Poređenje kinetike bubrenja hidrogela delimično neutralisane poli(akrilne) kiseline u destilovanoj vodi i fiziološkom rastvoru

The isothermal kinetics Curves of the swelling of a poly(acrylic acid) hydrogel in distilled water and physiological Solution at temperatures ranging from 20 to 40 degrees C were determined. The possibility of applying both the Fick's kinetics model anti kinetics model of the first order chemical reaction to the swelling kinetics of the PAA hydrogel in distilled water and physiological Solution were examined. It was found that the possibilities of applying these models were limited. The new model of the kinetics of swelling in distilled water and physiological solution was established. The kinetic parameters (E-a, ln A) for the swelling in distilled water and physiological solution were determined. The decrease of the equilibrium degree of swelling and the saturation swelling rate of the swelling of the PAA hydrogel in physiological solution compared to swelling in distilled water could be explained by the decreased differences in the ionic osmotic pressures between the hydrogel and the swelling medium. The increase of the initial swelling rate in the physiological solution might be caused by an increased density of charges at the network and by an increased affinity of the network towards the water molecules. The increase of the activation energy of the swelling of the PAA hydrogel in the physiological solution is a consequence of its additional "ionic crosslinking".U radu su ispitivane izotermalne kinetičke krive bubrenja hidrogela delimično neutralisane poli(akrilne) kiseline u destilovanoj vodi i fiziološkom rastvoru u temperaturnom opsegu od 20 do 40 °C. Ispitivana je mogućnost primene Fikovog kinetičkog modela kao i kinetike i reda hemijskih reakcija na kinetiku bubrenja poliakrilnog hidrogela.Utvrđeno je da su mogućnosti za njihovu primenu vrlo ograničene. Iz tih razloga primenjen je novi model kinetike bubrenja. Određeni su kinetički parametri (Ea, lnA) za procese bubrenja u destilovanoj vodi i fiziološkom rastvoru. Smanjenje ravnotežnog stepena bubrenja i saturacione brzine bubrenja hidrogela delimično neutralisane poli(akrilne) kiseline u fiziološkom rastvoru u odnosu na destilovanu vodu može se objasniti smanjenjem razlike u jonskom osmotskom pritisku između hidrogela i medijuma za bubrenje. Povećanje inicijalne brzine bubrenja u fiziološkom rastvoru u odnosu na destilovanu vodu prouzrokovano je povećanjem gustine naelektrisanja na polimernoj mreži i povećanim afinitetom prema molekulima vode. Povećanje energije aktivacije hidrogela delimično neutralisane poli(akrilne) kiseline pri bubrenju u fiziološkom rastvoru se objašnjava dodatnim "jonskim umreženjem" hidrogela u fiziološkom rastvoru

Smrt Napoleona - rak, trovanje, hemodinamika ili nešto četvrto?

The cause of death of Napoleon Bonaparte was, for years, the subject of discussion and different interpretations. In this article, without any intention to give full and final answer about the cause of his death, one of potential versions is described. This version, probably the one most interesting for chemists, is suggesting that due to biotransformation of arsenic compounds present in the wallpapers of Napoleon's house at St. Helena, volatile arsenic compounds were formed. Consequence of inhalation of these toxic compounds of arsenic could be the death of the Imperator.Smrt Napoleona Bonaparte je godinama bila predmet rasprava. U ovom tekstu se, bez namere da se daje konačni sud o tome zbog čega je Napoleon umro, prikazuje jednu od mogućih verzija, za hemičare najinteresantnije, koja kaže da su, zahvaljujući biotransformaciji jedinjenja arsena prisutnih u tapetama kojima su bili obloženi zidovi kuće u kojoj je Napoleon na Svetoj Jeleni živeo, stvarana isparljiva jedinjenja arsena, čije je dugotrajno udisanje dovelo do smrti imperatora

Supplementary material for the article: Nikolic, V.; Loncarevic, B.; Popovic, A. Biodegradation of Copolymer Obtained by Grafting Reaction between Methacrylic Acid and Starch. Polymer Bulletin 2019, 76 (5), 2197–2213. https://doi.org/10.1007/s00289-018-2484-x

Supplementary material for: [https://doi.org/10.1007/s00289-018-2484-x]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/341

Supplementary material for the article: Nikolic, V.; Loncarevic, B.; Popovic, A. Biodegradation of Copolymer Obtained by Grafting Reaction between Methacrylic Acid and Starch. Polymer Bulletin 2019, 76 (5), 2197–2213. https://doi.org/10.1007/s00289-018-2484-x

Supplementary material for: [https://doi.org/10.1007/s00289-018-2484-x]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/341

Supplementary data for article: Relić, D.; Đorđević, D. S.; Popović, A. R. Assessment of the Pseudo Total Metal Content in Alluvial Sediments from Danube River, Serbia. Environmental Earth Sciences 2011, 63 (6), 1303–1317. https://doi.org/10.1007/s12665-010-0802-1

Supplementary material for: [https://doi.org/10.1007/s12665-010-0802-1]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1170

Specijacija odabranih mikro- i makroelemenata u uzorcima lignita termoelektrane 'Nikola Tesla A' (Obrenovac, Srbija)

