screening with machine learning to find optimal metal-organic frameworks (MOFs) with high ethane/ethylene selectivity. Using our algorithm, a hypothetical MOF structure with an ideal adsorption solution theory selectivity of 3.6 at 298 K and 1 bar was discovered. Furthermore, structural analysis was implemented, and the full adsorption isotherm of some of the top structures was obtained.

Effect of H/F Adsorption on the Electronic Structure of TH-Ge0.5Si0.5C2-zz

A new material TH-Ge0.5Si0.5C2-zz has been discovered, which has a direct bandgap and has a broad application prospect in photoelectric devices. The effect of H/F atom adsorption on the structural parameters and electrical properties of TH-Ge0.5Si0.5C2-zz was studied in this paper. In a nutshell,bandgap of TH-Ge0.5Si0.5C2-zz can be notable increased by H atom adsorption, and the work function and electron affinity energy are decreased. While the bandgap of TH-Ge0.5Si0.5C2-zz cannot be opened by the full adsorption of the F atom.

Metal-Organic Framework Aerogel for Full pH Range Operation and Trace Adsorption of Arsenic in Water.

The UiO-66-NH2 aerogel has been designed to remove As(III) and As(V) in the full pH range with a long lifetime. The efficiency of the aerogel for trace removal from river water samples at the sub-ppb level has been demonstrated. The feasibility for practical uses has been evaluated by breakthrough experiments operated at a liquid hourly space velocity (LHSV) of 38 h-1 using a real water sample with a significant capacity of 284 mg g-1. The UiO-66-NH2 aerogel provides a lifetime of over 600 min, which is one of the highest lifetimes among the reported adsorbents for arsenic decontamination.

Experimental investigation of dehumidification and regeneration of zeolite coated energy exchanger

Zeolite desiccant particles are well known for their strong affinity to adsorb water vapor molecules; however, they require significant regeneration energy to be created. This paper presents an experimental study of the adsorption and regeneration processes of a monolayer zeolite for indoor dehumidification to the 13X zeolite beads with a 4 × 8 mesh bead size and a pore opening 10 A⁰ were used as this monolayer. An experimental investigation was conducted to determine the effects of the relative humidity, temperature, and air flow rate on the adsorption and regeneration processes. The results show the effectiveness of the monolayer coating method and the relative humidity significantly affects the adsorption process, and that the airflow rate surrounding and through the zeolite beads increases the adsorption and desorption of the water vapor molecules. In the absence of the meniscus radius formation due to the monolayer arrangement prevents external condensation. With an airflow rate of Re = 1773, the full adsorption process at a relative humidity of 99% was obtained within 37 min; meanwhile, the regeneration process proceeded at 100 °C within 66 min. The adsorption time was reduced by 27% and 43% as the Reynold number increases to 2586 and 3325, respectively. Likewise, the effectiveness of the regeneration time is decreased by 0.07% and 14% within the same Reynold number increases. Results obtained from this research can be used to guide the future development of polymer-coated energy exchangers.

Experimental Results of a Gas Fired Adsorption Heat Pump and Simulative Prediction of Annual Performance in a Multi-Family House

Gas driven sorption heat pumps can be an efficient alternative to conventional gas condensing boilers for heating buildings. Measurement results of a functional prototype of a gas adsorption heat pump with 40 kW nominal capacity and the SAPO-34-water working pair are presented. The innovative adsorption heat exchanger is directly crystallized applying the partial support transformation technique. A transient lumped-parameter model of the gas adsorption heat pump is developed. For the first time, it is possible to perform an annual simulation of the GAHP within the heating system of a multi-family house with full adsorption dynamics based on calibrated and validated component models. This annual performance calculation is carried out for the two different low-temperature heat sources geothermal heat (bore hole heat exchanger) and exhaust air. Using exhaust air as low-temperature heat source for a GAHP is an entirely new approach that is evaluated in this study. Compared to a gas condensing boiler, the annual gas consumption is reduced by 22 % for the case of bore hole heat exchanger and by 27 % for the case of exhaust air as low-temperature heat source for a building with heating circuit design temperatures of 45 °C/35 °C.

