STUDY OF SORPTION OF RHENIUM IONS ON SOLID EXTRAGENTS

In this work, the aim is to study the possibility of extracting rhenium from sulfuric acid solutions by sorption of impregnated sorbents based on polystyrene-divinylbenzene (MN202) and an organic reagent MAB (2-amino-1-methylbenzimidazole).New sorbent based on MN202 (Purolite) impregnated with organic reagents have been obtained and investigated. The sorbent characteristics determined using SEM, XRD and FTIR methods. The optimal conditions for the sorption of rhenium (VII) ions for the "element-sorbent" systems have been established. Under static conditions, the sorption of rhenium on impregnated sorbents in a sulfuric acid solution was studied in the periodic system with respect to the contact time, sulfuric acid concentration, the ratio of the solid phase to liquid, and the initial concentration of rhenium. For the first time, the kinetics of sorption of rhenium (VII) ions with the obtained solid extractants has been studied. The kinetic parameters of the chemical reaction on the surface of the impregnate have been determined. Based on the processing of the integral kinetic curves of sorption, it was found that the sorption process proceeds in accordance with second-order models.

The role of the 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid reagent in determining the thorium ion (IV)

The aim is to develop a method for the amperometric determination of thorium (IV) ion with 2,7-dinitroso-1,8-dihydroxynaphthalene-3,6-disulfoxyl reagent. Methods of amperometric determination of thorium by solution of 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid on different acid-base properties of background electrolytes and buffer mixtures are considered. The half-wave potential of new reagent was found by logarithmic analysis equal 0.72 V at pH 2.82, which once again indicates on the irreversibility of the process of electrooxidation of the studied organic reagent in used acid-base medias. The conditions for amperometric titration of thorium are optimized, and the influence of outside accompanying metals on the shape of curves and the results of its determination are investigated.

High-Rate and Long-Life Cycle of Nano-LiMn2O4 Under High Cut-Off Potential

Nano-LiMn2O4 was successfully synthesized by a low-temperature hydrothermal route with the absence of post-calcination treatment. Employing ethanol as an organic reagent triggers the formation of nanostructured particles approximately 30.39 nm in diameter, associated with 0.7 % lattice strain. The pure phase of nano-LiMn2O4/Li displays outstanding electrochemical performances. Under 4.6 V vs Li+/Li cut-off potential, 74.3 % of capacity is reserved when C-rate is increased by 50 times, while excellent capacity restoration of 96.9 % after cycled again at 1 C. After 331 cycles, capacity retention of 84.3 % is harvested by nano-LiMn2O4/Li, implying the absence of phase transformations in spinel structures under such abuse condition. This remarkable structural stability can be attributed to the small lattice strain, associated with high Li+ diffusion coefficient, which is estimated to be 10-9.76 cm2 s-1 by the EIS technique. Additionally, Li+ extraction is more favourable when nano-LiMn2O4/Li is charged up to 4.6 V vs Li+/Li, interpreted by the polarization resistance (Rp) of the cell.

LUMINESCENT PROPERTIES OF TERBIUM WITH S- (4-BROMANILIDE) METHYL ETHER OF SULFOSALICYLIC ACID

It was of interest to search for luminescent reactions to terbium in complexes with sulfosalicylic acid derivatives and to strengthen them by studying the influence of the third components (aminopolycarboxylic acids, organic bases, and surfactants). Absorption spectra of solutions of rare earth element complexes in the wavelength range of 220-880 nm were recorded using the SF-26 spectrophotometer. To obtain the maximum luminescence of the luminescent reaction of rare earth elements in complexes with organic reagents, a number of factors that have a significant impact on the intensity of solutions of luminescent complexes have been studied. Such factors are the pH of the complexes, concentration of reagent, time of maturation complexes, the irradiation time, the order of adding the reagents and the ionic strength of the solutions. According to studies conducted, surfactants increase the luminosity of terbium ions in complexes with sulfosalicylic acid derivatives. As a surfactant, decylpyridinium chloride was used in solutions. The existence of a bright luminescent green reaction of terbium in a complex with methyl ester S- (4-bromanilide) sulfosalicylic acid was established. The optimal conditions for the complexation of terbium were selected and highly sensitive luminescent methods for determining terbium in various objects were developed. Terbium is converted into a luminescent complex compound with an organic reagent S- (4-bromanililide) sulfosalicylic acid methyl ester in the presence of a cationic surfactant decylpyridinium chloride in a ratio of 1: 2: 13, pH 7.9 ± 0.08. The resulting complex compound of terbium upon irradiation with a mercury lamp under ultraviolet light gives intense green luminescence that is stable during standing and irradiation. As a consequence, the proposed method allows to determine terbium in the oxides of rare earth elements, which are quenchers of luminescence with a sensitivity of 10-8%, bypassing the extraction stage. The sensitivity of the determination of terbium in the oxides of the remaining lanthanides is 2.4·10-10%.

