Phase Adsorption Research Articles

Evaluation of anion exchange resin for sorption of selenium (IV) from aqueous solutions

In this work, selenium (IV) ions were adsorbed from aqueous solutions by the strongly basic anion exchange resin Amberlite IRA-400. The morphology of the resin before and after Se(IV) sorption was investigated using different techniques such as energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). To determine the ideal sorption conditions, a batch approach was used to examine the variables affecting Se(IV) sorption performance, including pH, shaking time, adsorbent dosage, initial metal ion concentration, and temperature. The results showed the optimal parameters for the highest percentage of selenium (80.25%) at an initial concentration of 100.0 mg L−1, pH 3.0, the adsorbent dosage of 10.0 mg, and the shaking time of 60.0 min. According to the experimental findings, the sorption process was satisfactorily explained by the pseudo-second-order kinetic model. The maximum adsorption capacity at pH 3.0 was 18.52 mg g−1, and the adsorption rather well followed the Langmuir adsorption isotherm. Moreover, exothermic and spontaneous sorption reaction was the result of thermodynamic properties (negativity of both ΔG° and ΔH°). The adsorption phase's random distribution of the resin-solution interface is indicated by the positive value of ΔSo. Finally, the desorption study was performed using different concentrations of desorbing agents; HNO3, HCl, and sodium acetate. The results illustrated that the effective desorbing agent was 1.0 mol L-1 HNO3, with desorption efficiency reaching about 96.4%. Finally, the Amberlite IRA-400 demonstrated excellent adsorption–desorption behavior over five times, suggesting that the Amberlite IRA-400 could be an effective candidate for the sorption of Se(IV) from several metal ions that occur in fission products.

Thermal Desorption Hyphenated to Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry for Trace Analysis in Raw Renewable Gases-Application to Hydrothermal Gasification.

In the context of the energy transition, European countries pursue the common goal of increasing the share of renewable gases (from anaerobic digestion, pyrogasification, and hydrothermal gasification for instance) in the gas mix. Although produced gases are mainly composed of methane after upgrading, impurities of various natures and quantities may also be present in the produced raw gases and still after upgrading, including volatile organic compounds (VOCs) at trace levels that may have an impact on different stages of the gas chain even at low concentrations. These new renewable and/or low-carbon gases imply the need to develop new analytical tools to deeply characterize them, and thus fully manage their integration into the gas value chain. In this study focused on VOC analysis, a sampling approach using pre-concentration on an adsorbent phase was developed for gas sampling to ensure rapid collection, requiring only a small volume (≈100mL). Traces were then analyzed by thermal desorption hyphenated to a comprehensive two-dimensional gas chromatography time-of-flight mass spectrometer. After identifying the compounds, a semi-quantification method was developed to provide an estimation of the concentration of VOCs for each chemical family. The method was first developed on a biomethane sample before being successfully applied to a raw gas produced by hydrothermal gasification, in which around 250 compounds were detected at a trace level (total concentration equivalent at 200µg/L).

Facile Hydrothermal Assisted Basic Catalyzed Sol Gel Synthesis for Mesoporous Silica Nanoparticle from Alkali Silicate Solutions Using Dual Structural Templates.

This work presents a novel hydrothermally aided sol-gel method for preparation of mesoporous silica nanoparticles (MSNs) with a narrow particle size distribution and varied pore sizes. The method was carried out in alkaline media in presence of polyethylene glycol (PEG) and cetyltrimethylammonium chloride (CTAC) as dual templates and permitted the synthesis of spherical mesoporous silica with a high surface area (1011.42 m2/g). The MSN materials were characterized by FTIR, Thermogravimetric (TG), Nitrogen adsorption and desorption and Field emission scanning electron microscopic analysis (FESEM). The materials feasibility as solid phase adsorbent has been demonstrated using cationic dyes; Rhodamine B (RB) and methylene blue (MB) as models. Due to the large surface area and variable pore width, the adsorption behaviors toward cationic dyes showed outstanding removal efficiency and a rapid sorption rate. The adsorption isotherms of RB and MB were well-fitted to the Langmuir and Freundlich models, while the kinetic behaviours adhered closely to the pseudo-second-order pattern. The maximum adsorption capacities were determined to be 256 mg/g for MB and 110.3 mg/g for RB. The findings suggest that MSNs hold significant potential as solid-phase nanosorbents for the extraction and purification of dye pollutants, particularly in the analysis and treatment of effluents containing cationic dyes.

