Presence Of Ionic Species Research Articles

Sorption of Cd2+ on Bone Chars with or without Hydrogen Peroxide Treatment under Various Pyrolysis Temperatures: Comparison of Mechanisms and Performance

In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd2+ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and the number of oxygen-containing functional groups on the bone char surface increased. After being pyrolyzed, the specific surface area and the negative charge of the material were further improved. The adsorption kinetics and isotherms of Cd2+ adsorption were studied, and the influence of solution pH and the presence of ionic species were investigated. The experimental results showed that the samples with lower crystallinity exhibited less organic matter content and more surface oxygen-containing functional groups, resulting in stronger adsorption capacity. After being treated with hydrogen peroxide and pyrolyzed at 300 °C, the maximum adsorption capacity of bone char was 228.73 mg/g. The bone char sample with the lowest adsorption capacity(47.71 mg/g) was pyrolyzed at 900 °C without hydrogen peroxide pretreatment. Ion exchange, surface complexation, and electrostatic interactions were responsible for the elimination of Cd2+ by the bone char samples. Overall, this work indicates that hydrogen peroxide-treated pyrolytic bone char is a promising material for the immobilization of Cd2+.

Synthesis and characterization of self-healable poly (acrylamide) hydrogel electrolytes and their application in fabrication of aqueous supercapacitors

With overwhelming progress in the field of electronic technology, self-healable hydrogel electrolyte-based supercapacitors are of significant interest as a power source in wearable energy storage devices. Self-healable hydrogel with unique three-dimensional porous microstructure, unprecedented self-healing, high capacitive energy density, low power density has been synthesized by in situ polymerization of acrylamide in the presence of exfoliated sodium montmorillonite (Na-MMT) clay as non-covalent cross-linker. Furthermore, addition of lithium trifluoromethanesulfonate (LiTF) salt converted the hydrogel into electrolyte for use in supercapacitor. Hydrogel electrolytes were prepared containing 10, 20, 30, and 40 wt% salt (AAM1, AAM2, AAM3, and AAM4), respectively. Acrylamide, clay and salt interactions were explored by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and energy dispersive x-ray analysis (EDX). X-ray diffraction (XRD) analysis reveals amorphous nature whereas FTIR and transference number measurements prove the complexation and presence of ionic species in the hydrogel electrolytes. Ionic conductivity and transport studies for hydrogel electrolyte containing 30 wt% of LiTF showed maximum ionic conductivity of 9.34 × 10−3 S/cm and number density of 70.7 × 10 20 cm−3, diffusion coefficient of 2.16 × 10 −9 cm2/s, ionic mobility of 0.854 × 10−7 cm2/V.s among all the synthesized hydrogel electrolytes. The electrochemical performance of the fabricated device disclosed the maximum significant specific capacitance of 102 F/g at 3 mV/s and 157 F/g at 50 mA/g along with power density of 50 W/kg and energy density of 21.59 W h/Kg, respectively for hydrogel electrolyte (AAM3) containing 30 wt% of the LiTF. Self-healing properties of hydrogel electrolyte have been confirmed by its use in supercapacitor where it retained its self-healing properties. The self-healable supercapacitor was used to light up 2 V light emitting diode (LED). Hence, investigations suggest the potential application of the hydrogel electrolytes with 30 wt% LiTF in the supercapacitors.

Ion-size dependent electroosmosis of viscoelastic fluids in microfluidic channels with interfacial slip

We report a study on the ion-size dependent electroosmosis of viscoelastic fluids in microfluidic channels with interfacial slip. Here, we derive an analytical solution for the potential distribution in a parallel plate microchannel, where the effects of finite sized ionic species are taken into account by invoking the free energy formalism. Following this, a purely electroosmotic flow of a simplified Phan-Thien-Tanner (sPTT) fluid is considered. For the sPTT model, linear, quadratic, and exponential kernels are chosen for the stress coefficient function describing its viscoelastic nature across various ranges of Deborah number. The theoretical framework presented in our analysis has been successfully compared with experimental results available in the literature. We believe that the implications of the considered effects on the net volumetric throughput will not only provide a deeper theoretical insight to interpret the electrokinetic data in the presence of ionic species but also serve as a fundamental design tool for novel electrokinetically driven lab-on-a-chip biofluidic devices.

