Nitrogen Adsorption Isotherms Research Articles

Fabrication of new in‐situ ternary nano/microcomposite LDH/Ag2O/Bayerite in trimetallic NiAg/Al layered double hydroxides for CO2 capture material

AbstractWe reported new in‐situ ternary nano/microcomposite layered double hydroxides/Ag2O/bayerite in trimetallic NiAg/Al layered double hydroxides (LDH) via hydrothermal technique; and characterization by powder X‐ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT‐IR), field emission scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS), and N2 adsorption‐desorption. The formation of bayerite and silver oxide species on the LDH nanosheet depended on the excess of Al3+ and Ag+ in the solution under alkaline and hydrothermal conditions. The nitrogen isotherm adsorption profile for all ternary composites exhibited uniformity with mesoporous and lamellar characteristics. The surface area of all the composites ranged from 81.17 to 150.23 m2. g−1, the Barret‐Joyner‐Halenda (BJH) pore volume from 0.22 to 0.27 cm3. g−1, and the average pore diameter ranged from 3.47 to 5.78 nm. All composites show a laminar plate‐like structure covered with elongated pieces. The particle size of the composites ranged from 54.86 to 115.96 nm, indicating the size changed from nano to microcomposite because of the different molar ratios of Ag and Ni in the solid. The ternary composite reveals CO2 capture activity with adsorption capacity ranging from 13.93 to 19.61 mmol g−1. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Coin‐Shaped Carbon Prepared with Cerbera manghas Fibers via Multistage Carbonization and Activation for High‐Performance Symmetrical Supercapacitors

AbstractSupercapacitor energy storage devices and activated carbon (AC) manufacturing materials for producing high‐performance supercapacitors have received extensive attention from researchers. Biomass‐based AC has been extensively studied due to its environmental friendliness, abundant availability, porous structure, and high specific surface area. This work focuses on developing biomass‐based carbon electrodes derived from Cerbera manghas fiber (CMF) with variations in carbonization temperature to obtain optimum supercapacitor cell performance. The prepared CMF AC was characterized using energy dispersive X‐ray, Fourier transform infrared, X‐ray diffraction, scanning electron microscope, and nitrogen isothermal adsorption–desorption. CMF AC with the optimum carbonization temperature (CMF‐600) produced a fibrous structure with a lot of mesoporous so that the specific surface area and specific capacitance were high, namely, 721.495 m2 g−1 and 221 F g−1 at scan rate 1 mV s−1, respectively. The results of this study indicate that selecting the optimum temperature can enhance the performance of supercapacitor cells and make AC based on CMF biomass potential for cheap and efficient energy storage applications.

Organo acid-activated clays for water treatment as removal agent of Eosin-Y: Properties, regeneration, and single batch design absorber

Organoclays have been proposed as efficient removal agents for colored wastewater treatment. In this study, organo-acid-activated clays were investigated for their ability to remove eosin Y dye molecules. Firstly, the clay was acid activated using sulfuric solution at 90 °C for overnight. Secondly, the resulting materials were treated by hexadecyltetramethylammonium bromide solutions to obtain organo-acid-activated clays. Several techniques were used, such as X-ray diffraction, carbon hydrogen nitrogen analysis, silicon-29 and carbon-13 solid-state nuclear magnetic resonance, and nitrogen adsorption isotherms. The cation exchange capacity values were reduced and the specific surface area values increased from 80.1 m2/g to 183.2 m2/g during the acid activation process. The resulting organo-acid-activated clays had a similar expansion of interlayer spacing of 3.90 nm with less intercalated hexadecyltetramethylammonium surfactants, ranging from 0.80 mmol/g to 1.22 mmol/g; 13C solid NMR indicated that the intercalated surfactants exhibited different degree of conformation. Many factors, including the solid dose, solution pH, amount of intercalated surfactants, and starting eosin-Y concentrations, were studied in relation to the removal capabilities of organo acid-activated clays. Based on the Langmuir model, the removal capacity of the organo acid-activated clays ranged from a minimum of 43.5 mg/g to a maximum of 79.3 mg/g, dependent on the surfactant quantities and acid activation degree. , and the pH. The removal percentage of eosin-Y was increased from 50.5 % to 80.8 % by treating the organo acid-activated clay with HCl solution before the removal procedure. Regeneration and reuse of two selected organo acid-activated clays were carried out for seven successive cycles, and a reduction in the initial efficiency was in the range of 26.4 %–30.1 %. However, for organoclay (without acid activation), approximately 52.1 % efficiency was maintained. Using the Langmuir model and mass balance equations, a single-stage adsorber design was suggested for different dye volumes at a constant starting concentration.