One Receptor Show: Evaluation of Feature Extraction Methods for a Single Gas Sensor Based on α-Tocopherol-Substituted Zinc Phthalocyanine.

A consistent part of gas sensor research activities aims to improve sensing performances by synthesizing new sensing materials, improving the selection of elements in arrays, and optimizing the feature extraction and classification algorithms. This paper combines most of these aspects to confer selectivity to a low-selectivity sensor by using feature extraction algorithms applied to the sensor response kinetics. Several algorithms were employed to represent the kinetic behavior of the sensor response during the adsorption and desorption phases. In detail, we utilized fitting functions, dynamic descriptors, and a mirrored fast Fourier transform (FFT) to extrapolate information from the desorption and adsorption phases. As sensitive material, we synthesized as a receptor a novel Zn(II) phthalocyanine derivative bearing long aliphatic chains, namely, 4-[2,5,7,8-tetramethyl-2-(4,8,12-trimethyl-tridecyl)-chroman-6-yloxy] units that allow good solubilization of the complex in most of the solvents tested and confer a large set of sites to potentially interact with volatile compound (VC) analytes by different portions of the molecular skeleton. After deposition onto a quartz crystal microbalance (QMB) transducer, this single sensor has been tested to recognize five VCs as chemical probes of different chemical families. Remarkably, the results disclose that responses at equilibrium are mainly correlated with nonspecific interactions, while the kinetic parameters are more correlated with stronger and more specific interactions. Finally, the desorption phases bear a higher information content about the chemical identities of the compounds. Eventually, features extracted by a modified version of the FFT obtained the highest clustering (principal component analysis) and classification performances (95% classification accuracy with linear discriminant analysis), suggesting the possibility of developing virtual electronic noses based on a single sensor and a minimal set of descriptors.

Isolation and characterization of bacteriophages targeting methicillin-resistant Staphylococcus aureus (MRSA) from burn patients and sewage water: a genomic and proteomic study.

The spectrum of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) ranges from minor conditions to potentially life-threatening diseases. The rising antibiotic resistance in MRSA often leads to treatment failures, underscoring the urgent need for novel eradication strategies. This study focuses on isolating MRSA from burn patients, determining its antibiogram profile, and isolating and characterizing bacteriophages from sewage water that target MRSA, alongside conducting genomic analysis of the phages. A total of 70 samples were collected from burn patients, with MRSA identification and characterization performed using a combination of biochemical and molecular techniques, as well as antibiotic sensitivity testing. Based on host range analysis, a specific phage (phage-3) was selected for detailed characterization, including proteomic analysis, genetic mapping, phylogenetic studies, and analysis of open reading frames (ORFs) and motifs. The prevalence of MRSA in the samples was found to be 28.6%. Antibiotic susceptibility tests indicated that 94% of the MRSA isolates were sensitive to tobramycin and gentamicin, while vancomycin exhibited the lowest sensitivity, with only 2% effectiveness. Using the soft agar overlay method, three bacteriophages (phage-1, phage-2, and phage-3) were successfully isolated from sewage water. Among these, phage-3 exhibited the broadest host range. Further analysis showed that phage-3 demonstrated optimal activity at pH levels between 6 and 8, and within a temperature range of 20-40°C. Phage-3 also displayed a rapid adsorption phase within the first 0-5min, and its one-step growth curve revealed a latent period lasting up to 30min, followed by a significant increase in titer from 30 to 50min. Proteomic analysis of phage-3 identified the presence of 33kDa and 65kDa proteins. Phylogenetic analysis showed that phage-3 shares 96.6% similarity with Mammallicoccus phage vB_MscM-PMS3. The ORF analysis identified 80 potential ORFs within the phage's entire genome.

