New achievements and methodologies of electrochemistry and electrochemical engineering in the environmental protection and pollution control

During the last decades, many applications of Electrochemistry and Electrochemical Engineering have arisen for the characterization and remediation of environmental problems. As a result, now­adays this subject has become one of the most interesting areas of research in applied electrochemistry, with hundreds of papers published every year and many applications already ava­ilable in the market. This special issue contains sixteen very valuable contributions on these topics, written by highly recognized authors and covering the most relevant areas of interest within the topic. Environmental monitoring is a matter of the major importance because it helps to prevent and remediate pollution with the development of novel warning detection systems. For this reason, the first sets of contributions are related to characterization of environmental issues with electro­chemical methods and it contains valuable information about new tools for the characterization of organics, heavy metals and sulphur. Treatment of industrial wastes is one of the more stimulating environmental applications nowadays. Water is extensively used in industry not only as a heat exchanger fluid or a cleaning agent, but also for the production of many chemicals. As a consequence, significant volumes of waste­water are produced every day in our industries and they get into the environment after their treatment with technologies which are not always completely effective. An electrochemically-based solution to this problem is faced in this special issue with exciting contributions on electrolysis, electro-Fenton oxidation and electrocoagulation of wastewater, in which technologies for the efficient removal of dyes, persistent chemicals and inorganic pollutants are evaluated. Finally, the last set of papers included in this special issue focusses on soil remediation and bio-electrochemical treatments. Electrokinetic soil remediation (EKSR) is one of the most motivating topics of research for electrochemical and environmental engineering in our time. Many applications are currently working at the full scale and in this issue, an authoritative review is included, in which the fundamentals and applications of the technology are clearly described. To conclude, trying to save energy, one of the more exciting and innovative areas of research is the production of electricity from bio-electrochemical processes. Research on this topic is still at a very early stage but results are promising and the concept of producing energy directly from waste is an out breaking idea as it is explained in the last contribution of this special issue. As a conclusion, this special issue is a very good summary of the most exciting research on electrochemistry and electrochemical engineering in the environmental protection and pollution control and, for sure, it will become a reference for many researchers in the near future

Electro-oxidation of tetracycline in methanol media on DSA®-Cl2

The electro-oxidation of tetracycline (TeC) in methanol medium containing chloride or sulfate ions was evaluated using a DSA®-Cl2 in a flow reactor and compared with BDD. The results show that after 30 min of electrolysis no TeC is detected by liquid chromatography when chloride is used as supporting electrolyte. On the other hand, after 90 min of electrolysis using a BDD anode only 61% of TeC was removed from solutions with chloride, but in the presence of sulfate the removal reaches 94%. This evidences that the oxidizing species generated during electrochemical oxidation control the process and the mechanism of degradation of the TeC. Besides that, it was possible to infer that only a small amount of methanol might convert to formaldehyde or formic acid, although they were not detected according to the nil changes in the FTIR spectra or in the HPLC chromatograms recorded.La electrooxidación de tetraciclina (TeC) en medio metanol que contiene iones cloruro o sulfato se evaluó utilizando un DSA®-Cl 2en un reactor de flujo y comparado con BDD. Los resultados muestran que después de 30 min de electrólisis no se detecta TeC por cromatografía líquida cuando se usa cloruro como electrolito de soporte. Por otro lado, después de 90 min de electrólisis utilizando un ánodo BDD, solo se eliminó el 61% de TeC de las soluciones con cloruro, pero en presencia de sulfato la eliminación alcanza el 94%. Esto evidencia que las especies oxidantes generadas durante la oxidación electroquímica controlan el proceso y el mecanismo de degradación del TeC. Además de eso, fue posible inferir que solo una pequeña cantidad de metanol podría convertirse en formaldehído o ácido fórmico, aunque no se detectaron de acuerdo con los nulos cambios en los espectros FTIR o en los cromatogramas HPLC registrados

A Machine Learning-Based Methodology for in-Process Fluid Characterization With Photonic Sensors