Photocatalytic degradation of seawater organic matter using a submerged membrane reactor

A TiO 2 based advanced oxidation process is expected to degrade organic matter in seawater and thereby fouling would be mitigated in the membrane reactor. The effects of seawater sources on photocatalytic microfiltration treatment were investigated with respect to the removal of particulate and organic matter, as well as the control of membrane permeability. The TiO 2 mediated photocatalysis of seawater organic matter (SOM) was compared with that of natural organic matter (NOM) present in fresh water. The photocatalytic degradation of SOM was marginal, but it was enhanced significantly when sea salts were removed by electrodialysis. It revealed that the SOM photocatalysis was governed not by the molecular structure of SOM itself, but by the presence of ionic species in the seawater. To identify the ions responsible for the considerably reduced SOM photocatalysis, some major ionic species selected were dosed to desalted seawater. It was thus found that chloride ions were serving as a scavenger of photoinduced strong oxidizing radicals (e.g., hydroxyl or superoxide radicals), although they may contribute to the partial oxidization and chlorination of SOM molecules. The alteration of SOM molecular structures before and after the photocatalysis was confirmed by means of fluorescence spectroscopy. The X-ray fluorescence of TiO 2 surfaces showed that no significant adhesion of chloride ions onto the TiO 2 surface occurred during SOM photocatalysis.

CONTROLLING FACTOR IN ALUMINA PILLARED SAPONITE AND ALUMINA PILLARED MONTMORILLONITE SYNTHESIS

The effect of synthesis parameters to the physical properties of pillared saponite and pillared montmorillonite was examined. Mol ratio of Al to clay mass in the range 1.0 - 5.0 and two different calcination methods; conventional calcination and microwave irradiation method are evaluated as controlling factors to evolution of basal spacing d001 , surface acidity, specific surface area, pore distribution and catalytic activity in phenol hydroxylation reaction. XRD, FTIR, and N2-adsorption/desorption analysis were used to characterize the materials. Results showed that pillarization produced higher basal spacing d001 and surface acidity and crystalinity of materials in all Al/clay ratio and in both of the calcination methods. In general, Al to clay mass ratio and calcination method remarkably influence to the basal spacing d001, surface acidity and material crystallinity, but the effect of these factors to catalyst activity in phenol hydroxylation depends on nature of clay. It is concluded that the activity as catalyst is affected by the presence of ionic species and surface acidity in the minerals. Keywords: Pillared smectite, surface acidity, calcination

Simulation of water clusters in vapour, alkanes and polyethylenes

The Gibbs Ensemble Monte Carlo (GEMC) technique has been used to study the clustering of water in vapour, alkanes and polyethylene, where the water clusters are in equilibrium with liquid phase water. The effect of an external electric field and ionic impurities on the clustering of water in the hydrocarbons (alkanes and polyethylene) has also been studied. The simulations of water clustering in polyethylene were made more efficient by using a connectivity altering osmotic Gibbs ensemble method. It was found that trends in the size distribution of water clusters in the hydrocarbons are similar to those found in the pure vapour, but that fewer and smaller clusters are formed as the length of the hydrocarbon chain increased. Also, large external electric fields decrease the solubility of water in hydrocarbons, whereas the presence of ionic species dramatically increases the solubility.

Heterogeneous Membrane and Coated Wire Type Electrode with Chitosan as Ionophore in the Potentiometric Determination of Glutamate: Comparative Study

AbstractThis study reports on two types of glutamate sensors based on chitosan, i) heterogeneous membrane and ii) coated wire (CWE). The linearity ranges are: i) membrane, 1.0×10−5 to 1.0×10−1 M and ii) CWE, 1.0×10−5 to 1.0×10−3 M. The LODs, and pH ranges are i) membrane, 5.0×10−6 M and 4–8 and ii) CWE, 1.0×10−5 M and 3–5, respectively. The presence of ionic species normally found in foodstuffs did not interfere in both electrodes. Interference in CWE was minimized by prior dilution of the sample. The CWE was further investigated for on‐line analysis. The material for proposed electrodes was cheaper and environmental friendly. Hence, they were suggested as alternative tools for the analysis of glutamate.

