Luis A. Godínez

Novel Electro-Fenton Approach for Regeneration of Activated Carbon

An electro-Fenton-based method was used to promote the regeneration of granular activated carbon (GAC) previously adsorbed with toluene. Electrochemical regeneration experiments were carried out using a standard laboratory electrochemical cell with carbon paste electrodes and a batch electrochemical reactor. For each system, a comparison was made using FeSO4 as a precursor salt in solution (homogeneous system) and an Fe-loaded ion-exchange resin (Purolite C-100, heterogeneous system), both in combination with electrogenerated H2O2 at the GAC cathode. In the two cases, high regeneration efficiencies were obtained in the presence of iron using appropriate conditions of applied potential and adsorption-polarization time. Consecutive loading and regeneration cycles of GAC were performed in the reactor without great loss of the adsorption properties, only reducing the regeneration efficiency by 1% per cycle during 10 cycles of treatment. Considering that, in the proposed resin-containing process, the use of Fe salts is avoided and that GAC cathodic polarization results in efficient cleaning and regeneration of the adsorbent material, this novel electro-Fenton approach could constitute an excellent alternative for regenerating activated carbon when compared to conventional methods.

Design, Syntheses, Complexation, and Electrochemistry of Polynuclear Metallodendrimers Possessing Internal Metal Binding Loci

Dendrimers possessing internal bipyridine ligands have been synthesized and transformed into their [Ru(bpy′) (bpy)2]2+ complexes (see figure). These metallodendrimers have been characterized by using UV-VIS spectroscopy, Cyclic Voltammetry, and MALDI-TOF Mass spectrometry.

Electrocatalytic Activity of Three Carbon Materials for the In-situ Production of Hydrogen Peroxide and Its Application to the Electro-Fenton Heterogeneous Process

Abstract The in-situ generation of hydrogen peroxide in the electro-Fenton process is paramount. For this reason, in this research the electrocatalytic activity of three carbon materials was evaluated in the reaction of oxygen reduction via two electrons. Furthermore, in order to eliminate the use of iron salts in solution (homogeneous process), the iron was electrodeposited on the surface of the carbon material and was applied in a heterogeneous electro-Fenton process for the degradation of methyl orange dye. The largest amount of generated H2O2 was achieved with the Carbon Felt (CF) electrode (460 mg L−1) without iron after 60 minutes. The electrodes with electrodeposited iron were characterized by SEM and EDS, which showed that the surface of the Carbon Sponge (CS) electrode had the largest amount of iron (23.84 %). However, the CF electrode showed a greater and faster degradation of the dye (98 %) after 30 minutes of treatment. The CF material was the best and most-viable choice of material compared to the CS and Carbon Cloth (CC) for industrial application in electro-Fenton processes, due to its greater catalytic activity in the production of H2O2, uniform distribution of iron, more efficient TOC removal and lower cost per cm2 of material.

Iron Supported on Ion Exchange Resin as Source of Iron for Fenton Reagent: A Heterogeneous or a Homogeneous Fenton Reagent Generation?

Abstract The aim of this work is to discuss the relative contribution of homogeneous and heterogeneous Fenton processes in the treatment of Orange II dye solutions at pH 3 and 7 using an ion exchange resin as iron support. While at pH 3, 99% of the colour was removed, under neutral conditions a decoloration of 56% was observed. Studying the release of iron from the resin, we found a concentration of 1.49 mg/L of ferric ion and 0.31 mg/L of ferrous ion at pH 3 and 1.08 mg/L and 0.11 mg/L at pH 7, revealing that as expected, dissolution of iron ions at pH 3 is larger. Using these concentrations in a homogeneous process, 45% of the colour can be removed at pH 3 and 10% at pH 7, so it was infered that there is an effect of the iron that is still supported on the resin. In this way, a mixed homogeneous/heterogeneous mechanism could be proposed. While the experimental data for the desorption of iron at pH 3 was well suited to a pseudo second order kinetic model, the desorption of iron at pH 7 was fit to pseudo-first order kinetics. Experimental results of dye decolorization were on the other hand, fitted to a pseudo first order kinetics.

