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This work is focused on the characterization of the production of ozone, hydrogen peroxide and hydroxyl radicals (peroxone) in pressurized undivided electrochemical cells. BDD and MMO electrodes were compared as anodes and RVC, graphite and stainless steel as cathodes. Gauge pressures in the range 2–4 bar were applied. Results demonstrate the complexity in the production of oxidants in an undivided cell, allowing to propose a model of the set of reactions (both electrochemical and in the bulk) occurring in the system. A higher pressure decreases the accumulation of ozone meanwhile hydrogen peroxide production is maximized at intermediate values of pressure. Combining BDD and graphite is the best combination for enhancing the production of hydroxyl radicals for which a negligible influence of pressure was observed. These results would allow to select the proper design to maximize the efficiency in the production of each of the oxidants studied.

Bentonite was used as model clay to evaluate the electrochemical degradation and removal of phenanthrene in clay-soils, by applying a dimensionally stable electrode. Gas chromatography couple to mass spectrometry (GC–MS) was used to identify and analyze the post-treatment greases and oils extracted from bentonite. Phenanthrene removal and the products generated by its degradation were evaluated indirectly in bentonite after the process, using physicochemical parameters such as pH, cation exchange capacity, electrical conductivity and zeta potential clay substrate. An acidic front close to the IrO2–Ta2O5|Ti anode was formed in the presence of OH free radicals. As a result, the physicochemical soil parameters changed throughout the electrochemical cell. The results show that phenantrene was removed from bentonite and degraded after 4 h of electrokinetic treatment in presence of 0.1 M NaOH.

The present work deals with the use of ultrafiltration as a pre-concentration stage in the electrochemical degradation of a non-polar organochlorine compound (oxyfluorfen) with boron-doped diamond (BDD) anodes. The first stage of the work consisted in evaluating the performance of a pilot scale ultrafiltration unit to concentrate a solution of a commercial formulation of oxyfluorfen (Barre®) at total recirculation mode. The ultrafiltration membrane exhibited a total rejection of oxyfluorfen, around 70% rejection of TOC and a permeate flux of 285.1 L h−1 m−2 at 4 bar and 25 °C. The rejection of oxyfluorfen is higher than expected due to the presence of surfactant compounds in the commercial formulation selected, which promotes a mechanism of micellar enhanced ultrafiltration. Next, a discontinuous ultrafiltration test was performed, maintaining this high rejection of oxyfluorfen and observing a limited contribution of fouling mechanisms, according to the adjustment of the data to fouling models. Regarding the electrochemical oxidation of the concentrate with BDD anodes, it was observed an increase in the specific power consumption from 590 kWh kg−1 for the raw solution to 882 kWh kg−1 for the concentrate. This unexpected result can be explained due to the limited rejection of the soluble fraction in the ultrafiltration stage, what produced a lower concurrence of oxidants in the electrochemical oxidation step. According to these results, it can be stated that it is worth using ultrafiltration as a concentration stage for commercial formulations of non-polar organochlorines with both high rejection and flux, although it should be combined with degradation technologies different from electrochemical oxidation.

In-doped SnO2 (ITO) cathodes bearing Ag, Cu and bimetallic Ag/Cu nanoparticulate arrays (cathode systems ITO//Ag, ITO//Cu and ITO//Ag/Cu, respectively) were prepared by a potentiostatic double-pulse technique and employed for studying the multi-step charge-transfer kinetics of CO2 electrochemical reduction (CO2ER) in propylene carbonate solution. Our results demonstrated, on one hand, that the current exchange density of the rate-determining step (rds) for the CO2 electrochemical reduction (io,rds) depends, predominantly, on the values achieved by the outer-Helmholtz plane (OHP) potential (ΔψOHP,rds) on the three cathode systems here explored. Furthermore, these results showed that a large ΔψOHP,rds (−647 mV) promoted a large io,rds (1.09 × 10−2 A⋅ cm−2) for CO2 reduction at the cathode system ITO//Cu, whereas a small ΔψOHP,rds (−168 mV) produced a small io,rds (2.05 × 10−4 A⋅ cm−2) for CO2 reduction at the cathode system ITO//Ag. In contrast, intermediate values of ΔψOHP,rds and io,rds (−333 mV, 1.09 × 10−3 A⋅ cm−2) were found for CO2 reduction on the cathode system ITO//Ag/Cu, demonstrating that the individual electrocatalytic properties of Ag and Cu can be coupled in a bimetallic array to intentionally tune the CO2ER rate in nonaqueous solvents having low proton availability.

