Ionic Substance Research Articles

Titelbild: From salt to ionic substance: a language‐responsive teaching sequence for discovering salts in the Dead Sea (CHEMKON 5/2024)

Titelbild: From salt to ionic substance: a language‐responsive teaching sequence for discovering salts in the Dead Sea (CHEMKON 5/2024)

From salt to ionic substance: a language‐responsive teaching sequence for discovering salts in the Dead Sea

AbstractViele Schüler:innen stehen im Chemieunterricht vor großen Herausforderungen, wenn von ihnen verlangt wird, fachliches und konzeptionelles Wissen aufzubauen sowie gleichzeitig bildungs‐ und fachsprachliche Kompetenzen zu erwerben. In aller Regel bestimmen die sprachlichen Fähigkeiten in der Bildungs‐ und Unterrichtssprache Deutsch bereits, inwieweit Lernende überhaupt in der Lage sind, am Unterrichtsdiskurs teilzunehmen: Fehlen entsprechende bildungs‐ und fachsprachliche Kenntnisse, so führt das zumeist dazu, dass die fachliche Lernentwicklung hinter den Möglichkeiten der Lernenden zurückbleibt. Der Ansatz Disaggregate Instruction im Chemieunterricht (DICE) nimmt für sich in Anspruch, Schüler:innen mit sprachlichen Förderbedarfen nachweislich darin zu unterstützen, ein solides Verständnis chemiebezogener Fachkonzepte aufzubauen und fachsprachliche Kompetenzen auszubilden. In diesem Artikel stellen wir die Konzeption eines Lehr‐Lern‐Arrangements unter Anwendung von sprachsensiblen DICE‐ und Scaffolding Prinzipien sowie ausgewählte Unterrichtsmaterialien vor.

Milestone Studies on Ion-exclusion Chromatography of Ionic and Nonionic Substances Utilizing Multifunctional Separation Mechanism of Ion-exchange Resins.

Ion-exclusion chromatography (IEC) is categorized as a type of ion chromatography and is recognized as a simple and convenient water quality monitoring technology for a variety of ionic and nonionic substances. This review, mainly focusing on historical milestone studies by various authors, outlines the archives that concern the separation sciences and practical applications obtained from a variety of IEC modes used for water-quality monitoring as follows: (1) early-developed IEC; (2) IEC using enhanced conductivity detection for weak ionic substance; (3) IEC using nonionic substances eluents such as sugars or polyols; (4) vacancy IEC based on a novel separation concept; (5) applications to the water quality monitoring of inorganic ionic-nutrients; (6) simultaneous IEC and cation-exchange chromatography of anions and cations; and (7) the multicomponent IEC combining different separation modes and detection methods with the expansion of applicable fields, such as for food analysis or material evaluations.

Synthesis and characterization of poly(ethylene terephthalate) fibers grafted with N-(hydroxymethyl) acrylamide by free radical: its application in elimination of Congo red

In this study, firstly, N-(hydroxymethyl) acrylamide (HMAAm) was grafted on poly(ethylene terephthalate) fibers (PET) by utilizing benzoyl peroxide (Bz2O2) as an initiator. The alteration in graft percentage with the polymerization time, temperature, concentration of initiator and monomers were investigated. For grafting experiments, the optimum temperature, duration for grafting and initiator concentration were found be 85 °C, 4 h and 0.008 M, respectively, and the maximum grafting yield was determined to be 25% at these conditions. After grafting, the morphological and chemical changes on the grafted fibers were examined scanning electron microscopy and Fourier-transform infrared spectroscopy. The thermal properties of the obtained PET fibers were examined with differential scanning calorimeter analysis. In addition, the water absorption capacities of the grafted fibers obtained at optimal conditions were investigated and it was found the maximum percentage of water retention reached 56%. Removal of Congo red (CR) with the grafted fibers was performed using a batch process. The effects of different parameters such as pH, grafting yield of HMAAm, adsorption time and CR concentration on the sorption capacity of the grafted fibers were investigated. The optimal pH for adsorption of CR was found to be 2, and the adsorption process reached equilibrium in 4 h. The amount of adsorbed CR molecules increased with the increment in the grafting yield up to 17%, and the graft copolymers adsorbed CR with 5.62 mg/g efficiency when the initial CR concentration was 80 ppm. The PET-g-HMAAm fibers synthesized in this study can be obtained easily and inexpensively, and the constructed fibers could be used to remove ionic substance from aqueous solution.

