Effect Of Cation Species Research Articles

Effect of cation species on pressure-driven electrokinetic energy conversion in charged conical nanochannels

Electrokinetic energy conversion (EEC) offers a promising avenue for transforming elusive natural energy into electric power, showing a wide application spectrum. Unlike prevalent studies that chiefly utilize symmetrical electrolyte solution (e.g., KCl) and uniformly structured negatively charged nanochannels for EEC, this paper delves into a thorough examination of EEC characteristics—streaming current, streaming potential, and output power—in both positively and negatively charged conical nanochannels with symmetrical and asymmetric (CaCl2 and LaCl3) electrolytes solutions. Operating under the assumption that the electrolyte solutions (KCl, CaCl2, and LaCl3) possess equivalent ionic strength and, thereby, a common Debye length, our findings reveal a significant dependency of EEC characteristics and their regulation parameters on the electrolyte type, nanochannel charge polarity, and ionic strength. As the ionic strength increases, both the streaming current and output power initially rise to a peak before subsequently declining, with the ionic strength at the peak being influenced by the cation valence: lower valence leads to lower ionic strength. In asymmetric electrolyte scenarios, optimal EEC characteristic is observed in positively charged conical nanochannels under a reverse pressure difference, attributed to the ion-selective and ionic concentration distribution in the charged conical nanochannels. Moreover, the complex behaviors of the regulation parameters of EEC characteristics are unveiled. Notably, a tri-valent electrolyte's regulation parameters exceed those of a bi-valent electrolyte, indicating that ionic valence asymmetry enhances the regulation effects on EEC in conical nanochannels.

Tartaric acid-based ionic liquid-type chiral selectors: Effect of cation species on their enantioseparation performance in capillary electrophoresis

Ionic liquids (ILs) have proven to be a promising alternative to traditional chiral selectors in chiral capillary electrophoresis (CE). However, the number of IL-type chiral selectors currently available is quite limited and their types of structure are generally restricted to tetraalkylammonium salts. In this work, six tartaric acid (TT)-based ILs (TTILs) were designed containing different cation species, including di-1-butyl-3-methylimidazolium-L-tartrate ([BMIM]2-L-TT), di-1-butyl-pyridinium-L-tartrate ([BPY]2-L-TT), di-tetrabutylphosphonium-L-tartrate ([TBP]2-L-TT), di-choline-L-tartrate ([CHO]2-L-TT), di-1-butyl-1-methylpiperidinium-L-tartrate ([BMPIP]2-L-TT), and di-1-butyl-1-methylpyrrolidinium-L-tartrate ([BMPYR]2-L-TT). These novel IL-type chiral selectors were successfully synthesized and applied to the enantioseparation of ten amino alcohols in CE. Under selected CE conditions (60 mM TTILs, 150 mM boric acid in 80–90% methanol, pH 4.5), [BMPIP]2-L-TT showed the best chiral separation performance, followed by [BMPYR]2-L-TT and [TBP]2-L-TT. Most amino alcohols were resolved with enantioresolutions (Rs) above 4.0. The enantioselectivity demonstrated by [CHO]2-L-TT was relatively moderate (Rs ranging from 1.50 to 4.50), but it proved that the suppression of electroosmotic flow (EOF) is not the main contribution of TTILs to chiral CE. The enantioselectivities of [BMIM]2-L-TT and [BPY]2-L-TT were also shown to be satisfactory but their interference with UV detection is a negative factor in CE application. To the best of the authors’ knowledge, this is the first time that the influence of various achiral cation species of IL-type chiral selectors on CE enantioseparations has been systematically evaluated. Since there has been controversy regarding the true role of chiral ILs in CE enantioseparations, the parallel comparison of these TTILs in this work clearly shows that their cations are able to participate in the enantiorecognition process by introducing steric hindrance effect, rather than merely influencing the EOF in the separation systems.

Effects of Cationic Species in Salts on the Electrical Conductivity of Doped PEDOT:PSS Films

The electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films with four salts that have various cations but the same bis(trifluoromethanesulfonyl)amide (TFSI) anion was studied. We found that doping salts of small-sized cations led to better conductivity because of the improved crystalline order and p-doped level of PEDOT, as revealed by the grazing-incidence wide-angle X-ray scattering (GIWAXS) and UV-vis spectrum. This phenomenon can be rationalized with the fact that small-sized cations with stronger Coulombic interactions can lead to high doping and rearrangement of PEDOT:PSS. These findings will help to develop recipes based on the PEDOT:PSS/salt composite toward the applications for printed flexible electronics.