Coupling coagulation-flocculation-sedimentation with adsorption on biosorbent (Corncob) for the removal of textile dyes from aqueous solutions

This study evaluated the efficacy of combining the coagulation-flocculation-sedimentation (CFS) process with adsorption onto corncob biosorbent for the removal of textile dyes from aqueous solutions. The synthetic dyes tested were Bemacron Blue RS 01 (BB-RS01), a disperse dye, and Bemacid Marine N-5R (BM-N5R), an acid dye. Aluminum sulfate (Al₂ (SO₄)₃·18H₂O) was used as the coagulant, followed by superfloc 8396 as the flocculant. During coagulation, optimal parameters included coagulant doses (50-600 mg/L), flocculant doses (30-125 mg/L), and pH (2-11). For the adsorption phase, factors such as pH (2-11), temperature (25-45°C), contact time (0-480 min), and initial dye concentration (15-100 mg/L) were investigated. The corncob was characterized using FTIR, SEM, and pHpzc. Both Langmuir and Freundlich isotherm models were applied, with the Langmuir model demonstrating the best fit (0.92 < R² < 0.96). The CFS process achieved dye removal rates of 95.1% for BB-RS01 at pH 8 and 92.3% for BM-N5R at pH 6.5. Adsorption efficiency varied with solution pH, yielding removal rates of 26.19% for BB-RS01 at pH 6 and 7.69% for BM-N5R at pH 4. Maximum adsorption capacities were 99.5 mg/g for BB-RS01 and 46.08 mg/g for BM-N5R. This study demonstrates the effectiveness of coupling CFS with corncob adsorption for economical dye removal, utilizing agricultural waste as a biosorbent.

Stability Assessment through HPTLC for Concurrent Assessment of Azelnidipine and Telmisartan in Mass and Integrated Tablet Drug Formulation

This study aims to estimate the stability assessment through HPTLC for the concurrent assessment of (±)3-(1-diphenylmethylazetidin-3-yl)5-isopropyl-2-amino-1,4-dihydro-6-methyl-4-(3-nitrophenyl)-3,5-pyridine dicarboxylate (Azelnidipine) and 2-[4-[[4-methyl-6-(1-methylbenzimidazol-2-yl)-2-propylbenzimidazol-1-yl]methyl] phenyl]benzoic acid (Telmisartan) in combined tablet formulation, a new HPTLC approach devised and validated that is simple, quick, precise, selective, and accurate stability suggesting. The adsorbent phase used is previously coated with a silica pack on TLC aluminum plates with 60F-254 using Chloroform: Ethyl acetate (5:5 v/v) of a total of 10 ml as the mobile phase. Both Azelnidipine (Rf 0.70) and Telmisartan (Rf 0.17), at 254 nm, densitometric scanning was performed in the reflectance absorptivity mode. In the linearity range of 1-6 μg/ml for Azelnidipine and 5-30 μg/ml for Telmisartan, the calibration graph demonstrated satisfactory linearity with r2 = 0.9967 and 0.9966, respectively. Azelnidipine and Telmisartan percentage assays were discovered to be 98.87 and 100.17. The percent RSD for intraday AZL and TLM experiments was 0.0184 and 0.0068. The percent RSD for AZL and TLM interday trials was discovered as 0.0126 and 0.0068. The LOD for AZL and TLM was discovered as 910 ng/mark and 4570 ng/mark. AZL and TLM were discovered to have LOQs of 2763 ng/mark and 13850 ng/mark, respectively. According to the ICH guidelines, drugs were exposed to acidic, basic, oxidative, photo, and heat-activated degradation. The medication degrades in acidic, basic, oxidative and heat environments but not in light or neutral environments (water). This procedure can be used to efficiently isolate the drug substance from its degradation products and this is used to indicate strength and stability.. KEYWORDS :Azelnidipine, Telmisartan, HPTLC, UV-visible spectroscopy, Validation, Stability studies.

Emerging and legacy organophosphate flame retardants in the tropical estuarine food web: Do they exhibit similar bioaccumulation patterns, trophic partitioning and dietary exposure?

