Adsorption Interaction Research Articles

Study on the effects of a novel imidazoline siliconophilic collector in the desilication process of magnesite: Separation experiments, adsorption mechanisms, and separation model

This study innovatively introduced heptadecenyl amine ethyl imidazoline quaternary ammonium salt (ODD) as a siliconophilic flotation collector, effectively facilitating the achievement of high-efficiency separation of magnesite from quartz. ODD exhibits unique properties such as high selectivity and environmental friendliness. Through a comprehensive series of experiments, including flotation tests, zeta potential characterization, atomic force microscopy (AFM) imaging, Fourier-transform infrared (FTIR) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the flotation performance and selective adsorption mechanisms of ODD were thoroughly investigated. The experiments demonstrated that at a pH of 7.00 and an ODD concentration of 40 mg/L, quartz achieved a flotation recovery rate of 95.16 %, while magnesite was only 2.99 %, underscoring the high selectivity of ODD in mineral separation. Zeta potential measurements indicated that ODD exhibits strong adsorption interactions with quartz over magnesite. AFM observations confirmed that ODD forms significant adsorption structures on quartz surfaces, in contrast to weaker interactions with magnesite. FTIR analysis further revealed the robust interactions between ODD and quartz through hydrogen bonds and electrostatic forces, which were significantly diminished on magnesite surfaces. ToF-SIMS analysis provided direct evidence of ODD’s selective adsorption on quartz, contributing to a better understanding of the flotation mechanisms involved. This research not only offers a novel approach for the purification of magnesite and effective removal of quartz but also demonstrates the potential of ODD as an eco-friendly collector in mineral processing, potentially advancing a green transformation in the industry. The findings provide a solid theoretical and experimental basis for future industrial applications and innovative development of flotation collectors.

Strategic design and facile synthesis of porous hyper-cross-linked phosphonium bromide microspheres for catalyzing CO2 conversion to cyclic carbonates

Heterogeneous ionic liquid (IL) catalysts with multiple active sites can be considered as the highly efficient catalyst for CO2 conversion to cyclic carbonates. It is extremely challenging to achieve the strategic design and precise control of multi-site polymeric ILs’ morphology and properties. In this work, we developed a novel and facile polymerization-ionization method employing flexible brominated monomers as raw materials (e.g. 4‑bromo-1-butene) to successfully synthesize porous hyper-cross-linked phosphonium bromide-microspheres (PBr-microspheres), in order to break through the drawbacks of multi-step preparation and difficulty in microsphere forming. Compared with conventional bromine spheres of the same size, the specific surface area of the new synthetic bromine sphere is 16 times, and the average pore size is one-eighth, with 3-times CO2 adsorption capacity, with rich microporous structure and exposed active sites, excellent CO2 adsorption capacity and thermal stability. PBr-microspheres can achieve synergistic effect of physical adsorption and chemical interaction for CO2, thus enhancing the catalytic performance in CO2 conversion process, affording propylene oxide conversion of 99.7 % and propylene carbonate selectivity of 99.9 %, while the catalytic activity did not decrease significantly after reusing 8 runs. This facile controllable synthesis of PBr-microspheres with excellent catalytic performance provides a new idea for heterogeneous ILs-catalyzed CO2 utilization.

Effect analysis of temperature and initial water content on the adsorption and separation of VOCs by ZIF‐8 based on molecular simulation

AbstractVolatile organic compounds (VOCs) have seriously polluted the atmospheric environment and caused harmful effects on human beings, so it is imperative to control oil vapor emissions. Metal organic framework materials, as one of the porous materials, have a good application prospect in the field of gas adsorption separation. In this paper, the effects of temperature and initial water content (IWC) on the adsorption properties of methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), and propylene (C3H6) by ZIF‐8 were studied by combining the large gauge Monte Carlo (GCMC) and ideal adsorption solution theory. The results show that the higher the temperature is, the lower the adsorption capacity is, the higher the threshold pressure is, and the single molecule interaction energy changes little with temperature. But pore volume is still the main influencing factor. The IWC also reduces the saturated adsorption capacity. Preloaded water molecules can enhance the electrostatic interaction at low pressure, thus affecting the adsorption heat and interaction energy of single molecules. Overall, these findings provide valuable mechanistic insights into the effects of temperature and IWC on the adsorption properties of ZIF‐8 for VOCs.

