Reaction Order Research Articles

Reaction kinetics of molybdenum dissolution by hydrogen peroxide in acidic and alkaline solutions using tartaric acid and sodium hydroxide: A semi‐empirical model with rotating disc method

AbstractMolybdenum is an amphoteric metal that dissolves in both acidic and alkaline solutions. This fundamental study explores a sustainable process for the dissolution of molybdenum, focusing on the reaction kinetics in H2O2, H2O2‐NaOH, and H2O2‐C4H6O6 solutions. A rotating disc method was applied with the Levich's equation. Semi‐empirical models with activation energy were developed for the H2O2‐NaOH and H2O2‐C4H6O6 solutions. The study examined the effects of rotating speed, disc surface area, temperature, H2O2, NaOH, and C4H6O6 concentrations, along with rotating speed, disc surface area, and temperature. Hydrogen peroxide significantly impacted molybdenum dissolution rates across all three solutions. The reaction order of hydrogen peroxide concentration in the H2O2 solution was greater than that of the H2O2‐NaOH and H2O2‐C4H6O6 solutions. The complex of molybdenum peroxo was formed in H2O2 and H2O2‐NaOH solutions but decomposed at a temperature ≥50°C. The activation energies were determined to be 49.90, 43.60, and 41.10 kJ/mol for the H2O2, H2O2‐NaOH, and H2O2‐C4H6O6 solutions.

Syn vs. Anti? What Controls Addition Stereochemistry in Chlorolactonization.

The stereochemistry of the uncatalyzed chlorolactonization of 4-phenylpent-4-enoic acid at room temperature was examined to probe the reaction's intrinsic diastereoselectivities as a function of chlorenium ion donor, solvent polarity, and reactant concentration ranges. Kinetic studies using Variable Time Normalization Analysis (VTNA) revealed differing reaction orders for the syn and anti alkene addition processes. Aided and illustrated by quantum chemical modeling, this detailed mechanistic analysis of the substrate's intrinsic chlorolactonization reactions points to concerted AdE3-type paths for both syn and anti additions. By illuminating the factors selecting for syn- vs anti-addition paths, the results provide key reference points for future studies of stereocontrol in halofunctionalization reactions.

Ag induced plasmonic TiO2 for photocatalytic degradation of pharmaceutical under visible light: Insights into mechanism, antimicrobial and cytotoxicity studies

Global concerns include water scarcity and shortage, which are escalated by organic pollutants such as naproxen (NPX) that deteriorate drinking water and taint access to safe drinking water by humans. Moreover, NPX may cause gastrointestinal difficulties, cardiovascular risks, kidney damage, allergic reactions, liver toxicity, bleeding issues and pregnancy risks, hence it is essential to remove it in water. Ag-TiO2 was synthesized by hydrothermal method for NPX degradation. Ag on TiO2 reduced the band gap and surface area of TiO2 and resulted in a plasmonic Ag-TiO2 composite of 0.2 % Ag. The photocatalytic degradation of 0.2 % Ag-TiO2 was 80 % in 180 minutes using a solar simulator during NPX degradation with a first order reaction rate that was 3.6 times faster than that of pure TiO2 and the catalyst showed good stability for four cycles. The dual activity of Ag0 surface plasmon resonance improved light absorption capability and enhanced charge transfer for increased photodegradation rate and stability. The antibacterial studies demonstrated that 0.2 % Ag-TiO2 posted strong antibacterial properties under light irradiation and less in the dark, with a greater effect on gram-negative than gram-positive bacteria. The minimum inhibitory concentration (MIC) values of 620, 1250, 2500, 2500 µg/mL were attained against B. subtilis, S. aureus, E. coli and S. typhimurium bacteria, respectively. The low cell toxicity of 0.2 % Ag-TiO2 was determined using human embryonic kidney (HEK293) cells with an inhibitory concentration (IC50) of 61.09 ± 0.24 µg/mL under light irradiation. Radical trapping experiments demonstrated that hydroxyl radicals (OH•) played a vital role during the degradation and bactericidal activity of NPX under light irradiation. This work advances new insights on the synthesis of less toxic nanoparticles with high photocatalytic and bactericidal activity for possible applications at industrial scale.