Emerging organophosphate flame retardants (E-OPFRs) are a new class of pollutants that have attracted increasing attention, but their bioaccumulation patterns and trophodynamic behaviors in aquatic food webs still need to be validated by comparison with legacy OPFRs (L-OPFRs). In this study, we simultaneously investigated the bioaccumulation, trophic transfer, and dietary exposure of 8 E-OPFRs and 10 L-OPFRs in a tropical estuarine food web from Hainan Island, China. Notably, the Σ10L-OPFRs concentration (16.1-1.18 × 105 lipid weight (lw)) was significantly greater than that of Σ8E-OPFRs (nondetectable (nd) - 2.82 × 103 ng/g lw) among the investigated organisms, and they both exhibited similar trends: fish<mollusk<crustacean. Significant biomagnification was found only for triphenyl phosphate (TPHP, an L-OPFR) with a trophic magnification factor (TMF) of 1.55, whereas other E- and L-OPFRs showed limited trophic transfer potential. Storage lipid was the dominant adsorption phase for most E-OPFRs and L-OPFRs on the basis of the fugacity approach. The water content controls the main trophic partitioning for the L-OPFRs of triethyl phosphate (TEP) and tris(2-chloroethyl) phosphate (TCEP) in the food web. Storage lipid and structure protein are equally important for 2,2-bis(chloromethyl)-propane-1,3-diyltetrakis(2-chloroethyl) biphosphate (V6, an emerging OPFR). The investigation of metabolites and the biotransformation rate (K M) confirmed the role of biotransformation in offsetting trophic transfer for both legacy and emerging OPFRs. Furthermore, the hazard quotients (HQs) were found to be <1 for South China residents for both the E- and L-OPFRs, but the health risks of these two kinds of OPFRs should be given sustained attention.

Analyzing the Roles of Copper in Carbon Capture and Sequestration Using Mean Field Density Functional Theory and Scanning Transmission Electron Microscopy

Exploring the role of Copper (Cu) in carbon capture and sequestration presents a rich area for research, including but not limited to Nanostructure copper materials, Copper-based hybrid materials, Copper-based electrocatalysts, copper in biomimetic systems, Copper-based membranes for gas separation, Copper in carbon mineralization, Copper in photochemical conversion, and copper-based direct air capture technologies that can enhance the capture and conversion. In this regard, efficient methods to characterize the role of Cu in carbon sequestration processes should be developed computationally and experimentally.Among the computational methods, the mean-field density functional theory (DFT) is capable of calculating the adsorption isotherms of on Cu-containing materials, such as Cu nanoparticles or surfaces. By modeling the existing interactions between molecules and Cu sites using classical force fields or empirical potentials, it is possible to estimate the adsorption capacity, energetics, and equilibrium behavior of Cu-based adsorbents under various temperature and pressure conditions. Additionally, DFT is capable to provide insights into the surface chemistry and reactivity of Cu-based materials during adsorption and catalytic conversion reactions. In this regard, surface defects, step edges, and coordination sites can be elucidated to facilitate the activation, chemisorption, and subsequent reactions. As another application of DFT, the thermodynamic properties and phase equilibria of Cu- systems can be determined particularly in multi-component fluid mixtures where phase behavior, solubility limits, and speciation of Cu complexes in -rich environments can be predicted by modeling the interactions between Cu ions or clusters and molecules. Sorption mechanisms and kinetics of on Cu adsorbents can be modeled by DFT by presenting the diffusion processes, surface interactions, and pore-filling phenomena. Lastly, mean-field DFT can establish structure-property relationships between the atomic-scale structure and macroscopic properties of Cu-based materials in carbon sequestration applications. The result of DFT can be correlated to the experimental results to understand key structural features, surface modifications, or compositional variations that influence the performance of Cu catalysts or sorbents, leading to rational design strategies to improve carbon capture and sequestration.Although DFT is a powerful computational tool to study the atomic-scale adsorption phenomena, surface reactivity, phase behavior, and kinetic mechanisms of Cu in carbon sequestration mechanisms, experimental techniques such as electron microscopy and spectroscopy are needed to verify the results. In this regard, the Nion UltraSTEM (STEM is the abbreviation of Scanning Transmission Electron Micrsoscopy) microscope offers unique capabilities that can significantly contribute to understanding the functionalities of Copper (Cu) in carbon sequestration processes. Among the existing options, Nion UltraSTEM provides the highest resolution at the highest stability which can even results in the visualization of the phonons. Similar to other microscopes in this level, energy dispersive X-ray spectroscopy (EDXS) is being offered for elemental mapping and chemical analysis of Cu-containing materials. Furthermore, the Electron Energy Loss Spectroscopy (EELS) capabilities of the mentioned microscope enable the characterization of electronic and chemical bonding properties of Cu-based materials. In this regard, the oxidation state, coordination environment, and chemical bonding configurations of Cu atoms in various oxidation states can be determined. Surface characterization to investigate the surface defects, crystal facets, and surface reconstructions of Cu catalysts or sorbents can be developed to correlate the surface properties with catalytic activities and adsorption capacity. The obtained information will lead to tailored designs of Cu-nanostructures to improve carbon capture and sequestrations by controlling the size, shape, and morphology of Cu nanoparticles that result in optimized surface area, porosity, and active sites. Lastly, in-situ and operando studies can be developed to enable real-time imaging and spectroscopic analysis of Cu-based catalysts or sorbets under reaction conditions relevant to carbon sequestration processes.Overall, the goal of this research is to provide insights into the applications of mean-field DFT and advanced STEM microscopy as computational and experimental tools to characterize copper-based materials in carbon capture and sequestration. The main novelty of this research is to provide future research directions aimed at optimizing Cu-based materials for enhanced capture and sequestration efficiency. Keywords : Mean field Density Functional Theory; Scanning Transmission Electron Microscopy (STEM); Carbon capture and Sequestration; Copper-based materials

