جستجوی مقالات مرتبط با کلیدواژه « الکتروکینتیک » در نشریات گروه « عمران »

Nitrates and sulfates are commonly present as common pollutants in most natural waters. Sometimes, human activities such as excessive use of chemical fertilizers, lack of proper control over water sources, and improper treatment of industrial wastewater cause an increase in the concentration of these types of pollutants in surface and groundwater. This study focuses on the efficient removal of nitrates and sulfates from contaminated water using a combination of permeable reactive barriers (PRB) containing zero-valent iron nanoparticles (nZVI) and an electrokinetic (EK) process. In this research, which was carried out on a laboratory scale, by using the PRB system, the nitrate, and sulfate in the polluted groundwater were removed, and simultaneously, with the help of the EK process, the early saturation of the bed was prevented and system performance time is increased. To check the system efficiency, various parameters on the system performance were investigated, and the optimal conditions were determined to grow the system performance time. Additionally, the experiments were repeated using PRB containing granular activated carbon for comparison. The results reveal that the substrate containing nZVI exhibited superior performance in removing nitrates and sulfates from groundwater compared to the modified activated carbon. According to the results, the best system performance was obtained at pH 7, initial nitrate concentration of 200 mg/L, initial sulfate concentration of 450 mg/L, 2.14 gr of nZVI per Kg of sand, and a potential difference of 20 volts. Under these conditions, the use of the PRB containing nZVI not only extended the system operation time by 35 hours for sulfate removal and 30 hours for nitrate removal but also increased the system's removal efficiency by 13% for sulfate and 10% for nitrate after 80 consecutive hours of use, compared to the PRB containing modified activated carbon. Overall, this research contributes to the development of more effective strategies for the simultaneous removal of nitrate and sulfate from contaminated groundwater, using a combination of PRB with nZVI and the EK process.

Every year, millions of tons of toxic and hazardous waste, including heavy metals, are generated. Numerous studies have been conducted to develop more effective and environmentally safe methods for removing contaminants from soil. Electrokinetics remediation is an emerging technology that has received significant interest among environmental scientists. The primary mechanisms driving contaminant movement in electrokinetics include ion migration, electro-osmosis, electrolysis, and electrophoresis. This research primarily aims to ascertain the influence of kaolinite's different phases on the retention of heavy metal contaminants. The secondary goal is to evaluate the efficacy of EDTA in extracting heavy metals from various phases of kaolinite. The results of this study is applicable to optimize the choice of enhancement materials for contaminant removal via electrokinetics, leading to reduced material requirements, consistent contaminant removal throughout the sample, and heightened soil decontamination efficiency. To meet these objectives, a range of tests were conducted, including batch equilibrium, zeta potential measurement, and selective sequential extraction on kaolinite, contaminated kaolinite, and EDTA-treated contaminated kaolinite samples. The soil sample analyzed contained primarily kaolinite, calcite, and quartz, as revealed by XRD diffraction. Lead nitrate served as the heavy metal contaminant, and the GBC 932 AA Plus apparatus was employed for its quantification. For zeta potential analysis, 0.05 g of soil was mixed with 50 ml of distilled water, agitated on a mechanical shaker, and measured using the Zeta Sizer Nano Zs after pH adjustment. The SSE tests further investigated the role of soil phases in contaminant retention, providing insight for the optimal selection of enhancement materials in electrokinetics remediation. The findings of this study indicate that by monitoring the variations in soil surface potential and understanding contaminant retention in soil phases, it is possible to propose an optimal enhancement strategy to improve the efficiency of heavy metal removal. The study also reveals that using either 0.01 or 0.1 molar concentrations of EDTA results in a similar level of contaminant extraction. Moreover, applying 4 cmol/kg of EDTA and washing the soil five times can remove approximately 87% of heavy metals. Given that electrokinetics remediation primarily employs electric current for contaminant extraction, using a lower concentration of EDTA combined with multiple soil washes is a more practical and cost-effective approach.

