Search results for "INGENIERIA QUIMICA"
showing 10 items of 54 documents
Degradation of Diazinon based on photoelectrocatalytic technique using enhanced WO3 nanostructures: Mechanism and pathway
2021
[EN] In this work, a resistant and toxic pesticide called diazinon was degraded through the photoelectrocatalysis (PEC) technique using tungsten oxide (WO3) nanostructures, applying an external bias of 1VAg/AgCl and simulated solar illumination. For this, WO3 nanostructures have been synthesized using electrochemical anodization in 0.05 M hydrogen peroxide and 1.5 M of different acidic electrolytes: H2SO4, CH4O3S or HNO3. Morphology, composition and crystallinity of the samples were evaluated through Field Emission Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and Raman Spectroscopy. Then, the photoelectrochemical properties of the samples were analyzed by Photo-Elect…
Electrochemical formation of novel TiO2-ZnO hybrid nanostructures for photoelectrochemical water splitting applications
2020
[EN] In this study, hybrid ZnO-TiO2 nanostructures have been synthesised by means of a simple electrochemical anodisation of titanium and subsequently ZnO electrodeposition. The influence of Zn(NO3)(2) concentration and temperature during the electrodeposition process was evaluated. Different techniques were used to analyse the synthesised nanostructures, notably Field Emission Scanning Electron Microscopy (FE-SEM) with Energy-dispersive X-ray spectroscopy (EDX) and Confocal Microscopy with Raman spectroscopy coupled with an Atomic Force Microscope. Photoelectrochemical water splitting tests were also performed at the hybrid nanostructures. According to the results, the photoelectrochemical…
Study of Passive Films Formed on AISI 316L Stainless Steel in Non-Polluted and Underwater-Volcano-Polluted Seawater
2014
This work studies the semiconducting behavior of passive films formed on AISI 316L (UNS S31603) in two different sea-water solutions, non-polluted and polluted, collected from the volcano of El Hierro Island. Polarization measurements, potentiostatic passivation tests, electrochemical impedance spectroscopy, and capacitance measurements were performed. Results show that the polluted seawater worsens passivation kinetics. Additionally, passive films formed on AISI 316L stainless steel in polluted seawater have been found to be less protective than those formed in non-polluted seawater, showing a more defective structure, owing to the acidity of the polluted medium.
Passive Behavior and Passivity Breakdown of AISI 304 in LiBr Solutions through Scanning Electrochemical Microscopy
2014
The passive behavior and passivity breakdown of AISI 304 stainless steel in LiBr solutions has been investigated by means of scanning electrochemical microscopy (SECM). The sample generation - tip collection (SG-TC) mode was used to operate the SECM and the tip potential was biased to detect the electroactive species. The evolution of the current at the ultramicroelectrode tip with the applied potential within the passive range was followed at different LiBr concentrations. Results show that the absolute value of the current at the tip increases with the applied potential. Additionally, SECM was also used to detect stable pits formed on the stainless steel surface in a 0.2 M LiBr solution. …
Customized WO3 nanoplatelets as visible-light photoelectrocatalyst for the degradation of a recalcitrant model organic compound (methyl orange)
2018
[EN] WO3 nanoplatelets have been synthesized by electrochemical anodization in acidic electrolytes containing two different complexing agents: fluorides and hydrogen peroxide. The influence of the morphology and size of these nanoplatelets on their photoelectrocatalytic performance has been studied following the degradation of a model organic recalcitrant compound, such as methyl orange (MO). The effect of several supporting electrolytes on this photodegradation process has also been checked. The best MO decoloration was observed for nanoplatelets fabricated in the presence of low H2O2 concentrations, whose distribution and small size made them expose a very high surface area to the problem…
Organophosphorus pesticides (chlorfenvinphos, phosmet and fenamiphos) photoelectrodegradation by using WO3 nanostructures as photoanode
2021
[EN] The photoelectrocatalytic (PEC) degradation of recalcitrant and toxic organophosphorus pesticides, fenamiphos, chlorfenvinphos and phosmet, has been performed by using an innovative WO3 nanostructure as photoanode. The nanostructure has been synthesized by anodization in acidic media in the presence of a very small amount (0.05 M) of H2O2, and its composition as well as its photoelectrochemical properties have been characterized using X-ray Photoelectron Spectroscopy and X-ray diffraction as composition technique and photoelectrochemical impedance spectroscopy as photoelectrochemical analysis. After 24 h of experiment, a degradation of 95% of chlorfenvinphos, 99.9% of phosmet and 100% …
Elimination of pesticide atrazine by photoelectrocatalysis using a photoanode based on WO3 nanosheets
2018
[EN] The photoelectrocatalytic (PEC) degradation of a persistent and toxic herbicide, atrazine, has been investigated by using a novel and high-performance WO3 nanostructure in the form of nanosheets/nanorods as photoanode. The nanostructure has been synthesized by anodization in acidic media in the presence of a very small amount (0.05 M) of H2O2, and its morphology, as well as its electrochemical and photoelectrochemical properties have been characterized. Atrazine was completely degraded after similar to 180 min of reaction following pseudo-first order kinetics, and 2-hydroxyatrazine was identified as the main intermediate species. Moreover, the s-triazine ring in cyanuric acid (the fina…
Influence of annealing conditions on the photoelectrocatalytic performance of WO3 nanostructures
2020
[EN] Nanostructured WO3 photoanodes have been synthesized by electrochemical anodization under controlled hydrodynamic conditions in acidic media in the presence of 0.05 M H2O2. Subsequently, samples have been subjected to a thermal treatment (annealing) at different temperatures (400 degrees C, 500 degrees C and 600 degrees C) and under different gaseous atmospheres (air, N-2, Ar). The influence of these annealing conditions on the morphology, crystallinity, photoelectrochemical behavior and dopant chemistry of the different photoanodes has been investigated through Electronic Microscopy, Raman Spectroscopy, Photoelectrochemical Impedance Spectroscopy and Mott-Schottky analysis. In general…
Synthesis of WO3 nanorods through anodization in the presence of citric acid: Formation mechanism, properties and photoelectrocatalytic performance
2021
[EN] In this study, WO3 nanomds have been fabricated by simple anodization in the presence of different amounts of citric acid and at different anodization times. A comprehensive morphological, structural, electrochemical and photoelectrochemical characterization of different samples has been carried out. Moreover, a formation mechanism for WO3 nanorods has been proposed. Finally, these nanostructures have been proven to be excellent visible-light photoelectrocatalysts to remove persistent organic pollutants present in wastewaters, such as fenamiphos. Almost the 80% of this molecule was eliminated from the test solution after 180 min of irradiation, indicating the great potential of these W…
Formation of ZnO nanowires by anodization under hydrodynamic conditions for photoelectrochemical water splitting
2020
[EN] The present work studies the influence of hydrodynamic conditions (from 0 to 5000 rpm) during Zn anodization process on the morphology, structure and photoelectrocatalytic behavior of ZnO nanostructures. For this purpose, analysis with Confocal Laser-Raman Spectroscopy, Field Emission Scanning Electron Microscope (FE-SEM) and photoelectrochemical water splitting tests were performed. This investigation reveals that hydrodynamic conditions during anodization promoted the formation of ordered ZnO nanowires along the surface that greatly enhance its stability and increases the photocurrent density response for water splitting in a 159% at the 5000 rpm electrode rotation speed.