Effect of tannic acid binding on the thermal degradation behavior and product toxicity of boscalid

The effect of tannic acid (TA) binding on the thermal degradation of boscalid was studied in this work. The results revealed that TA binding has a significant impact on boscalid degradation. The degradation rate constant of bound boscalid was reduced, and its corresponding half-life was significantly prolonged compared to the free state. Four identical degradation products were detected in both states through UHPLC-Q-TOF-MS, indicating that degradation products were not affected by TA binding. Based on DFT and MS analysis, the degradation pathways of boscalid included hydroxyl substitution of chlorine atoms and cleavage of CN and CC bonds. The toxicity of B2 and B3 exceeded that of boscalid. In summary, the binding of TA and boscalid significantly affected the thermal degradation rate of boscalid while preserving the types of degradation products. This study contributed to a fundamental understanding of the degradation process of bound pesticide residues in complex food matrices.

Thermal degradation of greenhouse gas SF6 at realistic temperatures: Insights from atomic-scale CVHD simulations

Sulfur hexafluoride (SF6), recognized as a potent greenhouse gas with significant contributions to climate change, presents challenges in understanding its degradation processes. Molecular dynamics simulations are valuable tools for understanding modes of decomposition while the traditional approaches face limitations in time scale and require unrealistically high temperatures. The collective variable-driven hyperdynamics (CVHD) approach has been introduced to directly depict the pyrolysis process for SF6 gas at practical application temperatures, as low as 1600 K for the first time. Achieving an unprecedented acceleration factor of up to 107, the method extends the simulation time scale to milliseconds and beyond while maintaining consistency with experimental and theoretical models. The differences in the reaction process between simulations conducted at actual and elevated temperatures have been noted, providing insights into SF6 degradation pathways. The work provides a basis for the further studies on the thermal degradation of pollutants.

Analysis of the degradation and crystallization behavior during the thermal degradation of poly(lactic acid)/modified hectorite nanocomposites films by simultaneous rheology and FTIR technology

This study presents the synthesis of Hec-g@PS through the innovative surface modification of hectorite via photocatalytic atom transfer radical polymerization (ATRP). Then, PLA/Hec-g@PS nanocomposites films was prepared with Hec-g@PS as additives by blown molding technique. Furthermore, the thermal degradation kinetics and crystallization kinetics during the thermal degradation of PLA based nanocomposites films were investigated with simultaneous rheology and FTIR technology. The findings indicated that the activation energies for PLA and PLA/Hec-g@PS were -54,702.12 J/mol and -107,963.47 J/mol, respectively, demonstrating that Hec-g@PS substantially influenced PLA thermal stability. Additionally, while the crystallization rates of PLA based films decreased with rising degradation temperatures. Quantum chemical calculations revealed that the mode of interaction between Hec-g@PS and PLA was mainly dominated by dispersion, supplemented by electrostatic and induced interactions of -22.2103 kcal/mol, -16.0779 kcal/mol and -5.4954 kcal/mol, respectively. The combination of crystallization kinetics and quantum chemical calculations further confirmed that Hec-g@PS promoted the alignment of PLA molecular chains due to the enhanced interaction force between them. Hec-g@PS functioned as a nucleating agent, facilitating PLA crystallization and effectively mitigated its thermal degradation. Hec-g@PS as a nucleating agent provides valuable insights into the potential application prospects of biodegradable materials, particularly in the fields of biomedicine and packaging.

Waste natural fibers for polymer toughening and biodegradability of epoxy-based polymer composite through toughness and thermal analysis

Polymeric materials are being increasingly used to replace many metallic components due to their beneficial properties such as higher strength-to-weight ratio and corrosion resistance. However, the widespread use of polymers poses a risk to the environment as they are not biodegradable. The addition of the waste jute fiber and sawdust fiber as reinforcement to the epoxy resin improved its toughness and induced the biodegradability of the polymer. To examine the effect of the jute fiber and sawdust fiber on biodegradability, the composites were then kept in the drainage system for one year, and the impact energy and fracture morphology of the as-cast and weathered samples were examined using a drop ball impact test and a Charpy impact test. During the weathering period, weight gain was initially observed due to the water absorption by the porous fibers, but after three months, the composites started to lose weight due to the degradation of the fiber by swelling and microbial attacks. Microorganisms in the drainage system used the fiber as their energy source, which resulted in the deterioration of the fiber and the production of CO2. The production of CO2 was identified by the FTIR analysis of the weathered composite samples. TGA analysis of the as-cast and weathered samples reveals the reduction of the onset thermal degradation temperature of the weathered composites due to the degradation of the composites. The fiber disintegrated through microbial attack and the fiber swelling caused by the absorption of water by jute fiber and sawdust fiber is identified through SEM imaging. The SEM image also reveals the formation of biofilms and the growth of microorganisms at the fibers. A higher growth rate of the microorganisms was observed in the jute fiber composite than in the sawdust fiber composite, as sawdust contains a high level of lignin that protects it from degradation. The results of this study suggest that both sawdust fiber and jute fiber composites induce biodegradability in the epoxy matrix, but jute fiber was more prominent in this regard. The discovery paves the way for using natural fibers in biodegradable polymer composites, reducing polymeric pollution in the environment.

A New Single-Step Approach Based on Supramolecular Solvents (SUPRAS) to Extract Bioactive Compounds with Different Polarities from Eugenia pyriformis Cambess (Uvaia) Pulp

This work employed supramolecular solvents (SUPRAS) made up of octanoic acid, ethanol, and acidified water (pH ~ 3) to extract and concentrate bioactive compounds from Eugenia pyriformis Cambess (uvaia) pulp. At first, the SUPRAS phase characterization demonstrated the spherical aggregates' formation with an internal hydrophobic structure and an external hydrophilic media. Subsequently, the simultaneous production and extraction (SUPRAS-SPE) method was employed in the solid-liquid extraction (SLE) of uvaia pulp. The extracts were evaluated through Folin-Ciocalteu reducing capacity, antioxidant activity (DPPH assay), total carotenoid content (TCC), and total flavonoid content (TFC). The results showed that reducing the ethanol concentration in the SUPRAS composition boosted the TCC extraction while increasing the ethanol presence, promoting a high TFC yield. Moreover, the SUPRAS-SPE method was compared with the ex situ method (SUPRAS-ES), where the solvent was previously produced and then applied to the SLE. Both methods were evaluated concerning their EE% and thermal degradation. The SUPRAS-SPE method increased the EE% of uvaia pulp bioactive compounds compared to the SUPRAS-SE method, providing a suitable microenvironment to extract, concentrate, and stabilize carotenoids from uvaia pulp, offering a sustainable alternative to obtain valuable compounds.

Degradation of glucosinolates and formation of isothiocyanates, nitriles, amines, and N,N'-dialk(en)yl thioureas during domestic boiling of red cabbage

Red cabbage is a popular vegetable in Central Europe and a rich source of glucosinolates (GLSs). Upon hydrolysis, GLSs form health-promoting isothiocyanates (ITCs), but also nitriles and epithionitriles. Recently, ITCs were shown to undergo further hydrolysis, yielding amines. Here, we analyzed the degradation of GLSs and the formation of ITCs, nitriles, epithionitriles, and amines during domestic-like cooking of red cabbage with addition of vinegar or baking soda. Both additives strongly affected the stability of GLSs and the formation of nitriles during boiling. Primary amines were found as a major degradation product of GLSs. In control and vinegar samples, formation of methylsulfinylalkyl amines increased during boiling. Additionally, for the first time, the formation of several N,N'-dialk(en)yl thioureas during boiling of Brassica vegetables was demonstrated, resulting from the reaction of GLS-derived ITCs and amines, and they were subsequently quantified. As references, five N,N'-dialk(en)yl thioureas were synthesized and characterized by NMR and HRMS.

