Iron Electrodes Research Articles

Investigating the integration of physical-electrochemical-biological processes in the rehabilitation of dead soils contaminated with lead and phenanthrene

<p>This study was carried out with the aim of using three processes of soil washing, electrofenton and biological leaching method in order to rehabilitate the soil contaminated with lead and phenanthrene around the south Tehran oil refinery. The variables examined in this study are the amount of soil (500, 1000, 1500, 2000 mg), the ratio of surfactant to soil (7.50, 15, 22.50, 30, 37.50 L/Kg), time (6, 12, 18, 24, 30 hours), lead concentration (25, 50, 37.50, 62.50 mg/kg) and phenanthrene concentration (50, 100, 15, 200 mg/kg). In the washing process, the highest percentage of lead removal is 78.23% at the contact surface of 2000 mg, the surfactant-to-soil ratio is 30 ml/kg, the time is 24 hours, the concentration of lead and phenanthrene is 50 and 100 mg/kg and the highest removal percentage of phenanthrene (73.4%) in the soil amount of 1000 mg, the ratio of soil to surfactant equal to 30 liters/kg, in 12 hours, the amount of lead and phenanthrene were obtained equal to 25 and 100 mg/kg. Next, the soil was placed in a discontinuous reactor with graphene electrode as cathode and iron electrode as anode to conduct electrofenton. The investigated variables are solution pH (2, 4, 6, 8, 10), reaction time (12.5, 25, 37.5, 50, 62.5 minutes), hydrogen peroxide concentration (0.5, 1, 1.5, 2, 2.5 w/w) and direct electric current (0.75, 1.5, 2.25, 3, 3.75 A). The results indicated that in the electrofenton pH process, hydrogen peroxide concentration and then voltage had the greatest effect and time had the least effect on the removal of lead and phenanthrene. In this way, the highest percentage of lead removal was 85.4% at pH equal to 8, hydrogen peroxide concentration equal to 2 W/W, current equal to 1.5 A and 50 minutes and the highest percentage of phenanthrene removal (85.9%) at pH equal to 6, hydrogen peroxide concentration equal to 1.5W/W, current equal to 2.25 A and 37.5 minutes were obtained. In the biological leaching method, the purified strain (Pseudomonas aeruginosa) was isolated from the soils around the refinery. Environmental pH (3, 5, 7, 9, 11), pollutant to biomass ratio (7.50, 15, 22.50, 30, 37.5 mg/g) and retention time (1, 2, 3, 4, 5 hour) were considered as main variables. pH was the most important parameter influencing the removal of lead and phenanthrene from soil in biological method. The highest percentage of lead removal with 85.4% was obtained at pH equal to 8, hydrogen peroxide concentration equal to 2W/W, current 1.5 A and 50 minutes time. In the case of phenanthrene, the highest removal percentage of phenanthrene (85.9%) was measured at pH equal to 6, hydrogen peroxide concentration of 1.5 W/W, current of 2.25 A and in 37.5 minutes. Comparing the results of the third stage of soil cleaning with the control sample without preparation steps with the removal percentage of 0.67 and 0.42 for lead and phenanthrene, shows the effect of the soil preparation process in order to improve the ability of bacteria to function and shows that by combining three methods of washing, electrofenton and biologic, it is possible to rehabilitate contaminated soils resistant to biological decomposition.</p>

Evaluation of the electroflotation efficiency for the oil-containing shipping waters treatment

The article describes the problems of formation and purification of ship oil-containing waters. The effectiveness of electroflotation using aluminum and iron anodes for the extraction of oil from water-oil emulsions with different mineralization was assessed.
 Electroflotation treatment of water-oil solutions provides 98.6–99.9 % oil removal using aluminum or iron electrodes at an anodic current density of 1.65–7.39 A/dm2 for highly mineralized waters and 0.07–0.50 A/dm2 for fresh water.
 Water treatment during the first 15 minutes provides a sharp decrease in oil content from 100 mg/dm3 to 1.31–2.52 mg/dm3, almost regardless of the type of anode metal. The efficiency of oil extraction from water mainly depends on its mineralization. In mineralized (salty) water, the treatment process is more efficient. In fresh waters, aluminum anode provides higher water purification efficiency compared to iron anode. However, in the case of pre-treatment of the iron anode with an alkali solution with the formation of a magnetite layer on it, this anode is characterized by the highest purification efficiency for low-salt waters, providing a degree of water purification at the level of 99.9 %.

