First-order Reaction Research Articles

Thermal Decomposition of Date Seed/Polypropylene Homopolymer: Machine Learning CDNN, Kinetics, and Thermodynamics

The buildup of abandoned plastics in the environment and the need to optimize agricultural waste utilization have garnered scrutiny from environmental organizations and policymakers globally. This study presents an assessment of the thermal decomposition of date seeds (DS), polypropylene homopolymer (PP), and their composites (DS/PP) through experimental measurements, machine learning convolutional deep neural networks (CDNN), and kinetic and thermodynamic analyses. The experimental measurements involved the pyrolysis and co-pyrolysis of these materials in a nitrogen-filled thermogravimetric analyzer (TGA), investigating degradation temperatures between 25 and 600 °C with heating rates of 10, 20, and 40 °C.min−1. These measurements revealed a two-stage process for the bio-composites and a decrease in the thermal stability of pure PP due to the moisture, hemicellulose, and cellulose content of the DS material. By utilizing machine learning CDNN, algorithms and frameworks were developed, providing responses that closely matched (R2~0.942) the experimental data. After various modelling modifications, adjustments, and regularization techniques, a framework comprising four hidden neurons was determined to be most effective. Furthermore, the analysis revealed that temperature was the most influential parameter affecting the thermal decomposition process. Kinetic and thermodynamic analyses were performed using the Coats–Redfern and general Arrhenius model-fitting methods, as well as the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose model-free approaches. The first-order reaction mechanism was identified as the most appropriate compared to the second and third order F-Series solid-state reaction mechanisms. The overall activation energy values were estimated at 51.471, 51.221, 156.080, and 153.767 kJ·mol−1 for the respective kinetic models. Additionally, the kinetic compensation effect showed an exponential increase in the pre-exponential factor with increasing activation energy values, and the estimated thermodynamic parameters indicated that the process is endothermic, non-spontaneous, and less disordered.

Acid-catalyzed conversion of sesamolin to sesamol: Kinetics and reaction mechanism based on density functional theory.

Sesamol is a significant lignan in sesame oil, which can be converted from sesamolin under acid-catalyzed conditions. The effects of several factors on the conversion of sesamolin to sesamol under acid-catalyzed conditions were investigated. The conversion kinetics were studied and the relevant conversion mechanism was revealed by density functional theory (DFT). The results indicated that catalyst dosage and substrate concentration had significant effects on the yield of sesamol. The conversion of sesamolin conformed to the characteristics of a first-order kinetics reaction within the range of 50-70°C. The activation energy of the reaction was 35.78±1.21kJ/mol. The energy barrier to be crossed for the formation of intermediates in generating sesamol was 237.83kJ/mol; the energy barrier to be overcome for the formation of intermediates in generating sesaminol was 266.95kJ/mol. This study provides information relevant to increasing the percentage of sesamol in processed sesame oil.

Distinguishing Ideal and Non-Ideal Chemical Systems Based on Kinetic Behavior.

This paper focuses on differentiating between ideal and non-ideal chemical systems based on their kinetic behavior within a closed isothermal chemical environment. Non-ideality is examined using the non-ideal Marcelin-de Donde model. The analysis primarily addresses 'soft' non-ideality, where the equilibrium composition for a reversible non-ideal chemical system is identical to the corresponding composition for the ideal chemical system. Our approach in distinguishing the ideal and non-ideal systems is based on the properties of the special event, i.e., event, the time of which is well-defined. For the single-step first-order reaction in the ideal system, this event is the half-time-decay point, or the intersection point. For the two consecutive reversible reactions in the ideal system, A ↔ B ↔ C, this event is the extremum obtained within the conservatively perturbed equilibrium (CPE) procedure. For the non-ideal correspondent models, the times of chosen events significantly depend on the initial concentrations. The obtained difference in the behavior of the times of these events (intersection point and CPE-extremum point) between the ideal and non-ideal systems is proposed as the kinetic fingerprint for distinguishing these systems.

Intermediates of Hydrogen Peroxide-Assisted Photooxidation of Salicylic Acid: Their Degradation Rates and Ecotoxicological Assessment.

