Adsorption Amount Research Articles

Enantioselective adsorption on chiral ceramics with medium entropy

Chiral metal surfaces provide an environment for enantioselective adsorption in various processes such as asymmetric catalysis, chiral recognition, and separation. However, they often suffer from limitations such as reduced enantioselectivity caused by kink coalescence and atomic roughness. Here, we present an approach using medium-entropy ceramic (MEC), specifically (CrMoTa)Si2 with a C40 hexagonal crystal structure, which overcomes the trade-off between thermal stability and enantioselectivity. Experimental confirmation is provided by employing quartz crystal microbalance (QCM), where the electrode is coated with MEC films using non-reactive magnetron sputtering technology. The chiral nature is verified through transmission electron microscopy and circular dichroism. Density-functional theory (DFT) calculations show that the stability of MEC films is significantly higher than that of high-index Cu surfaces. Through a combination of high-throughput DFT calculations and theoretical modeling, we demonstrate the high enantioselectivity (42% e.e.) of the chiral MEC for serine, a prototype molecule for studying enantioselective adsorption. The QCM results show that the adsorption amount of L-serine is 1.58 times higher than that of D-serine within a concentration range of 0-60 mM. These findings demonstrate the potential application of MECs in chiral recognition.

Adsorption Behavior of Fluorocarbon Surfactants on Polytetrafluoroethylene Surface

By using the sessile drop method, the wetting properties of nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and anionic fluorocarbon surfactant (FAS) solutions on the surface of polytetrafluoroethylene (PTFE) were investigated. Meanwhile, the effects of surfactant concentration on the contact angle, adhesion tension, PTFE–liquid interfacial tension, and work of adhesion of the fluorocarbon surfactant with different structures were detected. The results demonstrate that the adsorption amount of the three fluorocarbon surfactants at the air–liquid interface is 1.5~2 times higher than their adsorption amount at the PTFE–solution interface. Before critical micelle concentration (CMC), the fluorocarbon surfactant molecules rely on their hydrophobic groups to adsorb on the PTFE surface. The smallest molecular size of FNS-2 results in the largest adsorption amount, while electrostatic repulsion and large steric hindrance result in the smallest adsorption amount for FAS. Above CMC, the fluorocarbon surfactants form semi-micelles to adsorb on the PTFE surface. The hydrophilic modification ability of the three fluorocarbon surfactants for the PTFE surface is stronger than that of reported surfactants, and the contact angle can be reduced to about 20° at high concentrations. The order of the hydrophilic modification ability is FNS-2 > FNS-1 > FAS. Hydrophilic EO groups can effectively enhance the hydrophilicity of FNS-1 and FNS-2. Due to the hydrophobic -CH3 group and the smaller adsorption amount, FNS-1 possesses a weaker hydrophilic modification ability than FNS-2. Investigating the adsorption behavior of fluorocarbon surfactants on the PTFE surface can help us to better utilize fluorocarbon surfactants. This could have broad implications for colloid and interface science.

Preparation of a novel porous organic polymer for selective extraction/determination of palladium ions from water samples

In this research, a new porphyrin-based porous organic polymer (POP), named here PPOP-UOZ-1 (UOZ stands for the University of Zabol), was synthesized through a solvothermal condensation reaction between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP, Porph-NH2) and 2,2'-[ethane-1,2-diylbis(oxy)]dibenzaldehyde (Dialdehyde, DA). The chemical structure, morphology, and surface properties of the PPOP-UOZ-1 were assessed using numerous techniques, including TGA, BET, FT- IR, PXRD, and SEM/EDX. The nominal PPOP-UOZ-1 was then used as an adsorbent for selective (better than 92 %) extraction of Pd(II) from aqueous solutions. The adsorption process was optimized by studying the effect of various factors such as pH, the type and volume of eluent, adsorption and desorption time, and the amount of adsorbent. The results exhibited that the maximum adsorption capacity of PPOP-UOZ-1 for Pd(II) was 208.3 mg/g at a pH of 3.0, based on the Langmuir isotherm model (a determination coefficient of 0.9887). The adsorbent showed excellent selectivity for Pd(II) over other coexisting metal ions, with a recovery rate higher than 92 %. Furthermore, the PPOP-UOZ-1 could be reused for at least six adsorption-desorption cycles without substantial loss of efficiency. This proposed adsorbent and approach was further applicable for the efficient extraction of Pd(II) from environmental water samples.

