Anodic oxidation of mecoprop herbicide at lead dioxide

The electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has been studied at PbO₂ anodes by cyclic voltammetry and bulk electrolysis. The influence of current density, hydrodynamic conditions, temperature and pH on the degradation rate and current efficiency is reported. The results obtained show that the use of PbO₂ leads to total mineralization of mecoprop due to the production of oxidant hydroxyl radical electrogenerated from water discharge. The current efficiency for the electro-oxidation of mecoprop is enhanced by low current density, high recycle flow-rates and high temperature. In contrast, the pH effect was not significant. It has also been observed that mecoprop decay kinetics follows a pseudo-first-order reaction and the rate constant increases with rising current density.     

Influence of anode material on the electrochemical oxidation of 2-naphthol: Part 2. Bulk electrolysis experiments

The electrochemical oxidation of 2-naphthol has been studied by galvanostatic electrolysis, using a range of electrode materials such as lead dioxide, boron-doped diamond (BDD) and Ti-Ru-Sn ternary oxide anodes. The influence of some operating parameters, such as current density, flow-rate and chloride concentration on naphthol oxidation has been investigated in order to find the optimum experimental conditions. Measurements of chemical oxygen demand, HPLC and total organic carbon have been used to follow the oxidation. The experimental data indicate that on PbO₂ and BDD, naphthol oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high flow-rate. On the contrary, on a Ti-Ru-Sn ternary oxide the mineralisation of naphthol occurs only in the presence of chloride ions that act as redox mediators and COD removal is affected by chloride concentration and is not significantly influenced by the current density and mass-transfer coefficient. From a comparison of the results of the three electrodes it has been found that boron-doped diamond gives a faster oxidation rate and better current efficiency.     

Creativity and local economic development: The role of synergy among different talents

The role of creativity in local economic development has been widely discussed. The evidence on this linkage is, however, mixed. This work tries to highlight the nexus by taking into consideration a new aspect, that is, the multidimensional nature of creativity and the potential synergic and complementary effects of creative talents of different nature. The merging of talents is, indeed, a source of original, complex and synergic ideas which are at the basis of the positive relation between creativity and local development. The work addresses this issue conceptually and proves the expectations through an empirical application on Italian provinces (NUTS 3).     

Study of metal protective hydrophobic coatings from waterborne polyurethane ionomers

A series of waterborne coatings obtained from aqueous dispersions of fluorinated polyurethane ionomers were characterized by Differential Scanning Calorimetry (DSC), Contact Angle measurements (CA), and Electrochemical Impedance Spectroscopy (EIS) with evaluation of water uptake and barrier properties at prolonged exposure. All the considered materials showed two glass transition temperatures and the formation of highly hydrophobic surfaces with CA values against water well above 100°. On the other hand the compositive parameters of the polymers—presence and concentration of cationic as well as anionic groups, linear or crosslinked molecular structure—showed a significant effect on the electrochemical behaviour. In particular it resulted that less water absorption is shown by coatings with lower ionic character, while crosslinked anionomer structures show excellent long-term barrier properties. The research offers useful indication towards the design of a new class of hydrophobic barrier coatings from aqueous dispersions.     

Study of the physico-chemical properties oforganic coatings for concrete degradation control

The main properties of a protective coating for concrete and reinforced concrete structures are discussed. The importance of evaluating water and water-vapour permeability is highlighted. Two new methods for testing water and water-vapour permeability of protective coatings are presented. The reliability of these tests is studied. The proposed measurements could be seen as a preliminary screening test that would easily and economically evaluate coating performances.     

