Dipropyl ammonium ionic liquids to prepare Ti/RuO2-Sb2O4 anodes at different calcination temperatures.

The development of technologies capable of producing efficient and economically viable anodes is essential for the electrochemical treatment of water contaminated with complex organic pollutants. In this context, the use of ionic liquids as solvents to prepare mixed metal oxide (MMO) anodes has proven to be an up-and-coming alternative. Here, we analyze the influence of the temperature of calcination (300, 350, and 400 ºC) on the production of Ti(RuO2)0.8-(Sb2O4)0.2 anodes made using the thermal decomposition method using three ionic liquids (IL) as solvents: dipropyl ammonium acetate (DPA-Ac), dipropyl ammonium propionate (DPA-Pr), and dipropyl ammonium butyrate (DPA-Bu). The decomposition temperature for all IL, accessed by thermogravimetry, is below 200 ºC. Physical and electrochemical analyses demonstrate that the calcination temperature of the anodes is decisive for their durability and electrochemical properties. Anodes prepared with DPA-Bu at 350 ºC show higher stability (around 35 h) than those made with other ILs at temperatures of 300 and 400 ºC and improved results in terms of 4-NP mineralization, where 97% of TOC removal was achieved in 120 min. It could be verified that the calcination temperature and IL employed had a decisive influence on the characteristics of the presented anodes. Therefore, the anode prepared with DPA-Bu at 350 ºC is promising for application in the degradation of organic compounds.

Enhanced HCB removal using bacteria from mangrove as post-treatment after electrochemical oxidation using a laser-prepared Ti/RuO2-IrO2-TiO2 anode.

The environmental persistence of hexachlorobenzene (HCB) is a challenge that promotes studies for efficient treatment alternatives to minimize its environmental impact. Here, we evaluated the HCB removal by electrochemical, biological, and combined approaches. The electrochemical treatment of 4 µM HCB solutions was performed using a synthesized Ti/RuO2-IrO2-TiO2 anode, while the biological treatment using mangrove-isolated bacteria was at 24, 48, and 72 h. The HCB degradability was assessed by analyzing chemical oxygen demand (COD), microbial growth capacity in media supplemented with HCB as the only carbon source, gas chromatography, and ecotoxicity assay after treatments. The synthesized anode showed a high voltammetric charge and catalytic activity, favoring the HCB biodegradability. All bacterial isolates exhibited the ability to metabolize HCB, especially Bacillus sp. and Micrococcus luteus. The HCB degradation efficiency of the combined electrochemical-biological treatment was evidenced by a high COD removal percentage, the non-HCB detection by gas chromatography, and a decrease in ecotoxicity tested with lettuce seeds. The combination of electrochemical pretreatment with microorganism degradation was efficient to remove HCB, thereby opening up prospects for in situ studies of areas contaminated by this recalcitrant compound.

Environmental aspects of hormones estriol, 17ß-estradiol and 17α-ethinylestradiol: Electrochemical processes as next-generation technologies for their removal in water matrices.

Hormones as a group of emerging contaminants have been increasingly used worldwide, which has increased their concern at the environmental level in various matrices, as they reach the water bodies through effluents due to the ineffectiveness of conventional treatments. Here we review the environmental scenario of hormones estriol (E3), 17ß-estradiol (E2), and 17α-ethinylestradiol (EE2), explicitly their origins, their characteristics, interactions, how they reach the environment, and, above all, the severe pathological and toxicological damage to animals and humans they produce. Furthermore, studies for the treatment of these endocrine disruptors (EDCs) are deepened using electrochemical processes as the remediation methods of the respective hormones. In the reported studies, these micropollutants were detected in samples of surface water, underground, soil, and sediment at concentrations that varied from ng L-1 to µg L-1 and are capable of causing changes in the endocrine system of various organisms. However, although there are studies on the ecotoxicological effects concerning E3, E2, and EE2 hormones, little is known about their environmental dispersion and damage in quantitative terms. Moreover, biodegradation becomes the primary mechanism of removal of steroid estrogens removal by sewage treatment plants, but it is still inefficient, which shows the importance of studying electrochemically-driven processes such as the Electrochemical Advanced Oxidation Processes (EAOP) and electrocoagulation for the removal of emerging micropollutants. Thus, this review covers information on the occurrence of these hormones in various environmental matrices, their respective treatment, and effects on exposed organisms for ecotoxicology purposes.

