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In recent years, various industrial and agricultural problems have been highlighted, and the pollution of heavy metal ions to water bodies has become a considerable serious phenomenon. Adsorption method is an efficient, low‐cost, and easy to implement method for removing heavy metal ions, which does not produce secondary pollution, and has been widely used in water treatment. Polysaccharides are natural polymers, and their hydroxyl, carboxyl, and amine groups provide feasibility for the synthesis of hydrogels with various structures. The synthesized polysaccharide hydrogel has the characteristics of high adsorption capacity, specific adsorption, nontoxic, and so on. In this review, the kinds of polysaccharide hydrogels and different synthesis methods were discussed first. Then, the adsorption mechanism and different adsorption modes of polysaccharide hydrogels were reviewed. Finally, the effects of different environmental factors on the adsorption capacity of polysaccharide hydrogel were studied. The future research on the adsorption of heavy metal ions by polysaccharide hydrogels was proposed. [ABSTRACT FROM AUTHOR]

Inspired by the "electric jellyfish group" in the ocean, the Ti O H O strong correlation strategy is first proposed and used to construct Hexagon MXene heterojunction for potassium-ions hybrid supercapacitor with high energy density. The adsorption rules and electron transport mechanism of potassium-ions at the Ti O H O interface revealed in this work provide valuable insights into the regulation of ions/electrons at the energy storage interface. [Display omitted] • Inspired by the "electric jellyfish group" in the ocean, the Ti O H O strong correlation strategy is first proposed and used to construct Hexagon MXene heterojunction for potassium-ions hybrid supercapacitor with high energy density. • The Ti O H O interface not only effectively improves the adsorption capacity and adsorption energy of potassium-ions, but also provides a fast channel for electron transport, thus obtaining a remarkable rate performance in neutral electrolyte. • The adsorption rules and electron transport mechanism of potassium-ions at the Ti O H O interface revealed in this work provide valuable insights into the regulation of ions/electrons at the energy storage interface. Potassium-ion hybrid capacitors (PIHC) are considered as ideal large-scale rechargeable energy storage devices due to their low-cost, high-power density and environmental protection. However, a low energy density is the main factor restricting the practical application of PIHC. The interface is formed on the surface of electrode material of PIHC through strong correlation to construct heterojunction, which can significantly improve the performance of ion energy storage. However, how to reveal the influence of the interfacial state of the heterojunction on the adsorption and electron transmission of energy storage ions at the atomic level is still one of the key scientific problems in this field. In this work, metal ion intercalation and microwave-assisted in-situ etching are used to construct the Hexagon MXene Ti 3 C 2 heterojunction with Ti O H O strong correlation. At the interface of heterojunction, Ti O H O highway for electron transmission is developed to improve the rate performance of PIHC. Through experimental and theoretical calculation, the optimum adsorption position and maximum adsorption amount of potassium-ion at the single interface of heterojunction are obtained, and the specific energy density of PIHC is increased. This lays a foundation for the practical application of high-performance soft-package PIHC. [ABSTRACT FROM AUTHOR]

A number of regolith-hosted REE occurrences have recently been discovered in the Esperance region in southern Western Australia. This paper summarizes major characteristics of REE mineralization and discusses contributing factors and potential controls. The main aim is to explain why there is a lack of highly sought-after ion-adsorption-clay-type REE deposits across the region despite the presence of the regolith-hosted REE mineralization on a regional scale. Local mineralization mostly occurs as continuous flat-lying enrichment "blankets" within the residual regolith developed over Archaean–Proterozoic granite gneisses and granitoids with elevated REE content. The enriched horizon is commonly located in the lower saprolite and saprock and is accompanied by an overlying REE-depleted zone. This distribution pattern, together with the data on HREE fractionation and the presence of the supergene REE minerals, indicates chemogenic type enrichment formed by supergene REE mobilization into groundwater, downward transport, and accumulation in the lower part of the weathering profile. Residual REE accumulation processes due to bulk rock volume and mass reduction during weathering also contribute to mineralization. It is proposed that climate and groundwater chemistry are the critical regional controls on the distribution of REEs in the weathering profile and on their speciation in the enrichment zone. Cenozoic aridification of climate in southwest Australia heavily overprinted pre-existing REE distributions in the weathering profile. Acidic (pH < 4), highly saline groundwaters intensely leached away any relatively weakly bound, adsorbed or colloidal REE forms, moving them downward. Dissolved REEs precipitated as secondary phosphates in neutral to alkaline environment at lower Eh near the base of the weathering profile forming the supergene enrichment zone. Low denudation rates, characteristic of areas of low relief under the arid climate, are favourable for the preservation of the existing weathering profiles with REE mineralization. [ABSTRACT FROM AUTHOR]

Smaller Kapitza resistance is known to be the most crucial factor responsible for the larger thermal conductivity of nanofluids. But what the underlying mechanism is remains ambiguous. Non-equilibrium molecular dynamics simulations were performed in the present work to examine the effect of ionic addition on the Kapitza resistance of Cu-water nanofluids. The temperature profile indicates that the concentration and type of the additive slightly affects the thickness of the interfacial layer, but the temperature drops significantly. For concentrations of 1 M, the interfacial thermal conductance (ITC, the reciprocal of the Kapitza resistance) of Cu-water with NaCl, NaOH and HCl increases by 48.1 %, 29.2 % and 22.6 % respectively, compared to that without additives. The greatest ITC improvement of 123.7 % can be achieved by adding 3 M NaCl. The density profiles of Cu-water nanofluids with various additives suggest that the changes in the interfacial structure are primarily due to the positions of the added cations and anions. It is important to note, however, that the ITC is closely related to the orderliness of the interfacial layer and the matching of the phonon density of states, since the addition of NaCl can increase the PDOS at lower frequencies 1–5 THz, where that for the Cu nanoparticle appears. The findings provide a practical approach to tailor the thermal conductivity of nanofluids by the addition of appropriate ions.

The ion extraction and electro/photo catalysis are promising methods to address environmental and energy issues. Covalent organic frameworks (COFs) are a class of promising template to construct absorbents and catalysts because of their stable frameworks, high surface areas, controllable pore environments, and well‐defined catalytic sites. Among them, ionic COFs as unique class of crystalline porous materials, with charges in the frameworks or along the pore walls, have shown different properties and resulting performance in these applications with those from charge‐neutral COFs. In this review, current research progress based on the ionic COFs for ion extraction and energy conversion, including cationic/anionic materials and electro/photo catalysis is reviewed in terms of the synthesis strategy, modification methods, mechanisms of adsorption and catalysis, as well as applications. Finally, we demonstrated the current challenges and future development of ionic COFs in design strategies and applications. [ABSTRACT FROM AUTHOR]

