Efficiency Of Electrokinetic Remediation Research Articles

Introduction of Resin Barrier to Improve the Efficiency of Electrokinetic Remediation for Pb-Contaminated Soil

Introduction of Resin Barrier to Improve the Efficiency of Electrokinetic Remediation for Pb-Contaminated Soil

Effectiveness and Mechanisms of Chemical Leaching Combined with Electrokinetic Technology on the Remediation of Heavy Metal Contaminated Soil

In this study, chemical leaching and electrokinetic technology were used to remediate heavy metal contaminated soil to elucidate its effectiveness and mechanisms. Chemical leaching agents of FeCl3, Fe(NO3)3, KCl, KNO3, and HCl solutions were selected, and the effects of Fe3+, K+, H+, and Cl- on four heavy metal (Cd, Pb, Cu, and Zn) removals were compared and analyzed. Then, the influence of the speciation of heavy metals in soil after chemical leaching on the electrokinetic remediation efficiency was studied. The results showed that Fe3+, K+, H+, and Cl- had different effects on the four heavy metal removals; for Cd and Zn, the removal effect of H+was the most effective, but for Pb and Cu, the effect of Fe3+ was the most obvious. On the whole, FeCl3 and Fe(NO3)3 showed the best removal effect for Cd, Pb, and Cu. For the removal of Zn from the soil, the difference in the removal effect of the five leaching agents was not obvious. In comparison with that of FeCl3 and Fe(NO3)3, the HCl solution had a moderate removal effect on the four heavy metals in the soil, and the neutral salts KCl and KNO3 had little removal effect on the four heavy metals. Especially for Cd and Cu, KCl and KNO3 addition significantly increased the removal of heavy metals through the subsequent electrokinetic remediation. After the chemical leaching, electrokinetic remediation could make heavy metals in the topsoil (0-10 cm) migrate downward and enrich the 10-20 cm and 20-30 cm soil layers, which requires further studies to resolve.

Preparation of a novel iron oxychloride (FeOCl) auxiliary electrode in promoting electrokinetic remediation of Cr(VI) contaminated soil: An experimental and DFT calculation analysis.

The utilization of auxiliary electrode can improve substantially the electrokinetic remediation efficiency of heavy metal contaminated soil. The increase in the auxiliary electrode performance is the key to further promote the electrokinetic remediation efficiency. In this study, two kinds of auxiliary electrodes, pure FeOCl and doped FeOCl with W and S, were prepared and used in the electrokinetic remediation of Cr(VI) contaminated soil. The system equipped with the auxiliary electrode doped FeOCl brought more stable system current (202mA) and more uniform electric field than blank group (130mA). The reduction rate of Cr(VI) was increased by 50% due to the presence of Fe2+ and S2-. The accelerating migration of ions by auxiliary electrode was responsible for the improvement in electrokinetic remediation efficiency. Density functional theory (DFT) calculation showed that Cl vacancy formation energies of pure FeOCl, S-doped FeOCl (S/FeOCl) and W-doped FeOCl (W/FeOCl) were 1.29, 1.15 and 1.49eV respectively, and the ion diffusion barriers were 0.093, 0.099 and 0.148eV respectively. Calculation results indicated that the doping of S was conducive to the diffusion of Cl ions, and the bonding of W-Cl was stronger than Fe-Cl. The charging and discharging process of auxiliary electrode became easier due to the formation of lower vacancy in S-doped FeOCl, which could bring a higher current for the electrokinetic remediation system. The electrochemical performance of FeOCl doped with W and S was improved obviously. This study provided a further explanation for the positive role of auxiliary electrode in electrokinetic remediation system.

