Analysis Of Oxidation Kinetics Research Articles

Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis

To explore the spontaneous combustion characteristics and hazards of the low-temperature oxidation (LTO) stage in the process of spontaneous combustion of coal and mudstone, the pore structure, spontaneous combustion characteristic parameters, and exothermic characteristics of coal and mudstone were tested and studied, and the oxidation kinetic parameters were calculated. The results show that mudstone has a larger specific surface area and pore volume than coal. From the fractal characteristics, the pore structure of mudstone is more complex than that of coal. According to the comparison of theoretical and actual gas generation and oxygen consumption rate curves, it is found that there is an interaction between coal and mudstone in the LTO process. With the increase of mudstone mass ratio, gas production, and its oxygen consumption rate increase. Among them, CM-4 (Coal:Mudstone = 1:1) has the highest exothermic intensity and the exothermic factor (A) and fire coefficient (K) increase with the increase of mudstone content. The apparent activation energy of the mudstone sample is lower than that of the raw coal, indicating that the sample after adding mudstone is more likely to have spontaneous combustion in the LTO stage.

The cyclic oxidation behavior and kinetics of W-Cr-Nb-Y2O3 alloys processed by powder metallurgy route

In the present investigation, yttria (Y2O3) has been added to the W-Cr-Nb alloys to study the cyclic oxidation behavior of on W-Cr-Nb- Y2O3 alloys processed by the powder metallurgy route. The cyclic oxidation tests are performed at 800 °C, 1000 °C, and 1200 °C for 15 h in the air. The oxidation kinetic analysis and implementation of a double Voigt function to calculate the domain size (crystallite size) and microstrain are also investigated. The results show that the cyclic oxidation tests on the sintered W-Cr-Nb-Y2O3 samples have exhibited that [(W0.5Cr0.5)90Nb10]98 - (Y2O3)2 alloy is marginally more oxidation resistant than [(W0.7Cr0.3)90Nb10]98 - (Y2O3)2 alloy at temperatures 800 °C and 1000 °C. In contrast, the [(W0.7Cr0.3)90Nb10]98 - (Y2O3)2 composite shows more oxidation resistance than [(W0.5Cr0.5)90Nb10]98 - (Y2O3)2 composite at temperature 1200 °C, apparently due to the formation of a large number of protective oxides like Cr2WO6, 2NbO5.7WO3 and Y2WO6, and absence of WO3 oxide on the former composite at 1200 °C in air. The values of oxidation exponent n ≈ 2 obtained for the oxidation tests on the [(W0.5Cr0.5)90Nb10]98 - (Y2O3)2 indicate that approximately parabolic rate law is being followed in the range of 800–1200 °C. In the case of [(W0.7Cr0.3)90Nb10]98 -(Y2O3)2 alloy (1 < n < 2) indicates that the rate of oxidation is faster than that predicted by the parabolic rate law but slower than that expected from the linear relationship between mass change per unit area (Δm/S) and time (t).

MgAl2O4–C refractories with balanced properties for a delivery device used in the double-roll thin strip continuous casting

To realize the double-roll thin strip continuous casting process for the production of high-quality steels, it is necessary to seek a new type of refractory material tailored for delivery device employed in this process. Therefore, the present study aimed to design and prepare MgAl2O4–C refractories for this purpose as well as to study their physical and mechanical properties, thermal shock resistance, oxidation kinetics, and to perform molten steel experiments after pre-oxidation treatment. The results of the present study demonstrated that the specimens could maintain high mechanical and thermal shock properties even after pre-oxidation treatment. After pre-oxidation at 1100 °C/1 h, the cold compressive strength of the specimen reached 17.63 MPa, with a residual strength ratio (thermal shock resistance) of 77.99%. Analysis of oxidation kinetics based on the shrinking core model indicated an increase in the effective diffusion coefficient and complete oxidation time with higher pre-oxidation temperature. Pre-oxidation of MgAl2O4–C refractories has been shown to be effective in reducing carbon penetration into the molten steel from carbon-containing refractories, thus maintaining the stability of the molten steel composition. This effect was attributed to enhanced contact and wettability between the steel and refractories, an augmented thickness of the pre-oxidized decarburized layer, the formation of a dense magnesium oxide layer, and the emergence of the MgAl1·9Fe1O4 phase. Consequently, an MgAl2O4–C refractories designed for the delivery device was proposed along with anticipated applicability in the double-roll continuous casting process.

