Supplementary data for the article: Savić, B. G.; Stanković, D. M.; Živković, S. M.; Ognjanović, M. R.; Tasić, G. S.; Mihajlović, I. J.; Brdarić, T. P. Electrochemical Oxidation of a Complex Mixture of Phenolic Compounds in the Base Media Using PbO2-GNRs Anodes. Applied Surface Science 2020, 529, 147120. https://doi.org/10.1016/j.apsusc.2020.147120

Supplementary material for: [https://doi.org/10.1016/j.apsusc.2020.147120]Related to published version: [https://cherry.chem.bg.ac.rs/handle/123456789/4177

Application of Peleg Model on Mass Transfer Kinetics During Osmotic Dehydratation of Pear Cubes in Sucrose Solution

The applicability of Peleg model was investigated for predicting mass transfer kinetics during the osmotic dehydration (OD) process of pears, at different concentrations (40, 60 and 70%, w/w) and temperatures (20, 35 and 50 degrees C) of sucrose solution. Increase in sucrose solution concentration resulted in higher water loss (WL) and solid gain (SG) values through the osmotic treatment period. After 360 min of osmotic treatment of pears, WL ranged from 23.71 to 31.68% at 20 degrees C, from 24.80 to 40.38% at 35 degrees C and from 33.30 to 52.07% at 50 degrees C of initial weight of pears. The increase of dry mass of the samples, SG, after 360 min of osmotic treatment ranged from 3.02 to 6.68% at 20 degrees C, from 4.15 to 7.71% at 35 degrees C and from 5.00 to 8.92% at 50 degrees C. Pelegs rate constants, k(1)(WL) and k(1)(SG), decreased with increasing temperature, as well as decreased with increasing concentration of osmotic solution at constant temperature. Both capacity constants k(2)(WL) and k(2)(SG) also exhibited the inverse relationship between capacity constant and temperature, as well as concentration of the osmotic solution. Pelegs rate constants for WL and SG at all temperatures followed an Arrhenius type relationship. The predicted equilibrium values were very close to experimental ones, which was confirmed with high coefficients of determination and by the residual analysis

Spectroscopic investigation of the antiradical activity of hydroxy flavones and their iron(III) complexes

