Gibbs Free Energy Of Activation Research Articles

Purification and characterization of a novel Aspergillus heteromorphus URM 0269 protease extracted by aqueous two-phase systems PEG/citrate

A novel Aspergillus heteromorphus URM 0269 protease (EC 3.4.21) was extracted by aqueous two-phase systems PEG/citrate (ATPS). Extraction was performed by factorial design 24 for analyzing the independent variable effects named PEG molar mass (MPEG), PEG concentration (CPEG), sodium citrate concentration (CCIT) and pH. Afterwards, extracted protease was characterized in terms of kinetic and thermodynamic parameters. Protease partitioned preferentially for the PEG rich phase displaying the highest purification factor of 7.83 with a 157.53% yielded. Despite the enzyme acted optimally at 50 °C and pH 8.0, it was more stable in lower temperatures (10–40 °C) and pH conditions (5.0–10.0). The kinetic parameters of activation for casein hydrolysis revealed higher affinity by casein (KM = 2.8 mg/mL) with maximum catalysis rate of 45.0 U/mL. The reaction activation energy and the standard enthalpy variation of enzyme unfolding were 24.2 and 54.2 kJ/mol, respectively. Protease catalyzed casein hydrolysis at 25 °C, showed activation Gibbs free energy, enthalpy and entropy of 65.8 kJ/mol, 21.8 kJ/mol and −146.7 J/mol·K, respectively. The thermodynamic parameters of protease thermoinactivation suggested a predominating mechanism of reversible unfolding since the inactivation Gibbs free energy increased from 91.0 to 102.3 kJ/mol. These results displayed the great potential of the protease to be exploited in industrial applications.

Thermodynamic Study on Density and Viscosity of Binary Mixtures of Ethyl acetoacetate with (C4-C9) Aliphatic Ketones at (303.15 and 308.15) K

Investigation on Density (ρ) and viscosity (η) of various binary mixtures of ethylacetoacetate and straight chain aliphatic ketones (butan-2-one, pentan-2- one, hexan-2-one, heptan-2-one, octan-2-one and nonan2-one) have been carried out over the entire solvents composition range at temperatures of 303.15K and 308.15K. From the data obtained, the excess molar volumes (V E ), the excess viscosity (η E ) and excess Gibbs free energy of activation for viscous flow (ΔG*E) have been calculated from the experimental density and viscosity measurements at the working temperatures. Excess molar volumes, V E results are negative and positive over the entire range of mole fractions and become more positive as the chain length increases. The excess viscosities, η E were both positive and negative over the entire mole fraction range. While the observed excess Gibbs free energies of activation of viscous flow, ΔG*E data are positive throughout the entire mole fraction range of solvents composition at all investigated temperatures. These observed results of the excess functions have been interpreted in terms of possible molecular interactions in the binary mixtures.

Transition state theory application to ZnO nanocluster sensitivity to H2 gas

The sensitivity of zinc oxide nanoclusters to hydrogen molecules is discussed using transition state theory. Thermodynamic quantities of activation and reaction are calculated that includes Gibbs free energy, enthalpy, and entropy in the temperature range 25−500 °C. Results show that Gibbs free energy of activation that controls the reaction rate, and the values of response and recovery times increase with temperature. The oxygen recovery reaction rate is higher than the response reaction rate because of the low value of its activation energy. The response time is inversely proportional to the concentration of H2 molecules, while the recovery time increases with the concentration of H2 molecules due to diffusion. The variation of the sensitivity, response, and recovery times with the concentration of H2 molecules agree with available experimental results.

