Abstract Quantitative knowledge of competitive adsorption isotherms is essential for the design and optimization of adsorption-based separation processes. To adjust the retention times of the components to be separated in liquid phase applications, mixtures of two or more solvents are often selected as the mobile phase. The solvent composition thus has an influence on the courses of the adsorption isotherms. The paper presents the results of breakthrough curve (BTC) experiments considering the separation of three benzene derivatives characterized by different aliphatic carbon chains, exploiting conventional reversed-phase chromatography (RP18). As the mobile phase, different mixtures of acetonitrile (ACN) and water (W) were used. Equilibrium loadings were extracted from characteristic features of the observed BTCs for single components, binary mixtures, and ternary mixtures. The analysis ignored kinetic effects and exploited classical equilibrium theory. For an initially selected solvent composition, the courses of the isotherms revealed an anti-Langmuir behavior for the two longer retained components. All single-component and mixture equilibrium data could be well described with a newly derived widely applicable multi-component single-site BET adsorption model, assuming a finite number of adsorbed layers. The analysis was applied again to determine and analyze the courses of BTCs and the corresponding multi-component adsorption isotherms for three other solvent compositions. The slopes of the single-component isotherms changed significantly for the different components. The derived BET-type equation could again be used to describe rather well the isotherms for increasing amounts of ACN with specific numbers of adsorbed layers. For ACN/W = 90/10, the layer number approached unity and, thus, an almost perfect Langmuir behavior was identified. The identified trends between the solvent compositions and the estimated isotherms model parameters could be well described with the LSS model. Finally, suggestions were made for further improving the agreement between measured and predicted isotherms.

Abstract Adsorption-induced deformation in porous materials refers to the structural change that occurs due to the adsorption of guest molecules. This effect can be neglected for many systems because the variation in pore volume is practically zero. This fact led to the hypothesis of a rigid pore structure, which in turn gave rise to numerous adsorption models. However, for many new porous materials, such as metal-organic frameworks (MOFs), the effects of these deformations are significant and specific for different components and temperatures, requiring detailed models. The hybrid Monte Carlo/molecular dynamics method is the most direct approach for capturing volumetric deformation during adsorption. However, this method involves multiple iterations of Grand Canonical Monte Carlo (GCMC) and molecular dynamics simulations in an NPT ensemble (NPT-MD), which requires computer optimization to reduce computational time. In this work, we develop an efficient iterative GCMC/NPT-MD method, leveraging the GPU parallelization of gRASPA and GROMACS software, to study the effects of flexibility in IRMOF-1. Using this framework, we analyze the deformation of IRMOF-1 during the adsorption of CO $$_2$$ and Ar, systematically evaluating the influence of key simulation parameters, including the size of the simulation box and the non-bonded cutoff radius.

Abstract 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).

Abstract 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.

Herein, the oxidized biochar (OBC) derived from rice straw was prepared and homogeneously embedded into TEMPO-mediated oxidized cellulose nanofiber (TOCNF). The resulting colloidal suspension, when mixed with OBC and crosslinked via ionic interaction using branched polyethyleneimine, forms nanocomposites with promising potential. The characterization of these composites, including SEM, EDX, surface morphology, and spatial elemental composition, reveals their unique properties. The effect of adding OBC to TOCNF at different ratios is estimated by surface area analysis following the BET and BJH methods. The adsorption settings for the as-formed composites were investigated to optimize the adsorption effectiveness of the fabricated sorbents. These conditions included contact time, Cd(II) concentration, pH, and sorbent dosage. With greater adsorption effectiveness of 70% and 90% at 1 h and 2 h, the nanocomposite with an equal ratio of OBC and TOCNF was discovered to be a valuable sorbent for Cd(II) elimination (0.15 g of BCC3 composite in 50 mL of 100 mg/L Cd(II) at pH 7.0). The adsorption process was modeled using kinetic and isotherm models. The correlation coefficients for the pseudo-first and second-order kinetics are similar and closest to 1.0 based on the data. Thus, Cd(II) adsorption may involve both physio-sorption and chime-sorption. Additionally, the linear fitting of the Freundlich isotherm model demonstrated a heterogeneous and multilayer surface interaction with the greatest adsorption capability of 44 mg/g. Suggesting potential applications in environmental engineering and materials science.