Electroremediation Process Research Articles

Experimental study of the effect of material and arrangement of electrodes and voltage on the electro-remediation of saturated clays containing chloride and sulfate ions

Electro-remediation process (ERP) is used for dewatering and decontaminating of the soil and improving its mechanical properties. In this study, the effect of voltage, electrode materials, and their arrangement on ERP were studied. The saturated clayey soil was remolded in four boxes at a dry density of 16.2 kN/m3. The process was performed in three stages. The chemical tests at the end of ERP indicated that the absorption of chloride ions in the anode may differ from 89 to 642% due to electro-migration phenomenon. The pH of the soil decreases in anode zone and increases towards the cathode zone. Up to 92% of the sulfate ions were transported and accumulated in the anode. However, in highly contaminated soil, the absorption ratio is 5% in the cathode due to the domination of electro-osmosis process. It was indicated that the electro-osmosis permeability coefficient (Ke) depends on the applied voltage, the soil type, and temperature and its reduction versus time is inversely related to applied voltage. Also, sulfate ions reduced by 74% in the anode due to a change in absorption direction. The results showed that the optimum configuration is linear along with a voltage of 18 V.

Decolorization of Artificial Waste Remazol Black B using Electrogenerated Reactive Spesies

Electrolysis method (electrodecolorization) coupled with ●OH radicals and chlorine generation has been performed in decolorizing of artificial waste of remazol black B (reactive black 5). The electrodecolorization as one of advanced oxidation process (AOP) shows its determinant potential in overcoming environmental problems due to dye contained waste as well as its green in desaign and efficiency. The project aim was to decolorize the RBB solution completely and effectively. The mission was completed by designing decolorizing reactor working with electrolytic system in tandem with electrogeneration of reactive species from HCl and NaCl electrolyte. Lead oxide, PbO2 was choosen as anode. The efficiency of decolorization process was comparated with those of Na2SO4 as electrolyte. Data of UV-Vis spectrometry, atomic absorption spectrophotometry and COD showed that the performance of electrolysis design was significantly enhanced with the reactive species generation process. Electrolysis of 100 mL sample of 200 mgL-1 RBB with reactive species generation was rearched almost two-fold faster in decolorizing the dye solution rather than in Na2SO4 one. The design rearchs more than 99 % in decoloriziation percentages, reducing COD more than 96 % indicating the potential and effectiveness of electroremediation process.

Asymptotic Analysis of Three-Scale Model of pH-Dependent Flows in 1:1 Clays with Danckwerts’ Boundary Conditions

The electroremediation process is an efficient method for removing pollutants from clayey soils. We model this process in kaolinite clays considering three scales—nano, micro and macro—under the assumption of a stratified geometry in conjunction with more realistic Danckwerts’ boundary conditions imposed at the electrodes. The resulting multiscale model is a coupled system of nonlinear partial differential equations. We derive analytical solutions of the macroscopic equations considering the asymptotic behavior of strongly convective and diffusive regimes. We perform numerical simulations of different scenarios for the electroremediation using the Galerkin finite element method together with a staggered algorithm and the Newton–Raphson method. We validate the accuracy of the proposed algorithm by comparing the discrete solutions to the analytical ones. Finally, we explore and discuss optimal scenarios for the electroremediation process depending on the input values of pH, electrical current, and mass inflow using dimensionless numbers defined from the analytical solutions.

Performance of wind-powered soil electroremediation process for the removal of 2,4-D from soil

In this work, it is studied a wind-powered electrokinetic soil flushing process for the removal of pesticides from soil. This approach aims to develop an eco-friendly electrochemical soil treatment technique and to face the in-situ treatment of polluted soils at remote locations. Herbicide 2,4 dichlorophenoxyacetic acid (2,4-D) is selected as a model pollutant for the soil treatment tests. The performance of the wind-powered process throughout a 15 days experiment is compared to the same remediation process powered by a conventional DC power supply. The wind-powered test covered many different wind conditions (from calm to near gale), being performed 20.7% under calm conditions and 17% under moderate or gentle breeze. According to the results obtained, the wind-powered soil treatment is feasible, obtaining a 53.9% removal of 2,4-D after 15 days treatment. Nevertheless, the remediation is more efficient if it is fed by a constant electric input (conventional DC power supply), reaching a 90.2% removal of 2,4-D with a much lower amount of charge supplied (49.2 A h kg−1 and 4.33 A h kg−1 for wind-powered and conventional) within the same operation time.

Influence of the Type of Surfactant on the Mobility of Flushing Fluids for Electro-Remediation Processes

The mobility of four flushing fluids in an electro-remediation process has been studied. A mock-up plant with two rows of three electrodes positioned in semipermeable electrolyte wells was used in this study. Two different cases were considered: first an initial state when the soil was wet with water and the addition of surfactant starts, and second a second state when the surfactant front had passed through the soil. The results show that the electro-osmotic flux strongly depends on the nature of the flushing fluid and on the voltage gradient applied between electrode rows. The presence of ionic surfactants (both cationic and anionic) led to lower electro-osmotic flow-rates. The concentration of surfactants in the drain tanks increased in the case of the flushing fluid with the non-ionic surfactant because the surfactant transport was more efficient. Conversely, the anionic surfactant accumulated more in the injection well. This finding is related to the effect of migration, which in the reception wells was opposite to the electro-osmotic flux.

Physical and Mathematical Study of the Electroremediation Process in a Cylindrical Cell

A three dimensions mathematical modeling was developed with COMSOL 3.2 software of an electroremediation cell. The Navier Stokes and Darcy equations were used to model the behavior of the electrolyte and the sand, respectively. The mass balance for hydrogen ion was carried out with Nernst-Planck equation for the anode and soil regions. The main factors that contribute to the hydrogen ion balance were the diffusive flux and electric migration. The mathematical modeling was validated with an experimental arrangement consisted in an electroremediation cell which contains sand as porous medium and water as electrolyte. A potential of 20 V was applied for 24 hours and the pH was measured continuously. The results of the model are in good agreement with those obtained experimentally.

Electrokinetic remediation of PAH mixtures from kaolin

Because of increased industrialisation and new manufacturing processes, elevated amounts of organic pollutants are released into the environment. Hydrophobic organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), are toxic and persistent contaminants that are not treatable by natural attenuation. In this work, electroremediation is proposed for cleaning soil contaminated by organic compounds. Model samples of kaolin clay polluted with a mixture of PAHs (fluoranthene, pyrene, and benzanthracene) were treated. Electroremediation of kaolin contaminated with a mixture of these three PAHs was carried out using a solution of 1% Tween 80 and 0.1 M Na 2SO 4 as the processing fluid. Under these conditions, low removal was obtained. However, by using the same processing fluid and controlling the pH at 7 in the anode chamber, high electro-osmotic flow was detected. After the treatment, removal of around 40% of the PAHs was achieved. The created environment inside the soil during the electrokinetic treatment greatly influenced the process. The results of this work reveal the high potential for the application of the electroremediation process on soil polluted with different PAHs.

Enhanced electrokinetic treatment of different marine sediments contaminated by heavy metals

In the present work, the application of an assisted electrokinetic process for the removal of heavy metals from real contaminated sediments was investigated. The process made use of both chemical and physical methods, including addition of chelating and acid agents, as well as application of a hydraulic gradient. Lab-scale electrokinetic runs were applied on two different dredged sediments varying the applied voltage gradient and the treatment duration. The use of EDTA significantly improved the overall performance of the electrokinetic treatment for sediment V (more than 60% mobilized for each metal), while only aggressive acid conditioning with nitric acid was able to remove significant amounts of heavy metals (up to 40.5% for Pb) from sediment S due to the strong buffering capacity of this material. This clearly assesses that the specific characteristics of the materials under concern and the reactions occurring at the electrodes must be carefully evaluated when applying an electroremediation process.