Facile synthesis of silver nanoparticles loaded spent cathodic Lithium-Ion battery components for enhanced bifunctional photocatalysis: Investigating the influence of magnetic properties

Due to resource depletion and environmental concerns regarding battery disposal, it is becoming more essential to recycle valuable metals from wasted lithium-ion batteries (LIBs). A novel approach is proposed in this study for the efficient bifunctional photocatalysis of LIBs components by integrating AgNPs in an environmentally sustainable manner via a sustainable hydrothermal process. The HRTEM and image mapping reveal a carbon matrix (C/Li3Fe5O8/Ag) with a dispersed arrangement of AgNPs (5–10 wt%). By acting as a reducing agent, graphite plays a crucial role in the transformation of Ag+ ions into AgNPs. The homogenous distribution of Ag NPs observed in the high-resolution TEM images further supports the role of graphite in the modification and decoration of Ag NPs onto the surface of the extracted spent cathode sample. The detection of a spot matching the (200) plane of Ag in the selected area electron diffraction (SAED) measurements confirms the successful formation of AgNPs. Additionally, the presence of a ring corresponding to the (110) plane of graphite in the SAED measurements suggests the coexistence of graphite with AgNPs in the composite heterostructures. The nitrogen adsorption isotherm analysis was conducted to explore the physical properties of the AgNPs@LIBs nanocomposite, providing valuable insights into its pore size distribution and Brunauer–Emmett–Teller (BET) surface area. The nanocomposites exhibited paramagnetic behavior, as revealed by vibrational sample magnetometer (VSM) measurements, with saturation magnetization values ranging from 76.3 × 10−3 to 36.13 × 10−3 emu/g. The study involved the photodegradation of oxytetracycline (OTC), a representative pharmaceutical pollutant, along with an investigation into the potential of Cr(VI) reduction. Under optimal component ratios, a significant improvement in pollutant removal was achieved under UV radiation, reaching up to 75 % for OTC and 80 % for Cr(VI), highlighting the efficiency of the process.

Enhancing antimicrobial efficacy: 8-Hydroxyquinoline incorporation into metal-organic frameworks with iron ion coupling

The antimicrobial properties of 8-Hydroxyquinoline (8-Hq), a small organic compound known for its metal-chelating capabilities, hold significant promise. However, its limited solubility in water poses a challenge for practical applications. In this study, we address this limitation by augmenting the antimicrobial efficacy of 8-Hq through its integration into the metal-organic framework UiO-66 (named 8-Hq@UiO-66) and coupling it with iron ions (designated as Fe/8-Hq@UiO-66) via an adsorption process. The sorption isotherm and adsorption kinetics were meticulously examined using Langmuir's adsorption model and the pseudo-second-order kinetic model. Material characterization techniques including powder X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption isotherms, ultraviolet–visible spectroscopy, and photoluminescence spectroscopy revealed the coordination of zirconium clusters and iron with the nitrogen and hydroxyl groups of 8-Hq, respectively. Furthermore, our investigation into metal ion adsorption demonstrated that the 8-Hq@UiO-66 composite displayed a notable selectivity for iron ions over other metal ions in aqueous media. Under optimized conditions, the adsorption capacity for iron ions ranged from approximately 34–46 mg g−1. Importantly, the Fe/8-Hq@UiO-66 composite exhibited potent antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. These findings underscore the potential of incorporating 8-Hq into porous metal-organic frameworks and coupling it with iron ions to enhance its antimicrobial efficacy.