Accelerated photooxidation of salicylic acid (SA) was performed using UV radiation and hydrogen peroxide. HPLC-MS analysis showed that the primary intermediates are 2,5-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, pyrocatechol, and phenol. Deeper oxidation leads to low molecular weight aliphatic acids, such as maleic, fumaric, and glyoxylic. The photooxidation of the main intermediates was carried out in the same conditions. The degradation of SA and its main intermediates follows first-order reaction kinetics. In the case of UV irradiation alone, photodegradation of 2,5-dihydroxybenzoic acid is slightly faster (reaction rate constant is 0.007 min-1) compared to SA (0.0052 min-1). Other products degrade more slowly than SA. Hydrogen peroxide, in concentrations of 1.8-8.8 mM, accelerates the photodegradation of salicylic acid and intermediate products. An ecotoxicological evaluation of SA and the main products was performed using the EPI SuiteTM software. The overall persistence (POV) and long-range transport potential (LRTP) of all transformation products were assessed using OECD POV and the LRTP screening tool. Salicylic acid and its transformation products have low toxicity. Due to their high solubility, these contaminants can travel considerable distances in the aquatic environment. SA and phenol have LRTP values of 156-190 km. Other products can travel shorter distances (less than 100 km).

Quality and Flavor of Kiwifruit with Storage Using Kinetic Modeling and Gas Chromatography–Mass Spectrometry (GC–MS)

Kiwifruit (Actinidia chinensis) stored at 0, 4, 10, and 25 °C were assessed for quality indices including hardness, soluble solid content (SSC), reducing sugar (RS), ascorbic acid (AA), and volatile compounds. The results of Kinetic models indicated that SSC and RS followed zero-order kinetics, whereas changes in hardness and AA followed first-order reaction kinetics. Storage life prediction models were constructed by combining reaction kinetics equations with the Arrhenius equation. Headspace-solid-phase microextraction‒gas chromatography‒mass spectrometry (HS-SPME-GC‒MS) revealed 49‒58 volatile flavor compounds in kiwifruit stored at different temperatures. A total of 8 substances were identified as differentia metabolites that could be used to distinguish edible and decayed fruit.

Decolorization of Rhodamine B by Fenton Processes Enhanced by Cysteine and Hydroxylamine Reducers

Fe3+-reducing agents have been used to enhance Fenton process efficiency in degrading dyes commonly found in textile wastewater. The present work consisted of evaluating the effect of two compounds that reduce Fe3+, cysteine (Cys) and hydroxylamine (HA), on the oxidative decolorization of Rhodamine B dye by homogeneous Fenton processes, Fe2+/H2O2 and Fe3+/H2O2. The kinetics of the reactions were analyzed to better interpret the decolorization data. Due to the addition of the two reducing agents and the increase in temperature, there were increases in decolorization and the values of the reaction rate constants. The first-order reaction kinetic model was the one that best fit the experimental data. Comparing the two reducers, Cys was more effective. As an example, for reactions initially containing Fe2+ in just 20 min and at a temperature of 30 °C, the HA and Cys reducers increased the decolorization from 33% to 48% and 64%, respectively. It was possible to verify a decrease in the activation energy (Ea) due to the presence of the two reducing agents, but more significantly for reactions containing Fe3+. The values of Ea to Fe3+/H2O2, Fe3+/H2O2/Cys, and Fe3+/H2O2/HA were 85.7, 52.2, and 50.9 kJ∙mol−1, respectively. This way, it can be inferred that the two reducers decreased the energy barrier to enhance the Fenton-based oxidation of Rhodamine B.