Experimental and numerical analysis of the effects of thermal degradation on carbon monoxide oxidation characteristics of a three-way catalyst

This work investigates oxygen-storage capacity (OSC) changes during thermal degradation in modern three-way catalysts. Two experiments are performed using catalysts with different degradation degrees to evaluate OSC and reaction rates. The CO2 production test, where CO and O2 are supplied at a constant temperature, shows decreased CO2 production with more degraded catalysts and reduced purification. The CO2 production test is conducted using transient temperature increases, showing that the maximum CO2 production temperature increases with catalyst degradation. The results reveal an increase in activation energy in the oxygen desorption reaction caused by thermal degradation progresses and a decrease in OSC, resulting in temperature increases in the oxygen storage reaction. In the surface reaction and mass transport model considering the 30 elementary reactions, the predicted results are well-validated for CO2 production, enabling good oxygen storage predictions based on actual data. These results can be used to predict OSC by formulating the changes in active site density and activation energy due to degradation.

Melt crystallization and thermal degradation profile of the antichagasic drug nifurtimox

Despite nifurtimox (NFX) being a traditional drug for treating Chagas disease, some of its physicochemical properties are still unknown, especially its thermal behavior, which brings important outcomes regarding stability and compatibility. In this work, a comprehensive study of NFX's thermal properties was conducted to assist incremental innovations that can improve the efficacy of this drug in novel pharmaceutical products. For this purpose, thermal analyses associated with spectroscopy and spectrometry techniques were used. DSC analyses revealed that the melt crystallization of the NFX led to its amorphous form with the possible formation of a minor fraction of a different crystalline phase. Coats-Redfern method using TGA results indicated the activation energy of NFX non-isothermal degradation as 348.8 ± 8.2 kJ mol-1, which coincides with the C-NO2 bond dissociation energy of the 2-nitrofuran. Investigation of the isothermal degradation kinetics using FTIR 2D COS showed the possible detachment of radical NO2 and ethylene from the NFX structure, which could affect its mechanism of action. A preliminary mechanism for the thermal degradation of this drug was also proposed. The results enhanced the understanding of NFX's thermal properties, providing valuable insights, especially for developing NFX-based pharmaceutical products that involve thermal processing.

The biological effects and thermal degradation of NPB-22, a synthetic cannabinoid

PURPOSE

NPB-22 (quinolin-8-yl 1-pentyl-1H-indazole-3-carboxylate), Adamantyl-THPINACA (N-(1-adamantantyl)-1-[(tetrahydro-2H-pyran-4-yl)methyl]-1H-indazole-3-carboxamide), and CUMYL-4CN-B7AICA (1-(4-cyanobutyl)-N-(2-phenylpropan-2-yl)-1H- pyrrolo[2,3-b]pyridine-3-carboxamide), synthetic cannabinoids were evaluated in terms of CB1 (cannabinoid receptor type 1) and CB2 (cannabinoid receptor type 2) activities, and their biological effects when inhaled similar to cigarettes were examined.

METHODS

The half maximal effective concentration values of the aforementioned synthetic cannabinoids at the CB1 and CB2 were investigated using [35S]guanosine-5'-O-(3-thio)-triphosphate binding assays. In addition, their biological effects were evaluated using the inhalation exposure test with mice. The smoke generated was recovered by organic solvents in the midget impingers, and the thermal degradation compounds of the smoke components were identified and quantified using a liquid chromatography-photo diode array detector.

RESULTS

NPB-22 and Adamantyl-THPINACA had equivalent CB1 activity in in vitro assays. Meanwhile, NPB-22 had a weaker biological effect on some items on the inhalation exposure test than Adamantyl-THPINACA. When analyzing organic solvents in the midget impingers, it was revealed that NPB-22 was degraded to 8-quinolinol and pentyl indazole 3-carboxylic acid by combustion. In addition, these degradation compounds did not have CB1 activity.

CONCLUSION

It was estimated that the biological effects of NPB-22 on the inhalation exposure test weakened because it underwent thermal degradation by combustion, and the resultant degradation compounds did not have any CB1 activity in vitro.

Thermal degradation and oxidation of glucosinolates in model systems and Brassica vegetable broth is mediated by redox-active compounds

Glucosinolates (GLSs) are secondary plant metabolites with health-promoting effects found in Brassica vegetables. Recently, next to non-enzymatic degradation yielding nitriles, 4-(methylthio)butyl GLS (4MTB-GLS) was shown to undergo side chain oxidation during thermal treatment, forming 4-(methylsulfinyl)butyl GLS (4MSOB-GLS). Here, we investigated natural plant components and artificial analogs on their capability of altering the thermal reactivity of 4MTB-GLS in vegetable broths and model systems using buffers. Addition of ascorbic acid and dehydroascorbic acid caused varying effects: in broth samples, it increased nitrile formation, while in buffer, 4MSOB-GLS was formed. In further experiments, the antioxidant compounds quercetin and Trolox triggered the side chain oxidation of 4MTB-GLS, while H2S terminated its degradation. A synergistic effect of ascorbic acid and Fe2+ was observed, degrading 98% of 4MTB-GLS to the nitrile after 60 min of boiling. Deepening the understanding of factors that influence the non-enzymatic degradation of GLSs will help to preserve their health-promoting effects.

Improved miscibility and toughness of biological poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/poly(lactic acid) blends via melt-blending-induced thermal degradation

Polymer blending has been a facile method to resolve the brittle issue of poly(lactic acid) (PLA). Yet, miscibility becomes the primary concern that would affect the synergy effect of polymer blending. This study aimed to improve the miscibility of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) and PLA by lowering their molecular weights via a melt-blending-induced thermal degradation during mechanical mixing to form m-P34HB/PLA blends. The molecular weight of the P34HB was significantly reduced after blending, thereby improving the miscibility of the blends, as evidenced by the shift of glass transition temperatures. Also, simulation based on Flory-Huggins theory demonstrated increased miscibility with decreasing molecular weight of the polymers. Moreover, the thermal gravimetric analysis revealed that the PLA provided a higher shielding effect to the P34HB in the blends prepared by melt-blending than those by solution-blending, that the addition of PLA could retard the chain scission of P34HB and delay its degradation. The addition of m-P34HB at 20 wt% in the blend contributed to a 60-fold enhancement in the elongation at break and an increment of 4.6 folds in the Izod impact strength. The enzymatic degradation using proteinase K revealed the preferential to degrade the PLA in the blends and followed the surface erosion mechanism.

A novel material for the microbiological, oxidative, and color stability of salmon and chicken meat samples: Nanofibers obtained from sesame oil

Sesame oil nanofibers (diameter min: 286 max: 656nm), starting thermal degradation at 60 °C, were successfully obtained using the electrospinning technique in Türkiye. The distance, high voltage, and flow rate in electrospinning parameters were defined as 10 cm, 25 kV, and 0.065 mL/min. Mesophilic, psychrophilic bacteria, and yeast & molds counts of control group samples were higher (up to 1.21 log CFU/g) than those of salmon and chicken meat samples treated with sesame oil nanofibers. Thiobarbituric acid (TBA) value in control salmon meat samples stored for 8 days was defined between 0.56 and 1.48 MDA/kg (increase: 146%). However, the rise in TBA for salmon samples treated with sesame oil nanofibers was 21%. Also, nanofiber application for chicken samples limited the rapid oxidation up to 51.51% compared to control samples on the 8th day (p < 0.05). b* value (decline: 15.23 %) associated with rapid oxidation of the control group in salmon samples was more rapidly decreased than that of fish samples treated with sesame-nanofibers (b*: 12.01%) (p < 0.05). Chicken fillets b* values were more stable compared to control chicken meat samples for 8 days. Sesame oil-nanofiber application did not adversely affect the L* value color stability of all meat samples.