Effects of polystyrene microplastics on the distribution behaviors and mechanisms of metalloid As(III) and As(V) on pipe scales in drinking water distribution systems

Pipe scales have long been considered the primary adsorption medium for trace heavy metals in drinking water distribution systems (DWDSs). Microplastics (MPs) potentially affect the distribution of metalloid arsenic (As) pollutants in DWDSs. Herein, the accumulation behaviors of As(Ⅲ) and As(V) on pipe scales and polystyrene microplastics (PSMPs) under different water conditions were studied. Additionally, As(Ⅲ) and As(V) accumulation behaviors on pipe scales coexisting with PSMPs were investigated. Results showed that pipe scales played a key role in the accumulation of As (pipe scales = 1.08–4.80 mg/g > PSMPs = 0.02–3.38 mg/g). The adsorption amount of As(Ⅲ) on PSMPs was higher than that of As(V). The addition of PSMPs promoted the accumulation of As(Ⅲ) on pipe scales at pH = 3–8 while inhibiting the accumulation of As(V) on pipe scales at pH = 3–10 due to the competitive adsorption. The oxidation of As(III) and the reduction of As(V) occurred during the accumulation of As(Ⅲ) and As(V) on pipe scales. Notably, PSMPs accumulated on pipe scales were beneficial to the oxidation of As(Ⅲ), potentially reducing the As-related risks. Overall, our results provide new insights into the hazards posed by MPs in DWDSs.

Investigation of Methane Adsorption and Diffusion Behavior in Hydrogen Sulfide-Containing Coal Seams.

This study aimed to investigate the methane adsorption-diffusion problem in coal seams containing hydrogen sulfide. Molecular simulations and Materials Studio software were used to study the difference in behavior between hydrogen sulfide and methane adsorption, as well as the effect of hydrogen sulfide on methane adsorption-diffusion behavior in coal seams. Comprehensive data were obtained on the influence of hydrogen sulfide on methane's adsorption amount, probability density distribution, interaction energy, and diffusion coefficient during the adsorption. The results showed that as the hydrogen sulfide content increased from 0 to 1.9%, porosity decreased from 14.41% to 11.25%, representing a 21.93% reduction. When methane and hydrogen sulfide were adsorbed in the coal seam, the adsorption amount of hydrogen sulfide was notably higher, with an adsorption heat of 38.25 kJ/mol, which is 24.65 kJ/mol greater than that for methane. An increase in the hydrogen sulfide content caused several adverse effects, including a decrease in methane's adsorption amount, Langmuir adsorption constant, and number of available adsorption sites within bituminous coal. Furthermore, the interaction energy and diffusion coefficient of methane molecules diminished during adsorption.

Simultaneous determination of nineteen azo dyes in water samples by gas chromatography-mass spectrometry after Fe3O4@COF based dispersive solid phase extraction

This study was performed for the determination of nineteen azo dyes at trace levels in stream water sample by gas chromatography-mass spectrometry (GC-MS). The selected analytes were preconcentrated with the help of dispersive solid phase extraction (DSPE). Fe3O4 magnetic nanoparticle was modified with covalent organic framework (COF) and the synthesized Fe3O4@COF nanocomposite was used as adsorbent for the separation of the analytes from aqueous solution. The synthesized Fe3O4@COF was introduced to the literature for the first time in this study. Five different parameters (pH, volume of buffer solution, volume of desorption solvent, mixing period and amount of adsorbent) were univariately optimized to acquire high extraction outputs for each analyte. Under the optimum Fe3O4@COF-DSPE-GC-MS conditions, limit of detection (LOD), limit of quantitation (LOQ), linear range (LR), coefficient of determination (R2) and percent relative standard deviation (%RSD) were calculated using external calibration plots belonging to each analyte. LOD values were found between 2.8 and 70.7 μg/kg with corresponding LOQ values ranging between 9.5 and 235.7 μg/kg. In addition, %RSD values were lower than 12.8%. Matrix matching calibration method was used in spiking experiments. Percent recovery results obtained for spiked stream water samples were between 83.1 and 122.4%, with %RSD ≤ 17.5. The high percent recoveries confirmed the accuracy and applicability of the developed Fe3O4@COF-DSPE-GC-MS method for stream water samples.