Preparation of ternary composite (WS2-FeOCl-PANI) and its performance as auxiliary electrode in electrokinetic remediation of simulated Cr(VI) contaminated soil

The utilization of an auxiliary electrode is a promising approach for improving the electrokinetic remediation efficiency of anionic metal contaminated soil. In this study, the ternary composite of Tungsten disulfide-Iron oxychloride-Polyaniline (WS2-FeOCl-PANI) was synthesized and employed as an auxiliary electrode for electrokinetic remediation of simulated Cr(VI) contaminated soil. The ternary composite of WS2-FeOCl-PANI was successful prepared by the polymerization of aniline monomer on the surface of WS2-FeOCl, and its specific capacitance was enhanced to 268 F/g, which was higher than PANI by 87.9%. The application of WS2-FeOCl-PANI as an auxiliary electrode improved remarkably the electrical migration and the electric field distribution. The current was elevated from 128 mA to 225 mA, and electric potential difference was extended from 17.9 V to 23.6 V. The removal ratio of total Cr with the use of WS2-FeOCl-PANI was enhanced significantly, which is higher by 20% than that without an auxiliary electrode. Meanwhile, the reduction ratio of Cr(VI) in contaminated soil was promoted to around 90%. The combined actions of PANI and S2- are mainly responsible for the considerable reduction of Cr(VI). This study provides an excellent auxiliary electrodes material for improving electrokinetic remediation of Cr(VI) contaminated soil.

Remediation of High Concentration Chromium Contaminated Soil by Enhanced Electrodynamic Method

High concentration of chromium salt has caused serious pollution to the environment since its production. The long-standing chromium residue has polluted the soil, and the total chromium concentration of some polluted soil has reached 30000 mg / kg. For the remediation of chromium contaminated soil, the enhanced electrodynamic method was proposed. In order to improve the efficiency of electrokinetic remediation of chromium contaminated soil, two enhanced electrokinetic remediation technologies were proposed: Electrokinetic oxidation enhanced remediation technology and electrokinetic enhanced remediation technology. (III) in soil was polluted by oxidant chromium oxide to increase the content of dissolved (VI),so as to improve the efficiency of electric repair, in order to find a suitable PRB medium as a breakthrough to improve the repair efficiency. The experimental results show that compared with the traditional electrodynamic technology, the enhanced electrodynamic method can effectively improve the removal rate of total chromium in the soil, and provide technical support for the enhanced electrodynamic remediation of chromium contaminated soil. The pH control system makes the pH of anode and cathode electrolyte always maintain acidic, and the H+ migration speed is faster than that of OH-, and the pH of soil near the anode is lower than that near the cathode.

Enhanced Electrokinetic Remediation of Pyrene-Contaminated Soil Through pH Control and Rhamnolipid Addition

Abstract Electrokinetic (EK) remediation is considered an effective technology for removal of persistent, toxic, and hydrophobic polycyclic aromatic hydrocarbons, such as pyrene, from soils. We propose a method involving use of pH control and rhamnolipid addition for enhancing pyrene removal efficiency of EK remediation. Pyrene removal efficiency was successfully improved by cycling the electrolyte, exchanging electrodes, and implementing an electrolyte pH of 7, with high values of 12.12%, 10.48%, and 14.00% being achieved, respectively, compared to the 0.35% achieved with traditional EK treatment. Effect of rhamnolipid addition on the EK removal of pyrene was also investigated. When rhamnolipid was added to the electrolyte, solubility of pyrene increased, thus resulting in improved removal efficiency. With an increase in rhamnolipid concentration from 0.5 to 2 g/L, pyrene removal efficiency increased from 14.74% to 24.81%, reaching 93.60% in the section closest to the anode. These results indicate that u...

Electrokinetic Remediation Technique: An Integrated Approach to Finding New Strategies for Restoration of Saline Soil and to Control Seawater Intrusion

AbstractMany applications of electrokinetic remediation have focused on the removal of heavy metals. However, the application of electrokinetic technology in salt removal from contaminated soils and groundwater has not been extensively explored. Given the current global challenge and the impact of soil and groundwater salinity, it is tempting to suggest that the research community should apply this technology to generate in‐depth knowledge for determining the feasibility and efficiency of electrokinetic remediation in salt removal, particularly in addressing seawater intrusion in coastal aquifers, which is creating growing challenges in the freshwater supply, mainly in coastal and arid regions, in view of growing populations, economic and industrial growth, and climate change. This Review shows that there is a need to begin formulating a knowledge base about categories of materials, efficiencies, and limitations. Furthermore, the viability of this technology in the real field suggests a need to gain more insight into electrokinetic applications in this area. The versatility of electrokinetic remediation in different settings is demonstrated in this Review, as is its capability to address diverse remediation challenges. The available literature is critically assessed; novel and improved electrokinetic remediation and the important trends in this field are outlined. The Review aims to summarize the evolution and current status of electrokinetic remediation research with a view of starting a debate around the possibility of applying it as a pretreatment mechanism to control seawater intrusion.

Enhanced electrokinetic remediation of lead-contaminated soil by complexing agents and approaching anodes

Optimizing process parameters that affect the remediation time and power consumption can improve the treatment efficiency of the electrokinetic remediation as well as determine the cost of a remediation action. Lab-scale electrokinetic remediation of Pb-contaminated soils was investigated for the effect of complexant ethylenediaminetetraacetic acid (EDTA) and acetic acid and approaching anode on the removal efficiency of Pb. When EDTA was added to the catholyte, EDTA dissolved insoluble Pb in soils to form soluble Pb-EDTA complexes, increasing Pb mobility and accordingly removal efficiency. The removal efficiency was enhanced from 47.8 to 61.5 % when the EDTA concentration was increased from 0.1 to 0.2 M, showing that EDTA played an important role in remediation. And the migration rate of Pb was increased to 72.3 % when both EDTA and acetic acid were used in the catholyte. The "approaching anode electrokinetic remediation" process in the presence of both EDTA and acetic acid had a higher Pb-removal efficiency with an average efficiency of 83.8 %. The efficiency of electrokinetic remediation was closely related to Pb speciation. Exchangeable and carbonate-bounded Pb were likely the forms which could be removed. All results indicate that the approaching anode method in the presence of EDTA and acetic acid is an advisable choice for electrokinetic remediation of Pb-contaminated soil.

Effect of Alternative Electrolytes on Enhanced Electrokinetic Remediation of Hexavalent Chromium in Clayey Soil

Hexavalent chromium is mobile and hazardous in the environment. Electrokinetic remediationof chromium (IV)-contaminated soils is intended either to remove or to reduce Cr (VI) to Cr (III). This studyexamines the effectiveness of utilizing EDTA and acetic acid solutions as alternative electrolytes in theelectrokinetic (EK) process, with coupled nano-scale zero-valent iron (nZVI) as a barrier for the remediationof Cr (VI)-contaminated clay. An nZVI barrier was installed adjacent to the anode, and different electrolytesolutions (0.1 M EDTA and 1 M acetic acid) were used to investigate the effect of both on the electrokineticremediation efficiency. Soil was contaminated to 300 ppm of Cr (IV), and a constant DC voltage gradient of1 V/cm was applied to the soil sample for 72 h. It was found that an nZVI permeable reactive barrier (PRB)could improve the Cr (VI) remediation efficiency and reduce electrical energy consumption. Results alsoshowed that acetic acid as electrolyte promoted the reduction of Cr (VI) to Cr (III), while EDTA applicationas electrolyte led to more chromium removal and reduction than an EK-nZVI barrier.

Influence of Cations in Anolytes on the Power Efficiency in the Electrokinetic Remediation of Chromium(VI)-Contaminated Soils

In the electrokinetic (EK) remediation of contaminated soils, the ions in porous fluid move out of soil and meanwhile the ions in electrolytes move in, resulting in the changes of soil conductance and remediation efficiency. This paper investigated the influence of different cations on the power efficiency of EK remediation of chromium-contaminated soils with Fe2+, Ca2+, H+, K+, and Na+ ions. Results showed that the cations of low equivalent ionic conductance can effectively decrease the power consumption meanwhile not deteriorating the removal rate of total chromium.

