Portugaliae
Electrochimica Acta

The redox properties of the 1,10-phenanthroline containing Robson type symmetrical macrocyclic dicopper(II) complex [Cu2L(H2O.phen)2](ClO4)2 1 (L = μ-11,23-dimethyl-3,7,15,19-tetraazatricyclo-[19.3.1.18 19,13,21] he p t a c o s a-1(24) , 2, 7, 9, 11, 13(26), 14, 19, 21(25), 22-decaene-25,26-diolate) and of its dicopper(II) precursor [Cu2L(H2O)2](ClO4)2 2 have been investigated by cyclic voltammetry and controlled potential electrolysis in different organic solvents. They exhibit two consecutive reversible one-electron reductions assigned to the CuIICuII  CuICuII  CuICuI cathodic processes. The results suggest that, in solution, phenanthroline does not coordinate to the metal in complex 1, but its H-bonding interaction with the water ligands can be preserved.

Nickel coatings were obtained from Watts bath containing sodium dodecyl sulfate (SDS) or polyvinylpyrrolidone (PVP) surfactants by direct current plating. The influence of electrolysis parameters, temperature, current density, concentration of surfactants and pH on the nickel deposits brightness is investigated through a multiple linear regression model with interaction. The models obtained fitted very well the experimental data. ANOVA statistical analysis shows that all design factors are significant, and the brightness of nickel deposits obtained from bath containing PVP is more sensitive to the changes in the factors levels. The electrochemical behaviour of baths was discussed; the results revealed an inhibitive effect exerted by both SDS and PVP. We have also found that the brightness and the inhibition are well linked and directly proportional. In addition, the corrosion resistance of the nickel coatings was slightly improved, especially with PVP. Finally, the optimization analysis showed that PVP could efficiently and eco-friendly substitute SDS as an additive of nickel electroplating.

In this work, electrocoagulation (EC) was used to treat meat industry (frigorific) wastewater. Effects of EC process variables such as distance between electrodes and potential on the removal efficiency of chemical oxygen demand (COD), were examined. Two factors with three levels response surface design coupled with response surface methodology (RSM) were employed to optimize the EC process variables. Second order polynomial models were developed for the responses and three dimensional (3D) response surface plots were used to study the interactive effects of the process variables on the EC efficiency. Experimental results showed that EC treatment, using a potential of 40 V and electrodes with a 3 cm gap between them, presented a COD removal of over 90% for the meat industry wastewater.

Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to measure the corrosion rate of aluminium in 0.1 M HCl in the absence and presence of different concentrations of chitosan. Inhibition efficiency up to 90% in the presence of 0.028 g/L chitosan was achieved. Increasing the concentration of chitosan shifted the breakdown potential, Eb, of aluminium to more noble values and inhbitied the pitting corrosion of aluminium. Measurements of the break potential, Eb, and the electrical double layer capacity (Qdl) indicated that chitosan is adsorbed at the aluminium/solution interface.

The application of combined chemical coagulation and electrochemical oxidation processes to treat a leachate from an intermunicipal sanitary landfill was evaluated. Chemical coagulation (CC) experiments were performed with lime (Ca(OH)2), and the influence of the lime concentration, stirring speed and assay duration were studied. In the electrochemical oxidation (EO) assays, a boron-doped diamond anode was used, and two applied current intensities were tested. It was also evaluated the influence of the lime concentration used in the CC pre-treatment on the EO performance. In the CC assays, the highest COD removals were obtained for lime concentrations of 20 and 25 g L-1, at 100 rpm stirring speed, during 2 h. In the CC+EO combined treatment the highest removals were obtained at the applied current intensity of 0.6 A, being the influence of the lime concentration used in the pre-treatment almost insignificant. The highest current efficiency was obtained for the combined treatment with EO assays performed at 0.4 A.