Competitive Adsorption Mechanism Research Articles

Molecular simulation on CO2/H2S co-adsorption in organic and inorganic shale nanopores

Geological CO2 sequestration (GCS) in depleted shale reservoirs is recognized as one of promising techniques to mitigate CO2 emissions, while the high cost of CO2 purification greatly hinders its deployment. Co-injection of CO2/H2S mixtures has been proposed as an economical alternative to further promote GCS application. In this work, we used Grand Canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations to investigate CO2/H2S mixture adsorption in organic and inorganic shale nanopores (at 333.15 K and pressure up to 50 MPa). CO2 and H2S present distinct adsorption behaviors on the different surfaces. H2S adopts unordered structures on kerogen surfaces, but a perpendicular orientation on illite due to H-bonding, which also results in higher adsorption, while CO2 is preferentially distributed parallel along the surfaces. Furthermore, CO2 and H2S accumulate in the concave parts of kerogen surfaces, while they concentrate around the tetrahedral aluminum (AT) atoms and K+ cations on illite surfaces. The adsorption selectivity of H2S over CO2 is always greater than 1, indicating the stronger adsorption propensity of H2S. The preferential adsorption of H2S on illite surface is facilitated by the stronger dipole–dipole interactions. PMF results show that the binding interaction between CO2 or H2S and illite is higher than on kerogen, and H2S always shows a stronger interaction than CO2. Overall, the total CO2 and H2S adsorption is higher in illite nanopores, implying a new promising storage method. This study provides important insights into the competitive adsorption mechanisms of CO2 and H2S in depleted shale reservoirs and sheds light on how sour gas geological sequestration capacity can be further improved.

Superefficient separation of Th(IV) and U(VI) by lignin-derived magnetic biochar via competitive adsorption mechanism

Thorium (Th) and uranium (U) separation remains a huge challenge due to their high similarity in chemical behavior. In this study, lignin-derived magnetic biochar (AL-Fe/BC), which can provide functional sites for adsorbing Th(IV) and U(VI), was synthesized for the selective extraction of Th(IV) from the binary U(VI)-Th(IV) matrix. Characterizations results confirm the successful zero-valent iron loading, and the AL-Fe/BC exhibited a developed polyporous structure, high surface area, stable crystallinity, high defects degree, and advantageous magnetic feature of expedient recovery from water without energy consumption. The optimist AL-Fe/BC-800 showed an outstanding adsorption capacity with a maximal Th(IV) uptake of 2000 mg/g, and a small absorption of 3 mg/g of U(VI) (Th(IV) = 180 mg/L, U(VI) = 20 mg/L, AL-Fe/BC-800 = 0.05 g/L). Moreover, the separation factor of Th(IV) from the Th(IV)-U(VI) matrix reached 90,000 even concomitant with high a concentration of co-existing ions. The active adsorption sites on AL-Fe/BC-800, such as COOH, C-OH, C=O, pyridinic N, graphitic N, and pyrrolic N, exhibited a stronger binding affinity with Th(IV) than U(VI), achieving selective Th(IV) adsorption via a chemisorption process on the basis of competitive adsorption. In summary, AL-Fe/BC-800 is a potential adsorbent in industrial application for the superefficient separation of Th(IV) and U(VI) with high-performance magnetic recovery, promoting the sustainable development of nuclear industry, especially considering the necessary development of Th(IV) fuel.

Effect of SO2 on HCl removal over ethanol-hydrated CaO adsorbent: Mechanism of competitive adsorption and product layer shielding

The elimination of hydrogen chloride (HCl) is essential for wastewater sequestration and safe operation of equipment in coal-fired power plants. A new adsorbent of ethanol-hydrated CaO has been developed, which possesses a 100% HCl removal efficiency lasting 30 min in a fixed bed reactor being much superior to traditional dechlorinators. Nevertheless, SO2 in flue gas has instinctive and strong competition with HCl on the alkaline adsorbent that results in detrimental effects and makes the removal mechanisms confused and unclear. To solve this issue, a series of experiments were designed to evaluate how SO2 influences the performance of HCl adsorption over the adsorbent. Comprehensive characterizations and density functional theory (DFT) calculations further studied the mechanisms of the competition mechanism between SO2 and HCl. The results indicate that SO2 has a detrimental impact on HCl removal by consuming the active Ca site, diminishing the alkalinity and worsening the surface activity due to the product layer formation. DFT calculations reveal that the high adsorption energy of SO2 suppresses the active sites for HCl removal. The faded surface electrostatic potentials (ESP) around the sulfurized Ca active sites lead to apparent activity shielding on the absorbent surface. Besides, the frontier molecular orbital (FMO) theory unveils a narrow electronic transfer energy gap for SO2 adsorption. These findings contribute to elucidation of SO2 competition to HCl on the calcium-based adsorbent in coal-fired flue gas.

