Ligia Frunza

Bio: Ligia Frunza is an academic researcher from University of Salamanca. The author has contributed to research in topics: Liquid crystal & Dielectric. The author has an hindex of 14, co-authored 43 publications receiving 726 citations.

Photocatalytic decomposition of pharmaceutical ibuprofen pollutions in water over titania catalyst

Abstract: Due to the growing importance of low concentrated pollution of surface, ground and drinking, the photocatalytic decomposition of ibuprofen down to low ppm concentrations over titania catalyst has been investigated in detail. The catalyst was characterized by XRD, TEM, diffuse reflection UV–Vis and nitrogen adsorption measurement. The photocatalytic abatement of ibuprofen was monitored by UV–Vis spectrometry, chromatographic by GC/MS, and HPLC coupled electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Catalytic performance has been studied by varying the catalyst and substrate concentration as well as decreasing the catalyst-to-substrate mass ratio over a wide range. The photocatalytic treatment with titania catalyst leads to rapid mineralization of ibuprofen. Formation of intermediate reaction products has been investigated. It is proposed that intermediates in part form oligomeric species, which are responsible for catalyst poisoning. Additional, the influence of the pH value, oxygen supply and catalyst re-use have been checked.

Removal of Reactive Black 5 azo dye from aqueous solutions by catalytic oxidation using CuO/Al2O3 and NiO/Al2O3

Abstract: CuO/Al2O3 and NiO/Al2O3 catalysts prepared by incipient wetness impregnation were used for the oxidation of Reactive Black 5 (RB5) in aqueous solution. Removal of the dye was assessed by High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) measurements and the generation of the hydroxyl radicals in the process was evaluated by chemiluminescence measurements. To put in evidence the interaction RB5 – catalyst and the surface species formed onto catalysts during the oxidation, Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis was performed. A different behavior of the two catalytic systems was revealed by the comparative analysis of the data obtained from the adsorption and oxidation tests. Only CuO/Al2O3 was effective in the RB5 degradation, NiO/Al2O3 acted as a simple adsorbent. In the presence of CuO/Al2O3, at H2O2 concentration of 40 mM the azo dye was totally eliminated from both solution and catalyst surface after 4 h, with a mineralization degree higher than 90%. However, a strong inhibition of the catalytic oxidation of RB5 was observed in the presence of phosphate ions. In the conditions of hydrogen peroxide excess, the rate equation in the case of copper catalyst was simply expressed by a pseudo-first order equation and the model was found to fit well the data. The amount of copper leached from catalyst during the oxidation process was only 1.0–1.6% per cycle leading to the conclusion that the decrease of the dye mineralization with the number of cycles has to be explained mostly by the surface covering with the reaction products, at least to a certain extent.

Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies

Abstract: Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

Electrode polarization in dielectric measurements: a review

Abstract: In this review, we present an overview of the state of the art concerning the fundamental properties of electrode polarization (EP) of interest in the measurement of high conductivity samples and its implications for both dielectric (DS) and impedance spectroscopy (IS). Initially a detailed description of what constitutes EP is provided and the problems that it induces. Then, we review some of the more popular models that have been used to describe the physical phenomena behind the formation of the ionic double layer. Following this we shall enumerate the common strategies used historically to correct its influence on the measured signals in DS or in IS. Finally we also review recent attempts to employ fractal electrodes to bypass the effects of EP and to offer some physical explanation as to the limitations of their use.