Magnetic nanocomposite cobalt-multiwalled carbon nanotube and adsorption kinetics of methylene blue using an ultrasonic batch

Herein, cobalt (0) metals loaded on multiwalled carbon nanotube nanoadsorbents were synthesized by a straightforward ultrasonic technique, and the removal efficiency of cobalt (0) multiwalled carbon nanotube nanoadsorbents were evaluated in the adsorption of methylene blue at various experimental conduction in an ultrasonic bath. Nanoadsorbents amount, solution pH, ultrasonic power, methylene blue concentrations, temperature, and H2O2 concentrations were studied as experimental parameters in the study. The synthesized cobalt (0) multiwalled carbon nanotube nanoadsorbents were characterized using some advanced spectroscopic techniques. The adsorption mechanism of methylene blue using the as-synthesized nanoadsorbents was evaluated by investigating some kinetic models including intra-particles diffusion, the pseudo-first-order, and the second-order models. The experimental findings of methylene blue adsorption by cobalt multiwalled carbon nanotube was found to be compatible with the pseudo-second-order model. Additionally, some kinetic activation studies like Gibbs free energy, enthalpy, and activation energy for the methylene blue adsorption were investigated. The enthalpy of the process was found to be 25.29 kJ mol−1 that shows the adsorption process is endothermic. The maximum adsorption efficiency of the nanoadsorbents was found to be 1.04 × 10−3 mol g−1 (324.34 mg g−1). The comparisons of results to the previous studies revealed that the synthesized nanoparticles were found to be very effective for the removal of methylene blue from the aquatic mediums.

Better late than never! Transition state character involved in the neutral solvolysis of an oxalic ester determined by the ionizing power of ethanol/water and methanol/water mixtures

Solvation effects and solvolysis extent are major aspects of the decomposition of esters, particularly in polar protic media. Among the many different ester derivatives, oxalic esters are substances that have two ester groups in the same molecular framework, but with potentially different reactivities. Aryl oxalic esters are commonly used in efficient organic chemiluminescent reactions, leading to important analytical and biological applications. We studied the decomposition of bis(2,4,6-trichlorophenyl) oxalate (TCPO) in 100, 98, 95, 90, 80, 70, 60, and 50% ethanol/water (EtOH/W) and 100, 90, 80, and 70% methanol/water (MeOH/W) mixtures (% in v/v). In these media, one phenolic residue is generated in a fast addition–elimination (step 1), followed by a second slower addition–elimination (step 2), thus, two rate constants are observed. Using a Grunwald–Winstein (G–W) relationship between these rate constants and the solvent ionizing power (Υ), we determined the sensibility (m) to solvation effects and charge development associated with the transition state (TS) of the rate-determining step (rds). We also determined the Gibbs free energy of activation (∆‡G, at 25 °C) associated with each step, and used it to rationalize the TS character of the rds, considering that in both steps a zwitterionic intermediate is generated and that the addition step is rate limiting. In EtOH/W binary mixtures a non-linear G–W plot was observed, and for 100–95% EtOH/W mixtures the sensibility was m = 1.0 (step 1, ∆‡G = 21.6 to 20.6 kcal mol−1) and 1.1 (step 2, ∆‡G = 23.9 to 23.0 kcal mol−1), indicating full ionization in the TS of the addition step. Smaller Y values in 90–50% EtOH/W reflect a more symmetrical TS, with not as many charges being generated (step 1, m = 0.196, ∆‡G = 20.3 to 19.4 kcal mol−1; step 2, m = 0.30, ∆‡G = 22.6 to 21.7 kcal mol−1). In 100%–70% MeOH/W binary mixtures, with Y values similar to those for 90–50% EtOH/W, m = 0.52 (step 1, ∆‡G = 20.3 to 18.8 kcal mol−1) and 0.27 (step 2, ∆‡G = 21.5 to 20.9 kcal mol−1) were observed. Particularly for step 1 in MeOH/W, the observation of a solvent kinetic isotope effect that varies from inverse (0.63 ± 0.09 in pure MeOH) to normal (1.9 ± 0.3 in 70% MeOH/W) is consistent with the significant participation of the solvent in TS stabilization, resembling general acid catalysis.

Activated complex theory is a classical theory suitable for food science with appropriate use.

