Alkaline Earth Cations Research Articles

Complexation of magnesium ions in sodium dodecyl benzenesulfonate-Flopaam AN125SH mixtures using sodium citrate

Presence of divalent metal ions, especially alkaline earth cations in brine water is an important factor during different processes applying anionic surfactants and negatively charged polymers, because these cations bind to the anionic head group of surfactants and may cause the precipitation of these materials. They also interact with the polymer chains, decreasing the polymer’s viscosity, reducing the net charge of the polymer chains, which also may lead to precipitation. The present study focuses on describing the interactions between magnesium ions with anionic sodium dodecyl benzenesulfonate (SDBS)–Flopaam AN125SH mixtures and the complexation of the magnesium with sodium citrate. Description of these interactions are important to evaluate the applicability of sodium citrate to decrease the undesired effects of alkaline earth cations in polymer-surfactant mixtures. The mixtures contained the high molecular weight anionic polymer in constant 1.0 g/L concentration and the surfactant in 5.0 g/L concentration. The magnesium ion concentration was systematically increased in the samples (0.03–1.5 g/L) and sodium citrate was added to the magnesium ion containing samples in 2.0 and 3.0 M equivalent amount compared to the magnesium ion concentration. The samples were characterized by using turbidimetry and rheology measurements (measuring consistency index, yield stress, flow number and zero shear viscosity), as the change of viscosity is an important parameter during application of polymers in different processes. The formed precipitates were characterized using infrared spectroscopy. The results showed that sodium citrate successfully inhibited the magnesium ions caused precipitation up to 1.2 g/L metal ion concentration (1200 ppm), but caused a considerable decrease in the viscosity of the samples (the consistency index of the mixtures decreased from 47.5 mPa s to 7.53 mPa s) and that magnesium ions do not induce precipitation of the polymer. However, this amount of decrease in viscosity did not change the flow properties of the polymer, all the investigated samples were measured to possess pseudoplastic flow behavior. The viscosity decreasing effects of the sodium citrate were also measured and approximately 13.0 mPa s decrease was measured in zero shear viscosity.

Adamantane-Type Nitridophosphate Phosphors AExLi10-2xP4N10 : Eu2+ via Medium-Pressure Ion-Exchange Reactions.

Nitridophosphates have emerged as promising host compounds in the field of solid-state lighting. Their industrial relevance has increased significantly, mainly due to recent advances in synthetic approaches under medium-pressure (MP) conditions, including ammonothermal synthesis and hot isostatic pressing (HIP). In this study, we report on the synthesis and characterization of the quaternary representatives CaxLi10-2xP4N10 (x=2, 2.7, 4) and Sr3Li4P4N10, prepared via a simplified ion exchange reaction under MP conditions, starting from the nitridophosphate-based lithium ion conductor Li10P4N10. The synthesis route allowed for the preservation of the anionic [P4N10]10- structural motif of the starting material, while simultaneously introducing potential doping sites for Eu2+ by incorporating divalent alkaline earth cations (Ca2+/Sr2+). Upon excitation of Eu2+ doped samples with blue light, strong luminescence due to parity-allowed 4f6(7F)5d1→4f7(8S7/2) transition can be observed in the red (Ca2Li6P4N10 : Eu2+: λmax=626 nm), yellow/orange (Ca2.7Li4.6P4N10 : Eu2+: λmax1=506 nm, λmax2=592 nm and Sr3Li4P4N10 : Eu2+: λmax=596 nm) and green (Ca4Li2P4N10 : Eu2+: λmax=546 nm) spectral regions of the visible light. The compounds presented, together with the simplified synthetic approach, demonstrate the significant potential of ion exchange on Li ion conductors for the development of novel nitridophosphates in the future.

Synergistic Regulation of DNA Morphology by Metal Cations and Low pH.