Electrokinetic technique is one of the common methods that can be used for removal of ‎organic contaminants in soil. There are some of organic contaminants with low solubility ‎in water. In order to improve the efficiency of remediation in this method it is possible to use appropriate ‎surfactants as flushing solution.‎ In this work SDS, Poloxamer 407 and Brij 35 surfactants were selected for improving the ‎remediation of a clay soil contaminated with Dimethyl phthalate (DMP). The contaminated ‎soil was prepared artificially with the concentration of 40 mg/kg in the laboratory. ‎Experimental tests were conducted in a special apparatus. It was consisted of a Plexiglas ‎with 1 cm thickness as the main cell. The main cell dimensions were 30 cm in length, 10 ‎cm in width and 30 cm in height. Two reservoirs as anode and cathode were added on ‎the two sides of the main cell and they were connected to the main cell. The prepared ‎contaminated soil after saturated was poured into the main cell of apparatus. The anode ‎and cathode reservoirs were filled with desired solution of surfactant and distilled water ‎respectively. A constant voltage of 50 V was applied to the soil for duration of 7 days for all tests. ‎A reference test was also conducted with distilled water in anode and cathode reservoirs ‎under the same voltage and duration. During each test the pH, EC (electrical ‎conductivity) and volume of outflow liquid discharge were measured. At the end of each test, ‎the shear strength of soil was measured by shear van at the distance of 4, 12, 19 and 26 ‎cm from anode. A number of soil samples were also extracted from these points for pH ‎measurement and removal of DMP by using GC (Gas Choromatography) ‎apparatus. The results showed that the shear strength of soil is increased with increasing ‎the distance from anode. The values of shear strength around the cathode were measured ‎as 7, 5.5, 8 and 42 kPa for distilled water and solutions of Brij 35, Poloxamer 407 and ‎SDS respectively. It was revealed that by increasing the distance from anode the value of ‎pH was also changed from acidic to alkaline. In addition, the results indicated that the ‎percentage of remediation at the distance of 4, 12, 19 and 26 cm from anode for solution ‎of SDS were 73, 70.5, 14 and 20.12 and for Brij 35 they were changed to 69.55, 66 ,21 ‎and 17 % respectively. The percentage of remediation for solution of Poloxamer 407 were ‎also determined 68.94, 65.89, 10.97 and -1.24 and for distilled water as 55, 53.3, 7.77 and -20 % at the ‎same distance from anode respectively. The results showed that the effectiveness of ‎solution surfactants in removal of DMP was SDS>Brij 35> Poloxamer ‎‎407.‎‎

One of the most critical discussions about environmental pollution is soil pollution. Contaminated soil can endanger the life of organisms. For this reason, removing all types of soil contamination and even reducing the types of soil contamination is a fundamental and critical issue. One of the ways to clean and improve contaminated soils is the electrokinetic method; The principle of this method is to transfer the contaminated ions in the soil by an electric field and to eliminate and neutralize the contaminated ion or remove them from the soil. This practical method can remove various contaminants such as petroleum products and heavy metals. In some cases, this method can be seen along with other methods of soil improvement or even combining this method with some other methods to see a much better result. The present study will present the research on soil contamination by the electrokinetic method and its limitations.

In the present era, environmental pollution is a global crisis, increasing population growth and urban development, industrial expansion and unlimited use of natural resources, are among the increasingly important factors of pollutants (Reilley, 1996). Vocciante (2021) found in the study of stability in electrokinetic modification processes that the electrokinetic method is suitable for cleaning inorganic pollutants from clay. Zhou (2021) found that using the electrokinetic method is effective in removing heavy metals zinc, cadmium, and manganese from the soil and leads to the removal of about 72% of the pollutant from the soil sample. Vaishnavi (2021) in the study of bio-electrokinetic modification of diesel-contaminated environment with biosurfactant found that this method is an effective method for cleaning and cleaning soils contaminated with diesel hydrocarbons. Hanaei et al. (2021) found that the direct shear test showed that the adhesion of the soil sample increased and the friction angle decreased after oil contamination, and the permeability test showed that the contamination of the soil sample decreased the permeability of sandy soil and this change It is a function of the amount of oil and the viscosity of oils.

