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Collegno, Italy

Cravotto G.,University of Turin | Garella D.,University of Turin | Beltramo L.,University of Turin | Carnaroglio D.,University of Turin | And 2 more authors.
Chemosphere | Year: 2013

Dielectric heating and acoustic cavitation (ultrasound or high-performance disperser) may all dramatically enhance conversion rates and yields in heterogeneous metal-assisted organic reactions even when low reagent excesses are used. These so called "enabling technologies" bring with them process intensification, safer protocols, cost reduction and energy savings. We herein describe a series of rapid polychlorinated aromatic and PCBs dechlorinations (15. min) carried out in a moderate excess of metallic sodium and using non-conventional techniques. We compared the results with those obtained for reactions carried out under conventional heating and with those performed with less reactive metals such as magnesium and zinc. In this comparison, high-intensity ultrasound stands out as the technique of choice. © 2013 Elsevier Ltd.

Bruzzoniti M.C.,University of Turin | Maina R.,Sea Marconi Technologies | Tumiatti V.,Sea Marconi Technologies | Sarzanini C.,University of Turin | And 2 more authors.
Journal of Chromatography A | Year: 2012

A new technology equipment for low-pressure microwave assisted extraction (usually employed for organic chemistry reactions), recently launched in the market, is used for the first time in environmental analysis for the extraction of commercial technical Aroclor mixtures from soil. Certified reference materials of Aroclor 1260, Aroclor 1254 and Aroclor 1242 in transformer oils were used to contaminate the soil samples and to optimize the extraction method as well as the subsequent gas chromatographic electron capture detection (GC-ECD) analytical method. The study was performed optimizing the extraction, the purification and the gas chromatographic separation conditions to enhance the resolution of difficult pairs of congeners (C28/31 and C141/179). After optimization, the recovery yields were included within the range 79-84%. The detection limits, evaluated for two different commercial polychlorinated biphenyl (PCB) mixtures (Aroclor 1260 and Aroclor 1242) were 0.056 ± 0.001. mg/kg and 0.290 ± 0.006. mg/kg, respectively. The method, validated with certified soil samples, was used to analyze a soil sample after an event of failure of a pole-mounted transformer which caused the dumping of PCB contaminated oil in soil. Moreover, the method provides simple sample handling, fast extraction with reduced amount of sample and solvents than usually required, and simple purification step involving the use of solvent (cyclohexane) volumes as low as 5. mL. Reliability and reproducibility of extraction conditions are ensured by direct and continuous monitoring of temperature and pressure conditions. © 2012 Elsevier B.V.

Maina R.,Sea Marconi Technologies | Tumiatti V.,Sea Marconi Technologies | Scatiggio F.,TERNA S.p.A | Pompili M.,University of Rome | Bartnikas R.,Hydro - Quebec
IEEE Transactions on Power Delivery | Year: 2011

Over the last decade, dibenzyl-disulphide was found to be present in a large number of mineral insulating oils. This sulfur compound tends to react with the copper of the windings, forming harmful byproducts, such as Cu 2 S. Different techniques to overcome the problem, including metal deactivation, oil change, and chemical treatment, have been applied. The long-term effectiveness of these techniques is examined and compared. © 2011 IEEE.

Bruzzoniti M.C.,University of Turin | De Carlo R.M.,University of Turin | Sarzanini C.,University of Turin | Maina R.,Sea Marconi Technologies | Tumiatti V.,Sea Marconi Technologies
Talanta | Year: 2012

Copper is one of the main constituents of the components in power transformers and its presence both in liquid (mineral oil) and in solid (Kraft paper) insulators can lead to enhanced dielectric losses and to the subsequent deterioration of their insulating properties. Recently the latter have been correlated to plant failures which in turn may have severe impact on the environment. This paper describes the direct analysis of copper in insulating mineral oil by ICP-OES and how it was first optimized compared to the official American Society for Testing and Materials (ASTM) D7151 method. Detection and quantification limits of 8.8 μg kg -1 and 29.3 μg kg -1 were obtained. Secondly, copper determination was improved by coupling a microwave assisted dissolution procedure of the mineral oil which avoided the problems, in the real samples, due to the presence of solid species of copper which cannot be nebulized following traditional methods described in literature. Sixteen mineral insulating oils sampled from transformers in service were analyzed before and after dissolution. In order to evaluate copper speciation, size fractionation was performed by filtration on PTFE filters (0.45, 1 and 5 μm). This test was performed on all the oil samples. Finally, because of the key role of the solid insulator in failed transformers, the Authors applied the developed method to study the copper deposition tendency onto the insulating Kraft paper tapes exerted by two unused oils (a corrosive and a non-corrosive one) under defined ageing conditions. © 2012 Elsevier B.V.

De Carlo R.M.,University of Turin | Bruzzoniti M.C.,University of Turin | Sarzanini C.,University of Turin | Maina R.,Sea Marconi Technologies | Tumiatti V.,Sea Marconi Technologies
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2013

Reactions between the liquid insulation and the copper conductors in power transformers and other electrical apparatus may lead to the formation of dissolved and suspended copper in the insulating oil. In this work a study concerning the correlation between the copper form and the dielectric properties of the fluid is presented. In particular, to determine the total copper content in oil and consequently to discriminate by subtraction the presence of particulate copper, we optimized a method of oil mineralization. Moreover, by filtering the oils with PTFE filters (0.45, 1 and 5 μm), the dimension of suspended copper content has been quantified and discriminated from the dissolved one: in such way, we investigated the influence of particulate copper on the characteristics of the oils and we determined the physical form that mostly affect the dielectric properties. © 1994-2012 IEEE.

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