Activated complex theory (ACT), apart from Van 't Hoff equation, has long been applying as an alternative tool to connect the kinetics (reaction rate constant, k) and thermodynamics parameters (including standard enthalpy of activation, △H++; standard entropy of activation, △S++; standard Gibbs free energy of activation, △G++). The study mainly focuses on ACT application in food systems, especially oil and fruit juice processing. Considering there are several improper calculations or mistakes often found in papers published recently in 2014-2019, three considerations are presented when applying the ACT, including 1) Understand that the reaction should be a single chemical elementary step; 2) Ensure that the units used should be consistent; 3) Effectively analyze the kinetics and thermodynamic parameters by choosing proper temperatures. This study is expected to further improve the understanding and correct application of this well-known theory in future work.

Electrochemical and Anticorrosive Behavior of Synthesized Diimine-Based Compound on X80 Steel in Acidic Oil and Gas Well Treatment Fluids at Different Temperatures

A green compound, N,N′-bis(2,4,6-trihydroxybenzaldehyde)-2,2-dimethylpropandiimine, was studied as an acid corrosion inhibitor for X80 steel. Aqueous 15% HCl was utilized for simulating the oil well acidizing fluid at various temperatures. The inhibition performance was assessed using the weight loss method, the electrochemical impedance, the polarization, and the scanning electron microscopy. Polarization investigations showed that the studied diimine inhibitor delays both the cathodic and anodic reactions over chemical adsorption and blocks the active corrosion sites. The adsorption procedure was performed physically as best estimated using the Langmuir adsorption isotherm. It was observed that, the adsorption process was spontaneous and exothermic in the direction of a rise in the bulk phase entropy. The efficiency of the inhibitor was reduced by increasing temperature and raised with an increasing amount of the inhibitor. Impedance data indicated that as the inhibitor amount enhanced the charge transfer resistance of steel also increased while the double layer capacitance decreased. Kinetic and thermodynamic factors such as the activation energy, enthalpy, entropy and the Gibbs free energy of activation and adsorption were computed. Scanning electron microscopy was utilized to examine the steel surface in the presence or the absence of the inhibitor, showing excellent surface protection by the studied inhibitor.

Microwave dielectric relaxation spectroscopy of paracetamol and its aqueous solutions

The complex dielectric function ε∗(ω) = ε ′ (ω) – jε ″ (ω) is studied for aqueous solutions of Paracetamol (PCM) (at four different temperatures 293.15 K, 303.15 K, 313.15 K and 323.15 K) across the frequency range of 200 MHz to 30 GHz and of pure PCM in pellet form (at a constant temperature of 300.15 K) over the frequency ranging from 200 MHz to 20 GHz. Dielectric properties are measured using Anritsu Shockline Vector Network Analyser (VNA) Model No. MS46322A, SPEAG DAK – 1.2 (5–50 GHz) and DAK – 3.5 (200 MHz–20 GHz) probes. Obtained dielectric data are further analysed with Debye relaxation model in order to understand the dipolar relaxation behaviour of these solutions. From obtained dielectric data; other parameters like power reflected (Pr), power transmitted (Pt), penetration depth (dp) have also been determined at 2.45 GHz and analysed in view of its applicability for microwave dielectric heating in pharmaceuticals. Temperature dependence of the dipolar relaxation time is used to evaluate thermodynamical parameters: Gibbs free energy of activation (ΔFe), entropy of activation (ΔSe) and enthalpy of activation (ΔHe).

Focused–type ultrasound extraction of phenolic acids from Q.Infectoria galls: Process modelling and sequential optimization

Phenolic acids from Q.Infectoria (QI) galls were extracted using focused–type ultrasound extraction method and further optimized using sequential optimization by response surface methodology (RSM). Different independent variables of sonication time, A (6–10 h), solvent concentration, B (0.05–0.15 M), ratio, C (1:05–1:15), duty cycle, D (30–50 %) and temperature, E (60–80 °C) were first screened via full factorial design (FFD) and the obtained results indicated that sonication time, ratio and temperature were the most significant variables in attaining higher yields. The significant curvature from focused–type ultrasound performance provides insights to a subsequent optimization of the factorial model via face–centred central composite design (FCCCD). The later results revealed that temperature highly impacted the yield with highest contribution percentage of 56.76 %. Notably, maximum extraction yield of 4119.77 mg/g was achieved at optimum condition of 9 h sonication time, ratio of 1:6 and temperature of 75 °C. Besides, Fick’s model successfully promotes diffusivity and appropriately foreseen that temperature factor governed the extraction process from QI galls. Relevant activation energy of 83.39 J/mol, along with the thermodynamic factors which include activation enthalpy (ΔH*) and activation Gibbs free energy (ΔG*), affirmed the extraction process was endothermic and non-spontaneous in identity.