Theoretical Calculation of the Thermodynamic Properties of 20 Amino Acid Ionic Liquids.

The thermodynamic properties of gas-phase amino acid ionic liquids (AAILs) containing 20 amino acids ([AA]-) and 1-ethyl-3-methylimidazolium ([Emim]+) are studied using a combination of the ab initio method, molecular dynamics simulations, Born-Haber (BH) cycle analysis, and isodesmic reactions. The M06-2X/TZVP method is used to explore the structure and dissociation enthalpies of [Emim][AA] by considering dispersion interaction, and the MP2/Aug-cc-pVTZ method is used to correct these enthalpies. The vaporization enthalpies of all 20 AAILs are calculated by molecular dynamics simulations, and the gas-phase formation enthalpies (Δf H) of the 20 [AA]- anions and [Emim]+ cation are calculated by the density functional theory/M06-2X method and isodesmic reaction approaches. To obtain the Δf H of the AAILs, interconnections in the corresponding BH cycles are evaluated. A systematic study of the 20 [Emim][AA] ion pairs provides some initial factors contributing to the thermodynamic properties of AAILs: including length of the alkyl chain, interatomic electronic effects, steric repulsion from the cyclic group, and H-bonds formed by functional groups. Generally speaking, the results of this work provide insights into the structure-property relationships of not only ILs but also any ionic or molecular substance.

Design of Thermophysical Properties of Semiclathrate Hydrates Formed by Tetra-n-butylammonium Hydroxybutyrate

Semiclathrate hydrates form from aqueous solution of ionic guest substance such as tetra-n-butylammonium (TBA) and tetra-n-butylphosphonium (TBP) salts. Thermophysical properties of these materials are varied by the ionic guest cations and anions. Investigation of the modification of the semiclathrate hydrates by ionic guest substances is needed to design and improve properties of semiclathrate hydrates for applications such as cool energy storage and for gas separation and storage. Here we report synthesis of semiclathrate hydrates of tetra-n-butylammonium 3-hydroxybutyrate (TBA 3HB) and measurements for melting temperatures and a heat of fusion. We performed phase equilibrium measurements under optical observation for crystal morphology. A heat of fusion was measured by differential scanning calorimetry (DSC) measurements, and a crystal structure of TBA 3HB hydrate was identified to be tetragonal by single-crystal X-ray diffraction (XRD) measurements. The results showed that the highest melting temperat...

Mechanisms of the Diffusion of Nonpolar Substances in a Hydrophilic Ionic Liquid

The structural-dynamic features of ionic liquid-nonpolar substance systems are studied by means of molecular dynamics using Frenkel’s fundamental theory of a liquid and the phonon theory of the thermodynamics of a liquid, in combination with the DL_POLY_4.05 software package. Argon, methane, and benzene molecules serve as the dissolved substances. Model concepts are proposed and analyzed to describe the diffusion of molecules of a dissolved substance in an ionic liquid. It is shown that an increase in the mass of the molecules of a dissolved nonpolar substance correlates with their mobility in a hydrophilic ionic liquid (IL). This determines the diffusion of the components of dmim+/Cl− IL solutions and is responsible for the anomalous behavior of the solubility of nonpolar substances in them.