Competitive adsorption of heavy metals between Ca–P and Mg–P products from wastewater during struvite crystallization

Wastewater usually contains high concentration of calcium (Ca), posing a competitive reaction with magnesium (Mg) on phosphorus (P) recovery during the struvite crystallization. The differences in the adsorption of heavy metals by Ca–P and Mg–P (struvite) generated are still unclear. Herein, we analyzed the residues of four kinds of common heavy metals (Cu, Zn, Cd, Pb) in Ca–P and Mg–P (struvite) under varying conditions (solution pH, N/P ratio, Mg/Ca ratio) in the swine wastewater and explored their possible competitive adsorption mechanisms. The experiments using synthetic wastewater and real wastewater have similar experimental patterns. However, under the same conditions, the metal (Pb) content of struvite recovered from the synthetic wastewater (16.58 mg/g) was higher than that of the real wastewater (11.02 mg/g), as predicted by the Box-Behnken Design of Response Surface Methodology (BBD-RSM). The results demonstrated that Cu was the least abundant in the precipitates compared to Zn, Cd, and Pb of almost all experimental groups with an N/P ratio greater than or equal to 10. The fact might be mainly attributed to the its stronger binding capacity of Cu ion with NH3 and other ligands. Compared with struvite, the Ca–P product had a higher adsorption capacity for heavy metals and a lower P recovery rate. In addition, the higher solution pH and N/P ratio were favorable to obtain qualified struvite with lower heavy metal content. It can be applied to reduce the incorporation of heavy metals by modulating pH and N/P ratio through RSM, which is suitable for different Mg/Ca ratios. It is anticipated that the results obtained would offer support for the safe utility of struvite from wastewater containing Ca and heavy metals.

Competitive adsorption mechanisms of pigments in sugarcane juice on starch-based magnetic nanocomposites

The pigments in sugarcane result the crystallised sucrose appears unsatisfactorily yellow. In this study, cationic tapioca starch (CTS)-functionalized magnetic nanoparticles (CTS@Fe3O4) were synthesized and used as adsorbents for the removal of undesirable pigments. The adsorption properties of CTS@Fe3O4 were investigated by a sugarcane juice colorant model consisting of caffeic acid (CA), gallic acid (GA) and melanoidin (ME). The equilibrium adsorption capacities of CTS@Fe3O4 for CA, GA, and ME were 185, 160 and 580 mg g−1 at the optimal conditions (60, 60 and 180 mg L−1 initial concentrations, respectively; 0.3 mg mL−1 CTS@Fe3O4 dosage, 313 K temperature, and pH value of 7). The adsorption process was described well by second-order kinetic and Langmuir isotherm models with a high fitting correlation coefficient approaching 1, suggesting that the pigments formed a surface monolayer with a homogenously distributed adsorption energy and was mainly dominated by chemisorption. The thermodynamic parameters (Gibbs free energy <0, enthalpy >0, and entropy >0) revealed that the adsorption process was endothermic and spontaneous. For the binary system, the competitive adsorption between pigments was primarily antagonistic. The speed of adsorption was the main factor affecting competitive adsorption, and the additional adsorption force reduced the effects of coexisting adsorbates.