Electrochemical oxidation of indanthrene blue dye in a filter-press flow reactor and toxicity analyses with Raphidocelis subcapitata and Lactuca sativa.

Alternative routes to degrade dyes are of crucial importance for the environment. Hence, we report the electrochemical removal of indanthrene blue by using a boron-doped diamond anode, focusing on the toxicity of the treated solutions. Different operational conditions were studied, such as current density (5, 10, and 20 mA cm-2) and electrolyte composition (Na2SO4, Na2CO3, and NaNO3). Besides, the pH was monitored throughout the experiment to consider its direct influence on the ecotoxicity effects. The highest electrochemical oxidation efficiency, measured as color removal, was seen in the 180 min condition of electrolysis in 0.033 M Na2SO4, applying 20 mA cm-2, resulting in a color removal of nearly 91% and 40.51 kWh m-3 of energy consumption. The toxicity towards Lactuca sativa depends solely on pH variations being indifferent to color removal. While the inhibition concentration (IC50) for Raphidocelis subcapitata increases 20% after treatment (in optimized conditions), suggesting that the byproducts are more toxic for this specific organism. Our data highlight the importance of analyzing the toxicity towards various organisms to understand the toxic effect of the treatment applied.

Characterization and comparison of Ti/TiO2-NT/SnO2-SbBi, Ti/SnO2-SbBi and BDD anode for the removal of persistent iodinated contrast media (ICM).

In this study, we investigated the impact of a TiO2 nanotube (NT) interlayer on the electrochemical performance and service life of Sb and Bi-doped SnO2-coatings synthesized on a titanium mesh. Ti/SnO2-SbBi electrode was synthetized by a thermal decomposition method using ionic liquid as a precursor solvent. Ti/TiO2-NT/SnO2-SbBi electrode was obtained by a two-step electrochemical anodization, followed by the same process of thermal decomposition. The synthesized electrodes were electrochemically characterized and analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Terephthalic acid (TA) experiments showed that Ti/SnO2-SbBi and Ti/TiO2-NT/SnO2-SbBi electrodes formed somewhat higher amounts of hydroxyl radicals (HO) compared with the mesh boron doped diamond (BDD) anode. Electrochemical oxidation experiments were performed using iodinated contrast media (ICM) as model organic contaminants persistent to oxidation. At current density of 50 A m-2, BDD clearly outperformed the synthesized mixed metal oxide (MMO) electrodes, with 2 to 3-fold higher oxidation rates observed for ICM. However, at 100 and 150 A m-2, Ti/SnO2-SbBi had similar performance to BDD, whereas Ti/TiO2-NT/SnO2-SbBi yielded even higher oxidation rates. Disappearance of the target ICM was followed by up to 80% removal of adsorbable organic iodide (AOI) for all three materials, further demonstrating iodine cleavage and thus oxidative degradation of ICM mediated by HO. The presence of a TiO2 NT interlayer yielded nearly 4-fold increase in anode stability and dislocated the oxygen evolution reaction by +0.2 V. Thus, TiO2 NT interlayer enhanced electrode stability and service life, and the electrocatalytic activity for the degradation of persistent organic contaminants.

Environmental Biotechnology: Challenges and perspectives in applying combined technologies to enhance remediation and renewable energy generation / Biotecnología ambiental: desafíos y perspectivas en la aplicación de tecnologías combinadas para mejorar la remediación y la generación

Abstract The various industrial sectors, as well as livestock and agricultural activities, are increasing the production of inputs to meet the demand of the worldwide demographic explosion, making a challenge the clean maintenance of water, soil, and air. Therefore, the search for solutions for a pollutant-free environment without compromising economic development has become extremely important. Thereby, biotechnological studies in order to solve environmental issues have been gaining extensive attention through the coupling of technology procedures to biological systems as sustainable solutions to remediate contaminated areas. In this sense, this review covers topics such as the role of Omics era in microbial environmental biotechnology for pollution control as well as the microbial fuel cell use in energy production. Moreover, phytoremediation and the perspective of applying chemical methods are approached as environmentally friendly tools for the pollutant control to improve remediation processes.

