Electrochemical behaviour of serpentinite and forsterite in ferri/ferro cyanide benchmark redox system

Serpentinite rock collected near Kopaonik Mountain in Serbia is considered as a multiphase assemblage mostly consisting of mineral lizardite. Forsterite has been obtained by chemical-thermal treatment of grounded sample of serpentinite. Electrochemical features of these two materials were investigated by using modified carbon paste electrode (CPE) which included mixing analytes, graphite powder and parafin oil as a binder and packing the mixture in a Teflon holder. Morphological and structural characteristics of the samples were analyzed by SEM and XRD techniques which revealed presence of certain crystal phases and agregates of irregular shapes sized from 10 to 40 μm. Cyclic voltammetry was employed to study their electrochemical characteristics. The peak current height and peak-to-peak separation showed that the electrochemical reaction is quasi-reversible. Kinetic parameters were derived from Tafel analysis. Calculated kinetic parameters indicated prominent electrocatalytic effect of the minerals for ferri/ferro cyanide redox reaction in aquaeous solutionBook Of Abstracts of 4th Conference of The Serbian Society for Ceramic Material

Effective determination of clomazone and oxyfluorfen in aqueous samples by differential pulse stripping voltammetry

Two novel types of electrochemical sensors were obtained by chemical deposition of Pt and MoO2 nanoparticles onto multi walled carbon nano tubes (MWCNT) and used for determination of frequently used pesticides clomazone and oxyfluorfen in aqueous media via differential pulse stripping voltammetry (DPSV). Clomazone was determined in 0.1 M phosphate buffer solution at pH 7.0 in the concentration range 0.61-20.56 ng cm-3, with LOQ = 0.61 and LOD = 0.38 ng cm-3. Oxyfluorfen was determined with good reproducibility (RSD <2.4%) in the concentration range 2.5-34.5 ng cm-3, with r = 0.99 and a LOQ of 1.5 ng cm-3. Results were in the same range measured by HPLC/DAD, which was used as comparative method. Structural characterization of the dopped MWCNT performed by Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron (HR-TEM), and X-ray crystallography revealed a preserved MWCNT structure decorated with well dispersed species of the platinum and MoO2 nanoparticles.IX International Scientific Conference "Technics. Technologies. Education. Safety"; June 07-10, 2021; Borovets, Bulgari

The effects of colloidal SiO2 and inhibitor on the solid deposit formation in geothermal water of low hardness

Low solubility of SiO2 and its occurrence in geothermal waters in the form of ionic, colloidal and suspended state are the main cause of the solid deposit occurrence. Certain chemical types of silica, under the influence of Fe2+, Al3+, F−, OH- ions and other micro-constituents, and due to significantly decreased solubility of SiO2, stimulate nucleation, particle growth and solid deposit formation. The aim of this paper is to inhibit the process of nucleation and solid deposit formation by adding originally designed inhibitor in the form of an emulsion, when the total concentration of the present and added colloidal SiO2 is beyond the solubility limit (120 mg/dm3). By turbidimetric, SEM, EDS and XRD analysis, the processes of solid deposit formation were investigated in Vranjska Banja (Serbia) spa geothermal water source (water hardness of 4ºdH), and theoretical and practical conclusions were made

Removal of cationic dye from water by activated pine cones

Adsorption of a cationic phenothyazine dye methylene blueonto activated carbon prepared from pine cones was investigated with the variation in parameters of contact time, dye concentration and pH. The kinetic data were found to follow the pseudo-second-order kinetic modelclosely. The equilibrium data were best represented by the Langmuir isotherm with maximum adsorption capacity of 233.1 mg g-1. Adsorption was favored by using a higher solution pH. Textural analysis by nitrogen adsorption was used to determine specific surface area and pore structure of the obtained carbon. Boehm titrations revealed that carboxylic groups are present in the highest degree on the carbon surface. The results indicate that the presented method for activation of pine cones could yield activated carbon with significant porosity, developed surface reactivity and considerable adsorption affinity toward cationic dye methylene blue

Degradation of crystal violet over heterogeneous TiO2-based catalysts: The effect of process parameters

In this study, modified sol-gel method was employed to synthesize the pure and Zr-doped titania catalysts. Brunauer-Emmett-Teller (BET) method was applied to determine porosity, X-ray diffraction (XRD) analysis was used to study crystal structure, scanning electron microscopy (SEM) was used to investigate morphology and Fourier transform infrared spectroscopy (FTIR) was used to examine surface properties/total acidity of the obtained catalysts samples. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolourization/degradation under UV light irradiation. The effects of several photocatalysis operational parameters were considered, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment, as well as catalysts calcination temperatures and dopant amounts. The obtained results indicated faster dye decolourization/degradation with the increase of the catalyst dosage and the decrease of initial CV concentrations. The Zr-doping affects photocatalytic properties, i.e. CV decolourization/degradation of the prepared catalytic materials. Thus, addition of 5 wt.% of ZrO2 to titania increases photocatalytic effect for similar to 15% and addition of 10 wt.% of ZrO2 improves the photocatalytic efficiency of titania for nearly 30%