Water Phase Synthesis Method of CuInS2 Nanoparticles and Its Application of Photovoltaic Device

CIS (CuInS2) is one of the most effective photovoltaic devices with high stability and efficiency, because of its suitable bandgap (1.5eV). Moreover, it does not contain toxic materials, such as Se, within its components. However, productivity and utilization of natural resources under the gas phase synthesis method is relatively low, since vaporizing temperature of elements is extremely different. Thus, it is required to develop a synthesis method of CIS solar cell materials within liquid phase.Here, we have already developed a synthesizing method of single phase and homogenous CI (CuIn) alloy nanoparticles in aqueous solution. In this method, the concentration of the metal complexes in the solution are calculated by using the critical stability constants, and the reduction reaction rate of both metal ions is also controlled. Synthesized CI nanoparticles were spin coted onto Mo/glass substrate and selenized, consequently it shows the photo voltaic effect. Thus, printable solar cells can be formed by using this method. The synthesizing method contains the selenization which is a sort of evaporation method, so it is not liquid process completely. To synthesize CIS solar cells without the selenization, we tried to sulfurize CI nanoparticles but CIS particles were not synthesized. It is difficult to sulfurize CI nanoparticles because they are stable and hard to react with sulfur ions, so it is necessary to synthesize from copper ions and indium ions to CuInS2 particles directly.However, nobody can synthesize CuInS2 particles in aqueous solution because there is a difference between the sulfurization reaction rate of copper and indium ions. If the sulfurization reaction rate of both metal ions is different, they are sulfurized independently to form their own sulfides, such as Cu2S or CuS and In2S3. It is necessary to control and approximate the sulfurization reaction rate of both metal ions for synthesis of CuInS2 particles. Here, in the sulfurization process, the sulfurization reaction rate is correlation with potential energy such as gibbs free energy (ΔG) or activation energy (Ea ). Hence, CuInS2 particles can be synthesized under the condition that the ΔG or Ea in the sulfurization reaction of copper and indium ions are approximated.To synthesize CuInS2 particles in aqueous solution, we tried to approximate the ΔG of the sulfurization reaction of copper and indium ions.By calculating ΔGCu2S and ΔGIn2S3 , we obtained the correlation of KIn and KCu and we were able to select appropriate complexing agents, so we tried to synthesize CuInS2 particles by using these reagents.XRD data indicates that several peaks with a dominant CuInS2 peak were observed. From the above results, it can be said that the synthesis of the precursor of CuInS2 particles in aqueous solution was successful because the Ea of the sulfurization process are approximated in both metal ions.In addition, it was found that the ΔG of copper and indium ions are approximated in the sulfurization system (Cu-In-IDA), so it is necessary to control and approximate both the ΔG and Ea for synthesis of CuInS2 particles in aqueous solution.Although the precursor of CuInS2 were synthesized in aqueous solution, the size and shape of the particles were not uniform. Therefore, for preventing degradation of conversion efficiency, it is needed to develop a technique for homogenizing the shape and the size of the particles.Detailed and another results will be introduced in our presentation. This work has been supported by the Grant-in-Aid for Scientific Research (B) (18H03416).

