Platinum-Niobium(V) Oxide/Carbon Nanocomposites Prepared By Microwave Synthesis For Ethanol Oxidation

In the present work, Pt nanoparticles were deposited by means of microwave synthesis on the primary carbon supported Nb2O5 composite which was prepared in two different ways: (A) by dispersion of Nb2O5 and carbon with the mass ratio equal to 1:1 in a 2-propanol solution by ultrasonication for 30 min. with further desiccation of the mixture and (B) by heating the Nb2O5/C composite obtained according to the procedure (A) at 500 °C for 2 h. The transmission electron microscopy was used to determine the shape and the size of catalyst particles. X-ray diffraction and inductively coupled plasma optical emission spectroscopy were employed to characterize the structure and composition of the synthesized catalysts. The electrocatalytic activity of the synthesized catalysts towards the oxidation of ethanol in an alkaline medium was investigated by means of cyclic voltammetry

Modifying effects of leaf litter extracts from invasive versus native tree species on copper-induced responses in Lemna minor

Invasive plant species tend to migrate from their native habitats under favourable climatic conditions; therefore, trophic and other relationships in ecosystems are changing. To investigate the effect of natural organic matter derived from native Alnus glutinosa tree species and from invasive in Lithuania Acer negundo tree species on copper toxicity in Lemna minor, we analysed the dynamics of Cu binding in aqueous leaf litter extracts (LLE) and plant accumulation, morphophysiological parameters, and antioxidative response. The results revealed that A. glutinosa LLE contained polyphenols (49 mg pyrogallol acid equivalent (PAE)/g DM) and tannins (7.5 mg PAE/g DM), while A. negundo LLE contained only polyphenols (23 mg PAE/g DM). The ability of LLE to bind Cu increased rapidly over 1.5-3 h to 61% and 49% of the total Cu concentration (6.0 +/- 0.9 mg/L), respectively for A. glutinosa (AG) and A. negundo (AN), then remained relatively stable until 48 h. At the same time, L. minor accumulated 384, 241 or 188 mu g Cu/g FW when plants were exposed to Cu (100 mu M CuSO4), Cu with 100 mg/L dissolved organic carbon (DOC) from either AG LLE or AN LLE, accordingly. Catalase (CAT) and guaiacol peroxidase (POD) played a dominant role in hydrogen peroxide scavenging when plants were exposed to Cu and 10 or 100 mg/L DOCAG mixtures in both the first (up to 6h) and the second (6-48 h) response phases. Due to functioning of oxidative stress enzymes, the levels of the lipid peroxidation product malondialdehyde (MDA) reduced in concentration-dependent manner, compared to Cu treatment. When combining Cu and DOCAN treatments, the most sensitive enzymes were POD, ascorbate peroxidase and glutathione reductase. Their activities collectively with CAT were sufficient to reduce MDA levels to Cuinduced in the initial, but not the second response phase. These data suggest that leaf litter extracts of different phenolic compositions elicited different antioxidant response profiles resulting in different reductions of Cu stress, thus effecting L. minor frond and root development observed after seven days. The complex data from this study may be useful in modelling the response of the aquatic ecosystem to a changing environment

Antibiotic resistance of Streptococcus pneumoniae, isolated from nasopharynx of preschool children with acute respiratory tract infection in Lithuania

Background: Increasing pneumococcal resistance to commonly used antibiotics and multidrug resistance is a serious public health concern. Data on distribution of resistant Streptococcus pneumoniae (SPn) strains among children in Lithuania are limited. We evaluated the circulation of SPn serotypes and antimicrobial susceptibility among preschool children in Lithuania before the introduction of universal infant pneumococcal vaccination. Methods: A prospective study was carried out from February 2012 to March 2013 in five cities of Lithuania. A total of 900 children under six years of age who presented to primary care centre or a hospital emergency department with acute respiratory tract infection were enrolled in the study. Nasopharyngeal swabs were obtained and cultured for SPn. Positive samples (n = 367) were serotyped and tested for antimicrobial susceptibility. Associations of pneumococcal non-susceptibility with study site, season, age, sex, attendance of day care centre and treatment with antimicrobials (between one and six months prior the study) were evaluated. Results: About a half (56.7 %) of SPn strains were susceptible to all the antibiotics tested. Pneumococcal non-susceptibility to penicillin, erythromycin, clindamycin and trimethoprim–sulphamethoxazole was 15.8, 21.3, 16.9 and 27.3 %, respectively. None of the tested isolates was resistant to norfloxacin or vancomycin. We found a geographical variation of pneumococcal resistance within the cities of the country. Age, sex, the attendance of day care centre and treatment with antimicrobials prior the study was not significantly associated with a carriage of non-susceptible SPn strains. Among non-susceptible SPn serotypes 67.9 %–82.4 % were present in currently available pneumococcal conjugate vaccines. Conclusions: The rates of nasopharyngeal SPn susceptibility to penicillin and macrolides are still high among preschool children in Lithuania, however they are lower compared with previous studies. A strict policy with respect to antibiotic prescription together with widespread use of vaccination could potentially reduce the carriage rate of antibiotic-resistant pneumococci in our country

Adsorption of cyanides from aqueous phase onto two macroporous anion exchange resins

Fizinių ir technologijos mokslų centro Chemijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Anijoninio dažiklio ir vario(II) šalinimo iš vandeninių tirpalų aktyvintosiomis anglimis efektyvumas: temperatūros ir tirpalo sudėties įtaka