Flavonoidi se već duži niz godina nalaze u vrhu aktuelnosti fundamentalnih i primenjenih istraživanja iz razloga velike biološke i fiziološke aktivnosti, složenosti biosinteze i metabolizma kao i sve većih mogućnosti primene u raznim oblastima industrije. Pretpostavlja se da je biološka aktivnost flavonoida prvenstveno zasnovana na njihovom antioksidativnom delovanju koje se ispoljava višestruko, u direktnim interakcijama sa slobodnim radikalima (antiradikalska aktivnost) kao i indirektno u reakcijama kopigmentacije, inhibicije enzima, eliminaciji singletnog kiseonika, smanjenju stepena lipidne peroksidacije, zaustavljanju faze propagacije u kojoj nastaju hidro-peroksi lipidi, detoksifikaciji vodonik peroksida u ne-enzimskim mehanizmima odbrane ili uklanjanjem oksidacijom oštećenih biomolekula i u reakcijama kompleksiranja sa jonima prelaznih metala. Sa druge strane flavonoidi mogu da deluju i kao redukcioni agensi čime menjaju redoks svojstva prelaznih metala sa kojima grade komplekse što im, pod određenim uslovima, daje mogućnost i prooksidativnog delovanja. Iako su reakcije komplekisranja flavonoida i metalnih jona do sada bile predmet mnogih naučnih istraživanja rezulatati na tom polju, posebno oni koji se odnose na kompleksiranje u vodenoj sredini, nisu u potpunosti usaglašeni, a često su i kontradiktorni po pitanju definisanja mehanizma reakcije, helatnih položaja molekula uključenih u strukturu nagrađenih kompleksa, stehiometrije i stabilnosti kompleksa. U ovoj doktorskoj disertaciji predstavljeni su rezultati in vitro ispitivanja reakcije kompleksiranja odabranih hidroksi-flavonskih molekula različitih supstitucionih shema (kvercetin, fisetin, morin i baikalein) i gvožđe(III) jona. Određeni su optimalni uslovi za odigravanje reakcije i razmatran je uticaj strukture molekula na stabilnost i stehiometrijski sastav kompleksa. Takođe, istraživanja u okviru ove...Due to their high biological and physiological activity, biosyntheses and metabolism complexity, as well as to the growing possibilities of their application in the various fields of industry, the flavonoids have been for many years extremely popular in both fundamental and applied research. It is believed that the biological activity of the flavonoids is primarily based on their antioxidative action which is manifested in various ways: both in the direct interaction with free radicals (antiradical activity) and indirectly in the copigmentation reactions, inhibition of the enzymes, the elimination of singlet oxygen, reduction of lipid peroxidation, stopping the propagation stage in which hydro-peroxy lipids are generated, detoxification of hydrogen peroxide in nonenzymatic defense mechanisms or removing damaged biomolecules by oxidation and in transition metal complexation reactions of flavonoids. On the other hand, flavonoids can act as reducing agents altering the redox properties of transition metal complexes, which, under certain conditions, give them an ability of prooxidative activity. Although the reactions of flavonoids and metal ions complexation has been the subject of many scientific research, the results in this field, particularly those relating to the complexation in aqueous media, are not fully harmonized, and are often contradictory in terms of defining the mechanism of the reaction, the position of chelating molecules involved in the structure of these complexes, the stoichiometry and stability of complexes. Within the scope of this doctorial thesis, in vitro complexation reactions of the selected hidroxy-flavon molecules, with various substitution variations (quercetin, fisetin, morin, baicalein), and iron(III) ion are investigated. The optimal conditions of the reactions are determined as well as the influence of the molecular structure on the complex stoichiometry. Also, the research within this thesis involve the examination of the activity of pure molecules and their complexes towards a few differently nitrogen..

Spectroscopic investigation of the antiradical activity of hydroxy flavones and their iron(III) complexes

Flavonoidi se već duži niz godina nalaze u vrhu aktuelnosti fundamentalnih i primenjenih istraživanja iz razloga velike biološke i fiziološke aktivnosti, složenosti biosinteze i metabolizma kao i sve većih mogućnosti primene u raznim oblastima industrije. Pretpostavlja se da je biološka aktivnost flavonoida prvenstveno zasnovana na njihovom antioksidativnom delovanju koje se ispoljava višestruko, u direktnim interakcijama sa slobodnim radikalima (antiradikalska aktivnost) kao i indirektno u reakcijama kopigmentacije, inhibicije enzima, eliminaciji singletnog kiseonika, smanjenju stepena lipidne peroksidacije, zaustavljanju faze propagacije u kojoj nastaju hidro-peroksi lipidi, detoksifikaciji vodonik peroksida u ne-enzimskim mehanizmima odbrane ili uklanjanjem oksidacijom oštećenih biomolekula i u reakcijama kompleksiranja sa jonima prelaznih metala. Sa druge strane flavonoidi mogu da deluju i kao redukcioni agensi čime menjaju redoks svojstva prelaznih metala sa kojima grade komplekse što im, pod određenim uslovima, daje mogućnost i prooksidativnog delovanja. Iako su reakcije komplekisranja flavonoida i metalnih jona do sada bile predmet mnogih naučnih istraživanja rezulatati na tom polju, posebno oni koji se odnose na kompleksiranje u vodenoj sredini, nisu u potpunosti usaglašeni, a često su i kontradiktorni po pitanju definisanja mehanizma reakcije, helatnih položaja molekula uključenih u strukturu nagrađenih kompleksa, stehiometrije i stabilnosti kompleksa. U ovoj doktorskoj disertaciji predstavljeni su rezultati in vitro ispitivanja reakcije kompleksiranja odabranih hidroksi-flavonskih molekula različitih supstitucionih shema (kvercetin, fisetin, morin i baikalein) i gvožđe(III) jona. Određeni su optimalni uslovi za odigravanje reakcije i razmatran je uticaj strukture molekula na stabilnost i stehiometrijski sastav kompleksa. Takođe, istraživanja u okviru ove...Due to their high biological and physiological activity, biosyntheses and metabolism complexity, as well as to the growing possibilities of their application in the various fields of industry, the flavonoids have been for many years extremely popular in both fundamental and applied research. It is believed that the biological activity of the flavonoids is primarily based on their antioxidative action which is manifested in various ways: both in the direct interaction with free radicals (antiradical activity) and indirectly in the copigmentation reactions, inhibition of the enzymes, the elimination of singlet oxygen, reduction of lipid peroxidation, stopping the propagation stage in which hydro-peroxy lipids are generated, detoxification of hydrogen peroxide in nonenzymatic defense mechanisms or removing damaged biomolecules by oxidation and in transition metal complexation reactions of flavonoids. On the other hand, flavonoids can act as reducing agents altering the redox properties of transition metal complexes, which, under certain conditions, give them an ability of prooxidative activity. Although the reactions of flavonoids and metal ions complexation has been the subject of many scientific research, the results in this field, particularly those relating to the complexation in aqueous media, are not fully harmonized, and are often contradictory in terms of defining the mechanism of the reaction, the position of chelating molecules involved in the structure of these complexes, the stoichiometry and stability of complexes. Within the scope of this doctorial thesis, in vitro complexation reactions of the selected hidroxy-flavon molecules, with various substitution variations (quercetin, fisetin, morin, baicalein), and iron(III) ion are investigated. The optimal conditions of the reactions are determined as well as the influence of the molecular structure on the complex stoichiometry. Also, the research within this thesis involve the examination of the activity of pure molecules and their complexes towards a few differently nitrogen..