In this study, the removal of PAHs from a clay-based soil, using electrokinetic remediation, was explored. The experiments used phenanthrene-spiked bentonite as a simplified model representative of a Vertisol soil polluted by hydrocarbons. Experiments were performed using a 1-D cell where 80 cm3 of phenanthrene-spiked bentonite was subjected to electrokinetic remediation using a constant current density. The results obtained from these experiments were compared with those predicted by a mathematical model based on a Nernst-Plank equation for the description of electromigration, electroosmosis and diffusion. Although significant electro-osmotic flow was observed, comparison between the experimental and predicted results indicated that the removal of phenanthrene was experimentally faster than predicted by the model. The greatest differences were found in the soil regions closer to the anode. To account for this behavior a first-order reaction in the aqueous phase in the regions closer to the anode was postulated and introduced into the model as the observed sink for phenanthrene. Under these conditions, much better agreement was observed between the experimental and model results.

Titanium dioxide nanotubes (TiO2-Nts) array morphology and its high specific surface area provide a suitable substrate for PbO2 electrodeposition. PbO2 was effectively dispersed on the whole nanotubes surface, including both their walls and mouths (electrocatalyst of the type: Ti/TiO2-Nts::PbO2). Scanning electron microscopy and EDS microanalyses showed that PbO2 grows from the bottom to the surface of the nanotubes, firstly covering their walls. A simple growth mechanism previously proposed was confirmed by electrochemical methods. Cyclic voltammetry characterization of Ti/TiO2-Nts::PbO2 electrodes (2 cm2 geometric area) allowed to obtain the double layer capacitances that were directly related to PbO2 electroactive area, indicating that it grows inversely with deposition time. Also, electrocatalytic features (high oxygen evolution overpotential, open-edge morphologies and larger network structures to PbO2 crystals formed) depend on the PbO2 dispersion as well as electrodeposition time. Their electrooxidation properties were tested for electrolysis of 15 ppm methyl red (MR) and 50 ppm p-nitrophenol (PNP) acidic aqueous solutions at a current density of 30 mA cm− 2. Results clearly showed the effect of PbO2 deposition time on the electrocatalytic area and on the electrooxidation of PNP and MR. That is, Ti/TiO2-Nts::PbO2 with the shortest electrodeposition time has the highest surface and active area, efficiently degrading MR (100% of discoloration and 90% of organic removal) and PNP (90% of concentration removal after 3.5 h) in solutions. HPLC analyses of the final samples showed that carboxylic acids are the main remnant of electrooxidation.

Conventional agricultural systems can lead to degradation of the environment due to the high dependence on chemical fertilizers and pesticides; therefore, it is important to search for new technologies that help maintain the ecological balance. An example of this type of new technology is the electrofarming technique. This technology has been shown to improve the soil properties and the germination and growth processes of different types of plants. In this research, the effect of applying a low-intensity electric field using a 2D arrangement of electrodes with six modified IrO2-Ta2O5|Ti anodes around a bare Ti cathode as an in situ pilot level in 5.4 m3 of Anthrosol was determined. Electrofarming showed higher germination (59%) than farming (41%) after 18 days. This result validated the efficiency of the electrical stimulation of the seeds of cucumber in an Anthrosol with benefits on the physiological properties of cucumber plants (stem thickness, stem elongation, cotyledon length, true leaf size, root length), amount of biomass in the microbial population present in the soil (bacteria and fungi), as well as in its physicochemical properties (pH, soil organic matter, cationic exchange capacity, enzymatic activity, Ca+2, Mg+2, K+, and Na+), specifically in the area close to the anodes compared to farming.

Titanium electrodes coated with transition metal oxides are used in many applications such as the electrogeneration of hydroxyl radicals (•OH) via catalytic water oxidation. Here, we present electrochemical measurements of IrO2-Ta2O5|Ti electrodes with four different Ir:Ta ratios in the coating (100:0, 70:30, 30:70, 0:100) to better understand their electrochemical behavior. From the results, an Ir:Ta content of 70:30 reveals a homogeneous morphology, an outstanding mechanical stability, and the best generation of •OH radicals due to a cooperative enhancement of the electrocatalytic and proton (H+) transfer properties of IrO2 and Ta2O5, which are complemented by a small ohmic drop due to a junction established during the electrophoretic deposition of IrO2 and Ta2O5. The electrochemical data in this work in conjunction with density functional theory calculations provide in-depth insights into the outstanding electrocatalytic properties of the as-prepared IrO2-Ta2O5|Ti electrodes, which may have applications in environmental processes.

