A thermal analysis calculation of pharmaceutical wastewater sludge

Thermal pyrolysis of pharmaceutical wastewater sludge, brown coal, and sludge-coal blends were studied by TG dynamic runs carried out at 20 °C min⁻¹ in the temperature range from 25 to 850 °C. Different possible kinetic models of thermal decomposition have been considered. The best models of mechanism function for brown coal, pharmaceutical wastewater sludge, and coal–sludge blends are a first-order reaction, a N-dimensional nucleation, and growth reactions with N = 2 and 4, respectively. The Arrhenius kinetic parameters for brown coal, pharmaceutical wastewater sludge, and coal–sludge blends are proposed.     

Pyrolysis characteristics and kinetics of sewage sludge for different sizes and heating rates

The pyrolysis characteristics and kinetics of sewage sludge for different sizes (d < 0.25 mm, 0.25 mm < d < 0.83 mm, and d > 0.83 mm) and heating rates (5, 20, and 35 °C/min) were investigated in this article. The STA 409 was utilized for the sewage sludge thermogravimetric analysis. FTIR analysis was employed to study the functional groups and intermediates during the process of pyrolysis. Meanwhile, a new method was developed to calculate pyrolysis kinetic parameters (activated energy E, the frequency factor A, and reaction order n) with surface fitting tool in software MATLAB. The results show that all the TG curves are divided into three stages: evaporation temperature range (180–220 °C), main decomposition temperature range (220–650 °C), and final decomposition temperature range (650–780 °C). The sewage sludge of d < 0.25 mm obtains the largest total mass loss, especially at the heating rate of 5 °C/min. By FTIR analysis, the functional groups including NH, C–H, C=C, etc., are all found in the sewage sludge. There is a comparison between the FTIR spectra of sludge heated to 350 °C (temperature associated to maximum devolatilization rate in the second stage) and the FTIR spectra of sludge heated to 730 °C (temperature associated to maximum devolatilization rate in the third stage). In the second stage, the alcohols, ammonia, and carboxylic acid in the sludge have been mostly decomposed into gases, and only a little bit of compounds containing CH and OH of COOH exist. The pyrolysis kinetic parameters of second stage are as follows: the reaction orders are in the range of 1.6–1.8 and the activation energy is about 45 kJ/mol. The frequency factor increases with the increase of heating rate and sewage sludge size.     

The kinetics of gasification of char derived from sewage sludge

Gasification of char derived from sewage sludge was studied under different oxidizing atmospheres containing CO₂, O₂ or H₂O. The gasification tests were carried out in thermobalance at different temperatures and oxidizing reagent concentrations. The most efficient were the gaseous mixtures containing oxygen. The reaction took place at temperature 400–500 °C, whilst in the case of CO₂ and steam much higher temperatures (700–900 °C) were necessary to complete the conversion. Two rate models for gas–solid reaction were applied to describe the effect of char conversion on reaction rate. The shrinking core model for reaction-controlled regime was found to be the best for predicting the rate of char gasification in CO₂ and O₂ atmosphere. The experimental data for steam gasification of the char were fitted best by the first-order kinetics. The kinetic parameters estimated from the experimental data are in accordance with the literature for lignocellulosic char gasification and are the first published for sewage sludge char gasification.     

Kinetic Aspect of Thermal Decomposition of Natural Phosphate and its Kerogen. Influence of heating rate and mineral matter

The natural phosphate and its demineralization products from Moroccan deposit were pyrolysed in a thermogravimetric analyser (TG) to examine the influence of the heating rate and mineral matter on their thermal decomposition. The heating rates investigated in the TG were 5–100°C min⁻¹ to final temperature of 1200°C. The integral method was used in the analysis of the TG to determine the kinetic parameters. It has been found that for the natural phosphate and corresponding kerogen analysed in the TG, the increase of the heating rate shifts the maximum rate loss to higher temperature. A first order reaction was found to be adequate for pyrolysis in the range 150–600°C which was attributed to kerogen decomposition. In addition, the results indicate that the removal of mineral matter affected the kinetic parameters found for kerogen in the natural phosphate. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition reaction of 3,3,6,6-tetramethyl- 1,2,4,5-tetroxane in 2-methoxy- ethanol solution

