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The widespread production of polymeric materials has precipitated severe environmental challenges, prompting a pressing need for effective solutions. Among these materials, polyurethanes (PUs) stand out significantly due to their versatility in synthetic approaches, manufacturing, properties, and applications. This versatility has led to a high demand for PUs, resulting in significant waste accumulation at the end of their lifecycle. Along with that, the PU's inherent chemical stability prevents the occurrence of natural hydrolytic processes. Consequently, there is a critical need for sustainable recycling methods, particularly those capable of recovering reusable monomers. Recycling is a leading way to manage waste by reducing plastic pollution and its environmental impact, which can be performed through mechanical, chemical, and biological processes. Biological degradation occurs through the action of enzymes and microbes that can potentially convert the polymers into monomers or other valuable chemicals. This approach presents an opportunity to establish a sustainable and circular economy within the PUs industry while considerably reducing the environmental impact. This review highlights enzymatic degradation as a promising solution for PU recycling by discussing the types of enzymes utilized in the process, potential biochemical pathways for PU degradation, recent achievements, and future remarks for this process.

Mushroom cultivation and consumption have been steadily increasing in recent decades, however, after mushroom cultivation, a large amount of by-products, known as spent mushroom substrate (SMS), are left behind in open dumps where about 5 kg of SMS are generated for every kilogram of mushroom (Agaricus bisporus). Around 51 million tons of SMS are produced in the world every year. Hydrothermal carbonization (HTC) is a promising technology for the conversion of SMS into a rich carbon product, hydrochar. The hydrochar was synthesized in a hydrothermal reactor at a temperature of 180 °C for a reaction time of 1 h. The characterization of the SMS and its chars was done by FTIR, SEM, and TGA analysis. The FTIR analysis showed that aromatic and oxygen-rich functional groups are dominant on the hydrochar surface. It was noticed that the hydrochar had more visible pores compared to the SMS. The porous structure and oxygen functional groups of hydrochar probably influenced the improvement of adsorption performance, since the adsorption capacity of SMS for Cd2+ ions was 28 mg L-1, while for hydrochar it was 92 mg L-1. On the other hand, the thermal kinetic analysis has shown that hydrothermally treatment upgrades the combustion behavior of hydrochar. The kinetic parameters were determined by Kissinger and Ozawa methods. The hydrochar had notably lower activation energy compared to the SMS, which means that this hydrochar requires a smaller amount of energy to start combustion. The preliminary results show that HTC effectively transforms SMS into alternative solid biofuel and eco-friendly sorbent.

Liqueur from green walnuts is one of the many traditional medicines in folk medicine. It owes its healing properties to the main ingredient - unripe green walnuts. Green walnuts are a natural reservoir of vitamin C, vitamin B complex, vitamin E, calcium, potassium, magnesium, phosphorus, iron, zinc and iodine. Liqueur made from green walnuts is mostly used for problems with the thyroid gland, anemia, and various stomach infections. The liqueur is made by adding green walnuts to a container with sugar or honey and brandy, and leaving them to be exposed to the sun's rays for a period of 40 days. Photons accelerate the release of medicinal substances from green walnuts. This period of exposure is quite long, the quality of the liqueur is affected by the amount of solar energy delivered during that period, and contamination may occur during manual handling. All these problems can be solved by using photons from a radioactive gamma source instead of photons from the sun. The paper describes the process of obtaining liqueur from green walnuts using gamma radiation, as well as the comparison of the composition of liqueur obtained in the traditional way, with the effect of sunlight, and the application of an innovative method using gamma rays.

Chitosan is a natural polymer obtained by deacetylation of chitin. Due to its biocompatibility and biodegradability, chitosan-based materials have a wide range of biomedical applications in wound dressings, drug delivery systems, and tissue engineering. Also, studies in the fields of organic and medicinal chemistry show that compounds based on the pyridone core exhibit biological properties including antimicrobial, anticancer, and antioxidant activity, and moreover have the potential as new therapeutics for various diseases from cardiovascular to antitumor therapy. In this study, new biomaterials were synthesized using low and medium molecular weight chitosan polymers and pyridone-based hydrazone. In order to improve stability of the obtained scaffolds, scaffolds’ neutralization was carried out using ethanol and sodium hydroxide solutions. The interactions established between chitosan polymer chains and pyridone compound were analyzed by FT-IR spectroscopy. Swelling and degradation tests of the materials were studied in water and PBS, and the influence of different polymer molecular weights on the scaffolds’ properties was evaluated. The results indicated that synthetized scaffolds have a high potential for biomedical use.