Biodiesel production in the presence of heterogeneous catalyst of alumina: Study of kinetics and thermodynamics

AbstractIn the current research, biodiesel production was investigated in the presence of solid catalysts of K2CO3/Al2O3 by transesterification of rapeseed oil. The specifications of produced fatty acid methyl esters like viscosity and flash point were studied, and it was noted that they complied with the requirements of ASTM D6751. In addition, the kinetic and thermodynamic parameters were explored considering the temperature changes between 318.15 and 348.15 K. Mass transfer resistance (external diffusion or internal diffusion) over the catalyst was neglected with regard to theWeisz‐Prater criterion and Mears criterion. The kinetic models containing Eley‐Rideal, Langmuir‐Hinshelwood, pseudo–first‐order, pseudo–second‐order, and α‐order models were investigated. Corrected Akaike information criterion was utilized to find the best model fitted with the experimental data. The greatest illustration for the K2CO3/Al2O3‐catalyzed reaction was the nonlinear model with an order of α = 1.287 and the activation energy of 12.12 kJ/mol. Using transition state theory (Eyring‐Polanyi equation), the activation Gibbs free energy, activation enthalpy, and activation entropy were calculated at different temperatures. The equilibrium thermodynamic properties depicted that this process is endothermic and spontaneous toward biodiesel production and tends to be irreversible.

Co–Mo–B nanoparticles supported on carbon cloth as effective catalysts for the hydrolysis of ammonia borane

The application of carbon cloth (CC) as the catalyst substrate has been gradually concerned because of its novel physical and chemical properties. Herein, Co–Mo–B nanoparticles grown on CC to form film samples (denoted as Co–Mo–B/CC–F) were prepared, characterized, and applied as effective catalysts for catalyzing the ammonia borane (NH3BH3) hydrolysis. The synthesized Co–Mo–B/CC–F sample at pH = 11.5 shows exceptional catalytic properties, including a fast hydrogen generation rate of 3916.1 mL⋅min−1⋅g−1at room temperature of 298 K, and an extremely low activation energy of 25.2 kJ mol−1. The experimental results indicate that the stacked spherical structure, as well as the synergism between bimetal Co–Mo and nonmetal boron, may bring about the improved catalytic properties of Co–Mo–B/CC–F catalyst. Further investigation about the thermodynamic property has shown that Gibbs free energy of activation is reckoned to be 77.6 kJ· mol−1, demonstrating that NH3BH3 hydrolysis is a non-spontaneous reaction in the presence of Co–Mo–B/CC–F catalyst. This study illustrates that the stacked Co–Mo–B/CC–F catalyst has prosperous application in the non-noble metal catalyst field for the dehydrogenation from NH3BH3.

Identification and functional characterization of a β-glucosidase from Bacillus tequelensis BD69 expressed in bacterial and yeast heterologous systems.

BackgroundThe identification and characterization of novel β-glucosidase genes has attracted considerable attention because of their valuable use in a variety of industrial applications, ranging from biofuel production to improved digestibility of animal feed. We previously isolated a fiber-degrading strain of Bacillus tequelensis from buffalo dung samples, and the goal of the current work was to identify β-glucosidase genes in this strain. We describe the cloning and expression of a new β-glucosidase gene (Bteqβgluc) from Bacillus tequelensis strain BD69 in bacterial and yeast hosts. The recombinant Bteqβgluc were used to characterize specificity and activity parameters, and candidate active residues involved in hydrolysis of different substrates were identified through molecular docking.MethodsThe full length Bteqβgluc gene was cloned and expressed in Escherichia coli and Pichia pastoris cultures. Recombinant Bteqβgluc proteins were purified by immobilized metal affinity or anion exchange chromatography and used in β-glucosidase activity assays measuring hydrolysis of ρ-nitrophenyl-β-D-glucopyranoside (pNPG). Activity parameters were determined by testing relative β-glucosidase activity after incubation under different temperature and pH conditions. Candidate active residues in Bteqβgluc were identified using molecular operating environment (MOE) software.ResultsThe cloned Bteqβgluc gene belongs to glycoside hydrolase (GH) family 4 and encoded a 54.35 kDa protein. Specific activity of the recombinant β-glucosidase was higher when expressed in P. pastoris (1,462.25 U/mg) than in E. coli (1,445.09 U/mg) hosts using same amount of enzyme. Optimum activity was detected at pH 5 and 50 °C. The activation energy (Ea) was 44.18 and 45.29 kJ/mol for Bteqβgluc produced by P. pastoris and E. coli, respectively. Results from other kinetic parameter determinations, including pKa for the ionizable groups in the active site, Gibbs free energy of activation (ΔG‡), entropy of activation (ΔS‡), Michaelis constant (Km) and maximum reaction velocity (Vmax) for pNPG hydrolysis support unique kinetics and functional characteristics that may be of interest for industrial applications. Molecular docking analysis identified Glu, Asn, Phe, Tyr, Thr and Gln residues as important in protein-ligand catalytic interactions.