Unravelling the effects of active site density and energetics on the water oxidation activity of iridium oxides

Understanding what controls the reaction rate on iridium-based catalysts is central to designing better electrocatalysts for the water oxidation reaction in proton exchange membrane electrolysers. Here we quantify the densities of redox-active centres and probe their binding strengths on amorphous IrOx and rutile IrO2 using operando time-resolved optical spectroscopy. We establish a quantitative experimental correlation between the intrinsic reaction rate and the active-state energetics. We find that adsorbed oxygen species, *O, formed at water oxidation potentials, exhibit repulsive adsorbate–adsorbate interactions. Increasing their coverage weakens their binding, thereby promoting O–O bond formation, which is the rate-determining step. These analyses suggest that although amorphous IrOx exhibits a higher geometric current density, the intrinsic reaction rates per active state on IrOx and IrO2 are comparable at given potentials. Finally, we present a modified volcano plot that elucidates how the intrinsic water oxidation kinetics can be increased by optimizing both the binding energy and the interaction strength between the catalytically active states.

Exploring diclofenac potassium adsorption on activated carbon: A comprehensive statistical physics and experimental approach

This study aims to contribute to understanding the removal processes of diclofenac potassium (DP) medicine in wastewater treatment systems, employing activated carbon (AC) as an adsorbent. To achieve this goal, a multidisciplinary approach was adopted, integrating experimental and theoretical analyses of equilibrium data regarding the adsorption of DP on AC. Five statistical physics models were applied to determine the model best for the adsorption process. The selection of the most appropriate model considered both the performance of the models and the analysis of the estimated parameters. Statistically, all models exhibited satisfactory results. However, when analyzing the estimated parameters, the double-layer model with single adsorption energy emerged as the most suitable model to describe the analyzed process. Based on the chosen model’s parameters, we observed that as the temperature increases, the number of active sites occupied during adsorption and their availability on the adsorbent also increases. However, the number of available adsorption sites decreases as the temperature rises. The half-saturation concentration, in turn, increases with increasing temperature, suggesting that the process is favored when temperatures above room temperature are used. Additionally, higher temperatures provide better removal results, indicating that DP molecules’ non-parallel and parallel orientations on the AC surface favor the adsorption process. Finally, our combined results led to the proposal of a mechanism for DP adsorption on AC, which is based on physical adsorption interactions between adsorbate-adsorbent and adsorbate–adsorbate.

RGO/ZIF-8 Aerogel for Effective Removal of Malachite Green from Wastewater.

In this study, dopamine-modified graphene aerogel (DGA) is synthesized through a one-step hydrothermal method using graphene oxide as the precursor and dopamine as the reducing agent. Subsequently, in situ immersion synthesis is conducted to obtain ZIF-8 loaded on a dopamine-modified graphene aerogel skeleton (ZDGA), featuring a regular honeycomb interconnected mesoporosity and a high specific surface area of 532.8 m2/g. The synthesized ZDGA exhibited exceptional adsorption performance for the cationic dye malachite green. At room temperature, ZDGA achieved an impressive equilibrium adsorption capacity of 6578.34 mg/g. The adsorption process followed pseudo-secondary kinetics and adhered to the Langmuir model, indicating chemically dominated adsorption on a monomolecular layer. Intraparticle diffusion was the primary rate determinant, with π-π stacking, electrostatic adsorption, hydrogen bonding, and Lewis acid-base interactions serving as the key driving forces. It has an ideal specific surface area and good cycling performance, which highlights its potential application in dye wastewater treatment.