As a flexible biomolecule, the spatial structure of DNA is variable. The effects of concentration, metal cations, and low pH on DNA morphology were studied. For the high concentration of DNA, the cross-linked branch-like or network structures were formed. For the low concentration of DNA, isolated, random and freely loose linear DNA chains were presented. These phenomena were related to the intermolecular interactions. Branch-like DNA structures were reformed with the addition of metal cations to the low concentration of DNA at pH 7-4, suggesting the negative charges of DNA were neutralized, thus transforming the spatial structure of DNA into a low charge density morphology and presenting the hypochromic effect. Compared to the monovalent alkaline metal cations, more negative charges of DNA were screened by the alkaline-earth metal cations. Distinct DNA morphologies were observed for pH 3. The linear and condensed DNA structures were simultaneously observed, which was met regardless of the solution with or without the addition of metal cations. This was further confirmed by the absorbance of DNA. Compared to the pure DNA, bulky and aggregated DNA collapsed structures were formed when the sodium and magnesium cations were added to the reaction solution. In addition, it was verified that the condensed DNA structures failed to revert back to the chain structure by neutralizing acidic solutions with alkali, but the compacted DNA spheres became loose. The conductivities of various DNA morphologies were measured. They were morphology-dependent. This study provides guidance forthe behavior of DNA in the acidic solutions and further promotes the application of DNA in DNA-based nano-optoelectronic devices.

Identifications of False Positives Amongst Sodium(I) Cations in Protein Three-Dimensional Structures—A Validation Approach Extendible to Any Alkali or Alkaline Earth Cation and to Any Monoatomic Anion

Validation of the data deposited in the Protein Data Bank is of the upmost importance, since many other databases, data mining processes, and artificial intelligence tools are strictly grounded on them. The present paper is divided into two parts. The first part describes and analyzes validation methods that have been designed and used by the structural biology community. Everything began with the Ramachandran plot, with its allowed and disallowed types of backbone conformations, and evolved in different directions, with the inclusion of additional stereochemical features, distributions’ analyses of structural moieties, and scrutiny of structure factor amplitudes across the reciprocal lattice. The second part of the paper is focused on the largely unexplored problem of the high number of false positives amongst the sodium(I) cations observed in protein crystal structures. It is demonstrated that these false positives, which are atoms wrongly identified with sodium, can be identified by using electrostatic considerations and it is anticipated that this approach can be extended to other alkali and alkaline earth cations or to monoatomic anions. In the end, I think a global initiative, accessible to all volunteers and possibly overseen by the Protein Data Bank, should take the place of the numerous web servers and software applications by providing the community with a select few reliable and widely accepted tools.

Pb2TeV2O10: A Lead Vanadate Tellurate with Wide Mid-IR Transparency and Large Birefringence Induced by Multiple Birefringence-Active Groups.

Birefringent materials as the key materials in laser science and technology have attracted continuous attention due to their ability to modulate polarized light. Herein, a new lead vanadate tellurate, Pb2TeV2O10, has been synthesized through the rational integration of different kinds of birefringence-active functional units. Pb2TeV2O10 features a unique two-dimensional (2D) [TeV2O10]∞ layered structure consisting of [VO6]7- and [TeO6]6- octahedra, and Pb2+ cations reside between the [TeV2O10]∞ layers. In addition, the rare edge-sharing mode of [VO6]7- and [TeO6]6- octahedra was found in this structure. Attributed to the high polarizability and appropriate arrangement of PbO8, VO6, and TeO6 units, Pb2TeV2O10 possesses a great theoretical birefringence of 0.275 at 532 nm, which is the largest among the vanadate tellurate family. The spectral tests also prove that Pb2TeV2O10 showcases a broad transparency window (439 nm-10 μm), covering an important mid-infrared (IR) atmospheric window (3-5 μm). In addition, in order to improve the transparency, alkali and alkaline earth metal cations were introduced by the substitution strategy, and then the compound K2Sr2Te2O9 was synthesized. It owns a shorter ultraviolet (UV) cutoff edge of 234 nm and a wider transparency window (234 nm-13.8 μm). The findings of Pb2TeV2O10 and K2Sr2Te2O9 enrich the structure chemistry of the tellurate family and provide new insights for designing new compounds with large optical anisotropy and wide spectral transparency.