In recent years, physicochemical processes such as the electrokinetic treatment (EKT) have gained acceptance as suitable alternatives to restore hydrocarbon (HC)-contaminated sites. EKT entails relatively short times, moderate operation costs and high removal efficiencies, being usually applied in heterogeneous soils with low permeability. In this work, 1D and 2D configurations, which require one sole pair of electrodes (facing each other) or six anodes around a central cathode (radial array), respectively, have been tested by employing Ti cathodes and anodes, as well as purpose-made IrO2-Ta2O5|Ti as dimensionally-stable anodes (DSA). The electrodes were partially introduced into a real Vertisol soil contaminated with heavy and intermediate fractions of HC. The distance between the cathode and each anode was of 6 cm at laboratory scale employing a 276 cm3 container with 2.2 kg of polluted soil and a 115 cm3 container with 87.8 g of polluted soil for the 2D and 1D arrays, respectively. From GC-MS analysis of fat and oil content, it has been found that the radial 2D array with one central Ti cathode and six IrO2-Ta2O5|Ti anodes performed better, reaching 58% HC removal near the anode applying 30 V and an electric field of 2.4 A cm-1. The effect of the treatment on the morphology of the anodes has been analyzed by SEM-EDX.

A soil sample polluted with mercury was treated with electrokinetic treatment (EKT). Seventy-two h was necessary to remove most of the mercury present in soil from the cathode to the anode with a removal percentage of 76.30%. During this period, we measured the interfacial potential and current. We analyzed the physicochemical properties before and after EKT where physical properties such as color, soil particle, real density, porosity and fraction of organic matter did not change; chemical properties such as pH and electric conductivity changed due to the electric field applied to the soil and the addition of ethylenediaminetetraacetic acid as a facilitating agent. Finally, the remaining solution obtained from the EKT was treated in a reactor with a permeable reactive barrier of Fe°, where 84.47% of the Hg 2+ was recovered from water.

Four phenolic compounds, either as single molecules or in mixtures, were treated by heterogeneous electro-Fenton using an undivided cell with a Ti mesh cathode, put in contact with a composite made of Fe3O4 nanoparticles (NPs) on chitosan (CS) made by chemical reduction, and a boron-doped diamond (BDD) anode. The removals attained upon the application of 2.3 V for 4 h to model solutions with 0.5 mol dm−3 H2SO4 as electrolyte were: 93% for phenol, 30% for m-chlorophenol, 24% for o-chlorophenol and 22% for p-chlorophenol. COD removal efficiencies reached 95% for phenol and m-chlorophenol, 88% for p-chlorophenol and 57% for o-chlorophenol. The degradation was feasible thanks to the production of hydroxyl radicals, both on the BDD surface (i.e., BDD( OH)) from water oxidation and in the bulk from Fenton’s reaction. The composite cathode allowed the continuous H2O2 electrogeneration and Fe(III) reduction to Fe(II). The reaction between H2O2 and Fe(II) in solid or liquid phase yielded OH. The disappearance of phenols was much slower in the absence of the composite catalyst.

This work investigates the feasibility of producing IrO2-Ta2O5|Ti electrodes by electrodeposition. Using precursor solutions with Ir:Ta molar ratios from 0:100 to 100:0, followed by thermal treatment, the goal was to find the optimal composition for enhancing the formation of hydroxyl radicals and providing long service lives. Scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDX), revealed that the production of homogeneous coatings with a good surface coverage and absence of agglomerates was only possible for electrodes with 70% or 100% Ir. The potential for O2 evolution was similar for all the electrodes containing Ir, at about 0.90 V vs Ag|AgCl. However, the ability to produce M( OH) clearly increased with increasing Ir in the Ir:Ta ratios (100:0 > 70:30 > 30:70 > 0:100). This observation was confirmed by the transformation of coumarin to 7-hydroxycoumarin as determined by spectroscopic and chromatographic techniques after treatment. Once manufactured and characterized, the electrodes were tested, as anodes, for the electro-oxidation of polycyclic aromatic hydrocarbons in aqueous solutions at natural pH (i.e., without pH adjustment). The anodes prepared from 70:30 and 100:0 ratios produced the fastest and highest removal, reaching 86% and 93% for phenanthrene and naphthalene, respectively, after 120 min at 50 mA. This was accompanied by a high degree of mineralization, as the result of direct and M( OH)-mediated oxidation, with some refractory intermediates remaining in the final solutions. The interaction between IrO2 and Ta2O5 oxides appeared to be important. The 100:0 anode provided high electrocatalytic effectiveness, whereas the anode with the 70:30 ratio provided improved long-term stability, as confirmed by its service life of about 93 h.

