Kinetic Aspects Research Articles

Modern Trends in Polymerization-Induced Self-Assembly.

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

CryoEM-sampling of metastable conformations appearing in cofactor-ligand association and catalysis of glutamate dehydrogenase

Kinetic aspects of enzymatic reactions are described by equations based on the Michaelis–Menten theory for the initial stage. However, the kinetic parameters provide little information on the atomic mechanism of the reaction. In this study, we analyzed structures of glutamate dehydrogenase in the initial and steady stages of the reaction using cryoEM at near-atomic resolution. In the initial stage, four metastable conformations displayed different domain motions and cofactor/ligand association modes. The most striking finding was that the enzyme-cofactor-substrate complex, treated as a single state in the enzyme kinetic theory, comprised at least three different metastable conformations. In the steady stage, seven conformations, including derivatives from the four conformations in the initial stage, made the reaction pathway complicated. Based on the visualized conformations, we discussed stage-dependent pathways to illustrate the dynamics of the enzyme in action.

Designing Pathway-Controlled Multicomponent Ultrashort Peptide Hydrogels with Diverse Functionalities at the Nanoscale for Directing Cellular Behavior.

Tuning self-assembling pathways by implementing different external stimuli has been extensively studied, owing to their effective control over structural and mechanical properties. Consequently, multicomponent peptide hydrogels with high structural tunability and stimuli responsiveness are crucial in dictating cellular behavior. Herein, we have implemented both coassembly approach and pathway-dependent self-assembly to design nonequilibrium nanostructures to understand the thermodynamic and kinetic aspects of peptide self-assembly toward controlling cellular response. Our system involved an ultrashort peptide gelator and a hydrophilic surfactant which coassembled through different pathways, i.e., heat-cool and sonication methods with variable energy input. Interestingly, it was possible to access diverse structural and mechanical properties at the nanoscale in a single coassembled system. Further, the hydrophilic surfactant provided additional surface functionalities, thus creating an efficient hydrophilic matrix for cellular interaction. Such diverse functionalities in a single coassembled system could lead to the development of advanced scaffolds, with applications in various biomedical fields.

Mechanisms of interstellar synthesis of glycine, alanine, and serine from aminonitriles, OH, and H2O

AbstractA new potential energy surface for forming glycine in the gas phase, starting from association of aminoacetonitrile (NH2CH2CN) with OH followed by subsequent hydrolysis, was determined using CBS‐QB3 calculation. The overall activation energy was 90 kJ mol−1 or 0 without or with catalytic H2O, respectively. Alanine or serine was formed from 2‐aminopropionitrile (CH3CH(NH2)CN) or 2‐amino‐3‐hydrxypropionitrile (HOCH2CH(NH2)CN) instead of aminoacetonitrile with the overall activation energies of 89 or 49 kJ mol−1, respectively. When an additional H2O was involved in each reaction as a catalyst, barrierless reaction pathways were obtained. These results suggest that it is possible for investigated reactions to occur in interstellar ices along the proposed pathways, taking kinetic aspects into account.

Kinetics and thermodynamics in microwave-assisted transesterification of palm oil utilizing sulphonated bio-graphene catalysts for biodiesel production

Enhanced reaction performance is what has piqued interest in using graphene-based catalysts in producing biodiesel. However, in-depth analyses were lacking from a kinetic and thermodynamic standpoint. This means that a well-designed experiment is necessary to determine the effect that the graphene catalysts have on the reaction rates and yields. This work addresses the kinetic and thermodynamic aspects of heterogeneously catalyzed transesterification using sulphonated biomass-derived graphene catalysts, i.e., bGO-SO3H and brGO-SO3H. It was accomplished using the pseudo-first order mechanism and the Eyring-Polanyi equation, with all data fitting satisfactorily in both models at the ideal reaction temperature of 353.15 K, resulting in R2 values of 0.9784 (bGO-SO3H) and 0.9884 (brGO-SO3H). The calculated activation energy (Ea) was determined to be 44.45 and 51.73 kJ mol-1 for bGO- and brGO-SO3H, respectively. Additionally, the Gibbs free energy (ΔG) values were determined at −38.09 and −31.81 kJ mol−1 for bGO- and brGO-SO3H, respectively. Meanwhile, the values for ΔH and ΔS were obtained as 41.69 kJ mol−1 and 225.93 J mol−1 K−1, respectively, and 48.96 kJ mol−1 and 228.72 J mol−1 K−1, respectively. These collective outcomes collectively signify the endothermic nature of the reaction and their spontaneity, particularly under elevated temperature conditions.

