Portugaliae
Electrochimica Acta

In this paper, a glassy carbon electrode is modified by Bismuth-Chitosan (Bi-Chit) nanosheets. Bismuth, that is “environmentally friendlier” than mercury, is deposited on a glassy carbon electrode by electrolysis at - 0.75 V vs. SCE in a stirring solution containing 0.18 mg mL-1 Bi(NO3)3, 0.05 mg mL-1 KBr and acetate buffer 0.1 M (pH=4.5) for 200 s. Furthermore, the electrode is modified by chitosan by the means of sonication of bismuth-modified glassy carbon electrode in chitosan solution for 15 minutes. Study of the field emission by scanning electron microscopy (SEM) shows the formation of Bi-Chit nanosheets on the glassy carbon electrode. The modified electrode surface is also characterized by energy dispersive X-ray analysis (EDX). In this research the Bi-Chit modified glassy carbon electrode exhibits excellent catalytic activity toward the electro-reduction of Tartrazine. The modified electrode is successfully used for determination and measurement of Tartrazine in Bisacodyle tablets and chocolates with colorful coatings.

The objective of this study is the valorization of the essential oil (EO) of Lippia citriodora irrigated by urban wastewater from the city of Settat-Morocco. We have tested it as a corrosion inhibitor of aluminum in 0.1 M Na2CO3 using polarization method, weight loss, and EIS measurements. The inhibition efficiency of lippia citriodora oil was calculated and compared. We found good agreement between the referred methods. The results obtained revealed that the tested inhibitor reduces differently the kinetic of the corrosion process of aluminum. Its efficiency increases with the concentration and attained 90.33% at 1800 ppm. The effect of temperature on the corrosion behaviour of aluminum in 0.1 M Na2CO3 was also studied in the range 283 K and 313 K. The thermodynamic data of activation were determined. The analysis of Lippia citriodora oil, obtained by hydro-distillation, using gas chromatography (GC), showed that the major components are neral 13.85%, geranial 14.06% and limonene 28.32%.

The corrosion inhibition and adsorption of ethanol extracts of leaves (LV), stems (ST) and roots (RT) of Rotula aquatica plant for mild steel in H2SO4 solutions were investigated using conventional weight loss, gasometric techniques, electrochemical polarizations and electrochemical impedance spectroscopy. The results showed that all the three extracts of Rotula aquatica plant performed well as inhibitor for the corrosion of steel in sulphuric acid media and the inhibition efficiencies of the extract follow the trend RT > LV > ST. Inhibition efficiencies increased with increasing concentration of the plant extracts but decreased with the temperature rise for all cases. Both the cathodic hydrogen evolution and the anodic dissolution of mild steel were inhibited, hence the active molecules of all the extracts studied acted as mixed type corrosion inhibitors.

Electrochemical reduction of boron from boron containing fluoroborate species present in KCl (81.54 mol%)-KF (18.45 mol%)-NaBF4 (1.67x10-4 mol cm-4) melt on a platinum electrode was studied by cyclic voltammetry and chronoamperometry. These studies were carried out over the temperature range 1073 – 1123 K. Boron-containing electroactive species is shown to reduce quasi-reversibly at low scan rates (ν < 0.1 Vs-1) and irreversibly at higher scan rates (> 0.1 V s-1) through a single-step three-electron process (B(III) + 3e → B). The transfer and diffusion coefficients of the electroactive species were measured for sodium fluoroborate in KCl-KF melt over the temperature range 1073 – 1123 K.

Inhibition effect of poly 3-dodecyloxy aniline polymeric surfactant (PC12H) on the corrosion of aluminum in 0.5 M HCl solution was investigated using potentiodynamic polarization technique under different experimental conditions. Inhibition efficiency and thermodynamic functions for dissolution and adsorption of PC12H are compared with Poly 3-(dodecyloxy sulfonic acid) aniline (PC12SO3H) to explain the effect of terminal side chain on the corrosion protection. Data show that the presence of –SO3H as a terminal group in PC12SO3H decreases the inhibition efficiency from 88.7%, in case of PC12H, to 55.1% in case of PC12SO3H. Quantum chemical calculations were performed on PC12H and PC12SO3H to investigate the relationship between the molecular structures and their inhibition efficiencies.