Computations of local nonsimilar solutions for MHD flow of Reiner–Rivlin fluid

Here local nonsimilar solution for hydromagnetic stretched flow of Reiner–Rivlin material is constructed. Heat generation, radiation, and dissipation in thermal expression are studied. Joule heating and chemical reaction of first order are under consideration. Entropy generation is computed. Nonlinear system is derived by adequate transformations. Optimal homotopy analysis technique computes the analysis. Attention is focused to achieve the results of concentration, fluid flow, entropy rate, and temperature. In addition, the skin friction, solutal transport rate and Nusselt number have been explained. Outcomes of magnetic field on velocity and entropy rate are found opposite. Large approximation of fluid parameter improves the fluid flow. Larger estimation of Brinkman number yields same results of entropy generation and temperature. Reduction in concentration is noted through Schmidt number. Higher reaction variable correspond to reduce concentration. Temperature and entropy generation through radiation variable has similar trend. Material variable has similar results for rate of mass transport and coefficient of skin friction. Radiation amplifies the thermal transport rate. Reverse effect for entropy rate and Bejan number is detected for magnetic field.

Efficient visible light-driven Photodegradation of malachite green dye using carbon quantum dots-MXene nanocomposite: Synthesis, characterization, and performance evaluation

BackgroundRemoval of azo dyes is one of important issue in water treatment studies and many of research works focused on it. Current work represents a simple and economical feasible to synthesize carbon quantum dots (CQDs) integrated with Ti3C2(OH)2 MXene nanocomposite (CQDs/MXene) for rapid photodegradation of Malachite green (MG) under visible light irradiation. In practice, CQDs were synthesized via a hydrothermal method from Petroselinum crispum leaves, while Ti3C2(OH)2 nanosheets resulted from a simple etching process of Ti3AlC2 using an alkaline solution (KOH with a trace amount of water). MethodsSubsequently, nanocomposites (CQDs/MXene) were prepared by a self-assembly process through sonication-assisted mixing process under ambient conditions. The prepared catalysts were characterized using various analyses like analysis employing field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and an energy dispersion X-ray (EDX) spectrometer to determine the chemical composition. The optimum measurement of this activity of the CQDs/MXene was attained through adjusting several constraints such as pH, dye concentration, amount of temperature and photocatalyst. Significant findingsThe kinetics of the degradation process were represented using the Langmuir–Hinshelwood model, with a rate constant (k) of 0.1382 min−1. This means that the degradation of MG dye follows a first-order reaction with respect to the dye concentration. In addition, the study also looked at the reusability of the prepared CQDs/MXene nanophotocatalyst and found that it exhibited outstanding stability after three reaction cycles. This suggests that the nanophotocatalyst is a promising material for efficient and sustainable degradation of MG dye. The nanocomposite displays high photocatalytic activity with the ability to reduce 96.1 % of the MG dye concentration after being exposed to 25 min of visible light.

The accurate determination of Perfluorooctane sulfonic acid (PFOS) removal efficiency by integrated-sonochemical system.

Perfluorooctanesulfonic acid (PFOS) is one of the most investigated Per- and polyfluoroalkyl substances (PFAS) for being the strongest compound to eliminate and having adverse health concerns. In this work, we have conducted the sonochemical treatment of PFOS simulated water under high (500kHz) and low (22kHz) frequencies while monitoring the operational parameters via an integrated sonochemical system. The integrated advanced sonochemical system includes software to monitor treatment power, solution temperature and frequency while allowing distinctive control of the reaction conditions. Considering the lack of calorimetric measurements in earlier studies and the difficulty in achieving comparative outcomes, precise calorimetric measurements and determination of electrical energy per order (EEO) were performed in this study. The complete PFOS removal was achieved under 500kHz frequency with optimum parameters including initial pollutant concentration (5mg/L), ultrasound power density (400W/L) and solution temperature (25°C) within 180min of treatment. The removal and mineralization extents (defluorination) were determined by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS) and ion-chromatography (IC) analysis. Under optimum conditions, 100% removal and 99% mineralization were achieved. The rate constant (k) ranged from 0.011 to 0.031 min-1 (first-order reaction), which increased with the increase in the power density. While the solution temperature did not significantly affect the PFOS removal efficiency, the initial concentration was found to have a prominent effect on the reaction rate constant. However, experiments at low frequency (22kHz) showed negligible removal efficiency. The specific energy requirement for reaching 90% removal while considering the power consumed by the ultrasonic system from the main electrical source was determined to be 700 kWh/m3, which is much lower than other reported work under similar conditions. This work will be useful for both laboratory and industrial upscaling while acting as a benchmark reference to follow.