Remediation of PO43– and Ni2+ from aqueous solution by novel jarosite: competitive adsorption performance and mechanism

Remediation of PO43– and Ni2+ from aqueous solution by novel jarosite: competitive adsorption performance and mechanism

A hydrophobic and hierarchical porous resin-based activated carbon modified by g-C3N4 for toluene capture from humid conditions

The synthesis of hydrophobic and hierarchical porous activated carbon (AC) used for toluene capture from a humid atmosphere still remains a challenge. In this work, a novel hydrophobic and hierarchical porous AC was prepared from resorcinol-formaldehyde resin spheres using g-C3N4 as a new pore-forming agent. By the proper participation of g-C3N4, the obtained adsorbent GNHRC-1.5 was endowed with an excellent toluene adsorption capacity (10 mmol/g) under low pressure of P = 0.2 kPa, which was 54% higher than that of nonmodified resin-based AC. By DIH (Difference of Isosteric Heats) prediction, the adsorption selectivity of GNHRC-1.5 to toluene/water was further enhanced to 139.55, higher than that of other reported adsorbents. Toluene breakthrough tests and kinetic analysis showed that GNHRC-1.5 possessed a faster intraparticle diffusion and outstanding reusability, which was ascribed to its a certain amount of mesopores. Grand Canonical Monte Carlo and molecular dynamics simulation were applied to explore the competitive adsorption mechanism of toluene and water vapor from the perspective of pore size and surface functional groups. The results indicated that the competitive adsorption was controlled by Van der Waals energy, intramolecular energy and electrostatic energy. Both the higher content of narrow micropores below 1 nm and carboxyl are not beneficial for toluene adsorption under humid conditions. For GNHRC-1.5, an appropriate micropore distribution, a certain amount of mesopores, and a lower content of oxygen functional groups, afford it excellent adsorption selectivity for toluene and fast adsorption kinetics under humid conditions.

Effect of oxygen functional groups on competitive adsorption of benzene and water on carbon materials: Density functional theory study

It is important to study the effect of oxygen-containing functional groups on the competitive adsorption mechanism of benzene and water on the surface of carbon materials, and to directional modification of activated carbon to improve its selective adsorption of benzene in air. In this study, the adsorption characteristics of benzene and water on original and linked ester, carboxyl, hydroxyl, carbon materials linked by ether groups were calculated by quantum chemical simulation based on density functional theory. The types and proportions of weak interactions in the adsorption process were calculated by energy decomposition analysis, and the adsorption mechanism of carbon materials for water and benzene was described. The influence and contribution of oxygen-containing functional groups on the adsorption of benzene and water were further analyzed by van der Waals potential and electrostatic potential, respectively, so as to determine the difference in the adsorption effect of different types of oxygen-containing functional groups on the two molecules. It was found that the carboxyl group has a great influence on the hydrophilicity of carbon materials, and the electrostatic potential distribution before and after linking the carboxyl group changed significantly. Therefore, they can attract each other with water through hydrogen bonds and occupy the surface adsorption sites of carbon materials, thereby inhibiting the adsorption of benzene on carbon materials. On the contrary, due to its hydrophobic properties, the ether group will free up adsorption space for the adsorption of benzene on the surface of the carbon material, which is beneficial to the adsorption of benzene. The adsorption experiments were carried out, and the results were consistent with the simulation. This study provides an idea for preparing efficient carbonaceous adsorbent of benzene and reducing benzene pollution in industry.

Gas content prediction model of water-sensitive shale based on gas–water miscible competitive adsorption

The evaluation of gas content plays a key role in determining the efficient development of shale reservoirs. To better understand the gas–water miscible competitive adsorption mechanism in the pore-fracture system of water-bearing shale, the water vapor adsorption experiment of dry shale and the methane gas adsorption experiment of water-bearing shale were carried out to compare and analyze the competitive adsorption laws of formation water and methane gas on the shale surface under different temperatures, pressures, and water saturation conditions. Moreover, based on the molecular layer adsorption theory, the gas–liquid–solid interface competitive adsorption model considering the coupling of temperature, pressure, and water saturation was established to predict the actual gas content of water-bearing shale reservoirs. The results show that the main controlling factors affecting the adsorbed gas content of water-bearing shale are specific surface area, temperature, and water content in turn according to weight coefficients; Compared with the gas–solid adsorption model, the gas–liquid–solid competitive adsorption model has higher accuracy in calculation results, which are much closer to the desorption data of shale cores in Jiaoshiba area, Fuling, China. Hence, the competitive adsorption model provides a theoretical foundation for reasonably evaluating the exploitation potential of shale gas reservoirs.

