Russian Journal of Physical Chemistry A最新文献

The H₂TiO₃ ion sieves have demonstrated as a promising adsorbent for lithium extraction from liquid lithium resources. However, it is still challenging to simultaneously manipulate the surface hydrophilicity and micro-structure of ion sieves for efficient lithium extraction. Here, we have grafted sodium dodecyl sulfate (SDS) on H₂TiO₃ ion sieves to enhance its hydrophilicity, and simultaneously promoted the formation of porous structure for the ion sieves with the addition of aluminum chloride (AlCl₃⋅6H₂O) through the solid-phase method. The effects of SDS and Al co-modification on the hydrophilicity, morphology, structure, and adsorption properties of the H₂TiO₃ ion sieve have been systematically investigated. The modified ion sieve features a uniform and dense mesoporous structure with improved surface hydrophilicity, enhancing its lithium extraction capability and increasing its contact sites with Li⁺ in solution. As a result, the modified H₂TiO₃ ion sieves demonstrated efficient lithium extraction performance with the maximum adsorption capacity reached 64.4 mg/g, significantly outperforming the unmodified ion sieves (56.3 mg/g). Furthermore, the adsorption isotherms of Li⁺ on the SDS and Al co-modified titanium lithium ion sieve follow the Langmuir model, and the adsorption kinetics fit the pseudo-second-order model.

Here, the ground and excited state dynamics of [Ru(bpy)₂(η²-tpy)]²⁺ were studied. Protonation of the pendant pyridine ring of [Ru(bpy)₂(η²-tpy)]²⁺ demonstrates that intra-ligand charge transfer (ILCT) occurs between the pendant pyridine and adjacent bpy ligand in the [Ru(bpy)₂(η²-tpy)]²⁺ complex. The addition of trifluroacetic acid (TFA) results in slight spectral changes which have been assigned to the protonation of the pendant pyridine of [Ru(bpy)₂(η²-tpy)]²⁺. The protonation of the pendant pyridine increases the lifetime from 0.082 ns to 2.6 ns. Mulliken-Hush analysis of the ILCT of [Ru(bpy)₂(η²-tpy)]²⁺ has been done and compared with that of [Ru(bpy)₃]²⁺. The value for the electronic coupling element (H_DA) for [Ru(bpy)₂(η²-tpyH⁺)]³⁺ suggests that the electronic coupling between bpy and the pendant pyridine is quite strong.

The charge distribution of cyclic phosphenium cation and its mechanism of cycloaddition reaction with methyleneimine have been systematically investigated at the M06-2X/6-311++G** level of theory in order to better understand the reactivity for the valence isoelectronic species of cyclic carbene. The cyclic phosphenium cation acts as an electrophilic reagent, accepting the σ electrons of the methyleneimine in the first addition step to form an intermediate complex. The more positive charges on the phosphorus atom in the cyclic phosphenium cation, the more stable the complex formed. Double bond and conjugated system can reduce the positive charges on phosphorus, in turn stabilizes the cyclic phosphenium cation. Design usable and stable cyclic phosphenium cation through introduction of double bond and conjugated system, which will expand their applications in coordination chemistry and catalytic systems. The second step is the complex transforms to a spiro-heterocyclic product via a transition state, the complexes are more stable than the products.

Adsorption behavior of paracetamol (Par) and sodium naproxen (Nap) onto a low-cost activated carbon prepared from waste avocado peels (APAC) has been investigated. The surface characteristics of APAC were analyzed using SEM, XRD, and FT-IR techniques. Batch adsorption experiments were carried out to investigate the influence of various parameters, such as initial drug concentration, adsorbent dosage, contact time, temperature, and pH. The experimental data for Par and Nap were analyzed using various adsorption isotherm models. Par demonstrated a good fit with both the Langmuir and Freundlich models, while the Freundlich equation provided the best fit for Nap. The data revealed that the kinetics of both drugs followed a pseudo-second order model. The estimated thermodynamic parameters ΔH°, ΔS°, and ΔG° indicate that the adsorption of Par and Nap onto the activated carbon is an exothermic, spontaneous, and physical sorption process. Furthermore, density functional theory (DFT) calculations were employed to provide insights into the adsorption mechanism. This study concludes that waste avocado peels offer a viable and economical adsorbent for the effective removal of paracetamol and sodium naproxen from aqueous solutions.

Organic-inorganic hybrid materials show great application prospects in many fields such as sensors, intelligent switches and optoelectronics because of their adjustable structure and functional properties. An organic-inorganic hybrid one-dimensional perovskite type crystal [(CH₂)₃NH₂S]CdCl₃ ((CH₂)₃NH₂S = thiazolidinium, 1) has been synthesized. A structural phase transition occurs at 219/209 K (cooling/heating). The structural analysis of single crystal at variable temperature shows that the kinetic change of c and the deformation of anionic framework contribute to the structural transformation. This order-disorder transition of thiazolidinium causes the dielectric state to shift between low and high dielectric states, making it a switchable dielectric material. In addition, the reversibility of the dielectric switch of the crystal under temperature stimulation was determined. Our research has promoted the research progress of novel five-membered heterocyclic organic-inorganic hybrid perovskites and provided a good platform for realizing switchable dielectric properties.

