Adsorption最新文献

Metal-organic frameworks (MOFs) are 3-dimensional coordination polymers which contain metals and organic linkers. MOFs are of strong interest in the fields of separation, catalysis, chemo-sensing, and pollution remediation. MOFs are highly desired, which have complex and controlled composition, structure and functional properties. Here, we report the copper porphyrin aluminum MOF (actAl-MOF-TCPPCu) denoted compound 4, and mechanistic and kinetic studies of adsorption of volatile organic sulfur compound, diethyl sulfide (DES) by it. The characterization is conducted by qualitative and quantitative methods, structural analysis with the Rietveld crystal lattice refinement, and complementary microscopy and spectroscopy. Then a comprehensive study of mechanism and kinetics of DES sorption is presented, under the dynamic conditions in the flow of air. The latter is conducted by a novel method of in-situ time-dependent ATR-FTIR spectroscopy in the controlled environment. The binding sites of DES include the µ(O–H), the COO⁻ group, phenyl and pyrrole groups and they are ranked by the strengths of bonding. The kinetics of sorption obeys the Langmuir model of the pseudo-first order rate law with effective rate constant k_eff = 0.95 ± 0.05 min^− 1. Moreover, the linear dependence of kinetic rate constant on concentration of DES suggests that the sorption is diffusion limited. The sorption of DES in the static equilibrium conditions results in the binary stochiometric adsorption complex with formula (Al-MOF-TCPPCu)₂(DES)₇. Finally, a facile regeneration of the adsorption complex was achieved, without using chemicals. The copper-containing porphyrin aluminum MOF and related materials are promising for the removal of volatile organic sulfur compounds from air.

Towards the beneficiation of agricultural waste for water treatment and energy, Hura crepitans pods (HC), pyrolysed at 500, 600 and 700 °C with holding times of 30 and 60 min, were modified with chitosan and used for the adsorption of methylene blue. The biochar was characterised using pH of point of zero charge (pHpzc), elemental analysis, BET, FTIR spectroscopy, XRD and SEM–EDX. The pHpzc of HC was 9.2 and elemental analysis showed that the % carbon of the biochar was higher than that of the feedstock. The higher heating value of HC biochar was greater than 20 MJ kg⁻¹; projecting it as alternative solid-fuel source. The biochar appeared in the region for anthracite on van Krevelen diagram. Modification of the biochar with chitosan decreased the BET surface area. The FTIR spectra showed distinctive functional groups responsible for adsorption, XRD depicted the amorphous nature of the biochar. The adsorption capacity of HC biochar increased as the pyrolytic temperature and holding time increased from 500 to 700 °C and 30 to 60 min, respectively. Langmuir isotherm and pseudo-second order kinetic models gave the best fit to the experimental data. The monolayer adsorption capacity of HC7B biochar was 48.78 mg g⁻¹. Thermodynamic parameters showed that the adsorption process was endothermic, disorderly and spontaneous. The mechanism of adsorption was mainly by non-electrostatic interaction such as π-π interaction. The highest percentage desorption was achieved with 0.1 M H₂SO₄ and HC biochar was successfully regenerated after 5 cycles. Hura crepitans pod biochar was effective in the adsorption of MB from aqueous solution and modification with chitosan improved its adsorption capacity.

This Density Functional Theory (DFT) study, utilizing the B3LYP-D3 functional with a 6-311+ +G(d,p) basis set, explores the efficacy of B₁₂N₁₂ and B₁₂P₁₂ nanocages for detecting Bromochlorodifluoromethane (BCF), a potent greenhouse gas and ozone-depleting substance. Our investigations reveal that both B₁₂P₁₂ and B₁₂N₁₂ nanocages show a notable affinity for BCF. Specifically, B₁₂P₁₂ nanocage demonstrates a stronger interaction with BCF, evidenced by an interaction energy of − 23.89 kJ mol⁻¹ compared to − 20.17 kJ mol⁻¹ for BCF@B₁₂N₁₂. The interaction energy, along with charge transfer and non-covalent interaction (NCI) analyses, confirms the physisorption nature of the BCF adsorption on the nanocages. UV/Vis spectroscopy predicts significant bathochromic shifts upon BCF adsorption, indicating potential for optical sensing. Moreover, BCF adsorption significantly reduces the HOMO-LUMO gap by 43.9% for BCF@B₁₂P₁₂ and by 22.3% for BCF@B₁₂N₁₂, thereby enhancing conductivity. This increased conductivity can be converted to an electrical signal, that correlates with the presence of BCF in the environment, affirming the potential of these nanocages as effective BCF detectors.