Construction of a microscopic molecular model of Hongqingliang long-flame coal for potential application in adsorption simulation

The present study aims to develop a tailored microscopic molecular model for analyzing the adsorption properties of Hongqingliang (HQL) coal. The chemical structure of the coal was thoroughly analyzed through the utilization of various techniques, including elemental analysis, Carbon-13 Nuclear Magnetic Resonance spectroscopy (13C NMR), X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FTIR). Subsequently, a three-dimensional periodic microscopic molecular model for HQL coal was constructed, followed by the development of a 4 nm fracture pore model. To validate the modeling approach, a comprehensive comparative analysis was conducted utilizing nitrogen adsorption isotherms at 77.35 K. The results indicate that the amorphous cell model constructed in Material Studio solely comprises micropores narrower than 1 nm, making it unsuitable for simulating coal's pore characteristics. Conversely, the nitrogen adsorption isotherm of the 4 nm fracture pore model matches actual results. Therefore, to analyze the pore adsorption characteristics of coal, it is necessary to utilize the amorphous cell model to construct a characteristic pore model for coal.

Structure and properties of self-assembled graphene oxide–detonation nanodiamond composites

The properties of graphene oxide–detonation nanodiamond composites obtained as a result of heterocoagulation of graphene oxide and hydrogenated detonation nanodiamonds in aqueous mixtures were studied. The resulting composites with different proportions of graphene oxide and detonation nanodiamond were subjected to drying and subsequent heat treatment in a vacuum, converting graphene oxide into graphene. The structure of the composites was studied using electron microscopy and Raman spectroscopy. The specific surface area and porosity of the obtained samples were studied by analyzing nitrogen adsorption isotherms. A model for the composite formation and a possible technology for producing a material based on it with different specific surface area values and pore structure are proposed. It is shown, that the largest possible specific surface area of two-component structures of the «DND/GO» type does not exceed 500 m2·g−1. It was also concluded that it is necessary to achieve a uniform distribution of detonation nanodiamond particles over the surface of graphene sheets.

Simultaneous impregnation and microencapsulation of CaCl2 using silica gel and methyl cellulose for thermal energy storage applications

Thermal energy storage utilizing the adsorption of moisture from air is a promising energy storage technology due to its high energy density and minimum heat losses. Salt hydrates and salt hydrate composites, such as calcium chloride (CaCl2) and CaCl2-based composites, have shown favourable energy storage properties in this area of research. However, these materials have shown issues with stability due to swelling and deliquescence. In this work, CaCl2 was stabilized using three methods: impregnation into silica gel, encapsulation in methyl cellulose, and both impregnation and encapsulation stabilization techniques used simultaneously. Therefore, three CaCl2-based composites were synthesized. For the first composite, silica gel was impregnated with CaCl2. For the second composite, CaCl2 was encapsulated by methyl cellulose. For the third composite, silica gel was impregnated with CaCl2 and the CaCl2 was encapsulated with methyl cellulose. These samples were structurally characterized using scanning electron microscopy as well as Brunauer-Emmett-Teller (BET) to determine surface area, pore size distribution and nitrogen adsorption isotherms at 77 K. Water vapour adsorption isotherms were also determined at 25 °C for different relative humidities by dynamic vapor sorption (DVS). Similarly, LiCl-based composites were also synthesized and examined in this work, but issues of deliquescence, swelling, and agglomeration made the materials impractical to work with. To determine the prepared materials’ thermal energy storage performance, 2–6 g of each sample was tested in a lab-scale apparatus. This process uses the exothermic adsorption of moisture from ambient air in an open thermal energy storage system. The CaCl2 impregnated silica gel that was encapsulated in methyl cellulose showed reasonably high stability and energy storage performance after 3 hydration and dehydration cycles with minimum agglomeration. An energy storage density of 241 kWh/m3 (0.87 GJ/m3) and specific energy of 630 Wh/kg (2268 kJ/kg) was achieved with this material for 90% inlet relative humidity after a regeneration at 90 °C.

Surface-Constrained Metropolis Monte Carlo: Simulation of Reactions on Triply Periodic Minimal Surfaces.