Rapid economic development and increased demand for mineral products in China have led to extensive extraction of various ores, resulting in significant environmental challenges associated with the generation of industrial solid waste, particularly iron tailings. Despite being a major mining nation, China faces issues of wasteful practices, with substantial amounts of valuable elements lost during the processing of iron ore. This study addresses the urgent need for sustainable solutions by proposing an innovative approach for the recovery of valuable elements from iron tailings. The proposed process involves a sequential application of acid leaching, chemical precipitation, and Metal-Organic Frameworks (MOFs) ion adsorption. The pre-treated iron tailings were leached in HCl solution with pH 1.5 at 70 °C for 2 h, and the co-leaching efficiency of 98.1% V, 98.2% Mo, 99.3% Fe, and 98.7% Mg was obtained. Chemical precipitation is then employed to isolate Fe, Mg V, and Mo and promote the formation of targeted compounds, ensuring concentration and purity. The integration of MOF ion adsorption, known for its high surface area and tunable pore structures, provides an efficient platform for selectively capturing and recovering target ions. 97.7% V and 96.3% Mo were selectively extracted from Zirconium 1,4-carboxybenzene metal-organic framework (UiO-66) adsorption system with pH 5.0 at 30 °C for 6 h, and 91.7% V and 90.3% Mo were selectively extracted from 2-methylimidazole zinc salt metal-organic framework (ZIF-8) adsorption system with pH 5 at 30 °C for 6.0 h. This three-stage process offers an efficient method for the recovery of valuable elements from iron tailings. [ABSTRACT FROM AUTHOR]

The adsorption of ions to water-hydrophobe interfaces influences a wide range of phenomena, including chemical reaction rates, ion transport across biological membranes, and electrochemical and many catalytic processes; hence, developing a detailed understanding of the behavior of ions at water-hydrophobe interfaces is of central interest. Here, we characterize the adsorption of the chaotropic thiocyanate anion (SCN-) to two prototypical liquid hydrophobic surfaces, water-toluene and water-decane, by surface-sensitive nonlinear spectroscopy and compare the results against our previous studies of SCN- adsorption to the air-water interface. For these systems, we observe no spectral shift in the charge transfer to solvent spectrum of SCN-, and the Gibb's free energies of adsorption for these three different interfaces all agree within error. We employed molecular dynamics simulations to develop a molecular-level understanding of the adsorption mechanism and found that the adsorption for SCN- to both water-toluene and water-decane interfaces is driven by an increase in entropy, with very little enthalpic contribution. This is a qualitatively different mechanism than reported for SCN- adsorption to the air-water and graphene-water interfaces, wherein a favorable enthalpy change was the main driving force, against an unfavorable entropy change.

The adsorption of divalent ions on metal oxides is controlled by the pH of a solution. It is commonly assumed that this is a reversible process for pH changes. However, there are reports that the sorption of ions on oxides may not be reversible. To verify this, we used potentiometric titration, ion-selective electrodes (ISEs), and electrokinetic measurements to examine the reversibility of the adsorption of hydrogen ions and three metal ions (Ca2+, Cu2+, and Fe2+) on TiO2. The ferrous ion was used as a reference because its adsorption is entirely irreversible. The surface charge determined by potentiometric titration and the adsorption edges measured using ISE indicate that the adsorption of copper ions is reversible with changes in pH. In the case of calcium ions, the results suggest a certain degree of irreversibility. There are apparent differences in the electrokinetic potential data obtained during titration with base and acid, which suggests that the adsorption is irreversible. We have explained this contradiction by considering the complex and dynamic nature of electrophoretic mobility. In our opinion, potentiometric titration may be the simplest and most reliable method for assessing the reversibility of multivalent ion adsorption. [ABSTRACT FROM AUTHOR]

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Capacitive deionization (CDI), an emerging method for water desalination and ion separation, has received much attention due to its advantages of high ion selectivity, high water recovery and low energy consumption. Compared with the traditional carbon electrodes, the emerging Faraday electrode offers a unique opportunity to make the desalination performance of CDI significantly improved through the Faraday reaction of ion capture. Transition metal-based electrodes have received much attention in the field of CDI electrode design due to their highly reversible Faraday response, relatively high conductivity, and excellent theoretical pseudocapacitance values. In this paper, we systematically summarize and sort out the material classification of transition metal-based electrodes in CDI applications, and summarize the modification engineering performed for their intrinsic defects, mainly including conductive material coupling, functional architecture engineering and defect engineering, etc., and summarize their performance in CDI applications; in addition, the specific applications of transition metal-based electrodes in CDI are particularly introduced in terms of ion selective separation, metal ion removal and nutrient element recovery. Finally, the paper also outlines the remaining challenges and research directions to provide guidance for future development and research of transition metal chemical substance electrodes. [ABSTRACT FROM AUTHOR]

It is common to say that the origin of the membrane potential is attributed to transmembrane ion transport, but it is theoretically possible to explain its generation by the mechanism of ion adsorption. It has been previously suggested that the ion adsorption mechanism even leads to potential formulae identical to the famous Nernst equation or the Goldman-Hodgkin-Katz equation. Our further analysis, presented in this paper, indicates that the potential formula based on the ion adsorption mechanism leads to an equation that is a function of the surface charge density of the material and the surface potential of the material. Furthermore, we have confirmed that the equation holds in all the different experimental systems that we have studied. This equation appears to be a key equation that governs the characteristics of the membrane potential in all systems. [ABSTRACT FROM AUTHOR]

Since lead is a highly toxic metal, it is necessary to detect its presence in different samples; unfortunately, analysis can be complicated if the samples contain concentrations below the detection limit of conventional analytical techniques. Solid phase extraction is a technique that allows the carrying out of a pre-concentration process and thus makes it easy to quantify analytes. This work studied the efficiency of sorption and preconcentration of lead utilizing polysulfone (PSf) fibers grafted with acrylic acid (AA). The best conditions for Pb(II) extraction were: pH 5, 0.1 mol L−1 of ionic strength, and 40 mg of sorbent (70% of removal). The sorbed Pb(II) was pre-concentrated by using an HNO3 solution and quantified using flame atomic absorption spectrometry. The described procedure was used to obtain a correlation curve between initial concentrations and those obtained after the preconcentration process. This curve and the developed methodology were applied to the determination of Pb(II) concentration in a water sample contained in a handmade glazed clay vessel. With the implementation of the developed method, it was possible to pre-concentrate and determine a leached Pb(II) concentration of 258 µg L−1. [ABSTRACT FROM AUTHOR]

This study investigates the dissolution of calcite's (1 0 4) and (1 0 0) surfaces under alkaline conditions (pH 8.8–13.1) using vertical scanning interferometry under flow-through conditions. The dissolution rate of (1 0 0) surfaces decreases with increasing pH. For example, the dissolution rate at pH 8.8 is more than 20 times higher than that at pH 13.1. In contrast, the dissolution rate of (1 0 4) surfaces is far less sensitive to pH. We explain these observations as being on account of the preferential adsorption of [OH−] on (1 0 0) surfaces, inhibiting their dissolution. Particularly, this is because Ca-surface sites on (1 0 0) surfaces are less coordinated and have a stronger tendency for [OH−] adsorption. As a result, (1 0 0) surfaces dissolve nearly twice as fast as (1 0 4) surfaces at pH 8.8, whereas (1 0 4) surfaces dissolved ∼4.5 times faster than (1 0 0) surfaces at pH 13.1; indicating an inversion in dissolution behavior. The dissolution rate of (1 0 4) surfaces at pH 13.1 is 60 % of the rate at pH 10–12 because of the formation of slow dissolving microfacets of other orientations. The rhombohedral dissolution etch-pits formed on (1 0 4) surfaces, at lower pH's, disappeared upon exposure to solutions with pH > 12 and were replaced by protrusions. The addition of up to 4 m (molality) NaCl enhances the dissolution of (1 0 4) surfaces at pH 8.8–13.1 and (1 0 0) surfaces at pH 8.8–11.0, and inhibited the dissolution of (1 0 0) surfaces at pH = 12.0–13.1. In addition, the competing adsorption between OH− and CO 3 2− species mitigates the inhibition effects of CO 3 2− on both surfaces at pH 13.1 compared to pH 11, and the dissolution of (1 0 0) surfaces is far less affected by CO 3 2− than (1 0 4) surfaces. These results provide new insights into the rates and mechanisms of how crystallographic orientations affect calcite's dissolution at alkaline pH conditions. [ABSTRACT FROM AUTHOR]

