Electrokinetic Soil Remediation Research Articles

A comprehensive analysis of the advantages and disadvantages of pulsed electric fields during soil electrokinetic remediation

AbstractSoil electrokinetic remediation (SEKR) is considered an effective method for removing pollutants by integrating chemical, physical, and biological treatments. It has multiple applications in fields such as dewatering, consolidation, sedimentation, seed germination, etc. This work builds upon a series of recent publications on SEKR, covering topics like electrode approaches, reverse polarity-based SEK, SEK design modifications, installation of perforated materials, and chemical-based SEK. This review focuses on the role of pulsed electric field (PEF) in enhancing the performance of SEKR. There are several other names for the PEF, including periodic, interval, “ON” and “OFF”, intermittent, and breaking electric fields. PEF is proposed as a solution to overcome certain obstacles in SEKR. The review evaluates PEF's impact on (a) remediating organic and inorganic hazards, anions, and salt, (b) integrating with other processes (reverse polarity, phytoremediation, and bioremediation), and (c) electro-dewatering and consolidation. PEF offers several advantages, such as reducing energy consumption, converting the residual fractions into weakly bound fractions, achieving satisfactory remediation, avoiding the voltage drop in the area across the cation exchange membrane, enhancing desorption and/or migration of charged species, permits the exchange of contaminant from solid to the liquid phase (interstitial fluid), allows contaminant diffusion through the soil pores during the off time, generate high electroosmotic flow, avoiding electrode corrosion, decreasing concentration polarization, etc. However, it may also prolong the remediation period and cause contaminant diffusion through the soil pores, which are considered obstacles for SEKR. This review also describe different techniques related to PEF and highlights the potential use of solar cells as a renewable energy source for SEKR. Graphic abstract

Efficient removal of Cr(VI) from contaminated kaolin and anolyte by electrokinetic remediation with foamed iron anode electrode and acetic acid electrolyte.

Combined electrokinetic remediation employing reducing agents represents an extensively utilized approach for the remediation of hexavalent chromium (Cr(VI))-contaminated soil. In this investigation, electrokinetic remediation of artificially contaminated kaolin was conducted utilizing a separate circulation system for the anolyte, with a 0.5M solution of acetic acid (HAc) as the electrolyte and foamed iron serving as the anode. The experimental outcomes demonstrated that employing HAc as the electrolyte enhances the electromigration of Cr(VI) and establishes an acidic milieu conducive to the reduction of Cr(VI) by foamed iron, thereby facilitating the rapid reduction of Cr(VI) accumulated in the anolyte through electrokinetic remediation. In the self-prepared contaminated kaolin, the initial concentration of Cr(VI) was 820.26mg/L. Following the remediation process under optimal experimental conditions, the concentration was significantly reduced to 11.6mg/L, achieving a removal efficiency of Cr(VI) in the soil of 98.59%. In the optimal experimental setup, the Cr(VI) concentration in the anolyte was reduced to 0.05mg/L, which is below the EPA's Safe Drinking Water Act standard for Cr(VI) content of 0.1mg/L. The removal mechanism of Cr(VI) from the electrolyte primarily involves reduction, precipitation, and co-precipitation, with the foamed iron playing a predominant role. HAc and foamed iron exhibit a synergistic effect. The findings of this study substantiate that the integration of foamed iron with HAc is efficacious for the electrokinetic remediation of soil contaminated with Cr(VI).

Reverse Polarity-Based Soil Electrokinetic Remediation: A Comprehensive Review of the Published Data during the Past 31 Years (1993–2023)