Oxygen diffusion in cation-form Nafion membrane of microbial fuel cells

The diffusion process of O2 in the cation-form Nafion membrane is investigated by molecular dynamics simulations. Moreover, the effects of cation species and concentration on O2 diffusion are elucidated systematically. The results show that for the H+-form Nafion membrane, the average size of hydrophilic clusters in the membrane increases and these clusters will interconnect gradually as the membrane water content increases. Thus, the diffusion coefficient of O2 increases with the increase of water content. In addition, O2 molecules tend to diffuse along the hydrophilic/hydrophobic phase interface and within the hydrophobic phase of the membrane. Na+ or Ca2+ promotes while K+ hinders O2 diffusion compared with H+ when there is only one kind of cation in the Nafion membrane. As to the membrane contains both H+ and one kind of metal cations mentioned above, although the ratios of these two kinds of cations change linearly, the diffusion coefficient of O2 changes nonlinearly. It is mainly because that the factors affecting O2 diffusion in the Nafion membrane have different priorities under different cation species and concentration conditions. In general, the factors such as the large free volume fraction of the membrane, the large average size of hydrophilic clusters with better connectivity and the wide distribution of O2 molecules close to the hydrophobic phase are conducive to O2 diffusion in the cation-form Nafion membrane.

Alkali-metal-modified ZSM-5 zeolites for improvement of catalytic dehydration of lactic acid to acrylic acid

Various ZSM-5 zeolites modified with alkali metals (Li, Na, K, Rb, and Cs) were prepared using ion exchange. The catalysts were used to enhance the catalytic dehydration of lactic acid (LA) to acrylic acid (AA). The effects of cationic species on the structures and surface acid-base distributions of the ZSM-5 zeolites were investigated. The important factors that affect the catalytic performance were also identified. The modified ZSM-5 catalysts were characterized using X-ray diffraction, temperature-programmed desorptions of NH3 and CO2, pyridine adsorption spectroscopy, and N2 adsorption to determine the crystal phase structures, surface acidities and basicities, nature of acid sites, specific surface areas, and pore volumes. The results show that the acid-base sites that are adjusted by alkali-metal species, particularly weak acid-base sites, are mainly responsible for the formation of AA. The KZSM-5 catalyst, in particular, significantly improved LA conversion and AA selectivity because of the synergistic effect of weak acid-base sites. The reaction was conducted at different reaction temperatures and liquid hourly space velocities (LHSVs) to understand the catalyst selectivity for AA and trends in byproduct formation. Approximately 98% LA conversion and 77% AA selectivity were achieved using the KZSM-5 catalyst under the optimum conditions (40 wt% LA aqueous solution, 365 °C, and LHSV 2 h−1).

Effect of cation species on surface-induced phase transition observed for platinum complex anions in platinum electrodeposition using nanoporous silicon.

In an earlier work [K. Fukami et al., J. Chem. Phys. 138, 094702 (2013)], we reported a transition phenomenon observed for platinum complex anions in our platinum electrodeposition experiment using nanoporous silicon. The pore wall surface of the silicon electrode was made hydrophobic by covering it with organic molecules. The anions are only weakly hydrated due to their large size and excluded from the bulk aqueous solution to the hydrophobic surface. When the anion concentration in the bulk was gradually increased, at a threshold the deposition behavior exhibited a sudden change, leading to drastic acceleration of the electrochemical deposition. It was shown that this change originates from a surface-induced phase transition: The space within a nanopore is abruptly filled with the second phase in which the anion concentration is orders of magnitude higher than that in the bulk. Here we examine how the platinum electrodeposition behavior is affected by the cation species coexisting with the anions. We compare the experimental results obtained using three different cation species: K(+), (CH3)4N(+), and (C2H5)4N(+). One of the cation species coexists with platinum complex anions [PtCl4](2-). It is shown that the threshold concentration, beyond which the electrochemical deposition within nanopores is drastically accelerated, is considerably dependent on the cation species. The threshold concentration becomes lower as the cation size increases. Our theoretical analysis suggests that not only the anions but also the cations are remarkably enriched in the second phase. The remarkable enrichment of the anions alone would give rise to the energetic instability due to electrostatic repulsive interactions among the anions. We argue that the result obtained cannot be elucidated by the prevailing view based on classical electrochemistry. It is necessitated to consult a statistical-mechanical theory of confined aqueous solutions using a molecular model for water.