Coal mining produces a large amount of gangue that pollutes the environment, causing surface subsidence and damaging the groundwater systems. Backfill mining is an effective technology used to solve this problem, but there is a risk of polluting the groundwater due to the heavy metal ions present in the backfill material. Pb2+ has been determined to be a representative element because of its existence in coal gangue samples but not in fly ash. The risk of gangue-based cemented backfill causing groundwater pollution can be evaluated by studying the Pb2+ leaching from gangue under various conditions. When comparing the leaching amounts of Pb2+ from the coal gangue particles and the test blocks, it was found that cement filling has an obvious consolidation effect on the Pb2+ in coal gangue. The above process shows that cemented backfill has an obvious consolidation effect on the Pb2+ in gangue. The results of the theoretical analysis, X-ray, and SEM show that the consolidation mechanism can be divided into four modes: physical encapsulation, ion exchange, ion adsorption, and chemical reaction. The results are of great significance for revealing the leaching mechanism of the heavy metals in coal gangue, assessing the risk of heavy metal pollution in groundwater via gangue-cemented backfill, and improving the mining theory of the gangue-cemented filling and groundwater protection. [ABSTRACT FROM AUTHOR]

The adsorption of divalent ions on metal oxides is controlled by the pH of a solution. It is commonly assumed that this is a reversible process for pH changes. However, there are reports that the sorption of ions on oxides may not be reversible. To verify this, we used potentiometric titration, ion-selective electrodes (ISEs), and electrokinetic measurements to examine the reversibility of the adsorption of hydrogen ions and three metal ions (Ca2+, Cu2+, and Fe2+) on TiO2. The ferrous ion was used as a reference because its adsorption is entirely irreversible. The surface charge determined by potentiometric titration and the adsorption edges measured using ISE indicate that the adsorption of copper ions is reversible with changes in pH. In the case of calcium ions, the results suggest a certain degree of irreversibility. There are apparent differences in the electrokinetic potential data obtained during titration with base and acid, which suggests that the adsorption is irreversible. We have explained this contradiction by considering the complex and dynamic nature of electrophoretic mobility. In our opinion, potentiometric titration may be the simplest and most reliable method for assessing the reversibility of multivalent ion adsorption.

The increasing demand for lithium-ion batteries has led to a surge in global lithium consumption, calling for efficient extraction and recovery methods. Adsorption-based lithium recovery has gained attention for its simplicity, selectivity, and low energy requirements. However, conventional adsorption materials for lithium-ion (Li+) suffer from low surface area and covered active sites, resulting in slow recovery and inefficient uptake. Herein, we present a facile photoinduced synthesis of crown ether (CE)-based polymer grafted covalent organic framework (COF) microspheres, termed COF-CE, as an efficient lithium adsorbent. The COF-CE hybrid material possesses abundant nanochannels and highly porous surfaces, enabling rapid ion diffusion and enhancing ion accessibility to functional groups with the exclusive selectivity imparted by the grafted CE polymer towards Li+ over other monovalent cations. Notably, COF-CE exhibits exceptional absorption capacity (7.4 mg/g), rapid adsorption rates (k 2 = 0.137 g mg−1 min−1) and high selectivity towards Li+, outperforming existing adsorbents. Moreover, COF-CE demonstrates remarkable Li+ regeneration and recycling capabilities, achieving near-unity recovery of lithium during the desorption phase and retaining 97 % of its adsorption capacity after five cycles. These results highlight the potential of COF-CE as an advanced adsorbent for lithium recovery in various applications, including industrial wastewater treatment and environmental remediation efforts. [Display omitted] • Photoinduced polymerization to graft crown ether on covalent organic frameworks. • Abundant nanochannels and porous surfaces of COF enable efficient adsorption of ion. • High selectivity to Li ion, fast adsorption and high adsorption capacity. [ABSTRACT FROM AUTHOR]

Microporous carbonaceous electrode materials store charge by ion electrosorption onto the electrode surface. Despite significant efforts to understand this phenomenon, a definitive picture of the adsorption mechanisms within these complex nanoscale structures is lacking. Here, we use nuclear magnetic resonance (NMR) spectroscopy to directly observe and quantify aqueous adsorbate partitioning behavior driven by spontaneous physisorption within the micropores. Our results show that the solvation properties of the electrolyte ions influence the ionophilicity/ionophobicity of the adsorbate-carbon system, with ionophilic and ionophobic systems exhibiting distinct behavior concerning the electrolyte loading volume. Micropore diameter is also shown to influence spontaneous electrolyte partitioning behavior and disturb ion solvation. In situ NMR spectroscopy using a working supercapacitor comprising microporous carbon electrodes with aqueous sodium sulfate and aqueous sodium bis(trifluoromethane)sulfonimide electrolytes indicates that spontaneous electrolyte partitioning behavior influences the charge-balancing mechanism. Our results suggest that spontaneously ionophilic systems favor charge-balancing by counter-ion adsorption under an applied voltage, and spontaneously ionophobic systems favor a co-ion ejection mechanism under an applied potential. These results provide new molecular-level insight into the role of electrolyte properties on spontaneous physisorption behavior and charged electrosorption behavior within microporous carbon electrodes. [Display omitted] • Ion solvation determines the spontaneous distribution across microporous carbons. • Ionophilic and ionophobic systems show unique volume-dependent adsorption behavior. • Confinement-driven changes to ion hydration and pore-accessibility are observed. • Electrosorption mechanisms are influenced by spontaneous ion adsorption behavior. [ABSTRACT FROM AUTHOR]

It is now well established by numerous experimental and computational studies that the adsorption propensities of inorganic anions conform to the Hofmeister series. The adsorption propensities of inorganic cations, such as the alkali metal cations, have received relatively little attention. Here we use a combination of liquid-jet X-ray photoelectron experiments and molecular dynamics simulations to investigate the behavior of K+ and Li+ ions near the interfaces of their aqueous solutions with halide ions. Both the experiments and the simulations show that Li+ adsorbs to the aqueous solution-vapor interface, while K+ does not. Thus, we provide experimental validation of the "surfactant-like" behavior of Li+ predicted by previous simulation studies. Furthermore, we use our simulations to trace the difference in the adsorption of K+ and Li+ ions to a difference in the resilience of their hydration shells.