The thermal decomposition study of 3,3,6,6-tetramethyl-1,2,4,5-tetroxane (acetone cyclic diperoxide) was carried out in 2-methoxyethanol solution in the 130-166 °C temperature range. The overall reaction follows a first-order kinetic law up to at least 75% diperoxide conversion. The activation parameters (ΔH^# = 22.5 ± 0.7 kcal⋅mol^–1 and ΔS^# = -25.6 ± 0.5 cal⋅mol^–1⋅K^–1) for the unimolecular rupture of the O–O bond in the diperoxide molecule were obtained by measuring the remnant diperoxide at different reaction times by the CG technique. Acetone was detected by GC as the major organic product of the reaction.     

Cross-linking epoxide resins with hydrolysates of chrome-tanned leather waste

Differential scanning calorimetry was employed to investigate the reaction of diglycidyl ethers of bisphenol A (DGEBA) of mean molecular mass 348–480 Da, with collagen hydrolysate of chrome-tanned leather waste in a solvent-free environment. The reaction leads to biodegradable polymers that might facilitate recycling of plastic parts in products of the automotive and/or aeronautics industry provided with protective films on this basis. The reaction proceeds in a temperature interval of 205–220°C, at temperatures approx. 30–40°C below temperature of thermal degradation of collagen hydrolysate. The found value of reaction enthalpy, 519.19 J g⁻¹ (= 101.24 kJ mol⁻¹ of epoxide groups) corresponds with currently found enthalpy values of the reaction of oxirane ring with amino groups. Reaction heat depends on the composition of reaction mixture (or on mass fraction of diglycidyl ethers in the reaction mixture); proving the dependence of kinetic parameters of the reaction (Arrhenius pre-exponential factor A (min⁻¹) and activation energy E _a (kJ mol⁻¹)) did not succeed. Obtained values of kinetic parameters are on a level corresponding to the assumption that reaction kinetics is determined by diffusion.     

The simulation of the thermal behavior of energetic materials based on DSC and HFC signals

Two small calibre and four medium calibre types of propellants were investigated non-isothermally (0.25–4K min⁻¹) by differential scanning calorimetry (DSC) in the range of RT-260°C and isothermally (60–100°C) by heat flow calorimetry (HFC). The data obtained from both techniques were used for the calculation and comparison of the kinetic parameters of the decomposition process. The application of HFC allowed to determine the kinetic parameters of the very early stage of the reaction (reaction progress α below 0.02) what, in turn, made possible the precise prediction of the reaction progress under temperature mode corresponding to real atmospheric changes according to STANAG 2895. In addition, the kinetic parameters obtained from DSC data enabled determination of self-accelerating decomposition temperature (SADT) and comparison of the predicted ignition temperature during slow cook-off with the experimental results. The study contains also the results of the calculation of the time to maximum rate (TMR_ad) of the propellants under adiabatic conditions.     

Thermal behaviour of cephalexin in different mixtures

The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate, starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min⁻¹. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min⁻¹. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears. These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates: 5, 7, 10 and 12 °C min⁻¹. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C).     

Investigation of thermal behavior of nicotinic acid

The thermal behavior of nicotinic acid under inert conditions was investigated by TG, FTIR and TG/DSC-FTIR. The results of TG/DSC-FTIR and FTIR indicated that the thermal behavior of nicotinic acid can be divided into four stages: a solid-solid phase transition (176–198°C), the process of sublimation (198–232°C), melting (232–263°C) and evaporation (263–325°C) when experiment was performed at the heating rate of 20 K min⁻¹. The thermal analysis kinetic calculation of the second stage (sublimation) and the fourth stage (evaporation) were carried out respectively. Heating rates of 1, 1.5, 2 and 3 K min⁻¹ were used to determine the sublimation kinetics. The apparent activation energy, pre-exponential factor and the most probable model function were obtained by using the master plots method. The results indicated that sublimation process can be described by one-dimensional phase boundary reaction, g(α)=α. And the ‘kinetic triplet’ of evaporation process was also given at higher heating rates of 15, 20, 25, 30 and 35 K min⁻¹. Evaporation process can be described by model of nucleation and nucleus growing, .     

