Alkaline Cations Research Articles

Cadmium (II) ion sensing through p-tert-butyl calix[6]arene based potentiometric sensor

Poly (vinyl chloride) (PVC) based membranes containing p-tert-butylcalix [6] arene (I) in the molecular form as an electroactive material along with anion excluder sodium tetraphenyl borate (NaTPB) and plasticizer Di-Octyl phthalate (DOP) have been used to fabricate a new cadmium-selective sensor. Out of the various compositions, the best performance was exhibited by the membrane having I-PVC-NaTPB-DOP in the ratio 1:33:1:65 (w/w). The sensor works well in the concentration range 9.7×10−5 to 1×10−1moldm−3 with a near-Nernstian slope of 29.0±1mV/decade of activity. The working pH range of this sensor is 2.8 to 6.2 and its performance was found satisfactory up to 20% non-aqueous medium. It exhibits a fast response time of 35s and could be used for more than 4months without any considerable change in response characteristics. It has excellent selectivity for Cd(II) over alkali, alkaline and other heavy metal cations.

Iridium oxide based coaxial pH ultramicroelectrode

In this communication, a coaxial pH microelectrode consisting of a working electrode made of IrOx and a Ag/AgCl reference electrode has been developed. The outer wall of the glass capillary with a tip diameter of 5μm was sputtered with Au and then IrOx film was electrodeposited on the Au layer, while the inside of the capillary was a Ag/AgCl wire which can serve as a reference electrode. This electrode presented a linear response in the pH range from 2.0 to 12.0 with a sensitivity of 58.73±0.41mV/pH. In selectivity tests, several alkaline cations such as Na+ and K+ didn't interfere with the performance of the electrode. Furthermore, the ultramicroelectrode exhibited rapid response times ranging from 0.5s to 5s depending on the solution pH. The excellent performance and ultramicro-size of this pH sensor make it very promising for in situ/in vivo pH measurements.

Biodegradation potential of cyano-based ionic liquid anions in a culture of Cupriavidus spp. and their in vitro enzymatic hydrolysis by nitrile hydratase

Biodegradation tests with bacteria from activated sludge revealed the probable persistence of cyano-based ionic liquid anions when these leave waste water treatment plants. A possible biological treatment using bacteria capable of biodegrading similar compounds, namely cyanide and cyano-complexes, was therefore examined. With these bacteria from the genera Cupriavidus, the ionic liquid anions B(CN)4 −, C(CN)3 −, N(CN)2 − combined with alkaline cations were tested in different growth media using ion chromatography for the examination of their primary biodegradability. However, no enhanced biodegradability of the tested cyano-based ionic liquids was observed. Therefore, an in vitro enzymatic hydrolysis test was additionally run showing that all tested ionic liquid (IL) anions can be hydrolysed to their corresponding amides by nitrile hydratase, but not by nitrilase under the experimental conditions. The biological stability of the cyano-based anions is an advantage in technological application, but the occurrence of enzymes that are able to hydrolyse the parent compound gives a new perspective on future cyano-based IL anion treatment.

The effect of the shape of the mesogenic group on the structure and phase behavior of 2,3,4-tris(dodecyloxy)benzenesulfonates with alkaline cations

Synthesis and mesophase structure characterisation are reported for a group of alkali salts of 2,3,4-tris(dodecyloxy)benzenesulfonic acid. As revealed by a combination of polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, variation of the effective mesogen shape due to changes of the cation size leads to systematic transformation of the materials' phase behaviour. Thermotropic mesophases of different types and dimensionalities were observed: 1D (smectic bilayers), 2D (ordered and disordered columnar phases), and 3D (high-temperature micellar mesomorphic phase, low-temperature crystalline one). Cubic packing prevails when the cation size is small and, thus, the effective mesogen shape is close to the conic one. With increasing ion size, the mesogen shape becomes more tapered, and columnar mesophases appear to be more stable.