Mesoporous, high surface area and microrod-shaped cobalt (II) coordination polymer for assessment of molecular structure, thermolysis and non-isothermal kinetics parameters

This study is significant as it presents the assessment of molecular identification, thermal degradation, and non-isothermal kinetics of a cobalt (II) coordination polymer [Co (II) CPs] synthesized from suberoyl bis (2-ethoxybenzamide) (sbebz) and cobalt acetate through the condensation process. The condensation product sbebz was obtained from suberoyl chloride and 2-ethoxybenzamide. The XRD, FT-IR, Raman, and XPS investigated as aspects to identify its structure, purity, and chemical state. The morphological facet was confirmed by SEM and TEM. The morphology data revealed a microrod-shaped morphology of Co (II) CPs with an average particle size 0.7 µm to 1 µm. The pore size, and surface properties were examined by Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM), revealing a highly large surface area (1076 m2/g), mesoporous and monodisperse nature. The molecular interaction of ligand was estimated using protein molecule. The thermal-decomposition behavior and non-isothermal kinetics of Co (II) CPs were estimated at different heating rates (5 °C/min, 10 °C/min, 15 °C/min, and 20 °C/min) under nitrogen atmosphere by thermogravimetry/Derivative thermogravimetry (TG/DTG). As-synthesized Co (II) CPs show enhanced thermal stability compared to the ligand (sbebz). The multiple heating TG/DTG curve exhibits a more or less identical degradation profile/pattern. The kinetic parameters like order of reaction (n), pre-exponential Arrhenius factor (A), activation entropy (∆s), activation energy (Ea), activation free-energy (∆G), and activation enthalpy (∆H) were calculated using Coats-Redfern (CR) method.

Ru(II)-Catalyzed C7 Trifluoromethylthiolation and Thioarylation of Indolines Using Bench-Stable Reagents.

A Ru(II)-catalyzed C(sp2)-H trifluoromethylthiolation and thioarylation of indolines using bench-stable reagents have been explored. Diversely substituted indolines were functionalized at C7 position in good to excellent yields. Radical quenching, deuterium labeling, KIE, and reaction order determination experiments were performed to support the proposed reaction pathway. Gram-scale synthesis and post-transformation of the synthesized products have also been carried out to demonstrate the applicability of the developed catalytic protocol.

Polyethylene glycol promoted Cs/Zr-SiO2 bifunctional catalyst for aldol condensation of methyl propionate and formaldehyde to methyl methacrylate

The production of methyl methacrylate (MMA) via one-step gaseous aldol condensation of methyl propionate (MP) and formaldehyde (FA) has received wide attention. Herein, series of polyethylene glycol (PEG) promoted Cs-Zr/SiO2 catalysts were developed and characterized by XRD, FT-IR, HR-TEM, BET, NH3–/CO2-TPD and Py-IR etc. The dispersion of active acid and base sites and their balance in catalyst could be significantly improved with the addition of PEG, which facilitated the activation of reactants and conversion towards product MMA. Furthermore, the relationship between the acid-base properties and catalytic performance was revealed, the acid and base sites were responsible for the decomposition of trioxane, which was used as the source of FA, and transformation of MP, respectively. The in-situ DRIFTS experiments unraveled two catalytic pathways through the synergistic effects between the acid and base sites during the aldol condensation of MP with FA to MMA. Kinetic studies revealed that the activation energy of this aldol condensation on the optimal catalyst is 97.9 kJ/mol, with the reaction order of 0.98 and 1.18 corresponding to MP and FA. Deactivation behavior studies demonstrated that the decrease of catalytic activity as a function of time-on-stream was resulting from the deposition of predominant amorphous carbon instead of the loss of active components.