Do microplastics affect sulfamethoxazole sorption in soil? Experiments on polymers, ionic strength and fulvic acid

Microplastics (MPs) and sulfamethoxazole (SMX) are emerging contaminants that are ubiquitous in the soil environment. In this study, we investigated MPs polymer type and soil environmental factor effects on SMX adsorption behavior in the soil system. Our results showed that MPs dosage affected the soil particles' SMX adsorption rate and capacity (Qe). Adding 1 % polystyrene (PS) increased the SMX adsorption rate significantly. The value of K1, which represented the adsorption rate, increased from 0.569 h−1 to 1.019 h−1. However, the addition of MPs reduced the soil's SMX equilibrium adsorption capacity slightly. Moreover, increasing salinity strength enhanced SMX adsorption capacity by MPs significantly. However, increasing calcium ions concentration decreased SMX adsorption in the MPs amended soil due to multivalent cationic bridging and competitive adsorption mechanisms. In addition, we observed that fulvic acid addition inhibited SMX adsorption. This study suggests that the addition of MPs reduced the adsorption of SMX in the soil slightly due to dilution effect. Meanwhile, changes in environmental factors also affected the adsorption behavior of SMX in soil amended with MPs.

The remediation efficiency of heavy metal pollutants in water by industrial red mud particle waste

This study aims to treat heavy metal pollutants in water by applying red mud particle waste. An experiment on the static adsorption of heavy metal ions Pb 2 + (or Cd 2 + and Cu 2 + ) by red mud particles was carried out, and the influences of the type of heavy metal ion, ion concentration, pH value, red mud dosage, reaction time, and temperature on adsorption performance were explored. The competitive adsorption mechanisms of various coexisting heavy metal ions by red mud particles were compared. The red mud samples loaded and not loaded with heavy metal ions were detected by zeta potential measurement, scanning electron microscopy, and Fourier transform infrared spectrometry. The adsorption strength of red mud particles for heavy metal ions was ranked in the sequence of Pb 2 + , Cd 2 + , and Cu 2 + , while increasing temperature enhanced their adsorption. When the initial pH values were 4.3, 5.0, and 3.6 for Pb 2 + , Cd 2 + , and Cu 2 + solutions, the removal peaks were 94.5%, 92.8%, and 78.1%, respectively. The preferred order of adsorption for red mud was Pb 2 + , Cd 2 + and then Cu 2 + under the competitive mechanism of binary/ternary systems due to the discrepancy in the functional groups of red mud particles loaded with different heavy metal ions. • A concept for purifying heavy metal pollutants in water using red mud is proposed. • The competitive adsorption mechanism of various heavy metal ions is revealed. • The influence of temperature on the interaction of heavy metal ions and red mud is emphasized. • An adsorption–desorption model with hysteresis is verified by experimental results.

Competitive removal mechanism to simultaneously incarcerate bisphenol A, triclosan and 4-tert-octylphenol within beta-cyclodextrin crosslinked citric acid used for encapsulation in polypropylene membrane protected-micro-solid-phase extraction

Endocrine disrupting compounds (EDCs) are extensively found in the environment and severely impacting human health. In addressing this issue, the beta-cyclodextrin crosslinked citric acid (BCD-CA) had been previously employed in membrane-protected micro-solid phase extraction for sequestering EDCs from water medium; and the findings revealed that BCD-CA possessed a selectivity property. On that account, the potential of BCD-CA towards competitive adsorption of selected EDCs was investigated in terms of adsorption mechanism and selectivity property. Factors that affected the removal efficiencies such as sample pH, sorbent dosage, contact time and initial concentration were evaluated. The characterization results revealed that the carbon percentage of BCD-CA had increased by 2.04%, while the hydrogen percentage had reduced by 1.83%, signifying the successful crosslinking of BCD-CA. Besides, the amount of active BCD was calculated to be 3.2 × 10−7 mol, while the amount of carboxyl group was 2.48 × 10−5 mol per 4 mg of BCD-CA. Moreover, BCD-CA was stable in an aqueous medium with the zeta potential obtained at −36.5 mV and had a high-water retention capacity (∼150%). The competitive adsorption mechanism by BCD-CA with EDCs followed the pseudo-second-order kinetics and Freundlich isotherm, suggesting that the adsorption process was dominated by chemisorption on the heterogeneous surface of the adsorbent. Thermodynamic results revealed that adsorption of 4-tert-octylphenol had the most negative ΔG value, indicating most favorable to be adsorbed by BCD-CA as opposed to triclosan and bisphenol A, which was coherent with the apparent formation constant results. These unique properties manifested the practicality of BCD-CA as a selective adsorbent to detect and remove EDCs from the water medium.