Electrochemical incineration of dyes using a boron‐doped diamond anode

The electrochemical oxidation of a synthetic wastewater containing the model dyes alizarin red (an anthraquinone) and Eriochrome black T (an azoic compound) has been studied on a boron‐doped diamond electrode (BDD) by both cyclic voltammetry and bulk electrolysis. The influence of the current density and dye concentration were investigated. The results obtained show that complete chemical oxygen demand (COD) and colour removal was obtained for both wastewaters. However, the nature of the pollutant, and specially the presence of functional groups (such as the azoic group) seems to strongly influence the performance and efficiency of the electrochemical process. The electro‐oxidation of alizarin red behaves as a mass‐transfer‐controlled process. In such a system, an increase in the current density leads to a decrease in the current efficiency. This can be explained by direct or hydroxyl radical mediated oxidation. The contrary tendency has been observed in Eriochrome black T electro‐oxidation. In this case, higher efficiencies were obtained working at high current densities. This may indicate that the mediated oxidation by electrogenerated reagent (such as peroxodisulphate) is the main oxidation mechanism involved in Eriochrome black T treatment. These compounds have a longer average lifetime than hydroxyl radicals, and it allows the reaction to be extended to the whole wastewater volume. This study has shown the suitability of the electrochemical process for completely removing the COD and total organic carbon and effectively decolourising of wastewaters containing synthetic dyes. Copyright © 2007 Society of Chemical Industry     

Influence of thickness on mechanical properties and crack-bridging ability of coatings for concrete

Different variables can influence the crack-bridging ability (CBA) of a coating. These parameters can be related to: (i) the substrate, i.e. the way the crack opens and develops in the concrete; (ii) the substrate/coating interface, i.e. the adhesion of the organic coating to the concrete; (iii) the coating, i.e. its thickness and mechanical properties; (iv) the external conditions, i.e. the temperature in field and the mechanical solicitation of the structure. In the present paper, some experiments were performed to analyse the third point, i.e. to find possible relationships between the variation of the CBA (in situ failure of the coating applied to the concrete substrate) and the mechanical properties (free-film failure) of coatings with thickness. Experimental results suggest that the value of strain at break is a key factor in the variation of CBA of a coating with thickness.     

Corrosion fatigue behaviour of iron in different aqueous environments

The corrosion-fatigue behaviour of iron is investigated from an electro-chemical point of view. A good correlation exists in many cases between corrosion electrochemical measurements (E_corr evolution $\text{vs}$ time, polarization curves, polarization resistance evolution $\text{vs}$ time) on a fatigue stressed specimen and its behaviour. A discussion of the considered electrochemical parameters and their application to corrosion-fatigue studies is also presented.New data on the corrosion-fatigue behaviour of steel in saturated Ca(OH)₂ solutions are reported. This environment simulates the conditions existing within concrete. The detrimental effect of the presence of chloride ions is also discussed.     

Electrochemical oxidation as a final treatment of synthetic tannery wastewater

Vegetable tannery wastewaters contain high concentrations of organics and other chemicals that inhibit the activity of microorganisms during biological oxidations, so biorefractory organics that are not removed by biological treatment must be eliminated by a tertiary or advanced wastewater treatment. In this paper, the applicability of electrochemical oxidation as a tertiary treatment of a vegetable tannery wastewater was investigated by performing galvanostatic electrolysis using lead dioxide (Ti/PbO2) and mixed titanium and ruthenium oxide (Ti/TiRuO2) as anodes under different experimental conditions. The experimental results showed that both the electrodes performed complete mineralization of the wastewater. In particular, the oxidation took place on the PbO2 anode by direct electron transfer and indirect oxidation mediated by active chlorine, while it occurred on the Ti/TiRuO2 anode only by indirect oxidation. Furthermore, the Ti/PbO2 gave a somewhat higher oxidation rate than that observed for the Ti/TiRuO2 anode. Although the Ti/TiRuO2 required almost the same energy consumption for complete COD removal, it was more stable and did not release toxic ions, so it was the best candidate for industrial applications. With the Ti/TiRuO2 anode, the rate of tannery wastewater oxidation increased with the current density, pH, and temperature of the solution. These results strongly indicate that electrochemical methods can be applied effectively as a final treatment of vegetable tannery wastewater allowing the complete removal of COD, tannin, and ammonium and decolorization.