Light switchable radical and non-radical periodate activation by Fe3O4/g-C3N4 for efficient organic contaminant elimination

Although the heterogeneous activation of periodate (PI) has recently garnered significant attention for organic pollutant degradation, regulating the non-radical and radical reaction pathways remains a challenge. Herein, a Z-scheme Fe3O4/g-C3N4 heterojunction (FCN) was developed to achieve controllable radical and non-radical PI activation using a light switch. In the dark, the interaction between FCN and PI gave rise to metastable surface-activated PI complexes (PI*) via the non-radical pathway, which served as the dominant reactive species for organic elimination. Upon light irradiation, FCN acted as an electron donor for PI activation via the radical pathway, forming iodate radicals (IO3•) for pollutant destruction. Consequently, the FCN/PI/VIS system achieved complete removal of acid orange 7 in 30 min, with a pseudo-first order reaction rate about 3.5 times higher than that of FCN/PI system. The involved reactive species were validated by scavenging tests, electron paramagnetic resonance (EPR) analysis, Raman spectra and electrochemical measurements. Moreover, the light switchable FCN-based PI activation system exhibited high recyclability and practicability for the treatment of various organic pollutants in water. This study provides new insights into the PI activation-mediated wastewater treatment processes.

IPLOT-VKA: an Integral-method Powell-pLOT-enhanced Visual Kinetic Analysis for the Determination of Orders of Reaction.

Determination of partial orders of reactions in kinetics is a general entry step for any mechanistic investigation; recently, considerable attention has been given to the benefits of using visual methods to help in this task, such as easy utilization and data-efficiency. In this respect, we here revisit and improve the classic method by Powell and Margerison for kinetic analysis. For the first time, analytical equations for a bimolecular reaction have been worked out for all values of partial orders of reactions, and the solutions have been implemented in a free, open-access and easy-to-use Web-application, named IPLOT-VKA, which also allows estimation of the errors on the kinetic constant, and residual standard error on concentrations. Several examples, taken from reference teaching experiences and from recent literature in catalysis show the efficacy and accuracy of our approach, which also has the advantage of requiring less experimental runs than other visual methods currently available.

Magnetohydrodynamic flow of Casson fluid on an inclined permeable moving plate with viscous dissipation, thermal radiation, joule heating and Soret effect

Here, a steady magnetohydrodynamic flow of Casson fluid on an inclined permeable moving plate through a porous medium is investigated. The influence of viscous dissipation, thermal radiation, Joule heating, heat sink, Soret effect with first order chemical reaction is considered. The impact of relevant flow parameters on fluid speed, temperature, species concentration, skin-friction and Sherwood number are deliberated. It is noticed that the flow velocity intensifies with an increase in the Soret number and inclination angle while the Casson parameter and Magnetic parameter decreases the fluid flow. In addition, the Prandtl number and the radiation parameter slow down the temperature and Schmidt number declines the concentration field.

Kinetics of Chlorophyll Degradation in Malabar Spinach (Basellae alba) and Waterleaf (Talinum triangulare) during Hydrothermal Processing

Hydrothermal processing of vegetables often results in a number of changes including degradation of chlorophyll, the green plant pigment that is considered to be of therapeutic benefits. This study was aimed at investigating the kinetic degradation of chlorophyll in Malabar spinach (Basella alba) and waterleaf (Talinum triangulare) during hydrothermal processing. Freshly harvested leafy vegetables-- Malabar spinach and waterleaf, were obtained and subjected to various hydrothermal conditions (60, 65, 70, 75 and 80˚C at 0, 5, 10, 15 and 20 minutes) simulating typical cooking conditions. The chlorophyll of the crushed leaf was extracted using acetone. Changes in chlorophyll was determined using spectrophotometric analysis and the kinetics of degradation for each of the vegetables were determined at varying temperatures and times. Kinetics analysis revealed that the degradation of chlorophyll in Malabar spinach and waterleaf followed the first order reaction. The rate constant obtained from the kinetic analysis provided insights into the reaction rates and allowed for the prediction of chlorophyll degradation during hydrothermal processing. The results showed that the lowest percentage decrease in chlorophyll concentration during the blanching process was obtained at 65˚C for 5 minutes for Malabar spinach and for waterleaf at 60˚C for 5 minutes. Blanching temperature and time have significant effects on degradation of chlorophyll of Malabar spinach and waterleaf which could consequently determine the economic value and overall degree of acceptability of the green leafy vegetables. The findings provide baseline against which future work can be compared and importance of maintaining quality of the vegetables during processing.

Intrinsic Metal Component-Assisted Microwave Pyrolysis and Kinetic Study of Waste Printed Circuit Boards

Waste printed circuit boards (WPCBs) hold great recycling value, but improper recycling can lead to environmental issues. This study combines pyrolysis and microwave technologies, leveraging the unique phenomenon where metal materials tend to “spark” in a microwave field, to develop a microwave pyrolysis process for WPCBs that incorporates metal fillers. The research analyzes the effects of microwave power, metal filler addition, and pyrolysis time on the efficiency of microwave pyrolysis. It explores the mechanisms of microwave pyrolysis and the pathways of pyrolysis product formation, and the kinetics of the pyrolysis reaction of WPCBs. The results indicate that microwave-assisted pyrolysis greatly improves efficiency. Within the experimental range, the optimal conditions are found to be a microwave power of 1600–1800 W, a metal filler addition of 10%, and a pyrolysis time of 10 min. Under these conditions, the yield of pyrolysis liquid was 12.8%, with approximately 5–12 different components, while the yield of pyrolysis gas was 12.7–13.4%, with about 9–11 different components. Compared to conventional pyrolysis products, the liquid products from microwave pyrolysis are simpler and more advantageous for resource utilization. Theoretical calculations show that the average activation energy for the microwave pyrolysis process is 81.05 kJ/mol, with an average reaction order of 0.93, which is greatly better than the 147.75 kJ/mol of the conventional pyrolysis process.

Kinetic characteristics of bornite and chalcopyrite dissolution in nitric acid

The kinetic characteristics of dissolution of copper-bearing sulfides – chalcopyrite (CuFeS₂) and bornite (Cu₅FeS₄) – in nitric acid were studied. The kinetics of the dissolution process was described using a compressible nucleus model. Chalcopyrite of the Vorontsovskoye deposit and bornite of the Karabash deposit were used as research objects. Solution and cake samples were analyzed by optical emission spectrometry and X-ray fluorescence analysis, respectively. The results obtained were processed in the MS Excel software package. The influence of various factors, including temperature, solvent concentration, particle size, and process duration on the dissolution degree of minerals was studied. The process parameters were varied as follows: temperature – from 35 to 95°C; HNO₃ concentration – from 1 to 9 mol/dm³; particle size – from +0.1 to 0.056 mm; duration – from 0 to 60 min. It was established that an increase in temperature and acid concentration leads to a significant increase in the degree of dissolution of both chalcopyrite and bornite. A decrease in particle size also contributes to a more efficient dissolution of both minerals in nitric acid. The calculated activation energy values were 55 kJ/mol for chalcopyrite and 43 kJ/mol for bornite, which is characteristic of the kinetic region of the process. The reaction orders in terms of reactant were determined: 1.62 for chalcopyrite and 1.57 for bornite. In terms of particle size, these were -1.16 for chalcopyrite and -2.53 for bornite. On this basis, generalized equations of dissolution kinetics for both minerals were derived. The results obtained allow an assumption about the kinetic nature of dissolution of chalcopyrite and bornite under the studied conditions.

Highly Acidic Electron-Rich Brønsted Acids Accelerate Asymmetric Pictet-Spengler Reactions by Virtue of Stabilizing Cation-π Interactions.

