جستجوی مقالات مرتبط با کلیدواژه « electrocoagulation » در نشریات گروه « فنی و مهندسی »

Detergents are one of the most widely used chemicals in the daily life of humans. Their entry into the environment, especially water, can increase the COD of water and cause serious problems for living organisms. There are different methods to reduce COD. The electrocoagulation process as an electrochemical method is a suitable solution to reduce COD. In this study, the effect of electrocoagulation to reduce COD caused by laundry detergent has been surveyed. Process voltage, the number of electrodes, along with coagulation time as key parameters were investigated as influential parameters. The results showed that the 2-electrode mode reduced COD by 70% in 40 minutes at a voltage of 15 volts. This value was the most optimal energy consumption in terms of process time and the amount of reducing the pollution index.

Dyeing wastewater is one of the most important environmental problems in the textile industry. This wastewater contains harmful pollutants that can damage human health and the environment. Electrocoagulation (EC) is a promising technology for dyeing wastewater treatment. This technology passes an electric current through the wastewater, which generates metal hydroxides that act as coagulants to remove pollutants. This article first introduces the EC system and its operation mechanism, then discusses the components that affect the system's performance in removing dye and chemical oxygen demand. The article also summarizes the studies that have been conducted on the use of this process in the treatment of textile dyeing wastewater. In addition, the economic aspects of the EC process and recommendations for its improvement are provided. Finally, the challenges and prospects of the process are discussed. This article provides an effective overview of the current advances and achievements in the EC process for dyeing wastewater treatment, which provides new insights into improving dyeing wastewater treatment with promising environmental applications.

Cutting oils are used in machining operations to reduce friction, provide lubrication and cooling properties, and prevent corrosion. Biological methods for treating wastewater from these oils have low efficiency. Therefore, other methods should be considered to treat this type of wastewater. The purpose of this study was to investigate the use of electrocoagulation for treatment of wastewater containing cutting oil. In this regard, an electrochemical reactor equipped with two aluminum electrodes and a direct power source was used. The efficiency of the electrocoagulation process was evaluated by measuring the removal percentage of chemical oxygen demand in a certain time range. The effect of various operating parameters such as oil concentration, applied voltage, stirring speed, initial pH, distance, and surface of electrodes on the efficiency of the electrocoagulation process was investigated. The results of the experiments showed that reducing the oil concentration from 3% by volume to 0.5% by volume led to an increase in the efficiency of the purification process up to 97.3%. Increasing the voltage from 40V to 60V reduced the time required for wastewater treatment with the same efficiency from 50 min to 20 min. Decreasing the distance between the electrodes from 6 cm to 2 cm and increasing the effective area of the electrodes from 60 cm2 to 180 cm2 reduced the time required for purification to 20 min. Also, the results of the tests showed that the time required for the purification process at medium stirring speeds (150 rpm) is low. The obtained results showed that the removal percentage of chemical oxygen demand in the neutral environment was high (95.9%). Therefore, due to the simplicity of the method, low operating cost, and the ability to design on an industrial scale, the electrocoagulation method can be used for the treatment of wastewater containing cutting oil.

In the current work, the capability of uncoated titanium anode in the electrochemical treatment of textile wastewater has been investigated with the aim of simultaneously benefiting from electrooxidation and electrocoagulation treatment processes. In the present work, the feasibility of using uncoated titanium anodes for wastewater treatment is studied in an electrochemical pre-pilot set-up with polymeric casing and an electrical supply power of 150 W, operated under galvanostatic regime in batch mode, focusing on the current density as the main subject of assessment, and its performance is evaluated using metrics such as chemical oxygen demand removal and specific energy consumption. A noticeable finding of this work, is the flexibility of the set-up to combine the electrocoagulation and electro-oxidation mechanisms with the current density as the controlling parameter, leading to a remarkable decontamination capability, so that reductions in the total chemical oxygen demand as large as 75–80% in the neutral and 90–95% in the acidic environments were achieved. At low current densities (< 100 μA/cm2), the anodic corrosion was limited and the electro-oxidation was the dominant wastewater treatment mechanism. At high current densities (> 100 μA/cm2), the anodic corrosion was accelerated and the dominant wastewater treatment mechanism was switched to electrocoagulation. Along with the chemical oxygen demand removal capability, the energetic cost-effectiveness of the set-up was a major concern, particularly from the industrial point of view, which was assessed in both neutral and acidic environments, and it was realized optimization occurred at 600 μA/cm2, so that the specific energy consumption and the rate specific energy consumption, were both minimized at this current density, in respective order, 8.9 kWh/kgCOD and 3.52 kWh/kgCOD/h in neutral, and 10 kWh/kgCOD and 2.34 kWh/kgCOD/h in acidic environments.