Four samples of milled lignite used in the "Nikola Tesla A" power plant located in Obrenovac near Belgrade, were subjected to a five-step sequential extraction, comprising of the following phases: distilled water, 1M ammonium acetate, 0.2M ammonium oxalate/0.2M oxalic acid, acidic solution of H2O2and a 6M solution of HCl. The concentrations of the different elements obtained in the extractions were statistically analyzed. The majority of the examined elements were found to be most probably associated with inorganic fractions of lignite, only aluminum, silicon, chromium and arsenic have a larger extractable organic/sulfide fraction than an extractable inorganic fraction. Alumosilicates of magnesium (carriers of arsenic, zinc, lead, copper and chromium), silicates of potassium (scavengers of lead and nickel), mixed aluminates of iron and magnesium (carriers of arsenic, zinc, copper and chromium) and compounds of iron that do not contain aluminum and magnesium (scavengers of manganese) were dissolved in the fifth phase of the sequential extraction. Copper is a substrate of alumosilicates of potassium and magnesium, while zinc and chromium are substrates of compounds of iron leached in the third phase of the sequential extraction. Interphase correlation revealed that the adsorbed and ion-exchangeable fractions of most of the examined elements do not exhibit preferential binding to the components of the inorganic matrix of lignite ash.Četiri uzorka mlevenog lignita korišćenog u Termoelektrani "Nikola Tesla A" u Obrenovcu u Beograda su podvrgnuta sekvencijalnoj ekstrakcija koja se sastojala od pet faza: u prvoj je korišćena destilovana voda, u drugoj 1M amonijum-acetat, u trećoj 0,2M amonijum-oksalat i 0,2M oksalna kiselina, u četvrtoj kiseo rastvor H2O2 i u petoj 6M rastvor HCl. Dobijene koncentracije izabranih elemenata su statistički analizirane, kako bi se utvrdile veze između različitih elemenata. Najveći deo ispitivanih elemenata je uglavnom asociran sa ekstrahovanom neorganskom fazom uglja, samo aluminijum silicijum, hrom i arsen imaju unutar ekstraktibilnog dela elemenata veću organsku/sulfidnu frakciju od neorganske. Od jedinjenja rastvornih u petoj fazi ekstrakcije uglja, alumosilikati magnezijuma su nosilac arsena, cinka olova, bakra i hroma, silikati kalijuma nosilac olova i nikla, mešoviti aluminati gvožđa i magnezijuma nosilac arsena, cinka, bakra i hroma, a jedinjenja gvožđa koja nisu povezana sa aluminatima ni magnezijumom nosilac mangana. U trećoj fazi ekstrakcije uglja se rastvaraju alumosilikati kalijuma i magnezijuma asocirani sa bakrom, dok su jedinjenja gvožđa rastvorna u trećoj fazi ekstrakcije asocirana sa cinkom i hromom. Interfazna korelaciona analiza je pokazala da se adsorbovana i jonoizmenjiva frakcija većine ispitivanih elemenata ne vezuje preferencijalno za delove neorganske matrice čestica pepela

Neural network prediction of the gas chromatographic separation of polycyclic aromatic hydrocarbons

This paper describes the application of artificial neural networks (ANNs) method to the modeling of 13 polycyclic aromatic hydrocarbons (PAHs)retentionsin temperature - programmed gas chromatography.The ANN method used resulted in relatively good agreement (RMStesting = 0.018) between the measured and the predicted retention times for 13 PAHs. Somewhat higher discrepancy in prediction was observed for the late – eluted PAHs at lower temperature ramps.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Trace and minor elements determination in some herbal drugs by faas

In this paper trace (Cu and Zn) and minor (Mn and Fe) elements in some herbal drugs originating from the plants of the family Asteracae were determined by flame atomic absorption spectrometry. Chamomillae flos, Milefolii herba and Absinthii herba were analyzed taking into account their importance in phytotherapy in different diseases and disorders and the essentiality of mentioned elementsfor plantslife cycle. Validation of proposed method was performed by using CRM, NIST 1573a.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Optimization of the preparation of novel polymer/clay nanocomposites

Recent advances in material technologies have resulted in the preparation of novel polymer/clay composites with improved thermal, mechanical, optoelectronic/ magnetic properties and increased biodegradability [1]. In this study, six samples of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) nanocomposites with organically-modified montmorillonite clay Cloisite 30B® (C30B), were prepared via suspension copolymerization. In order to obtain nanocomposites with fine spherical beads of regular shape and satisfying thermal stability the optimization of the synthesis conditions was performed. Firstly, the influence of the poly(N-vinyl pyrrolidone) (PVP) quantity in the aqueous phase was varied (1, 3 and 5 wt.%) at a constant stirring rate of 250 rpm and constant clay content C30B (10 wt.%). In the second phase of the optimization of the preparation, samples with a constant composition of the composite reaction mixture (5 wt.% PVP and 10 wt.% C30B) at a stirring rate of 250, 325 and 400 rpm, were prepared. According to the obtained results, it was concluded that the optimal conditions for preparation of these composites are 5 wt.% of PVP and 400 rpm. The prepared nanocomposites were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in air. The structure of the prepared nanocomposites was confirmed with FTIR spectroscopy. According to the obtained SEM microphotographs the fine spherical beads, with desired size and homogeneous morphology, were prepared. Furthermore, SEM analysis was also showed that clay nanoparticles are homogeneously dispersed both inside surface and cross-section area. The incorporation of C30B clay increased the thermal stability of the prepared polymer/clay nanocomposites in comparison to the pure PGME copolymer