Nutrient Removal and Recovery from Municipal Wastewater

With the ongoing amendment of the EU legislation on the treatment of urban wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Biological systems are still the first choice. A survey of typical bioreactors applied in wastewater treatment is presented. The wastewater treatment objective, biochemical environment, and microbial growth are selected as the main criteria for the classification of these bioreactors. Hydraulic and kinetic aspects are considered, along with the advantages and drawbacks of these bioreactors regarding the selection of the appropriate type of reactor; as well, details regarding the operation of reactors are mentioned. The aim of this paper is to provide operators and designers with a brief overview of the selected traditional and advanced processes, reactors, and technologies for nutrient removal from municipal wastewater. The possibilities and limitations in complying with more strict effluent standards are also discussed. Methods of nutrient recovery are added value. From the evaluation of the published papers, we determine that the currently applied traditional methods for nutrient removal have the potential to also convey the expected stricter limits.

Colorimetric Quick Response (QR) Tags and Other Time-Temperature Indicators (TTIs) for Remote Quality Assessment: Theoretical Kinetics Aspects

Colorimetric Quick Response (QR) Tags and Other Time-Temperature Indicators (TTIs) for Remote Quality Assessment: Theoretical Kinetics Aspects

In vitro simulated study of macronutrient digestion in complex food using digestive enzyme supplement

Digestive enzymes secreted by the body are vital for digestion and nutrient absorption. Enzyme supplements are commonly used to support them in achieving optimal digestion. Herein, the efficacy of digestive enzyme supplement (DigeSEB Super) in digestion of complex food was assessed using INFOGEST simulated static and modified semi-dynamic in vitro digestion models. Digestive enzyme supplement was found to assist the endogenous digestive enzymes to disintegrate the food matrix. Hence, it reduced the viscosity of the gastric digesta by 2.75 fold (p = 0.04) compared to the control digestion (only endogenous digestive enzymes) during the first hour of digestion. Similarly, enzyme supplement showed statistically higher release of reducing sugars in the gastric digestion (p ≤ 0.05) indicating improved digestion of carbohydrates. Further, digestion of proteins and fats was also improved in the presence of enzyme supplement. The kinetic aspects of the semi-dynamic model (transient nature of gastric secretions and gradual acidification) was found to alter the macronutrient digestion compared to the static digestion. Thus, semi-dynamic model should be preferred for the in vitro studies. Overall, current study demonstrated the potential of a digestive enzyme supplement to improve digestion by aiding digestive action of the endogenous enzymes.

Synthesis and characterization of coprecipitated layered NCM oxide as cathode for sodium-ion batteries: Kinetics and hydrodynamics studies

Interest in the development of high-performance sodium-ion batteries (SIBs) as a sustainable alternative to lithium-ion batteries (LIBs) for emerging energy storage systems has motivated to delve into a novel approach for the synthesis of layered transition metal oxide (LTMO) type cathode for SIBs batteries. In this study, we introduce novel chemical synthesis method that diverges from traditional methodologies reported till date. Rather than relying on sulfur, nitrate, or acetate metal precursor salts, we employ metal carbonate salt coupled with oxalic acid as a chelating agent, and sodium carbonate as a precipitating agent. This novel chemistry enhances the microstructure of the cathode material inherited from its precursor exhibiting spherical morphology, influence on the electrochemical properties, bestowing the material with high specific capacity, extended cycle life, and an elevated charge–discharge rate. The primary focus of this work centers on a comprehensive investigation of the hydrodynamic and kinetics aspects of the co-precipitation reaction, guided by the principles of chemical engineering. The effects of key parameters such as impeller speed, impeller type, and scale-up effects on the co-precipitation process have been systematically explored. This research introduces insights into optimizing reaction conditions such as pH, reaction temperature, metal precursor salt ratio, precipitating agent, through rigorous experimentation and characterization reports. The notable effect of precipitating agent on morphology has been demonstrated by electron microscopy images. The kinetics study shows the activation energy of 8.9 kJ mol−1 depicts the reaction is controlled by mass transfer resistance and to overcome this effect, impeller type and speed plays significant role and experimentation results shows the axial mixing pattern created by pitched blade impeller is effective to improvise electrochemical properties. The synthesized cathode material exhibits remarkable electrochemical properties, including tap density of approximately 1.3 g cc−1 with reversible capacity of 215 mAh g−1, along with excellent cyclic stability (90 %) over 60 cycles. Furthermore, it shows the high energy density up to 1300 Wh/L and a rapid charge–discharge rate. These findings contribute to the advancement of SIBs technology and offer promising prospects for future researchers to efficient development of high-performance energy storage solutions.

Kinetic plasma-wall interaction using immersed boundary conditions

The interaction between a plasma and a solid surface is studied in a (1D-1V) kinetic approach using immersed boundary conditions and penalization to model the wall. Two solutions for the penalized wall region are investigated that either allow currents to flow within the material boundary or not. Essential kinetic aspects of sheath physics are recovered in both cases and their parametric dependencies investigated. Importantly, we show how the two approaches can be reconciled when accounting for relevant kinetic effects. Non-Maxwellian features of the ion and electron distribution functions are essential to capture the value of the potential drop in the sheath. These features lead to a sheath heat transmission factor for ions 60% larger than usually predicted and 35% for electrons. The role of collisions is discussed and means of incorporating minimally-relevant kinetic sheath physics in the gyrokinetic framework are discussed.

Femtosecond laser fabrication of 3D vertically aligned micro-pore network on thick-film Li4Ti5O12 electrode for high-performance lithium storage

The development of energy storage devices with high energy density relies heavily on thick film electrodes, but it is challenging due to the limited ion transport kinetics inherent in thick electrodes. Here, we report on the preparation of a directional vertical array of micro-porous transport networks on LTO electrodes using a femtosecond laser processing strategy, enabling directional ion rapid transport and achieving good electrochemical performance in thick film electrodes. Various three-dimensional (3D) vertically aligned micro-pore networks are innovatively designed, and the structure, kinetics characteristics, and electrochemical performance of the prepared ion transport channels are analyzed and discussed by multiple characterization and testing methods. Furthermore, the rational mechanisms of electrode performance improvement are studied experimentally and simulated from two aspects of structural mechanics and transmission kinetics. The ion diffusion coefficient, rate performance at 60 C, and electrode interface area of the laser-optimized 60-15% micro-porous transport network electrodes increase by 25.2 times, 2.2 times, and 2.15 times, respectively than those of untreated electrodes. Therefore, the preparation of 3D micro-porous transport networks by femtosecond laser on ultra-thick electrodes is a feasible way to develop high-energy batteries. In addition, the unique micro-porous transport network structure can be widely extended to design and explore other high-performance energy materials.

Investigation of unexpected silane ions caused by gas-phase reactions in Orbitrap gas chromatography-mass spectrometry.