Solubility of Nitrogen Gas in Aqueous Solution of Tetra-n-Butylammonium Bromide

Semiclathrate hydrates are water-based host-guest compounds formed from aqueous solutions of ionic guest substances. These materials can greatly moderate formation pressures and temperatures from canonical gas hydrates. This is a significant advantage for industrial applications such as gas separation and storage. $$\hbox {N}_{2}$$ gas is a major component contained in various flue gases and is usually mixed with $$\hbox {CO}_{2}$$ . Semiclathrate hydrates can separate these gases under moderate thermodynamic conditions. Tetra-n-butylammonium bromide (TBAB) is a widely used ionic guest substance. To develop the application technologies and their theoretical models, solubility data of $$\hbox {N}_{2}$$ gas in TBAB aqueous solutions are required. In this study, we report $$\hbox {N}_{2}$$ gas solubility measured by an absolute gravimetric method for the semiclathrate hydrate formation system of $$\hbox {TBAB} + \hbox {H}_{2}\hbox {O} + \hbox {N}_{2}$$ . The measurement pressures, temperatures and TBAB mass fractions were 3 MPa, 5 MPa and 7 MPa, 292.15 K, 302.15 K and 307.15 K, and 0 (pure water), 0.10, 0.20, 0.32 and 0.40, respectively. The uncertainties were 0.056 MPa, 0.44 K and 0.00012 in mole fraction. Although the technical difficulty lays on measurements of small $$\hbox {N}_{2}$$ gas solubility by the absolute gravimetric method, our data implied the unique gas dissolution property of aqueous TBAB solution depending on the TBAB concentration. The aqueous TBAB solutions with mass fractions of 0.10 and 0.20 had similar $$\hbox {N}_{2}$$ gas solubility as that in pure water. With higher mass fractions, 0.32 and 0.40, the $$\hbox {N}_{2}$$ gas solubility slightly increased from that in pure water, which implies the salting-in effect of TBAB.

Gas separation of flue gas by tetra-n-butylammonium bromide hydrates under moderate pressure conditions

Ionic clathrate hydrates are composed of water and ionic guest substance, which can selectively capture gas under moderate conditions. We performed gas separation experiments with tetra-n-butylammonium bromide (TBAB) widely-used for an ionic guest substance. The experiments in a closed system showed good CO2 gas selectivity of the TBAB hydrates even under the mild conditions: 1 MPa and 282 K. We also performed the gas separation with tetrahydrofuran (THF) which is a guest substance forming the structure II clathrate hydrate. Comparison with THF clearly revealed the better CO2 selectivity of TBAB than that of the structure II clathrate hydrate. We further compared our data with the literature, and found that the condition of low pressure and dense TBAB concentration provided superior CO2 selectivity. Gas separation with continuous gas flow was demonstrated. The hydrate formation behavior was similar to the cases without gas flow. The results showed that controlling the crystal growth temperature is important to capture gases by the TBAB hydrates.

Thermodynamic Properties at Saturation Derived from Experimental Two-Phase Isochoric Heat Capacity of 1-Hexyl-3-methylimidazolium Bis[(trifluoromethyl)sulfonyl]imide.

New measurements are reported for the isochoric heat capacity of the ionic liquid substance 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C6mim][NTf2]). These measurements extend the ranges of our earlier study [N.G. Polikhronidi et al., Phys. Chem. Liq. 52, 657 (2014)] by 5 % of the compressed liquid density and by 75 kelvins. An adiabatic calorimeter was used to measure one-phase (CV1) liquid and two-phase (CV2) liquid + vapor isochoric heat capacities, densities (ρS ), and phase-transition temperatures (TS ) of the ionic liquid (IL) substance. The combined expanded uncertainty of the density ρ and isochoric heat capacity CV measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 0.15 % and 3 %, respectively. Measurements are concentrated in the immediate vicinity of the liquid + vapor phase transition curve, in order to closely observe phase transitions. The present measurements and those of our earlier study are analyzed together, and are presented in terms of thermodynamic properties (TS, ρS, CV1 and CV2) evaluated at saturation and in terms of key derived thermodynamic properties Cp, CS, [Formula: see text], and [Formula: see text] on the liquid + vapor phase transition curve. A thermodynamic relation by Yang and Yang is used to confirm the internal consistency of measured two-phase heat capacities CV2, which are observed to fall perfectly on a line as a function of specific volume at a constant temperature. The observed linear behavior is exploited to evaluate contributions to the quantity CV2 = f(V,T) from chemical potential [Formula: see text] and from vapor pressure [Formula: see text]. The physical nature and specific details of the temperature and specific volume dependence of the two-phase isochoric heat capacity and some features of the other derived thermodynamic properties of IL at liquid saturation curve are considered in detail.

