Electrokinetic Fenton Process Research Articles

Soil flushing and simultaneous degradation of organic pollutants in soils by electrokinetic-Fenton treatment

Abstract This study focuses on the evaluation of a combination of electrokinetic technology and Fenton's process to remediate a soil polluted with organic compounds. To determine the influence of the several variables such as hydrogen peroxide dosage, iron soil concentration and porosity, different experiments using kaolinite spiked by Rhodamine B were performed. The use of this coloured sample permitted an easy monitoring of the oxidation reactions across the soil bed. From the obtained results, it is concluded that the highest colour removal rate was reached when a solution of hydrogen peroxide around 10% was used, and slight influence of iron soil concentration was detected at the range of concentrations used in these experiments. In all cases, citric acid was added in the anolyte and catholyte solutions in order to solubilize the iron as Fe-citrate complex and to keep the pH in acid environment favouring that the Fenton's reactions take place into the soil. Based on these preliminary experiments, the electrokinetic-Fenton process was applied to total petroleum hydrocarbons (TPH) polluted soil. After 15 and 27 days of treatment, a homogeneous removal of pollutants, around 54.4% and 58.2% of TPH removal efficiency, was reached, respectively. In addition, the Microtox bioassays confirmed the reduction of the Vibrio fischeri inhibition after the soil treatment. Summing up, in situ electrokinetic-Fenton treatment seems to be a suitable technique for the remediation of organics such as hydrocarbons present in polluted soils.

Treatment of Artificial and Real Co-contaminated Soil by an Enhanced Electrokinetic-Fenton Process with a Soil Flushing Method

The electrokinetic process with Fenton oxidation is a useful method to remediate soils co-contaminated with hydrophobic organics and heavy metals. In this study, an enhanced electrokinetic-Fenton process with a soil flushing method was investigated for the homogeneous and simultaneous removal of total petroleum hydrocarbons (TPHs) and zinc from contaminated soil. In addition, we investigated the removal mechanisms of different types of organic contaminants in real co-contaminated soil with TPHs, polycyclic aromatic hydrocarbons (PAHs), and zinc. In the artificially spiked soil, TPHs were homogeneously treated, and the removal of TPHs and zinc significantly improved using 10 % hydrogen peroxide (H2O2) with 20 mM sodium dodecyl sulfate (SDS) in the anode and 20 mM SDS and 20 mM NaOH in the cathode. In the real co-contaminated soil, the remediation efficiencies of TPHs and zinc decreased because of the natural soil properties. However, we found satisfactory simultaneous treatability of TPHs and PAHs using 20 % H2O2 with 20 mM SDS in the anode and 20 mM SDS and 20 mM NaOH in the cathode. Furthermore, the removal of individual PAHs was different depending on the individual PAH.

Application of the Electrokinetic-Fenton Process for the Treatment of Lubricant-Contaminated Railroad Soil

Soil pollution around railroad sites is mainly caused by heavy oils such as diesel and lubricants. In particular, the majority of contamination in soil around railroad turnouts is caused by oil that drips off of railcars and lubricants that leak during vehicle maintenance. Generally, removing lubricants from contaminated soil is more difficult than removing diesel, due to the properties of the respective oils. This study aims to investigate alternative remediation method of lubricant-contaminated soils around railroad turnouts. The EK-Fenton process was used to clean up the lubricant-contaminated railroad soil. Several operating conditions were tested, including the concentration of hydrogen peroxide, and electrolyte types and concentrations. We determined that the removal efficiency was affected by the amount of EOF in the soil and its oxidizing capacity. The TPH removal efficiency was greatest at 0.1 M of NaCl electrolyte and 5 % (v/v) of hydrogen peroxide. This shows that the in-situ EK-Fenton process is a promising remediation technique for decontaminating railroad soil polluted with lubricant oil.

Stability and performance enhancements of Electrokinetic-Fenton soil remediation

Electrokinetic process is a potential in situ soil remediation process which transports the contaminants via electromigration and electroosmosis. For organic compounds contaminated soil, Fenton’s reagent is utilized as a flushing agent in electrokinetic process (Electrokinetic-Fenton) so that removal of organic contaminants could be achieved by in situ oxidation/destruction. However, this process is not applied widely in industries as the stability issue for Fenton’s reagent is the main drawback. The aim of this mini review is to summarize the developments of Electrokinetic-Fenton process on enhancing the stability of Fenton’s reagent and process efficiency in past decades. Generally, the enhancements are conducted via four paths: (1) chemical stabilization to delay H2O2 decomposition, (2) increase of oxidant availability by monitoring injection method for Fenton’s reagent, (3) electrodes operation and iron catalysts and (4) operating conditions such as voltage gradient, electrolytes and H2O2 concentration. In addition, the types of soils and contaminants are also showing significant effect as the soil with low acid buffering capacity, adequate iron concentration, low organic matter content and low aromatic ring organic contaminants generally gives better efficiency.

