Interelectrode Distance Research Articles

Role of anodically electrogenerated hydroxyl radicals in minimizing mineral cathodic electroprecipitation in the presence of hard water

Electrochemical systems are attracting increasing interest in environmental protection as relatively sustainable processes, particularly in wastewater treatment and reuse. However, cathode scaling in electrochemical processes for wastewater treatment is a major issue that is often overlooked. It is proposed for the first time to investigate the anodic contribution towards CaCO3 electroprecipitation phenomena under the advanced electrooxidation conditions applied to remove organic biorecalcitrant pollutants. The contribution of the reaction of the hydroxyl radical (•OH) with carbonates, which reduces cathodic scaling at a micrometric interelectrode distance (500 µm) and at a high current density (16 mA cm−2), is described in detail. In addition, the anti-scaling effect of local anodic acidification should be considered. A new kinetic model of electroprecipitation fits the experimental curves well (root mean square error (RMSE) < 0.19 for Ca2+) and confirms this anodic role, combined with the gas hindrance and scale detachment induced by gas bubble electrogeneration at sufficiently high current intensities.

Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: A dual-center experience.

The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. We conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n = 14) or recurrent VT (n = 7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n = 9). The associations of peak-to-peak maximum standard bipolar (BVc ) and minibipolar (PentaRay, BVp ) with microbipolar (BVμMax ) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. BVμMax was moderately associated with both BVc (β = .85, p < .01) and BVp (β = .56, p < .01). BVμMax was 0.98 (95% CI: 0.93-1.04, p < .01) mV larger than corresponding BVc , and 0.27 (95% CI: 0.16-0.37, p < .01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm2 , p < .01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm2 , p = .03) regions in microbipolar maps compared to standard bipolar maps. Late potentials areas were nonsignificantly greater in microelectrode maps, compared to standard electrode maps. At sites of VT termination (n = 14), μBE were of higher amplitude (0.9 [0.8] vs. 0.4 [0.2] mV, p < .01), longer duration (117 [66] vs. 74 [38] ms, p < .01), and with greater number of peaks (4 [2] vs. 2 [1], p < .01) in sinus rhythm compared to BE. microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for CA.

Green electrochemical polishing of EBM Ti6Al4V samples with preliminary fatigue results

Additive manufacturing technologies have several well-known advantages; however, the surface quality of the printed parts is poor, compromising the corrosion and mechanical properties. Thus, surface finishing treatments are necessary. The most post-processing treatments proposed in the literature are mechanical or chemical. The formers are contact techniques and cannot be suitable for complex geometry, while the latter use strong and dangerous reagents. This paper is aimed to investigate the effect of the electropolishing treatment, a contactless technique, using an eco-friendly electrolytic solution in reducing the roughness and improving the fatigue properties of Ti6Al4V specimens produced by electron beam melting technology. Several parameters affecting the effectiveness of the electropolishing treatment have been investigated, as interelectrode distance, stirring rate and duration time. An optimal combination of them allowed a uniform surface treatment and a significant roughness reduction (64% of Sa reduction for cylindrical specimens). Under sinusoidal loading conditions with a maximum stress of 378 MPa and a stress ratio equal to R = 0.1, the mean fatigue life of electropolished dog-bone specimens was 250% longer than that of as-built specimens.

Modeling of pertinent parameters influence on the time dependent mass transfer coefficient of particulate matter under the sink effect

One of the most crucial evaluation metrics for the performance of particle sink purification technology is the time-dependent mass transfer coefficient (TDMTC). Therefore, it is very helpful for designers and developers to accurately describe the functional relationship between different influence parameters and the TDMTC. In this paper, four influence parameters (the applied voltage (V), interelectrode distance (dc), porosity (P), and shape (n) of the collecting electrode) were considered, and then non-linear multiple regression (NLMR) and multi-gene genetic programming (MGGP) methods were used to establish prediction models of the TDMTC. Results showed that V and n were the most significant factors, followed by dc and P. Both multi-factor models could accurately predict the TDMTC under the sink effect with a maximum prediction error of 20% and 15%, respectively. Moreover, for particulate matter (PM) with different size fractions, MGGP models could improve the prediction accuracy by 5–10% compared to NLMR models.