Solvothermal syntheses, structures and properties of quaternary alkaline earth metal sulfides BaCu6Ge2S8 and BaCuAsS3

Two quaternary alkaline earth metal sulfides, BaCu6Ge2S8(1) and BaCuAsS3 (2), were synthesized under low-temperature solvothermal conditions. Compound 1 features a three-dimensional (3D) [Cu6Ge2S8]n2n- framework comprising CuS3, CuS4, and GeS4 units, with Ba2+ cations occupying the channels. Compound 2 exhibits a one-dimensional (1D) chained structure, with Ba2+ cations situated between the chains. Alkaline earth metal ions exhibit a structural directing effect that is distinct from that of other guest cations. Specifically, Compound 1 presents a rare instance of a 3D Cu-Ge-S framework formed by condensation of two parallel layers. Compound 2 is the first 1D A-Cu-As-S compound (where A represents guest cations). Additionally, compound 2 presents the first example of AⅡ-Cu-As-S (where AⅡ represents alkaline earth metal cations) compounds. Their optical properties and theoretical calculations were also investigated. Our results demonstrate that solvothermal synthesis is a promising method for obtaining multinary alkaline earth metal sulfides with diverse structures and properties.

Crosslinking assembly of Propenyl-Calix[4]-Crown-6 interpenetrating functional mesoporous carbon Spheres: High selectivity and stability to Remove Cs(I) from high acid solution

The calix[4]-crown-6 ligand shows high selectivity for Cs(I) over other alkali and alkaline earth metal cations, making it a promising candidate for radiocesium separation. However, its high viscosity and poor adhesion limit its practical use and stability. In this study, an alkenyl-functionalized calix[4]-crown-6 (p-C[4]C6) was developed. Using a mesoporous structure and post-assembly techniques, a composite (p-C[4]C6/MMCs) was created via crosslinking within mesoporous matrix channels. The p-C[4]C6/MMCs exhibited high stability and practicality. The p-C[4]C6/MMCs demonstrated high selectivity, good reusability, and significant adsorption capacity (47.76 mg/g) for Cs(I) in 3.0 M HNO3. Kinetic, isotherm, and thermodynamic studies suggest a spontaneous chemical adsorption mechanism. This research provides insights into the design of calix[4]-crown-6 based materials and offers a viable approach for Cs(I) separation from high-level liquid waste (HLW).

Exploring the effects of the alkaline earth metal cations on the electronic structure, photostability and radiation hardness of lead halide perovskites

The growing interest to the application of perovskite solar cells (PSC) in aerospace requires great attention to the design of new absorber materials with enhanced photostability and radiation hardness. We addressed this challenge through the B-site engineering by partial replacing of Pb2+ in the complex halides with Ca2+, Sr2+, and Ba2+. Change in the material electronic properties suggests the incorporation of the substituent cations in the perovskite lattice. However, when the loading of alkaline earth halides is high, they tend to segregate to the film surface and grain boundaries. The modification of MAPbI3 and Cs0.12FA0.88PbI3 by replacing a 1% of Pb2+ with alkaline earth metal cations resulted in improvements in the photostability and radiation hardness under exposure to gamma rays and electrons beam. Depending on the material formulation, it was possible to mitigate the photochemical and radiation-induced Pb0 formation and the univalent cation phase segregation. The best of the designed perovskite absorbers could successfully tolerate high doses of gamma rays (5.5 MGy) and electron fluences (3 × 1016 e/cm2), thus outperforming significantly the non-modified material. These findings feature the incorporation of alkaline earth metal cations as a promising approach for the development of PSC with enhanced radiation hardness for aerospace applications.

