Adsorption最新文献

Bacterial cellulose (BC)/kappa carrageenan (κ-C) hydrogel was synthesized via in-situ method by inoculating the κ-C into the Acetobacter xylinum cell culture medium. The structural features of the hydrogel was characterized using Fourier Transform Infrared Spectroscopy. The presence of both biopolymers in the hydrogel was confirmed by the O–H stretching of BC at 3390 cm⁻¹ and the sulfate group (-SO₃) of κ-C at 1226 cm⁻¹. Scanning electron microscope images of the hydrogel showed A 3-D network of fibrils with high porosity. The enhanced swelling capacity of the hydrogel in water at pH 7 is due to the combined number of hydrophilic groups from BC and κ-C. The conductivity of the hydrogel increased with increasing κ-C due to the increased number of sulfate groups (-SO₃). The hydrogel had the ability to adsorb organic dyes; Congo red, Crystal violet and Methylene blue from neutral water at 27 °C. All the dyes fitted the pseudo second order kinetic model and followed both the Langmuir and the Freundlich adsorption isotherms indicating monolayer adsorption on heterogeneous surfaces. The ΔG^o_ad was negative indicating spontaneous physisorption for the three dyes. The prepared hydrogel being environmentally friendly also showed an improved ability to adsorb the organic dyes.

The environmental devastation, caused by unscrupulous and recurrent human intervention in the ecosystem is a global concern. Within the scope of relevance, this work discusses the development of adsorbents which eliminate both water and air pollutants. Graphene oxide/polyaniline hybrid incorporated polyvinyl alcohol (PVA) composite aerogels were successfully fabricated by environmentally friendly lyophilization method. Various fillers such as polyaniline (PANI), graphene oxide (GO), reduced graphene oxide (rGO), binary hybrids of GO/PANI and rGO/PANI was synthesized and characterized for structural and morphological peculiarities. The filler system which shows the highest anionic dye (model organic pollutant) adsorption ability was selected for the preparation of PVA composite. The freeze dried aerogel samples were characterized and it shows 98% removal of anionic dye (methyl orange, MO) within 24 h. The high percentage of anionic dyes removal from aqueous solutions is attributed to different mechanisms such as electrostatic attraction between positively charged PANI backbones and negatively charged MO molecules, π-π interaction & hydrogen bond formation between different functional groups present in adsorbate and adsorbent. The dye adsorption mechanism was well established based on the Boyd, Werber & Morris models and the adsorption isotherms were fitted in agreement with the Freundlich and pseudo-second-order models. The reusability studies on dye adsorption were also carried out up-to three cycles without much loss in the adsorption capacity. In addition, the preliminary analysis of CO₂ adsorption at 25 °C and 900 bar indicates the suitability of the proposed composite aerogels for environmental remediation.

In this work, we investigate the structural parameters that affect water adsorption on amorphous carbon nitride thin films synthesized by pulsed laser deposition. The study includes the case of ablation of graphite targets within molecular nitrogen and within a stream of nitrogen plasma afterglow. The results obtained showed that, the effect of Csp²-Csp² bonds concentration on the adsorption of water molecules depends strongly on the ratio and distortion of the hexagonal rings. Furthermore, analysis of the spectral data showed that, the relationship between the hydrogen bonding strength of water molecules with the film surface and the concentration of Csp²-Csp² bonds takes a specific mathematical formula in the case of structures composed mainly of hexagonal rings.

Capturing CF₄ is crucial for mitigating its substantial greenhouse effect and environmental impact in the microelectronics industry. Here we employed a hybrid approach combining grand canonical ensemble Monte Carlo molecular simulations and neural network models to screen over 100 amorphous materials for N₂/CF₄ gas adsorption storage and separation. Materials with higher adsorption capacities exhibited densities around 0.7 to 1.0 g/cm³ and pore sizes within the range of 1.4–1.6 Å. At 298 K and 1000 kPa, HCP-Colina-id0016 and aCarbon-Bhatia-id001 demonstrated the highest CF₄ adsorption, reaching 5.65 and 5.34 mmol/g, respectively. For the separation of N₂/CF₄ mixtures, considering the comprehensive CF₄ adsorption selectivity and capacity, we recommend HCP-Colina-id0016 at high pressure conditions (4500 kPa) and aCarbon-Bhatia-id001 at medium to low pressures (below 500 kPa). The separation of mixtures is more favorable at low CF₄ concentrations, becoming more challenging as CF₄ concentration increases. Additionally, the Ideal Adsorbed Solution Theory (IAST) accurately predicted the separation of the N₂/CF₄ system on amorphous materials. We found that the genetic algorithm-optimized neural network (GA-BP) outperformed the standalone backpropagation neural network (BP) in accurately predicting the relationship between material structural properties and CF₄ adsorption, showing its potential for widespread application in large-scale material screening.