In order to obtain gold electrode surfaces modified with Human Papillomavirus L1 protein (HPV L1)-derived peptides, two sequences, SPINNTKPHEAR and YIK, were chosen. Both have been recognized by means of sera from patients infected with HPV. The molecules, Fc-Ahx-SPINNTKPHEAR, Ac–C–Ahx-(Fc)KSPINNTKPHEAR, Ac–C–Ahx-SPINNTKPHEAR(Fc)K, C–Ahx–SPINNTKPHEAR, and (YIK)2–Ahx–C, were designed, synthesized, and characterized. Our results suggest that peptides derived from the SPINNTKPHEAR sequence, containing ferrocene and cysteine residues, are not stable and not adequate for electrode surface modification. The surface of polycrystalline gold electrodes was modified with the peptides C-Ahx-SPINNTKPHEAR or (YIK)2-Ahx-C through self-assembly. The modified polycrystalline gold electrodes were characterized via infrared spectroscopy and electrochemical measurements. The thermodynamic parameters, surface coverage factor, and medium pH effect were determined for these surfaces. The results indicate that surface modification depends on the peptide sequence (length, amino acid composition, polyvalence, etc.). The influence of antipeptide antibodies on the voltammetric response of the modified electrode was evaluated by comparing results obtained with pre-immune and post-immune serum samples.

The regeneration of dye-adsorbed activated carbon (AC) using an electro-Fenton approach was studied and compared with typical regeneration methodologies (thermal, solvent extraction, and Fenton). The cathodic polarization effect of the electro-Fenton process on the AC surface was compared based on the textural and structural properties surface via physicochemical characterization techniques. The total organic carbon decay and color removal of a dye-contaminated model solution were also studied using the different methodologies, and several regeneration cycles were employed for each methodology in order to assess the regeneration efficiency and correlate it with AC structural changes. The results show that the electrochemical process is the best method to regenerate AC because it maximizes the adsorption efficiency (approximately 80–90 %) compared to other methods of regeneration (

Ruthenium (II) complex-sensitized TiO 2 electrodes were chemically coated with NH 2 -terminated poly(amidoamide) dendrimers generation 4.0 in order to improve the performance of dye-sensitized solar cells using these photoanodes. The presence of dendrimers in these photodevices produced a global photovoltaic conversion efficiency of 6.78%, which was higher than that obtained for photocells without them (5.43%). The experimental results indicated that this treatment of the dye-sensitized TiO 2 electrodes allowed for controlling the concentrations of I 3 − anions and Li + cations into the dendrimers-modified dyed-TiO 2 pores during operation of the photocells. Consequently, the charge interception reaction and the charge accumulation process at the conduction band of the TiO 2 electrodes were simultaneously balanced by the establishment of I 2 ···NH 2 , NH···I − and C = O···Li + bonds at the branches of the confined dendrimers for increasing their global conversion efficiency.

An air diffusion activated carbon packed electrode was used to promote the in-situ generation of hydrogen peroxide (H 2 O 2 ) to support an electro-Fenton based method for the degradation of a typical dye, Methyl Orange (MO) at two different concentrations in an aqueous effluent (250 mg L −1 and 97 mg L −1 ). Electrochemical experiments were carried out using a one compartment cylindrical cell with granular activated carbon (GAC) configured as an air diffusion cathode. The efficiency of the electrode was explored as a function of H 2 O 2 produced reaching a maximum value of 10 mM. Experimental parameters such as applied current (300, 200, 100 and 50 mA), initial Fe 2+ concentration (0.2, 0.5 and 0.8 mM) and electrode stability (10 cycles) were studied. High Total Organic Carbon (TOC) decay (90%) and color removal (100%) were obtained using this electrode under appropriate operation conditions. Consecutive degradation cycles of electro-Fenton process were performed in the electrochemical cell without great loss of the removal efficiency. Considering that, in the proposed packed electrode, the use of air diffusion GAC as cathode results in efficient degradation and cost reduction for the conventional electro-Fenton process, this electrode approach could constitute an excellent alternative for H 2 O 2 generation when compared to conventional carbon electrodes.