Triply periodic minimal surfaces (TPMS) inspired by nature serve as a foundation for developing novel nanomaterials, such as templated silicas, graphene sponges, and schwarzites, with customizable optical, poroelastic, adsorptive, catalytic, and other properties. Computer simulations of reactions on TPMS using reactive intermolecular potentials hold great promise for constructing and screening potential TPMS with the desired properties. Here, we developed an off-lattice, surface-constrained Metropolis Monte Carlo (SC-MMC) algorithm that utilized a temperature quench process. The presented SC-MMC algorithm was used to investigate the process of graphitization reactions on the Schwarz primitive, Schwarz diamond, and Schoen gyroid TPMS, all with a cubic lattice parameter of 8 nm. We show that the optimized carbon TPMS exhibits a low energy, approximately -7.1 eV/atom, comparable to that of graphite and diamond crystals, along with a variety of topological defects. Furthermore, these structures showcase extensive and smooth surfaces characterized by a negative discrete Gaussian curvature, a distinctive feature indicative of an interconnected morphology. They possess specific surface areas of ∼2700 m2/g, comparable to graphene, and exhibit a significant porosity of around 90%. The theoretical X-ray correlation functions and nitrogen adsorption isotherms confirm that the constructed TPMS exhibit remarkably similar surface properties, although the pore space topology varies significantly.

Pore Structure and Fractal Dimension in Marine Mature Silicon-Rich Shale of the Dalong Formation in Western Hubei.

How shale reservoirs and gas contents are affected by the pore structure of shale is very important. Low-temperature nitrogen isothermal adsorption experiments were conducted by us to investigate the pore structure of the Dalong Formation shale. We measured the specific surface area and fractal dimension of the pores and also considered the mineral fraction and organic matter content of the rock. The results show that the Dalong Formation shale contains a lot of organic carbon, with a total organic carbon (TOC) value between 1.20 and 10.82% (mean: 5.02%). Quartz and clay minerals are the main components of the shale, with quartz making up 40.30 to 85.60% (mean: 67.21%) and clay minerals making up 9.20 to 34.10% (mean: 20.26%) of the shale. Most of the pore space in the shale of the Dalong Formation is formed by intragranular and intergranular pores, organic matter pores, and some microfissures. The pore structure is complex, with parallel-plate and ink-bottle pores being the most common types. Most of the pores are 0-2 or 2-5 nm in size. D1 and D2 are the fractal dimensions, with averages of 2.66 and 2.81, respectively. D1 can range from 2.55 to 2.78, while D2 can range from 2.66 to 2.94. The TOC content, mineral composition, and pore structure characteristics determine the fractal dimension. Higher levels of the TOC content, quartz mineral content, and specific pore surface area result in a higher fractal dimension, while higher levels of feldspar content result in a lower one. There is no apparent correlation to clay minerals or other mineral compositions.

Kinetic and mechanistic study of CO2 adsorption on activated hydrochars

Four activated hydrochars (AHCs) were obtained by hydrothermal carbonization of pine sawdust followed by physical and chemical activation in mild conditions. The effects of the activating agents on the porous structure of AHCs were analysed using nitrogen adsorption isotherms. Their CO2 adsorption capacity was assessed by means of carbon dioxide isotherms at 25 and 50 ºC and thermogravimetry, and compared with a commercial activated carbon (AC). SBET values greater than 2000 m2/g were obtained. A narrow micropore volume of 0.392 cm3/g was obtained for the hydrochar activated with KHCO3. The highest CO2 uptake of 3.3 mmol/g (145.2 mg/g) was obtained at room temperature (25 ºC) for the hydrochar activated with KHCO3. Three kinetic models (pseudo-first, pseudo-second and fractional order Avrami’s models) were used to examine the rate parameters of CO2 uptake, with Avrami’s model giving the most accurate prediction of CO2 adsorption. The intraparticle diffusion model and Boyd’s film-diffusion model were applied to identify the CO2 adsorption mechanism.

Temperature Evolution of Sorbonorit-4 Methane-Induced Deformation through the Eyes of Classical Density Functional Theory.