Well entrapped platinum-iron nanoparticles on three-dimensional nitrogen-doped ordered mesoporous carbon as highly efficient and durable catalyst for oxygen reduction and zinc-air battery

The high-performance and durable oxygen reduction reaction (ORR) catalyst on air cathode is a key component in assembly of Zn-air batteries. Herein, three-dimensional N-doped ordered mesoporous carbon (3D N-OMC) was first prepared with silica as a template via pyrolysis with assistance of dicyandiamide as a N-doping agent, combined by full adsorption of platinum (II) acetylacetonate (Pt(acac)2) and iron (II) phthalocyanine (FePc) via π-π interactions. After further pyrolysis of the resulting mixture, many PtFe nanoparticles were efficiently incorporated in 3D N-OMC (termed as PtFe@3D N-OMC for simplicity). Control experiments were certificated the important role of the pyrolysis temperature played in this synthesis. The resultant composite synergistically combines advantages of hierarchically accessible surfaces, highly open structure, and well-dispersed PtFe particles, which endow the PtFe@3D N-OMC with onset and half-wave potentials of 0.98 and 0.86 V in alkaline media, respectively, showing appealing catalytic activity for the ORR. Most significantly, the PtFe@3D N-OMC based Zn-air battery has a high power density of 80.57 mW cm−2 and long-term durability (220 h, 660 cycles). This work opens a new avenue for design of high-efficiency and durable ORR electrocatalysts in energy conversion and storage systems.

Application of silver-exchanged zeolite for radioxenon mitigation at fission-based medical isotope production facilities

Atmospheric radioxenon releases from fission-based medical isotope production facilities are the main contributors to the radioxenon background being observed in the International Monitoring System (IMS) for the verification of the Comprehensive Nuclear-Test-Ban Treaty. This background is impacting the detection capability of the IMS network for potential nuclear explosions. Reducing the radioxenon emissions from these facilities requires the optimization of the corresponding filtration process. The investigation of more efficient Xe adsorption materials than Activated Carbon (AC), which is currently used for this application, can play an important role for such an optimization. In this work, the Xe adsorption capacity of silver-exchanged zeolites (AgZs) is compared to the one of ACs in relevant conditions for fission-based medical isotope production facilities. The most promising AgZ candidate, a silver-exchanged titanosilicate (Ag-ETS-10), is investigated in more detail for its application to further reduce radioxenon releases. As operational conditions depend on the production and off-gas treatment processes, the effect of Xe concentration, flow rate, temperature and moisture on the Xe adsorption in Ag-ETS-10 is reported. Furthermore, since AgZs are far more expensive than ACs, it is crucial to be able to regenerate the material, whilst maintaining its full Xe adsorption properties for successive reuse. Accordingly, the durability of Ag-ETS-10 is investigated with regard to desorption and adsorption cycles but also with regard to gamma irradiation.

Computational Study of the Adsorption of Phosphates as Wastewater Pollutant Molecules on Faujasites

The adsorption of sodium dihydrogen phosphate (NaH2PO4) onto X- and Y-type faujasite zeolites was computationally studied using the Density Functional Theory (DFT) method. The structures were modeled using the Materials Studio software. The Si/Al ratios for the X- and Y-type zeolite models were 1.2 and 2.5, respectively. The central pore of the zeolite provided a more favorable coordination for adsorbing NaH2PO4. Full molecular optimization and adsorption energy calculations were performed using the VASP code. The adsorption was more effective on zeolite Y, with an adsorption energy of 161 kJ/mol, compared to the zeolite X system, with an adsorption energy of 31.64 kJ/mol. This calculated value for X-type faujasite was found in the interval of the adsorption energy of H2PO4− on hydrated Fe oxide (94.4 kJ/mol) and modified polyether sulfone (22.5 kJ/mol), and the calculated adsorption energy of the molecule on Y-type faujasite coincides with the reported value for this adsorbate on Mg/Ca-modified biochar structures. The molecular conformations of the adsorbate on the two studied models are very different, so the difference between the adsorption energy values of each type of zeolite model is comprehensible. On the one hand, the oxygen atoms of the molecule formed a bidentate complex with the hydrogen atoms of the pore in the X-type faujasite model, and the O-H distance was 1.5 Ǻ. On the other hand, an adsorbed oxygen atom of the phosphate was placed on a hydrogen atom at site II of the Y-type faujasite zeolite, and two of the hydrogen atoms of the phosphate were placed on the oxygen atoms. The Bader analysis results indicated that the negative charge of the phosphate anions was delocalized on the zeolites protons. The hydroxy groups of the phosphate form bonds between their hydrogen atoms and the oxygen atoms of the zeolite porous structure; therefore, we concluded that these sites have an alkaline character. The aim of this study was to include a computational analysis of possible phosphate adsorption mechanisms in faujasite zeolites that can be confirmed by experimental tests, and hence contribute to the generation of new technologies for capturing pollutant molecules in wastewater. The results are in agreement with the experimental information concerning the influence of pH on the adsorption activity of phosphate adsorption on zeolites.