In this study, the adsorption capacity of Pb2+ removal from aqueous solution was examined by hydrochar of the spent mushroom substrate. In order to improve the adsorption capacity, hydrochar was previously activated with 2M KOH. The obtained results demonstrated that alkally activation increased the sorption capacity from 36 mg g-1 to 74 mg g-1. Structural characterization of activated and inactivated hydrochars were performed by FTIR analysis. Toward to obtained results of FTIR analysis, the increased of the oxygen functional groups (OFG) in activated hydrochars was perceived, which is contributed to the increase in the adsorption capacity of this carbonized material. Results indicated that spent mushroom substrate can be converted into hydrochar as a perspective sorbent for removal of Pb2+.

The heterocyclic azo dyes represent significant synthetic organic colorants. In addition to their exceptional coloration properties, heterocyclic azo compounds exhibit antibacterial, antifungal, an-tiviral, antioxidant, anti-inflammatory and anticancer properties. The antimicrobial resistance is one of the major problems for global public health. Therefore, finding new organic structures with anti-microbial properties represents a challenging research field. In this study, antimicrobial screening of two Biginelli-based azo pyridone dyes has been carried out. The antimicrobial activity of synthe-tized dyes wasstudied against bacteria (Staphylococcus aureus, Escherichia coli) and yeast (Candida albicans), using agar diffusion method. The preliminary research results indicate the antimicrobial potential of the investigated compounds., Heterociklična azo jedinjenja predstavljaju značajnu klasnu organskih sintetskih boja. Pored njihovih izuzetnih svojstava za bojenje, heterociklična azo jedinjenja imaju i biološku aktivnost. Mnoge studije pokazuju da azo boje sa heterocikličnim fragmentima u strukturi mogu ispoljavati antibakterijska, antifungalna, antivirusna, antiinflamatorna i antikancerogena svojstva. Rezistencija mikroorganizama na postojeće antimikrobne agense predstavlja jedan od najvećih problema u svetskom zdravstvu. Zbog toga je razvijanje novih molekula sa antimikrobnim svojstvima kako značajno, tako i neophodno za globalno očuvanje zdravlja. U ovom radu, ispitivanje antimikrobne aktivnosti dve Biđineli-azo piridonske boje je urađeno pomoću metode difuzije na agarnoj podlozi. Antimikrobna svojstva su ispitana prema patogenim sojevima Staphylococcus aureus (Gram-pozitivna bakterija), Escherichia coli (Gram-negativna bakterija) i Candida albicans (oportunistički kvasac). Preliminarni rezultati istraživanja ukazali su na antimikrobni potencijal ispitivanih azo jedinjenja.

In this study, the adsorption capacity of Pb2+ removal from aqueous solution was examined by hydrochar of the spent mushroom substrate. In order to improve the adsorption capacity, hydrochar was previously activated with 2M KOH. The obtained results demonstrated that alkally activation increased the sorption capacity from 36 mg g-1 to 74 mg g-1. Structural characterization of activated and inactivated hydrochars were performed by FTIR analysis. Toward to obtained results of FTIR analysis, the increased of the oxygen functional groups (OFG) in activated hydrochars was perceived, which is contributed to the increase in the adsorption capacity of this carbonized material. Results indicated that spent mushroom substrate can be converted into hydrochar as a perspective sorbent for removal of Pb2+.

