Electrokinetic Process Research Articles

Theory and simulation of electrokinetic fluctuations in electrolyte solutions at the mesoscale

Electrolyte solutions play an important role in energy storage devices, whose performance relies heavily on the electrokinetic processes at sub-micron scales. Although fluctuations and stochastic features become more critical at small scales, the long-range Coulomb interactions pose a particular challenge for both theoretical analysis and simulation of fluid systems with fluctuating hydrodynamic and electrostatic interactions. Here, we present a theoretical framework based on the Landau–Lifshitz theory to derive closed-form expressions for fluctuation correlations in electrolyte solutions, indicating significantly different decorrelation processes of ionic concentration fluctuations from hydrodynamic fluctuations, which provides insights for understanding transport phenomena of coupled fluctuating hydrodynamics and electrokinetics. Furthermore, we simulate fluctuating electrokinetic systems using both molecular dynamics (MD) with explicit ions and mesoscopic charged dissipative particle dynamics (cDPD) with semi-implicit ions, from which we identify that the spatial probability density functions of local charge density follow a gamma distribution at sub-nanometre scale (i.e. $0.3\,{\rm nm}$ ) and converge to a Gaussian distribution above nanometre scales (i.e. $1.55\,{\rm nm}$ ), indicating the existence of a lower limit of length scale for mesoscale models using Gaussian fluctuations. The temporal correlation functions of both hydrodynamic and electrokinetic fluctuations are computed from all-atom MD and mesoscale cDPD simulations, showing good agreement with the theoretical predictions based on the linearized fluctuating hydrodynamics theory.

Influence of Electrokinetic Process on Compressibility Behaviour of Salt Affected Soils

Influence of Electrokinetic Process on Compressibility Behaviour of Salt Affected Soils

Effects of variations of voltage and pH value on the shear strength of soil and durability of different electrodes and piles during electrokinetic phenomenon

Electrokinetic (EK) treatment is an effective method in accelerating the consolidation and improving the geotechnical properties of fine-grained soils. This method stabilizes the soil and increases the bearing capacity of piles by improving the soil shear strength. Changing the soil pH, due to the occurrence of chemical reactions of electrolysis in the soil, can increase its shear strength. However, the electrodes used in this method corrode due to the change in the soil pH, which in turn reduces the electrical potential. Electrode corrosion and loss of electrical potential can significantly reduce the efficiency of the EK method. In addition, when using the EK method to increase the bearing capacity of piles, changing the pH can cause corrosion and damage to the piles. One of the most important factors influencing the change in the pH of soil is the voltage applied during the EK process. It was reported that increasing the voltage affects the intensity of chemical reactions and electroosmotic flow and thus increases the efficiency of EK. However, very limited research has been conducted on the effect of voltage on the performance of EK method. In the present study, the effects of three voltages on soil pH and corrosion resistance of four types of electrodes including iron (Ir), stainless steel (St), copper (Co), and aluminium (Al) were studied. In addition, the effects of pH variations on the corrosion rate of three types of piles including steel pile (SP), reinforced cement concrete pile (RCCP), and reinforced lime-cement concrete pile (RLCCP) were investigated. It was observed that increasing the voltage from a specific limit had no effect on the intensity of electrolysis reactions and the soil pH adjacent to the electrodes did not change more than a specific limit. Moreover, increasing the voltage to higher than 35 V (i.e. 45 V) did not increase the volume of drained water from the soil, but caused more electric current than the allowable current for Ir, St, and Al electrodes, and the corrosion intensity of these electrodes increased significantly. RCCP reduced the soil pH to 2.4 within 7 d of curing due to severe corrosion (13% corrosion rate). The soil pH values adjacent to RCCP and RLCCP within 28 d of curing reduced to 3.7 and 3.8, respectively, but the two piles were not damaged. In general, the results of this research showed that selecting an optimized voltage had a significant effect on the efficiency of EK, and increasing the voltage did not always lead to increase in the efficiency of EK process.

