Publications by authors named "N B Mandache"

7 Publications

Characterization of the chemical activity of a pulsed corona discharge above water.

Chemosphere 2019 Dec 9;236:124302. Epub 2019 Jul 9.

Department of Plasma Physics and Nuclear Fusion, National Institute for Lasers, Plasma and Radiation Physics, Atomistilor Str. 409, P.O. Box MG-36, Magurele, Bucharest, 077125, Romania. Electronic address:

A pulsed corona discharge above liquid combined with ozonation has been investigated for the degradation of organic pollutants in water, as well as regarding the generation of several oxidizing species: ozone in gas phase, hydrogen peroxide and hydroxyl radicals in the liquid. A considerable improvement in the energy efficiency for organic compounds removal has been observed when reducing the width of the discharge pulses. This finding was correlated with the efficient formation of oxidizing species in case of short pulses. Recycling of the effluent gas from the plasma also enhances contaminants degradation. This was mainly attributed to an in situ peroxone process, i.e. the reaction between plasma-generated O and HO, forming highly reactive OH radicals, largely responsible for organic compounds degradation. This assumption is supported by the decline in O and HO concentrations and simultaneous increase in OH concentration detected in plasma-ozonation experiments as compared to results obtained with plasma alone.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2019.07.033DOI Listing
December 2019

New evidence on the formation of oxidizing species in corona discharge in contact with liquid and their reactions with organic compounds.

Chemosphere 2016 Dec 30;165:507-514. Epub 2016 Sep 30.

University of Bucharest, Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, Bd. Regina Elisabeta 4-12, 030016, Bucharest, Romania.

The objective of these investigations is to understand in more detail how organic compounds in water are degraded during plasma treatment. The formation of oxidizing species (ozone (O), hydrogen peroxide (HO) and hydroxyl radicals (OH)) in a pulsed corona discharge in contact with liquid is investigated. The degradation of a target organic compound (methylparaben) in aqueous solution was increased when combining plasma treatment with ozonation, using the O generated in the discharge. Enhanced mass transfer of O obtained in this plasma+O configuration leads to a six fold increase of MeP oxidation rate. The evolution of oxidants concentration during treatment of MeP solutions provides information on their consumption in reactions with MeP and its oxidation products. The correlation of MeP degradation results (MeP removal and mineralization) with O consumption and the identified reaction products confirms that although O plays an important role in the degradation, for the mineralization OH radicals have an essential contribution. The concentration of OH radicals is diminished in the solutions containing MeP as compared to plasma-treated water, indicating OH consumption in reactions with the target compound and its degradation products. The concentration of HO in the liquid can be either increased or reduced in the presence of MeP, depending on its initial concentration. On the one hand, decomposition of HO by OH or O is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2016.09.073DOI Listing
December 2016

Degradation of pharmaceutical compounds in water by non-thermal plasma treatment.

Water Res 2015 Sep 5;81:124-36. Epub 2015 Jun 5.

University of Bucharest, Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, Bd. Regina Elisabeta 4-12, 030016 Bucharest, Romania.

Pharmaceutical compounds became an important class of water pollutants due to their increasing consumption over the last years, as well as due to their persistence in the environment. Since conventional waste water treatment plants are unable to remove certain non-biodegradable pharmaceuticals, advanced oxidation processes was extensively studied for this purpose. Among them, non-thermal plasma was also recently investigated and promising results were obtained. This work reviews the recent research on the oxidative degradation of pharmaceuticals using non-thermal plasma in contact with liquid. As target compounds, several drugs belonging to different therapeutic groups were selected: antibiotics, anticonvulsants, anxiolytics, lipid regulators, vasodilatators, contrast media, antihypertensives and analgesics. It was found that these compounds were removed from water relatively fast, partly degraded, and partly even mineralized. In order to ensure the effluent is environmentally safe it is important to identify the degradation intermediates and to follow their evolution during treatment, which requires complex chemical analysis of the solutions. Based on this analysis, degradation pathways of the investigated pharmaceuticals under plasma conditions were suggested. After sufficient plasma treatment the final organic by-products present in the solutions were mainly small molecules in an advanced oxidation state.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2015.05.037DOI Listing
September 2015

Degradation of methylparaben in water by corona plasma coupled with ozonation.

Environ Sci Pollut Res Int 2014 Nov 8;21(21):12190-7. Epub 2014 May 8.

Department of Plasma Physics and Nuclear Fusion, National Institute for Lasers, Plasma and Radiation Physics, Atomistilor Str. 409, Box MG-36, 077125, Magurele-Bucharest, Romania.

The degradation of methylparaben (MeP) in water was investigated using a pulsed corona discharge generated in oxygen, above the liquid. A comparison was made between results obtained in semi-batch corona (SBC) configuration (stationary solution, continuous gas flow) and results obtained in a semi-batch corona with recirculation combined with ozonation (SBCR + O3), where the liquid is continuously circulated between a solution reservoir and the plasma reactor and the effluent gas containing ozone is bubbled through the solution in the reservoir. It was found that MeP was completely degraded after 10-15 min of treatment in both configurations. Oxidation by ozone alone, in the absence of plasma, was a slower process. The energy efficiency for MeP removal (Y MeP) and for mineralization (Y TOC) was significantly higher in the SBCR + O3 configuration (Y MeP = 7.1 g/kWh at 90 % MeP removal and Y TOC = 0.41 g/kWh at 50 % total organic carbon (TOC) removal) than in the SBC configuration (Y MeP = 0.6 g/kWh at 90 % MeP removal and Y TOC = 0.11 g/kWh at 50 % TOC removal).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11356-014-2964-yDOI Listing
November 2014

Toluene oxidation by non-thermal plasma combined with palladium catalysts.

Front Chem 2013 20;1. Epub 2013 Jun 20.

Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest Bucharest, Romania.

The oxidation of toluene in air was investigated using a dielectric barrier discharge (DBD) combined with a Pd/Al2O3 catalyst. When using only plasma, rather low selectivity toward CO2 was obtained: 32-35%. By filling the DBD reactor with Pd/Al2O3 catalyst the CO2 selectivity was significantly enhanced (80-90%), however, a large amount of toluene was desorbed from the catalyst when the discharge was operated. By filling a quarter of the discharge gap with catalyst and placing the rest of the catalyst downstream of the plasma reactor, an important increase of CO2 selectivity (~75%) and a 15% increase in toluene conversion were achieved as compared to the results with plasma alone. The catalyst exhibited a very good stability in this reaction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fchem.2013.00007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3982557PMC
May 2014
-->