Anijoninio metalo kompleksinio dažiklio Lanasyn Navy M-DNL (LN) ir Cu(II) jonų šalinimo efektyvumas tirtas naudojant vienkomponenčius ir dvikomponenčius tirpalus bei komercines aktyvintąsias anglis Norit PK 1-3. Šalinimo proceso ypatybėms nustatyti statinėmis sąlygomis buvo tiriama įvairių veiksnių (pradinės Cu(II) jonų koncentracijos (1-4 mM), sąveikos laiko (5-180 min.) ir temperatūros (293–333 K)) įtaka. Viename litre tirpalo naudojant 4,0 g aktyvintųjų anglių nustatyta, kaip bėgant laikui kinta 0,05 mM dažiklio LN ir Cu(II) jonų koncentracija tirpale. Tirpalo sudėtis turi didelės įtakos šalinimo procesui ir tirpalo pH kitimui. Adsorbcijai vykstant aukštesnėse temperatūrose, nustatytas sinergizmas. 40 ir 60 °C temperatūroje dažiklio pašalinama 15-20 % daugiau iš tirpalo, kuriame yra Cu(II) druskos. Cu(II) jonų pašalinama taip pat 10 % daugiau tuo atveju, kai tirpale yra dažiklio LN. Adsorbuoti dažiklio LN ir Cu(II) jonų kiekiai šiek tiek mažesni iš mišrių tirpalų 20 °C temperatūroje, tačiau Cu(II) pašalinama beveik tiek pat, kai pradinė Cu(II) koncentracija 2 mM. Adsorbcijos procesas vyksta kaip pseudoantrojo laipsnio reakcija, tai būdinga abiems adsorbentams esant skirtingoms pradinėms Cu(II) koncentracijoms. Kylant temperatūrai didėja adsorbuotų dalelių difuzijos į vidines adsorbento poras greitisThe removal efficiency of anionic metal complex dye Lanasyn Navy M-DNL (LN) and Cu(II) ions has been studied in single and LN dye-Cu(II) binary solutions using the commercial activated carbon. To determine the removal process and properties, the effects of various operating parameters, the initial concentration of Cu(II) ions (1-4 mM), contact time (5-180 min) and temperature (293-333 K) were investigated in a batch adsorption technique. The time profiles for 0.05 mM LN dye and Cu(II) have been obtained using 4.0 g of activated carbon per liter of the solution. The composition of the solution plays an important role in the removal process and the evolution of solution pH. A synergic effect was observed when carrying out the adsorption process at higher temperatures. At the temperatures of 40 and 60 °C the removal percentage of the dye increases by 15-20% in presence of Cu(II) salt. The uptake of Cu(II) also increases by 10% in the presence of LN dye. The adsorbed amount of LN and Cu(II) slightly decreased at 20 °C temperature when the two solutes were present in the solution while the Cu(II) removal almost remained unchanged when Cu(II) concentration was equal to 2 mM. The adsorption process is governed by the pseudo-second-order reaction, at various initial Cu(II) concentrations for the two adsorbates. An increase in temperature leads to an increase in the rate of diffusion of the adsorbed particles into the internal pores of the adsorbentFizinių ir technologijos mokslų centro Chemijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Evaluation of impregnated activated carbons for removal of free cyanides: kinetics and equilibrium

Fizinių ir technologijos mokslų centro Chemijos institutasFizinių ir technologijos mokslų centro Chemijos institutas, [email protected] Didžiojo universitetasŠvietimo akademij

Sidabro cianidinių kompleksų ir laisvųjų cianidų šalinimas modifikuotomis ir nemodifikuotomis aktyvintosiomis anglimis

Statinėmis sąlygomis buvo tiriama sidabro cianidinių kompleksų ir laisvųjų cianidų adsorbcija iš jų mišraus tirpalo nemodifikuotomis bei Ag(I) ir Cu(II) impregnuotomis aktyvintosiomis anglimis Norit AB 0.8 CC ir AC-20. Nustatyta adsorbento koncentracijos įtaka cianidų šalinimo efektyvumui bei sorbcinei gebai. Sidabro arba vario druskomis impregnuotų aktyvintųjų anglių sorbcinė geba laisvųjų cianidų atžvilgiu žymiai didesnė nei nemodifikuotų adsorbentų, tačiau aktyvintųjų anglių modifikavimas nėra palankus sidabro cianidinių kompleksų adsorbcijai, ypač kai šalinimas vyksta iš didesnės koncentracijos tirpalųFizinių ir technologijos mokslų centro Chemijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Comparison of the Activity of 3D Binary or Ternary Cobalt Coatings for Hydrogen and Oxygen Evolution Reactions

In this study, cobalt-nickel (Co-Ni), cobalt-iron (Co-Fe), cobalt-iron-manganese (Co-Fe-Mn), cobalt-iron-molybdenum (Co-Fe-Mo), and cobalt-zinc (Co-Zn) coatings were studied as catalysts towards the evolution of hydrogen (HER) and oxygen (OER). The binary and ternary Co coatings were deposited on a copper surface using the electroless metal plating technique and morpholine borane (MB) as a reducing agent. The as-deposited Co-Ni, Co-Fe, Co-Fe-Mn, Co-Fe-Mo, and Co-Zn coatings produce compact and crack-free layers with typical globular morphology. It was found that the Co-Fe-Mo coating gives the lowest overpotential of 128.0 mV for the HER and the lowest overpotential of 455 mV for the OER to achieve a current density of 10 mA cm−2. The HER and OER current density values increase 1.4–2.0 times with an increase in temperature from 25 °C to 55 °C using the prepared 3D binary or ternary cobalt coatings for HER and OER. The highest mass electrocatalytic activity of 1.55 mA µg−1 for HER and 2.72 mA µg−1 for OER was achieved on the Co-Fe coating with a metal loading of 28.11 µg cm−2 at 25 °C