Heterociklična azo jedinjenja predstavljaju značajnu klasnu organskih sintetskih boja. Pored njihovih izuzetnih svojstava za bojenje, heterociklična azo jedinjenja imaju i biološku aktivnost. Mnoge studije pokazuju da azo boje sa heterocikličnim fragmentima u strukturi mogu ispoljavati antibakterijska, antifungalna, antivirusna, antiinflamatorna i antikancerogena svojstva. Rezistencija mikroorganizama na postojeće antimikrobne agense predstavlja jedan odnajvećih problema u svet-skom zdravstvu. Zbog toga je razvijanje novih molekula sa antimikrobnim svojstvima kako značajno, tako i neophodno za globalno očuvanje zdravlja. U ovom radu, ispitivanje antimikrobne aktivnosti dve Biđineli-azo piridonske boje je urađeno pomoću metode difuzije na agarnoj podlozi. Anti-mikrobna svojstva su ispitana prema patogenim sojevima Staphylococcus aureus (Gram-pozitivna bakterija), Escherichia coli (Gram-negativna bakterija) i Candida albicans (oportunistički kvasac). Preliminarni rezultati istraživanja ukazali su na antimikrobni potencijal ispitivanih azo jedinjenja., The heterocyclic azo dyes represent significant synthetic organic colorants. In addition to their exceptional coloration properties, heterocyclic azo compounds exhibit antibacterial, antifungal, an-tiviral, antioxidant, anti-inflammatory and anticancer properties. The antimicrobial resistance is one of the major problems for global public health. Therefore, finding new organic structures with anti-microbial properties represents a challenging research field. In this study, antimicrobial screening of two Biginelli-based azo pyridone dyes has been carried out. The antimicrobial activity of synthe-tized dyes wasstudied against bacteria (Staphylococcus aureus, Escherichia coli) and yeast (Candida albicans), using agar diffusion method. The preliminary research results indicate the antimicrobial potential of the investigated compounds

Fig (Ficus carica L.) is a fruit of the Moraceae family, which is mostly grown in subtropical regions, but also grows in Serbia. Fig trees are usually grown in warm and dry climates. According to the FAO world production of figs is stable, with a decade-long average of about 1.1 million tons a year. Fig pomace are formed after fermentation of this fruit which is used for the preparation of brandy. The brandy industry generates huge amounts of pomace as industrial waste, so pyrolysis as thermochemical technologies was used for organic agro-industrial waste treatment. Biochar produced by pyrolysis of fig pomace at 500 °C were characterized and investigated as adsorbents for the removal of Pb2+ ions from aqueous solution. Fig pomace before and after pyrolysis was characterized using proximate, inorganic and elemental analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Biochar has a carbon matrix with a high degree of porosity and large surface area, suggesting that it can be used as a surface adsorbent and thus have a significant role in controlling environmental contaminants. The surface modification by gamma irradiation was done to enhance the adsorption capacity of biochar. The Pb2+ ions contents in aqueous solution were analyzed using ICP-OES. The adsorption capacity was estimated using the Freundlich and Langmuir model. The results of this work suggest that pyrolysis and irradiation of biomass is a promising way to produce efficient heavy metal sorbents for waste-water treatment.

The use of waste biomass for the production of fuels, sorbent of different pollutants or natural fillers has significant economic and environmental benefits. Plum (Prunus domestica) is a lush fruit consisting of bones, flesh and skin. It can be consumed fresh, dried or used to make juices, jams and brandies known as plum brandy. Plum is also known as a laxative. During processing, plum pomace is formed as a by-product of plum brandy production. Plum pomace contains a large proportion of polyphenols, so it can be used to produce dietary supplements. Therefore, in this study, the gamma irradiation activated biochar of plum pomace was examined as a lowcost biosorbent of Cd2+ ions from aqueous solution. It was prepared using pyrolysis process at 500 °C for a reaction time of 1 h, then was activated by gamma irradiation. The characterization of plum pomace before and after pyrolysis was done by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Analysis of morphology and functional groups presented the formation of cracks on the biochar surface, which are mainly dominated by oxygen-rich functional groups. The adsorption capacity of activated biochar was higher than inactivated biochar because its improved surface functional properties after gamma activation. The Cd2+ ions contents in aqueous solution were analyzed using ICP-OES. The adsorption capacity was estimated using the Langmuir and Freundlich model. The findings of this study confirm that pyrolysis is a promising way to produce efficient environmentally friendly sorbents for wastewater treatment.

Hydrothermal carbonization (HTC) was employed for the conversion of the spent mushroom substrate (SMS) into a carbonaceous hydrochar. The effect of operating temperature (180, 200, 220, 240, and 260 °C) on the physicochemical, structural, and combustion properties of the obtained hydrochars was analyzed. The HTC treatment caused the increase of the higher heating value (HHV) and the lower heating value (LHV) of hydrochars for 58 % and 65 % in comparison with SMS, respectively. Analysis of morphology and functional groups showed the formation of microspheres and cracks on the hydrochar surface, which are predominantly dominated by aromatic and oxygen-rich functional groups. Thermal and kinetics analysis showed that HTC treatment improves the combustion behavior of the obtained solids. Combustion kinetic parameters of SMS and hydrochars were determined by the methods of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The thermodynamic parameters and pre-exponential factors reveal a complex mechanism of SMS and hydrochars decomposition process. © 2021 Elsevier B.V.