The mass spectra of compounds containing dimethyl (phenyl)silyl group (-SiMe2Ph) sometimes exhibit unusual ion peaks when measured using Orbitrap gas chromatography-mass spectrometry (GC-MS). This would complicate the mass spectra and may limit the matching of spectral data with preexisting resources for compound annotation. These peaks were identified as products from reactions with residual water. A series of dimethyl (phenyl)silyl compounds were dissolved in methanol and investigated using Orbitrap GC-MS. Certain ions reacted with residual water in the C-trap. The reaction was confirmed using accurate mass and elemental composition analysis via MS studies, and the active center of the reaction was determined using density functional theory (DFT) calculations. Two types of gas-phase reactions between gaseous water and cations from a series of silanes were identified. DFT calculations indicate that silicon (Si) acts as the active center for these gas-phase water reactions. Compounds with multiple Si atoms generate a larger number of additional ions, which would complicate the mass spectra. The mass spectra of vinylsilanes and alkylsilanes with -SiMe2Ph indicate that the conjugated group linked to -SiMe2Ph can affect the water adduction process. Silane ions could react with residual water in the C-trap of an Orbitrap mass spectrometer. The mass spectra of these compounds may exhibit unexplained peaks arising from gas-phase reactions. Although these reactions may decrease spectral matching scores for compound annotation, they offer opportunities for systematic investigations into the mechanistic and kinetic aspects of high-energy ion reactivity.

Transformation reactions of NO ligand in cationic nitrosyl iron complex [Fe(SC(NH2)2)2(NO)2]+ in aerobic aqueous solution: quantum chemical modeling and kinetic aspects

Transformation reactions of NO ligand in cationic nitrosyl iron complex [Fe(SC(NH2)2)2(NO)2]+ in aerobic aqueous solution: quantum chemical modeling and kinetic aspects

Degradation of trimethoprim by advanced oxidation process using UV/TiO2 and H2O2: Kinetic and economic aspects

AbstractTrimethoprim (TMP) is an effective antibiotic for treating many different infections, but it can lead to water pollution and pose a threat of generating antibiotic‐resistant bacteria through waste in the drug manufacturing process, use, and excretion of humans as well as animals. Due to its strong and non‐selective oxidizing ability, advanced oxidation processes (AOPs) utilizing UV/TiO2 and H2O2 are more efficient in removing them than conventional wastewater treatment. This work investigates TMP degradation in different water substrates by AOPs using UV/TiO2 and H2O2. The results show that the apparent reaction rate constant to the TMP's degradation in the de‐ion water matrix is 0.0379; 0.1937; and 0.209 min−1 for UV/TiO2, UV/H2O2, and UV/TiO2/H2O2 processes. The rate of degradation of TMP in hospital wastewater is lower than that of lake water and de‐ion water. The major intermediate products obtained from the degradation of TMP in de‐ion water by UV/TiO2/H2O2 process were recognized as C14H19O4N4 (m/z: 307), C5H7ON4 (m/z: 139), and C5H6O2N4 (m/z: 155). Finally, the cost of TMP treatment in de‐ion water by several AOPs using photocatalyst and hydrogen peroxide was calculated, it is 0.88 $/m3 for UV/H2O2; 33.01 $/m3 for UV/TiO2 process, and 18.77 $/m3 for UV/TiO2/H2O2 process.

Adsorptive removal of Cu(II) ions from aqueous solution using Teff (Eragrostis tef) hay based magnetized biocarbon: RSM-GA, ANN based optimization and kinetics aspects

Abstract Teff (Eragrostis tef) is known as a staple grain crop which grown as edible seeds, remarkably in Ethiopia. However, after removal of its seeds, the hay obtained from this crop, are considered as agro-waste. Such a lignocellulosic agro-waste can be potentially exploited to prepare activated carbon to treat the harmful industrial effluents for detoxification. In this study, Teff hay (TH) was used as a precursor for preparing the activated carbon. The using H2SO4, chemical activation was carried out followed by carbonaceous process was undertaken to prepared activated carbon (AC) by pyrolysis. The prepared AC was modified as magnetized AC and characterized by various characterization methods. Further, as a bio-absorbent, its potency for adsorptive removal of Cu(II) ions was ascertained. Notably, the most studied and important process factors for adsorption, such as, initial concentration of metal ion, adsorbent dosage, pH, and contact time were subjected to optimization using response surface method (RSM). Further, to ensure the statistical optimization of aforementioned factors, the non-statistical techniques, genetic algorithm (GA) and artificial neural network (ANN) tools have been executed. In addition, the use of prepared Teff-hay based magnetized AC for the removal of Cu(II) by adsorption process was evaluated through different isotherms and kinetic approaches.