A Kinetic‐Thermodynamic Study of the Effect of the Cultivar/Total Phenols on the Oxidative Stability of Olive Oils

AbstractPhysicochemical parameters, total phenols contents (TPC), and oxidative stabilities at 120–160 °C were evaluated for two monovarietal (Arbequina and Cobrançosa cultivars, cvs.) and one blend extra‐virgin olive oil, confirming the label quality grade and allowing grouping them according to the different TPC (TPC = 88 ± 7, 112 ± 6 and 144 ± 4 mg CAE/kg, for cv. Arbequina, blend and cv. Cobrançosa oils, respectively). The lipid oxidation rate increased with the decrease of the TPC, being Cobrançosa oils (higher TPC) more thermally stable. Kinetic‐thermodynamic parameters were determined using the activated complex/transition‐state theory and the values did not significantly differ for Cobrançosa and blend oils, which had the highest TPC, suggesting a hypothetically threshold saturation of the beneficial effect. Cobrançosa oils had a significant more negative temperature coefficient, higher temperature acceleration factor, greater activation energy and frequency factor, higher positive enthalpy of activation, lower negative entropy of activation, and greater positive Gibbs free energy of activation, probably due to the higher TPC. The results confirmed that lipid oxidation was a nonspontaneous, endothermic, and endergonic process with activated formed complexes structurally more ordered than the reactants. A negative deviation from the Arrhenius behavior was observed for all oils being the super‐Arrhenius behavior more marked for Arbequina oils that had the lowest TPC. Finally, the kinetic‐thermodynamic parameters allowed classifying oils according to the binomial olive cultivar/total phenols level, being the temperature acceleration factor and the Gibbs free energy of activation at 160 °C the most powerful discriminating parameters.

Effect of temperature and solvents on ultrasonic speed and related acoustical thermodynamic parameters of epoxy resin of (2E,6E)-bis(4-hydroxybenzylidene)cyclohexanone solutions

The density (ρ), viscosity (η) and ultrasonic speed (U) of pure solvents: 1,4-dioxane (DO), tetrahydrofuran (THF), chloroform (CF) and (2E,6E)-bis(4-hydroxybenzylidene)cyclohexanone (EBHBC) solutions of different concentrations were investigated at four different temperatures: 298, 303, 308 and 313 K to understand the effect of solvents on molecular interactions in these solutions. Various acoustical and thermodynamic activation parameters such as specific acoustical impedance (Z), adiabatic compressibility (κa), Rao’s molar sound function (Rm), van der Waals constant (b), internal pressure (π), free volume (Vf), intermolecular free path length (Lf), classical absorption coefficient (α/f2)cl, viscous relaxation time (τ), Gibbs free energy of activation (ΔG*), enthalpy of activation (ΔH*) and entropy of activation (ΔS*) were determined using the ρ, η and U data and correlated with concentration (C) at different temperatures (T). Very good to excellent correlation between a given parameter and concentration is observed at different T. Linear/nonlinear increase or linear/nonlinear decrease in acoustical parameters, solvation number and thermodynamic activation parameters suggested structure-forming tendency of EBHBC in the selected solvent systems.