Effect of adsorption interactions of Arabic gum with cement

This study seeks to investigate the influence of cement and Arabic gum on the physico-mechanical and microstructural properties of cementitious composites. The influence of varying quantities of Arabic gum on the hydration, fluidity, mechanical performance and microstructure of cement paste was investigated. The influence of Arabic gum on slant shear performance and capillary water absorption was also investigated. The results indicate that the workability of cement was diminished as a result of the ability of Arabic gum to make the cement paste cohesive. It is evident that when the gum Arabic concentration increases from 147 to 174 mm, the resultant slump value for various w/b ratios drops. The adsorption characteristics showed that for a 15 mg g−1 dosage at 60, 45, 30, and 15 min, respectively, 1.43, 1.32, 1.25, and 1.03 mg g−1 are achieved. For 1% gum Arabic substitution, the highest flexural strength percentage growth is achieved at 38.46%, 23.74%, and 17.29% at 7, 14, and 28 days, respectively. In addition, the inclusion of Arabic gum improved the slant shear strength of cement composite, making it ideal for use as a building repair material with significant application potential. Experiments on the bonding behavior of the produced cementitious composite with the old mortar reveal that the shear bond strength was greatly increased, demonstrating the compatibility between the old and new cement composites. The microstructure and the porosity of the cement matrix also showed denser and compact matrix making them durable to attain better service life.

Oxygen reduction reaction activity of Co3O4-modified Pt-graphene electrocatalysts

Abstract In this paper, the ORR activity of Pt/Co3O4-modified N-doped graphene electrocatalysts was investigated based on DFT theory. The Dmol3 module in Materials Studio software was used to optimize the construction of NG models under different doping conditions and to calculate the adsorption and desorption properties of oxygen molecules by optimizing the conformation of Pt13 clusters and substrates. A comparative analysis revealed that the Co3O4 modification reduced the oxygen adsorption energy of the Pt/G catalyst. However, after N doping, the oxygen adsorption energy of Pt/Co3O4/NG was superior to that of Pt/NG. After theoretical analysis, it was determined that it was because the doping of N atoms in graphene could promote the release of oxygen vacancies in Co3O4 and strengthen the adsorption interaction between Pt and graphene carriers to improve the oxygen adsorption energy.

Straightforward synthesis of novel chitosan bio-based flame retardants and their application to epoxy resin flame retardancy

Epoxy resin (EP) is widely used in various industries. However, its inherent flammability characteristics limit its application, so there is an urgent need to develop bio-based flame retardants for efficient flame retardant EP. Chitosan (CS) is one of the most commonly used bio-based raw materials, but most chitosan-based flame retardants are synthesised using large amounts of organic solvents, with low yields and not in line with the theme of green and sustainable development. In this paper, we report a facile, eco-friendly, and solvent-free approach to chitosan-based flame retardants. A novel full biomass flame retardant, chitosan-based ammonium phytate (PUCS), was synthesised without the organic solvent by using chitosan and phytanic acid as raw materials and the electrostatic adsorption interaction between them and urea, and it was used as a flame retardant additive for EP. The results showed that the EP samples with 7.5 wt% PUCS added increased the limiting oxygen index from 22.2 % to 32.2 % and the vertical burning rating from no rating to V-0. Moreover, the cone calorimeter test results showed that the EP/PUCS composites with adding PUCS showed a significant decrease in the peak heat release rate, and it has excellent flame retardancy. It is worth mentioning that the mechanical property test results showed that the mechanical properties of EP/PUCS composites with adding PUCS could still reach the scope of the needs for engineering applications. This work provides an economical, convenient, and eco-friendly feasible route for bio-based flame retardants.

In-depth study of adsorption mechanisms and interactions in the removal of pharmaceutical contaminants via activated carbon: a physicochemical analysis.

This study presents a theoretical analysis of the adsorption process of pharmaceutical pollutants, specifically acetaminophen (ATP) and diclofenac (DFC), onto activated carbon (AC) derived from avocado biomass waste. The adsorption isotherms of ATP and DFC were analyzed using a multilayer model, which revealed the formation of two to four adsorption layers depending on the temperature of the aqueous solution. The saturation adsorption capacities for ATP and DFC were 52.71 and 116.53mg/g, respectively. A steric analysis suggested that the adsorption mechanisms of ATP and DFC involved a multi-molecular process. The calculated adsorption energies (ΔE1 and ΔE2) varied between 12.86 and 22.58kJ/mol, with the highest values observed for DFC removal. Therefore, the adsorption of these organic molecules was associated with physisorption interactions: van der Waals forces and hydrogen bonds. These findings enhance the understanding of the depollution processes of pharmaceutical compounds using carbon-based adsorbents and highlight the potential of utilizing waste biomass for environmental remediation.