Effect of Linoleic and Linolenic Acid Contents on the Oxidation Stability of Interesterified Fats under Rancimat Test Conditions.

This study aimed to better understand the association between the amount of polyunsaturated fatty acids, namely, linoleic acid (LA) and linolenic acid (LNA), and the increases in the peroxide value that results from storing interesterified fats, which are used as sources of solid fats in edible oil and fat products, at high temperatures. Six interesterified fats with different LA and LNA contents were prepared and oxidized at 50°C, 60°C, 70°C, and 80°C under Rancimat test conditions. The oxidation rate increased with LA and LNA contents and increasing temperature. The oxidation kinetic analysis during the early oxidation stages demonstrated that when LA and LNA exceeded 8% and 2% respectively, the oxidative stability decreased as expected. However, the total LA and LNA contents had a higher correlation with the reaction rate constant [k (meq kg-1 h-1 )] than each amount of LA and LNA contained therein. In other words, the oxidation stability of the interesterified fats used in this study depended on the total LA and LNA contents.

Enhancing oxidation resistance of MoAlB based on its anisotropic oxidation mechanism: A theoretical calculation guided experimental investigation

MoAlB is considered the most promising material for oxidation resistance among the MAB phase family. However, the anisotropic oxidation mechanism at the atomic scale has not been fully investigated, which may limit its practical applications. In this work the anisotropic oxidation mechanism of MoAlB was first explored through systematic theoretical calculations, based on which an effective strategy to enhance its oxidation resistance was identified and successfully implemented in the experimental work. The theoretical calculation revealed that the anisotropic oxidation of MoAlB was primarily related to the difference in free energy of surface oxidation reactions due to the degrees of electron interaction localization of O-Al bonding. A series of candidates of various transition metal-doped MoAlB materials were then designed to improve the weaker surface of MoAlB for oxidation resistance enhancement. Among these candidates, Zr-doped MoAlB was selected to further evaluate the effects of doping on the anisotropic oxidation through the electronic structure and Ab initio molecular dynamics (AIMD). Finally, Zr-doped MoAlB was experimentally synthesized to validate the theoretical design. Non-isothermal oxidation kinetics analysis indicated that Zr doping can enhance the oxidation resistance of MoAlB by promoting the formation of a protective oxide scale and increasing the formation activation energy of volatile products, which finally reduced the thickness of the oxidation scale on the surface after isothermal oxidation of the bulk material. This work not only contributes to an in-depth understanding of the oxidation mechanisms in MoAlB but also presents a new approach to enhance its oxidation resistance and other Al containing ceramic materials beyond MAB phases.

Analysis and Kinetics Modeling of the Isothermal Oxidation Behavior of Silicide Coatings

In this paper, an online apparatus was developed for isothermal thermogravimetric measurement of silicide coatings within a wide temperature range (from −180 °C to 2300 °C) based on thermogravimetric analysis. Firstly, the measuring principle and method regarding silicide coatings of this apparatus were studied. Secondly, on the basis of oxidation kinetics analysis, the intrinsic mechanism and kinetic parameters of three stages (oxidation, diffusion, and fall-off) of silicide coatings were studied, and the oxidation kinetics features were also analyzed. In addition, according to mathematical physics methods, a kinetics model of silicide coatings in different stages of oxidation was established, including parameters such as weight change, oxidation rate, oxidation time, etc. Finally, online isothermal experiments from −180 °C to 2300 °C werecarried out and analyzed. The results showed that the kinetic model established in this paper was in good agreement with the oxidation process of silicide coatings. In this paper, a complete kinetics model including different oxidation stages is proposed for the entire oxidation process of a silicide coating, revealing its oxidation mechanism. The research will play a significant role in the study of preparation technology improvement and high-temperature environment application. This paper studied two measuring methods: weight gain and weight loss measuring methods. Also, an experiment was carried out on the silicide coatings to explore the physical oxidation process between −180 °C and 2300 °C. The results proved the perfect consistency of the kinetics model proposed by this paper and the oxidation process of silicide coatings. This paper will play a significant role in the study of preparation technology enhancement and high-temperature environment application. It also provides a theoretical foundation for accelerated aging and life evaluation methods.