On the interplay between electromigration and electroosmosis during electrokinetic transport in heterogeneous porous media

Electrokinetic techniques represent a valuable approach to enhance solute transport, reactant delivery and contaminant degradation in complex environmental matrices, such as contaminated soil and groundwater, and have a great potential for the remediation of many organic and inorganic pollutants.This study investigates the complex interplay between the key electrokinetic transport mechanisms, electromigration and electroosmosis, in physically heterogeneous porous media and its impact on tracer distribution, reactant mixing and degradation efficiency. We perform experiments in a multidimensional setup, considering different types of heterogeneities, injected tracers and reactants, as well as background electrolyte pore water with different chemical composition and pH. We show that EK transport is significantly affected by the physical heterogeneities, due to the interaction between electrokinetic and hydraulic processes, and by the pore water chemistry that plays a key role on the magnitude and spatial distribution of electroosmotic fluxes. The latter affect the overall transport of charged and non-charged species, including the migration velocity of injected plumes, their spatial patterns, spreading and mixing with the background groundwater, and the extent of degradation and the spatio-temporal evolution of reactive zones in the heterogeneous porous media. Process-based numerical modeling allowed us to interpret the experimental observations and to disentangle the coupled effects of physical, chemical and electrostatic processes in the multidimensional, heterogeneous setups. Besides elucidating the mechanisms controlling electrokinetic transport, the results of this study have also important implications for practical field implementation of EK approaches in intrinsically heterogeneous subsurface systems.

Optimization for enhanced electrokinetic treatment of air pollution control residues using response surface methodology focusing on heavy metals leaching risk and extractability

Waste like air pollution control (APC) residues from incineration are potentially valuable resources. This paper reports the application of enhanced electrokinetic (EK) treatment processing to APC residues using an approaching anode coupled with a permeable reactive barrier (PRB). The changes of heavy metals (HMs) leaching risk and the effect of EK on metals extractability were explored for the possibilities of treated APC residues and metals recovery. The impact of various factors on HMs leaching was evaluated through response surface experiments. The adsorption ability of PRB and H+ provided by approaching anode could alleviate HMs accumulation during treatment caused by high pH and buffer capacity. Compared with conventional EK treatment, the HMs extraction and leaching reduction improved significantly, with more than 30% energy saved after enhanced EK treatment. The best HMs leaching reduction was obtained after 16 days treatment at 1.97 V/cm of voltage gradient with 14.64 g modified activated carbon used as PRB while the anode was moved after 6.35 days. The results showed fraction conversions could increase the extractability of HMs with the electric field application, and the environmental risk of remaining HMs was reduced through the effective removal of HMs with potential risk after enhanced EK treatment.

Effect of AC/DC electrical fields on ZnO nanoparticles kinetics

Long-term electrokinetic processes affect the motion of different soil fractions mainly ionic-species in soil-type environments. Primarily, this governs direct (DC) and alternating (AC) electrical fields due to the different thermal, acid-base ion gradients generated close to electrodes resulted in electro-migration, electrophoresis, and other electrolysis-related-processes. The migration of metal ionic-species, including zinc, which occurs mainly under DC electrical field is generally acknowledged, but metal-corresponding nanoforms such as ZnO nanoparticles (ZnO-NP) under low-level DC and AC electrical fields absent in the literature. The aims of the research was the analysis of pressure-driven transport at two different electric potentials; the equipotential-voltage lines in sand-media with ZnO-NP under 1 V, and 3 V (for DC), and AC under 1 V, 3 V (1 kHz of sinusoidal waves), detection of the migration of Zn from ZnO-NP to anode-to-cathode area (DC), and to the electrodes areas for AC with pH changes within three-hours of treatment and X-ray diffraction investigation of structural changes of ZnO-NP. The results showed that the AC electric field had more uniform equipotential-voltage pattern of sand-media than the DC fields for both voltages applied. In addition, different zinc concentrations up to 11% and electro-active substances were detected between the DC anode-to-cathode and Electrode 1 area compared to the AC Electrode 2 area. The higher pH value also correlated only with DC. X-ray diffraction analysis detected no structure transformation of ZnO-NP, but deterioration of relatively stable graphite electrodes appeared. Our results at the low-level AC and DC electrical fields confirmed the potential of electro-accelerated nanoparticle kinetics.

Comparison of Cr/Ni removal by electrokinetic (EK) and electrochemical geooxidation (ECGO) processes: Remediation performance and economic analysis in an in-situ system

This study aimed to evaluate the in-situ remediation performance of Cr/Ni contaminated soil by the electrokinetic (EK) and the Electrochemical Geooxidation (ECGO) processes. The standard operating procedures, including Phase I-III (pre-engineering, remediation, and site restoration), in an in-situ EK/ECGO system were established. The effects of electrode configuration (Honeycomb and Square), potential gradient, and processing fluid on remediation performance were investigated. Results showed that the removal efficiencies of Ni and Cr were 27.3–39.3% and 6.1–30.1% in the honeycomb system, respectively, and were 46.2–48.5% and 3.1–12.2% in the square system, respectively. In particular, using the Fe/Al oxidation electrode hugely shifted the soil-metal bonds from stable to a less stable. Results showed that the cost of Phase II varied under different experimental conditions. In contrast, the cost of Phase I and III was independent experimental parameters. Cr and Ni removal cost was 0.34–1.01 USD g-1 and 0.23–0.36 USD g-1 in the honeycomb system, respectively, and was 1.41–5.58 USD g-1 and 0.50–0.71 USD g-1 in the square system, respectively. In terms of remediation efficiency and cost analysis, this study demonstrated that the overall performance in the honeycomb system was better than that in the square system.

Efficient Removal of Copper and Cadmium from Contaminated Soil Utilizing Electrokinetic Process

Present manuscript demonstrates the efficient removal of copper and cadmium from contaminated soil utilizing electrokinetic process. The results of systematic bench-scale study on improved extraction of copper and cadmium shows the suitability of process to decontaminate low permeable soil. The influence of operating parameters such as electrode material, soil pH, current density, soil temperature, inter-electrode spacing and initial soil moisture content on the decontamination performance is investigated. Study revealed that, removal of copper and cadmium reached to 89.4% and 62.7% respectively while using titanium electrodes. Removal efficiency improved with the increase in current density, soil temperature and initial soil moisture content. About 74.5% of copper removal achieved within 20 hours at soil temperature of 35°C and current density was kept at 9.3 mA/cm2. During this study, soil pH decreased from 6.7 to 2.4 near anode and reached up to 12.3 near cathode resulting in augmented metal removal. An improvement of 33% in removal efficiency observed when moisture content increased from 45% to 73%. Rate of metal removal increased as the inter-electrode spacing decreased to 15 cm, which demonstrated the highest copper removal at a current density of 9.3 mA/cm2. The maximum energy consumption found to be 5.2 kWh/m3 of soil volume demonstrated the economy of process, which can be scaled up at cleanup sites.

Kinetic Modelling of Electrokinetic Separation of Sulfate and Hydrogen Ions from Acidic Hot Spring Discharges

Electrokinetic separation has been widely utilized to remove ionic compounds from wastewaters due to its high energy-efficient feature. Hot spring dischages usually contain abundant amounts of sulfate and chloride with a strong acidity, e.g., the pH value is around 1.6. In this study, two stacks with different configurations of electrokinetic separation processes were designed and used to remove SO4 -2 and H+ from hot spring discharges. The results indicated that, with an applied voltage of 10 V for 60 min, the removal ratios of sulfate, chloride, and hydrogen ions were 99%, 98% and 98%, respectively. The kinetic models were established to evaluate and predict the performance of SO4-2 and H+ separation under different operating conditions using the developed electrokinetic processes. The kinetic rate constants of various applied voltages (ranged from 2.9 to 17.0 V) using electrokinetic separation were determined accordingly. The mechanisms of different configuration designs for ions removal using electrokinetic stacks were also elucidated. The obtained paramters of kinetics could be used for reactor designs, cost evaluation and performance improvement in large-scale demonstrations. It was thus concluded that the developed electrokinetic separation processes could be a potential solution to the acidic wastewater discharges with an significant amount of dissolved solids.

Preliminary Study of the Influence of Supplementary Cementitious Materials on the Application of Electro Remediation Processes.

Supplementary cementitious materials (SCMs), based on pozzolanic materials, improve durability against corrosion and mechanical properties of concrete structures by decreasing their permeability. Even though the influence of SCMs on the chloride combination with the cement phases has been widely studied, its effects on electrokinetic remediation processes such as electrochemical chloride extraction (ECE) have not been clarified. For this reason, the influences of two SCMs, fly ash (FA) and blast-furnace slag, on the extraction of chloride through the concrete net pore have been studied in this paper to determine the viability of the application of electrochemical chloride treatments in these structural materials. Alternative electrochemical indicators to the ones included in the standards are also proposed to better determine the final point of the treatment. A cement replacement of 8% on both SCM (FA and slag) has been tested, and in addition to charge density, chloride content, and corrosion measurement at the end of the treatment (included in the standards), different electrical and electrochemical indicators such as electrical resistivity, EIS, or depolarized potentials are used to monitor the ECE. The influence of the treatment on disconnected steel has been also studied. In the case of slag mortar, no steel passivation was reached, while in the case of FA, the passivation of the steels connected to treatment was reached in the same way as in plain CEM I specimens. A degree of protection is also detected in the nonconnected steel, which means that substitution of 8% in FA does not affect treatment efficiency and can also partially protect the metallic elements embedded in the same electrolyte but not connected to the treatment.

Mechanistic insights into soil heavy metals desorption by biodegradable polyelectrolyte under electric field

In this study, we firstly used alginate to enhance an electrokinetic technology to remediate soil contaminated with divalent heavy metals (Pb2+, Cu2+, Zn2+). The mechanisms of alginate-associated migration of metal ions in electric field were confirmed. Alginate resulted in a high electrical current during electrokinetic process, and soil conductivity also increased after remediation. Obvious changes in both electroosmotic flow and soil pH were observed. Moreover, these factors were affected by increasing alginate dosage. The highest Cu (95.82%) and Zn (97.33%) removal efficiencies were obtained by introducing 1 wt% alginate. Alginate can desorb Cu2+ and Zn2+ ions from soil by forming unstable gels, which could be dissociated through electrolysis. However, Pb2+ ions did not easily migrate out of the contaminated soil. The density functional theory (DFT) calculations show Pb2+ ions could form a more stable coordination sphere in metal complexes than Cu2+ and Zn2+ ions. The metal removal efficiency was decreased by increasing alginate dosage at a high level. More alginate could provide more carboxyl ligands for divalent metal ions to stabilize gels, which were difficult to dissociate by electrolysis. In summary, the results indicate it is potential for introducing alginate into an electrokinetic system to remediate Cu- and Zn- contaminated soil.

Removal of zinc, lead and nickel from contaminated soil by electro-kinetic technology under the influence of washing and buoyance forces with different purging solutions

ABSTRACT The effects of the washing process, purging solution, and buoyance force (inclined topography action) on the effectivity of the electro-kinetic method used to remediate of a silty clay loam and natural soils contaminated with Zn, Pb and/or Ni were investigated by applying 12 different experiments. The results revealed that the washing process and buoyance force can cause a small increase in the Zn removal efficiency (≤ 31%) when compared with non-washing approach using distilled water purging solution. Using 0.1 M of EDTA solution for the soil contaminated with listed metals in combination with washing can lead to significant increase in the removal efficiencies with percentages not greater than 58.4, 60.68 or 42.8%, respectively. In the presence of EDTA, however, the majority of metals passed through the soil media to the anode area. In contrast, these metals are accumulated near the cathodic region in the presence of distilled water. The results demonstrated that the buoyance force (resulted from inclination angle of 30°) with EDTA had adverse influence on the metal profile along the treated soil. Finally, the results certified that EDTA in electro-kinetic process coupled with soil washing is a new hybrid technique which achieved Pb removal efficiency from natural soil reached to 58% by improving the solubilization and transport of metal ions.

An Effect of Electrokinetics Phenomena on Nonlinear Wave Propagation in Bubbly Liquids

A study of nonlinear waves in liquid-gas mixtures with the consideration of internal effects is an important problem of both the fundamental and the applied fluid mechanics. Investigation of nonlinear waves in the gas-liquid mixtures with allowance for internal effects is an important task of both fundamental and applied fluid mechanics. These problems often arise in industrial processes such as oil and gas production, hydrocarbons pipeline transportation, gas-saturated fluids flow in pipelines, etc. In this work, we investigate the effect of the internal electric field on the nonlinear wave propagation in a bubbly liquid. Numerical simulations have been conducted to study the nonlinear waves described by the nonlinear Burgers-Korteweg-de Vries equation. The numerical simulations showed that the electrokinetic processes significantly affect the wave propagation process. The amplitude of the waves gradually decreases when the size of the gas bubble is decreasing and the electrical potential increases. A good agreement of obtained results with our previous predictions is found.

Mechanism of bio-electrokinetic remediation of pyrene contaminated soil: Effects of an electric field on the degradation pathway and microbial metabolic processes

In this study, the mechanism of bio-electrokinetic (BIO-EK) remediation to improve the degradation of pyrene was evaluated based on an analysis of the intermediate products and the microbial community. The results show that BIO-EK remediation has a higher pyrene degradation efficiency on pyrene and its intermediate products than the bioremediation and electrokinetic (EK) remediation processes. A series of intermediate products were detected. According to the type of the intermediate products, two degradation pathways, biological metabolism and electrochemical oxidation, are proposed in the BIO-EK remediation of pyrene. Furthermore, the primary microbial taxa involved in the pollutant degradation changed, which led to variations in the functional gene components. The abundant and functional genes related to metabolism were specifically analyzed. The results indicate that the electric field promotes the expression of metabolisms associated with 14 carbohydrates, 13 lipids, 13 amino acids, five energies, and in particular, 11 xenobiotics. These results suggest that in addition to the promotion effect on the microbial metabolism caused by the electric field, BIO-EK remediation can promote the degradation of pollutants due to the coexistence of a microbial metabolic pathway and an electrochemical oxidation pathway.

