Remediation of persistent organic pollutant-contaminated soil using biosurfactant-enhanced electrokinetics coupled with a zero-valent iron/activated carbon permeable reactive barrier

Abstract

Zero-valent iron/activated carbon (Fe/C) particles can degrade persistent organic pollutants via micro-electrolysis and therefore, they may be used to develop materials for permeable reactive barriers (PRBs). In this study, surfactant-enhanced electrokinetics (EK) was coupled with a Fe/C-PRB to treat phenanthrene (PHE) and 2,4,6-trichlorophenol (TCP) co-contaminated clay soil. An environment-friendly biosurfactant, rhamnolipid, was selected as the solubility-enhancing agent. Five bench-scale tests were conducted to investigate the performance of EK-PRB on PHE and TCP removal from soil as well as the impact of pH and rhamnolipid concentration. The results show that both PHE and TCP, driven by electro-osmotic flow (EOF), moved toward the cathode and reacted with the Fe/C-PRB. Catholyte acidification and rhamnolipid concentration increase improved the removal efficiencies of PHE and TCP. The highest removal efficiency of PHE in soil column was five times the efficiency of the control group on which only EK was applied (49.89 versus 9.40%). The highest removal efficiency of TCP in soil column was 4.5 times the efficiency of the control group (64.60 versus 14.30%). Desorption and mobility of PHE and TCP improved with the increase of rhamnolipid concentration when this exceeded the critical micelle concentration. This study indicates that the combination of EK and a Fe/C-PRB is efficient and promising for removing persistent organic pollutants (POPs) from contaminated soil with the enhancement of rhamnolipid.

Testing different strategies for the remediation of soils polluted with lindane

“…In general, a PRB is constructed perpendicular to the groundwater flow and below the phreatic level so that the natural hydraulic gradient carries the contaminant through the reactive medium of the PRB and can degrade or immobilize it as water flows through the barrier. Previous works focused on the use of Granular Activated Carbon and biological barriers for the remediation of soils polluted with different species also pointed out the relevance of this technology for the removal of this species (Ruiz et al, 2013;Souza et al, 2017;Sun et al, 2017). Also, in a recent study (Vidal et al, 2018), it was evaluated the use of, two types of zero valent iron (ZVI) PRBs (nano-ZVI and milli-ZVI) that were used as a quick treatment that managed to reduce the hazardousness of the halogenated pollutant contained in the soil; thus, transforming it in a less dangerous nonhalogenated species.…”

Critical Review of Electro-kinetic Remediation of Contaminated Soils and Sediments: Mechanisms, Performances and Technologies

“…The non-ionic surfactant Tween 80 (Polysorbate 80) and the anionic surfactant sodium dodecyl sulfate (SDS) were used to aid desorption of PAH from the soil, and the removal rate of PAH reached a maximum of almost 87% (Lima et al, 2012). Tween 80, polyoxyethylene ether, modified cyclodextrin, and N-butyl amine are often used as the surfactants to improve EKR performance (Sun et al, 2017). The requirements of selecting complexing agents are that (a) the ligands should have high solubility in solutions with a wide pH range; (b) formers are not easy to adsorb on the soil surface; and (c) formers should be non-toxic or have low toxicity with little potential risk to the environment.…”

“…Research found that EKR technology combined with permeable reaction barriers composed of zero-valent iron (Fe 0 ) can remove 80% of perchloroethylene from soil within 10 days, which was much higher than the removal rate of EKR technology alone (Kebria et al, 2016). The use of Fe 0 /activated carbon as the permeable reaction barrier material in combination with EKR has also increased the removal rates of phenanthrene and trichlorophenol by 5 and 4.5 times, respectively (Sun et al, 2017).…”

Environmental applications of electrochemical technology. What is needed to enable full-scale applications?

“…Some authors have focussed on the treatment of hospital urines, where both pharmaceuticals and pathogens are more concentrated and an improvement in the process efficiency is expected, as well as lower investment and operational costs. Among the available technologies, a single electrochemical technique such as electrochemical oxidation or electro-Fenton and the combination of free radicaleassisted electrochemical technologies have demonstrated complete disinfection and partial oxidation of chemicals towards the decrease of toxicity and increase of biodegradability of urines and sanitary effluents [48,49].…”