C-sp2 (graphite) impurities are undesirable in synthetic diamond electrodes (C-sp3), because they can affect the electrochemical response. In this work, we demonstrate that C-sp3 surfaces can be activated successfully by applying an anodic current density corresponding to sufficiently high potential where the hydroxyl radicals (●OH) are generated. The effectiveness of this activation process was verified by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and cyclic voltammetry.

The conductivity mechanism of non-illuminated n-type TiO2 semiconductor films (prepared by electrophoretic deposition) modified with either terpyridine “tpy-Ru(II)” or bipyridine “bpy-Ru(II)” ruthenium complexes, has been investigated using Electrochemical Impedance Spectroscopy (EIS) measurements at different temperatures. While all the films (bare TiO2 and TiO2/Dye) showed that the electronic conductivity in a low temperature window (T 313.24 K), the conduction mechanism corresponds to the Nearest Neighbor Hopping (NNH) mechanism. The effect of the complexes is reflected in changes of the energetic parameters caused by the modifications in the distribution of energetic sites induced by the electronic overlapping of the πmolecular orbitals in the bpy or tpy ligands and the TiO2 films. © 2013 The Electrochemical Society. [DOI: 10.1149/2.102311jes] All rights reserved.

There are diverse alternatives for treating polluted soil. However, one of the most promising and innovating technologies is the electrokinetic remediation process. In the electrokinetic process, pollutant removal is influenced by several factors such as the material used as electrodes and their arrangement in the electrokinetic system, among others. This paper investigates the feasibility of removing hydrocarbon from a polluted soil, analyzing first some properties of different electrode materials by electrochemical techniques for the purpose of selecting the best to be used as an anode in the electrokinetic process. Also, two different cathode materials were tested during the electrokinetic remediation process – carbon cloth and titanium. However, results indicated the carbon cloth adsorbed the organic compounds; for that reason, it was discarded from the electrokinetic remediation process. In addition, two electrode arrangements were evaluated in the electrokinetic system, those where the electrodes were in direct contact with the soil and those where the electrodes were separated from soil by a physical barrier. The first array showed less electrical resistance and more hydrocarbon removal than the second.

After intense years of great development, the electrochemical technologies have become very suitable alternatives in niche markets like industrial wastewater reclamation and soil remediation. A key role to achieve a high efficiency in such treatments is played by the characteristics of the coating of the electrodes employed. This paper compares three techniques, namely immersion, painting and electrophoresis, for the preparation of IrO2-Ta2O5ǀTi, so-called dimensionally stable anodes (DSA(®)). The quality of the coatings has been investigated by means of surface and electrochemical analysis. Their ability to generate hydroxyl radicals and degrade aqueous solutions of hydrocarbons like phenanthrene, naphthalene and fluoranthene has been thoroughly assessed. Among the synthesis techniques, electrophoretic deposition yielded the best results, with DSA(®) electrodes exhibiting a homogeneous surface coverage that led to a good distribution of active sites, thus producing hydroxyl radicals that were able to accelerate the degradation of hydrocarbons.

Electrochemical incineration using boron-doped diamond electrodes was applied to samples obtained from a refinery and compared to the photo-electro-Fenton process in order to selectively eliminate the phenol and phenolic compounds from a complex matrix. Due to the complex chemical composition of the sample, a pretreatment to the sample in order to isolate the phenolic compounds was applied. The effects of the pretreatment and of pH on the degradation of the phenolic compounds were evaluated. The results indicate that the use of a boron-doped diamond electrode in an electrochemical incineration process mineralizes 99.5% of the phenolic sample content. Working in acidic medium (pH = 1), and applying 2 A at 298 K under constant stirring for 2 hours, also results in the incineration of the reaction intermediates reflected by 97% removal of TOC. In contrast, the photo-electro-Fenton process results in 99.9% oxidation of phenolic compounds with only a 25.69% removal of TOC.