Enhancement of Trihalomethane Adsorption Capacity Using Chitosan-Modified Coconut Shell Activated Carbon: Adsorption Characteristics and Mechanisms

There is a rising concern about the safety risk that trihalomethanes (THMs) in drinking water pose. In this work, to adsorb THMs such as chloroform (TCM), dibromochloromethane (DBCM), bromodichloromethane (BDCM), and bromoform (TBM), we coated chitosan (CS) on coconut shell activated carbon (CAC). The adsorbents were characterized using BET, XRD, FTIR, and SEM techniques. The impact of various variables was examined, including contact time, quantity of adsorbent, initial pH, and initial THM concentrations. Under the same conditions, TCM was adsorbed most efficiently, followed by BDCM, DBCM, and TBM. When the pH was between 4 and 8, the adsorption of THMs onto the coconut shell activated carbon supported chitosan (CS/CAC) varied relatively little; however, when the pH increased above 8, the adsorption of THMs decreased. For THMs, CS/CAC adsorption was a chemical reaction and monolayer adsorption that fit better with the pseudo-second-order kinetic model and the Langmuir isotherm model. According to the thermodynamic study, THMs were adsorbed endothermically and spontaneously on CS/CAC. For column experiments, the adsorption of THMs was influenced by bed height and flow rate. After up to four cycles of adsorption and desorption, it was found that the adsorbent was reusable. The maximum adsorption capacities for Langmuir were 187.27, 114.29, 93.28, and 89.61 µg/g for TCM, BDCM, DBCM, and TBM, respectively. CS/CAC has a high adsorption capacity, especially for TCM, which is responsible for a major portion of THMs in drinking water. This indicates that CS/CAC has a lot of potential uses when it comes to removing THMs from water.

A concurrent approach for determining binary isotherm and optimizing moving bed adsorber for solid amine adsorbent in the coexistence of CO2 and H2O

A concurrent approach, which allows for determining multi-component equilibrium isotherms and designing a multi-component adsorption process within a realistic amount of time and effort, is demonstrated for the first time in a moving bed process using an amine-impregnated solid adsorbent in the presence of CO2 and H2O. The proposed approach extracts measurement points for the binary isotherms from the temperature and partial pressure regions that exist in the optimized process from all potential combinations of CO2 partial pressure, H2O partial pressure, and temperature. At the extracted points, the equilibrium adsorption amounts were measured experimentally to obtain multi-component adsorption amount data, with which the binary isotherm parameters were determined by the Tikhonov regularization. The accuracy of the equilibrium isotherm was further improved iteratively by repeating the steps described above. The proposed approach enables us to determine the binary interactions parameters in the isotherm model reducing the multi-component measurement points only to 12, while obtaining the optimized process operation at the same time.

Hydrogen-Bonded Organic Framework and Metal-Organic Framework Assembly of Waterwheel PgC-Noria Molecule: Regulating Microstructure Enables Iodine Transfer.

Hydrogen-bonded organic frameworks (HOFs) are a type of crystalline porous materials self-assembled from organic or metal-organic building blocks via intermolecular hydrogen bonding, which have received increasing attention due to their reversible and flexible hydrogen bonding properties. Currently, it remains a challenge to construct HOFs based on complex or porous organic cages as molecular building blocks. Herein, a 3D HOF (PgC-HOF) featuring honeycomb-shaped channels is crafted utilizing a sizable waterwheel-like PgC-noria organic molecule cage. The pivotal role of intermolecular multipoint hydrogen bonding interactions in upholding structural integrity and stability is underscored by the possession of 36 phenolic hydroxyl groups in PgC-HOF. Interestingly, the introduction of calcium ions into the reaction system results in the formation of the metal-organic framework (PgC-MOF), with the channel dimensions increasing from 6.8 to 9.1Å. Furthermore, I2 sorption/release experiments are conducted on PgC-HOF and PgC-MOF, achieving an increase in the optimal adsorption amount from 1.45 to 2.19gg-1 and a transition from an irreversible adsorbent to a reversible adsorbent.

