Dynamic Sorption Properties Research Articles

High-value utilization of lignin to prepare N,O-codoped porous carbon as a high-performance adsorbent for carbon dioxide capture

The concern for environmental sustainability has increased the interest in biomass materials for the synthesis of porous carbon, especially as an effective alternative and multifunctional adsorbent in the field of adsorption of a wide range of pollutants and carbon dioxide. Lignin has high carbon content, abundant aromatic rings and condensation bonds, which make it suitable as a precursor for carbon-containing materials. In this study, lignin was firstly precarbonized to achieve its degradation and efficient conversion, and then chemically activated by KOH to prepare a low-cost porous carbon materials with finely developed microporous structure, which showed excellent gas adsorption performance of 3.98 and 5.82 mmol/g at 1 bar, 298 K and 273 K, respectively. In addition to this, we have also investigated the dynamic sorption properties of the samples on CO2. The original lignin contains N,O functional groups that can be doped to the surface of the porous carbon, and previous studies have confirmed that the porosity and functional groups on the surface of the carbon material play a positive role in improving the defective and adsorption properties of the material. Our work provided a promising strategy for valorization of lignin as a precursor for producing advanced carbon materials.

Using silver exchange to achieve high uptake and selectivity for propylene/propane separation in zeolite Y

Adsorptive separation of propylene and propane, an important step of polypropylene production, is more energy-efficient than distillation. However, the challenge lies in the design of an adsorbent which exhibits both high selectivity and uptake. Herein, we hypothesise that enhancing the propylene affinity of the adsorption sites while keeping a suitable pore size can address this challenge. To do so, we performed silver exchange of a commercial zeolite Y, thereby making the adsorbent design easily scalable. We characterised the adsorbent using analytical, spectroscopic and imaging tools, tested its equilibrium and dynamic sorption properties using volumetric and gravimetric techniques and compared its performance to those of state-of-the-art adsorbents as well as other silver-functionalised adsorbents. The silver-exchanged zeolite Y (Ag-Y) exhibited one of the best selectivity vs uptake performances reported so far. Ag-Y also displayed fast adsorption kinetics and reversible propylene sorption, making it a promising new benchmark for propylene/propane separation. Synchrotron-based pair distribution function analyses identified the silver cations’ location which confirmed that the silver sites are easily accessible to the adsorbates. This aspect can, in part, explain the propylene/propane separation performance observed. The overall design strategy proposed here to enhance sorption site affinity and maintain pore size could be extended to other adsorbents and support the deployment of adsorption technology for propylene/propane separation.

The Influence of Clay Structures to the Hygrothermal Component of the Indoor Environment.

In this article, research on the sorption properties of clay materials in comparison with commonly used building materials is published. The topic is mainly focused on the dynamic sorption properties and their influence on the relative humidity in the indoor environment. The results of comparisons of clay structures, rammed earth panels, clay plaster, and unburned bricks, with commonly used building materials, concrete, lime plaster, and gypsum board are examined. Statistically evaluated results in the form of confidence intervals are presented and the rate of dynamic sorption is analyzed. It is clear from the results that clay materials have a positive effect on the rapid adsorption and desorption of air moisture in the interior of buildings. However, there are many variables, band not every clay material has such excellent sorption properties.

Dynamic sorption properties of Metal-Organic Frameworks for the capture of methyl iodide

In this work, methyl iodide (CH3I) sorption properties of Metal-Organic Frameworks (MOFs) were experimentally studied. CH3I adsorption capacities were determined at 35 °C for the different prototypical selected MOFs, MIL-53(Al), MIL-100(Al), MIL-120(Al), CAU-1(Al), UiO-66(Zr), HKUST-1(Cu) and ZIF-8(Zn) from fixed-bed reactor measurements by using infrared spectroscopy. Quantitative exploitation of breakthrough curves reveals higher sorption performances (Qsat up to 425 mg/g) for materials showing pore size and geometry well-adjusted to CH3I dimension, such as MIL-120(Al), MIL-53(Al) and HKUST-1(Cu). In situ DRIFTS (Diffuse Reflection Infrared Fourier Transform Spectroscopy) experiments were also carried out in order to further investigate the interaction modes of physisorbed CH3I species within MIL-53 and MIL-120 compounds. For MIL-120, the confinement of adsorbed CH3I molecules within the pores is strengthened by specific interactions with the ligand and hydroxyl groups. For a breathing compound like MIL-53(Al), the adsorption measurement confirmed a swelling related to CH3I adsorption.

Experimental and numerical analysis of adhesion failure in moist packaging material during excessive heating

In the presented paper experimental and numerical analyses are made of the failure due to blister formation in moist packaging material when exposed to excessive heating. The basic concept of the experimental analysis is to expose a package material to a hot air jet and measure the time until the material experience internal failure. For the numerical analysis, a triphasic macroscale hybrid mixture theory approach is adopted. The in-plane permeability and the static and dynamic sorption properties of the paperboard are believed to have significant influences on the blister formation. For this reason in-plane permeability experiments and sorption experiments are performed to retrieve proper constitutive coefficients for the numerical simulations. Results from numerical simulations are compared with the experimental tests in order to better understand the physics behind the forming of a blister. The results indicate that the blister formation primarily depends on the in-plane permeability and the sorption properties of the paperboard as well as the properties of the adhesion between the paperboard and the Al-foil.