Removal of aqueous phenanthrene by brown seaweed Sargassum hemiphyllum: Sorption-kinetic and equilibrium studies

The batch sorption-kinetics and equilibrium uptake of phenanthrene (PHE), a hydrophobic organic compound (HOC), in aqueous compartment were investigated using dead tissue of brown seaweed Sargassum hemiphyllum under various conditions for 24 h. It was found that the higher the shaking rates (50–250 rpm) and temperatures (15–35 °C), the higher the sorption rates of PHE, but no significant changes were observed for the maximum sorption capacities. Study with different initial PHE concentrations (50–1000 μg L −1) showed that a higher ambient level of PHE resulted in a faster initial uptake rate and greater sorption capacity. The presence of ionic species (0.01–1 M NaCl) changed the sorption-kinetics of PHE markedly by altering the maximum removal of PHE, but not the initial sorption rates. No significant removal variations were noted under various initial pH (pH 2–11), while constant alkalinity resulted in an alleviated PHE sorption by Sargassum. The sorption-kinetics of PHE typically followed more closely to the pseudo-second-order model ( r 2 > 0.85) than pseudo-first-order equation ( r 2 > 0.72). Removal capacities were in the range of 430–460 μg g −1 for tests spiked with 1000 μg L −1 PHE. Typical percentage removals of aqueous PHE by Sargassum for all the investigated factors (e.g. initial pH and ionic strength) were in the range of 91.7–98.4%. Log Sargassum-water and the organic carbon normalized partition coefficient were calculated as 3.83 and 3.96 mL g −1, respectively. The present study provided valuable information for achieving optimal sorption of aqueous PHE using Sargassum as an effective sorbent for removing HOCs in wastewaters and urban runoffs.

Formation of Molecular Wires by Nanospace Polymerization of a Diacetylene Derivative Induced with a Scanning Tunneling Microscope at a Solid-Liquid Interface

A nanospace polymerization reaction was initiated using a scanning tunneling microscope in a monolayer of a diacetylene derivative, 10, 12-nonacosadiynoic acid (NCDA), at a solid-liquid interface to obtain molecular wires. The polymerization threshold with respect to the applied voltage was 2 V, which was 1 V lower than that observed at a solid-air interface. The presence of ionic species considerably enhanced the reaction probability. At more than ±2 V, the addition of N(CH3)4ClO4 resulted in the expansion of the reaction region and the increase in reaction probability regardless of the sign of the bias voltage applied. Different from the case at the solid-air interface, polymerization at the solid-liquid interface was probably induced through the multiple vibrational excitation of NCDA by repetitive collisions with charged carriers activated by the strong electric field involved in electron avalanche.

A study of formation of solid ionic conductors in the mixed system (CdI2)b[(Ag2O)·(CrO3)]100-b (20≤b≤80)

Using Wagner's polarization technique and EMF method the joinic and silver ionic transport number measurements of various compositions of the mixed system CdI2-Ag2O-CrO3 have been made. The presence of AgI in these materials has been inferred from the typical β → α phase transition of AgI, which is characterized by an endothermic peak at around 420 K in the DSC traces of these specimens. While the structural analysis performed by means of powder X-ray diffraction has revealed the formation of ionic phases involving polycrystalline compounds, the Fourier transform infrared (FTIR) spectroscopic results have indicated the presence of ionic species thus confirming the ionic nature of the products. The complex impedance studies carried out in the frequency range 20 Hz - 1 MHz and over the temperature range 294 – 442 K have revealed that the best conducting composition, namely 55%(CdI2) – 45%(Ag2O·CrO3), would exhibit a silver ionic conductivity of 1.3×10−5Scm−1 at 294 K.