Highly effective catalytic degradation of bisphenol a through activation of peroxymonosulfate by an Fe-Nx structure anchored on novel lignin-based graphitic biochar: Electron transfer mechanism

A lignin-based Fe/N co-doped carbonaceous catalyst was synthesized via freeze-drying followed by pyrolysis to activate peroxymonosulfate (PMS) for efficient degradation of bisphenol A (BPA). The Fe/N co-doped biochar exhibited a high specific surface area (364.84 m2/g), hierarchical porous structures, and abundant oxygen-containing functional groups (hydroxyl and carboxyl groups), which enhancing the dispersion of Fe3O4 nanoparticle and exposure of catalytic site. The Fe8-N10-C/PMS system achieved 100 % BPA degradation within 20 min with a corresponding first-order reaction rate constant (kobs) of 0.4056 min−1, which outperformed most reported catalysts in efficiency. Quenching and EPR analyses revealed that both free radicals (•OH, SO4•−, and O2•−) and non-radical (1O2) were rate-limiting steps, while graphitic N and Fe-Nx structures facilitated direct electron transfer from BPA to PMS in electrochemical tests. XPS results confirmed that pyrrolic N, rather than pyridinic N, played a crucial role in forming the Fe-Nx structure. Moreover, the catalyst showed excellent stability, regeneration capability, and adaptability under diverse conditions, highlighting the potential of the Fe-N-C/PMS system for practical wastewater treatment applications.

Experimental and computational kinetic evaluations of silver(I)-catalyzed oxidation of p-chlorophenol by hexacyanoferrate(III): exploring the mechanistic pathway.

The present investigation delves into the redox reaction between p-chlorophenol (p-CP) and hexacyanoferrate(III) [HCF(III)], catalyzed by Ag(I) in an alkaline environment. Findings reveal a first-order dependence on both p-CP and the oxidant, and the reaction rate showcased a first-order reaction towards Ag(I), which was further amplified by the medium as per the equation kobs = a + b[OH-]. Interestingly, the ionic strength remained unchanged throughout the reaction, exerting no discernible effect on the reaction rate. For the evaluation of activation and thermodynamic parameters, Arrhenius and Eyring equations were utilized. Spectral analysis identified the oxidation product of p-CP as hydroquinone. The exploration was further extended to various organic solvents, with their effects scrutinized through Taft's and Swain's multiparametric equations. Notably, the rate constants failed to correlate satisfactorily with Kamlet-Taft's solvatochromic parameters (α, β, π*). Based on the kinetic findings, a plausible reaction mechanism was proposed, which was further supported by the density functional theory (DFT) calculations performed at the b3lyp/6-311*g (d,p) level. The activation energy values obtained from the DFT results were consistent with the reactivity trends observed in the experimental data, thereby validating the proposed mechanism.

Mixed convection flow in a porous channel under the effects of exothermic chemical reactions and local thermal non-equilibrium

The effect of a first-order exothermic chemical reaction on the mixed flow in a vertical channel filled with a porous medium has been studied using the local thermal non-equilibrium model. A mathematical model including the exponen-tial term for heat generation in the fluid phase and interphase heat transfer terms in both the fluid and solid phases was considered. The above dimensionless model has been solved numerically using the Matlab routine bvp4c for the energy equations together with an in-house developed code for the momentum equation. The existence of dual solutions is reported for certain values of the Frank-Kamenetskii number. The obtained profiles of temperature and velocity have been plotted. In addition, the ranges of existence of the dual solutions are reported.

Adaptive Proportional-Integral Control Design for a Class of Continuous Stirred Tank Reactors with Uncertain Parameters

Mathematical model of reaction systems contains experimental parameters such as reaction enthalpies, which may be inaccurate and, therefore, severely affect the computation as well as the implementation of feedback control laws. This paper aims to design an adaptive PI-like controller to regulate a chemical reaction system by means of the Lyapunov theory. More precisely, uncertain model parameters are updated online by solving a set of ordinary differential equations while the global asymptotic convergence of closed-loop system trajectories towards the desired equilibrium is ensured by using the proposed adaptive PI-like controller under the assumption of stability of isothermal conditions. The applicability of theoretical developments is illustrated with an irreversible first-order reaction system having multiple steady states and taking place in a non-isothermal continuous stirred tank reactor. Simulation results show that system trajectories initiated at different conditions are asymptotically stabilized at the desired values and the closed-loop system is robust against the uncertainty of heat exchange coefficient and dilution rate.