The state of ionic balance in selected plant species from natural habitats of the Piska Primeval Forest (NE Poland)

Abstract The objective of this paper was an attempt to estimate the impact of variable habitat conditions on the ionic state and ionic balance of selected species of plants occurring in an environment with scarce anthropogenic pressure in the Piska Primeval Forest, north-eastern Poland. The analysed mono- and dicotyledonous plants showed very high amounts of total nitrogen, exceeding sum of alkaline cations (Ca2+, Mg2+, K+, Na+), particularly at poor natural habitats (Sphagno-girgensohni-Picetum and Pino-Quercetum communities). Lack of alkaline cations is probably compensated by nitrogen in the form of NH4+, therefore maintaining the ionic balance of cations and anions in plants. Plants inhabiting habitats such as the Tilio-Carpinetum community show very high amounts of potassium. Some potassium radioactivity is probably indispensable for the physiological processes in plants instead of solar radiation

Surface potential of hematite particles in high concentration electrolytes: Electroacoustic measurements and suspension stability

The behavior of hematite particles and their surface charge in the presence of various electrolytes ranging from 10−3 to 10molL−1 has been investigated. Zeta potential measurements were performed using an electroacoustic device, and results showed that the nature of the alkaline cation in solution (Li+, Na+, K+, Cs+ or tetramethylammonium) leads to the presence or absence of a charge neutralization for higher concentrations. This behavior follows the indirect Hofmeister series (lithium has the strongest effect) and may be attributed to the hard or soft nature of the cation. This effect was also shown by experiments with various anions (OH−, Cl−, Br−, NO3−, ClO4−). Calculations using the classical DLVO theory predicted stability in agreement with the observed macroscopic behavior of the hematite suspensions, and most notably the rate and degree of sedimentation.

Thermal decomposition of K1 − x Cs x BSi2O6 borosilicates

Thermal decomposition of mixed K1 − x Cs x BSi2O6 borosilicates by the methods of thermal analysis, annealing, and quenching, with the following refining of the structure by the Rietveld method on the example of solid solutions with x = 0.3 and 0.7 crystallizing in the space groups \(I4\bar 3d\) and \(Ia\bar 3d\), respectively, is studied. It is shown that the solid-phase decomposition of borosilicates proceeds with the release of the gas- eous phase and formation of cristobalite and/or tridymite of SiO2 at the final stage. In this case the solid solutions enriched by potassium decompose in one stage with the formation of SiO2, while the solutions enriched by cesium decompose with the formation of the intermediate zeolite-like CsBSi5O12 borosilicate, which also decomposes during further thermal treatment. According to the data of the structure, the refining of K1 − x Cs x BSi2O6 solid solutions obtained by thermal treatment at 1000°C for 20, 65, 80, and 100 h, it is detected that for the samples with x = 0.3 and 0.7 the parameter of the cubic cell of the leucite-like phase decreases and the vacancies in the position of alkaline cation appear. During the solid-phase decomposition of K1 − x Cs x BSi2O6 solid solutions the structure degrades.

Solvent isotope effects on the hydration of alkaline cations: H/D secondary isotope effects on electrostatic interactions

We investigate H/D secondary isotope effects on the binding energies of water alkaline cation complexes, Alk+(X2O)n (X = H, D; Alk = Li, Na, K; n = 1 − 4), using the any particle molecular orbital approach. Our results reveal that deuteration reduces water’s capacity to solvate alkaline cations. An explanation to this behaviour is proposed in terms of the observed changes in distances, partial charges, electrostatic potentials and polarisation induced by deuteration.

Synthesis and characterization of aluminium-free ZSM-5 type chromosilicates in different alkaline systems and investigation of their pore structures

Aluminium-free ZSM-5 type chromosilicates as M[Cr]ZSM-5 (M=Na, K and Cs), were synthesized successfully from silicic acid, sodium (or potassium or cesium) carbonate and chromium (III) nitrate using hydrothermal procedure in the presence of tetrapropylammonium bromide (TPABr) as a template. These samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TG), Fourier transform infrared spectroscopy (FT-IR) and N2 physical adsorption analysis. The experimental results show that M[Cr]ZSM-5 mesoporous molecular sieves were successfully synthesized. In the synthesis of M[Cr]ZSM-5, a pure MFI phase was obtained with a relatively low concentration of chromium in the synthesis gel. For higher chromium concentration in the synthesis gel, the final product was found to be amorphous. According to N2 physical adsorption analysis, the linear portion of the last section of t-plot, is extrapolated to the adsorption axis of the comparison plot, and this intercept is used to obtain the volume of the micropores. By using different alkalin cations in the synthesis process such as Na or K or Cs, the crystallinity of the zeolite, decreases with the order of Na>K>Cs; studying the porosity characterization of the system with different alkaline cations, also shows the same order for the BET surface area of the samples, but reverse order for the size of pores in the structures of chromosilicates. The effect of various factors, such as crystallization temperature, crystallization time and pH of reaction system on the crystallization process was investigated in detail.