Investigation of retardation effects on the titanium dioxide photodegradation system

The photocatalytic bleaching of dyes using TiO 2 has appeared promising in laboratory studies, but little attention has been focused on whether other species such as might be found in wastewater have a deleterious effect on the photobleaching. This study describes the effects that result from the presence of ionic species, organic solvents and humic substances on the photobleaching of several dyes. The manner in which the photobleaching was affected by the presence of adventitious materials was carefully examined with an eye toward elucidating the mechanistic origin of the loss of the photochemical efficiency in the reaction. The overall retardation effects can be attributed to the combination of light attenuation, inhibition and competition effects.

Liquid-phase hydrogenation of citral over Ir-supported catalysts

The hydrogenation of citral over a series of supported iridium catalysts was investigated. The nature of the support (TiO 2 and SiO 2), the effect of additives (Fe and Ge), and the influence of the reduction temperature on catalyst performance have been examined. It was found that the presence of ionic species, such as, promoters or species generated upon reduction at high temperature of the reducible TiO 2 support, i.e. TiO x moieties, leads to catalysts active and highly selective to the hydrogenation of the carbonyl bond. This is explained in terms of the presence of positively charged (Fe 3+, Ge 4+) species in intimate contact with Ir, which are responsible for the polarisation of the CO bond.

Composite Polymer Electrolytes Based on Poly(ethylene glycol) and Hydrophobic Fumed Silica: Dynamic Rheology and Microstructure

Dynamic rheological techniques are used to probe the microstructures present in fumed silica-based composite polymer electrolytes. These electrolytes are obtained by dispersing hydrophobic fumed silica in a poly(ethylene glycol)−lithium salt solution and display high conductivities (σ298K > 10-3 S/cm), mechanical stability, and easy processability. The materials behave as soft solids (gels) under ambient conditions due to the presence of a three-dimensional network of silica entities. Network formation occurs as a result of van der Waals (dispersion) forces between the nonpolar surface layers on silica units. Factors which affect the van der Waals interaction, and hence the gel network density, include the nature of the PEG end group, the presence of ionic species, and the size of the hydrophobic surface group on the silica. The composites also exhibit shear-thinning behavior due to the shear-induced disruption of network bonds, and this behavior can be advantageously utilized in electrolyte processing.

Organometallic Compounds of the Alkali Metals with Phenylsilyl Substituents at the Carbanionic Center. Crystal Structures of LiC(SiMe3)2(SiMe2Ph)·Et2O, NaC(SiMe3)2(SiMe2Ph)·TMEDA, NaC(SiMe3)(SiMe2Ph)2·TMEDA, {LiCH(SiMe2Ph)2}2, RbC(SiMe2Ph)3, and CsC(SiMe2Ph)3 (TMEDA = Tetramethylethylenediamine)

The syntheses of a number of alkali metal compounds MC(SiMe3)3-n(SiMe2Ph)n, are described (n = 1, M = Li(TMEDA) (3a), Li(Et2O) (3b), or Na(TMEDA) (3c); n = 2, M = Li(THF)2 (6a), Li(TMEDA) (6b), Na(TMEDA) (6c), or K (6d); n = 3, M = Rb (7d) or Cs (7e); THF = tetrahydrofuran, TMEDA= tetramethylethylenediamine). The compounds 3b, 3c, and 6c adopt molecular structures with intramolecular metal−phenyl interactions. The lithium compound LiCH(SiMe2Ph)2, 5, is dimeric with electron-deficient μ-Li bridges and intramolecular metal−phenyl interactions. The compounds MC(SiMe2Ph)3, M = Na (7b), K (7c), Rb (7d), or Cs (7e), form polymeric chains in the solid state with both intra- and intermolecular metal−phenyl interactions. For the lighter alkali metals the interaction is unsymmetrical and mainly with the ipso and ortho carbon atoms, but for the heavier metals there are almost equal metal−carbon distances to all six atoms of the phenyl ring. The long M−C and short Si−C bond lengths and the wide Si−C−Si angles indicate that the structures are highly ionic. The presence of ionic species in solution is revealed by multinuclear NMR data, in particular by the low frequency shifts associated with the central carbon atoms, by the high carbon−silicon coupling constants, and by the low barriers to inversion compared with those in the trisilylmethanes from which the carbanions are derived.