Resumen Los diversos sectores industriales, así como las actividades ganaderas y agrícolas, están aumentando la producción de insumos para satisfacer la demanda de la explosión demográfica mundial, lo cual dificulta el mantenimiento limpio del agua, el suelo y el aire. Por lo tanto, la búsqueda de soluciones para un medio ambiente libre de contaminantes sin comprometer el desarrollo económico se ha vuelto extremadamente importante. De este modo, los estudios biotecnológicos para resolver problemas ambientales han recibido una gran atención a través del acoplamiento de procedimientos tecnológicos a sistemas biológicos como soluciones sostenibles para remediar áreas contaminadas. En este sentido, esta revisión cubre temas como el papel de la era Ómica en la biotecnología ambiental microbiana para el control de la contaminación, así como el uso de celdas de combustible microbianas en la producción de energía. Además, la fitorremediación y la perspectiva de aplicar métodos químicos se abordan como herramientas ecológicas para el control de contaminantes y mejorar los procesos de remediación.

Electrochemical Synthesis of La-Doped BaTiO3 Nanopowders.

Electrochemical synthesis has been presented as a powerful technique to produce nanoparticles. However, it has been especially focused on noble metal particles, while few studies have been done on oxides production. On the other hand, when partially doped with trivalent cations at the barium sublattice, BaTiO3-based ceramics are well known to exhibit semiconductive character, accompanied by a positive temperature coefficient of resistivity (PTCR). Here, we synthesized pure and La-doped BaTiO3 nanoparticles electrochemically using a metallic titanium electrode as a Ti source. The powder synthesis was made in an electrochemical cell coupled to a thermostatic bath under mild conditions (ambient temperature and pressure) with an electrical potential up to 50 V and current of 3.2 A. In these conditions, the synthesized powders present nanometric size, confirmed by transmission electron microscopy images. The pseudo-cubic BaTiO3 phase is confirmed by X-ray diffraction and Raman spectroscopy techniques. To check the quality, the powders were sintered at 1250 °C and the ceramics achieved a relative density of 95%. The BaTiO3:La sintered ceramics present a PTCR jump of up to three orders of magnitude on resistivity with minimum value at room temperature of 105 Ω·cm.

A simple and sensitive detection of diquat herbicide using a dental amalgam electrode: a comparison using the chromatographic technique.

This paper describes the use of a dental amalgam electrode (DAE) to evaluate the electrochemical behaviour and to develop an electroanalytical procedure for determination of diquat herbicide in natural water and potato samples. The work was based on the square wave voltammetry responses of diquat, which presented two well-defined and reversible reduction peaks, at -0.56 V (peak 1) and -1.00 V (peak 2). The experimental and voltammetric parameters were optimised, and the analytical curves were constructed and compared to similar curves performed by high performance liquid chromatography coupled to ultraviolet-visible spectrophotometric detector (HPLC/UV-vis). The responses were directly proportional to diquat concentration in a large interval of concentration, and the calculated detection limits were very similar, around 10 microg L(-1) (10 ppb) for voltammetric and chromatographic experiments. These values were lower than the maximum residue limit established for natural water by the Brazilian Environmental Agency. The recovery percentages in pure electrolyte, natural water and potato samples showed values from 70% to 130%, demonstrating that the voltammetric methodology proposed is suitable for determining any contamination by diquat in different samples, minimising the toxic residues due to the use of liquid mercury or the adsorptive process relative to use of other solid surfaces.

Sequence-specific electrochemical detection of Alicyclobacillus acidoterrestris DNA using electroconductive polymer-modified fluorine tin oxide electrodes.

This study outlines the quantification of low levels of Alicyclobacillus acidoterrestris in pure cultures, since this bacterium is not inactivated by pasteurization and may remain in industrialized foods and beverages. Electroconductive polymer-modified fluorine tin oxide (FTO) electrodes and multiple nanoparticle labels were used for biosensing. The detection of A. acidoterrestris in pure cultures was performed by reverse transcription polymerase chain reaction (RT-PCR) and the sensitivity was further increased by asymmetric nested RT-PCR using electrochemical detection for quantification of the amplicon. The quantification of nested RT-PCR products by Ag/Au-based electrochemical detection was able to detect 2 colony forming units per mL (CFU mL(-1)) of spores in pure culture and low detection and quantification limits (7.07 and 23.6 nM, respectively) were obtained for the target A. acidoterrestris on the electrochemical detection bioassay.