Enhancing styrene monomer recovery from polystyrene pyrolysis: insights from density functional theory

CONTEXT

Plastic waste pyrolysis offers a potential solution to reduce plastic accumulation, but prioritizing monomer recovery from the process is crucial to effectively address the environmental consequences of plastic accumulation. This study focuses on enhancing the yield of styrene during the pyrolysis of polystyrene by investigating thermal and kinetic data. A comprehensive investigation into the thermal degradation pathways of polystyrene is imperative to overcome the challenges associated with its waste management. The calculated bond dissociation energies reveal that the cleavage of non-terminal carbon-carbon bonds is energetically favorable, resulting in the formation of high molecular weight benzylic radicals. Based on these findings, four pyrolysis pathways are proposed, and the associated thermodynamic and kinetic parameters are determined using the DFT method. The major products identified in this study include styrene, α-methylstyrene, isopropylbenzene, methylbenzene, ethylbenzene, and methane. Furthermore, optimizing the temperature profile of the reactor is shown to enhance the recovery of styrene, thereby contributing to the reduction of plastic waste. This study provides valuable insights into the effective resource recovery from polystyrene waste pyrolysis, emphasizing the significance of managing pyrolysis conditions to achieve maximum yield. By controlling the temperature profile during the pyrolysis process, it is possible to obtain a high yield of styrene, facilitating the efficient recovery of the monomer from waste polystyrene and addressing the environmental concerns associated with plastic accumulation.

METHODS

In this study, all calculations were performed using the B3LYP/6-31G(d) level of theory with the Gaussian 16 program package. The proposed model underwent geometry optimization and frequency calculations. Transition states were optimized using the TS Berny method, and energy profiles along reaction pathways were refined using the QST3 method. The IRC method validated proposed mechanisms and investigated energy profiles. Structural models were visualized using GaussView 6.0.

Widely targeted metabolomic approach reveals dynamic changes in non-volatile and volatile metabolites of peanuts during roasting

Roasting influences the color, flavor, and antioxidant activities of peanuts. However, the biochemical mechanisms that occur during roasting are not well known. In this study, the dynamic changes in non-volatile and volatile metabolites in raw, light, and dark roasted peanuts were investigated using ultra-performance liquid chromatography with a widely targeted metabolomic approach based on tandem mass spectrometry and gas chromatography-mass spectrometry. A total of 738 non-volatile metabolites (comprising 12 subclasses) and 71 volatile metabolites (comprising 14 subclasses) were identified in raw and roasted peanuts. Significantly different non-volatile and volatile metabolites were detected. Among them, amino acids, sugars, and lipids (lysophosphatidylethanolamines and oxidized fatty acids) were found to be highly linked to flavor formation. In addition, the enhanced color and antioxidant activities of peanuts were attributed to the Maillard reaction and sugar degradation. These results provide comprehensive insights into the quality improvements of peanuts during roasting.

Spectral evidence of acetamiprid's thermal degradation products and mechanism

Herein we unequivocally identify the mechanism of zeolite-catalysed thermal degradation of pesticide, employing Fourier-transform infrared spectroscopy (FTIR), Raman and mass spectrometry following temperature decomposition (TPDe/MS). We demonstrate that Y zeolite can effectively adsorb a significant amount of acetamiprid both in a single trial (168 mg/g) and in 10 cycles (1249 mg/g) with intermittent thermal regeneration at 300 °C. Sectional vibrational analysis of acetamiprid two-stage thermal degradation is performed for pristine and supported pesticide. The acetamiprid Raman spectral changes appear at 200 °C, while partial carbonization occurs at 250 °C. The gradual disappearance of the FTIR bands of acetamiprid is seen up to 270 °C when two Raman signature bands for carbonised material emerged. The TPDe/MS profiles reveal the evolution of mass fragments - in the first step, cleavage of the CC bond occurs between the aromatic core of the molecule and its tail-end, followed by cleavage of the CN bond. The mechanism of adsorbed acetamiprid degradation follows the same step, at significantly lower temperatures, as the process is catalysed by the interaction of acetamiprid nitrogens and zeolite support. Reduced temperature degradation allows for a quick recovery process that leaves 65% efficacy after 10 cycles. After numerous cycles of recovery, a subsequent one-time heat treatment at 700 °C completely restores initial efficacy. The efficient adsorption, novel details on degradation mechanism and ease of regeneration procedure place the Y zeolite at the forefront of future all-encompassing environmental solutions.

Spectroscopic studies on thermal degradation and quantitative prediction on acid value of edible oil during frying by Raman spectroscopy

The health risks posed by harmful substances resulting from the thermal degradation of frying oils are of great concern. Characteristic peak intensity ratios (PIRs) screened from Raman spectra were used to characterize the thermal degradation. High correlation coefficients between PIRs and acid values (AVs) of 0.972 (linear fitting), 0.984 (logarithmic function fitting), and 0.954 (linear fitting) for fried soybean oil, canola oil, and palm oil, were obtained at the PIRs of I₁₂₆₇/I₁₇₄₉, I₁₂₆₇/I₁₆₅₉, and I₁₂₆₇/I₁₇₄₉, respectively. The highly correlated PIRs common to the three oils were determined by Pearson's correlation coefficient combined with heat maps. To accommodate both linear and nonlinear features, a global model for predicting AVs of multi-varieties frying oils was constructed using a least-squares support vector machine algorithm, and the results performed well with a root mean square error of prediction of 0.016 and a ratio of prediction to deviation of 11.351. The whole results demonstrate that Raman spectroscopy could characterize the thermal degradation and has excellent quantitative analysis ability for food control based on AV in frying oils, thus providing a new approach to quality control of frying oils.

Production of liquid hydrocarbons by thermo-acidic method from waste high-density polyethylene

AIMS

The study explains the production of useful liquid hydrocarbons by thermo-acidic catalytic thermal degradation of waste high-density polyethylene. A comparative study of the liquid samples with or without catalysts.

BACKGROUND

Energy demand is high in the world. Waste plastic conversion is nowadays a concern of interest research for scientists. HDPE (High-density polyethylene) is the most common plastic used in households. Different types of catalysts and techniques have been used in the alteration process of waste HDPE. This paper deals with the kandite group of catalyst kaolin and the montmorillonite group of catalyst sodium bentonite in acid-activated mutated form.

OBJECTIVE

This paper aims to explore the prominent utilization of kaolin clay and sodium bentonite clay minerals as a catalyst for the alteration of waste HDPE into fuel resources and to develop a cost-effective recycling experimental set-up for plastic waste conversion.

METHOD

Thermo-catalytic acid activation has been done for clay mutation. Hydrochloric acid-activated catalysts have been used in this study. FT-IR (Fourier Transform Infrared Spectroscopy) and GC-MS (Gas Chromatography and Mass Spectrometer) techniques have been used to explore the prominent compounds in the product samples.

RESULT

Maximum energy per photon for RO (Parent Oil/Raw Oil) and AO(Acid treated thermo-catalytic oil) samples are respectively 58034.01×1024 Joules and 59271.40×1024 Joules concerning wave numbers 2921.42 and 2983.71 cm-1. Compounds of functional groups C-CH3, CH2, alkenes, and CH3 have been identified for RO and AO samples. Less gaseous hydrocarbons 31.79% (outcomes) or 29.66 % (production yield) and 150.06 % of increment in wax have been calculated after using acid-treated catalysts. Aliphatic compounds like alkanes and alkenes are present in the samples.

CONCLUSION

A mixture of acid-treated kaolin and acid-treated sodium bentonite as the catalysts for degrading waste HDPE into liquid oil greatly reduces wax formation. Average outcomes and production of liquid hydrocarbons are good results with the acid-treated catalytic degradation of HDPE waste. One remarkable fact is that the yield percentage of liquid products is higher in acid-activated catalytic thermal degradation.

A review on the scope of remediating chlorinated paraffin contaminated water bodies and soils/sediments

Chlorinated paraffins (CPs) involve a wide range of complex mixtures of chlorinated alkanes. The versatility of their physicochemical properties and their wide range of use has turned them into ubiquitous materials. This review covers the scope of remediating CP-contaminated water bodies and soil/sediments via thermal, photolytic, photocatalytic, nanoscale zero-valent iron (NZVI), microbial and plant-based remediation techniques. Thermal treatments above 800 °C can lead to almost 100 % degradation of CPs by forming chlorinated polyaromatic hydrocarbons and thus should be supported with appropriate pollution control measures leading to high operational and maintenance costs. The hydrophobic nature of CPs lowers their water solubility and reduces their subsequent photolytic degradation. However, photocatalysis can have considerably higher degradation efficiency and generates mineralized end products. The NZVI also showed promising CP removal efficiency, especially at lower pH, which is challenging to achieve during field application. CPs can also be bioremediated by introducing both naturally occurring bacteria and also by engineered bacterial strains which are capable of producing specific enzymes (like LinA2 and LinB) to catalyze CP degradation. Depending on the type of CP, bioremediation can even achieve a dechlorination efficiency of >90 %. Moreover, enhanced degradation rates can be achieved through biostimulation. Phytoremediation has also exhibited CP bioaccumulation and transformation tendencies, both at lab-scale and in field-scale studies. The future research scope can include developing more definitive analytical techniques, toxicity and risk assessment studies of CPs and their degradation products, and technoeconomic and environmental assessment of different remediation approaches.