In the field of chemical engineering, achieving deep thiophene removal from coked benzene is a formidable challenge. This, coupled with the limitation of low sulfur capacity, has been major obstacle to the large-scale application of adsorption desulphurisation technology. In this study, Ni-Pt/Al₂O₃-CA adsorbent was prepared. The citric acid treated γ-Al₂O₃ was used as the carrier, and Ni-Pt bimetal as the active component. The relationship between the microstructure and adsorption performance of the adsorbent was investigated by BET, XRD, SEM, TEM, TPR, XPS and Py-FTIR. The results showed that the Ni-Pt/Al₂O₃-CA adsorbent could not only reduce the thiophene content in benzene to less than 10 ppb but also had sulfur capacity of 2.73 mg S/g compared with the monometallic adsorbent. The adsorption performance of the Ni-Pt/Al₂O₃-CA adsorbent was restored to 95% of the initial one after three repetitive experiments. Meanwhile, based on the kinetic modelling results, the quasi-secondary kinetic model fitted the adsorption data of thiophene on Ni-Pt/Al₂O₃-CA adsorbent better. And the process of thiophene adsorption was described in depth in the diffusion model.

The most commonly used methods of characterization of mesoporous materials involve measurement of the adsorption isotherm for a simple gas at some low fixed temperature, usually the normal boiling point. Observation of the condensation pressure in the pores makes it possible to estimate the pore size distribution and the surface area. In this note we review experimental and molecular simulation results for the pressure-temperature phase diagram for adsorbates confined within nano-porous materials, and point out that both the triple point and the pressure-dependence of the melting line are strikingly different from these properties for the bulk adsorbate. We suggest that further investigation of these two properties, and of their underlying interpretation at the molecular-level, are worthy of further study, with a view to improved characterization of nano-porous materials.

The aim of the present study was to synthesise and characterise innovative pectin/pine sawdust/magnetite composite membranes as potential sorbents for the purification of water contaminated with color pollutants. Methylene blue (MB) was employed as the pollutant model for sorption. Fourier-transform infrared spectroscopy (FTIR) was performed to analyse the formation of crosslinked membrane chains and confirm the sorption processes of the dye molecules. Thermogravimetry (TGA) and derivative thermogravimetry (DTG) indicated that the polymer matrix is stable at low temperatures and begins to degrade at temperatures above 250 °C, whereas X-Ray diffraction (XRD) patterns confirmed crystalline and amorphous regions. Mechanical assays confirmed an increase in the modulus of elasticity and tensile strength of the biopolymer membranes after incorporating PS. Moreover, a reduction in mechanical deformation was found after the incorporation of Fe₃O₄. Pollutant separation experiments were performed in a pH range from 3.0 to 10.0 with initial pollutant concentrations of 5 to 25 mg L⁻¹ and separation times from 1 to 3050 min. Higher sorption capacity was found after 1800 min with an initial pollutant concentration of 20 mg L⁻¹ and pH 10.0. The best isotherm fit was found using the Redlich-Peterson model, with fits using the Langmuir model depending on the experimental conditions. The best kinetic fit was found using the pseudo-first-order or pseudo-second-order models at pH 3.0, with differences in more alkaline solutions. The pectin-based composite membranes proved to be viable options for the purification of wastewater from industry using dye and could also be tested for the photodegradation of organic pollutants in water due to the presence of Fe₃O₄.

This study addresses the challenges of desulfurizing natural gas condensate through selective adsorption using hexagonal boron nitride (h-BN) material. h-BN was synthesized from thermal process of boric acid and mixture of urea and melamine with high specific surface area to be examined for light mercaptans removal from liquid fuel. characterization of synthesized adsorbent was done using X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), elemental analysis (CHN and ICP), and nitrogen adsorption/desorption analysis. Our findings confirmed synthesizing h-BN with high specific surface area of 1263 m²/g and hydroxyl group. This product was used as the adsorbent of ethyl, propyl and butyl mercaptans from the solution of n-heptane as the model molecule of the gas condensate liquid to obtain the equilibrium isotherms’ and kinetic adsorption data. It was revealed that the adsorption capacities were determined as 89.29 mg S/g for ethyl mercaptan, 103.66 mg S/g for propyl mercaptan, and 120.91 mg S/g for butyl mercaptan, significantly surpassing the commercial zeolite 13X adsorbent by 233% at room temperature. Kinetic experiments revealed that the pseudo-second-order model could best describe the rate of mercaptans’ adsorption. Notably, the synthesized h-BN was easily regenerated through the thermal treatment at moderate temperature of 150 °C, highlighting its potential for cyclic adsorption processes of desulfurization.