Study on the influence of electrodes on the collection efficiency during the treatment of welding fume in electrostatic precipitators

Welding fume is hazardous to the environment and human health and is purified using an electrostatic precipitator (ESP). Electrostatic precipitators are widely used in waste gas treatment processes in thermal power plants, cement plants and other factories. The use of electrostatic precipitators to treat welding fumes requires further research. Corona discharge occurs at the electrostatic precipitator, the primary condition for particle charging. The components and physical parameters of the treated particles should be considered in the numerical simulation. This paper investigates the effects of polygonal electrode form, deflection angle, and spacing on the electric field distribution and collection efficiency. The physical quantities in the vicinity of the electrodes vary greatly. Therefore, the focus is on the vicinity of the electrode, and curves describing the trend. It is shown that the maximum velocity did not vary monotonically with increasing the number of tips and that the highest collection efficiency is obtained with a triangle electrode. Furthermore, it is shown that the variation of interelectrode distance leads to variations in the inter-electrode shielding effect.

First Review of Conductive Electrets for Low-Power Electronics

This is the first review of conductive electrets (unpoled carbons and metals), which provide a new avenue for low-power electronics. The electret provides low DC voltage (μV) while allowing low DC current (μA) to pass through. Ohm’s Law is obeyed. The voltage scales with the inter-electrode distance. Series connection of multiple electret components provides a series voltage that equals the sum of the voltages of the components if there is no bending at the connection between the components. Otherwise, the series voltage is below the sum. Bending within the component also diminishes the voltage because of the polarization continuity decrease. The electret originates from the interaction of a tiny fraction of the carriers with the atoms. This interaction results in the charge in the electret. Dividing the electret charge by the electret voltage V’ provides the electret-based capacitance C’, which is higher than the permittivity-based capacitance (conventional) by a large number of orders of magnitude. The C’ governs the electret energy (1/2 C’V’2) and electret discharge time constant (RC’, where R = resistance), as shown for metals. The discharge time is promoted by a larger inter-electrode distance. The electret discharges occur upon short-circuiting and charge back upon subsequent opencircuiting. The discharge or charge of the electret amounts to the discharge or charge of C’.

Optimization of phosphorus recovery using electrochemical struvite precipitation and comparison with iron electrocoagulation system.

A batch monopolar reactor was developed for total phosphorus (TP) recovery using electrochemical struvite precipitation. This study involves the optimization of factors using response surface methodology to maximize the TP recovery. The optimal parameters for this study were found to be a pH of 8.40, a retention time of 35 min, a current density of 300 A/m2 , and an interelectrode distance of 0.5 cm, resulting in 97.3% of TP recovery and energy consumption of 2.35 kWh/m3 . A kinetic study for TP removal revealed that at optimum operating conditions, TP removal follows second-order kinetics (removal rate constant(K) = 0.0117 mg/(m2 ·min)). The system performance was compared to the performance of an iron electrocoagulation system. The composition of the precipitate obtained during the optimal runs were analyzed using X-ray diffraction and EDS analysis. X-ray diffraction analysis of the magnesium precipitate revealed the presence of struvite as the only crystalline compound. PRACTITIONER POINTS: Electrochemical struvite precipitation has the potential to recover total phosphorus from anaerobic bioreactor effluent. Optimum conditions for phosphorus recovery was found at a pH of 8.4, retention time of 35 min, current density of 300 A/m2, and interelectrode distance of 0.5 cm. The quadratic model predicted complete (100 %) TP recovery under optimized conditions, whereas 97.3 % recovery was observed under experimental conditions. TP removal under optimum conditions followed second-order rate equation (removal rate constant(K) = 0.0117 mg/(m2 ·min)). XRD analysis of the precipitate revealed struvite as the only crystalline compound.