Surface-Roughened Graphene Oxide Microfibers Enhance Electrochemical Reversibility.

Here, we provide an optimized method for fabricating surface-roughened graphene oxide disk microelectrodes (GFMEs) with enhanced defect density to generate a more suitable electrode surface for dopamine detection with fast-scan cyclic voltammetry (FSCV). FSCV detection, which is often influenced by adsorption-based surface interactions, is commonly impacted by the chemical and geometric structure of the electrode's surface, and graphene oxide is a tunable carbon-based nanomaterial capable of enhancing these two key characteristics. Synthesized GFMEs possess exquisite electronic and mechanical properties. We have optimized an applied inert argon (Ar) plasma treatment to increase defect density, with minimal changes in chemical functionality, for enhanced surface crevices to momentarily trap dopamine during detection. Optimal Ar plasma treatment (100 sccm, 60 s, 100 W) generates crevice depths of 33.4 ± 2.3 nm with high edge plane character enhancing dopamine interfacial interactions. Increases in GFME surface roughness improve electron transfer rates and limit diffusional rates out of the crevices to create nearly reversible dopamine electrochemical redox interactions. The utility of surface-roughened disk GFMEs provides comparable detection sensitivities to traditional cylindrical carbon fiber microelectrodes while improving temporal resolution ten-fold with amplified oxidation current due to dopamine cyclization. Overall, surface-roughened GFMEs enable improved adsorption interactions, momentary trapping, and current amplification, expanding the utility of GO microelectrodes for FSCV detection.

Development and Application of a Selective Analytical Method for Indole Metabolites in Urine: Dietary Exposure Biomarkers for Broccoli Consumption.

The identification of dietary exposure biomarkers is crucial for advancing our understanding of the health benefits of specific foods. Broccoli, a vegetable with well-known anticancer properties, contains active ingredients, such as isothiocyanates with indole side chains. Hence, indole metabolites related to broccoli consumption have the potential to serve as biomarkers of dietary exposure. In this work, we developed a new analytical method for indole metabolites in urine using a poly(deep eutectic solvents)-molecularly imprinted polymer/vinyl-functionalized graphene oxide (PDESs-MIP/VGO) in miniaturized centrifugal pipet-tip solid-phase extraction (CPT-SPE) coupled with liquid chromatography. This method integrates the strengths of PDESs-MIP/VGO, including rich adsorption interactions, high adsorption capacity, and excellent selectivity, with the simplicity and cost-effectiveness of CPT-SPE. The proposed method demonstrated low limits of quantification (1.2-2.5 ng mL-1), high accuracy (91.7-104.8%), and good precision (relative standard deviation ≤4.4%). By applying this method to analyze indole metabolites in urine, our results suggested that indole-3-carbinol and indole-3-acetonitrile have the potential to emerge as reliable dietary exposure biomarkers for broccoli intake. Furthermore, highly selective analytical methods based on molecular imprinting technology are advantageous for precise screening and analysis of dietary exposure biomarkers associated with food consumption.

Nanobody immobilization on magnetic nanoparticles via monomeric streptavidin-biotin specific interaction for aflatoxin adsorption

Nanobody immobilization on magnetic nanoparticles via monomeric streptavidin-biotin specific interaction for aflatoxin adsorption

Structural Characterisation of Zeolites Derived from Lithium Extraction: Insights into Channel- and Cage-Type Frameworks

This study investigates the structural and adsorption characteristics of channel- and cage-type zeolites obtained through lithium extraction. Through XRD, FT-IR spectroscopy, and adsorption isotherm analyses, distinct adsorption behaviours of CH4 and CO2 were observed in both zeolite types. Cage-type zeolites exhibited higher adsorption capacities attributed to their structural advantages, highlighting the importance of structural framework selection in determining adsorbent efficacy. The presence of structural defects and an amorphous phase influenced adsorption behaviours, while thermodynamic data underscored the role of adsorbate properties. Kinetics studies revealed the influence of the structural framework on CH4 adsorption and CO2 adsorption kinetics. Analysis of adsorbate–adsorbent interactions demonstrated robust interactions, particularly with LPM16-Y. These findings offer insights into the potential applications of zeolites in gas adsorption processes, emphasising the importance of structural properties and adsorbate characteristics in determining adsorption performance.