This paper proposes a novel methodology for run-time fluid characterization through the application of machine learning techniques. It aims to integrate sophisticated multi-dimensional photonic sensors inside the chemical processes, following the Industry 4.0 paradigm. Currently, this analysis is done offline in laboratory environments, which increases the decision-making times. As an alternative, the proposed method tunes the spectralbased machine learning solutions to the requirements of each case enabling the integration of compound detection systems at the computing edge. It includes a novel feature selection strategy that combines filters and wrappers, namely Wavelength-based Hybrid Feature Selection, to select the relevant information of the spectrum (i.e., the relevant wavelengths). This technique allows providing different trade-offs involving the spectrum dimensionality, complexity, and detection quality. In terms of execution time, the provided solutions outperform the state-of-the-art up to 61.78 times using less than 99% of the wavelengths while maintaining the same detection accuracy. Also, these solutions were tested in a real-world edge platform, decreasing up to 68.57 times the energy consumption for an ethanol detection use case

Reversible electrokinetic adsorption barriers for the removal of organochlorine herbicide from spiked soils

This work aims to describe the removal of clopyralid from clay soils using electrokinetically assisted soil flushing (EKSF) coupled with a permeable reactive barrier (PRB), consisting of beds of Granulated Activated Carbon (GAC). To do this, two strategies have been evaluated on bench-scale electroremediation facilities (175 dm3): electrokinetic adsorption barrier (EKAB) and reversible electrokinetic adsorption barrier (REKAB). Likewise, to clarify the contribution of the different mechanisms to remediation process results are compared to those obtained in a reference test (without applying an electric field) and to results obtained in the EKSF of soils polluted with compounds with different polarity and vapour pressure. Results show that during EKAB and REKAB tests, clopyralid is removed from the soil by adsorption in PRB, electrokinetic transport and, very less decisively, by evaporation. The application of polarity reversion attains a higher retention of clopyralid in the activated carbon-PRB and a better regulation of pH because of the neutralization of H+ and OH− generated in the electrolyte wells. After 30 days of operation, the removal of clopyralid by EKAB is 45% while it reaches 57% in the case of REKAB

Chloralkali low temperature PEM reversible electrochemical cells

This work demonstrates the viability of MEAs based on Nafion membranes for being used in reversible electrochemical cells for the chloralkali process. It also shows the effect of the operation temperature, from room temperature up to 80 °C, and humidification of the chlorine stream on the performance of these cells as fuel cell. Results demonstrate that these cells can be operated in reversible mode, yielding a current density of approximately12 mA cm−2 at a cell potential of 0.5 V, when operating as fuel cells fed with gaseous chlorine and hydrogen. The maximum power density achieved is 7.0 mW cm−2, which is much higher than that obtained with the same system fed with hydrogen and chlorine dissolved into liquid electrolytes. It is important to operate at room temperatures because efficiency decreases dramatically with temperature in an irreversible way, affecting the electrode. Humidification is necessary for the hydrogen stream and convenient for the chlorine stream, although it does not solve the irreversible cell damage caused by operation at high temperatures. Current efficiency of chlorine production is above 95 %, when operating as electrolyzer feeding a solution containing 2.0 M of NaCl. The rate of production of chlorine was 45.4 mmol h−1 at 100 mA cm−2 and the Cl2/O2 molar ratio is 9.54, which is much higher than the values obtained in previous works which are between 3 and 5.Este trabajo demuestra la viabilidad de los MEA basados ​​en membranas de Nafion para ser utilizados en celdas electroquímicas reversibles para el proceso de cloro-álcali. También se muestra el efecto de la temperatura de operación, desde temperatura ambiente hasta 80 °C, y la humidificación de la corriente de cloro sobre el desempeño de estas celdas como pila de combustible. Los resultados demuestran que estas celdas pueden operar en modo reversible, produciendo una densidad de corriente de aproximadamente 12 mA cm- 2 a un potencial de celda de 0,5 V, cuando operan como celdas de combustible alimentadas con cloro gaseoso e hidrógeno. La máxima densidad de potencia alcanzada es de 7,0 mW cm −2, que es muy superior a la obtenida con el mismo sistema alimentado con hidrógeno y cloro disueltos en electrolitos líquidos. Es importante operar a temperatura ambiente porque la eficiencia disminuye drásticamente con la temperatura de manera irreversible, afectando al electrodo. La humidificación es necesaria para la corriente de hidrógeno y conveniente para la corriente de cloro, aunque no soluciona el daño irreversible de las celdas causado por la operación a altas temperaturas. La eficiencia actual de producción de cloro es superior al 95 %, cuando opera como electrolizador alimentando una solución que contiene 2,0 M de NaCl. La tasa de producción de cloro fue de 45,4 mmol h -1 a 100 mA cm -2 y el Cl 2 /O 2relación molar es de 9,54, muy superior a los valores obtenidos en trabajos anteriores que se sitúan entre 3 y 5