(Invited) Ion Diffusion in Ionic Liquids: Effects of Electric Fields

An ionic liquid is an ionic substance in which its constituent ions are in motion. Consequently, it is not possible to understand the nature of an ionic liquid without understanding how its constituent ions move. However, gaining a thorough understanding the nature of ion motion in ionic liquids remains a fundamental challenge. Single molecule fluorescence (SMF) confocal spectroscopy offers a powerful, but as yet largely underutilized tool to measure the diffusion of probe ions in an ionic liquid under a variety of conditions. To enable SMF measurements, it was necessary to develop the synthesis of ionic liquids with very low background fluorescence. The SMF derived diffusivity of the cationic probe dyes in dilute (ca. 100 pM) solutions in [C4C1im][NTf2] and [C4C1pyrr][NTf2] solutions was compared to diffusivity of the ionic liquid cations derived from Pulse Gradient Stimulated Echo NMR measurements. The SMF derived diffusivities of the cationic probes were measured under various applied potentials and throughout the system’s relaxation back to its unperturbed state. This relaxation was found to be markedly slower than in salt solutions in molecular solvents. These results were compared to measurements of microscopic viscosity using the fluorescence spectra of molecular rotors.

(Invited) Ion Diffusion in Ionic Liquids: Single Molecule Fluorescence Spectroscopy

An ionic liquid is an ionic substance in which its constituent ions are in motion. Consequently, it is not possible to understand the nature of an ionic liquid without understanding how its constituent ions move. However, gaining a thorough understanding the nature of ion motion in ionic liquids remains a fundamental challenge. Single molecule fluorescence (SMF) confocal spectroscopy offers a powerful, but as yet largely underutilized tool to measure the diffusion of probe ions in an ionic liquid under a variety of conditions. To enable SMF measurements, it was necessary to develop the synthesis of ionic liquids with very low background fluorescence. The SMF derived diffusivity of the cationic probe Rhodamine 123 in dilute (ca. 100 pM) solutions in [C4C1im][NTf2] solutions was compared to diffusivity of the ionic liquid cations derived from Pulse Gradient Stimulated Echo NMR measurements. The SMF derived diffusivity of the cationic probe Rhodamine 123 was measured under various applied potentials and throughout the system’s relaxation back to its unperturbed state. This relaxation was found to be markedly slower than in salt solutions in molecular solvents.

염 함유 폐수처리수에 대한 Daphnia magna 및 Vibrio fischeri 급성독성 비교연구

This paper aims to evaluate the results of acute toxicity testing with Daphnia mag<TEX>$Na^+$</TEX> and Vibrio fischeri and characteristics of ionic substance of treated effluent which contained salt. Acute toxicity with Daphnia mag<TEX>$Na^+$</TEX> and Vibrio fischeri and salinity of 19 samples (4 business categories) were a<TEX>$Na^+$</TEX>lysed. Salinity of effluent could explain the fluctuation of toxicity with D. mag<TEX>$Na^+$</TEX> about 66% ~ 91% (<TEX>$r^2=0.66{\sim}0.91$</TEX>). The results of acute toxicity testing with V. fischeri of treated effluent (aggregate manufacture facilities) did not indicate toxicity (TU = 0), whereas that of chemical manufacture facilities indicated toxicity. V. fischeri, a candidate test organism, seemed suitable test organism for acute toxicity testing of effluent except high salinity (above 65‰ ~ 70‰) in aggregate manufacture facilities (nonmetalic minerals facilities). The performance of ion composition about treated effluent of surveyed facilities indicated that ion concentration of <TEX>$Na^+$</TEX> (5,740 mg/L) and <TEX>$Cl^-$</TEX> (9,727 mg/L) showed high level among 6 major ions (<TEX>$Na^+$</TEX>, <TEX>$K^+$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$Mg^{2+}$</TEX>, <TEX>$SO_4{^{2-}}$</TEX>, <TEX>$Cl^-$</TEX>) in effluent of nonmetalic minerals facilities. In addition, Clion seemed to influence the D. magna survival rather than <TEX>$Na^+$</TEX> ion.