Nanoporous materials are frequently characterized as simple geometries such as slit-like, cylindrical, or spherical pores. However, these approximations cannot account for the surface roughness and chemical heterogeneity inherent to clay minerals. Here, we present a comprehensive computational examination of methane (CH(_4)) adsorption in nanoporous clay minerals, applying three complementary approaches-three-dimensional classical Density Functional Theory (3D-cDFT), one-dimensional (1D) cDFT, and Grand Canonical Monte Carlo (GCMC) simulations-to elucidate the roles of fluid-solid interactions and fluid-fluid correlations under confinement. We show that 3D-cDFT accurately captures high-pressure adsorption phenomena in illite and provides a powerful framework for reconstructing pore size distributions from experimental data, thereby enabling a more nuanced characterization of heterogeneous nanoporous materials.

Novel structured graphene oxide@microalgae-based nanohybrids have been prepared by incorporating green microalgae biomass (Algae) with graphene oxide (GO) or N-doped graphene oxide (NGO) in different ratios (e.g., 3:1, 1:1 and 1:3). Biogenic GO-Algae and NGO-Algae nanohybrids were synthesized via a self-assembly method. Morphological and structural characterizations and adsorption performance of the nanostructured material towards Cr(VI) species were studied extensively. The removal of Cr(VI) species by GO-Algae and NGO-Algae nanohybrids was highly pH dependent, with the maximum adsorption removal occurring at pH 2. The results indicate that the adsorption of Cr(VI) by GO-Algae and NGO-Algae nanohybrids was as follows: GO@Algae-3:1 (90.5%) < GO@Algae-1:1 (98.7%) < GO@Algae-1:3 (99.6%) and NGO@Algae-3:1 (79.2%) < NGO@Algae-1:1 (82.3%) < NGO@Algae-1:3 (92.6%), respectively. The GO: Algae-1:3 and NGO: Algae-1:3 nanohybrids with a high microalgae content ratio exhibited high maximum removal, owing to the presence of more active sites within their lattice compared to their counterparts. On the other hand, pseudo-first-order, pseudo-second-order, intraparticle diffusion, Langmuir, and Freundlich models adequately simulated adsorption mechanisms, suggesting that the adsorption process involved a combination of external mass transfer and chemisorption, with electrostatic and complexation interactions being the dominant mechanisms for Cr(VI) removal. Additionally, GO@Algae-1:3 and NGO@Algae-1:3 displayed outstanding reusability. Therefore, these structured graphene@microalgae-based nanohybrids can simultaneously serve as adsorbents for Cr(VI) removal from wastewater and contaminated water sources.

Treating wastewater contaminated with toxic pollutants is becoming increasingly challenging for chemical processes and allied industries due to stringent environmental legislation and the focus on sustainability. Conventional wastewater treatment processes involve multiple stages with many unit operations and processes. To meet the growing technical, economical, and environmental sustainability needs, industries are interested in innovative processes and technologies offering compact, small-sized equipment with improved mass transport, heat, and momentum and reduced capital and operating expenses. The Process Intensification (PI) approach is gaining importance in wastewater treatment as it offers these advantages. Among the various separation methods involved in wastewater treatment, adsorption is considered to be one of the most robust methods in the series of treatments for removing low concentrations of contaminants. The design of adsorption columns with alternate bed geometries is desirable to meet the requirements of less installation cost, small footprint area, and compact adsorption columns without compromising performance. However, there is limited literature are available related to bed geometries (helical and tapered) other than the vertical fixed type. Therefore, a systematic literature review was performed with an interest in adsorption bed configuration and separation performance. Key technical aspects are explored, including the influence of bed geometry, adsorbent stratification (normal and reverse), and flow dynamics on mass transfer kinetics. Computational Fluid Dynamics (CFD) modeling employs governing equations such as the Advection-Dispersion Equation and Darcy’s Law, which aids in optimizing column performance. The incorporation of adsorption isotherms, such as Langmuir and Freundlich models, provides a deeper understanding of pollutant-adsorbent interactions. The study also evaluates economic aspects, comparing CAPEX and OPEX across configurations. Fixed beds feature low initial costs but face challenges like clogging and pressure drops. Tapered beds, while more expensive to fabricate, achieve efficient flow distribution and reduced adsorbent usage. With their intricate design, Helical coil columns demand higher manufacturing and operational investments but excel in compactness and efficiency. The review can help the researchers to leverage the potential of process intensification to enhance the adsorption column design and advance in wastewater treatment.