Electrokinetic (EK) remediation is a very effective option for the soil decontamination; however, its efficiency depends on several factors. In the present study, the ability of Ethylene-diaminete-traacetic-acid (EDTA) and pulse current to improve this method for treating fine-grained soils containing heavy metals (HMs) was investigated. In so doing, first, the studied sample (mainly kaolinite) was mixed with a concentration of 5000 mg/kg zinc (Zn) and lead (Pb) and then subjected to an electrokinetic test with voltage gradient of 2 V(DC)/cm2 (in the form of continuous current and pulse) under 7, 14 and 28 days. The pulse current used was ON for 30 minutes and OFF for 10 minutes. In this process, different concentrations of EDTA (including a concentration of 0.1 M and 0.2 M) were also added to the anode and cathode reservoirs, separately and simultaneously. The obtained results showed that in the conditions of continuous current and without EDTA addtion (the common EK method), the EK removal efficiency, especially for lead, was not noticeable. According to the changes in the microstructure of soil sample and its electrical conductivity (EC) between the anode and the cathode electrodes, the reason can be ascribed to the decrease in current density due to precipitation of pollutants in the soil matrix and decresing the HMs transportation in the cathode side, as clearly confirmed by the XRD patterns and EC tests. In this case, increasing the test time from 7 to 28 days (despite more energy consumption) mainly caused the change of the pollution position in the around of anode side and the HMs removal in the cathode side is not enhanced, indicating that there is a limited effect (about 20%) on the total efficiency of the EK tests. It was found that the addition of EDTA only in the form of catholyte solution, even with the equivalent concentration of soil pollution, has a low effect on improving the electrokinetic response. On the other hand, the presence of the chelating agent in both reservoirs of the EK device, especially by applying the pulse current (with a frequency equal to 36 cycles/day) accelerates the treating process of EK remediation. In fact, as the results of macro-structural tests, scanning electron microscope (SEM) images and X-ray diffraction (XRD) analyses indicated, such improvement can be attributed to two major changes in soil-pollutant interaction. First of all, the presented EK method, by developing the penetration of the acid front towards the cathode side and limiting the polarization ability of clay particles, causes the formation of flocculation and reduces the soil ability to keep pollutants. Also, this system greatly reduces the contribution of insoluble phases through the processes of redissolution and formation of the stable complexes as well as generates a disturbance in the initial formation of metal precipitation due to the reduction in the hydrolysis reaction of the cathode part. Synergy of these changes has an prominent role in accelerating the EK mechanisms; so that compared to the conventional EK model, while reducing energy consumption by 25%, it can also increase the removal efficiency by nearly 2.6 times.

Pollution of soils containing petroleum products is one of the most important environmental challenges. Therefore, it is necessary to take measures for the purification of petroleum products, including diesel, to clean these compounds from the soil, various solutions are used, including the use of electrokinetic process. The result of the electrokinetic process in the soil is the movement of water, ions and charged particles due to the difference in electrical potential. In this study, the purification of diesel-contaminated clay by electrokinetic method in the presence of ABTS and saponin surfactants is investigated and the effect of pH control on catolite and anolite on the electrokinetic modification process of clay is evaluated, The results show that in the absence of the surfactant, the electrokinetic method has a very low removal efficiency of 3% to 7%, but in the presence of the surfactant, the efficiency is significantly increased by 20% to 54%, with pH control in Velit. and anolyte and the amount of active substance increase the level of efficiency of diesel removal from soil. With the use of Saponin, the lowest amount of removal at a concentration of 0.05% equal to 20% has been obtained, while ABTS has been able to remove about 54% of diesel at the highest concentration of surfactant (0.15%), in the continuation of the research A uniaxial test has been conducted to determine the unconfined compressive strength of the soil sample, which shows that the cleaning process increases the compressive strength of the soil by 15%.

In this research work, the remediation of a clay soil contaminated with dimethyl phthalate ‎was ‎studied by using electrokinetic method. Contaminated soil was made with the ratio ‎of 0.04 mg/g. ‎Non-ionic (Tween 80) surfactant and solution of 0.1 M NaOH were ‎used as anolyte. A reference ‎test was also considered with distilled water as ‎anolyte and catholyte. pH and EC and volume of ‎flow out fluid were measured ‎during the tests in both electrode reservoirs. At the end of each test ‎the shear ‎strength, pH, EC and degree of remediation of soil was measured at different ‎distance ‎from anode. The removal of contaminated was measure by a GC (Gas ‎Chromatography) apparatus. ‎The results showed that the amount of flow out fluid ‎for NaOH was nearly 20% more than the ‎solution of Tween 80 and distilled water. The ‎results also indicated that the strength of soil for ‎different solution is increased ‎by increasing the distance from anode. The value of it around the ‎cathode for ‎solution of NaOH was 14 kPa that was about 50 and 57% more than the distilled ‎water ‎and Tween 80. It was found that the degree of remediation at cathode is less than ‎anode. The ‎percentage of remediation for Tween 80 solution around the anode and ‎cathode were 53.88 and ‎‎16.5% respectively but for NaOH they changed to 50.82 and ‎‎23.26 near anode and cathode ‎reservoir. It was resulted that the effectiveness of NaOH ‎solution in remediation of soil was more ‎than the other used solutions.