How Bulk Versus Surface Chemistry Affects the Surface Reconstruction of Perovskite Nickelates and Their Activation By Fe Impurities

Whether surface reconstruction of LaNiO3 and the related Ruddlesden-Popper oxide La2NiO4 occurs during the oxygen evolution reaction has only recently emerged as a topic of rigorous study despite the implications this would have for its activity and stability at scales from the three-electrode cell to electrolyzer stacks. Correlation of structure to reconstruction propensity is much needed, but not well-understood. Building off of our work suggesting that these oxides do electrochemically reconstruct to the thermodynamically stable, amorphous, Fe impurity-sensitive, nickel hydroxide, we extend our observations to materials doped with alternative rare earth and alkaline earth metal cations at the La-site. First, we find that undoped La2NiO4 has a higher tendency to reconstruct, forming almost twice as much Ni(OH)2 for a given electrochemical treatment as LaNiO3 which we attribute to differences in Ni valence state between the two materials. This leads to a higher current density when exposed to Fe impurities by formation of more NiFeOxHy, the highest activity catalyst for OER known. Yet, the intrinsic activity of the Fe sites formed are equivalent within experimental error suggesting a convergence in surface composition despite different bulk composition. We find this reconstruction also occurs for doped materials, extending the library of materials expected to have dynamic surfaces during OER. Further, we use XPS coupled with argon ion sputtering to connect differences in reconstruction extent to the bulk and surface composition, with particular emphasis on the valence state of nickel as a possible descriptor.

The centrosymmetric to non-centrosymmetric transformation induced by alkaline-earth cations producing infrared nonlinear optical AeMn6Ga6S16 (Ae = Ca, Sr)

The centrosymmetric to non-centrosymmetric transformation induced by alkaline-earth cations producing infrared nonlinear optical AeMn6Ga6S16 (Ae = Ca, Sr)

Inorganic‐Organic Hybrid Crystals Derived from Polyoxovanadate and Ionic‐Liquid toward Promising Conductive Materials

AbstractConductive polyoxovanadate inorganic‐organic hybrid crystals comprising alkaline earth metal (divalent) cations were successfully obtained with the use of an ionic‐liquid cation having imidazolium and methacryloyl moieties (denoted as MAImC1). Two types of crystals containing decavanadate ([V10O28]6−, V10) anion were obtained as [MAImC1]2Ca2[V10O28] ⋅ 16H2O ⋅ 2 C2H5OH (MAImC1−Ca−V10) and [MAImC1]2Mg2[V10O28] ⋅ 18H2O ⋅ 2 C2H5OH (MAImC1−Mg−V10). Connection modes of the divalent cations were different: Ca2+ cations were connected to V10 to form a {[Ca(H2O)5]2V10O28]}2− anion in MAImC1−Ca−V10, while a discrete [V10O28]6− and hydrated [Mg(H2O)6]2+ were present in MAImC1−Mg−V10. Conductivities under a fully humidified condition at 353 K (80 °C) were high values of 3.0×10−4 S cm−1 for MAImC1−Ca−V10 and 3.3×10−3 S cm−1 for MAImC1−Mg−V10, respectively. The higher conductivity under hydrated conditions suggests proton as a conductive carrier. The better conductivity of MAImC1−Mg−V10 is plausibly derived from the more effective hydrogen‐bonded network in the crystal lattice.

Exploring the influence of metal cations on individual hydrogen bonds in Watson-Crick guanine-cytosine DNA base pair: An interacting quantum atoms analysis.

This study delves into the nature of individual hydrogen bonds and the relationship between metal cations and hydrogen bonding in the Watson-Crick guanine-cytosine (GC) base pair and its alkali and alkaline earth cation-containing complexes (Mn+-GC). The findings reveal how metal cations affect the nature and strength of individual hydrogen bonds. The study employs interacting quantum atoms (IQA) analysis to comprehensively understand three individual hydrogen bonds within the GC base pair and its cationic derivatives. These analyses unveil the nature and strength of hydrogen bonds and serve as a valuable reference for exploring the impact of cations (and other factors) on each hydrogen bond. All the H D interactions (H is hydrogen and D is oxygen or nitrogen) in the GC base pair are primarily electrostatic in nature, with the charge transfer component playing a substantial role. Introducing a metal cation perturbs all H D interatomic interactions in the system, weakening the nearest hydrogen bond to the cation (indicated by a) and reinforcing the other (b and c) interactions. Notably, the interaction a, the strongest H D interaction in the GC base pair, becomes the weakest in the Mn+-GC complexes. A broader perspective on the stability of GC and Mn+-GC complexes is provided through interacting quantum fragments (IQF) analysis. This approach considers all pairwise interactions between fragments and intra-fragment components, offering a complete view of the factors that stabilize and destabilize GC and Mn+-GC complexes. The IQF analysis underscores the importance of electron sharing, with the dominant contribution arising from the inter-fragment exchange-correlation term, in shaping and sustaining GC and Mn+-GC complexes. From this point of view, alkaline and alkaline earth cations have distinct effects, with alkaline cations generally weakening inter-fragment interactions and alkaline earth cations strengthening them. In addition, IQA and IQF calculations demonstrate that the hydration of cations led to small changes in the hydrogen bonding network. Finally, the IQA interatomic energies associated with the hydrogen bonds and also inter-fragment interaction energies provide robust indicators for characterizing hydrogen bonds and complex stability, showing a strong correlation with total interaction energies.

