Removal of oxyfluorfen from spiked soils using electrokinetic soil flushing with the surrounding arrangements of electrodes (original) (raw)
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Chemosphere, 2017
This work studies the feasibility of the periodic polarity reversal strategy (PRS) in a combined electrokinetic-biological process for the remediation of clayey soil polluted with a herbicide. Five two-weeks duration electrobioremediation batch experiments were performed in a bench scale set-up using spiked clay soil polluted with oxyfluorfen (20 mg kg(-1)) under potentiostatic conditions applying an electric field between the electrodes of 1.0 V cm(-1) (20.0 V) and using PRS with five frequencies (f) ranging from 0 to 6 d(-1). Additionally, two complementary reference tests were done: single bioremediation and single electrokinetic. The microbial consortium used was obtained from an oil refinery wastewater treatment plant and acclimated to oxyfluorfen degradation. Main soil conditions (temperature, pH, moisture and conductivity) were correctly controlled using PRS. On the contrary, the electroosmotic flow clearly decreased as f increased. The uniform soil microbial distribution at ...
Industrial & Engineering Chemistry Research, 2017
The treatment of soil-washing effluents polluted with herbicide oxyfluorfen is studied using a combined process consisting of biosorption and electrolysis. Results show that oxyfluorfen is very efficiently removed from synthetic soil by soil washing with sodium dodecyl sulfate (SDS). The effluent can be treated by biosorption with fresh activated sludge coming from a municipal wastewater treatment plant, and the maximum adsorption capacity of this activated sludge was found to be 18 mg of oxyfluorfen per gram of biomass. Biosorption fits well to a type I adsorption isotherm. Effluents of the biosorption process underwent anodic oxidation, photoelectrolysis, and sonoelectrolysis at high and low frequency. The four technologies were able to mineralize completely the effluent, although important differences arose during the treatment which depended significantly on the application of ultrasound or ultraviolet irradiation and on the release of sulfate from the oxidation of SDS: intermediates were removed faster because of the activation of sulfate radicals. Oxyfluorfen and its oxidation intermediates are removed faster than SDS, and when they are fully depleted there are still large concentrations of SDS in the treated solution. This opens the possibility of reusing the soil washing fluid.
UV assisted electrochemical technologies for the removal of oxyfluorfen from soil washing wastes
Chemical Engineering Journal, 2017
In this work, it is studied the treatment of soil polluted with oxyfluorfen by Surfactant-aided Soil-Washing (SASW) and after that, photo-electrolysis was used for the treatment of the soil-washing fluid produced. This liquid waste is characterized by the high concentration of micelles of pesticide and surfactant (sodium dodecyl sulfate, SDS), whose initial size depends on the ratio soil-surfactant used in the soil washing treatment. The waste treatment is studied in terms of the decrease in size of the particles and the depletion of the pollutants. Results clearly demonstrate that photo-electrolysis with diamond electrodes is a very effective treatment technology with results that overcome those obtained by single photolysis and/or single electrolysis with diamond electrodes. The greater improvements attained by combining UV irradiation to the electrolysis were observed in the removal of the pesticide while the removal of the surfactant was little affected. Electrolysis does not only deplete the complete concentration of pesticide but it also shows to be very efficient in the depletion of the surfactant, preventing its potential recycle. The significant concentration of sulfate released during the attack to the surfactant and the effect of the peroxosulfate anions that are formed from the anodic oxidation of that anion, explain the improved performance of the technology in the treatment of washing fluids with higher concentrations of SDS.
Water, Air, & Soil Pollution, 2019
This work studies the in-situ electrobioremediation of an oxyfluorfen polluted clay soil in a two-stage method. First, a fixed bed biofilm reactor for oxyfluorfen biodegradation in wastewater was developed; It treated wastewater with 200 mg L-1 of oxyfluorfen and reached 100% of oxyfluorfen degradation in 30 h. Second, a portion of the biofilmcovered bed was included into the polluted soil and it was used as a biological permeable reactive barrier (BioPRB), whereas electrokinetics were applied to promote the contact between the pollutant and microorganisms into the soil. The electrobioremediation study was performed in a bench scale setup under 1.0 V cm-1 at room temperature and under periodic polarity reversal (2 d-1) in a two-week batch experiment. Two reference tests were done: (i) a conventional in-situ biological test without electrokinetics and (ii) a conventional in-situ electrokinetic test without using microorganisms. The experimental conditions (temperature, pH, moisture) were correctly controlled in the soil and enabled the microbial activity during the process. A low oxyfluorfen removal efficiency was obtained after 2 weeks (11%) because of the low electrokinetic mobility of such non-polar pollutant into the soil. Despite this low efficiency value, it was considered that the combined biological-electrokinetic technology could be used as a bioaugmentation procedure to perform electrobioremediation processes because the results of both reference tests showed negligible removal efficiencies when using only biological or only electrochemical methods. According to these results, electrobioremediation could be considered as a feasible technology although more retention time would be required to achieve successful remediation results.