Electrocoagulation (EC) process is an economical and environmental option for water and wastewater treatment systems. In the present study, a laboratory-scale electrocoagulation unit with a volume of 1.2 liters, equipped with iron and aluminum electrodes with dimensions of 1×50×120 mm, was used to remove nickel. Influence of the electrode type and distance, initial concentration, voltage, and pH on the nickel removal efficiency were studied in addition to reaction kinetics. Energy and electrode consumptions of these mentioned arrangements were obtained for different current intensities. The results demonstrated that the Ni removal efficiency changed from 93.7% to 98.1% by electrocoagulation using different arrangements of iron and aluminum electrodes at 20 V and 60 min. EC with an Fe(+)/Al(-) electrode pair after 60 min was able to achieve a 93.7% removal efficiency at 20 V, pH 7, and 250 mg/l initial concentration. The present study demonstrated that nickel removal increased with increasing voltage, pH and initial concentration. The increase in current intensity led to an increase in the energy consumption, which was obtained less for the pair of iron electrodes than other arrangements. Corresponding electrode consumptions of iron and aluminum anodes were determined as 0.87-1.31 and 0.28-0.45 kg/m3, respectively. In addition, the first-order model demonstrated an acceptable agreement with the experimental data.

The excessive usage of nitrogen fertilizers leads to phosphate and nitrate become as a common inorganic pollutants in groundwater resources. Therefore, an alternative process performance seems to be examined to remove these anions from water resources. This study aims to investigate the effect of two variables, water hardness and electrodes distance on electrocoagulation process for simultaneous phosphate and nitrate removal. For this purpose, initial concentration=100 mg/l, current density=22.5 A/m2, pH=6 and retention time=40 min were considered. Under these conditions, the optimum removal efficiency of phosphate and nitrate were achieved at 2 cm electrode distance with 93.8% and 78%, respectively. While, the water hardness of 65 mg/l CaCO3 was shown 99.3% and 86% removal efficiency, respectively. Then, in order to improve the electrocoagulation process and reduce the passivation rate of the aluminum anode, the electrodes were modified with ZnO nanoparticles by sol-gel method. The accuracy of electrode coating with zinc oxide nanoparticles was determined by SEM, EDX and XRD tests. The effect of coating was investigated by cyclic voltammetry, showing that current intensity at modified electrode has improved 202.44%.

A vital stage in oil refining is elimination of hydrogen sulfide, which is done by means of sodium hydroxide solution in petrochemical industries, leaving a spent caustic soda (NaOH solution) as the product. In the process, hazardous gases react with sodium hydroxide and hydrogen sulfide solutions and Thiol compounds to form a rich brown to nearly black effluent demonstrating the fragrant toxic components such as methanethiol, enzene, toluene and phenol. Despite all these odorous noxious organosulfur compounds, spent caustic soda leads to environmental problems due to its alkalinity (pH>12), salinity (5-12 wt.%) and high sulfide content (1-4 wt.%). Spent NaOH was registered as industrial dangerous waste in resource conservation and recovery act law. Inefficient and inappropriate management in spent NaOH treatment and disposal causes stability challenges, reduction in energy resources and water security attenuation. Techniques for spent caustics treatment have been neutralization with acid, wet air oxidation, combination of neutralization and Fenton (i.e. electro-Fenton), biologic treatment and ignition each of which would face some limitations. In recent decades, electrocoagulation (EC) has engrossed much attention as an Environmental-friendly and effective process.  In addition, the EC process is a potential suitable way for treatment of wastewater with a view to costs and environment. Furthermore, EC offers further advantages as simple operation facilities, small occupying area, dispensability of chemical additives and short treatment time. EC often consists of anodes and DC cathodes a part of which are immersed in wastewater container. Shape, number and configuration of electrodes may be different but rectangular types are preferred. The widespread anodes are iron and aluminum based for their availability, reasonable cost and harmless media. In electrocoagulation, electrolysis takes place to dissolve metal anode (sacrificial electrode) in wastewater. Metal ion flow from sacrificial electrode as coagulant surrounds wastewater particles. After release of Al3+ and Fe2+, the ions react with hydroxide groups and metal hydroxides turn to insoluble agglomerates able to trap contaminants and increase particle size by complexation of electrostatic attraction. In addition, hydrogen gas produced in cathode, allows agglomerates to float on surface. The object of this study is electrochemical evaluation of COD removal from refinery wastewater, specifically refinery spent caustic, using iron and aluminium (anode) and graphite (cathode) electrodes. Therefore, the effect of key variables including electrode arrangement (bipolar-serie, monopolar-serie and monopolar-parallel), anode electrode material (iron and aluminium), using pierced anode electrode and cathode graphitem initial pH (7-11), electrolysis time (0 to 120 minute), current density (15.6 to 28.125 mA/cm2) was evaluated. The three parameters of current density, electrolysis time and initial pH has been modeled with design expert software with response surface method (RSM) and central composite design (CCD). Impact of other variables has been investigated with single parameter method. According to the results, the optimum conditions including, parallel mono-polar electrode arrangement, aluminium electrode has been achieved. In designing experiments in accordance with the model provided by the software, quadratic analysis design with R2=0.96 had a high accuracy in designing the experiment. According to the model analysis and laboratory work, optimum electrolysis time was 116 min, current density was 25 mA/cm2 and initial pH=8 reached COD removal percentage of 85.1% in vitro and 88.9% for model.

