title: Influence of solubilizing agents (cyclodextrin or surfactant) on phenanthrene degradation by electro-Fenton process--study of soil washing recycling possibilities and environmental impact.
abstract: 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(®) (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(2+)] = 0.05 mM (catalyst), I = 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(2+)-HPCD-organic pollutant) (equilibrium constant K = 56 mM(-1)) that allows OH to directly degrade the contaminant. This confirms that Fe(2+) 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 (BOD5/COD = 0.1) and lower toxicity (80% inhibition of luminescence of Vibrio fischeri bacteria) than TW 80/phenanthrene (BOD5/COD = 0.08; 99% inhibition of V. fischeri bacteria). According to these data, HPCD employed in this integrated (soil washing + EF degradation) approach gave promising results in order to be reused whereas the pollutant is degraded in the meanwhile.
authors.affiliation: Université Paris-Est, Laboratoire Géomatériaux et Environnement (EA 4508), UPEMLV, 77454 Marne-la-Vallée, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mousset
authors.forename: Nihal
authors.initials: N
authors.lastname: Oturan
authors.forename: Eric D
authors.initials: ED
authors.lastname: van Hullebusch
authors.forename: Gilles
authors.initials: G
authors.lastname: Guibaud
authors.forename: Giovanni
authors.initials: G
authors.lastname: Esposito
authors.forename: Mehmet A
authors.initials: MA
authors.lastname: Oturan
mesh_terms: D003505:Cyclodextrins / Q000737:chemistry*; D055664:Electrochemical Techniques; D010616:Phenanthrenes / Q000737:chemistry*; D059027:Recycling; D012989:Soil Pollutants / Q000737:chemistry*; D012995:Solubility; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D003505:Cyclodextrins; D010616:Phenanthrenes; D012989:Soil Pollutants; D013501:Surface-Active Agents; C031181:phenanthrene
keywords: Advanced oxidation processes; Bioassays; HPCD; PAHs; Recycling; Tween 80