Hydrophobic‐Binding‐Driven and Fluoresence‐Free Development of Aged Fingerprints Based on Zinc Oxide Nanoparticles

AbstractThe requirement of nonfluorescent developers for aged latent fingerprint development is still of great urgency in forensic science. To enhance the specific interaction between fingerprint residue and nano‐developers, a γ‐methacryloxy propyl trimethoxyl silane (MPTS) modified zinc oxide nanoparticle (ZnO NP) was synthesized. The crystal structure, morphology, surface functional group, thermostability, UV/Vis spectra, photoluminescence and stability of sedimentation were characterized to prove the hydrophobicity, UV blocking nature and nonfluorescence of as‐prepared MPTS‐modified ZnO NPs. Additionally, after the specific surface area (SSA) of samples with different MPTS amount was analyzed by BET, a competitive adsorption mechanism between silane‐ZnO bonding and silane oligomer‐ZnO deposition was suggested. In the demonstration of latent fingerprint development, the powder dusting method was utilized on various surfaces both in positive and reversed imaging modes, exhibiting the high contrast, high sensitivity, high selectivity and wide applicability, even for aged fingerprints. Therefore, it provides a new strategy for fast, efficient and inexpensive development of older latent fingerprints in forensic analysis.

Competition adsorption of malachite green and rhodamine B on polyethylene and polyvinyl chloride microplastics in aqueous environment.

Microplastics (MPs) will cause compound pollution by combining with organic pollutants in the aqueous environment. It is important for environmental protection to study the adsorption mechanism of different MPs for pollutants. In this study, the adsorption behaviors of malachite green (MG) and rhodamine B (RhB) on polyethylene (PE) and polyvinyl chloride (PVC) were studied in single systems and binary systems, separately. The results show that in single system, the adsorptions of between MPs for pollutants (MG and RhB) are more consistent with the pseudo-second-order kinetics and Freundlich isotherm model, the adsorption capacity of both MPs for MG is greater than that of RhB. The adsorption capacities of MG and RhB were 7.68 mg/g and 2.83 mg/g for PVC, 4.52 mg/g and 1.27 mg/g for PE. In the binary system, there exist competitive adsorption between MG and RhB on MPs. And the adsorption capacities of PVC for the two dyes are stronger than those of PE. This is attributed to the strong halogen-hydrogen bond between the two dyes and PVC, and the larger specific surface area of PVC. This study revealed the interaction and competitive adsorption mechanism between binary dyes and MPs, which is of great significance for understanding the interactions between dyes and MPs in the multi-component systems.

Competitive or synergetic? Adsorption mechanism of phosphate and oxytetracycline on chestnut shell-derived biochar

In the present study, the potential competitive or synergetic adsorption mechanism of phosphate and antibiotics from a solution using chestnut shell (CS)-derived biochar was explored. CSs were utilized as the raw material to prepare biochar (BCCS) and modified biochar (MBCCS) via an oxygen-isolated pyrolysis, and subsequent modification using KMnO4 and FeCl3. Following the carbonization, the biochar was deoxidized, which enhanced its porous structure and specific surface area. The MBCCS, which contained Fe and Mn ions on its surfaces, showed theoretical adsorption capacities of 0.7880 mg/g P and 6.2854 mg/g oxytetracycline (OTC), respectively. The adsorption of both PO43− and OTC by the MBCCS fitted better to the pseudo-second-order kinetic model. The PO43− adsorption on the MBCCS fitted better to the Langmuir isotherm, whereas that of the OTC was adequately described via the Freundlich isotherm. The adsorption processes were both endothermic. The pH and cation strength of the solution significantly affected the adsorption of both PO43− and OTC. Low concentrations of OTC favored competitive adsorption with PO43−, while high concentrations of both components produced synergetic adsorption on the MBCCS. In the present study, a potential method with good reusability for the utilization of agricultural and forestry wastes is highlighted. The results also provide a scientific basis for elucidating the adsorption mechanisms of coexisting pollutants in water on biochar.