Synthesis and Electrochemical Characterization of Platinum and Ruthenium Nanoparticles Encapsulated in PAMAM-G4OH Dendrimer for Oxygen Reduction in the Presence of Methanol.

I. L. Escalante-Garcia, J. Ledesma-Garcia, Francisco J. Rodriguez, Thomas W. Chapman and Luis A. Godinez. Electrochemistry Department, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., Parque Tecnologico Queretaro-Sanfadila, Pedro Escobedo, Queretaro, Mexico. C. P. 76703 In this work, we describe the preparation of composites of Pt, Ru and bimetallic Pt-Ru nanoparticles encapsulated in generation-four hydroxyl-terminated dendrimers (PAMAM-G4OH). The absorption of the metal ions and their chemical reduction were followed by UV-vis spectroscopy. Subsequently, the dendrimers encapsulating the Pt, Ru or Pt-Ru particles were immobilized on the oxidized surface of a glassy carbon electrode (GCE). Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were used to determine the oxygen reduction reaction (ORR) kinetics on this surface in aqueous sulfuric acid media and in sulfuric acid solution containing methanol. Preliminary results show that the nanoelectrocatalyst exhibits good stability in these media and good electrocatalytic activity for the ORR in the presence of methanol.

Sensitized Solar Cells based on Hexagonal Dyes of Terpyridine-Ruthenium(II): Effect of the Electropolymerization of Dyes during their Performance in Solar Cells

Effect of the Electropolymerization of Dyes during their Performance in Solar Cells J. Manriquez, Seok-Ho Hwang, Tae Joo Cho, Charles N. Moorefield, George R. Newkome and Luis A. Godinez* a Department of Electrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Sanfandila, Pedro Escobedo, Queretaro, 76700, Mexico; E-mail : lgodinez@cideteq.mx b Department of Polymer Science and c Maurice Morton Institute of Polymer Science, The University of Akron, Akron, OH, 44325, USA A study of the photovoltaic properties and performance for dyesensitized solar cells, using three hexagonal macrocycles based on terpyridine-ruthenium (II) is reported. Photoand electrochemical results suggest that the global conversion efficiencies for these devices were strongly dependent of the electropolymerization of dyes during the cells performance.

Preparation Of Carbon-Fiber Electrodes Modified With Platinum Nanoparticles Encapsulated In PAMAM Dendrimers

J. Ledesma-Garcia, I. L. Escalante Garcia, Thomas W. Chapman, Francisco J. Rodriguez, Luis A. Godinez. Department of Electrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro, Sanfandila, Pedro Escobedo, C. P. 76700, Queretaro, Mexico. This work examines the effect of the degree of surface oxidation of carbon fibers on the anchoring of hydroxyl-terminated dendrimers that encapsulate platinum nanoparticles. Several methods of electrochemical pretreatment were investigated for the preparation of the carbon-fiber surfaces to obtain electrodes with functional groups of varying characteristics. The resulting carbon-fiber surfaces were modified with platinum-encapsulating dendrimers by means of ether linkages. The coverage of active groups on the oxidized carbon surfaces as well as the active area of the dendrimer-encapsulated platinum (G4OHPt) were evaluated with respect to the pretreatment method. The results showed that cyclic voltammetry as the pretreatment method immobilizes a significant amount of dendrimer-encapsulated platinum on the carbon-fiber surface. Accordingly, kinetic parameters obtained for the oxygen-reduction reaction on this surface indicate acceptable catalytic activity.

Dye-sensitized Solar Cells Based on Perpendicularly-oriented Porphyrin Monolayers Obtained by Electrophoretic Deposition on Nanocrystalline TiO2 Electrodes

A study of the photovoltaic properties and performance for dyesensitized solar cells using mesoporphyrin IX electrophoretically deposited on nanocrystalline TiO2 photoanodes is reported. Performance data obtained from these photovoltaic devices were compared with photocells having TiO2 films sensitized by dipcoating deposition in absence of electric field. Global conversion efficiencies achieved for the solar cells containing porphyrins electrophoretically deposited were 4 times higher than for cells containing porphyrins deposited by dip-coating. Preliminary results suggest that conversion efficiencies for these photovoltaic devices depend from the orientation acquired by the dye monolayers on the TiO2 surfaces.