Oxidation Kinetics Analysis of Crude Oils with Different Viscosities

In order to compare the oxidation kinetics parameters of crude oils with different properties in the process of crude oil oxidation, six different crude oil samples were selected to analyze the oxidation characteristics of crude oils with different properties. In order to study the oxidation of crude oil, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) synchronous analyzer were used for crude oil in the oxygen environment between 25 °C and 900 °C at a heating rate of 20 °C/min. The experimental results were based on crude oil oxidation using TGA and DTG experimental data to evaluate the oxidation mechanism of different crude oils, so as to better understand the situation in the oxidation reaction process. At the same time, the oxidation stage of crude oil was divided according to DSC data. Arrhenius method was used to analyze the oxidation kinetic parameters of crude oils with different properties, and the activation energies and pre-exponential factors of different crude oils were calculated. The experimental results show that the oxidation stage of crude oil can be divided into three stages: low-temperature oxidation, fuel deposition, and high-temperature oxidation. The low-temperature oxidation reaction begins at 280 °C, and the high-temperature oxidation reaction occurs at 400 °C. The low-temperature oxidation activation energy of an oil sample is 39.73–77.74 kJ/mol. The activation energy of the high-temperature oxidation is in the range of 106.27–264.47 kJ/mol. The activation energy of crude oil in the low-temperature oxidation stage increases with the increase of crude oil viscosity and decreases with the increase of crude oil viscosity in the high-temperature oxidation stage. Therefore, during the high-temperature oxidation stage, high-viscosity crude oil is more prone to reactions.

Preparation and properties of tea polyphenol nanofoamed gel for preventing coal spontaneous combustion

The current technologies employed to prevent the spontaneous combustion of coal, such as grouting, inert gas, retardants, gels and foams have the disadvantages of high pollution, easy failure at high temperature, and high cost. In this study, in order to develop an environmentally friendly, efficient and low-cost composite gel material to inhibit coal spontaneous combustion, tea polyphenols were added to the gel for grafting, while nanomaterial halloysite nanotubes were introduced for intercalation reaction. Finally, sodium bicarbonate and acetic acid were used as foaming agents to produce tea polyphenol nanofoaming gels. The microscopic characterization of the composite gel was studied using X-ray diffraction experiments and scanning electron microscopy. Experiments on physical properties such as fluidity, thermal stability and adhesion were also carried out. In addition, fire performance studies such as thermogravimetric experiments, oxidation kinetic analysis, infrared spectroscopy of gas products, analysis of the change law of active functional groups and crossing-point temperature analysis were completed. The results show that composite gel renders the activity of active functional groups inert, which inhibits coal spontaneous combustion, while it can cover the surface of coal and plug the fissures efficiently. Therefore, it is an ideal material to inhibit the spontaneous combustion of coal.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

Oxidation thermodynamics and oxidation kinetics analysis of Au-20Sn solder

In this paper, the oxidation thermodynamics and oxidation kinetics of Au-20Sn solder at various temperatures were analyzed. The results indicated that the critical oxygen partial pressure to form SnO and SnO2 in Au-20Sn solder could be 1 × 10−44 Pascal (Pa) and 1 × 10−91 Pa at the temperature of 298 K, respectively. The oxidation kinetics analysis results indicated that the oxide on the surface of Au-20Sn solder consists mainly SnO2, while the major constituent of internal oxide is SnO. The reliability test results under salt spray environment have showed that the hermeticity of the package device gradually decreased with the increasing oxygen content in Au-20Sn solder. Meanwhile, the measured leakage rate of the packaging device could be lowered than 5 × 10−9 Pa·m–3·s–1 when the oxygen content in Au-20Sn solder is less than 28 ppm after high temperature aging.