Electron-rich heteroaromatic imidodiphosphorimidates (IDPis) catalyze the asymmetric Pictet-Spengler reaction of N-carbamoyl-β-arylethylamines with high stereochemical precision. This particular class of catalysts furthermore provides a vital rate enhancement compared to related Brønsted acids. Here we present experimental studies on the underlying reaction kinetics that shed light on the specific origins of rate acceleration. Analysis of Hammett plots, kinetic isotope effects, reaction orders, Eyring plots, and isotopic scrambling experiments, allowed us to gather insights into the molecular interactions between the chiral Brønsted acid and catalytically formed intermediates. Based on rigorously determined pKa values as well as the experimental evidence, we propose that attractive intermolecular forces offered by electron-rich π-surfaces of the chiral counteranion enthalpically stabilize cationic intermediates and transition states by way of cation-π interactions. This view is furthermore supported by in-depth density functional theory calculations. Our deepened understanding of the reaction mechanism allowed us to develop a method for accessing 1-aryltetrahydroisoquinolines from aromatic dimethyl acetals, a substrate class that was thus far inaccessible via catalytic asymmetric Pictet-Spengler reactions.

Investigation of the impurity effect on the kinetics of thermal decomposition of natural gypsum at high temperatures

Natural gypsum is the most common sulfate on our planet, which is widely used in construction due to its excellent astringent properties, environmental friendliness, thermal and fire resistance, accessibility in nature and low price. Currently, the influence of modifiers, impurities and additives that can improve the strength, acoustic and thermal insulation characteristics of gypsum, which is so important in modern architecture, construction and reducing power consumption, is being increasingly studied. However, additives and impurities, controlled and uncontrolled, as in natural gypsum, can unpredictably affect the thermal stability and fire resistance of gypsum. The purpose of our work is to study the thermal characteristics of gypsum from various deposits in a wide temperature range. Our work shows that the temperature and rate of dissociation of gypsum directly depends on impurities that can change the process of its decomposition. As a result of the decomposition of natural gypsum with impurities, new phases are formed.It has been experimentally shown that the process of thermal destruction of gypsum with impurities has a complex multistage character, which is described by successive reactions of the nth order of the Avrami-Erofeev equation. It can be assumed that the reaction mechanism consists in the rapid formation of numerous nucleation centers on the surface of solid anhydrite. Kinetic parameters of thermal decomposition of gypsum of complex composition and phase formation at high temperatures are calculated. This experimental study shows the dependence of thermal stability on the amount and grade of impurities in gypsum. The results obtained contribute to the improvement of the basic concepts of the mechanism of decomposition of gypsum, as well as the explanation of some high-temperature phase formation processes in nature.

Gyrotactic micro-organism dusty fluid flow over an extended surface

The conventional magnetohydrodynamics (MHD) equations are modeled for the dusty fluid flow past a stretching sheet embedded in a porous medium. These equations are coupled with motile microorganisms, temperature and concentration equations for both fluid and dust particles dynamical equations. The two-phase dusty fluid flow is subjected to magnetic effect, porosity factor, 2nd order chemical reaction, Brownian diffusion, thermophoretic effect and Arrhenius activation energy. An appropriate transformation is used to reset the system of partial differential equations (PDEs) into non-linear system of ODEs (ordinary differential equations). The flow equations are numerically solved by using the parametric continuation method (PCM). For validity of the applied methodology, the results are compared using numerical and graphical results of Matlab built-in package “BVP4c”. Both results show accuracy up to four decimal places. Furthermore, from graphical results, it can be noticed that the fluid particles interaction parameter causes an attractive force among fluid particles which prevents the dust particles phase flow. This technique can be used for biological separations, filters, fluid dust separators and crude oil purification.

Sorption properties of a new modified flax fibre sorbent

The purpose of this study is to develop a modified sorbent of flax waste and investigate its sorption properties towards Cu (II) ions. The authors conducted the modification in two steps. The first step was oxidation of flax fibre cellulose with sodium metaperiodate to dialdehyde cellulose, the second one was the addition of taurine to increase the sorption characteristics of the modified sorbent. The paper presents the conditions for the periodate oxidation reaction of flax fibre and the treatment of the resulting dialdehyde cellulose with taurine. We determined the sorption characteristics of the modified sorbent in comparison with the original flax fibre. Kinetic studies allowed us to establish the time of reaching sorption equilibrium in the heterophase system ‘aqueous solution of metal salt-sorbent’ and determine the reaction order using pseudo first and pseudo-second order kinetics models. The authors processed the sorption isotherms obtained during the experiments using the Langmuir model. The maximum sorption capacity increased by 3 times compared to the original flax fibre. IR spectroscopy confirmed the improvement of equilibrium and kinetic characteristics of flax fibre occuring as a result of the appearance of new sorption centres in its structure.