Highly efficient hydrogen evolution from the hydrolysis of ammonia borane solution with the Co–Mo–B/NF nanocatalyst

Catalytic hydrolysis of ammonia borane (NH3BH3) is considered as a secure and effective way to supply hydrogen (H2) source for the proton exchange membrane fuel cell. Hence, cheap and high activity catalysts need to be exploited. In this work, a series of cobalt–molybdenum–boron (Co–Mo–B) composites were successfully supported on the surface of Ni foam (NF in short) via electroless plating method by tuning the depositional pH values. The as-prepared nanocatalysts were marked as Co–Mo–B/NF and characterized using the inductively coupled plasma-mass spectroscopy, scanning electron microscopy, X–ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy technology. These catalysts showed highly efficient catalytic performance for H2 evolution toward the hydrolysis of NH3BH3 solution, and the optimized Co–Mo–B/NF nanocatalyst deposited at pH = 11.5 achieved a higher H2 evolution rate of 6027.1 mL·min−1·g−1 under ambient temperature. The kinetics tests displayed that hydrolysis reaction catalyzed by Co–Mo–B/NF was zero-order in terms of the NH3BH3 concentration, while it was first-order in view of the catalyst concentration. In addition, the activation energy of NH3BH3 hydrolysis was calculated to be 43.6 kJ·mol−1 with the Co–Mo–B/NF nanocatalyst (pH = 11.5), which was lower than that of most of the previous precious metal and non-precious metal catalysts. The corresponding Gibbs free energy of activation was 43.1 kJ·mol−1, meaning that NH3BH3 hydrolysis reaction was non-spontaneous.

Co-pyrolysis behavior, engine performance characteristics, and thermodynamics of liquid fuels from mahua seeds and waste thermocol: A comprehensive study

Abstract In the present study, the co-pyrolysis of mahua seeds (MS) and waste thermocol (WTC) (1:1) blends was performed at 450–600 °C. The obtained co-pyrolysis oil (CPO) was characterized for physicochemical properties and its suitability as an alternative fuel. The performance, emission, and combustion characteristics of six different CPO diesel (CPOD) blends (B10, B20, B30, B40, B50, and B60) were also assessed at various engine loads. The experimental results indicated a maximum pyrolysis oil yield of 99.6% for waste thermocol pyrolytic oil (WTCPO) and 74.2% for CPO at 525 °C. The physicochemical characterization specified that CPO has a specific gravity, kinematic viscosity, and calorific value of 0.91 mL g−1, 1.94 cSt, and 40.6 MJ kg−1, respectively with a carbon chain length of C7–C24. The brake thermal efficiency (30.9 to 27.1%) and NO emission decreased with an increase in CPO percentage in the blends. The maximum heat release rate of CPOD blends increased with an increase in the percentage of CPO in diesel. The estimated mean value of activation energy (Ea), pre-exponential factors, enthalpy (ΔH), and Gibbs free energy (ΔG) for MS, WTC, and MS:WTC (1:1) blend were 135.1, 186.3, and 171.4 kJ mol−1; 18.1, 25.6, and 24.4 min−1; 130.6, 180.5, and 165.6 kJ mol−1; and 188.5, 301.1, and 206.3 kJ mol−1, respectively. The reaction function for the thermal degradation of MS and WTC was expressed as f(x) = (1– x)2.9, and f(x) = (1 – x)0.93 (0.017 + x 0.35) using multivariate nonlinear regression. The present research provides comprehensive data in understanding the engine performance characteristics, thermal behavior of biomass, and waste plastics that coexist in municipal solid waste.

Iron recovery from acid mine drainage sludge as Fenton source for municipal wastewater treatment

