1,720,973 research outputs found
Development of sensors for the on-site monitoring of dry-type electrical machines
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
A new flow reactor for the treatment of polluted water with microwave and ultrasound
No full textMicrowave (MW) and high-intensity ultrasound (US) provide innovative techniques for the degradation of persistent organic pollutants (POPs). When Fenton's reagent is used to treat industrial wastes, organic pollutants are degraded by highly reactive hydroxyl radicals (HO·) that can oxidize almost any organic compound to carbon dioxide and water. These reactions, when carried out under US or MW, are faster and much more efficient. The present work assesses the combined effect of US and MW using a new flow reactor developed in our laboratory. In this 5 L pilot reactor the liquid was pumped in parallel through a modified domestic MW oven and through a cell where it was irradiated with two US generators working at 20 and 300 kHz, while MW irradiation took place in a modified domestic oven. We studied the degradation of 2,4-dibromophenol (0.1 g L−1 in water) by Fenton's reagent, assessing the contribution of each energy source to the overall effect, and found that MW and US-300 kHz played the main role. A modest amount of oxidant (6 mL 30% H2O2 per 1 L of polluted water) sufficed to achieve complete degradation within 6 h, at which time organic compounds were no longer detectable. Even if no Fenton's reagent was added, about one half of the pollutant was degraded after 3 h irradiation. Copyright © 2007 Society of Chemical Industr
Degradation of Persistent Organic Pollutants by Fenton's Reagent Facilitated By Microwave or High-intensity Ultrasound
No full textMicrowave (MW) and high-intensity ultrasound (US) have emerged as powerful techniques for the elimination of persistent organic pollutants (POPs) that constitute a major health hazard, whether by direct exposure or through accumulation in biota. In order to achieve decontamination, POPs should be completely mineralized to CO2, H2O and smaller amounts of inorganic ions, or at least converted to less harmful chemical species. Under US or MW irradiation rapid degradation of aromatic halides, halogenated phenols and polychlorinated biphenyls in polluted waters was achieved at neutral pH in the presence of a moderate excess (5-30 eq) of Fenton's reagent. Acidification with acetic acid (pH 2.0-2.3) did not affect the process, but sulphuric acid (pH 1.7-2.0) facilitated complete degradation. Thus, compared to conventional methods, US and MW processes are faster and much more efficient
IEC 62697-2012: State of the art methods for quantification of DBDS and other corrosive sulfur compounds in unused and used insulating liquids
No full textThis article describes state of the art methods developed by IEC TC-10 WG-37 for quantitative determination of a highly corrosive sulfur compound dibenzodisulfide (DBDS) and other corrosive sulfur compounds in unused and used insulating liquids. The methods permit an objective approach for assessing corrosiveness of insulating liquids rather than subjective assessment based on color perception that is prevalent in the current standard test methods for corrosive or potentially corrosive sulfur in insulating liquids. In addition, quantification of total corrosive sulfur (TCS) in insulating liquids permits an objective ranking of sulfur compounds according to their corrosivity towards copper
Decontamination of soil containing POPs by the combined action of solid Fenton-like reagents and microwaves
No full textRapid and Specific Determination of Contaminants, By-Products, and Additives in Insulating Mineral Oils with Tandem Mass Spectrometry
No full textInsulating oils are often considered the life blood of electrical devices such as transformers. Proper functioning of these devices is essential for uninterrupted electrical power over long periods, often stretching into decades. To ensure longevity of insulating oils and improve certain characteristics additives are often added to the oils. On the other hand, the presence of contaminants can deteriorate the performance of the oils and can cause extensive damage to the electrical devices. To ensure optimal operation of electrical devices, additive and contaminant levels should be periodically monitored. Because of the complex chemical composition of insulating mineral oils, the determination of additives and contaminants is a difficult and often laborious task. However, the task can be made manageable with the use of current state-of-the art analytical instrumentation. This article demonstrates the use of electrospray ionization–mass spectrometry for rapid and specific determination of widely used metal deactivators Irgamet 30 and Irgamet 39. The article also presents specific quantitative determination of a highly corrosive sulfur compound dibenzyl disulfide and its principle nonsulfur by-product bibenzyl with gas chromatography and tandem mass spectrometry (GC–MS-MS)
- …