Strategies for the sustainable practice of electrokinetic technology: The case of mixed contaminants in a clayey soil

Electrokinetic (EK) remediation is a developing technology for treating a wide range of organic and inorganic contaminants from soil. One aspect of a sustainable remediation is to be economically viable. Various strategies have been used for evaluating the energy consumption and costs in the EK process. This study investigated the effect of voltage gradient (1.0 and 2.0 V cm −1 ), pH controlling, and duration time (7 and 15 days) on contaminants distribution and energy consumption during EK. An alkaline clayey soil was artificially contaminated with lead, zinc, nickel, and phenanthrene. Increasing voltage and controlling pH was ineffective on the mobility of mixed contaminants as they increased soil resistivity. Controlling pH accounted for 70% of the increasing total energy consumption (1521.65 kWh m −3 ) and failed to mitigate soil contamination. Brij 35 worked better than Tween 80 in the transportation of the target contaminants in the clayey soil. By Brij 35, 32% of total contaminants were removed from the studied soil with an optimal energy consumption of 892.8 kWh m −3 . The strategies of increasing voltage gradient and pH control are not recommended for EK remediation of alkaline clayey soils. • pH control was not a sustainable strategy in EK remediation of mixed contaminants. • The soil electric resistance increased with time and impeded contaminant mobility. • Increasing voltage was unsatisfactory and costly for clayey alkaline soil.

Effective remediation of heavy metals in contaminated soil by electrokinetic technology incorporating reactive filter media

Soil contamination is increasingly a global problem with serious implications for human health. Among different soil decontamination approaches, electrokinetic (EK) remediation is a relatively new technology for treating organic and inorganic contaminants in soil. This research aims to develop an enhanced EK treatment method incorporating a compost-based reactive filter media (RFM) with the advantages of low-cost and strong affinity for heavy metals and test and improve the treatment efficiency for multiple heavy metals in natural soil. A series of EK operations were performed to investigate the performance of EK-RFM under different operating conditions such as the electric current and voltage, processing time, and the amount of RFM. The electric current and treatment time demonstrated a significant positive impact on removing Zn, Cd and Mn ions while changing the amount of RFM had an insignificant impact on the efficiency of heavy metals removal. Overall, 51.6%–72.1% removal of Zn, Cd, and Mn was achieved at 30.00 mA of electric current and 14 days of treatment duration. The energy consumption of the EK process was 0.17 kWh kg−1. The soil organic matter adversely affected the mobilization and migration of heavy metals such as Cu and Pb during EK treatment. The results are valuable in optimizing the design of the EK-RFM system, which will extend its application to field-scale soil decontamination practices.

Transportation and augmentation of the deposited soil bacteria in the electrokinetic process: Interactions between soil particles and bacteria

The use of electrokinetic (EK) phenomena can facilitate bioaugmentation by enhancing the mobility and redistribution of deposited soil bacteria through heterogeneous soil. In this research, batch treatments (T1-T6) were used to assess the characteristics of bacterial transportation and proliferation under a weak electric field (1 V/cm). The strain Bacillus cereus was mainly transported toward the cathode by electro-osmosis flow (EOF). The bacterial transport efficiency was 1.07 × 107 CFUs/mL from days 0–9 when deionized water was used as the electrolyte solution and was elevated by 46% when EOF was enhanced with 0.010 mol/L NaHCO3 solution containing 0.04 mol/L Na2SO4. However, in all treatments, bacterial transport efficiency decreased by 70%-95% after 9 days. The bacterial transport efficiency was closely related to the EOF effective action distance (ED) which narrowed as soil and bacterial properties changed after the EK process. Correspondingly, the bacteria in soil were transformed from loose-bound to tight-bound status due to the deepened secondary minimum depth of XDLVO interaction energy after EK treatment. In addition to bacterial transportation, the electric field stimulated the proliferation of bacteria to achieve higher counts by promoting bacterial adhesion and facilitating fluid contact between ions, dissolved organic carbon, and bacteria. The stimulatory effect of electric field on bacteria was stronger than the transportation effect of the electric field on bacteria. Improvements in both bacterial migration and proliferation contributed to bioaugmentation under EK conditions. Near-cathode sections (S3, S4) are optimal for bacterial augmentation under the EK treatment for a long duration.