Degradation of trichloroethene in water by electron supplementation

Trichloroethene (TCE) is a common and recalcitrant contaminant in groundwater. Microbially catalyzed reductive dechlorination is a dominant pathway for TCE degradation, in which substrates and electron donors are essential. In this study, extraneous electron supplementation was attempted to enhance reductive dechlorination of TCE and its derivatives. Reactors were established with groundwater containing TCE, and a 6-V battery was used to supply an average current of 29 μA of dc power to feed electrons to the microcosms. We measured 80–90% depletion of TCE within 70 d in reactors (both sterile and non-sterile) containing 300–400 μg TCE/l and from 97 to 98% depletion in microcosms containing 10 mg TCE/l. No intermediate products such as dichloroethylene or vinyl chloride were detected during this study. Results demonstrate that electron-supplemented degradation of TCE appears to be an abiotic process that is unassociated with microbial populations or indigenous redox conditions. No apparent accumulation of TCE daughter products were observed and overall efficiency of this electroremediation process was calculated to be 6.9 g TCE degraded/kW h. This efficiency would make electron supplementation an attractive alternative to the substrate-amended biological reductive dechlorination of TCE.

Evaluation of Electroremediation Process on Hydrocarbon Polluted Soils

not Available.

An experiment in the electrokinetic removal of copper from soil contaminated by the brass industry

The feasibility of electrokinetic remediation of copper-contaminated soil was evaluated following eight days of electroreclamation. The results indicate that electrokinetic reclamation of Cu is totally ineffective in soil composed primarily of clay minerals and organic matter. The strong absorption of copper by this kind of soil, in our view mainly a result of retention by the clay component, makes it resistant to mobilization by the electrogenerated acidic front as well as by citrates (the competitors of natural chelating agents, i.e., humates). Such conditions, while adverse for the electroremediation process, may cause this kind of soil to act as a natural barrier to the leaching of copper ions.

Mathematical modeling of a galvanostatic soil electroremediation process

AbstractA mathematical model for galvanostatic soil electroremediation of cadmium‐spiked kaolinite was built considering: chemical and electrical properties from both phases, assumption of local equilibrium conditions, electroneutrality from phase interactions, a dynamic surface charge, and surface adsorbed concentrations defined by Boltzmann's equation. Model prediction trends agree with the expected phenomena to occur during an electroremediation process, as far as they show: a right electroosmotic fluid velocity with a suction effect at the anode position, a pH drop at the cathode position, soluble cadmium transport from anode to cathode, as well as cadmium accumulation before reaching the cathode, and a drop in electric potential gradient. Also, model strength allows the prediction of chemical species transient concentration; and provides an insight on species distribution through the spatial domain, while electroremediation takes place. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Electroremediation part II: A study of the movement of heavy metals during an electroremediation process in Andisol soil

In the Summer 2004 issue of Remediation, the authors presented a study of the influence of buffering behavior in contaminated Andisol soil. This article, Part II, expands on this research by presenting the results of laboratory tests conducted to study the movement of heavy metals in contaminated Andisol soil during the first stage of an electrochemical remediation process. The analysis was performed on the soil after treatment and also on the washing solutions collected during the first four hours. In order to analyze the effectiveness of fast and simple techniques for monitoring the electroremediation process, computer-aided modeling of speciation in the soil solution was performed in connection with the remediation treatment. The results show that the metals moved mainly as positive species in the soil and later occurred as insoluble forms relative to the pH value in the washing solution from the cathode chamber. © 2005 Wiley Periodicals, Inc.

Effect of Applied Electrical Field and the Initial Soil Concentration on Species Recovery During Application of the Electroremediation Process

Electrokinetic phenomena can be employed for a soil decontamination process generally called electroremediation. The ionic species in solution migrate through a porous medium essentially by electro-osmosis and electromigration. The aim of this work was to contribute to knowledge of this process by studying the effect of some operating conditions on the species recovery through an experimental program. The influence of the electrical field applied to the medium and the initial concentration of the soil solution, in particular, are studied. First, the electrokinetic transport phenomena are presented. Then, the experimental set-up and procedures carried out are described. The set-up consists of a specific electroremediation cell containing a Na-doped kaolinite medium. Chemical reactions were limited by using the sodium as a tracer. The experimental results show the important coupling existing between solution concentration and the electrical current and their influence on both the amount and the rate of transported mass. Moreover, the dependence of the electro-osmotic coefficient on the electrical field applied was demonstrated. The influence of the solution concentration on the electro-osmosis is not obvious, probably due to the light modification of the zeta potential for the system studied.