Modification of metal surfaces with complex molecules opens interesting opportunities to build additional functionality into these surfaces. In this work, self assembled monolayers (SAMs) based on the same photoswitchable azobenzene motif but with different head groups have been synthesized and their SAMs on Au(111)/Si substrates have been characterized. 3-[(4-phenylazo)phenoxy]propyl thiol (PAPT) and its acetyl group protected analog, 3-[(4-phenylazo)phenoxy]propyl thioacetate (PAPA), have been synthesized. SAMs from PAPT and PAPA have been characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ellipsometry and cyclic voltammetry (CV). The SAM-forming units of both SAMs are the same, as confirmed by IR and XPS, and the SAMs have similar surface coverage, as evidenced by analysis of the reductive desorption peaks in CVs. The tilt angle of the azobenzene moiety was ca. 75° with respect to the surface normal as determined by IR spectroscopy, i.e., the molecules are lying quite flat on the gold surface. Despite similar surface coverages, the CVs for PAPT in aqueous perchlorate solution show a typical perchlorate adsorption peak to gold, whereas the corresponding experiments with PAPA show no perchlorate adsorption at all. In conclusion, SAM formation can lead to an increase in the number of electrochemically accessible surface sites on the final, SAM covered surface. Whether the amount of such sites increases or decreases, depends on the precursor. The precursor most likely affects the adsorption mechanism and thus the atomic surface structure of the metal at the metal/SAM interface. Thus, details of the SAM formation mechanism, which is affected by the precursor used, can have quite strong effects on the electrochemical properties, and likely also electrocatalytic properties, of the resulting modified surface. [ABSTRACT FROM AUTHOR]

Water-enabled electricity generation (WEG), which harvests energy from the natural water cycle, is a novel strategy for producing green electricity. Taking advantage of the ion sieving effect based on evaporation-induced water flows in charged nanopores, various WEG devices have been developed. Here, we report that a carbonized mushroom produces a record-high current output of up to 96.7 μA, which is attributed to a unique ion adsorption effect combined with an ion sieving effect. Specifically, the natural gradient potential from root to cap in a mushroom caused by tissue differentiation adsorbs different ions, enhancing the traditional ion sieving current. In synergy with the two effects, the mushroom can operate under a broad range of concentrations (0 to 0.6 mol L -1 ) and represents significant improvements in current, duration, and total charge transfer. These findings reveal the hidden talent of mushrooms as natural materials for WEG, providing inspiration for the development of high-performance WEG devices.

Solid surfaces in contact with nonaqueous solvents play a key role in electrochemistry, analytical chemistry, and industrial chemistry. In this work, the zeta potentials of cotton membranes in acetonitrile solutions were determined by streaming potential and bulk conductivity measurements. By applying the Gouy-Chapman theory and the Langmuir adsorption isotherm of ions to the experimental data, the mechanism of the electrification at the cotton/acetonitrile interface is revealed for the first time to be solely due to ion adsorption on the surface, rather than proton dissociation at the interface. Different salts were found to produce opposite signs of the zeta potentials. This behavior can be attributed to ion solvation effects and the strong ordering of acetonitrile molecules at the interface. Furthermore, a trend of the electroviscous effect was observed, in agreement with the standard electrokinetic theory. These findings demonstrate that electrokinetics in acetonitrile, a polar aprotic solvent, can be treated in the same manner as in water.

A capillary column coated with 3-aminophenylboronic acid (APBA)-functionalized gold nanoparticles (AuNPs@APBA) was prepared via electrostatic self-assembly. The coated column exhibited anti-nonspecific adsorption of glycoproteins, enabling selective online enrichment during capillary electrophoresis (CE). First, gold nanoparticles (AuNPs) were synthesized using the sodium citrate reduction method. Then, APBA was self-assembled electrostatically on the surface of the AuNPs to obtain AuNPs@APBA. This nanomaterial was bonded to the inner wall of a capillary through ion adsorption to produce a AuNPs@APBA-coated capillary column. Glycoproteins were adsorbed via bond formation with boric acid groups under alkaline conditions (pH 8) to generate borate esters. Under acidic conditions (pH 3), the borate esters dissociated to release the glycoproteins, thereby achieving the selective online enrichment and separation of glycoproteins. The AuNPs and AuNPs@APBA were characterized using Fourier transform infrared spectroscopy, and their sizes and Zeta potentials were determined. In addition, the electroosmotic flow (EOF) of the AuNPs@APBA-coated capillary column was measured. The results showed that the surface of the AuNPs was successfully modified with APBA and that AuNPs@APBA was adsorbed on the inner wall of the capillary. The peak area of ovalbumin (OVA) on the AuNPs@APBA-coated column was 26.46 times higher than that on a bare column via conventional electrophoresis. In contrast, the peak area of bovine serum albumin (BSA) only increased by 8.47 times, indicating that the AuNPs@APBA coated column selectively enriched glycoproteins. Evaluation of the reproducibility and stability of this method revealed that the AuNPs@APBA coated capillary column could be used continually for 33-67 h. The relative standard deviations (RSDs) of the peak areas for intra-day ( n =5) and inter-day ( n =6) analyses were 2.2% and 3.0%, respectively. The developed method was successfully applied to enrich glycoproteins in a 1×10 6 -fold diluted egg white sample. Glycoproteins were not detected using conventional electrophoresis on the bare column, whereas the AuNPs@APBA-coated capillary column effectively enriched and separated glycoproteins, resulting in a peak area of 10469 mAU·ms. Furthermore, the entire enrichment and separation process was completed within 3 min. This new online enrichment and separation method for glycoproteins has the advantages of low sample consumption, simple operation, and high separation efficiency.

Graphene oxide is a promising, emerging separation material, as it is durable, dispersible in water, and has naturally forming functional groups. Bulk studies using graphene oxide flakes have demonstrated impressive metal adsorption. However, little interfacial information about water and metal organization near graphene oxide is available. A mechanistic understanding of water and ions interactions with graphene oxide films is critical toward advanced separations, including improved sorption efficiency and membrane regeneration. We study metal ion and local water organization near graphene oxide thin films formed at the air/water interface. These films are not typical membranes and allow us to determine nanoscale information about the graphene oxide-water interface. We accomplish this with x-ray reflectivity (XR), x-ray fluorescence near total reflection (XFNTR), and vibrational sum frequency generation spectroscopy (SFG). These interface-specific techniques provide the electron density profile normal to the interface, number of adsorbed ions, and information about the orientational ordering and hydrogen-bonding network of interfacial water, respectively. Via XFNTR and SFG, we find that trivalent yttrium ions preferentially adsorb to graphene oxide and affect its structure, compared to divalent strontium and monovalent cesium ions. Two different interfacial water populations can be described, based on their hydrogen bonding strength, and the adsorbed ions affect these populations differently. These results provide fundamental information about ion and water organization at the interface and help address the large computational-experimental agreement gap for graphene oxide systems. Additionally, they are relevant for improved soft-scaffold graphene oxide membranes and downstream applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Accumulation of H+ can cause soil acidification, affect soil particle interactions, and alter soil processes. In this study, aggregation kinetics of montmorillonite colloids induced by monovalent ions of Li+ and H+ were determined by dynamic light scattering. The experimental results indicated that the critical coagulation concentration (CCC) value of Li+ was 4.5 times that of H+, indicating that H+ can strongly promote montmorillonite colloids aggregation. Joint analysis of the adsorption force type and energy of Li+ and H+ as well as the infrared spectroscopy of Li+ and H+ montmorillonite indicated that there was only electrostatic adsorption for Li+, while there was not only electrostatic adsorption but also a new type of covalent adsorption for H+: polarisation‐induced covalent adsorption. The total adsorption energy of H+ is thus much higher than that of Li+ on montmorillonite surfaces. Moreover, the polarisation‐induced covalent adsorption energy of H+ increased linearly with increasing electric field strength, which is consistent with the quantum mechanical analysis of the asymmetric orbital hybridisation of surface O atoms on montmorillonite. On this basis, the polarisation‐induced covalent adsorption energy of H+ was employed to predict the CCC value of H+ induced montmorillonite aggregation, and it was 7.40 mmol L−1. The high agreement with experimental results (7.26 mmol L−1) proved that the polarisation‐induced covalent interactions between H+ and surface O atoms promotes montmorillonite aggregation. This polarisation induced covalent effect between H+ and surface O atoms might further affect the formation and stability of soil aggregates and the pore status of soil structure, especially as soil acidification is currently becoming a global issue. The discovery from this study will improve our understanding of the effects of soil acidification on soil properties and processes. Highlights: H+ greatly promoted clay aggregation.Polarization‐induced covalent between H+ and surface O presented at clay surface.Polarization‐induced covalent bonding energy increase with increasing electric field.Electrostatic and covalent bonding forces jointly determined clay aggregation. [ABSTRACT FROM AUTHOR]