Hydrated cation-π interactions of π-electrons with hydrated Mg2+ and Ca2+ cations.

Hydrated cation-π interactions at liquid-solid interfaces between hydrated cations and aromatic ring structures of carbon-based materials are pivotal in many material, biological, and chemical processes, and water serves as a crucial mediator in these interactions. However, a full understanding of the hydrated cation-π interactions between hydrated alkaline earth cations and aromatic ring structures, such as graphene remains elusive. Here, we present a molecular picture of hydrated cation-π interactions for Mg2+ and Ca2+ by using the density functional theory methods. Theoretical results show that the graphene sheet can distort the hydration shell of the hydrated Ca2+ to interact with Ca2+ directly, which is water-cation-π interactions. In contrast, the hydration shell of the hydrated Mg2+ is quite stable and the graphene sheet interacts with Mg2+ indirectly, mediated by water molecules, which is the cation-water-π interactions. These results lead to the anomalous order of adsorption energies for these alkaline earth cations, with hydrated Mg2+-π < hydrated Ca2+-π when the number of water molecules is large (n ≥ 6), contrary to the order observed for cation-π interactions in the absence of water molecules (n = 0). The behavior of hydrated alkaline earth cations adsorbed on a graphene surface is mainly attributed to the competition between the cation-π interactions and hydration effects. These findings provide valuable details of the structures and the adsorption energy of hydrated alkaline earth cations adsorbed onto the graphene surface.

Hybridization makes the difference: [2Oxa.2Oxa.2Oxa] a sp2-Carbon dominated Lehn-type cryptand - Prediction of ion selectivity by quantum chemical calculations. XVIII

Substituting the O-C2H4-O-moiety of [2.2.2] by the O2CCO2-core of oxalic acid leads to the new Lehn-type cryptand [M ⊂ 2Oxa.2Oxa.2Oxa]m+. We explored by quantum chemical methods (B3LYP/LANL2DZp) the complexation behaviour and compared it with the original cryptand [2.2.2]. The cryptands [2Oxa.2Oxa.2Oxa] and [2.2.2] exhibit the same ion selectivity against alkaline and alkaline earth metal cation (K+ followed by Rb+; Ba2+ preferred over Sr2+). The exchange of the OC2H4O-moiety by the O2CCO2-moiety (the subsequent exchange of sp3- by sp2-carbon atoms) makes [2Oxa.2Oxa.2Oxa] less flexible in the OCCO-diether angle as [2.2.2]. This rigidity results in higher complexation energies for [M ⊂ 2Oxa.2Oxa.2Oxa]m+ and that the twisting of the dihedral angle CN…NC improves the nesting of the guest cations in the cryptand [2Oxa.2Oxa.2Oxa].