Effect of different metal element substitution on microstructural and comprehensive hydrogen storage performance of Ti0·9Zr0·1Mn0·95Cr0·7V0.2M0.15 (M = Fe, Co, Ni, Cu, Mo) alloy

Hydrogen is now being used as a renewable clean energy carrier. One of the main issues with the application of hydrogen energy is a shortage of security and efficient hydrogen storage technology. TiMn-based alloys are considered promising hydrogen storage materials, but their comprehensive hydrogen storage properties and cyclic stable performance limit their further practical application. The hydrogen storage properties of alloys can be enhanced by substituting transition metal elements. Therefore, the comprehensive hydrogen storage performance of the Ti0·9Zr0·1Mn0·95Cr0·7V0.2M0.15 (M ​= ​Fe, Co, Ni, Cu, Mo) alloys was systematically investigated according to the Mn element on the B side is partially replaced by variety of transition metal elements. The M ​= ​Ni alloy, which showed the highest hydrogen storage capacity among the group of alloys, was used to explore cycle stability. The plateau pressures of the series alloys decreased in order, Fe ​> ​Co ​> ​Ni ​> ​Cu ​> ​Mo. Aspects of hydrogen absorption kinetics, all of the alloys can reach full hydrogen absorption saturation within 400 ​s at 303 ​K. The Ti0·9Zr0·1Mn0·95Cr0·7V0·2Mo0.15 alloy possessed the fastest hydrogen absorption kinetic rate (t0.9 ​= ​65 ​s) and the smallest hysteresis factor. This suggests that the substitution of Mo elements is effective in improving the hysteresis of the Laves phase alloys. Among the series of alloys, the M ​= ​Ni alloy exhibited the best overall hydrogen storage performance, which hydrogen storage capacity can reach 1.81 ​wt% and 97% of its capacity is kept after 100 cycles.

Role of Explicit Solvation in Computational Modeling of Chemical Reactions: Mechanism of Cu(I) Transfer Between Thiolate-Based Chelators in Water.

Solvation plays important roles in controlling the thermodynamic and kinetic aspects of chemical reactions. The conventional approaches to treat solvation via electronic structure methods are likely to become inadequate, when the reacting solutes have strong electrostatic and hydrogen bonding interactions with the solvent and undergo significant structural changes during the course of the reaction. In this article, we present evidence of such solvent and structural effects in the computational study of the Cu(I) transfer reaction between thiolate-based chelators dithiobutylamine (DTBA) and dithiotheritol (DTT) in water, inspired from biological copper trafficking phenomena. We propose a general solution to the problem by combining classical molecular dynamics (MD) simulations of the bulk system and static quantum chemistry calculations. The fluctuating solvation shell was estimated from MD, and energetics was assessed by averaging QM energies of a series of molecular clusters constructed from the MD snapshots. Applying this approach, we propose a reaction pathway with estimates of relative intermediate stabilities and barriers, which suggest the overall reaction to be reversible in nature and likely to go through both two and three coordinated intermediates, confirming previous studies of similar protein analogues. An interesting fact that emerged from our study was the strong indication that the rate-determining step is the deprotonation of initial thiol bound Cu(I) complex, without involving any Cu(I)-S bonds. The proposed method will lead to a better treatment of solvations, and these mechanistic insights will aid our understanding of biological copper(I) trafficking.

