27 research outputs found
Voltammetric screen-printed carbon sensor modified with multiwalled carbon nanotubes and bismuth film for trace analysis of thallium(I)
No full textThe paper investigates the possibility of using commercially available screen-printed sensors with carbon nanomaterials modified working electrodes to anodic stripping voltammetric determination of trace concentrations of Tl(I). Each working electrode was additionally plated in-situ with a bismuth film (BiF). The highest analytical signal of Tl(I) at potential of -0.65 V (vs. pseudo- reference silver electrode) was achieved at the screen-printed carbon sensor with multiwalled carbon nanotubes and bismuth film modified working electrode (SPCE/MWCNTs/BiF). The calibration curve was linear in the range of Tl(I) concentrations from 1·10-8 to 1·10-6 mol·dm-3 (-0.9 V, 180 s). The developed procedure of Tl(I) determination at this sensor allowed to achieve the low limits of detection and quantification of Tl(I), 2.8·10-9 and 9.3·10-9 mol·dm-3 respectively. The method was used to determine thallium in the spiked water samples from the Vistula river
Isotopic Transient Kinetic Analysis of Soot Oxidation on Mn3O4, Mn3O4-CeO2, and CeO2 Catalysts in Tight Contact Conditions
No full textThe reaction mechanism of soot oxidation on Mn (Mn3O4), Mn-Ce (Mn3O4-CeO2), and Ce (CeO2) catalysts in tight contact conditions was investigated using ITKA (isotopic transient kinetic analysis). The obtained results suggest that lattice-bulk oxygen from all studied catalysts takes part in the soot oxidation process but with varying relative contributions: for the Ce catalyst, this contribution is practically 100%, whereas with decreasing Ce content in Mn-Ce catalysts, the significance of lattice-bulk oxygen for soot oxidation diminishes. For the Mn catalyst, it is estimated to be below 50%. Moreover, strong interactions between Mn and Ce ions were observed, increasing oxygen mobility in the catalyst crystal lattice and affecting the activity of Mn-Ce catalysts
Kodeksowe pozwolenie zintegrowane a sektorowe pozwolenie wodnoprawne - doświadczenia niemieckie
No full textThe author takes the issue of individual administrative acts aimed at rational use of the environment. He is focused on the German experiences. The rationale for this choice is, on one hand, a considerable number of such instruments, provided especially in the water law. On the other hand it is an significant and extensive literature devoted to such instruments. Special role in the development of doctrine played the work on the code of environmental law, which was the central point of an integrated permit. Although there has been no adoption of the Code, but accumulated experiences influence the theory and practice of application of this law. Proof of this is also a history of Water Resources Act, passed in 2009. The need for the adoption of this Act was the result of the consequences of competence changes made to the constitution. These changes were made in order to allow the adoption of the Code. In the new law types of water permits known from previous regulations were repeated, but also there were added selected solutions for environmental integrated protection. That was modeled on the draft Code. It was also added one kind of permission functioning in legislation of federal states
Effect of Potassium Doping on the Structural and Catalytic Properties of Co/MnOx Catalyst in the Steam Reforming of Ethanol
No full textThe promotional effect of potassium (~1.25 wt%) on a Co/MnOx catalyst was studied for samples prepared by the impregnation method in the steam reforming of ethanol (SRE) process at 420 °C for a H2O/EtOH molar ratio of 12/1. The catalysts were characterized using physicochemical methods to study their textural, structural, and redox properties. The XRD studies revealed that, during the treatment of both cobalt-based catalysts under a hydrogen atmosphere at 500 °C, Co0 and MnO phases were formed by the reduction in Co3O4 and Mn2O3/Mn3O4 phases, respectively. Potassium doping significantly improved stability and ability for the C–C bond cleavage of the Co/MnOx catalyst. The enhancement of activity (at ~25%) and selectivity to hydrogen (at ca. 10%) and the C1 product, mainly carbon dioxide (at ~20%), of the Co/MnOx catalyst upon potassium doping was clarified by the alkali promoter’s impact on the reducibility of the cobalt and manganese oxides. The microscopic observations revealed that fibrous carbon deposits are present on the surface of Co/MnOx and KCo/MnOx catalysts after the SRE reaction and their formation is the main reason these catalysts deactivate under SRE conditions. However, carbon accumulation on the surface of the potassium-promoted catalyst was ca. 12% lower after 18 h of SRE reaction compared to the unpromoted sample