Electrochemical degradation of a methyl paraben and propylene glycol mixture: Interference effect of competitive oxidation and pH stability

Endocrine disrupting compounds (EDCs) are one of the many classes of harmful pollutants frequently found in water resources. Even at low concentrations, EDCs might accumulate in the organisms and interfere on numerous processes controlled by hormones. Parabens, for example, are preservatives widely used in pharmaceutical and cosmetic industries, but several studies related them to human breast cancer. It is well-known that electrochemical technologies are an efficient alternative for wastewater treatment, promoting the appropriate destruction of EDCs. However, most studies are applied to single target contaminant solutions, which may neglect the impact from co-exited inorganic/organic pollutants. Based on that, this study aimed to elucidate the interfering effects of two target organic contaminants of very different nature during electrochemical mediated process. For that, methyl paraben (MeP) and propylene glycol (PG) were selected as models of aromatic/phenolic and carboxylate compounds versus low-molecular aliphatic alcohols. These two compounds are often together used in preservative blends and cosmetic/pharmaceutical formulations. PG is not a harmful chemical, but it is present in several types of effluents in relatively high concentrations. Thus, it may interfere on the degradation of numerous pollutants of low concentrations. The electrochemical treatment of a mixture containing 100 mg L−1 MeP +1000 mg L−1 PG showed that both contaminants suffered interfering effects. The presence of MeP negatively interfered on PG degradation; the carboxylate compound is more easily oxidized even at lower molecular concentration. On the other hand, the presence of PG showed an unexpected positive effect on MeP degradation, that was not reflected on its mineralization. The results indicate that in addition to the expected effect of anodic competition, polymerization and copolymerization reactions may also occur in the studied system. The use of an acidic buffer medium increased the removal of both contaminants and favored the oxidation pathway over the polymerization. In this case, the increase in the removal was reflected in the mineralization process, which increased up to 6 times when the mixture was treated in the buffered medium.Los compuestos disruptores endocrinos (EDC) son una de las muchas clases de contaminantes nocivos que se encuentran con frecuencia en los recursos hídricos. Incluso en bajas concentraciones, los EDC pueden acumularse en los organismos e interferir en numerosos procesos controlados por hormonas. Los parabenos, por ejemplo, son conservantes muy utilizados en la industria farmacéutica y cosmética, pero varios estudios los relacionan con el cáncer de mama humano. Es bien sabido que las tecnologías electroquímicas son una alternativa eficiente para el tratamiento de aguas residuales , promoviendo la destrucción adecuada de los EDC. Sin embargo, la mayoría de los estudios se aplican a soluciones de contaminantes de un solo objetivo, que pueden ignorar el impacto de los contaminantes inorgánicos/orgánicos co-salidos. Basado en eso, este estudio tuvo como objetivo dilucidar los efectos de interferencia de dos objetivoscontaminantes orgánicos de muy diferente naturaleza durante procesos mediados electroquímicos. Para ello, se seleccionaron metilparabeno (MeP) y propilenglicol(PG) como modelos de compuestos aromáticos/fenólicos ycarboxilatos versus alcoholesalifáticos de bajo peso molecular. Estos dos compuestos a menudo se usan juntos en mezclas conservantes y formulaciones cosméticas/farmacéuticas. El PG no es un químico dañino, pero está presente en varios tipos de efluentes en concentraciones relativamente altas. Así, puede interferir en la degradación de numerosos contaminantes en bajas concentraciones. El tratamiento electroquímico de una mezcla que contiene 100 mg L−1MeP +1000 mg L−1PG mostró que ambos contaminantes sufrieron efectos de interferencia. La presencia de MeP interfirió negativamente en la degradación de PG; el compuesto de carboxilato se oxida más fácilmente incluso a una concentración molecular más baja. Por otro lado, la presencia de PG mostró un efecto positivo inesperado en la degradación de MeP, que no se reflejó en su mineralización . Los resultados indican que además del efecto esperado de competencia anódica, polimerización y copolimerizaciónreacciones también pueden ocurrir en el sistema estudiado. El uso de un medio tampón ácido incrementó la remoción de ambos contaminantes y favoreció la vía de oxidación sobre la de polimerización. En este caso, el aumento en la remoción se reflejó en el proceso de mineralización, el cual aumentó hasta 6 veces cuando la mezcla fue tratada en el medio tamponado