Feasibility study on CO2-rich industrial waste gas storage and replacement in carbonate gas reservoir based on adsorption characteristics

The emission of CO2-rich industrial waste gas (CO2-rich IWG) poses a huge challenge to environmental protection. If the CO2-rich IWG could be used directly or after simple treatment for underground storage and replacement, then clean utilization of CO2-rich IWG will certainly be promoted. In this paper, the feasibility of CO2-rich IWG for underground storage and replacement in carbonate gas reservoirs was studied from the perspective of gas adsorption characteristics. Firstly, the reliability of the molecular model was verified by fitting Monte Carlo simulation data of four representative gases with isothermal adsorption experimental data. Then, molecular dynamics simulation was used to study the adsorption mechanism of various components on the calcite surface in CO2-rich IWG. Finally, the competitive adsorption mechanism between CO2-rich IWG and methane, and the multi-component competitive mechanism between dominant gases are studied. The results show that the adsorption capacity of each component on calcite surface is HF > CO2>SO2>H2S > NO2>CH4>CO. Hydrogen bond and electrostatic force are the main adsorption forces of HF. The electrostatic force between negatively charged atoms in the molecule and Ca2+ is the main adsorption force for CO2, SO2 and H2S. The weak van der Waals force is the main adsorption force for NO2, CH4 and CO. In the competitive systems, the absolute adsorption capacity of CO2-rich IWG is reduced by 25–50% compared with single component adsorption. However, in the competitive adsorption systems of HF/CH4, CO2/CH4, H2S/CH4 and SO2/CH4, the relative adsorption capacity of the four industrial waste gases to methane is increased by 9 times, 5.5 times, 4 times and 3.75 times as compared with the non-competitive ones. In the competitive adsorption systems of HF/CH4, CO2/CH4, H2S/CH4, and SO2/CH4 the negatively charged atoms are more likely to combine with Ca2+ to generate strong electrostatic attraction, while generating electrostatic repulsion to the negatively charged C atoms in CH4, leading to the weakening or even disappearance of CH4 adsorption. Therefore, CO2-rich IWG has a good application prospect in carbonate gas reservoirs, but the CO and NO2 should be removed before use.

Competitive adsorption of asphaltene and n-heptane on quartz surfaces and its effect on crude oil transport through nanopores

• Competitive adsorption mechanism between asphaltene and n-heptane on quartz surfaces was illustrated from molecular perspective. • Influence of asphaltene deposition on the transport of light oil is clarified. • Work of adhesion and adsorption time ratio were proposed to quantify adsorption strength. • Flow behaviors of asphaltene and n-heptane in two quartz nanopores were compared. Asphaltene deposition is a ubiquitous problem in crude oil exploitation, which can cause the blockage of pore throat, leading to a significant reduction of oil recovery. Understanding the microscopic mechanism of asphaltene deposition and its influence on the oil flow in nanopores is critical for effective exploitation of crude oil. In this study, we investigated the competitive adsorption of asphaltene and n-heptane on quartz surfaces using molecular dynamics simulations. We found that asphaltene shows a much stronger adsorption ability on the quartz surfaces than n-heptane, resulting from both interfacial energy strength and the poly-aromatic ring interactions among asphaltene molecules. With the deposition of asphaltene, the flux of n-heptane transport in nanopores is greatly decreased, which can be attributed to the reduction of effective aperture size and the disappearance of possible slip near the surface. The difference in adsorption and flow behaviors between asphaltene and n-heptane can be further elucidated by the comparison in work of adhesion for several interfaces. Besides, the effect of surface hydroxyl groups of quartz substrates was proved to have a prominent impact on the adsorption of asphaltene on the quartz surfaces, leading to a considerable enhancement of oil flux through SiO 2 nanopores. Our work advances the understanding of the low oil recovery caused by asphaltene deposition and has a significant reference value to the effective production and evaluation of crude oil.