Electromagnetic characterization of Ni0.5Zn0.3Co0.2Fe2O4 bulk ceramics in the 1 MHz-12 GHz frequency range

In this paper, NiZnCo ferrite was produced by solid state synthesis, calcination at 1000 °C and sintering at 1250 °C in air atmosphere. The microstructure and phases of the sintered sample were analysed by scanning electron microscopy and X-ray diffraction, respectively. The magnetic properties of the ferrite were evaluated by magnetization and magnetostriction measurements. The complex magnetic permeability and complex permittivity were also measured between 1 MHz-12 GHz and the reflection loss (RL) was calculated in the 100 MHz-12 GHz frequency range. The results show that the ferrite sample presents magnetostrictive behaviour and a saturation magnetization of 71 Am2/kg. Complex permittivity measurements indicate that the material has dielectric behaviour in the whole frequency range studied, with ε′ varying between 7-40, and magnetic behaviour in frequencies between 1 MHz-5 GHz. The minimum RL was found at frequencies between 2.4-3.3 GHz and the calculated RL value for a thickness of 3 mm was lower than −10 dB in frequencies between 2.3-7.3 GHz. These results indicate potential application as microwave absorber in the S band

Decolorization of crystal violet over TiO2 and TiO2 doped with zirconia photocatalysts

Titania based catalyst and TiO2 doped with zirconia were prepared by modified sol-gel method. The synthesized catalysts samples were characterized by BET, XRD, SEM and FTIR techniques. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolorization/decomposition under UV light irradiation. The effect of several operational parameters, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment and number of reaction cycles were also considered. The obtained results indicated faster dye decolorization with the increase of the catalyst amount and a decrease of initial CV concentrations. An influence of doping with zirconia on the physico-chemical properties of bare titania was studied. The doping procedure had affected photocatalytic properties of the final catalytic material, and had improved photocatalytic performances of doped catalyst on crystal violet decolorization/degradation in comparison to bare titania

Electromagnetic characterization of Ni0.5Zn0.3Co0.2Fe2O4 bulk ceramics in the 1 MHz-12 GHz frequency range

In this paper, NiZnCo ferrite was produced by solid state synthesis, calcination at 1000 °C and sintering at 1250 °C in air atmosphere. The microstructure and phases of the sintered sample were analysed by scanning electron microscopy and X-ray diffraction, respectively. The magnetic properties of the ferrite were evaluated by magnetization and magnetostriction measurements. The complex magnetic permeability and complex permittivity were also measured between 1 MHz-12 GHz and the reflection loss (RL) was calculated in the 100 MHz-12 GHz frequency range. The results show that the ferrite sample presents magnetostrictive behaviour and a saturation magnetization of 71 Am2/kg. Complex permittivity measurements indicate that the material has dielectric behaviour in the whole frequency range studied, with ε′ varying between 7-40, and magnetic behaviour in frequencies between 1 MHz-5 GHz. The minimum RL was found at frequencies between 2.4-3.3 GHz and the calculated RL value for a thickness of 3 mm was lower than −10 dB in frequencies between 2.3-7.3 GHz. These results indicate potential application as microwave absorber in the S band

Recent Advances in Electrochemical Determination of Pesticides

Widespread usage of pesticides in agricultural practice caused their residues to appear in water and food products intended for human consumption. The potential toxicity of these resources has raised awareness about pesticide tracking in the environment. Development of reliable electrochemical sensors for the on-site determination of pesticide concentrations is envisioned as an alternative to conventional chromatographic methods which are robust, expensive and require skilled work force. Modification of the working electrode surface can result in enhanced electrochemical response towards selected pesticide making such electrode convenient sensor for facile and efficient determination of pesticides in low concentrations. New generation of nanomaterials is applied in electrode modification in order to improve its sensitivity and selectivity. The present review summarizes significant advances in voltammetric detection of pesticides for the period of the past five years. The major focus of this review is set to the types of carbon and oxide based materials, metal nanoparticles, composites and other materials employed to upgrade standard electrode configurations such as glassy carbon and carbon paste electrodes, boron doped diamond electrodes, screen printed and film electrodes, metal and amalgam, and other kinds of electrodes