Impact of carbonate on the efficiency of heavy metal removal from kaolinite soil by the electrokinetic soil remediation method

While the feasibility of using electrokinetics to decontaminate soils has been studied by several authors, the effects of soil composition on the efficiency of this method of decontamination has yet to be fully studied. This study focuses its attention on the effect of “calcite or carbonate” (CaCO 3) on removal efficiency in electrokinetic soil remediation. Bench scale experiments were conducted on two soils: kaolinite and natural-soil of a landfill in Hamedan, Iran. Prescribed quantities of carbonates were mixed with these soils which were subsequently contaminated with zinc nitrate. After that, electrokinetic experiments were conducted to determine the efficiency of electrokinetic remediation. The results showed that an increase in the quantity of carbonate caused a noticeable increase on the contaminant retention of soil and on the resistance of soil to the contaminant removal by electrokinetic method. Because the presence of carbonates in the soil increases its buffering capacity, acidification is reduced, resulting in a decrease in the rate of heavy metal removed from the contaminant soil. This conclusion was validated by the evaluation of efficiency of electrokinetic method on a soil sample from the liner of a waste disposal site, with 28% carbonates.

Effects of Chelating Agents on Zeta Potential of Cadmium-Contaminated Natural Clay

The effects of pH, ionic strength, cadmium concentration, and chelating agents on the zeta potential of a natural clay of high acid/base buffer capacity from Shanghai, China were investigated in this study, with a view to enhancing the efficiency of electrokinetic remediation of the cadmium-contaminated clay. An increase in the ionic strength of the background solution or cadmium concentration increases the zeta potential on soil particle surfaces, i.e., less negative. CAIW increases the zeta potential slightly but the effects are not pronounced. EDTA and phosphonates decrease the zeta potentials of soil particle surfaces, thus enhancing forward electroosmotic flow.

Electrokinetic removal of 2,6-dichlorophenol and diuron from kaolinite and humic acid-clay system

This paper presents the results of a study on the electrokinetic treatment of kaolinite and humic acid kaolinite complexes spiked with 2,6-dichlorophenol or 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron). In particular, the attention was paid to the interaction between solid surface and dissolved organics: the effects of contaminant sorption as well as the physicochemical reactions on the efficiency of electrokinetic remediation were investigated. Using a 3 V/cm voltage gradient, approximately 90% of diuron was removed from kaolinite after one water pore volume was collected in the cathode reservoir, but much lower efficiency was obtained in the electrokinetic removal of this compound from humic acid-coated kaolinite. The results also showed that partial degradation of the contaminant occurred during electrokinetic treatment of kaolinite clay spiked with 2,6-dichlorophenol: the contamination in the clay could be remediated by the combination of electrokinetic extraction and electrochemical reactions.

Enhanced electrokinetic remediation of contaminated manufactured gas plant soil

This paper evaluates different flushing agents to enhance the efficiency of electrokinetic remediation of a manufactured gas plant (MGP) soil contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Because of high concentrations, PAHs were of environmental concern and required to be removed to acceptable levels. Four flushing agents, which included two surfactants (3% Tween 80, and 5% Igepal CA-720), one cosolvent (20% n-Butylamine) and one cyclodextrin (10% hydroxypropyl-β-cyclodextrin or HPCD), were examined to enhance the solubilization of PAHs in the soil. Four electrokinetic experiments were conducted at 2.0 VDC/cm voltage gradient and 1.4 hydraulic gradient in order to assess the effectiveness of these flushing solutions for the removal of PAHs. Variables measured during the application of electric potential were electric current, electroosmotic flow, and contaminant removal from the soil. After the completion of each test, the soil was further examined for moisture content, pH, redox potential, electrical conductivity, and residual contaminant distribution. It is found that cosolvent increased the soil pH, while the surfactants and HPCD did not induce substantial change in the soil pH. The current densities fluctuated with time for all tests and remained less than 1 mA/cm 2. The current density for the test conducted with cosolvent was higher as compared to the tests conducted with surfactants and HPCD. Electroosmotic flow was the maximum with the cosolvent, while the lowest flow was observed with Tween 80 surfactant. Overall, Igepal CA-720 surfactant yielded the highest removal efficiency due to partial solubilization of PAHs, causing some PAHs to migrate towards the cathode. Heavy metals are found to be strongly adsorbed/ precipitated and showed negligible migration behavior in all the tests. Based on the contaminant mass remaining in the soil, it is apparent that further optimization of the electrokinetic system is required to improve PAH removal efficiency for the MGP soil.