Effects of different types of flame-retardant treatment on the flame performance of polyurethane/wood-flour composites

To improve the flammability of foamed polyurethane/wood-flour composites (FWPC), ammonium polyphosphate (APP) was used as a flame retardant to modified FWPC. The effects of different flame treatment processes on flame performance, smoke suppression, thermal property, and surface micrographs of flame retardant FWPC were investigated. The results showed that FWPC with the addition or impregnation process both improved the combustion behaviors. Compared with the addition process, FWPC-impregnation (FWPC-I) had a lower total heat release (THR), lower peak heat release rate (PHRR), prolonged time to ignition (TTI), more residues, and better combustion safety. FWPC-I had the highest residual carbon rate reaching 39.98%. A flame-retardant layer containing the P-O group was formed in the residual carbon of FWPC-I. Although APP had negative effects on the physical properties of FWPC, it was an effective flame-retardant ability for foamed polyurethane/wood-flour composites.

Investigation of the degradation and in-situ amorphization of the enantiomeric drug escitalopram oxalate during Fused Deposition Modeling (FDM) 3D printing

Hot-melt extrusion (HME) and subsequent FDM 3D printing offer great potential opportunities in the formulation development and production of customized oral dosage forms with poorly soluble drugs. However, thermal stress within these processes can be challenging for thermo-sensitive drugs. In this work, three different formulations were prepared to investigate the degradation and the solid state of the thermo-sensitive and poorly soluble drug escitalopram oxalate (ESC-OX) during the two heat-intensive processes HME and FDM 3D printing. For this purpose, hydroxypropyl methyl cellulose (HPMC) and basic butylated methacrylate copolymer (bPMMA) were chosen as polymers. DSC and XRD measurements revealed that ESC-OX is amorphous in the HPMC based formulations in both, extrudates and 3D printed tablets. In contrast, in-situ amorphization of the drug from crystalline state in bPMMA filaments was observed during FDM 3D printing. With regard to the content, it was found that degradation of ESC-OX in extrudates with bPMMA could be avoided and in 3D printed tablets almost fully reduced. Furthermore, a possible conversion into the R-enantiomer in the formulation with bPMMA could be excluded using a chiral column. Compared to the commercial product Cipralex®, drug release from extrudates and tablets with bPMMA was slower but still qualified as immediate drug release.

Thermal degradation model of used surgical masks based on machine learning methodology

Background

The COVID-19 pandemic has leveraged facial masks to be one of the most effective measures to prevent the spread of the virus, which thereby has exponentially increased the usage of facial masks that lead to medical waste mismanagements which pose a serious threat to life. Thermal degradation or pyrolysis is an effective treatment method for the used facial mask wastes and this study aims to investigate the thermal degradation of the same.

Methods

Predicted the TGA experimental curves of the mask components using a Machine Learning model known as Artificial Neural Network (ANN).

Significant findings

Three different parts of the mask namely- ribbon, body, and corner were separated and used for the analysis. The thermal degradation behavior is studied using Thermogravimetric Analysis (TGA) and this is crucial for determining the reactivity of the individual mask components as they are subjected to a range of temperatures. Using the curves obtained from TGA, kinetic parameters such as Activation energy (E) and Pre-exponential factor (A) were estimated using the Coats-Redfern model-fitting method. Using the determined kinetic parameters, thermodynamic quantities such as a change in Enthalpy (ΔH), Entropy (ΔS), and Gibbs-Free energy (ΔG) were also calculated. Since TGA is a costly and time-consuming process, this study attempted to predict the TGA experimental curves of the mask components using a Machine Learning model known as Artificial Neural Network (ANN). The dataset obtained at a heating rate of 10°C/min was used to train the 3 different neural networks corresponding to the mask components and it showed an excellent agreement with experimental data (R² > 0.99). Through this study, a complex chemical process such as thermal degradation was modelled using Machine Learning based on available experimental parameters without delving into the intricacies and complexities of the process.

Thermal degradation and combustion properties of most popular synthetic biodegradable polymers

Various products made from biodegradable polymers have been increasing rapidly in the market since the use of non-biodegradable materials has been banned, particularly for the disabled packaging materials. Burning remains the most popular method that is increasingly used in treating city wastes. The impact of these polymers on environmental during thermal degradation and combustion is an important issue for city waste management. In this work, the thermal degradation and combustion behaviours of the most popular synthetic biodegradable polymers in the market, poly(lactide acid) (PLA), poly(e-caprolactone) (PCL), poly(butylene succinate) (PBS), poly(butylene adipate-co-terephthalate) (PBAT) and polyhydroxyalkenoates (PHA), are investigated. Both isothermal and non-isothermal thermal decomposition in oxygen and nitrogen environment were studied using thermogravimetric analysis combining with differential scanning calorimeter and coupled with Fourier transform infrared spectroscopy and gas chromatograph/mass spectroscopy. The combustion behaviour was investigated by a combustion colorimeter. The study results show that thermal degradation temperatures are PCL > PBS > PLA > PBAT > PHA. The thermal decomposition of all the polyesters started from scission reaction (cis-elimination), and then a stereoselective cis-elimination, which resulted in the formation of trans-crotonic acid and its oligomers. They all decomposed into CO₂ and water in excess oxygen environment above 800°C. Various chemical products with smaller molecules were detected under oxygen-free conditions, including oligomers and unsaturated carboxylic acid. The order of the total heat release of the materials from high to low is as follows: PHA > PCL > PBAT > PBS > PLA. The combustion values of these polyesters are lower than those of polyolefins; thus, they will not damage furnace used currently. The results provide some important and useful data for managing these new city waste.

Polyphenol extracts from Ascophyllum nodosum protected sea cucumber (Apostichopus japonicas) body wall against thermal degradation during tenderization

To retard the protein degradation during sea cucumber processing, polyphenol extracts from Ascophyllum nodosum (PhE) was used as a potential antioxidant to maintain the structural integrity of sea cucumber body wall. Accordingly, the protection effects of PhE (0, 0.5, 1.0 and 1.5 mg PhE/g SFBW) against thermal degradation of the solid fragments of body wall (SFBW) have been investigated in order to evaluate their impact on the oxidation level and structural changes. Electronic Spin Resonance results showed that PhE could significantly inhibit the occurrence of oxidation by scavenging the free radicals. The effect of PhE on chemical analysis of soluble matters in SFBW was characterized by SDS-PAGE and HPLC. Compared with thermally treated SFBW, samples with PhE presented a decrease in protein dissolution. Thermal treatment resulted in the disintegration of collagen fibrils and fibril bundles in SFBW samples, while the density of collagen fibrils was increased, and the porosity decreased in samples with PhE. The results of FTIR and intrinsic tryptophan fluorescence confirmed that the structures of SFBW were modified by PhE. Besides, the denaturing temperature and decomposition temperature were both improved with the addition of PhE. These results suggested that PhE appeared to have a positive effect on lowering oxidation and improving thermostability and structural stability of SFBW, which could provide a theoretical basis for protecting sea cucumber body wall against degradation during thermal tenderization.

Sustainable valorization of water hyacinth waste pollutant via pyrolysis for advance microbial fuel investigation

Present study has been focused on the bio-energy potential of waste biomass (water hyacinth leaves and its stem). Pyrolysis of both biomasses were investigated at five different heating rates (5-25 ^°C/min) using thermogravimetric analyzer. For both biomasses, maximum thermal degradation occurred within the temperature range of 200-400 °C, which is the active pyrolytic zone. Three non-iso-conversional (degradation models) including the Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Starink were used to calculate the activation energy of both biomasses. The activation energy was around 92-98 kJ/mol for water hyacinth leaves and 151-153 kJ/mol for water hyacinth stems. The results suggest that these low-cost abundantly available biomasses have a good potential for the production of solid bio-fuel.