Comprehensive characterization of micro-pore structures in different lithologies of the lacustrine fine-grained mixed sedimentary reservoir of the Shahejie Formation in the Jiyang Depression

Several methods, such as field-emission environmental scanning electron microscope (FE-SEM), low-temperature nitrogen adsorption-desorption, high-pressure mercury injection tests, focused ion beam scanning electron microscope (FIB-SEM), and high-magnification and large-scale quantitative analytical methods involving argon ion polishing-FE-SEM, have been carried out on lacustrine fine-grained mixed sedimentary reservoirs of the upper fourth-lower third members of the Shahejie Formation in the Jiyang Depression, with the aim of clarifying their microstructural characteristics. Five types of reservoir spaces of fine-grained mixed sedimentary reservoirs were recognized in this study, including intergranular, dissolution, intercrystalline and intracrystalline pores, and fractures. The favorable reservoir spaces are pores with diameters ranging from 40 nm to 300 nm, which are dominated by intergranular pores, grain edge seams, and dissolution pores. The high-pressure mercury injection curves can be divided into three types. Types I and II, with good pore structures, occur mainly in mudstone and dolomite facies, whereas type III, with poor pore structures, is present in limestone facies. The low-temperature nitrogen adsorption-desorption showed that the adsorption volume of dolomite facies is the highest, and the pore morphologies are plate-like. The adsorption amount of mudstone facies is higher than limestone facies, and the pore morphologies are dominated by ink bottle-shaped and parallel plate-like. FIB-SEM analyses reveal that the samples display moderate connectivity. These findings suggest that the different types of lithologic reservoirs of fine-grained mixed sedimentary rocks in the Jiyang Depression have different microstructures, with the argillaceous dolomite, calcareous mudstone, calciferous mudstone, and argillaceous limestone changing gradually from good to poor.

Mn3O4-MnOOH nanocomposites for the adsorption-based removal of nickel ions from wastewater.

The removal of nickel from wastewater is a significant environmental concern because of its potential hazards to environment. Adsorption is known as an efficient water treatment strategy and there is a growing interest in the development of new adsorbent materials providing rapid adsorption kinetics, cost-effectiveness, and high adsorption capacity. In this study, the feasibility of Mn3O4-MnOOH nanocomposites was evaluated as the adsorbent material for the removal of nickel ions from wastewater. The nanocomposites were prepared using a modified sonochemical method and characterized by XRD analysis and SEM images. Batch adsorption experiments were carried out under different experimental conditions obtained by varying solution pH, adsorbent amount, and contact period. Under the optimum adsorption conditions, the %RE value was recorded around 80% for 10mg/L Ni(II) ions. The adsorption characteristics were investigated with respect to adsorption isotherms and kinetics. Langmuir and Freundlich isotherm models were used to fit the adsorption data and the results indicated that adsorption of nickel ions onto nanocomposite could be complex and obey both monolayer adsorption and heterogeneous surface. Accordingly, maximum adsorption capacity of nanocomposites were calculated as 12.387mg/g. Research works comparing the kinetic models of pseudo-first-order, pseudo-second-order, and Elovich revealed that chemical sorption plays an important role as the rate-limiting step in the adsorption of nickel ions.

Optimization of the Combined Use of Z-Sep Plus and EMR-Lipid in QuEChERS Procedure for the Analysis of Eight Pesticides in Real Milk Samples

AbstractOne of the most applied procedures for the determination of trace analytes in complex matrices is QuEChERS (an acronym for Quick, Easy, Cheap, Effective, Rugged, and Safe). QuEChERS procedures include an extraction step followed by a dispersive solid-phase extraction (dSPE) for analytes cleaning-up from the matrix components. A challenging task in QuEChERS procedures is extracting and determining pesticides from samples of high fat such as milk samples. This challenge induced the innovation of new adsorbents for the clean-up step such as Z-Sep Plus® and EMR-Lipid® to enable removal of fatty matrix components without affecting the recovery of hydrophobic analytes. This work aims to apply experimental design to optimize the combined application of both QuEChERS clean-up adsorbents; Z-Sep Plus® and EMR-Lipid® in addition to other QuEChERS parameters in the determination of eight pesticides: hexachlorocyclohexane, dichlorodiphenyldichloroethane, dichlorodiphenyltrichloroethane, primiphos ethyl, diazinon, malathion, endrin, and dimethoate in milk matrix. This was augmented by optimization of GC–MS/MS and UPLC-MS/MS to detect and determine analytes in extracts. The experimental design of QuEChERS procedure enabled the optimization of Z-Sep Plus®- and EMR-Lipid®-added adsorbent amounts with other method parameters to enable the maximum recovery of analytes. Furthermore, the optimized methods enabled low detection limits of the studied pesticides within a short analysis time (28 min for GC and 12 min for LC methods, respectively). The procedure was validated according to European SANTE/11312/2021 Guideline. Quantitation limit ranged from 1.7 to 3.2 ng/mL for GC–MS/MS method and from 1.7 to 3 ng/mL for UPLC-MS/MS method. Greenness assessment of the methods followed four approaches indicating an excellent value of greenness for the proposed methods. Furthermore, 45 real milk samples collected from the Egyptian market were tested with the developed procedure for the presence of pesticides.

