Applying multi-criteria analysis for preliminary assessment of the properties of alginate immobilized Myriophyllum spicatum in lake water samples

The preliminary assessment of the properties of alginate immobilized aquatic weed Myriophyllum spicatum beads-MsAlg in a multi-element system of nine Serbian lakes water samples was done. Herein, the results obtained in the biosorption experiment with MsAlg contents of twenty-two elements analysed by inductively coupled plasma-optical emission spectrometry, biosorption capacity, element removal efficiency, total hardness (TH) and quality index of water (WQI) are presented. Scanning electron microscopy with energy dispersive X-ray spectroscopy was used for the characterization of M. spicatum and its beads. The study showed that aluminium, magnesium and strontium were adsorbed by MsAlg in the water samples from all examined lakes; barium and iron in the water samples from six lakes. The overall average efficiency of MsAlg in biosorption of elements was in the following order: Al > Ba > Sr > Fe > Mg (58.6, 51.7, 48.2, 23.9 and 17.7%, respectively). The increase of TH and WQI values after the biosorption was noticed in all studied lake water samples. The most significant correlations for pH were regarding the contents of B, Mg and Ca, whereas WQI was highly correlated to the contents of B and Mg, and pH. The complexity of the obtained data was explained by Cluster Analysis and Principal Component Analysis, which showed good discrimination capabilities between the water samples taken from different locations. Considering that the invasive M. spicatum is natural, widespread and that its immobilization is cheap and eco-friendly, presented findings could be helpful in further assessment of MsAlg beads for its potential use as biofilter

Promotivni efekat Zn u platinskom katalizatoru za efikasnu reakciju elektrooksidacije etanola

Polymer electrolyte membrane fuel cells (PEMFCs) are pure electrochemical energy converters that are key components of energy sources for vehicles and for stationary and portable energy suppliers. Searching for a good catalyst for the ethanol oxidation reaction is one of the most significant issues in material science. To increase the economic potential of fuel cell technology, catalyst must be extremely active, stable, and inexpensive. Due to its high catalytic activity, structural and chemical stability, and widespread use in commercial fuel cells, platinum is still the material of choice for making cathodes. Although there is extensive continuing research to reduce the Pt concentration while keeping the high catalytic activity, its high cost remains a barrier to a wider adoption of fuel cell technology.Therefore, the potential for cost reduction lies in the optimization of the catalyst, i.e. obtaining the maximum catalytic efficiency with the lowest possible content of noble metals. The focus of this research will be on novel synthesis techniques for PtSnZn catalysts with better efficiency and durability for the ethanol oxidation reaction. This research demonstrates the potential of studying new PtSnZn catalytic materials as catalysts for the oxidation of ethanol. This study used the microwave assisted polyol technique to create PtZn and PtSnZn nanoparticles supported on high surface area carbon Vulcan XC-72R material. By using cyclic voltammetry, electro-oxidation of adsorbed CO, and the chronoamperometric method, the electrochemical behavior of synthesized catalysts was examined. X-ray diffractometry, transmission electron microscopy analysis and thermogravimetric analysis were applied to obtain the physicochemical properties of the catalyst. The advantages of microwave synthesis and carefully balanced metal alloying in the PtSnZn/C catalysts led to a high catalytic activity of the synthesized catalyst in the ethanol oxidation reaction compared to the Pt/C catalyst

Elektrooksidacija metanola na binarnim i ternarnim platinskim katalizatorima na ugljeničnom nosaču

One of the most popular alternative sources of energy are direct methanol fuel cells (DMFCs) with platinum-based catalysts due to their non-toxicity, reduced emissions of hazardous pollutants and high energy density. However, significant challenges of the scientific community related to Pt catalysts are the high cost, depletable resources and formation of poisoning species i.e. CO, during the methanol oxidation reaction. To reduce the amount of expensive Pt and susceptibility of Pt to poisoning species and simultaneously improve its catalytic performance, recent studies are focusing on the synthesis of Pt alloys in which a certain amount of platinum is replaced with less expensive metals such as Ru, Sn, Ni, Cu, Rh and Co. The usage of carbon (Vulcan XC-72R) for catalyst support enables high dispersion of metal, high surface area and good electrical conductivity improving overall performances of DMFCs. In this work, PtZn/C and PtSnZn/C catalysts were synthesized by the microwave-assisted polyol method. The structure and morphology of the catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TG) and X-ray diffraction (XRD) analysis. The activity and stability of synthesized catalysts for methanol oxidation in 0.5 M sulfuric acid were investigated. It was demonstrated that the activity of the platinum catalysts was improved thanks to the synergistic effects caused by the addition of different metals, such are bifunctional and electronic effects