Effect of Polarity Reversal on Hexachlorobenzene Removal during Electrokinetic Fenton Process

AbstractExperimental evidence shows that the electrokinetic Fenton process is very effective for cleaning soil contaminated with organic compounds, especially hydrophobic and persistent organic pollutants. Despite the technological progress in recent years, there are still several performance-related issues to be addressed, such as its implication on the final soil quality and different oxidant delivery schemes. This paper reports the results of a series of experiments carried out to explore the possibilities of using polarity reversal as an enhancement during electrokinetic Fenton treatment of soil contaminated with persistent organic pollutants. Laboratory-scale experiments were conducted with kaolin and hexachlorobenzene (HCB) as the model soil and contaminant, respectively. Experiments were performed both with and without added iron (Fe). Reversing the polarity of electrodes after a period during the experiments was found to be effective in aiding the reachability of the oxidant to the soil specimen i...

산 완충능력과 토양 성분이 동전기-펜톤 공정에 의한 phenanthrene 오염토양 정화에 미치는 영향

This research was conducted to investigate effects of acid buffering capacity and soil component in treatment of phenanthrene using electrokinetic-Fenton process. In Hadong clay of high acid buffering and low iron oxide content, it was difficult to oxidize phenanthrene due to shortage of iron catalyst and scavenger effect of carbonate minerals. The desorbed phenanthrene conductive to Fenton oxidation was transported toward cathode by electroosmotic flow. However, in Youngdong illitic clay, oxidation of phenanthrene near anode readily occurred compared to Hadong clay due to high iron content and low acid buffering capacity.

Switching effects of electrode polarity and introduction direction of reagents in electrokinetic-Fenton process with anionic surfactant for remediating iron-rich soil contaminated with phenanthrene

This study investigated effective operating method of enhanced electrokinetic-Fenton (EK-Fenton) process with anionic surfactant to remediate contaminated iron-rich clayey soil with phenanthrene, which had soil properties being frequently in contaminated sites. Introduction of 30 mM SDS as H 2O 2 stabilizer improved not only H 2O 2 stability but also degradation of phenanthrene compared to experiment without SDS. However, electrical potential drop in regions near cathode terminated electro-osmotic flow, and then phenanthrene in region near cathode kept initial concentration before switching of the electrodes polarities and introduction direction of reagents. After the polarity of the electrodes and introduction direction of reagents were switched, electro-osmotic flow was re-generated with re-distribution of electrical potential and electrical current. Furthermore, after switching electrode, decrease of iron concentration and pH in the soil specimen near cathode before switching electrode generated decrease of H 2O 2 decomposition rate. Therefore, H 2O 2 could be introduced in the cathode regions before switching the polarity of the electrodes and introduction direction of reagents. Furthermore, residual phenanthrene was degraded homogeneously after switching of the electrodes polarity and introduction direction of reagents, and then about 70% phenanthrene could be degraded.

Oxidant availability in soil and its effect on HCB removal during electrokinetic Fenton process

Electrokinetic technology in its various forms has already shown its potential as a promising technology for the remediation of organic compounds in soil. Efforts to improve and optimise the process have eventually led to the coupling of electrokinetics with other remediation techniques like chemical oxidation. This paper reports the results of a series of electrokinetic Fenton experiments carried out to investigate the effect of oxidant delivery and availability on contaminant removal and its subsequent impact on the treatment duration. In doing so, we have tried to show that the treatment duration can be considerably reduced by the proper introduction of the oxidants to the soil for a better oxidant availability throughout the soil section. Experiments were conducted at laboratory scale using kaolin spiked with hexachlorobenzene (HCB). Though each experiment resulted in different removal rates, under specific experimental conditions, a maximum of 57% contaminant removal was obtained. However, the oxidation reactions in these experiments did not show any pH dependence in the range 2.9–5. A more uniform and better HCB degradation was possible in a shorter duration by the proper introduction of oxidant into the soil.

Effect of cyclodextrin on the remediation of hexachlorobenzene in soil by electrokinetic Fenton process

Integration of electrokinetics with chemical oxidation especially Fenton's process is a widely accepted technique for the degradation of organic compounds in soil. This paper presents a study on the effect of cyclodextrin as an enhancing agent during the electrokinetic Fenton process for the remediation of soil contaminated with a hydrophobic organic compound. Kaolin was used as the model clay and was spiked with hexachlorobenzene (HCB) to get an initial concentration of 100 mg/kg. An attempt was made to evaluate the performance of high concentration hydrogen peroxide (H 2O 2) to oxidize the contaminants in the sorbed state in the presence and absence of cyclodextrin. The treatment was carried out for 15 consecutive days. The results clearly demonstrate the efficiency of the process while at the same time, the distribution of the residual contaminant in the soil is greatly influenced by the presence of cyclodextrin. There was no soluble iron addition during the process and the system used the inherent iron in kaolin to catalyze the Fenton-like reactions. A maximum of 76% removal of the contaminant from the soil was observed when 30% H 2O 2 was used in the absence of cyclodextrin.