Application of Magnetic Nanoparticles Coated with Crosslinked Zwitterionic Poly(ionic liquid)s for the Extraction of Oligonucleotides.

Magnetic nanoparticles coated with zwitterionic poly(ionic liquid)s were applied for dispersive solid-phase extraction of oligonucleotides. The materials were synthesized by miniemulsion copolymerization of ionic liquids and divinylbenzene on magnetic nanoparticles. The functional monomers contain a positively charged imidazolium ring and one of the anionic groups: derivatives of acetate, malonate, or butyl sulfonate ions. Adsorption of unmodified DNA oligonucleotide on obtained materials was possible in ion-exchange (IE) and hydrophilic interactions (HI) mode. The adsorption in IE was possible at low pH and was almost complete. The adsorption in HI mode required the usage of appropriate addition of organic solvent but did not provide full adsorption. Studies on the desorption of the analytes included determining the impact of ammonium acetate concentration and pH and organic solvents addition on the recovery. The material containing acetic fragments as an anionic group was selected for the final procedure with the use of 10 mM ammonium acetate (pH = 9.5)/methanol (50/50, v/v) as an elution solution. The magnetic dispersive solid-phase extraction procedure was tested for the oligonucleotides with various modifications and lengths. Moreover, it was applied to extract DNA oligonucleotide and its synthetic metabolites from enriched human plasma without any pre-purification, with recoveries greater than 80%.

Simultaneous adsorption of mercury species from aquatic environments using magnetic nanoparticles coated with nanomeric silver functionalized with l-Cysteine

We introduce a novel, efficient and fast method for the total and simultaneous removal of monomethylmercury, dimethylmercury, ethylmercury and Hg (II) from aquatic environments using magnetic core nanoparticles, coated with metallic nanomeric silver and functionalized with l-Cysteine. As far as the authors know, simultaneous removal has not been achieved previously. The experimental design was based on exploring a wide range of experimental conditions, including pH of the medium (2−12), contact time (up to 20 min), adsorbent dose (50–800 μL) and temperature (293–323 K), in order to achieve the highest adsorption efficiency. The results show that, for a pH equal to 6.2 at room temperature, 400 μL of nanoparticles is sufficient to achieve 100% adsorption efficiency for all the studied Hg species after a contact time of 30 s. The adsorbent was characterized by means of Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Fourier-Transform Infrared Spectroscopy and a BET test. Moreover, the procedure allows the total recovery and recycling of the nanoparticles using 50 μL of 0.01 M KI. As regards reuse, the adsorbent exhibits no loss of adsorption capacity during the first three adsorption cycles. Thermodynamics reveals that adsorption is of a physicochemical nature, the equilibrium isotherms being described by a Langmuir model for all the Hg species. The ability of the method to simultaneously adsorb all species of mercury present in water, achieving full adsorption in just a few seconds, along with the simple experimental conditions and its cost-effectiveness, strongly support the approach as an alternative to current procedures.

Benchtop In Situ Measurement of Full Adsorption Isotherms by NMR.

Physisorption using gas or vapor probe molecules is the most common characterization technique for porous materials. The method provides textural information on the adsorbent as well as the affinity for a specific adsorbate, typically through equilibrium pressure measurements. Here, we demonstrate how low-field NMR can be used to measure full adsorption isotherms, and how by selectively measuring 1H spins of the adsorbed probe molecules, rather than those in the vapor phase, this "NMR-relaxorption" technique provides insights about local dynamics beyond what can be learned from physisorption alone. The potential of this double-barreled approach was illustrated for a set of microporous metal-organic frameworks (MOFs). For methanol adsorption in ZIF-8, the method identifies multiple guest molecules populations assigned to MeOH clusters in the pore center, MeOH bound at cage windows and to MeOH adsorption on defect sites. For UiO-66(Zr), the sequential pore filling is demonstrated and accurate pore topologies are directly obtained, and for MIL-53(Al), structural phase transitions are accurately detected and linked with two populations of dimeric chemical species localized to specific positions in the framework.