Storage of energy using a gas-liquid H2/Cl2 fuel cell: A first approach to electrochemically-assisted absorbers

In this work, the use in fuel cell mode of three electro-absorbers is evaluated for the chloralkaline process and performance is compared with that of a conventional PEMFC operated at the same operation conditions (room temperature). To do this, four cells have been in-house manufactured and compared, in order to determine which electrolyte (solution containing the active species or the membrane) is the best and which is the influence of the absorption stage on the operation of the cell. Because of the high solubility of chlorine, only the hydrogen absorption has been considered in order to evaluate relevant differences in the performance. Results demonstrate that design of the cell has a superb significance on the performances obtained. Cells with membrane-electrode assemblies are more efficient than those in which the membrane is used only as an electrodic compartment separator and utilization of devices which produce tiny bubbles of gas into the electrolyte is also very advantageous in order to obtain higher efficiencies. Results are of a great significance for the design of electro-absorbers and this paper is a first approach to face the design of reversible electrochemical cells for the chloralkaline process

Improving stability of chloralkaline high-temperature PBI-PEMFCs

This work focuses on the production of electricity using chloralkaline high temperature PEM fuel cells (HT-PEMFC) comparing, within the range 120–180 °C, the performance of a cell equipped with a cathode containing a novel Ru/Pt catalyst manufactured at mild temperature conditions with another cell which contains a conventional Ru based catalyst (Ru0.75Pt0.25O2). Performance of the cell equipped with the conventional electrode at 120 °C is much better, but this situation reverses at higher operation temperatures, where the novel catalyst outperforms the conventional Ru0.75Pt0.25O2 in terms of production of electricity. In addition, the new catalyst allows to operate even at 180 °C, temperature at which the cell equipped with the conventional electrode is completely deteriorated. Results pointed out that materials are the bottleneck for the chloralkaline HT-PEMFC technology but opens the window for the search of new materials that help to improve their future development.Este trabajo se centra en la producción de electricidad utilizando pilas de combustible PEM de alta temperatura cloralcalinas (HT-PEMFC) comparando, en el rango de 120-180 °C, el rendimiento de una pila equipada con un cátodo que contiene un catalizador novedoso de Ru/Pt fabricado a temperatura templada. condiciones de temperatura con otra celda que contiene un catalizador basado en Ru convencional (Ru 0.75 Pt 0.25 O 2 ). El desempeño de la celda equipada con el electrodo convencional a 120 °C es mucho mejor, pero esta situación se revierte a temperaturas de operación más altas, donde el nuevo catalizador supera al convencional Ru 0.75 Pt 0.25 O 2en términos de producción de electricidad. Además, el nuevo catalizador permite operar incluso a 180 °C, temperatura a la que la celda equipada con el electrodo convencional se deteriora por completo. Los resultados señalaron que los materiales son el cuello de botella para la tecnología cloroalcalina HT-PEMFC pero abren la ventana para la búsqueda de nuevos materiales que ayuden a mejorar su desarrollo futuro