Biochar produced by pyrolysis of plum and fig pomace at 500 C were characterized and investigated as adsorbents for the removal of heavy metal ions from aqueous solution. Plum and fig pomace are formed after fermentation of this fruit which is used for the preparation of brandy. The brandy industry generates huge amounts of pomace as industrial waste, so pyrolysis as thermochemical technologies was used for organic agro-industrial waste treatment. Plum and fig pomace before and after pyrolysis was characterized using proximate, inorganic and elemental analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Biochar has a carbon matrix with a high degree of porosity and large surface area, suggesting that it can be used as a surface adsorbent and thus have a significant role in controlling environmental contaminants. The surface modification by gamma irradiation was done to enhance the adsorption capacity of biochar. The heavy metals contents in aqueous solution were analyzed using ICP-OES. The adsorption capacity was estimated using the Langmuir and Freundlich model. The results of this work suggest that pyrolysis and irradiation of biomass is a promising way to produce efficient heavy metal sorbents for waste-water treatment.

A carbon-rich product, hydrochar, was synthesized by hydrothermal carbonization (HTC) of spent mushroom substrate (SMS), at temperature of 260 °C. The thermal kinetic analysis has shown that hydrothermally treatment improve the combustion behavior of hydrochar. The kinetic parameters were determined by Kissinger and Ozawa methods. The SMS-260 had a significantly lower activation energy compared to the SMS, which means that this hydrochar needs a smaller amount of energy to start combustion. Generally, the preliminary results show that HTC is an effective way to transform SMS into alternative solid biofuel.

A new heterocyclic azo dye 5-(2,6-dimethylphenyl)-6-hydroxy-4-methyl-2-oxo-1,2- dihydropyridine-3-carboxamide was synthesized and structurally characterized by elemental analysis, FTIR, 1H and 13C NMR spectroscopy techniques. These analysis have confirmed that synthesized dye exists in the tinctorial strongest tautomeric form, hydrazone form. The dye is characterized by reflection spectrum, while absorption and emisson spectra are recorded in nine different solvents. The antioxidant activity of the synthesized dye has been chemically tested and has been shown to have great potential as an antioxidant molecule.

Removal of heavy metals is important because of their toxic effects on living organisms and unwanted anthropogenic effects. Biochar is suitable as an adsorbent of heavy metals due to its advantages such as various sources of biomass, a large number of microporous channels and surface functional groups, as well as due to its economic viability. There is no data about the plum pomace biochar usage as adsorbent for lead removal. In this study, the plum pomace biochar modified with gamma irradiation (IrPP) is used for the removal of Pb2+ ions from the aqueous solution. The SEM micrographs revealed that surface morphology of plum pomace is suitable for metal adsorption. The results of adsorption kinetics demonstrated that the removal process of Pb2+ ions onto IrPP follows a pseudo-second kinetic model, which is confirmed by a better agreement between qe,cal=227 mg g–1 and qe,exp=224 mg g–1. Therefore, based on preliminary research, it can be concluded that IrPP originating from biowaste is a promising, eco-friendly sorbent of heavy metal from wastewater.

Molecular imaging is a relatively new research field, which has demonstrated great potential, especially in clinical oncology – from drug development to cancer early detection. The key of fluorescence imaging is the construction of fluorescent probe which is composed of two parts, the recognition groups to recognize cancer cells, and fluorophores to signal the recognition events. In this research, the structure of new fluorescent azo dye based on 2-oxo-1,2,3,4-tetrahydropyrimidin and 2-pyridone moieties has been reported. The absorption and emission properties of the investigated azo dye have been studied using UV-Vis and fluorescence spectroscopy. The obtained results suggest that studied dye meets the requirements for new green-emitting fluorescent probe, suitable for further application in biomedical researches.

A facile and efficient, one step synthesis of macrocyclic molecule zinc phthalocyanine (ZnPc), was proposed. Dark violet crystals of ZnPc dye were obtained in high boiling point solvent of dimethylformamide (DMF) in the presence of 2,2,6,6-tetramethylpiperidine (TMP) as a catalyst. Detailed thermogravimetric and kinetic analysis revealed high thermal stability of the investigated compound.