Tetracyclines (TCs) constitute a group of antibiotics that are commonly used to treat bacterial diseases, in veterinary medicine and as an additive in animal feed. This broad application has led to their accumulation in food products and the environment because sewage treatment plants cannot completely remove them. Therefore, the aim of this study was to synthesize graphene oxide (GO) and evaluate its TC adsorption properties in aqueous media. The effects of pH (between 2.5 and 11) and Ca²⁺ concentration (between 0 and 1 M) were thoroughly investigated. Structural, textural, and electrokinetic properties of the prepared GO were determined by N₂ adsorption/desorption, XRD, TEM, UV–vis, FTIR, XPS, thermogravimetry and electrophoretic mobility measurements. TC adsorption on GO is an interplay between the two main roles played by Ca²⁺: competitor or bridging cation. At low pH, there is cation exchange, and Ca²⁺ behaves as a competitor of the positively charged TC species, decreasing adsorption as calcium concentration increases. At high, the formation of Ca bridges between the surface and TC (GO-Ca²⁺-TC) is favored, increasing the adsorption of the antibiotic by increasing calcium concentration. Different combinations of Ca²⁺ and pH effects are important to improve the use of GO either as a pH-dependent and reversible TC adsorbent for decontamination or as pH-independent adsorbent for TC quantification with electrochemical sensors.

This study investigates the sensitivity and selectivity of gas adsorption (SF₆, SO₂F₂, SOF₂, SO₂, and HF) on SiGe surfaces and Ca atom-decorated SiGe surfaces using Density Functional Theory (DFT). The optimized structures, bond lengths, and angles of the gas molecules are analyzed, providing valuable insights into their geometric features and bonding configurations. For every gas on both surfaces, important variables such as adsorption energy, and charge transfer are examined. In particular, there is a significant increase in charge transfer and adsorption energy when SF₆ interacts with Ca$2D-SiGe as opposed to the SiGe surface. To emphasize changes in band gap and electronic structure, the study explores electronic properties such as density of states (DOS) and projected density of states (PDOS) spectra before and after gas adsorption. Electron density differences (EDD) analysis is used to clarify the type of interactions, including accumulation and depletion of charge. The results reveal that all gases except HF/ Ca$2D-SiGe showed chemical adsorption. The study also takes into account recovery time, an important metric for sensor materials, which is calculated for the breakdown gases of SF₆ on both surfaces at different temperatures and shows potential uses for gas detection. Future research should focus on a broader range of gas molecules and their interactions with SiGe and Ca-decorated SiGe surfaces. Ultimately, the integration of SiGe-based sensor devices in real-world applications such as environmental monitoring, industrial safety, and medical diagnostics can be explored to understand the broader potential of these materials in the field of gas detection.

This paper investigates the use of the Ideal Adsorbed Solution Theory (IAST) for alcohol/water breakthrough separation simulations on an all-silica beta zeolite. Because of its very hydrophobic nature, this zeolite presents peculiar isotherms for water and the alcohols, 2-methylpropan-1-ol, and ethanol. Isotherm fitting was performed using the Dual Langmuir-Sips (DLS) model for 2-methylpropan-1-ol and ethanol, while the Brunauer–Emmett–Teller (BET) model was chosen for water. To overcome the issues for evaluating the BET spreading pressure integral during IAST calculations, its isotherm at high partial pressures was limited to a capacity where its pore volume equals the pore volume occupied by ethanol and 2-methylpropan-1-ol. A 1D, trace, isothermal, axially dispersed plug flow model was employed to simulate and predict breakthrough curves for binary and ternary mixtures containing 2-methylpropan-1-ol, ethanol, and water. The IAST breakthrough separation simulations were validated with experimental data where both the equilibrium and dynamic behavior match well. This study concludes that IAST can be applied to alcohol/water mixtures when it is combined with a uniform and almost defect-free all-silica adsorbent.

In this study, a discontinuous Galerkin (DG) finite element method is employed to solve the nonlinear equilibrium dispersive (ED) model, for the simulation of multi-component gradient elution chromatography using a liquid mobile phase in fixed-bed columns. The ED model comprises a set of coupled nonlinear convection-dominated partial differential equations integrated with nonlinear Langmuir type adsorption isotherms. Gradient elution, characterized by the gradual increase in eluent strength through variations in the chemical composition of the mobile phase, is analyzed. An investigation into the advantages of gradient elution chromatography in comparison to isocratic elution is conducted via a sequence of numerical test experiments that assess the influence of solvent strength, modulator concentration, gradient start and end times, and gradient slope on the elution profiles and temporal moments. It has been observed that gradient elution chromatography influences the behavior, shape, and propagation speed of elution profiles, which subsequently affect the cycle time and column efficiency. The results of this study provide significant insights that are critical for understanding, optimizing, and enhancing gradient elution chromatography.

Silica-supported chitosan adsorbent was synthesized by sol–gel process and evaluated for desulfurization of sulfur compounds. Removal of thiophene from thiophene/ n-heptane solutions has been investigated on silica-chitosan hybrid as a new adsorbent. The reduction of sulfur compound happens with strong adsorption between sulfur and the surface of the silica/ chitosan hybrid. This adsorption is the result of the interaction between sulfur atoms in thiophene and NH₂ groups in chitosan as well as, the penetration of thiophene molecules into the pores of silica. Recyclability and reusability of this composite is a main advantage of this adsorbent. The preparation method as well as sulfur removal and adsorption characteristics of this adsorbent are described in this paper.