Uniform Action of Plasma of a Nanosecond Pulsed High-Voltage Discharge on the Surface of a Flat Anode

The results of an experimental study of the effect of a plasma of a nanosecond pulsed high-voltage discharge in air at atmospheric pressure, excited in a sharply nonuniform electric field, on the surface of a flat-grounded electrode are presented. It is shown that at relatively large interelectrode distances between the pointed cathode and the flat anode, a diffuse discharge is implemented, which ensures a uniform action of the discharge plasma on the anode surface.

Electrocoagulation treatment of furniture industry wastewater

Electrocoagulation was investigated as a method for treating wastewater containing polyvinyl acetate (PVAc) from the furniture industry. The study evaluated the evolution of iron concentration and passivation during the treatment process. Laboratory-scale experiments were conducted to evaluate the effects of inter-electrode distance (d), current density, and mode on treatment performance. Three values of d (0.3, 0.6, and 0.9 cm) were studied and found to have no significant effect on performance. However, lower d values resulted in reduced energy consumption due to a decrease in applied voltage. Three values of current density (132, 158, and 197 A m−2) were studied under two current modes, Direct Current (DC) and Alternating Pulsed Current (APC). The best treatment performance for DC occurred under 158 A m−2 (the treated wastewater was characterized by pH = 4.59 ± 0.02, conductivity = 996 ± 21 μS cm−1, COD = 1940 ± 55 mgO2 L−1, TSS = 105 ± 14 mg L−1, and Fe = 50.39 ± 1.87 mgFe L−1). For APC, the best performance was achieved under 197 A m−2 (the treated wastewater was characterized by pH = 6.33 ± 0.06, conductivity = 988 ± 17 μS cm−1, COD = 1942 ± 312 mgO2 L−1, TSS = 199 ± 55 mg L−1, and Fe = 44.68 ± 4.60 mgFe L−1). Despite the promising results, treatment performance was insufficient to meet the legal requirements for water discharge. APC was found to be a more economically viable approach, as it reduced anode wear, electrode passivation, and energy consumption. The quantity of iron released increased with d, and the effect of current density on iron concentration was found to be non-linear. However, applying APC reduced the iron content for all tested current densities. The tests showed that EC was effective in removing chemical oxygen demand (COD) and total suspended solids (TSS), achieving removal efficiencies above 92% and 99%, respectively. However, the studied treatment procedures were insufficient to meet the EU legal requirements for water discharge. Therefore, the obtained wastewater should undergo a post-treatment process.

MODULATION OF NEGATIVELY CHARGED PARTICLE FLUX FROM PENNING DISCHARGE WITH METAL HYDRIDE CATHODE

The features of modulation of negatively charged particle flux extracted along the magnetic field from Penning discharge with metal hydride cathode have been investigated. The separation of negative ions from coextracted electrons was performed by an electromagnetic filter with efficiency not worse than 90 %. It is shown that electrons in the extracted flow are deeply modulated with the frequency of the diocotron instability of the anode layer, while negative ions are not. An increase in the interelectrode distance and anode length resulted in a more pronounced expression of this effect due to the minimization of the influence of the magnetic field of the filter on the discharge.

The surface electrode placement determines the magnitude of motor potential evoked by transcranial magnetic stimulation