Uticaj sadržaja Zn na aktivnost PtZn katalizatora u reakciji elektrooksidacije metanola

This work highlights a simple and efficient approach for the development of PtZn catalyst materials with tunable content of Zn. Nanoparticles of PtZn deposited on high surface area carbon Vulcan XC-72R material were synthesized by microwave-assisted polyol method, giving control over the size and dispersion of nanoparticles. Cyclic voltammetry and electrooxidation of adsorbed CO were used to investigate the electrochemical behavior of synthesized catalysts: PtZn/C (90:10); PtZn/C (85:15) and PtZn/C (75:25). It was found that PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. In comparison to the corresponding catalyst with the different Zn loading, it was concluded that PtZn (90:10)/C catalyst had better activity compared to PtZn/C (85:15) and PtZn/C (75:25) catalysts. The observed high catalytic activity in the methanol oxidation reaction of synthesized catalysts can be ascribed to the very efficient microwave synthesis and well-balanced content of Zn as alloying metal.Ovaj rad predstavlja jednostavan i efikasan pristup za razvoj PtZn katalizatora sa različitim sadržajem Zn. Nanočestice PtZn istaložene na ugljeničnom materijalu Vulcan XC-72R velike površine, sintetisane su poliol metodom pomoću mikrotalasne pećnice, dajući kontrolu nad veličinom i disperzijom nanočestica. Za ispitivanje elektrohemijskog ponašanja sintetisanih katalizatora PtZn/C (90:10); PtZn/C (85:15) i PtZn/C (75:25) korišćeni su ciklična voltametrija i elektrooksidacija adsorbovanog CO. Utvrđeno je da PtZn/C katalizatori imaju visoke elektrokatalitičke performanse u reakcijama oksidacije metanola. Poređenjem katalizatora sa različitim sadržajem Zn, zaključeno je da PtZn/C (90:10) katalizator ima bolju aktivnost u odnosu na PtZn (85:15) i PtZn (75:25) katalizatore. Uočena visoka katalitička aktivnost sintetisanih katalizatora u reakciji oksidacije metanola može se pripisati veoma efikasnoj mikrotalasnoj sintezi i dobro izbalansiranom dodavanju Zn kao legirajućeg metala sa različitim sadržajem u PtZn/C katalizatorima

Design of Pt-Sn-Zn Nanomaterials for Successful Methanol Electrooxidation Reaction

This work highlights the potential for the synthesis of new PtSnZn catalysts with enhanced efficiency and durability for methanol oxidation reaction (MOR) in low-temperature fuel cells. In this research, PtZn and PtSnZn nanoparticles deposited on high surface area Vulcan XC-72R Carbon support were created by a microwave-assisted polyol method. The electrochemical performances of synthesized catalysts were analyzed by cyclic voltammetry and by the electrooxidation of adsorbed CO and the chronoamperometric method. The physicochemical properties of obtained catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TGA) analysis, energy dispersive spectroscopy (EDS) and by X-ray diffraction (XRD). The obtained findings showed the successful synthesis of platinum-based catalysts. It was established that PtSnZn/C and PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. Catalysts stability tests were obtained by chronoamperometry. Stability tests also confirmed decreased poisoning and indicated improved stability and better tolerance to CO-like intermediate species. According to activity and stability measurements, the PtSnZn/C catalyst possesses the best electrochemical properties for the methanol oxidation reaction. The observed great electrocatalytic activity in the methanol oxidation reaction of synthesized catalysts can be attributed to the beneficial effects of microwave synthesis and the well-balanced addition of alloying metals in PtSnZn/C catalysts

