Advances in Electrocoagulation for wastewater treatment: porous vs nonporous electrodes

Reduced stimulation thresholds, improved sensing and better attachment have been claimed for totally porous and porous surfaced electrodes. In this study, the potential for clinical use of two new types of porous electrodes and a non-porous, textured high microsurface area electrode, has been evaluated by comparison with equivalent sized, smooth non-porous controls. Eighteen sintered and seven laser drilled porous electrodes, seven-non-porous textured electrodes, and sixteen controls, were implanted singly in the right ventricles of sheep. Measurements of threshold, pacing, sensing and bulk impedances were taken at regular intervals for up 180 days. At sacrifice, only three of the thirteen non-porous controls were attached. All laser porous electrodes, apart from two which were dislodged, were attached, as were eleven of fifteen sintered porous, and five of seven textured non-porous electrodes. Tissue ingrowth was found for both porous electrode types. Stimulation thresholds were not statistically different for all electrode types (p less than 0.05). Pacing and bulk impedances of the two porous and surface textured electrodes were significantly higher (p less than 0.10, p less than 0.05, respectively) than those of controls. The three new electrodes exhibited similar chronic sensing impedance values, 30% less than equivalent non-porous electrodes. The similar sensing performance of the porous and high microsurface area non-porous electrodes indicates that the nature of the external surface, rather than internal porosity, determines sensing impedance. All three new electrode types showed improved attachment and sensing compared with similar smooth electrodes. The laser porous electrode, which permits fixation by tissue ingrowth and maintains simplicity of construction, is promising for routine clinical use.

Transport in solid oxide porous electrodes: Effect of gas diffusion

The kinetics of the reduction of thionyl chloride

Various techniques are employed for wastewater treatment, among which electrocoagulation (EC), an electrochemical process, has emerged as an efficient and environmentally friendly approach, particularly for removing heavy metals, organic pollutants, and suspended solids. The performance of EC is strongly influenced by the type and structure of electrode material, as these factors directly affect pollutant removal efficiency, electrochemical activity, and operational stability. Aluminum (Al) and iron (Fe) electrodes are widely used because of their high efficiency in generating coagulant species. However, recent studies have shifted toward advanced modified electrodes to address concerns related to energy consumption, which depends on electrode type, configuration, and applied current density. Optimizing these parameters can substantially reduce energy usage while maintaining high treatment efficiency. Porous electrodes offers significant potential, as their high surface area reduces cell voltage, enhances electro-dissolution, and enables considerable energy savings compared to nonporous electrodes. Nevertheless, further research is required to overcome their limitations and ensure long-term applicability in sustainable water treatment. This review aims to critically evaluate recent research on EC for heavy metal removal, with a particular focus on the influence of emphasizing the role of porous versus nonporous electrode materials on pollutant removal efficiency, energy consumption, and operational stability.

In a two-electrode system, freshwater sediment was used as a fuel to examine the relationship between current generation and organic matter consumption with different types of electrode. Sediment microbial fuel cells using porous electrodes showed a superior performance in terms of generating current when compared with the use of non-porous electrodes. The maximum current densities with thicker and thin porous electrodes were 45.4 and 37.6 mA m(-2), respectively, whereas the value with non-porous electrodes was 13.9 mA m(-2). The amount of organic matter removed correlated with the current produced. The redox potential in the anode area under closed-circuit conditions was +246.3 +/- 67.7 mV, while that under open-circuit conditions only reached -143.0 +/- 7.18 mV. This suggests that an application of this system in organic-rich sediment could provide environmental benefits such as decreasing organic matter and prohibiting methane emission in conjunction with electricity production via an anaerobic oxidation process.

Capacitive humidity sensor design based on anodic aluminum oxide

The influence of the poling time and the polarity of the applied voltage on the time dependence of the gas emission of PVDF is investigated. If PVDF films are poled in electric fields of about 100MV/m, charges are injected and ions are formed by electrochemical reactions. By recombination and by other reactions of these ions, HF gas is evolved, diffusing out of the sample through the porous electrode. This gas emission increases with increasing field strength. At constant field it decreases to a steady state value comparable to the space-charge-limited poling current of PVDF. Free ions are trapped in the polarization zone. Under short-circuit conditions shallow trapped ions are freed and the gas emission increases strongly. The longer the poling time, the broader the polarization distribution. If the polarization zone is located near the nonporous electrode, the recombined gas molecules need longer time to reach the porous electrode. Therefore, the gas emission under short-circuit conditions is delayed by poling with negative polarity compared to positive polarity. >

The mechanical deformation of thin films and membrane carbon electrodes during galvanostatic charge‐discharge cycles has been measured by a simple optical technique. We have considered the deformations of coke and of graphite membrane electrodes to be due to the variations in the volume of grains and to the surface forces resulting from the electrochemical double layer. For such composite electrodes the minimum stress can be associated with the potential of zero charge of the electrode. The results show that the stress is due mainly to variations of volume in nonporous electrodes, to surface forces, and to the presence of passivating layers in very porous electrodes. The stress observed in the membrane electrodes after intercalation consists of an irreversible compressive tension and results in a permanent deformation of the electrodes.

Improvement of high-rate charging/discharging performance of a lithium ion battery composed of laminated LiFePO4 cathodes/ graphite anodes having porous electrode structures fabricated with a pico-second pulsed laser

Cadmium and lead are generally taken as model heavy metal ions in water to scale the detection limit of various electrode sensors, using electrochemical sensing techniques. These ions interact with the electrochemically deposited antimony electrodes depending on the diffusion limitations. The phenomenon acts differently for thein-situandex-situdeposition as well as for porous and non-porous electrodes. A method has been adopted in this study to discourage the stripping and deposition of the working ions (antimony) to understand the principle of heavy metal ion detection. X-ray photoelectron spectroscopy (XPS) technique was used to establish the interaction between the working and dissolved ions. In addition to the distinct peaks for each analyte, researchers also observed a shoulder peak. A possible reason for the presence of this peak was provided. Different electrochemical tests were performed to ascertain the theory on the basis of the experimental observations.