The simultaneous control of crystal phase stability and one-dimensional growth has always been the major challenge for the preparation of tetragonal zirconia whiskers. In this study, we report a facile molten salt processing that utilizes CaF2 as a stabilizer and adsorbent to meet the phase and morphology requirements. The processes of stabilization, phase transition, ion adsorption and formation of special morphology involved in zirconia growth were investigated by XRD, IR, SEM, DTA-TG and TEM. By controlling the amount of CaF2 (15 wt%) added in the reaction precursor, tetragonal zirconia whiskers with a desired aspect ratio (>16) can be synthesized, which show single crystalline nature and [001] preferred direction. Ca ions doped at low temperature inhibit the occurrence of phase transition, which allows the tetragonal structure to be retained to room temperature. The inducement and pattern of whisker growth are supposed to be F-adsorption and screw dislocation elongation, respectively. The specific selectivity of surface adsorbed ions to certain zirconia crystal planes reduces or even inhibits the epitaxial growth rate in this direction, offering a viable avenue for the morphology modulation of inorganic nanomaterials.

We theoretically investigate the effects of ion adsorption on nanofiltration by simultaneously solving the modified Navier-Stokes, Poisson, and Nernst-Planck equations. Considering the confined space in the nanopore and the layered structure of water near the nanopore surface, hindered transport and anisotropic dielectric exclusion are separately incorporated to demonstrate the corresponding influences on salt rejection. For symmetric electrolytes, ion adsorption decreases the rejection of NaCl slightly but alters the rejection performance of CaSO 4 significantly. In particular, ion adsorption improves the rejection of asymmetric electrolytes due to the charge polarity reversal. With ion adsorption, the susceptibility of rejection to pH changes diminishes, and the dependence of rejection on feed concentration decreases. Owing to the counteracting effects of increased surface charge density and more pronounced ion screening as feed concentration rises, the rejection of CaCl 2 and Na 2 SO 4 exhibits a maximum under specific pH ranges. 2D surface plots illustrate the dependence of rejection on concentration and pH. In addition, the effect of hindered transport is beneficial to rejection. As the diffusivities of ionic species drop or the diffusivity ratio of co-ions (relative to the surface charge polarity) to counterions decreases, the rejection increases pronouncedly. Lastly, dielectric exclusion in the nanopore results in a more negative surface charge density due to the repulsion of protons from the surface, thereby causing a shift of the isoelectric point towards lower pH values. The effect of the reduction in the perpendicular dielectric permittivity may be enhanced or offset partially by that of the increase in the parallel dielectric permittivity. [Display omitted] • The effects of ion adsorption on nanofiltration have been investigated. • The rejection of asymmetric salts can be improved through charge polarity reversal. • Maximal rejection with concentration is due to ion adsorption on the nanopore. • The effects of ion diffusivity and diffusivity ratio of co-ion to counterion have been investigated. • Anisotropic dielectric exclusion decreases the occurrence of ion adsorption. [ABSTRACT FROM AUTHOR]

Although continuous mobile ion passage across the plasma membrane is responsible for the generation of the membrane potential, some experiments suggest that the membrane potential can be generated even without the ion passage across the membrane. This potential could be due to the ion adsorption–desorption phenomenon, and it is even possible to derive a potential formula under such a mechanism. This potential formula is somehow identical to the well-known Nernst equation. We investigated this potential formula in depth and found that the profile of "the membrane surface potential versus the logarithm of ion concentration" exhibits the Nernst slope, and this Nernst slope is the key to the identical potential formula to the Nernst equation even for the system without the passage of ions across the membrane. This work may trigger new information about the membrane potential generation mechanism. [Display omitted] • Nonzero membrane potential can be generated even across the impermeable membrane. • Nernst slope indicates the constant surface charge density of membrane. • The constant membrane surface charge density causes the ion adsorption-origin membrane potential. [ABSTRACT FROM AUTHOR]

Phyllosilicate clay minerals have been proposed as a possible buffer material to be used in deep geological repositories containing high-level waste and used nuclear fuel. This work precisely characterizes ion interactions with two types of adsorption sites present in these clays: Mg Al ' substitutions and undercoordinated edge surface atoms. A number of unique structural models were considered to represent the diverse local environments that ions in these systems are likely to encounter. Using molecular dynamics simulation with the CLAYFF potential, the spatial distribution, interlayer composition, and residence times of Na+ and Cl− ions as radionuclide analogs in pyrophyllite and montmorillonite clay models were investigated to identify the most favorable conditions for sequestration. The most significant factor impacting ion adsorption was found to be the localization of charge density at substitution sites. In a montmorillonite system in which substitution sites were distributed evenly to produce a low charge density, sequestration performance was found to be comparable to pyrophyllite. • MD simulation of phyllosilicate edge surfaces in NaCl solution reveal favorable adsorption sites. • Arrangement of Mg Al ' substitution sites can impact interlayer ion content and residence time. • Local charge density is the primary driver in determining adsorption site favorability. • Unhealed edge surfaces promote ion sequestration in the absence of Mg Al ' substitutions. • Evenly distributed Mg Al ' substitutions exhibit low interlayer residence time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-idealities at the solid/liquid interface obtained from molecular simulations. • Molecular dynamics simulations maintain a constant solution composition. • NaCl(aq) at graphite and at NaCl(s) surfaces displays asymmetric ion adsorption. • Asymmetric adsorption induces an electric potential at the solid/liquid interface. Solid/liquid interfaces control various processes of technological relevance in the process industry and many fundamental physicochemical phenomena. This work examines the link between the atomistic description of mass transfer at solid/liquid interfaces out of equilibrium and constitutive mass transfer equations which are typically used to model these processes at the mesoscale. In our analyses we discuss the microscopic inconsistencies apparent in simplified models of mass transfer whenever non-idealities dominate the liquid phase in the proximity of solid/liquid interfaces. Using C μ MD – a molecular simulation technique to investigate out-of-equilibrium, concentration-driven processes with pseudo open-boundary conditions – we outline a strategy to capture and quantify non-idealities induced by specific interactions between the solid surface and molecules in the fluid phase. We demonstrate our approach by studying electrolyte solutions in technologically important, multi-component systems where the introduction of a solid/liquid interface induces substantial deviations in the composition and electrochemical properties locally compared to the bulk fluid phase. To this aim, we analyse NaCl(aq) solutions in contact with (i) the graphite basal surface and (ii) {100} NaCl(s) crystalline surfaces. We uncover the tendency of the sodium cation to preferentially adsorb at the surfaces considered, which induces local violations of electroneutrality that leads to the emergence of an electric potential in the fluid phase at the solid/liquid interface. [ABSTRACT FROM AUTHOR]