Electrokinetic remediation is one of the methods for cleaning of soil and sediments (Rozas and Castellote, 2012). In this case, by applying a weak electric field using the external power supply, the pollutants are separated from the soil or sediment by various mechanisms, especially electrical migration. But due to the cost of supplying electricity, it is not affordable(Acar et al., 1995). On the other hand, in the microbial fuel cells, bacteria release electrons by consuming organic matter and producing electric current. Therefore, in this study, microbial fuel cells process with three different electrodes at the anode and combination with granular activated carbon was used to produce green weak electric field. Based on the electrical migration mechanism, the removal rate of hexavalent chromium from marine sediments was evaluated by combining three physical, chemical and biological processes.

Every year with the expansion and development of industrial and mining activities, millions of tonnes of toxic waste are produced throughout the world. Soil contamination by organic material as a result of various incidents and the leakage of organic compounds into the soil solid porous media will have an adverse effect on the environment. There are several methods for soil remediation contaminated with hydrocarbon compounds. Electrokinetic is one of the effective remediation which includes three main mechanisms for remediation, electroosmotic flow, ionic migration and electrophoresis. Electrokinetic is suitable in terms of cost and time for solid and porous fine-grained environment media that have high adsorption capacity of moisture and also organic pollutants. Kerosene is considered as one of the hydrophobic organic compounds with harmful physical and chemical properties to ecosystems and high adsorption onto the water and soil media. It has different hydrocarbons in its composition, each molecule having an average of 10 to 16 carbon atoms. It is so durable in the ecosystem, including the soil environment. The soil used in this study was fine-grained kaolinite due to the nature and effectiveness of the electrokinetic method for porous media. In this study, five series of experiments were carried out using electrokinetic method and its combination with improved techniques. The parameters including cumulative electroosmotic flow, electrical current intensity, reservoir and soil pH variation and residual kerosene concentrations in soil were studied. The highest electrical current devoted to increased voltage and pH control tests with 48 and 94 mA respectively for a time interval of 80 to 90 hours after the start of the tests were observed. The higher electric current intensity causes faster migration of ionic species to the opposite-electrode, resulting in greater electroosmotic flow transportation. In the present study, the removal percentage of kerosene from kaolinite soil through the different electrokinetic techniques including changing the electrolyte solution (nitrate potassium and tap water), increasing the-voltage (2 volts per cm of soil), and pH control over 5 and 7 days were investigated. Results revealed, using potassium nitrate as electrolyte solution, the the removal efficiency of kerosene was 47.24% and 50%, respectively, according to the remediation time of 5 and 7 days. With an increase of 2.9 times in the electroosmotic flow over a period of 48 hours from 5 to 7 days, the removal efficiency of the kerosene increased by 2.76%. Using distilled water as electrolyte solution despite the volume of 555 milliliters of electroosmotic flow, kerosene removal efficiency decreased to 33.02% in 7 days. The percentage of kerosene removal by pH control and increased voltage up to 2 v/cm, respectively with electroosmotic flow of 372 and 452 was 47.69 and 61.43%. Hence, a higher volume of electroosmotic flow represents a greater removal of kerosene in the soil. According to the obtained results, the best removal efficiency of kerosene (inspite of higher electroosmotic flow in tests with no enhancement technique) was due to the use of electrokinetic method by combining the higher voltage enhancement technique and the use of potassium nitrate electrolyte as solution over a period of 7 days.