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 ± 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

3,4-Dihydroxyphenylalanine (DOPA) was covalently grafted onto a glassy carbon electrode (GCE) by the formation of an amine cation radical in the electro-oxidation of the amino-containing compound. Cyclic voltammetric experiments proved that the DOPA was formed on the GCE as a monolayer. Its electron transfer over the GCE surface at different pH values was studied by cyclic voltammetry. Changes in solution pH resulted in the variation of the charge state of the terminal group and the surface pKa was estimated on the basis of these results. Because of electrostatic interactions between the negatively charged groups on the electrode surface and the alanine (Ala) in solution, the modified electrode was used as an enantioselective sensor. The peak current for d (+) or l (−)DOPA over the modified electrode decreased as a result of the chiral recognition across the blocking interaction with the respective enantiomer of l (−) or d (+)Ala. The recognition was verified with the protection of l (−)DOPA with a Fmoc group.

Sensors using nanostructured materials have been under development in the last decade due to their selectivity for the detection and quantification of different compounds. The physical and chemical characteristics of carbon nanotubes provide significant advantages when used as electrodes for electronic devices, fuel cells and electrochemical sensors. This paper presents preliminary results on the modification of vitreous carbon electrodes with Multiwall Carbon Nanotubes (MWCNTs) and composites of Pt nanoparticles–dopamine (DA) as electro-catalytic materials for the hydrogen peroxide (H 2 O 2 ) reaction. Chemical pre-treatment and consequent functionalization of MWCNTs with carboxylic groups was necessary to increase the distribution of the composites. In addition, the presence of DA was important to protect the active sites and eliminate the pasivation of the surface after the electro-oxidation of H 2 O 2 takes place. The proposed H 2 O 2 sensor exhibited a linear response in the 0–5 mM range, with detection and quantification limits of 0.3441 mM and 1.1472 mM, respectively.

This paper describes the tethering of ferrocene (Fc) onto polycrystalline gold electrodes by immobilized polyamidoamine (PAMAM) dendrimers films. The resulting electroactive surface provides a viable route for investigating quantitatively the host-guest binding of ferrocene with cyclodextrin (CD). In particular, electrochemical measurements reveal the effect of adsorbate-adsorbate interactions on the association constant K for the formation of the 1:1 βCD•Fc complex at the electrode-electrolyte interface. The results obtained from fitting the Frumkin isotherm to the adsorption data indicate that adsorbate-adsorbate interactions can have a strong impact on the βCD affinity for the ferrocenyl-modified surfaces studied here. The technique presented may be useful for investigating other host-guest binding reactions. Este artigo descreve a fixação de ferrocenos (Fc) sobre eletrodos policristalinos de ouro, por filmes dendrímeros de poliamidoamina (PAMAM). A superfície eletroativa fornece uma rota viável para investigar quantitativamente a ligação do ferroceno com a ciclodextrina (CD). Em particular, as medidas eletroquímicas, revelam o efeito das interações adsorção-adsorção sobre a constante de associação K, na interface eletrodo-eletrólito, durante a formação do complexo de 1:1 βCD •Fc. Os resultados obtidos a partir da investigação da isoterma de adsorção de Frumkin indicam que as interações podem ter um forte impacto na afinidade do βCD com as superfícies do ferrocenil modificado, estudadas aqui. A técnica apresentada pode ser útil para investigar outras reações de ligação entre hóspede-hospedeiro.

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing either Ir, Pt or Rh nanoparticles were synthesized and characterized in solution. Each one of these composites was then immobilized on a glassy carbon electrode (GC) and incorporated as an amperometric detector for dopamine in a high-performance liquid chromatograph (HPLC). Comparison of the analytical performance of the novel electrochemical detectors with a typical UV–vis optical detector for dopamine revealed that the sensitivity of the GC electrode modified with dendrimer-Rh composite is comparable to that of the spectroscopic detector, with a detection limit of 0.15 μM, and is linear up to at least 1.0 mM ( R 2 = 0.998). Furthermore, it was found that the electroanalytical approach suffers minimal matrix effects that arise in the analysis of dopamine in samples of urine.

