Adsorption最新文献

Accurate experimental adsorption equilibrium measurements are necessary for benchmarking adsorbents, validating molecular simulations and setting up process simulations. Although many sources of errors in these measurements have been reported in the literature, the purity of the gas used is generally not considered a major problem as long as research grade gases are used. In this work, we propose that significant deviations in the measured isotherms can potentially arise due to the accumulation of impurities in the measurement cell, especially in the low-pressure region, which is important for systems dealing with low partial pressure, such as (hbox {CO}_2) direct air capture (DAC). We conduct numerical studies to highlight this issue. The first part of our analysis uses the Langmuir isotherm equation to generate baseline isotherms representative of adsorbents with varying affinities for (hbox {CO}_2), enabling a parametric assessment of impurity effects. This is followed by a material-specific study examining the influence of impurities on isotherms for several zeolites and metal-organic frameworks (MOFs).

Monolithic adsorbents offer an opportunity to intensity cyclic adsorption processes, but uniformity of channel size and flow distribution have a detrimental effect on separation performance. Mathematical modelling and optimisation techniques require repeated process simulations up to cyclic steady state but the real monolith model representing the response of a distribution of channels is computationally expensive. This study explores the possibility of employing the ideal single channel monolith model to do an initial search, followed by a secondary search with the computationally more complex and more accurate real monolith model. Two case studies have been considered here to cover the different nature of the product of interest (i.e., heavy or light), and whether the optimisation is constrained or unconstrained. For unconstrained optimisation, the optimum decision variable values found with the ideal monolith model are similar to those obtained when only the real monolith model is used for all the functional evaluations (i.e., the real optimum). However, the corresponding objective function values were not the same due to the ideal and real monolith model predictions differing for certain combinations of decision variables. In this case, a quick secondary refinement search with the real monolith model yielded the real optimum objectives. In the case of constrained optimisation, the optimum objective and decision variable values predicted from the initial search differed substantially from the real optimum. Optimum values close to the real optimum could still be obtained with the two-step search strategy. The two-step search strategy required approximately half the computational effort, compared to the approach where only the real monolith model was used for all the evaluations.

Materials capable of effectively storing (hbox {H}_{2}) and (hbox {CH}_{4}) are essential for the enhancement of hydrogen and methane-based transportation. Metal-Organic Frameworks (MOFs) are strong contenders for meeting the gas storage targets of the Department of Energy (DOE). Many Cu(I)-based MOFs degrade in air and moisture. NU-2100, a newly developed Cu(I)-based MOF, shows air stability. The total and usable (hbox {H}_{2}) and (hbox {CH}_{4}) storage capacities of NU-2100 at 298.15 K and 0.5–35 MPa are calculated and analyzed by means of Grand Canonical Monte Carlo (GCMC) studies. A comparative assessment is performed, including MOFs with similar metal compositions, pore size, density and porosity at 298.15 K and 25 MPa. The findings demonstrate that NU-2100 exhibits storage capacities that match or outperform the MOFs included in this investigation. The origin of these higher capacities is that the molecules interact with the atoms of NU-2100 in wider regions or pores than in the other MOFs. The autonomy range of a hydrogen and a methane vehicle containing NU-2100 are also calculated. A hydrogen or a methane vehicle storing the gas on this new material would reach the same autonomy as a vehicle storing the gas by compression, using a larger tank volume and lower pressures.

Efficiently recovering the natural gas from the gas mixture is crucial to its application. Grand Canonical Monte Carlo (GCMC) molecular simulations were performed to screen MOFs from 100 samples covering four typical kinds of MOFs based on the selective performance of methane and carbon dioxide mixtures at 298 K and 0–0.1 MPa. Incorporation was introduced to ameliorate the performances of the selected MOFs, and the effect of mixing carbon molecular sieve (CMS), activated carbon and graphene oxide (GO) on the structure, the adsorption selectivity as well as the adsorbent performance score (APS) for carbon dioxide was also evaluated. Researches were conducted on the samples by performing the structural characterization, microscopic morphology observation and the measurements of the adsorption isotherms of methane and carbon dioxide. It shows that, at 298 K under pressure 0.1 MPa, the adsorption selectivity coefficient for the gas mixture contained the equal molar volume fraction of methane and carbon dioxide on Ni-MOF-74 is about 60 and the APS is larger than 500; within the range of incorporated amount 1–15 wt%, only the sample prepared by 5 wt% GO respectively obtained 15.4% and 47.9% increment in the adsorption selectivity coefficient and the adsorption capacity of CO₂. Results also reveal that, during three adsorption and desorption cycles, the fluctuation amplitude of the adsorption capacity, adsorption selectivity coefficient, APS on the sample can all be kept within 0.03%, and the largest adsorption selectivity coefficient is about 25.65 with 4.1% increment in APS within the molar volume fraction range of methane 50–90%. It suggests that the composite of Ni-MOF-74 incorporated by 5 wt% GO is suitable for separating the natural gas from the mixture of methane and carbon dioxide.

Nutrient recovery from sewage wastewater through nanomaterial adsorbents is a promising method for reducing environmental pollution and recycling essential nutrients. In this study, various adsorbents, specifically Chitosan (CHI), Ceramic-based Zeolite nanomaterial (N-Zs), and Silica-assisted Nano hemicellulose (Si-NHC), were prepared to analyze their capacity to adsorb NH₄⁺ and PO₄³⁻ from synthetic and real wastewater sources. The study revealed a notable adsorption capacity of 84.734 ± 10.165 mg/g and 0.192 ± 0.024 mg/g for NH₄⁺ and PO₄³⁻, respectively, by Si-NHC. The hydrothermally synthesized N-Zs show poor efficiency compared to other adsorbents. Optimal conditions for NH₄⁺ adsorption were identified at a pH of 5.5, utilizing 0.1 g of Si-NHC per 50 ml of solution, with a contact time of 2.5 h. An economic analysis of NH₄⁺ recovery from treated wastewater indicated advantages due to its lower cost and higher adsorption capacity. The higher adsorption capacity and degradable nature position Si-NHC as a viable candidate for use as a fertilizer. The detailed adsorption and desorption cycle durability and efficiency of the Si-NHC were also evaluated.

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.

Graphical abstract

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.