ObjectiveDifferent electrode montages have been adopted to record the surface electromyographic signal (sEMG) from which motor potentials (MEP amplitude) evoked by transcranial magnetic stimulation (TMS) are extracted. It can lead to divergences in comparing treatment outcomes or comparisons across them. This study aimed to evaluate the effect of three different sEMG electrode montages on the MEP amplitude. MethodsEight healthy right-handed participants (6 women; 24–28 years) without sensorimotor disorders participated in the present study, which the local ethical committee approved. Surface EMG signals were recorded from both upper limbs’ biceps brachii (BB) muscles. Three sEMG electrode montages (E1-E2 differential) were placed according to the following protocols: Protocol by Garcia et al. [E1 – Innervation zone]–[E2 – epicondylus lateralis] (Garcia⊢IZ-BP); Protocol by IFCN [E1 – Muscle belly]–[E2 – epicondylus medialis] (IFCN⊢MB-BP); and Protocol by Munneke et al. [E1-E2 over the muscle belly, but with an inter-electrode distance between 40 and 90% of the total muscle length] (Munneke⊢40-90%). Thirty single TMS pulses were applied on the BB hotspot with a figure of eight coil at 120% of the resting motor threshold (rMT). ResultsThe rMTs were significantly higher (p < 0.05) for Munneke⊢40-90% protocol than for the other two, and IFCN⊢MB-BP protocol was the lowest. IFCN⊢MB-BP protocol also provided MEP amplitudes about 2.0 to 4.0 times greater (p < 0.05) than the other two. ConclusionDifferent electrode montages can provide contrasting MEP amplitudes. SignificanceIt sounds imperative to create standard recommendations on electrode placement for MEP recordings.

Muscle innervation zone estimation from monopolar high-density M-waves using principal component analysis and radon transform.

This study examined methods for estimating the innervation zone (IZ) of a muscle using recorded monopolar high density M waves. Two IZ estimation methods based on principal component analysis (PCA) and Radon transform (RT) were examined. Experimental M waves, acquired from the biceps brachii muscles of nine healthy subjects were used as testing data sets. The performance of the two methods was evaluated by comparing their IZ estimations with manual IZ detection by experienced human operators. Compared with manual detection, the agreement rate of the estimated IZs was 83% and 63% for PCA and RT based methods, respectively, both using monopolar high density M waves. In contrast, the agreement rate was 56% for cross correlation analysis using bipolar high density M waves. The mean difference in estimated IZ location between manual detection and the tested method was 0.12 ± 0.28 inter-electrode-distance (IED) for PCA, 0.33 ± 0.41 IED for RT and 0.39 ± 0.74 IED for cross correlation-based methods. The results indicate that the PCA based method was able to automatically detect muscle IZs from monopolar M waves. Thus, PCA provides an alternative approach to estimate IZ location of voluntary or electrically-evoked muscle contractions, and may have particular value for IZ detection in patients with impaired voluntary muscle activation.

Stormwater runoff treatment through electrocoagulation: antibiotic resistant bacteria removal and its transmission risks

ABSTRACT Recently, increasing attention has been paid to antibiotic resistant bacteria (ARB) in stormwater runoff. However, there were little data on ARB removal through electrocoagulation (EC) treatment. In this study, batch experiments were conducted to investigate key designs for ARB removal, role of SS, effects of water matrix, and potential risks after EC treatment under the pre-determined conditions. EC treatment with 5 mA/cm2 of current density and 4 cm of inter-electrode distance was optimal with the highest ARB removal (3.04 log reduction for 30 min). The presence of SS significantly improved ARB removal during EC treatment, where ARB removal increased with the increase of SS levels when SS less than 300 mg/L. Large ARB removal was found under particles with size lower than 150 μm with low contribution (less than 10%) of the settlement without EC treatment, implying that the enhancement of ARB adsorption onto small particles could be one of the reasonable approaches for ARB removal through EC treatment. ARB removal increased firstly and then decreased with the increase of pH, while had proportional relationship with conductivity. After the optimal condition, there were weak conjugation transfer but high transformation frequency (5.5 × 10−2 for bla TEM) for target antibiotic resistance genes (ARGs), indicating that there could be still a risk of antibiotic resistance transformation after EC treatment. These suggested that the combination of EC and other technologies (like electrochemical disinfection) should be potential ways to control antibiotic resistance transmission through stormwater runoff.

