Preparation of organic acid anion-modified magnesium hydroxides by coprecipitation: A novel material for the uptake of heavy metal ions from aqueous solutions

New layered magnesium hydroxides whose brucite layers had been bridged with malate²⁻ and tartrate²⁻ were prepared by dropwise addition of Mg(NO₃)₂ to malate and tartrate solutions at a constant pH of 10.5. Malate²⁻ and tartrate²⁻ may have been also absorbed on the surfaces of hydroxides. In the case of using citrate solution, Mg(OH)₂ absorbed with citrate³⁻ was produced. These materials were found to take up Cu²⁺ rapidly from an aqueous solution at pH 5.0. Copper uptake by precipitates is attributed to the formation of chelate complexes of Cu²⁺ with citrate³⁻, malate²⁻, and tartrate²⁻.     

Kinetics of the dehydrochlorination of poly(vinyl chloride) in the presence of NaOH and various diols as solvents

The dehydrochlorination of PVC in the presence of NaOH was investigated in different diols. Diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG) were found to be effective in accelerating the dechlorination of PVC. The dehydrochlorination was promoted in the order TEG > DEG > PG, which was in agreement with the compatibility between PET and the diol. Compatibility resulted in an improved penetration of the PVC particle by the solvent, leading to the acceleration of the dehydrochlorination. The dehydrochlorination of PVC in NaOH/diol followed first-order kinetics, confirming the progress of the reaction under chemical reaction control. The apparent activation energies were 82 kJ mol⁻¹, 109 kJ mol⁻¹, and 151 kJ mol⁻¹ for TEG, DEG, and PG, respectively. The lower the activation energy became the faster the dehydrochlorination of PVC proceeded.     

A B3LYP study on counterpoise-corrected geometry optimizations for hydrated complexes of [K(H2O)n] and [Na(H2O)n]

We report the basis set dependencies and the basis set superposition errors for the hydrated complexes of K⁺ and Na⁺ ions in relation to the recent studies of the KcsA potassium channel. The basis set superposition errors are estimated by the geometry optimizations at the counterpoise-corrected B3LYP level. The counterpoise optimizations alter the hydration distances by about 0.02–0.03 Å. The enthalpies and free energies for K⁺ + n(H₂O) → [K(H₂O)_n]⁺ and Na⁺ + n(H₂O) → [Na(H₂O)_n]⁺ (n = 1–6) are compared between the theoretical and experimental values. The results show that the addition of diffuse functions to K, Na, and O species are effective. However, it is also found that the counterpoise corrections using diffuse functions work so as to underestimate the free energies for the complexes with increasing the hydration number. The stabilization energies in aqueous solution are larger for a Na⁺ ion than for a K⁺ ion, suggesting the contributions of their dehydration processes to the ion selectivity of the KcsA potassium channel. The changes in coordination distance between the isolated [K(H₂O)₈]⁺ and the [K(H₂O)₈]⁺ in the KcsA potassium channel indicate the importance of hydrogen bondings between the first hydration shell and the outer hydration shells.     

Synthesis, cyclic voltammetry, and UV–Vis studies of ferrocene-dithiafulvalenes as anticipated electron-donor materials

Abstract  

New ferrocenyl ketones were obtained as precursors of novel π-conjugated ferrocene-dithiafulvalene (Fc-DTF) and π-extended-ferrocenedithia-fulvalenes (π-exFc-DTF) as electron-donor conducting materials from ferrocene by a direct aroylation process using the Friedel–Crafts reaction. Novel Fc-DTF conjugates were synthesized using the Wittig–Horner reaction and their structures were determined. The redox behavior of the ferrocenyl carbonyl compounds Fc-DTF and Fc-π-exDTF was investigated in comparison to the parent ferrocene by means of cyclic voltammetry. A one-electron redox behavior was observed for carbonylferrocenes as one wave potential, while a two-electron process was observed as two oxidation waves for the conjugates. Introduction of electron-withdrawing groups led to increasing E _pa values and decreasing ΔE _p values. The UV–Vis spectra of some compounds were studied in comparison with ferrocene. The absorption spectra showed a red-shift with a slight increase in the absorption intensities.     