Methanation of syngas from biomass gasification: Small-scale plant design in Aspen Plus

The objective of this study is to investigate the upgrading of low-quality nitrogen-diluted syngas derived from biomass air gasification processes into a methane-rich gas stream. Both the thermodynamic and the kinetic aspects are addressed in the paper. Using the Aspen Plus software, a thermodynamic analysis was conducted; then, different plant designs are simulated and compared, including reactor sizing and performance. The results demonstrate that the upgrading of diluted syngas poses challenges which limit its application to small-scale decentralized systems. It was found that a system comprising of four adiabatic fixed-bed reactors, inter-cooling, and efficient water removal achieves a favorable balance between performance and cost. Operating the system at a pressure of 5 bar is deemed adequate as it reduces the required catalyst mass and prevents solid carbon deposition. Notably, this configuration achieved good results, including a 99.4 % CO conversion, 89.3 % CO2 conversion, and 95.6 % CH4 yield. The final methane molar content reached 26.4 %, with a calorific value of 8.62 MJ/Nm3(STP).

Kinetic, Isothermal, and Thermodynamic Analyses of Adsorption of Humic Acid on Quaternized Porous Cellulose Beads

Porous cellulose beads were quaternized with glycidyltrimethylammonium chloride (GTMAC), and the potential use of the quaternized cellulose beads as an adsorbent was explored for the removal of humic acid (HA) from aqueous media. The introduction of quaternary ammonium groups was verified by FT-IR and XPS analyses, and their content increased to 0.524 mmol/g-Qcell by increasing the GTMAC concentration. The adsorption capacity of the HA increased with decreasing initial pH value and/or increasing content of quaternary ammonium groups, and a maximum adsorption capacity of 575 mg/g-Qcell was obtained for the quaternized cellulose beads with a content of quaternary ammonium groups of 0.380 mmol/g-Qcell. The removal % value increased with increasing dose of quaternized cellulose beads, and HA was highly removed at higher quaternary ammonium groups. The kinetics of the HA adsorption in this study followed a pseudo-second-order equation, and the process exhibited a better fit to the Langmuir isotherm. In addition, the k2 value increased with increasing temperature. These results emphasize that HA adsorption is limited by chemical sorption or chemisorption. The quaternized cellulose beads were repetitively used for the adsorption of HA without appreciable loss in the adsorption capacity. The empirical, equilibrium, and kinetic aspects obtained in this study support that the quaternized cellulose beads can be applied to the removal of HA.

Semiclathrate-based CO2 capture from pre-combustion fuel gas using tetra-n-butylammonium chloride: A thermodynamic, kinetic, and spectroscopic study

The primary objective of this study was to investigate the feasibility of pre-combustion CO2 capture using tetra-n-butylammonium chloride (TBAC) semiclathrate in a fuel gas mixture comprising CO2 (40%) + H2 (60%), with a primary focus on examining the thermodynamic, kinetic, and spectroscopic aspects of this process. Phase equilibria measured at various TBAC concentrations revealed that the CO2 + H2 + TBAC semiclathrates exhibited maximum thermodynamic stability at a stoichiometric concentration (3.3 mol%). CO2 concentrations in both the vapor and semiclathrate phases, along with gas consumption during and after semiclathrate formation, were measured to assess CO2 selectivity and gas uptake in the semiclathrate phase. Notably, CO2 enrichment was approximately 90% in the semiclathrate phase. In-situ Raman spectroscopy provided clear confirmation of the enclathration of both CO2 and H2 in the semiclathrate lattices, while powder X-ray diffraction analysis revealed the tetragonal (P42/m) structure of the CO2 + H2 + TBAC (3.3 mol%) semiclathrate. Furthermore, a high-pressure micro-differential scanning calorimeter was used to measure the dissociation enthalpies of the CO2 + H2 + TBAC (3.3 mol%) semiclathrate at various pressures. The comprehensive results obtained in this study strongly support the potential use of TBAC semiclathrate as a material for pre-combustion CO2 capture.