Dynamics of sorption of cesium radionuclides on selective ferrocyanide sorbents. Distribution of the 137Cs activity in the stationary phase

A method was suggested for studying the dynamic sorption properties of ferrocyanide sorbents toward Cs radionuclides by analyzing the radiocesium distribution in the solid phase of the sorbent. The dynamic sorption characteristics are determined by measuring the activity of successive sorbent layers after passing definite volumes of the solution. The method is efficient in analysis of the stability of various sorbents in liquid media. The sorption characteristics of the following ferrocyanide sorbents were examined: Termoksid-35 (nickel-potassium ferrocyanide on zirconium hydroxide), FNS-2 (nickel-potassium ferrocyanide on silica), and FS-2 (copper-potassium ferrocyanide on silica). In alkaline solutions, Termoksid-35 is the most stable. The effect of oxalic acid on the activity distribution in a ferrocyanide sorbent bed was studied. In alkaline solutions containing oxalic acid, copper ferrocyanide (FS-2) is the least stable. At the same time, at low pH values and in the absence of oxalic acid, it is preferable to use sorbents based on copper ferrocyanides.

Three‐Dimensional Open‐Frameworks Based on LnIIIIons and Open‐/Closed‐Shell PTM Ligands: Synthesis, Structure, Luminescence, and Magnetic Properties

A series of isostructural open-framework coordination polymers formulated as [Ln(dmf)(3)(ptmtc)] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5); PTMTC = polychlorotriphenylmethyl tricarboxylate) and [Ln(dmf)(2)H(2)O(αH-ptmtc)] (Ln = Sm (1'), Eu (2'), Gd (3'), Tb (4'), Dy (5')) have been obtained by treating Ln(III) ions with PTMTC ligands with a radical (PTMTC(3-)) or a closed-shell character (αH-PTMTC(3-)). X-ray diffraction analyses reveal that these coordination polymers possess 3D architectures that combine large channels and fairly rare lattice complex T connectivity. In addition, these compounds show selective framework dynamic sorption properties. For both classes of ligands, the ability to act as an antenna in Ln sensitization processes has been investigated. No luminescence was observed for compounds 1-5, and 3' because of the PTMTC(3-) ligand and/or Gd(III) ion characteristics. Conversely, photoluminescence measurements show that 1', 2', 4', and 5' emit dark orange, red, green, and dark cyan metal-centered luminescence. The magnetic properties of all of these compounds have been investigated. The nature of the {Ln-radical} exchange interaction in these compounds has been assessed by comparing the behavior of the radical-based coordination polymers 1-5 with those of the compounds with the diamagnetic ligand set. While antiferromagnetic {Sm-radical} interactions are found in 1, ferromagnetic {Ln-radical} interactions propagate in the 3D architectures of 3, 4, and 5 (Ln = Gd, Tb, and Dy, respectively). This procedure also provided access to information on the {Ln-Ln} exchange existing in these magnetic systems.

Equilibrium and dynamics of acetylene sorption in multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNT) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and by adsorption of N 2 and acetylene. The dynamics of acetylene sorption was studied by frequency response spectroscopy. The average tube dimension and the shell number were determined from a statistical evaluation of the TEM images. This value agreed with that obtained from XRD via the Scherrer equation only if a shape factor of 0.49 was used. The diffusion of acetylene in the nanotubes of the MWCNT sample was found to be the rate-controlling step of the sorption process. Relationships between the tube dimensions and the equilibrium and dynamic sorption properties were demonstrated.

Hydration properties of durum wheat semolina: influence of particle size and temperature

The hydration of semolina particles is an essential step in couscous processing which leads to binding between particles for the formation of agglomerates. Despite this importance, the hydration properties of such food products are rarely studied and in particular, durum wheat semolina has never been investigated. Here we present a study of the hydration properties of durum wheat semolina by determination of water sorption isotherms, and other characterisation techniques to obtain a better understanding of hydration mechanisms. Equilibrium and dynamic sorption properties have been measured as a function of relative humidity by means of a controlled atmosphere microbalance. It is found that durum wheat semolina presents a type II isotherm [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids—Principles Methodology and Applications, Academic Press, 1999] indicative of multi-layer adsorption. The Guggenheim–Anderson–de Boer (GAB) model is used to describe the isotherm and obtain a better understanding of hydration mechanisms and liquid/solid interactions. The effects observed are related to physical properties of the semolina. In particular, the size of the semolina particles is found mainly to influence sorption kinetics: the finer the particles, the faster their sorption kinetics. Increasing temperature in the range 25–45 °C accelerates sorption kinetics. Furthermore, hydration causes no irreversible transformation of semolina components. Thus, absorption kinetics seem to be influenced by physical mechanisms, while the biochemical composition determines the amount of water sorbed.