Electrochemically Pretreated Sensor Based on Screen-Printed Carbon Modified with Pb Nanoparticles for Determination of Testosterone
No full textTestosterone (TST), despite its good properties, may be harmful to the human organism and the environment. Therefore, monitoring biological fluids and environmental samples is important. An electrochemically pretreated screen-printed carbon sensor modified with Pb nanoparticles (pSPCE/PbNPs) was successfully prepared and used for the determination of TST. The surface morphology and electrochemical properties of unmodified and modified sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive X-ray spectroscopy (EDS). Selective determinations of TST at the pSPCE/PbNPs were carried out by differential pulse adsorptive stripping voltammetry (DPAdSV, E(Pb dep.and TST acc.) of −1.1 V, t (Pb dep.and TST acc.) of 120 s, ΔE(A) of 50 mV, ν of 175 mV s(−1), and t(m) of 5 ms) in a solution containing 0.075 mol L(−1) acetate buffer of pH = 4.6 ± 0.1, and 7.5 × 10(−5) mol L(−1) Pb(NO(3))(2). The analytical signal obtained at the potential around −1.42 V (vs. silver pseudo-reference electrode) is related to the reduction process of TST adsorbed onto the electrode surface. The use of pSPCE/PbNPs allows obtaining a very low limit of TST detection (2.2 × 10(−12) mol L(−1)) and wide linear ranges of the calibration graph (1.0 × 10(−11)–1.0 × 10(−10), 1.0 × 10(−10)–2.0 × 10(−9), and 2.0 × 10(−9)–2.0 × 10(−8) mol L(−1)). The pSPCE/PbNPs were successfully applied for the determination of TST in reference material of human urine and wastewater purified in a sewage treatment plant without preliminary preparation
Activity and stability of cobalt-manganese catalysts in the process of methane flameless combustion
No full textOxide cobalt-manganese catalysts with different contents of cobalt and manganese, as well as pure cobalt and manganese catalysts have been tested in the process of methane flameless combustion (complete catalytic oxidation). The X-ray diffraction and X-ray photoelectron spectroscopy results showed that cobalt-manganese catalysts mainly composed of the spinel phase of Co3O4, Mn2CoO4 and/orMnCo2O4. The highest initial activity was presented bythe cobalt-manganese catalyst withahigh cobalt content.However, after 50-hours stability test the highest activity was presented by the cobalt-manganese catalyst with Co and Mn content close to the equimolar value
First Screen-Printed Sensor (Electrochemically Activated Screen-Printed Boron-Doped Diamond Electrode) for Quantitative Determination of Rifampicin by Adsorptive Stripping Voltammetry
No full textIn this paper, a screen-printed boron-doped electrode (aSPBDDE) was subjected to electrochemical activation by cyclic voltammetry (CV) in 0.1 M NaOH and the response to rifampicin (RIF) oxidation was used as a testing probe. Changes in surface morphology and electrochemical behaviour of RIF before and after the electrochemical activation of SPBDDE were studied by scanning electron microscopy (SEM), CV and electrochemical impedance spectroscopy (EIS). The increase in number and size of pores in the modifier layer and reduction of charge transfer residence were likely responsible for electrochemical improvement of the analytical signal from RIF at the SPBDDE. Quantitative analysis of RIF by using differential pulse adsorptive stripping voltammetry in 0.1 mol L−1 solution of PBS of pH 3.0 ± 0.1 at the aSPBDDE was carried out. Using optimized conditions (Eacc of −0.45 V, tacc of 120 s, ΔEA of 150 mV, ν of 100 mV s−1 and tm of 5 ms), the RIF peak current increased linearly with the concentration in the four ranges: 0.002–0.02, 0.02–0.2, 0.2–2.0, and 2.0–20.0 nM. The limits of detection and quantification were calculated at 0.22 and 0.73 pM. The aSPBDDE showed satisfactory repeatability, reproducibility, and selectivity towards potential interferences. The applicability of the aSPBDDE for control analysis of RIF was demonstrated using river water samples and certified reference material of bovine urine
Evolution of the structure of unpromoted and potassium-promoted ceria-supported nickel catalysts in the steam reforming of ethanol
No full textHydrogen production by steam reforming of ethanol over Co/CeO2 catalysts: Effect of cobalt content
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