Soil restoration by exploiting the principles and basics of electrokinetic (EK) has been extended to involve several categories, such as electrokinetic remediation in soil (SEKR), soil consolidation, the prevention of soil pollution, reclaiming salt-affected soil, the dewatering/dryness of wet soils, water reuse, seed germination, sedimentation, etc. As an extension of our recently published review articles on the soil electrokinetic (SEK) process intensification/optimization, the present review illustrates the effect of a reverse-polarity mode (RPM) on the efficiency of the SEK. Based on several searches of six database search engines, we did not find any relevant reviews focused on SEK improvements using the RPM. The influences of the RPM are described by various features, including (a) pollutant removal (organic, inorganic, and mixed pollutants) and (b) integration with other processes (phyto/bioremediation and Fenton oxidation), geosynthetics (consolidation, stabilization, and sedimentation), SEK operation conditions, and soil properties. Most of the RPM studies have focused on the remediation of organic pollutants. Several benefits can be gained from applying the RPM, such as (a) controlling the soil’s temperature, pH, and moisture values at desirable levels, (b) reducing a large number of chemical additives, (c) high remediation efficiency, (d) maintaining the indigenous fungal community’s appropriate diversity and abundance, (e) a stable and higher electric current, (f) enhancing microbial growth, etc. However, the hindrances to applying the RPM are (a) reducing the electroosmosis flow, (b) relatively high energy consumption, (c) reducing the diversity of soil microbes with a prolonged experiment period, (d) providing oxygen for a microbial community that may not be desirable for anaerobic bacteria, etc. Finally, the RPM is considered an important process for improving the performance of the SEK, according to experimental endeavors.

Electrokinetic Remediation of Cadmium-Spiked Soil Using Tea Saponins Powered by Solar Energy

Electrokinetic Remediation of Cadmium-Spiked Soil Using Tea Saponins Powered by Solar Energy

Electrokinetic remediation of real soils polluted with chlorinated hydrocarbons: relevance of dichlorination and volatilization processes

Electrokinetic remediation of real soils polluted with chlorinated hydrocarbons: relevance of dichlorination and volatilization processes

Enhancing electrokinetic remediation of soil contaminated with As, Cd, Cu, and Pb using the biodegradable chelator GLDA: A pilot study

Enhancing electrokinetic remediation of soil contaminated with As, Cd, Cu, and Pb using the biodegradable chelator GLDA: A pilot study

On the electrokinetic remediation of Pb-contaminated soil: A coupled electro-transport-reaction modelling study based on chemical reaction kinetics

The accumulation of lead (Pb) in soil resulted from industrialization and urbanization poses a threat to human health and the ecosystem. This study proposes a mathematical model for Pb migration and transformation in soil porous media, aiming to guide the design of electrokinetic remediation schemes for Pb-contaminated soils. To improve the validity of the model, the chemical reactions considered in the model are all based on chemical reaction kinetics, which were usually overlooked for model simplification. The model quantitatively describes various physical and chemical processes of Pb at the soil-pore fluid interface and in the pore fluid, including diffusion, electromigration, electroosmosis, electrolytic water reaction, precipitation, adsorption/desorption, protonation/deprotonation reaction, and water self-ionization reaction. The numerical results show that the pH value is a key factor affecting the distribution of Pb in the soil and determining the removal efficiency of Pb. The effects of different enhancement methods on Pb concentration distribution and removal efficiency were evaluated with this model. It was found that placing a cation exchange membrane at the cathode boundary while using 0.01 M nitric acid as anode electrolyte can effectively improve Pb removal efficiency from 3.9% to 93.6%. The developed model can be used to guide the design of the enhanced electrokinetic remediation schemes.

Electrokinetic remediation of chromium-contaminated saline soil coupled with permeable reactive barrier of biochar

Electrokinetic remediation of chromium-contaminated saline soil coupled with permeable reactive barrier of biochar

Genetic programming-based predictive model for the Cr removal effect of in-situ electrokinetic remediation in contaminated soil