Activated carbons are widely used industrial adsorbents due to their attractive sorption properties. Although extensive research on activated carbon has been carried out for several centuries, some aspects of the adsorption-induced deformation of activated carbon remain unclear. The puzzling temperature dependence of the methane-induced deformation of activated carbon is investigated in the present work. Several experimental studies have shown that an increase in temperature leads to a reversal of the sign of adsorption strain at low pressures, i.e., the contraction turns into an expansion. Here we suggest a possible explanation for this effect by applying classical density functional theory to the adsorption isotherms of nitrogen, carbon dioxide, and methane as well as to methane-induced deformation isotherms. Our calculations show that the adsorption stress generated in the smallest pores predominates at higher temperatures and leads to material swelling. Lowering the temperature, on the other hand, leads to a predominance of larger pores and compression of the activated carbon material. We also investigated the possibility of determining the pore size distribution from methane-induced deformation and adsorption data and the predictive capabilities of our theoretical approach.

Reservoir characteristics and formation model of Upper Carboniferous bauxite series in eastern Ordos Basin, NW China

Through core observation, thin section identification, X-ray diffraction analysis, scanning electron microscopy, and low-temperature nitrogen adsorption and isothermal adsorption experiments, the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs. A petrological nomenclature and classification scheme for bauxitic rocks based on three units (aluminum hydroxides, iron minerals and clay minerals) is proposed. It is found that bauxitic mudstone is in the form of dense massive and clastic structures, while the (clayey) bauxite is of dense massive, pisolite, oolite, porous soil and clastic structures. Both bauxitic mudstone and bauxite reservoirs develop dissolution pores, intercrystalline pores, and microfractures as the dominant gas storage space, with the porosity less than 10% and mesopores in dominance. The bauxite series in the North China Craton can be divided into five sections, i.e., ferrilite (Shanxi-style iron ore, section A), bauxitic mudstone (section B), bauxite (section C), bauxite mudstone (debris-containing, section D) and dark mudstone-coal section (section E). The burrow/funnel filling, lenticular, layered/massive bauxite deposits occur separately in the karst platforms, gentle slopes and low-lying areas. The karst platforms and gentle slopes are conducive to surface water leaching, with strong karstification, well-developed pores, large reservoir thickness and good physical properties, but poor strata continuity. The low-lying areas have poor physical properties but relatively continuous and stable reservoirs. The gas enrichment in bauxites is jointly controlled by source rock, reservoir rock and fractures. This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.

Stable "snow lantern-like" aggregates of silicon nanoparticles suitable as a drug delivery platform.

Nanomedicine is a growing field where development of novel organic and inorganic materials is essential to meet the complex requirements for drug delivery. This includes biocompatibility, suitability for surface modifications, biodegradability, and stability sufficient to carry a drug payload through various tissues for the desired timespan. Porous silicon nanoparticles (pSi NP) are shown to have several beneficial traits in drug delivery in addition to a porous structure to maximize drug loading. The conventional synthesis of pSi NP using electrochemical etching is costly, time-consuming and requires large quantities of highly toxic hydrofluoric acid (HF). As such this research attempted a novel method to address these limitations. Mesoporous silicon nanoparticles were prepared by centrifugal Chemical Vapor Deposition (cCVD) without the use of HF. This process generated aggregates consisting of multiple primary particles fused into each other, similar to snowballs fused together in a snow-lantern (snowball pyramid). Our results demonstrated that the cCVD Si particles were versatile in terms of surface chemistry, colloidal stability, degradability, minimization of acute in vitro toxicity, and modulation of drug release. Dynamic light scattering, scanning electron microscopy, and cryogenic nitrogen adsorption isotherm measurements confirmed the overall size (210 nm), morphology, and pore size (14-16 nm) of the prepared materials. Agglomeration in phosphate-buffered saline (PBS) was minimized by PEGylation by a two-step grafting procedure that employed a primary amine linker. Finally, the release rate of a model drug, hydrocortisone, was evaluated with both PEGylated and pristine particles. Conclusively, these snow-lantern cCVD Si particles do indeed appear suitable for drug delivery.