Remediasi Tanah Terkontaminasi Logam Berat Krom (Cr) dengan Teknik Remediasi Elektrokinetik

This research was conducted on the laboratory scale. The research methode of electrokinetic remediation with type of 2-D hexagonal electrode configuration are use voltage 40 Volt and 0.2 A of DC electric. Soil contaminated with Cr heavy metal was made by kaolinit soil from Godean distric in which that soil have initial concentration Cr 9.52 µg/g, and then the soil are contaminated by Cr2O3 500 µg/g solution, soil weight 150 kg then homogenized on the reactor with 1 m x 1 m x 1 m dimentions. In electrokinetic remediation, electrodes are implanted in the soil, and direct current imposed between the electrodes then running for 12 hours. The electrodes are made from graphite and placed with hexagonal configuration which spacing of electrodes on between 15 cm. The result of research was shown that the avarege of soil pH before remediated in the condition strong acid i.e 2.4 while soil pH remediated within the range 8.4 to 10.2 in the serounding cathode. Mean while, in the serounding anode on the condition strong acid that are about pH 3 to 5.4. It means there are chemical reactions called electrolysis. That Electrolysis reaction are oxidation reaction of the water from anode resulted acid conditions and also base condition in the cathode caused by reduction reaction of the water. The removal of Cr concentration having remediate for 12 hours in the site I to III are avarege 111.46 to 281.22 mg/g, in the other wards the removal efficiency of electrokinetic remediation are about 64.90 to 78.13%. It was shown that there are Cr3+ ion migrations phenomena moved to cathode. That ion migration was influnced by electrical current. Electrical current flowing in the soil had been caused ion migration to counter electrode. As finally, Cr3+ ion that formed from Cr2O3 contaminant will reduce to elemental and then attached to cathode. keyword : Cromium (Cr), electrokinetic remediation, electrolysis, electromigration

Zeta potential of soils with surfactants and its relevance to electrokinetic remediation

There are numerous studies on the application of electrokinetic decontamination technique to remediate heavy metal contaminated fine-grained soils. In recent studies, surfactants have been used to increase the efficiency of contaminant removal. However, there is limited data available on how physicochemical parameters such as zeta potential ( ζ) of soils changes in the presence of surfactants. Understanding the ζ potential variations of soils with surfactant addition is important because it controls the direction and magnitude of electro-osmotic permeability, which plays important role on the efficiency of electrokinetic remediation. In this study, ζ potentials of kaolinite, montmorillonite and quartz powder with Li +, Ca +2, Cu +2, Pb +2 and Al +3 in the presence of anionic, cationic and non-ionic surfactants were determined. The results indicate that anionic surfactants produce negative ζ potentials. The other surfactants produce both positive and negative ζ potentials depending on soil type and ion present in the system. The results also indicate that the ζ potential of kaolinite and quartz powder with surfactants showed similar trends; however, the absolute magnitude of the ζ potential of quartz powder is higher than that of kaolinite. The ζ potential of montmorillonite commonly shows a different trend from those of kaolinite and quartz powder. Based on the test results, it is recommended that ζ potential of soils be determined before the electrokinetic decontamination in order to maximize the efficiency of the technique.

Assessing effect of electrode configuration on the efficiency of electrokinetic remediation by sequential extraction analysis

