Slobodan Brinić

Impedance investigation of corrosion inhibition of armco iron by thiourea

The inhibitive action of thiourea on the corrosive behaviour of ARMCO iron was investigated in deaerated 0.5 M H2SO4 solution, by means of electrochemical impedance spectroscopy. The inhibitor effectiveness increases with concentration, reaches a maximum (at about 1 mm) and then decreases. The adsorptive behaviour of thiourea on the electrode surface up to its peak follows a Frumkin-type isotherm with lateral repulsion, where the molecules are vertically adsorbed on the iron surface via the sulfur atom. Thiourea acts as a mixed inhibitor up to the critical concentration. It decreases the dissolution of iron and the hydrogen evolution reaction by blocking the electrode surface. The free energy of adsorption ΔGad = −39 kJ mol−1 and the attraction constant a = −4.4.

Characterization of anodic films on lead and lead alloys by impedance spectroscopy

Abstract The behaviour of lead and lead-antimony binary alloys with 1.3–4.5 wt.% antimony was investigated in the lead sulfate and lead oxide potential regions by means of cyclic voltammetry and electrochemical impedance spectroscopy. The impedance data show that the inner PbO barrier layer is formed beneath the initially grown PbSO 4 porous layer at potentials positive to −0.2 V versus SCE. The antimony content influences the characteristics of the anodic layer by decreasing its resistance and increasing its capacity. These changes were observed both on the lead sulfate and especially the lead oxide layers. With increased anodic polarization, the film resistance increases as well while the capacity shows the opposite change.

Fluoride electrode with LaF3-membrane and simple disjoining solid-state internal contact

Fluoride-selective electrode with LaF(3)-membrane and stainless steel internal contact has been prepared. The electrode has been tested in F(-) concentration range 10(-2)-10(-6) M and the results compared with those of commercial electrode and electrode with laboratory renewed internal electrolytic contact. The properties of simple disjoining solid-state contact have been investigated by means of electrochemical impedance spectroscopy (EIS). The impedance spectra show two time constants, which suggest that, at lower frequencies, proceed some Faradic reaction which probably stabilizes the potential between LaF(3)-membrane and stainless steel disk.

The effect of alloying with antimony on the electrochemical properties of lead

The electrochemical behaviour of lead, antimony and lead-antimony binary alloys has been studied as a function of sulfuric acid and antimony concentrations in the lead alloy. The investigation was performed by means of cyclic voltammetry and impedance spectroscopy methods. Cyclic voltammetry, performed between the hydrogen and oxygen evolution and over narrower regions of potential coupled with systematic variation of the scan rates and the positive or negative reversal potential, revealed more details on the oxidation and reduction processes in the potential region of Pb(II)-, Pb(IV)- and Sb(III)-containing species which give further insight into the nature of the reactions of the lead/acid battery. The impedance measurements performed in the potential range of lead oxide, in which antimony oxidation in the alloys takes place, show the decrease in film resistance with increasing antimony content.

Influence of antimony on the properties of the anodic oxide layer formed on Pb-Sb alloys

Abstract Electric and dielectric properties, changes in structure and kinetics of formation and reduction of anodic phase layers on Pb and Pb-Sb electrodes in H 2 SO 4 have been studied by means of electrochemical and structure characterizing impedance spectroscopy methods. The results obtained were discussed with respect to the effectiveness of Sb on the solid-state PbO → PbO n and PbO n → PbO 2 transformations. It is found that Sb facilitates the appearance of a potential region in which non-stoichiometric mixed oxides are formed; it has a catalytic effect on the PbO into the PbO n transformation. The formation of the mixed oxide leads to a shift in the potential of the oxidation of PbSO 4 to PbO 2 of about 200 mV in comparison with the pure-Pb electrode. It seems that the observed effects could explain why Sb prolongs the positive plate cycle life. It was shown that the electrochemical impedance spectroscopy is a very sensitive and suitable method for in situ investigation of solid-state processes in the positive lead/acid battery plate.

Development of a flow manifold for Fe(III) ion determination with a fluoride ion-selective electrode.