Recovery of fine particles of activated carbon with gold by the electrocoagulation process using a Taguchi experimental design

The high efficiency of gold recovery via the industrial metallurgical process is increasingly relevant because gold is present at low concentrations in mineral bodies and is difficult to extract. In the mining–metallurgical industry, gold adsorption on activated carbon (AC) includes stages that compromise the structural integrity of the particle. In particular, carbon is an organic material that tends to wear and break down in recovery systems, causing fine particles losses of up to 41% of the average consumption (40 g/t of AC). Carbon-in-columns (CIC) for gold recovery systems lacks on a measure to prevent losses of particles <0.040 mm. Electrocoagulation (EC) technology is an option to improve AC particles recovery from CIC systems, thus increasing the recovery efficiency of ultra-fine particles of AC without requiring additional chemicals. To find the optimal working parameters of gold recovery by EC, the present study conducts laboratory-scale, batch-type EC experiments on AC particles of different sizes (0.106 and 0.053 mm) using different electrodes (iron and aluminum). The EC process was performed in synthetic aqueous medium with an AC particle concentration of 0.80 g/L. The experimental design and results were carried on using the Taguchi statistical method. Scanning electron microscopy images of the filtered and recovered elecrocoagulated product revealed partially coated AC and aggregates of various AC particles with gold. The EC process with the aluminum electrode more effectively recovered the 0.106-mm-sized AC particles, with a more uniform coating, than EC with the iron electrode. Small particles tended to aggregate into larger particles with aluminum hydroxide species, enabling extremely fine AC particle recovery by EC. When used with the aluminum and iron electrodes, the gold–AC recoveries of the EC process exceeded 96% and 88%, respectively.

Enhancement of biogas production from sugarcane molasses-based distillery wastewater with electrocoagulation pretreatment using iron electrodes

Anaerobic digestion (AD) of distillery wastewater (DW) is not optimal because DW contains too high chemical oxygen demand (COD) concentrations. This research aimed to enhance biogas yield from DW with electrocoagulation (EC) pretreatment using iron electrodes. The novelty of this study is the combination of EC-AD for producing biogas from DW. The EC pretreatment was operated at various current densities of 39.31, 47.17, and 55.03 mA/cm2 for 8 h. Then, the supernatants were fed into the anaerobic digesters. The results showed that EC at 39.31, 47.17, and 55.03 mA/cm2 can decrease COD from 116,130 mg-O2/L to 93,976, 85,122, and 76,033 mg-O2/L. The AD with EC pretreatment at 39.31, 47.17, and 55.03 mA/cm2 resulted in biogas yields 6.8-fold, 11-fold, and 12-fold higher than the AD without pretreatment. The future research prospects are the techno-economic analysis and feasibility study of the combination of EC-AD for treating DW.

STATISTICAL ANALYSIS IN SELECTING THE BEST ELECTRODE BETWEEN ALUMINUM AND IRON IN TSS REMOVAL USING ELECTROCOAGULATION

Indonesia is a country that has considerable coal reserves with coal resources of 149.01 billion tons. One of the problems of coal mining is turbidity. The turbidity is caused by the excavation of the open pit mine so that rainwater contact with the main wall. So that mud is formed, which can increase turbidity levels. The concentration of Total Suspended Solids (TSS) due to this phenomenon reaches 5,400 mg/L. Aim: This study aims to set aside TSS by electrocoagulation processing method using a batch system with eight pairs of iron electrodes arranged monopolarly. Methodology and Results: Comparisons using statistically independent t-tests showed that there was no significant difference between the iron and aluminium electrodes in the pH parameter. Conclusion, significance, and impact study:There were significant differences between iron and aluminum electrodes in the parameters of TDS and TSS. In the measured TDS and TSS parameters, the electrocoagulation process using iron electrodes has a higher value than aluminum electrodes. In the TSS removal, there is no significant difference between the two electrodes (iron and aluminium).

Modeling the Coulombic Efficiency of the Aqueous Iron Electrode

The aqueous iron electrode is attractive for large-scale energy storage because of its long life and low materials cost. The redox potential of the Fe ↔ Fe2+ reaction is approximately 50 mV negative of that of the hydrogen evolution reaction. Hydrogen evolution therefore causes self discharge of the iron electrode during rest and competes with the iron reaction during charge. Here we model the effect of electrode design and cell operation on the coulombic efficiency of charging the iron electrode at modest charging rates (<C/20). Kinetic parameters (exchange current density and transfer coefficients) for the iron dissolution-precipitation reaction and for the hydrogen evolution reaction are estimated from experimental measurements of electrode overpotential and hydrogen generation rate. The volume change from Fe(OH)2 to Fe metal results in a significant increase in porosity during charge and results in change in electrochemically active surface area. The porous-electrode model includes transport in the electrolyte, Butler-Volmer kinetics, and change in volume and surface area.The model provides a theoretical explanation for experimental observations that coulombic efficiency decreases with decreasing charge rate, and that coulombic efficiency is lower in thicker electrodes. We then use the model to explore the impact for large-format cells of electrode size and design on coulombic efficiency.

A comparison between iron and mild steel electrodes for the treatment of highly loaded grey water using an electrocoagulation technique

In the last years, the electrocoagulation (EC) process has been widely used as a potential technique for grey water treatment. However, only a few studies have focused on treating highly loaded GW (HLGW) by EC. In this study, the EC technique was used to compare iron and mild steel electrodes for the treatment of HLGW under different current densities (CDs) (5, 10, 15, and 20 mA/cm2) during 10 min of EC time. The performance criteria included chemical oxygen demand (COD) and turbidity removal efficiencies, current efficiency, energy consumption, and operational costs. It was found that EC using iron or mild steel can be effective electrodes for removing high levels of COD and turbidity from HLGW. At optimum conditions, the study demonstrated that at a CD of 5 mA/cm2, mild steel-based electrodes reduced COD by 86.5% while iron-based electrodes achieved 85.3% reduction at 10 mA/cm2. In conjunction with these removals, the turbidity removals were 92% and 94% achieved by steel and iron electrodes, respectively. The current efficiency of all the conducted experiments exceeded 90% but was generally higher for iron electrodes. At optimum conditions, analysis of operating costs in terms of energy consumptions and electrode materials requirements were 0.054 $/m3 and 0.097 $/m3 achieved by steel and iron electrodes, respectively. Thus, mild steel-based electrodes are considered superior to iron electrodes. Based on the obtained results, the study recommends that further investigations should give attention to the effect of metal alloy type or physical properties of electrodes as performance criteria and designing aspects when studying EC technology for HLGW treatment due to its notable effect on removal efficiency and operational costs.

A sequential aerated electrocoagulation and peroxicoagulation process for the treatment of municipal stabilized landfill leachate by iron and graphite electrodes

Electrochemical treatment has emerged as a viable technology for the treatment of leachate due to its efficient removal of ammonaical nitrogen and other recalcitrant organics. The main technical issues that prevent its practical deployment are restricted performance of a single electrochemical process and the lengthy tertiary treatment time required to achieve the disposal quality standards. This study demonstrates the performance of electrochemical treatments such as peroxicoagulation (PC) and aerated electrocoagulation (A-EC) separately and also sequentially for the treatment of stabilized leachate. In aerated electro coagulation iron is used as both anode and cathode, whereas in peroxicoagulation, iron is used as anode and graphite as cathode. The area of electrode used for treatments was fixed as 12.5 cm2. The initial concentration of NH4–N, TN, COD, and TOC of the leachate was found to be 480 mg/L, 997 mg/L, 40,200 mg/L, and 9850 mg/L respectively. Removal efficiency of aerated electrocoagulation for NH4–N, TN, COD and TOC were 25.6%, 23.67%, 25.6% and 28.7% respectively, current density of 30 mAcm−2, electrolysis time of 60 min and pH 7.3. Meanwhile for peroxicoagulation, the removal efficiency was found to be 37.2%, 43%, 37.3%, and 45.6% for NH4–N, TN, COD, and TOC respectively, at an current density of 30 mAcm−2, electrolysis time of 120 min and a pH of 3. The sequential aerated electrocoagulation – peroxicoagulation process achieves a maximum removal efficiency of 63%, 68%, 78%, and 75% for NH4–N, total nitrogen, COD, and TOC respectively for a reaction time of 180 min. Removal of NH4–N, total nitrogen, COD and TOC from stabilized landfill leachate with a BOD/COD ratio less than 0.1 was very much effective with the sequential aerated electrocoagulation – peroxicoagulaton treatment. The results also indicate that for the treatment of leachate, a significant synergistic index of 1.22 exists between aerated electrocoagulation and peroxicoagulation.

A novel sinusoidal design for an electrocoagulation reactor followed by an electro-Fenton reaction and a porous ceramic filter for the treatment of polluted waters.

In this research work, a novel design of an electro-Fenton reactor for the treatment of polluted water was investigated. In addition to the reactor with iron electrodes, a ceramic filter was also used. An electrical circuit was designed to change the cathodes and anodes every 24 s via an electrical relay between the electrodes. The untreated water was sucked into the reactor with an air pump and entered the electrocoagulation chamber after filtration with a ceramic filter. Then, it flows to the polyethylene filter to separate the coagulated particles from the fresh water. To produce 12 L of clean water, the system consumed 100 W of energy. Analysis of a river sample showed a reduction in nephelometric turbidity units (NTUs), total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Turbidity reduction studies have shown that the system can improve water transparency by 95%, thereby improving water quality to acceptable levels. Further, this system reduced TSS by more than 86%. In addition, BOD was reduced by more than 84% and COD by more than 88%, as shown by the change in the ratio of BOD to COD from 0.44 to 0.625, indicating improved water quality. According to the results, the treatment system can clean polluted waters, particularly during floods and when industries discharge their effluents into rivers.

Ductile Iron: A Low-Cost Optimal Anode Material for Electrochemical Generation of Ferrate(VI)

The effects of anode composition and temperature on anode electrochemical properties, the passivation layer’s structure, and ferrate(VI) generation in 14 M NaOH were investigated. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic polarization (GP) were used to analyze the electrochemical processes involving the electrosynthesis of ferrate using some low-cost anode materials: ductile iron, grey cast iron, and mild steel. The results proved that the presence of silicon and graphite with sphere form in the ductile iron anode significantly increased ferrate electro-generation. The optimal temperature for the electro-generation of ferrate was 30 °C–40 °C. The current efficiency using the ductile iron anode was constantly at least about 30% superior to that of the grey cast iron and mild steel electrodes. The ductile iron anode material was the most feasible option because it provides the highest ferrate concentration (1.58 g L−1) with the highest current efficiency of 74% and the lowest specific energy consumption of 1.2 kWh kg−1 ferrate.

Corrosion Potential Oscillation of Iron Electrodes in Nitric Acid

Although iron dissolves in diluted nitric acid solutions, it does not dissolve in concentrated solutions because of surface passivation. When a small amount of water is added to a concentrated solution, the dissolution and passivation of iron occur alternately, and the amount of gaseous products generated by nitric acid reduction varies in an oscillatory manner. During the corrosion process, the corrosion potential of iron oscillates spontaneously. In this study, we investigated the factors that cause oscillations in corrosion potential through electrochemical measurements using a three-electrode system and numerical simulations. The study revealed that an N-shaped negative differential resistance characteristic of iron oxidation plays a vital role in the oscillation of the corrosion potential and, simultaneously, the reduction of nitric acid results in oscillation. We considered metal corrosion has essential factors resulting in oscillatory instability. Thus, the corrosion potentials of various metals are expected to oscillate spontaneously under the appropriate conditions.

Investigation of the properties influencing the deactivation of iron electrodes in iron-air batteries

Iron-air batteries hold the potential to be a key technology for energy storage, thanks to their energy density, low cost, safety and abundance of their materials. In order to scale the technology up and optimize the cell formulations, it is key to obtain a clear understanding of how the physical-chemical properties of the electrode influence their electrochemical behaviour, in particular, the capacity loss. In this work, we propose for the first time mathematical correlations between textural and crystallographic properties of iron electrodes and their electrochemical stability. By adjusting synthesis parameters, we were able to tune pore size and volume, surface area and crystal size of iron oxides, and found that stability is highly correlated to both surface area and pore size. Large surface area and small average pore size provide electrodes with enhanced stability. We hypothesize that the cause for deactivation is the passivation of the electrodes ascribed to the formation of a non-conductive, non-reactive iron (II) hydroxide layer during discharge, which then cannot be reduced to iron again. We validate this hypothesis with electrochemical impedance spectroscopy studies, which show that, in the more stable electrodes, the charge transfer resistance in the Fe(OH)2 to Fe reduction does not significantly change after cycling, contrary to the behaviour of the less stable electrodes, corroborating our hypothesis. Furthermore, the electrode with the best properties was cycled 100 times, retaining almost 75% of its initial capacity at the end of the 100 cycles. These results are highly relevant for the future design and operation of iron-air batteries.

Electrocoagulation Process Efficiency for Removing Effluent Pollution Caused by Drilling of Oil Rigs

Background: Electrocoagulation (EC) is a safe method for removing environmental pollutants without the need for additional chemical materials. This study investigates the performance of EC in removing chemical oxygen demand (COD), total organic carbon (TOC), total suspended solids (TSS), and turbidity from drilling waste generated by oil rigs. Methods: An experimental study was performed on a pilot scale in an EC reactor provided from a cylindrical glass cell (height: 30 cm and inner diameter: 5 cm), a pair of aluminum and iron electrodes, a power supply, an aeration system. wastewater Samples were collected from one of the drilling rigs in Khuzestan. The effect of current density, operation time and pH parameters on removal of COD, TOC, TSS and turbidity were determined and the optimal values of the parameters were determined. Results: It was found that system voltage, operation time and pH values on the removal efficiency of pollutants were statistically significant at the 0.01 level. The optimum values of pH, current density and operation time were obtained 7, 20 mA/cm2 and 60 minutes, respectively and the removal efficiencies of COD, TOC, TSS and turbidity under the optimum conditions were 72%, 79%, 67% and 63%, respectively. Also, the consumption of energy was estimated to be 8.4 kWh/m3 . Conclusion: The results indicated that the EC process is a cost-effective method in removing pollutants caused by drilling of oil rigs and its efficiency can be improved by applying optimal conditions such as current density and pH.

Development of electrocoagulation-based continuous-flow reactor for leachate treatment: Performance evaluation, energy consumption, modeling, and optimization

This study investigated the performance of continuous-flow electrocoagulation (CFR-EC) reactor for aged landfill leachate treatment with a novel configuration of iron and aluminum electrodes to enhance the applicability of the process. The effects of the applied current density (ACD), initial pH, and hydraulic retention time (HRT) on the percentage removal of COD, TOC, BOD5, color, turbidity, and heavy metals (HMs) were modeled with Box-Behnken design (BBD). The results demonstrated that the models are significant (R2 0.97—p-value < 0.0029 and R2 0.92—p-value < 0.0001 for Fe and Al electrodes). COD, TOC, BOD5, and NH3-N removal were maximized at HRT 50 min (40.0 mL min−1) and pH 11 reaching 59, 64, 55, and 27%, respectively, by applying the ACD of 1.1 mA cm−2 in the CFR-ECFe reactor. The CFR-ECFe reactor presented a higher color (59%) and turbidity reduction (86%) than the CFR-ECAl reactor. At optimum condition, the removal percentages of HMs: Cr6+, Pb2+, As3+, Mg2+, B3+, Mn3+, Ni2+, and Ba2+ were 50, 70, 80, 99, 81, 99, 20, and 65%, respectively. The total process cost for landfill leachate treatment was 0.21 $/m3. The CFR-ECFe was an effective and affordable reactor for pollutant removal from landfill leachate.

Degradation of Reactive Black 5 Dye (RB5) using Iron Electrode (Fe.S) Derived from Iron Sludge Steel Waste via Electrochemical Method

A study has been performed on the degradation of Reactive Black 5 (RB5) as pollutant using iron electrode (Fe.S) derived from iron sludge steel waste via electrochemical method. The Fe.S and titanium graphite electrodes were applied as anode and cathode respectively during the studied. The studied operating parameters were the effect of current density, initial pH, initial concentration, and the reusability of the Fe.S electrode. The experiment was carried out for 120 minutes of electrolysis time. From results revealed that Fe.S could be used three times with complete degradation of RB5 from initial concentration of 50 ppm. A complete RB5 colour removal can be achieved in any pH range (3,6, and 9). The current density at 4 mA/cm2 showed a faster RB5 degradation compared to at 2, 6,8, and 10 mA/cm2.

Investigation of experimental parameters and It‘s optimization on iron plate electrodes for the removal of phosphates by electrocoagulation process using Box–Behnken design

Phosphorus must be removed from wastewater because it significantly contributes to eutrophication of water bodies. Chemical precipitation, is the primary method used to remove phosphates during the treatment of wastewaterwhich is typically costly and has a substantial environmental impact. The goal of this study was to determine how well iron plate electrodesare usedto remove phosphate from wastewater. Investigations into electrocoagulation (EC) treatment processes has gained interest due to its ability to remove a variety of contaminates, such as heavy metals, organic matter etc. To investigate the effects of the various operating parameters, such as electrolysis time, voltage, pH, NaCl concentration and initial concentration of phosphates has been studied for the removal of phosphate by EC process using iron electrodes. The optimum parameters observed to be electrolysis time (25 min), Voltage (10 V), pH (7), NaCl Concentration (2.0 g/lt) and initial concentration of phosphates (20 mg/L) gives the highest removal of phosphate obtained is 93.94% at 303 k. Kinetic, isothermal and thermodynamic studies has been studied and obtained best results. Characterization using SEM and FTIR analysis has been done for the iron plate electrodes obtained before and after EC process. Using the experimental data, the predicted data is been analyzed by Box-Behnken design and found to be best fitted.

Synergistic analysis for co-treatment of poultry wastewater and sewage in electro-chemical system: Operational parameters, kinetics and energy estimation

This research deals with the investigation of poultry wastewater (PW) treatment by electrocoagulation (EC) using iron (Fe) and stainless-steel (SS) electrodes for COD, NO3− and TSS removal. Meanwhile, effect of operational parameters i.e. treatment time (0–180 min), voltage (5–30 V), pH (3-11), number of electrodes (2–6), electrode combination (Fe−SS−Fe−SS and SS−Fe−SS−Fe) and electrode spacing (1–3 cm) on removal of COD, NO3− and TSS were investigated. Subsequently, first-order and second-order kinetic models were adopted for determining rate constants. Furthermore, the efficacy of potential application of EC technique for cotreatment of PW and sewage (SW) at different volumetric ratios PW + SW (mL + mL) viz. 1000 + 0, 800 + 200, 600 + 400, 400 + 600 and 0 + 1000 was examined. From results, it was observed that optimum operating conditions were found to be 120 min, 25 V voltage, 4 electrodes and 1 cm electrode distance at neutral pH. At optimized conditions, Fe electrodes were found to be more efficient in COD (99%), NO3− (85%) and TSS (89%) removal of comparison to SS electrodes (COD (84%), NO3− (71%) and TSS (72%)). Furthermore, synergistic index and electrical energy order elucidated the feasible application of EC treatment using Fe electrode for co-treatment of PW + SW efficiently.

Humic Acid Removal by Electrocoagulation Process from Natural Aqueous Environments

Humic acid results in formation of highly toxic and carcinogenic byproducts during the disinfection process of water by chlorine. In this study, removal of industrial humic acid from artificial and natural aqueous media is investigated using electrocoagulation process. To reach the goal, first, humic acid-contaminated water samples with concentrations of 20 mg/L were prepared in a reactor with the effective volume of 1 L, equipped with iron electrodes. Then, the effects of pH (2 up to 9) and electric potential of 30 V was studied by measurement of UV radiation absorption and total organic materials methods, on the coagulation process in removal of humic acid within 80 min. According to the results of this study, the best efficiency in removal of humic acid was obtained as 92.69 by electrochemical process when the parameters were adjusted as; potential difference of 50 V, 80 min reaction time, pH 5, and electric conductivity of 3000 I¼S/cm. In the optimum condition, the efficiency of humic acid removal from natural water was obtained as 68.8. The results indicated that, the electrochemical process equipped with iron electrodes could remove humic acid from aqueous media, efficiently. © 2018 The Authors.

Modeling electrochemical oxide film growth—passive and transpassive behavior of iron electrodes in halide-free solution

The phenomenon of passivity is crucial for many areas of our technological and metal-based civilization. Nevertheless, the mechanisms leading to passivity are still under investigation and not fully understood. Modeling passive film growth can bring insights into these processes, which are experimentally hard or impossible to access. Therefore, this paper presents a comprehensive model which can describe oxide film growth and dissolution under an external potential for various metal oxides. The simulation gives insights into the defect concentrations and electric field during passive film growth and film dissolution and delivers an anodic transpassive dissolution mechanism. The simulation is compared to experiments derived from the oxidation of iron electrodes and shows very good agreement. The addition of a transpassive dissolution mechanism to oxide film models is the next step toward model-based corrosion prediction.

The efficiency of the electro-osmosis method on the consolidation and strength properties of the gray clay of Tabriz

BackgroundConsolidation of clays could be a very time-consuming procedure. However, preloading can increase the speed of consolidation; applying an electric field can accelerate this procedure significantly. The efficiency of the electroosmosis approach has been studied for different types of clays previously. At the same time, there is no information about the performance of the EO method for Tabriz gray clay.MethodsThis paper investigates the effects of the EO technology on Tabriz gray clay using a modified oedometer consolidation apparatus. The achieved results of the EO consolidation of the Gray clay of Tabriz are compared with the standard Kaolin clay (KC-which produced industrially). Three different electrodes (Iron, Copper, and Aluminum) are employed to study about effects of the electrode type, and two different voltages (12 V and 24 V) are applied to assess the impact of the input electric field on the settlement of samples.ResultsIt is shown that the copper electrode leads to maximum volumetric strains while the iron electrode results in minimum volumetric strains. In addition, it is shown that the larger input voltage leads to larger settlements. The results indicate that the EO approach is more efficient for the Gray clay of Tabriz in comparison to the KC, where gray clay shows larger settlements while subjected to an electric field. Unconfined compression tests are also applied to some samples, and the EO method’s influence on the samples’ strength is discussed.ConclusionsThe achieved results demonstrated that the EO method can be efficiently used to improve the consolidation and strength properties of the gray clay of Tabriz.