Ketoprofen–cysteine equimolar salt

Pharmaceutical salts had been defined as “compounds” formed between a molecular or ionic active pharmaceutical substance and a salt former. Like cocrystals, salts are mainly prepared in order to increase the biodisponibility of the active substance. In this paper, we present the formation of a pharmaceutical salt prepared by cocrystallization which was obtained from ketoprofen (KT) and cysteine (Cys). The physicochemical properties of the KT–Cys salt were investigated by thermal analysis, Fourier-transform infrared spectroscopy and powder X-ray diffraction (PXRD) techniques. The heat flow curve of the KT–Cys is different from the ones of KT and Cys and suggests that under experimental conditions, the interaction between the two compounds occurred. This aspect and the corroboration with the results from spectroscopy and PXRD data confirmed the formation of a salt and the absence of any unbound component.

Notable Stabilization of α-Chymotrypsin by the Protic Ionic Additive, [ch][dhp]: Calorimetric Evidence for a Fine Enthalpy/Entropy Balance.

An impact of 0.5 to 3 M choline dihydrogen phosphate, [ch][dhp], the biotechnologically relevant ionic substance, on the thermal stability of a model globular protein, α-chymotrypsin (α-CT), has been studied exploiting the highly sensitive differential scanning calorimetry (DSC) technique. The notable overall stabilizing effect of 11 ± 2 K regarding the thermal transition (melting) temperature, T m, has been detected. For this kind of series, for the first time, the calorimetric melting enthalpy (ΔH cal) and transition entropy (ΔS m) parameters have been determined simultaneously throughout. The first analysis indicated a two-phase impact implying (a) the initial, dramatic drop in both ΔH cal and ΔS m, obviously connected to specific, direct interaction between the [ch][dhp] components and α-CT's charged groups (within 0 to 1 mol/L [ch][dhp]), leading to the essential rearrangement of the interfacial hydrogen-bonded (HB) network; and (b) the follow-up (within 1 to 3.0 mol/L [ch][dhp]), modest changes in ΔH cal and lack of changes in ΔS m, seemingly connected with a subsequent steady strengthening of already reformed HB network, respectively. These changes, presumably, are primarily facilitated by Coulombic interactions between the [dhp] anions and solvent-exposed positively charged amino groups of α-CT.

Effects of Ionic Substances on the Adsorption of Egg White Proteins to a Stainless Steel Surface

The surface fouling of food processing equipment by proteins was studied by investigating the adsorption of egg white proteins to the surface of stainless steel (SS) at pH 7.4 and 30 °C, and particularly the effects of different types of ionic substances. Ovalbumin and ovomucoid, acidic egg white proteins, were less adsorbed in the presence of phosphate (P(i)), a multivalent anion, than in the presence of HEPES, an amphoteric ion. On the other hand, lysozyme, a basic egg white protein, was more adsorbed in the presence of P(i) than in the presence of HEPES. Citrate as another multivalent anion and taurine as another amphoteric ion affected the respective adsorption of those egg white proteins similarly to P(i) and HEPES. The adsorption of an egg white protein to an SS surface therefore depended on the combination of the type of protein and the effective charge of the coexisting ionic substance. This behaviour can be well explained by assuming that a small ionic substance precedes a protein in attaching to an SS surface, resulting in an alteration to the effective surface charge. Pretreating SS with a P(i) buffer lowered the amount of ovalbumin adsorbed with the HEPES buffer, demonstrating that P(i) can attach to and remain on the SS surface to affect the subsequent protein adsorption.