Constructing AgY@Cu-BTC hybrid composite for enhanced sulfides capture and moisture resistance

Metal-modified zeolites and function-matched metal organic frameworks (MOFs) have been adapted to different scenarios of sulfides capture in order to meet increasingly stringent quality requirements and environmental regulations. However, achieving enhanced performances of both adsorption capacity and moisture resistance is still challenging. In this study, we provided an approach to the synthesis of [email protected] hybrid composite for enhanced sulfides capture and moisture resistance. Multiple characterizations confirmed the hybrid structure of [email protected] Additionally, computational simulation and dynamic adsorption measurement were combined to evaluate the adsorption of several typical sulfides on synthesized adsorbents, and reveal the competitive adsorption mechanism. Both Ag species and ethanol solvent lead to the partial reduction of Cu(II) to Cu(I) within the [email protected] framework. The dynamic adsorption capacity of the [email protected] is 1.54 times and 1.38 times higher than those of the parent AgY and Cu-BTC, respectively. Moreover, the [email protected] retains much more adsorption capability for sulfides than the AgY sample with the same water content. Present study highlights the competitive adsorption of various sulfides on the hybrid structures as well as the influences of pre-adsorbed water on sulfide adsorption, and provides insights into the function-oriented development of adsorption materials.

Enhanced oil recovery by sacrificing polyelectrolyte to reduce surfactant adsorption: A classical density functional theory study

During the process of chemical enhanced oil recovery (CEOR), surfactants are widely used as they can reduce interfacial tension and change surface wettability, but the huge economic losses caused by the adsorption of surfactants on rock surface need to be resolved. Therefore, polyelectrolyte is introduced to reduce the adsorption amount of surfactant. However, how to select appropriate polyelectrolyte suitable for different reservoirs is always lack of theoretical guidance. Herein, the competitive adsorption mechanism between surfactant and polyelectrolyte on rock surface is studied by classical density functional theory (CDFT). Having investigated the effects of different polyelectrolytes on the adsorption of surfactants, the optimal polyelectrolyte concentration and chain length suitable for different potentials were found. Also, the influence of rock crevices width on displacement effect was considered. Moreover, we proposed a comprehensive evaluation of polyelectrolytes in terms of both the performance and economy. The findings of this study benefit for further understanding of the competitive adsorption in CEOR, and provide guidance for the practical application of polyelectrolytes.

Differential Surface Adsorption Phenomena for Conventional and Novel Surfactants Correlates with Changes in Interfacial mAb Stabilization.

Protein adsorption on surfaces can result in loss of drug product stability and efficacy during the production, storage, and administration of protein-based therapeutics. Surface-active agents (excipients) are typically added in protein formulations to prevent undesired interactions of proteins on surfaces and protein particle formation/aggregation in solution. The objective of this work is to understand the molecular-level competitive adsorption mechanism between the monoclonal antibody (mAb) and a commercially used excipient, polysorbate 80 (PS80), and a novel excipient, N-myristoyl phenylalanine-N-polyetheramine diamide (FM1000). The relative rate of adsorption of PS80 and FM1000 was studied by pendant bubble tensiometry. We find that FM1000 saturates the interface faster than PS80. Additionally, the surface-adsorbed amounts from X-ray reflectivity (XRR) measurements show that FM1000 blocks a larger percentage of interfacial area than PS80, indicating that a lower bulk FM1000 surface concentration is sufficient to prevent protein adsorption onto the air/water interface. XRR models reveal that with an increase in mAb concentration (0.5-2.5 mg/mL: IV based formulations), an increased amount of PS80 concentration (below critical micelle concentration, CMC) is required, whereas a fixed value of FM1000 concentration (above its relatively lower CMC) is sufficient to inhibit mAb adsorption, preventing mAb from co-existing with surfactants on the surface layer. With this observation, we show that the CMC of the surfactant is not the critical factor to indicate its ability to inhibit protein adsorption, especially for chemically different surfactants, PS80 and FM1000. Additionally, interface-induced aggregation studies indicate that at minimum surfactant concentration levels in protein formulations, fewer protein particles form in the presence of FM1000. Our results provide a mechanistic link between the adsorption of mAbs at the air/water interface and the aggregation induced by agitation in the presence of surfactants.