Complexation of bis(aza-18-crown-6)-containing dibenzylidenecyclopentanone with alkali and alkaline-earth metal cations: specific features and photoinduced recoordination in the complexes

Complexation of bis(aza-18-crown-6)-containing dibenzylidenecyclopentanone with alkali and alkaline-earth metal cations: specific features and photoinduced recoordination in the complexes

Alkaline earth metal ions affect the dissolution of kaolinite-bearing olivine and its carbon storage effects

Olivine dissolution applications in coastal environments hold great promise for both ocean alkalinity enhancement and carbon dioxide storage. Yet the dissolution mechanism of olivine and the influence of metal ions, such as Mg2+ and Ca2+, remain unclear. Moreover, the weathering products, such as clay minerals are usually mixed with olivine, and the influence of the associated minerals on the dissolution also unexplored. In this study, an 80-day dissolution experiment was performed in Ca2+-free artificial seawater (ASW-Ca) and ASW lacking both Ca2+ and Mg2+ (ASW-CaMg), to elucidate the mechanism of olivine dissolution and the impact of Ca2+ and Mg2+ on the presence of an associated clay mineral, kaolinite. To evaluate the mineral properties before and after dissolution, X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analyses were used. Etch pits were observed on olivine's surface as well as its reduced crystallinity. The atomic ratio of Mg/Si in olivine decreased from 1.49 ± 0.56 in the raw samples to 1.29 ± 0.53 in the samples obtained from ASW-CaMg after undergoing the 80-day dissolution, whereas it was much higher, at 1.85 ± 0.32, in the samples from ASW-Ca. The increasing Mg/Si was attributed to the Mg2+ adsorption on the surface of olivine, which inhibited the release of structural Mg2+. Hence, Mg2+ was a key environmental factor influencing the process of olivine dissolution, and estuaries, which have low Mg2+ content and low pH may be the promising areas for the olivine application. Moreover, in ASW-CaMg, the total alkalinity (TA), dissolved inorganic carbon (DIC) concentration, and charge concentration of alkaline earth metal ions increased by 3392 ± 28, 2922 ± 3, and 3740 ± 91 μmol kg−1, respectively, compared to the data from the blank experiment. Notably, TA and DIC had strong linear relationships with the alkaline earth metal ions (Mg2+ and Ca2+). The release of free alkaline earth metal cations during olivine dissolution was a controlling factor for long-term carbon dioxide storage in ASW-CaMg. Finally, during the 80-day dissolution experiment, no dissolution of the associated kaolinite was observed, however, kaolinite may influence the olivine dissolution by adsorbing the released Si.

Intense NIR-II luminescence through stabilization of tetrahedral (Mn5+O4) lumophore in apatites with high external quantum efficiency

The discovery of highly efficient near-infrared (NIR) emitting phosphors is essential for multiple spectroscopic applications. Pentavalent-manganese (Mn5+) is a rarely-reported NIR-II activator due to the its instability in inorganic solids. In this study, Mn5+-activated apatite phosphors A5(B1-xMnxO4)3X (A = Sr, Ba; B = P, V; X = OH, F, Cl, Br) were reported. Benefiting from the discrete P/VO4 tetrahedron and stabilization effect of alkaline-earth cation, Mn5+ existed as MnO43− anion can be effectively incorporated into the A5(P/VO4)3X. A selection of 16 different apatites is conducted to test the structural and compositional effect on Mn5+ stabilization and luminescence. The structure-property relationship was discussed with a detailed analysis on Mn5+ Tanabe-Sugano diagram and Dq/B calculation. Particularly, the optimized Ba5(VO4)3Cl: 0.01Mn5+ (λex = 650 nm, λem = 1181 nm) reveals an exceptional external quantum efficiency of 61.1 % with vivid turquoise body color. The multiparametric thermometry by luminescence intensity ratio (LIR) and 1E lifetime were demonstrated with excellent linear regressions (R2 > 99.9 %) and high relative sensitivities of > 1.0% K−1 in the range of physiological temperatures. A NIR-II phosphor-converted light-emitting diode (pc-LED) is fabricated with a NIR output power of 30.18 mW at 60 mA driven current and photoelectric conversion efficiency of 6.63 %.

Effect of Organic Cation Adsorption on Ion-Transport Selectivity in a Cation-Permselective Nanopore Membrane.