Prototype of Automation for Car Washing

En el presente documento se describe el desarrollo de un prototipo electrónico a escala automatizado para un lavado de autos por medio de un microcontrolador, a partir de una estructura tipo ascensor que controla las diferentes fases del proceso. Esta estructura tipo ascensor de un metro de altura cuenta con seis módulos; cada uno de los niveles cuenta con diferentes actuadores ejecutados por comandos programables realizando los procesos de lavado en cada estación de acuerdo a los requerimientos del usuario. Esta estructura cuenta con 2 interruptores de ingreso los cuales por medio de pulsos dan la indicación al microcontrolador PIC 18f4550 a el tipo de lavado que el usuario pretende realizar, los sistemas actuadores cuenta con cinco ELECTROVALVULAS y dos PUENTE H los cuales dan activación a todos los procesos encargados del lavado; cada nivel del ascensor cuenta con sensores que indican la posición el auto en todo momento, estos representan pulsos de entrada al microcontrolador; se cuenta con un elevador con 2 motores controlados por el micro (el primero ubicado en la parte superior de la estructura encargada de subir y bajar, el segundo en la bandeja de ingreso y salida del auto para cada módulo). Luego de finalizar los procesos automáticamente el auto es desplazado al primer nivel del ascensor “Entrada” para completar la secuencia programadaThe present document describes the development of an electronic prototype at an automated scale for a car wash by means of a microcontroller, from a lift-type structure that controls the different phases of the process. This one-meter-tall elevator-type structure has six modules; each of the levels has different actuators executed by programmable commands performing the washing processes in each station according to the user's requirements. This structure has two input switches which by means of pulses give the indication to the PIC 18f4550 microcontroller to the type of washing that the user intends to carry out, the actuator systems has five SOLENOID VALVES and two H-BRIDGE which activate all the processes responsible for washing; each level of the elevator has sensors that indicate the position of the car at all times, these represent pulses of input to the microcontroller; It has an elevator with two engines controlled by the micro (the first located in the upper part of the structure responsible for raising and lowering, the second in the input and output tray of the car for each module). After finishing the processes automatically the car is moved to the first level of the elevator "Entrance" to complete the programmed sequence

First approaches for hydrogen production by the depolarized electrolysis of SO2 using phosphoric acid doped polybenzimidazole membranes

Renewable energy storage and conversion is nowadays a major target for the scientific community. Their conversion into hydrogen is a clear and clean alternative for their storage. This work shows, for the first time, the results of the SO2 depolarized electrolysis for hydrogen production at high temperature (120–170 °C) using phosphoric acid doped polybenzimidazole (PBI) membranes. A standard and a thermally cure PBI membrane doped with phosphoric acid were used for manufacturing the MEA of two electrolyzers. The benefit of the temperature was demonstrated but an unexpected behavior occurs at voltages higher than 0.8 V when temperature increases. Moreover, the thermally cured membrane shows a superior performance as compared with the standard one. Production of sulfur by reduction of SO2 becomes an important drawback and advices not operating above 130 °C. Results show that PBI membranes doped with phosphoric acid are suitable for high temperature operation for the sulfur dioxide depolarized electrolysis. Increasing temperature is beneficial up to a certain value of potential, showing a considerable influence in the charge transfer resistance of the system.El almacenamiento y conversión de energía renovable es hoy en día un objetivo importante para la comunidad científica. Su conversión en hidrógeno es una alternativa clara y limpia para su almacenamiento. Este trabajo muestra, por primera vez, los resultados de la electrólisis despolarizada con SO 2 para la producción de hidrógeno a alta temperatura (120-170 °C) utilizando ácido fosfóricoMembranas de polibencimidazol dopado (PBI). Se utilizaron una membrana PBI estándar y una de curado térmico dopada con ácido fosfórico para fabricar el MEA de dos electrolizadores. Se demostró el beneficio de la temperatura pero se presenta un comportamiento inesperado a voltajes superiores a 0.8 V cuando la temperatura aumenta. Además, la membrana curada térmicamente muestra un rendimiento superior en comparación con la estándar. La producción de azufre por reducción de SO 2 se convierte en un inconveniente importante y aconseja no operar por encima de 130 °C. Los resultados muestran que las membranas de PBI dopadas con ácido fosfórico son adecuadas para operaciones a alta temperatura para la electrólisis despolarizada con dióxido de azufre . El aumento de la temperatura es beneficioso hasta cierto valor de potencial, mostrando una influencia considerable en laresistencia de transferencia de carga del sistema