Hydrogen desorption from nanostructured magnesium hydride composites

The influence of 3d transition metal addition (Fe, Co and Ni) on the desorption properties of magnesium hydride were studied. The ball milling of MgH2-3d metal blends was performed under Ar. Microstructural and morphological characterization were performed by XRD and SEM analysis, while the hydrogen desorption properties were investigated by DSC. The results show a strong correlation between the morphology and thermal stability of the composites. The complex desorption behavior (the existence of more than one desorption peak) was correlated with the dispersion of the metal additive particles that appear to play the main role in the desorption. The desorption temperature can be reduced by more than 100 degrees if Fe is added as additive. The activation energy for H2 desorption from the MgH2-Fe composite is 120 kJ/mol, implying that diffusion controls the dehydration process

Comparison, artificial neural network modeling and genetic algorithm optimization of the resinoid and potassium yields from white lady’s bedstraw (Galium mollugo L.) by conventional, reflux and ultrasound-assisted aqueous-ethanolic extraction

In this work, the yields of resinoid and potassium obtained from aerial parts of white lady’s bedstraw (Galium mollugo L.) by maceration, reflux extraction and ultrasound-assisted extraction using aqueous ethanol solutions as solvents. The main goal was to define the influence of the extraction technique and the ethanol concentration on the resinoid and potassium yields. The resinoid and potassium yields were determined by the solvent evaporation from the liquid extracts to constant weight and the AAS emission method, respectively. The dependence of resinoid and potassium yields on the ethanol concentration was described by linear and quadratic polynomial models, respectively. The best potassium extraction selectivity of 0.077 g K/g of dry extract was achieved by maceration at the ethanol concentrations of 10 g/100 g. The artificial neural network (ANN) was successfully applied to estimate the resinoid and potassium yields based on the ethanol concentration in the extracting solvent and the time duration for all three extraction techniques employed. The response surface methodology was also used to present the dependence of ANN results on the operating factors. The extraction process was optimized using the ANN model coupled with genetic algorithm. The maximum predicted resinoid and potassium yields of 30.4 and 1.67 g/100 g of dry plant were obtained by the ultrasonic extraction (80 min) using the 10 g/100 g aqueous ethanol solution