Treating hydraulic fracturing produced water by electrocoagulation

ABSTRACT Hydraulic fracturing oil- and gas-produced water is frequently highly impaired. While it is often deep well injected, there is a great deal of interest in treating and recovering this water for beneficial uses. However, multiple-unit operations are needed if these wastewaters are to be recovered. Electrocoagulation is considered a promising pretreatment technology. Herein, we have investigated the use of aluminum electrodes for electrocoagulation as a pretreatment operation. The effects of electrode arrangement, applied current, reaction time, pH and inter-electrode distance on the quality of the treated water have been investigated. The results obtained here indicate that electrocoagulation can obtain good removal of turbidity (95%), total suspended solids (TSS) (90%) and total organic carbon (TOC) (69%) by carefully choosing the reaction conditions. Sedimentation was used to separate the treated water from the sludge. The performance of the electrocoagulation process depends strongly on the quality of the feed water. The viability of a practical continuous electrocoagulation process will depend on the volume (footprint) of the reactor, which in turn will depend on operating conditions and the quality of the feed water.

Sensor selection and miniaturization limits for detection of interictal epileptiform discharges with wearable EEG

Objective. The goal of this paper is to investigate the limits of electroencephalography (EEG) sensor miniaturization in a set-up consisting of multiple galvanically isolated EEG units to record interictal epileptiform discharges (IEDs), referred to as ‘spikes’, in people with epilepsy. Approach. A dataset of high-density EEG recordings (257 channels) was used to emulate local EEG sensor units with short inter-electrode distances. A computationally efficient sensor selection and interictal spike detection algorithm was developed and used to assess the influence of the inter-electrode distance and the number of such EEG units on spike detection performance. Signal-to-noise ratio, correlation with a clinical-grade IEDs detector and Cohen’s kappa coefficient of agreement were used to quantify performance. Bayesian statistics were used to confirm the statistical significance of the observed results. Main results. We found that EEG recording equipment should be specifically designed to measure the small signal power at short inter-electrode distance by providing an input referred noise 300 nV. We also found that an inter-electrode distance of minimum 5 cm between electrodes in a setup with a minimum of two EEG units is required to obtain near equivalent performance in interictal spike detection to standard EEG. Significance. These findings provide design guidelines for miniaturizing EEG systems for long term ambulatory monitoring of interictal spikes in epilepsy patients.

An in silico assessment on the potential of using saline infusion to overcome non-confluent coagulation zone during two-probe, no-touch bipolar radiofrequency ablation of liver cancer.

No-touch bipolar radiofrequency ablation (bRFA) is known to produce incomplete tumour ablation with a 'butterfly-shaped' coagulation zone when the interelectrode distance exceeds a certain threshold. Although non-confluent coagulation zone can be avoided by not implementing the no-touch mode, doing so exposes the patient to the risk of tumour track seeding. The present study investigates if prior infusion of saline into the tissue can overcome the issues of non-confluent or butterfly-shaped coagulation. A computational modelling approach based on the finite element method was carried out. A two-compartment model comprising the tumour that is surrounded by healthy liver tissue was developed. Three cases were considered; i) saline infusion into the tumour centre; ii) one-sided saline infusion outside the tumour; and iii) two-sided saline infusion outside the tumour. For each case, three different saline volumes were considered, i.e. 6, 14 and 22 ml. Saline concentration was set to 15% w/v. Numerical results showed that saline infusion into the tumour centre can overcome the butterfly-shaped coagulation only if the infusion volume is sufficient. On the other hand, one-sided infusion outside the tumour did not overcome this. Two-sided infusion outside the tumour produced confluent coagulation zone with the largest volume. Results obtained from the present study suggest that saline infusion, when carried out correctly, can be used to effectively eradicate liver cancer. This presents a practical solution to address non-confluent coagulation zone typical of that during two-probe bRFA treatment.