Assessing 16-Year-Old Students’ Understanding of Aqueous Solution at Submicroscopic Level

Submicrorepresentations (SMR) could be an important element, not only for explaining the experimental observations to students, but also in the process of evaluating students’ knowledge and identifying their chemical misconceptions. This study investigated the level of students’ understanding of the solution concentration and the process of dissolving ionic and molecular crystals at particulate level, and identifies possible misconceptions about this process. Altogether 408 secondary school students (average age 16.3) participated in the study. The test of chemical knowledge was applied and the analysis of four selected problems related to drawing SMRs in solution chemistry is presented. Selected students were also interviewed in order to gain more detailed data about their way of solving problems comprised in the knowledge test. The average achievement on solution chemistry items was only 43%. It can be concluded from the results that students have different misconceptions about arrangements of solute particles in the solution and presentation of its concentration at particulate level. Students show quite low achievement scores on the problem regarding drawing the SMR of ionic substance aqueous solution (7.6% correct answers) and even lower ones on the problem regarding drawing the SMR of diluted and saturated aqueous solutions of molecular crystal (no completely correct answers). It can be also concluded that many different misconceptions concerning the particulate level of basic solution chemistry concepts can be identified. In the conclusion some implications for teaching to reach a higher level of understanding of solution chemistry are proposed.

Preparation of Perpendicular GdFeCo Magnetic Thin Films with Pulse Electrodeposition Technique Utilizing Molten Salt as Electrolyte

We have utilized ZnCl2-dimethylsulfone (DMSO2) as the electrolyte with added GdCl3, FeCl2, and CoCl2, for electrodepositing a perpendicular GdFeCo magnetic thin film. The reaction at the electrode surface and the electrical conductivity of the ionic substance at different ionic concentrations were studied by cyclic voltammetry and a computerized direct current method. Moreover, the electrodeposition of the GdFeCo thin film was determined by a pulse potential method. Relation between the composition of the deposited thin film and control parameters including applied potentials was determined by EDS analysis. An amorphous structure and the thickness of the thin film were obtained by TEM analysis. Its roughness and uniformity were determined by AFM analysis. Meanwhile, a perpendicular magnetic property and pinning magnetic domain of the thin film were analyzed from results of AGM and MFM.

Surveying Students' Conceptual and Procedural Knowledge of Acid–Base Behavior of Substances

By the end of their high school studies, students should be able to understand macroscopic and sub-microscopic conceptualization of acid�base behavior and the relationship between these conceptual models. The aim of this article is to ascertain whether grade-12 students have sufficient background knowledge to explain the properties of acids, bases, and salts from their constituent ions or molecules. In addition, this research seeks to discern if certain learning difficulties are due to this lack of knowledge. Two concept maps are used for evaluation including the conceptual and procedural knowledge of acid�base behavior of substances. The diagnostic instrument consists of five questionnaires and two interviews. This study reveals that grade-12 students lack some of the necessary knowledge and skills to understand the acid�base behavior of substances. This could explain why students cannot differentiate between an ionic and non-ionic substance and that they associate the existence of H or OH in the formula with acid or basic reaction, respectively, without differentiating between atoms and ions. Students do not understand the different types of particles or the meaning of the subscript or superscript in a polyatomic ion formula. They do not differentiate between the ion and atom of an element and consequently find it difficult to interpret the properties of substances such as solution in water and electrical conductivity.

Ion-pair reversed-phase HPLC: Assay validation of sodium tanshinone IIA sulfonate in mouse plasma

Sodium tanshinone IIA sulfonate (STS), a hydrophilic ionic substance, is used as a cardiovascular drug. An ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) method for the determination of STS in mouse plasma was initially developed. The assay involved a rapid and simple extraction process and subsequent detection at 271 nm. The retention time for STS was 7.5 min. Based on extracted STS standard mouse plasma at 1.5,10 and 50 microg/ml, the assay precision were 2.7, 2.1 and 1.7% with a mean accuracy of 96.7, 98.5 and 99.4%, respectively. At plasma concentration of 1.5, 50 and 75 microg/ml, the mean recovery of STS were 93.1, 96.3 and 97.5%. The limit of detection (LOD) and limit of quantification (LOQ) for STS was 0.1 microg/ml and 0.5 microg/ml, respectively. Linear responses were observed over a wide concentration range (0.5-100 microg/ml) for STS in mouse plasma. STS can be detected after intravenous administration. This method was performed for the first time in pharmacokinetic studies of STS in the mouse.