Kinetics, catalyst design, and hydrodynamic analysis in Fischer–Tropsch synthesis: Fixed Bed vs Fluidized Bed Reactors

While fixed beds maximize contacting between the fluid and solid phase, commercial processes operate with fluidized beds for highly exothermic reactions, like Fischer–Tropsch (FT), to maximize heat transfer thereby minimizing catalyst sintering and deactivtion. However, conversion is lower due to gulf-streaming and poorer gas-solids contacting. In experimental reactors (<10mm) gulf-streaming is negligible and gas-solids contacting is excellent as bubbles are small. Here, we measure CO conversion over 3 FT catalysts—Fe/Ce/SiO2-K, Cu, Fe/Zr/SiO2-K, Cu, Fe/Catalox-K, Cu—across the same reactor operating in the fluidized bed and fixed bed regime. Flow rates were increased up to a maximum of 5 times the minimum fluidization velocity (Umf). The reactor operated at 2MPa, with a H2/CO molar ratio of 2, and 275°C≤T≤325°C. The average CO conversion was higher in the fixed bed but temperature control was more difficult, which could account for some of the differences. The highest ▪ selectivity (80% to 84%) was with the Fe/Catalox-K, Cu at 275°C, 2 to 4×Umf, in the fixed bed reactor. A first order reaction model characterized CO conversion well (R2>0.91) for the Fe-Catalox and Fe-Zr catalysts with activation energies >70kJmol−1. Conversion was essentially independent of temperature for the Fe-Ce composition in both the fixed bed and fluidized bed. BET surface area decreased 22% to 52% after the reaction. XRD analysis after the reaction revealed a 4% to 10% decrease in crystallinity, along with the presence of various Fe carbide compounds. Post-reaction SEM-EDS images indicated particle agglomeration and carbon deposition on the catalyst surface. Despite these morphological changes, the impact on CO conversion seemed minimal. Residence time distribution tests confirmed that gas was essentially in plug flow for both the fixed bed and fluidized bed configurations.

Enhancing selectivity through forced dynamic operation with intraparticle diffusion limitations: Ethane oxidative dehydrogenation

During steady state operation (SSO) of industrial fixed-bed reactors diffusion limitations are often present. Well-known impacts include the reduced rate of a positive order reaction and reduced selectivity of the desired intermediate product in a sequential reaction system. This work presents an approach for circumventing diffusion limitations through forced dynamic operation (FDO) of metal oxide catalyzed partial oxidation reactions. Through coupled experiments and modeling, we examine the use of FDO to mitigate selectivity losses of the intermediate product in a parallel-consecutive reaction. With the oxidative dehydrogenation (ODH) of ethane (C2H6) to ethylene (C2H4) over an Al2O3 supported VOx catalyst as the model reaction system, FDO is shown to mitigate undesired C2H4 overoxidation to COx that predominates in steady state diffusion-limited pellets, resulting in C2H4 selectivities that are 15 % (absolute) higher compared to SSO in 2.6 mm catalyst pellets. A kinetic model reveals that FDO beneficially alters the distribution of chemisorbed (O*) and lattice (OL) oxygen, which respectively primarily participate in reactions consuming C2H4 and C2H6. FDO is shown to lead to less detrimental impact of diffusion on the ethylene selectivity and yield compared to SSO. During FDO, generated C2H4 reacts with unselective O*, leaving behind selective OL. The reduced bulk phase O2 in the reductive half cycle leads to accumulation of OL, suppressing C2H4 overoxidation. This effect is amplified via C2H4 trapping in the catalyst pellet. Thus, larger catalyst pellets exhibit selectivities that more rapidly increase with reduction time, inducing higher FDO cycle averages compared to SSO. The findings raise the prospect of applying FDO through feed switching or chemical looping as a way to increase intermediate yield in the class of partial oxidation reactions.