Toward high selectivity of sensor arrays: Enhanced adsorption interaction and selectivity of gas detection (N2, O2, NO, CO, CO2, NO2, SO2, AlH3, NH3, and PH3) on transition metal dichalcogenides (MoS2, MoSe2, and MoTe2)

Resistive gas sensors are essential for monitoring air quality, ensuring industrial safety, and controlling automotive emissions. However, conventional materials used for sensing layers often suffer from poor selectivity and require elevated operating temperatures, limiting their effectiveness. This study introduces a novel approach to address these challenges by utilizing the intrinsic physicochemical properties of Mo-bearing transition-metal dichalcogenides (TMDs). The findings reveal that variable charge availability on TMD surfaces leads to highly selective adsorption enhancements, resulting in significant differences in the TMD responses to various molecules, even at room temperature. This results in an exceptional relative sensitivity of the TMD monolayers, which in the case of combustion products exceeds what is feasible under the same conditions by conventional sensing materials such as ZnO and TiO2 by three orders of magnitude. Such an unprecedented variation in responses results in distinct sensing profiles. This enables effective cross-referencing of responses, offering significant benefits for sensor arrays. Consequently, even in relatively simple setups, TMD-based devices have the potential to prevent false-positive signals and even enable the determination of the composition of gas mixtures, which, if utilized, could revolutionize the field of gas monitoring with innovative lab-on-a-chip solutions.

Stabilization of Pd0 by Cu Alloying: Theory‐Guided Design of Pd3Cu Electrocatalyst for Anodic Methanol Carbonylation

AbstractElectrocatalytic carbonylation of CO and CH3OH to dimethyl carbonate (DMC) on metallic palladium (Pd) electrode offers a promising strategy for C1 valorization at the anode. However, its broader application is limited by the high working potential and the low DMC selectivity accompanied with severe methanol self‐oxidation. Herein, our theoretical analysis of the intermediate adsorption interactions on both Pd0 and Pd4+ surfaces revealed that inevitable reconstruction of Pd surface under strongly oxidative potential diminishes its CO adsorption capacity, thus damaging the DMC formation. Further theoretical modeling indicates that doping Pd with Cu not only stabilizes low‐valence Pd in oxidative environments but also lowers the overall energy barrier for DMC formation. Guided by this insight, we developed a facile two‐step thermal shock method to prepare PdCu alloy electrocatalysts for DMC. Remarkably, the predicted Pd3Cu demonstrated the highest DMC selectivity among existing Pd‐based electrocatalysts, reaching a peaked DMC selectivity of 93 % at 1.0 V versus Ag/AgCl electrode. (Quasi) in situ spectra investigations further confirmed the predicted dual role of Cu dopant in promoting Pd‐catalyzed DMC formation.

Stabilization of Pd0 by Cu Alloying: Theory-Guided Design of Pd3Cu Electrocatalyst for Anodic Methanol Carbonylation.

Electrocatalytic carbonylation of CO and CH3OH to dimethyl carbonate (DMC) on metallic palladium (Pd) electrode offers a promising strategy for C1 valorization at the anode. However, its broader application is limited by the high working potential and the low DMC selectivity accompanied with severe methanol self-oxidation. Herein, our theoretical analysis of the intermediate adsorption interactions on both Pd0 and Pd4+ surfaces revealed that inevitable reconstruction of Pd surface under strongly oxidative potential diminishes its CO adsorption capacity, thus damaging the DMC formation. Further theoretical modeling indicates that doping Pd with Cu not only stabilizes low-valence Pd in oxidative environments but also lowers the overall energy barrier for DMC formation. Guided by this insight, we developed a facile two-step thermal shock method to prepare PdCu alloy electrocatalysts for DMC. Remarkably, the predicted Pd3Cu demonstrated the highest DMC selectivity among existing Pd-based electrocatalysts, reaching a peaked DMC selectivity of 93 % at 1.0 V versus Ag/AgCl electrode. (Quasi) in situ spectra investigations further confirmed the predicted dual role of Cu dopant in promoting Pd-catalyzed DMC formation.

