Portugaliae
Electrochimica Acta

The inhibition efficiency (IE) of Amino Trimethylene phosphonic acid (ATMP) in controlling corrosion of carbon steel immersed in ground water in the absence and presence of Zn2+ has been evaluated by weight loss method. It is observed that the synergistic formulation consisting of 250 ppm ATMP and 10 ppm of Zn2+ has 98% IE. Polarization study reveals that ATMP-Zn2+ system functions as a cathodic inhibitor system. AC impedance study reveals that a protective film is formed on the metal surface.

The inhibitive effect of Treculia Africana leaves extract (TALE) in the corrosion of aluminium in HCl solution was studied using weight loss and thermometric methods at 30 - 60 ºC. The results showed that TALE acted as a corrosion inhibitor of aluminium in HCl. Inhibition efficiency increased with increase in TALE concentration, but decreased with increase in temperature. TALE interaction with the metal surface was found to obey Freundlich and El-Awady adsorption isotherms. The obtained heats of adsorption values were negative. A phenomenon of physical adsorption is proposed for the adsorption behavior of TALE.

Cyclic voltammetry was used in cetyltrimethylammonium bromide (CTAB) micellar solution to determine the half-wave potentials of selected chlorophenols, CPs. It is observed that all the electrochemical parameters of the studied CPs decrease with an increase in the number of chlorine atom(s) attached to the parent compound. The mathematical relationship between the obtained E1/2 and the number of chlorine atoms in the parent compound is given. The formal potentials, E0', of the CPs are approximated from the obtained half-wave potentials.

Four torsemide-selective electrodes all on solid state graphite support were developed and characterized in polyvinylchloride matrices. Precipitation-based technique with tetraphenylborate (TPB) as an electroactive material in polyvinylchloride (PVC) matrix was used for sensor 1 fabrication without incorporation of an ionophore. 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) based technique with tetraphenylborate and either dioctyl phatalate (DOP), dibutyl sebasate (DBS) or 2-nitrophenyl octyl ether (o-NPOE) as plastisizer in carboxylated polyvinylchloride (PVC- COOH) matrix were used for sensor 2, 3 and 4 fabrications, respectively. Fast and stable Nernstian responses were evaluated according to IUPAC recommendations in the concentration ranges from 1x10-5 to 1 x 10-3 M for sensor 1 , from 1x10-5 to 1x 10-2 M for sensor 2, from 1x10-6 to 1 x 10-4 M for sensor 3, and from 1x10-6 to 1 x 10-3 M for sensor 4 . The sensors show good selectivity to the drug in presence of a variety of inorganic and organic interferents including acid degradation product of torsemide, related substances and pharmaceutical excipients. Validation of the method showed the suitability of the proposed electrodes for the use in the quality control assessment of the drug. Furthermore, statistical comparison between the results obtained by the proposed method and the official method of the drug was performed and no significant difference was found.

Kinetic study of the indirect oxidation of methylene blue on Pt electrode in presence of several strong electrolytes is undertaken. Different operating conditions that affected the treatment process were studied in order to find the best conditions. The order with respect to methylene blue is zero order in presence of chloride, but it is second order in presence of bromide. The oxidation rate was affected by current density, halide concentration (KCl, KBr), nature of supporting electrolyte and initial pH. However, the initial dye concentration and temperature did not show a significant effect. The oxidation of methylene blue in presence of iodide, fluoride and sulfate is absent, but it is important in presence of chloride and bromide. The product of the indirect oxidation is the chloronated (bromonated) methylene violet bernthsen.

The electrokinetic technique is used to remediate hydrocarbon-contaminated soil. The aim of this paper is to evaluate the feasibility of using this technology to remediate oil- contaminated soils in the Gulf of San Jorge. The soils used in this experiment were unsaturated soils contaminated by oil field operations being carried out in the area and previously remediated by landfarming. A potential difference of 0.5V cm-1 was applied to the electroremediation cells for 120 days; bridges of phosphate salt were used for the cells. Total hydrocarbons decreased from 4.22% to 3%, modifying the percentages of aliphatic, aromatic and polar hydrocarbons. The pH changed from 7.96 to 8.6 and 7.1 in the cathode and anode, respectively. The final pH values were compatible with the degrading bacterial community, whose colony-forming numbers did not present any alteration. On the cathode, there was an increase in the percentage of Gram-positive bacteria. Most of the species isolated were identified as Microbacterium luteus.