Evaluation of ORAC methodologies in determination of antioxidant capacity of binary combinations of quercetin and 3-(3,4,5-trihydroxybenzoyl) coumarin derivatives

Antioxidant capacity is used to refer to ability of compounds to react with free radicals, it is also described as ability to inhibit oxidation processes. There are different methods that evaluate the antioxidant capacity of compounds of natural origin or extracts. ORAC methodologies measure the ability to transfer hydrogen atoms to RO·/ROO· radicals generated by the AAPH thermolysis, in presence of a probe that accounts for oxidation of antioxidant. Despite extensive use of these methods to assess antioxidant capacity, they have been questioned by type of radical generated and information they can deliver, especially if it is a mixture of compounds. In this work, antioxidant capacity of binary combinations of quercetin with synthetic 3-phenylcoumarins was evaluated through ORAC-FL, PGR and quantification techniques after oxidation kinetics via free radicals, through HPLC. It was found through ORAC-FL that derived 3-(3,4,5-trihydroxybenzoyl) coumarin have greater antioxidant capacity than Trolox: 1 < 2 < 3 < quercetin. Determination of ORAC-FL indices of combination showed an antagonistic effect among the antioxidants. Also, ORAC-PGR method did not allow determination of antioxidant capacity of compounds, separately, indicated high reactivity of compounds. However, unusual behaviors were observed in combinations, unable to explain antagonistic effect observed in ORAC-FL. HPLC oxidation kinetics analysis showed that in the combination the consumption of the most reactive antioxidant dominated the antioxidant capacity and followed a similar trend as observed by ORAC-FL. Therefore, ORAC methodologies would not be useful in characterizing antioxidant capacity of mixture in relation to reactivity of metabolites present therein, but in relation to amount of hydroxyl groups available.

Comparative study of the reactive elements effects on oxidation behavior of a Ni-based superalloy

Hf, Y, and Ce (0.1 wt % each) were added in Ni-based superalloy, prepared by vacuum induction melting (VIM), and their effects on oxidation behavior were investigated after 300 h, over the temperature range 900–1100 °C. The surface of the oxide layer predominantly consisted of Al2O3 and NiO at 900 °C. At 1000 °C, most of the surface is covered by Al2O3 along with a small amount of NiAl2O4. However, at 1100 °C, the oxide layer's surface mainly formed of NiAl2O4 with plate-like α-Al2O3. It has been found that Hf produced excellent oxidation resistance and improved the scale adhesion to the alloy surface. On the other hand, Ce has a limited effect at high temperatures, and the scale adhesion is decreased with increasing oxidation time. From the analysis of oxidation kinetics and microstructure, it has been proposed that the dynamic segregation of reactive elements does not physically leads to the blocking of ions outward diffusion through Al2O3. The improvement in oxidation resistance of alumina forming alloys produced by reactive elements is explained based on ionic radii, chemical reactivity with alloying elements, and alteration in the alumina grain boundary's electronic properties.

Fatty Acid Stable Carbon Isotope Ratios Combined with Oxidation Kinetics for Characterization and Authentication of Walnut Oils.

Walnut oil is vulnerable to oxidation due to its high content of polyunsaturated fatty acids and adulteration due to its high price. This study investigated 12 typical walnut oils from six main walnut-producing areas in China, using differential scanning calorimetry (DSC), Rancimat test, gas chromatography (GC), elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) and GC-IRMS combined with oxidation kinetic analysis, Pearson correlation analysis, and principal component analysis (PCA). The melting and crystallization profiles using DSC indicated that walnut oils with a relatively high crystal onset temperature tended to be more stable against oxidation. Oleic acid was found to be the most characteristic fatty acid in walnut oil, with a content ranging from 13.84 to 35.08%. Two walnut oils with the highest oleic acid contents of 35.08 and 32.78% had the highest activation energies in nonisothermal DSC. Their predicted shelf lives based on the Rancimat test were 3.5-4.0 times longer than that of the oil with the highest α-linolenic acid at 4 °C and 3.1-3.5 times longer at 25 °C. The δ13C values of walnut oils were determined by EA-IRMS, and the δ13C values of fatty acids were determined by GC-IRMS. Fatty acid stable carbon isotope ratios combined with PCA were successfully applied to intuitively discriminate different walnut oils. The results suggested that fatty acid δ13C values determined by IRMS combined with chemometrics and lipid compositions are promising as a powerful means of vegetable oil authentication and discrimination.

