Efficient photocatalytic oxidation of arsenite from contaminated water by Fe2O3-Mn2O3 nanocomposite under UVA radiation and process optimization with experimental design.

The effect of mass ratio of fuel to oxidant in pyrotechnic compositions of Mg/Ba(NO3)2 and Mg/Sr(NO3)2 was studied using the non-isothermal thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. The mass ratios 10:90, 25:75 and 50:50 of Mg powder to oxidant (nitrate salt) were used for preparation of pyrotechnic compositions. The kinetic parameters of thermal ignition reactions of pyrotechnics were obtained by using TG/DSC curves under nitrogen atmosphere at heating rates of 20, 25 and 30 °C min−1. The DSC curves showed that the 25:75 weight ratio of fuel to oxidant resulted in a complete ignition reaction and showed the highest enthalpy of the reaction. Also, this mass ratio was not indicated a mass gain after the combustion step in the TG curves. The model-free methods of Kissinger, Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS) were used for calculation of activation energy (Ea) of ignition reactions of pyrotechnics. The Ea values 130.5 and 146.3 by Kissinger, 138.3 and 153.2 by OFW and 132.2 ± 2.4 and 146.3 ± 1.7 kJ mol−1 by KAS methods, respectively, were obtained for Mg/Ba(NO3)2 and Mg/Sr(NO3)2 pyrotechnics. Also, the nonlinear model-fitting method was used to determine the pre-exponential factor (A) and kinetic model function. The sigmoidal shapes were resulted from the curves of conversion factor (α) versus T. The model of A3/2 with the functions of g(α) = [− ln(1 − α)]2/3 and f(α) = 3/2(1 − α)[− ln(1 − α)]1/3 as a nucleation reaction model was proved by using the model-fitting method for the ignition reaction of both pyrotechnic compositions. The ln A values 8.1 and 7.6 min−1 were obtained, respectively, for the ignition reaction of magnesium powder with Ba(NO3)2 and Sr(NO3)2.

Study of the ratio of fuel to oxidant on the kinetic of ignition reaction of Mg/Ba(NO 3 ) 2 and Mg/Sr(NO 3 ) 2 pyrotechnics by non-isothermal TG/DSC technique

The catalytic effect of lead oxide nano- and microparticles (PbO) on the thermal behavior and decomposition kinetics of energetic formulations composed of nitrocellulose (NC), triethyleneglycol dinitrate (TEGDN) and diaminoglyoxime (DAG) was investigated by simultaneous thermogravimetric analysis and differential scanning calorimetry. The results show that lead oxide nano- and microparticles could significantly alter thermal pattern of the studied energetic compositions. The effect of lead oxide content on thermal behavior of energetic compositions was also studied, and the results revealed that addition of different amounts of lead oxide caused to shift in the DSC peaks. Moreover, the catalyst decreases activation energy of the decomposition stage of energetic composition at about 20–40 kJ mol−1. However, the catalyst enhances decomposition temperature of TEGDN/NC/DAG energetic compositions. By the aid of DSC data resulted by non-isothermal methods, the thermokinetic parameters such as activation energy (E
 a), frequency factor (A), the critical ignition temperature of thermal explosion, the self-accelerating decomposition temperature (T
 SADT) and also thermodynamic parameters of the studied energetic compositions were calculated and compared.

Catalytic effect of lead oxide nano- and microparticles on thermal decomposition kinetics of energetic compositions containing TEGDN/NC/DAG

The non-isothermal TG/DTA technique has been used to study the thermal decomposition of PETN, Pentastite (93:7 of PETN:wax) and Pentolite (50:50 of TNT:PETN). The DTA curves were showed an exothermic peak for decomposition of PETN and Pentastite and the exothermic double peaks for decomposition of Pentolite over the range of 150–270 °C at heating rates of 4, 6, 8 and 10 K min−1 under argon atmosphere. The double peaks in decomposition of Pentolite were related to PETN and TNT, respectively. The overlapped peaks were resolved by peak fitting procedure. Then, the activation energy (E
 a) of thermal decomposition of PETN, Pentastite and Pentolite was calculated by model-free methods of KAS, OFW and Friedman for different conversion fraction (α) values in the range 0.1–0.9. The pre-exponential factor and the best kinetic model for decomposition of explosives were determined by means of the compensation effect, and the selected model was confirmed by the nonlinear model-fitting method. The activation energy was 135.1–136.9, 143.6–149.2, 123.0–125.0 and 59.9–75.2 kJ mol−1 for PETN, Pentastite and first peak of Pentolite (PETN) and second peak of Pentolite (TNT), respectively. The higher activation energy and thermal stability of Pentastite versus PETN is related to the additive paraffin wax. While, the synergic effect between two explosives in Pentolite is due to decrease of the E
 a of its components. The mechanism function of Avrami–Erofeev A
 3/2, A
 5/4, A
 2 and A
 3 was the most probable models for description of thermal decomposition reactions of PETN, Pentastite, PETN (first peak) in Pentolite and TNT (second peak) in Pentolite, respectively.