X-ray Reflectivity Probing the Structural Evolution of Sunflower Proteins Adsorbed at the Air-Water Interface.

The study delves into the adsorption of sunflower proteins at the air/water interface using specular X-ray reflection. The research involved fitting models of the protein films to the reflectivity data, resulting in detailed images of the X-ray scattering length density profiles perpendicular to the air/water interface. The sunflower protein isolate that is examined consists of multiple components, and the study proposes a transition from a 1-slab model to a 4-slab model to represent the changing layer structure over time. This transition is significant as it reflects the increasing complexity of the protein film as more proteins adsorb at the interface. Initially, sunflower proteins form a monolayer at the air/water boundary, consisting of a protein-rich, hydrophobic portion closest to the interface and a more diffuse, hydrophilic portion extending into the bulk aqueous phase. The structural changes at the interface over time depend on the bulk protein concentration in the solution. For solutions at relatively low concentrations (C ≤ 0.5 g/L), a lower amount of adsorption results in a larger, more extensive interface area for each species and a thinner protein adsorption layer. The overall thickness of a saturated monolayer is approximately 100 Å, which is close to the maximum dimension of sunflower globulins, with the thickness of the corresponding hydrophobic portion being about 20 Å. For solutions at relatively high concentrations (C ≥ 1.0 g/L), even after forming a saturated monolayer, structural evolution continues within the experimental time frame, occurring on both hydrophilic and hydrophobic sides. Additional proteins from the bulk diffuse toward the interface, forming an extra layer in the water phase and causing an increase in the overall thickness. Furthermore, a distinct sublayer develops next to the air phase, indicating a further structuration of the hydrophobic portion.

Removal of Cr(VI) from aqueous phase using dimethylaminopropylamine anchored polystyrene‐co‐divinylbenzene polymer as adsorbent

AbstractThe current investigation delves into the effectiveness of dimethylaminopropylamine tethered onto polystyrene‐co‐divinylbenzene polymer for the proficient elimination of hexavalent chromium from simulated wastewater. The resin was characterized using SEM, FT‐IR spectroscopy, EDX, elemental analysis, thermogravimetry, and solid state 13C NMR spectroscopy. The experimental investigation into sorption dynamics involved varying process parameters, including initial Cr(VI) concentration, amount of adsorbent used, solution pH, temperature, and contact between phases. The binding modes of chromate ions, either bidentate or monodentate, were observed, with their manifestation influenced by the solution's pH. Sorption capacity was found to be pH‐dependent, with removal efficiencies of 98.27%, 96.38%, and 85.52% observed at pH levels of 3, 6, and 9, respectively. PS‐DMAPA resin demonstrated robust regeneration capabilities, throughout five consecutive adsorption–desorption cycles. The Langmuir adsorption model exhibited excellent agreement with the experimental findings (R2 = 0.9994), revealing a maximum adsorption capacity of 70.15 mg g−1 at 298 K. Additionally, the experimental findings closely matched the second‐order kinetic model. The kinetics of sorption and the thermodynamic parameters were also investigated. Performance evaluating of the PS‐DMAPA resin under dynamic conditions included analyzing the Cr(VI) breakthrough curve. The 10% sodium chloride solution was employed to effectively recover the extracted Cr(VI) quantitatively.

The role of copper ions in improving the flotation of chalcopyrite at low temperatures

It is of great significance to improve the flotation of copper sulfide minerals at low temperatures. In this study, the reduction mechanism of chalcopyrite flotation performance and the role of copper ions in improving the flotation of chalcopyrite at low temperatures were systematically investigated. The results of the flotation tests prove that the chalcopyrite flotation recovery is lower at low temperatures (5℃) than at room temperatures (20℃), which is directly related to the changes in the surface hydrophobicity. However, the addition of copper ions can effectively improve the chalcopyrite flotation at low temperatures. Electrochemical measurements indicate that copper ions positively affect the redox reaction and electron transport on the chalcopyrite surface at low temperatures, thereby increasing the current density and surface activity of chalcopyrite. Besides, X-ray photoelectron spectroscopy analysis and adsorption measurements clearly indicate that copper ions mainly adsorbed on chalcopyrite surface in the form of CuS species by chemisorption, thereby significantly enhancing the adsorption amounts of xanthate on the chalcopyrite surface and improving the flotation of chalcopyrite at low temperatures.