An effective enzymatic assay for pH selectively measuring direct and total bilirubin concentration by using of CotA

In this study, we aimed to develop B. subtilis spore coat protein A (CotA) for the enzymatic determination of bilirubin. Firstly, molecular docking and oxidation kinetic analysis confirmed the feasibility of CotA for oxidizing bilirubin. Secondly, CotA showed pH-preferable oxidization performance to direct bilirubin (DB) in acidic conditions and an alkaline-catalytic oxidation capacity to total bilirubin (TB). Mechanism analysis results confirm that the conformational changes of CotA, DB and UB caused by pH changes are responsible for the selective oxidation of DB and TB by CotA. Then, CotA exhibits better structural characteristics and enzymatic performance than M. verrucaria-derived bilirubin oxidase (Mv-BOD). Besides, the strong anti-interference ability helps CotA adapt to complex catalytic environment in the detection of DB and TB. Our results prove that CotA can be used as a promising candidate bio-enzymatic detection reagent for DB and TB.

Effects of Co(II) ion exchange, Ni(II)- and V(V)-doping on the transformation behaviors of Cr(III) on hexagonal turbostratic birnessite-water interfaces

Natural birnessite-like minerals are commonly enriched in various transitional metals (TMs), which greatly modify the mineral structure and properties. However few studies are yet conducted systematically on the effects of TM doping on birnessite reactivity towards Cr(III) oxidation. In the present study, the transformation behaviors of Cr(III) on Co-, Ni-, V-containing birnessites were investigated. Co and Ni doping generally decrease the mineral crystalline sizes and hydrodynamic sizes (DH) while V-doping greatly decreases the crystalline sizes but not the DH, owing to particle aggregation. Co and Ni firstly decrease and then increase the mineral zeta potentials (ζ) at pH4 while V decreases ζ. Electrochemical specific capacitances for Co-containing birnessites are gradually reduced, while those for Ni-doped birnessites are slightly reduced and for V-doped birnessites increased, which have a positively linear relationship with the amounts of Cr(III) oxidized by these samples. Cr(III) removal efficiencies from solution by these Co-, Ni- and V-containing birnessites are 26–51%, ∼62–72% and ∼96–100%, respectively, compared to ∼92% by pure birnessite. Cr(III) oxidation kinetics analysis demonstrates the gradual decrease of Mn(IV) and concurrent increase of Mn(III) and the adsorption of mainly Cr(III) on mineral surfaces. A negatively linear relationship exists between birnessite lateral sizes and the proportions of Mn(IV/III) consumed to oxidize Cr(III). Apparent initial Cr(III) oxidation rate (kobs) for Co-containing birnessites are greatly reduced, while those for Ni-doped samples moderately decreased and for V-doped samples first increased and then decreased. A positively or negatively linear relationship exists between kobs or the amount of Mn(II) released and the mineral Mn(IV) content respectively. Cr(III) oxidation probably initiates from layer edge sites of Ni-doped birnessites but the vacancies of Co- and V-containing birnessites. These results provide insights into the reaction mechanisms of Cr(III) with natural birnessite-like minerals.

Effect of Fe addition on the microstructure and oxidation behavior of MgO–C refractory

With the aim to solve the problem of structure degradation of MgO–C refractory during high-temperature oxidation, iron powder (Fe) was introduced as both antioxidant and ceramic bond former, and its effect on the microstructure evolution, physical and mechanical properties was investigated. Oxidation kinetics analysis, based on the shrinking core model, was also performed to reveal the quantitative effect of Fe on the oxidation resistance. Compared to the traditional MgO–C refractory, both densification and bonding degree of Fe-containing refractory after high-temperature oxidation were greatly improved by the formation of Mg(Fe1·2Al0.8)O4 bridges and magnesio-wustite [(Mg,Fe)Oss]. This change of microstructure caused a dramatic decrease in the effective diffusion coefficient of oxygen (Deff, decreased from 18.3 to 5.0 cm2/min), which contributed the most to the improvement of the oxidation resistance. The maintenance of strength against oxidation time was another important finding for the newly designed refractory, providing a basis for developing new carbon-containing refractories with self-repairing function.

Comparison of differential and integral methods for coal oxidation kinetic analysis

The influence of two different methods of kinetic analysis on obtained values of kinetic constants of coal oxidation process was studied. The oxidation of T-grade bituminous coal of Kuznetskiy deposit and 2B-grade lignite of Borodinskoe deposit was investigated by means of thermogravimetric analysis. All measurements were carried out with heating rates 2,5, 10, 25 and 40 K/min in temperature range 300-1100 K in air medium. The dependences of activation energy and frequency factor on conversion were obtained using two isoconversional methods: differential method of Freidman and integral method of Kissinger-Akahira-Sunose. The average values of activation energy which were obtained by KAS method were higher by 14.5 % for bituminous coal and 23.3 % for lignite in comparison with values obtained by Freidman method. The same relations were observed for frequency factor values.