Masks thermal degradation as an alternative of waste valorization on the COVID-19 pandemic: A kinetic study

The COVID-19 pandemic generated a new dynamic around waste management. Personal protective equipment such as masks, gloves, and face shields were essential to prevent the spread of the disease. However, despite the increase in waste, no technical alternatives were foreseen for the recovery of these wastes, which are made up of materials that can be valued for energy recovery. It is essential to design processes such as waste to energy to promote the circular economy. Therefore, techniques such as pyrolysis and thermal oxidative decomposition of waste materials need to be studied and scaled up, for which kinetic models and thermodynamic parameters are required to allow the design of this reaction equipment. This work develops kinetic models of the thermal degradation process by pyrolysis as an alternative for energy recovery of used masks generated by the COVID-19 pandemic. The wasted masks were isolated for 72 h for virus inactivation and characterized by FTIR-ATR spectroscopy, elemental analysis, and determinate the higher calorific value (HCV). The composition of the wasted masks included polypropylene, polyethylene terephthalate, nylon, and spandex, with higher calorific values than traditional fuels. For this reason, they are susceptible to value as an energetic material. Thermal degradation was performed by thermogravimetric analysis at different heating rates in N₂ atmosphere. The gases produced were characterized by gas chromatography and mass spectrometry. The kinetic model was based on the mass loss of the masks on the thermal degradation, then calculated activation energies, reaction orders, pre-exponential factors, and thermodynamic parameters. Kinetics models such as Coats and Redfern, Horowitz and Metzger, Kissinger-Akahira-Sunose were studied to find the best-fit models between the experimental and calculated data. The kinetic and thermodynamic parameters of the thermal degradation processes demonstrated the feasibility and high potential of recovery of these residues with conversions higher than 89.26% and obtaining long-chain branched hydrocarbons, cyclic hydrocarbons, and CO₂ as products.

Recent advances on PFAS degradation via thermal and nonthermal methods

Per- and polyfluoroalkyl substances (PFAS) are a set of synthetic chemicals which contain several carbon-fluorine (C-F) bonds and have been in production for the past eight decades. PFAS have been used in several industrial and consumer products including nonstick pans, food packaging, firefighting foams, and carpeting. PFAS require proper investigations worldwide due to their omnipresence in the biotic environment and the resulting pollution to drinking water sources. These harmful chemicals have been associated with adverse health effects such as liver damage, cancer, low fertility, hormone subjugation, and thyroid illness. In addition, these fluorinated compounds show high chemical, thermal, biological, hydrolytic, photochemical, and oxidative stability. Therefore, effective treatment processes are required for the removal and degradation of PFAS from wastewater, drinking water, and groundwater. Previous review papers have provided excellent summaries on PFAS treatment technologies, but the focus has been on the elimination efficiency without providing mechanistic understanding of removal/degradation pathways. The present review summarizes a comprehensive examination of various thermal and non-thermal PFAS destruction technologies. It includes sonochemical/ultrasound degradation, microwave hydrothermal treatment, subcritical or supercritical treatment, electrical discharge plasma technology, thermal destruction methods/incinerations, low/high-temperature thermal desorption process, vapor energy generator (VEG) technology and mechanochemical destruction. The background, degradation mechanisms/pathways, and advances of each remediation process are discussed in detail in this review.

Co-pyrolysis of neem wood bark and low-density polyethylene: influence of plastic on pyrolysis product distribution and bio-oil characterization

In this study, the investigation on the effect of plastic during co-pyrolysis with biomass was carried out in a fixed reactor. Pyrolysis of neem wood bark (NB), low density polyethylene (LDPE) and their blends at different ratios was performed in order to evaluate the product distribution. The effects of reaction temperature and NB-to-LDPE blend ratio on product distribution and the chemical compositions of pyrolysis oil were examined. The co-pyrolysis of NB and LDPE increased the yield and quality of the bio-oil. The experiments were conducted under different LDPE addition percentages such as 20%, 40%, 50%, 60% and 80%. Under the optimum experimental condition of 60% addition of LDPE and a temperature of 450 °C, the maximum yield of bio-oil (64.8 wt%) and hydrocarbon (75.2%) was achieved with the lowest yield of oxygenated compounds. The calorific value of the co-pyrolysis oil was found to be higher than that of the NB pyrolysis oil. The relationship between NB and LDPE during co-pyrolysis was validated with the help of gas chromatography-mass spectrometry (GC-MS) analysis, which showed decreased oxygenated compounds.

Completion of the impurity profile of lymecycline: Formal identification of impurities E and F

Lymecycline is the drug substance (DS) used in the Galderma drug product Tetralysal® capsules with 7 impurities currently described in the pharmacopeia labelled as A-G. In the current monograph, the structural identity of all impurities except E and F have been formally identified. In this manuscript, through both formal synthesis and preparative chromatography, we are the first group to confirm the structural identity, response factor of Impurity F and conditions which exacerbate the formation of both impurities.

Effects of heating rate on thermal degradation behavior and kinetics of representative thermoplastic wastes

Waste thermoplastics are the most common solid wastes, and thermal degradation has excellent advantages in the disposal of these wastes and obtaining valuable hydrocarbon fuels. As a significant factor, the heating rate is crucial to the thermal degradation process. Consequently, thermal degradation behavior and kinetics of representative thermoplastics under different heating rates were investigated by using thermogravimetric analysis and differential scanning calorimetry in the air. Kinetic parameters were estimated by using the Coats-Redfern method. Subsequently, the Shuffled Complex Evolution (SCE) method was used to optimize kinetic parameters, and the optimized results were compared with the calculated kinetics of distributed activation energy model (DAEM) method to find the effects of heating rate on kinetic parameters. The results showed that with the increase of heating rate, thermogravimetric curves moved to the right, which corresponded to a higher temperature range. The number of mass loss rate peaks and exothermic peaks decreased. Additionally, activation energy was the same at the determined minimum and maximum heating rates, and other heating rates had little effect on kinetic parameters. Moreover, the calculated activation energy of the DAEM method at the minimum heating rate of 5 K/min was closest to the optimized values of the SCE method, indicating that the lower the minimum heating rate was, the more accurate the activation energy was.

Synthesis, characterization, thermal properties, antimicrobial evaluation, ADMET study, and molecular docking simulation of new mono Cu (II) and Zn (II) complexes with 2-oxoindole derivatives

One of the interesting research fields is developing and assessing novel metal-containing medications. A new isatin-3-thiosemicarbazone derivative 4 was synthesized by two different methods based on hydrazone derivatives 2 and 3. Additionally, the chelation of thiosemicarbazone with copper (II) and zinc (II) forms a monobasic tridentate (ONS) complex with two five-member rings and a tetrahedral geometry structure. The structure of synthesized complexes was characterized using elemental analysis, FT-IR, mass spectra, and ¹H/¹³C NMR. Thermogravimetric analysis revealed the upgrading of the thermal stability of metal complexes compared to their thiosemicarbazone ligand. The stoichiometric ratio of the coordination confirmed the formation of 1:1 (M: L) stoichiometry. In vitro antimicrobial activity was screened against two gram-positive, two gram-negative, and one fungal strain. Both ligand 4 and Zn complex 6 displayed high antimicrobial activity compared with copper complex 5 based on the zone of inhibition. Further, MIC and MBC were determined for both zinc and ligand. The zinc complex 6 displayed excellent antimicrobial activity with (MIC = 3.9-27.77 μg/mL) against bacterial strains and (MIC = 7.81 μg/mL) against C. albicans, as well as exhibited MBC values ranging between (MBC = 6.51-45.58 μg/mL) and (MFC = 13.58 μg/mL), respectively, and demonstrated bactericidal and fungicidal behavior. The in-silico ADMET study for ligand and two complexes were determined and showed non-AMES toxicity, non-carcinogenic, and obey the rule of five. A comparative docking study provided more insight into the binding mechanisms and suggested that antimicrobial activity may be due to inhibition of different targets.