The paper describes the synthesis and characterization of a set of chromium oxide catalyst systems that contain 5 wt % of chromium and are supported on various commercial supports: 5Cr/SiO₂, 5Cr/Al₂O₃, 5Cr/Al₂O₃(Si), 5Cr/Al₂O₃(Ca,Mg), 5Cr/Al₂O₃(Si,Na), 5Cr/TiO₂, 5Cr/ZrO₂(W), 5Cr/ZrO₂(Si), and 5Cr/ZrO₂(La). The catalyst systems are studied by XRD, UV–Vis diffuse reflectance spectroscopy, and SEM–EPMA methods; all the samples are tested in the CO₂-assisted oxidative dehydrogenation of propane. The catalyst system exhibiting the highest activity in the propane dehydrogenation reaction in the presence of CO₂ in the gas phase is studied under supercritical conditions. The prospects for using high pressure in the studied reaction are shown.

As crucial additives and solvents in organic synthesis, the efficient separation of the cyclohexane + 1-propanol azeotropic system holds significant industrial importance. This study systematically evaluates the separation efficiency of ionic liquids for this azeotropic system using the COSMO-RS model. First, a database containing 364 ionic liquids was constructed by combining 26 anions with 14 cations, from which the high-performance extractant C5A20 was selected. Subsequently, vapor-liquid phase equilibrium experiments verified the reliability of the model predictions, demonstrating that the azeotropic point completely disappears when the mole fraction of C5A20 reaches 0.02. Further analysis through σ-profiles and hydrogen bonding interactions revealed the selective separation mechanism of C5A20 towards 1-propanol, providing molecular-level theoretical insights for the rational design of efficient ionic liquid extractants.

The conformational rearrangement of single or paired homogeneous polypeptide macromolecules of the same length, including those with different types of units, lying on the surface of a carbon nanotube were studied by molecular dynamics simulation at different pH levels. A mathematical model of macrochain conformations is presented, which allows for interactions in the complex of two similar polypeptides on the surface of the carbon nanotube, at different pH values of the solvent. When pH departed from the isoelectric point, the single polypeptide uncoiled and wound around the nanotube, while the two identical polypeptides repelled each other, shifting to the opposite ends of the nanotube. When two oppositely charged polypeptides were adsorbed on the surface of the carbon nanotube, they became tightly intertwined, forming a generally neutral polyelectrolyte complex. If the electric charge of one of the polypeptides in the complex did not change with a change in the pH level, while the electric charge of the other polypeptide decreased in magnitude, then the first polypeptide unfolded, dragging the second one along with it, and together they wound around the carbon nanotube.

A kinetic model of the catalytic hydroisomerization of n-hexadecane is developed. It is shown that the relevance of this process is attributed to the necessity to improve the low-temperature properties of diesel fuel and Group III and IV oils. The process is run for the selective isomerization of normal alkanes contained in the feedstock in the presence of a Pt/SAPO-11 catalyst based on platinum supported on SAPO-11 with a one-dimensional channel pore structure. The studies are conducted at temperatures of 300–360°C in increments of 20°C. Rate constants for the steps, preexponential factors, and activation energies for kinetic models for simplified and detailed n-hexadecane hydroisomerization schemes are calculated by solving the inverse kinetic problem. Numerical solution methods, in particular, the multistep variable-order Gear method and a genetic algorithm, are used. According to the calculated kinetic parameters, the dehydrogenation and protonation reactions that initiate the process are characterized by high activation energies. It is shown that an increase in temperature leads to an abrupt increase in the cracking rate relative to the isomerization rate.

The Y₂O₃ catalyst was prepared by using citric acid complexation method and the decorated Y₂O₃ catalyst was obtained through industrial carbonic acid (CA) impregnation. The phase structure characterization confirmed that the cubic phase of Y₂O₃ was not destroyed by CA impregnation, but C–O functional groups were still present on the surface. After impregnating with CA, the surface contour of Y₂O₃ particles becomes clearer and the agglomeration phenomenon is weakened. The average particle size of the decorated Y₂O₃ is approximately 60 nm. Element mapping characterization also confirmed the presence of a small amount of C element in the decorated Y₂O₃. The photoresponse capability of the decorated Y₂O₃ catalyst can be extended from 400 nm to a visible light range of 800 nm. The optical bandgap value of the decorated Y₂O₃ decreased from the undecorated 3.15 to 2.88 eV. The degradation experiment carried out with chlortetracycline hydrochloride as the degradation target pollutant found that when the catalyst content was 1 g/L, the pollutant concentration was 150 mg/L and pH 5, the degradation percentage of the decorated Y₂O₃ catalyst reached 94.6%. Experiments and band theory have confirmed that the decorated Y₂O₃ catalyst has a high photocatalytic activity, which is related to the free radicals and its point of zero charge (PZC). The use of this new processing technology enables the expansion of the application range of wide bandgap semiconductor materials in the field of photocatalysis.