Investigation of different amendments for dump reclamation in Northern Vietnam

Giant spoil dumps originate in the course of open-cast mining. The initial properties of Triassic spoil as well as pedogenesis are characterized by weathering processes. Due to the poor conditions in dump spoil a natural succession of plants or a re-vegetation is a lengthy process. The Chinh Bac field experiment (Ha Long City, Quang Ninh province, Vietnam) was planned to investigate the possible impacts of three amendments – charred rice straw, power station ashes and fine material originating from the mining area in combination with sieved spoil of substrate quality – to enhance plant growth. The main focus of this study was directed towards the impact of added amendments on spoil chemical parameters. The investigations demonstrated that simply sieving the spoil leads to better substrate conditions. It increases the fine material which in turn leads to easier plantation conditions. At the same time oxidative processes and leaching acid products are stimulated which raises the pH values afterwards. The application of charred rice straw increased the amount of alkaline cations, in particular potassium, boosting the pH value. This led to an enhanced supply of nutrients for the plants in comparison to the other amendment variations which were very poor in nutrient availability. Adding power station ash resulted in a short-term pH value increase, however potential pollution caused by heavy metals cannot be ruled out. The pyrite containing fine material was identified as the poorest amendment. It may allow vegetation to grow quickly, however the proceeding weathering processes cause a strong acidification. This mobilizes heavy metal and aluminum ions which prevent healthy plant growth.

Rutile Surface Properties Beyond the Single Crystal Approach: New Insights from the Experimental Investigation of Different Polycrystalline Samples and Periodic DFT Calculations

The relationships between particle morphology and surface properties for different kinds of rutile polycrystalline samples have been thoroughly investigated, combining FTIR spectroscopy of CO adsorbed at 60 K through the carbon end on surface Ti4+ centers, electron microscopy, and periodic DFT calculations. We provide a complete assignment of the FTIR spectra of CO adsorbed on micro- and nanorutile crystals with well-defined morphology, on commercially sourced nanorutile, and on the P25 rutile component. On the basis of these results, the spectrum of CO on native P25(1) is revisited. Of special interest is the fact that the (110) rutile main surface undergoes a thermally induced relaxation process, leading to the shielding of exposed Ti4+ sites and consequently to the reduction of the polarizing power. This process can be reversed by inducing an outward relaxation of the shielded Ti atoms by treating the sample in water at 573 K. A red-shifted band ascribed to CO adsorbed through the oxygen end on the low polarizing sites of relaxed surfaces provides the signature of surface relaxation. CO species interacting through the oxygen end have already been studied for CO on zeolites exchanged with low polarizing alkaline cations but not yet properly discussed for CO on metal oxides.

Selective sodium removal from lithium chloride brine with novel inorganic ion exchanger

Natrium superionic conductor (NASICON) ceramics present interesting sensitive and selective properties against alkaline cations due to their structure. The powder of Li1.4La0.4Zr1.6(PO4)3 has been synthesized by a solid phase reaction. The removal of sodium was studied in an extensive series of tests involving different ionic exchange process variables such as time and temperature. The results indicated that its exchange capacity is very high, even reach 41.3 mg/g. The Na/Li ion exchange reaction rate increased obviously with increasing temperature, and the kinetic data fitted well to the equation of Johnson-Mehl-Avrami-Kolmogorov with a regression coefficient value of above 0.99. KEY WORDS: Brine, Lithium chloride, Sodium, Separation Bull. Chem. Soc. Ethiop. 2013, 27(2), 241-248.DOI: http://dx.doi.org/10.4314/bcse.v27i2.9

“Metakaolin‐Slag‐Clinker Blends.” The Role of Na+ or K+ as Alkaline Activators of Theses Ternary Blends

