Mechanisms of 4-phenylazophenol elimination in micro- And nano-ZVI assisted-Fenton systems

The 4-phenylazophenol (4-PAP), was treated with two different sources of metallic iron (ZVI): commercial micrometric powder (pZVI) and nanoparticles synthetized by the borohydride reduction method (nZVI). 4-PAP degradation was studied both in the absence and in the presence of H2O2 at different pHs. The degradation products of 4-PAP in each treatment were followed by LC-MS and CG-MS. Results showed that, in the absence of H2O2, the azo bond reduction of 4-PAP with the formation of amines was the main mechanism involved for both ZVI sources and nZVI exhibited a faster substrate removal than pZVI. In the presence of H2O2, an additional mechanism involving the oxidation mediated by hydroxyl radicals takes place. For pZVI, the addition of H2O2 produced a complete inhibition of the reduction pathway, being the oxidation the main degradation mechanism. In the case of nZVI, the system behavior showed an important dependence on the working pH. At pH 3.00, oxidative transformation pathways prevailed, whereas at pH 5.00 an almost negligible degradation -mainly driven by 4-PAP reduction- was observed. The assessment of the involved reaction mechanisms under different conditions allows the selection of the most suitable source for a specific treatment.Fil: Donadelli, Jorge Andrés. YPF - Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caram, Bruno Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Kalaboka, Maria. University of Ioannina; GreciaFil: Kapsi, Margarita. University of Ioannina; GreciaFil: Sakkas, Vasilios A.. University of Ioannina; GreciaFil: Carlos, Luciano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Garcia Einschlag, Fernando Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Antibacterial Efficacy of Commercially Available Essential Oils Tested Against Drug-Resistant Gram-Positive Pathogens

The potential antibacterial activity of basil (Ocimum basilicum), chamomile (Matricaria chamomilla), origanum (Thymus capitatus), tea tree (Melaleuca alternifolia) and thyme (Thymus vulgaris) essential oils, was investigated against 29 Gram-positive bacterial strains isolated from wastewater treatment plants, clinical samples (n = 25) and American Type Culture Collection (ATCC) reference strains (n = 4). Wild bacterial strains included methicillin-resistant Staphylococcus aureus (n = 16) and vancomycin-resistant Enterococcus spp. (n = 9). The antimicrobial activity of the selected oils was studied using the broth macrodilution method. The Minimal Inhibitory Concentration (MIC) values for S. aureus ranged from 0.06 to 0.5% (v/v) for origanum oil, 0.06 to 1% (v/v) for thyme oil, 0.12 to 1% (v/v) for tea tree oil, 0.25 to 4% (v/v) for basil oil and 2 to >4% (v/v) for chamomile oil. For enterococci the MIC values were significantly higher ranging from 0.25 to 1% (v/v), 0.5 to 2% (v/v), 1 to 4% (v/v), 4 to >4% (v/v) and >4% (v/v) for the above-mentioned oils, respectively. The main compounds of the tested essential oils were: estragole (Ocimum basilicum), bisabolol and trans-b-farnesene (Matricaria chamomilla), carvacrol and thymol (Thymus capitatus), terpinen-4-ol and p-cymene (Melaleuca alternifolia), thymol, linalool, and p-cymene (Thymus vulgaris). Origanum essential oil yielded the best antimicrobial results followed by thyme, tea tree, and basil oil, while chamomile oil exhibited weak antibacterial properties

Photochemical transformation and toxicity of dichloran in pure water and water sampled from lake Pamvotis

Photodegradation of dichloran, 2,6-dichloro-4-nitroaniline, a fungicide used to control fungi diseases on fruits and vegetables due to Botrytis, Monilia, Rhizopus, Sclerotinia, has been investigated. In distilled water as well as in the water sampled from the lake Pamvotis (Greece) the fungicide follows a first order reaction kinetics although with different half-lives: 117 and 74 h, respectively. To better understand the ecological behaviour of this chemical, the acute toxicity of photodegradation intermediates has been evaluated on Daphnia magna (freshwater crustacean, water flea), Vibrio fischeri bacteria (Microtox) and Lactuca sativa. The toxicity tests evidenced that the mixture of dichloran by-products was more toxic than the pure active compound

Mechanisms of 4-phenylazophenol elimination in micro- And nano-ZVI assisted-Fenton systems

The 4-phenylazophenol (4-PAP), was treated with two different sources of metallic iron (ZVI): commercial micrometric powder (pZVI) and nanoparticles synthetized by the borohydride reduction method (nZVI). 4-PAP degradation was studied both in the absence and in the presence of H₂O₂ at different pHs. The degradation products of 4-PAP in each treatment were followed by LC-MS and CG-MS. Results showed that, in the absence of H2O2, the azo bond reduction of 4-PAP with the formation of amines was the main mechanism involved for both ZVI sources and nZVI exhibited a faster substrate removal than pZVI. In the presence of H₂O₂, an additional mechanism involving the oxidation mediated by hydroxyl radicals takes place. For pZVI, the addition of H₂O₂ produced a complete inhibition of the reduction pathway, being the oxidation the main degradation mechanism. In the case of nZVI, the system behavior showed an important dependence on the working pH. At pH 3.00, oxidative transformation pathways prevailed, whereas at pH 5.00 an almost negligible degradation -mainly driven by 4-PAP reduction- was observed. The assessment of the involved reaction mechanisms under different conditions allows the selection of the most suitable source for a specific treatment.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada