Initial Current Density Research Articles

A Systematic Performance History Analysis of a Chlor-Alkali Membrane Electrolyser under Industrial Operating Conditions

The history of the potential and electrical current evolution of an industrial chlor-alkali membrane electrolyser is a powerful tool to track its operational efficiency progress over time and for deciding the required maintenance instants. For this reason, the performance of a dedicated industrial NaCl electrolyser was systematically analysed as a function of its service time for about 8 years, recording the cell potential versus current density. The documented potential values were normalized taking into account the initial current density, which allowed to reduce data scattering due to small fluctuations of the current density values. The ohmic overpotential contribution, associated to the ion-exchange membranes, showed an average relative error smaller than 3% and the activation overpotential, related to the electrodes’ performance, displayed an average relative error of 6%. Thus, the proposed approach enables rigorous assessing of the performance of industrial chlor-alkali membrane electrolysers for adequate scheduling of their maintenance, which leads to significant operational and economic improvements of the chlor-alkali process.

Degradation of emerging contaminants by Co (III) ions in situ generated on anode surface in aqueous solution

Cobalt ion is an environmental contaminant in general. But interestingly, it can also be used to degrade some refractory organic contaminants in water by mediated electrochemical oxidation process (MEOP) based on Co (III). MEOP is a very promising technology, and it can recycling use the mediator ions, Co (III), to degrade refractory organic contaminants in water. However, previous studies for this technology mainly conducted in strong acidic medium, the oxidation ability of this process for emerging contaminants near neutral pH condition was still unclear. Therefore, this study evaluated the emerging contaminants removal and mineralization efficiency of the MEOP-Co (III) around neutral pH, and investigated systematically the influence of series of operating parameters, including initial Co (II) concentration, current density, initial pH, electrolyte, and anions. Results from these studies indicated that the MEOP-Co (III) had a fairly good contaminants removal and mineralization ability for sulfamethoxazole, tetracycline, carbamazepine, diclofenac, and phenol at neutral pH. Besides, no radical was detected in MEOP-Co (III), and the main oxidizing substance was Co (III) ions, which was generated on anode surface. The addition of CO32−/HCO3− could weaken the oxidation ability of MEOP-Co (III), while Cl− and PO43− could enhance the system's oxidation ability. Moreover, a reasonable energy consumption was achieved in MEOP-Co (III), and the highest electric energy per order (EE/O) value was 2.4 kWh·m−3 in this study.

Pollutant Removal from Wastewater at Different Stages of the Tanning Process by Electrocoagulation

The removal of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and chromium content from tannery wastewater at different stages of the process was experimentally investigated using electrocoagulation (EC) with iron and aluminium electrodes. In the EC of the beamhouse wastewater (S1), the effects of initial pH and current density were analyzed and electrical energy consumption was determined. The COD and TOC in the solution were effectively removed, with an initial pH 7.0, using either metallic electrode. With a current density of 28 mA/cm2 for an electrolysis procedure of 60 minutes, the removal efficiency of COD and TOC was 72% and 57% with aluminium electrodes and 69% and 60% with iron electrodes, respectively. The minimum energy consumption for the highest COD and TOC removal was 0.37 and 0.69 kWh/m3 when employing iron or aluminium electrodes, respectively. At the optimal conditions, removal efficiencies close to 100% for turbidity and chromium content for wastewaters S1-beamhouse, S2-tanning, S3-retanning, and S4-a mixture 1 : 1 : 1 (v/v/v) were achieved. Results show that a pseudosecond-order rate equation provides a good correlation for the removal rate of the parameters. Finally, the results indicate that for tannery wastewater, the EC process does not depend noticeably on the electrode material, but that the stage of the tanning process of wastewater sample has the principal effect on treatment efficiency.

Facile solvothermal synthesis of Pt-Cu nanocatalyst with improved electrocatalytic activity toward methanol oxidation

A binary metal nanocatalyst of platinum and copper was synthesized using a facile solvothermal process (polyol method). The synthesized catalyst was characterized using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical performance of the synthesized carbon supported binary metal catalyst, Pt?Cu/?, toward methanol oxidation reaction was checked and then compared with the commercial Pt/C (ETEK) catalyst, using cyclic voltammetry and chronoamperometric techniques. The Pt?Cu/C catalyst was found to be cubic in shape with indentations on the particle surface, having platinum to copper atomic composition of 4:1, i.e., (Pt4Cu). The peak current density for Pt?Cu/C catalyst recorded as 2.3 mA cm-2 at 0.7 V (vs Ag/AgCl) and 50 mV s-1, was two times higher than the current density of the commercially available Pt/C catalyst (1.16 mA cm-2 at 0.76 V). Moreover, the Pt?Cu/C catalyst was found to be more durable than the commercial Pt/C catalyst, as the Pt?Cu/C retained 89 % of its initial current density, while the commercial Pt/C catalyst retained 65 % of its initial current density after 300 potential cycles.

Application of a Continuous Bipolar Mode Electrocoagulation (CBME) system for polishing distillery wastewater

A continuous bipolar mode electrocoagulation (CBME) unit was used in this study for polishing a biologically treated distillery wastewater at laboratory scale. This study focuses on optimizing the process for removal of Total Organic Carbon (TOC) from an anaerobically-treated distillery wastewater. Response surface methodology (RSM) was used for optimizing the process. The study was conducted by varying three operating parameters: Initial pH (2-10), reaction time (0.5-15 min), and current density (13-40 A/sqm). High R-square values, above 0.9, were obtained with ANOVA. Optimal point was observed to be at pH-6.04, Reaction time-11.63 min, current density-39.2 A/sqm. Experimental values of TOC removal at optimal point were found to be 73% against maximum predicted value of 79%. Color removal efficiency was observed to be 85% at the optimal points. It can be concluded that CBME system can be a suitable alternative for removal of recalcitrant carbon and color post-biological treatment in distillery wastewaters.

Modeling the Spatial and Temporal Distribution of Current in a Carbon Monoxide Poisoned Polymer Electrolyte Fuel Cell Using a Dynamic Pseudo 1-D Approach

A zero-dimensional segmented model is developed to predict the spatial and temporal behavior of the current in a polymer electrolyte fuel cell when carbon monoxide (CO) is introduced into the fuel stream. The calculated results are consistent with previous experimental observations that CO poisoning occurs first on the anode region close to the inlet. In the potentiostatic mode, this leads to a sequential drop of the segment currents. The steady state current in the segments near the inlet are generally lower than those near the outlet when the anode potential rises high enough to remove CO by electro-oxidation and reduce its concentration in the fuel stream. The situation when the cell is operated in the galvanostatic mode is more complex. As the segments near the inlet become poisoned and the segment currents drop, the current in the other segments must increase to maintain constant cell current. However, the reverse trend occurs as subsequent segments experience CO poisoning, forcing the local current at the first segments to increase even beyond their initial CO-free current density. A comprehensive assessment of the effects of CO concentration, current density, fuel stoichiometry and temperature on the segment currents in the galvanostatic mode is provided.

Self-powered reduced-dimensionality perovskite photodiodes with controlled crystalline phase and improved stability

In this work, we developed the perovskite photodiodes based on the dimensionality-reduced quasi two-dimensional (Q-2D) photoactive layer structure by incorporating phenylethylammonium iodide (PEAI) into methylammonium lead iodide (MAPbI3), which effectively enhanced both the crystalline phase and the ambient stability of the perovskite. The Q-2D perovskite photodiode exhibited a dark current of 1.76 × 10−7 A/cm2, resulting in the detectivity (D*) of 2.20 × 1012 J and responsivity of 0.53 A/W, which is among the highest performance levels without the voltage bias (0 V) due to the systematically optimized perovskite phase resulting in the reduced leakage current. In addition, the current density of Q-2D perovskite photodiode maintained 76% of the initial level current density even after 80 days in the ambient condition, compared to 15% of 3D perovskite photodiode control sample. Such superior performance and stability were mainly attributed to the enhanced degree of crystallization of the Q-2D perovskites, which was confirmed by X-ray diffraction and grazing incidence wide-angle X-ray scattering (GIWAXS) measurement. Also, the improved stability of Q-2D perovskite films was confirmed by both lifetime test and atomic force microscopy studies where the negligible number of pinholes was observed in the quasi-2D perovskite films while considerable deformations were found in the 3D perovskites photodiode. Our study suggests a simple and robust protocol for the development of stable and high-performance perovskite photodetectors via dimensional and constitutional optimization of conventional perovskites for the practical usage of perovskite in the photodiode applications.

A study of the effect of cycling modes on the electrochromic properties of Ni(OH)2 films

As a result of conducted studies, a series of electrochromic Ni(OH)2 films were prepared using the cathodic template method under the same conditions. Prepared films have been used for comparison of regimes for coloration-bleaching cycling. Main qualitative characteristics were also evaluated – averaged absolute coloration degree, averaged irreversibility on bleaching and visual comparison in the colored state after cycling.To compare the influence of different regimes, potentiodynamic, galvanostatic and complex regimes were proposed. For potentiodynamic regimes, different upper and lower potential limits were chosen. Initial current density for galvanostatic and complex regimes was chosen based on the results of the cyclic voltamperometry curve. Chosen current density was equal to the cathodic peak value on the fifth cycle of the cyclic voltamperometry curve recorded in the following regime: potential window [201–751 mV], scan rate 1 mV/s.Coloration-bleaching cycling in different regimes revealed high effectiveness of potentiodynamic regimes which showed the highest coloration degree of the films. On the other hand, it was found that narrowing and widening of potential windows relative to optimal resulted in worse characteristics of electrochromic films. Galvanostatic regimes showed the most optimal results in terms of absolute coloration degree and time required for coloration/bleaching. Complex regimes demonstrated the worst results. Theses regimes resulted in significant irreversibility and average rate of coloration and bleaching.Galvanostatic and complex regimes revealed the presence of two plateaus on the current density curves, which indicates the presence of both α-Ni(OH)2 and β-Ni(OH)2 in electrochromic material

Application of Response Surface Methodology for analysis and optimization of the operational parameters for turbidity removal from oily wastewater by electrocoagulation process

The purpose of this work was to study the effectiveness of electrocoagulation process for turbidity removal from oily wastewater. Synthetic oily wastewater was used for conducting batch experiments, and the turbidity introduced to the wastewater by (0.3 gm) of Sodium Bentonite giving an initial turbidity of (200 NTU). Anode of aluminum and cathode of Iron were immersed in 1.5 L solution. An experimental design of (52 run) based on a central composite design (CCD), and the analyze of data was carried out using response surface methodology (RSM) in (Design Expert software) for evaluating the effect and interaction of several parameters including: initial pH (5-9), initial oil concentration (50-500 ppm), current density (5-25 mA/cm2), NaCl concentration (40-400 ppm), and electrolysis time (10-30 min). The response variable was Turbidity%. The experimental results were fitted to a quadratic equation and analysis of variance (ANOVA) was also performed. Results of the ANOVA showed that the model fitted well with turbidity% giving less than 0.05 of probability of error (p), and the variables had a significant effect on the removal. The high R-squared of 88% indicate the high correlation between the predicted and experimental values. In addition, the estimated optimum conditions of the treatment system were (pH= 6, [oil]= 387.5 ppm, Current density= 20 mA/cm2, [NaCl]= 310 ppm, and time= 25 min) giving a predicted turbidity% of 98% and experimental of 97.4%.

Initial dissolved oxygen-adjusted electrochemical generation of sulfate green rust for cadmium removal using a closed-atmosphere Fe–electrocoagulation system

In this study, the effect of initial dissolved oxygen (DOi) on the efficiency of removing Cd2+ from wastewater using a newly designed closed-atmosphere electrocoagulation (CAEC) system was investigated. The effects of factors such as temperature, initial pH, current density, and electrolyte composition (NaCl and Na2SO4) were investigated. The results indicated that the removal efficiency of Cd2+ could be enhanced by increasing the initial pH, current density, and Na2SO4 dosage at initial DO concentration of 1.6 mg/L. However, a low current efficiency was also obtained when a high current density was applied because the high anodic potential resulted in water electrolysis. In brief, the generation of green rust (GR) promotes Cd2+ removal, particularly under anaerobic conditions, and Na2SO4 positively affects the flocculation and adsorption efficiencies of GR by strong charge neutralization. The obtained results can provide meaningful insights for the application of Fe–electrocoagulation in real industrial wastewater and understanding the mechanism of Fe based hydroxide coagulations for toxic metal removal.

A comprehensive study on the electrocatalytic degradation, electrochemical behavior and degradation mechanism of malachite green using electrodeposited nanostructured β-PbO2 electrodes

This work has investigated the electrocatalytic degradation of malachite green (MG) in aqueous solution with G/β-PbO2, SS316/β-PbO2, Ti/β-PbO2 and Pb/β-PbO2 electrodes. These electrodes show high oxygen evolution over-potential and excellent electrochemical degradation efficiency for organic pollutants. The optimum conditions for the degradation of MG were obtained by studying the effects of different parameters, such as initial current densities and initial MG concentration. The remaining organic compounds concentrations (color) and chemical oxygen demand (COD) removal efficiency were investigated and compared. The results indicate that the efficiency of G/β-PbO2 electrode for both color and COD removals is more than those of other electrodes. At the optimum conditions, the color and COD removal efficiencies of MG reached up to 100% and 94%, respectively. The observed degradation rate of MG was found to vary in the order G/β-PbO2> SS316/β-PbO2> Ti/β-PbO2> Pb/β-PbO2. Moreover, in this paper, the electrochemical behavior and adsorption characteristic of MG in aqueous solutions with different pH values were studied in details at glassy carbon electrode using both constant-current coulometry and cyclic voltammetry techniques. This study has led to the proposed mechanism for the oxidation pathway of MG and determine the absorption properties of MG in acidic, neutral and basic solutions. We also proposed the mineralization pathway of MG at β-PbO2 electrode.

Mn3O4/carbon nanotubes nanocomposites as improved anode materials for lithium-ion batteries

Mn3O4 and Mn3O4 (140)/CNTs have been investigated as high-capacity anode materials for lithium-ion batteries (LIBs) applications. Nanoparticle Mn3O4 samples were synthesized by hydrothermal method using Mn(Ac)2 and NH3·H2O as the raw materials and characterized by XRD, TG, EA, TEM, and SEM. Its electrochemical performances, as anode materials, were evaluated by galvanostatic discharge-charge tests. The Mn3O4 (140)/CNTs displays outstanding electrochemical performances, such as high initial capacity (1942 mAh g−1), stable cycling performance (1088 mAh g−1 and coulombic efficiency remain at 97% after 60 cycles) and great rate performance (recover 823 mAh g−1 when return to initial current density after 44 cycles). Compared to pure Mn3O4 (140), the improving electrochemical performances can be attributed to the existence of very conductive CNTs. The Mn3O4 (140)/CNTs with excellent electrochemical properties might find applications as highly effective materials in electromagnetism, catalysis, microelectronic devices, etc. The process should also offer an effective and facile method to fabricate many other nanosized metallic oxide/CNTs nanocomposites for low-cost, high-capacity, and environmentally benign materials for LIBs.

Electrocoagulation process for propiconazole elimination from wastewater: experimental design for correlative modeling and optimization

Electrocoagulation process is an electrochemical method to remove variety of contaminants (i.e., pesticides) from water and wastewater effluents. The current research examines the elimination of propiconazole by electrocoagulation technique. For this aim, after the preliminary screening tests (using factorial design) for the identification of the significant and remarkable factors, response surface methodology based on central composite design is employed to develop a correlative model for the efficiency of the electrocoagulation process. Furthermore, simultaneous optimization of the operational process variables [electrolysis duration (10–60 min), propiconazole initial concentration (10–50 mg/L), current density (2.5–12.5 mA/cm2), and solution conductivity (0.5–2.5 mS/cm)], is carried out to find the most appropriate strategy. The screening of the prime considered factors indicates that pH is not a significant variable and consequently is excluded from further deliberations. A quadratic correlative model is prepared, and model-based optimization is further performed and experimentally verified. The maximum removal efficiency (79.83%) is attained regarding the following process factors: the propiconazole initial concentration of 25.93 mg/L, the time duration of 36.44 min, the current density of 10.95 mA/cm2, and the solution conductivity of 2.44 mS/cm. The results demonstrate that through electrocoagulation process with proper operational variables, the amounts of propiconazole in wastewater effluents can adequately get lowered to acceptable levels.

Treatment of Automotive Paint Wastewater Using Electroflotation: Kinetic Study, Influencing Factors and Data Analysis

A comprehensive laboratory experimental study was conducted on the application of electroflotation in removal of paint from automotive paint system. In 40 min testing time and under 44 A/m2 current density, the total suspended solids (TSS) removal rates ranged from 90.39 to 97.43%. The first and second-order rate constants were developed. The kinetics of the TSS removal from the automotive paint wastewater was best described with the second-order rate constants. Two statistical methods were applied to identify the key factors for electroflotation performance among the Initial TSS Concentration, Current Density, water pH, Zeta Potential and Electrical Conductivity. It was confirmed that in both methods, the Initial TSS Concentration and Current Density were the most significant variables. Further, through Response Surface Methodology and Stepwise Regression analysis, equations of the removal rate of TSS vs reaction time and applied current density were produced for different wastewater samples.

Removal of COD from landfill leachate by advanced Fenton process combined with electrolysis

Zero-valent iron (ZVI) was used as the iron source for the advanced Fenton treatment of landfill leachate in an electrochemical cell. In this process, Fe0 was dissolved from the surface of ZVI powder and then the generated Fe2+ would activate the added H2O2 to produce hydroxyl radical (OH), which is a strong oxidant and can lead to the removal of COD from landfill leachate. The effect of initial pH, H2O2 dosage, Fe0 dosage, current density and inter-electrode gap on the COD removal of landfill leachate was investigated. The results indicate that COD removal followed pseudo-second order kinetic model. The rate constant and efficiency of COD removal increased with Fe0 dosage being increased from 0.524 to 1.745 g/L, but decreased when initial pH rose from 2 to 4. The optimal conditions of H2O2 dosage, current density and inter-electrode gap were determined to be 0.187 mol/L, 20.6 mA/cm2 and 1.8 cm, respectively. The humic acid-like organics in the leachate were effectively degraded and over 70% of COD could be removed from the leachate, showing high efficiency of the electro-advanced Fenton process.

Formation Mechanism of Argon Clathrates with Carbon Dendrites

The formation mechanism of argon clathrates with carbon dendrites obtained in the plasma of an atmospheric-pressure gas discharge has been studied. It has been shown that the formation of these clathrates is due to the difference between characteristic times: the lifetime of molecules surrounding argon atoms and the time of C–C bonding. It has been noted that argon clathrates with carbon dendrites can form only if a number of conditions are met: formation of molecular traps in the discharge, provision of a sufficiently low temperature at the center of the arc discharge, and the presence of active carbon particles arising from plasma decomposition of hydrocarbon precursors. Whether or not these conditions are met depends primarily on the composition of the initial hydrocarbon mixture and discharge current density, as follows from experimental data.