Thermal degradation of stigmasterol under the deodorisation temperature exposure alone and in edible corn oil

Phytosterols are commonly found in vegetable oils and possess health benefits for humans. While investigating the chemical conversion of stigmasterol at deodorisation temperatures, gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) experiments led to the identification of 5-ethyl-6-methyl-3-heptene-2-one, 3-hydoxy-steroid, 3-ketostigmasterol, and 3,7-diketostigmasterol as by-products. The identification of these compounds assisted in the interpretation of the stigmasterol oligomers characterised by high-pressure size exclusion chromatography (HPSEC). A similar analysis was conducted in stripped corn oil at the deodorisation temperatures. As such, 5-ethyl-6-methyl-3-heptene-2-one, 3-hydoxy-steroid, 3-ketostigmasterol and 3,7-diketostigmasterol were also detected in stripped corn oil, while the contents of 3-hydoxy-steroid and 5-ethyl-6-methyl-3-heptene-2-one were higher than those of 3-ketostigmasterol, as revealed by quantum chemical simulations. In addition, stripped corn oil exhibited the characteristic of preventing stigmasterol degradation below 200 °C, whereas it enhanced the chemical conversion (such as esterification and degradation) of stigmasterol at higher temperatures.

Assessment of flumioxazin soil behavior and thermal stability in aqueous solutions

Flumioxazin is a preemergence, N-phenylpththalimide herbicide that can be applied to control a broad spectrum of weeds in a variety of cropping systems. Limited information exists concerning the environmental fate of flumioxazin, therefore the present studies investigated the kinetic behavior of flumioxazin in soil and aqueous solution using field and analytical techniques to establish its degradation properties. Flumioxazin half-life in a Greenville sandy clay loam and Faceville loamy sand was 26.6 d. Flumioxazin was determined to have a groundwater ubiquity score of 1.79, indicating a low leachability potential. There was an inverse correlation between flumioxazin concentration in soil, rainfall, and solar radiation. There was no direct correlation between flumioxazin concentration and soil temperature. Flumioxazin activation energy was 58.4 (±1.2) kJ mol^-1 with a Q₁₀ value of 2.2. Even at the lowest amount of solar radiation and soil temperature, the energy from these environmental measures exceeded the activation energy needed for flumioxazin degradation. Flumioxazin stability in solution and field dissipation indicate that, with the input of thermal energy, degradation can be rapid.

A novel method for the microencapsulation of curcumin by high-pressure processing for enhancing the stability and preservation

Curcumin is used for the development of new pharmaceutical and food products, but its application is generally hindered by the poor solubility of curcumin and thermal instability during storage and processing. In this study, the liposomes of curcumin (cur-liposomes) were prepared by a novel combination of ethanol injection and high-pressure processing (HPP) to enhance the stability and preservation of curcumin. The pasteurization, mean particle size, size distribution, and encapsulation efficiency of cur-liposomes and the kinetics of their thermal degradation were also investigated in this research. From the results, the kinetic rate constants of curcumin in samples of free curcumin and cur-liposome at 25 °C were found to be 1.6 × 10^-3 and 0.8 × 10^-3 min^-1, respectively. The phospholipid bilayer structure could protect curcumin. The results propose that the HPP method for liposome preparation is superior to the probe-sonication method in terms of stability, encapsulation efficiency, and homogeneity. Furthermore, the preparation of cur-liposomes by HPP with a hydrostatic pressure of 200 MPa could maintain the optimal particle size (206.4 nm) and polydispersity index (0.19). Conclusively, the combination of ethanol injection and HPP can not only successfully inactivate the microorganisms during liposome preparation for microencapsulation of bioactive compounds but also effectively preventthe thermal degradation of heat-sensitive substances in non-thermal processing for practical applications.

Acceleration of the thermal degradation of PETN in the microdroplets flow reactor

Thermal degradation of pentaerythritol tetranitrate (PETN) was investigated in microdroplets within a heated capillary used as a flow reactor. The thermal degradation was monitored by aerodynamic thermal breakup droplet ionization mass spectrometry. It was shown that the PETN degradation in microdroplets occurs much faster than the bulk reaction (by 4-5 orders of magnitude). The effect of the capillary material [stainless steel (Fe, Cr), copper (Cu), or fused quartz (SiO₂)] on the thermal PETN degradation in microdroplets of water or acetonitrile was studied next. The capillary material affected the rate of thermal PETN degradation much more weakly than did the use of microdroplets (pure Cu was most conducive to the degradation). Kinetic parameters (activation energy and the frequency factor) of the PETN degradation for all the studied materials of the flow-through reactor and the solvents were estimated under the assumption that the thermal degradation is a first-order reaction. Implications of the acceleration of PETN degradation in microdroplets are discussed.

Improving chemical stability of resveratrol in hot melt extrusion based on formation of eutectic with nicotinamide

Hot melt extrusion (HME) is a technique applied in the preparation of pharmaceutical amorphous solid dispersions (ASD). Notably it is important to prevent thermal degradation of heat-sensitive drugs during HME. In this study, we present a new strategy to improve chemical stability of pharmaceutical compounds during HME through the formation of eutectics with small molecules. Resveratrol (RES) was selected as the model compound because it is a heat-liable natural product with a very high melting point of 267 °C. When heated at its melting point for 3 min, it degrades by 40%. RES can co-crystallize with nicotinamide (NIC) in solution, however, it can only form a eutectic with NIC during heating. HPMCAS was selected as the polymer matrix and the drug loading of RES was fixed as 20% (weight ratio). The lowest extrusion temperature that can result to RES-HPMCAS ASD is 215 °C. At this temperature, RES shows 7.36% degradation during extrusion. Replacement of 21.4% HPMCAS with NIC decreased the melting temperature of NIC and thus lowered the minimal extrusion temperature to 155 °C. This effectively prevented thermal degradation of RES without negatively affecting non-sink dissolution. The only extra cost for this method is stricter storage conditions (low temperature and low humidity) due to the low glass transition temperature of NIC. Similar strategy may be applied to other heat-liable drugs in similar ways. This study demonstrates the use of eutectic formation for preventing thermal degradation of drug during extrusion of ASD.

Thermal degradation of metabolites in urine using multiple isotope-labelled internal standards for off-line GC metabolomics - effects of injector and oven temperatures

Thermal processes are widely used in small molecule chemical analysis and metabolomics for derivatization, vaporization, chromatography, and ionization, especially in gas chromatography mass spectrometry (GC/MS). An optimized derivatization protocol has been successfully applied using multiple isotope labelled analytical internal standards of selected deuterated and ¹³C selected compounds, covering a range of different groups of metabolites for non-automated GC metabolomics (off-line). Moreover, the study was also realized in a pooled urine sample, following metabolic profiling. A study of thermal degradation of metabolites due to GC inlet and oven programs (fast, slow) was performed, where the results indicated that both GC oven programs (fast and slow) negatively affected the thermal stability of the metabolites, while the fast-ramp GC program also suppressed MS signals. However, the use of multiple internal standards can overcome this drawback. The application of extended temperature ramp GC program presented identical behaviour on metabolite stability and better chromatographic separation combined with much lower signal suppression, compared to a short temperature ramp program. No effects were observed for organic acids, fatty acids, sugars and sugar alcohols, while significant differences were observed for amino acids. GC metabolomics is a strong tool that can facilitate analysis, but special attention is required for sampling handling and heating, before and during the GC analysis. The use and application of multiple multi-group internal standards is highly recommended.