The electroremediation experiments were conducted on artificially polluted soils by introducing a single metallic contaminant (Pb, Zn and Cu) and multiple metallic contaminants (Pb + Zn + Cu). Based on sequential extraction results, it was observed that the removal efficiencies of lead, zinc and copper vary depending on types of contamination. When the soil was contaminated only by lead, the removal efficiency was found to be 48%. However, the removal efficiency of lead decreased to 32% when the soil was contaminated by the combination of lead, zinc and copper. Similar results were observed for zinc and copper. The corresponding removal efficiency values for zinc and copper were 92% and 37%, and 34% and 31%, respectively. Effects of electrode geometry on the removal efficiency of metals were investigated by constructing a multiple anode arrangement. In this arrangement, the electrokinetic unit consists of three cylinders, which lie one inside the other, and the soil was placed in the middle cylinder. The central cylinder was the cathode well and the outer cylinder was the anode well, where eight identical anode electrodes were placed in octagonal with respect to the cathode electrode. By using this electrode arrangement in removal of metals from the soil contaminated with the combination of three metals (Pb + Zn + Cu), the removal efficiencies of lead, zinc and copper were found to be 29%, 18% and 18%, respectively. As it can be seen, these numerical values are much lower than the values that were obtained when the traditional two-plate electrode arrangement used in the electroremediation experiments (32%, 37% and 31%).

Use of Auxiliary Electrode to Prevent Alkalinization of Soil in Electrokinetic Remediation

We devised an improved electrokinetic remediation method in which an auxiliary electrode was placed at the cathode-side end of the soil to be treated. The electric potential difference between the anode and the auxiliary electrode was fixed constant while that between the cathode and the auxiliary electrode was controlled to make the auxiliary electrode function as a secondary anode. To test the performance of the method, we carried out a bench scale remediation experiment on cadmium-contaminated soil, in which the electrodes and soil etc. were. arranged in the following order; anodelanolytelsoil-auxiliary electrodelelectrolytic diaphragmlH-saturated cation exchange resinlcatholyielcathode. During 1 12 h of the treatment, the net voltage applied to the soil could be maintained and the alkalinization of the soil could be prevented partly due to the acid-neutralization in the cation exchange resin, and partly due to the secondary anode. These results indicated the auxiliary anode was effective to improve the efficiency of electrokinetic remediation of heavy metals contaminated soils.

Electrode Layout and Process Kinetics of Electroremoval of Copper from Sand

This research paper concentrates on the efficiency of electrokinetic remediation of copper contaminated sand employing different electrode material, number and spacing. By optimising the selection of suitable electrode materials, coupled with the application of the appropriate number of electrodes and electrode spacing, it is expected that the remediation time will be drastically reduced. In addition, the methodology being investigated in this study will reduce inefficiencies in electrical field distribution. The effect of various electrode materials such as silver and graphite, and the influence of changes in the number and the layout of the electrodes on the overall remediation efficiency and time was investigated and evaluated. Experiments with one, two and three one-dimensional anode system have proved that remediation efficiencies as high as 91% can be attained.

Electrokinetic remediation of a Cu contaminated red soil by conditioning catholyte pH with different enhancing chemical reagents

The effect of enhancement reagents on the efficiency of electrokinetic remediation of Cu contaminated red soil is evaluated. The enhancement agents were a mix of organic acids, including lactic acid + NaOH, HAc–NaAc and HAc–NaAc + EDTA. The soil was prepared to an initial Cu concentration of 438 mg kg −1 by incubating the soil with CuSO 4 solution in a flooded condition for 1 month. Sequential extraction showed that Cu was partitioned in the soil as follows: 195 mg kg −1 as water soluble and exchangeable, 71 mg kg −1 as carbonate bound and 105 mg kg −1 as Fe and Mn oxides. The results indicate that neutralizing the catholyte pH maintains a lower soil pH compared to that without electrokinetic treatment. The electric currents varied depending upon the conditioning solutions and increased with an increasing applied voltage potential. The electroosmotic flow rate changed significantly when different conditioning enhancing reagents were used. It was observed that lactic acid + NaOH treatments resulted in higher soil electric conductivities than HAc–NaAc and HAc–NaAc + EDTA treatments. Ultimately, enhancement by lactic acid + NaOH resulted in highest removal efficiency (81% Cu removal) from the red soil. The presence of EDTA did not enhance Cu removal efficiencies from the red soil, because EDTA complexed with Cu to form negatively charge complexes, which slowly migrated toward the anode chamber retarding Cu 2+ transport towards the cathode.