Hybrid Electrocoagulation–Adsorption Process for Montelukast Sodium Antibiotic Removal from Water

This study addresses the significant environmental challenge of pharmaceutical pollutants by demonstrating the effectiveness of a hybrid electrocoagulation–adsorption (EC-A) technique for removing Montelukast Sodium (MS) from contaminated water. The research was conducted in three stages—adsorption, electrocoagulation, and adsorption using the residual water from the electrocoagulation process. The adsorbent materials were characterised using various analytical techniques: X-ray Diffraction (XRD) for determining the crystalline structure, Energy-Dispersive X-ray Spectroscopy (EDX) for elemental composition, Scanning Electron Microscopy (SEM) for surface morphology, and Fourier Transform Infrared Spectroscopy (FTIR) for identifying functional groups before and after interaction with the pollutants. The adsorption phase achieved optimal results at a pH of 3 and a contact time of 120 min, with a maximum removal efficiency of 99.5% for a starting MS concentration of 50 mg/L using Calcium Ferric Oxide–Silica Sand (CFO-SS) adsorbent. The electrocoagulation phase showed a 97% removal efficiency with a pH of 11, a current density of 20 mA, and a 5 mm electrode distance, achieved in just 20 min. Finally, the combined EC-A process, with the pH of residual water adjusted to 3, further enhanced the removal efficiency to 74%, highlighting the method’s potential for pharmaceutical contaminant removal. These findings underscore the potential of the EC-A technique as a highly effective and adaptable solution for mitigating pharmaceutical contaminants in water.

Use of a humidity adsorbent derived from cockleshell waste in Thai fried fish crackers (Keropok)

Abstract In this research, cockleshell waste from food processing is developed into a humidity adsorbent using a simple technique. Cockleshells were first heated at 1,000°C. The crystal structure, functional group, and morphology of cockleshells before and after heat treatment were investigated. Cockleshells before heat treatment had the aragonite phase of CaCO3 compound, but it transformed into the CaO phase after heat treatment. Next, fried fish crackers, Keropok, were selected for humidity testing. The behavior of the humidity adsorbent and fried fish crackers was investigated for 0–180 days. After humidity testing, the CaO phase of the humidity adsorbent reacted with the humidity or water molecules and transformed into the Ca(OH)2 phase. The amount of crack and roughness on the humidity adsorbent surface increased with the increase in humidity testing time. The humidity adsorbent underwent a high humidity reaction and transformed into Ca(OH)2 after 30 days. The water activity, crispness, and thiobarbituric acid-reactive substances (TBARS) of fried fish crackers were analyzed. The water activity of fried fish crackers rapidly decreased, whereas the crispness slowly decreased in the range of 0–30 days. The humidity adsorbent controlled the TBARS value by increasing slowly. Based on these results, cockleshell waste can be developed as a humidity adsorbent and used to prolong the shelf-life of local food products to at least 90 days.

New solid phase microextraction fibers with green clay coating via radio frequency magnetron sputtering for detecting low-polar compounds in water samples