Chloramphenicol loaded polylactide melt electrospun scaffolds for biomedical applications

Melt electrospinning of polylactide (PLA) loaded with chloramphenicol (CAM) has been performed and characteristics of fibers, physical properties of scaffolds, CAM release behavior, antibacterial properties and biocompatibility have been evaluated. The interest of CAM loaded samples is nowadays enhanced for biomedical applications since this antibiotic has been demonstrated to be efficient for the treatment of cancer. Melt electrospinning has been selected as an ideal preparation process because it avoids the use of toxic solvents which are harmful to the environment and could be problematic for biomedical applications. The electrospinning process rendered fibers with a relatively large diameter (between 20 μm and 40 μm depending on the load) and minimum polymer degradation. Characteristics of melt electrospun scaffolds were also compared with those prepared by solution electrospinning. Differences consisted in a more sustained release and a higher biocompatibility for the melt processed samples. Bactericide effect was evaluated as an evidence of the maintenance of the CAM bioactivity after melt processing at high temperature and the slower release caused by the relatively high diameter of the constitutive fibers. Since pure CAM showed thermal degradation at temperatures relatively close to the PLA melting temperature, a complete analysis of the degradation process of pure CAM as well as of PLA samples loaded with CAM was performed. The Invariant Kinetic Parameters method allowed determining an initial decomposition step that followed an autoaccelatory Avrami model, and then an autocatalytic decomposition reaction took place for conversions higher than 50%. Dispersion in the PLA matrix enhances the thermal stability of the antibiotic, with an onset temperature of degradation that was higher by 16 °C in the melt-electrospun fibers than in the liquid state of pure CAM.

Effect of granular activated carbon and other porous materials on thermal decomposition of per- and polyfluoroalkyl substances: Mechanisms and implications for water purification

Thermal treatment is routinely used to reactivate the spent granular activated carbon (GAC) from water purification facilities. It is also an integral part of sewage sludge treatment and municipal solid waste management. This study presents a detailed investigation of the fate of per- and polyfluoroalkyl substances (PFAS) and one PFAS alternative (GenX) in thermal processes, focusing on the effect of GAC. We demonstrate that the thermolysis of perfluoroalkyl carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), and GenX can occur at temperatures of 150‒200 °C. Three temperature zones were discovered for PFOA, including a stable and nonvolatile zone (≤90 °C), a phase-transfer and thermal decomposition zone (90‒400 °C), and a fast decomposition zone (≥400 °C). The thermal decomposition began with the homolysis of a C‒C bond next to the carboxyl group of PFCAs, which formed unstable perfluoroalkyl radicals. Dual decomposition pathways seem to exist. The addition of a highly porous adsorbent, such as GAC or a copolymer resin, compressed the intermediate sublimation zone of PFCAs, changed their thermal decomposition pathways, and increased the decomposition rate constant by up to 150-fold at 250 °C. The results indicate that the observed thermal decomposition acceleration was linked to the adsorption of gas-phase PFCA molecules on GAC. The presence of non-activated charcoals/biochars with a low affinity for PFOA did not accelerate its thermal decomposition, suggesting that the π electron-rich, polyaromatic surface of charcoal/GAC played an insignificant role compared to the adsorbent's porosity. Overall, the results indicate that (1) substantial decomposition of PFCAs and GenX during conventional thermal GAC/sludge/waste treatment is very likely, and (2) the presence or addition of GAC or other highly porous materials can accelerate thermal PFAS decomposition and alter decomposition pathways.

Thermal Processing of a Degradable Carboxylic Acid-Functionalized Polycarbonate into Scaffolds for Tissue Engineering

Degradable polymers are often desirable for the fabrication of medical implants, but thermal processing of these polymers is a challenge. We describe here how these problems can be addressed by discussing the extrusion of fibers and injection molding of bone pins from a hydrolytically degradable tyrosine-derived polycarbonate. Our initial attempts produced fibers and pins with bubbles, voids, and discoloration, and resulted in the formation of large polymer plugs that seized screws and blocked extruder dies. The material and process parameters that contribute to these issues were investigated by studying the physical and chemical changes that occur during processing. Differential scanning calorimetry (DSC) scans and thermogravimetric analysis combined with IR (TGA-IR) analysis revealed the role of residual moisture and residual solvents that in conjunction with heat cause degradation and crosslinking as indicated by gel permeation chromatography (GPC). Rheology and melt-flow index measurements were useful in characterizing the extent of dependence of polymer viscosity on temperature and molecular weight. With these insights, we could process our polymer into fibers and rods by controlling residual moisture, time and temperature, and by adjusting processing parameters in real-time. The systematic approach described here is applicable to other degradable polymers that are difficult to process.

Thermolabile essential oils, aromas and flavours: Degradation pathways, effect of thermal processing and alteration of sensory quality

Plant-based aroma chemicals, constituting the essential oils play a great role as the natural flavours and preservatives in the food industries. Many of these metabolites are susceptible to degradation under heat (i.e. thermolabile aroma chemicals) which may influence the organoleptic properties of the end-products e.g. essential oil, oleoresin, dry herb, tea and packaged juice. The current review identified in total 42 thermolabile aroma and/or flavour molecules belonging to monoterpenoids, sesquiterpenoids and phenolics. The probable pathway of their degradation and its promoting conditions were also described. Degradation pathways were categorized into five major classes including oxidation, C-C bond cleavage, elimination, hydrolysis and rearrangement. Numerous evidences were cited in support of the thermosensitivity of these phytochemicals under pyrolytic, thermal heating or gas chromatographic conditions. Various post-harvest processes involved in the manufacturing such as drying and distillation of the crops or thermal treatment of the food-products for storage were highlighted as the root cause of degradation. The influence of thermolabile aroma chemicals to maintain the sensory quality of the end-products such as citrus juices, floral oils and thermally cooked foods was discussed in detail. In the present article, detailed insight into the chemical and sensory aspects of thermosensitive aromas and flavours was provided, covering the period from 1990 up to 2020.

Thermostable and rheological properties of natural and genetically engineered xanthan gums in different solutions at high temperature

Thermostability is an important indicator to evaluate xanthan applied in the oilfield industry. Besides reductive agents, salts, and pH, the inherent primary structure is also an important determinant of thermostability. In this work, the thermal conformational transition and degradation of natural xanthan XG and variants XG-A0, XG-AA, and XG-0P dissolved in different solvents were compared. Acetylated XG-A0 and XG-AA both showed the highest initial conformational transition temperature (Tm₀) in distilled water, NaCl, and CaCl₂ brines. Additionally, the variant XG-A0 dissolved in water was more thermostable although its acetyl group was hydrolyzed easily after a hot-rolling test at 110 °C. Thermostability could be reinforced by adding antioxidant Na₂SO₃ and saturated NaCl through improving Tm₀ value or inhibiting degradation of the molecular chain and acyl groups. Furthermore, pyruvyl-rich XG-0P dissolved in saturated NaCl showing multi-stranded helix structure was also stable after a hot-rolling process. Therefore, xanthan variants, as biological products, will have broader application potential in the oilfield industry.

Reviewing the thermo-chemical recycling of waste polyurethane foam

The worldwide production of polymeric foam materials is growing due to their advantageous properties of light weight, high thermal insulation, good strength, resistance and rigidity. Society creates ever increasing amounts of poly-urethane (PU) waste. A major part of this waste can be recycled or recovered in order to be put into further use. The PU industry is committed to assist and play its part in the process. The recycling and recovery of PU foam cover a range of mechanical, physical, chemical and thermo-chemical processes. In addition to the well-documented mechanical and chemical processing options, thermo-chemical treatments are important either as ultimate disposal (incineration) or towards feedstock recovery, leading to different products according to the thermal conditions of the treatment. The review focuses on these thermo-chemical and thermal processes. As far as pyrolysis is concerned, TDI and mostly polyol can be recovered. The highest recovery yields of TDI and polyols occur at low temperatures (150-200 °C). It is however clear from literature that pure feedstock will not be produced, and that a further upgrading of the condensate will be needed, together with a thermal or alternative treatment of the non-condensables. Gasification towards syngas has been studied on a larger and industrial scale. Its application would need the location of the PU treatment plant close to a chemical plant, if the syngas is to be valorized or considered in conjunction with a gas-fired CHP plant. Incineration has been studied mostly in a co-firing scheme. Potentially toxic emissions from PU combustion can be catered for by the common flue gas cleaning behind the incineration itself, making this solution less evident as a stand-alone option: the combination with other wastes (such as municipal solid waste) in MSWI's seems the indicated route to go.