Development of Machine Learning-based Shelf Life Prediction Models for Pearl Millet (Pennisetum glaucum L.) Grains using Oxidation Kinetics Data

By observing oxidation kinetics, this study examined how storage temperature (5°C, 25°C, 45°C) and duration (0 to 120 days) affect the quality of raw and fermented pearl millet grains. The study also compared the accuracy of different machine-learning approaches for predicting shelf life of pearl millet grains. The results showed that the levels of free fatty acid (FFA), acid value (AV), peroxide values (PV) and lipase activity (LA) increased with the temperature and duration of storage, regardless of the treatment. For raw grains, the FFA, AV, PV and LA content varied from 0.89% to 6.23%, 1.3 to 8.84 mg NaOH 100g-1, 5 to 88.33 mEq kg-1 of flour, and 4.34 to 23.47 mg KOH g-1, respectively during 120 days of storage over the storage temperature range under consideration. On the other hand, in the case of fermented grains, the values of FFA, AV, PV and LA content ranged from 0.85% to 4.52%, 1.2 to 6.41 mg NaOH 100g-1, 5 to 51.67 mEq kg-1 of flour, and 4.29 to 12.36 mg KOH g-1, respectively. The FFA, AV, and PV values for raw and fermented grains were used to estimate the shelf life using oxidation kinetics data. The kinetics data fit a pseudo- zero-order reaction model better than a first-order reaction model (R2 =0.8901 to 0.9927). Among all the machine learning techniques, artificial neural network (ANN) was found to be a better predictor with the least error functions and higher accuracy (R2 =0.9847 to 0.9969) as compared with the Gradient Boosting and the Support Vector Machine models.

Chemical reaction and heat source effects on oscillatory suction in MHD flow through permeable media with Soret effect

PurposeThe current investigation is concerned with the Soret effect along with chemical reaction and radiation on flow of an electrically conductive, viscous fluid through a perpendicular plate, which is porous with oscillatory suction. The aim of this study is to investigate the effects of first-order temperature and chemical reaction and the transverse magnetic field characteristics. The closed form of solutions are obtained using the governing equations for concentration, energy and momentum. The perturbation technique was applied to find the result for the velocity field, temperature profiles and concentration distributions. Furthermore, the impact of various nondimensional parameters on fluid flow variables on the temperature field, velocity field and concentration dispersal was analyzed and the results were depicted graphically. Moreover, the skin friction and the rate of mass transfer (local Sherwood number) were analyzed using tables. In this work, an unsteady 2D flow of a laminar, viscid (Newtonian), electrically conducting fluid across a semi-infinite perpendicular permeable plate under motion in its plane (x-axis) embedded in a constant permeable structure was investigated.Design/methodology/approachIn this work, an unstable 2D flow of a laminar, viscid (Newtonian), electrically conducting fluid across a semi-limitless perpendicular permeable plate under motion in its plane (x-axis) embedded in a constant permeable structure was investigated. The medium is considered to be under a transverse magnetic field with concentrated buoyancy effects. Furthermore, it is considered that no voltage is supplied, which indicates that there is no electrical field. The fluid properties are considered to be uniform. The concentration of the imparting species is considered as C′w at the plate; the concentration of the specimens away from the wall, C′8, is considered to be limitlessly less. The first-order chemical reaction is considered to be seen in the flow. Due to the semi-limitless plane surface considerations, the flow parameters are the functions of y′ and the time t′ only. The oscillatory suction velocity of the fluid at the plate normal to it is v′; initially, the plate relocates with the oscillatory velocity u′, in the direction of x that is in its plane. The pressure gradient is toward the x-axis.FindingsThe analytical solutions were obtained using the above analytical method for a few values of the governing parameters, such as the magnetic parameter (M), the permeability parameter (K), Schmidt number (Sc), chemical reaction parameter (Kr), Grashoff number for the concentration (Gm), Radiation parameter (N), Prandtl number (Pr), Chemical reaction parameter (Kr), Grashof number for heat transfer (Gr) and Heat source parameter (s). The influence of M, K, Sc, Kr, Gm, N, Pr, Kr, Gr and s on the fluid velocity, temperature and the concentration over the semi-infinite porous plate was obtained. Furthermore, the numerical computation was carried out using MATLAB.Originality/valueIn this chapter, the analysis of a free convective flow of a viscid compact, electrically conductive fluid was discussed during its flow through a plate in permeable condition with oscillatory suction with first-order temperature and chemical reaction and the transverse magnetic field. The problem formulation and the results were discussed. The following chapter explain the Soret effect of mass transfer and radiation with heat source on magnetohydrodynamics oscillatory viscoelastic fluid in a channel filled with porous medium.