Polycyclic aromatic hydrocarbons are hydrocarbons that composed of two or more benzene rings. These compounds are produced by incomplete burning or pyrolysis of organic matter. Phenanthrene is a type of aromatic hydrocarbon composed of three benzene rings, whose known effects can be attributed to its stimulating effect and skin sensitivity. The remediation of contaminated soil with hydrocarbon pollutants is crucial issue due to the soil connection with the food cycle. There are several methods for contaminated soil remediation. Electrokinetic (EK) is considered as one of the innovative technique that capable to remove both heavy metals and hydrocarbon contaminant from the soil matrix. The oxidation and reduction agents are added to change the chemical and microbiological properties of the soil that improve the extraction of pollutants or reduce their toxicity through the oxidation-reduction reactions. Oxidation agents can include air or oxygen, or chemical oxidants (such as hydrogen peroxide, sodium or potassium permanganate, ozone, chlorine, or oxygenated compounds). On the other hand, , , Calcium Polysulfide, and Sodium Ditonite are used as reducing agents. Fenton is one of the subsets of oxidation-reduction methods that has been considered by researchers for the last few years to remove pollutants from the soil. In the present study, the capability of EK combined with the Fenton was investigated to remove phenanthrene from contaminated soil. The effect of soil remediation time was studied for the EK only and EK combined with Fenton. The applied soil w::as char::acterized through the XRF and XRD. Based on the XRF, ,  ,  are the most prevalent component. Noteworthy is the presence of 6% hematite in the soil composition tested. Iron as a catalyst in the Fenton process plays an important role, which should be in contact with hydrogen peroxide to complete this process. Because of the proper percentage of hematite in the soil, it is not necessary to add iron from the outside of the system to complete the Fenton process. Based on the obtained results, the intensity of the electric current in all experiments rises rapidly at 1 to 20 hours of each test, reaching its peak of about 810 mA, then decreases and becomes almost constant. The reason for the rapid increase in the intensity of electric current in the early hours of the experiment, which was also observed in other researches, is the presence of metal salts and ions in the pore-water of the soil, which causes high electrical conductivity in the soil. With the increasing of the time, due to the electrical migration of these ions to the electrolyte reservoirs and the precipitation of a non-conducting layer on the surface of the electrodes, the intensity of the current decreases after 20 hours. In all experiments, the electroosmosis flow was from the anode to the cathode is due to the positive zeta potential of the soil. In experiments 3 and 4, using the Fenton technique, the rate of electroosmosis flow decreased due to the precipitation of the catalyst particles in the soil. Despite the reduction of the electroosmosis flow rate (test 3 and 4), the percentage of phenanthrene removal from soil has increased, which is due to the decomposition of pollutants into simple compounds during the Fenton technique. Overall, results revealed that, when the EK without any enhancement was applied in the seven days the phenanthrene concentration was decreased from 1000 to 600 mg/Kg. However, with the increasing time to 10 days, the phenanthrene concentration was decreased to 580 mg/Kg. When the EK combined with Fenton was conducted, the phenanthrene concentration was reduced to 500 mg/Kg after 5 days. However, with the increasing time to 10 days, the phenathrene removal was increased to 540 mg/Kg. Moreover, the energy consumed in experiment 3, where 50% of the pollutant was removed from the soil environment, was the lowest. Also, experiment 4 has eliminated 54% of the phenanthrene in the soil, had the most energy during the process.

Heavy metals are among the most serious environmental pollutants. Contamination of industrial waste water treatment sludge with heavy metals represents a potential threat to human and animal health. Electrokinetic remediation is one way of removing pollutants such as heavy metals from the contaminated soils. This technique is also highly cost-eective and practical for remediation of industrial sludge. In electrokinetic remediation a low-intensity electrical current is made to ow through electrodes (cathode and anode) embedded in the contaminated soil. Small ions and charged particles migrate between the electrodes encased with water. Due to electrical potential dierences, pollutants, such as heavy metals in uenced by the ow of electric current, move into the electrolytic solution. The main objective of this study is to investigate the eect of magnetic separation and sulfuric acid leaching pretreatment asawayofboostingzincandNickelremovalfromindustrial wastewater sludge through an electrokinetic process. This laboratory-scale study uses real sludge samples taken out from a wastewater treatment plant of industrial park. In this study, changes in pH, electrical current, electro-osmosis ow and energy consumption in dierent processes have been studied and the ability of each processes for the removal of zinc and nickel from sludge is determined. The results of pre test showed that enhanced electrokinetic process (the use of EDTA andcitricacidastheelectrolyte)comparedwithconventional electrokinetic (the use of water as the electrolyte) has a better performance in the removal of metals from thesludge. Inthisstudy, removalofzincusingenhanced electrokinetic process was 31% more than that in conventional method. The results revealed that leachingelectrokinetic combined process increases the removal eciency of zinc and nickel to 94% and 82%, respectively. Decreasing pH and removing unwanted elements by leaching were the major factors to improve the electrokinetic performance. The results also showed that themagneticseparation-electrokineticcombinedprocess has no considerable eect on heavy metal removal from sludge.