Construction of rigid ionic porous organic polymers (iPOPs) via Zincke reaction with tunable absorption behaviors

Two rigid ionic porous organic polymers (iPOPs-1 and iPOPs-2) were fabricated via the well-known Zincke reaction. Starting from different monomers which bring the different bridging structures, the porosity and dye-removal capacities of two polymers can be handled readily. Both polymers exhibited excellent capacity for dye-removal (e.g., 1823.1 mg g−1 of iPOPs-1 and 1247 mg g−1 of iPOPs-2 for methyl orange), which are the highest among all reported iPOPs. Interestingly, iPOPs-1 absorbed solely methyl orange (MO) in the mixtures of MO and methyl blue (MB), and as a contrast, iPOPs-2 showed the full adsorption of MO/MB dyes indicating the apparent size effect. Furthermore, by using a gentle washing program, they can be recycled and reused at least five times without significantly reducing performance. This research thereby provides a new strategy and insight to rationally tune the porous properties and the following adsorption capacity of iPOPs.

Simulation of Biomolecular Adsorption on a Microcantilever Biosensor Regarding Surface Charge Distribution

Researches implement microcantilevers (MCs) as a biosensing technique lately. Various researches develop such platforms experimentally. Herein, simulation is the method of the choice to predict accurate response of the biosensor during design. The current study aims to provide a prediction method that enables adequate response order. Such results enable the enhanced design of the sensor. Regarding the nature of the phenomena, the current survey studies the adsorption and the charge distribution on the biosensor using multiscale simulation and also considers their reciprocal. The current study provides understanding of the effect of electric potential distribution on simulations of a biosensor based on microcantilever. This study uses molecular dynamics (MD) simulation to calculate the response of the biosensor. Energy method and steering molecular dynamics (SMD) methods are used in discreet media simulation. Results of nano-electronics show semi-uniform distribution of potential along the sensor’s surface and a linear pattern through the thickness. It is found the deviations in the gradient of potential reach 1e−10 at around 20 nm distance from the edge. The MD simulation regarding total deformation of microcantilever around 190 nm for a corrected charge of the substrate and 366 nm for an un-corrected model; the former coincides better with previous experiments. Deflection prediction using overall multiscale simulation has good agreement with experimental results within 13% deviation, regarding charge distribution on the substrate of the sensor, though the latter lacks any experimental verifications. Together, SMD analysis and MD energy analysis show the adsorption trend gets more stable as it moves toward full adsorption.

Adsorption of vancomycin, gentamycin, ciprofloxacin and tygecycline on the filters in continuous renal replacement therapy circuits: in full blood in vitro study

The aim of this study was to assess the in vitro adsorption of antibiotics: vancomycin, gentamicin, ciprofloxacin and tigecycline on both polyethyleneimine-treated polyacrylonitrile membrane of AN69ST filter and polysulfone membrane of AV1000 filter using porcine blood as a model close to in vivo conditions. The porcine blood with antibiotic dissolved in it was pumped into hemofiltration circuit (with AN69ST or AV1000 filter), ultrafiltration fluid was continuously returned to the reservoir containing blood with antibiotic. Blood samples to determine antibiotic concentrations were taken at minutes 0, 5, 15, 30, 45, 60, 90 and 120 from the pre- blood pump of the hemofiltration circuit. To assess possible spontaneous degradation of the drug in the solution there was an additional reservoir prepared for each antibiotic, containing blood with the drug, which was not connected to the circuit. In the case of vancomycin, ciprofloxacine and tigecycline, a statistically significant decrease in the drug concentration in the hemofiltration circuit in comparison to initial value as well as to the concentrations in the control blood was observed, both for polyacrylonitrile and plolysulfone membrane. In the case of gentamicin, significant adsorption was noted only on polyacrylonitrile membrane. Our studies demonstrated that in full blood adsorption of antibiotics may be big enough to be of clinical significance. In particular in the case of polyacrylonitrile membrane.