Determination of the Kinetic Parameters of Cholesterol Oxidation using Cholesterol Oxidase from Streptomyces sp.

Cholesterol oxidase (CO) was successfully produced from Streptomyces sp. via the submerged fermentation method, and 69 U/mL enzyme activity was obtained. This study aimed to determine cholesterol oxidation kinetics and the production of CO as a catalyst. The enzyme was diluted to 0.15, 0.075, and 0.00375 U/mL for the oxidation reaction. The substrate was also prepared in three concentrations: 3.23, 6.46, and 12.93 mM. The optimization of conditions for enzymatic cholesterol oxidation was investigated through measurement of the effect of initial cholesterol and enzyme concentrations. Cholesterol concentration was rapidly measured via high-performance liquid chromatography (HPLC). The kinetics of CO were modeled using the first-order irreversible reaction. An enzymatic kinetic model was derived, and it was verified using experimental data and sensitivity analysis. Based on the experiment, the highest enzyme concentrations of crude and commercial CO can oxidize the substrate up to 84% within 240 min. However, the oxidation reaction showed a slightly different behavior in the early 60 min, and crude CO exhibited a slower substrate oxidation. The kinetic rate constant obtained by Euler’s method reached 1.0 x 10−3/min and 1.41 x 10−3/min for 0.15 U/mL crude and commercial CO, respectively.

Enhanced humic acid removal by sludge activated carbon/Fe2+ composite in peroxymonosulfate activation: mechanism and performance.

In subsurface water, humic acid (HA) can react with active chlorine to form carcinogenic compounds, posing ecological issues and health risks. This study aims to create sludge activated carbon (SAC), combine it with Fe2+, and activate peroxosulfate (PMS) to remove HA from water. To verify the successful modification of SAC, the physicochemical properties were characterized using various methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Moreover, in the Fe2+/SAC/PMS system, the removal rate of HA rose significantly, peaking at 96%. The removal of HA conformed to the first-order reaction kinetic equation, with a reaction rate constant of 0.048min-1, showing that activated PMS generates potent oxidative radicals or non-radicals, boosting reaction efficiency. After four repeated cycles of use, the removal rate of HA remained above 90%, demonstrating its excellent stability and reusability. The results of three-dimensional fluorescence spectroscopy (3D-EEM) indicated that the Fe2+/SAC/PMS system could effectively degrade dissolved organic matter (DOM) in water. Quenching experiments and electron paramagnetic resonance (EPR) analysis further confirmed that singlet oxygen (1O2) is the primary oxidative species for degrading HA. Therefore, the Fe2+/SAC/PMS reaction system presented promising application prospects to remove HA from water.

Electrospun Carbon Nanofibers Derived from Polyvinyl Alcohol Embedded with Bimetallic Nickle-Chromium Nanoparticles for Sodium Borohydride Dehydrogenation.