[Display omitted] The mechanism leading to the extraordinary stability of bulk nanobubbles in aqueous solutions remains an outstanding problem in soft matter, modern surface science, and physical chemistry science. In this work, the stability of bulk nanobubbles in electrolyte solutions under different pH levels and ionic strengths is studied. Nanobubbles are generated via the technique of ultrasonic cavitation, and characterized for size, number concentration and zeta potential under ambient conditions. Experimental results show that nanobubbles can survive in both acidic and basic solutions with pH values far away from the isoelectric point. We attribute the enhanced stability with increasing acidity or alkalinity of the aqueous solutions to the effective accumulation of net charges, regardless of their sign. The kinetic stability of the nanobubbles in various aqueous solutions is evaluated within the classic DLVO framework. Further, by combining a modified Poisson-Boltzmann equation with a modified Langmuir adsorption model, we describe a simple model that captures the influence of ion species and bulk concentration and reproduce the dependence of the nanobubble's surface potential on pH. We also discuss the apparent contradiction between quantitative calculation by ion stabilization model and experimental results. This essentially requires insight into the structure and dynamics of interfacial water on the atomic-scale. [ABSTRACT FROM AUTHOR]

The presence of cadmium in the environment requires attention, due to its carcinogenic and bioaccumulative power. To remedy water bodies contaminated with trace metal, different materials are reported in the literature. This work describes a method able to remove 10–25% of Cd2+ from aqueous solutions in a single batch using layered and cationic exchanger cerium hydrogenphosphate (CeP) material. In the present study, this material was obtained in three forms after hydrothermal treatment for 4 h, 16 h and 24 h. Powder X-rays diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, 31P nuclear magnetic resonance (31P NMR) and thermogravimetric analysis evidenced that CeP 24 h had a surface-like sorption in contrast to CeP 4 h. SEM visualizations showed a much pronounced fibrillar morphology for CeP 24 h. Also, we studied the Cd sorption mode by each material either applying agitation (dynamic) or not (static). Considering all this, the best results were obtained for Cd adsorption using CeP 24 h in dynamic mode according to ion adsorption capacity% values calculated from atomic absorption data. This is in contrast to data in the literature that mostly applies CeP 4 h as the metal ion sorptive material. [ABSTRACT FROM AUTHOR]

The dissociation of negative molecular ions of tetracyanoquinodimethane (TCNQ) on the surface of the ionization chamber of the ion source of a mass spectrometer modified for operation in the mode of resonant electron capture by molecules is studied. Based on the helium-puffing experiment and calculations by the B3LYP/6-31G method, it is shown that, under the influence of the induced charge, TCNQ– ions on the surface can dissociate through channels which is not possible in the gas phase due to lack of energy. The result is significant for improving the experiment on the resonant capture of electrons by molecules and solving the well-known problem of the destruction of materials based on TCNQ in electronic devices. [ABSTRACT FROM AUTHOR]

Two mathematically distinct physiological concepts, the Goldman-Hodgkin-Katz eq. (GHK eq.) and the Hodgkin-Huxley model (HH model) were successfully associated with each other in a prior work. The previous work was performed on the following premises (i) The membrane potential is generated by ion adsorption, as opposed to the classical ion transport mechanisms, (ii) The living cell is a thermodynamically real system rather than an ideal system, and (iii) The conductance employed in the HH model is replaced by the ion activity coefficient, which is weighted with the role of conductance. Consequently, the GHK eq. was mathematically associated with the HH model through the intermediary of Boltzmann ion distribution and mass action law. To verify if our theoretical formularization could afford a physiologically, physically and chemically viable model, we performed computational analysis using the formulae (quantitative correlations between various variables) we derived in the previous work. The computational results obtained through associating the GHK eq. with the HH model validated our model and its predictions. This outcome suggests that the current prevailing physiological concepts could be expanded further, to incorporate the newly proposed mechanisms. That is, GHK eq. and HH model could be interpreted via another set of founding principles that incorporate the ubiquitous phenomena of ion-adsorption. [ABSTRACT FROM AUTHOR]

Organic matter (OM) interactions with minerals are essential in OM preservation against decomposition in the environment. Here, by combining potentiometric and electrophoretic measurements, we probed the mode of coordination and the role of pH-dependent electrostatic interactions between organic acids and an iron oxide surface. Specifically, we show that malonate ions adsorbed to a hematite surface in a wide pH window between 3 and 8.7 (point of zero charge). The mode of interactions varied with this pH range and depended on the acid and surface acidity constants. In the acidic environment, hematite surface potential was highly positive (+47 mV, pH 3). At pH < 4 malonate adsorption reduced the surface potential (+30 mV at pH 3) but had a negligible effect on the diffuse layer potential, consistent with the inner-sphere malonate complexation. Here, the specific and electrostatic interactions were responsible for the malonate partial dehydration and surface accumulation. These interactions weakened with an increasing pH and near PZC, the hematite surface charge was neutral on average. Adsorbed malonates started to desorb from the surface with less pronounced accumulation in the diffuse layer, which was reflected in zeta potential values. The transition between specific and non-specific sorption regimes was smooth, suggesting the coexistence of the inner- and outer-sphere complexes with a relative ratio that varied with pH. [ABSTRACT FROM AUTHOR]

Reducing friction is of great interest, and an external potential applied to the friction pair can regulate lubricity. Electrochemical atomic force microscopy (EC-AFM) is used to study the tribological and adsorption behavior of monovalent and trivalent ionic solutions between charged surfaces. An opposite trend of coefficient of friction (COF) and normal force that varies with the applied electric potential is witnessed. Direct force measurements and theoretical models have disclosed that, for the NaCl solution, the negative electric field reduces the COF by increasing cation adsorption. As for LaCl 3 solution, the positive electric field promotes the primary adsorption of anions on HOPG, resulting in the disappearance of the attractive ion-ion correlation between the trivalent ions, thereby reducing the COF. The shear behavior of adsorbed ions in electrolyte solution is sensitive to their valence, because of their different surface force contribution. The study further provides a framework to optimize the design of hydration lubrication.