Electrochemical oxidation of a complex mixture of phenolic compounds in the base media using PbO2-GNRs anodes

A novel anode based on PbO2-GNRs nanocomposites was synthesized in order to investigate the simultaneous electrochemical oxidation of phenolic compounds in a mixture of methyl and chloro substituted phenols in alkaline solution (pH = 8.3). The crystal structure, morphology and composition of the synthesized materials were characterized using X-ray powder diffraction (XRPD), field emission scanning electron microscopy with energy dispersive X-ray spectrometer (FESEM-EDX) and transmission electron microscopy (TEM). FESEM images confirmed the presence of PbO2 nanoparticles on the PbO2-GNRs composite. The cyclic voltammetry measurements of the PbO2-GNRs electrode in 0.1 M Na2SO4 electrolyte indicated the electrochemical oxidation of phenol via indirect mechanism by hydroxyl radicals. Electrolytic oxidation of phenolic compounds was performed under potentiostatic conditions at potentials 2.3 V and 3 V. Removal efficiency of phenolic compounds increased with increasing the time of electrolysis and applied potential, up to 78% for 300 min and potential of 3 V. GC–MS chromatograms confirmed that mechanism of phenolic compounds degradation is based on their dechlorination and demethylation followed by the process of aromatic ring degradation. Newly synthesized PbO2-GNRs as electrode material could be successfully implemented in wastewater treatment of phenolic compounds by the electrochemical oxidation process.Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/4207

Validation and uncertainty estimation of an analytical method for the determination of phenolic compounds in concrete

Organic contaminants from building materials negatively affect the health of people. This study presents an analytical method for the simultaneous identification and quantification of 9 phenolic compounds, i.e., phenol, 2-chlorophenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 4-chloro-3- -methylphenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrahlorophenol and pentachlorophenol, in concrete by a gas chromatographic method with mass spectrometric detection (GC–MS). By comparing the MS spectra of the test compounds with MS spectra of analytical standards, reliable identification was achieved. The method could be applied in a given range (from 0.01 to 7.5 mg kg-1) with appropriate parameters of precision, accuracy, repeatability and linearity. The developed method could be used for quality control testing of phenols in concrete during the construction of new buildings, old residences and construction waste. The measurement uncertainty of the phenolic compounds in concrete was evaluated using two approaches, i.e., GUM recommendations and a Monte Carlo method. Disagreement of those methods was observed. The Monte Carlo method could be used in the evaluation of combined measurement uncertainty for the determination of phenolic compounds in concrete. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 37021

Degradation of bisphenol A on SnO2-MWCNT electrode using electrochemical oxidation

Bisphenol A (BPA) is an organic pollutant that is widely spread in waterbody with effluents as a result of its extensive use in the plastics industry. It posses to the class of compounds that are endocrine disruptors and has a great negative impact on living organisms. Therefore, the progress in development of green technology for BPA removal from the aquatic media is crucial for environmental protection. This paper presents BPA removal by electrochemical oxidation on SnO2-MWCNT (tin dioxide-multi walled carbon nanotube) nanocomposite anode. The nanocomposite was structural and morphological characterized by X-ray powder diffraction and transmission electron microscopy. Electrochemical properties of the SnO2-MWCNT anode were investigated using cyclic voltammetry, linear sweep voltammetry and electrical impedance spectroscopy. The electrochemical behavior of anodes toward BPA in sodium sulfate solutions has shown that BPA is oxidized by indirectly mechanism via hydroxyl radicals (verified by quenching tests). Electrolysis of BPA has been done in galvanostatic regime at current densities 2.5, 5.0, 10.0, 15.0 and 20.0 mA cm−2 in 0.1 M sodium sulfate supported electrolyte pH 4.0. Complete degradation of BPA was accomplished after 5 h of electrolysis at a current density of 20 mA cm−2. The proposed electrochemical technology using a low-cost SnO2-MWCNT electrode is promising for wastewater BPA removal