The physical chemistry of light-curable glass-ionomers

This paper reviews aspects of the physical chemistry of light-curable glass-ionomer cements. These materials have a tendency to undergo phase separation in solution and, when set, to take up water and swell. Other likely features of their behaviour include: (i) retardation of the ionic curing reaction by the presence of organic components; (ii) modification of the photochemical cure process by the presence of ionic species; and (iii) gradual phase separation on setting, leading to a domain structure in the solid state. The paper concludes that longer-term clinical studies are needed to demonstrate whether these features lead to durable materials or to materials containing inherent physico-chemical weaknesses that will limit their overall usefulness.

Potentiometric and conductometric determination of ammonium by gas-diffusion flow injection analysis

Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas-diffusion separation in flow injection analysis. Ammonium and potassium selective liquid membrane electrodes can be used for determinations in the concentration range 10−7–10−2 mol/l with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.

Growth of potassium hydrogen sulphate crystals in the presence of ionic species

The effects of Co 2+ and Fe 3+ cationic species are studied on the growth habits of KHSO 4 single crystals. Using a tracer technique, it is found that the concentration of these ionic impurities in KHSO 4 single crystals increases linearly with increase on impurity concentration in their saturated solutions and their distribution coefficients are 1.478 × 10 -2 and 1.938 × 10 -1 respectively. The presence of Fe 3+ increases the growth rate of X(113) and O(111) planes, which results in tapering of crystal faces. The small amount of Fe 3+ can act as a growth aid for KHSO 4 single crystals.

A mechanism for the habit modification of ammonium dihydrogen phosphate crystals in the presence of ionic species in aqueous solution

AbstractAmmonium dihydrogen phosphate (ADP) crystals develop new high index faces when grown from aqueous solution containing up to 1000 ppm of added CrCl3 · 6 H2O. The crystallographic nature of these faces has been studied as a function of the CrCl3 · 6 H2O concentration in the growth solution (24.0°C, σ = 0.06) and their high morphological importance is explained, using a modification of the Hartman‐Perdok theory of crystal morphology, but postulating that the adsorption of impurity species at specific sites transform K‐faces into pseudo‐F‐faces.

Growth of the {100} faces of ammonium dihydrogen phosphate crystals in the presence of ionic species

The kinetics of movement of elliptical growth layers on the {100} faces of ammonium dihydrogen phosphate crystals are reported for growth from aqueous solution at 19.3 6, 23.9 6 and 28.5 4°C in the supersaturation range 0.025< σ<0.08. The layers are shown to be step bunches and surface diffusion is considered to play the rate determining role in the growth process. The effects of trace amounts (up to 100 ppm) of CrCl 3 s ̇ 6 H 2 O FeCl 3 and AlCl 3 on the kinetics of movement of the growth layers were studied at 23.9 6°C and σ=0.052. The results are interpreted in terms of adsorption of the impurity species at kink, step or ledge sites.

Growth of the {101} faces of ammonium dihydrogen phosphate crystals in the presence of ionic species

Measurements have been made of the chromium and Cl - uptake by ammonium dihydrogen phosphate (ADP) crystals growing in aqueous solutions containing up to 1000 ppm of CrCl 3·6H 2O. The possible nature of the incorporated chromium species is discussed. The effects of trace amounts (up to 100 ppm) of CrCl 3·6H 2O, FeCl 3 and AlCl 3 on the growth kinetics of the {101} faces of ADP crystals are also reported. Under these conditions growth was a non-steady state process. The results are interpreted in terms of entry of impurity species into the adsorbed surface layer and their subsequent interference with the rate controlling surface processes.