Water/oxide interfaces are ubiquitous on earth and show significant influence on many chemical processes. For example, understanding water and solute adsorption as well as catalytic water splitting can help build better fuel cells and solar cells to overcome our looming energy crisis; the interaction between biomolecules and water/oxide interfaces is one hypothesis to explain the origin of life. However, knowledge in this area is still limited due to the difficulty of studying water/solid interfaces. As a result, research using increasingly sophisticated experimental techniques and computational simulations has been carried out in recent years. Although it is difficult for experimental techniques to provide detailed microscopic structural information, molecular dynamics (MD) simulations have satisfactory performance. In this review, we discuss classical and ab initio MD simulations of water/oxide interfaces. Generally, we are interested in the following questions: How do solid surfaces perturb interfacial water structure? How do interfacial water molecules and adsorbed solutes affect solid surfaces and how do interfacial environments affect solvent and solute behavior? Finally, we discuss progress in the application of neural network potential based MD simulations, which offer a promising future because this approach has already enabled ab initio level accuracy for very large systems and long trajectories. This article is categorized under:Theoretical and Physical Chemistry > SpectroscopyMolecular and Statistical Mechanics > Molecular InteractionsStructure and Mechanism > Molecular Structures [ABSTRACT FROM AUTHOR]

In this work, a novel functionalized magnetic Fe3O4@SiO2 core-shell nanoparticles grafted with carboxymethyl β-cyclodextrin (CM-β-CD) is utilized for adsorption of Pb(II) ions from aqueous solutions. The grafting reaction was performed via carbodimide method by using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The as-prepared nanoadsorbents were characterized by FTIR, SEM, TEM, XRD, TGA, and VSM. The grafting CM-β-CD on the Fe3O4@SiO2 core-shell nanoparticles enhances the ion adsorption capacity due to the strong abilities of the enormous –OH and –COOH functional groups in CM-β-CD to adsorb Pb(II) ions. The effects of factors such as the concentration of β-CD, contact time, initial ion concentration, adsorbent dosage, adsorption kinetics, and isotherms on the adsorption behavior were studied properly. The results depicted that the nanoadsorbents had good adsorption with the maximum adsorption capacity of 170 mg g−1 at 25 °C and pH 6.0. All the equilibrium adsorption kinetics of Pb(II) are fitted well to the pseudo-second-order model. The adsorption data were also found to follow the Langmuir adsorption isotherm model. In summary, the experimental Pb(II) ion adsorption data showed the prepared nanocomposites would be as promising adsorbents to remove various heavy metals from wastewater. Highlights: A magnetic nanocomposite adsorbent based on β-cyclodextrin was synthesized easily. The adsorbent was used for selective removal of Pb(II) ions from contaminated waters. The adsorbent exhibited high adsorption capacity of 170 mg g−1. Adsorption of Pb(II) followed by pseudo-second-order and Langmuir isotherm models. [ABSTRACT FROM AUTHOR]

Zeolite internal curing has been proven to be effective in reducing shrinkage of cement-based materials, but the sulfate erosion resistance of materials internally cured by zeolite is unclear. In this study, the interaction between zeolite and sulfate, and its effects on cement hydration were experimentally investigated. Firstly, the effects of sulfate on pore structure characteristics and pozzolanic activity of zeolite were studied, then sulfate ion adsorption and sodium ion exchange property of zeolite were tested. Finally, cement paste specimens with zeolite and sulfate were prepared, cement hydration degree, zeolite pozzolanic reaction degree, hydration product characteristics, and compressive strength of the specimens were studied. The test results show that, 1) Sodium sulfate can increase the pore content and pozzolanic activity of zeolite; 2) Zeolite particles can adsorb sulfate ions, sodium ions can exchange calcium ions in zeolite, alkaline environment inhibits the ion exchange process but promotes the ion adsorption process; 3) Sulfate-zeolite addition increases the hydration degree of cement, the pozzolanic reaction degree of zeolite, and the compressive strength of cement paste; 4) Sulfate erosion increases the porosity of Ordinary Portland cement (OPC) materials and reduces the porosity of Sulphoaluminate cement (SAC) materials, zeolite has an inhibitory effect on the influence of sulfate on pore structure. [ABSTRACT FROM AUTHOR]

This study delves into the impact of nanomaterials on early cement hydration, aiming to elucidate their mechanism of action. Four nanomaterials were selected, including carbon-based nanomaterials (multi-walled carbon nanotubes (CNT) and graphene oxide (GO)) and inorganic nanomaterials (nano-SiO 2 and nano-CaCO 3). Initially, the zeta potential was employed to examine nanomaterial adsorption on relevant ions in simulated solutions. Subsequently, SEM NMR, XRD, and TGA were utilized to assess the influence of different nanomaterials on hydration product morphology, content, and structure. Utilizing the Krstulovic-Dabic model, the hydration kinetics based on the heat of hydration in cement paste containing nanomaterials was simulated. Results revealed nanomaterials exhibited stronger Ca2+ ion adsorption than cement particles, with CNT and GO particles displaying weaker adsorption relative to SO 4 2- ions. Conversely, nano-SiO 2 and nano-CaCO 3 particles exhibited a stronger adsorption capacity for Ca2+ ions than SO 4 2- ions. This robust adsorption facilitated hydration product generation, yielding fine and regular C-S-H particles in carbon-based nanomaterial-containing cement pastes, contrasting with coarse and irregular particles in inorganic nanomaterial-containing pastes. Nanomaterial introduction increased polymerization and the average chain length of hydration products. Furthermore, it heightened exothermic peak intensity and total exothermic amount, while reducing the induction period and exothermic peak length. Hydration kinetics, simulated through the Krstulovic-Dabic model, aligned with the nucleation and growth (NG)-phase boundary reaction (I)-diffusion (D) process. In the NG stage, nanomaterials accelerated hydration by reducing reaction stages (n) and increasing the rate constant (K 1 '). In the I stage, hindered Ca2+ ion migration led to decreased K 2 ' , slowing hydration. Stage D witnessed a rapid decline in K 3 '. • The effect of nanomaterials on early cement hydration was investigated. • The nanomaterials were found to adsorb Ca2+ ions more strongly. • Different nanomaterials form different C-S-H particle morphologies in cement pastes. • Hydration kinetics showed fast adsorption of Ca2+ and high exothermic strength of the nanomaterials. • The hydration kinetics follow the NG-I-D process, where nanomaterials sped up initial hydration stages. [ABSTRACT FROM AUTHOR]

Electrostatic interactions near surfaces and interfaces are ubiquitous in many fields of science. Continuum electrostatics predicts that ions will be attracted to conducting electrodes but repelled by surfaces with lower dielectric constant than the solvent. However, several recent studies found that certain "chaotropic" ions have similar adsorption behavior at air/water and graphene/water interfaces. Here we systematically study the effect of polarization of the surface, the solvent, and solutes on the adsorption of ions onto the electrode surfaces using molecular dynamics simulation. An efficient method is developed to treat an electrolyte system between two parallel conducting surfaces by exploiting the mirror-expanded symmetry of the exact image-charge solution. With neutral surfaces, the image interactions induced by the solvent dipoles and ions largely cancel each other, resulting in no significant net differences in the ion adsorption profile regardless of the surface polarity. Under an external electric field, the adsorption of ions is strongly affected by the surface polarization, such that the charge separation across the electrolyte and the capacitance of the cell is greatly enhanced with a conducting surface over a low-dielectric-constant surface. While the extent of ion adsorption is highly dependent on the electrolyte model (the polarizability of solvent and solutes, as well as the van derWaals radii), we find the effect of surface polarization on ion adsorption is consistent throughout different electrolyte models. [ABSTRACT FROM AUTHOR]

Ion adsorbing ultrafiltration membranes provide an interesting possibility to remove toxic ions from water. Furthermore, it is also possible to recover valuable elements. In this work, we demonstrate two easy strategies to modify polyacrylonitrile membranes with anion and cation adsorbing groups. The membranes were modified to have positively charged amine groups or negatively charged carboxyl groups. The success of the reactions was confirmed using IR spectroscopy and zeta-potential measurements. The membranes carrying negatively charged groups provided a negative zeta-potential and had an isoelectric point at pH 3.6, while the membranes carrying positively charged groups had a positive zeta-potential in the analyzed pH range. Since only the surface of the polymer was modified, the pore size and permeance of the membranes were not drastically affected. The membranes prepared by both modification strategies had a pure water permeance higher than 1000 L/(m2 h bar) and a water contact angle of 44.3 and 57.2°, respectively. Therefore, the membranes can be operated at low pressures with reasonable flux. Additionally, SEM images showed that the membranes were still open-pored. Adsorption tests using a positively and a negatively charged dye as well as a toxic cation and an anion were performed to analyze the adsorption behavior. Both membranes were able to adsorb the oppositely charged dyes as well as the copper and chromate ions. Therefore, these membranes are good candidates to purify water streams containing hazardous ions.

