G. Mordarski

Simultaneous removal of dyes and metal cations using an acid, acid-base and base modified vermiculite as a sustainable and recyclable adsorbent

The aim of this work was the modification of vermiculite in order to produce a low cost, efficient and sustainable adsorbent for dyes and metals. Three activation methods consisting of acid, base and combined acid/base treatment were applied to improve the of vermiculites adsorption properties. Adsorbents were tested in single, bi- and tricomponent solutions containing cationic dyes and Cu2+ cations. The raw material showed low adsorption capacity for dyes and metal. The acid/base treated vermiculite had very good adsorption capacity toward dyes while the maximum adsorption capacity for Cu2+ did not change comparing to the starting material. The alkaline treated vermiculite was a good adsorbent for metals, while still being able to remove dyes on the level of the not treated material. Moreover, it was shown that the materials may be regenerated and used in several adsorption-desorption cycles. Furthermore, it was possible to separate adsorbed dyes from metals that were desorbed, using as eluents ethanol/NaCl and 0.05M HNO3, respectively. This opens a possibility for sustainable disposal and neutralization of both of the pollutants or for their further applications in other processes.

Kinetics of the oxygen electrode reaction in molten Li + Na carbonate eutectic: Part 4. Quantitative analysis of the potential-step chronoamperometric curves at Au electrodes

Abstract The potential-step chronoamperometric data for the oxygen reduction process “1” (reported in Part 1) at gold electrodes in a molten Li+Na carbonate eutectic have been analysed using the theory reported in Part 2. The analysis confirmed the previous conclusion, obtained in Part 3 for the linear scan voltammetric results, which identified process “1” as the diffusion-controlled reaction O22−+2e−⇌ 2 O2−. The equilibrium constants of the homogeneous reactions 1 2 O2+O2− ⇌ O22− and CO32− ⇌ CO32−. were estimated using the results of the chronoamperometric and linear scan voltammetric measurements and compared with the thermodynamic data.

Electrodeposition of thin metallic layer for solar cell electrodes

Purpose – The paper aims to show application of the electrochemically deposited coatings for thickening of the screen printed electric paths potentially applied in photovoltaic cells. Design/methodology/approach – The electric paths were screen printed with the use of silver-based paste. The paths were thickened by electrodeposition of thin copper layer in potentiostatic regime from surfactant-free plating bath. The morphology and surface quality of the paths were studied by imaging with scanning electron microscopy. Findings – The electric paths can be thickened successfully, but quality for the screen printed substrate determines quality of deposited layer. The EDX analysis confirmed that the deposited copper layer covered uniformly the printed paths. Research limitations/implications – The adhesion of the copper-covered path to the silicon wafer surface depends on adhesion of the original screen printed path. Originality/value – This paper confirms that electrodeposited copper can be applied for screen...

PDDA-Montmorillonite Composites Loaded with Ru Nanoparticles: Synthesis, Characterization, and Catalytic Properties in Hydrogenation of 2-Butanone

The effect of synthesis parameters on the physicochemical properties of clay/ polydiallyldimethylammonium (PDDA)/Ru composites and their applicability in hydrogenation of 2-butanone under very mild conditions (room temperature, atmospheric pressure, and aqueous solution) was studied. Three synthetic procedures were employed, differing in the order of addition of components and the stage at which metallic Ru species were generated. The materials were characterized with XRD (X-ray diffraction), XRF (X-ray fluorescence), EDS (energy-dispersive spectroscopy), AFM (atomic force microscopy), TEM/HRTEM (transmission electron microscopy/high resolution transmission electron microscopy), and TG/DSC (thermal gravimetry/differential scanning microscopy techniques. The study revealed that the method of composite preparation affects its structural and thermal properties, and controls the distribution and size of Ru particles. All catalysts are active in hydrogenation of 2-butanone. For best catalytic performance (100% conversion within 30 min) both the size of Ru particles and the load of polymer had to be optimized. Superior catalytic properties were obtained over the composite with intermediate crystal size and intermediate PDDA load, prepared by generation of metallic Ru species in the polymer solution prior to intercalation. This method offers an easy way of controlling the crystal size by modification of Ru/PDDA ratio.

Physicochemical and electrochemical properties of the carbon materials containing nitrogen and cobalt derived from acetonitrile and Co–Al layered double hydroxides

Two sets of the carbon materials containing nitrogen and cobalt were prepared by simultaneous carbonization of CH3CN and decomposition of Co–Al layered double hydroxides (LDHs) (of Co/Al atomic ratios equal to 2 or 3) at 600, 700 and 800xa0°C followed by treatment with HCl. The physicochemical features of the samples were characterized by means of XRD, TG, EA, XPS, XRF, FT-IR, SEM, Raman spectroscopy and nitrogen sorption. All of the composites were active in oxygen reduction reaction (ORR) in alkaline medium. Their ORR behaviour was determined by the contribution of structural defects and N-doping in graphitic lattice. The beneficial effect of metallic cobalt encapsulated inside the N-CNTs on the ORR performance was also taken into consideration. The studies showed that the likelihood of the existence of Co–N–C species and their participation in ORR seemed to be suppressed by the formation of CoAl2O4. The samples prepared at 600 and 700xa0°C appeared to be more active in ORR than that obtained at 800xa0°C. The number of electrons involved in ORR (2.89, 2.82 and 2.77) decreased with increasing synthesis temperature for the samples prepared with LDHs of Co/Alu2009=u20092 as a consequence of lowering concentration of nitrogen (3.2, 2.4 and 1.5xa0wt%), in particular diminishing contribution of pyridinic nitrogen, and decreasing exposure of graphitic edges (ID1/IGu2009~u20092.6, 2.0 and 1.0). The ORR performance of the samples prepared with LDHs of Co/Alu2009=u20093 is comparable to that of the corresponding samples prepared with LDHs of Co/Alu2009=u20092.