Selective conversion of stearic acid into high-added value octadecanedioic acid using air and transition metal acetate bromide catalyst: Kinetics, pathway and process optimization

Liquid phase selective homogeneous catalytic oxidation of stearic acid (SA) was carried out to obtain industrially important carbon neutral high-added value octadecanedioic acid (ODDA). The oxidation was carried using air, cobalt(II)-acetate, manganese(II)-acetate and HBr catalyst in acetic acid (AcOH) solvent at an elevated temperature and pressure. SA oxidation products were analyzed by gas chromatography–mass spectrometry (GC–MS), gas chromatography (GC) and CO2 analyzer, and SA was oxidized selectively to ODDA without producing CO2 and intermediates like alcohols, aldehydes and ketones. The effect of SA loading (5–20%), pressure (2.8–5.8 barg) and temperature (353–383 K) on ODDA yield was studied by varying one variable at a time. Central composite design assisted response surface methodology was employed to find (i) the optimal design of experiments involving several combination of cobalt(II)-acetate (Co: 0–700 ppm), manganese(II)-acetate (Mn: 0–700 ppm) and HBr (Br–: 0–1144 ppm) and (ii) the most influencing variable and interaction among the variables. The synergistic effect of cobalt(II)-acetate in presence of HBr was observed and suggested that SA oxidation proceeds via bromine-bromide cycle. The elevated temperature and pressure along with reduced SA loading enhanced the yield of ODDA. The maximum ODDA yield was found to be 90.5% and corresponding optimum cobalt (II), manganese (II) and bromide concentration were 600.4, 452.2 and 1016.6 ppm, respectively, at fixed SA:AcOH-10:90, pressure-2.8 barg and temperature-383 K. Finally, SA oxidation kinetic analysis was determined based on the pseudo-first order homogeneous catalysis and found to be kinetically controlled with an average activation energy 34.55 kJ mol−1. The proposed kinetic model fitted well with the time-variant experimental SA and ODDA concentration under varying operating condition with percent average absolute deviation less than 5.0%.

A kinetic analysis of oxidation of the antioxidant N-acetyl-l-cysteine (NAC) by Pt(IV) complexes

N-acetyl-l-cysteine (NAC) is an antioxidant and a supplement and has been demonstrated to have protective effects for a variety of toxic effects of heavy metals. Although previous works have shown that NAC can ameliorate the severe toxic effects of cisplatin, there is a lack of understanding of the interactions between NAC and Pt(IV)-based prodrugs. In this work, the oxidation of NAC by a cisplatin prodrug (cis-[Pt(NH3)2Cl4]), by a prototype of Pt(IV) anticancer drug ormaplatin ([Pt(dach)Cl4]) and by a model compound (trans-[PtCl2(CN)4]2–) was characterized in detail. NAC was oxidized to NAC-disulfide as identified by mass spectrometric analysis. Time-resolved spectral and stopped-flow kinetic measurements were carried out over a wide pH range, demonstrating that the oxidation followed overall second-order kinetics. The observed second-order rate constants k′ versus pH profiles were established. A reaction mechanism was deduced, involving three parallel rate-determining steps; conceivable transition states were also proposed for these steps. Rate constants of the rate-determining steps, obtained from the simulations of rate equation to the k′–pH profiles, were largely correlated with the electron density on the sulfur atom in NAC. The Pt(IV) prodrugs can execute oxidative stress in the biological systems of the human body by direct oxidation of relevant molecules, similar to HOCl/OCl− and chloroamines. Instead, the oxidative stress involved in the severe toxic effects of cisplatin is produced via a different mode. NAC could be a chemoprotecting agent also for the Pt(IV) anticancer drugs if recent drug delivery technologies are used.

Impact of blend ratio on the co-firing of post-methanated distillery effluent solid waste and low-rank Indian coal via analysis of oxidation kinetics through TGA

An attempt has been made to study the oxidation kinetics of dried Post-Methanated Distillery Effluent (PMDE) solid waste blended with Low Rank Indian Coal (LRIC) at different blending ratios in a thermogravimetric analyzer (TGA).