Performance of electrocoagulation process for copper removal in simulated artisanal and small-scale mining wastewater

Electrocoagulation treatment was applied in the simulated artisanal and small-scale mining wastewater for 60 minutes. Copper concentration of 625 mg.L−1 was used in the study which was based on the real artisanal and small-scale mining wastewater (conductivity = 13 mS.cm−1, initial pH = 10) collected from Paracale, Camarines Norte, Philippines. Batch experiments using a pair of iron electrodes with an interelectrode distance of 2 cm were used for this study and we have determined the optimized conditions such as conductivity, initial pH, and current density for the various electrocoagulation runs. Decreasing initial conductivity and pH of real mining wastewater while increasing current density favours higher removal efficiency. With the conductivity of 3.5 mS.cm−1, initial pH of 9, and current density of 33.5 mA.cm−2, copper removal efficiency was 93.5%. Based on these operating conditions, energy consumption was 36.82 kWhr.m−3 and electrodes consumption were 2.09 kg.m−3. This study revealed that electrocoagulation is feasible to treat higher concentrations of copper present in mining wastewater.

Impact of operating parameters of electrocoagulation-flotation on the removal of turbidity from synthetic wastewater using aluminium electrodes

This study analyzed the dominant operating parameters of electrocoagulation-flotation (ECF) that would influence the removal efficiency of turbidity from synthetic wastewater using aluminium electrodes with an inter-electrode distance of 5 mm. These parameters included current density (CD), initial pH, electrolytic conductivity, coagulant dosage, operating time, initial turbidity concentration, and stirring speed. The initial turbidity concentration and electrolytic conductivity were synthesized based on typical concentrations of various resources such as drinking water, wastewater, seawater, and oil field-produced water. A novel approach has also been proposed for the evaluation of EC performance and selection of an appropriate process for the removal of sludge based on the intake’s initial concentration. The experimental results revealed that the optimal conditions for removal of turbidity (90 %) were attained at CD = 0.0028 A/cm2, initial pH = 7.3, operating time = 5 min, and stirring speed = 500 rpm. The settling times of 5 and 15 min were also evaluated, in order to optimize the design of the settling tank. The results also revealed that ECF formed the flocs larger than 20 µm, so that after filtration with a filter paper of 20 µm, a removal efficiency of 98 % was attained.

The impact of electric field on the demulsification efficiency in an electro-coalescence process

In this study, the influence of the electric field and its determining parameters such as voltage, inter-electrode distance and frequency on the demulsification efficiency of a water-in-oil emulsion was studied. The numerical analysis showed that the water droplets trapped onto the hydrophobic titanium dioxide (TiO2) coated electrodes and at 2 mm inter-electrode distance can increase the electric field intensity above 300 kV/m, where droplet rupture takes place. Experimental study showed highest demulsification efficiency of 76% while applying AC voltage of 250 V, frequency of 200 kHz and inter-electrode distance of 4 mm.

Performance assessment of electrode configurations for the estimation of omnipolar electrograms from high density arrays

Objective:The aim of this study is to propose a method to reduce the sensitivity of the estimated omnipolar electrogram (oEGM) with respect to the angle of the propagation wavefront. Methods:A novel configuration of cliques taking into account all four electrodes of a squared cell is proposed. To test this approach, simulations of HD grids of cardiac activations at different propagation angles, conduction velocities, interelectrode distance and electrogram waveforms are considered. Results:The proposed approach successfully provided narrower loops (essentially a straight line) of the electrical field described by the bipole pair with respect to the conventional approach. Estimation of the direction of propagation was improved. Additionally, estimated oEGMs presented larger amplitude, and estimations of the local activation times were more accurate. Conclusions:A novel method to improve the estimation of oEGMs in HD grid of electrodes is proposed. This approach is superior to the existing methods and avoids pitfalls not yet resolved. Relevance:Robust tools for quantifying the cardiac substrate are crucial to determine with accuracy target ablation sites during an electrophysiological procedure.