Photocatalytic degradation of the carbamate insecticide methomyl and its commercial product Lannate-90 in aqueous suspension of TiO2 and ZnO using an Osram ultra-vitalux lamp (315-400 nm) was investigated. The objective of the investigation was to study and compare the rates of photochemical degradation of the pure active compound and its formulated product in order to find out the impact of inert ingredients on degradation processes. The photo-chemical degradation of pure methomyl was found to be slower than the degradation of its commercial product Lannate-90. Photodegradation was investigated by UV-Vis spectrometry and HPLC, while mineralization was monitored using IC and TOC analyses. Light absorption capabilities of catalysts were characterized by ultraviolet-visible diffuse reflectance spectroscopy method, while the stability of catalysts was studied by infrared analyses. Degradation products of methomyl and its formulated product were identified by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) results and tentative photodegradation pathways were proposed.

Heterociklične azo boje sa piridonovim jezgrom predstavljaju značajnu klasu organskih azo boja jer pokazuju visoki molarni ekstinkcioni koeficijent i dobru postojanost na razne vidove obrade. Sintezom 2-piridona sa amidnom grupom u položaju 3, i kuplovanjem dobijenog piridona sa supstituisanim i disupstituisanim diazonijumovim solima dobijene su dvije serije novih azo boja. Struktura novosintetisanih boja na bazi 6-hidroksi-4-metil-2-okso-1,2-dihidropiridin-3- karboksamida je potvrđena elementalnom analizom, FT-IR i NMR spektroskopijom. Termička stabilnost boja je ispitana TG/DTA i DSC metodama, i upoređena sa bojama slične hemijske strukture. Amidna grupa u strukturi sintetisanih boja dovodi do drugačije uređenosti molekula u odnosu na jedinjenja ranije poznate strukture, što je predstavljalo veliki izazov za detaljnu analizu njihove stabilnosti i ponašanja. U ovoj disertaciji je prvi put urađeno detaljno ispitivanje termičke stabilnosti i određivanje kinetičkih i termodinamičkih parametara termički aktiviranih procesa degradacije arilazo piridonskih boja. Tehnološki procesi u kojima se azo boje koriste zahtjevaju povišenu temperaturu pa je termička stabilnost od velikog značaja za implementaciju sintetisanih boja. Nova saznanja o odnosu elektronske strukture i svojstava sintetisanih boja dobijena su ispitivanjem uticaja rastvarača različitih svojstava na apsorpcione i fluorescentne spektre boja. Korelacijom apsorpcionih i fluorescentnih frekvenci izvršena je kvantitativna procjena uticaja dipolarnosti, polarizabilnosti, proton-donorskih i proton-akceptorskih karakteristika rastvarača na položaje apsorpcionih i fluorescentnih maksimuma ispitivanih azo boja. Kvantno-hemijski proračuni su primjenjeni za analizu strukture novosintetisanih boja. DFT metodom je analiziran uticaj supstituenata i rastvarača, promjene u osnovnom i pobuđenom stanju kao i oblik i energije graničnih molekulskih orbitala (HOMO, LUMO i Egap). Poređenje eksperimentalnih i izračunatih vrijednosti, Heterocyclic azo dyes with a pyridone moiety represent a significant class of organic azo dyes because of its high molar extinction coefficient and good resistance to various types of processing. Synthesis of 2-pyridone with the amide group in position 3, and coupling of the obtained pyridone with substituted and disubstituted diazonium salts gave two series of new azo dyes. The structure of newly synthesized dyes based on 6-hydroxy-4-methyl-2-oxo-1,2- dihydropyridine-3-carboxamide was confirmed by elemental analysis, FT-IR and NMR spectroscopy. The thermal stability of the dyes was performed by TG/DTA and DSC methods and compared with dyes of similar chemical structure. The amide group in the structure of the synthesized dyes leads to a different arrangement of the molecules in relation to the compounds of the previously known structure, which posed a great challenge for a detailed analysis of their stability and behavior. In this dissertation, for the first time, a detailed examination of thermal stability and determination of kinetic and thermodynamic parameters of thermally activated degradation processes of arylazo pyridone dyes was performed. Technological processes in which azo dyes are used require elevated temperature, so thermal stability is of great importance for the implementation of synthesized dyes. New knowledge about the relationship between the electronic structure and the properties of synthesized dyes was obtained by examining the influence of solvents of different properties on the absorption and fluorescent spectra of dyes. By correlating the absorption and fluorescent frequencies, a quantitative assessment of the influence of dipolarity, polarizability, proton-donor and proton-acceptor characteristics of the solvent on the positions of absorption and fluorescent maxima of the investigated azo dyes was performed. Quantum chemical calculations were applied to analyze the structure of newly synthesized dyes. The influence of substituents and solv