Advanced ammonia nitrogen removal and recovery technology using electrokinetic and stripping process towards a sustainable nitrogen cycle: A review

Ammonia removal and recovery from wastewater have been a critical issue worldwide and a key to achieve a sustainable nitrogen cycle and circular economy. Conventional ammonia removal via air stripping needs pH adjustment pretreatment with chemical additives while electrokinetic technologies can provide electrochemically in-situ pH control without chemicals needed. The integration of electrokinetic and air stripping technologies is a potential process for the simultaneous removal/recovery of ammonia/ammonium from wastewater. This study consolidates research findings of the separate research domains of electrokinetic and air stripping technologies and aims to identify an integrated process for the simultaneous nitrogen removal/recovery from waste streams. Process integration involves research on improved ammonia removal efficiencies and liquid side mass transfer performances using innovative air stripping system designs and gas-liquid contactors, e.g., rotating packed beds and membrane contactors, compared with the conventional stripping tower process. Findings in the applications and performances of electrokinetic separation processes, including electrodialysis, electrodeionization, capacitive deionization, electrochemical cell, and bio-electrochemical systems, on the removal/recovery of ammonia/ammonium, are a crucial link to integration as well. Energy consumptions between 5–20.4 kWh/kg–NH4-N with a removal ratio of around 90% for electrokinetic processes are currently achievable, and some groups can be implemented on the biodegradable organic substrates from urine. Innovative hybrid technologies of ammonia nitrogen removal/recovery with energy production and co-product valorization that reduce the overall cost and energy consumption via integrated processes optimization, and discussions on the environmental impact assessment (via life cycle assessment) and economic benefit analysis (via techno-economic analysis) of ammonia recovery practices on waste streams are investigated.

Influences of K+, Ca2+, and Al3+ on electrokinetic process and conductive mechanism of sludge electro-dewatering

In the process of sludge electro-dewatering (EDW), ions migration accompanied has significant influences on the dewatering efficiency. However, the effects of ions on sludge electrochemical properties and the roles in EDW are still not well understood. In this paper, influences of K+, Ca2+, and Al3+ on the mechanical dewatering and EDW process were investigated, and the mechanisms of EDW were analyzed from electrokinetic phenomena and electric conduction model. The results showed that the increase of cationic valence improved sludge mechanical dewatering but deteriorated EDW performance. The spatially distributed voltage used for ionic electromigration indicated that the lagged migration of divalent cation Ca2+ consumed more energy and reduced the dewatering rate in the later stage of EDW compared to that of monovalent cation K+. And trivalent cation Al3+ migrated less and took less water out, while it made the electrochemical reaction of EDW system easier to carry out. The decrease of the absolute zeta potential value of K+, Ca2+, and Al3+ also revealed the degeneration of dewaterability limit. An electric conduction model of partially water-saturated state porous media related to geometric factors was used and clarified the weight variation of continuous phase conductivity and surface conductivity during EDW. The results showed that the conductivity of Al-sludge was more affected by geometric factors and resulted in worse dewatering performance. This study provided a theoretical guidance for understanding the ions behavior affecting the dewatering efficiency and energy consumption of EDW.

Enhanced electrokinetic remediation of heavy metals contaminated soil by biodegradable complexing agents

In this study, an electrokinetic technique for remediation of Pb2+, Zn2+ and Cu2+ contaminated soil was explored using sodium alginate (SA) and chitosan (CTS) as promising biodegradable complexing agents. The highest Cu2+ (95.69%) and Zn2+ (95.05%) removal rates were obtained at a 2 wt% SA dosage, which demonstrated that SA significantly improved the Cu2+ and Zn2+ removal efficiency during electrokinetic process. The abundant functional groups of SA allowed metal ions desorption from soil via ion-exchange, complexation, and electrolysis. Pb2+ ions were difficult to remove from soil by SA due to the higher gelation affinity with Pb2+ than Cu2+ and Zn2+, despite the Pb2+ exchangeable fraction partially transforming to the reducible and oxidizable fractions. CTS could complex metal ions and migrate into the catholyte under the electric field to form crosslinked CTS gelations. Consequently, this study proved the suitability of biodegradable complexing agents for treating soil contaminated with heavy metals using electrokinetic remediation.