Removal of oxyfluorfen from ex-situ soil washing fluids using electrolysis with diamond anodes
Journal of environmental management, 2016
In this research, firstly, the treatment of soil spiked with oxyfluorfen was studied using a surfactant-aided soil-washing (SASW) process. After that, the electrochemical treatment of the washing liquid using boron doped diamond (BDD) anodes was performed. Results clearly demonstrate that SASW is a very efficient approach in the treatment of soil, removing the pesticide completely by using dosages below 5 g of sodium dodecyl sulfate (SDS) per Kg of soil. After that, complete mineralization of organic matter (oxyflourfen, SDS and by-products) was attained (100% of total organic carbon and chemical oxygen demand removals) when the washing liquids were electrolyzed using BDD anodes, but the removal rate depends on the size of the particles in solution. Electrolysis of soil washing fluids occurs via the reduction in size of micelles until their complete depletion. Lower concentrations of intermediates are produced (sulfate, chlorine, 4-(trifluoromethyl)-phenol and ortho-nitrophenol) dur...
Chemical engineering transactions, 2014
Chemical Engineering Department. Faculty of Chemical Sciences and Technology. University of Castilla La Mancha, 13071, Ciudad Real, Spain. Chemical Engineering Department. Research Institute for Chemical and Environmental Technology (ITQUIMA). University of Castilla La Mancha, 13071, Ciudad Real, Spain. Department of Civil Building Engineering, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Castilla-La Mancha, Campus Universitario s/n, 13071 Ciudad Real, Spain *Corresponding author: manuel.rodrigo@uclm.es
Integrated electrokinetic-soil flushing to remove mixed organic and metal contaminants
Journal of Applied Electrochemistry, 2010
The integrated use of hydraulic flushing and electrokinetic treatment was investigated for the remediation of silty sand contaminated by both PAHs and heavy metals. The soil was collected from a polluted former manufactured gas plant (MGP). Four bench-scale experiments were conducted to analyze the ability of the combined hydraulic flushing and the electrokinetic treatment for the simultaneous removal of PAHs and heavy metals. Sequential flushing with ethylenediaminetetraacetic acid (EDTA) or Igepal CA-720 were tested with or without the simultaneous application of a low intensity direct electric field (1 VDC cm -1 ). The best results were obtained with 0.2 M EDTA flushing in two stages (without and with voltage gradient, 1 VDC cm -1 ), followed by 5% Igepal flushing in two stages (without and with 1 VDC cm -1 ). Heavy metals were removed mainly during the EDTA flushing, with removal efficiencies of about 60% for Zn, 80% for Pb, and 30% for Cu. During Igepal flushing, no heavy metals were removed, but PAHs were removed, including 40% phenanthrene, 30% pyrene, and 20% benzo[a]pyrene. Overall, this study showed that a carefully designed sequential hydraulic flushing scheme with selected chelant and surfactant is needed for the removal of both heavy metals and PAHs from MGP silty sands. Combining electrokinetics with hydraulic flushing may not necessarily improve contaminant removal from such soils.
Journal of hazardous materials, 2017
This study demonstrates the application of reversible electrokinetic adsorption barrier (REKAB) technology to soils spiked with low-solubility pollutants. A permeable reactive barrier (PRB) of granular activated carbon (GAC) was placed between the anode and cathode of an electrokinetic (EK) soil remediation bench-scale setup with the aim of enhancing the removal of two low-solubility herbicides (atrazine and oxyfluorfen) using a surfactant solution (sodium dodecyl sulfate) as the flushing fluid. This innovative study focused on evaluating the interaction between the EK system and the GAC-PRB, attempting to obtain insights into the primary mechanisms involved. The obtained results highlighted the successful treatment of atrazine and oxyfluorfen in contaminated soils. The results obtained from the tests after 15days of treatment were compared with those obtained using the more conventional electrokinetic soil flushing (EKSF) technology, and very important differences were observed. Al...
Journal of Electroanalytical Chemistry, 2017
Nowadays, the majority of the remediation studies have been carried out using artificially spiked soils with individual target pollutants. One of the bottlenecks is the application of developed technologies to the removal of pollutants in real aged contaminated soils, which is much more difficult than in spiked ones. Thus, in this study, the performance of a combined technology as flushing using different oxidants coupled with the electrokinetic technique was performed and its feasibility was evaluated to remediate a real industrial polluted soil with low permeability in which is not possible the conventional flushing system. Initially, the characterization of this soil showed a wide distribution of hydrocarbons with a total petroleum hydrocarbons content of 29,666 mg•kg − 1. Based on the hydrocarbons distribution, the source of the pollutants was identified as a spillage of motor oil and diesel. Moreover, the aging of the pollution was evaluated (around 16 years) resulting in a historically polluted soil. Initially, an ex-situ oxidative treatment was considered. This treatment demonstrated the feasibility of the different oxidants on the removal of the hydrocarbons, achieving removal values higher than 65% in all the experiments. Furthermore, a critical parameter in the treatment, as pH, was also evaluated resulting in an acidic environment for KMnO 4 and Na 2 S 2 O 8 and basic environment for NaOCl. Later, the simulated bench scale in situ removal of the contaminants was considered, but the delivery of the oxidants into the polluted soil is hard, and for this reason, the coupling of flushing and electrokinetics was carried out. Working at the optimal conditions determined before, the treatment with the selected oxidants was performed. The total petroleum hydrocarbons (TPH) removal (40-60%), the profile of hydrocarbons and metals in the different sections of the soil after the treatments proved the efficiency of the system. The viability of the selected hybrid technique in the removal of TPH from historically polluted soils was demonstrated.