Synergistic enhancement of N, S co-modified biochar for removal of tetracycline hydrochloride from aqueous solution: Tunable micro-mesoporosity and chemisorption sites

The misuse of tetracycline hydrochloride (TCH) antibiotics has caused irreversible hazards to ecosystem. In this study, a series of porous biochar with tunable micro-mesoporosity and chemisorption sites are designed by cleverly exploiting the pyrolysis properties of active agents in various temperature regions. Benefiting from the existence of more pore structures matching the adsorbate while exposing more chemisorption sites, the maximum adsorption capacity (Qm) of NSC-1.0 for TCH is up to 1480.1 mg g−1 at 303 K. A combination of model fitting, post characterization and density functional theory (DFT) calculations confirms that the adsorption process involves the pore filling, the formation of non-covalent bonds (weak hydrogen bond, π-π stacking, electrostatic interaction) and ligand covalent bonding (Lewis acid-base interaction). The Qm is positively correlated with the volume of pore size greater than 1 nm (R2 = 0.9879), indicating that the pore filling effect is a decisive factor for adsorption performance. Post-characterization directly demonstrates that weak hydrogen bonding and π-π stacking are pivotal physical interactions for adsorption. DFT calculations show that partial N, S species and oxygen-containing functional groups can significantly reduce the adsorption energy of intrinsic graphene, especially the chemisorption sites of pyrrolic N (N5) and thiophene S (S5) containing lone-pair electrons. Furthermore, the competitiveness of NSC-1.0 is revealed in practical evaluation, including cation strength, regenerability, actual water source and fixed-bed column. This study not only contributes new insights to synergistically enhance the removal of macromolecular antibiotics by coupling matchable pore sizes and chemisorption sites, but also develops theoretical support for the fabrication of such efficient adsorbents.

Synthesis and application of anthraquinone quaternary phosphonium salt electroplating copper leveler based on expanded electrostatic adsorption area strategy and physicochemical salt bridge mechanism

Four anthraquinone quaternary phosphate molecules (AQS-a, AQS-b, AQS-c, AQS-d) with different electrostatic adsorption areas were constructed as electroplating levelers based on the strategy of expanding the electrostatic adsorption area of the molecules. AQS-d with the largest electrostatic adsorption area was demonstrated to have the most excellent electrochemical performance by electrochemical tests. The physicochemical adsorption sites and interactions with copper ions of AQS levelers were proposed by theoretical calculations, molecular dynamics simulations, Raman spectroscopy and fluorescence absorption spectroscopy, and the electroplating salt bridge mechanism was proposed. Based on optical microscope, scanning electron microscope, atomic force microscope and X-ray diffractometer, it is proved that AQS-d has the ability to perfectly fill the microvia in actual plating by actual PCB blind hole filling experiment.

Ammonia-Responsive Colorimetric Film of Phytochemical Formulation (Alizarin) Grafted onto ZIF-8 Carrier with Poly(vinyl alcohol) and Sodium Alginate for Beef Freshness Monitoring.

In this study, we devised a photothermally stable phytochemical dye by leveraging alizarin in conjunction with the metal-organic framework ZIF-8 (AL@ZIF-8). The approach involved grafting alizarin into the microporous structure of ZIF-8 through physical adsorption and hydrogen-bonding interactions. AL@ZIF-8 significantly enhanced the photostability and thermostability of alizarin. The nanoparticles demonstrate substantial color changes in various pH environments, showcasing their potential for meat freshness monitoring. Furthermore, we introduced an intelligent film utilizing poly(vinyl alcohol)-sodium alginate-AL@ZIF-8 (PA-SA-ZA) for detecting beef freshness. The sensor exhibited a superior water contact angle (52.34°) compared to the alizarin indicator. The color stability of the film was significantly enhanced under visible and UV light (ΔE < 5). During beef storage, the film displayed significant color fluctuations correlating with TVB-N (R2=0.9067), providing precise early warning signals for assessing beef freshness.