Novel carboxymethyl cellulose-based hydrogel embedded with metal organic framework for efficient cationic dye removal from water

The rGO/CMC/β-CD (RCβ) hydrogel was synthesized from reduced graphene oxide (rGO), β-cyclodextrin (β-CD) and sodium carboxymethyl cellulose (CMC) by radical polymerization. A novel hydrogel adsorbent was created by growing the metal-organic framework (Cu-BTC) in-situ on RCβ hydrogel, which has excellent adsorption capacities for cationic dyes in wastewater. The adsorption parameters such as the amount of adsorbent, pH of solution and adsorption time were optimized through batch adsorption experiments. Under the optimal conditions of pH 6.0, adsorbent dosage of 0.01 g and experimental temperature of 25 °C, Langmuir isothermal model was used to fit the maximum adsorption capacities of methylene blue (MB), crystal violet (CV) and malachite green (MG), which were 892.66, 842.75 and 633.77 mg g−1, respectively. The fitting results of adsorption kinetics revealed that the pseudo-second-order model can describe the adsorption process better. Based on proposed studies, the dye molecules were adsorbed onto RCβ@Cu-BTC hydrogel mainly through electrostatic interaction, hydrogen bonding and π–π interactions. After five cycles, the adsorption efficiency of the RCβ@Cu-BTC hydrogel for MB, CV and MG can still reach 80 %, 77 % and 72 %, which shows that the adsorbent has good adsorption performance. Various adsorption experiments show that RCβ@Cu-BTC hydrogel has great potential in treating dye wastewater.

Investigating the impact of ITO substrates on the optical and electronic properties ofWSe2monolayers.

Two-dimensional (2D) materials, particularly transition metal dichalcogenides (TMDCs), have gathered significant attention due to their interesting electrical and optical properties. Among TMDCs, monolayers of WSe2exhibit a direct band gap and high exciton binding energy, which enhances photon emission and absorption even at room temperature. This study investigates the electronic and optical properties of WSe2monolayers when they are mechanically transferred to indium tin oxide (ITO) substrates. ITO is a transparent conducting electrode (TCE) used in many industrial opto-electronic applications. Samples were mechanically transferred under ambient conditions, consequently trapping an adsorbate layer of atmospheric molecules unintentionally between the monolayer and the substrate. To reduce the amount of adsorbates, some samples were thermally annealed. Atomic force microscopy (AFM) confirmed the presence of the adsorbate layer under the TMD and its partial removal after annealing. X-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon species among the adsorbates even after annealing. Photoluminescence (PL) measurements show that WSe2remains optically active on ITO even after annealing. Moreover, the luminescence intensity and energy are affected by the amount of adsorbates under the WSe2monolayer. Scanning Tunnelling Spectroscopy reveals that the TMD monolayer is n-doped, and that its band edges form a type I band alignment with ITO.. Surface potential measurements show a polarity change after annealing, indicating that polar molecules, most likely water, are being removed. This comprehensive study shows that a TCE does not quench WSe2luminescence even after a prolonged thermal annealing, although its optical and electronic properties are affected by unintentional adsorbates. These findings provide insights for better understanding, controlling, and design of 2D material heterostructures on TCEs.

A highly sensitive and selective label-free impedimetric immunosensor for the detection of interleukin-6 based on AuNPs@pDA@NiCo2S4@MoS2 nanocomposite.

