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Benhiba F.,Laboratory of Separation Processes | Benhiba F.,Universite Ibn Tofail | Zarrok H.,Laboratory of Separation Processes | Elmidaoui A.,Laboratory of Separation Processes | And 7 more authors.
Journal of Materials and Environmental Science | Year: 2015

Corrosion inhibition by 2-phenyl-1, 4-dihydroquinoxaline (PHQ) on carbon steel in 1.0 M HCl is investigated using electrochemical techniques (EIS and Potentiodynamic polarization), SEM and quantum chemical calculation. Inhibition efficiency of 89% is reached with 5×10-3 M of PHQ at 303 K. Potentiodynamic polarization showed that the PHQ behaves as mixed-type inhibitor. The Nyquist plots showed that increasing PHQ concentration, charge-transfer resistance increased and double-layer capacitance decreased, involving increased inhibition efficiency. Adsorption of the inhibitor molecules corresponds to Langmuir adsorption isotherm. Also, the activation thermodynamic parameters of dissolution were calculated and discussed. Theoretical calculations have been used to make the correlation between the effectiveness of inhibition of our studied inhibitor and their molecular structure.

Larouj M.,Universite Ibn Tofail | Lgaz H.,Universite Ibn Tofail | Serrar H.,Universite Ibn Tofail | Zarrok H.,Universite Ibn Tofail | And 6 more authors.
Journal of Materials and Environmental Science | Year: 2015

Ethyl 3-hydroxy-8-methyl-4-oxo-6-phenyl-2-(p-toly)-4,6-dihydropyrimido[2,1-b] [1,3]thiazine-7-carboxylate. (PT) was examined as a corrosion inhibitor for carbon steel in 1.0 M HCl by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Results show that PT is a good inhibitor and its inhibition efficiency reaches 95 % at 10-3 M. The percentage inhibition efficiency (η) was found to increase with increase of the inhibitor concentration due to the adsorption of the inhibitor molecules on the metal surface. Tafel polarisation study revealed that (PT) acts as a mixed type inhibitor. In addition it was established the adsorption follows Langmuir adsorption isotherm. Moreover, the thermodynamic activation parameters for the corrosion reaction were calculated and discussed in relation to the stability of the protective inhibitor layer. Quantum chemical parameters are calculated using the Density Functional Theory method (DFT). Correlation between theoretical and experimental results is discussed.

Pazinato R.,Santa Catarina State University | Klauck V.,Santa Catarina State University | Volpato A.,Santa Catarina State University | Tonin A.A.,Federal University of Santa Maria | And 10 more authors.
Experimental and Applied Acarology | Year: 2014

The aim of this study was to verify the influence of tea tree oil (TTO) (Melaleuca alternifolia) tested in its pure and nanostructured (TTO nanoparticles) forms on the reproduction of female Rhipicephalus microplus. For our purpose, female ticks were collected from naturally infected animals and treated in vitro with TTO (1, 5, and 10 %) and TTO nanoparticles (0.075, 0.375, and 0.75 %). In order to validate the tests, they were performed in triplicate using positive (amitraz) and negative (untreated) controls. It was possible to observe that pure TTO (5 and 10 %) and TTO nanoparticles (0.375 and 0.75 %) showed 100 % reproductive inhibition on female ticks. Additionally, pure TTO (1 %) also showed an acaricide effect (70 %), similarly to the positive control (78.3 %). This is the first study demonstrating the activity of pure TTO and TTO nanoparticles on female ticks. Therefore, based on these results, we were able to show that both forms and all concentrations of M. alternifolia affected tick reproduction by inhibiting egg laying and hatching. We were also able to show that TTO nanoparticles potentiated the inhibitor effect of pure TTO on the reproduction of R. microplus. © 2013 Springer Science+Business Media Dordrecht.

Klauck V.,Santa Catarina State University | Pazinato R.,Santa Catarina State University | Stefani L.M.,Santa Catarina State University | Santos R.C.,Centro Universitario Franciscano | And 9 more authors.
Medical and Veterinary Entomology | Year: 2014

This study aimed to evaluate the insecticidal and repellent effects of tea tree, Melaleuca alternifolia (Myrtales: Myrtaceae), and andiroba, Carapa guianensis (Sapindales: Meliaceae), essential oils on two species of fly. For in vitro studies, free-living adult flies were captured and reared in the laboratory. To evaluate the insecticidal effects of the oils, adult flies of Haematobia irritans (L.) and Musca domestica L. (both: Diptera: Muscidae) were separated by species in test cages (n=10 per group), and subsequently tested with oils at concentrations of 1.0% and 5.0% using a negative control to validate the test. Both oils showed insecticidal activity. Tea tree oil at a concentration of 5.0% was able to kill M.domestica with 100.0% efficacy after 12h of exposure. However, the effectiveness of andiroba oil at a concentration of 5.0% was only 67.0%. The insecticidal efficacy (100.0%) of both oils against H.irritans was observed at both concentrations for up to 4h. The repellency effects of the oils at concentrations of 5.0% were tested in vivo on Holstein cows naturally infested by H.irritans. Both oils demonstrated repellency at 24h, when the numbers of flies on cows treated with tea tree and andiroba oil were 61.6% and 57.7%, respectively, lower than the number of flies on control animals. It is possible to conclude that these essential oils have insecticidal and repellent effects against the species of fly used in this study. © 2014 The Royal Entomological Society.

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