Continuous-flow (CF) and flow-injection (FI) analysis using the fluoride ion-selective electrode (FISE) as detector have been investigated. The measurements were performed in a home-made cell under appropriate flow conditions (2.86 or 3.45mlmin(-1), 0.2ml samples, 10(-6)M sodium fluoride). The calibration graph was obtained by plotting the signal height versus concentration of iron in the range of Fe(III) concentration from 10(-5) to 10(-1)M in acetate buffer (pH 2.8 or 3.4). In all described procedures, the range of linear response extends to the Fe(III) concentration from 1x10(-3) to 1x10(-1)M, with detection limit 9x10(-5)M. The effect of double-line, two-line flow manifold and CF was investigated and discussed.

Cadmium and Lead Distribution in Marine Soil Sediments, Terrestrial Soil, Terrestrial Rock, and Atmospheric Particulate Matter around Split, Croatia

The distributions of cadmium and lead in marine sediments, surrounding soil, stones, and atmospheric particulate matter were determined at different locations in Split, Croatia. The determination of cadmium and lead was performed by flame atomic absorption spectrometry whereas atmospheric particulate matter samples were analyzed by inductively coupled plasma–optical emission spectrometry. Cadmium concentrations in the stones and soil were between 0.2 to 0.6 µg g−1 and 0.2 to 0.9 µg g−1. The concentration in the atmospheric particulate matter were <0.2 µg m−2 d−1(detection limit) to 1.4 µg m−2 d−1. Lead concentrations in marine sediments, stones, soil, and atmospheric particulate matter ranged from 31.2 to 144.4 µg g−1, 9.3 to 29.4 µg g−1, 11.3 to 66.1 µg g−1, and 0.5 to 241.4 µg m−2 d−1, respectively. The relationship between determined parameters was established using principal component analysis and the results are in agreement with the assumption that anthropogenic sources play important roles for lead and cadmium distribution.

Real-time monitoring of “self-oxidation” of cysteine in presence of Cu2+ : Novel findings in the oxidation mechanism

A novel approach for investigation of a mechanism and rate of “self-oxidation” of cysteine in the presence of Cu2+ is presented. Continuous monitoring was performed using simple, low-cost, and widely available commercial ion-selective electrode for Cu2+. Presented procedure provides a complete real-time picture of overall oxidation process and has revealed a sequentially organized process, with the domination of certain reactions in each stage. A plausible mechanism, in the light of the previously reported explanation, has been proposed to account for the experimental results together with an adequate scheme of the overall process. The dependence of both the pH (measurements were performed at pH 5, 7, 8) and the concentration of the initially present Cu2+ is presented and discussed. Additionally, information into the process was collected by experiments performed in oxygen-free atmosphere and changes in the mechanism of oxidation, at weakly alkaline pH values, were observed. Information presented in this study can be utilized in advanced biochemical monitoring systems, when considering the importance of the position of cysteine and cysteine containing peptides in metabolic processes.Graphical abstract

Characterization of the Air Quality in Split, Croatia Focusing Upon Fine and Coarse Particulate Matter Analysis

The study presents statistical analysis of air quality parameters for a five-year period including PM2.5 (particles with an aerodynamic diameter, d a < 2.5 µm) and PM10 (d a < 10 µm) concentrations measured at three stations in Split region, along with NO, NOx, NO2, SO2, and black smoke data. Average concentrations of PM2.5 at three different stations were 28.2, 19.9, and 14.3 µg m−3, whereas those for PM10 were 17.8, 25.8, and 15.2 µg m−3. Generally, high correlations between PM2.5 and PM10 (0.62 and 0.54 respectively) were determined between industrial and residential stations, while lower correlation (0.22 between PM2.5 and PM10) was observed at a station in traffic and industrial area. Contributions of different sources were determined using multivariate receptor modeling (principal component analysis and cluster analysis) and it was found that the major source of pollution was in accordance with the station position. Comparison of particle mass concentrations with those reported for different European cities indicate lower loading for PM in the Split Region.