Removal of hexachlorobenzene from soil by electrokinetically enhanced chemical oxidation

This study investigates the feasibility of enhanced electrokinetic Fenton process for the remediation of hexachlorobenzene (HCB) in low permeable soil. Laboratory scale experiments were carried out in two different type of experimental setup to evaluate the influence of electrode positions in the system. Kaolin was artificially contaminated with HCB and treated by electrokinetic Fenton process. β-Cyclodextrin was used to enhance the solubility of HCB in pore fluid. Results show that the position of electrodes in the system and the way in which Fenton's reagent was added to the system has a significant influence on the treatment efficiency.

Remediation of hexachlorobenzene in soil by enhanced electrokinetic Fenton process

The feasibility of enhanced electrokinetic Fenton process for the remediation of Hexachlorobenzene (HCB) in low permeability soil was investigated. Kaolin was artificially contaminated with HCB and treated by electrokinetic and electrokinetic Fenton processes. β -Cyclodextrin was used to enhance the solubility of HCB in pore fluid. Three tests were carried out, of which two were electrokinetic experiments to observe the suitability of β -cyclodextrin as a flushing solution for these processes. The third experiment was the electrokinetic Fenton test using β -cyclodextrin as an enhancing agent. Results show that the removal efficiency depends on the choice of a suitable flushing solution and physical parameters like pH, electric current and electro-osmotic flow.

Role of stabilizers for treatment of clayey soil contaminated with phenanthrene through electrokinetic-Fenton process—Some experimental evidences

In electrokinetic-Fenton (EK-Fenton) process, the effects of the phosphate and SDS introduced from the anode chamber were investigated for the treatment of clay contaminated with phenanthrene. In tests with phosphate and SDS, the electrochemical phenomena were complicate trend compared to tests with HCl. These results resulted from complexation of phosphate with oxides and SDS, and then increase of dissolved SDS concentration with pH increase in regions near cathode. The electro-osmotic flow increased as zeta-potential on the soil surface decreased due to complexation of phosphate and SDS with oxides. In test with phosphate, the transportation of dissolved Fe ions toward the cathode was hindered significantly due to complexation with phosphate. However, in test with SDS, the dissolved Fe ions could be transported in the regions near cathode compared to test with phosphate. These results indicate that SDS dissolved the Fe ion from Fe oxide of soil structure and then the dissolved Fe ions with SDS as counter ion could be transported in regions near cathode. Furthermore, transition metal complexation with phosphate and SDS generated improvement of H 2O 2 stability. Particularly, in test with SDS, the improvement of H 2O 2 stability in high pH regions resulted from SDS transportation in regions near cathode. Consequently, in EK-Fenton process with longer reaction time, the increase of H 2O 2 stability resulted in increase of phenanthrene treatment efficiency.

Effect of soil chemical properties on the remediation of phenanthrene-contaminated soil by electrokinetic-Fenton process

The electrokinetic-Fenton (EK-Fenton) remediation of soil contaminated with phenanthrene was studied. Two different soils were chosen to investigate the effects of chemical properties, such as Fe oxide contents and acid soil buffer capacity. The H 2O 2 concentrations in pore water, the electrical potential distributions and the electrical currents were monitored to assess the electrochemical effect in relation to the soil properties. Hadong caly had high acid buffer capacity, and thus the amount of electroosmotic flow was lager in the experiment with Hadong clay than with EPK kaolin. The major mechanism of phenanthrene removal was a degradation in the experiment with EPK Kaolin, while it was a simple transport away from the system in experiment with Hadong clay. It was mainly because of the lower acid buffering capacity and better H 2O 2 stability in case with EPK Kaolin than with Hadong clay.

Application of the electrokinetic-Fenton process for the remediation of kaolinite contaminated with phenanthrene

This study explored the feasibility of applying the electrokinetic-Fenton process (EK-Fenton process) for the remediation of contaminant sorbed onto soil possessing low-permeability. The relationship of H 2O 2 stability and phenanthrene treatment, and the variation in the monitoring values were also investigated during the EK-Fenton process when catalyzed by heterogeneous minerals. Phenanthrene was chosen to represent hydrophobic organic contaminants (HOCs), which are widespread in the environment, and kaolinite was used as the low-permeability soil. In these experiments, the H 2O 2 concentrations in pore water, the electrical potential distributions and the electrical currents were measured or monitored to assess the electrochemical effect in relation to injections of H 2O 2 from the anode. The results suggested that intermediate anions (HO 2 −, O 2 −) with Fenton-like reaction affected significantly the variations in the electrical current during the EK-Fenton process. The addition of 0.01 N H 2SO 4 to the anode reservoir improved the H 2O 2 stability and the treatment of phenanthrene in the entire soil specimen. Therefore, use of H 2O 2 and dilute acid, as an anode purging solution is a possible method for treating HOCs in low-permeability subsurface environments.