Uncontrolled emission of different contaminants in environment, such as soil and groundwater, leads to increasing the contamination and causing risks for the ecosystem and human health. Over the last century, the oil has been one of the energy sources and the raw material for many industries. It must be mentioned that about 0.1% of its production enters the seas and oceans due to various events and pollutes the water and soil. Among the different methods of soil treatment, Electrokinetic is one of the most widely used methods, especially in the case of fine-grained soils. Due to low solubility of organic contaminants in water, such as oil, application of surfactants is necessary to improve the Electrokinetic method. Surfactants can increase the solubilization of organic compounds by reducing the surface tension and interfacial tension. So, the electroosmosis flow is the most important mechanism of pollutant transport. In this study, treatment of contaminated soils with crude oil, using enhanced Electrokinetic method by surfactants in pilot scale has been investigated. For this purpose, SDS and Saponin were used to remove the oil crude (6000 mg/Kg) from soil. Each test was conducted in cells made of Plexiglas with dimensions of 30*6*5 cm during 7 days. The effect of surfactant concentration (0.1, 0.2, and 0.3 wt % for SDS and 0.05, 0.1, and 0.2 wt % for Saponin) and applied voltage gradient (1 and 2 V/cm) to the oil removal from soil were investigated in the experiments. According to results, in the tests conducted with Saponin in 1 V/cm, the maximum removal rate of 18.35% was obtained in critical concentration (0.1 %), while using the SDS leads to a removal percentage equaling to 26.14 % in the highest concentration of SDS (0.3%). In addition, increasing the applied voltage gradient to 2 V/cm in the tests with critical concentration of surfactants raised the removal efficiency

The electrokinetic (EK) approach is one of the popular choices for the extraction of inorganic contaminants (e.g. heavy metals) from a soil matrix. On the other hand, many factors can affect the performance of EK contaminant remediation. Therefore, in the present study a series of macro and micro level tests including electrokinetic experiments, pH and electrical conductivity (EC), adsorption and desorption, X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were performed to investigate the effects of time and pore fluid characteristics on the efficiency of EK remediation. For this purpose, the kaolinite clay was separately infected with different solutions containing zinc nitrate and lead nitrate in concentrations of 20 and 40 cmol/kg and then electrokinetic experiments on a laboratory scale were conducted at 2 V/cm voltage gradient in time periods of 3, 6, 12, 24 and 48 days. Nitric acid was also used as a catholyte solution to enhance the soil remediation process. The results obtained show that the soil response to the EK remediation is a function of the contaminant characteristics, the pH of soil-electrolyte system and the time of testing. In EK contaminant remediation from a soil matrix, it is significant to pay particular attention to the effect of the concentration and type of contaminant on the applicability and efficiency of this method. The results reveal that under the same conditions, especially in the low times, extraction efficiency from samples containing lead was measured approximately 70 percent of the samples containing zinc. This is because the lead tends to more adsorbe on the clay surface and has a greater tendency to form precipitate. In addition to the type of contaminants, it was found that the increase in concentration of contaminants in the soil through a series of physical-chemical reactions accelerates clean up capabilities, particularly in the initial time period of the EK experiments. Catholyte conditioning with acidic solution enhanced the removal of heavy metals, which is mainly due to microstructural changes and an increase in the mobility of pollutants. In fact, based on the X-ray diffraction and scanning electron microscope analyses, the microstructural characteristics and the arrangement of the clay particles have an important role in the process of electrokinetic soil remediation. The formation of flocculated structure decreases the retention capacity of the clay particles and also increases the flow path, which enhance the efficiency of pollutant extraction. It was found that the soil remediation, especially in the parts close to the anode, greatly enhanced with increase the time of EK test; however, the further increase in time had a limited impact on results, especially in the samples containing high concentrations of zinc. This indicates that there is an optimum time in the process of cleaning up heavy metals from the soil by EK method, which depends on the type and concentration of contaminant. Moreover, it was seen that the extent of contaminant removal from anode side towards the cathode side is considerable when catholyte conditioning with acidic solution is used. In other words, reducing the pH of soil-electrolyte system has a significant impact in increasing the efficiency of pollutant extraction.