Synthesis and thermal decomposition of ditetrazol-5-ylamine

Ditetrazol-5-ylamine (DTA) was synthesized from cyanuric chloride in four steps. The thermal decomposition of DTA in the solid state was studied by thermogravimetry, volumetry, mass spectrometry, IR spectroscopy, and calorimetry. Under isothermal conditions at 200–242 °C, thermal decomposition obeys the first order autocatalytic kinetics. The kinetic and activation parameters of DTA decomposition were determined. The composition of gaseous reaction products and the structure of condensed residue were studied. The thermal effect of thermal DTA decomposition is 281.4 kJ mol⁻¹. The nitrogen content in a mixture of gaseous products formed by the reaction in a temperature interval of 200–242 °C exceeds 97 vol.%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1660–1664, July, 2005.     

Kinetic study of pyrolysis of waste water treatment plant sludge

Activated sewage sludge samples obtained from two different waste water treatment plants were investigated by thermogravimetric analysis. Due to a very high content of water in the sludge samples, these had to be dried at 160°C in an electrical oven in order to remove all adsorbed water. To ensure pyrolysis conditions, nitrogen atmosphere was applied. The pyrolysis decomposition process was carried out in the temperature range from ambient temperature to 900°C at three different heating rates: 2 K min⁻¹, 5 K min⁻¹, 10 K min⁻¹. TGA and DTG curves of the decomposition processes were obtained. Temperature of onset decomposition, final temperature of decomposition, maximum decomposition rate, and decomposition temperature were determined by thermogravimetric analysis for both sludge samples used. The main decomposition process takes place at temperatures in the range from 230°C to 500°C. Above this temperature, there are only small changes in the mass loss which are often attributed to the decomposition of carbonates present in the sewage sludge samples. To determine the apparent kinetic parameters such as the activation energy and the preexponential factor, the so called Friedman isoconversional method was used. Because of the requirements of this method, initial and final parts of the decomposition process, where crossings of the decomposition lines occurred, were cut off. Obtained dependencies of the apparent activation energies and preexponential factors as a function of conversion were used backwards to calculate the modeled decomposition process of sewage sludge and the experimental data were in good accordance with the data obtained by simulation.     

Effect of a thin spreading solvent film on the efficiency of the hexadecan-1-ol monolayer deposited for water evaporation retardation

The influence of a thin spreading solvent film (ethanol, diethyl ether, and three fractions of petroleum ether boiling at 30–60 °C, 60–90 °C, and 90–120 °C) on the properties of hexadecan-1-ol (C₁₆H₃₃OH) monolayers at the air—water interface was studied. The specific evaporation resistance and the surface pressure were determined to describe the spreading behavior of the C₁₆H₃₃OH monolayers. The physical properties of the solvents and the images obtained in an atomic force microscope were examined. The time of establishing the equilibrium spreading surface pressure of monolayers can be reduced using a more volatile solvent with a lower boiling point and a lower relative density. The influence of the monolayer nature on water evaporation corresponds to the order of changing the solvent spreading rate: petroleum ether (30–60 °C) > diethyl ether > ethanol > petroleum ether (60–90 °C) > petroleum ether (90–120 °C). The monolayers formed upon petroleum ether (30–60 °C) spreading form a film with a less deficient and relatively planar surface. When ethanol is used as a spreading solvent, water evaporation is accelerated rather than retarded, while petroleum ether (30–60 °C) is more appropriate for this purpose.     

Pyrolysis of petroleum fractions

Dynamic kinetic analyses were performed on different Brazilian petroleum fractions by thermogravimetry. The data were treated by a multiple heating rate methodology. The apparent activation energies for the light and middle fractions within the range of 62–74 kJ mol⁻¹ and for heavy distillation residues were within the range of 80–100 kJ mol⁻¹ at lower conversions and 100–240 kJ mol⁻¹ at higher conversions. The kinetic study can be a criterion for tells apart the main phenomena involved in the thermal behavior of the refinery feedstock.     