Ordered mesoporous silicas for potential applications in solid vaccine formulations

In an effort to develop efficient vaccine formulations, the use of ordered mesoporous silica (SBA-15) as an antigen carrier has been investigated. SBA-15 has required properties such as high surface area and pore volume, including narrow pore size distribution to protect antigens inside its matrix. This study aimed to examine the impact of solvent removal methods, specifically freeze-drying and evaporation on the intrinsic properties of an immunogenic complex. The immunogenic complexes, synthesized and incorporated with BSA, were characterized by various physicochemical techniques. Small Angle X-ray Scattering measurements revealed the characteristic reflections associated to pure SBA-15, indicating the preservation of the silica mesostructured following BSA incorporation and the formation of BSA aggregates within the macropore region. Nitrogen Adsorption Isotherm measurements demonstrated a decrease in surface area and pore volume for all samples, indicating that the BSA was incorporated into the SBA-15 matrix. Fluorescence spectroscopy evidenced that the tryptophan residues in BSA inside SBA-15 or in solution displayed similar spectra, showing the preservation of the aromatic residues’ environment. The Circular Dichroism spectra of BSA in both conditions suggest the preservation of its native secondary structure after the encapsulation process. The immunogenic analysis with the detection of anti-BSA IgG did not give any significant difference between the non-dried, freeze-dried or evaporated groups. However, all groups containing BSA and SBA-15 showed results almost three times higher than the groups with pure BSA (control group). These facts indicate that none of the BSA incorporation methods interfered with the immunogenicity of the complex. In particular, the freeze-dried process is regularly used in the pharmaceutical industry, therefore its adequacy to produce immunogenic complexes was proved Furthermore, the results showed that SBA-15 increased the immunogenic activity of BSA.

The Influence of Silica Dioxide in the Electrocatalytic Performances of rGO/Fe<sub>3</sub>O<sub>4</sub> as Oxygen Reduction Electrocatalyst

In this study, synthesis of reduced graphene oxide-iron oxide-silica dioxide (rGO/Fe3O4/SiO2) was done through a facile chemical process. Physical characterization was carried out as such Fourier transform infrared spectroscopy (FTIR) which confirmed the presence of silica peak in the spectrum of rGO/Fe3O4/SiO2, while RAMAN displayed the vibrational bands of carbon materials studied. Results of SEM-EDX and TEM confirmed the unification of SiO2 on rGO/Fe3O4 nanocomposite with difference in morphologic structure. X-ray diffraction (XRD) analysis exhibited that addition of SiO2 increased the crystalline size of the nanocomposite. Nitrogen adsorption isotherm analysis describes the nanocomposites fall in the mesopore region. The nanocomposite was then drop-casted on the surface of glassy carbon electrode (GCE) for fabrication of the electrode which denoted as rGO/Fe3O4/SiO2/GCE. Electrochemical characterization of modified electrode was studied using electron impedance spectroscopy (EIS), which showed the minimal resistance charge transfer. Oxygen reduction reaction analysis shows that electrocatalytic reduction of oxygen was excellent with four-electron transfer when calculated using Randles-Sevcik equation. All the analysis was compared to the nanocomposites without the addition of silica oxide (rGO/Fe3O4). This work proves that addition of nanoparticle in a compound as a matrix improves the oxygen reduction potential of rGO/Fe3O4/SiO2/GCE composite.

Synthesis and Characterization of Two Novel Naphthalenediimide/Zinc Phosphonate Crystalline Materials Precipitated from Different Solvents.

Hybrid naphthalenediimide/zinc phosphonate materials (NDI/Zn) were prepared by mixing solutions of N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) and zinc nitrate, resulting in the precipitation of the desired compounds. Samples precipitated from water and N,N-dimethylformamide (DMF) were produced. The obtained samples had the expected elemental composition, and the presence of naphthalenediimides (NDI) was ascertained by infrared and UV-visible spectroscopy. All the samples were crystalline, according to powder X-ray diffraction. Nitrogen adsorption isotherms showed the presence of porosity in the NDI/Zn samples. Mesopores with a diameter = 4.1 nm were present in the sample from DMF, with total pore volume reaching 0.13 cm3/g.