A key knowledge gap in the emerging field of nanofluidics concerns how the ionic composition and ion-transport properties of a nanoconfined solution differ from those of a contacting bulk solution. We and others have been using potentiometric concentration cells, where a nanopore or nanotube membrane separates salt solutions of differing concentrations to explore this issue. The membranes studied contained a fixed pore/tube wall anionic charge, which ideally would prohibit anions and salt from entering the pore/tube-confined solution. We have been investigating experimental conditions that allow for this ideally permselective cation state to be achieved. Results of potentiometric investigations of a polymeric nanopore membrane (10 ± 2 nm-diameter pores) with anionic charge due to carbonate are presented here. While studies of this type have been reported using alkaline metal and alkaline earth cations, there have been no analogous studies using organic cations. This paper uses a homologous series of tetraalkylammonium ions to address this knowledge gap. The key result is that, in contrast to the inorganic cations, the ideal cation-permselective state could not be obtained under any experimental conditions for the organic cations. We propose that this is because these hydrophobic cations adsorb onto the polymeric pore walls. This makes ideality impossible because each adsorbed alkylammonium must bring a charge-balancing anion, Cl-, with it into the nanopore solution. The alkylammonium adsorption that occurred was confirmed and quantified by using surface contact angle measurements.

Separation of CO2/N2 in Ion-Exchange binder-free beads of zeolite NaY for Post-Combustion CO2 capture

Ion-exchange on bare commercial zeolites can offer improved adsorption processes. In the context of CO2/N2 separation for post-combustion CO2 capture (PCC), here, we report, the effect of ion-exchange on commercial binder-free NaY zeolite with alkali (K+) and alkaline earth (Ca2+) metal cations, achieving exchange levels of 23 %, 58 %, and 95 % for K+ and 56 % and 71 % for Ca2+. Adsorption isotherms of CO2 and N2 were measured over a temperature range of 306–344 K and pressures up to 350 kPa. At low pressures, the CO2 adsorption capacity increases as Na+ ions are exchanged to a higher level of K+, while a reverse trend is observed for Ca2+ exchange. At 25 kPa and 306 K, the CO2 loading (mol∙kg−1) follows the order 2.01-Ca(71)Y < 2.63-Ca(56)Y < 4.05-NaY < 4.29-K(23)Y < 4.59-K(58)Y < 4.72-K(95)Y. The selectivities of CO2 (15 %)/N2 (85 %) at 306 K and 101.3 kPa range from 52 for Ca(71)Y to 101 for K(23)Y, compared to 89 in the bare NaY zeolite. The working capacities for the most promising exchanged sample (K(23)Y) exhibit superior values of 4.51, 2.98, and 2.41 mol∙kg−1 considering regeneration pressures of 3, 10, and 15 kPa, relative to a feed pressure of 101.3 kPa, respectively. Dynamic simulations were conducted using the Aspen Adsorption package to accurately predict both single- and binary-component breakthrough curves.

Application of Alcohols to Inhibit the Formation of Ca(II) Dodecyl Sulfate Precipitate in Aqueous Solutions.

The presence of alkaline earth cations, in particular, Ca2+ and Mg2+ ions in brine, causes undesired effects in solutions containing anionic surfactants because of precipitate formation. In the present study, an anionic surfactant, sodium dodecyl sulfate (SDS), was investigated, focusing on the determination of various properties (surface tension, critical micelle concentration, micelle size, turbidity) in the presence of alcohols and, in particular, the inhibition of the precipitation of SDS with calcium ions. The calcium ions were added to the surfactant in increasing concentrations (3.0-10.0 g/L), and short-carbon-chain alcohols (methanol, ethanol, n-propanol and n-butanol) were used to shift the onset of precipitate formation. The critical micelle concentration (CMC) of SDS in the presence of alcohols was also determined. It was established that among these alcohols, methanol and ethanol did not exert significant effects on the solubility of the Ca(DS)2 precipitate, while n-propanol and n-butanol were found to be much more efficient inhibitors. In addition, all the alcohols in the applied concentration range (up to 20 V/V%) were found to decrease the critical micelle concentration of SDS.