Thermal degradation and lifetime of β-chitin from Dosidicus gigas squid pen: Effect of impact at 9.7 GPa and a comparative study with α-chitin

The kinetics of thermal degradation of β-chitin extracted from Dosidicus gigas squid pen, was studied at normal conditions as well as after being subjected to the action of high-pressure impact of 9.7 GPa. The integral iso-conversional procedure of Kissinger-Akahira-Sunose (KAS) recommended by the ICTAC kinetics committee was applied to the non-isothermal data obtained from thermogravimetry (TGA). Lifetimes were predicted without assumption of any reaction model. Heating rates of β = 10, 15, 20 and 25 °C/min under nitrogen atmosphere were used from room temperature to 1300 °C. A comparative study with α-chitin was performed. All the samples were structurally and chemically characterized by several techniques. The extracted β-chitin was found to be in the monohydrate form; while with the action of high-pressure impact, it was transformed into β-chitin dehydrate showing slightly higher stability. Reliable prediction for lifetimes considering working temperatures over 425 K was found for α and β-chitin.

Analysis of non-derivatized 2-(4-R-2,5-dimethoxyphenyl)-N-[(2-hydroxyphenyl)methyl]ethanamine using short column gas chromatography - mass spectrometry

The 25R-NBOH family is a group of thermally labile compounds that are relevant for forensic sciences and traditionally analyzed by GC-MS after derivatization - a step that is time consuming in a routine work. In this paper, the use of short analytical columns (4 and 10 m) showed to decrease compound degradation in the GC oven during chromatographic separation and to allow the analysis of non-derivatized 25R-NBOH compounds by GC-MS. A shorter column demanded a higher gas flow rate, and both factors decreased residence time of the analytes in the column and their degradation. The inlet temperature (250° C or 280°C) did not impact the response of 25R-NBOH. A 25R-NBOH fragmentation pathway by electron ionization was also presented for the first time. The GC-MS method with a 4 m column was successfully applied to other compounds of forensic interest, and it can be tested in the analysis of biological samples in toxicological investigations.

Recent advances in the removal of persistent organic pollutants (POPs) using multifunctional materials:a review

Persistent organic pollutants (POPs) have gained heightened attentions in recent years owing to their persistent property and hazard influence on wild life and human beings. Removal of POPs using varieties of multifunctional materials have shown a promising prospect compared with conventional treatments. Herein, three main categories, including thermal degradation, electrochemical remediation, as well as photocatalytic degradation with the use of diverse catalytic materials, especially the recently developed prominent ones were comprehensively reviewed. Kinetic analysis and underlying mechanism for various POPs degradation processes were addressed in detail. The review also systematically documented how catalytic performance was dramatically affected by the nature of the material itself, the structure of target pollutants, reaction conditions and treatment techniques. Moreover, the future challenges and prospects of POPs degradation by means of multiple multifunctional materials were outlined accordingly. Knowing this is of immense significance to enhance our understanding of POPs remediation procedures and promote the development of novel multifunctional materials.

Tylosin degradation during manure composting and the effect of the degradation byproducts on the growth of green algae

In this study, we investigate the tylosin degradation in sheep feces during composting. The sheep feces containing tylosin were composted using the laboratory-scale composting units. Tylosin was degraded during composting, and the half-life of tylosin degradation decreased with increasing temperature from 40 °C to 65 °C. The tylosin degradation in sheep feces can be attributed to the microorganisms in the feces and not to heating because tylosin did not degrade over a period of 48 h at temperatures of 0 °C-65 °C in sterilized water. The artificial rainwater solution extracted from the composted sample did not inhibit the growth of Raphidocelis subcapitata, a type of green alga. Our results indicate that composting the feces containing tylosin is effective in degrading tylosin, which may result in the preservation of agricultural fields as well as nearby aquatic environments.

Challenges in the identification of new thermolabile psychoactive substances: The 25I-NBOH case

The continuous emergence of NPS over the last years poses a series of novel challenges for forensic analysts. Most of those new compounds are synthesized with minimal chemical modifications to the structure of already known chemicals in order to avoid regulations. Some of these new compounds may undergo chemical changes during analysis leading to misidentification and detrimental legal consequences. GC-MS is one of the most widely used analytical techniques employed by forensic laboratories all over the world for drug analysis. Nevertheless, thermolabile NPS, such as 25I-NBOH can generate artefacts in the traditional GC-MS analysis. In this paper, we describe the fragmentation mechanism of the 25I-NBOH into a major peak corresponding to 2C-I and a minor one corresponding to the associated ortho-phenolic benzyl ether (o-PBE), which exact identity is directly linked with the solvent used for the analysis. Also, a series of method adjustments is displayed, encompassing variation on the injector temperature, split ratio and flow ratio, although with no success to prevent 25I-NBOH thermo degradation in the GC injector. Furthermore, differential scanning calorimetry and thermogravimetric analysis demonstrated that 25I-NBOH's thermal stability is due to a smaller temperature window between fusion and decomposition points. Finally, we perform derivatization experiments and demonstrate how to overcome 25I-NBOH degradation in the GC/MS analysis.

Thermal degradation of eco-friendly alternative plastics: kinetics and thermodynamics analysis

This work reports the thermal degradation behaviour, kinetics and thermodynamics of two different eco-friendly plastics, viz. non-woven plastic and corn starch-based biodegradable plastics, which are commonly used nowadays as an alternative to synthetic plastics. In this context, thermogravimetric analysis of plastic waste samples was carried out at wide range of heating rates of 10, 20, 40, 60, 80 and 100 °C/min in nitrogen atmosphere, and activation energy is determined by first-order model-fitting method while thermodynamic parameters are determined on the basis of Eyring theory of activated complex. The regression coefficient obtained from kinetic study of thermal degradation of these plastics best fits to the first-order kinetic equation. The kinetics and thermodynamic parameters obtained for both the plastics are found very close to each other. So, this study would help design more effective conversion system for the recycling of both the wastes together.

Thermal decomposition kinetics and properties of grafted barley husk reinforced PVA/starch composite films for packaging applications

Thermal degradation kinetics was performed on thermogravimetric (TGA) curves of crosslinked PVA/starch composite films reinforced with barley husk (BH) and grafted BH (using lauric acid) obtained by heating samples in an inert atmosphere with different heating rates (5, 10, 15 and 20 °C/min). The activation energy for composite films was determined using Flynn-Wall-Ozawa (FWO) Kissinger-Akahira-Sunose (KAS), Friedman (FR) and modified Coasts Redfern (CR) methods. The results showed that activation energy for thermal degradation of grafted BH composite film was higher than of BH. Incorporation of grafted BH into crosslinked PVA/starch matrix improved the mechanical performance of the films compared to BH and showed 30 % increase in tensile strength after reinforcement. Grafted BH composite films showed higher barrier properties for light, water vapor and oxygen as required for packaging applications. Biodegradability of the films improved significantly after incorporation of BH into the polymer matrix and showed 70 % degradation after 180 days.

Influence of pH, temperature, and light on the stability of melatonin in aqueous solutions and fruit juices

The ability to predict melatonin stability during food processing or storage is important. Therefore, the degradation of melatonin in both aqueous solutions and fruit juice samples was investigated. The pH values of aqueous solutions were set over a pH range from 1 to 13 and at four different temperatures (60, 70, 80 and 90 °C). The highest remaining melatonin (C_R) was observed in the lowest pH solution (pH = 1, C_R > 65%). Melatonin concentrations decreased with rising pH levels from pH 4 to 13 during storage time. The thermal degradation rate constant of melatonin (k) values obtained followed the order: k_90°C (0.175) >k_80°C (0.123) >k_70°C (0.082) >k_60°C (0.027). Thermal degradation kinetics followed the first-order reaction model with a high range of coefficients of determination (0.9744 < R² < 0.995). The temperature also affected on melatonin degradation in fruit juices which the degradation rate was increased with the presence of light and high temperature. Our results can be used as guidelines to develop a processing method that predicts melatonin degradation during thermal processing of food products.