ABSTRACT Iron recovered from acid mine drainage (AMD) waters effluent and introduced as an advanced oxidation processes (AOPs) source, namely, Fenton reagent (FR) for municipal wastewater (MWW) treatment. Acid mine drainage-based Fenton reagent’s (AMD-FR) experiments were carried out in a lab-scale facility and various operating parameters such as reaction time, solution pH, AMD as the iron source dose and H2O2 concentration were investigated. Box–Behnken design was applied to optimise the multiple variables and a mathematical model was developed with a high correlation coefficient (R2 = 96%). The maximum Chemical Oxygen Demand (COD) removal reached 73% within 30 min of reaction time. Optimum AMD sludge introduced to the system was 41 mg/L and H2O2 of 398 mg/L at the optimum operating pH 2.7. Kinetic study of AMD-FR revealed that COD removal followed the second-order reaction kinetic model. Thermodynamic analysis of the results with positive values of enthalpy (∆H`) suggested the endothermic nature of the reaction. Positive Gibbs free energy of activation (∆G`) and negative entropy of activation (∆S`) values verified the non-spontaneous nature of the oxidation reaction with a low energy of activation barrier (55.59 kJmol−1).

Kinetic and thermodynamic parameters of nisin thermoinactivation

Understanding the thermal inactivation of biopreservatives in food matrixes is essential for their proper use in the food industry, enabling reduction of heating time and optimization of heating temperature. With this aim in mind, the effect of heat treatment on the activity and thermostability of commercial nisin from Lactococcus lactis was investigated. Residual activity tests performed for 90 min in the 70–86 °C temperature range at pH 3.0 demonstrated that bacteriocin thermoinactivation followed first-order kinetics. Low values of the inactivation rate constant (0.0089–0.0892 min−1) and high values of the decimal reduction time (25.8 ≤ D-value ≤ 258.4 min) indicated excellent nisin thermostability in the lower end of the investigated temperature range, but the thermal resistance constant (z-value) was only 15.4 °C, which pointed out poor thermoresistance at the higher end. Thermodynamic parameters estimated for nisin irreversible thermal inactivation were energy, enthalpy and Gibbs free energy of activation of 155.1, 152.2–152.3 and 83.5–86.6 kJ mol−1, respectively, and activation entropy of 188.6–192.5 J mol−1 K−1. If on the one hand these results taken together confirm the thermostability of nisin as a biopreservative in use in the food industry, on the other hand suggest the importance of looking for new more thermostable antimicrobials to use in operations at higher temperatures.

The Effects of Structural Modifications of Bis‐tert‐alcohol‐Functionalized Crown‐Calix[4]arenes as Nucleophilic Fluorination Promotors and Relations with Computational Predictions

We prepared four structurally modified bis‐tert‐alcohol functionalized crown ether‐strapped calix[4]arene promoters, that is, bis‐tert‐alcohol functionalized crown‐5‐calix[4]arene (BA5C), bis‐tert‐alcohol functionalized crown‐7‐calix[4]arene (BA7C), bis‐1,1‐dimethylbutanol functionalized crown 6‐calix[4]arene (B3A6C), and bis‐1,1‐dimethylhexanol functionalized crown 6‐calix[4]arene (B5AC6C). Nucleophilic fluorinations were conducted using alkali metal fluorides to investigate phase‐transfer catalytic activities with respect to the sizes of crown ether‐strapped calix[4]arene (CEC) subunits and lengths of alkyl chain spacers between tert‐alcohol and CEC subunits. The reactivity of potassium fluoride was significantly enhanced by BA5C promoter because its crown‐5‐calix[4]arene subunit had cavity size appropriate for K+ capture. In contrast, BA7C did not efficiently enhance cesium fluoride SN2 fluorination because its crown‐7‐calix[4]arene cavity was too large to capture Cs+. The alkyl spacer of bis‐tert‐alcohol functionalized CEC provided sufficient distance between F– and Cs+. In particular, the three‐component alkyl carbon chain of B3A6C was optimal in terms of increasing CsF reactivity. Systematic quantum chemical analysis predicted that fluorination reactions facilitated by bis‐tert‐alcohol‐substituted crown‐6‐calix[4]arene (BACCA) and B3A6C might proceed via separated ion‐pair type pre‐reaction complexes, which suggested that these two promotors act as Lewis bases that essentially separate CsF ion‐pairs. The lower (by 0.4 kcal/mol) Gibbs free energy of activation for the reaction promoted by B3A6C than that facilitated by BACCA concurred with the experimentally observed slightly greater efficiency of B3A6C than BACCA.