Corina Bradu

Degradation of antibiotics in water by non-thermal plasma treatment

The decomposition of three β-lactam antibiotics (amoxicillin, oxacillin and ampicillin) in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration. Solutions of concentration 100 mg/L were made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gas-liquid interface. The electrical discharge was operated in pulsed regime, at room temperature and atmospheric pressure, in oxygen. Amoxicillin was degraded after 10 min plasma treatment, while the other two antibiotics required about 30 min for decomposition. The evolution of the degradation process was continuously followed using liquid chromatography-mass spectrometry (LC-MS), total organic carbon (TOC) and chemical oxygen demand (COD) analyses.

Ozonation of substituted phenols in aqueous solutions over CuO-Al2O3 catalyst

The oxidation of aqueous solutions of substituted phenols, chlorophenols (CPs) and nitrophenols (NPs), at 21±0.5°C and atmospheric pressure, by ozone over a copper–alumina catalyst system was studied. The total disappearance of phenol compounds for 15 to 30 minute reaction times was observed. The presence of the catalyst increased the reaction rate, diminished the ozone consumption and caused an advanced degradation of phenols. A number of six by-products was identified by gas chromatography/mass spectrometry technique (GC/MS), with or without silylation. Based on the experimental data several mechanistic suggestions for the catalytic ozonation are made.

Total Antioxidant Activity and Phenols and Flavonoids Content of Several Plant Extracts

Alcoholic extracts of six culinary and medicinal plants have been analyzed for their antioxidative properties. Extracts were obtained by continuous (Soxhlet) and ultrasounds extraction. A new flow injection analysis method with chemiluminescence detection based on a luminol/Co(II)/EDTA/H2O2 system was set up for the total antioxidant capacity determination of the studied extracts. For comparison, total phenols and flavonoids contents of plant extracts were determined by spectrophotometric methods. A good correlation between total phenols and total antioxidant capacity was found for some determinations.

Degradation of the chlorophenoxyacetic herbicide 2,4-D by plasma-ozonation system

A novel advanced oxidation process based on the combination of ozonation with non-thermal plasma generated in a pulsed corona discharge was developed for the oxidative degradation of recalcitrant organic pollutants in water. The pulsed corona discharge in contact with liquid, operated in oxygen, produced 3.5mgL-1 ozone, which was subsequently introduced in the ozonation reactor. The solution to be treated was continuously circulated between the plasma reactor and the ozonation reactor. The system was tested for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and considerably improved performance as compared to ozonation alone, both with respect to the removal of the target compound and to mineralization. The apparent reaction rate constant for 2,4-D removal was 0.195min-1, more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60min treatment and the chlorine balance confirms the absence of quantifiable amounts of chlorinated by-products. The energy efficiency was considerably enhanced by shortening the duration of the discharge pulses, which opens the way for further optimization of the electrical circuit design.

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

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 (O3), hydrogen peroxide (H2O2) 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 O3 generated in the discharge. Enhanced mass transfer of O3 obtained in this plasma+O3 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 O3 consumption and the identified reaction products confirms that although O3 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 H2O2 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 H2O2 by OH or O3 is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation.

Combination of non-thermal plasma and ozonation for the degradation of endocrine disrupting compounds in water

Non-thermal plasma generated in a pulsed corona discharge in contact with liquid was used for the degradation of methyl paraben (MeP) in water. In the combined NTP-ozonation system the liquid is recirculated between a reservoir and the plasma reactor and the effluent gas containing ozone is passed through the solution in the reservoir. The comparison between results obtained by plasma treatment and by NTP-ozonation showed considerably higher efficiency for MeP removal and for mineralization in the latter case.

Hemp-Based Materials for Metal Removal

With the increasing focus on renewable materials and sustainability issues, the development of non-conventional materials from natural resources and possessing complexing properties is currently an area of extensive research due to their potential applications in biosorption processes for pollutant removal. Among them, the hemp plant, an annual high yielding industrial crop grown for its fibres and seeds, is one of the most promising material for biosorption of metal ions from diluted waste streams. In this chapter, an extensive list of hemp-based biosorbent literature has been compiled and discussed. After a brief description of hemp and its properties and applications, the chapter gives a general overview of liquid-solid biosorption processes for metal removal from aqueous solutions onto hemp-based materials.

Hemp-based adsorbents for sequestration of metals: a review

With the increasing focus on renewable materials and sustainability issues, the development of non-conventional materials from natural resources and possessing complexing properties is currently an area of extensive research due to their potential applications in biosorption processes for pollutant removal. Among them, the hemp plant (Cannabis sativa), an annual high yielding industrial crop grown for its fibres and seeds, is one of the most promising materials for biosorption of metal ions from diluted waste streams. In this review, an extensive list of hemp-based biosorbent literature has been compiled and discussed. After a brief description of hemp and its properties and applications, the review gives a general overview of liquid–solid biosorption processes for metal sequestration from aqueous solutions onto hemp-based materials.

Degradation of pharmaceutical compounds in aqueous solution using non-thermal plasma

The decomposition of the pharmaceutical compound enalapril in aqueous solution using non-thermal plasma has been investigated. The plasma was generated in a dielectric barrier discharge reactor (DBD) in coaxial configuration, at the interface between gas (oxygen at atmospheric pressure and room temperature) and the solution which flows as a thin film on the surface of the inner electrode of the plasma reactor. The discharge was operated in pulsed mode, at low power, in order to prevent unnecessary heating. The evolution of the degradation process was continuously followed using liquid chromatography - mass spectrometry (LC-MS). Total organic carbon (TOC) and chemical oxygen demand (COD) analyses were used to determine the mineralization degree.