Supplementary material for the article: Milojković, J. V.; Popović-Djordjević, J. B.; Pezo, L. L.; Brčeski, I. D.; Kostić, A. Ž.; Milošević, V. D.; Stojanović, M. D. Applying Multi-Criteria Analysis for Preliminary Assessment of the Properties of Alginate Immobilized Myriophyllum Spicatum in Lake Water Samples. Water research 2018, 141, 163–171. https://doi.org/10.1016/j.watres.2018.05.014

Supplementary material for: [https://doi.org/10.1016/j.watres.2018.05.014]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2186]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3029

Cultural heritage criminality: Case analyses

The aim of this paper is to present crime related to cultural heritage in the world, and to determine through theoretical analysis whether it is increasing or decreasing. Reading the literature, it was concluded that crime in the field of cultural heritage is growing, and that it is most common in economically and socially underdeveloped countries. The countries of South America and the Middle East are at the top in this type of crime. The Western world is the ultimate destination for antique smuggling

Acid leaching of oxide-sulphide copper ore prior the flotation: A way for an increased metal recovery

Copper mine "Cerovo"- East Serbia as well as the other ore bodies in its vicinity contain a significant amount of oxide copper minerals in their uper layers (>40%). Processing of such mixed ores by the existing concentration technologies leads to a substantial copper losses (<60%). Reduction of "oxide copper", by acid leaching prior the flotation concentration, can increase the overall copper efficiency up to more than 70% in the single-stage leaching, achieving an efficiency in the flotation concentration stage higher than 75%. Based on the performed experimental results the flow sheet for processing of the mixed oxide-sulphide copper ore is proposed

Platinski katalizatori na ugljeničnoj osnovi za efikasnu oksidaciju metanola

Горивне ћелије са метанолом (DMFC) као горивом cу веома перспектпвни извори енергије за стационарне и преносиве електричне уређаје пре свега због своје високе ефикасности и ниске емисије загађујућих материја, ниске радне температуре, велике густине енергије, нетоксичних и еколошки прихватљивих карактеристика. Међутим, њихова шира комерцијална употреба ограничена је факторима као што су: високи трошкови племенитог метала у електрокатализатору (на пример, Pt) и лоша радна издржљивост, односно брза деградација катализатора. У овом раду је представљена активност електрооксидације метанола код PtSn, PtSnO2, PtZn и PtSnZn катализатора у киселој средини. Стабилне наночестице cу успешно синтетизоване модификованим полиол поступком уз помоћ микроталасне пећнице. Ефекти састава, степена легирања, величине и морфологије синтерованих честица на електрокаталитичку активност су испитивани СО стрипинг волтаметријом и реакцијом електрооксидације метанола. Добијени резултати указују на појачане каталитичке актигвности за реакцију оксидације метанола побољшану отпорност на инхибицију СО, након додавања Sn или Zn у Pt катализатор

Prognostic value of early post-infarction angina in elderly patients

Although numerous studies have shown that early post-infarction angina was a predictor of poor prognosis in patients with acute myocardial infarction, not a single study has considered this issue in the elderly. The goal of this study, based on a five-year follow-up of elderly patients with acute myocardial infarction, was to determine whether early post-infarction angina in the elderly had any influence on mortality and the incidence of additional coronary events. The study population consisted of 51 patients, aged 60 years or more, with acute myocardial infarction. Early post-infarction angina occurred in 31 subjects (Group 1), while it did not in 20 subjects (Group 2). Patients were monitored for five years and the incidences of death and new coronary events were recorded. A survival analysis was carried out using the Kaplan-Meier method. The survival analysis showed no difference between the observed groups concerning the following probabilities: death (p=0.9459), cardiac death (p=0.8253), myocardial reinfarction (p=0.7405), new coronary events (p=0.1708), unstable angina (p=0.1788), myocardial revascularisation (p=0.0691), and heart failure (p=0.7047j. In contrast to the younger population, where numerous studies have confirmed the link between early post-infarction angina and poor long-term prognosis, such findings could not be replicated in this study of the elderly population