This article reports on research into the use of solid alkalis (Na2CO3 and K2CO3) as activators to obtain hybrid cement (cement whose hydration generates a mix of C–A–S–H and (N,C)–A–S–H gels) from a blend of 20% clínker + 40% blast furnace slag + 40% metakaolin. More specifically, the study aimed to determine the effect of activator dosage (5 and 8 wt%) and type of alkaline cation (Na+ or K+) on the 2‐ and 28‐d mechanical strength of the end materials. The findings showed that the highest mechanical strength values were obtained with 5% Na2CO3. According to the XRD, NMR, and SEM/EDX analyses conducted on the reaction products, the alkalinity and solubilized chemical species generated by adding 5% Na2CO3 to the system yielded a mix of (N,C)–A–S–H and C–A–S–H cementitious gels as the main reaction products. The secondary reaction products included metastable (3CaO·Al2O3·CaCO3·11H2O‐type) carboaluminates that evolved into the calcite or vaterite forms of calcium carbonate. When K2CO3 was used (instead of Na2CO3), a (3CaO·Al2O3·0.5Ca(OH)2·0.5CaCO3·11H2O‐type) hemicarboaluminate also formed. The study also revealed that Na+ favors coagulation/precipitation more effectively than K+, generating gels with a wider range of Qn species.

Effect of Lithium and Potassium Cations on the Electrocatalytic Properties of Carbon and Manganese Oxide Electrocatalysts Towards the Oxygen Reduction Reaction in Concentrated Alkaline Electrolyte

The impact of alkaline cations (Li+ and K+) on the electrocatalytic properties of high-surface-area carbon (HSAC) and nanometric manganese oxides (MnOx) deposited onto HSAC (MnOx/C) used as oxygen reduction reaction (ORR) electrodes has been studied in concentrated LiOH or KOH media. The electrochemical characterizations firstly reveal that HSAC have good ORR electrocatalytic properties in these strong alkaline electrolytes, in agreement with the literature. However, although MnOx/C exhibits high ORR activity in NaOH and KOH media below 1 M (Roche et al., J Phys Chem C 111:1434, 2007), the present study reveals their deactivation in concentrated LiOH or KOH electrolytes because of an insufficient activity of water. The latter is indeed not compatible with a sufficient presence of protons in solution, thereby limiting the necessary proton insertion into the MnOx lattice, a prerequisite for ORR activity (Roche et al., J Phys Chem C 111:1434, 2007). In addition, when LiOH electrolyte is used, another effect penalizes the electrode performances; Li+ ions may insert into the MnOx lattice and stabilize both the Mn atoms at the oxidation state 3 and the oxygen groups at the carbon surface, which prevents their role of redox mediating species and further blocks the catalytic process, eventually yielding increased ORR overpotential.

Structure composition correlation in KNN–BT ceramics – An X-ray diffraction and Raman spectroscopic investigation

Lead free (1 − x)K0.5Na0.5NbO3–(x)BaTiO3 ceramics were synthesized by solid state reaction. The influence of the addition of BaTiO3 on the phase and crystalline symmetry of the KNN-based ceramics was investigated. X-ray analysis confirmed that the addition of BaTiO3 results in the change of structure from orthorhombic towards tetragonal at x = 0.04 and cubic phase above x = 0.1. The tetragonality ratio increased from 1.005 at x = 0.04 to 1.022 at x = 0.08 and then decreased. Raman spectra demonstrated a variety of changes with BT addition, mainly classified as lattice translations involving motions of the alkaline cations and internal modes of NbO6 octahedra. The symmetric stretching mode ν1 shifted to a higher wavenumber as the concentration of BT is increased, because the incorporation of BaTiO3 in the perovskite unit distorted the O–Nb–O bond angles. A linear relationship was observed in tetragonality ratio calculated by XRD and Raman shifts. This correlation between XRD and Raman spectroscopy results can be used to assess the crystalline symmetry in KNN-modified systems.

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs3(UO2)2(PO4)O2: Spectroscopic characterization and cationic mobility studies

The reaction of triuranyl diphosphate tetrahydrate precursor (UO2)3(PO4)2(H2O)4 with a CsI flux at 750°C yields a yellow single crystals of new compound Cs3(UO2)2(PO4)O2. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13)Å, b=8.1081(8)Å, c=12.3983(12)Å, β=114.61(12)°, V=1245.41(20)Å3 with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F2 yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupled device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains [UO5]∞1 and by one phosphorus atom in a tetrahedral environment PO4. The two last entities [UO5]∞1 and PO4 are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs+ alkaline cations. Their mobility within the tunnels were studied between 280 and 800°C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound.