Study of Kinetic Parameters of Reject/Clay/Composites by Thermal Analysis

Thermal degradation of granite and marble industry reject (GMIR), a red clay (RC)and their composites were studied by non-isothermal thermogravimetry (TG/DTG) in nitrogen atmosphere, differential thermal analysis (DTA) and derivative thermogravimetry(DTG) in air atmosphere. Measurements were made in the temperature range of 25–1000,25–1200 and 25–1400°C. The kinetic parameters were determined by Flynn–Wall and Kissinger's methods. The results indicate the absent dominance of one mechanism of reaction, and the composites show smaller values of kinetic parameters than GMIR or RC. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of glucose decomposition during dilute-acid hydrolysis of lignocellulosic biomass

Recent research work in-house both at Auburn University and National Renewable Energy Laboratory has demonstrated that extremely low concentrations of acid (e.g., 0.05–0.2 wt% sulfuric acid) and high temperatures (e.g., 200–230°C) are reaction conditions that can be effectively applied for hydrolysis of the cellulosic component of biomass. These conditions are far from those of the conventional dilute-acid hydrolysis processes, and the kinetic data for glucose decomposition are not currently available. We investigated the kinetics of glucose decomposition covering pH values of 1.5–2.2 and temperatures of 180–230°C using glass ampoule reactors. The primary factors controlling glucose decomposition are the reaction medium, acid concentration, and temperature. Based on the experimental data, a kinetic model was developed and the best-fit kinetic parameters were determined. However, a consistent discrepancy in the rate of glucose disappearance was found between that of the model based on pure glucose data and that observed during the actual process of lignocellulosic biomass hydrolysis. This was taken as an indication that glucose recombines with acid-soluble lignin during the hydrolysis process, and this conclusion was incorporated accordingly into the overall model of glucose decomposition.     

Thermal behavior of drugs

Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300 and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the heating rate (5, 10, 15, and 20 °C min⁻¹) on the DSC behavior of the both drug samples was verified. The results showed that, as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by various methods, the following order for the thermal stability was noticed: naproxen > celecoxib. Finally, the values of ΔS ^#, ΔH ^#, and ΔG ^# of their decomposition reaction were calculated.     

Kinetic study of wood chips decomposition by TGA

Pyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min⁻¹, 5 K min⁻¹, 10 K min⁻¹, and 15 K min⁻¹. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.     

Thermal degradation of poly(lactic acid) measured by thermogravimetry coupled to Fourier transform infrared spectroscopy

Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD) analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol⁻¹ for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT.     

Thermooxidative decomposition of oil shales

The thermooxidative decomposition of four oil shale samples from Estonia, Jordan, Israel and Morocco and one sample of Estonian oil shale derivative, semicoke, was studied with the aim to determine the characteristics of the process and the differences of it related to the origin of oil shale. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer were carried out under non-isothermal conditions up to 1000 °C at the heating rates of 1, 2, 5, 10 and 20 °C min⁻¹ in an oxidizing atmosphere. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results of TG–DTA–FTIR analyses and the variation of activation energy E along the reaction progress α indicated the complex character of thermooxidative decomposition of oil shale and semicoke, being at that the most complicated for Estonian and Jordanian oil shale characterized by higher content of organic matter as compared to the other samples studied.     

Pyrolysis study of sewage sludge by TG-MS and TG-GC-MS coupled analyses

The pyrolysis of an urban plant sewage sludge carried out under He atmosphere was studied by thermogravimetric-mass spectrometric (TG-MS) and thermogravimetric-gas chromatographic-mass spectrometric (TG-GC-MS) analyses. The sludge was thermally degraded with a heating rate of 10°C min^–1 in the 20–1000°C interval; its mass loss is 51.8% up to 600°C and 61.4% up to 1000°C. Gas chromatographic analyses of the gas released during major thermogravimetric events allow the identification of various chemical species. Water, carbon mono- and di-oxide, several hydrocarbons (up to C5, both saturated and unsaturated) were the major detected species. Minor amount of pollutant species, such as cyano-compounds, were also detected. Among the released species hydrocarbons constituted the major fraction (53%), thus suggesting their immediate exploitation as fuel gas. The pyrolysis behaviour of this sample was then compared with other sewage sludge arising from wastewater treatment plants subjected to anaerobic digestion as found in literature data.