Soil electrokinetic remediation is an emerging and efficient in-situ remediation technology for reducing environmental risks. Promoting the dissolution and migration of Cr in soil under the electric field is crucial to decrease soil toxicity and ecological influences. However, it is difficult to establish strong relationships between soil treatment and impact factors and to quantify their contributions. Machine learning can help establish pollutant migration models, but it is challenging to derive predictive formulas to improve remediation efficiency, describe the predictive model construction process, and reflect the importance of the predictors for better regulation. Therefore, this paper established a predictive model for the electrokinetic remediation of Cr-contaminated soil using genetic programming (GP) after determining the characteristic parameters which influenced the remediation effect, described the model's adaptive optimization process through the algorithm's function, and identified the sensitivity factors affecting the Cr removal effect. Results showed that the Cr(VI) and total Cr concentrations predicted by GP were in satisfactory agreement with the experimental values, 92% of the training data and 90% of the validation data achieved errors within 1%, and could fully reflect the target ions’ content variation in different soil layers. By substituting the above prediction formulas into Sobol sensitivity analysis, it was determined that conductivity, pH, current, and moisture content dramatically affected the Cr content variation in distinguished regions. For overall contaminated area, the system current and soil pH were the most sensitive factors for Cr(VI) and total Cr contents. Remediation efforts throughout the contaminated area should focus on the role of current versus soil pH. GP and sensitivity analysis can provide decision support and operational guidance for in-situ soil electrokinetic treatment by establishing a remediation effect prediction model, expediting the development and innovation of electrokinetic technology.

Self-Driven Electrokinetic Remediation of Cd Contamination Soil by Using Double-Chamber Microbial Fuel Cell

Green and sustainable techniques are in great demand for the remediation of heavy metal-contaminated soil. Cadmium ion (Cd2+) in soil could be extracted under the internal electric field and participating on the surface of the electrode. Here, we proposed a sediment microbial fuel cell (SMFC) for the electrokinetic remediation of cadmium (Cd) contamination soil. Within the 7 weeks of SMFC operation, the removal efficiency for total Cd could be up to 70.04 ± 0.45%, which was significantly higher than that obtained by open circuit SMFC. The maximum output power density was 71.00 ± 0.82 mW m−2 with a current density of 0.60 ± 0.03 A m−2. Results obtained by electrochemical impedance showed that the inter resistance of SMFC was 944 ± 14 Ω. High-throughput sequencing revealed that the Alpha-, Beta- and Gammaproteobacteria increased to 67.85%–80.99% in the SMFC. The relative abundance of Cd2+/Zn2+-exporting ATPase, participating in Cd2+ reduction, in SMFC varied from 25.83% to 30.68%, which were significantly higher than that of control (11.21% to 19.94%). Our findings have presented an effective energy-saving method for the remediation of heavy metal-contaminated soils.

Multi-electrode System for Electrokinetic Remediation of Paddy Soil to Remove Toxic Metals

Multi-electrode System for Electrokinetic Remediation of Paddy Soil to Remove Toxic Metals

Multi-dimensional modeling of H+ and OH− mass transfer during soil electro-kinetic remediation

Multi-dimensional modeling of H+ and OH− mass transfer during soil electro-kinetic remediation

Effect of ascorbic acid and combination with fulvic acid on the electrokinetic remediation of paddy soil contaminated by arsenic-containing acid mine drainage

Electrokinetic remediation (EKR) of soil contaminated by arsenic-containing acid mine drainage is usually challenging due to the strong adsorption capacity of iron oxides to arsenic. To solve this problem, ascorbic acid and fulvic acid were used as additives to enhance the mobility of arsenic in this study. Both ascorbic acid (EK-AA) and its combination with fulvic acid (EK-AF) increase soil water content and conductivity, forming more conducive reducing conditions, and augmenting the reduction and removal of iron, especially in the EK-AF treatment. After 14 days of EKR, the arsenic removal efficiency in EK-AF treatment reached 29.1%, while the control group was only 5.5%. The removal of arsenic in this study was attributed to the reductive dissolution of iron oxides and the activation of residual arsenic. The co-existing heavy metals antimony, copper, lead, and zinc could also be removed, with the highest antimony removal efficiency of 31.7%. Our results demonstrated that ascorbic and fulvic acids can be ideal green additives to achieve the reductive dissolution of iron oxides and activate arsenic, while maintaining soil physicochemical properties favorable to EKR, which effectively improves the removal of arsenic and co-existing heavy metals.