Driving force for the hydration of the swelling clays: Case of montmorillonites saturated with alkaline-earth cations

Important structural modifications occur in swelling clays upon water adsorption. The multi-scale evolution of the swelling clay structure is usually evidenced by various experimental techniques. However, the driving force behind such phenomena is still not thoroughly understood. It appears strongly dependent on the nature of the interlayer cation. In the case of montmorillonites saturated with alkaline cations, it was inferred that the compensating cation or the layer surface could control the hydration process and thus the opening of the interlayer space, depending on the nature of the interlayer cation.In the present study, emphasis is put on the impact of divalent alkaline-earth cations compensating the layer charge in montmorillonites. Since no experimental technique offers the possibility of directly determining the hydration contributions related to interlayer cations and layer surfaces, an approach based on the combination of electrostatic calculations and immersion data is developed here, as already validated in the case of montmorillonites saturated by alkaline cations. This methodology allows to estimate the hydration energy for divalent interlayer cations and therefore to shed a new light on the driving force for hydration process occurring in montmorillonites saturated with alkaline-earth cations. Firstly, the surface energy values obtained from the electrostatic calculations based on the Electronegativity Equalization Method vary from 450mJm−2 for Mg-montmorillonite to 1100mJm−2 for Ba-montmorillonite. Secondly, considering both the hydration energy for cations and layer surfaces, the driving force for the hydration of alkaline-earth saturated montmorillonites can be attributed to the interlayer cation in the case of Mg-, Ca-, Sr-montmorillonites and to the interlayer surface in the case of Ba-montmorillonites.These results explain the differences in behaviour upon water adsorption as a function of the nature of the interlayer cation, thereby allowing the macroscopic swelling trends to be better understood. The knowledge of hydration processes occurring in homoionic montmorillonites saturated with both the alkaline and the alkaline-earth cations may be of great importance to explain the behaviour of natural clay samples where mixtures of the two types of interlayer cation are present and also provides valuable information on the cation exchange occurring in the swelling clays.

The Study of Activated Carbon/CNT/MoO3 Electrodes for Aqueous Pseudo-Capacitors

There is an emerging need to develop renewable energy, power sources and technologies for sustainable energy storage and conversion. Capacitive energy storage in the so-called supercapacitors is distinguished from other types of electrochemical energy stoage devices such as batteries by short charging times, the ability to deliver significantly higher power and to demonstrate very prolonged cycling (orders of magnitude better than rechargeable batteries). A key limitation to this technology is its low energy density and for that reason there is a considerable interest in exploring pseudo-capacitive electrodes’ materials where faradaic mechanisms based on surface red-ox activity offer higher energy density than simple electrostatic interactions, yet with a very prolonged cycle life and high rate capability. Among the materials studied, one can find conductive polymers, redox functional groups and transition metals sulfides, nitrides, carbides and oxides. MoO3 is a transition metal oxide which has several options for redox activities with protons and alkaline cations in aqueous solutions due to the multi-valence nature of molybdenum. In this work, we report on pseudo-capacitor electrodes, composed of monolithic, binder free, activated-carbon/carbon-nanotubes/molybdenum-trioxide (AC/CNT/MoO3) matrices, demonstrating stable capacity up to 400 Fg−1, within a potential window of 1V in acidic aqueous solutions, during at least 10,000 cycles. They also exhibit high and stable capacity (up to 250 Fg−1) in alkaline solutions.

Li内包C<sub>60</sub>の岩塩型結晶の構造と相転移

Fullerene with encapsulated lithium cation, Li+@C60, can be regarded as an alkaline cation owing to the spherical shape and positively charged Li+ cation. We present the crystal structure and phase transition of a rock-salt-type Li+@C60 crystal that consists of the freely rotating Li+@C60 cations and orientationally disordered PF6− anions at 400 K. The orientations of the C60 cages and PF6− anions are perfectly ordered below TC＝370 K, whereas the Li+ cations are thermally hopping within the cages even at 155 K. A gradual localization of the Li+ cations at polar two positions in each C60 below 100 K and a negative thermal expansion of the static C60 are demonstrated.

Alkaline cations directing the transformation of FAU zeolites into five different framework types

Exposure of faujasite zeolites to different alkali hydroxide solutions readily yields zeolites with ABW, CHA, MER and ANA topologies. In NaOH faujasite persisted. Aside from new opportunities for zeolite synthesis, this reveals that a suitable aluminosilicate connectivity in the source material significantly facilitates zeolite crystallization.