Adequate electrochemical characterization of electrode material/biofilms is crucial for a comprehensive understanding and comparative performance of bioelectrochemical systems (BES). However, their responses are greatly affected by the metabolic activity and growth of these living entities and/or the interference of electrode wiring that can act as an electroactive surface for growth or constitute a source of contamination by corrosion. This restricts the meaningful comparison of the performance of distinct electrode materials in BES. This work describes a methodology for simultaneous electrochemical control and measurement of the microbial response on different electrode materials under the same physicochemical and biological conditions. The method is based on the use of a single channel potentiostat and one counter and reference electrodes to simultaneously polarize several electrode materials in a sole bioelectrochemical cell. Furthermore, various strategies to minimize wiring corrosion are proposed. The proposed methodology, then, will enable a more rigorous characterization of microbial electrochemical responses for comparisons purposes.•Experimental Set-up allows to polarize several working electrodes at the same time.•Chronoamperometry can be performed simultaneously with a potentiostat.•The physicochemical and biological conditions in each working electrode will be exactly the same

Electrochemical membranes (ECMs) and porous electrodes have gained much attention in a broad range of applications including water and wastewater treatment, energy production and storage, and carbon dioxide capture. Lab scale batch experiments (electrochemical stirred cells) are the baseline for developing ECMs and porous electrodes. We observed electrochemical dissolution of metal fasteners (alligator clips), used to hold porous conductive and non‐conductive membranes in batch electrochemical cells, despite being kept outside the electrolyte. The electrolyte migrated through the porous membranes by the action of capillary forces, forming a closed electrochemical circuit with the metal fasteners. This unexpected leaching can lead to misleading results for electrochemical experiments on porous electrodes and ECMs. In this study, we compared (1) porous membranes versus non‐porous electrodes, (2) hydrophilic versus hydrophobic membranes, and (3) conductive versus non‐conductive membranes in their ability to cause capillary wetting‐induced corrosion of metal fasteners. We proposed a simple solution for the problem: separating the metal fasteners from the porous membrane electrode with a non‐porous conductive graphite foil, which keeps the electrochemical circuit open. We have validated this solution and propose it as a standard method for experiments using porous electrodes and electrically conductive membranes.

Electrocoagulationhas attracted significant attention as an alternativeto conventional chemical coagulation because it is capable of removinga wide range of contaminants and has several potential advantages.In contrast to most electrocoagulation research that has been performedwith nonporous electrodes, in this study, we demonstrate energy-efficientiron electrocoagulation using porous electrodes. In batch operation,investigation of the external pore structures through optical microscopysuggested that a low porosity electrode with sparse connection betweenpores may lead to mechanical failure of the pore network during electrolysis,whereas a high porosity electrode is vulnerable to pore clogging.Electrodes with intermediate porosity, instead, only suffered a moderatesurface deposition, leading to electrical energy savings of 21% and36% in terms of electrocoagulant delivery and unit log virus reduction,respectively. Neutron computed tomography revealed the critical roleof electrode porosity in utilizing the electrode’s internalsurface for electrodissolution and effective delivery of electrocoagulantto the bulk. Energy savings of up to 88% in short-term operation wereobtained with porous electrodes in a continuous flow-through system.Further investigation on the impact of current density and porosityin long-term operation is desired as well as the capital cost of porouselectrodes.

An experimental system for evaluation of well-defined catalysts on nonporous electrodes in realistic DMFC environment

A typical microfluidic fuel cell is comprised of a Y- or T-shaped microchannel. The fuel and the oxidant streams are introduced from the two different inlets. The anodic and cathodic flows meet each other at the beginning of the main channel and start to travel together along the channel. Due to the fact that the viscous forces dominate the inertia forces in microchannels, the oxidant and the fuel streams establish a side-by-side co-laminar flow which makes the anolyte and catholyte flow together without turbulent mixing. Laminar flow in microfluidic fuel cells plays the role of the membrane in proton exchange membrane (PEM) fuel cells by maintaining the separation of the fuel and oxidant. This eliminates the need for the membrane and overcomes the membrane-related issues such as the ohmic overpotential and water management which are relevant to PEM fuel cells. In addition to the above advantage, the high surface-to-volume ratio of these micron-scale devices contributes to their high power density. This advantage is due to the fact that the electrochemical reactions in fuel cells are surface-based. The electrodes on which the electrochemical reactions are occurring are installed appropriately on the walls of the channel in a way that reacting flows are restricted to the proper electrodes. Since the flow is laminar the performance of the microfluidic fuel cell significantly depends on the device geometry. In this paper, different channel geometries and different electrode configurations are modeled and their performances are compared through the polarization curves. It has been found that the high aspect ratio provides the largest power density. In this work, the performance of the flow-through porous electrode was also modeled and compared against the conventional non-porous electrode microfluidic fuel cells. The flow-through porous electrode design is based on cross-flow of aqueous vanadium redox species through the electrodes into an exit channel, where the waste solutions meet and establish a co-laminar flow. This co-laminar flow of reacted species facilitates ionic charge transfer in a membraneless configuration. It has been found that the flow-through porous architecture provides an increased active surface area which contributes to a higher power density as opposed to the fuel cells with non-porous electrodes.