Monitoring the efficiency of electro-kinetic soil remediation process with geophysical surveying method

Geoelectric surveying is a useful method of non-invasive investigation (e.g.: for the purpose of space delineation or time dependant monitoring) of subsurface contaminants. The measured onsite electrical resistivity values are a function of certain soil parameters and the electric properties of the contaminant. With executing time domain field surveys before and after the remediation process its efficiency on contamination removal can be valorized.In this study we present a field case to illustrate the applicability of the geoelectric method for monitoring the efficiency of hydrocarbon removal and highlighting the problems of interpretation due to change of soil parameters and various hydrocarbon composition. Due to the side effects of electro-kinetic soil remediation process some soil parameters affecting the electrical resistivity are also changed. Therefore, when interpreting the data the of field survey one must be able to separate the geoelectric response of the remnant contamination from the changed soil parameters. The paper presents a multilevel interpretation method when the measured electrical resistivity data were correlated with the time-domain results of detailed soil sample analytics including particle size distribution, physical properties, and chemical composition. As a result we were able to separate the time domain geoelectric effects of the soil from the geoelectric response of the hydrocarbon contamination and we could correlate the electrical resistivity anomalies with the integrated effects of hydrocarbon content and changes in the soil due to the remediation treatment.

Numerical simulation of electrokinetic control of miscible viscous fingering

Active control of viscous fingering (VF) is of critical importance for many industrial and experimental systems. Here, we numerically study the electrokinetic control of miscible VF using an externally applied electric field. Simulations for three intrinsically hydrodynamically unstable mobility ratios are carried out using two different configurations for each: case I where the high-viscosity resident fluid has higher electroosmotic mobility than the invading low-viscosity fluid and case II where the resident fluid has a lower electroosmotic mobility than the invading fluid. For both cases, the theoretical critical electric field value required to (de)-stabilize the interface is computed and electric fields around this value are applied in simulations. Qualitative results show that VF can be fully suppressed if an electric field is applied with an absolute value above the critical field strength. For case I, this means an electric field in the direction of the pressure-driven flow, while for case II, a field in opposite direction is required. Our quantitative analysis using interfacial and mixing lengths was used to support the qualitative findings. Even though any field strength applied in the right direction will reduce the instability, full suppression is only achieved if the absolute field strength is higher than the required critical field strength. The results from this work provide useful insights that can be applied to electrokinetically enhanced oil recovery, spreading of pollution zones in aquifers, band broadening in liquid chromatography, and electrokinetic soil remediation.

Tandem Electrokinetic/Electrocatalytic Remediation of Pfas in Soils

Per-/polyfluorinated species (PFAS) are a class of widely used, highly stable chemicals that do not readily break down in the environment or human body. As a result of their widespread use and persistence in the environment, PFAS can be found in soil, air, and water at numerous sites across the United States. Recent work has linked exposure to some types of PFAS found in the environment to adverse health effects in humans. The bio-accumulative nature of PFAS along with the potential adverse health effects has provided strong motivation for active remediation of these emerging contaminants at environmental sites. Development of energy- and cost-efficient technologies for the in-situ treatment of PFAS-contaminated soils would greatly facilitate efforts to remediate these contaminated sites and alleviate the public health threat they represent.This talk will discuss recent efforts to develop a tandem electrokinetic/electrocatalytic technology for energy-efficient concentration and destruction of PFAS in contaminated soils. In this approach (Figure A), electrokinetic soil remediation technology is used to drive the PFAS contaminants to a localized area around the electrokinetic anode and electrocatalysis reactors situated near this electrokinetic anode degrade and destroy the concentrated PFAS species. Data will be presented describing the electrokinetic transport observed for various C4-C12 linear-chain PFAS in a Dayton, OH till soil on the bench scale (see Figure B). Experimental results to date suggest that larger PFAS species (above ~C6) experience sufficiently strong physicochemical attraction to the soil particles that electrokinetic transport is mostly or completely suppressed. Based on these results, current work is identifying ways to improve electrokinetic PFAS remediation by disrupting these PFAS-soil interactions in a fashion that is economically and environmentally favorable. Results demonstrating the ability to enhance electrocatalytic PFAS destruction through the use of pulsed-waveforms (relative to traditional direct current methods) will also be presented.Figure Caption. (A) Mechanism of tandem electrokinetic/electrocatalytic PFAS destruction. (B) Bench-scale apparatus for soil electrokinetics tests. Figure 1