Antibiotics, which are extensively produced and used all over the world, are considered as emerging contaminants. These organic compounds cannot be efficiently removed by traditional methods applied in wastewater treatment plants. Continuous discharge of antibiotic-containing wastewaters into the aquatic environments can lead to long-term adverse effects on aquatic life and human health. Rifampin is the most widely used antibiotic for treatment of tuberculosis. For this reason, its removal from water and wastewater is of high importance. Electrocoagulation is an advanced treatment method which has been effectively applied for removal of complex organic compounds such as chemical drugs. The main aim of the present study is to investigate the techno-economic aspects of the EC process for removal of RIF antibiotic from aqueous solution. In this study, effects of different parameters including initial pH, voltage, stirring speed, initial RIF concentration, reaction time, inter-electrode distance (die), shape of electrodes and their arrangement inside the reactor were evaluated on RIF removal efficiency using the EC process and its operating costs. The EC process was induced in batch mode using a 1 L reactor and synthetic RIF containing solution. The experiments were designed by one-factor-at-a-time method and relative standard deviation was used to compare the grade of the effect of the parameters on removal efficiency and operating costs of the process. Based on the obtained results, under optimal conditions, i.e., initial pH of 5, die of 1 cm, voltage of 20 volt, stirring speed of 200 rpm, initial RIF concentration of 10 mg/l, reaction time of 30 min and hole-punched shape electrodes in horizontal arrangement, the removal efficiency and the operating costs of the process reached about 92.49% and 89 US$/kg RIF removed, respectively. According to RSD values, among all the parameters investigated, reaction time, initial RIF concentration, voltage and initial pH were distinguished as the most effective ones on both RIF removal efficiency and operating costs. Generally, results of the study showed that the EC process has a high ability for removal of RIF antibiotic from water.

One of the environmental problems of wastewater is the presence of micro and macro nutrients, the most important of which is phosphorus and nitrate. Hence, in this study removal of phosphate and nitrate from aqueous solution was conducted using electrocoagulation (EC) processes with Al electrodes. In the present study, an electrocoagulation reactor was used in a laboratory scale with a volume of approximately 1200 ml equipped with 3 Al-electrode in a size of 5 × 12 cm to remove phosphate and nitrate. The effects of operating parameters such as applied voltage, initial pH of the solution, value of FeCl2 and reaction times were evaluated. The effect of pH and FeCl2 parameters in inlet and facultative ponds were also studied. Also, pH changes in the oxidation process were investigated. Finally, it can be said that phosphate was completely eliminated in facultative and outflow ponds, but due to the low initial concentration of phosphate in the outlet, less voltage (10 V), less time (about 3 minutes), low FeCl2 dosage (0.2 mg/l) and original pH of the solution were applied compared to the facultative pond., 100 % of nitrate in optimum condition (pH =5.5, applied voltage = 25 V, FeCl2 = 0.65 mg/l, time = 11.50 min) in output pond has been removed. In EC process the electrocoagulation process using aluminum electrode, as well as it's relatively low cost and simplicity, has a good effect on phosphorus and nitrate removal compared to other methods.

Leather tannery industry is one of the main economic sectors in many countries and release of various recalcitrant pollutants by that is considered to be an environmental concern.To treat these wastewaters, various physical, chemical & biological methods can be used, each of which depending on the conditions, can be consideredas a suitable solution for the purification & removal of chromium from these hazardous streams. Obviously, the cost-effectivenes of each method depends on several factors.In this paper, a comprehensive approach to different used technologies in the world is performed using literature review. Results are indicative of assurance and reliability of combinedprocesses for reduction of contamination degree of tannery wastewaters. However, the ion exchange technology to recover chromium from waste streams is the most effective solution. Furthermore, electrocoagulation technology has attracted significant attention for pre-treatment of tannery wastewater due to its operational simplicity.

In this research, removal of nitrate from water resources was investigated with a comprehensive survey of affecting factors on electrocoagulation process including electrolysis time, the electrodes distance, the initial concentration of nitrate and the pH of the solution. Also, stainless steel and iron were used as anode and cathode. The results of this study showed that, by increasing the voltage and decreasing the variables such as the initial concentration of nitrate and the electrodes distance, efficiency of nitrate removal will increase. Also, the maximum efficiency of nitrate removal was obtained 88% with the SS-Fe arrangement under optimum condition: electrolysis time= 180 min, pH=8, initial nitrate concentration= 150 mg/l, voltage = 25 v and electrodes distance = 4 cm.

The response surface statistical model developed via the central composite design (CCD) is a tool for optimizing manufacturing processes. Phrmaceutical plants depend on many such processes and i is essential to remove medicinal compounds from their effluents before they are discharged into the environment. The objective of the present study was to employ the response surface model for the optimization of the removal of the pharmaceutical compound ciprofloxacin from aqueous media via the electrochemical coagulation process. In this study, a reactor containing two iron electrodes used as the anode and two titanium ones used as the cathode was employed to remove ciprofloxacin from municipal effluents. The electrodes were connected in a monopolar fashion to a DC power supply. Parameters such as pH (4‒8), current (0.5‒1.5 A), initial ciprofloxacin concentration (15‒40 mg/L), and reaction time (15‒30 min) were introduced into the Design Expert software as the main design parameters. FT-IR analysis was conducted and SEM images were prepared while COD removal and changes in UV-VIS spectrum were determined under optimum conditions. Process modeling was accomplished using the response surface methodology (RSM) which is a statistical model for process optimization drawing upon central composite design (CCD). Modeling results showed that process efficiency was affected by the above parameters and that the optimum conditions for a process efficiency of 85.91% at an initial CIP concentration of 15mg/L would include pH=7.68, a current of 1.5 A, and a reaction time of 30 min. Under these conditions, COD removal efficiency would be 64%. FT-IR analysis and SEM images indicated changes during the process. Wavelength scanning also indicated reducing concentration of the contaminant due to mineralization. The results of the study indicate that optimization by RSM reduces the number of tests required and enhances their accuracy. It was also found that electrocoagulation has a high CIP and COD removal efficiency which makes it capable of being successfully exploited for the removal of organic pollutants from effluents before their discharge into the environment

Electrocoagulation process is including new and developing processes which used to remove suspended matter. In this study, assessment of electrocoagulation to reduce total suspended solids (TSS), turbidity and hardness of the overflow Thickener of hematite in Gole-Gohar Sirjan has been done. Therefore, in a laboratory scale of glass container were made with volume 3 liter and equipped to 6 electrodes. The electrodes are made of iron, steel and aluminum, which are located separately on each of the electrodes. Parameters such as electrode material, contact time and voltage were studied. The results showed that the aluminum electrode than to the electrodes of iron and steel have the highest TSS removal. However, voltage of 6V and retention time of 5 minutes is removed 88.5 percent of TSS. Although, the steel electrode in voltage of 6 V and retention time of 15 minutes have maximum turbidity equal to 81% (NTU 21). Also in various voltages and different retention time, there is no significant change in hardness. Based on technical and economic studies, capital, operating and maintenance costs for electrodes of aluminum, iron and steel were calculated separately. The results illustrated that iron electrode with respect to the total performance costs (878 Ria) is preferred in compare to steel electrodes (2978 Ria) and aluminum electrode (3160 Ria). The iron electrode with respect to ease of operation, the settling of solid sludge, dewatering capability suitable and less sludge production volume, is appropriate.