Research on Ca2+ adsorption onto the mineral surface is of significant importance with regard to geochemical processes. Sverjensky (Geochim Cosmochim Acta 70(10), 2427–2453, 2006) assumed that alkaline earths form two types of surface species on oxides: tetranuclear (> SOH)2(> SO−)2_M(OH)+ and mononuclear > SO−_M(OH)+. To look into the above assumption we investigated calcium adsorption on SiO2 and Al2O3 because they are the most widespread minerals in the environment. We have determined the proton surface charge, electrokinetic potential and metal adsorption as a function of pH. The Ca2+ uptake and concentration in the system were monitored by the calcium ion-selective electrode (Ca-ISE). The Ca-ISE measurements indicated a similar affinity of Ca2+ for both materials despite their differently charged surface, negative for silica and mainly positive for alumina. This may suggest that simple electrostatic interactions are not the primary driving force for calcium adsorption, and that solvation of calcium ions at the surface may be crucial. We have analyzed our experimental data using the 2-pK triple-layer model (2-pK TLM). Three calcium complexes on the mineral surface were reported. Two of them were the same for both oxides, i.e. the tetranuclear (> SOH)2(> SO−)2_Ca2+ and mononuclear complexes > SO−_CaOH+. Additionally, minor contribution from >SOH...Ca2+ for silica was assumed. In the case of Al2O3 the hydrolyzed tetranuclear complexes (> SOH)2(> SO−)2_CaOH+ at pH > 7.5 occurred based on the modeling results. Two types of surface complexes suggested by Sverjensky allowed for the correct description of proton and calcium uptake for alumina. However, the electrokinetic data excluded hydrolyzed tetranuclear surface species for this oxide. [ABSTRACT FROM AUTHOR]

Superlubricity is known to dramatically reduce frictional energy consumption and to improve service life of mechanical devices and biological systems. However, reduction of wear during the running-in period of friction pairs, especially under high contact pressures, still remains an unresolved issue affecting all machines. Here the lubrication, adsorption, and conformational properties of hydrated ions and polyethylene glycol (PEG) mixtures were evaluated at different mass fractions and concentrations of PEG and salts by ball-on-disc tribometer, ζ -potential, quartz crystal microbalance with dissipation (QCM-D), and dynamic light scatting (DLS) analyses. These mixtures exhibited superlubricity between Si 3 N 4 and sapphire surfaces in a wide range of concentrations and ions valency. Interestingly, a running-in phase shorter than 1 min and low wear rate of 1.85 μm3/(N·m) were observed at contact pressures up to 555 MPa, significantly higher to earlier findings. PEG chains retain random coils filling the bulk of the interfacial film without strongly adsorbing on the interfaces but significantly increasing the viscosity of lubricating film, thereby favoring hydrodynamic lubrication. Hydrated ions are strongly adsorbed on the negatively charged ceramic surfaces, ensuring a sustained hydration effect maintaining superlubricity. The outstanding lubrication characteristics of the PEG/ions mixtures were attributed to the synergistic action of hydration and hydrodynamic lubrication, which appears as a promising avenue for developing new green lubricants and has implications for industrial and biological applications. [ABSTRACT FROM AUTHOR]

SBA-15 mesoporous materials functionalized with N-propyl-2-pyridylimine and ethylenediaminepropyl-2-pyridylimine denoted as SBA-PA and SBA-NPA were prepared and used as adsorbents for decontamination of aqueous solutions from Cu(II) and Pb(II) ions. Batch tests were carried out and pH value of 5.0 was selected for the adsorption process. The experimental data were well represented by pseudo-second-order kinetic model and Langmuir isotherm model, indicating the adsorption was promoted by chemical process and occurred on monolayer. The theoretical maximum values of sorption capacities of SBA-PA and SBA-NPA for Cu(II) were 35.87 and 48.26 mg/g, and for Pb(II) were 82.05 and 106.62 mg/g, respectively. The adsorption of Cu(II) and Pb(II) was enhanced with the increase of temperature and the thermodynamics parameters were also studied. In addition, the two adsorbents could be easily regenerated over four times without significant loss of adsorption efficiency. Therefore, these nanocomposites prepared here could be promising for heavy metal ions removal in aqueous solution. Highlights: Two types of pyridyl Schiff base functionalized SBA-15 mesoporous silica materials denoted as SBA-PA and SBA-NPA were prepared for the removal of Cu(II) and Pb(II) from aqueous solution. The theoretical maximum values of sorption capacities of SBA-PA and SBA-NPA for Cu(II) were 35.87 and 48.26 mg/g, and for Pb(II) were 82.05 and 106.62 mg/g, respectively. Considering the good reusability and regeneration of the adsorbents, these nanocomposites are potential for the removal of aqueous heavy metal ions in practical application. [ABSTRACT FROM AUTHOR]

The change of wettability toward more water-wet by the injection of low salinity water can improve oil recovery from porous rocks, which is known as low salinity water flooding. To simulate this process at the pore-scale, we propose that the alteration in surface wettability mediated by thin water films which are below the resolution of simulation grid blocks has to be considered, as observed in experiments. This is modeled by a wettability alteration model based on rate-limited adsorption of ions onto the rock surface. The wettability alteration model is developed and incorporated into a lattice Boltzmann simulator which solves both the Navier-Stokes equation for oil/water two-phase flow and the advection-diffusion equation for ion transport. The model is validated against two experiments in the literature, then applied to 3D micro-CT images of a rock. Our model correctly simulated the experimental observations caused by the slow wettability alteration driven by the development of water films. In the simulations on the 3D rock pore structure, a distinct difference in the mixing of high and low salinity water is observed between secondary and tertiary low salinity flooding, resulting in different oil recoveries. [ABSTRACT FROM AUTHOR]

Membrane theory attributes the cause of action potential generation to the ion transport across the plasma membrane. It even states that the action potential generation is a unique phenomenon in the living cell. There have been some reports that the action potential-like potential spike is induced even in the nonliving system. Ling's adsorption theory (LA theory) is a typical opposing concept to the membrane theory. The LA theory attributes the action potential generation mechanism to the ion adsorption-desorption process. The authors examined the LA theory and found that the membrane theory has a limitation. By contrast, the LA theory is in line with the experimental results. Therefore, it might be necessary to take into consideration the ion adsorption-desorption effect at least as a part of the action potential generation mechanism. [ABSTRACT FROM AUTHOR]