Effect of cation species on solubilities of metal chlorides in water vapor at high temperatures and pressures

A flow type apparatus was used for the measurements of the solubilities of lithium chloride and calcium chloride in water vapor from 623 to 673 K and from 6.0 to 14.0 MPa. The solubilities of both metal chlorides increase with temperatures at the constant pressure. This behavior implies that the systems form the vapor–liquid equilibria at the conditions focused in this work unlike the case of sodium chloride and potassium chloride reported previously. A correlation model was developed for the solubilities of the metal chlorides in water vapor. The ionizations and hydrations of the metal chlorides were considered in the correlation model. The solubility data for the sodium chloride, potassium chloride, lithium chloride and calcium chloride in water vapor were correlated. The correlated results are in good agreement with the experimental data. The hydration numbers of metal chlorides were obtained from the correlations. It was found that the hydration numbers for the metal chlorides with monovalent cations increase with the radii of cations. For calcium chloride, the value of the hydration number is larger than those for metal chlorides with monovalent cations.

Effects of Cationic Species on Visual Color Formation in Model Maillard Reactions of Pentose Sugars and Amino Acids

Effects of cationic species on Maillard browning were examined after heating (ca. 100 degrees C) aqueous pH 7.2 buffered solutions of amino acids and pentose sugars. Metallic ions of Group I metals (Li, Na, K, Rb and Cs) produced a small increase in browning (A420), but somewhat greater effects were observed with ions of Group II metals Ca and Mg. Browning was suppressed by triethylammonium ion, but unaffected by a salt of the stronger base, guanidine. The quaternary amine salt choline chloride produced enhanced browning and served as a model for phospholipid involvement in Maillard reactions. With alpha,omega-diamino acids increases in browning were observed which related to lowered pK2 values resulting from positively charged omega-substituents in these molecules.

Effect of cation species on equilibrium of reversed micellar extraction of lysozyme

Ion strength is one of the important conditions to control extraction of lysozyme with AOT reversed micelles. The extraction equilibrium changes largely with a type of the salt, i.e. cation species. For the three salt systems, KCl, BaCl2 and CaCl2, extracted fraction of lysozyme is measured for various pH values. For divalent cation systems, the behavior of the protein-extracted fraction against pH is quite different from that for KCl system. The salt concentration has a strong influence on the extracted fraction and the characteristic trend is explained by the manner of the interaction between divalent cation and anionic surfactant, AOT. Difference of the trend in the extracted fraction between barium and calcium systems is also discussed in terms of hydration of the cations. Because of the larger hydration number, combination of calcium ion to interfacial layer of AOT makes the interface rather flexible, thus the cation exchange occurs more frequently than in barium system.

Effect of cation species on equilibrium of reversed micellar extraction of lysozyme

Abstract Ion strength is one of the important conditions to control extraction of lysozyme with AOT reversed micelles. The extraction equilibrium changes largely with a type of the salt, i.e. cation species. For the three salt systems, KCl, BaCl2 and CaCl2, extracted fraction of lysozyme is measured for various pH values. For divalent cation systems, the behavior of the protein-extracted fraction against pH is quite different from that for KCl system. The salt concentration has a strong influence on the extracted fraction and the characteristic trend is explained by the manner of the interaction between divalent cation and anionic surfactant, AOT. Difference of the trend in the extracted fraction between barium and calcium systems is also discussed in terms of hydration of the cations. Because of the larger hydration number, combination of calcium ion to interfacial layer of AOT makes the interface rather flexible, thus the cation exchange occurs more frequently than in barium system.

Effects of Cationic Species on Strain Changes of Polypyrrole Doped with Perchlorate Anions

Strain changes of polypyrrole (PPy) during electropolymerization and redox (reduction and oxidation) switching in perchlorate aqueous solutions were investigated using strain gages. It was found that the magnitude of strain changes during redox switches of PPy depends on the counter cations used during electropolymerization. For PPy films of the same thicknesses, PPy synthesized in LiClO 4 demonstrated the largest strain changes during redox switching and. as the cation size increased, the strain changes became smaller. Because, regardless of the identity of counter cations. PPy showed similar strain behaviors in perchlorate solutions during redox switching, it is believed that the cations are involved in the electropolymerization process and likely to affect the formation of polymer chain structures.