Effect of the moisture content in aerosol on the spray performance of Stmerin D HFA preparations

Stmerin D, a pressurized metered dose inhaler (MDI) for treatment of asthma, contains CFCs (chlorofluorocarbons) as a propellant. For the CFC replacement study, two formulations were prepared using hydrofluoroalkanes (HFA-134a and HFA-227) and the effect of storage on the spray performance was investigated under accelerated stress conditions. Drug stability, moisture content and spray performances such as the emitted dose uniformity and aerodynamic particle size distribution were evaluated. Drug content did not change after 3 months storage at 40 degrees C/75% RH. However, the emitted dose uniformity varied and the respirable fraction (RF) was reduced remarkably. While stored at 40 degrees C/ambient for 3 months, no change was observed in either drug content or spray performances. This study clarified that the moisture content in the canister played an important role on the spray performance, and it changed not only the emitted dose uniformity but also the particle size distribution. Consequently, in order to improve the stability of the spray performance of aerosol prepared with HFAs, moisture permeation into the canister must be controlled.     

Physical stability of amorphous acetanilide derivatives improved by polymer excipients

Crystallization rates of drug-polymer solid dispersions prepared with acetaminophen (ACA) and p-aminoacetanilide (AAA) as model drugs, and polyvinylpyrrolidone and polyacrylic acid (PAA) as model polymers were measured in order to further examine the significance of drug-polymer interactions. The crystallization of AAA and ACA was inhibited by mixing those polymers. The most effective inhibition was observed with solid dispersions of AAA and PAA. The combination of AAA and PAA showed a markedly longer enthalpy relaxation time relative to drug alone as well as a higher T(g) than predicted by the Gordon-Taylor equation, indicating the existence of a strong interaction between the two components. These observations suggest that crystallization is effectively inhibited by combinations of drug and polymer that show a strong intermolecular interaction due to proton transfer between acidic and basic functional groups.     

Mass selective ejection by axial resonant excitation from a linear ion trap

We describe a new mass selective ejection method from a linear ion trap, which we call axial resonant excitation (AREX). A set of vane lenses are inserted between each quadrupole rod to produce electrostatic potential that is approximately harmonic along the central axis of the quadrupole field. After ions with specific m/z are resonantly oscillated in the axial direction, the ions are mass selectively ejected in the axial direction. At a high scan rate of 11 Th/ms, AREX achieved a high ejection efficiency of more than 60%, which is more than three times higher than a conventional mass selective axial ejection method from a linear trap using fringing field.     

Synthesis and structure of new water-soluble and stable tantalum compound: ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)

The stable water-soluble tantalum complex with lactic acid (ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)), (NH4)4[Ta2(C3H4O3)4(O2)2O].3H2O, was prepared in the crystalline form. According to the single-crystal X-ray diffraction data, this compound forms a monoclinic cell with a = 13.85(2) A, b = 9.06(1) A, c = 12.32(2) A, and beta = 116.30 degrees , space group C2 (No. 2), and has Z = 2 molecules per unit cell. The solid-state 13C NMR data and low flack parameter are consistent with the determined structure. Appearance of the same vibration modes in Raman and IR spectra supports the choice of the space group without inversion symmetry. The solution of the tantalum complex was successfully applied for the synthesis of two photocatalytic materials, NaTaO3 and Sr2Ta2O7.     

Effect of ultrasonic irradiation on nucleation phenomena in a Na2HPO4.12H2O melt being used as a heat storage material

The effect of ultrasound on nucleation phenomena in the heat storage material Na2HPO4.12H2O was investigated by determining the primary nucleation probability and induction time, and by looking at heat generation phenomena in the initial stage of nucleation. The experimental results show that the primary nucleation probability dramatically increased, and the induction time decreased under the ultrasound irradiation, and in addition, the rate of temperature rise was dependent upon the ultrasonic output. Based on these results and the theoretical relationship between the number of primary nuclei and the heat generation rate, it is proposed that the number of primary nuclei depends upon the ultrasonic output.