A highly sensitive and selective label-free impedimetric immunosensor based on AuNPs@pDA@NiCo2S4@MoS2 nanocomposite modified on the surface of a screen-printed electrode (SPE) was designed for the detection of interleukin-6 (IL-6). The distribution of NiCo2S4 nanoparticles on MoS2 nanosheets was able to prevent them from agglomerating. The polydopamine (pDA) layer was coated on the surface of NiCo2S4@MoS2 nanosheets by self-polymerization, which improved the stability and biocompatibility of the nanomaterial. The excellent reduction ability of pDA promoted the synthesis of gold nanoparticles (AuNPs), which increased the amount of antibody adsorption and the conductivity of the material. Finally, the antibody (Ab) of IL-6 was immobilized on the surface of AuNPs@pDA@NiCo2S4@MoS2 nanocomposite. Electrochemical impedance spectroscopy (EIS) was used to detect the change of impedance before and after the immune response between Ab and IL-6 antigen (IL-6). Under the optimal experimental conditions, the relative change in impedance and the logarithmic concentration of IL-6 showed a good linear relationship in the range 1.00 to 1.00 × 106pg/mL, with a low detection limit of 0.97pg/mL. In addition, the proposed immunosensor performed with good reproducibility, stability, and specificity. It was successfully applied to the determination of IL-6 in patient's serum samples of head and neck carcinoma with recoveries of 98.40% to 106.5%. To sum up, the proposed label-free impedimetric immunosensor was successfully constructed for IL-6 detection in real samples.

A study on the thermal behavior of coal gangue mountains under airflow influence based on MD and CFD simulations

The long-term accumulation of coal gangue can lead to an increase in internal temperature. If the temperature becomes excessive, it can cause spontaneous combustion, posing serious environmental risks. The process is significantly influenced by external airflow. This study analyzes the thermodynamic properties and oxidation heat release rate of coal gangue samples through laboratory experiments. Subsequently, molecular dynamics (MD) simulations are used to investigate the mechanism of oxidation heat release during the heating process of coal gangue under varying oxygen supply conditions. Based on these findings, a coupled three-field model for the heating process of coal gangue mountains is developed. Using computational fluid dynamics (CFD) methods, transient simulations are conducted to analyze the internal thermal behavior of coal gangue mountains under the influence of external airflow, clarifying the risks of spontaneous combustion. The results indicate that after reaching T2 (295.16 °C), coal gangue enters an accelerated oxidation phase, with an increased heat release rate, heightening the risk of spontaneous combustion. The oxidation heat release rate of coal gangue accelerates with rising temperature and oxygen concentration, entering a rapid reaction phase after 300 °C, with a sharp increase in reaction rate. Compared to N2, coal gangue surfaces exhibit stronger adsorption of O2, and temperature changes affect N2 diffusion more sensitively (O2 diffusion coefficient increases by 0.312 Å2/ps, N2 diffusion coefficient increases by 0.334 Å2/ps). The isosteric heat of O2 adsorption in coal gangue decreases significantly with increasing adsorption amount, and higher temperatures hinder competitive adsorption of O2. The temperature in the deep and foot areas of the coal gangue mountains is lower, while the middle and upper areas near the slope surface exhibit higher temperatures, indicating a higher risk of spontaneous combustion in these regions. When environmental wind speed is too high or too low, both the internal temperature of the coal gangue mountains and the area of spontaneous combustion risk zones decrease. At a wind speed of 3 m/s, the spontaneous combustion risk zone reaches its maximum area of 73.47 m2, but when the wind speed increases to 7 m/s, the risk area decreases to 65.72 m2.

Extraction of methamphetamine and pseudoephedrine by modified graphene oxide solid phase extraction method coupled to HPLC-UV in urine sample.

Methamphetamine, pseudoephedrine, and related drugs are among the first drugs used for the stimulation of the central nervous system. In this study, two adsorbents based on graphene oxide (GO) were synthesized and used for the analysis of methamphetamine and pseudoephedrine. The prepared nano-adsorbents based on GO in this study were coated by polyaniline (PANI) and Fe3O4/C-nanodot/GO (magnetic adsorbent). The average size of nanoparticles (GO/PANI) was 18.43nm. The specific surface area and pore size diameter of Fe3O4/C-nanodot/GO were 22.71 m2 g- 1 and 15.23nm, respectively. Experimental variables affecting the extraction efficiency of the analytes such as pH of the sample solution, amount of adsorbent, extraction time, and type of eluents were investigated and optimized by response surface methodology. Under optimum conditions, GO/PANI and Fe3O4/C-nanodot/GO were considered appropriate solid phase extraction adsorbents for HPLC-based analyses of the studied drugs in human urine samples. However, GO/Fe3O4 nano adsorbent (Fe3O4/C-nanodot/GO) showed superior working condition than GO/PANI. The validated proposed analytical methods can be used for the quantitative determination of methamphetamine and pseudoephedrine in actual samples.