Gelation Mechanism of κ- and ι-Carrageenan Investigated by Correlation between the Strain−Optical Coefficient and the Dynamic Shear Modulus

The temperature and frequency dependence of the dynamic shear modulus, strain−optical coefficient, and the optical transmission of κ- and ι-carrageenan aqueous solutions were measured in order to clarify the gelation mechanism. The growing of the gel network and the effect of cation species (K, Cs, and Ca) and the amount of added KCl are discussed on the basis of the correlation between the shear modulus and strain−optical coefficient. For all samples, these correlations can be described by a power function in the low-temperature region in the gel state. The exponent can be interpreted as a characteristic parameter reflecting the growing process of the gel network. We found two groups in terms of the value of the exponent. In the case of 2.0 wt % (high polymer concentration) K-form and Cs-form κ-carrageenan, the exponent is much higher than unity, but in the case of 1.0 wt % K-form (low polymer concentration) κ-carrageenan with added KCl and 2.0 wt % K-form ι-carrageenan, it is close to unity. For the former group, the stress required to induce the unit orientation increases, while for the latter group it does not increase much with decreasing temperature. In other words, the structure inside cross-link region changes markedly during the growing process of gel network only for the former group. We concluded that increasing schemes of the number of aggregated helical molecules during the gel growing process strongly depends on the cation species and carrageenan type.

The Effect of Cation Species on the Anodic Oxidation of Organic Solvent Electrolytes

The Effect of Cation Species on the Anodic Oxidation of Organic Solvent Electrolytes

Adsorption of Amyl Xanthate at Pyrrhotite in the Presence of Nitrogen and Implications in Flotation

AbstractAdsorption of xanthate at pyrrhotite with air and nitrogen, and the effects of cationic species have been investigated. The results have been correlated with flotation of pyrrhotite with air and nitrogen. While the use of nitrogen in place of air causes depression of pyrrhotite the effect is significantly reduced in presence of cationic species. The results are discussed on the basis of a suggested mechanism of the adsorption of xanthate at pyrrhotite.

Effect of Cation Species on the Desorption of Phosphorus in Soils Treated with Carbonate

AbstractThree‐month incubation of soils with K2CO3 raised the pH about the same as did an equivalent amount of CaCO3 but was substantially more effective in enhancing the water solubility of P (4–14‐fold at the solution to soil ratio of 60:1). In the K2CO3‐treated samples, the KCl added to achieve a 25% increase in ionic strength caused an 11–44% drop in the water‐soluble P. However, if the water to soil ratio increased, the P desorption in the CaCO3 amended samples approached that in the K2CO3‐treated soils, and the KCl‐induced reduction in water‐soluble P diminished. These responses to changes in the extraction ratio were taken to indicate that the cation species of the liming material and the ionic strength in the matrix solution affected the rate more so than the absolute quantity of P desorption. The significance of these factors under field conditions was discussed.

Electrolytic Reduction of Carbon Dioxide at Mercury Electrode in Aqueous Solution

Abstract Cathodic reduction of carbon dioxide at a mercury pool electrode was investigated in aqueous solutions of NaHCO3, NaH2PO4–Na2HPO4, NaCl, NaClO4, Na2SO4, LiHCO3, and KHCO3 as well as their combinations. The reaction product was confirmed to be HCOO− by a qualitative spot test. HCOO− was quantitatively analyzed by a permanganate titration. The partial current densities of HCOO− formation (ic) and H2 evolution (iH) were calculated. In the present paper, relationships between electrode behavior and solution properties, some of which have been qualitatively described in previous papers, are quantitatively clarified as follows. The electrode potential Ec for constant ic (0.5 mA/cm2) remains constant irrespective of pH and anions in the pH region of 2.4 to 7.8, whereas the potential EH for constant iH (0.5 mA/cm2) varies linearly with a slope of 125 mV/pH. The present experimental results verify Eyring et al.’s presumption that in a relatively high overvoltage region (region 2) the cathodic reduction of CO2 at Hg proceeds with the charge transfer to CO2 as the rate determining step. CO2 reduction and H2 evolution are concluded to proceed independently at the Hg electrode. The dependence of Ec on electrolyte concentration is interpreted in terms of the diffuse double layer theory. The effect of cation species on Ec also is discussed.