BackgroundDeveloping highly sensitive and selective measurement techniques to detect trace compounds in diverse matrices is a significant challenge in analytical chemistry. These techniques must adhere to green chemistry principles by minimizing organic solvent use, simplifying sample preparation, and streamlining process steps. Additionally, there is a growing need for sustainable analytical methods due to increased environmental awareness. The problem addressed in this work is the need for an eco-friendly and efficient method for the extraction and detection of trace organochlorine pesticides in water samples. ResultsWe employed SPME using a novel clay thin film sorbent, deposited on a nickel-titanium alloy wire via magnetron sputtering. Montmorillonite clay was chosen for its excellent adsorption properties and eco-friendly nature, aligning with green chemistry principles. The approach involved coating the SPME fiber with hydrophobic modified montmorillonite clay, followed by silylation. The method was tested for extracting 12 model organochlorine pesticides, including BHC, lindane, and DDT, demonstrating high isolation efficiency. The coated thin film and its silylation modification were characterized using standard spectroscopic techniques, confirming the successful creation of a new adsorbent phase. The direct immersion SPME approach achieved relative recoveries ranging from 65 % to 99 %, with reproducibility (RSD) below 6 %. This method provided low detection limits (10–15 ng L−1) and quantitation limits (32–50 ng L−1). SignificanceOur approach offers an eco-friendly, highly efficient solution for the extraction and detection of trace organochlorine pesticides. The significant improvement in recovery rates and reproducibility, combined with low detection and quantitation limits, underscores the potential of this method to enhance analytical practices in environmental monitoring and public health. Furthermore, the use of sustainable materials and processes aligns with global efforts to reduce environmental impact in analytical chemistry.

Adsorption Thermodynamics for Process Simulation.

Adsorption has rapidly evolved in recent decades and is an established separation technology extensively practiced in gas separation industries and others. However, rigorous thermodynamic modeling of multicomponent adsorption equilibrium remains elusive, and industrial practitioners rely heavily on expensive and time-consuming trial-and-error pilot studies to develop adsorption units. This article highlights the need for rigorous adsorption thermodynamic models and the limitations and deficiencies of existing models such as the extended Langmuir isotherm, dual-process Langmuir isotherm, and adsorbed solution theory. It further presents a series of recent advances in the generalization of the classical Langmuir isotherm of single-component adsorption by deriving an activity coefficient model to account for the adsorbed phase adsorbate-adsorbent interactions, substituting adsorbed phase adsorbate and vacant site concentrations with activities, and extending to multicomponent competitive adsorption equilibrium, both monolayer and multilayer. Requiring a minimum set of physically meaningful model parameters, the generalized Langmuir isotherm for monolayer adsorption and the generalized Brunauer-Emmett-Teller isotherm for multilayer adsorption address various thermodynamic modeling challenges including adsorbent surface heterogeneity, isosteric enthalpies of adsorption, BET surface areas, adsorbed phase nonideality, adsorption azeotrope formation, and multilayer adsorption. Also discussed is the importance of quality adsorption data that cover sufficient temperature, pressure, and composition ranges for reliable determination of the model parameters to support adsorption process simulation, design, and optimization.

Determining Supercritical Methane Adsorption Phase Density in Nanoscale Shale: from Polanyi Theory to Machine Learning

Determining Supercritical Methane Adsorption Phase Density in Nanoscale Shale: from Polanyi Theory to Machine Learning

Effects of Spontaneous Curvature on Interfacial Adsorption and Collapse of Phospholipid Monolayers.

To function effectively, pulmonary surfactant must adsorb rapidly to the alveolar air/water interface, but avoid collapse from the interface when compressed to low surface tensions. Prior studies show that phospholipids in the cylindrical monolayers of the inverse hexagonal (HII) phase adsorb quickly. The monolayers have negative curvature, defined by the concave shape of the hydrophilic face. Formation of the HII structures, however, involves significant disruption of optimal chain-packing. Samples with significant spontaneous curvature, formed in the absence of applied force, may nonetheless have lamellar structures. The experiments here tested whether planar lamellar bilayers formed by phospholipids with negative spontaneous curvature might adsorb rapidly but collapse slowly. Prior studies have shown that binary mixtures of dioleoyl phosphatidylcholine-dioleoyl phosphatidylethanolamine (DOPC-DOPE) with higher mol fractions of DOPE (XPE) have more negative spontaneous curvature. Samples with higher XPE adsorbed more rapidly but also collapsed more quickly. Over that range of XPE, small angle X-ray scattering showed only lamellar structures. The HII phase was undetectable. The results suggest that the innate tendency of the phospholipids to form curved structures has primary importance for adsorption rather than the presence of HII structures. Planar structures are insufficient to minimize the tendency of spontaneous curvature to promote collapse. These findings are consistent with adsorption and collapse that occur via rate-limiting structures with significant negative curvature.