A hybrid method for the removal of fluoride from drinking water: Parametric study and cost estimation

Abstract A hybrid technique (electrocoagulation followed by microfiltration) was utilized for an efficient defluoridation of contaminated drinking water. Three samples of drinking water with an initial fluoride concentration of 7.89, 4.79 and 1.78 mg/L were collected from a hand tube well located in Karbi Anglong district of Assam, India. Effects of different operational parameters such as initial fluoride concentration, current density and pH on the removal of fluoride were extensively investigated in the electrocoagulation chamber. For a current density of 15 A/m2 and an electrode distance of 0.005 m, an efficient removal of 0.0097, 0.335 and 0.656 mg/L was observed for initial fluoride concentration of 1.78, 4.79 and 7.89 mg/L, respectively. The uptake of fluoride was the highest at pH = 7.9 with a final fluoride concentration of 0.43 mg/L. Filtration studies were performed using indigenously prepared membrane. An increase in flux from 7.98 × 10−5 to 19.19 × 10−5 m3/m2 s was observed with an increase in transmembrane from 196 to 509 kPa. Produced flocs were scraped from the membrane surface, dried and characterized to confirm the presence of fluoride. The proposed hybrid technique was able to lower the concentration of fluoride from contaminated drinking water within the permissible limit as per WHO of 1.5 mg/L.

Electrochemical treatment of sugar industry wastewater: process optimization by response surface methodology

Wastewater from sugar industry has multiple combinations of organic and inorganic contaminants. It has an adverse impact on nearby environment and requires specific type of treatment to minimize the effect. To treat the sugar industry wastewater, an attempt has been made with the electrochemical process by using aluminum electrode. Four process parameters were selected, namely initial pH (pH 4–10), current density (44.5–133.5 A/m2), electrode spacing (10–20 mm), and experimental time (20–100 min) to optimize the condition with surface response methodology. At optimum condition maximum, 69.2% chemical oxygen demand and 88.6% color reduction were archived at pH 7, current 1 A, electrode distance 1.5 cm and treatment time 60 min. The coefficient of the model predicted (R2) value of 0.87 and 0.48, and adjusted (R2) value of 0.64 and 0.45 for chemical oxygen demand and color reduction were obtained. The physicochemical characteristic indicates that settling sludge has more inorganic material as compared to floating sludge; hence, settling sludge has low calorific value than floating sludge.

Investigation on the Removal of Chromium from Wastewater using Electrocoagulation

Abstract Nowadays, treatment of chromium wastewater is very critical also important. The current study investigates the influence of electrocoagulation process parameters to reduce the chromium from wastewater. It has been observed that the initial pH (6), current density (25 mA/cm2), electrode distance (4 cm) and electrolysis time (30 min) were found to be optimum for a 97 % chromium removal. For the above said optimum condition, the electrical energy consumption was found to be 0.12 kWh/m3. A comparison between BBD and ANN shows high correlation coefficient values (R2 (ANN) > 0.90 and R2 (RSM) > 0.90). Results indicated that electrocoagulation process is a cheap and effective method to treat chromium wastewater.

Colloidal synthesis of 1T' phase dominated WS2 towards endurable electrocatalysis

Transition metal dichalcogenide (TMD) nanomaterials have attracted tremendous attention due to their great potential for hydrogen evolution reaction (HER), especially with their metallic 1T/1T′ phase, which possesses much higher HER activity than the 2H phase. But the metallic phase can transform to 2H phase accompanied by an undesirable degradation in HER activity. Currently, how to prepare the stable metallic phase TMD nanomaterials enabling an endurable HER is one of the main challenges for practical application. Herein, we establish an effective colloidal chemistry strategy for the controllable synthesis of metallic 1T′ phase dominated WS2 (1T′-D WS2) nanostructures. Such 1T′-D WS2 exhibits higher performance and more stable HER activity than 2H phase WS2 in the H2SO4 electrolyte. The endurance half-life of 1T′-D WS2 from stability testing under constant overpotential of 0.3 V vs. RHE and an initial current density of 41 mA/cm2 is about 46 days, despite vigorous erosion due to continuous H2 bubbling which exerts large capillary stresses on the atomic sheets. The facile preparation of highly stable 1T′-phase dominated TMD nanomaterials advances them as competitive sustainable HER electrocatalysts.