The kinetic of thermal decomposition of PETN, Pentastite and Pentolite by TG/DTA non-isothermal methods

Synthesis of mesoporous Fe-Mn bimetal oxide nanocomposite by aeration co-precipitation method: Physicochemical, structural, and optical properties

The non-isothermal TG/DSC technique has been used to study the kinetic triplet of ignition reaction of Mg/NaNO3 pyrotechnic under nitrogen atmosphere at different heating rates (5, 10, 15, and 20 °C min−1). The TG/DSC results showed that the mass gain after ignition increased and the heat of ignition reaction decreased with increasing heating rate, indicating that the reaction between Mg and NaNO3 was not complete during the ignition process. The activation energy (Ea) was calculated using Starink model-free method. The pre-exponential factor (A) and kinetic model function were determined by means of the compensation effect and the selected model was confirmed by the nonlinear model fitting method. The average values of Ea and logA for the ignition reaction of Mg/NaNO3 were found to be 148.46 ± 3.37 kJ mol−1 and 10.04 min−1, respectively. The model fitting method proved that the ignition reaction of Mg/NaNO3 pyrotechnic follows the mechanism of A4 (g(α) = [−ln(1−α)]1/4) as a nucleation reaction model.

Kinetic study of ignition of Mg/NaNO 3 pyrotechnic using non-isothermal TG/DSC technique

The kinetic and activation energies of thermal decomposition of KNO3 as an oxidizer in pyrotechnic compositions were studied in the presence of Fe2O3, Mn2O3, and TiO2 nanoparticles as catalysts, using thermogravimetric analysis under argon atmosphere at different heating rates (10, 15, and 20 K min−1). The prepared nanoparticles were characterized by XRD patterns, SEM images, and BET surface area analysis. For verification of data, the activation energies for thermal decomposition of KNO3 were calculated using non-isothermal isoconversional methods of KAS, OFW, and Friedman for different conversion fraction (α) values in the range 0.1–0.9. The activation energies were 201.6–208.2, 170.0–177.9, 173.9–181.6, and 213.0–223.8 kJ mol−1, respectively, in the absence and presence of 5 mol% of Fe2O3, Mn2O3, and TiO2. The results indicated that while Fe2O3 and Mn2O3 nanoparticles have catalytic effects, TiO2 nanoparticles show inhibitory effect on the thermal decomposition of KNO3.

Catalytic effect of Fe 2 O 3 , Mn 2 O 3 , and TiO 2 nanoparticles on thermal decomposition of potassium nitrate

The non-isothermal TG/DSC technique has been used to study the kinetic triplet of the thermal decomposition of potassium chlorate at different heating rates (5, 10, 15 and 20 °C·min−1). The DSC results showed two consecutive broad exothermic peaks after melting. The first peak contains a shoulder indicating the presence of at least two processes. The overlapped peaks were resolved by a peak fitting procedure, and the three resolved peaks were used for evaluation of the kinetic triplet for each step. The TG results also showed two consecutive mass losses after melting. The kinetics of the mass loss processes were studied using resolved DTG peaks. The activation energies were calculated using the KAS model-free method. The pre-exponential factor and the best kinetic model for each step were determined by means of the compensation effect, and the selected models were confirmed by the nonlinear model fitting method. The average activation energies obtained from the DSC results were 237.3, 293.8, and 231.3 kJ·mol−1 for the three consecutive steps of thermal decomposition of KClO3. The activation energies were 231.0 and 239.9 kJ·mol−1 for the first and second mass loss steps. The Avrami-Erofeev of Ax/y with the function of g(α) = [−ln(1−α)]x/y (x/y = 5/4 and 3/2) was the most probable model for describing the reaction steps.

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Mohsen Ravanbod

Papers

Kinetic study of ignition of Mg/NaNO 3 pyrotechnic using non-isothermal TG/DSC technique

The kinetic of thermal decomposition of PETN, Pentastite and Pentolite by TG/DTA non-isothermal methods

Catalytic effect of Fe 2 O 3 , Mn 2 O 3 , and TiO 2 nanoparticles on thermal decomposition of potassium nitrate

Kinetic Study of the Thermal Decomposition of Potassium Chlorate Using the Non-isothermal TG/DSC Technique

The Effect of HMX Impurity and Irganox Antioxidant on Thermal Decomposition Kinetics of RDX by TG/DSC Non‐Isothermal Method