Bimetallic NiCr nanoparticles decorated on carbon nanofibers (NiCr@CNFs) were synthesized through electrospinning and investigated as catalysts for hydrogen generation from the dehydrogenation of sodium borohydride (SBH). Four distinct compositions were prepared, with chromium content in the catalysts ranging from 5 to 25 weight percentage (wt%). Comprehensive characterization confirmed the successful formation of bimetallic NiCr@CNFs. Notably, among the compositions, the catalyst containing 20 wt% Cr exhibited the highest efficiency in SBH dehydrogenation. Kinetic studies revealed that hydrogen production followed a first-order reaction with respect to the catalyst quantity. Additionally, the reaction time decreased with increasing temperature. The activation energy (Ea), entropy change (ΔS), and enthalpy change (ΔH) were calculated as 34.27 kJ mol-1, 93.28 J mol·K-1, and 31.71 kJ mol-1, respectively. The improved catalytic performance is attributed to the synergistic interaction between Ni and Cr. This study proposes a promising strategy for the advancement of Ni-based catalysts.

Electrostatic Spray Drying of a Milk Protein Matrix-Impact on Maillard Reactions.

Electrostatic spray drying (ESD) of a milk protein matrix comprising whey protein isolate (WPI), skim milk powder (SMP), and lactose was compared to conventional spray drying (CSD) and freeze-drying (FD). ESD and CSD were used to produce powders at low (0.12-0.14), medium (0.16-0.17), and high (0.31-0.36) levels of water activity (aw), while FD powders targeted low aw (0.12). Maillard reaction indicators were studied after drying and during storage for up to 28 days at 20, 40, or 60 °C by measuring free -NH2 groups, as an indicator of available lysine, and 5-hydroxymethylfurfural (HMF). After drying, levels of residual free -NH2 groups were ~15% higher in ESD and FD powders than in their CSD counterparts. CSD powders also had ~14% higher HMF concentrations compared to their ESD and FD counterparts. Storage led to reductions in free -NH2 groups and increases in HMF content in all powders, the extent of which increased with increasing storage temperature. Reductions in free -NH2 groups followed first-order reaction kinetics at 20 and 40 °C but second-order reaction kinetics at 60 °C. Lactose crystallization was detected in high-aw CSD powders after 14 d at 40 °C and in both CSD and ESD powders after 7 d at 60 °C. Overall, we found that ESD is a gentle drying technology which enables production of powders with lower Maillard reaction markers.

Introduction of a consecutive first-order reaction model for soil nitrogen mineralization and derivation of parameters based on chemical analysis values

ABSTRACT A number of exponential models, classified as first-order reaction models, have been proposed for predicting the mineralization rate of soil organic nitrogen (SON). However, the considerable fluidity and uncertainty associated with the model parameters present a significant challenge. This issue is thought to be attributable to two principal factors: Initially, there is a discrepancy between the model structure and the actual phenomena. Secondly, the model parameters are derived from intra-model calculations. To address these issues, we propose introducing a consecutive first-order reaction model that embodies the recent paradigm for understanding soil nitrogen dynamics, namely the relationship between organic nitrogen (N) polymers, organic N monomers, and inorganic N, and further links the parameters to soil chemistry. The model comprises two discrete pools of SON, specifically persistent organic N (PON) and easily degradable organic N (EON). The model hypothesizes that PON is converted to EON, which then results in N mineralization. The first-order rate law was applied to both reactions. Concurrently, eight paddy soils that had been managed for two years and seven months under non-flooding (oxidative) conditions were maintained in an incubator under oxidative conditions at temperatures 20°C, 25°C, and 30°C for 511 days. N mineralization was quantified on 13 occasions The model parameters were calibrated in accordance with the soil chemistry. The capacity of the EON pool was found to be dependent on the contents of ATP (adenosine triphosphate) and LFN (light fraction N). The capacity of the PON pool was contingent upon the total N and EON pools. The reaction rate constant for PON was found to be a function of the acidic ammonium oxalate extracted aluminum content and pH, and the reaction rate constant for EON was observed to be a function of pH. The activation energies for both reactions were found to be constants specific to all soils, respectively. The root mean square error (RMSE) of the model calculation results for measured values from 0 to 409 mg kg−1 was as low as 6.9 mg kg−1, indicating that the model has robust predictive ability across a wide variety of soil types, temperatures, and incubation periods.