Method to Predict Reagents in Iridium-Based Photoredox Catalysis

Visible-light photoredox catalysts with oxidizing excited states have been broadly applied in organic synthesis. Following photon absorption by the photocatalyst, electron transfer from an organic reagent is the most common mechanistic outcome for this class of reaction. Reduction potentials for organic reagents are therefore useful to predict reactivity and DFT proved to be useful as a predictive tool in this regard. Due to the complex mechanisms that follow electron transfer, kinetics play a crucial role in the success of photoredox reactions. We extend the predictive tools of DFT to estimate the electron transfer <i>rates</i> between an excited photocatalyst and various organic substrates. To calibrate our model, 49 electron transfer rate constants were experimentally measured in acetonitrile for the catalyst Ir[dF(CF₃)ppy]₂(dtbpy)⁺. The rate constants, k<i>_q</i>, gave a clear predictive trend when compared to calculated ionization energies in “frozen solvent”, which was a better predictor than standard reduction potentials in our case. The calculated k<i>_q</i> gave an average error of 17% for log(k_q) values between 4 and 11. This simple method can predict the reactivity of hundreds of reagents <i>in silico</i>. Notably, the calculations offered unexpected insight that we could translate into success for the C-H activation of acetylacetone as a proof-of-concept.

Method to Predict Reagents in Iridium-Based Photoredox Catalysis

Visible-light photoredox catalysts with oxidizing excited states have been broadly applied in organic synthesis. Following photon absorption by the photocatalyst, electron transfer from an organic reagent is the most common mechanistic outcome for this class of reaction. Reduction potentials for organic reagents are therefore useful to predict reactivity and DFT proved to be useful as a predictive tool in this regard. Due to the complex mechanisms that follow electron transfer, kinetics play a crucial role in the success of photoredox reactions. We extend the predictive tools of DFT to estimate the electron transfer <i>rates</i> between an excited photocatalyst and various organic substrates. To calibrate our model, 49 electron transfer rate constants were experimentally measured in acetonitrile for the catalyst Ir[dF(CF₃)ppy]₂(dtbpy)⁺. The rate constants, k<i>_q</i>, gave a clear predictive trend when compared to calculated ionization energies in “frozen solvent”, which was a better predictor than standard reduction potentials in our case. The calculated k<i>_q</i> gave an average error of 17% for log(k_q) values between 4 and 11. This simple method can predict the reactivity of hundreds of reagents <i>in silico</i>. Notably, the calculations offered unexpected insight that we could translate into success for the C-H activation of acetylacetone as a proof-of-concept.

Spectrophotometric Determination of Sulphamethoxazole Drug by New Pyrazoline Derived from 2,4-Dinitro Phenyl Hydrazine

Simple, sensitive and accurate spectrophotometric methods have been developed for the determination of Sulphamethoxazole (SMZ) drug . This method based on the reaction of Sulphamethoxazole (SMZ) with new organic reagent (BYN) it was prepare by reaction between ethyl acetoacetate with 2,4-Dinitrophenylhydrazine. The azo dye product shows absorption maximum at 435 nm. The linearity ranges of Sulphamethoxazole are (2-14 μg.mL-1) with molar absorptivity (14412.77 L.mol-1.cm-1), Sandell's sensitivity index (0.0175 μg.cm-2) , detection limit and Quantification limit ( 0.057, 0.175 μg / ml) respectively. The results showed there are no interferences of excipients on the determination of the drug. The proposed method has been successfully applied for the determination of sulfanilamide in pure and pharmaceutical formulations.