A series of nine 5-(4-substituted phenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones were synthesized and characterized by FT-IR, H-1 and C-13 NMR, UV-Vis, and PL spectroscopy. Photophysical properties of the dyes were examined in solvents of various polarities and at different pH values. The solvent effects on the absorbance and emission spectral shift were analyzed using Lippert-Mataga, Reichardt-Dimroth and Kamlet-Taft equations. Moreover, UV-Vis absorption and emission frequencies were correlated with Hammett substituent constants applying the linear free energy relationships. DFT calculations of the investigated dyes were accomplished to determine their structural and electronic properties.

Urea-formaldehyde resin (F/U ratio of 0.8)/thermally activated montmorillonite (UF/Delta TK10) nanocomposite was synthesized. The hydrolytical, thermal, and UV radiation stability of UF/Delta TK10 nanocomposites are determined. UF hybrid nanocomposites have been irradiated with UV light with a wavelength of 254 nm and 366 nm, and after that, their radiation stability was evaluated. The free formaldehyde (FA) percentage in all prepared samples was determined. The sample was characterized by using X-ray diffraction analysis (XRD), nonisothermal thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential thermal gravimetry (DTG), with infrared (FTIR) spectroscopy. Crosslinked UF/Delta TK10 nanocomposite shows the highest resistance to acid hydrolysis after UV irradiation at a wavelength of 254 nm. The values for T-5% are identical for the unirradiated and UV irradiated (wavelength of 366 nm) UF/Delta TK10 nanocomposite. It can be concluded that this sample is thermally most stable and shows good resistance to UV irradiation.

Simultaneous thermal analysis (TG–DTA) of low-rank coals from different annual periods (2015 and 2018) which originate from Kolubara and Nikola Tesla A (TENT A) coal-fired power plants was studied to identify their combustion characteristics and self-ignition risks. In order to investigate kinetics of thermo-oxidative degradation, model-free models including the Friedman and Kissinger–Akahira–Sunose methods were applied. In accordance with obtained kinetic results, numerical optimization of combustion process was implemented. Homogeneous and heterogeneous types of ignition were identified for the tested coals, and factors that affect their occurrence are the used heating rate and volatile matter content. From thermal susceptibility graph, it was found that the tested coals expand in a wide range of self-ignition risk, depending on their coal rank. The youngest coal (TENT A (2018)) has the largest propensity to self-ignite among high-ranking coals. It was found that less tendency of 2018 coals to show true isokinetic temperature in comparison with 2015 coals is a consequence of intraparticle diffusion limitations, and change of char properties, at higher conversion values. Gamma spectrometry analysis of coals showed that higher concentration of 40K radionuclide (which is in mineral composition) may contribute through its deposition on available sites, decreasing surface area for reaction with oxidizing species. © 2020, Akadémiai Kiadó, Budapest, Hungary.

Thermal degradation properties of the newly synthesized azo dyes derived from 6-hydroxy4-methyl-2-okso-1,2-dihydropyridine-3-carboxamidewere examined Depending on the nature of substituent that is located on the para position of the diazo components of azo pyridone dyes, different thermal stability can be obtained The thermal behaviour of the present dyes has been determined using thermogravimetric analysis (TGA), derivative thermogravimetry (DTG) and differential thermal analysis (DTA) On the basis of this method, non-isothermal kinetics was monitored To explain kinetics behavior of the investigated dyes during their degradation in an inert atmosphere, ASTM E698, ASTM E2890, Friedman’s (FR), OzawaFlynn-Wall (OFW) as well as Kissinger-Akahira-Sunose (KAS) isoconversional (modelfree) methods were applied. Numerical optimization was used in order to judge fitting capabilities including simulated and experimental curves, for estimated kinetic parameters It was found that different thermal stabilities of various dyes are the consequence of their different chemical structures, including diverse substituents. It was shown that significant difference in reactivity for hydroxy substituted and unsubstituted dyes is a consequence of reactivity dissimilarities between •OH and H• species.It was assumed that reactions with •OH are characterized with changing in limiting stage, from kinetic to diffusion controlled The numerical optimization shows a good fitting correlation between experimental and simulated process data Based on multi-level conversion analysis, using differential (FR) and integral (OFW and KAS) model-free methods, the all dyes, exhibit the different E-conversion dependency