Thermodynamics and kinetics of evaporation and thermal decomposition of 1-ethyl- and 1-butyl-3-methylimidazolium methanesulfonate ionic liquids: Experimental and computational study

Knudsen cell mass spectrometry was used to study the evaporation of two ionic liquids, 1-ethyl-3-methylimidazolium methanesulfonate ([EtMIm][MS], MS = CH3SO3) and 1-butyl-3-methylimidazolium methanesulfonate ([BuMIm][MS]), accompanied by thermal decomposition (thermolysis). The independent occurrence of evaporation and thermolysis reactions made it possible to determine their thermodynamic and kinetic characteristics under identical experimental conditions. The saturated vapor pressures were measured and the standard enthalpies of vaporization of [EtMIm][MS](l) and [BuMIm][MS](l) were obtained. The standard thermodynamic functions of formation in the liquid and gaseous states at 298.15 K were estimated from the available experimental data and the results of quantum chemical calculations. The gaseous decomposition products of ionic liquids were identified and the pressures of the thermolysis products of [EtMIm][MS](l) were determined. According to the experimental data and quantum chemical calculations, the thermolysis of [EtMIm][MS](l) occurs through heterogeneous reactions far from the equilibrium state. The kinetics of the reactions is described in two ways. When the degree of sample conversion is used as a variable, the constant reaction rates at the initial stage of thermolysis correspond to a pseudo-zero order reaction with a monotonic increase in the degree of conversion. In the proposed alternative approach, the reaction rates are estimated from the fluxes of thermolysis products and are expressed in terms of ionic liquid concentration.

Green synthesis of Z-scheme CeO2 decorated ZnO nanocomposites for photodegradation of organic pollutants, antioxidant activity and its effects on seed germination

The present work aimed to report a green synthesis of CeO2@ZnO nanocomposites via co-precipitation method using azadirachta indica aqueous leaf extract. The characterization of the prepared CeO2@ZnO nanocomposites were done using XRD, FTIR, SEM, EDAX, UV–vis, and PL techniques to examine the structural properties, functional group, morphological and electronic properties. As prepared CeO2@ZnO nanocomposites have been used for photo degradation of Crystal Violet (CV), Methylene blue (MB) and Rhodamine B (RhB) dyes in presence of solar light in aqueous solution. From structural analysis the mean crystallite sizes of the synthesized nanocomposites varied from 27 nm to 9 nm. The degradation of MB, CV and RhB dyes follows pseudo-first order reaction rate with the rate constantsk1 for MB is 10.09 × 10−3 min−1, k1 for CV is 8.71 × 10−3 min−1, k1 for RhB is 0.92 × 10−3 min−1.The characterized nanocomposites were used for seedling growth, physiological and biochemical responses during seed germination. In CeO2@ZnO nanocomposites treatments, significantly higher values of shoot length and root length were observed in CZ1 (0.5, and 1 mg/ml) treated seedlings as compared to other samples. Similarly, the activities of ɑ-amylase and protease enzymes were recorded to be maximum for CZ1 nanocomposites. For instance, the increased activity of α-amylase was observed to be 2.12, 2.09, and 1.33 folds higher in CZ1, CZ2, and CZ3 (1 mg/ml) treated seedlings as compared to the control. Similarly, the protease activity was reported to be increased by 0.011 folds in CZ1 nanocomposites (1 mg/ml) treated seedlings as compared to the control. Furthermore, all the CeO2@ZnOnanocomposites have excellent DPPH, and ABTS free radical scavenging activities, confirmed by the Ferric-Reducing Antioxidant Power (FRAP) assay. The CZ1 nanocomposites showed the best results. The CeO2@ZnO nanocomposites were found to have no toxic effects on cellular division confirmed with improved mitotic index under different treatment regimens.