Numerical Analysis of the Influence of Preadsorbed Water on Methane Transport in Crushed Shale

Summary Methane migration in shale is affected by preadsorbed water. To understand this effect, we examined several key parameters, including the effective pore diameter Le, the pore volume distribution of Le, the effective porosity ϕe, the equivalent particle diameter da, and the water film thickness h. Using these parameters, we established an equivalent relationship linking the particle packing da and the Le and the ϕe of the capillary pores within a unit-length cuboid of particles. Based on this relationship, a conceptual model was developed to simulate methane adsorption and transport in partially saturated crushed shale, incorporating parameter estimation for the tangential momentum adjustment factor δ and methane desorption rate coefficient kd, where δ characterizes the slip flow intensity and kd is related to the Langmuir adsorption constant. The finite element method was used to calculate the methane permeability ke, Knudsen diffusion coefficient Dke, surface diffusion coefficient Ds, and adsorption phase transition rate Rm, which are all affected by adsorbed water. The model’s numerical results were validated through comparison with the results from adsorption experiments. These results revealed three distinct regions in the trend of the variation in δ with Le: a rapid increase in Region I (Le &amp;lt; 10 nm), a slowing increase in Region II (10 ≤ Le ≤ 100 nm), and a gradual increase in Region III (Le &amp;gt; 100 nm). In addition, kd is positively correlated with da. kd is also correlated with water saturation S; specifically, kd decreases when S ≤ 12%, increases when S = 12% to 45.8%, and decreases again when S exceeds 45.8%. The results also reveal overall negative correlations between h and ke, Dke, Ds and Rm. Furthermore, the rates of change in ke, Dke, Ds and Rm with increasing ε (ε is the bending coefficient associated with adsorbed water) range from 7.5% to 49.4%. Similarly, ke, Dke, and Ds increase by factors of 0.73–7.19 with increasing χ (χ is the coverage rate of the adsorbed water film). Additionally, as the adsorption time t increases, Ds initially increases rapidly, followed by a gradual increase. Between t = 500 seconds and 1,500 seconds, the rate of change in Ds decreases by 20%. Rm shows a three-stage relationship with t, namely, a rapid decrease from t = 0 seconds to 500 seconds, a steady decrease from 500 seconds to 1,000 seconds, and a stabilization from 1,000 seconds to 1,500 seconds, with Rm ranging from 1.10×10-11 mol/(m3·s) to 9.45×10-11 mol/(m3·s) overall. Ds increases with the adsorption amount ratio Ed (Ed is the ratio of the adsorption amount at t to the equilibrium adsorption amount). As Ed ranges from 0.2 to 0.6, the rate of change in Ds increases by 87% to 100%. Furthermore, Rm is negatively linearly correlated with Ed.

Pore-Scale Simulation of Deep Shale Gas Flow Considering the Dual-Site Langmuir Adsorption Model Based on the Pore Network Model.

As a key resource in the oil and gas sector, shale gas development profoundly influences the advancement of the global energy industry. Deep shale gas reservoirs, typically found at depths exceeding 3500 m, represent a significant portion of total shale gas reserves. Currently, pore network models primarily simulate middle and shallow shale gas, insufficiently addressing the unique challenges posed by high-temperature and high-pressure conditions in deep shale gas formations. There is an urgent need to explore the microscale flow dynamics of deep shale gas. In this work, we use the pore network model to simulate the flow dynamics of deep shale gas, particularly under nanoconfinement conditions. The simulation integrates adsorption, slip flow, Knudsen diffusion, and bulk flow phenomena. Utilizing the dual-site Langmuir adsorption model tailored for high-temperature and high-pressure conditions enhances the accuracy of gas conductivity calculations for the adsorbed phase, thereby reflecting the specific characteristics of deep shale gas reservoirs. Moreover, this research investigates the flow characteristics of deep shale gas under varying sensitivity parameters, such as water saturation, temperature, and pressure. It explores methane flow dynamics, focusing on effective diffusion coefficients and permeability. The modified approach to calculating adsorption phase conductivity using the dual-site Langmuir adsorption model accurately captures the adsorption behaviors and characteristics of deep shale gas reservoirs.