Manure application facilitated electrokinetic remediation of antibiotic-arsenic co-contaminated paddy soil

The co-existence of antibiotics and heavy metals in soil with manure application poses high risk to both environment and human health, and thus effective remediation methods are in urgent need. This study investigated the synergistic effects of electrokinetic remediation (EKR) on antibiotic resistance and arsenic (As) in co-contaminated paddy soils. EKR treatments in soil amended with pig manure (EKR-PD) showed better remediation efficiency compared with that without pig manure. In detail, the content of available As and the abundance of antibiotic-resistant bacteria (ARB) decreased by 25.2 %−41.4 % and 9.5 %−21.1 % after 7-d remediation, respectively, due to a relatively higher current density for EKR-PD. The role of the electric field contributed to 33.9 % of antibiotic degradation. Antibiotic resistance genes (ARGs) with ribosomal-protection and enzymatic-deactivation types were easier to remove, with the removal ratio of 37.8 %−41.6 % in EKR-PD. Brevundimonas was the most significantly different species during remediation. Bacillus and Clostridium_ sensu_stricto_1 were potential host bacteria of ARGs in the electric field. Membrane transport might be an effective strategy for microorganisms to respond to the stress of both electric field and co-contaminated environments. This study supports the potential role of EKR in the co-contamination of heavy metals and antibiotic resistance under manure application.

Enhanced Electrokinetic Remediation of Copper-Contaminated Soil by Combining Steel Slag and a Permeable Reactive Barrier

Electrokinetic (EK) remediation methods can remove heavy metals from the soil, but the removal efficiency is generally low. In this paper, indoor remediation experiments of simulated copper-contaminated clay under four different types of electrolyte conditions (KCl, HAc, AC, and PASP (polyaspartic acid)) are carried out to validate the theory of an electrodynamically coupled steel slag permeability reactive wall (PRB). By comparison with EK remediation, it has been shown that the EK-PRB coupled remediation method can promote the removal of heavy metal copper in the soil, especially in the removal of reducible copper and exchangeable copper. The method can effectively avoid the increase in soil pH value and reduce the accumulation range of heavy metals while reducing the accumulation amount of heavy metals. This method has better energy utilization efficiency, and the unit energy consumption is smaller than the single electric remediation test.

Spatiotemporal Profiles of the Concentrations of Contaminants During Electrokinetic Remediation of Soils

Spatiotemporal Profiles of the Concentrations of Contaminants During Electrokinetic Remediation of Soils

Enhancement of the electrokinetic removal of heavy metals, cations, anions, and other elements from soil by integrating PCPSS and a chelating agent

BackgroundRecently, we have developed a new soil electrokinetic remediation (SEKR) process, hereinafter referred to as the perforated cathode pipe SEKR system (PCPSS), to achieve remediation intensification. Some obstacles, such as the low removal of some heavy metals, particularly Ni, limited our previous PCPCS. MethodsWe aim to improve the removal efficiency of the PCPSS by adding a chelating agent (i.e., ethylenediaminetetraacetic acid (EDTA)). Given the unsatisfactory remediation results obtained in our previous studies, the Taguchi approach (L9OA) was exploited in this work as an experimental design to determine the optimal level of factors that could enhance Ni removal. Significant findingsResults showed that an electric potential of 3 V, addition of 0.5 mol of EDTA, and an initial Ni concentration in the range of 10–20 mg kg−1 could optimize Ni removal. Confirmation experiments conducted on natural contaminated soil showed the following order of removal of heavy metals and other elements: Al (70%) > Co (69%) > Fe (63.5%) > Cu (55%) > Mn (52.8%) > Zn (43.17%) > Cr (41.41%) > Ni (22.26%). Among the studied soil cations, Mg showed the best removal rate, Ba showed moderate removal rate, and Ca showed the lowest removal rate. Notably, the removal rate of V was much higher than that of born (B).