Phenanthrene removal in unsaturated soils treated by electrokinetics with different surfactants—Triton X-100 and rhamnolipid (original) (raw)
Related papers
Journal of Environmental Engineering, 2010
Removal of nonpolar contaminants such as most organic compounds are transported primarily by electroosmosis in electrokinetic remediation, thus the process is effective only if the contaminants are soluble in pore fluid. Hydrophobic organic compounds such as hexachlorobenzene ͑HCB͒ and phenanthrene ͑PHE͒ can adsorb strongly to clayey soil. Therefore, in this study, enhancements were done by adding 2-hydroxylpropyl--cyclodextrin surfactant and ultrasonication comparably to assist the electrokinetic treatment in improving the mobility of these hydrophobic compounds. The results show that HCB and PHE were mobilized and removed in both cases. But HCB is more difficult to remove than PHE, because of its highly stable nature and low water-solubility property. Ultrasound-assisted test performed better PHE reduction than surfactant-assisted test, because ultrasound can degrade the contaminant through oxidation by free radicals.
Electrokinetically Enhanced Remediation of Hydrophobic Organic Compounds in Soils: A Review
Critical Reviews in Environmental Science and Technology, 2005
Electrokinetically enhanced remediation is an innovative technology that has the potential to remediate hydrophobic organic compound (HOC) contamination in soils and groundwater. A surfactant/cosolvent is used to increase HOC desorption and solubilization, and an applied electric potential facilitates contaminant transport primarily by electroosmosis and/or electrophoresis. Electroosmotic flow generally improves soil-solution-contaminant interaction, especially in zones of high organic content and/or low hydraulic conductivity. The electrokinetically enhanced remediation process is fairly simple to implement and operate, but the fundamental reactions that govern the remediation method are complex. An adequate knowledge of the contaminant transport mechanisms and the physical, chemical, and electrochemical processes is essential in order to optimize system performance. This article reviews previous research efforts on HOC remediation and the use of in situ flushing and electrokinetics for organic contaminants. In addition, to gain a better understanding of the individual components and the complexities of the electrokinetically enhanced in situ flushing process, this article presents background information on HOCs and surfactants/cosolvents, as well as the basic parameters that affect the performance of in situ flushing and electrokinetic technologies. Since the success or failure of electrokinetic remediation for HOC pollutants in low permeability soils largely depends
Effect of pH control at the anode for the electrokinetic removal of phenanthrene from kaolin soil
Chemosphere, 2003
Polycyclic aromatic hydrocarbon (PAH)-contaminated soils exist at numerous sites, and these sites may threaten public health and the environment because many PAH compounds are toxic, mutagenic, and/or carcinogenic. PAHs are also hydrophobic and persistent, so conventional remediation methods are often costly or inefficient, especially when the contaminants are present in low permeability and/or organic soils. An innovative technique, electrokinetically enhanced in situ flushing, has the potential to increase soil–solution–contaminant interaction and PAH removal efficiency for low permeability soils; however, the electrolysis reaction at the anode may adversely affect the remediation of low acid buffering capacity soils, such as kaolin. Therefore, the objective of this study was to improve the remediation of low acid buffering soils by controlling the pH at the anode to counteract the electrolysis reaction. Six bench-scale electrokinetic experiments were conducted, where each test employed one of three different flushing solutions, deionized water, a surfactant, or a cosolvent. For each of these solutions, tests were performed with and without a 0.01 M NaOH solution at the anode to control the pH. The test using deionized water with pH control generated a higher electroosmotic flow than the equivalent test performed without pH control, but the electroosmotic flow difference between the surfactant and cosolvent tests with and without pH control was minor compared to that observed with the deionized water tests. Controlling the pH was beneficial for increasing contaminant solubilization and migration from the soil region adjacent to the anode, but the high contaminant concentrations that resulted in the middle or cathode soil regions indicates that subsequent changes in the soil and/or solution chemistry caused contaminant deposition and low overall contaminant removal efficiency.
Journal of Environmental Chemical Engineering, 2015
Petroleum hydrocarbons are hydrophobic and tend to adhere to soil when released into the environment. Desorption of the contaminant from soil is necessary for most remediation technologies. In subsurface and for in-situ remediation, the dominant desorption mechanism is back diffusion. In this study, three tests were conducted to establish sorption and desorption kinetics for phenanthrene as a contaminant and kaolinite as a soil matrix. Sorption isotherm tests were conducted at temperatures of 14, 22, and 30 C using six phenanthrene solution containing concentrations from 300 to 800 mg/L. Freundlich constant, K f, values of 0.147, 0.133, 0.109 (mgL n /g (1+n)), were determined for the three temperatures. Desorption tests were conducted using phenanthrene-free solution to determine desorption parameters at room temperature ($22 C). In addition, two test series were performed to compare phenanthrene desorption by hydraulic and electroosmotic flows at room temperature. A fixed wall hydraulic permeability apparatus was used to generate a hydraulic flow rate of 1.4 Â 10 À3 mL/s at a pressure of 260 kPa, while a low level direct current density (0.3-0.43 mA/cm 2) was applied to generate electroosmotic flow rate equivalent to the hydraulic flow. The phenanthrene concentration in effluent samples after desorption by electroosmotic flow was found to be three to four times the concentration after desorption by hydraulic flow. Moreover, the power required in the hydraulic flow test was three orders of magnitude higher than the consumed power in the electrokinetic flow test. These results show that phenanthrene desorption by electroosmotic flow is more efficient than by hydraulic flow.
Environmental Science and Pollution Research, 2020
The objective of this work was to investigate the modification of soil contaminated with phenanthrene (PHE) by electro-kinetic remediation (EKR) process using response surface methodology (RSM). The soil sample was obtained from the subgrades (0-30 cm) of an area close to Shahroud City, Northeast of Iran. The effect of variables such as initial pH, voltage, electrolyte concentration, and reaction time on PHE removal was studied. Based on the results obtained from the central composite design (CCD) experiment, the highest and lowest amount of PHE removal was 97 and 20%, respectively. In this study, the variables A, B, C, AB, AC, and C 2 with a p value < 0.05 were significant model terms and the parameter of the lack of fit was not significant (p value = 0.0745). Findings indicated that the "predicted R-squared" of 0.9670 was in reasonable agreement with the "adj R-squared" of 0.9857 and the plot of residual followed a normal distribution and approximately linear. Also, the kinetic rates of the removal PHE by the EKR process best fitted with a first-order kinetic model (R 2 : 0.926). Results of the investigation of the effective variables showed that in values of pH 3, time of 168 h, voltage of 3 V, and electrolyte concentration of 4 mg/L, the removal efficiency of PHE reached 96.6%.
2006
The applicability of the combined solubilization-biodegradation process was examined using soil-packed column. In the solubilization step, 50 pore volumes of 150 mg/l biosurfactants solution was injected and the percentage removal of phenanthrene (mg) was 17.3% and 9.5% from soil with pH 5 and 7, respectively. The highest solubility was detected at pH 5 and this result confirmed that adjusting the pH of the biosurfactants solution injected could enhance the solubility of phenanthrene. Following this, soil samples were completely transferred to batches and incubated for 10 weeks to monitor phenanthrene degradation. The phenanthrene concentration in the soil samples decreased significantly during the biodegradation step in all soil samples, except for the soil sample that was flushed with biosurfactants solution with pH 4. This indicated that the degradation of contaminants by specific species might not be affected by the residual biosurfactants following application of the solubilization process. Moreover, these results suggested that the biosurfactant-enhanced flushing process could be developed as a useful technology with no negative effects on subsurface environments and could be combined with the biodegradation process to increase the removal efficiency.
Water Research, 2014
Advanced oxidation processes Recycling Bioassays a b s t r a c t One of the aims in soil washing treatment is to reuse the extracting agent and to remove the pollutant in the meantime. Thus, electro-Fenton (EF) degradation of synthetic soil washing solutions heavily loaded with phenanthrene was suggested for the first time. Two solubilising agents hydroxypropyl-beta-cyclodextrin (HPCD) and Tween 80 Ò (TW 80) were chosen as cyclodextrin (CD) and surfactant representatives, respectively. In order to reuse HPCD and to degrade the pollutant simultaneously, the following optimal parameters were determined: [Fe 2þ ] ¼ 0.05 mM (catalyst), I ¼ 2000 mA, and natural solution pH (around 6), without any adjustment. Only 50% of TW 80 (still higher than the critical micelle concentration (CMC)) can be reused against 90% in the case of HPCD while phenanthrene is completely degraded in the meantime, after only 180 min of treatment. This can be explained by the ternary complex formation (Fe 2þ -HPCD-organic pollutant) (equilibrium constant K ¼ 56 mM À1 ) that allows OH to directly degrade the contaminant. This confirms that Fe 2þ plays an important role as a catalyst since it can promote formation of hydroxyl radicals near the pollutant and minimize HPCD degradation. After 2 h of treatment, HPCD/ phenanthrene solution got better biodegradability (BOD 5 /COD ¼ 0.1) and lower toxicity (80% inhibition of luminescence of Vibrio fischeri bacteria) than TW 80/phenanthrene (BOD 5 / COD ¼ 0.08; 99% inhibition of V. fischeri bacteria). According to these data, HPCD employed in this integrated (soil washing þ EF degradation) approach gave promising results in order to be reused whereas the pollutant is degraded in the meanwhile. ª journal homepage: www.else vier.com/locate /wa tres w a t e r r e s e a r c h 4 8 ( 2 0 1 4 ) 3 0 6 e3 1 6 0043-1354/$ e see front matter ª
Electrokinetic Remediation of a Soil Contaminated with Anthracene Using Different Surfactants
Environmental Engineering Science, 2019
Electrokinetic technique is one of the common methods that can be used for removal of organic contaminants in soil. There are some of organic contaminants with low solubility in water. In order to improve the efficiency of remediation it is possible to use appropriate surfactants as flushing solution. In this work non-ionic (Poloxamer 407 and Tween 80), anionic (sodium dodecyl sulfate, SDS) and humic acid (HA) with solution of 0.1 M NaOH were selected for improving the remediation of a soil contaminated with anthracene. The solution of NaOH and surfactants were used as anolyte but humic acid was mixed with contaminated soil. At the end of each test a number of soil samples were extracted from the middle of the soil at different distances from the anode and the removal of contaminant was measured by a HPLC (High Performance Liquid Chromatography) apparatus. The results show that the effectiveness of solution surfactants and NaOH in removal of anthracene was SDS>Tween 80> Poloxamer 407. In addition, the results indicate that effect of humic acid on remediation is less than SDS and more than non-ionic surfactants.