There are many techniques for the remediation of contaminated soil. One of these methods is electrokinetics. The electrokinetics technique is comprised of three major processes such as: electro-osmosis، electro osmosis and electrolysis. Electropheresis is referred to the process that causes the movement of colloid sized particles under an electrical field within the soil moisture. Electro-osmosis is the process of movement soil moisture from anode to cathode. The electrolysis is only due to the movement of ions and ion complexes in soil. The electrokinetics method is recognized as an effective technique in remediation of metal contaminated soils. Recently researchers showed that showed that it is possible to use this technique to remove a range of water soluble organic contaminates from soil. A review of the literature shows that the treatment of soils contaminated with MTBE has not beenstudied. Therefore،the aim of this work is to investigate the remediation of a soil contaminated with MTBE using the electrokinetic method

Electrokinetic soil remediation is a promising technology that can be used for insitu treatment of fine-grained soils. In this study the numerical analyses of electro kinetic process in soil is considered. Numerical model is formulated for simulating mercury transport under an electric field using one-dimensional convection-diffusion equation that describes contaminant transport. The presented model is used for demonstrating the pH changes and mercury removal from kaolinite clay at last day. The finite difference method is used for solving the model. Computational programs were written in two ways of FTCS and Crank-Nicolson using MATLAB software. The Crank-Nicolson scheme has been more consistent with experimental results. Experimental results are used for the calibration of the model. The proposed numerical model shows good agreement with experimental results.

There are known techniques for cyanide remediation from contaminated soil such as soil washing, soil oxidation and biological degradation. However, there is very little research forelectrokinetic remediation of cyanide from soil. This study investigates the application of electrokinetic remediation to contaminated soil with high clay content and low coefficient of permeability. The experiments were conducted with two electrodes as cathode and anode poles, which were placed inside the soil using the direct electrical current. Thus cyanide ions were transported to the anode pole and caused the remediation of the soil. The contaminated soil from tailing dam of Takab gold processing plant was used. Contaminated soil with the concentration of 420 mg/kg, distilled water and NaOH were employed in the electrokinetic cell. The experiments were conducted on the optimum moisture content of clayed soil at two voltage gradients (1.0 and 1.5 VDC/cm for the duration of 7 and 14 days) in order to assess the effect of voltage gradient when employing 1M NaOH solutions and distilled water at the anode pole. For each test, cyanide removal efficiency, the pH of the soil, moisture content, electrical conductivity and the electrical current and flow were determined. The measurements were conducted for the entire duration of electrokinetic experiments and at the end of the test. The results indicated that the cyanide removal obtained in 7 and 14 days was approximately 65% and 80%, respectively. The results also showed the pH of the soil was changed from 8.83 to 1-2 for the anode and to 12-13 for the cathode pole. The cyanide transported to the cathode and the pH were the most important dominant factors for cyanide remediation.

In this study, a non-plastic silt is grouted by sodium silicate in an electrokinetic cell. The silicate solutions are injected through the reservoir next to the anode electrode. The injection of Na- silicate solution increases the strength adjacent to the anode electrode between 5 to 8 times compared with the base soil. Increasing silicate concentration generates lower increase in strength across the specimen. This means that decreasing the silicate concentration increases the penetration length of the grout. Neglecting the results for anode side of the specimens, the maximum increase in strength has been observed for injection of 5% silicate solution through the anode with acid in the cathode chamber. The obtained strength is 3.3 to 4.0 times greater than the strength of the base soil with the highest penetration length. The application of this technology for increasing the strength of the soil underneath an existing foundation or generation of pile through the soil is proven.