During the crude oil refining process, NaOH solutions are used to remove H2S, H2Saq, and sulfur compounds from different hydrocarbon streams. The residues obtained are called “spent caustics.” These residues can be mixed with those obtained in other processes, adding to its chemical composition naphthenic acids and phenolic compounds, resulting in one of the most dangerous industrial residues. In this study, the use of electrochemical technology (ET), using BDD with Ti as substrate (Ti/BDD), is evaluated in electrolysis of spent caustic mixtures, obtained through individual samples from different refineries. In this way, the Ti/BDD’s capability of carrying out the electrochemical destruction of spent caustics in an acidic medium is evaluated having as key process a chemical pretreatment phase. The potential production of•OHs, as the main reactive oxygen species electrogenerated over Ti/BDD surface, was evaluated in HCl and H2SO4through fluorescence spectroscopy, demonstrating the reaction medium’s influence on its production. The results show that the hydrocarbon industry spent caustics can be mineralized to CO2and water, driving the use of ET and of the Ti/BDD to solve a real problem, whose potential and negative impact on the environment and on human health is and has been the environmental agencies’ main focus.

Gold-bead electrodes were modified by covalent bonding or physical adsorption of several Starburst PAMAM dendrimers (generations 2.0, 3.0 and 4.0) followed by absorption of Prussian Blue (PB). The covalent dendrimer-PB-modified electrodes can be used as amperometric sensors of H2O2 in aqueous solution. They offer enhanced sensitivity with correspondingly lower detection and quantification limits compared to similar amperometric detectors.

Dendrimers resemble covalent micelles that provide well defined cavities and can enhance the hydrophobic nature of an electrode- solution interface. Dendrimers attached to an electrode can stabilize and concentrate mediators such as catalytic nanoparticles by forming nanocomposites. Such nanocomposites can improve the kinetics of specific electrochemical reactions. In this work we describe the preparation and testing of electrodes modified with nanocomposites of inorganic electrocatalysts, namely, Prussian Blue (PB) and platinum-group metals (Ir, Os, Pd, Pt, Rh and Ru), within tethered PAMAM dendrimers for use as amperometric sensors. These electrodes offer good sensitivity in the detection of molecules with biological importance, such as H2O2 and dopamine, in neutral aqueous media.

The semiconductor–electrolyte interface have interesting similarities and differences with their semiconductor–metal (or metal oxide) and metal–electrolyte counterparts. Thus, approaches to garnering a fundamental understanding of these interfaces have stemmed from both electrochemistry and solid-state physics perspectives and have proven to be equally fruitful. Electron transfer theories were also rapidly evolving during this period, starting from homogeneous systems to heterogeneous metal–electrolyte interfaces leading, in turn, to semiconductor–electrolyte junctions.

Nanocrystalline TiO2 silanized electrodes were prepared and further modified in a sequential fashion with C60 and Starburst PAMAM G0.0 dendrimers, resulting in a novel photoelectrochemical sensitization film that showed particularly high photocurrent (IPCE) and global photoconversion efficiencies (eta).

Gold bead electrodes were modified with submonolayers of 3-mercaptopropionic acid or 2-aminoethanethiol and further reacted with poly(amidoamine) (PAMAM) dendrimers (generation 4.0 and 3.5, respectively) to obtain films on which Prussian Blue (PB) was later absorbed to afford mixed and stable electrocatalytic layers. Experiments carried out with these novel materials not only showed an improved surface coverage of PB on the dendrimer modified electrodes as compared to PB modified gold electrodes prepared under acidic conditions, but also showed an increased stability at neutral pH values for one of the dendrimer containing substrates where the PB film on a bare gold electrode is simply not formed. The dendrimer modified electrodes were also tested as electrocatalytic substrates for the electroxidation of L(+)-ascorbic acid (AA), and it was found that their sensitivity as well as the corresponding detection limits were improved as compared to the voltammetric response of a Au-PB modified electrode. On the basis of UV-visible (UV-vis) spectroscopy and electrochemical experiments, it is suggested that the PB molecules are located within the dendritic structure of the surface attached PAMAM dendrimers.

The removal of mercury from soil and Ca-bentonite was performed using electrochemical treatment adding ethylendiamine- tetra acetic acid (EDTA) as a complexing agent to improve the elec- trochemical removal of Hg (II) in soil from San Joaquin, Queretaro, Mexico. During the electrokinetic treatment in the presence of 0.1 M EDTA, most of Hg (II) migrates toward the anode obtaining the high- est removal efficiencies close to 70 % in bentonite after 9 h. Using 0.1M HCl only 65 % efficiency was attained after 13 h in the cathodic side. EDTA formed a negatively charged stable complex that migrates to the cathode by the application of the electrokinetic treatment across Hg - EDTA synthesized complex.