Liquid-phase adsorption of nitrogen compounds from model diesel fuel on activated carbons

One of the great challenges in deep hydrodesulfurization (HDS) to produce ultra-low-sulfur diesel (ULSD) is the coexisting heterocyclic nitrogen-containing compounds in middle distillates, which significantly inhibit the HDS reactions. This study investigates various activated carbon (AC) samples for selectively removing nitrogen compounds from a model diesel fuel through adsorption. The physical and chemical properties of the AC samples were characterized using low-temperature N2 adsorption–desorption, SEM–EDS, and FT-IR to explore their impact on the adsorption performance. The results indicate that the adsorption performance is influenced not only by the surface area and by the number of oxygen-containing functional groups on the surface but also by the pore diameter distribution. Among all AC samples tested, AC-W exhibited the highest adsorption capacity, achieving a nitrogen removal rate of 97.8% with the addition of 10 wt.% of AC-W. The adsorption capacity was approximately 24.0 mg-N/g-A at a nitrogen equilibrium concentration of 200 ppmw. The adsorption isotherms for total nitrogen and individual nitrogen compounds in the fuel over AC can be described well by the Freundlich isotherm model. An approach for improving the ADN performance of AC is discussed based on the findings in this study.

Molecular Simulation of Nitrogen Adsorption in Multidimensional Nanopores and New Insights into the Inversion of Pore Size Distribution for Gas Shale

Low-temperature nitrogen adsorption is a widely used method for the research and evaluation of gas shale’s pore structure. The existing interpretation method, utilizing gas adsorption isotherms to obtain pore size distribution (PSD), is always based on the one-dimensional geometry model, while the void space of gas shale has strong multi-dimensional characteristics. It is necessary to investigate the nitrogen condensation and evaporation behavior in multidimensional structures. In this study, a series of two-dimensional and three-dimensional models based on ink-bottle pores were constructed. A hybrid molecular simulation approach combining grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) is proposed to simulate the low-temperature nitrogen adsorption isotherms. Three aspects have been analyzed in detail. Compared with the conventional understanding that the threshold of cavitation in the ink-bottle pore only relates to throat diameter, this study discloses a wider and more comprehensive range of conditions of cavitation that considers both the throat length and diameter. As pore spaces of shale samples consist of many complex interconnected pores, the multi-stage ink-bottle pore model is more suitable than the single ink-bottle pore model to similarly reproduce the wider cavitation pressure range. A more universal parameter is proposed that quantitatively unifies the influence of cavity diameter and length on condensation pressure and has good applicability in cavities with different shapes. This work quantitatively studies the nitrogen adsorption isotherms of three-dimensional complex nanopore structures using molecular simulation and provides a reasonable explanation for the low-temperature nitrogen adsorption isotherms of gas shale.

Nitrogen-Doped Starbons®: Methodology Development and Carbon Dioxide Capture Capability.

Five nitrogen sources (glycine, β-alanine, urea, melamine and nicotinamide) and three heating methods (thermal, monomodal microwave and multimodal microwave) are used to prepare nitrogen-doped Starbons® derived from starch. The materials are initially produced at 250-300 °C (SNx 300y ), then heated in vacuo to 800 °C to produce nitrogen-doped SNx 800y 's. Melamine gives the highest nitrogen incorporation without destroying the Starbon® pore structure and the microwave heating methods give higher nitrogen incorporations than thermal heating. The carbon dioxide adsorption capacities of the nitrogen-doped Starbons® determined gravimetrically, in many cases exceed those of S300 and S800. The carbon dioxide, nitrogen and methane adsorption isotherms of the most promising materials are measured volumetrically. Most of the nitrogen-doped materials show higher carbon dioxide adsorption capacities than S800, but lower methane and nitrogen adsorption capacities. As a result, the nitrogen-doped Starbons® exhibit significantly enhanced carbon dioxide versus nitrogen and methane versus nitrogen selectivities compared to S800.