Recovering Nitrogen from Anaerobic Membrane Bioreactor Permeate Using a Natural Zeolite Ion Exchange Column

In the framework of a circular economy, wastewater treatment should be oriented toward processes that allow the recovery of the resources present in the wastewater while ensuring good effluent quality. Nitrogen recovery is usually carried out in streams concentrated in this nutrient because these high concentrations facilitate nitrogen valorization. On the other hand, the mainstream of a wastewater treatment plant (WWTP) has a high potential for nitrogen recovery, but it is not usually considered because it is hard to manage due to its low nitrogen concentration. To solve this problem and facilitate the recovery of nitrogen in the mainstream, this work proposes ion exchange with zeolites as a stage of ammonium concentration, to provide a nitrogen-concentrated stream that could be valorized by another technology, while obtaining a nitrogen-free effluent. The working stream, the permeate of an AnMBR process in the mainstream, has suitable characteristics to be treated in an ion exchange column (free of suspended solids and with very low organic matter content). To this end, the effect of the working flow rate (17.5 to 4.4 BV/h) and the ammonium concentration (54 to 17 mg NH4-N/L) on the adsorption capacity of the zeolite in the loading phase was evaluated. The adsorption curves were fitted to three mathematical models: Thomas, Bohart–Adams, and Yoon–Nelson. The effect of the regeneration flow rate (from 8.7 to 2.2 BV/h) and the regenerant concentration (NaOH at 0.2, 0.1, and 0.05 M) on regeneration capacity and efficiency were also studied. A novel control strategy based on effluent conductivity was used in both phases to control the duration of the adsorption and regeneration phases.

Unraveling the adsorption-limited hydrogen oxidation reaction at palladium surface via in situ electron microscopy

Palladium (Pd) catalysts have been extensively studied for the direct synthesis of H2O through the hydrogen oxidation reaction at ambient conditions. This heterogeneous catalytic reaction not only holds considerable practical significance but also serves as a classical model for investigating fundamental mechanisms, including adsorption and reactions between adsorbates. Nonetheless, the governing mechanisms and kinetics of its intermediate reaction stages under varying gas conditions remain elusive. This is attributed to the intricate interplay between adsorption, atomic diffusion, and concurrent phase transformation of catalyst. Herein, the Pd-catalyzed, water-forming hydrogen oxidation is studied in situ, to investigate intermediate reaction stages via gas cell transmission electron microscopy. The dynamic behaviors of water generation, associated with reversible palladium hydride formation, are captured in real time with a nanoscale spatial resolution. Our findings suggest that the hydrogen oxidation rate catalyzed by Pd is significantly affected by the sequence in which gases are introduced. Through direct evidence of electron diffraction and density functional theory calculation, we demonstrate that the hydrogen oxidation rate is limited by precursors' adsorption. These nanoscale insights help identify the optimal reaction conditions for Pd-catalyzed hydrogen oxidation, which has substantial implications for water production technologies. The developed understanding also advocates a broader exploration of analogous mechanisms in other metal-catalyzed reactions.

Influence of Supercritical Conditions on Isothermal Adsorption Capacity Calculation of Methane and Model Optimization.

The study of isothermal adsorption models for coal and methane under supercritical conditions helps us to understand the gas content distribution in coal seams and improve gas management in coal mines. Coal samples from the Hebi mine and Longshan coal mine were selected for this research. Using the weight method, isothermal adsorption curves of supercritical methane at temperatures of 308, 313, and 318 K were measured. The adsorption phase density of supercritical methane was obtained by using the intercept method and model fitting, and the absolute adsorption capacity of methane was calculated. Simultaneously, the pore volume and specific surface area of the coal samples were tested, and the isothermal adsorption model for supercritical methane was studied and optimized. The results indicate that using mercury intrusion, low-temperature N2, and low-temperature CO2 adsorption methods for testing coal sample pore structures allows for multiscale characterization of the coal pore structure. Based on the Gibbs excess adsorption theory, the phase density of methane obtained from the intercept method and model fitting effectively represent the isothermal adsorption curve of supercritical methane. By combination of the specific surface area and pore volume distribution of the coal with the absolute adsorption capacity of methane, the number of methane adsorption layers on the coal surface was calculated to be between 1.11 and 1.3 layers. This suggests that the isothermal adsorption model for supercritical methane on coal is not solely micropore filling or single molecular layer adsorption but primarily single molecular layer adsorption with concurrent micropore filling adsorption. Based on this adsorption mechanism, an L-DA isothermal adsorption model for supercritical methane on coal was established. The L-DA isothermal model shows good fitting results and effectively explains the adsorption characteristics of supercritical methane on coal.